Separation of the rare-earth fission product poisons from spent nuclear fuel

Patent metadata

Field	Value
Publication number	US-9428401-B1
Application number	US-201213622034-A
Country	US
Kind code	B1
Filing date	Sep 18, 2012
Priority date	Sep 18, 2012
Publication date	Aug 30, 2016
Grant date	Aug 30, 2016

Abstract

A method for the separation of the rare-earth fission product poisons comprising providing a spent nuclear fuel. The spent nuclear fuel comprises UO 2 and rare-earth oxides, preferably Sm, Gd, Nd, Eu oxides, with other elements depending on the fuel composition. Preferably, the provided nuclear fuel is a powder, preferably formed by crushing the nuclear fuel or using one or more oxidation-reduction cycles. A compound comprising Th or Zr, preferably metal, is provided. The provided nuclear fuel is mixed with the Th or Zr, thereby creating a mixture. The mixture is then heated to a temperature sufficient to reduce the UO 2 in the nuclear fuel, preferably to at least to 850° C. for Th and up to 600° C. for Zr. Rare-earth metals are then extracted to form the heated mixture thereby producing a treated nuclear fuel. The treated nuclear fuel comprises the provided nuclear fuel having a significant reduction in rare-earths.

First claim

The embodiment of the invention in which an exclusive property or privilege is claimed is defined as follows:

1. A method for the separation of rare-earth fission product poisons from spent nuclear fuel comprising:
a) providing a spent nuclear fuel comprising UO 2 and rare-earth oxides;
b) said step of providing said nuclear fuel comprises providing a nuclear fuel and performing one or more oxidation-reduction cycles each cycle comprising:
i. oxidizing said nuclear fuel; and
ii. reducing said nuclear fuel;

c) providing a compound comprising Th or Zr;
d) mixing said provided nuclear fuel and said Th or Zr into a mixture;
e) heating said mixture to a temperature sufficient to reduce said UO 2 of said provided nuclear fuel; and
f) extracting rare-earth metals or oxides from said heated mixture thereby producing a treated nuclear fuel, whereby said treated nuclear fuel comprises said nuclear fuel with a significant reduction in rare-earths.

2. The method for the separation of rare-earth fission product poisons from spent nuclear fuel of claim 1 whereby said step of extracting rare-earth metals or oxides comprises extracting rare-earth metals or oxides from the group consisting of Sm, Gd, Nd, Eu, and combinations thereof metals or oxides thereof.

3. The method for the separation of rare-earth fission product poisons from spent nuclear fuel of claim 1 whereby:
a) said step of mixing said provided nuclear fuel comprises mixing said provided nuclear fuel and Th into a mixture; and
b) said step of heating said mixture comprises heating said mixture to a temperature sufficient to reduce both UO 2 and any rare-earth oxides.

4. The method for the separation of rare-earth fission product poisons from spent nuclear fuel of claim 1 further comprising:
a) said step of mixing said provided nuclear fuel comprises mixing said provided nuclear fuel and Zr into a mixture; and
b) said step of heating said mixture comprises heating said mixture to a temperature sufficient to reduce UO 2 .

5. The method for the separation of rare-earth fission product poisons from spent nuclear fuel of claim 1 whereby said step of providing said nuclear fuel comprises:
a) providing nuclear fuel;
b) crushing said nuclear fuel into a powder; and
c) oxidizing said nuclear fuel to a temperature between 200-800° C.

6. The method for the separation of rare-earth fission product poisons from spent nuclear fuel of claim 1 whereby said step of oxidizing said nuclear fuel comprises:
a) oxidizing said nuclear fuel to a temperature of 400-600° C.

7. The method for the separation of rare-earth fission product poisons from spent nuclear fuel of claim 1 whereby said step of heating said mixture comprises:
a) heating said mixture in a vacuum, heating said mixture in an inert gas, heating said mixture in a reducing fluid, or a combination thereof.

8. The method for the separation of rare-earth fission product poisons from spent nuclear fuel of claim 1 whereby said step for extracting rare-earth metals comprises vaporization, selective chlorination, air classification, or a combination thereof.

