CN113593730B - Heterogeneous MA transmutation rod for fast neutron reactor - Google Patents
Heterogeneous MA transmutation rod for fast neutron reactor Download PDFInfo
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Abstract
The invention discloses a heterogeneous MA transmutation rod for a fast neutron reactor, which comprises the following components: a fuel rod main body, the outside of which is provided with a MA nuclide coating or MA nuclide and 6 and (3) a mixed coating of LiD. The invention is realized by arranging MA coating or MA and MA on the outer part of the fuel rod 6 Hybrid coating of LiD due to 6 The addition of LiD can convert thermal neutrons into fast neutrons of 14MeV, and further can improve the average energy of neutrons in a reactor core, so that the heterogeneous MA transmutation rod for the fast neutron reactor provided by the invention deepens the burnup depth and improves the transmutation rate of MA nuclides.
Description
Technical Field
The invention belongs to the technical field of nuclear reactor components, and particularly relates to a heterogeneous MA transmutation rod for a fast neutron reactor.
Background
Nuclear energy is used as a novel energy source, and although the nuclear energy facilitates our lives, the radioactive nuclear waste generated along with the nuclear energy seriously threatens the natural environment and the personal safety of human beings. Nuclear waste is an useless material which spontaneously generates alpha, beta and gamma radiation and emits heat by itself, and the sources of the nuclear waste are various, and there are the following cases (1) the processing of uranium ores before being used as fuel and (2) the operation of various reactors (3) the retirement of nuclear equipment. The nuclear waste is simply classified into medium-low level waste and high level waste.
The high level waste has extremely high radioactivity, is extremely harmful, and has actinides as main component, such as 237 Np、 241 Am、 243 Am、 244 Cm、 245 Minor amounts of long-lived actinides such as Cm are referred to as minor actinides [8] The minor actinides have high radioactivity and long half-life time, and cause serious harm to the environment, so the minor actinides are the most difficult to treat in nuclear waste, and are easy to cause great safety and hidden by common geological deep-buried storageResearch shows that 100 years of nuclear waste can be prevented from leaking through glass or ceramic solidification geological deep burying, and because minor actinides have the characteristic of long decay period, other methods are needed to be considered for treating minor actinides, and minor actinides also have the characteristic of strong radioactivity, so that once leakage is extremely harmful. The method has better treatment means for medium and low level wastes, and the treatment means for high level wastes are under development, and the main characteristics of the high level wastes are long radioactive duration and high nuclide toxicity. The radioactive specific activity of the high radioactive waste is more than 3.7X10 9 Bq/L. Np-237 in minor actinides has a half-life of more than 10 thousand years. Once the radionuclides enter the biosphere, the radionuclides are extremely harmful, and can not be degraded or eliminated by common physical, chemical or biological methods, the harm of the radionuclides can be reduced only by radioactive decay of the radionuclides, and substances generated by the radioactive decay can initiate ionization to cause radiation damage when passing through a human body, so that the cancer probability of the human body is increased. The high level waste needs thousands of years, tens of thousands of years or even longer to be harmless. Thus, the environmental impact of leakage once the high level waste is poorly disposed is severe and profound.
The technology of separation and transmutation is to separate high-radioactivity waste generated by a reactor and long-life nuclides to prepare target pieces, and make the target pieces react with neutrons in the reactor or a neutron accelerator, wherein the nuclear reactions can be fission reactions or neutron capture, and the nuclear reactions can be converted into short-life nuclides or stable nuclides, so that the harm of radioactivity is reduced.
The nuclear weapons are researched in the forties of the last century, nuclear power generation is started after ten years, a large amount of radioactive waste generated by nuclear reaction is accumulated in the sixties, the medium-low level waste is treated in landfills and sea filling, and no reasonable treatment method is provided for the high level waste. Scientists then propose a number of schemes for deep buried geological disposal, antarctic ice layer disposal, cosmic disposal, separation-transmutation, and the like. In the 70 s of the 19 th century, there was a hot tide of high level waste separation-transmutation, but separation-transmutation was difficult to achieve due to the defects of equipment and technology at that time, and the cost was high, and the research on separation transmutation technology presented a valley. The last eighties of the century has received attention again through the separation-transmutation technology for the following reasons:
(1) The high level waste has a large amount of fissionable nuclides and fissionable nuclides, and the separation-transmutation technology can well utilize the part of resources
(2) With the development of scientific technology, separation-transmutation technologies, such as extraction separation technology and ion exchange technology, are becoming possible.
