Nuclear reprocessing

Nuclear reprocessing technology was developed to chemically separate and recover fissionable plutonium from irradiated nuclear fuel.[1] Reprocessing serves multiple purposes, whose relative importance has changed over time. Originally, reprocessing was used solely to extract plutonium for producing nuclear weapons. With the commercialization of nuclear power, the reprocessed plutonium was recycled back into MOX nuclear fuel for thermal reactors.[2] The reprocessed uranium, which constitutes the bulk of the spent fuel material, can in principle also be re-used as fuel, but that is only economic when uranium prices are high. Finally, a breeder reactor is not restricted to using recycled plutonium and uranium. It can employ all the actinides, closing the nuclear fuel cycle and potentially multiplying the energy extracted from natural uranium by about 60 times.[3][4]

Nuclear reprocessing reduces the volume of high-level waste, but by itself does not reduce radioactivity or heat generation and therefore does not eliminate the need for a geological waste repository. Reprocessing has been politically controversial because of the potential to contribute to nuclear proliferation, the potential vulnerability to nuclear terrorism, the political challenges of repository siting (a problem that applies equally to direct disposal of spent fuel), and because of its high cost compared to the once-through fuel cycle.[5] In the United States, the Obama administration stepped back from President Bush's plans for commercial-scale reprocessing and reverted to a program focused on reprocessing-related scientific research.[6] Nuclear fuel reprocessing is performed routinely in Europe, Russia and Japan.

Separated components and disposition

The potentially useful components dealt with in nuclear reprocessing comprise specific actinides (plutonium, uranium, and some minor actinides). The lighter elements components include fission products, activation products, and cladding.

materialdisposition
plutonium, minor actinides, reprocessed uraniumfission in fast, fusion, or subcritical reactor
reprocessed uranium, cladding, filters less stringent storage as intermediate-level waste
long-lived fission and activation products nuclear transmutation or geological repository
medium-lived fission products 137Cs and 90Srmedium-term storage as high-level waste
useful radionuclides and noble metals industrial and medical uses

History

The first large-scale nuclear reactors were built during World War II. These reactors were designed for the production of plutonium for use in nuclear weapons. The only reprocessing required, therefore, was the extraction of the plutonium (free of fission-product contamination) from the spent natural uranium fuel. In 1943, several methods were proposed for separating the relatively small quantity of plutonium from the uranium and fission products. The first method selected, a precipitation process called the bismuth phosphate process, was developed and tested at the Oak Ridge National Laboratory (ORNL) between 1943 and 1945 to produce quantities of plutonium for evaluation and use in the US weapons programs. ORNL produced the first macroscopic quantities (grams) of separated plutonium with these processes.

The bismuth phosphate process was first operated on a large scale at the Hanford Site, in the later part of 1944. It was successful for plutonium separation in the emergency situation existing then, but it had a significant weakness: the inability to recover uranium.

The first successful solvent extraction process for the recovery of pure uranium and plutonium was developed at ORNL in 1949. The PUREX process is the current method of extraction. Separation plants were also constructed at Savannah River Site and a smaller plant at West Valley Reprocessing Plant which closed by 1972 because of its inability to meet new regulatory requirements.[7]

Reprocessing of civilian fuel has long been employed at the COGEMA La Hague site in France, the Sellafield site in the United Kingdom, the Mayak Chemical Combine in Russia, and at sites such as the Tokai plant in Japan, the Tarapur plant in India, and briefly at the West Valley Reprocessing Plant in the United States.

