Another great post from
@moosey , that I thought I would attach to this thread as it seems related.
QUOTE
I will provide this link, it proves what I am saying about no longer needing to separate out the Uranium bundle.
https://www.world-nuclear.org/infor...ecycling/processing-of-used-nuclear-fuel.aspx
Processing of Used Nuclear Fuel
(Updated December 2020)
- Used nuclear fuel has long been reprocessed to extract fissile materials for recycling and to reduce the volume of high-level wastes.
- Recycling today is largely based on the conversion of fertile U-238 to fissile plutonium.
- New reprocessing technologies are being developed to be deployed in conjunction with fast neutron reactors which will burn all long-lived actinides, including all uranium and plutonium, without separating them from one another.
- A significant amount of plutonium recovered from used fuel is currently recycled into MOX fuel; a small amount of recovered uranium is recycled so far.
A key, nearly unique, characteristic of nuclear energy is that used fuel may be reprocessed to recover fissile and fertile materials in order to provide fresh fuel for existing and future nuclear power plants. Several European countries, Russia, China and Japan have policies to reprocess used nuclear fuel, although government policies in many other countries have not yet come round to seeing used fuel as a resource rather than a waste.
Over the last 50 years or so the principal reason for reprocessing used fuel has been to recover unused plutonium, along with less immediately useful unused uranium, in the used fuel elements and thereby close the fuel cycle, gaining some 25-30% more energy from the original uranium in the process. This contributes to national energy security. A secondary reason is to reduce the volume of material to be disposed of as high-level waste to about one-fifth. In addition, the level of radioactivity in the waste from reprocessing is much smaller and after about 100 years falls much more rapidly than in used fuel itself.
These are all considerations based on current power reactors, but moving to fourth-generation fast neutron reactors will change the outlook dramatically, and means that not only used fuel from today’s reactors but also the large stockpiles of depleted uranium (from enrichment plants, about 1.2 million tonnes end 2018) become a fuel source. Uranium mining will become much less significant.
Another major change relates to wastes. In the last decade interest has grown in recovering all long-lived actinides* together (
i.e. with plutonium) so as to recycle them in fast reactors so that they end up as short-lived fission products. This policy is driven by two factors: reducing the long-term radioactivity in high-level wastes, and reducing the possibility of plutonium being diverted from civil use – thereby increasing proliferation resistance of the fuel cycle.
* Actinides are elements 89 to 103, actinium to lawrencium, including thorium, protactinium and uranium as well as transuranics, notably neptunium, plutonium, americium, curium and californium. The minor actinides in used fuel are all except uranium and plutonium.
mce-anchorReprocessing used fuel
a to recover uranium (as reprocessed uranium, or RepU) and plutonium (Pu) avoids the wastage of a valuable resource. Most of it – about 96% – is uranium, of which less than 1% is the fissile U-235 (often 0.4-0.8%); and up to 1% is plutonium. Both can be recycled as fresh fuel, saving up to 30% of the natural uranium otherwise required. The RepU is chiefly valuable for its fertile potential, being transformed into plutonium-239 which may be burned in the reactor where it is formed.
mce-anchorSo far, about 400,000 tonnes of used fuel has been discharged from commercial power reactors, of which about 30% has been reprocessed
1. Current commercial reprocessing capacity is about 2000 tonnes per year (see below). With the startup of the Rokkasho-Mura plant in Japan, capacity would increase by 800 tHM per year.
mce-anchor
World commercial reprocessing capacity2
|
{caption}(tonnes per year){/caption} |
|
|
| 1 |
LWR fuel |
France, La Hague |
1700 |
| 2 |
Russia, Ozersk (Mayak) |
400 |
|
| 3 |
Japan (Rokkasho) |
800* |
|
| 4 |
Total LWR (approx) |
2100 |
|
| 5 |
Other nuclear fuels |
UK, Sellafield (Magnox) |
1500 |
| 6 |
India (PHWR, 4 plants) |
260 |
|
| 7 |
Total other (approx) |
1760 |
|
| 8 |
Total civil capacity |
|
3860 |
* now expected to start operation in 2022
Used fuel from PHWRs such as CANDU is not attractive for reprocessing as it has a very low proportion of U-235 and Pu – typically 0.2% and 0.4% respectively. Also for fast reactors, depleted uranium is plentiful and cheap.
