• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
  • 引用文献
  • 法律状态
  • 优先权
    • 专利摘要:
    According to one embodiment, a method for designing a light water reactor fuel assembly comprises: accumulating determined fuel data (S 10), showing that each pair of a combination of p * n / N and e for the core is feasible or not, in which N is a number of fuel rods of the fuel assembly, n is a number of fuel rods containing consumable poison, p is a ratio in% by weight of the consumable poison in the fuel assembly and e is an enrichment in% by weight of the uranium 235 contained in the fuel assembly; formulating a criterion formula (S11) that determines whether a combination of p * n / N and e for a core is feasible or not and is formulated on the basis of the determined fuel data; and determining (S 13) whether a temporarily defined fuel composition is approved for a heart or not based on the criterion formula.
    公开号:FR3062746A1
    申请号:FR1851064
    申请日:2018-02-08
    公开日:2018-08-10
    发明作者:Satoshi Wada；Hiroshi Matsumiya；Tsukasa SUGITA；Rei KIMURA；Rie Aizawa；Noriyuki Yoshida
    申请人:Toshiba Corp；Toshiba Energy Systems and Solutions Corp；
    IPC主号:
    专利说明:

    Holder (s): KABUSHIKI KAISHA TOSHIBA, TOSHIBA ENERGY SYSTEMS & SOLUTIONS CORPORATION.
    Extension request (s)
    Agent (s): CABINET FEDIT LORIOT.
    FUEL ASSEMBLY, METHOD FOR DESIGNING A HEART AND METHOD FOR DESIGNING A LIGHT WATER REACTOR.
    FR 3,062,746 - A1 (5 /) According to one embodiment, a method of designing a fuel assembly of a light water reactor comprises: the accumulation of determined fuel data (S 10), showing that each pair d 'a combination of p * n / N and e for the core is feasible or not, in which N is a number of fuel rods of the fuel assembly, n is a number of the fuel rods containing the consumable poison, p is a ratio in% by weight of the poison consumable in the fuel assembly and e is an enrichment in% by weight of the uranium 235 contained in the fuel assembly; the formulation of a criterion formula (S11) which determines whether a combination of p * n / N and e for a core is feasible or not and is formulated on the basis of the determined fuel data; and determining (S 13) whether or not a temporarily defined fuel composition is approved for a core on the basis of the criterion formula.

    -1 FUEL ASSEMBLY, METHOD OF DESIGNING A CORE AND METHOD OF DESIGNING A LIGHT WATER REACTOR
    In its field, the embodiments of the present invention relate to a fuel assembly, to a process for designing a core and to a process for designing a fuel for a light water reactor.
    In the background, a nuclear reactor is generally controlled such that an excess of fuel reactivity becomes zero at the end of the cycle (FDC) in a light water reactor fuel assembly and a light water reactor core .
    In a boiling water reactor (REB), a concentration control is implemented so that the neutron absorption capacity of a consumable poison, such as gadolinium oxide (gadoline), is fully consumed at the end of the cycle (FDC). There are cases in which thermal characteristics of the core are improved for an IPL core, which is a first cycle core of the REB reactor, by intentionally ensuring that the consumable poison of a minor proportion of the fuel is not consumed, while compensating for the lack of excess reactivity with the remaining fuel.
    In a pressurized water reactor (PWR), a concentration control is implemented so that a concentration of boric acid for chemical compensation is zero at the end of the cycle (FDC). The enrichment in fissile material is controlled according to a nuclear combustion objective
    -2 unloading (same meaning as completion of nuclear combustion) etc., and thus an excessively high enrichment is not used.
    In addition, when the used nuclear fuel is recycled, the light water reactor fuel mentioned above and the fuel used in the light water reactor core are discharged from the core and then reprocessed. Then, the uranium and plutonium isotopes are extracted for reuse, and minor actinides are discarded as highly radioactive waste. Minor actinides have a high toxicity, so that particularly dangerous minor actinides are separated by a reprocessing process called separation. The separated minor actinides are added to the MOX fuel (mixed oxide) and burned in a fast reactor or subjected to irradiation in an accelerator with the minor actinides as a target in order to undergo transmutation into a low toxicity nuclide. As described above, what is called separation and transmutation processing is considered to be accomplished.
    The drawings are briefly described below.
    Figure 1 is a plan cross-sectional view showing a control rod, four fuel assemblies surrounding the control rod, and their environment in a REB reactor core according to an embodiment of the present invention.
    FIG. 2 is a view showing in detail an example of the internal configuration of the fuel assembly in the REB reactor core according to the embodiment of the present invention and, more specifically, FIG. 2 is a schematic view detailed in Part II of Figure 1.
