Patent Application
20200303082
The present invention claims priority under 35 U.S.C. 119(a-d) to CN 201910609286.6, filed Jul. 8, 2019.
The present invention relates to a technical field of nuclear reactor engineering, and more particularly to a honeycomb-shaped fuel assembly cooled by liquid chloride salt and a small reactor core using this assembly.
Small modular reactors (SMRs) have remarkable market potential. It is expected that by 2035, the market size of SMRs will be about 65-85 GWe. Liquid three-phase chloride salt NaCl—KCl—MgCl2, as a new type of coolant, has the following advantages: transparent, relatively low melting point (396° C.), high boiling point (about 1400° C.), low density, low viscosity, high specific heat capacity, being stable under irradiation conditions, good compatibility with reactor materials, weak neutron moderation, low thermal expansion coefficient and high chemical inertness. Liquid three-phase chloride salt NaCl—KCl—MgCl2 is used as coolant for SMRs design, which is conducive to the design of compact and light reactors and the transportation, safe operation and deployments of SMRs.
An object of the present invention is to provide a honeycomb-shaped fuel assembly cooled by liquid chloride salt and a small reactor core using this assembly, wherein rated thermal power of the reactor core is 40 MW; the reactor core can be operated for 10 effective full power years without refueling, and can be transported by vehicle or ship.
Accordingly, in order to accomplish the above object, the present invention provides:
a honeycomb-shaped fuel assembly cooled by liquid chloride salt, comprising: a fuel assembly box (8); fuel coolant channel pipelines (9) which vertically penetrate the fuel assembly box (8), laterally merge with each other, and arranged in a triangular layout; and a fuel coolant (5) contained in the fuel coolant channel pipelines (9); wherein the fuel coolant channel pipelines (9) have holes for laterally merging with each other with the fuel coolant (5); parts in the fuel assembly box (8) but outside the fuel coolant channel pipelines (9) comprises, from a bottom to a top: a fuel lower endcap (7), a fuel lower reflector (6), a fuel zone (4), a fuel gas plenum (3), a fuel upper reflector (2) and a fuel upper endcap (1); the fuel coolant (5) is a mixture of liquid three-phase chloride salt NaCl—KCl—MgCl2.
The fuel coolant channel pipelines (9) have 37 pipes.
The fuel zone (4) uses U3Si2 with an enrichment of 19.75% or 16.0% as fuel; the fuel upper reflector (2) and the fuel lower reflector (6) are both made of titanium; the fuel upper endcap (1), the fuel lower endcap (7), the fuel assembly box (8) and the fuel coolant channel pipelines (9) are all made of Hastelloy.
The present invention also provides a reactor core cooled by liquid chloride salt, comprising: inner fuel assemblies (12), outer fuel assemblies (13), control assemblies (10), safety assemblies (11), reflector assemblies (14), and shielding assemblies (15); wherein the inner fuel assemblies (12) and the outer fuel assembly (13) are both honeycomb-shaped fuel assemblies cooled by the liquid chloride salt; the inner fuel assemblies (12) use U3Si2 with an enrichment of 16.0% as fuel, and the outer fuel assemblies (13) use U3Si2 with an enrichment of 19.75% as fuel; radial power distribution of the reactor core is flattened by zoning; assemblies of the reactor core are arranged in a triangular layout, wherein 31 inner fuel assemblies (12) are arranged in first to fourth circles of the reactor core; 3 control assemblies (10) and 3 safety assemblies (11) are arranged symmetrically and uniformly in the third circle; 54 outer fuel assemblies (13) are arranged in fifth to seventh circles; 12 control assemblies (10) are arranged symmetrically and uniformly in the fifth circle; 42 reflector assemblies (14) are arranged in seventh to eighth circles; and 48 shielding assemblies (15) are arranged in the eighth to ninth circles; reactor core coolant gaps are reserved between the assemblies in the reactor core, and a reactor core coolant is a mixture of liquid three-phase chloride salt NaCl—KCl—MgCl2.
Each of the reflector assemblies (14) adopts a honeycomb-shaped structure, comprising: a reflector assembly box (16-1); reflector coolant pipes (19-1) which are vertically penetrating; a reflector coolant (18-1) contained in the reflector coolant pipes (19-1); a titanium reflector (17-1); a reflector upper seal endcap (20-1); and a reflector lower endcap (21-1); wherein the titanium reflector (17-1) is filled outside the reflector coolant pipes (19-1) in the reflector assembly box (16-1); the reflector upper endcap (20-1) and the reflector lower endcap (21-1) are arranged on a top and a bottom of the titanium reflector (17-1), respectively; each of the shielding assemblies (15) adopts the same structure of the reflector assemblies (14), comprising: a shielding assembly box (16-2); shielding coolant pipes (19-2) which are vertically penetrating; a shielding coolant (18-2) contained in the shielding coolant pipes (19-2); a B4C shield (17-2) with a natural enrichment of 10B; a shielding upper endcap (20-2); and a shielding lower endcap (21-2).
