CN108198635B - A kind of thorium base molten-salt breeder reactor (MSBR) reactor core - Google Patents

Abstract

The invention discloses a thorium-based molten salt breeder core, comprising an active area and a reflective layer, the reflective layer wraps the active area, and the active area is a moderator made of fuel molten salt and graphite The active area includes a neutron supply area, a power flattening area and a multiplying area, the power flattening area surrounds the neutron providing area, and the multiplying area surrounds the power flattening area. The thorium-based molten salt breeder reactor core of the present invention divides the activity of the core into several areas mixed with thermal spectrum and fast spectrum by changing the volume ratio of molten salt and graphite in the graphite moderator cell, thereby improving the breeding performance of the reactor; By setting the power flattening zone, the graphite replacement cycle can be extended to 10 years, so that the reactor has a negative temperature reactivity coefficient; by setting the axial breeder zone, the breeder performance of the reactor can be further improved, and at the same time, it is beneficial to the thermal-hydraulic characteristics of the reactor. .

Description

A Thorium-based Molten Salt Breeder Core

technical field

The invention relates to the field of molten salt reactor core design, in particular to a thorium-based molten salt breeder reactor core.

Background technique

The molten salt reactor is the only reactor using liquid fuel among the six candidate types of fourth-generation reactors, and has its unique advantages in terms of inherent safety, economy, non-proliferation and sustainable development of nuclear fuel. On the one hand, the fuel of molten salt reactor does not need to be manufactured like traditional reactors, and on the other hand, it also takes into account the function of coolant. When the molten salt of fuel containing fissile material enters the core at an inlet temperature higher than its own melting point and becomes critical, the fuel Fission occurs to generate heat, and at the same time, the heat is brought to the secondary circuit.

Since the birth of the molten salt reactor concept, the world's main molten salt breeder conceptual design research is mainly: Molten Salt Breeder Reactor MSBR (Molten Salt Breeder Reactor) of the Oak Ridge National Laboratory in the United States, non-moderation of the French National Academy of Sciences Molten Salt Fueled Reactor MSFR (Molten Salt Fueled Reactor), Molten Salt Reactor Experiment MSRE (Molten Salt Reactor Experiment), Japan's FUJI series molten salt reactor and Russia's molten salt transmutation reactor MOSART.

Molten Salt Reactor Experiment MSRE (Molten Salt Reactor Experiment) is the only molten salt reactor built and running that uses graphite as moderator. The moderator cells are quadrangular prisms with side grooves and approximately square cross-sections. The grooves of the adjacent moderators are assembled together to form a molten salt flow channel for the fuel salt to flow and bring out the heat. The lower end of the moderator cell is inserted into the perforated grid plate to fix its position, and is arranged into an approximately circular core.

The typical type of thermal reactor is MSBR, which uses FLiBe molten salt as carrier salt and graphite as moderator and reflector. It is estimated that MSBR has a positive temperature reactivity coefficient, which has a serious impact on the safety of the reactor, and its core graphite needs to be replaced every four years, which makes the cost of the reactor relatively high, and its breeding ratio is about 1.06 .

The typical representative of fast reactor MSFR is the fast reactor concept of molten salt reactor without graphite moderation proposed by CNRS of the French National Academy of Sciences. The transformation of MSFR energy spectrum from thermal spectrum to fast spectrum can obtain unique advantages such as larger negative temperature reactivity coefficient and cavitation coefficient, larger reproduction ratio and no graphite lifetime limitation. However, the better moderation performance of fluorine salts makes MSFR have a large fuel loading, high cost, long doubling time of the reactor (more than 30 years), and the technical difficulty of fast reactors is also relatively large.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is to provide a high-power hybrid energy-spectrum thorium-based melting pot in order to overcome the defects in the prior art that the core breeding ratio does not exceed 1.06, the graphite replacement cycle does not exceed 4 years, and the temperature reactivity coefficient is positive. For the salt breeder reactor core, the breeder ratio of the core can reach more than 1.08, the graphite replacement cycle can reach 10 years, an increase of more than 100%, and the temperature reactivity coefficient is negative.