    FIG. 3 is a view showing in detail another example (different from the example in FIG. 2) of the internal configuration of the fuel assembly in the REB reactor core according to the embodiment of the present invention and, more specifically, FIG. 3 is a detailed schematic view of part II of FIG. 1.
    Figure 4 is a plan cross-sectional view showing the structure of a fuel rod constituting a REB reactor fuel assembly according to the embodiment of the present invention.
    FIG. 5 is an example of a graph representing results on the feasibility of the core which is determined for different combinations of an average mass ratio of consumable poison and an enrichment of uranium in the fuel assembly of REB reactor according to the embodiment of the present invention by applying an analysis calculation to the latter.
    Figure 6 is a graph showing an example of an analysis result on the relationship between a nuclear combustion cycle and excess reactivity when the fuel assembly falls within the optimal range of the average mass ratio of consumable poison of Figure 5 is burned in a REB reactor.
    FIG. 7 is a graph schematically representing a change in an infinite multiplication factor of fuel assembly when the enrichment of uranium is increased in a design of the fuel assembly according to the embodiment of the present invention.
    Figure 8 is a graph schematically showing a change in the number of fuel rods containing consumable poison corresponding to a change in the reactivity of the consumable poison in the design of the fuel assembly according to the embodiment of the present invention.
    Fig. 9 is an algorithm showing a procedure of the fuel assembly design method according to the embodiment of the present invention.
    FIG. 10 is a graph representing values of the ten best control rods in terms of reactivity value in a control cell core of a conventional conventional REB reactor.
    A detailed description will now be made.
    When a single-treatment cycle is adopted (that is, the reuse of nuclear fuel is not implemented), the spent fuel is subject to final disposal as is. In a single treatment cycle, a process such as separation and transmutation mentioned above is not
    -4not implemented, so that the toxicity of minor actinides is not reduced.
    On the other hand, an intentional use of fuel with high uranium enrichment allows the reduction of the production of minor actinides. This is due to the fact that the use of uranium fuel with a high uranium 235 enrichment increases the nuclear fission reaction rate with uranium 235 reducing the absorption reaction rate caused by uranium 238 , thus ensuring the reduction of the production of minor actinides. However, an increase in uranium-235 enrichment increases the excess reactivity, with the result that the excess reactivity can exceed a reactivity value given by reactivity control devices such as control bars, which can make it difficult to control responsiveness.
    The increase in excess reactivity caused by the increase in uranium enrichment can be suppressed by using a consumable poison. Consumable poison can also be used effectively for a fuel assembly whose uranium enrichment is increased to ensure a reduction in the toxicity of minor actinides. However, a large number of complex calculations have to be performed in order to determine the concentration or the number of fuel rods containing consumable poison, and thus an efficient design has so far not been obtained.
    The embodiments of the present invention were created in order to solve the above problems, and their objective is to reduce the excess reactivity when the enrichment of uranium is increased in a light water reactor.
    According to one embodiment, a method of designing a fuel assembly of a light water reactor is created, which comprises a plurality of fuel rods arranged in parallel, separated by a certain distance in a direction perpendicular to the longitudinal axis of the fuel rods, the fuel rod having a fuel coating and a fuel
    -5in the fuel coating, the fuel containing uranium dioxide material containing uranium enriched in U235, some of the fuel rods having a poison consumable in the fuel, the method comprising: accumulating data of determined fuel studied by analyzes or experiments, showing that each couple of a combination of p- n / 04 and e is either feasible for the heart or is not approved for the heart, in which N is a higher whole number or equal to 2 and a number of the fuel rods in the fuel assembly, n is a number of the fuel rods containing the consumable poison and an integer greater than or equal to 1 and less than N, p is a ratio in% by weight poison consumable in the fuel and e is an enrichment in% by weight of the uranium 235 contained in all the fuel rods in the fuel assembly; the formulation of a criterion formula which determines whether a combination of p · n / N and e is feasible for a core or is not feasible for a core and is formulated on the basis of the determined fuel data; and determining whether a temporarily defined composition of the fuel assembly is approved for a core or is not approved for a core based on the criteria formula.