(3) Currently, the only viable means for disposing of radioactive waste is deep geological disposal, and the geological conditions required by the deep geological disposal are very harsh, and some countries even have no conditions for the deep geological disposal, so that a new method for disposing of high-radioactivity waste is urgently needed.
The separation technique can be divided into: extraction separation, high-temperature separation, DIDPA flow, wet method, dry method and oxide volatilization method.
The transmutation techniques can be divided into: fast reactor transmutation, high-current proton accelerator transmutation, thermal reactor transmutation, light water reactor transmutation, fusion reactor transmutation, accelerator transmutation and other technologies.
The MA loading directly affects the operation of the reactor and also affects the transmutation rate. In the case of the MA, the reference number, 237 Np， 241 am account for the vast majority of the ratios, with emphasis on handling the transmutation rate 237 Np， 241 Am burn-up problem. The probability of nuclear reaction between the nuclide and fast neutrons in the MA is high, the MA nuclide has a larger neutron fission section at a higher neutron energy position, the nuclide in the MA can be subjected to capture fission reaction with neutrons to release energy, and the MA nuclide can be subjected to radiation capture reaction to be converted into fissionable nuclide, so that the MA can be used as a nuclear fission material in a sodium-cooled fast reactor, the backup reactivity of the reactor is increased, so that the MA nuclide is transmuted by the sodium-cooled fast reactor, the MA nuclide can be directly burnt by utilizing the characteristic that the MA nuclide has a large fission section at a high neutron energy position, and meanwhile, the MA nuclide can be easily converted into the fissionable nuclide in the sodium-cooled fast reactor to increase the backup reactivity of the reactor. But the addition of MA can have an impact on the safety factor of the core.
The transmutation modes of MA species in fast reactors can be broadly divided into two types: uniform transmutation and non-uniform transmutation, which generally do not change the core size, the size of the fuel rods, the proportion of primary nuclides of the fuel, add MA uniformly to the fuel. Non-uniform transmutation typically involves inserting a MA into the core as a transmutation rod instead of a fuel rod, or a MA coating that replaces a portion of the nuclear fuel without changing the size of the fuel rod. The two modes have advantages and disadvantages. Compared with non-uniform transmutation, the uniform transmutation rods are uniformly distributed, local power distortion cannot occur, and the defect is that the uniform transmutation changes fuel components of the reactor core, so that uncertain potential safety hazards are caused to the safety of the reactor core. The non-uniform transmutation rods are simple to manufacture and have low requirements on the manufacturing process, but because the arrangement positions of the non-uniform transmutation rods are limited, local power mutation is easy to occur, and the reactor core is easy to melt. There is therefore a need for improvements in the design and loading of non-uniform transmutation rods.
Disclosure of Invention
It is an object of the present invention to address at least the above problems and/or disadvantages and to provide at least the advantages described below.
To achieve these objects and other advantages and in accordance with the purpose of the invention, there is provided a non-uniform MA transmutation rod for a fast neutron reactor, comprising:
a fuel rod main body, the outside of which is provided with a MA nuclide coating or MA nuclide and 6 and (3) a mixed coating of LiD.
Preferably, wherein the MA species coating and MA species composition comprises 237 Np、 241 Am、 243 Am、 244 Cm, where 237 The mass ratio of Np is 56.2%, 241 am is 26.4% by mass, 243 am is 12% by mass, 244 the mass ratio of Cm is 5.4%.
Preferably, the radius of the heterogeneous MA transmutation rod is 0.5cm, and the thickness of the MA nuclide coating is 0.001-0.05 cm.
Preferably, wherein the MA species and 6 the LiD mixed coating is prepared from MA nuclide 6 The LiD is prepared by uniformly mixing according to the mass ratio, and MA nuclide 6 The mass ratio of LiD is 7:3, 5:5, 4:6Or one of 3:7.
Preferably, the loading of U and Pu isotopes in the fuel rod body decreases with increasing MA nuclide loading.