The present invention solves the above-mentioned technical problems through the following technical solutions:

A thorium-based molten salt breeder core includes an active region and a reflective layer, the reflective layer wrapping the active region, the active region including a fuel molten salt and an array of moderator cells made of graphite , the active area includes a neutron supply area and a breeder area, the volume ratio of the neutron supply area and the breeder area is 2.0:1 to 2.5:1, and the fuel molten salt and graphite in the neutron supply area are mixed The volume ratio is 1:7.2-1:3.2, and the volume ratio of the fuel molten salt and graphite in the breeding zone is 1:3.2-1:1.8. Through the calculation of a large number of cores with different volume ratios of fuel molten salt and graphite, and comprehensively considering the effective breeding coefficient, temperature reactivity coefficient and breeding ratio to optimize the selection, the volume ratio of fuel molten salt and graphite in the neutron supply zone is calculated. It is set to 1:7.2-1:3.2, and the volume ratio of the fuel molten salt and graphite in the breeding zone is set to be 1:3.2-1:1.8. The volume ratio of the fuel molten salt and the graphite is equal to the area ratio of the fuel molten salt and the graphite in the cross section of the core. In this way, the advantages of the thermal spectrum reactor and the fast spectrum reactor can be integrated, and a higher breeding ratio can be achieved, so that the breeding ratio is increased from 1.06 in the prior art to more than 1.08 in the present invention. Since in nuclear fuel fission, the number of fissionable nucleons increases exponentially with the breeding ratio as the base, so even a small increase will result in a huge increase after exponential operation, thereby significantly improving the efficiency of the reactor.

Preferably, the active region further includes a first power flattening region, the first power flattening region surrounds the neutron supply region, the breeding region surrounds the first power flattening region, and the neutron The volume ratio of the supply area and the first power flattening area is 1:1-2.0:1, and the volume ratio of the fuel molten salt and graphite in the first power flattening area is 1:1.8-1:0.01. By setting the first power flattening zone, the core power distribution is flattened. By setting the volume ratio of the fuel molten salt and graphite in the first power flattening zone to 1:1.8～1:0.01, the temperature reactivity coefficient is optimized. , to extend the graphite replacement cycle.

Preferably, the active region further includes a first power flattening region and a second power flattening region, and the volume ratio of the neutron providing region and the second power flattening region is 1:1˜2.0:1, The volume ratio of fuel molten salt and graphite in the first power flattening zone is 1:1.8-1:0.01, the second power flattening zone is fuel molten salt, and the breeding zone is adjacent to and surrounds the first power flattening zone. a power flattening region, the first power flattening region adjoins and surrounds the neutron providing region, the neutron providing region adjoins and surrounds the second power flattening region, the second power flattening region The flat area is located in the center of the active area. Through the cooperation of the first power flattening zone and the second power flattening zone, the temperature reactivity coefficient is further optimized, so that the temperature reactivity coefficient is negative, which ensures the safety of the reactor and prolongs the graphite replacement cycle.

Preferably, the active region further includes a first power flattening region and a second power flattening region, and the volume ratio of the neutron providing region and the second power flattening region is 1:1˜2.0:1, The volume ratio of fuel molten salt and graphite in the first power flattening zone is 1:1.8-1:0.01, the second power flattening zone is fuel molten salt, and the breeding zone is adjacent to and surrounds the first power flattening zone. a power flattening region, the first power flattening region adjoining and surrounding the second power flattening region, the second power flattening region adjoining and surrounding the neutron providing region, the neutron supplying region The supply area is located in the center of the active area. By stacking the first power flattening area and the second power flattening area, the temperature reactivity coefficient is further optimized, so that the temperature reactivity coefficient is negative, which ensures the safety of the reactor and prolongs the graphite replacement cycle.

Preferably, the fuel molten salt is FLiBe molten salt.

Preferably, the fuel molten salt is LiF-BeF ₂ -(Th+U)F ₄ molten salt.

Preferably, the fuel molten salt is a chloride salt.

Preferably, the proliferation region includes a radial proliferation region and an axial proliferation region, and the radial proliferation region and the axial proliferation region enclose the neutron supply region. Such a structure can provide neutron economy.

Preferably, the reflection layer includes a radial reflection layer and an axial reflection layer, the radial reflection layer surrounds the periphery of the active region, and the axial reflection layer is located on both sides of the radial reflection layer.

Preferably, the axial reflection layer includes an upper reflection layer and a lower reflection layer, the upper reflection layer is located directly above the active region and is in the shape of a truncated cone, and the lower reflection layer is located directly under the active region , and in the shape of a cone.

Preferably, a fuel channel is provided in the middle of the moderator cell for allowing the molten fuel salt to flow through and cool the graphite moderator. By changing the diameter of the fuel pores, the volume ratio of the fuel molten salt and graphite can be changed.