    According to one embodiment, a method of designing a core of a light water reactor is created, which comprises a plurality of fuel assemblies arranged in parallel and arranged in a square lattice matrix separated by a certain distance in a direction perpendicular to the longitudinal axis of the fuel assemblies, a device for reactivity control over the distance between the fuel assemblies, a plurality of fuel rods arranged in parallel, separated by a certain distance in a direction perpendicular to the longitudinal axis fuel rods in the fuel assembly, fuel rods having a fuel coating and a fuel in the fuel coating, the fuel containing uranium dioxide material containing uranium enriched in U235, some fuel rods having a poison consumable in the fuel, the pr oced including: accumulating fuel data
    -6 determinants studied by analyzes or experiments, showing that each couple of a combination of p · n / N and e is approved for the heart or is not approved for the heart, in which N is a whole number greater than or equal to 2 and a number of the fuel rods in the fuel assembly, n is a number of the fuel rods containing the consumable poison and an integer greater than or equal to 1 and less than N, p is a ratio in% by weight of the poison consumable in fuel and e is a% enrichment by weight of uranium 235 contained in all the fuel rods in the fuel assembly; the formulation of a criterion formula which determines whether a combination of p- n / N and e is approved for a core or is not approved for a core and is formulated on the basis of the determined fuel data; and determining whether a temporarily defined composition of the fuel assembly is approved for a core or is not approved for a core based on the criteria formula.
    Preferably, e is greater than or equal to 5%.
    Preferably, the criterion formula is al · e — b <p · n / N <a2- e — c, in which each of al, a2, b and c is a positive constant and al is greater than or equal to a2.
    Preferably, each of a1 and a2 is equal to 0.57, b is equal to 1.8 and c is equal to 0.8.
    Preferably, the enrichment of uranium enriched in U235 in the fuel containing the consumable poison is less than the maximum enrichment of uranium enriched in U235 in the fuel of the fuel assembly.
    Preferably, the fuel rods are arranged in a square lattice matrix and at least one of the fuel rods containing the consumable poison is not located opposite other fuel rods with at least one side of the four sides of the rods of fuel arranged in the square lattice matrix.
    Preferably, the fuel rods are arranged in a square lattice matrix and at least one of the fuel rods containing the poison
    - 7consumable is located opposite other fuel rods containing the consumable poison, at least one side of the four sides of the fuel rods being arranged in the square lattice matrix.
    Preferably, the consumable poison contains compounds containing gadolinium, erbium or boron.
    Preferably, the consumable poison is gadoline and the maximum concentration of gadoline in the fuel is less than 20% by weight.
    Preferably, the consumable poison is gadoline in which the odd atomic mass gadoline is more concentrated than the even atomic mass gadoline.
    The present invention also relates to a method for designing a core of a light water reactor, which comprises a plurality of fuel assemblies arranged in parallel and arranged in a square lattice matrix separated by a certain distance in a direction perpendicular to the longitudinal axis of the fuel assemblies, a device for controlling the reactivity over the distance between the fuel assemblies, a plurality of fuel rods arranged in parallel, separated by a certain distance in a direction perpendicular to the longitudinal axis of the fuel rods of fuel in the fuel assembly, the fuel rods having a fuel coating and a fuel in the fuel coating, the fuel containing uranium dioxide material containing uranium enriched in U235, some of the bars of fuel containing a poison consumable in the fuel, the proc dice including: the accumulation of determined fuel data studied by analyzes or experiments, showing that each couple of a combination of p · n / N and e is approved for the heart or is not approved for the heart, in which N is an integer greater than or equal to 2 and a number of the fuel rods in the fuel assembly, n is a number of the fuel rods containing the consumable poison and an integer greater than or equal to 1 and less than N, p is a ratio in% by weight of the poison consumable in the fuel and e is an enrichment in% by weight of the uranium 235 contained in all
    -8 fuel rods in the fuel assembly; the formulation of a criterion formula which determines whether a combination of p · n / N and e is approved for a core or is not approved for a core and is formulated on the basis of the determined fuel data; and determining whether a temporarily defined composition of the fuel assembly is approved for a core or is not approved for a core based on the criteria formula.
    Preferably, the fuel rods containing the consumable poison are not arranged near the reactivity control device.
    Preferably, the light water reactor includes a nuclear instrumentation device arranged in a gap between the fuel assemblies, different from a gap in which the reactivity control device is arranged, and the fuel rods containing the consumable poison do not are not arranged near the nuclear instrumentation device.
    Preferably, a reactivity controller and some of the fuel rods surrounding the reactivity controller make up a control cell, and the temporarily defined fuel composition of the control cell is determined by the criteria formula.
    According to one embodiment, a fuel assembly for a light water reactor is created comprising: a plurality of fuel assemblies arranged in parallel and arranged in a square lattice matrix separated by a certain distance in a direction perpendicular to the longitudinal axis of fuel assemblies; a plurality of fuel rods arranged in parallel, separated by a certain distance in a direction perpendicular to the longitudinal axis of the fuel rods in the fuel assembly; a coating of fuel contained in the fuel rods; a fuel contained in the fuel rods and covered by the fuel coating and containing a material based on uranium dioxide containing uranium enriched in U235, in which some of the fuel rods contain a poison which is consumable in the fuel, and p, η, N and e satisfy
    -9 a formula: 0.57 el, 8 <p * n / N <0.57 e - 0.8 in which N is an integer greater than or equal to 2 and a number of the fuel rods in the fuel assembly, n is a number of fuel rods containing the consumable poison and an integer greater than or equal to 1 and less than N, p is a ratio in% by weight of the consumable poison in the fuel and e is an enrichment in% by weight of l 235 contained in all fuel rods in the fuel assembly.
