CN113851233A - Radial shielding structure of molten salt reactor and molten salt reactor comprising same - Google Patents
Radial shielding structure of molten salt reactor and molten salt reactor comprising same Download PDFInfo
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- CN113851233A CN113851233A CN202111021313.1A CN202111021313A CN113851233A CN 113851233 A CN113851233 A CN 113851233A CN 202111021313 A CN202111021313 A CN 202111021313A CN 113851233 A CN113851233 A CN 113851233A
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- 150000003839 salts Chemical class 0.000 title claims abstract description 126
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 167
- 229910002804 graphite Inorganic materials 0.000 claims abstract description 164
- 239000010439 graphite Substances 0.000 claims abstract description 164
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 claims abstract description 134
- 229910052796 boron Inorganic materials 0.000 claims abstract description 134
- 239000000956 alloy Substances 0.000 claims abstract description 47
- 229910045601 alloy Inorganic materials 0.000 claims abstract description 44
- 239000000463 material Substances 0.000 claims abstract description 23
- 239000001307 helium Substances 0.000 claims abstract description 13
- 229910052734 helium Inorganic materials 0.000 claims abstract description 13
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 claims abstract description 13
- 239000002245 particle Substances 0.000 claims description 26
- 229910052580 B4C Inorganic materials 0.000 claims description 23
- INAHAJYZKVIDIZ-UHFFFAOYSA-N boron carbide Chemical compound B12B3B4C32B41 INAHAJYZKVIDIZ-UHFFFAOYSA-N 0.000 claims description 23
- 239000000446 fuel Substances 0.000 claims description 19
- 229910010271 silicon carbide Inorganic materials 0.000 claims description 18
- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 claims description 18
- 239000011449 brick Substances 0.000 claims description 17
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 claims description 12
- 239000011248 coating agent Substances 0.000 claims description 12
- 238000000576 coating method Methods 0.000 claims description 12
- 239000000758 substrate Substances 0.000 claims description 8
- 229910000856 hastalloy Inorganic materials 0.000 claims description 6
- 229910052759 nickel Inorganic materials 0.000 claims description 6
- 239000007770 graphite material Substances 0.000 claims description 4
- 239000011159 matrix material Substances 0.000 claims description 4
- 239000000126 substance Substances 0.000 claims description 4
- 230000000712 assembly Effects 0.000 claims description 3
- 238000000429 assembly Methods 0.000 claims description 3
- 239000011882 ultra-fine particle Substances 0.000 claims description 2
- 230000002093 peripheral effect Effects 0.000 claims 1
- 230000005855 radiation Effects 0.000 abstract description 10
- 239000012611 container material Substances 0.000 abstract description 2
- 230000004907 flux Effects 0.000 description 13
- 238000013461 design Methods 0.000 description 6
- 230000000694 effects Effects 0.000 description 5
- 239000007789 gas Substances 0.000 description 5
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 4
- 229910052799 carbon Inorganic materials 0.000 description 3
- 230000000052 comparative effect Effects 0.000 description 3
- 230000004992 fission Effects 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 238000000034 method Methods 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 239000010935 stainless steel Substances 0.000 description 2
- 229910001220 stainless steel Inorganic materials 0.000 description 2
- 238000000342 Monte Carlo simulation Methods 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000005253 cladding Methods 0.000 description 1
- 238000004140 cleaning Methods 0.000 description 1
- 239000004567 concrete Substances 0.000 description 1
- 239000002826 coolant Substances 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 238000009434 installation Methods 0.000 description 1
- 239000011133 lead Substances 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 238000009377 nuclear transmutation Methods 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 230000002265 prevention Effects 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 238000012106 screening analysis Methods 0.000 description 1
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 description 1
- 229910052721 tungsten Inorganic materials 0.000 description 1
- 239000010937 tungsten Substances 0.000 description 1
Images
Classifications
-
- G—PHYSICS
