CA3212783A1 - Gas-cooled micro-reactor core and gas-cooled micro-reactor - Google Patents
Gas-cooled micro-reactor core and gas-cooled micro-reactor Download PDFInfo
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- CA3212783A1 CA3212783A1 CA3212783A CA3212783A CA3212783A1 CA 3212783 A1 CA3212783 A1 CA 3212783A1 CA 3212783 A CA3212783 A CA 3212783A CA 3212783 A CA3212783 A CA 3212783A CA 3212783 A1 CA3212783 A1 CA 3212783A1
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- G—PHYSICS
- G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
- G21C—NUCLEAR REACTORS
- G21C3/00—Reactor fuel elements and their assemblies; Selection of substances for use as reactor fuel elements
- G21C3/30—Assemblies of a number of fuel elements in the form of a rigid unit
- G21C3/32—Bundles of parallel pin-, rod-, or tube-shaped fuel elements
- G21C3/326—Bundles of parallel pin-, rod-, or tube-shaped fuel elements comprising fuel elements of different composition; comprising, in addition to the fuel elements, other pin-, rod-, or tube-shaped elements, e.g. control rods, grid support rods, fertile rods, poison rods or dummy rods
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- G—PHYSICS
- G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
- G21C—NUCLEAR REACTORS
- G21C15/00—Cooling arrangements within the pressure vessel containing the core; Selection of specific coolants
- G21C15/02—Arrangements or disposition of passages in which heat is transferred to the coolant; Coolant flow control devices
- G21C15/14—Arrangements or disposition of passages in which heat is transferred to the coolant; Coolant flow control devices from headers; from joints in ducts
-
- G—PHYSICS
- G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
- G21C—NUCLEAR REACTORS
- G21C3/00—Reactor fuel elements and their assemblies; Selection of substances for use as reactor fuel elements
- G21C3/30—Assemblies of a number of fuel elements in the form of a rigid unit
- G21C3/32—Bundles of parallel pin-, rod-, or tube-shaped fuel elements
- G21C3/33—Supporting or hanging of elements in the bundle; Means forming part of the bundle for inserting it into, or removing it from, the core; Means for coupling adjacent bundles
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- G—PHYSICS
- G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
- G21C—NUCLEAR REACTORS
- G21C5/00—Moderator or core structure; Selection of materials for use as moderator
- G21C5/02—Details
-
- G—PHYSICS
- G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
- G21C—NUCLEAR REACTORS
- G21C5/00—Moderator or core structure; Selection of materials for use as moderator
- G21C5/12—Moderator or core structure; Selection of materials for use as moderator characterised by composition, e.g. the moderator containing additional substances which ensure improved heat resistance of the moderator
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E30/00—Energy generation of nuclear origin
- Y02E30/30—Nuclear fission reactors
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- Engineering & Computer Science (AREA)
- Plasma & Fusion (AREA)
- General Engineering & Computer Science (AREA)
- High Energy & Nuclear Physics (AREA)
- Monitoring And Testing Of Nuclear Reactors (AREA)
- Devices And Processes Conducted In The Presence Of Fluids And Solid Particles (AREA)
- Structure Of Emergency Protection For Nuclear Reactors (AREA)
Abstract
A gas-cooled micro-reactor core, comprising a reflecting layer, fuel units, and a control rod assembly (2), wherein the control rod assembly (2) and the fuel units are all arranged in the reflecting layer, a plurality of fuel units are provided, each fuel unit comprises a pressure pipe (8) and a fuel assembly (1), the fuel assembly (1) is arranged in the pressure pipe (8) so as to make the pressure pipe (8) act as a pressure bearing boundary of the reactor core, and the control rod assembly (2) is arranged outside the pressure pipe (8). The reactor core is easy to mount, and solves the problems of many elements to be transported, a complex assembly, and a slow response to deployment of a high-temperature gas-cooled reactor.
Description
GAS-COOLED MICRO-REACTOR CORE AND GAS-COOLED MICRO-REACTOR
[1] The present disclosure claims the priority of Chinese patent application No.
202110332498.1, titled "MODULAR PRESSURE PIPE TYPE GAS-COOLED MICRO-REACTOR CORE" filed on March 29, 2021.
TECHNICAL FIELD
[1] The present disclosure claims the priority of Chinese patent application No.
202110332498.1, titled "MODULAR PRESSURE PIPE TYPE GAS-COOLED MICRO-REACTOR CORE" filed on March 29, 2021.
TECHNICAL FIELD
[2] The present disclosure relates to the field of nuclear industry, and in particular, to a gas-cooled micro-reactor core and a gas-cooled micro-reactor including the same.
BACKGROUND
BACKGROUND
[3] Energy is an important basis for socio-economic development, but the increasingly prominent problem of environmental pollution poses higher challenges to the optimization of energy structures. As a clean, stable and new energy source with high power density, nuclear energy has become the best candidate for base load power. The safety of nuclear power is always a key concern of the general public as well as the direction of efforts of nuclear power researchers. Especially after the Fukushima accident in Japan, safe utilization of the nuclear energy are more and more emphasized, and the design and research and development of various advanced nuclear energy systems are accelerated.
[4] The high-temperature gas-cooled reactor, as one of the advanced reactor types of the fourth generation nuclear power systems, has gained lots of attention due to good intrinsic safety and a relatively high coolant outlet temperature. The superior intrinsic safety is mainly reflected in that the adopted TRISO coated fuel particles can effectively prevent release of fission products and fuel corrosion; due to a large heat capacity and slow temperature transient state, the adopted graphite core can bear a very high temperature and leave a large time margin for an emergency operation; and due to a relatively small power density and strong temperature negative feedback, the core can be shut down by means of the temperature negative feedback under accident conditions even without any emergency measures.
I
I
[5] In addition, a modular high-temperature gas-cooled reactor can reduce a plurality of emergency facilities through reasonable design and optimization, thereby simplifying the design of a nuclear power plant and forming certain competitiveness in economy.
Especially for some remote areas where power grids cannot reach and diesel oil power generation involves high costs and serious pollution, a small modular high-temperature gas-cooled reactor can supply power in a safe, stable and clean way, and satisfy energy requirements of those areas well.
Especially for some remote areas where power grids cannot reach and diesel oil power generation involves high costs and serious pollution, a small modular high-temperature gas-cooled reactor can supply power in a safe, stable and clean way, and satisfy energy requirements of those areas well.
[6] At present, the existing high-temperature gas-cooled reactor designs worldwide are all based on fixed non-movable cores. Various components of a core need to be manufactured and processed in the factory at an early stage, and then transported separately to the application site. In addition, a large number of components, such as fuel assemblies, reflectors, control rods and the like, can reach a normal operation state only after long-time installation and debugging on site, which can hardly meet the requirements of container transport, simple and convenient assembly and rapid deployment under special application scenes.
SUMMARY
SUMMARY
[7] In order to solve the above defects in the existing art, the present disclosure provides a gas-cooled micro-reactor core and a gas-cooled micro-reactor including the same which can meet the requirements of rapid transport and simple and convenient assembly.
[8] In a first aspect, the present disclosure provides a gas-cooled micro-reactor core, including reflectors, fuel units, and control rod assemblies, wherein the control rod assembly and the fuel unit are both disposed in the reflector, a plurality of fuel units are adopted, and each fuel unit includes a pressure pipe and a fuel assembly, wherein the fuel assembly is arranged inside the pressure pipe, to make the pressure pipe act as a pressure bearing boundary of the core, and the control rod assembly is arranged outside the pressure pipe.
[9] Preferably, the plurality of fuel units are arranged in a plurality of rings from inside to outside, and a plurality of control rod assemblies are adopted and arranged outside an outermost ring of fuel units, and/or arranged in any ring of fuel units, and/or arranged between two adjacent rings of fuel units.
[10]Preferably, within each pressure pipe, the fuel assembly includes a graphite block and fuel rods, and the graphite block has fuel rod channels in which the fuel rods are disposed.
[11]Preferably, the fuel assembly further includes burnable poison rods, and the graphite block further has burnable poison channels in which the burnable poison rods are disposed.
[12]Preferably, the fuel rod includes a plurality of fuel pellets stacked along a length direction of the core; wherein each fuel pellet includes fuel particles and matrix in which the fuel particles are dispersed.
[13]Preferably, each fuel particle includes a fuel kernel and coating layers covering the fuel kernel.
[14]Preferably, the fuel assembly further includes a coolant flow channel including one or more of the first type of coolant flow channels, the second type of coolant flow channels, and the third type of coolant flow channels, wherein the first type of coolant flow channel is disposed between the fuel rod and the inner wall of the fuel rod channel in the graphite block, the second type of coolant flow channel is disposed inside the fuel rod, and the third type of coolant flow channel is disposed in the graphite block and regularly spaced from the fuel rod channel and/or the burnable poison channel.
[15]Preferably, the reactor core further includes an inner pipe disposed inside the pressure pipe and covering an outside of the fuel assembly, wherein the coolant flow channel further includes the fourth type of coolant flow channel disposed between the inner pipe and the pressure pipe and in communication with the first type of coolant flow channels and/or the second type of coolant flow channels and/or the third type of coolant flow channels, respectively, so that coolant entering the fourth coolant flow channel gets converged in the end of reflector, and then flows out through the first type of coolant flow channels and/or the second type of coolant flow channels and/or the third type of coolant flow channels.
[16]Preferably, the fuel unit further includes a moderator material jacket sleeved outside the pressure pipe; and the control rod assembly, including a body and a control rod, is arranged adjacent to the fuel unit, wherein the body has control rod channels in which the control rod is disposed.
[17]Preferably, the fuel unit further includes a moderator material jacket sleeved outside the pressure pipe and having a control rod channel, the control rod assembly includes a body and a control rod, the body is the moderator material jacket, and the control rod is disposed in the control rod channel so that the control rod assembly and the fuel unit are integrally formed.
[18]In a second aspect, the present disclosure further provides a gas-cooled micro-reactor, including the gas-cooled micro-reactor core as described above.
[19]Compared with the existing art, the present disclosure has the following beneficial effects:
[2011. In the present disclosure, the fuel assembly is placed into the pressure pipe, and a modular structure is formed with the pressure pipe bearing the pressure, so that a modular pressure pipe type assembly that is easy to install is obtained, and the problems of massive elements to be transported, complex assembly, and slow response to deployment of a high-temperature gas-cooled reactor are solved.
[2112. By the design of the pressure pipe type assembly, long-time field assembly is avoided, and the transport, assembly and deployment of various components are facilitated. In addition, due to the excellent intrinsic safety, design flexibility, environmental adaptability and convenient transport and assembly, the core has great market potential in the fields of remote mountain power supply, aerospace, island power supply, deep sea power supply and the like.
[22]3. By means of the inner pipe, a fourth type of coolant flow channel used as a coolant inlet can be formed between the pressure pipe and the inner pipe, and the pressure pipe is cooled by the coolant at the inlet, so that the core outside the pressure pipe has a lower temperature, and the requirement of components such as a control rod on high temperature resistance can be reduced. In addition, the graphite jacket and the graphite in the reflector region outside the pressure pipe may be considered to be replaced by a moderator material with better moderating performance but a lower operating temperature, such as beryllium oxide, zirconium hydride, yttrium hydride and the like, so as to further reduce the size of the core.
BRIEF DESCRIPTION OF DRAWINGS
[23]FIG. 1 is a schematic structural diagram of a gas-cooled micro-reactor core according to an embodiment of the present disclosure;
[24]FIG. 2 is a schematic structural diagram of another gas-cooled micro-reactor core according to an embodiment of the present disclosure;
[25]FIG. 3 is an enlarged schematic view of a part of the structure in FIG. 2;
[26]FIG. 4 is a schematic axial sectional view of FIG. 2;
[27]FIG. 5 is a schematic grouping diagram of control rods in the core of FIG.