    Hereinafter, fuel assemblies, core design methods and fuel assembly design methods of a light water reactor according to embodiments of the present invention will be described with reference to the accompanying drawings. Although the following description is made primarily targeting a boiling water reactor, the present invention is also applicable to a pressurized water reactor.
    Figure 1 is a plan cross-sectional view showing a control rod, four fuel assemblies surrounding the control rod, and their environment in a REB reactor core according to an embodiment of the present invention. In FIG. 1, a detailed structure of each fuel assembly is omitted. FIG. 2 is a view showing in detail an example of the internal configuration of the fuel assembly in the REB reactor core according to the embodiment of the present invention. More specifically, FIG. 2 is a detailed schematic view of part II of FIG. 1. FIG. 3 is a view showing in detail another example (different from the example in FIG. 2) of the internal configuration of the fuel assembly in the REB reactor core according to the embodiment of the present invention. More specifically, FIG. 3 is a detailed schematic view of part II of FIG. 1. FIG. 4 is a plan cross-sectional view showing the structure of a fuel rod constituting a fuel assembly of REB reactor according to the embodiment of the present invention.
    In the REB reactor core of the embodiment, several hundred fuel assemblies 10 are arranged according to a square grid in a plane
    -10horizontal. Uranium enrichment is, for example, 3.8% on average on fuel assemblies based on normal uranium. In Japan, for example, facilities for conventional normal uranium fuel assemblies are designed assuming that the uranium enrichment is less than 5.0%. On the other hand, in the light water reactor fuel assemblies 10 of the present embodiment, the uranium enrichment is 5.0% which is higher than that in normal uranium fuel assemblies. In the following description, the uranium enrichment is assumed to be 5.0%, but this is not limiting. As will be described later, the uranium enrichment can be greater than or less than 5.0% as long as effects can be obtained.
    In each fuel assembly 10, a plurality of fuel rods 11 and 12 extending vertically in parallel with each other are arranged in a square grid (9 by 9 in the examples of Figures 2 and 3) in a horizontal plane. The outer periphery of the fuel assembly 10 is surrounded by a substantially cylindrical square-base channel box 13 which extends in the vertical direction. Two water bars 14 (marked by W in Figures 2 and 3) are arranged in the center of the fuel assembly 10. The water bars 14 each have a hollow cylindrical shape extending in the vertical direction to the inside which water circulates. Although the water bars 14 are constituted by two circular tubes in the examples of FIGS. 2 and 3, the number of water bars 14 can be equal to one or three or more, and their shape can be in a cylindrical tube square.
    Each of the fuel rods 11 and 12 has a circular coating tube 20 extending vertically and a nuclear fuel material 21 contained in the coating tube 20. The nuclear fuel material 21 contains uranium oxide containing enriched uranium. The nuclear fuel material 21 is normally formed into a plurality of pellets in a column and the pellets are stacked axially in the coating tube 20. The fuel rods 12 are fuel rods containing the consumable poison (marked with G in Figures 2 and 3), and the combustible material
    - It nuclear 21 in the fuel rod 12 contains a consumable poison (for example, gadoline). The fuel rods 11 are fuel rods containing no consumable poison (marked with R in Figures 2 and 3), and the nuclear fuel material 21 in the fuel rods 11 does not contain consumable poison.
    A command using a control cell core is considered as a reactivity command for the REB reactor. It is a heart design in which the number of unit cells, in each of which a control bar is inserted during normal operation, is reduced. Each of the control rods used for power control during normal operation is surrounded by four fuel assemblies to obtain a control cell. More specifically, in the control cell, a control bar (reactivity control device) 30 having the shape of a cross in horizontal cross section and extending vertically is disposed in the center of fuel assemblies 10 arranged 2 by 2 , mutually adjacent. During normal operation of the nuclear reactor, light water is placed outside the channel boxes 13. The control rods 30 are inserted into the water outside the channel boxes 13 and removed from that ci in the vertical direction so as to be able to control the power of the nuclear reactor.
    A local power range control device (LPRM) 31, as a nuclear instrumentation device, is disposed outside the channel boxes 13 at a position diagonal from the center of the control rod 30.
