Robust nuclear propulsion fission reactor with tri-pitch patterned core and drum absorbers

Patent metadata

Field	Value
Publication number	US-11990248-B2
Application number	US-202016999244-A
Country	US
Kind code	B2
Filing date	Aug 21, 2020
Priority date	Aug 29, 2019
Publication date	May 21, 2024
Grant date	May 21, 2024

Abstract

Nuclear propulsion fission reactor structure has an active core region including fuel element structures, a reflector with rotatable neutron absorber structures (such as drum absorbers), and a core former conformal mating the outer surface of the fuel element structures to the reflector. Fuel element structures are arranged abutting nearest neighbor fuel element structures in a tri-pitch design. Cladding bodies defining coolant channels are inserted into and joined to upper and lower core plates to from a continuous structure that is a first portion of the containment structure. The nuclear propulsion fission reactor structure can be incorporated into a nuclear thermal propulsion engine for propulsion applications, such as space propulsion.

First claim

What is claimed is:

1. A nuclear propulsion fission reactor structure, comprising:
an active core region including a plurality of fuel element structures and having an axial centerline defining a longitudinal axis of the nuclear propulsion reactor;
a core former radially outward of the active core region;
a reflector radially outward of the core former and having a radially inner surface oriented toward the active core region; and
a plurality of neutron absorber structures located within a volume of the reflector,
wherein each fuel element structure includes a cladding body having an inner surface defining a coolant channel, a fuel composition body radially outward of and surrounding the cladding body, and a moderator composition body radially outward of and surrounding the fuel composition body,
wherein an outer surface of a moderator composition body of a first fuel element structure abuts an outer surface of a moderator composition body of a plurality of nearest neighbor fuel element structures,
wherein the core former has a first surface radially inward of a second surface and the first surface is conformal to a radially outer surface of the active core region and the second surface is conformal to the radially inner surface of the reflector, and
wherein each of the plurality of neutron absorber structures includes a neutron absorber body movable between a first position and a second position, the first position being radially closer to the active core region than the second position.

2. The nuclear propulsion fission reactor structure according to claim 1 , further comprising:
an upper core plate; and
a lower core plate,
wherein the cladding body of each fuel element structure includes a first portion that extends axially past a first axial end of the fuel composition body and a second portion that extends axially past a second axial end of the fuel composition body, and
wherein the first portion of each fuel element structure is joined to the upper core plate and the second portion of each fuel element structure is joined to the lower core plate.

3. The nuclear propulsion fission reactor structure according to claim 1 , wherein the fuel composition body has the shape of an annular cylinder.

4. The nuclear propulsion fission reactor structure according to claim 1 , wherein the fuel element structure has a cross section that has a polygonal shape.

5. The nuclear propulsion fission reactor structure according to claim 4 , wherein the fuel element structure has a cross section that has a regular polygonal shape.

6. The nuclear propulsion fission reactor structure according to claim 4 , wherein the regular polygonal shape is a hexagon.

7. The nuclear propulsion fission reactor structure according to claim 1 , wherein side surfaces of the fuel element structures are in direct contact with side surfaces of adjacent fuel element structures.

8. The nuclear propulsion fission reactor structure according to claim 1 , wherein an arrangement of the plurality of fuel element structures in the active core region has translational symmetry.

9. The nuclear propulsion fission reactor structure according to claim 8 , wherein a distance between one or more repeated elements in the plurality of fuel element structures is constant.

10. The nuclear propulsion fission reactor structure according to claim 1 , wherein a fuel composition of the fuel composition body includes (i) uranium oxide that is less than 20% enriched, (ii) uranium with 10 wt. % molybdenum (U-10Mo), (iii) uranium nitride (UN), or (iv) a cermet of (i), (ii) or (iii).

11. The nuclear propulsion fission reactor structure according to claim 1 , wherein the neutron absorber body is movable between the first position and the second position to control reactivity of the active core region.