Preferably, the side surfaces of the moderator cells are provided with fins, which are used to form gaps between the cells for fuel molten salt to flow and to cool the graphite moderator. By changing the size of the fins, the size of the gap between the cells can be changed, thereby changing the volume ratio of the molten fuel salt and the graphite.

The graphite material is saved without affecting the neutron economy, and the positive temperature reactivity effect of the graphite reflective layer is alleviated.

On the basis of conforming to common knowledge in the art, the above preferred conditions can be combined arbitrarily to obtain preferred examples of the present invention.

The positive improvement effect of the present invention is that: the thorium-based molten salt breeder reactor core of the present invention divides the core activity into several types of mixed thermal spectrum and fast spectrum by changing the volume ratio of molten salt and graphite in the graphite moderator cells. By setting the power flattening zone, the graphite replacement cycle can be extended to 10 years, so that the reactor has a negative temperature reactivity coefficient; by setting the axial breeding zone, the reactor can be further improved The breeding performance is beneficial to the thermal-hydraulic properties of the reactor.

Description of drawings

FIG. 1 is a schematic cross-sectional structure diagram of a core according to Embodiment 1 of the present invention.

FIG. 2 is a schematic side view of the structure of the core according to Embodiment 1 of the present invention.

3 is a schematic cross-sectional structure diagram of a moderator cell according to Embodiment 1 of the present invention.

4 is a schematic cross-sectional structure diagram of another moderator cell according to Embodiment 1 of the present invention.

FIG. 5 is a schematic three-dimensional structure diagram of the moderator cells combined according to Embodiment 1 of the present invention.

FIG. 6 is a schematic structural diagram of the plate-type graphite prism in Example 1 of the present invention.

FIG. 7 is a schematic diagram showing the relationship between the cross section of the core and the neutron energy according to Embodiment 1 of the present invention.

FIG. 8 is a schematic side view of the structure of the moderator cell according to Embodiment 1 of the present invention.

FIG. 9 is a schematic cross-sectional structure diagram of the core according to Embodiment 2 of the present invention.

FIG. 10 is a schematic cross-sectional structure diagram of the core according to Embodiment 3 of the present invention.

FIG. 11 is a schematic cross-sectional structure diagram of the core according to Embodiment 4 of the present invention.

FIG. 12 is a schematic structural diagram of the reactor system of Embodiments 1-8 of the present invention.

Description of reference numbers:

Active Zone 1

Proliferation Zone 11

First Power Flattening Zone 12

Second Power Flattening Zone 13

Neutron supply area 14

Reflector 2

Radial Reflector 21

Axial Reflector 22

upper reflective layer 23

lower reflective layer 24

fuel port 3

Fin 4

Moderator Cell Head 51

Moderator Cell End 52

Reactor 61

main pump 62

Main Heat Exchanger 63

Aftertreatment System 64

Detailed ways

The present invention is further described below by means of examples, but the present invention is not limited to the scope of the examples.

Example 1

The high-power hybrid energy spectrum thorium-based molten salt breeder reactor core of this embodiment, as shown in FIG. 1 , includes an active region 1 and a reflective layer 2 , the reflective layer 2 coats the active region 1, and the active region 1 includes a neutron supply region 14 and the breeding area 11, the neutron energy spectrum peak of the neutron providing area 14 is less than 10 ^-6 MeV, and the neutron energy spectrum peak of the breeding area 11 is 10 ^-6 MeV～10 ^-3 MeV.

As shown in FIG. 2 , the reflective layer 2 is at the periphery of the active region 1 and at the upper and lower ends. The reflection layer 2 can also be divided into a radial reflection layer 21 and an axial reflection layer 22 . The radial reflection layer 21 surrounds the periphery of the active region 1 . The axial reflection layer 22 is divided into an upper reflection layer 23 and a lower reflection layer 24. The upper reflection layer 23 is located directly above the active area 1 and is in the shape of a truncated cone. The reflective layer 2 saves graphite materials on the premise of not affecting the neutron economy, and reduces the positive temperature reactivity effect of the graphite reflective layer.

The design uses LiF-BeF ₂ -(Th+U)F ₄ molten salt as the carrier salt for fission fuel and conversion fuel, and graphite as the moderator and reflector. The core includes an active area 1 and a reflective layer 2. The active area 1 is composed of a graphite moderator cell and a fuel molten salt flowing through it. The design of the graphite moderator cell can be flexibly changed by changing several key geometric dimensions. By adjusting the volume ratio of molten salt and graphite, the core is divided into a neutron providing region 14 with a thermal neutron spectrum (the peak of the energy spectrum is located in a region with energy less than 10 ^-6 MeV) and a neutron supply region 14 with an epithermal neutron spectrum (the peak of the energy spectrum is located at 10 ^-6 MeV ~ 10 ^-3 MeV energy region) proliferation zone 11.