- G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
- G21C—NUCLEAR REACTORS
- G21C13/00—Pressure vessels; Containment vessels; Containment in general
- G21C13/08—Vessels characterised by the material; Selection of materials for pressure vessels
-
- 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
- G21C3/42—Selection of substances for use as reactor fuel
- G21C3/44—Fluid or fluent reactor fuel
- G21C3/54—Fused salt, oxide or hydroxide compositions
-
- G—PHYSICS
- G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
- G21F—PROTECTION AGAINST X-RADIATION, GAMMA RADIATION, CORPUSCULAR RADIATION OR PARTICLE BOMBARDMENT; TREATING RADIOACTIVELY CONTAMINATED MATERIAL; DECONTAMINATION ARRANGEMENTS THEREFOR
- G21F1/00—Shielding characterised by the composition of the materials
- G21F1/12—Laminated shielding materials
- G21F1/125—Laminated shielding materials comprising metals
-
- 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)
- General Engineering & Computer Science (AREA)
- High Energy & Nuclear Physics (AREA)
- Plasma & Fusion (AREA)
- Ceramic Products (AREA)
- Carbon And Carbon Compounds (AREA)
Abstract
The invention discloses a radial shielding structure of a molten salt reactor and the molten salt reactor comprising the same. This radial shielding structure of fused salt heap, from the active area of fused salt heap to outlying direction, include in proper order: the molten salt reactor comprises a reflecting layer, a boron-containing graphite layer and an alloy shielding layer, wherein the reflecting layer coats an active region of the molten salt reactor, the boron-containing graphite layer coats the reflecting layer, and the alloy shielding layer coats the boron-containing graphite layer. The radial shielding structure of the molten salt reactor can reduce the radiation damage of the structural material and the reactor container material in the molten salt reactor, including the off-site atom damage rate and the helium generation rate, and can effectively reduce the radiation dose of neutrons and photons outside the reactor.
Description
Technical Field
The invention relates to a radial shielding structure of a molten salt reactor and the molten salt reactor comprising the same.
Background
The molten salt reactor as a fourth generation nuclear reactor has the advantages of economy, safety, sustainability, nuclear diffusion prevention and the like. The small modular molten salt reactor SM-MSR (small modular reactor) has the advantages of flexible site selection, modular installation and the like, combines the inherent advantages of safety, online refueling, good neutron economy and the like of the molten salt reactor, and has good development prospect. However, since the internal structural members are not easily replaced and the external shielding structure is limited, attention needs to be paid to the life of the reactor and the design of the internal shielding of the reactor.
At present, heavy elements such as tungsten, lead and stainless steel are generally used for shielding photons in a reactor, and light materials such as water, concrete, graphite or boron carbide are used for shielding neutrons. The goal of most shield designs is radiation protection outside of the reactor building. While the screening analysis of the reactor internals does not give sufficient attention.
In MSFR (molten salt fast reactor), curved sidewalls are employed as an in-stack shielding structure to reduce radiation damage to the main vessel. In HTGR (high temperature gas cooled reactor), the in-reactor shield employs a reactor core fixed reflector block to slow fast neutrons and boron carbide (B)4C) The side shield layer consisting of the pressed combination with carbon and the sus316 stainless steel shell served as the reactor internal shield. However, in a molten salt pile, boron carbide cannot be used as the boron-containing material in the pile, mainly because of incompatibility with the molten salt. In a pressurized water reactor, water serving as a reactor core coolant and a moderator has a good shielding effect on a main container and has an obvious effect on the attenuation of neutrons, the small modular reactor is made of graphite, the moderating capability of the graphite is weaker than that of water, the fuel in the molten salt reactor is directly contacted with structural materials such as a reactor core tank and a reactor container, the neutron flux and the gamma flux generated by reaction are relatively large, and the requirements on the radiation resistance and the corrosion resistance of the materials are high.