2;
[28]FIG. 6 is a schematic structural diagram of a control rod according to an embodiment of the present disclosure;
[29]FIG. 7 is a graph showing burnup characteristics of a gas-cooled micro-reactor according to an embodiment of the present disclosure;
[30]FIG. 8 is a normalized assembly power distribution plot of a zero burnup core in a gas-cooled micro-reactor according to an embodiment of the present disclosure with the control rods withdrawn;
[31]FIG. 9 is a graph showing changes in the fuel temperature coefficient of a gas-cooled micro-reactor according to an embodiment of the present disclosure at different burnup points and different temperatures;
[32]FIG. 10 is a graph showing changes in the core graphite temperature coefficient of a gas-cooled micro-reactor according to an embodiment of the present disclosure at different burnup points and different temperatures; and [33]FIG. 11 is a graph showing changes in the reflector graphite temperature coefficient of a gas-cooled micro-reactor according to an embodiment of the present disclosure at different burnup points and different temperatures.
[34]In the drawings: 1. fuel assembly; 2. control rod assembly; 3. side reflector; 4. control rod channel; 5. fuel pellet; 6. coolant flow channel; 7. poison rod; 8.
pressure pipe; 9.
inner pipe; 10. control rod; and 11. control rod cladding.
DETAIL DESCRIPTION OF EMBODIMENTS
[35]To improve understanding of the technical solution of the present disclosure for those skilled in the art, the present disclosure will now be described in detail with the help of accompanying drawings and embodiments.
Embodiment 1 [36]As shown in FIGs. 1 and 2, the present disclosure provides a modular pressure pipe type gas-cooled micro-reactor core, including fuel assemblies 1, reflectors, control rod assemblies 2, and pressure pipes 8.
[37]The reflectors, which completely cover the fuel assembly 1 and the control rod assembly 2, may be made of a graphite material, and may specifically include upper reflectors, lower reflectors, and side reflectors 3. The upper reflectors and the lower reflectors are disposed at two ends of the fuel assembly and the control rod assembly, respectively, and the side reflectors 3 are disposed at side of the fuel assembly and the control rod assembly.
[38]As shown in FIG. 3, the fuel assembly 1 is placed into a pressure pipe 8 to make the pressure pipe 8 act as a pressure bearing boundary of the core, while the reflectors and the control rod assembly 2 are installed outside the pressure pipe 8. The fuel assembly 1 includes a graphite block and fuel rods. The graphite block has fuel rod channels in which the fuel rods are disposed. A coolant flow channel (the first type of coolant flow channel) 6 for circulating coolant is formed between the fuel rod and the graphite block. The fuel rod may have an annular cross section so that a coolant flow channel (the second type of coolant flow channel), also for circulating the coolant, is formed in (at a center of) the fuel rod.
[39]In some implementations, a separate coolant channel (the third type of coolant flow channel) may be further provided in the graphite block. Specifically, the third coolant flow channel may be regularly spaced from the fuel rod channel. For example, a plurality of fuel rod channels may be arranged around one the third type of coolant flow channel, where the third coolant flow channel, also for circulating the coolant, may be disposed along a length direction of the graphite block or the fuel assembly.
[40]In other words, the coolant flow channels in the core of this embodiment may include one or more of the first type of coolant flow channel, the second type of coolant flow channel, and the third type of coolant flow channel.
[41]In some implementations, the core may further include an inner pipe 9, and the coolant flow channel may further include the fourth type of coolant flow channel. The inner pipe 9 is disposed inside the pressure pipe 8 and covers an outside of the fuel assembly. That is, the inner pipe 9 is located between the pressure pipe 8 and the fuel assembly 1, and a gapis left between the inner pipe 9 and the pressure pipe 8 so that a fourth type of coolant flow channel is formed between the pressure pipe 8 and the inner pipe 9.
Moreover, a clearance is left between the top/bottom of the fuel assembly and the upper/lower reflector, and the fourth type of coolant flow channel is in communication with the first type of coolant flow channels and/or the second type of coolant flow channels and/or the third type of coolant flow channels through the clearance between the top/bottom of the fuel assembly and the upper/lowerreflector, respectively, so that the coolant enters the coolant flow channel 6 (i.e., the fourth type of coolant flow channel) between the pressure pipe 8 and the inner pipe 9, gets converged in the top (upper) reflector or the bottom (lower) reflector, and flows out through any one or more of the coolant flow channels (i.e., the first type of coolant flow channels and the second type of coolant flow channels) both inside and outside of the fuel rod formed by the stacked fuel pellets 5 in the fuel channel (i.e., the fuel rod channel) in the fuel assembly 1, or the third type of coolant flow channels.
[42]The fuel rod includes a plurality of fuel pellets 5 stacked in an axial direction (or a length direction of the core). Each fuel pellet 5 is formed by fuel particles dispersed in a silicon carbide matrix. That is, the fuel pellet includes fuel particles and matrix which is made of a silicon carbide material. Each fuel particle includes a fuel kernel and four coating layers covering the fuel kernel. The fuel kernel is made of uranium dioxide, and the coating layer structure is made of high-temperature ceramic. Namely, the fuel particles are ceramic fuel particles.
[43]In this embodiment, the adopted fuel particles being ceramic fuel particles can effectively prevent release of fission products and fuel corrosion; the adopted coolant is helium, a single-phase inert gas; and the graphite block, acting as a neutron moderator and a core structural material as well as reflector material, has the advantages of large heat capacity, high-temperature resistance, high heat conductivity, high moderating ratio, small thermal neutron absorption cross section, and the like. Meanwhile, the use of the annular fuel element (fuel rod) can further improve the safety or economy of the reactor.
[44]By providing the fuel assemblies 1 inside each pressure pipe 8 and the graphite jacket (i.e., the moderator material jacket) outside the pressure pipe 8, the pressure pipe can bear a pressure to form a modular structure so that a modular pressure pipe type assembly (or pressure pipe type fuel assembly) is obtained. The gas-cooled micro-reactor core with the pressure pipe type assembly as the major component is the modular pressure pipe type gas-cooled micro-reactor core.
[45]With the design of the pressure pipe type assembly described in this embodiment, the pressure pipe 8 of the fuel assembly 1 can act as the pressure bearing boundary of the core, while components such as the reflectors and the control rods are not within the pressure boundary, thereby improving the convenience in installation, removal, and transport of those components including the reflectors and the control rods. Meanwhile, by providing the inner pipe, a fourth type of coolant flow channel used as coolant inlet flow passage can be formed between the pressure pipe and the inner pipe, and the pressure pipe is cooled by the coolant at the inlet, so that the core outside the pressure pipe 8 has a lower temperature, and the requirement of components such as control rods on high temperature resistance can be reduced. In addition, the core graphite (such as the graphite jacket) and the graphite in the reflectors outside the pressure pipe 8 may be considered to be replaced by a moderator material with better moderating performance but a lower operating temperature, such as beryllium oxide, zirconium hydride, and the like, so as to further reduce the size of the core.
[46]Specifically, in some implementations, when the disclosed modular pressure pipe type gas-cooled micro-reactor core employs a relatively small pressure pipe type fuel assembly, for example, when the pressure pipe has an inner diameter of 20 cm, the fuel assembly 1, the pressure pipe 8, and the moderator material jacket may together form a fuel assembly unit (also referred to as fuel unit in Embodiment 2), as shown in FIG. 1. The control rod assembly 2 is independently disposed outside the fuel assembly unit, and includes a body and a control rod. The body may be made of a graphite material, and has a control rod channel in which a control rod 10 is disposed. The control rod assembly 2 is arranged adjacent to the fuel assembly unit. In FIG. 1, each fuel assembly unit is adjacent to at least one control rod assembly 2. For ease of arrangement, the body of the control rod assembly 2 and the moderator material jacket (i.e., the graphite jacket) may each have a cross section with a regular hexagon profile.
[47]Specifically, in some other implementations, when the disclosed modular pressure pipe type gas-cooled micro-reactor core employs a relatively large pressure pipe type fuel assembly, for example, when the pressure pipe has an inner diameter of 54 cm, as shown in FIGs. 2 to 4, a control rod channel 4 may be provided in the moderator material jacket outside the pressure pipe 8, the control rod assembly 2 includes a body and a control rod, and the control rod 10 is disposed in the control rod channel 4 of the moderator material jacket so that the control rod 10 and the fuel assembly 1 are integrally formed. In this case, the independent control rod assembly 2 is saved, and the moderator material jacket having the control rod pore channel 4 corresponds to the body of the control rod assembly 2 shown in FIG. 1. In this embodiment, seven pressure pipes 8 may be divided into a group, with six peripheral pressure pipes around one central pressure pipe. The graphite jacket (i.e., the moderator material jacket) has a cross section with a regular hexagon profile, and each graphite jacket may be provided with three control rod pore channels 4 distributed near three vertexes of the hexagonal section of the graphite jacket at intervals.
[48]As shown in FIG. 2, taking the case of seven pressure pipes 8 as an example, the fuel assemblies 1 in the pressure pipes 8 may be divided into 2 regions (a central region and a peripheral region) in a radial direction of the core. One pressure pipe and the fuel assemblies therein are arranged in the central region, while the other 6 pressure pipes and the fuel assemblies therein are arranged in the peripheral region and distributed annularly around a periphery of the central region. The fuel assemblies 1 in each pressure pipe 8 may be arranged in 6 layers in the axial direction of the core (i.e., each pressure pipe 8 includes 6 layers of stacked fuel assemblies 1), resulting in 42 fuel blocks (fuel assemblies 1) in the core in total, where the size, structure and other characteristics of each fuel block may be substantially the same. A burnable poison channel, in which a burnable poison rod (i.e., a poison rod 7) is disposed, is further provided at an edge position of a fuel assembly 1 in the central region of the core. Six burnable poison channels may be provided in this embodiment. That is, six burnable poison rods 7 are arranged at edge positions of the fuel assemblies 1 in the central region of the core. The core may have an overall axial height of 2.7 m, and an overall radial diameter of 2.6 m.
[49]In some implementations, 1 control rod group may be arranged on the fuel assemblies 1 in the central region, while 3 groups may be arranged on the fuel assemblies 1 in the peripheral region, as shown in FIG. 5. The control rod group in the central region of the core may have only 3 rod-shaped control rods, while the other 3 control rod groups in the 6 peripheral fuel assembly regions may each have 6 rod-shaped control rods.
[50]Specifically, as shown in FIG. 5, according to a distance to a central axis of the pressure pipe in the central region, control rods in the control rod channels 4 outside the pressure pipes 8 are divided into a 0th control rod group (CRO), a 1st control rod group (CR1), a 2nd control rod group (CR2), and a 3rd control rod group (CR3). The 0th control rod group is a group of control rods at the center of the core, including 3 rod-shaped control rods. The 1st to 3rd control rod groups, each including 6 rod-shaped control rods, are located around the peripheral pressure pipes of the core, and distributed in concentric circles from near to far according to the distance from the center of the core.
[51]The 0th and 1st control rod groups may be used as shutdown rod groups for emergency shutdown and cold shutdown of the core. The 2nd and 3rd control rod groups may be used as starting rods and regulating rods for compensating reactivity changes, hot shutdown and the like caused by temperature changes, xenon-samarium toxicity, bumup and the like.
[52]As shown in FIG. 6, a control rod cladding 11 covers an outside of the control rod 10 in the control rod assembly 2.