Preferably, wherein the fuel rod body is made of MOX fuel, and the nuclide composition of the MOX fuel comprises 238 U、 235 U、 238 Pu、 239 Pu、 240 Pu、 241 Pu and 242 pu, wherein, 238 U、 235 the ratio of U is 0.003:1, 238 Pu、 239 Pu、 240 Pu、 241 pu and 242 pu is present in a ratio of 0.025:1.5375:0.55: 0.2975:0.1025.
Preferably, the heterogeneous MA transmutation rods are loaded in an inner region of the fuel assembly, the fuel assembly loaded with the heterogeneous MA transmutation rods is provided with a plurality of layers in the reactor core, each layer of fuel assembly is arranged in a hexagonal mode in the reactor core, and two adjacent layers of fuel assemblies are arranged at intervals.
The invention at least comprises the following beneficial effects: the invention is realized by arranging MA coating or MA and MA on the outer part of the fuel rod 6 Hybrid coating of LiD due to 6 The addition of LiD can convert thermal neutrons into fast neutrons of 14MeV, so that the average energy of neutrons in a reactor core can be improved, the burnup depth of MA is deepened, and the transmutation rate of MA is improved.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention.
Drawings
FIG. 1 is a schematic diagram of a heterogeneous MA transmutation rod structure of example 1;
FIG. 2 is a schematic diagram of the structure of a heterogeneous MA transmutation rod of example 2;
FIG. 3 is a schematic illustration of a non-uniform MA transmutation rods distribution in a fuel assembly;
FIG. 4 is a schematic diagram of the distribution of fuel assemblies in the core;
FIG. 5 is a schematic diagram of the relationship of neutron flux variation at core location;
FIG. 6 shows the thickness of MA coating versus core reactivity K eff The resulting influence curve;
FIG. 7 is a plot of neutron flux of a reactor as a function of MA addition;
FIG. 8 is a diagram of 6 A reaction chain of LiD and thermal neutrons;
FIG. 9 is a diagram of MA and 6 the ratio of LiD is in the case of 7:3 and 3:7 and 6:4, 6 schematic of the effect of LiD on reactor reactivity
FIG. 10 is a diagram of 6 The ratio of LiD/MA is 7:3 and 3:7, respectively.
Detailed Description
The present invention is described in further detail below with reference to the drawings to enable those skilled in the art to practice the invention by referring to the description.
It will be understood that terms, such as "having," "including," and "comprising," as used herein, do not preclude the presence or addition of one or more other elements or groups thereof.
It should be noted that, in the description of the present invention, the orientation or positional relationship indicated by the term is based on the orientation or positional relationship shown in the drawings, which are merely for convenience of describing the present invention and simplifying the description, and are not indicative or implying that the apparatus or element to be referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
In the description of the present invention, unless explicitly specified and limited otherwise, the terms "mounted," "configured to," "engaged with," "connected to," and the like are to be construed broadly, and for example, "connected" may be a fixed connection, may be a detachable connection, or may be integrally connected, may be mechanically connected, may be electrically connected, may be directly connected, may be indirectly connected through an intermediate medium, may be communication between two members, and may be understood in a specific manner by those skilled in the art.
Furthermore, in the present invention, unless expressly stated or limited otherwise, a first feature "up" or "down" a second feature may be a direct contact of the first and second features, or an indirect contact of the first and second features through an intervening medium. Moreover, a first feature being "above," "over" and "on" a second feature may be a first feature being directly above or obliquely above the second feature, or simply indicating that the first feature is level higher than the second feature. The first feature being "under", "below" and "beneath" the second feature may be the first feature being directly under or obliquely below the second feature, or simply indicating that the first feature is less level than the second feature.
Example 1
As shown in fig. 1: a heterogeneous MA transmutation rod for a fast neutron reactor of the embodiment comprises a fuel rod main body 1, wherein an MA nuclide coating 2 is arranged outside the fuel rod main body, and the nuclide composition of the MA nuclide coating 2 comprises 237 Np、 241 Am、 243 Am、 244 Cm, where 237 The mass ratio of Np is 56.2%, 241 am is 26.4% by mass, 243 am is 12% by mass, 244 the mass ratio of Cm is 5.4%. The fuel rod main body adopts MOX fuel, and the nuclide composition of the MOX fuel comprises 238 U、 235 U、 238 Pu、 239 Pu、 240 Pu、 241 Pu and 242 pu, wherein, 238 U、 235 the ratio of U is 0.003:1, 238 Pu、 239 Pu、 240 Pu、 241 pu and 242 pu is present in a ratio of 0.025:1.5375:0.55: 0.2975:0.1025. The radius of the heterogeneous MA transmutation rod is 0.5cm, the thickness of the MA nuclide coating 2 is 0.001cm, and the mass of MA in each fuel rod is 2.0g.
