Nuclear Wastes Technologies for Separations and Transmutation (1996) / Chapter Skim
Currently Skimming:
3 SEPARATIONS TECHNOLOGY
3 SEPARATIONS TECHNOLOGY
Pages 37-48
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 37... ...
Additional information on aqueous and nonaqueous processes, reprocessing experiences in the United States and abroad, and future separation processes is given in Appendix D of this report. It may be acceptable to dispose of spent LWR fuel with currently known mechanical disassembly methods and encapsulation (packaging)
|
From page 38... ...
. Nonaqueous Processes Nonaqueous processes have been used in reprocessing plants to separate materials for nuclear weapons and in plants for reprocessing spent reactor fuels, mostly to clean up the uranium product.
|
From page 39... ...
The defense nuclear wastes of greatest concern are those in liquid waste storage tanks at Hanford, although large amounts of wastes generated in the course of nuclear weapons production are stored at the Savannah River Site 39 and the Idaho Chemical Processing Site, and small amounts from the early years are stored at West Valley Demonstration Project and Oak Ridge. The needed separations range from those achievable with basic mechanical operations to those involving sophisticated chemical processing and complex engineering equipment.
|
From page 40... ...
Also present in spent LWR fuel are americium, curium, neptunium, and many additional fission products. The processing of spent reactor fuel is among the more demanding technologies in the chemical field.
|
From page 41... ...
The chemical basis for the PUREX process is that TBP selectively extracts uranium and plutonium when they are oxidized and in a complexant solution of high ionic strength, such as that provided by moderately concentrated nitric acid. Neptunium may also be extracted when conditions are adjusted properly.
|
From page 42... ...
Other separation steps would have to be added to isolate any of the individual fission product elements in the waste stream. TRUEX Process The TRUEX process is a solvent extraction process that was developed at Argonne National Laboratory to extract TRU elements selectively and nearly completely from acid solutions.
|
From page 43... ...
If specifically designed for such a purpose, pyrochemical processing of spent reactor fuel can provide high separation factors between members of chemically similar families of elements. However, it requires structural materials that can withstand the high temperatures and the corrosive molten salts.
|
From page 44... ...
The molten salt would be circulated through a side stream external to the target region, and separations would be performed on the molten salt to produce targets for reintroduction into the nuclear reaction zone. Separations processes for use in the ATW concept must be very tolerant of the intense radiation fields produced by the fission products present in the target fluid because of the proposed short cooling times and consequent high radiation fields.
|
From page 45... ...
Separations for Burning in LWRs Separation of plutonium and uranium from LWR spent nuclear fuel for future use in such reactors requires the partial separation of these elements from undesirable TRUs, fission products, and zirconium-alloy cladding hulls. With minor exceptions, all existing LWR fuel reprocessing plants have employed the PUREX process with the objective of producing pure plutonium and uranium.
|
From page 46... ...
This process, which employs direct electrochemical separation to purify the metallic reactor fuel from metal feed to metal product, could require fewer separations steps than aqueous processing when used on metallic fuels because the latter require that the metallic spent fuel be converted to an oxide or salt and then back again to metallic fuel in the course of recycling. An additional potential advantage is that it uses much smaller processing equipment because of the higher concentration of elements to be separated, although this is mitigated by the use of high temperatures, inert atmospheres, and batch processes.
|
From page 47... ...
For application to spent LWR fuel processing, an advanced technology (e.g., one that can separate elements in oxidation state III) could be used following an improved PUREX process to achieve very high decontamination factors for transuranium elements.
|
From page 48... ...
1992. Nuclear Waste from Pyrochemical Processing of LWR Spent Fuel for Actinide Recycle.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.