[53]In order to analyze the physical characteristics of the modular pressure pipe type gas-cooled micro-reactor core, a general Monte Carlo code is used in this embodiment to perform modeling and analysis on a gas-cooled micro-reactor adopting the modular pressure pipe type gas-cooled micro-reactor core as described above, where the core temperature is assumed to be 1200K. Specifically:
[54]The calculation result of the burnup characteristics of the gas-cooled micro-reactor is shown in FIG. 7, where at a thermal power of 5MW, the gas-cooled micro-reactor core has a lifetime of about 650EFPD, which satisfies the design lifetime of 1.5 years. The provision of the burnable poison effectively reduces the excess reactivity of the core without causing any reactivity penalty or influencing the lifetime of the core.
[55]The power distribution of the gas-cooled micro-reactor core is shown in FIG. 8, which is an assembly power distribution normalized based on an average power under zero burnup with the control rod completely withdrawn from the core. In the radial direction, the power distribution is relatively uniform, with a radial power peak factor being about 1.21; in the axial direction, the power distribution is presented as a cosine function, with an axial power peak factor being 1.21; and the full reactor assembly power factor is at most 1.46 and at least 0.71. Apparently, the core power distribution can be further optimized if the fuel enrichments are partitioned according to positions of the fuel assemblies.
[56]FIGs. 9 to 11 show calculation results of the temperature reactivity coefficient of the gas-cooled micro-reactor. FIG. 9 shows the fuel temperature coefficient at the beginning of lifetime (0 EFPD) and at the end of lifetime (600 EFPD) at different temperatures, with a value ranging between -2.2 pcm/K and -4.5 pcm/K; FIG. 10 shows the core graphite temperature coefficient at the beginning of lifetime (0 EFPD) and at the end of lifetime (600 EFPD) at different temperatures, with a value ranging between -2.8 pcm/K
and -3.7 pcm/K; and FIG. 11 shows the reflector graphite temperature coefficient at the beginning of lifetime (0 EFPD) and at the end of lifetime (600 EFPD) at different temperatures, with a relatively small positive value ranging between 0.4 and 1.3 pcm/K. A total temperature reactivity coefficient of the core may be approximately regarded as the sum of the fuel temperature coefficient, the core graphite temperature coefficient and the =reflector graphite temperature coefficient, with a value ranging between -4.3 pcm/K and -6.6 pcm/K.
[57]The intrinsic safety of the gas-cooled micro-reactor is mainly embodied in the aspects of core operation and shutdown. Specifically:
[581(1) Emergency shutdown and cold shutdown of the core depend on shutdown rods of the core. Assuming that the core temperature is 300K upon cold shutdown, and considering the "one stuck rod" criterion, 10% uncertainty in the rod value (i.e., the multiplier factor is 0.9), and 10% uncertainty in the positive reactivity caused by temperature reduction (i.e., the multiplier factor is 1.1), the shutdown rods can provide a shutdown margin of at least -4636 pcm, which completely meets the shutdown margin requirement of cold shutdown, that is, -1000 pcm. (2) Hot shutdown of the core depends on starting rods and regulating rods in the core. Assuming that the core temperature is 700K upon hot shutdown, and considering the "one stuck rod" criterion, 10%
uncertainty in the rod value (i.e., the multiplier factor is 0.9), and 10% uncertainty in the positive reactivity caused by temperature reduction (i.e., the multiplier factor is 1.1), the starting rods and the regulating rods can provide a shutdown margin of at least -3765 pcm, which completely meets the shutdown margin requirement of hot shutdown, that is, -1000 pcm.
(3) The maximum intrinsic safety of the gas-cooled micro-reactor is embodied in that no emergency measure is taken under the condition of an accident, and the core is shut down merely depending on temperature negative feedback. Assuming that all control rods are completely ejected, the core has a maximum keff =1.023528 over the lifetime, and an excess reactivity of +2326 pcm. The total temperature reactivity coefficient of the core is between -4.3 pcm/K and -6.6 pcm/K. Assuming that the overall temperature coefficient is -4.3 pcm/K, when the temperature rises to 1740K, the reactor is shut down due to the negative reactivity introduced by the temperature rise, while the core temperature limit is 1600 C (1873K), still leaving a large margin for temperature rise. Therefore, the modular pressure pipe type gas-cooled micro-reactor takes no emergency measure even under accident conditions, and can realize automatic shutdown by merely depending on temperature negative feedback, thereby physically eliminating the possibility of core melting and radioactive substance release.
[59]The design scheme of the modular pressure pipe type gas-cooled micro-reactor core proposed by this embodiment may have a design lifetime of 1.5 years, and a design power of 5 MW. Over the lifetime, when the control rods are withdrawn, the radial power peak factor is about 1.21, the axial power distribution is presented in a cosine function form, and the axial power peak factor is around 1.21. The control rods of the core can implement cold shutdown and hot shutdown, respectively, and are provided with two independent shutdown rod groups. The core has strong temperature negative feedback, and the temperature negative reactivity coefficient can reach at least more than -4 pcm/K. The relatively large margin for temperature rise ensures that automatic shutdown can be implemented by merely depending on the temperature negative feedback under accident conditions without any emergency measure, even if the control rods are completely ejected. The design scheme of the modular pressure pipe type gas-cooled micro-reactor core has good physical properties of the core and excellent intrinsic safety.
[60]In addition, this embodiment can realize designs of different powers and different lifetimes of the reactor type by reasonably designing the core fuel and adjusting parameters such as the core size and the fuel enrichment; can optimize the core power distribution through partition of the enrichment of fuel assemblies at different positions;
can effectively control the reactivity by adjusting the arrangement of burnable poison and control rods; and can further reduce the size of the core by reasonably selecting the moderator material outside the pressure pipe. The design scheme of the modular pressure pipe type gas-cooled micro-reactor core has excellent design flexibility and environmental applicability.
Embodiment 2 [61]As shown in FIGs. 1 and 2, the present disclosure provides a gas-cooled micro-reactor core, including fuel assemblies 1, reflectors, fuel units, and control rod assemblies 2.
The control rod assembly 2 and the fuel unit are both disposed in the reflector. A plurality of fuel units are adopted, and each fuel unit includes a pressure pipe 8 and fuel assemblies 1. The fuel assembly 1 is arranged inside the pressure pipe 8, to make the pressure pipe act as a pressure bearing boundary of the core, and the control rod assembly 2 is arranged outside the pressure pipe 8.
[62]Details of the gas-cooled micro-reactor core according to the present embodiment will be described below.
[63]The pressure pipe 8 may be made of a zirconium-niobium alloy material.
[64]The plurality of fuel units are arranged in a plurality of rings from inside to outside, and a plurality of control rod assemblies 2 are adopted, as shown in FIG. 1.
The control rod assemblies 2 may be arranged outside an outermost ring of fuel units, and/or arranged in any ring of fuel units, and/or arranged between two adjacent rings of fuel units, as shown in FIG. 2.
[65]The reflectors may be made of a graphite material, and may specifically include an upper reflector, a lower reflector, and a side reflector 3. The upper reflector, the lower reflector and the side reflector 3 together completely cover the fuel assemblies 1 and the control rod assemblies 2. The upper reflector and the lower reflector are disposed at two ends of the fuel assembly 1 and the control rod assembly 2, respectively, and as shown in FIG. 4, the side reflector 3 is disposed at side of the fuel assembly 1 and the control rod assembly 2.
[66]Within each pressure pipe 8, the fuel assembly 1 may include a graphite block and fuel rods. As shown in FIGs. 1 to 3, the graphite block has fuel rod channels in which the fuel rods are disposed.
[67]Specifically, a plurality of graphite blocks may be provided in each fuel assembly 1, which may include some complete hexagonal graphite blocks and some incomplete hexagonal graphite blocks. The graphite blocks are sequentially arranged and filled in the pressure pipe 8, while the fuel rod channel may be provided in each of the complete hexagonal graphite blocks, or in each of the incomplete hexagonal graphite blocks, or both. Apparently, the graphite blocks in each fuel assembly 1 may be integrally formed, and not limited to being formed by arranging a plurality of graphite blocks.
[68]The fuel assembly 1 may further include burnable poison rods (i.e., a poison rod 7), and burnable poison channels may be further disposed in the graphite block.
The burnable poison channel is located in the graphite block at an edge position of the fuel assembly and close to the pressure pipe 8. As shown in FIG. 3, the burnable poison rod channel is provided in some incomplete hexagonal graphite blocks, while the burnable poison rod is disposed in the burnable poison rod channel.
[69]The fuel assembly 1 may further include coolant flow channels 6 for circulating coolant. The coolant flow channel 6 may include one or both of the first type of coolant flow channel provided between the fuel rod and an inner wall of the fuel rod channel of the graphite block and the second type of coolant flow channel in the fuel rod. The coolant may be helium, a single phase inert gas.
[70]Specifically, a gap is left between the fuel rod and the graphite block to form the first type of coolant flow channel. The fuel rod has an annular cross section so that the second type of coolant flow channel is formed in (at a center of) the fuel rod.
[71]The coolant flow channel 6 may further include the third type of coolant flow channel (not shown, i.e., the coolant channel in Embodiment 1) in the graphite block.
The third coolant flow channel is independently provided and regularly spaced from the fuel rod channel and/or the burnable poison channel. For example, a plurality of fuel rod channels may be arranged around one third type of coolant flow channel, where the third type of coolant flow channel may be disposed along a length direction of the graphite block or the fuel assembly 1.
[72]The core may further include an inner pipe 9 disposed inside the pressure pipe 8 and covering an outside of the fuel assembly 1. In other words, the inner pipe 9 is located between the pressure pipe 8 and the fuel assembly 1. The coolant flow channel 6 may further include the fourth type of coolant flow channel disposed between the inner pipe 9 and the pressure pipe 8 and in communication with the first type of coolant flow channels and/or the second type of coolant flow channels and/or the third type of coolant flow channels, respectively, so that a coolant entering the fourth type of coolant flow channel gets converged in the reflector, and then flows out through the first type of coolant flow channel and/or the second type of coolant flow channel and/or the third type of coolant flow channel.
[73]Specifically, a gap is left between the inner pipe 9 and the pressure pipe 8 so that a fourth type of coolant flow channel is formed between the pressure pipe 8 and the inner pipe 9 by providing the inner pipe 9. The inner pipe 9 may be made of a zirconium-niobium alloy material. Further, a clearance is left between a top/bottom of the fuel assembly 1 and the upper/lower reflector, and the fourth type of coolant flow channel is in communication with the first type of coolant flow channel and/or the second type of coolant flow channel and/or the third type of coolant flow channel through the clearance between the top/bottom of the fuel assembly and the upper/lower reflector, respectively, so that the coolant enters the fourth type of coolant flow channel between the pressure pipe 8 and the inner pipe 9, gets converged in the top (upper) reflector or the bottom (lower) reflector, and then flows out through any one or more of the first type of coolant flow channel between the fuel rod and the inner wall of the fuel rod channel in the graphite block, the second type of coolant flow channel in the annular fuel rod, and the third type of coolant flow channel between the inner pipe 9 and the pressure pipe 8.
[74]The fuel rod includes a plurality of fuel pellets 5 stacked along an axial direction (or a length direction of the core). Each fuel pellet 5 includes fuel particles and matrix in which the fuel particles are dispersed. In other words, the fuel pellet 5 is formed by fuel particles dispersed in a silicon carbide matrix. The matrix may be made of a silicon carbide material. Each fuel particle includes a fuel kernel and coatinglayers covering an outside of the fuel kernel. The coating layer may include one layer or multiple layers, such as four layers. The fuel kernel is made of uranium dioxide, and the coating layer is made of high-temperature ceramic. Namely, the fuel particles are ceramic fuel particles.
[75]In this embodiment, the adopted fuel particles being ceramic fuel particles can effectively prevent release of fission products and fuel corrosion; the adopted coolant is helium, a single-phase inert gas; and the graphite block, acting as a neutron moderator and a core structural material as well as reflector material, has the advantages of large heat capacity, high-temperature resistance, high heat conductivity, high moderating ratio, small thermal neutron absorption cross section, and the like. Meanwhile, the use of the annular fuel element (fuel rod)can further improve the safety or economy of the reactor.