Example 2
A heterogeneous MA transmutation rod for a fast neutron reactor of the embodiment comprises a fuel rod main body, wherein the outside of the fuel rod main body is provided with an MA nuclide coating, and the nuclide composition of the MA nuclide coating comprises 237 Np、 241 Am、 243 Am、 244 Cm, where 237 The mass ratio of Np is 56.2%, 241 am is 26.4% by mass, 243 am is 12% by mass, 244 the mass ratio of Cm is 5.4%. The fuel rod main body adopts MOX fuel, and the nuclide composition of the MOX fuel comprises 238 U、 235 U、 238 Pu、 239 Pu、 240 Pu、 241 Pu and 242 pu, wherein, 238 U、 235 the ratio of U is 0.003:1, 238 Pu、 239 Pu、 240 Pu、 241 pu and 242 pu is present in a ratio of 0.025:1.5375:0.55: 0.2975:0.1025. The radius of the heterogeneous MA transmutation rod is 0.5cm, the thickness of the MA nuclide coating is 0.002cm, and the mass of MA in each fuel rod is 3.9g.
Example 3
A heterogeneous MA transmutation rod for a fast neutron reactor of the embodiment comprises a fuel rod main body, wherein the outside of the fuel rod main body is provided with an MA nuclide coating, and the nuclide composition of the MA nuclide coating comprises 237 Np、 241 Am、 243 Am、 244 Cm, where 237 The mass ratio of Np is 56.2%, 241 am is 26.4% by mass, 243 am is 12% by mass, 244 the mass ratio of Cm is 5.4%. The fuel rod main body adopts MOX fuel, and the nuclide composition of the MOX fuel comprises 238 U、 235 U、 238 Pu、 239 Pu、 240 Pu、 241 Pu and 242 pu, wherein, 238 U、 235 the ratio of U is 0.003:1, 238 Pu、 239 Pu、 240 Pu、 241 pu and 242 pu is present in a ratio of 0.025:1.5375:0.55: 0.2975:0.1025. The radius of the heterogeneous MA transmutation rod is 0.5cm, the thickness of the MA nuclide coating is 0.015cm, and the mass of MA in each fuel rod is 29g.
Example 4
A heterogeneous MA transmutation rod for a fast neutron reactor of the embodiment comprises a fuel rod main body, wherein the outside of the fuel rod main body is provided with an MA nuclide coating, and the nuclide composition of the MA nuclide coating comprises 237 Np、 241 Am、 243 Am、 244 Cm, where 237 The mass ratio of Np is 56.2%, 241 amThe mass ratio is 26.4 percent, 243 am is 12% by mass, 244 the mass ratio of Cm is 5.4%. The fuel rod main body adopts MOX fuel, and the nuclide composition of the MOX fuel comprises 238 U、 235 U、 238 Pu、 239 Pu、 240 Pu、 241 Pu and 242 pu, wherein, 238 U、 235 the ratio of U is 0.003:1, 238 Pu、 239 Pu、 240 Pu、 241 pu and 242 pu is present in a ratio of 0.025:1.5375:0.55: 0.2975:0.1025. The radius of the heterogeneous MA transmutation rod is 0.5cm, the thickness of the MA nuclide coating is 0.05cm, and the mass of MA in each fuel rod is 93.1g.
Example 5
A heterogeneous MA transmutation rod for a fast neutron reactor of the embodiment comprises a fuel rod main body, wherein the outside of the fuel rod main body is provided with MA nuclides and 6 mixed coating of LiD, MA nuclide and 6 the mass ratio of LiD is 3:7, and the nuclide composition of MA nuclide comprises 237 Np、 241 Am、 243 Am、 244 Cm, where 237 The mass ratio of Np is 56.2%, 241 am is 26.4% by mass, 243 am is 12% by mass, 244 the mass ratio of Cm is 5.4%. The fuel rod main body adopts MOX fuel, and the nuclide composition of the MOX fuel comprises 238 U、 235 U、 238 Pu、 239 Pu、 240 Pu、 241 Pu and 242 pu, wherein, 238 U、 235 the ratio of U is 0.003:1, 238 Pu、 239 Pu、 240 Pu、 241 pu and 242 pu is present in a ratio of 0.025:1.5375:0.55: 0.2975:0.1025. The radius of the heterogeneous MA transmutation rod is 0.5cm, MA nuclides and 6 the thickness of the LiD hybrid coating was 0.05cm.
