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JP-2026076205-A - Thorium-based fuel design for pressurized heavy water reactors

JP2026076205AJP 2026076205 AJP2026076205 AJP 2026076205AJP-2026076205-A

Abstract

[Problem] To provide thorium-based fuel for pressurized heavy water reactors (e.g., fuel pellets, fuel pins, and/or fuel bundles), as well as a method for manufacturing and using the same. [Solution] The fuel composition of the bundle is such that thorium accounts for 60 wt% or more, and the remaining fuel is supplied by low-enriched uranium (LEU) of 235U with an enrichment level of 13–19.95%. The use of such a thorium-based fuel bundle provides a non-preservative spent fuel bundle having (1) 100% of the nominal power over the entire lifecycle of the core, (2) high burnup, and (3) a total isotope uranium concentration of less than 12 wt%. Reprocessing of spent fuel can also be avoided. [Selection Diagram] Figure 1

Inventors

  • シャー， メユール
  • ミラーニ， ライダー
  • シルバン， コーロッシュ

Assignees

  • クリーン コア トリウム エナジー エルエルシー

Dates

Publication Date
20260511
Application Date
20260114
Priority Date
20210511

Claims (20)

  1. Fresh fuel pellets configured for use in a pressurized heavy water reactor, containing thorium fuel and uranium fuel, The fuel composition of the aforementioned fuel pellet is 55-90 wt% thorium. The aforementioned fuel composition is 10 to 45 wt% uranium. The uranium-235U enrichment level of the aforementioned uranium is 10.5-20%, and the fuel pellets are of this type.
  2. The fuel pellet according to claim 1, wherein the fuel pellet is annular in shape and has a through hole.
  3. The fuel pellet according to claim 2, wherein the diameter of the through-hole is 0.3 to 1.0 cm.
  4. The fuel pellet according to claim 1, wherein the fuel composition contains 70-90 wt% thorium.
  5. The fuel pellet according to claim 1, wherein the uranium has a 235U enrichment level of 15-19%.
  6. A fuel pin configured for use in a pressurized heavy water reactor, A sealed tube and A plurality of fuel pellets according to claim 1, comprising: The aforementioned plurality of fuel pellets are arranged inside the sealed tube, forming a fuel pin.
  7. The fuel pin according to claim 6, wherein the fuel composition of the fuel pin is 70-85 wt% thorium.
  8. The fuel pin according to claim 6, wherein each of the plurality of fuel pellets contains a flammable poison.
  9. A fuel bundle configured for use in a pressurized heavy water reactor, wherein the fuel bundle comprises a plurality of fuel pins as described in claim 6, and the fuel composition of at least one of the plurality of fuel pins is different from the fuel composition of at least one other fuel pin.
  10. The fuel bundle is molded and configured for use in a 220 MWe pressurized heavy water reactor. The aforementioned plurality of fuel pins consist of exactly 19 fuel pins, including one central fuel pin, six intermediate fuel pins arranged radially outward from the central fuel pin, and twelve outer fuel pins arranged radially outward from the six intermediate fuel pins. The weight percentage of thorium in the fuel composition of the central fuel pin is lower than the weight percentage of thorium in the fuel composition of each of the twelve outer fuel pins. The fuel bundle according to claim 9.
  11. The fuel composition of the central fuel pin and the six intermediate fuel pins is such that the thorium content is 55 to 75 wt%, The fuel composition of each of the 12 outer fuel pins is such that the thorium content is 65 to 90 wt%, Each of the twelve outer fuel pins has a higher weight percentage of thorium than each of the central fuel pin and each of the six intermediate fuel pins. The fuel bundle according to claim 10.
  12. The fuel composition of the central fuel pin has a lower weight percentage of thorium than that of each of the six intermediate fuel pins. The fuel composition of each of the six intermediate fuel pins has a lower weight percentage of thorium than the fuel composition of each of the twelve outer fuel pins. The fuel bundle according to claim 10.
  13. The fuel composition of the aforementioned central fuel pin has a thorium content of 55-70 wt%, The fuel composition of each of the six intermediate fuel pins is such that the thorium content is 60-80 wt%, The fuel composition of each of the 12 outer fuel pins is such that the thorium content is 65 to 90 wt%. The fuel bundle according to claim 12.
  14. The fuel bundle according to claim 10, further comprising a flammable poison disposed within the sealed tube of each of the six intermediate fuel pins.
  15. The fuel bundle according to claim 14, wherein no flammable toxic material is placed in the sealed tube of any of the outer fuel pins.
  16. The fuel bundle according to claim 10, further comprising a flammable poison disposed within the sealed tubes of each of the central fuel pin and the six intermediate fuel pins, wherein no flammable poison is disposed within the sealed tubes of any of the outer fuel pins.
  17. The fuel bundle according to claim 16, wherein the flammable poison disposed in the sealed tubes of the central fuel pin and each of the six intermediate fuel pins is europium.
  18. The fuel bundle according to claim 10, further comprising a flammable poison disposed within the sealed tube of each of the twelve outer fuel pins.
  19. The fuel bundle according to claim 18, wherein no flammable toxic material is placed in the sealed tube of either the central fuel pin or the intermediate fuel pin.
  20. The fuel bundle according to claim 10, wherein no flammable toxic material is placed in the sealed tube of any of the fuel pins of the fuel bundle.

