Nuclear reactor neutron shielding

Patent metadata

Field	Value
Publication number	US-9761332-B2
Application number	US-201414299353-A
Country	US
Kind code	B2
Filing date	Jun 9, 2014
Priority date	Jun 9, 2014
Publication date	Sep 12, 2017
Grant date	Sep 12, 2017

Abstract

A nuclear reactor includes a reactor pressure vessel and a nuclear reactor core comprising fissile material disposed in a lower portion of the reactor pressure vessel. The lower portion of the reactor pressure vessel is disposed in a reactor cavity. An annular neutron stop is located at an elevation above the uppermost elevation of the nuclear reactor core. The annular neutron stop comprises neutron absorbing material filling an annular gap between the reactor pressure vessel and the wall of the reactor cavity. The annular neutron stop may comprise an outer neutron stop ring attached to the wall of the reactor cavity, and an inner neutron stop ring attached to the reactor pressure vessel. An excore instrument guide tube penetrates through the annular neutron stop, and a neutron plug comprising neutron absorbing material is disposed in the tube at the penetration through the neutron stop.

First claim

We claim:

1. An apparatus comprising:
a nuclear reactor including a reactor pressure vessel and a nuclear reactor core comprising fissile material disposed in a lower portion of the reactor pressure vessel;
a reactor cavity inside of which is disposed the lower portion of the reactor pressure vessel, the reactor cavity and a wall of the pressure vessel defining an annular gap therebetween; and
an annular neutron stop located at an elevation above the uppermost elevation of the nuclear reactor core, the annular neutron stop including an outer neutron stop ring including an outermost neutron stop ring attached to the wall of the reactor cavity and a middle neutron stop ring attached to the outermost neutron stop ring, an inner neutron stop ring attached to the reactor pressure vessel and comprising a high temperature neutron absorbing material that is stable at an exterior temperature of the reactor pressure vessel during nuclear reactor operation, and comprising neutron absorbing material filling, the annular neutron stop being disposed in the annular gap between the reactor pressure vessel and a wall of the reactor cavity,
wherein the outer neutron stop ring defines an annular cutout portion in which the inner stop ring is disposed, the middle neutron stop ring comprises the high temperature neutron absorbing material, and the outermost neutron stop ring comprises a neutron absorbing material that is different from the high temperature neutron absorbing material.

2. The apparatus of claim 1 wherein an interface between the outer neutron stop ring and the inner neutron stop ring is stair-stepped or staggered to block neutrons from streaming through the interface.

3. The apparatus of claim 1 wherein the high temperature neutron absorbing material comprises a composition including boron carbide (B 4 C).

4. The apparatus of claim 1 wherein the neutron absorbing material that is different from the high temperature neutron absorbing material comprises borated concrete.

5. The apparatus of claim 1 wherein the annular neutron stop comprises a boron containing neutron absorber component in a thermally insulating matrix material.

6. The apparatus of claim 5 wherein the thermally insulating matrix material comprises vermiculite.

7. An apparatus comprising:
a nuclear reactor including a reactor pressure vessel and a nuclear reactor core comprising fissile material disposed in a lower portion of the reactor pressure vessel;
a reactor cavity inside of which is disposed the lower portion of the reactor pressure vessel, the reactor cavity and a wall of the pressure vessel defining an annular gap therebetween;
an annular neutron stop located at an elevation above the uppermost elevation of the nuclear reactor core, the annular neutron stop including an outer neutron stop ring defining an annular cutout portion, an inner neutron stop ring disposed in the annular cutout portion, and comprising neutron absorbing material filling, the annular neutron stop being disposed in the annular gap between the reactor pressure vessel and a wall of the reactor cavity;
a tube penetrating through the annular neutron stop; and
a neutron plug disposed in the tube at the penetration of the tube through the neutron stop, the neutron plug comprising neutron absorbing material.

8. The apparatus of claim 7 wherein the neutron plug comprises a boron containing neutron absorbing material.

9. The apparatus of claim 7 wherein the tube comprises an excore instrument guide tube and the apparatus further comprises:
an excore instrument suspended from the neutron plug by a cable.

10. The apparatus of claim 9 wherein the neutron plug includes a tortuous path and the apparatus further includes:
one or more wires passing through the tortuous path and operatively connecting with the excore instrument.

11. An apparatus comprising:
a nuclear reactor including a reactor pressure vessel and a nuclear reactor core comprising fissile material disposed in a lower portion of the reactor pressure vessel;
a reactor cavity inside of which is disposed the lower portion of the reactor pressure vessel;
an annular neutron stop located at an elevation above the uppermost elevation of the nuclear reactor core, the annular neutron stop comprising neutron absorbing material filling an annular gap between the reactor pressure vessel and the wall of the reactor cavity;
an excore instrument guide tube penetrating through the annular neutron stop;
a neutron plug including a tortuous path disposed in the excore instrument guide tube at the penetration of the excore instrument guide tube through the neutron stop, the neutron plug comprising neutron absorbing material;
an excore instrument suspended from the neutron plug by a cable; and
one or more wires passing through the tortuous path and operatively connecting with the excore instrument.

12. The apparatus of claim 11 wherein the annular neutron stop comprises:
an outer neutron stop ring attached to the wall of the reactor cavity; and
an inner neutron stop ring attached to the reactor pressure vessel.

13. The apparatus of claim 12 wherein an interface between the outer neutron stop ring and the inner neutron stop ring is stair-stepped or staggered to block neutrons from streaming through the interface.

14. The apparatus of claim 12 wherein the inner neutron stop ring comprises a high temperature neutron absorbing material that is stable at an exterior temperature of the reactor pressure vessel during nuclear reactor operation and the outer neutron stop ring comprises a neutron absorbing material that is different from the high temperature neutron absorbing material.

15. The apparatus of claim 11 wherein the annular neutron stop comprises a boron containing neutron absorber component in a thermally insulating matrix material.

Assignees

• Babcock & Wilcox Mpower Inc
• Bwxt Mpower Inc

Inventors

• Speaker Daniel P
• Neeley Gary W
• Inman James B

Classifications

• G21C11/028 Primary

  characterised by the form or by the material · CPC title

• G21C11/00 Primary

  Shielding structurally associated with the reactor · CPC title

• Y02E30/40

  Cross-Sectional Technologies · mapped topic

• G21F3/04

  Bricks; Shields made up therefrom · CPC title

• Y02E30/30

  Nuclear fission reactors · CPC title