[76]In some implementations, the fuel unit may further include a moderator material jacket sleeved outside the pressure pipe 8. The moderator material jacket may be made of a graphite material, that is, the moderator material jacket may be a graphite jacket layer.
The control rod assembly 2, including a body and a control rod 10, is arranged adjacent to the fuel unit. The body has a control rod channel in which the control rod 10 is disposed.
[77]Specifically, when the disclosed gas-cooled micro-reactor core employs a relatively small pressure pipe type fuel assembly, for example, when the pressure pipe has an inner diameter of 20 cm, the fuel assembly 1, the pressure pipe 8, and the moderator material jacket may together form a fuel unit (also referred to as fuel assembly unit in Embodiment 1), as shown in FIG. 1. The control rod assembly 2 is independently disposed outside the fuel unit. The body of the control rod assembly 2 has a control rod channel in which the control rod 10 is disposed. The control rod assembly 2 is arranged adjacent to the fuel unit. In FIG. 1, each fuel unit is adjacent to at least one control rod assembly 2. For ease of arrangement, the body of the control rod assembly 2 and the moderator material jacket may each have a cross section with a regular hexagon profile.
[78]In some other implementations, the fuel unit further includes a moderator material jacket sleeved outside the pressure pipe 8. The moderator material jacket may be made of a graphite material, that is, the moderator material jacket may be a graphite jacket layer.
A control rod channel 4 is provided in the moderator material jacket. The control rod assembly 2 includes a body and a control rod 10, where the body forms the moderator material jacket, and the control rod 10 is disposed in the control rod channel 4 so that the control rod assembly 2 and the fuel unit are integrally formed.
[79]Specifically, when the disclosed gas-cooled micro-reactor core employs a relatively large pressure pipe type fuel assembly, for example, when the pressure pipe has an inner diameter of 54 cm, as shown in FIGs. 2 to 4, a control rod channel 4 may be provided in the moderator material jacket outside the pressure pipe 8, and the control rod 10 may be disposed in the control rod channel 4 of the moderator material jacket so that the control rod assembly 2 and the fuel unit are integrally formed. In this case, the independent control rod assembly 2 is saved, the moderator material jacket having the control rod channel 4 corresponds to the body of the control rod assembly 2 shown in FIG. 1, and the control rod 10 and the fuel assembly 1 are integrally formed. In this implementation, seven pressure pipes 8 may be divided into a group, with six peripheral pressure pipes around one central pressure pipe. The graphite jacket (i.e., the moderator material jacket) has a cross section with a regular hexagon profile, and each graphite jacket may be provided with three control rod channels 4 distributed near three vertexes of the hexagonal section of the graphite jacket at intervals.
[80]As shown in FIG. 2, taking the case of seven pressure pipes 8 as an example, the fuel assemblies 1 in the pressure pipes 8 may be divided into 2 regions (a central region and a peripheral region) in a radial direction of the core. One pressure pipe and the fuel assemblies therein are arranged in the central region, while the other 6 pressure pipes and the fuel assemblies therein are arranged in the peripheral region and distributed annularly around a periphery of the central region. The fuel assemblies 1 in each pressure pipe 8 may be arranged in 6 layers in the axial direction of the core (i.e., each pressure pipe 8 includes 6 layers of stacked fuel assemblies 1), resulting in 42 fuel blocks (fuel assemblies 1) in the core in total, where the size, structure and other characteristics of each fuel block may be substantially the same. The burnable poison channel is disposed in the graphite block at an edge position of the fuel assembly 1 in the central region of the core, and six burnable poison channels may be provided in this embodiment. That is, six burnable poison rods 7 are arranged at edge positions of the fuel assemblies 1 in the central region of the core. The core may have an overall axial height of 2.7 m, and an overall radial diameter of 2.6 m.
[81]In some implementations, 1 control rod group may be arranged on the fuel assemblies 1 in the central region, whi1e3 groups may be arranged on the fuel assemblies 1 in the peripheral region, as shown in FIG. 5. The control rod group in the central region of the core may have only 3 rod-shaped control rods, while the other 3 control rod groups in the 6 peripheral fuel assembly regions may each have 6 rod-shaped control rods.
[82]Specifically, as shown in FIG. 5, according to a distance to a central axis of the pressure pipe in the central region, control rods in the control rod channels 4 outside the pressure pipes 8 are divided into a 0th control rod group (CRO), a 1st control rod group (CR1), a 2nd control rod group (CR2), and a 3rd control rod group (CR3). The 0th control rod group is a group of control rods at the center of the core, including 3 rod-shaped control rods. The 1st to 3rd control rod groups, each including 6 rod-shaped control rods, are located around the peripheral pressure pipes of the core, and distributed in concentric circles from near to far according to the distance from the center of the core.
[83]The 0th and 1st control rod groups may be used as shutdown rod groups for emergency shutdown and cold shutdown of the core. The 2nd and 3rd control rod groups may be used as starting rods and regulating rods for compensating reactivity changes, hot shutdown and the like caused by temperature changes, xenon-samarium toxicity, bumup and the like.
[84]As shown in FIG. 6, a control rod cladding 11 covers an outside of the control rod 10.
[85]In this embodiment, by providing the fuel assemblies 1 inside each pressure pipe 8 and the moderator material jacket (i.e., the graphite jacket) outside the pressure pipe 8, the pressure pipe can bear a pressure to form a modular structure, so that a modular pressure pipe type fuel assembly (or pressure pipe type assembly) is obtained.
In other words, the gas-cooled micro-reactor core of this embodiment is a modular pressure pipe type gas-cooled micro-reactor core.
[86]With the design of the pressure pipe type fuel assembly described in this embodiment, the pressure pipe 8 of the fuel assembly 1 can act as the pressure bearing boundary of the core, while components such as the reflector and the control rod are not within the pressure boundary, thereby improving the convenience in installation, removal, and transport of those components including the reflector and the control rod. Meanwhile, by providing the inner pipe, the fourth type of coolant flow channel used as a coolant inlet flow passage can be formed between the pressure pipe and the inner pipe, and the pressure pipe is cooled by the coolant at the inlet, so that the core outside the pressure pipe 8 has a lower temperature, and the requirement of components such as control rods on high temperature resistance can be reduced. In addition, the graphite jacket and the graphite in the reflector outside the pressure pipe 8 may be considered to be replaced by a moderator material with better moderating performance but a lower operating temperature, such as beryllium oxide, zirconium hydride, and the like, so as to further reduce the size of the core.
[87]According to the core of this embodiment, the fuel assembly is placed into the pressure pipe, and a modular structure is formed with the pressure pipe bearing pressure, so that a modular pressure pipe type assembly that is easy to install is obtained, and the problems of massive elements to be transported, complex assembly, and slow response to deployment of a high-temperature gas-cooled reactor are solved. In addition, due to the excellent intrinsic safety, design flexibility, environmental adaptability and convenient transport and assembly, the core has great market potential in the fields of remote mountain power supply, aerospace, island power supply, deep sea power supply and the like.
[88]This embodiment further discloses a gas-cooled micro-reactor, including the gas-cooled micro-reactor core as described above.
[89]In order to analyze the physical characteristics of the gas-cooled micro-reactor core, a general Monte Carlo code is used in this embodiment to perform modeling and analysis on a gas-cooled micro-reactor with a core temperature assumed to be 1200K.
Specifically:
[90]The calculation result of the burnup characteristics of the gas-cooled micro-reactor is shown in FIG. 7, whereat a thermal power of 5MW, the gas-cooled micro-reactor core has a lifetime of about 650EFPD, which satisfies the design lifetime of 1.5 years.
The provision of the burnable poison effectively reduces the excess reactivity of the core without causing any reactivity penalty or influencing the lifetime of the core.
[91]The power distribution of the gas-cooled micro-reactor core is as shown in FIG. 8, which is a assembly power distribution normalized based on an average power under zero burnup with the control rod completely withdrawn from the core. In the radial direction, the power distribution is relatively uniform, with a radial power peak factor being about 1.21; in the axial direction, the power distribution is presented as a cosine function, with an axial power peak factor being 1.21; and the full reactor assembly power factor is at most 1.46 and at least 0.71. Apparently, the core power distribution can be further optimized if the fuel enrichments are partitioned according to positions of the fuel assemblies.
[92]FIGs. 9 to 11 show calculation results of the temperature reactivity coefficient of the gas-cooled micro-reactor. FIG. 9 shows the fuel temperature coefficient at the beginning of lifetime (0 EFPD) and at the end of lifetime (600 EFPD) at different temperatures, with a value ranging between -2.2 pcm/K and -4.5 pcm/K; FIG. 10 shows the core graphite temperature coefficient at the beginning of lifetime (0 EFPD) and at the end of lifetime (600 EFPD) at different temperatures, with a value ranging between -2.8 pcm/K
and -3.7 pcm/K; and FIG. 11 shows the reflector graphite temperature coefficient at the beginning of lifetime (0 EFPD) and at the end of lifetime (600 EFPD) at different temperatures, with a relatively small positive value ranging between 0.4 and 1.3 pcm/K.
As the core cooling performance and the heat conduction performance of the gas-cooled micro-reactor are better, the temperature difference between the fuel and the core graphite is very small and the temperature change is almost synchronous. A total temperature reactivity coefficient of the core may be approximately regarded as the sum of the fuel temperature coefficient, the core graphite temperature coefficient and the reflector graphite temperature coefficient, with a value ranging between -4.3 pcm/K and -6.6 pcm/K.
[93]The intrinsic safety of the gas-cooled micro-reactor is mainly embodied in the aspects of core operation and shutdown. Specifically:
[94](1) Emergency shutdown and cold shutdown of the core depend on shutdown rods of the core. Assuming that the core temperature is 300K upon cold shutdown, and considering the "one stuck rod" criterion, 10% uncertainty in the rod value (i.e., the multiplier factor is 0.9), and 10% uncertainty in the positive reactivity caused by temperature reduction (i.e., the multiplier factor is 1.1), the shutdown rods can provide a shutdown margin of at least -4636 pcm, which completely meets the shutdown margin requirement of cold shutdown, that is, -1000 pcm. (2) Hot shutdown of the core depends on starting rods and regulating rods in the core. Assuming that the core temperature is 700K upon hot shutdown, and considering the "one stuck rod" criterion, 10%
uncertainty in the rod value (i.e., the multiplier factor is 0.9), and 10% uncertainty in the positive reactivity caused by temperature reduction (i.e., the multiplier factor is 1.1), the starting rods and the regulating rods can provide a shutdown margin of at least -3765 pcm, which completely meets the shutdown margin requirement of hot shutdown, that is, -1000 pcm.
(3) The maximum intrinsic safety of the gas-cooled micro-reactor is embodied in that no emergency measure is taken under the condition of an accident, and the core is shut down merely depending on temperature negative feedback. Assuming that all control rods are completely ejected, the core has a maximum keff =1.023528 over the lifetime, and an excess reactivity of +2326 pcm. The total temperature reactivity coefficient of the core is between -4.3 pcm/K and -6.6 pcm/K. Assuming that the overall temperature coefficient is -4.3 pcm/K, when the temperature rises to 1740K, the reactor is shut down due to the negative reactivity introduced by the temperature rise, while the core temperature limit is 1600 C (1873K), still leaving a large margin for temperature rise. Therefore, the modular pressure pipe type gas-cooled micro-reactor takes no emergency measure even under accident conditions, and can realize automatic shutdown by merely depending on temperature negative feedback, thereby physically eliminating the possibility of core melting and radioactive substance release.