In October 1976,[8] concern of nuclear weapons proliferation (especially after India demonstrated nuclear weapons capabilities using reprocessing technology) led President Gerald Ford to issue a Presidential directive to indefinitely suspend the commercial reprocessing and recycling of plutonium in the U.S. On 7 April 1977, President Jimmy Carter banned the reprocessing of commercial reactor spent nuclear fuel. The key issue driving this policy was the serious threat of nuclear weapons proliferation by diversion of plutonium from the civilian fuel cycle, and to encourage other nations to follow the USA lead.[9] After that, only countries that already had large investments in reprocessing infrastructure continued to reprocess spent nuclear fuel. President Reagan lifted the ban in 1981, but did not provide the substantial subsidy that would have been necessary to start up commercial reprocessing.[10]

In March 1999, the U.S. Department of Energy (DOE) reversed its policy and signed a contract with a consortium of Duke Energy, COGEMA, and Stone & Webster (DCS) to design and operate a mixed oxide (MOX) fuel fabrication facility. Site preparation at the Savannah River Site (South Carolina) began in October 2005.[11] In 2011 the New York Times reported "...11 years after the government awarded a construction contract, the cost of the project has soared to nearly $5 billion. The vast concrete and steel structure is a half-finished hulk, and the government has yet to find a single customer, despite offers of lucrative subsidies." TVA (currently the most likely customer) said in April 2011 that it would delay a decision until it could see how MOX fuel performed in the nuclear accident at Fukushima Daiichi.[12]

Separation technologies

Water and organic solvents

PUREX

Main article: PUREX

PUREX, the current standard method, is an acronym standing for Plutonium and Uranium Recovery by EXtraction. The PUREX process is a liquid-liquid extraction method used to reprocess spent nuclear fuel, to extract uranium and plutonium, independent of each other, from the fission products. This is the most developed and widely used process in the industry at present. When used on fuel from commercial power reactors the plutonium extracted typically contains too much Pu-240 to be considered "weapons-grade" plutonium, ideal for use in a nuclear weapon. Nevertheless, highly reliable nuclear weapons can be built at all levels of technical sophistication using reactor-grade plutonium.[13] Moreover, reactors that are capable of refueling frequently can be used to produce weapon-grade plutonium, which can later be recovered using PUREX. Because of this, PUREX chemicals are monitored.[14]

Plutonium Processing

Modifications of PUREX

UREX

The PUREX process can be modified to make a UREX (URanium EXtraction) process which could be used to save space inside high level nuclear waste disposal sites, such as the Yucca Mountain nuclear waste repository, by removing the uranium which makes up the vast majority of the mass and volume of used fuel and recycling it as reprocessed uranium.

The UREX process is a PUREX process which has been modified to prevent the plutonium from being extracted. This can be done by adding a plutonium reductant before the first metal extraction step. In the UREX process, ~99.9% of the uranium and >95% of technetium are separated from each other and the other fission products and actinides. The key is the addition of acetohydroxamic acid (AHA) to the extraction and scrub sections of the process. The addition of AHA greatly diminishes the extractability of plutonium and neptunium, providing somewhat greater proliferation resistance than with the plutonium extraction stage of the PUREX process.

TRUEX

Adding a second extraction agent, octyl(phenyl)-N, N-dibutyl carbamoylmethyl phosphine oxide(CMPO) in combination with tributylphosphate, (TBP), the PUREX process can be turned into the TRUEX (TRansUranic EXtraction) process. TRUEX was invented in the USA by Argonne National Laboratory and is designed to remove the transuranic metals (Am/Cm) from waste. The idea is that by lowering the alpha activity of the waste, the majority of the waste can then be disposed of with greater ease. In common with PUREX this process operates by a solvation mechanism.

DIAMEX

As an alternative to TRUEX, an extraction process using a malondiamide has been devised. The DIAMEX (DIAMideEXtraction) process has the advantage of avoiding the formation of organic waste which contains elements other than carbon, hydrogen, nitrogen, and oxygen. Such an organic waste can be burned without the formation of acidic gases which could contribute to acid rain (although the acidic gases could be recovered by a scrubber). The DIAMEX process is being worked on in Europe by the French CEA. The process is sufficiently mature that an industrial plant could be constructed with the existing knowledge of the process.[15] In common with PUREX this process operates by a solvation mechanism.

