JP2017015602A - Fast reactor core of fast reactor and fast reactor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fast reactor capable of reducing void reactivity compared with a conventional technique without always making a premise of reduction of a height of a reactor core of the fast reactor.SOLUTION: According to an embodiment, a fast-reactor reactor core 1 of a fast reactor having a fuel containing a mixture of plutonium and either depleted uranium or recovered uranium and using a liquid metal as a coolant, comprises: an inner reactor core fuel assembly 110 having a plurality of inner reactor core fuel assembly elements; and an outer reactor core fuel assembly 120 having a plurality of outer reactor core fuel assembly elements. A plutonium enrichment of the fuel in the inner reactor core fuel assembly elements is higher than a plutonium enrichment in the outer reactor core fuel assembly elements, and a fuel loading weight per one inner reactor core fuel assembly 110 is lower than a fuel loading weight per one outer reactor core fuel assembly 120.SELECTED DRAWING: Figure 2

Description

  Embodiments described herein relate generally to a fast reactor core and a fast reactor having the same.

  Fast reactors generate nuclear fission by fast neutrons by using a liquid metal coolant such as sodium that is difficult to slow down neutron energy. Such a fast reactor is suitable for the proliferation of fissile material, and it is extracted by reprocessing spent fuel in a light water reactor to efficiently produce transuranium element (TRU) having a half-life of several hundred thousand years or more. It is characterized by being able to burn.

  On the other hand, in a medium-sized or large-sized (medium-sized) fast reactor, the reactivity (void reactivity) associated with the decrease in the density of the coolant and the generation of voids is positive, unlike the light water reactor. For this reason, the decrease in the density of the coolant and the generation of voids cause the output of the fast reactor core to increase, and if the reactor is not shut down by the control rod, it may lead to a fast reactor core damage accident.

  FIG. 19 shows an example of main specifications of a conventional fuel assembly for a fast reactor core.

  As shown in FIG. 19, the TRU fuel is a solid fuel in both the inner core and the outer core. The Pu enrichment is 20 wt% (wt%) for the inner core and 27 wt% for the outer core, which is lower for the inner core. Further, the fuel load amount is the same for the inner core and the outer core.

  In general, in the fast reactor, neutron leakage from the outer region is larger than that in the central region of the fast reactor core, so that the output in the outer region is smaller than that in the inner region, and the radial power distribution is distorted. Therefore, the power distribution in the radial direction is flattened by making the plutonium (Pu) enrichment of the outer core fuel radially outside the fast reactor core larger than the Pu enrichment of the inner core fuel.

  On the other hand, one of the major factors of void reactivity is an increase in the amount of neutron leakage from the fast reactor core due to the generation of voids, which causes negative reactivity. The other is an increase in neutron energy that accompanies a reduction in neutron moderation by the coolant, resulting in positive reactivity. In the medium and large-sized furnace, the absolute value of the reactivity due to the negative reactivity factor of the former becomes small, so that the reactivity becomes positive as a whole. Moreover, in the inner core where neutron leakage is small, the reactivity per unit coolant volume is larger than that in the outer core.

  On the other hand, in an infinite system with no neutron leakage, based on the results of examining the relationship between Pu enrichment and void reactivity, the lower the Pu enrichment, the greater the void reactivity. In uranium (U), there are a threshold fission reaction in a high energy region and a neutron capture reaction in a medium velocity energy region. As the coolant voids are generated, the neutron spectrum becomes harder, that is, shifted to a higher energy side, whereby the former threshold fission reaction is increased and the latter neutron capture reaction is decreased. As a result, in a fuel having a low Pu enrichment, that is, a fuel having a large proportion of U, U contributes to a large positive reactivity, so that a fuel having a lower Pu enrichment has a higher void reactivity.

  As described above, by loading fuel with low Pu enrichment into the inner core, the void reactivity per unit coolant volume in the inner core is larger than the void reactivity per unit coolant volume in the outer core. Prone.