[95]The design scheme of the gas-cooled micro-reactor core proposed by this embodiment may have a design lifetime of 1.5 years, and a design power of 5 MW. Over the lifetime, when the control rod is withdrawn, the radial power peak factor is about 1.21, the axial power distribution is presented in a cosine function form, and the axial power peak factor is around 1.21. The control rods of the core can implement cold shutdown and hot shutdown, respectively, and are provided with two independent shutdown rod groups. The core has strong temperature negative feedback, and the temperature negative reactivity coefficient can reach at least more than -4 pcm/K. The relatively large margin for temperature rise ensures that automatic shutdown can be implemented by merely depending on the temperature negative feedback under accident conditions without any emergency measure, even if the control rods are completely ejected. The design scheme of the modular pressure pipe type gas-cooled micro-reactor core has good physical properties of the core and excellent intrinsic safety.
[96]In addition, this embodiment can realize designs of different powers and different lifetimes of the reactor type by reasonably designing the core fuel and adjusting parameters such as the core size and the fuel enrichment; can optimize the core power distribution through partition of the enrichment of fuel assemblies at different positions;
can effectively control the reactivity by adjusting the arrangement of burnable poison and control rods; and can further reduce the size of the core by reasonably selecting the moderator material outside the pressure pipe. The design scheme of the gas-cooled micro-reactor core has excellent design flexibility and environmental applicability.
[97]It will be appreciated that the above embodiments are merely exemplary implementations for the purpose of illustrating the principle of the present disclosure, and the present disclosure is not limited thereto. It will be apparent to one of ordinary skill in the art that various modifications and variations may be made without departing from the spirit or essence of the present disclosure. Such modifications and variations should also be considered as falling into the protection scope of the present disclosure.
[2011. In the present disclosure, the fuel assembly is placed into the pressure pipe, and a modular structure is formed with the pressure pipe bearing the pressure, so that a modular pressure pipe type assembly that is easy to install is obtained, and the problems of massive elements to be transported, complex assembly, and slow response to deployment of a high-temperature gas-cooled reactor are solved.
[2112. By the design of the pressure pipe type assembly, long-time field assembly is avoided, and the transport, assembly and deployment of various components are facilitated. In addition, due to the excellent intrinsic safety, design flexibility, environmental adaptability and convenient transport and assembly, the core has great market potential in the fields of remote mountain power supply, aerospace, island power supply, deep sea power supply and the like.
[22]3. By means of the inner pipe, a fourth type of coolant flow channel used as a coolant inlet can be formed between the pressure pipe and the inner pipe, and the pressure pipe is cooled by the coolant at the inlet, so that the core outside the pressure pipe has a lower temperature, and the requirement of components such as a control rod on high temperature resistance can be reduced. In addition, the graphite jacket and the graphite in the reflector region outside the pressure pipe may be considered to be replaced by a moderator material with better moderating performance but a lower operating temperature, such as beryllium oxide, zirconium hydride, yttrium hydride and the like, so as to further reduce the size of the core.
BRIEF DESCRIPTION OF DRAWINGS
[23]FIG. 1 is a schematic structural diagram of a gas-cooled micro-reactor core according to an embodiment of the present disclosure;
[24]FIG. 2 is a schematic structural diagram of another gas-cooled micro-reactor core according to an embodiment of the present disclosure;
[25]FIG. 3 is an enlarged schematic view of a part of the structure in FIG. 2;
[26]FIG. 4 is a schematic axial sectional view of FIG. 2;
[27]FIG. 5 is a schematic grouping diagram of control rods in the core of FIG.
2;
[28]FIG. 6 is a schematic structural diagram of a control rod according to an embodiment of the present disclosure;
[29]FIG. 7 is a graph showing burnup characteristics of a gas-cooled micro-reactor according to an embodiment of the present disclosure;
[30]FIG. 8 is a normalized assembly power distribution plot of a zero burnup core in a gas-cooled micro-reactor according to an embodiment of the present disclosure with the control rods withdrawn;
[31]FIG. 9 is a graph showing changes in the fuel temperature coefficient of a gas-cooled micro-reactor according to an embodiment of the present disclosure at different burnup points and different temperatures;
[32]FIG. 10 is a graph showing changes in the core graphite temperature coefficient of a gas-cooled micro-reactor according to an embodiment of the present disclosure at different burnup points and different temperatures; and [33]FIG. 11 is a graph showing changes in the reflector graphite temperature coefficient of a gas-cooled micro-reactor according to an embodiment of the present disclosure at different burnup points and different temperatures.
[34]In the drawings: 1. fuel assembly; 2. control rod assembly; 3. side reflector; 4. control rod channel; 5. fuel pellet; 6. coolant flow channel; 7. poison rod; 8.
pressure pipe; 9.
inner pipe; 10. control rod; and 11. control rod cladding.
DETAIL DESCRIPTION OF EMBODIMENTS
[35]To improve understanding of the technical solution of the present disclosure for those skilled in the art, the present disclosure will now be described in detail with the help of accompanying drawings and embodiments.
Embodiment 1 [36]As shown in FIGs. 1 and 2, the present disclosure provides a modular pressure pipe type gas-cooled micro-reactor core, including fuel assemblies 1, reflectors, control rod assemblies 2, and pressure pipes 8.
[37]The reflectors, which completely cover the fuel assembly 1 and the control rod assembly 2, may be made of a graphite material, and may specifically include upper reflectors, lower reflectors, and side reflectors 3. The upper reflectors and the lower reflectors are disposed at two ends of the fuel assembly and the control rod assembly, respectively, and the side reflectors 3 are disposed at side of the fuel assembly and the control rod assembly.
[38]As shown in FIG. 3, the fuel assembly 1 is placed into a pressure pipe 8 to make the pressure pipe 8 act as a pressure bearing boundary of the core, while the reflectors and the control rod assembly 2 are installed outside the pressure pipe 8. The fuel assembly 1 includes a graphite block and fuel rods. The graphite block has fuel rod channels in which the fuel rods are disposed. A coolant flow channel (the first type of coolant flow channel) 6 for circulating coolant is formed between the fuel rod and the graphite block. The fuel rod may have an annular cross section so that a coolant flow channel (the second type of coolant flow channel), also for circulating the coolant, is formed in (at a center of) the fuel rod.
[39]In some implementations, a separate coolant channel (the third type of coolant flow channel) may be further provided in the graphite block. Specifically, the third coolant flow channel may be regularly spaced from the fuel rod channel. For example, a plurality of fuel rod channels may be arranged around one the third type of coolant flow channel, where the third coolant flow channel, also for circulating the coolant, may be disposed along a length direction of the graphite block or the fuel assembly.
[40]In other words, the coolant flow channels in the core of this embodiment may include one or more of the first type of coolant flow channel, the second type of coolant flow channel, and the third type of coolant flow channel.
[41]In some implementations, the core may further include an inner pipe 9, and the coolant flow channel may further include the fourth type of coolant flow channel. The inner pipe 9 is disposed inside the pressure pipe 8 and covers an outside of the fuel assembly. That is, the inner pipe 9 is located between the pressure pipe 8 and the fuel assembly 1, and a gapis left between the inner pipe 9 and the pressure pipe 8 so that a fourth type of coolant flow channel is formed between the pressure pipe 8 and the inner pipe 9.
Moreover, a clearance is left between the top/bottom of the fuel assembly and the upper/lower reflector, and the fourth type of coolant flow channel is in communication with the first type of coolant flow channels and/or the second type of coolant flow channels and/or the third type of coolant flow channels through the clearance between the top/bottom of the fuel assembly and the upper/lowerreflector, respectively, so that the coolant enters the coolant flow channel 6 (i.e., the fourth type of coolant flow channel) between the pressure pipe 8 and the inner pipe 9, gets converged in the top (upper) reflector or the bottom (lower) reflector, and flows out through any one or more of the coolant flow channels (i.e., the first type of coolant flow channels and the second type of coolant flow channels) both inside and outside of the fuel rod formed by the stacked fuel pellets 5 in the fuel channel (i.e., the fuel rod channel) in the fuel assembly 1, or the third type of coolant flow channels.
[42]The fuel rod includes a plurality of fuel pellets 5 stacked in an axial direction (or a length direction of the core). Each fuel pellet 5 is formed by fuel particles dispersed in a silicon carbide matrix. That is, the fuel pellet includes fuel particles and matrix which is made of a silicon carbide material. Each fuel particle includes a fuel kernel and four coating layers covering the fuel kernel. The fuel kernel is made of uranium dioxide, and the coating layer structure is made of high-temperature ceramic. Namely, the fuel particles are ceramic fuel particles.
[43]In this embodiment, the adopted fuel particles being ceramic fuel particles can effectively prevent release of fission products and fuel corrosion; the adopted coolant is helium, a single-phase inert gas; and the graphite block, acting as a neutron moderator and a core structural material as well as reflector material, has the advantages of large heat capacity, high-temperature resistance, high heat conductivity, high moderating ratio, small thermal neutron absorption cross section, and the like. Meanwhile, the use of the annular fuel element (fuel rod) can further improve the safety or economy of the reactor.
[44]By providing the fuel assemblies 1 inside each pressure pipe 8 and the graphite jacket (i.e., the moderator material jacket) outside the pressure pipe 8, the pressure pipe can bear a pressure to form a modular structure so that a modular pressure pipe type assembly (or pressure pipe type fuel assembly) is obtained. The gas-cooled micro-reactor core with the pressure pipe type assembly as the major component is the modular pressure pipe type gas-cooled micro-reactor core.
[45]With the design of the pressure pipe type assembly described in this embodiment, the pressure pipe 8 of the fuel assembly 1 can act as the pressure bearing boundary of the core, while components such as the reflectors and the control rods are not within the pressure boundary, thereby improving the convenience in installation, removal, and transport of those components including the reflectors and the control rods. Meanwhile, by providing the inner pipe, a fourth type of coolant flow channel used as coolant inlet flow passage can be formed between the pressure pipe and the inner pipe, and the pressure pipe is cooled by the coolant at the inlet, so that the core outside the pressure pipe 8 has a lower temperature, and the requirement of components such as control rods on high temperature resistance can be reduced. In addition, the core graphite (such as the graphite jacket) and the graphite in the reflectors outside the pressure pipe 8 may be considered to be replaced by a moderator material with better moderating performance but a lower operating temperature, such as beryllium oxide, zirconium hydride, and the like, so as to further reduce the size of the core.
[46]Specifically, in some implementations, when the disclosed modular pressure pipe type gas-cooled micro-reactor core employs a relatively small pressure pipe type fuel assembly, for example, when the pressure pipe has an inner diameter of 20 cm, the fuel assembly 1, the pressure pipe 8, and the moderator material jacket may together form a fuel assembly unit (also referred to as fuel unit in Embodiment 2), as shown in FIG. 1. The control rod assembly 2 is independently disposed outside the fuel assembly unit, and includes a body and a control rod. The body may be made of a graphite material, and has a control rod channel in which a control rod 10 is disposed. The control rod assembly 2 is arranged adjacent to the fuel assembly unit. In FIG. 1, each fuel assembly unit is adjacent to at least one control rod assembly 2. For ease of arrangement, the body of the control rod assembly 2 and the moderator material jacket (i.e., the graphite jacket) may each have a cross section with a regular hexagon profile.
[47]Specifically, in some other implementations, when the disclosed modular pressure pipe type gas-cooled micro-reactor core employs a relatively large pressure pipe type fuel assembly, for example, when the pressure pipe has an inner diameter of 54 cm, as shown in FIGs. 2 to 4, a control rod channel 4 may be provided in the moderator material jacket outside the pressure pipe 8, the control rod assembly 2 includes a body and a control rod, and the control rod 10 is disposed in the control rod channel 4 of the moderator material jacket so that the control rod 10 and the fuel assembly 1 are integrally formed. In this case, the independent control rod assembly 2 is saved, and the moderator material jacket having the control rod pore channel 4 corresponds to the body of the control rod assembly 2 shown in FIG. 1. In this embodiment, seven pressure pipes 8 may be divided into a group, with six peripheral pressure pipes around one central pressure pipe. The graphite jacket (i.e., the moderator material jacket) has a cross section with a regular hexagon profile, and each graphite jacket may be provided with three control rod pore channels 4 distributed near three vertexes of the hexagonal section of the graphite jacket at intervals.