As shown in FIG. 3 , the moderator cell can be a graphite hexagonal prism, with a fuel channel 3 in the middle for the molten salt of fuel to flow through and cool the graphite moderator, and fins 4 are arranged on three non-adjacent sides thereof for the purpose of The gaps between the cells are formed for the fuel molten salt to flow and to cool the graphite moderator. The cells are arranged in an equilateral triangle shape. As shown in FIG. 4 , the moderator cell can also be a regular quadrilateral graphite prism, with a fuel channel 3 in the middle for the molten salt to flow through and cool the graphite moderator, and its four sides are fins 4 to form the cell The gaps between are for the fuel molten salt to circulate and cool the graphite moderator, and the cells are arranged in a regular quadrilateral. As shown in FIGS. 5 and 6 , the moderator cells can also be plate-type graphite prisms with fins 4 on the plate to form gaps between the cells for the fuel molten salt to flow and cool the graphite moderator. The cells can be arranged in a regular hexagonal shape or a quadrilateral shape.

As shown in Figure 7, according to the comparison of U233 fission cross section and Th232 capture cross section, the neutron energy spectrum that is beneficial to proliferation (the energy spectrum peak is located in the energy region of 10 ^-5 MeV ~ 10 ^-3 MeV, that is, the resonance region) is more beneficial to The neutron energy spectrum of fission (the energy spectrum peak is located in the region with energy less than 10 ^-6 MeV, that is, the thermal energy region) is hard, so the volume ratio (1:3.2～1:1.8) of fuel and graphite in the breeding region 11 is greater than that provided by neutrons The volume ratio of fuel and graphite in the zone 14 (1:7.2 to 1:3.2), and, in order to effectively utilize the neutrons generated by the neutron-providing zone 14, the neutron-providing zone 14 is placed inside the active zone 1, and the breeding zone 11 Placed on the periphery of active area 1. In this embodiment, the volume ratio of fuel and graphite in the breeding zone 11 is 1:2.8, and the volume ratio of fuel and graphite in the neutron providing zone 14 is 1:6.

The breeding zone 11 can be further divided into a radial breeding zone (not shown in the figure) and an axial breeding zone (not shown in the figure), which wraps the neutron supplying zone 14 in order to provide neutron economy. The radial breeder region has fuel apertures and side fins 4 of graphite hexagonal cells. The axial breeder zone is formed by the axial geometry of the graphite moderator cell. As shown in FIG. 8, the graphite moderator cell includes a moderator cell head 51 and a moderator cell end 52. The cross section of the rod head at both ends is obviously smaller than that of the middle section, and the fuel-to-graphite volume ratio is large, which is beneficial to proliferation.

The MCNP is used to model the reactor, and the flexibly changeable fuel aperture or cell plate thickness and the cross-sectional circle diameter of the fin 4 are selected as optimization parameters. By changing the fuel aperture or cell of the moderator cell The thickness of the plate, as well as the cross-sectional circular diameter of the fins 4, can adjust the volume ratio of fuel and graphite, so that the energy spectrum of the local area of the active zone 1 is different. According to the change of the neutron capture cross section of Th and the fission cross section of U with neutron energy, an appropriate volume ratio of fuel and graphite is optimized to obtain energy spectra that are beneficial to breeding and fission, respectively. The sub-providing area 14 and the division of the proliferation area 11. Both the neutron supplying region 14 and the propagation region 11 are arranged in a substantially circular shape. According to the calculated effective reproduction coefficient, reproduction ratio and temperature reactivity coefficient, the appropriate diameters of the neutron supplying area 14 and the reproduction area 11 are optimized. The core thermal power given in this embodiment is 2250MW.

In this embodiment, the breeding ratio of the core calculated by simulation is increased to 1.085.