  In accidents such as loss of coolant flow rate, as the coolant temperature rises, the inner core fuel, which has a higher void reactivity, is injected with a higher reactivity, which may lead to fast core damage. For this reason, conventionally, research has been conducted to reduce the reactivity when the density of the coolant is reduced or when voids are generated (hereinafter referred to as void reactivity).

  The research aimed at reducing void reactivity is classified into the increase of neutron leakage from the fast reactor core and the reduction of neutron energy (softening of the neutron spectrum).

  As ideas for increasing the neutron leakage from the former fast reactor core, reduction of the fast reactor core height, devising of Pu enrichment distribution in the fast reactor core (for example, non-homogenization of the fast reactor core, etc.), neutrons A device by arrangement | positioning of an absorber, a structural material, a coolant, etc. are mentioned.

  The latter idea for reducing the fast reactor core neutron energy includes loading a neutron moderator on the fast reactor core.

Japanese Patent No. 3054449

  Conventional measures for reducing void reactivity have the following problems.

(1) Reduction of the fast reactor core height To reduce the void reactivity to zero or less (zero or negative) simply by reducing the fast reactor core height, the fast reactor core height needs to be about 30 cm or less. .

  In medium and large reactors with a fast reactor core height of about 100 cm, if the fast reactor core height is lowered to 30 cm, the diameter of the fast reactor core (fast reactor core diameter) will increase by about 80 wt%, and the economy will increase. You will lose. Therefore, in many cases, it is necessary to apply in combination with other measures.

(2) Loading of neutron moderator into the fast reactor core Loading of the neutron moderator into the fast core leads to softening of the neutron spectrum of the fast reactor core, and the breeding ratio decreases. Further, the space loaded with the neutron moderator needs to reduce the amount of fuel loaded or increase the fast reactor core volume accordingly. Furthermore, although it depends on the type of moderator, it is necessary to verify the irradiation characteristics.

(3) Device for Pu enrichment distribution Regarding the device for Pu enrichment distribution, in Patent Document 1, the Pu reactor core height is reduced to 45 cm, and the Pu enrichment in the axial center is increased or decreased in the axial direction. The amount of neutron leakage is increased by increasing the axial neutron flux gradient.

  That is, in this known example, the void reactivity is reduced by combining the reduction of the fast reactor core height and the Pu enrichment distribution in the axial direction. However, reducing the fast reactor core height increases the fast reactor core diameter and affects the radial size of the reactor vessel, which has a great impact on economic efficiency.

  Therefore, an object of the present invention is to provide a fast reactor core in which the void reactivity can be reduced as compared with the prior art without necessarily assuming the reduction of the fast reactor core height in the fast reactor.

  In order to achieve the above-mentioned object, the present embodiment is a fast reactor core of a fast reactor having a fuel containing a mixture of plutonium and deteriorated uranium or recovered uranium and using a liquid metal as a coolant, and is parallel to each other. An inner core fuel assembly having a plurality of inner core fuel assembly elements extending in the vertical direction, and a plurality of outer cores provided radially outside the inner core fuel assembly and extending in parallel to each other and extending in the vertical direction An outer core fuel assembly having a core fuel assembly element, the plutonium enrichment of the fuel in the inner core fuel assembly element being a plutonium enrichment of the fuel in the outer core fuel assembly element The fuel load amount per unit of the inner core fuel assembly is smaller than the fuel load amount per unit of the outer core fuel assembly.

  In addition, the fast reactor according to the present embodiment includes a core having a fuel containing a mixture of plutonium and deteriorated uranium or recovered uranium, a reactor vessel that stores the core and holds liquid metal as a coolant, A shielding plug that covers an upper portion of the reactor vessel and supports a control rod drive mechanism that drives a control rod that controls the reactivity of the core, and the cores are arranged in parallel to each other and extend in the vertical direction. An inner core fuel assembly having a plurality of inner core fuel assembly elements, and an outer side having a plurality of outer core fuel assembly elements arranged in parallel to each other and extending in the vertical direction. A plutonium enrichment of the fuel in the inner core fuel assembly element than a plutonium enrichment of the fuel in the outer core fuel assembly element. Ku, fuel loading weight per piece inner core fuel assemblies is less than the fuel loading weight per piece outer core fuel assemblies, it is characterized.