SANEX

Selective ActiNide EXtraction. As part of the management of minor actinides it has been proposed that the lanthanides and trivalent minor actinides should be removed from the PUREX raffinate by a process such as DIAMEX or TRUEX. In order to allow the actinides such as americium to be either reused in industrial sources or used as fuel, the lanthanides must be removed. The lanthanides have large neutron cross sections and hence they would poison a neutron driven nuclear reaction. To date the extraction system for the SANEX process has not been defined, but currently several different research groups are working towards a process. For instance the French CEA is working on a bis-triazinyl pyridine (BTP) based process.[16][17][18] Other systems such as the dithiophosphinic acids are being worked on by some other workers.

UNEX

The UNiversal EXtraction process was developed in Russia and the Czech Republic; it is designed to completely remove the most troublesome radioisotopes (Sr, Cs and minor actinides) from the raffinate remaining after the extraction of uranium and plutonium from used nuclear fuel.[19][20] The chemistry is based upon the interaction of caesium and strontium with polyethylene glycol)[21][22] and a cobalt carborane anion (known as chlorinated cobalt dicarbollide). The actinides are extracted by CMPO, and the diluent is a polar aromatic such as nitrobenzene. Other dilents such as meta-nitrobenzotrifluoride and phenyl trifluoromethyl sulfone[23] have been suggested as well.

Electrochemical methods

An exotic method using electrochemistry and ion exchange in ammonium carbonate has been reported.[24]

Obsolete methods

Bismuth phosphate

The bismuth phosphate process is an obsolete process that adds significant unnecessary material to the final radioactive waste. The bismuth phosphate process has been replaced by solvent extraction processes. The bismuth phosphate process was designed to extract plutonium from aluminium-clad nuclear fuel rods, containing uranium. The fuel was decladded by boiling it in caustic soda. After decladding, the uranium metal was dissolved in nitric acid.

The plutonium at this point is in the +4 oxidation state. It was then precipitated out of the solution by the addition of bismuth nitrate and phosphoric acid to form the bismuth phosphate. The plutonium was coprecipitated with this. The supernatant liquid (containing many of the fission products) was separated from the solid. The precipitate was then dissolved in nitric acid before the addition of an oxidant such as potassium permanganate which converted the plutonium to PuO22+ (Pu VI), then a dichromate salt was added to maintain the plutonium in the +6 oxidation state.

The bismuth phosphate was next re-precipitated leaving the plutonium in solution. Then an iron (II) salt such as ferrous sulfate was added, and the plutonium re-precipitated again using a bismuth phosphate carrier precipitate. Then lanthanum salts and fluoride were added to create solid lanthanum fluoride which acted as a carrier for the plutonium. This was converted to the oxide by the action of an alkali. The lanthanum plutonium oxide was next collected and extracted with nitric acid to form plutonium nitrate.[25]

Hexone or redox

This is a liquid-liquid extraction process which uses methyl isobutyl ketone as the extractant. The extraction is by a solvation mechanism. This process has the disadvantage of requiring the use of a salting-out reagent (aluminium nitrate) to increase the nitrate concentration in the aqueous phase to obtain a reasonable distribution ratio (D value). Also, hexone is degraded by concentrated nitric acid. This process has been replaced by the PUREX process.[26][27]

Pu4+ + 4 NO3− + 2S → [Pu(NO3)4S2]

Butex, β,β'-dibutyoxydiethyl ether

A process based on a solvation extraction process using the triether extractant named above. This process has the disadvantage of requiring the use of a salting-out reagent (aluminium nitrate) to increase the nitrate concentration in the aqueous phase to obtain a reasonable distribution ratio. This process was used at Windscale many years ago. This process has been replaced by PUREX.

Pyroprocessing

Pyroprocessing is a generic term for high-temperature methods. Solvents are molten salts (e.g. LiCl+KCl or LiF+CaF2) and molten metals (e.g. cadmium, bismuth, magnesium) rather than water and organic compounds. Electrorefining, distillation, and solvent-solvent extraction are common steps.