Processing perspective, and products of reprocessing
Conceptually, processing used fuel is the same as processing the concentrate of any metal mineral to recover the valued metals contained in it. Here the ‘ore’ (or effectively the concentrate from it) is hard ceramic uranium oxide with an array of other elements (about 4% in total), including both fission products and actinides formed in the reactor.
There are three broad kinds of metallurgical treatment at metal smelters and refineries:
- Pyrometallurgy using heat to initiate separation of the metals from their mineral concentrate (e.g. copper smelting to produce blister copper, lead smelting).
- Electrometallurgy using electric current to separate the metals (e.g. alumina smelting to produce aluminium).
- Hydrometallurgy using aqueous solutions that dissolve the metal, with sometimes also electrolytic cells to separate them (e.g. zinc production, copper refining).
The main historic and current process is Purex (
see below), a hydrometallurgical process. The main prospective ones are electrometallurgical – often called pyroprocessing since it happens to be hot. With it, all actinide anions (notably uranium and plutonium) are recovered together.
Used fuel contains a wide array of nuclides in varying valency states. Processing it is thus inherently complex chemically, and made more difficult because many of those nuclides are also radioactive.
The composition of reprocessed uranium (RepU) depends on the initial enrichment and the time the fuel has been in the reactor, but it is mostly U-238. It will normally have less than 1% U-235 (typically about 0.5% U-235) and also smaller amounts of U-232 and U-236 created in the reactor. The U-232, though only in trace amounts, has daughter nuclides which are strong gamma-emitters, making the material difficult to handle. However, once in the reactor, U-232 is no problem (it captures a neutron and becomes fissile U-233). It is largely formed through alpha decay of Pu-236, and the concentration of it peaks after about 10 years of storage.
mce-anchorThe U-236 isotope is a neutron absorber present in much larger amounts, typically 0.4% to 0.6% – more with higher burn-up – which means that if reprocessed uranium is used for fresh fuel in a conventional reactor it must be enriched significantly more (
e.g. up to one-tenth more) than is required for natural uranium
b. Thus RepU from low burn-up fuel is more likely to be suitable for re-enrichment, while that from high burn-up fuel is best used for blending or MOX fuel fabrication.
The other minor uranium isotopes are U-233 (fissile), U-234 (from original ore, enriched with U-235, fertile), and U-237 (short half-life beta emitter). None of these affects the use of handling of the reprocessed uranium significantly. In the future, laser enrichment techniques may be able to remove these isotopes.
Reprocessed uranium (especially from earlier military reprocessing) may also be contaminated with traces of fission products and transuranics. This will affect its suitability for recycling either as blend material or via enrichment. Over 2002-06 USEC successfully cleaned up 7400 tonnes of technetium-contaminated uranium from the US Department of Energy.
mce-anchorMost of the separated uranium (RepU) remains in storage, though its conversion and re-enrichment (in UK, Russia and Netherlands) has been demonstrated, along with its re-use in fresh fuel. Some 16,000 tonnes of RepU from Magnox reactors in UK has been used
c to make about 1750 tonnes of enriched AGR fuel. In Belgium, France, Germany and Switzerland over 8000 tonnes of RepU has been recycled into nuclear power plants. In Japan the figure is over 335 tonnes in tests and in India about 250 t of RepU has been recycled into PHWRs. In Russia RepU is used in all fresh RBMK fuel, and over 2500 tonnes has been recycled thus. Allowing for impurities affecting both its treatment and use, RepU value has been assessed as about half that of natural uranium.
mce-anchorPlutonium from reprocessing will have an isotopic concentration determined by the fuel burn-up level. The higher the burn-up levels, the less value is the plutonium, due to increasing proportion of non-fissile Pu isotopes (and minor actinides), and depletion of fissile plutonium isotopes
d. Whether this plutonium is separated on its own or with other actinides is a major policy issue relevant to reprocessing (see section on
Reprocessing policies below).