    In general, the thermal conductivity of consumable poison such as gadoline is lower than that of uranium oxide. Thus, the enrichment in uranium 235 in the nuclear fuel material 21 enclosed in the fuel bar containing consumable poison 12 is at a lower level than the maximum value of the enrichment in uranium 235 in the nuclear fuel material 21 contained in the fuel assembly 10. With this configuration, it is possible to prevent the thermal power of the
    - 12combustible containing consumable poison 12 is greater than the thermal power of the other fuel rods so as to prevent fuel rods containing consumable poison 12 from overheating.
    As shown in FIGS. 2 and 3, in the fuel assembly 10, the fuel rods containing consumable poison 12 cannot be placed at locations adjacent to the control rod 30. This configuration prevents reduction in the rate absorption if the control rod 30 absorbs thermal neutrons, which are capable of contributing to a nuclear fission reaction, so that a core can be designed without implying a reduction in the reactivity value of the control rod 30.
    Furthermore, preferably, as shown in FIGS. 2 and 3, in the fuel assembly 10, the fuel rods containing consumable poison 12 are not disposed adjacent to the nuclear instrumentation device 31. With this configuration, a core can be designed without reducing the precision of the nuclear instrumentation device 31.
    In addition, as shown in FIGS. 2 and 3, in the fuel assembly 10, at least one fuel bar containing consumable poison 12 may not be adjacent, on at least its first surface among the four surfaces corresponding to the four directions along which the fuel rods in the form of a square grid are arranged, to the other fuel rods 11 or 12. That is to say, that at least one fuel rod containing consumable poison 12 is disposed of adjacent, for example, to the water bar 14 or the channel box 13 at the outermost peripheral portion of the assembly. With this configuration, the thermal neutrons by which the consumable poison is likely to undergo an absorption response often collide with the consumable poison, thereby increasing the rate of neutrons absorbed by the consumable poison. This increases the reactivity value of the consumable poison in order to significantly remove the excess reactivity.
    In addition, as shown in FIGS. 2 and 3, in the fuel assembly 10, at least certain fuel rods containing consumable poison 12 can be arranged adjacent to each other. By adjacent arrangement of the fuel rods containing consumable poison 12, the number of collisions of the consumable poison on adjacent surfaces with thermal neutrons is reduced. This decreases the rate of combustion of the consumable poison, with the result that the reactivity of the consumable poison continues longer than in a case in which the fuel rods containing consumable poison 12 are not disposed adjacent to each other. the other.
    FIG. 5 is an example of a graph representing the feasibility results of the core which is determined for different combinations of average mass ratio of consumable poison and uranium enrichment in the REB reactor fuel assembly according to the mode of the present invention by applying an analysis calculation to them. The average mass ratio of consumable poison is represented by (concentration of consumable poison p) x (ratio of number of fuel rods containing consumable poison). The ratio of the number of fuel rods containing consumable poison is represented by (the number n of fuel rods containing consumable poison / total number N of fuel rods contained in the fuel assembly). Consequently, the average mass ratio of consumable poison is represented by (p · n / N). The core feasibility criterion concerns the fact that the excess fuel reactivity can be controlled or not by a reactivity control device such as a control bar, which can complicate the control of reactivity. Fuel is feasible when its excess reactivity is less than or equal to the reactivity that the control rods can control. Fuel is not feasible when its excess reactivity is greater than the reactivity that the control rods can control.
    In the nuclear characteristic evaluation analysis of FIG. 5, the same configuration as that of the fuel assembly shown on the
    - 14figures 2 and 3 is assumed. Assuming that an infinite number of fuel assemblies are arranged in a grid in horizontal directions, the feasibility of the core can be determined. The consumable poison is assumed to be gadolinium.
    In the nuclear characteristic evaluation analysis of FIG. 5, the fuel rods in the fuel assembly are arranged according to a grid of 9 by 9. However, the nuclear characteristics (neutron spectrum) of the fuel assembly have a strong influence on core characteristics, so that substantially the same results as those of FIG. 5 are obtained independently of the number of fuel rods in the fuel assembly if a hydrogen-uranium ratio of the fuel assembly is identical . For example, even when the fuel rods in the fuel assembly are arranged according to a 10 by 10 grid or an 11 by 11 grid, substantially the same results as those of FIG. 5 are obtained.
    In the example of FIG. 2, the number n of fuel rods containing consumable poison 12 is equal to 24 and the total number N of fuel rods contained in the fuel assembly is equal to 74; and in the example of figure 3, the number n is equal to 36 and the number N is equal to 74.