In a small modular molten salt reactor, the graphite reflector may also reduce fast neutron damage to the main vessel, but it brings a higher thermal neutron flux, which produces a large amount of helium in the main vessel. At present, a small modular molten salt reactor is in a conceptual design stage, the neutron physics and the thermal engineering safety are researched more, and the research on the stage of the integral shielding design of the reactor is less.
In summary, due to the particularity of miniaturization, high flux in the stack, limited overall shielding weight and thickness of the stack, and the like, how to reduce helium brittleness of the stack container and radiation damage dpa of structural materials by using the in-stack shielding method and reduce design thickness of the out-stack shielding is an urgent problem to be solved.
Disclosure of Invention
The invention aims to overcome the defect that irradiation damage to materials of an in-pile structure and materials of a pile container of a small modular molten salt pile in the prior art is large, and provides a radial shielding structure of the molten salt pile and the molten salt pile. The radial shielding structure of the molten salt reactor can reduce the irradiation damage of the structural material and the reactor container material in the molten salt reactor, including the off-site atom damage rate and the helium generation rate, and can effectively reduce the radiation dose of neutrons and photons outside the reactor.
The invention solves the technical problems through the following technical scheme.
A molten salt reactor radial shielding structure sequentially comprises the following components from an active area to the periphery of the molten salt reactor: the molten salt reactor comprises a reflecting layer, a boron-containing graphite layer and an alloy shielding layer, wherein the reflecting layer coats an active region of the molten salt reactor, the boron-containing graphite layer coats the reflecting layer, and the alloy shielding layer coats the boron-containing graphite layer.
In the present invention, the molten salt stack refers to a small-sized modular molten salt stack that is conventional in the art. The thermal power of the molten salt stack may be that of a small modular molten salt stack conventional in the art, such as 150 MWt.
In the present invention, the active zone refers to the active zone in a small modular molten salt stack as is conventional in the art.
Wherein the active region may be assembled from an array of fuel assemblies as is conventional in the art. Preferably, the fuel assembly is a smallest unit consisting of a graphite member and a molten salt channel located at the center thereof; the graphite member is preferably hexagonal prism graphite.
Wherein the radius of the active zone may be the radius of the active zone of a small modular molten salt stack conventional in the art, for example 135 cm.
In the present invention, the reflective layer may be a graphite reflective layer that is conventional in the art. The material of the graphite reflecting layer can be nuclear grade graphite material in a molten salt reactor, such as ultrafine particle graphite, which is conventional in the field. The reflecting layer in the invention can fully moderate fast neutrons, and reduce the irradiation fluence rate of the fast neutrons to the reactor core graphite material and the irradiation fluence rate of the alloy container.
In the present invention, the boron-containing graphite layer may be a graphite layer containing a boron element, which is conventional in the art.
Wherein, the boron element can be B-10 element which is conventional in the field.
Wherein, the mass fraction of the boron element is preferably 3-5%, more preferably 5%, and the% is the mass percentage of boron in the boron-containing graphite layer.
In the present invention, it is preferable that the surface of the boron-containing graphite layer is free from boron element, that is, boron element is present in the interior of the boron-containing graphite layer. For example: and injecting boron element into the graphite reflecting layer to obtain the boron-containing graphite layer.
More preferably, the boron element in the boron-containing graphite layer exists in the interior of the boron-containing graphite layer in the form of B-10 simple substance and/or coated boron-containing particles.
In the present invention, preferably, the boron-containing graphite layer comprises a graphite coating.
In the invention, preferably, the boron-containing graphite layer comprises a graphite coating and a boron-containing graphite brick.
In the present invention, preferably, the boron-containing graphite layer includes coated boron-containing particles and a graphite matrix, and the coated boron-containing particles are dispersed in the graphite matrix.