[48]As shown in FIG. 2, taking the case of seven pressure pipes 8 as an example, the fuel assemblies 1 in the pressure pipes 8 may be divided into 2 regions (a central region and a peripheral region) in a radial direction of the core. One pressure pipe and the fuel assemblies therein are arranged in the central region, while the other 6 pressure pipes and the fuel assemblies therein are arranged in the peripheral region and distributed annularly around a periphery of the central region. The fuel assemblies 1 in each pressure pipe 8 may be arranged in 6 layers in the axial direction of the core (i.e., each pressure pipe 8 includes 6 layers of stacked fuel assemblies 1), resulting in 42 fuel blocks (fuel assemblies 1) in the core in total, where the size, structure and other characteristics of each fuel block may be substantially the same. A burnable poison channel, in which a burnable poison rod (i.e., a poison rod 7) is disposed, is further provided at an edge position of a fuel assembly 1 in the central region of the core. Six burnable poison channels may be provided in this embodiment. That is, six burnable poison rods 7 are arranged at edge positions of the fuel assemblies 1 in the central region of the core. The core may have an overall axial height of 2.7 m, and an overall radial diameter of 2.6 m.
[49]In some implementations, 1 control rod group may be arranged on the fuel assemblies 1 in the central region, while 3 groups may be arranged on the fuel assemblies 1 in the peripheral region, as shown in FIG. 5. The control rod group in the central region of the core may have only 3 rod-shaped control rods, while the other 3 control rod groups in the 6 peripheral fuel assembly regions may each have 6 rod-shaped control rods.
[50]Specifically, as shown in FIG. 5, according to a distance to a central axis of the pressure pipe in the central region, control rods in the control rod channels 4 outside the pressure pipes 8 are divided into a 0th control rod group (CRO), a 1st control rod group (CR1), a 2nd control rod group (CR2), and a 3rd control rod group (CR3). The 0th control rod group is a group of control rods at the center of the core, including 3 rod-shaped control rods. The 1st to 3rd control rod groups, each including 6 rod-shaped control rods, are located around the peripheral pressure pipes of the core, and distributed in concentric circles from near to far according to the distance from the center of the core.
[51]The 0th and 1st control rod groups may be used as shutdown rod groups for emergency shutdown and cold shutdown of the core. The 2nd and 3rd control rod groups may be used as starting rods and regulating rods for compensating reactivity changes, hot shutdown and the like caused by temperature changes, xenon-samarium toxicity, bumup and the like.
[52]As shown in FIG. 6, a control rod cladding 11 covers an outside of the control rod 10 in the control rod assembly 2.
[53]In order to analyze the physical characteristics of the modular pressure pipe type gas-cooled micro-reactor core, a general Monte Carlo code is used in this embodiment to perform modeling and analysis on a gas-cooled micro-reactor adopting the modular pressure pipe type gas-cooled micro-reactor core as described above, where the core temperature is assumed to be 1200K. Specifically:
[54]The calculation result of the burnup characteristics of the gas-cooled micro-reactor is shown in FIG. 7, where at a thermal power of 5MW, the gas-cooled micro-reactor core has a lifetime of about 650EFPD, which satisfies the design lifetime of 1.5 years. The provision of the burnable poison effectively reduces the excess reactivity of the core without causing any reactivity penalty or influencing the lifetime of the core.
[55]The power distribution of the gas-cooled micro-reactor core is shown in FIG. 8, which is an assembly power distribution normalized based on an average power under zero burnup with the control rod completely withdrawn from the core. In the radial direction, the power distribution is relatively uniform, with a radial power peak factor being about 1.21; in the axial direction, the power distribution is presented as a cosine function, with an axial power peak factor being 1.21; and the full reactor assembly power factor is at most 1.46 and at least 0.71. Apparently, the core power distribution can be further optimized if the fuel enrichments are partitioned according to positions of the fuel assemblies.
[56]FIGs. 9 to 11 show calculation results of the temperature reactivity coefficient of the gas-cooled micro-reactor. FIG. 9 shows the fuel temperature coefficient at the beginning of lifetime (0 EFPD) and at the end of lifetime (600 EFPD) at different temperatures, with a value ranging between -2.2 pcm/K and -4.5 pcm/K; FIG. 10 shows the core graphite temperature coefficient at the beginning of lifetime (0 EFPD) and at the end of lifetime (600 EFPD) at different temperatures, with a value ranging between -2.8 pcm/K
and -3.7 pcm/K; and FIG. 11 shows the reflector graphite temperature coefficient at the beginning of lifetime (0 EFPD) and at the end of lifetime (600 EFPD) at different temperatures, with a relatively small positive value ranging between 0.4 and 1.3 pcm/K. A total temperature reactivity coefficient of the core may be approximately regarded as the sum of the fuel temperature coefficient, the core graphite temperature coefficient and the =reflector graphite temperature coefficient, with a value ranging between -4.3 pcm/K and -6.6 pcm/K.
[57]The intrinsic safety of the gas-cooled micro-reactor is mainly embodied in the aspects of core operation and shutdown. Specifically:
[581(1) Emergency shutdown and cold shutdown of the core depend on shutdown rods of the core. Assuming that the core temperature is 300K upon cold shutdown, and considering the "one stuck rod" criterion, 10% uncertainty in the rod value (i.e., the multiplier factor is 0.9), and 10% uncertainty in the positive reactivity caused by temperature reduction (i.e., the multiplier factor is 1.1), the shutdown rods can provide a shutdown margin of at least -4636 pcm, which completely meets the shutdown margin requirement of cold shutdown, that is, -1000 pcm. (2) Hot shutdown of the core depends on starting rods and regulating rods in the core. Assuming that the core temperature is 700K upon hot shutdown, and considering the "one stuck rod" criterion, 10%
uncertainty in the rod value (i.e., the multiplier factor is 0.9), and 10% uncertainty in the positive reactivity caused by temperature reduction (i.e., the multiplier factor is 1.1), the starting rods and the regulating rods can provide a shutdown margin of at least -3765 pcm, which completely meets the shutdown margin requirement of hot shutdown, that is, -1000 pcm.
(3) The maximum intrinsic safety of the gas-cooled micro-reactor is embodied in that no emergency measure is taken under the condition of an accident, and the core is shut down merely depending on temperature negative feedback. Assuming that all control rods are completely ejected, the core has a maximum keff =1.023528 over the lifetime, and an excess reactivity of +2326 pcm. The total temperature reactivity coefficient of the core is between -4.3 pcm/K and -6.6 pcm/K. Assuming that the overall temperature coefficient is -4.3 pcm/K, when the temperature rises to 1740K, the reactor is shut down due to the negative reactivity introduced by the temperature rise, while the core temperature limit is 1600 C (1873K), still leaving a large margin for temperature rise. Therefore, the modular pressure pipe type gas-cooled micro-reactor takes no emergency measure even under accident conditions, and can realize automatic shutdown by merely depending on temperature negative feedback, thereby physically eliminating the possibility of core melting and radioactive substance release.
[59]The design scheme of the modular pressure pipe type gas-cooled micro-reactor core proposed by this embodiment may have a design lifetime of 1.5 years, and a design power of 5 MW. Over the lifetime, when the control rods are withdrawn, the radial power peak factor is about 1.21, the axial power distribution is presented in a cosine function form, and the axial power peak factor is around 1.21. The control rods of the core can implement cold shutdown and hot shutdown, respectively, and are provided with two independent shutdown rod groups. The core has strong temperature negative feedback, and the temperature negative reactivity coefficient can reach at least more than -4 pcm/K. The relatively large margin for temperature rise ensures that automatic shutdown can be implemented by merely depending on the temperature negative feedback under accident conditions without any emergency measure, even if the control rods are completely ejected. The design scheme of the modular pressure pipe type gas-cooled micro-reactor core has good physical properties of the core and excellent intrinsic safety.
[60]In addition, this embodiment can realize designs of different powers and different lifetimes of the reactor type by reasonably designing the core fuel and adjusting parameters such as the core size and the fuel enrichment; can optimize the core power distribution through partition of the enrichment of fuel assemblies at different positions;
can effectively control the reactivity by adjusting the arrangement of burnable poison and control rods; and can further reduce the size of the core by reasonably selecting the moderator material outside the pressure pipe. The design scheme of the modular pressure pipe type gas-cooled micro-reactor core has excellent design flexibility and environmental applicability.
Embodiment 2 [61]As shown in FIGs. 1 and 2, the present disclosure provides a gas-cooled micro-reactor core, including fuel assemblies 1, reflectors, fuel units, and control rod assemblies 2.
The control rod assembly 2 and the fuel unit are both disposed in the reflector. A plurality of fuel units are adopted, and each fuel unit includes a pressure pipe 8 and fuel assemblies 1. The fuel assembly 1 is arranged inside the pressure pipe 8, to make the pressure pipe act as a pressure bearing boundary of the core, and the control rod assembly 2 is arranged outside the pressure pipe 8.
[62]Details of the gas-cooled micro-reactor core according to the present embodiment will be described below.
[63]The pressure pipe 8 may be made of a zirconium-niobium alloy material.
[64]The plurality of fuel units are arranged in a plurality of rings from inside to outside, and a plurality of control rod assemblies 2 are adopted, as shown in FIG. 1.
The control rod assemblies 2 may be arranged outside an outermost ring of fuel units, and/or arranged in any ring of fuel units, and/or arranged between two adjacent rings of fuel units, as shown in FIG. 2.
[65]The reflectors may be made of a graphite material, and may specifically include an upper reflector, a lower reflector, and a side reflector 3. The upper reflector, the lower reflector and the side reflector 3 together completely cover the fuel assemblies 1 and the control rod assemblies 2. The upper reflector and the lower reflector are disposed at two ends of the fuel assembly 1 and the control rod assembly 2, respectively, and as shown in FIG. 4, the side reflector 3 is disposed at side of the fuel assembly 1 and the control rod assembly 2.
[66]Within each pressure pipe 8, the fuel assembly 1 may include a graphite block and fuel rods. As shown in FIGs. 1 to 3, the graphite block has fuel rod channels in which the fuel rods are disposed.
[67]Specifically, a plurality of graphite blocks may be provided in each fuel assembly 1, which may include some complete hexagonal graphite blocks and some incomplete hexagonal graphite blocks. The graphite blocks are sequentially arranged and filled in the pressure pipe 8, while the fuel rod channel may be provided in each of the complete hexagonal graphite blocks, or in each of the incomplete hexagonal graphite blocks, or both. Apparently, the graphite blocks in each fuel assembly 1 may be integrally formed, and not limited to being formed by arranging a plurality of graphite blocks.
[68]The fuel assembly 1 may further include burnable poison rods (i.e., a poison rod 7), and burnable poison channels may be further disposed in the graphite block.
The burnable poison channel is located in the graphite block at an edge position of the fuel assembly and close to the pressure pipe 8. As shown in FIG. 3, the burnable poison rod channel is provided in some incomplete hexagonal graphite blocks, while the burnable poison rod is disposed in the burnable poison rod channel.
[69]The fuel assembly 1 may further include coolant flow channels 6 for circulating coolant. The coolant flow channel 6 may include one or both of the first type of coolant flow channel provided between the fuel rod and an inner wall of the fuel rod channel of the graphite block and the second type of coolant flow channel in the fuel rod. The coolant may be helium, a single phase inert gas.