Example 2

The structure of Embodiment 2 is basically the same as that of Embodiment 1, except that, as shown in FIG. 9 , a first power flattening area 12 is added to the active area 1 of Embodiment 2. The first power flattening region 12 surrounds the neutron providing region 14, the breeding region 11 surrounds the first power flattening region 12, and the neutron energy spectrum peak of the first power flattening region 12 is greater than ^10-3 MeV and has a fast neutron spectrum . The first power flattening region 12 can flatten the core power distribution and optimize the temperature reactivity coefficient. The first power flattening region 12 is arranged in the center of the core or between the neutron providing region 14 and the breeding region 11. The neutron energy The spectrum is a fast spectrum (the peak of the energy spectrum is located in the region where the energy is greater than 10 ^-3 MeV, and the volume ratio of fuel to graphite is 1:1.8～1:0.01). The control rods are placed in the power flattening area.

In this embodiment, according to the computer simulation results, the breeding ratio is increased to 1.09, and the replacement period of graphite is extended to 10 years, so that the reactor has a negative temperature reactivity coefficient.

Example 3

The structure of Embodiment 3 is basically the same as that of Embodiment 2, except that, as shown in FIG. 10 , the active region 1 further includes a first power flattening region 12 and a second power flattening region 13 . The first power flattening region The volume ratio of fuel molten salt and graphite in 12 is 1:1, the second power flattening area 13 is fuel molten salt, the breeding area 11 is adjacent to and surrounds the first power flattening area 12, and the first power flattening area 12 is adjacent to the first power flattening area 12. The neutron providing region 14 is adjacent to and surrounds the neutron providing region 14 , which is adjacent to and surrounds the second power flattening region 13 , which is located in the center of the active region 1 . According to the computer simulation results, through the cooperation of the first power flattening region 12 and the second power flattening region 13, the breeding ratio is increased to 1.1, and the temperature reactivity coefficient is further optimized, so that the temperature reactivity coefficient is negative, ensuring that the temperature reactivity coefficient is negative. Reactor safety, extended graphite replacement cycle.

Example 4

The structure of Embodiment 4 is basically the same as that of Embodiment 2, the difference is that, as shown in FIG. 11 , the active region 1 further includes a first power flattening region 12 and a second power flattening region 13 . The first power flattening region The volume ratio of fuel molten salt and graphite in 12 is 1:1, the second power flattening area 13 is fuel molten salt, the breeding area 11 is adjacent to and surrounds the first power flattening area 12, and the first power flattening area 12 is adjacent to the first power flattening area 12. The second power flattening region 13 is adjacent to and surrounds the neutron supplying region 14 , and the neutron supplying region 14 is located in the center of the active region 1 . According to the computer simulation results, by stacking the first power flattening region 12 and the second power flattening region 13 to increase the breeding ratio to 1.1, the temperature reactivity coefficient is further optimized, and the temperature reactivity coefficient is made negative, ensuring that the The safety of the reactor is improved and the graphite replacement cycle is extended.

Examples 5-8

Examples 5-8 are basically the same as Example 1, except that the volume ratio of fuel and graphite in the breeding zone 11 and the volume ratio of fuel and graphite in the neutron providing zone 14 are different.

The computer simulation results of Examples 5-8 are shown in Table 1:

Table 1: Computer Simulation Results of Examples 5-8

Comparative Examples 1-4

Comparative Examples 1-4 are basically the same as Example 1, except that the volume ratio of fuel and graphite in the breeding zone 11 and the volume ratio of fuel and graphite in the neutron providing zone 14 are different. The computer simulation results of Comparative Examples 1-4 are shown in Table 2:

Table 2: Computer Simulation Results of Comparative Examples 1-4

In Table 2, the conversion ratio refers to the ratio between the amount of fissile material produced and the amount of fissile material consumed in the reactor 61, and when the ratio is greater than 1, it is called the breeding ratio. Non-criticality refers to the state in which the neutron generation rate and disappearance rate of the reactor are no longer balanced, so that the chain reaction cannot continue.

As shown in FIG. 12 , the core of the high-power hybrid energy spectrum thorium-based molten salt breeder reactor of the present invention is arranged in the reactor 61 , and the fission heat in the reactor 61 is brought to the three-circuit heat exchanger 63 through the molten salt-molten salt main heat exchanger 63 . Thermoelectric conversion system (conventional island). In addition, the on-line post-processing of the fuel salt is carried out through a molten salt bypass, mainly to remove the neutron poison in the fission products and improve the breeding ratio of the core. The hot water heated by the reactor 61 reaches the main pump 62 , where it is delivered to the main heat exchanger, and then to the aftertreatment system 64 .