In a preferred embodiment of the invention, the boron-containing graphite layer is selected from one of two options:
selecting a first type: the boron-containing graphite layer consists of a graphite coating and a boron-containing graphite brick, wherein the graphite coating is arranged on the surface of the boron-containing graphite brick, the content of boron B-10 is 3% -5%, and the% refers to the mass of boron accounting for the mass of the boron-containing graphite layer.
Wherein, the boron-containing graphite brick can be a boron-containing graphite brick which is conventional and commercially available in the field, the composition of the boron-containing graphite brick is B-10 element and carbon element, and B exists in graphite in the form of B-10 simple substance. Because the surface is a graphite coating, the B-10 is mainly distributed in the graphite, and the surface does not contain the B-10.
If the mass fraction of boron in the boron-containing graphite brick is too large, on one hand, the actual production and manufacturing level can not be reached, and on the other hand, the utilization rate of fuel can be reduced; if the mass fraction is too small, the shielding effect of the neutron flux within the stack is affected.
Selecting a second type: the boron-containing graphite layer consists of a graphite substrate and boron carbide particles coated with silicon carbide, the boron carbide particles coated with the silicon carbide are uniformly dispersed in the graphite substrate, wherein the content of boron B-10 is 3% -5%, and% refers to the mass of boron accounting for the mass of the boron-containing graphite layer.
Wherein, preferably, the structure of the boron carbide particles coated with silicon carbide is as follows: the innermost layer is boron carbide particles, the next layer is a vacuum helium-containing layer, and the outermost layer is a silicon carbide layer.
Wherein, the radius of each layer from inside to outside in the silicon carbide coated boron carbide particles is preferably 250 μm to 280 μm, 340 μm to 350 μm and 380 μm to 400 μm; for example: the radii of the layers from the inside to the outside were 250 μm, 340 μm and 380 μm, respectively.
Wherein, the boron carbide particles coated with the silicon carbide can be prepared by the conventional preparation method in the field. For example: the boron element is wrapped by a silicon carbide cladding and then is filled and pressed in the graphite of the reflecting layer to prepare the material.
The boron-containing graphite layer adopted by the invention reduces the thermal neutron flux in the reactor to the maximum extent and reduces the irradiation fluence rate of the reactor vessel alloy.
According to the first type selection of the boron-containing graphite layer, the boron-containing graphite brick is used as the boron-containing graphite layer, and the part of the boron-containing graphite contacting with the molten salt is treated, namely a graphite coating is added on the surface of the boron-containing graphite brick, so that boron is prevented from being fused into molten salt in a reactor to influence the normal operation of the reactor.
According to the second type selection of the boron-containing graphite layer, boron carbide is coated into particles by adopting a silicon carbide material, and then the particles are uniformly filled in graphite to form the boron-containing graphite material taking graphite as a substrate. The boron-containing graphite shielding layer can effectively shield thermal neutrons, and can prevent boron from being fused into reactor molten salt to influence the normal operation of the reactor.
In the invention, the material of the alloy shielding layer is preferably nickel-based hastelloy. The alloy shielding layer not only has the function of fixing the in-reactor components, but also can shield photons generated by the reaction of neutrons and molten salt in the descending ring cavity and photons generated by the in-reactor fission chain reaction, so that the in-reactor photon flux can be effectively shielded, the photon fluence rate in the reactor container alloy is greatly reduced, and the radiation dose outside the reactor is reduced.
In the present invention, the thickness ratio of the reflective layer to the boron-containing graphite layer is preferably (0.75-1):1
In the present invention, the thickness of the reflective layer is preferably 15 to 25cm, more preferably 15 cm.
In the present invention, the thickness of the boron-containing graphite layer is preferably 10 to 20cm, more preferably 20 cm.
In the present invention, the thickness of the alloy shielding layer is preferably 1 to 5cm, and more preferably 1 cm.