Example 6
A heterogeneous MA transmutation rod for a fast neutron reactor of the embodiment comprises a fuel rod main body, wherein the outside of the fuel rod main body is provided with MA nuclides and 6 mixed coating of LiD, MA nuclide and 6 the mass ratio of LiD is 4:6, and the nuclide composition of MA nuclide comprises 237 Np、 241 Am、 243 Am、 244 Cm, where 237 The mass ratio of Np is 56.2%, 241 am is 26.4% by mass, 243 am is 12% by mass, 244 the mass ratio of Cm is 5.4%. The fuel rod main body adopts MOX fuel, and the nuclide composition of the MOX fuel comprises 238 U、 235 U、 238 Pu、 239 Pu、 240 Pu、 241 Pu and 242 pu, wherein, 238 U、 235 the ratio of U is 0.003:1, 238 Pu、 239 Pu、 240 Pu、 241 pu and 242 pu is present in a ratio of 0.025:1.5375:0.55: 0.2975:0.1025. The radius of the heterogeneous MA transmutation rod is 0.5cm, MA nuclides and 6 the thickness of the LiD hybrid coating was 0.05cm.
Example 7
A heterogeneous MA transmutation rod for a fast neutron reactor of the embodiment comprises a fuel rod main body, wherein the outside of the fuel rod main body is provided with MA nuclides and 6 mixed coating of LiD, MA nuclide and 6 the mass ratio of LiD is 5:5, and the nuclide composition of MA nuclide comprises 237 Np、 241 Am、 243 Am、 244 Cm, where 237 The mass ratio of Np is 56.2%, 241 am is 26.4% by mass, 243 am is 12% by mass, 244 the mass ratio of Cm is 5.4%. The fuel rod main body adopts MOX fuel, and the nuclide composition of the MOX fuel comprises 238 U、 235 U、 238 Pu、 239 Pu、 240 Pu、 241 Pu and 242 pu, wherein, 238 U、 235 the ratio of U is 0.003:1, 238 Pu、 239 Pu、 240 Pu、 241 pu and 242 pu is present in a ratio of 0.025:1.5375:0.55: 0.2975:0.1025. The radius of the heterogeneous MA transmutation rod is 0.5cm, MA nuclides and 6 the thickness of the LiD hybrid coating was 0.05cm.
Example 8
A heterogeneous MA transmutation rod for a fast neutron reactor of the embodiment comprises a fuel rod main body, wherein the outside of the fuel rod main body is provided with MA nuclides and 6 mixed coating of LiD, MA nuclideAnd 6 the mass ratio of LiD is 7:3, and the nuclide composition of MA nuclide comprises 237 Np、 241 Am、 243 Am、 244 Cm, where 237 The mass ratio of Np is 56.2%, 241 am is 26.4% by mass, 243 am is 12% by mass, 244 the mass ratio of Cm is 5.4%. The fuel rod main body adopts MOX fuel, and the nuclide composition of the MOX fuel comprises 238 U、 235 U、 238 Pu、 239 Pu、 240 Pu、 241 Pu and 242 pu, wherein, 238 U、 235 the ratio of U is 0.003:1, 238 Pu、 239 Pu、 240 Pu、 241 pu and 242 pu is present in a ratio of 0.025:1.5375:0.55: 0.2975:0.1025. The radius of the heterogeneous MA transmutation rod is 0.5cm, MA nuclides and 6 the thickness of the LiD hybrid coating was 0.05cm.