  According to the embodiment of the present invention, in a fast reactor, it is possible to provide a fast reactor core in which the void reactivity can be reduced as compared with the prior art, without necessarily reducing the fast reactor core height.

It is an elevation sectional view showing composition of a fast reactor concerning a 1st embodiment. 1 is a horizontal sectional view showing a configuration of a fast reactor core according to a first embodiment. 1 is an elevational sectional view showing a configuration of an inner core fuel assembly of a fast reactor core according to a first embodiment. It is a horizontal sectional view showing the composition of the inner core fuel assembly of the fast reactor core concerning a 1st embodiment. It is a horizontal sectional view showing the composition of the fuel element of the inner core fuel assembly of the fast reactor core according to the first embodiment. It is a horizontal sectional view showing the configuration of the outer core fuel assembly of the fast reactor core according to the first embodiment. It is a horizontal sectional view showing the composition of the fuel element of the outer core fuel assembly of the fast reactor core according to the first embodiment. It is a table | surface which shows the main specifications of the fuel assembly of the fast reactor core which concerns on 1st Embodiment. It is a table | surface which shows the comparison of the void reactivity of a fast reactor core which concerns on 1st Embodiment, and an output peaking coefficient. It is a table | surface which shows the main specifications in the case of the modification of the fuel assembly of the fast reactor core which concerns on 1st Embodiment. It is a horizontal sectional view showing the configuration of the inner core fuel assembly of the fast reactor core according to the second embodiment. It is a horizontal sectional view showing the composition of the fuel element of the inner core fuel assembly of the fast core according to the second embodiment. It is a table | surface which shows the main specifications of the fuel assembly of the fast reactor core which concerns on 2nd Embodiment. It is a table | surface which shows the main specifications of the fuel assembly of the fast reactor core which concerns on 3rd Embodiment. It is a horizontal sectional view showing the composition of the inner core fuel assembly of the fast reactor core concerning a 4th embodiment. It is a horizontal sectional view showing the composition of the fuel element of the inner core fuel assembly of the fast core according to the fourth embodiment. It is a horizontal sectional view showing the composition of all the empty elements of the inner core fuel assembly of the fast core according to the fourth embodiment. It is a table | surface which shows the main specifications of the fuel assembly of the fast reactor core which concerns on 4th Embodiment. It is a table | surface which shows the example of the main specifications of the fuel assembly of the conventional fast reactor core.

  Hereinafter, a fast reactor core according to an embodiment of the present invention will be described with reference to the drawings. Here, the same or similar parts are denoted by common reference numerals, and redundant description is omitted.

[First Embodiment]
FIG. 1 is an elevational sectional view showing the configuration of the fast reactor according to the first embodiment. The fast reactor 300 includes a fast reactor core 1, a core support plate 2 that supports the fast reactor core 1, a reactor vessel 6 that houses them and holds a reactor coolant therein, and a shield that covers the top of the reactor vessel 6. It has a plug 5. Here, the reactor coolant is a liquid metal, such as sodium (Na).

  Above the fast reactor core 1, the core upper mechanism 4 that penetrates the shielding plug 5 and is supported by the shielding plug 5 is suspended toward the reactor vessel 6. The core upper mechanism 4 includes a control rod drive mechanism 13 that drives the control rod assembly 11 (FIG. 2), a fast reactor core instrumentation (not shown), and the like.

  A core catcher 3 is provided below the fast reactor core 1 in the reactor vessel 6. The reactor vessel 6 is connected to a coolant inlet pipe 8 for sending the reactor coolant to the reactor vessel 6 and a coolant outlet pipe 9 for sending the reactor coolant from the reactor vessel 6.

  The reactor coolant that has flowed into the reactor vessel 6 from the coolant inlet pipe 8 flows into the lower plenum 8a in which the core catcher 3 is provided. The reactor coolant that has flowed into the lower plenum 8 a changes direction upward, then flows into the fast reactor core 1 from the core support plate 2, passes through the fast reactor core 1, and then flows into the upper plenum 9 a. The reactor coolant flowing into the upper plenum 9a flows out of the reactor vessel 6 through the coolant outlet pipe 9 for heat exchange with the outside.