In some preferred embodiments of the invention, the reflective layer has a thickness of 15cm and the boron-containing graphite layer has a thickness of 20cm for a molten salt stack with a thermal power of 150 MWt. In the use process of the radial shielding structure of the molten salt pile, the thickness and the proportion of each layer can be adjusted by referring to the embodiment under the condition that the power density of the molten salt pile is the same for molten salt piles with other thermal powers.
The invention also provides a molten salt pile which comprises the radial shielding structure of the molten salt pile.
In the present invention, the molten salt stack may be a small modular molten salt stack conventional in the art.
In the present invention, the molten salt heap may also include an active zone as is conventional in the art. The molten salt reactor radial shielding structure covers the active zone.
Wherein the active region may be assembled from an array of fuel assemblies as is conventional in the art. Preferably, the fuel assembly is the smallest unit of a graphite member, preferably hexagonal prism graphite, and a molten salt channel at its center.
In the present invention, the molten salt stack may also include a stack vessel, as is conventional in the art, which is wrapped around the outermost periphery of the molten salt stack radial shield structure.
The material of the reactor vessel is preferably nickel-based hastelloy.
Wherein the thickness of the stack container is preferably 3cm to 5cm, more preferably 3 cm.
Wherein, preferably, between the alloy shielding layer and the stack container, a molten salt descending chamber is further included.
The molten salt descending chamber preferably has a thickness of 3cm to 5cm, more preferably 4 cm.
On the basis of the common knowledge in the field, the above preferred conditions can be combined randomly to obtain the preferred embodiments of the invention.
The positive progress effects of the invention are as follows:
1) the invention provides a radial shielding structure of a molten salt reactor, which comprises a reflecting layer, a boron-containing graphite layer and an alloy shielding layer. The structure is suitable for a molten salt reactor, and has the advantages that the reactor core fast neutrons can be moderated by utilizing the graphite of the reflecting layer, the thermal neutrons formed by moderating the graphite reflecting layer can be absorbed by the outer boron-containing graphite layer, the fast neutrons reflected back are moderated, the fast neutrons at the position mainly come from fission fast neutrons generated by the reaction of the thermal neutrons and fuel salt in the descending cavity, and finally, the gamma flux is reduced to the maximum extent through the alloy shielding layer and the reactor vessel, so that the purpose of reducing the neutrons and the gamma flux simultaneously is achieved.
2) The invention can further adjust the thickness of the boron-containing graphite layer shielding structure, effectively reduce the neutron and photon flux outside the reactor vessel, ensure the irradiation life of the reactor core graphite and the reactor metal structure material to meet the expected design life, and ensure the high fuel utilization rate of the molten salt reactor.
3) In order to effectively absorb thermal neutrons in the reactor, boron is injected into graphite instead of alloy, so that a large amount of transmutation gas helium is prevented from being generated in the alloy, and the integrity of the structure and the function of alloy materials in the reactor is influenced.
Drawings
FIG. 1 is a top view of a molten salt stack radial shield scheme in example 1 of the present invention. Radial shielding layer schematic.
FIG. 2 is a modular molten salt reactor center longitudinal section.
FIG. 3 shows the radial graphite dislocation damage rate of the reactor core after adding the boron-containing graphite brick with the thickness of 20 cm.
FIG. 4 shows the change of fuel utilization rate after adding boron-containing graphite bricks with the thickness of 20 cm.
Fig. 5 is a boron-containing particulate graphite shield layer.
The reference numbers are as follows:
graphite component 1
Reflecting layer 3
Boron-containing graphite layer 4
Molten salt descending chamber 6
Stack container 7
Upper chamber molten salt channel 8
Lower chamber molten salt channel 9
Silicon carbide coated boron carbide particles 10
Vacuum helium-containing layer 102
Detailed Description
The invention is further illustrated by the following examples, which are not intended to limit the scope of the invention.
The molten salt in the molten salt passageway of the molten salt reactor core in the following examples may be conventional in the art, such as LiF-BeF2-ThF4-UF 4.