The heterogeneous MA transmutation rods of examples 1-8 are loaded into the inner layer of the MA transmutation assembly, respectively, and then the MA transmutation assembly loaded with the heterogeneous MA transmutation rods is loaded into the core. Before the experiment is carried out, the position of the MA transmutation rod in the reactor core is firstly determined, and as the neutron flux is higher, the neutron energy spectrum is harder, the influence on the MA transmutation rate is better, and the relation of the neutron flux in the reactor core position change is calculated through a program, as shown in figure 5. As can be seen from fig. 5, the neutron flux from inside to outside of the core sequentially decreases, and the average neutron energy is highest and the energy spectrum is hardest in the core center, so the MA transmutation rods need to be arranged near the center, and the non-uniform MA transmutation rods 4 are distributed in the fuel assembly 5 as shown in fig. 3. The distribution of the arrangement of the fuel assemblies 5 loaded with heterogeneous MA transmutation rods 4 in the core 6 is shown in fig. 4.
The MA nuclide coating provided in the embodiment 1 to the embodiment 4 has the following adding scheme: the radius of the fuel rod main body is kept unchanged, the thickness of the MOX fuel rod main body is replaced by the thickness of the MA coating, namely, the thickness of the MA nuclide coating and the radius of the fuel rod main body are equal to the radius of the original fuel rod main body, and the loading capacity of isotopes of U and Pu is reduced along with the increase of the loading capacity of MA, so that the operation of a reactor is directly influenced by the quantity of the loading capacity of MA, and the transmutation rate is also influenced.
In the case of a MA-type nuclide coating, 237 Np， 241 am occupies a vast proportion of the number, the treatment of transmutation rate is focused on 237 Np， 241 Am burn-up problem. The probability of nuclear reaction between the nuclide and fast neutrons in the MA is high, the MA nuclide has a larger neutron fission section at a higher neutron energy position, the nuclide in the MA can be subjected to capture fission reaction with neutrons to release energy, and the MA nuclide can be subjected to radiation capture reaction to be converted into fissionable nuclide, so that the MA can be used as a nuclear fission material in a sodium-cooled fast reactor, the backup reactivity of the reactor is increased, so that the MA nuclide is transmuted by the sodium-cooled fast reactor, the MA nuclide can be directly burnt by utilizing the characteristic that the MA nuclide has a large fission section at a high neutron energy position, and meanwhile, the MA nuclide can be easily converted into the fissionable nuclide in the sodium-cooled fast reactor to increase the backup reactivity of the reactor. But the addition of MA can have an impact on the safety factor of the core.
FIG. 6 shows the thickness of MA coating versus core reactivity K eff The resulting effect curve shows that the sodium-cooled fast neutron reactor operates independently for 300 days, the initial reactivity is about 1.14, the service life is reduced to 1.03, and the reactivity is gradually reduced with time. After the reactor core is added with the MA coating, when the thickness of the MA coating of the fuel rod is 0.001cm, the reactivity of the reactor is basically unchanged for three hundred days, and the ratio of the MA coating to the fission section is slightly increased, when the thickness of the coating is 0.015cm,0.05cm and 0.2cm respectively, the initial reactivity is lower than that of a sodium-cooled fast reactor without MA, but the reactor reactivity gradually increases along with the operation time of the reactor, the MA nuclide fission section is shown in the table 1, the capture section is shown in the capture section, the capture fission ratio is shown in the table 1, the probability of the MA nuclide in the fast reactor is higher than that of the MA nuclide in the fast reactor, the ratio of the capture section to the fission section is reduced along with the increase of neutron energy, and in the fast reactor with high average neutron energy, the MA nuclide can be used as extra fissile material, and the MA nuclide absorbs neutrons and has higher backup reactivity, so that the MA is added in the reactor core.
As shown in fig. 7, the curve of the neutron flux of the reactor with the amount of MA added is shown in fig. 7, and it is clear from fig. 7 that adding MA results in a lower neutron flux in the reactor than adding no MA, and that the more MA is, the lower neutron flux is, and the addition of MA nuclide consumes the neutrons in the reactor, resulting in a lower neutron flux.
But at the same time the addition of MA changes the fuel temperature coefficient of the reactor, the cavitation coefficient of the reactor, resulting in a decrease in the reactor safety coefficient.
TABLE 1 fission Cross section (σ) f ) Capture section (sigma) c ) Capture fission ratio (α)
TABLE 2MA nuclide coating thickness, transmutation rod radius, MA quality, and MA nuclide coating weight Mass Table
As can be seen from fig. 7, the greater the MA loading has a greater effect on the core reactivity, the lower the safety factor of the core, and studies have shown that the intrinsic safety doppler effect of the sodium-cooled fast reactor core becomes weaker with increasing MA addition, while K eff The sodium cavitation effect is reduced, which causes positive feedback of the core to be enhanced, so that the safety factor of the core should be considered while the loading capacity is considered.