These processes are not currently in significant use worldwide, but they have been researched and developed at Argonne National Laboratory and elsewhere.

Advantages

Disadvantages

Electrolysis

PYRO-A and -B for IFR

These processes were developed by Argonne National Laboratory and used in the Integral Fast Reactor project.

PYRO-A is a means of separating actinides (elements within the actinide family, generally heavier than U-235) from non-actinides. The spent fuel is placed in an anode basket which is immersed in a molten salt electrolyte. An electric current is applied, causing the uranium metal (or sometimes oxide, depending on the spent fuel) to plate out on a solid metal cathode while the other actinides (and the rare earths) can be absorbed into a liquid cadmium cathode. Many of the fission products (such as caesium, zirconium and strontium) remain in the salt.[31][32][33] As alternatives to the molten cadmium electrode it is possible to use a molten bismuth cathode, or a solid aluminium cathode.[34]

As an alternative to electrowinning, the wanted metal can be isolated by using a molten alloy of an electropositive metal and a less reactive metal.[35]

Since the majority of the long term radioactivity, and volume, of spent fuel comes from actinides, removing the actinides produces waste that is more compact, and not nearly as dangerous over the long term. The radioactivity of this waste will then drop to the level of various naturally occurring minerals and ores within a few hundred, rather than thousands of, years.[36]

The mixed actinides produced by pyrometallic processing can be used again as nuclear fuel, as they are virtually all either fissile, or fertile, though many of these materials would require a fast breeder reactor in order to be burned efficiently. In a thermal neutron spectrum, the concentrations of several heavy actinides (curium-242 and plutonium-240) can become quite high, creating fuel that is substantially different from the usual uranium or mixed uranium-plutonium oxides (MOX) that most current reactors were designed to use.

Another pyrochemical process, the PYRO-B process, has been developed for the processing and recycling of fuel from a transmuter reactor ( a fast breeder reactor designed to convert transuranic nuclear waste into fission products ). A typical transmuter fuel is free from uranium and contains recovered transuranics in an inert matrix such as metallic zirconium. In the PYRO-B processing of such fuel, an electrorefining step is used to separate the residual transuranic elements from the fission products and recycle the transuranics to the reactor for fissioning. Newly generated technetium and iodine are extracted for incorporation into transmutation targets, and the other fission products are sent to waste.

Voloxidation

Voloxidation (for volumetric oxidation) involves heating oxide fuel with oxygen, sometimes with alternating oxidation and reduction, or alternating oxidation by ozone to uranium trioxide with decomposition by heating back to triuranium octoxide.[29] A major purpose is to capture tritium as tritiated water vapor before further processing where it would be difficult to retain the tritium. Other volatile elements leave the fuel and must be recovered, especially iodine, technetium, and carbon-14. Voloxidation also breaks up the fuel or increases its surface area to enhance penetration of reagents in following reprocessing steps.

Volatilization in isolation

Simply heating spent oxide fuel in an inert atmosphere or vacuum at a temperature between 700 °C and 1000 °C as a first reprocessing step can remove several volatile elements, including caesium whose isotope caesium-137 emits about half of the heat produced by the spent fuel over the following 100 years of cooling (however, most of the other half is from strontium-90 which remains). The estimated overall mass balance for 20,000 grams of processed fuel with 2,000 grams of cladding is:[37]

Input Residue Zeolite
filter		Carbon
filter		Particle
filters
Palladium281414
Tellurium1055
Molybdenum70 70
Caesium46 46
Rubidium8 8
Silver2 2
Iodine4 4
Cladding20002000
Uranium1921819218 ?
Others614614 ?
Total220002185114540

Tritium is not mentioned in this paper.