  FIG. 2 is a horizontal sectional view showing the configuration of the fast reactor core of the fast reactor. The fast reactor core 1 is provided with a core fuel assembly 100, a control rod assembly 11, and a shielding body 12. The core fuel assembly 100 extends in the vertical direction and is arranged in parallel with each other, and the inner core fuel assembly 110 is arranged in parallel with the inner core fuel assembly 110 on the radially outer side of the inner core fuel assembly 110. A plurality of outer core fuel assemblies 120.

  The control rod assemblies 11 are arranged so as to be interspersed with each other in a region where the core fuel assemblies 100 are arranged. The shielding body 12 is disposed on the outer side in the radial direction of the outer core fuel assembly 120.

  In the case of a fast reactor and a breeder reactor, the radial blanket fuel is usually disposed outside the region where the outer core fuel assembly 120 is disposed. This embodiment shows the case of a fast reactor core intended to burn transuranium elements (TRU). Therefore, no blanket fuel is provided in the fast reactor core 1 in the present embodiment.

  FIG. 3 is an elevational sectional view showing the configuration of the inner core fuel assembly. FIG. 4 is a horizontal sectional view. The inner core fuel assembly 110 includes a plurality of inner core fuel assembly elements (fuel elements) 210 that extend in the vertical direction and are arranged in parallel to each other. The fuel elements 210 have a triangular arrangement and generally form a hexagonal cross section.

  The inner core fuel assembly 110 includes a hexagonal tubular trumpet tube 101 that covers the radially outer side of the fuel element 210, an entrance nozzle 102 that is connected to the lower portion of the trumpet tube 101, and a handling head that is connected to the upper portion of the trumpet tube 101. 103. The handling head 103 is formed with a coolant outlet 103a for outflow of the reactor coolant in the center, and has a shape that can be handled by a fuel handling device (not shown).

  The fuel element 210 is supported by the support plate 105. The entrance nozzle 102 is formed with a coolant inlet 102a. Further, a shielding body 104 supported by the entrance nozzle 102 is provided inside the entrance nozzle 102 and below the support plate 105.

  A gap between the fuel elements 210 in the trumpet tube 101 is a flow path for the reactor coolant. The reactor coolant flows in from the coolant inlet 102 a of the entrance nozzle 102 and rises in the flow path outside each fuel element 210 while cooling each fuel element 210. The reactor coolant that has risen in temperature and has flowed out of the fuel element 210 flows out of the inner core fuel assembly 110 from the coolant outlet 103 a of the handling head 103.

  FIG. 5 is a horizontal sectional view showing the configuration of the fuel elements of the inner core fuel assembly. The fuel element 210 includes a cladding tube 201 and a TRU fuel 211. The TRU fuel 211 is accommodated in the cladding tube 201 and is in the form of a rod or a pellet. The rod-shaped or pellet-shaped TRU fuel 211 is a hollow rod or a hollow pellet (that is, hollow fuel wt%).

  The TRU fuel 211 includes a mixture of plutonium and degraded uranium or recovered uranium. In the nuclear fuel recycling process, plutonium is recovered with mixed TRU as a main component in a state where some or all of elements of Pu, neptunium (Np), americium (Am), and curium (Cm) are mixed. Uranium may be recovered in a state where it is not separated from plutonium or the like, or a separately recovered product may be mixed.

  As a form of the TRU fuel 211, for example, a metal fuel of a metal form having a base material which is substantially the balance together with these. For example, zirconium (Zr) is used as the base material.

  FIG. 6 is a horizontal sectional view showing the configuration of the outer core fuel assembly. The outer core fuel assembly 120 has the same configuration as the inner core fuel assembly 110 and includes outer core fuel assembly elements (fuel elements) 220 arranged in a triangular pattern. Further, similarly to the inner core fuel assembly 110, it has a hexagonal tubular trumpet tube 101, an entrance nozzle 102 (FIG. 3), and a handling head 103 (FIG. 3).