Table 3 shows the nuclear reactor K at different loadings eff Values of (2)
TABLE 3 Nuclear reactor K at different loadings eff Values of (2)
| MA coating thickness/cm | Initial K eff | End of burn K eff | ΔK eff |
| 0.001 | 1.1414 | 1.1419 | 0.0005 |
| 0.002 | 1.1396 | 1.1423 | 0.0027 |
| 0.015 | 1.1244 | 1.1347 | 0.0103 |
| 0.05 | 1.1002 | 1.1250 | 0.0248 |
As can be seen from Table 3, with increasing MA coating thickness, ΔK eff The greater the value of (c) the more strongly the core reactivity is affected, so the lower the safety factor of the sodium cooled fast reactor core as the MA coating thickness increases.
Calculating the transmutation rate of different MA coating thicknesses by using the RMC, wherein the transmutation rate calculation mode is shown as follows:
transmutation rate = initial nuclear density of each nuclear species of MA/nuclear density of MA corresponding nuclear species at end-of-burn
The results of the transmutation rate study for each actinide species at different MA loadings are shown in table 4. From Table 4It is known that as the thickness of the MA coating increases, the rate of MA transmutation decreases gradually. The thickness of the MA coating is increased, so that the shielding effect of the MA coating on neutrons is enhanced, the inner MA nuclide cannot react with the neutrons, the MA and the neutrons are not fully reacted, and the MA transmutation efficiency of the sodium-cooled fast reactor is lower along with the thickness increase due to the limitation of the neutron mean free path. From Table 4 244 The transmutation rate of Cm is negative, thus it can be seen that for a sodium cooled fast reactor 244 The transmutation effect of Cm is poor because 243 Am is generated again by the capture reaction in the fast reactor 244 Cm.
TABLE 4 transmutation rates of actinides at various MA loadings
Examples 5 to 8 are the addition of a MA nuclide coating 6 Embodiments of the LiD. 6 LiD can be used as a raw material of thermonuclear weapon hydrogen bomb [10] Deuterium accounts for 0.015% of natural hydrogen, and a large amount of deuterium can be obtained in seawater, but tritium does not naturally exist. By the reaction:
n+6Li→4He+T+4.9MeV (1)
tritium can be obtained, then after reaction:
D+T→4He+n+17.6MeV (2)
T+6Li→Be+n+16.02MeV (3)
the neutrons produced by reactions (2) and (3) are both about 14MeV, the reaction chain is shown in FIG. 8.
Therefore, it is 6 LiD can increase the conversion of thermal neutrons into fast neutrons of 14Mev, simply because 6 This property of LiD will 6 LiD is added into the reactor core to improve the average energy of neutrons in the reactor core and deepen the burnup depth of MA.
6 LiD is added into the reactor core as a substance capable of converting slow neutrons into fast neutrons 6 LiD naturally affects the operation of the reactor, taking MA coating thickness of 0.05cm as an example, for preliminary investigation 6 The addition amount of LiD can cause reactivity of the reactorWhat affects. FIG. 9 is a diagram of MA and 6 the ratio of LiD is in the case of 7:3 and 3:7 and 6:4, 6 effect of LiD on reactor reactivity.
Different from 6 The effect on reactor reactivity at the LiD/MA loading ratio is shown in Table 5
TABLE 5 variation of 6 Influence on reactor reactivity at LiD/MA loading ratio
As can be seen from fig. 9, compared to adding MA alone, 6 the addition of LiD can negatively affect the reactor reactivity and 6 the higher the proportion of LiD in the mixture, the deeper the negative effect on reactivity, since 6 LiD is mixed with MA as a substance capable of converting slow neutrons into fast neutrons when 6 The proportion of MA in the fuel rods is relatively reduced as the proportion of LiD increases, and the reduction in MA as an additional fuel which increases the backup reactivity results in a reduction in reactor reactivity, but the overall trend in reactivity increases with reactor run time.
As can be seen from Table 5, the additives 6 LiD affects the core reactivity, and is added 6 The more ΔK the ratio of LiD eff The smaller the variation in (c) due to 6 The negative effect of LiD introduction compensates for the positive effect of MA addition on reactor reactivity, while it can be seen that 6 The higher the ratio of LiD/MA, the higher the initial K eff The lower, with 6 The reactor may reach sub-critical with an increase in the ratio of LiD/MA.