Example 1
The top view of the molten salt reactor core of the embodiment is shown in fig. 1, and the molten salt reactor core comprises a graphite member 1, a molten salt channel 2, a reflecting layer 3, a boron-containing graphite layer 4, an alloy shielding layer 5, a molten salt descending chamber 6, a reactor container 7, an upper chamber molten salt channel 8 and a lower chamber molten salt channel 9. The reflecting layer 3 coats an active region consisting of the graphite component 1 and the molten salt channel 2, the boron-containing graphite layer 4 coats the outside of the reflecting layer 3, the alloy shielding layer 5 coats the outside of the boron-containing graphite layer 4, and the molten salt descending chamber 6 is arranged between the alloy shielding layer 5 and the reactor container 7. The longitudinal section of the center of the molten salt reactor is shown in FIG. 2.
The active region of the molten salt reactor is assembled by a fuel assembly array, the fuel assembly is a minimum unit consisting of a hexagonal prism graphite member 1 and a molten salt channel 2 positioned in the center of the fuel assembly array, and two ends of the molten salt channel 2 are communicated with an upper chamber molten salt channel 8 and a lower chamber molten salt channel 9. The thermal power of the molten salt reactor is 150 MWt.
The radius of the core assembly active area is 135 cm; the reflecting layer 3 is a graphite reflecting layer, and the thickness of the graphite reflecting layer is 15 cm; the thickness of the boron-containing graphite layer 4 is 20 cm; the thickness of the alloy shielding layer 5 is 1 cm; the thickness of the molten salt descending chamber 6 is 4 cm; the alloy thickness of the stack container 7 was 3 cm.
The boron-containing graphite layer 4 consists of a graphite coating and a boron-containing graphite brick, wherein the elements of the boron-containing graphite brick are B-10 element and carbon element, B exists in graphite in a form of B-10 simple substance, a graphite coating is arranged on the surface of the boron-containing graphite brick, B-10 is mainly distributed in the graphite, and the surface does not contain B-10. The concentration of B-10 containing boron in the boron-containing graphite layer 4 is 5%, and the% refers to the mass percentage of boron in the boron-containing graphite layer 4.
The material of the stack container 7 and the alloy shielding layer 5 adopts nickel-based hastelloy.
In this example, the out-of-pile neutron flux drops to 8.33 × 1010cm-2s-1Comparison of the out-of-core neutron flux of the reactor without in-core shielding of 3.86X 1012cm-2s-1And decreased by 2 orders of magnitude. And the service life of the reactor core graphite, the in-reactor shielding alloy and the container alloy material can be ensured to be more than 10 years. Utensil for cleaning buttockThe dislocation damage rate of the bulk graphite is shown in fig. 3, when the thickness of the boron-containing graphite layer is larger, the irradiation damage of the core graphite assembly is larger, and when the thickness is not more than 20cm, the irradiation damage of the core graphite, the in-core radiation layer and the in-core alloy shielding layer within 10 years can be ensured to be within the maximum allowable range of the material (the maximum allowable value of the irradiation damage of the graphite is 20dpa, and the alloy is 1 dpa). The fuel utilization is reduced by 6.25% compared to the model without inner shielding, within an acceptable range, as shown in fig. 4.
Example 2
The molten salt reactor of this example is identical in physical and geometrical parameters to the molten salt reactor of example 1 except for the above boron-containing graphite layer 4. The device also comprises a graphite component 1, a molten salt channel 2, a reflecting layer 3, a boron-containing graphite layer 4, an alloy shielding layer 5, a molten salt descending chamber 6 and a reactor container 7. The reflecting layer 3 coats an active region consisting of the graphite component 1 and the molten salt channel 2, the boron-containing graphite layer 4 coats the outside of the reflecting layer 3, the alloy shielding layer 5 coats the outside of the boron-containing graphite layer 4, and the molten salt descending chamber 6 is arranged between the alloy shielding layer 5 and the reactor container 7.