12. The nuclear propulsion fission reactor structure according to claim 1 , wherein each cladding body is a continuous, extruded tube.

13. The nuclear propulsion fission reactor structure according to claim 1 , wherein the cladding body has a composition that includes (i) molybdenum; (ii) tungsten; (iii) rhenium; (iv) tantalum; (v) hafnium; (vi) alloys of (i), (ii), (iii), (iv) or (v); or (vii) carbides of (i), (ii), (iii), (iv), or (v).

14. The nuclear propulsion fission reactor structure according to claim 1 , wherein a first portion of the cladding body extends axially past a first axial end of the moderator composition body and a second portion of the cladding body extends axially past a second axial end of the moderator composition body.

15. The nuclear propulsion fission reactor structure according to claim 2 , wherein a portion of the upper core plate, a portion of the lower core plate, and the cladding body of each fuel element structure form a portion of a containment structure for the nuclear propulsion reactor.

16. The nuclear propulsion fission reactor structure according to claim 1 , wherein the fuel composition body has the shape of an annular cylinder, wherein the moderator composition body is a polygon-shaped sleeve with a central opening, and wherein an inner diameter of the central opening defines a space in which the fuel composition body is located.

17. The nuclear propulsion fission reactor structure according to claim 1 , wherein, when the neutron absorber body of each of the plurality of neutron absorber structures is at the first position, the neutron absorber body of each of the plurality of neutron absorber structures is radially equidistant from the axial centerline of the active core region.

18. The nuclear propulsion fission reactor structure according to claim 1 , wherein the neutron absorber body has a composition including beryllium, beryllium oxide, graphite, or combinations thereof.

19. The nuclear propulsion fission reactor structure according to claim 1 , wherein each of the plurality of neutron absorber structures includes a cylindrical drum encased in a tube, wherein the neutron absorber body occupies a first portion of the cylindrical drum and a second portion of the cylindrical drum is a secondary reflector, and wherein the first portion of the cylindrical drum is a volume of the cylindrical drum that includes a portion of an exterior surface of the cylindrical drum.

20. The nuclear propulsion fission reactor structure according to claim 19 , wherein the portion of the exterior surface of the cylindrical drum corresponds to a 120 degree arc of a circumference of the cylindrical drum,
wherein the tube is stainless steel,
wherein the cylindrical drum is rotatable, and
wherein a composition of the reflector includes beryllium, beryllium oxide or graphite, and wherein a composition of the secondary reflector includes beryllium, beryllium oxide or graphite.

21. The nuclear propulsion fission reactor structure according to claim 20 , further including a motor operatively attached to the cylindrical drum by a drum shaft to rotate the cylindrical drum.

22. The nuclear propulsion fission reactor structure according to claim 1 , wherein the coolant is a propulsion gas and the nuclear propulsion reactor further comprises an upper reactor plate including a plurality of first holes for passage of the propulsion gas and a lower reactor plate including a plurality of second holes for passage of the propulsion gas.

23. The nuclear propulsion fission reactor structure according to claim 2 , further comprising a hull,
wherein the active core region, the core former, the upper core plate, the lower

Assignees

• Bwxt Advanced Tech Llc

Inventors

• Gramlich Craig D
• Fisher Benjamin D
• Russell Ii William E

Classifications

• G21C17/102 Primary

  the sensitive element being part of a fuel element or a fuel assembly (structural combination with a thermoelectric element for direct production of electrical energy G21C3/40) · CPC title

• G21C3/04

  Constructional details · CPC title

• G21C19/30

  with continuous purification of circulating fluent material, e.g. by extraction of fission products {deterioration or corrosion products, impurities, e.g. by cold traps (purification of circulating fluid fuels G21C19/50; separation in general B01D)} · CPC title

• B64G1/408

  Nuclear spacecraft propulsion · CPC title

• B64G1/422

  Nuclear power generation · CPC title