    The uranium enrichment is assumed to be zero. In this case, whether the core is feasible or not is determined for different combinations of the average mass ratio of consumable poison (p · n / N) and the enrichment of uranium e by performing the analysis. As a result, two straight lines are obtained as the boundary condition determining whether the core is feasible or not as shown in Figure 5. That is, a range in which the average mass ratio of consumable poison (p · n / N) is greater than (0.57 e - 1.8) and less than (0.57 e - 0.8) is the optimum ratio of addition of consumable poison. That is to say, a criterion formula (1) indicating a specification of realization of the feasible core in this case is represented by the following expression:
    0.57 e - 1.8 <(p · n / N) <0.57 e - 0.8 - (1)
    -15 Thus, a real conception of the fuel assembly can be made using the formula of criterion (1).
    For the purpose of designing different types of fuel assemblies under different conditions, the fact that the core is feasible or not is determined for a sufficient number of different combinations of the average mass ratio of consumable poison (p · n / N) and enrichment of uranium e by performing the analysis or experiment satisfying the individual conditions, so that data (results) according to the individual conditions are accumulated, and thus, the graph as shown in the figure 5 can be obtained. On the basis of the graph obtained, criterion formulas corresponding to the criterion formula (1) under individual conditions can be obtained.
    The following criteria (2) are considered to be generally more appropriate.
    al · e - b <(p · n / N) <a2 · e - c - (2)
    In the previous expression, al, a2, b, and c each represent a positive constant, and al> a2.
    Although the previous criteria formulas (1) and (2) are linear expressions, they can be quadratic expressions or any other type of expression.
    Figure 6 is a graph showing an example of an analysis result on the relationship between a nuclear combustion cycle and excess reactivity when the fuel assembly falls within the optimal range of the average mass ratio of consumable poison of Figure 5 is burned in a REB reactor. FIG. 7 is a graph schematically representing a change in an infinite multiplication factor of fuel assembly when the enrichment of uranium is increased in a design of the fuel assembly according to the embodiment of the present invention. FIG. 8 is a graph schematically representing a change in the number of fuel rods containing consumable poison corresponding to a change in the reactivity of the consumable poison in the design of the assembly
    -16combustible according to the embodiment of the present invention. Although a straight line is shown in Figures 7 and 8, each of these graphs is schematic, and the change may not be represented by straight lines.
    FIG. 10 is a graph representing values of the ten best control rods in terms of reactivity value in a control cell core of a conventional conventional REB reactor. As shown in Figure 10, the control bar reactivity value of the control cell is slightly greater than 0.1% Ak at a maximum. In an advanced boiling water reactor (REBA), up to 29 control cells are provided, so that the excess reactivity which can be controlled by the control cell is less than or equal to 3% Ak.
    By defining a combination of the average mass ratio of consumable poison (p · n / N) and the enrichment of uranium e of the fuel assembly 10 so as to satisfy the formula of criterion (1) or (2) , the excess reactivity during a nuclear reactor operating cycle can be defined so as to be between 0 and 3.0% Ak which is a range which can be obtained under the control of the control bar, as shown in FIG. 6. This is due to the fact that a variation in reactivity (AS (Ae)) when the enrichment of uranium e in FIG. 7 is modified for (e + Ae) coincides with a variation in reactivity (AS (AGd)) of FIG. 8 when an absorbent material is modified relative to the number n of fuel rods containing consumable poison in the fuel assembly and to the average mass ratio added. That is, by changing the total amount of poison consumable per AGd, the variation Ae in uranium enrichment e can be compensated.
    Next, a method of defining a light water reactor fuel assembly using the investigation results described above will be described with reference to FIG. 9. FIG. 9 is an algorithm representing a procedure of the assembly design method fuel according to the embodiment of the present invention.
    - 17 First, the configuration of the light water reactor fuel assembly is assumed to be within a predetermined range, and the feasibility of the core is determined for different combinations of the average mass ratio of consumable poison (p · n / N) and enrichment of uranium e by performing an analysis calculation or an experiment, so that the data for determining the feasibility of the core are accumulated as shown in FIG. 5 (step S10 ).
    Then, like the previous criterion formula (1) or (2), a heart feasibility criterion formula is decided for different combinations of the average mass ratio of consumable poison (p · n / N) and the enrichment of uranium e on the basis of core feasibility determination data obtained in step S10 (step SI 1).
    Then, a specific combination of an average mass ratio of consumable poison (p · n / N) and an enrichment of uranium e of the light water reactor fuel assembly is assumed (step S12), and the feasibility of the heart is determined for the combination assumed on the basis of the formula of criterion of feasibility of the heart obtained in step SI 1 (step S13).
    When the determination result of step S13 is NO (not feasible), the combination of the average mass ratio of consumable poison (p · n / N) and the enrichment of uranium e is modified, and the steps S12 and S13 are executed again. On the other hand, when the result of determination of step S13 is YES (feasible), the definition of the fuel assembly is determined by the combination of the average mass ratio of consumable poison (p · n / N) and of enrichment of uranium e at this time (step S14).