Both the reflector coolant pipes (19-1) and the shielding coolant pipes (19-2) have 19 pipes.
The control assemblies (10) and the safety assemblies (11) adopt a rod bundle structure using B4C with a natural enrichment of 10B as absorbers; the control assemblies (10) and the safety assemblies (11) have same structures and same material compositions; each of the control assemblies (10) and the safety assemblies (11) comprises: an assembly box (22); absorber rods (24) and absorber rod cladding (25) evenly distributed in the assemblies box (22); and a coolant (23) filled outside the absorber rod cladding (25) in the assembly box (22); wherein each of the absorber rods (24) comprises, from a bottom to a top: a lower reflector (29), the B4C absorber rods (24), a gas plenum (28) and an upper reflector (27); wherein upper endcap (26) and lower endcap (30) are provided at tops and bottoms, respectively, of the control assemblies (10) and the safety assemblies (11).
Each of the control assemblies (10) and the safety assemblies (11) comprises 7 absorber rods (24).
The reactor core is operated at an atmospheric pressure; the reactor core coolant has a rated inlet temperature of 496° C. and a rated outlet temperature of 596° C.
Compared with the current technology, the present invention has advantages as follows.
1. The present invention uses the mixture of the liquid three-phase chloride salt NaCl—KCl—MgCl2 as the coolant, which has the advantages of transparent medium, low density, high boiling point, radiation resistance, high chemical inertness, etc. Compared with conventional liquid metal cooled reactors, the transparent medium is convenient for supervision and maintenance of the reactor. The low density makes the reactor light and easy to transport. The high chemical inertness and radiation resistance make the reactor safe, which can simplify reactor safety facilities and reduce costs.
2. The present invention uses the honeycomb-shaped fuel assembly. The coolant channels vertically penetrate and merge laterally, which eliminates conventional assembly grid spacer and wire wrap, so that fuel volume ratio of the assembly is increased and coolant content is reduced. Meanwhile, lateral mergence between the coolant channels prevents local fuel temperature from being too high due to local coolant channel blockage, and avoids coolant pipe melting or even fuel melting.
3. Two fuel assemblies with different fuel enrichment are arranged in the reactor core fuel zone, which can effectively flatten the core radial power distribution.
4. The reflector is made of metal titanium with low density, strong corrosion resistance, and lowered neutron reflectance as neutron energy spectrum becomes harder, which can significantly reduce positive void reactivity of the coolant.
5. Throughout the core lifetime, the coolant temperature is always below 850° C., which has a weak corrosion effect on the coolant channel pipes and structural materials. A maximum temperature at a fuel center is below 1400° C. Fast neutron fluence of cladding and the structural materials is lower than 3.3 E+23 n/cm2.
By adopting the mixture of the liquid three-phase chloride salt NaCl—KCl—MgCl2 as the coolant, the invention significantly reduces the weight of the reactor, making it convenient for transportation by vehicle or ship. Without refueling, the reactor core can be operated for 10 effective full power years
Referring to drawings and embodiments, the present invention will be further illustrated as follows.
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As the preferred embodiment of the invention, the fuel zone 4 uses U3Si2 with an enrichment of 19.75% or 16.0% as fuel.
As the preferred embodiment of the present invention, the fuel upper reflector 2 and the fuel lower reflector 6 are both made of titanium; the fuel upper endcap 1, the fuel lower endcap 7, the fuel assembly box 8 and the fuel coolant channel pipelines 9 are all made of Hastelloy.
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The present invention provides a honeycomb-shaped fuel assembly cooled by liquid chloride salt and a small reactor core using this assembly, wherein rated thermal power of the reactor core is 40 MW; the reactor core can be operated for 10 effective full power years without refueling, and can be transported by vehicle or ship. The reactor core adopts the honeycomb-shaped fuel assembly cooled by liquid chloride salt, which is divided into two radial zones to arrange two kinds of fuel assemblies. The reactor core can satisfy thermal limit during service life. And the reactor core has a small core volume, light weight, vehicle-transportable, long life and high safety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 201910609286.6 | Jul 2019 | CN | national |