  FIG. 7 is a horizontal sectional view showing the configuration of the fuel elements of the outer core fuel assembly of the fast reactor core according to the first embodiment. The fuel element 220 has a cladding tube 201 and a TRU fuel 221. The TRU fuel 221 is accommodated in the cladding tube 201 and has a solid rod shape or pellet shape.

  FIG. 8 is a table showing main specifications of the fuel assembly of the fast reactor core according to the first embodiment. The inner core fuel assembly 110 and the outer core fuel assembly 120 are contrasted. Each main specification will be described below. The reactor power is 700 MWt.

  First, for the inner core fuel assembly 110, the outer diameter and inner diameter of the cladding tube are 6.5 mm and 5.56 mm, the fuel composition is TRU-U-Zr, the outer diameter of the TRU fuel is 4.8 mm, and the inner diameter, that is, the hole diameter is 3.4mm, effective fuel density is 11.8g / cc, number of fuels per assembly is 169, Pu enrichment is 41wt%, relative value of fuel load per assembly is the outer core fuel assembly One half of 120 is 0.5 that is 1/2 of that.

  Next, for the outer core fuel assembly 120, the outer diameter and inner diameter of the cladding tube are the same as those of the inner core fuel assembly 110, the fuel composition is the same as that of the inner core fuel assembly 110, and the outer diameter of the TRU fuel is also the same. 8mm, no holes, effective fuel density and number of fuels per assembly are the same as the inner core fuel assembly 110, Pu enrichment is 25 wt%, and relative value of fuel load per assembly is 1. .

  Thus, the Pu enrichment is set higher in the inner core in which the inner core fuel assembly 110 is loaded than in the outer core in which the outer core fuel assembly 120 is loaded.

  On the other hand, the TRU fuel 211 of the fuel element 210 in the inner core is hollow with an outer diameter of 4.8 mm and an inner diameter of 3.4 mm, and is more aggregated than the TRU fuel 221 of the fuel element 220 with an outer diameter of 4.8 mm and a solid outer core. The fuel load per unit axial length in the horizontal section or the fuel load per unit fuel assembly is low.

  FIG. 9 is a table showing a comparison between the void reactivity and the power peaking coefficient of the fast reactor core according to the first embodiment. The performance of the fast reactor core 1 of the fast reactor configured as described above is compared with the performance of the conventional fast reactor core having the main specifications shown in FIG.

  In the conventional fast reactor core having the main specifications shown in FIG. 19, the void reactivity is 1.65 for the inner core and 0.00 for the outer core, which is 1.65 in total. The power peaking coefficient is 1.60 for the entire fast reactor core. On the other hand, in the fast reactor core 1 according to the present embodiment, the void reactivity is 0.92 for the inner core and -0.10 for the outer core, which is 0.82. The power peaking coefficient is 1.72 for the entire fast reactor core. However, the numerical value of the void coefficient whose notation is omitted is the input reactivity (unit: $) at the time of all region voiding.

  That is, the void reactivity aimed at reduction is greatly reduced from 1.65 to 0.92 in the inner core, and is negative from 0.0 to −0.10 in the outer core. As a result, in the entire fast reactor core 1, 1.65 is halved to 0.82. Thus, it is greatly reduced by this embodiment.

  On the other hand, the power peaking coefficient is increased from 1.60 to 1.72 in the entire fast reactor core 1. The output peaking coefficient is preferably as small as possible. For this reason, in order to suppress an increase in the output peaking coefficient, the diameter of the fast reactor core 1 is increased by about 3 to 4 wt%, or the effect of reducing the void reactivity coefficient is slightly reduced, but the height of the fast reactor core 1 is increased. The peak output density can be suppressed by reducing the average output density by increasing the output power.

  As described above, the Pu enrichment of the inner core is made higher than that of the conventional fast reactor core, and the ratio of uranium 238 is relatively reduced, whereby the void coefficient is set to the minus side or close to the minus side. In addition, by reducing the fuel load, the increase in the amount of fissile material in the inner core is suppressed, and by ensuring the balance of the power distribution between the inner core and the outer core, the increase in the output peaking coefficient is kept low. Yes. That is, the void coefficient can be reduced without significantly affecting the output peaking coefficient, the core size, and the like.