    According to the design process described above, the excess reactivity when uranium enrichment is increased in a light water reactor can be reduced. Furthermore, by deciding on the core feasibility criterion formula in advance, the core feasibility can be easily checked when different parameters are modified in a specific design of the fuel assembly, making it possible to accelerate the design work,
    -18 while saving labor.
    In the embodiment, the consumable poison to be added to the nuclear fuel material is preferably a gadolinium-containing compound, an erbium-containing compound, or a boron-containing compound.
    When the consumable poison to be added to the nuclear fuel material is gadoline, the maximum mass ratio thereof is preferably less than 20% by mass. This is due to the fact that when the maximum mass ratio of gadoline is greater than or equal to 20% by mass, a mixture of gadoline and uranium oxide is less likely to form a solid solution.
    As the consumable poison in the embodiment, gadolinium obtained by concentrating gadolinium with an odd atomic mass (for example, 155 or 157) is preferably used. This increases the absorption cross section of gadolinium, reducing the additive amount of the consumable poison.
    In addition, by installing the fuel assembly in the light water reactor core comprising the control cell, a range of change in reactivity due to the operation of the control rod can be reduced, making it possible to satisfy a thermal equilibrium of the fuel assembly in the light water reactor core.
    While certain embodiments have been described, these embodiments have been presented only by way of example and are not intended to limit the scope of the invention. Obviously, the new embodiments described here can be implemented in a variety of other forms; further, various changes, omissions and substitutions on the form of the embodiments described herein can be made without departing from the spirit of the invention. The invention described above and its equivalents are intended to cover such forms or variants which fall within the scope of the invention.
    权利要求:
    Claims (15)
    [1" id="c-fr-0001]
    1. Method for designing a fuel assembly (10) of a light water reactor, which comprises a plurality of fuel rods (11; 12) arranged in parallel, separated by a certain distance in a direction perpendicular to the longitudinal axis of the fuel rods, the fuel rod comprising a fuel coating (20) and a fuel in the fuel coating, the fuel containing a uranium dioxide material containing uranium enriched in U235, some of the fuel rods (12) comprising a poison consumable in the fuel, the method comprising:
    the accumulation of determined fuel data (S 10), studied by analyzes or experiments, showing that each pair of a combination of p- nXN and e is either feasible for the heart or is not approved for the heart, in which N is an integer greater than or equal to 2 and a number of the fuel rods in the fuel assembly, n is a number of the fuel rods containing the consumable poison and an integer greater than or equal to 1 and less than N, p is a ratio in% by weight of the poison consumable in the fuel and e is an enrichment in% by weight of the uranium 235 contained in all the fuel rods in the fuel assembly;
    the formulation of a criterion formula (Sll) which determines whether a combination of p · n / N and e is feasible for a core or is not feasible for a core and is formulated on the basis of the determined fuel data; and determining (S 13) whether a temporarily defined composition of the fuel assembly is approved for a core or is not approved for a core based on the criterion formula.
    [2" id="c-fr-0002]
    2. Method for designing the fuel assembly of the light water reactor according to claim 1, in which e is greater than or equal to 5%.
    [3" id="c-fr-0003]
    3. Method for designing the fuel assembly of the light water reactor according to claim 1 or 2, in which the criterion formula is
    -20al · e — b <p · n / N <a2 · e — c, where each of al, a2, b and c is a positive constant and al is greater than or equal to a2.
    [4" id="c-fr-0004]
    4. Method for designing the fuel assembly of the light water reactor according to claim 3, in which each of a1 and a2 is equal to 0.57, b is equal to 1.8 and c is equal to 0.8.
    [5" id="c-fr-0005]
    5. Method for designing the fuel assembly of the light water reactor according to any one of claims 1 to 4, in which the enrichment of uranium enriched in U235 in the fuel containing the consumable poison is less than maximum enrichment of uranium enriched in U235 in the fuel of the fuel assembly.
    [6" id="c-fr-0006]
    6. Method for designing the fuel assembly of the light water reactor according to any one of claims 1 to 5, in which the fuel rods are arranged in a square lattice matrix and at least one of the fuel rods containing the consumable poison is not located opposite other fuel rods with at least one side of the four sides of the fuel rods arranged in the square lattice matrix.
    [7" id="c-fr-0007]
    7. A method of designing the fuel assembly of the light water reactor according to any one of claims 1 to 6, in which the fuel rods are arranged in a square lattice matrix and at least one of the fuel rods containing the consumable poison is located opposite other fuel rods containing the consumable poison, at least one side of the four sides of the fuel rods being arranged in the square lattice matrix.
    [8" id="c-fr-0008]
    8. A method of designing the fuel assembly of the light water reactor according to any one of claims 1 to 7, wherein the consumable poison contains compounds containing gadolinium, erbium or boron.