Fluoride volatility

Main article: Fluoride volatility
Blue elements have volatile fluorides or are already volatile; green elements do not but have volatile chlorides; red elements have neither, but the elements themselves or their oxides are volatile at very high temperatures. Yields at 100,1,2,3 years after fission, not considering later neutron capture, fraction of 100% not 200%. Beta decay Kr-85→Rb, Sr-90→Zr, Ru-106→Pd, Sb-125→Te, Cs-137→Ba, Ce-144→Nd, Sm-151→Eu, Eu-155→Gd visible.

In the fluoride volatility process, fluorine is reacted with the fuel. Fluorine is so much more reactive than even oxygen that small particles of ground oxide fuel will burst into flame when dropped into a chamber full of fluorine. This is known as flame fluorination; the heat produced helps the reaction proceed. Most of the uranium, which makes up the bulk of the fuel, is converted to uranium hexafluoride, the form of uranium used in uranium enrichment, which has a very low boiling point. Technetium, the main long-lived fission product, is also efficiently converted to its volatile hexafluoride. A few other elements also form similarly volatile hexafluorides, pentafluorides, or heptafluorides. The volatile fluorides can be separated from excess fluorine by condensation, then separated from each other by fractional distillation or selective reduction. Uranium hexafluoride and technetium hexafluoride have very similar boiling points and vapor pressures, which makes complete separation more difficult.

Many of the fission products volatilized are the same ones volatilized in non-fluorinated, higher-temperature volatilization, such as iodine, tellurium and molybdenum; notable differences are that technetium is volatilized, but caesium is not.

Some transuranium elements such as plutonium, neptunium and americium can form volatile fluorides, but these compounds are not stable when the fluorine partial pressure is decreased.[38] Most of the plutonium and some of the uranium will initially remain in ash which drops to the bottom of the flame fluorinator. The plutonium-uranium ratio in the ash may even approximate the composition needed for fast neutron reactor fuel. Further fluorination of the ash can remove all the uranium, neptunium, and plutonium as volatile fluorides; however, some other minor actinides may not form volatile fluorides and instead remain with the alkaline fission products. Some noble metals may not form fluorides at all, but remain in metallic form; however ruthenium hexafluoride is relatively stable and volatile.

Distillation of the residue at higher temperatures can separate lower-boiling transition metal fluorides and alkali metal (Cs, Rb) fluorides from higher-boiling lanthanide and alkaline earth metal (Sr, Ba) and yttrium fluorides. The temperatures involved are much higher, but can be lowered somewhat by distilling in a vacuum. If a carrier salt like lithium fluoride or sodium fluoride is being used as a solvent, high-temperature distillation is a way to separate the carrier salt for reuse.

Molten salt reactor designs carry out fluoride volatility reprocessing continuously or at frequent intervals. The goal is to return actinides to the molten fuel mixture for eventual fission, while removing fission products that are neutron poisons, or that can be more securely stored outside the reactor core while awaiting eventual transfer to permanent storage.

Chloride volatility and solubility

Many of the elements that form volatile high-valence fluorides will also form volatile high-valence chlorides. Chlorination and distillation is another possible method for separation. The sequence of separation may differ usefully from the sequence for fluorides; for example, zirconium tetrachloride and tin tetrachloride have relatively low boiling points of 331 °C and 114.1 °C. Chlorination has even been proposed as a method for removing zirconium fuel cladding,[29] instead of mechanical decladding.

Chlorides are likely to be easier than fluorides to later convert back to other compounds, such as oxides.

Chlorides remaining after volatilization may also be separated by solubility in water. Chlorides of alkaline elements like americium, curium, lanthanides, strontium, caesium are more soluble than those of uranium, neptunium, plutonium, and zirconium.