9. The method for the separation of rare-earth fission product poisons from spent nuclear fuel of claim 1 whereby said step of extracting rare-earth metals or oxides comprises:
a) exposing said heated mixture to a chlorine gas at a temperature and pressure capable of converting said uranium to uranium chloride, rare-earth metals and oxides to rare-earth chlorides and rhodium metal to rhodium chloride;
b) heating said rare-earth chlorides and rhodium chloride to a temperature capable of creating a significant vapor pressure of the rare-earth chlorides and rhodium chloride; and
c) extracting said heated rare-earth chlorides and rhodium chloride using a carrier gas or in vacuum and fractional vaporization, whereby rare-earth chlorides and rhodium chloride are segregated from uranium chloride.

10. The method for the separation of rare-earth fission product poisons from spent nuclear fuel of claim 1 whereby said step of extracting rare-earth metals or oxides comprises:
a) oxidizing said heated mixture, whereby oxides of uranium and thorium are formed; and
b) exposing said oxidized heated mixture to temperature up to 750° C. and a pressure whereas the rare-earth oxides and rhodium form chlorides.

11. The method for the separation of the rare-earth fission product poisons from spent nuclear fuel of claim 1 further comprising:
a) enriching said treated nuclear fuel comprising the steps of adding U-235, said treated nuclear fuel not exceeding 17 weight percent of U-235; and
b) subjecting said enriched treated nuclear fuel to nuclear fission.

12. The method for the separation of the rare-earth fission product poisons from spent nuclear fuel of claim 1 further comprising:
a) enriching said treated nuclear fuel comprising the steps of adding U-235, said treated nuclear fuel not exceeding 8 weight percent of U-235; and
b) subjecting said enriched treated nuclear fuel to nuclear fission.

13. The method for the separation of the rare-earth fission product poisons from spent nuclear fuel of claim 1 whereby said step of mixing and heating further comprises:
a) adding a dissolving agent to said heated mixture; and
b) extracting said rare-earth metals with a dissolving agent.

14. The method for the separation of the rare-earth fission product poisons from spent nuclear fuel of claim 13 whereby said dissolving agent comprises nitric acid.

15. The method for the separation of the rare-earth fission product poisons from spent nuclear fuel of claim 1 whereby said step for extracting rare-earth metals comprises:
a) vaporizing rare-earth metals during said step of heating said mixture; and
b) collecting said vaporized rare-earth metals on a cooled surface, whereby said cooled surface has a temperature less than said mixture.

16. The method for the separation of the rare-earth fission product poisons from spent nuclear fuel of claim 2 whereby:
a) said step of mixing said provided nuclear fuel comprises mixing said provided nuclear fuel and Th into a mixture;
b) said step of heating said mixture comprises heating said mixture to a temperature above 850° C. and sufficient to reduce both UO 2 and any rare-earth oxides; and
c) said step for extracting rare-earth metals comprises:
i. vaporizing rare-earth metals during said step of heating said mixture; and

d) collecting said vaporized rare-earth metals on a cooled surface, whereby said cooled surface has a temperature less than said heated mixture.

17. The method for the separation of the rare-earth fission product poisons from spent nuclear fuel of claim 16 whereby:
a) said step of heating said mixture comprises heating said mixture in a vacuum, heating said mixture in an inert gas, heating said mixture in a reducing fluid, or a combination thereof;
b) said step for extracting rare-earth metals comprises vaporization, selective chlorination, air classification, or a combination thereof;
c) enriching said treated nuclear fuel comprising the steps of adding U-235, said treated nuclear fuel not exceeding 8 weight percent of U-235; and
d) subjecting said enriched treated nuclear fuel to nuclear fission.

18. The method for the separation of the rare-earth fission product poisons from spent nuclear fuel of claim 2 further comprising:
a) said step of mixing said provided nuclear fuel comprises mixing said provided nuclear fuel and Zr into a mixture;
b) said step of heating said mixture comprises heating said mixture to a

Assignees

• Christian Jerry D
• Sterbentz James W
• Us Dept Energy

Inventors

• Christian Jerry D
• Sterbentz James W

Classifications

• C01F17/271

  Chlorides · CPC title

• C01G43/025 Primary

  Uranium dioxide · CPC title

• C01G55/005

  Halides · CPC title

• G21G1/001

  Recovery of specific isotopes from irradiated targets · CPC title

• G21C3/62

  Ceramic fuel · CPC title