The active region of the molten salt reactor is assembled by a fuel assembly array, the fuel assembly is a minimum unit consisting of a hexagonal prism graphite member 1 and a molten salt channel 2 positioned in the center of the fuel assembly array, and two ends of the molten salt channel 2 are communicated with an upper chamber molten salt channel 8 and a lower chamber molten salt channel 9.
The radius of the core assembly active area is 135 cm. The reflecting layer 3 is a graphite reflecting layer, and the thickness of the graphite reflecting layer is 15 cm; the thickness of the boron-containing graphite layer 4 is 20 cm; the alloy shielding layer 5 is 1 cm; the thickness of the molten salt descending chamber 6 is 4 cm; the alloy thickness of the stack container 7 was 3 cm.
In this embodiment, the material of the boron-containing graphite layer 4 is a boron carbide particle graphite layer, a schematic view of a microstructure of the material is shown in fig. 5, and the material includes a graphite substrate 11 and silicon carbide-coated boron carbide particles 10, the silicon carbide-coated boron carbide particles 10 are uniformly filled in the graphite substrate 11, an innermost layer of the silicon carbide-coated boron carbide particles 10 is boron carbide particles 101, a next layer is a vacuum helium-containing layer 102, and an outermost layer is a silicon carbide layer 103. The structures have inner to outer radii of 250 μm, 340 μm and 380 μm, respectively. The mass fraction of B-10 containing boron in the boron carbide granular graphite layer is 5 percent, and the percent refers to the mass percentage of boron in the boron-containing graphite layer 4.
The material of the stack container 7 and the alloy shielding layer 5 adopts nickel-based hastelloy.
In this example, the graphite layer of the boron carbide particles ensures that boron element in the boron-containing material is not dissolved into the molten salt, thereby affecting the normal operation of the reactor. The neutron flux outside the reactor is reduced by 2 orders of magnitude, and the reactor core graphite, the in-reactor shielding alloy and the container alloy material can normally serve for more than 10 years. Compared with the model without the inner shield, the fuel utilization rate is reduced by 5.78%, and is within an acceptable range.
Comparative example 1
The example 1 is the same as the example 1 except that the boron-containing graphite layer in the example 1 is changed to the graphite layer (i.e., not containing boron), and the alloy shielding layer is changed to the boron-containing alloy layer obtained by implanting boron into the alloy layer.
Effect examples helium embrittlement results
Helium gas generation rates in examples and comparative examples were calculated by the monte carlo method. The results are shown in the following table:
as shown in the results of the above table, the helium gas generation rate in example 1 and example 2 is low, and almost no influence is generated on the performance of the alloy, but the boron element injected into the alloy in comparative example 1 generates a large amount of helium gas in the alloy, and seriously influences various performances of the alloy, including mechanical performance, radiation resistance and the like.
While specific embodiments of the invention have been described above, it will be appreciated by those skilled in the art that this is by way of example only, and that the scope of the invention is defined by the appended claims. Various changes and modifications to these embodiments may be made by those skilled in the art without departing from the spirit and scope of the invention, and these changes and modifications are within the scope of the invention.
Claims (10)
1. A molten salt reactor radial shielding structure, characterized by comprising, in order from the active zone of the molten salt reactor to the peripheral direction: the molten salt reactor comprises a reflecting layer, a boron-containing graphite layer and an alloy shielding layer, wherein the reflecting layer coats an active region of the molten salt reactor, the boron-containing graphite layer coats the reflecting layer, and the alloy shielding layer coats the boron-containing graphite layer.
2. The molten salt stack radial shield structure of claim 1, wherein the reflective layer satisfies one or more of the following conditions:
the reflecting layer is a graphite reflecting layer;
the graphite reflecting layer is made of nuclear-grade graphite materials in the molten salt reactor, such as ultrafine-particle graphite;
③ the thickness of the reflecting layer is 15-25cm, preferably 15 cm.