    [9" id="c-fr-0009]
    9. A method of designing the fuel assembly of the light water reactor according to any one of claims 1 to 8, in which the consumable poison is gadoline and the maximum concentration of gadoline in the fuel is less than 20%. in weight.
    -21
    [10" id="c-fr-0010]
    10. A method of designing the fuel assembly of the light water reactor according to any one of claims 1 to 9, in which the consumable poison is gadoline in which the gadoline of odd atomic mass is more concentrated than the gadoline of Even atomic mass.
    [11" id="c-fr-0011]
    11. Method for designing a core of a light water reactor, which comprises a plurality of fuel assemblies arranged in parallel and arranged in a square lattice matrix separated by a certain distance in a direction perpendicular to the longitudinal axis fuel assemblies, a device for reactivity control over the distance between the fuel assemblies, a plurality of fuel rods arranged in parallel, separated by a certain distance in a direction perpendicular to the longitudinal axis of the fuel rods of the assembly fuel, fuel rods having a fuel coating and fuel in the fuel coating, fuel containing uranium dioxide material containing uranium enriched in U235, some of the fuel rods having consumable poison in fuel, the process comprising:
    the accumulation of determined fuel data studied by analyzes or experiments, showing that each couple of a combination of p · n / N and e is approved for the heart or is not approved for the heart, in which N is an integer greater than or equal to 2 and a number of the fuel rods in the fuel assembly, n is a number of the fuel rods containing the consumable poison and an integer greater than or equal to 1 and less than N, p is a ratio in% by weight of the poison consumable in the fuel and e is an enrichment in% by weight of the uranium 235 contained in all the fuel rods in the fuel assembly;
    the formulation of a criterion formula which determines whether a combination of p · nXN and e is approved for a core or is not approved for a core and is formulated on the basis of the determined fuel data; and determining whether a temporarily defined composition of
    -22 the fuel assembly is approved for a core or is not approved for a core based on the criteria formula.
    [12" id="c-fr-0012]
    12. Method for designing the core of the light water reactor according to claim 11, in which the fuel rods containing the consumable poison are not arranged near the reactivity control device.
    [13" id="c-fr-0013]
    13. Method for designing the core of the light water reactor according to claim 11 or 12, in which the light water reactor comprises a nuclear instrumentation device arranged in a gap between the fuel assemblies, different from a gap in which the reactivity control device is arranged, and the fuel rods containing the consumable poison are not arranged near the nuclear instrumentation device.
    [14" id="c-fr-0014]
    14. Method for designing the core of the light water reactor according to any one of claims 11 to 13, in which a reactivity control device and some of the fuel rods surrounding the reactivity control device compose a control cell, and the temporarily defined fuel composition of the control cell is determined by the criteria formula.
    [15" id="c-fr-0015]
    15. Light water reactor fuel assembly comprising; a plurality of fuel assemblies (10) arranged in parallel and arranged in a square lattice matrix separated by a certain distance in a direction perpendicular to the longitudinal axis of the fuel assemblies;
    a plurality of fuel rods (11; 12) arranged in parallel, separated by a certain distance in a direction perpendicular to the longitudinal axis of the fuel rods in the fuel assembly;
    a fuel coating (20) contained in the fuel rods; a fuel contained in the fuel rods and covered by the fuel cladding and containing a uranium dioxide material containing uranium enriched in U235, in which some of the fuel rods (12) contain poison consumable in the fuel, and p,
    -23 η, N and e satisfy a formula: 0.57 el, 8 <p * n / N <0.57 e - 0.8 in which N is an integer greater than or equal to 2 and a number of the bars of fuel in the fuel assembly, n is a number of the fuel rods containing the consumable poison and an integer greater than or equal to 1 and
    5 less than N, p is a% by weight ratio of the consumable poison in the fuel and e is a% by weight enrichment of the uranium 235 contained in all the fuel rods in the fuel assembly.
    1/10 FIG. 1
    2/10 FIG. 2
    3/10 FIG. 3 © CES
    4/10 FIG. 4
    He (12)
    5/10
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    2020-04-17| PLSC| Publication of the preliminary search report|Effective date: 20200417 |
    2021-01-04| PLFP| Fee payment|Year of fee payment: 4 |
    2022-01-18| PLFP| Fee payment|Year of fee payment: 5 |
    优先权:
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    JP2017022319|2017-02-09|
    JP2017022319|2017-02-09|
    JP2017217136A|JP6878251B2|2017-02-09|2017-11-10|Fuel assembly for light water reactors, core design method for light water reactors, and fuel assembly design method for light water reactors|
    JP2017217136|2017-11-10|
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