[70]Specifically, a gap is left between the fuel rod and the graphite block to form the first type of coolant flow channel. The fuel rod has an annular cross section so that the second type of coolant flow channel is formed in (at a center of) the fuel rod.
[71]The coolant flow channel 6 may further include the third type of coolant flow channel (not shown, i.e., the coolant channel in Embodiment 1) in the graphite block.
The third coolant flow channel is independently provided and regularly spaced from the fuel rod channel and/or the burnable poison channel. For example, a plurality of fuel rod channels may be arranged around one third type of coolant flow channel, where the third type of coolant flow channel may be disposed along a length direction of the graphite block or the fuel assembly 1.
[72]The core may further include an inner pipe 9 disposed inside the pressure pipe 8 and covering an outside of the fuel assembly 1. In other words, the inner pipe 9 is located between the pressure pipe 8 and the fuel assembly 1. The coolant flow channel 6 may further include the fourth type of coolant flow channel disposed between the inner pipe 9 and the pressure pipe 8 and in communication with the first type of coolant flow channels and/or the second type of coolant flow channels and/or the third type of coolant flow channels, respectively, so that a coolant entering the fourth type of coolant flow channel gets converged in the reflector, and then flows out through the first type of coolant flow channel and/or the second type of coolant flow channel and/or the third type of coolant flow channel.
[73]Specifically, a gap is left between the inner pipe 9 and the pressure pipe 8 so that a fourth type of coolant flow channel is formed between the pressure pipe 8 and the inner pipe 9 by providing the inner pipe 9. The inner pipe 9 may be made of a zirconium-niobium alloy material. Further, a clearance is left between a top/bottom of the fuel assembly 1 and the upper/lower reflector, and the fourth type of coolant flow channel is in communication with the first type of coolant flow channel and/or the second type of coolant flow channel and/or the third type of coolant flow channel through the clearance between the top/bottom of the fuel assembly and the upper/lower reflector, respectively, so that the coolant enters the fourth type of coolant flow channel between the pressure pipe 8 and the inner pipe 9, gets converged in the top (upper) reflector or the bottom (lower) reflector, and then flows out through any one or more of the first type of coolant flow channel between the fuel rod and the inner wall of the fuel rod channel in the graphite block, the second type of coolant flow channel in the annular fuel rod, and the third type of coolant flow channel between the inner pipe 9 and the pressure pipe 8.
[74]The fuel rod includes a plurality of fuel pellets 5 stacked along an axial direction (or a length direction of the core). Each fuel pellet 5 includes fuel particles and matrix in which the fuel particles are dispersed. In other words, the fuel pellet 5 is formed by fuel particles dispersed in a silicon carbide matrix. The matrix may be made of a silicon carbide material. Each fuel particle includes a fuel kernel and coatinglayers covering an outside of the fuel kernel. The coating layer may include one layer or multiple layers, such as four layers. The fuel kernel is made of uranium dioxide, and the coating layer is made of high-temperature ceramic. Namely, the fuel particles are ceramic fuel particles.
[75]In this embodiment, the adopted fuel particles being ceramic fuel particles can effectively prevent release of fission products and fuel corrosion; the adopted coolant is helium, a single-phase inert gas; and the graphite block, acting as a neutron moderator and a core structural material as well as reflector material, has the advantages of large heat capacity, high-temperature resistance, high heat conductivity, high moderating ratio, small thermal neutron absorption cross section, and the like. Meanwhile, the use of the annular fuel element (fuel rod)can further improve the safety or economy of the reactor.
[76]In some implementations, the fuel unit may further include a moderator material jacket sleeved outside the pressure pipe 8. The moderator material jacket may be made of a graphite material, that is, the moderator material jacket may be a graphite jacket layer.
The control rod assembly 2, including a body and a control rod 10, is arranged adjacent to the fuel unit. The body has a control rod channel in which the control rod 10 is disposed.
[77]Specifically, when the disclosed gas-cooled micro-reactor core employs a relatively small pressure pipe type fuel assembly, for example, when the pressure pipe has an inner diameter of 20 cm, the fuel assembly 1, the pressure pipe 8, and the moderator material jacket may together form a fuel unit (also referred to as fuel assembly unit in Embodiment 1), as shown in FIG. 1. The control rod assembly 2 is independently disposed outside the fuel unit. The body of the control rod assembly 2 has a control rod channel in which the control rod 10 is disposed. The control rod assembly 2 is arranged adjacent to the fuel unit. In FIG. 1, each fuel unit is adjacent to at least one control rod assembly 2. For ease of arrangement, the body of the control rod assembly 2 and the moderator material jacket may each have a cross section with a regular hexagon profile.
[78]In some other implementations, the fuel unit further includes a moderator material jacket sleeved outside the pressure pipe 8. The moderator material jacket may be made of a graphite material, that is, the moderator material jacket may be a graphite jacket layer.
A control rod channel 4 is provided in the moderator material jacket. The control rod assembly 2 includes a body and a control rod 10, where the body forms the moderator material jacket, and the control rod 10 is disposed in the control rod channel 4 so that the control rod assembly 2 and the fuel unit are integrally formed.
[79]Specifically, when the disclosed gas-cooled micro-reactor core employs a relatively large pressure pipe type fuel assembly, for example, when the pressure pipe has an inner diameter of 54 cm, as shown in FIGs. 2 to 4, a control rod channel 4 may be provided in the moderator material jacket outside the pressure pipe 8, and the control rod 10 may be disposed in the control rod channel 4 of the moderator material jacket so that the control rod assembly 2 and the fuel unit are integrally formed. In this case, the independent control rod assembly 2 is saved, the moderator material jacket having the control rod channel 4 corresponds to the body of the control rod assembly 2 shown in FIG. 1, and the control rod 10 and the fuel assembly 1 are integrally formed. In this implementation, seven pressure pipes 8 may be divided into a group, with six peripheral pressure pipes around one central pressure pipe. The graphite jacket (i.e., the moderator material jacket) has a cross section with a regular hexagon profile, and each graphite jacket may be provided with three control rod channels 4 distributed near three vertexes of the hexagonal section of the graphite jacket at intervals.
[80]As shown in FIG. 2, taking the case of seven pressure pipes 8 as an example, the fuel assemblies 1 in the pressure pipes 8 may be divided into 2 regions (a central region and a peripheral region) in a radial direction of the core. One pressure pipe and the fuel assemblies therein are arranged in the central region, while the other 6 pressure pipes and the fuel assemblies therein are arranged in the peripheral region and distributed annularly around a periphery of the central region. The fuel assemblies 1 in each pressure pipe 8 may be arranged in 6 layers in the axial direction of the core (i.e., each pressure pipe 8 includes 6 layers of stacked fuel assemblies 1), resulting in 42 fuel blocks (fuel assemblies 1) in the core in total, where the size, structure and other characteristics of each fuel block may be substantially the same. The burnable poison channel is disposed in the graphite block at an edge position of the fuel assembly 1 in the central region of the core, and six burnable poison channels may be provided in this embodiment. That is, six burnable poison rods 7 are arranged at edge positions of the fuel assemblies 1 in the central region of the core. The core may have an overall axial height of 2.7 m, and an overall radial diameter of 2.6 m.
[81]In some implementations, 1 control rod group may be arranged on the fuel assemblies 1 in the central region, whi1e3 groups may be arranged on the fuel assemblies 1 in the peripheral region, as shown in FIG. 5. The control rod group in the central region of the core may have only 3 rod-shaped control rods, while the other 3 control rod groups in the 6 peripheral fuel assembly regions may each have 6 rod-shaped control rods.
[82]Specifically, as shown in FIG. 5, according to a distance to a central axis of the pressure pipe in the central region, control rods in the control rod channels 4 outside the pressure pipes 8 are divided into a 0th control rod group (CRO), a 1st control rod group (CR1), a 2nd control rod group (CR2), and a 3rd control rod group (CR3). The 0th control rod group is a group of control rods at the center of the core, including 3 rod-shaped control rods. The 1st to 3rd control rod groups, each including 6 rod-shaped control rods, are located around the peripheral pressure pipes of the core, and distributed in concentric circles from near to far according to the distance from the center of the core.
[83]The 0th and 1st control rod groups may be used as shutdown rod groups for emergency shutdown and cold shutdown of the core. The 2nd and 3rd control rod groups may be used as starting rods and regulating rods for compensating reactivity changes, hot shutdown and the like caused by temperature changes, xenon-samarium toxicity, bumup and the like.
[84]As shown in FIG. 6, a control rod cladding 11 covers an outside of the control rod 10.
[85]In this embodiment, by providing the fuel assemblies 1 inside each pressure pipe 8 and the moderator material jacket (i.e., the graphite jacket) outside the pressure pipe 8, the pressure pipe can bear a pressure to form a modular structure, so that a modular pressure pipe type fuel assembly (or pressure pipe type assembly) is obtained.
In other words, the gas-cooled micro-reactor core of this embodiment is a modular pressure pipe type gas-cooled micro-reactor core.
[86]With the design of the pressure pipe type fuel assembly described in this embodiment, the pressure pipe 8 of the fuel assembly 1 can act as the pressure bearing boundary of the core, while components such as the reflector and the control rod are not within the pressure boundary, thereby improving the convenience in installation, removal, and transport of those components including the reflector and the control rod. Meanwhile, by providing the inner pipe, the fourth type of coolant flow channel used as a coolant inlet flow passage can be formed between the pressure pipe and the inner pipe, and the pressure pipe is cooled by the coolant at the inlet, so that the core outside the pressure pipe 8 has a lower temperature, and the requirement of components such as control rods on high temperature resistance can be reduced. In addition, the graphite jacket and the graphite in the reflector outside the pressure pipe 8 may be considered to be replaced by a moderator material with better moderating performance but a lower operating temperature, such as beryllium oxide, zirconium hydride, and the like, so as to further reduce the size of the core.
[87]According to the core of this embodiment, the fuel assembly is placed into the pressure pipe, and a modular structure is formed with the pressure pipe bearing pressure, so that a modular pressure pipe type assembly that is easy to install is obtained, and the problems of massive elements to be transported, complex assembly, and slow response to deployment of a high-temperature gas-cooled reactor are solved. In addition, due to the excellent intrinsic safety, design flexibility, environmental adaptability and convenient transport and assembly, the core has great market potential in the fields of remote mountain power supply, aerospace, island power supply, deep sea power supply and the like.
[88]This embodiment further discloses a gas-cooled micro-reactor, including the gas-cooled micro-reactor core as described above.
[89]In order to analyze the physical characteristics of the gas-cooled micro-reactor core, a general Monte Carlo code is used in this embodiment to perform modeling and analysis on a gas-cooled micro-reactor with a core temperature assumed to be 1200K.
Specifically:
[90]The calculation result of the burnup characteristics of the gas-cooled micro-reactor is shown in FIG. 7, whereat a thermal power of 5MW, the gas-cooled micro-reactor core has a lifetime of about 650EFPD, which satisfies the design lifetime of 1.5 years.
The provision of the burnable poison effectively reduces the excess reactivity of the core without causing any reactivity penalty or influencing the lifetime of the core.
[91]The power distribution of the gas-cooled micro-reactor core is as shown in FIG. 8, which is a assembly power distribution normalized based on an average power under zero burnup with the control rod completely withdrawn from the core. In the radial direction, the power distribution is relatively uniform, with a radial power peak factor being about 1.21; in the axial direction, the power distribution is presented as a cosine function, with an axial power peak factor being 1.21; and the full reactor assembly power factor is at most 1.46 and at least 0.71. Apparently, the core power distribution can be further optimized if the fuel enrichments are partitioned according to positions of the fuel assemblies.