3. The molten salt stack radial shield structure of claim 1, wherein the boron-containing graphite layer satisfies one or more of the following conditions:
the boron element in the boron-containing graphite layer is B-10 element;
the mass fraction of boron element in the boron-containing graphite layer is 3-5%, wherein the% refers to the mass percentage of boron in the boron-containing graphite layer;
the surface of the boron-containing graphite layer does not contain boron, namely the boron exists in the boron-containing graphite layer;
the boron-containing graphite layer comprises a graphite coating;
the boron element in the boron-containing graphite layer exists in the interior of the boron-containing graphite layer in the form of B-10 simple substance and/or coated boron-containing particles;
sixthly, the boron-containing graphite layer comprises a graphite coating and a boron-containing graphite brick;
or, the boron-containing graphite layer comprises coated boron-containing particles and a graphite matrix, the coated boron-containing particles being dispersed in the graphite matrix;
the thickness of the boron-containing graphite layer is 10-20cm, preferably 20 cm.
4. The molten salt reactor radial shielding structure of claim 3, wherein the boron-containing graphite layer is composed of a graphite coating and boron-containing graphite bricks, the graphite coating is arranged on the surfaces of the boron-containing graphite bricks, wherein the content of boron B-10 is 3% -5%, and% refers to the mass of boron in percentage of the mass of the boron-containing graphite layer.
5. The molten salt reactor radial shielding structure of claim 3, wherein the boron-containing graphite layer is composed of a graphite substrate and silicon carbide-coated boron carbide particles uniformly filled in the graphite substrate, wherein the content of boron B-10 is 3% -5%, and% is the mass of boron in percentage of the mass of the boron-containing graphite layer.
6. The molten salt stack radial shield structure of claim 5, wherein the silicon carbide coated boron carbide particles are of the structure: the innermost layer is boron carbide particles, the next layer is a vacuum helium-containing layer, and the outermost layer is a silicon carbide layer;
preferably, the radii of the layers from the inside to the outside in the silicon carbide-coated boron carbide particles are 250 μm to 280 μm, 340 μm to 350 μm, and 380 μm to 400 μm, respectively; for example: the radii of the layers from the inside to the outside were 250 μm, 340 μm and 380 μm, respectively.
7. The molten salt stack radial shield structure of claim 1, wherein a thickness ratio of the reflective layer and the boron-containing graphite layer is (0.75-1): 1;
preferably, for a molten salt stack with a thermal power of 150MWt, the thickness of the reflective layer is 15cm, and the thickness of the boron-containing graphite layer is 20 cm.
8. The molten salt reactor radial shielding structure of claim 1, wherein the alloy shielding layer is made of nickel-based hastelloy;
and/or the thickness of the alloy shielding layer is 1-5cm, preferably 1 cm.
9. A molten salt stack comprising an active zone, a stack vessel, a molten salt stack radial shield structure as claimed in any one of claims 1 to 8, the molten salt stack radial shield structure encasing the active zone, the stack vessel encasing an outermost periphery of the molten salt stack radial shield structure.
10. The molten salt stack of claim 9, wherein the molten salt stack satisfies one or more of the following conditions:
the active region is assembled from an array of fuel assemblies; the fuel assembly is a minimum unit consisting of hexagonal prism graphite and a molten salt channel positioned in the center of the hexagonal prism graphite;
secondly, the material of the reactor is nickel-based hastelloy;
③ the thickness of the stack of containers is 3cm-5cm, preferably 3 cm;
a molten salt descending chamber is arranged between the alloy shielding layer and the reactor vessel; the thickness of the molten salt descending chamber is preferably 3cm-5cm, more preferably 4 cm;
the molten salt reactor is a small modular molten salt reactor;
sixthly, the thermal power of the molten salt reactor is 150 MWt.
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