  In the present embodiment, the case of a fast core intended for TRU combustion with the blanket removed is shown. When this is compared with a conventional fast reactor core without a conventional blanket, the TRU combustion amount is about 30 kg / cycle in the conventional fast reactor core and about 50 kg / cycle in the present embodiment, which is increased by about 70 wt%. This is because by increasing the Pu enrichment, uranium is decreased and Pu production from uranium is suppressed. Therefore, according to the present embodiment, the TRU firing efficiency can be increased.

  As described above, in the present embodiment, the TRU fuel 211 of the fuel element 210 of the inner core fuel assembly 110 is a hollow pellet or a hollow rod (that is, a hollow fuel), and the TRU fuel 221 of the fuel element 220 of the outer core fuel assembly 120 is Although the case of a solid pellet or a solid rod (that is, a solid fuel) has been shown, it is sufficient that the relationship between the two is satisfied even in the case of a hollow pellet or a hollow rod (hollow fuel).

  FIG. 10 is a table showing main specifications in the modification. In the table of FIG. 10, the TRU fuel 211 of the fuel element 210 of the inner core fuel assembly 110 is a hollow pellet or hollow rod (hollow fuel) having an outer diameter of 4.8 mm and an inner diameter of 3.6 mm. A case where the TRU fuel 221 of the fuel element 220 of the body 120 is a hollow pellet or a hollow rod (hollow fuel) having an outer diameter of 4.8 mm and an inner diameter of 1.75 mm is shown.

In this case, the weight of the TRU fuel 211 of the fuel element 210 of the inner core fuel assembly 110 is ½ of the weight of the TRU fuel 221 of the fuel element 220 of the outer core fuel assembly 120.
That is, since the conditions are the same as those in the first embodiment shown in FIG. 8, the void reactivity and the output peaking coefficient shown in FIG.

  As described above, according to the present embodiment and the modification thereof, it is possible to reduce the void reactivity as compared with the related art without depending on the reduction of the fast reactor core height.

[Second Embodiment]
FIG. 11 is a horizontal cross-sectional view showing the configuration of the inner core fuel assembly of the fast reactor core according to the second embodiment. This embodiment is a modification of the first embodiment. The inner core fuel assembly 130 according to the second embodiment includes an inner core fuel assembly element (fuel element) 230. The outer core fuel assembly 120 is the same as that of the first embodiment.

  FIG. 12 is a horizontal sectional view showing the configuration of the fuel element of the inner core fuel assembly. The fuel element 230 is filled with granular TRU fuel in the cladding tube 201.

  FIG. 13 is a table showing main specifications of the fuel assembly of the fast reactor core according to the second embodiment. The only difference is that the TRU fuel of the fuel element 230 of the inner core fuel assembly 130 is in the granular state with an effective density of 5.9 g / cc instead of being hollow in the case of the first embodiment.

  Since the effective density of the TRU fuel 221 of the fuel element 220 of the outer core fuel assembly 120 (FIG. 6) is 11.8 g / cc, the effective density of the TRU fuel 231 of the fuel element 230 of the inner core fuel assembly 130 is This is 1/2. As a result, the fuel load per assembly is also halved, which is the same as in the first embodiment. The respective Pu enrichments of the TRU fuel 231 in the fuel element 230 of the inner core fuel assembly 130 and the TRU fuel 221 (FIG. 7) in the fuel element 220 of the outer core fuel assembly 120 (FIG. 6) are the first. This is the same as the embodiment.

  Therefore, the same fast reactor core characteristics as in the first embodiment are obtained, and the same void reactivity and output peaking coefficient are obtained.

[Third Embodiment]
FIG. 14 is a table showing main specifications of the fuel assembly of the fast reactor core according to the third embodiment. This embodiment is a modification of the first embodiment. In this embodiment, the outer core fuel assembly 120 is the same as that of the first embodiment, but the fuel elements of the inner core fuel assembly are different. Specifically, the number of fuels per aggregate is 169, which is the same as in the first embodiment, but the dimensions of the cladding tube and TRU fuel are different.