[92]FIGs. 9 to 11 show calculation results of the temperature reactivity coefficient of the gas-cooled micro-reactor. FIG. 9 shows the fuel temperature coefficient at the beginning of lifetime (0 EFPD) and at the end of lifetime (600 EFPD) at different temperatures, with a value ranging between -2.2 pcm/K and -4.5 pcm/K; FIG. 10 shows the core graphite temperature coefficient at the beginning of lifetime (0 EFPD) and at the end of lifetime (600 EFPD) at different temperatures, with a value ranging between -2.8 pcm/K
and -3.7 pcm/K; and FIG. 11 shows the reflector graphite temperature coefficient at the beginning of lifetime (0 EFPD) and at the end of lifetime (600 EFPD) at different temperatures, with a relatively small positive value ranging between 0.4 and 1.3 pcm/K.
As the core cooling performance and the heat conduction performance of the gas-cooled micro-reactor are better, the temperature difference between the fuel and the core graphite is very small and the temperature change is almost synchronous. A total temperature reactivity coefficient of the core may be approximately regarded as the sum of the fuel temperature coefficient, the core graphite temperature coefficient and the reflector graphite temperature coefficient, with a value ranging between -4.3 pcm/K and -6.6 pcm/K.
[93]The intrinsic safety of the gas-cooled micro-reactor is mainly embodied in the aspects of core operation and shutdown. Specifically:
[94](1) Emergency shutdown and cold shutdown of the core depend on shutdown rods of the core. Assuming that the core temperature is 300K upon cold shutdown, and considering the "one stuck rod" criterion, 10% uncertainty in the rod value (i.e., the multiplier factor is 0.9), and 10% uncertainty in the positive reactivity caused by temperature reduction (i.e., the multiplier factor is 1.1), the shutdown rods can provide a shutdown margin of at least -4636 pcm, which completely meets the shutdown margin requirement of cold shutdown, that is, -1000 pcm. (2) Hot shutdown of the core depends on starting rods and regulating rods in the core. Assuming that the core temperature is 700K upon hot shutdown, and considering the "one stuck rod" criterion, 10%
uncertainty in the rod value (i.e., the multiplier factor is 0.9), and 10% uncertainty in the positive reactivity caused by temperature reduction (i.e., the multiplier factor is 1.1), the starting rods and the regulating rods can provide a shutdown margin of at least -3765 pcm, which completely meets the shutdown margin requirement of hot shutdown, that is, -1000 pcm.
(3) The maximum intrinsic safety of the gas-cooled micro-reactor is embodied in that no emergency measure is taken under the condition of an accident, and the core is shut down merely depending on temperature negative feedback. Assuming that all control rods are completely ejected, the core has a maximum keff =1.023528 over the lifetime, and an excess reactivity of +2326 pcm. The total temperature reactivity coefficient of the core is between -4.3 pcm/K and -6.6 pcm/K. Assuming that the overall temperature coefficient is -4.3 pcm/K, when the temperature rises to 1740K, the reactor is shut down due to the negative reactivity introduced by the temperature rise, while the core temperature limit is 1600 C (1873K), still leaving a large margin for temperature rise. Therefore, the modular pressure pipe type gas-cooled micro-reactor takes no emergency measure even under accident conditions, and can realize automatic shutdown by merely depending on temperature negative feedback, thereby physically eliminating the possibility of core melting and radioactive substance release.
[95]The design scheme of the gas-cooled micro-reactor core proposed by this embodiment may have a design lifetime of 1.5 years, and a design power of 5 MW. Over the lifetime, when the control rod is withdrawn, the radial power peak factor is about 1.21, the axial power distribution is presented in a cosine function form, and the axial power peak factor is around 1.21. The control rods of the core can implement cold shutdown and hot shutdown, respectively, and are provided with two independent shutdown rod groups. The core has strong temperature negative feedback, and the temperature negative reactivity coefficient can reach at least more than -4 pcm/K. The relatively large margin for temperature rise ensures that automatic shutdown can be implemented by merely depending on the temperature negative feedback under accident conditions without any emergency measure, even if the control rods are completely ejected. The design scheme of the modular pressure pipe type gas-cooled micro-reactor core has good physical properties of the core and excellent intrinsic safety.
[96]In addition, this embodiment can realize designs of different powers and different lifetimes of the reactor type by reasonably designing the core fuel and adjusting parameters such as the core size and the fuel enrichment; can optimize the core power distribution through partition of the enrichment of fuel assemblies at different positions;
can effectively control the reactivity by adjusting the arrangement of burnable poison and control rods; and can further reduce the size of the core by reasonably selecting the moderator material outside the pressure pipe. The design scheme of the gas-cooled micro-reactor core has excellent design flexibility and environmental applicability.
[97]It will be appreciated that the above embodiments are merely exemplary implementations for the purpose of illustrating the principle of the present disclosure, and the present disclosure is not limited thereto. It will be apparent to one of ordinary skill in the art that various modifications and variations may be made without departing from the spirit or essence of the present disclosure. Such modifications and variations should also be considered as falling into the protection scope of the present disclosure.
20
Claims (11)
1. A gas-cooled micro-reactor core, characterized in comprising reflectors, fuel units, and control rod assemblies, wherein the control rod assembly and the fuel unit are both disposed in the reflectors, a plurality of fuel units are adopted, and each fuel unit comprises a pressure pipe and fuel assemblies, wherein the fuel assembly is arranged inside the pressure pipe, to make the pressure pipe act as a pressure bearing boundary of the core, and the control rod assembly is arranged outside the pressure pipe.
2. The gas-cooled micro-reactor core according to claim 1, characterized in that the plurality of fuel units are arranged in a plurality of rings from inside to outside, and a plurality of control rod assemblies are adopted and arranged outside an outermost ring of fuel units, and/or arranged in any ring of fuel units, and/or arranged between two adjacent rings of fuel units.
3. The gas-cooled micro-reactor core according to claim 1, characterized in that within each pressure pipe, the fuel assembly comprises a graphite block and fuel rods, and the graphite block has fuel rod channels in which the fuel rods are disposed.
4. The gas-cooled micro-reactor core according to claim 3, characterized in that the fuel assembly further comprises burnable poison rods, and the graphite block further has burnable poison channels in which the burnable poison rods are disposed.
5. The gas-cooled micro-reactor core according to claim 4, characterized in that the fuel rod comprises a plurality of fuel pellets stacked along a length direction of the core; wherein each fuel pellet comprises fuel particles and matrix in which the fuel particles are dispersed.
6. The gas-cooled micro-reactor core according to claim 5, characterized in that each fuel particle comprises a fuel kernel and coating layers covering the fuel kernel.
7. The gas-cooled micro-reactor core according to claim 5, characterized in that the fuel assembly further comprises coolant flow channels comprising one or more of the first type of coolant flow channel, the second type of coolant flow channel, and the third type of coolant flow channel, wherein the first type of coolant flow channel is disposed between the fuel rod and an inner wall of the fuel rod channel in the graphite block, the second type of coolant flow channel is disposed in the fuel rod, and the third type of coolant flow channel is disposed in the graphite block and regularly spaced from the fuel rod channel and/or the burnable poison channel.
8. The gas-cooled micro-reactor core according to claim 7, characterized in further comprising an inner pipe disposed inside the pressure pipe and covering the outside of the fuel assembly, wherein the coolant flow channel further comprises the fourth type of coolant flow channel disposed between the inner pipe and the pressure pipe and in communication with the first type of coolant flow channel and/or the second type of coolant flow channel and/or the third type of coolant flow channel, respectively, so that coolant entering the fourth type of coolant flow channel gets converged in the reflectors, and then flows out through the first type of coolant flow channel and/or the second type of coolant flow channel and/or the third type of coolant flow channel.
9. The gas-cooled micro-reactor core according to any one of claims 1 to 8, characterized in that the fuel unit further comprises a moderator material jacket sleeved outside the pressure pipe; and the control rod assembly, comprising a body and a control rod, is arranged adjacent to the fuel unit, wherein the body has a control rod channel in which the control rod is disposed.
10. The gas-cooled micro-reactor core according to any one of claims 1 to 8, characterized in that the fuel unit further comprises a moderator material jacket sleeved outside the pressure pipe and having a control rod channel, the control rod assembly comprises a body and a control rod, the body forms the moderator material jacket, and the control rod is disposed in the control rod channel so that the control rod assembly and the fuel unit are integrally formed.
11. A gas-cooled micro-reactor, characterized in comprising the gas-cooled micro-reactor core according to any one of claims 1 to 10.
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| CN202110332498.1A CN113270205B (en) | 2021-03-29 | 2021-03-29 | Modularized pressure pipe type gas-cooled micro-reactor core |
| CN202110332498.1 | 2021-03-29 | ||
| PCT/CN2021/142915 WO2022206072A1 (en) | 2021-03-29 | 2021-12-30 | Gas-cooled micro-reactor core and gas-cooled micro-reactor |
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| CN113270205B (en) * | 2021-03-29 | 2023-12-22 | 中国核电工程有限公司 | Modularized pressure pipe type gas-cooled micro-reactor core |
| CN115101221B (en) * | 2022-08-05 | 2023-05-02 | 西安交通大学 | Integrated movable air-cooled miniature power reactor core |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1236331A (en) * | 1968-02-09 | 1971-06-23 | Hitachi Ltd | Pressure tube type fuel assembly for nuclear reactor |
| DE3016402A1 (en) * | 1980-04-29 | 1981-11-05 | GHT Gesellschaft für Hochtemperaturreaktor-Technik mbH, 5060 Bergisch Gladbach | HIGH-TEMPERATURE REACTOR IN MODULAR DESIGN |
| DE3335452A1 (en) * | 1983-09-30 | 1985-04-18 | Hochtemperatur-Reaktorbau GmbH, 4600 Dortmund | Control and shutdown device for a high temperature reactor |
| CN103137221A (en) * | 2013-01-15 | 2013-06-05 | 西安交通大学 | Subcritical wrapping layer of transmutation of pressure pipe type long-lived fission product |
| CN103778972B (en) * | 2014-02-24 | 2017-01-25 | 中国科学院合肥物质科学研究院 | Control rod assembly comprising axial partition control rod and heavy metal absorber rod |
| CN105405475B (en) * | 2015-10-30 | 2017-04-19 | 西安交通大学 | Long-service-life supercritical carbon dioxide cooled reactor |
| CN106229015B (en) * | 2016-08-24 | 2018-09-11 | 中国核动力研究设计院 | A kind of high-temperature molten salt pressure pipe and pipe tube type graphite high-temperature molten salt reactor |
| CN106683720B (en) * | 2017-01-13 | 2018-01-30 | 中国核动力研究设计院 | A kind of shell-and-tube lead-containing alloy cooled reactor |
| CN109801723A (en) * | 2019-01-29 | 2019-05-24 | 哈尔滨工程大学 | A kind of liquid fuel heat pipe reactor |
| CN110232979B (en) * | 2019-06-13 | 2020-09-01 | 西安交通大学 | Open grid type gas-cooled space nuclear reactor core |
| CN110634580B (en) * | 2019-09-26 | 2022-05-13 | 哈尔滨工程大学 | Heat pipe type deep sea application nuclear reactor system |
| CN113270205B (en) * | 2021-03-29 | 2023-12-22 | 中国核电工程有限公司 | Modularized pressure pipe type gas-cooled micro-reactor core |
-
2021
- 2021-03-29 CN CN202110332498.1A patent/CN113270205B/en active Active
- 2021-12-30 WO PCT/CN2021/142915 patent/WO2022206072A1/en active Application Filing
- 2021-12-30 CA CA3212783A patent/CA3212783A1/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| CN113270205A (en) | 2021-08-17 |
| WO2022206072A1 (en) | 2022-10-06 |
| CN113270205B (en) | 2023-12-22 |
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