Most of the separated plutonium is used almost immediately in mixed oxide (MOX) fuel. World MOX production capacity is currently around 480 tonnes per year, nearly all of which is in France (see information page on
Mixed Oxide (MOX) Fuel). In future, Russian REMIX fuel may become established for recycling, though whether minor actinides remain with wastes or are recycled with REMIX depends on the reprocessing procedure.
Estimated savings in natural uranium requirements due to recycled U & Pu (tU)
|
|
Use of enriched RepU |
Use of Pu in MOX |
Total Unat replaced |
| 1 |
2019 |
1200 |
1130 |
2330 |
| 2 |
2020 |
1080 |
1130 |
2210 |
| 3 |
2025 |
1760 |
1210 |
2970 |
| 4 |
2030 |
2590 |
1400 |
3990 |
| 5 |
2035 |
2660 |
2210 |
4870 |
| 6 |
2040 |
2520 |
2210 |
4730 |
Source: World Nuclear Association Nuclear Fuel Report 2019
History of reprocessing
mce-anchorA great deal of hydrometallurgical reprocessing has been going on since the 1940s, originally for military purposes, to recover plutonium for weapons (from low burn-up used fuel, which has been in a reactor for only a few months). In the UK, metal fuel elements from the Magnox generation gas-cooled commercial reactors have been reprocessed at Sellafield for about 50 years
e. The 1500 t/yr Magnox reprocessing plant undertaking this, which is due to close in 2021, has been developed to keep abreast of evolving safety, occupational hygiene and other regulatory standards. From 1969 to 1973 oxide fuels were also reprocessed, using part of the plant modified for the purpose, and the 900 t/yr Thermal Oxide Reprocessing Plant (THORP) at Sellafield was commissioned in 1994.
In the USA, no civil reprocessing plants are now operating, though three have been built. The first, a 300 t/yr plant at West Valley, New York, was operated successfully from 1966-72. However, escalating regulation required plant modifications which were deemed uneconomic, and the plant was shut down after treating 650 tonnes of used oxide and metal fuel using the Purex process. The second was a 300 t/yr plant built at Morris, Illinois, incorporating new technology based on the volatility of UF
6 which, although proven on a pilot-scale, failed to work successfully in the production plant. It was declared inoperable in 1974. The third was a 1500 t/yr Purex plant at Barnwell, South Carolina, which was aborted due to a 1977 change in government policy which ruled out all US civilian reprocessing as one facet of US non-proliferation policy. In all, the USA has over 250 plant-years of reprocessing operational experience, the vast majority being at government-operated defence plants since the 1940s.
The main one of these is H Canyon at Savannah River, which commenced operation in 1955. It historically recovered uranium and neptunium from aluminium-clad research reactor fuel, both foreign and domestic. It could also recover Np-237 and Pu-238 from irradiated targets. H Canyon also reprocessed a variety of materials for recovery of uranium and plutonium both for military purposes and later high-enriched uranium for blending down into civil reactor fuel. In 2011 reprocessing of research reactor fuel was put on hold pending review of national policy for high-level waste, but recommenced in 2016.
In 2014, H Canyon completed reprocessing the long-stored uranium-thorium metal fuel from the 20 MWt Sodium Reactor Experiment (SRE), which had a high proportion of U-233. The sodium-cooled graphite-moderated SRE operated in California over 1957-64 and was the first US reactor to feed electricity to a grid. The uranium and actinides will be vitrified.
In France a 400 t/yr reprocessing plant operated for metal fuel from gas-cooled reactors at Marcoule until 1997. At La Hague, reprocessing of oxide fuel has been done since 1976, and two 800 t/yr plants are now operating, with an overall capacity of 1700 t/yr.
French utility EDF has made provision to store reprocessed uranium (RepU) for up to 250 years as a strategic reserve. Currently, reprocessing of 1100 tonnes of EDF used fuel per year produces 11 tonnes of plutonium (immediately recycled as MOX fuel) and 1045 tonnes of RepU converted into stable oxide form for storage. EDF has demonstrated the use of RepU (enriched at Seversk) in its 900 MWe power plants.