Description

Cross-reference of related applications This application claims priority under U.S. Provisional Patent Application No. 63/186,990 (filed May 11, 2021, title: "Thorium-based fuel design for pressurized heavy water reactors"), the contents of which are incorporated herein by reference. Various embodiments relate, in general, to fuel pellets, pins, bundles, and core loading for pressurized heavy water reactors ("PHWRs"), and more particularly to thorium-based fuel compositions for such pellets, pins, bundles, and cores. The 220 MWe pressurized heavy water reactor is a heavy water-moderated, heavy water-cooled reactor having a reactor vessel 10. The reactor includes 306 fuel channels, each in the form of horizontal pressure tubes through which high-pressure coolant flows. Each channel contains 12 fuel bundles, although the core contains only 10. To isolate the high-temperature fuel channels from the low-temperature moderator, the pressure tubes are loaded into calandria tubes surrounded by a heavy water moderator. The pressure tubes are arranged in a square grid with a grid pitch of 22.84 cm. Figure 1 shows the shape of the core 20, including the heavy water moderator reflector and exemplary fuel bundles. While only two exemplary bundles are shown in Figure 1, it should be understood that additional fuel bundles (not shown in Figure 1) are provided in each of the 306 channels. The fuel bundle is an assembly of 19 fuel pins per bundle. The total length of the fuel bundle is 49.53 cm. The fuel is in the form of uranium dioxide pellets coated with Zircaloy-4 pins. The fuel stack is 48.1 cm long, and the fuel pins are sealed with end caps welded to the ends of the fuel pins. To maintain the structural integrity of the fuel bundle, two end plates are welded to the end caps of the fuel pins. In addition to the fuel channels, the reactor core contains numerous reactivity control devices. All reactivity devices are perpendicular to the fuel channels and penetrate the reactor pressure vessel from top to bottom. Reactor power adjustment is performed by two power adjustment rods, normally inserted 80%. Four additional adjustment rods, normally fully inserted, are installed for power shape control and xenon override. Reactor shutdown is performed by a primary shutdown system consisting of 14 shutdown rods, normally stored outside the core. In emergencies or failures of the primary shutdown system, a secondary shutdown system consisting of 12 liquid poison compartments can independently provide shutdown functionality. These liquid compartments are normally filled with helium gas and, as needed, can be injected with liquid neutron poison for a short time to safely shut down the reactor. Furthermore, the reactor has two shim rods to support shim mode operation as needed. These are normally stored outside the core. Canadian Patent Application Publication No. 2810133 discloses a thorium-containing nuclear fuel bundle and a nuclear reactor containing said nuclear fuel bundle. See also U.S. Patent Application Publication No. 2016/0035441. One or more non-limiting embodiments are disclosed herein and claimed to provide thorium-based fuels for pressurized heavy water reactors (e.g., fuel pellets, fuel pins, and/or fuel bundles), as well as methods for manufacturing and using the same. One or more non-limiting embodiments provide fresh fuel pellets configured for use in pressurized heavy water reactors. The fuel pellets contain thorium and uranium fuel. The fuel composition of the fuel pellets is 55–90 wt% thorium and 10–45 wt% uranium. The uranium-235U enrichment is 10.5% to 20%. According to one or more of these embodiments, the pellet is annular in shape with through holes. According to one or more of these embodiments, the through-hole has a diameter of 0.3 to 1.0 cm. According to one or more of these embodiments, the fuel composition contains 70-90 wt% thorium. According to one or more of these embodiments, the uranium-235U enrichment level is 15-19%. One or more non-limiting embodiments provide a fuel pin configured for use in a pressurized heavy water reactor. The fuel pin comprises a sealed tube and a plurality of fuel pellets according to one or more embodiments disclosed herein. The plurality of fuel pellets are arranged inside the sealed tube. According to one or more of these embodiments, the fuel composition of the fuel pin is 70-85 wt% thorium. According to one or more of these embodiments, each of the plurality of fuel pellets contains a flammable poison. One or more non-limiting embodiments provide a fuel bundle configured for use in a pressurized heavy water reactor. The fuel bundle includes a plurality of fuel pins according to one of the embodiments disclosed herein. The fuel composition of at least one of the plurality of fuel pins differs from the fuel composition of at least one other of the plurality of fuel pins. According to one or more of these embodiments, the fuel bundle is shaped and configured for use i