Radioanalytical separations

In order to determine the distribution of radioactive metals for analytical purposes, Solvent Impregnated Resins (SIRs) can be used. SIRs are porous particles, which contain an extractant inside their pores. This approach avoids the liquid-liquid separation step required in conventional liquid-liquid extraction. For the preparation of SIRs for radioanalytical separations, organic Amberlite XAD-4 or XAD-7 can be used. Possible extractants are e.g. trihexyltetradecylphosphonium chloride(CYPHOS IL-101) or N,N0-dialkyl-N,N0-diphenylpyridine-2,6-dicarboxyamides (R-PDA; R = butyl, octy I, decyl, dodecyl).[39]

Economics

The relative economics of reprocessing-waste disposal and interim storage-direct disposal has been the focus of much debate over the past ten years. Studies[40] have modeled the total fuel cycle costs of a reprocessing-recycling system based on one-time recycling of plutonium in existing thermal reactors (as opposed to the proposed breeder reactor cycle) and compare this to the total costs of an open fuel cycle with direct disposal. The range of results produced by these studies is very wide, but all are agreed that under current (2005) economic conditions the reprocessing-recycle option is the more costly.[41]

If reprocessing is undertaken only to reduce the radioactivity level of spent fuel it should be taken into account that spent nuclear fuel becomes less radioactive over time. After 40 years its radioactivity drops by 99.9%,[42] though it still takes over a thousand years for the level of radioactivity to approach that of natural uranium.[43] However the level of transuranic elements, including plutonium-239, remains high for over 100,000 years, so if not reused as nuclear fuel, then those elements need secure disposal because of nuclear proliferation reasons as well as radiation hazard.

On 25 October 2011 a commission of the Japanese Atomic Energy Commission revealed during a meeting calculations about the costs of recycling nuclear fuel for power generation. These costs could be twice the costs of direct geological disposal of spent fuel: the cost of extracting plutonium and handling spent fuel was estimated at 1.98 to 2.14 yen per kilowatt-hour of electricity generated. Discarding the spent fuel as waste would cost only 1 to 1.35 yen per kilowatt-hour.[44][45]

In July 2004 Japanese newspapers reported that the Japanese Government had estimated the costs of disposing radioactive waste, contradicting claims four months earlier that no such estimates had been made. The cost of non-reprocessing options was estimated to be between a quarter and a third ($5.5–7.9 billion) of the cost of reprocessing ($24.7 billion). At the end of the year 2011 it became clear that Masaya Yasui, who had been director of the Nuclear Power Policy Planning Division in 2004, had instructed his subordinate in April 2004 to conceal the data. The fact that the data were deliberately concealed obliged the ministry to re-investigate the case and to reconsider whether to punish the officials involved.[46][47]

List of sites

Country Reprocessing site Fuel type Procedure Reprocessing
capacity tU/yr		 Commissioning
or operating period
 Belgium Mol LWR, MTR (Material test reactor) 80[48] 1966–1974[48]
 China intermediate pilot plant[49] 60–100 1968-early 1970s
 China Plant 404[50] 50 2004
 Germany Karlsruhe, WAK LWR[15] 35[48] 1971–1990[48]
 France Marcoule, UP 1 Military 1,200[48] 1958[48]-1997[51]
 France Marcoule, CEA APM FBR PUREX DIAMEX SANEX[52] 6[15] 1988–present[15]
 France La Hague, UP 2 LWR[15] PUREX[53] 900[48] 1967–1974[48]
 France La Hague, UP 2–400 LWR[15] PUREX[53] 400[48] 1976–1990[48]
 France La Hague, UP 2–800 LWR PUREX[53] 800[48] 1990[48]
 France La Hague, UP 3 LWR PUREX[53] 800[48] 1990[48]
 UK Windscale Magnox BUTEX 1,000[48] 1956–1962[48]
 UK Sellafield, B205 Magnox[15] PUREX 1,500[48] 1964[48]
 UK Dounreay FBR[15] 8[48] 1980[48]
 UK THORP LWR PUREX 900[48][54] 1994[48][54]
 Italy Rotondella Thorium 5[48] 1968[48] (shutdown)
 India Trombay Military PUREX[55] 60[48] 1965[48]
 India Tarapur PHWR 100[48] 1982[48]
 India Kalpakkam PHWR and FBTR 100[56] 1998[56]
 India Tarapur PHWR 100[57] 2011[57]
 Japan Tokaimura LWR[58] 210[48] 1977[48]-2006[59]
 Japan Rokkasho LWR[15] 800[48][54] 2005[48]
 Pakistan New Labs, Rawalpindi Military/Plutonium/Thorium 80[60] 1982 – present
 Pakistan Khushab Nuclear Complex, Atomic City of PakistanHWR/Military/Tritium 22 kg[61] 1986 – present
 Russia Mayak Plant B Military 400 1948-196?[62]
 Russia Mayak Plant BB, RT-1 LWR[15] PUREX + Np separation[63] 400[48][54] 1978[48]
 Russia Zheleznogorsk (Krasnoyarsk-26), RT-2 VVER 800[48] under construction (2030)
 USA, WA Hanford Site Military bismuth phospate, REDOX, PUREX 1944–1988[64]
 USA, SC Savannah River Site Military/LWR/HWR/Tritium PUREX, REDOX, THOREX, Np separation 5000[65] 1952–2002
 USA, NY West Valley LWR[15] PUREX 300[48] 1966–1972[48]