In the high-power mixed-energy-spectrum thorium-based molten salt breeder reactor core of this embodiment, by changing the volume ratio of molten salt and graphite in the graphite moderator cells, the active zone of the core is divided into several zones with a mixture of thermal spectrum and fast spectrum, Increase the breeding ratio of the core to more than 1.08; extend the graphite replacement cycle to 10 years by setting the power flattening zone, so that the reactor has a negative temperature reactivity coefficient; by setting the axial breeding zone, the breeding of the reactor can be further improved. performance, while contributing to the thermal-hydraulic properties of the reactor.

Although the specific embodiments of the present invention are described above, those skilled in the art should understand that this is only an illustration, and the protection scope of the present invention is defined by the appended claims. Those skilled in the art can make various changes or modifications to these embodiments without departing from the principle and essence of the present invention, but these changes and modifications all fall within the protection scope of the present invention.

Claims (12)

1. A thorium-based molten salt breeder core, comprising an active region and a reflective layer, the reflective layer covering the active region, the active region comprising a fuel molten salt and a moderator cell made of graphite The active area includes a neutron providing area and a breeding area, the volume ratio of the neutron providing area and the breeding area is 2.0:1 to 2.5:1, and the fuel molten salt in the neutron providing area and The volume ratio of graphite is 1:7.2-1:3.2, and the volume ratio of the fuel molten salt and graphite in the breeding zone is 1:3.2-1:1.8. 2 . The thorium-based molten salt breeder core of claim 1 , wherein the active region further comprises a first power flattening region, and the first power flattening region surrounds the neutron supply region. 3 . , the breeding area surrounds the first power flattening area, the volume ratio of the neutron supply area and the first power flattening area is 1:1-2.0:1, and the first power flattening area The volume ratio of the fuel molten salt and graphite is 1:1.8～1:0.01. 3. The thorium-based molten salt breeder core of claim 2, wherein the active region further comprises a first power flattening region and a second power flattening region, the neutron providing region and all the The volume ratio of the second power flattening zone is 1:1-2.0:1, the volume ratio of the fuel molten salt and graphite in the first power flattening zone is 1:1.8-1:0.01, and the second power The flattening area is a fuel molten salt, the breeding area adjoins and surrounds the first power flattening area, the first power flattening area adjoins and surrounds the neutron providing area, and the neutron providing area Adjacent to and surrounding the second power flattening region, the second power flattening region is located in the center of the active region. 4. The thorium-based molten salt breeder core of claim 2, wherein the active region further comprises a first power flattening region and a second power flattening region, the neutron providing region and the The volume ratio of the second power flattening zone is 1:1-2.0:1, the volume ratio of the fuel molten salt and graphite in the first power flattening zone is 1:1.8-1:0.01, and the second power The flattening area is fuel molten salt, the breeding area adjoins and surrounds the first power flattening area, the first power flattening area adjoins and surrounds the second power flattening area, and the second power flattening area A power flattening region adjoins and surrounds the neutron providing region, which is located in the center of the active region. 5 . The thorium-based molten salt breeder reactor core of claim 1 , wherein the fuel molten salt is FLiBe molten salt. 6 . 6 . The thorium-based molten salt breeder reactor core according to claim 1 , wherein the fuel molten salt is LiF-BeF ₂ -(Th+U)F ₄ molten salt. 7 . 7. The thorium-based molten salt breeder reactor core of claim 1, wherein the fuel molten salt is a chloride salt. 8. The thorium-based molten salt breeder core of claim 1, wherein the breeder zone comprises a radial breeder zone and an axial breeder zone, the radial breeder zone and the axial breeder zone The neutron-providing region is enclosed. 9 . The thorium-based molten salt breeder reactor core according to claim 1 , wherein the reflection layer comprises a radial reflection layer and an axial reflection layer, and the radial reflection layer surrounds the active region. 10 . At the periphery, the axial reflection layer is located on both sides of the radial reflection layer. 10. The thorium-based molten salt breeder core of claim 9, wherein the axial reflection layer comprises an upper reflection layer and a lower reflection layer, and the upper reflection layer is located directly above the active region , and in the shape of a truncated cone, and the lower reflective layer is located just below the active area and in the shape of a truncated cone. 11 . The thorium-based molten salt breeder reactor core according to claim 1 , wherein a fuel channel is provided in the middle of the moderator cell, for allowing the fuel molten salt to flow through and cooling the graphite moderator. 12 . . 12. The thorium-based molten salt breeder reactor core according to any one of claims 1 to 11, wherein the side surfaces of the moderator cells are provided with fins for forming gaps between the cells , for the fuel molten salt to circulate and cool the graphite moderator.