  The outer diameter and inner diameter of the cladding of the fuel element of the inner core fuel assembly are 4.6 mm and 3.9 mm, respectively, and the outer diameter of the cladding of the fuel element of the outer core fuel assembly is 6.5 mm and the inner diameter of 5.56 mm. It is a small diameter reduced by about 30 wt% with respect to. Similarly, the outer diameter of the TRU fuel is 3.4 mm, which is reduced by about 30 wt% in the fuel element of the inner core fuel assembly, compared to 4.8 mm in the fuel element of the outer core fuel assembly.

  The Pu enrichment of the TRU fuel in the fuel element of the inner core fuel assembly and the TRU fuel in the fuel element of the outer core fuel assembly are the same as those in the first embodiment.

  As a result, the fuel load per unit fuel assembly is ½ that of the outer core fuel assembly in the inner core fuel assembly, as in the first embodiment. Therefore, the fast core characteristics similar to those of the first embodiment can be obtained.

[Fourth Embodiment]
FIG. 15 is a horizontal sectional view showing the configuration of the inner core fuel assembly of the fast reactor core according to the fourth embodiment. This embodiment is a modification of the first embodiment. In the fourth embodiment, the outer core fuel assembly 120 is the same as that of the first embodiment. The inner core fuel assembly 140 has the same number of inner core fuel assembly elements (fuel elements) as the inner core fuel assemblies 110 in the first embodiment. The inner core fuel assembly 140 includes a plurality of fuel elements 240 and a plurality of all-empty elements 250 as fuel elements. The plurality of fuel elements 240 and the plurality of all-empty elements 250 are substantially alternately arranged in layers in the radial direction.

  FIG. 16 is a horizontal sectional view showing the configuration of the fuel element 240. A solid TRU fuel 241 is accommodated inside the cladding tube 201. FIG. 17 is a horizontal sectional view showing the configuration of the all-empty element 250. There is no TRU fuel inside the cladding 201 and it is a space.

  FIG. 18 is a table showing main specifications of the fuel assembly. The inner core fuel assembly 140 has 169 fuel elements 240 and 162 all-empty elements 250. Both the fuel element 240 and the all-empty element 250 have a cladding tube outer diameter of 4.6 mm and a cladding tube inner diameter of 3.9 mm, which is smaller than the fuel elements 6.5 mm and 5.56 mm of the outer core fuel assembly 120. Is the diameter. Similarly, the outer diameter of the TRU fuel 241 in the fuel element 240 of the inner core fuel assembly 140 is 3.4 mm, and that of the TRU fuel 221 in the fuel element 220 of the outer core fuel assembly 120 (FIG. 6). The diameter is smaller than 8 mm.

  The Pu enrichment degree of the TRU fuel 241 in the fuel element 240 of the inner core fuel assembly 140 and the TRU fuel in the fuel element of the outer core fuel assembly are the same as those in the first embodiment.

  As a result, the relative values of the Pu enrichment and the fuel load are the same as those in the first embodiment, and the fast reactor core characteristics similar to those in the first embodiment are obtained.

[Other Embodiments]
As mentioned above, although some embodiment of this invention was described, these embodiment is shown as an example and is not intending limiting the range of invention.

  For example, in the embodiment, the case of metal fuel is shown, but the present invention is not limited to this. Even if the fuel element is an oxide fuel or a nitride fuel, substantially the same effect can be obtained. In addition, almost the same effect can be obtained regardless of the contents of Np, Am, Cm, etc. other than Pu and U.

  Furthermore, in the embodiment, the case where the blanket is deleted and the fast reactor core of the fast reactor whose main purpose is TRU combustion is shown, but even when applied to the fuel breeding fast reactor core provided with the blanket fuel, Similar effects can be obtained.

  Moreover, you may combine the characteristic of each embodiment. Furthermore, these embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention.

  These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and the equivalents thereof.