See also

References

  1. ↑ Andrews, A. (27 March 2008). Nuclear Fuel Reprocessing: U.S. Policy. CRS Report For Congress. Retrieved 25 March 2011
  2. ↑ MOX fuel can extend the energy extracted by about 12% but slightly reduces plutonium stocks. Information from the World Nuclear Association about MOX
  3. ↑ "Supply of Uranium". World Nuclear Association. Retrieved 29 January 2010.
  4. ↑ "Fast Neutron Reactors". World Nuclear Association. Retrieved 11 March 2012.
  5. ↑ Harold Feiveson; et al. (2011). "Managing nuclear spent fuel: Policy lessons from a 10-country study". Bulletin of the Atomic Scientists.
  6. ↑ "Adieu to nuclear recycling". Nature 460 (7252): 152. 2009. Bibcode:2009Natur.460R.152.. doi:10.1038/460152b.
  7. ↑ "Plutonium Recovery from Spent Fuel Reprocessing by Nuclear Fuel Services at West Valley, New York from 1966 to 1972". U.S. Department of Energy. February 1996. Retrieved 17 June 2007.
  8. ↑ Gerald Ford October 28 1976 Statement on Nuclear Policy. Retrieved 30 June 2012.
  9. ↑ Dr. Ned Xoubi (2008). "The Politics, Science, Environment, and common sense of Spent Nuclear Fuel Reprocessing 3 decades Later" (PDF). Symposium on the Technology of Peaceful Nuclear Energy, Irbid, Jordan. Archived from the original (PDF) on 16 May 2011.
  10. ↑ Nuclear Fuel Reprocessing: U.S. Policy Development. (PDF). Retrieved 10 December 2011.
  11. ↑ Duke, Cogema, Stone & Webster (DCS) Reports sent to NRC. Nrc.gov. Retrieved 10 December 2011.
  12. ↑ New Doubts About Turning Plutonium Into a Fuel, April 10, 2011
  13. ↑ U.S. Program for Disposition of Excess Weapons Plutonium, IAEA-SM-346/102, Matthew Bunn, 2002.
  14. ↑ Irvine, Maxwell (2011). Nuclear power : a very short introduction. Oxford: Oxford University Press. p. 55. ISBN 9780199584970.
  15. 1 2 3 4 5 6 7 8 9 10 11 "Nuclear Energy: Fuel of the Future?". Princeton University. Archived from the original on 1 October 2012. Retrieved 6 April 2013.
  16. ↑ C. Hill, D. Guillaneux, X. Hérès, N. Boubals and L. Ramain SANEX-BTP PROCESS DEVELOPMENT STUDIES
  17. ↑ C. Hill, L. Berthon, P. Bros, J-P. Dancausse and D. Guillaneux SANEX-BTP PROCESS DEVELOPMENT STUDIES. Commissariat à l'Énergie Atomique
  18. ↑ Béatrice Rat, Xavier Hérès Modelling and achievement of a SANEX process flowsheet for trivalent actinides/lanthanides separation using BTP extractant (bis-1,2,4-triazinyl-pyridine).
  19. ↑ "U.S.-Russia Team Makes Treating Nuclear Waste Easier". U.S. embassy press release(?). 19 December 2001. Archived from the original on 2014-07-28. Retrieved 14 June 2007.
  20. ↑ J. Banaee; et al. (1 September 2001). "INTEC High-Level Waste Studies Universal Solvent Extraction Feasibility Study". INEEL Technical report.