The thickness of the MA and LiD mixed coating is 0.05cm 6 LiD/MA 7:3:
table 6 MA disappearance of nuclides from 300 days of sodium cooled fast reactor model irradiation
MA and 6 the mixed thickness of LiD is 0.05cm, 6 LiD/MA 3:7
Table 7 MA disappearance of nuclides from sodium cooled fast reactor model irradiation for 300 days
Thus, when changing 6 The ratio of LiD/MA can influence the burning depth of MA, and the ratio of LiD/MA is mixed in MA in the design of a non-uniform transmutation rod of a sodium-cooled fast reactor 6 The ratio of LiD is not too high, and because the quantity of fast neutrons in the fast reactor is the majority, too much is added 6 LiD can influence the reactivity of the reactor, simultaneously reduce the share of each nuclide of MA in unit volume, reduce the probability of nuclear reaction between the unit volume and neutrons, reduce the MA transmutation rate, reduce the thermal neutron content in the fast reactor, and 6 LiD conversion is inefficient and therefore 6 The decrease in the fraction of MA per unit volume caused by the addition of LiD to the MA coating has a greater effect on the decrease in the rate of MA transmutation than 6 The effect of LiD on MA-transmutation rate increase, FIG. 10 compares 6 The neutron flux in a sodium-cooled fast reactor was varied at ratios of LiD/MA loading of 7:3 and 3:7, respectively 6 LiD and MA are increased under different loading ratios 6 The ratio of the LiDs has little effect on the variation in the neutron flux of the reactor.
The number of equipment and the scale of processing described herein are intended to simplify the description of the present invention. Applications, modifications and variations of the present invention will be readily apparent to those skilled in the art.
Although embodiments of the present invention have been disclosed above, it is not limited to the details and embodiments shown and described, it is well suited to various fields of use for which the invention would be readily apparent to those skilled in the art, and accordingly, the invention is not limited to the specific details and illustrations shown and described herein, without departing from the general concepts defined in the claims and their equivalents.
Claims (5)
1. A non-uniform MA transmutation rod for a fast neutron reactor, comprising:
a fuel rod main body, the outside of which is provided with a MA nuclide coating or MA nuclide and 6 a mixed coating of LiD;
the MA nuclide coating and the MA nuclide composition comprise 237 Np、 241 Am、 243 Am、 244 Cm, where 237 The mass ratio of Np is 56.2%, 241 am is 26.4% by mass, 243 am is 12% by mass, 244 the mass ratio of Cm is 5.4%;
the MA species 6 The LiD mixed coating is prepared from MA nuclide 6 The LiD is prepared by uniformly mixing according to the mass ratio, and MA nuclide 6 The mass ratio of LiD is one of 7:3, 5:5, 4:6 or 3:7.
2. The non-uniform MA transmutation rod for a fast neutron reactor according to claim 1, wherein the radius of the non-uniform MA transmutation rod is 0.5cm, and the thickness of the MA nuclide coating is 0.001-0.05 cm.
3. The non-uniform MA transmutation rod for a fast neutron reactor of claim 1, wherein the loading of U and Pu isotopes in the fuel rod body decreases with increasing MA nuclide loading.
4. The heterogeneous MA transmutation rod for a fast neutron reactor of claim 1, wherein the fuel rod body employs a MOX fuel, the nuclide composition of the MOX fuel comprising 238 U、 235 U、 238 Pu、 239 Pu、 240 Pu、 241 Pu and 242 pu, wherein, 238 U、 235 the ratio of U is 0.003:1, 238 Pu、 239 Pu、 240 Pu、 241 pu and 242 pu is present in a ratio of 0.025:1.5375:0.55: 0.2975:0.1025.
5. The non-uniform MA transmutation rod for a fast neutron reactor according to claim 1, wherein the non-uniform MA transmutation rod is loaded in an inner region of a fuel assembly, the fuel assembly loaded with the non-uniform MA transmutation rod is provided with a plurality of layers in a reactor core, each layer of fuel assemblies are arranged in a hexagonal manner in the reactor core, and two adjacent layers of fuel assemblies are arranged at intervals.
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