  DESCRIPTION OF SYMBOLS 1 ... Fast reactor core, 2 ... Core support plate, 3 ... Core catcher, 4 ... Core upper mechanism, 5 ... Shield plug, 6 ... Reactor vessel, 8 ... Coolant inlet piping, 8a ... Lower plenum, 9 ... Coolant Outlet piping, 9a ... upper plenum, 11 ... control rod assembly, 12 ... shielding body, 13 ... control rod drive mechanism, 100 ... core fuel assembly, 101 ... trumpet tube, 102 ... entrance nozzle, 102a ... coolant inlet 103 ... Handling head, 103a ... Coolant outlet, 104 ... Shielding body, 105 ... Support plate, 110, 130, 140 ... Inner core fuel assembly, 120 ... Outer core fuel assembly, 200, 210, 220, 230 , 240 ... fuel element, 201 ... cladding tube, 250 ... all-empty element, 211, 221, 231, 241 ... TRU fuel, 300 ... fast reactor

Claims (9)

A fast reactor core of a fast reactor having a fuel containing a mixture of plutonium and deteriorated uranium or recovered uranium, and using a liquid metal as a coolant,
An inner core fuel assembly having a plurality of inner core fuel assembly elements arranged in parallel to each other and extending in the vertical direction;
An outer core fuel assembly having a plurality of outer core fuel assembly elements provided on the radially outer side of the inner core fuel assembly and extending in the vertical direction in parallel with each other;
With
The plutonium enrichment of the fuel in the inner core fuel assembly element is higher than the plutonium enrichment of the fuel in the outer core fuel assembly element, and the fuel load per unit of the inner core fuel assembly is outside. Smaller than the amount of fuel loaded per core fuel assembly,
A fast reactor core of a fast reactor characterized by that.   The fast reactor of the fast reactor according to claim 1, wherein an effective density of fuel stored in the outer core fuel assembly element is larger than an effective density of fuel stored in the inner core fuel assembly element. Core.   The fast core of a fast reactor according to claim 1 or 2, wherein the inner core fuel assembly element has a hollow fuel, and the outer core fuel assembly element has a solid fuel.   The number of the inner core fuel assembly elements of the inner core fuel assembly is equal to the number of the outer core fuel assembly elements of the outer core fuel assembly, and the inner core fuel assembly elements contain hollow fuel; The outer core fuel assembly element has a hollow fuel having a fuel weight smaller than that of the hollow fuel in the inner core fuel assembly element in the same height range as the inner core fuel assembly element. The fast reactor core of the fast reactor according to claim 2.   The outer core fuel assembly element of the outer core fuel assembly is equal to the number of the inner core fuel assembly elements of the inner core fuel assembly and is stored in the inner core fuel assembly element. The fast core of the fast reactor according to claim 1 or 2, wherein the fast core has an outer diameter larger than an outer diameter of the core fuel assembly element.   The fast reactor core according to any one of claims 1 to 5, wherein the fuel includes any one of an oxide fuel, a metal fuel, and a nitride fuel.   The fast core of a fast reactor according to any one of claims 1 to 6, wherein the fuel further includes at least one of neptunium, americium, and curium.   The fast reactor core according to any one of claims 1 to 6, wherein only a mixture of plutonium and deteriorated uranium or recovered uranium is used as a fuel. A core having a fuel containing a mixture of plutonium and depleted or recovered uranium;
A reactor vessel that houses the core and holds liquid metal as a coolant;
A shielding plug that covers an upper portion of the reactor vessel and supports a control rod driving mechanism that drives a control rod that controls the reactivity of the core;
With
The core is
An inner core fuel assembly having a plurality of inner core fuel assembly elements arranged in parallel to each other and extending in the vertical direction;
An outer core fuel assembly having a plurality of outer core fuel assembly elements provided on the radially outer side of the inner core fuel assembly and extending in the vertical direction in parallel with each other;
Comprising
The plutonium enrichment of the fuel in the inner core fuel assembly element is higher than the plutonium enrichment of the fuel in the outer core fuel assembly element, and the fuel load per unit of the inner core fuel assembly is outside. Smaller than the amount of fuel loaded per core fuel assembly,
A fast reactor characterized by that.

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