  21. ↑ Law, Jack D.; Herbst, R. Scott; Todd, Terry A.; Romanovskiy, Valeriy N.; Babain, Vasily A.; Esimantovskiy, Vyatcheslav M.; Smirnov, Igor V.; Zaitsev, Boris N. (2001). "The Universal Solvent Extraction (Unex) Process. Ii. Flowsheet Development and Demonstration of the Unex Process for the Separation of Cesium, Strontium, and Actinides from Actual Acidic Radioactive Waste". Solvent Extraction and Ion Exchange 19: 23. doi:10.1081/SEI-100001371.
  22. ↑ Romanovskiy, Valeriy N.; Smirnov, Igor V.; Babain, Vasily A.; Todd, Terry A.; Herbst, R. Scott; Law, Jack D.; Brewer, Ken N. (2001). "The Universal Solvent Extraction (Unex) Process. I. Development of the Unex Process Solvent for the Separation of Cesium, Strontium, and the Actinides from Acidic Radioactive Waste". Solvent Extraction and Ion Exchange 19: 1. doi:10.1081/SEI-100001370.
  23. ↑ J.D. Law; et al. (1 March 2001). "Flowsheet testing of the universal solvent extraction process for the simultaneous separation of caesium, strontium, and the actinides from dissolved INEEL calcine" (PDF). WM 2001 conference proceedings. Archived from the original (PDF) on 2007-09-28. Retrieved 17 June 2006.
  24. ↑ Asanuma, Noriko; et al. (2006). "Andodic dissociation of UO2 pellet containing simulated fission products in ammonium carbonate solution". Journal of Nuclear Science and Technology 43 (3): 255–262. doi:10.3327/jnst.43.255. Archived from the original on 17 July 2012.
  25. ↑ Gerber, Michelle. "The plutonium production story at the Hanford Site: processes and facilities history (WHC-MR-0521) (excerpts)". Department of Energy.
  26. ↑ Seaborg, Glenn T.; et al. (23 August 1960). "Method for separation of plutonium from uranium and fission products by solvent extraction". U.S. Patent and Trademark Office. U.S. Patent 2,950,166
  27. ↑ L.W. Gray (15 April 1999). "From separations to reconstitution—a short history of plutonium in the U.S. and Russia (UCRL-JC-133802)" (PDF). Lawrence Livermore National Laboratory preprint.
  28. ↑ "PYROPROCESSING PROGRESS AT IDAHO NATIONAL LABORATORY" (PDF). Idaho National Laboratory article. September 2007.
  29. 1 2 3 Guillermo D. Del Cul; et al. "Advanced Head-End Processing of Spent Fuel: A Progress Report" (PDF). 2005 ANS annual meeting. Oak Ridge National Laboratory, U.S. DOE. Retrieved 3 May 2008.
  30. ↑ "Limited Proliferation-Resistance Benefits from Recycling Unseparated Transuranics and Lanthanides from Light-Water Reactor Spent Fuel" (PDF). p. 4.
  31. ↑ "Development of pyro-process fuel cell technology" (PDF). CRIEPI News. July 2002. Archived from the original (PDF) on 25 February 2009. Retrieved 22 June 2009.
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