The plutonium is immediately recycled via the dedicated Melox mixed oxide (MOX) fuel fabrication plant. The reprocessing output in France is co-ordinated with MOX plant input, to avoid building up stocks of plutonium. If plutonium is stored for some years the level of americium-241, the isotope used in household smoke detectors, will accumulate and make it difficult to handle through a MOX plant due to the elevated levels of gamma radioactivity.
India has two 100 t/yr oxide fuel plants operating, one at Tarapur since 1982, with another at IGCAR Kalpakkam, and a smaller one at BARC Trombay. Japan is starting up a major (800 t/yr) plant at Rokkasho while having had most of its used fuel reprocessed in Europe meanwhile. To 2006 it had a small (90 t/yr) reprocessing plant operating at Tokai Mura.
Russia has an old 400 t/yr RT-1 oxide fuel reprocessing plant at Ozersk (near Chelyabinsk, Siberia), the main feed for which has been VVER-440 fuel, including that from Ukraine and Hungary. The partly-built 3000 t/yr RT-2 plant at Zheleznogorsk in Siberia has been redesigned and first stage completion of 700 t/yr is expected about 2025. Another 800 t/yr is planned for 2028. This is apparently Purex though that is not confirmed. An underground military reprocessing plant there is decommissioned.
Reprocessing policiesmce-anchor
mce-anchorConceptually reprocessing can take several courses, separating certain elements from the remainder, which becomes high-level waste. Reprocessing options include:
- Separate U, Pu, (as today).
- Separate U, Pu+U (small amount of U).
- Separate U, Pu, minor actinidesf.
- Separate U, Pu+Np, Am+Cm.
- Separate U+Pu all together.
- Separate U, Pu+actinides, certain fission products.
In today's reactors, reprocessed uranium (RepU) needs to be enriched, whereas plutonium goes straight to mixed oxide (MOX) fuel fabrication. This situation has two perceived problems: the separated plutonium is a potential proliferation risk, and the minor actinides remain in the separated waste, which means that its radioactivity is longer-lived than if it comprised fission products only.
As there is no destruction of minor actinides, recycling through light water reactors delivers only part of the potential waste management benefit. For the future, the focus is on removing the minor actinides along with uranium and plutonium from the final waste and burning them all together in fast neutron reactors. (The longer-lived fission products may also be separated from the waste and transmuted in some other way.) Hence the combination of reprocessing followed by recycling in today’s reactors should be seen as an interim phase of nuclear power development, pending widespread use of fast neutron reactors.
All but one of the six Generation IV reactors being developed have closed fuel cycles which recycle all the actinides. (See information page on
Generation IV Nuclear Reactors).
United States
In February 2006 the US government announced the Global Nuclear Energy Partnership (GNEP) through which it would "work with other nations possessing advanced nuclear technologies to develop new proliferation-resistant recycling technologies in order to produce more energy, reduce waste and minimise proliferation concerns." GNEP goals included reducing US dependence on imported fossil fuels, and building a new generation of nuclear power plants in the USA. Two significant new elements in the strategy were new reprocessing technologies at advanced recycling centres, which separate all transuranic elements together (and not plutonium on its own) starting with the UREX+ process (see section on
Developments of PUREX below), and 'advanced burner reactors' to consume the result of this while generating power.
GE Hitachi Nuclear Energy (GEH) is developing this concept by combining electrometallurgical separation (see section on Electrometallurgical 'pyroprocessing' below) and burning the final product in one or more of its PRISM fast reactors on the same site. The first two stages of the separation remove uranium which is recycled to light water reactors, then fission products which are waste, and finally the actinides including plutonium.
Not sure if GEH will do this now or not? I think they may concentrate on making MOX fuels for SMR's and no longer separate out the Uranium?
mce-anchorIn mid-2006 a report
3 by the Boston Consulting Group for Areva and based on proprietary Areva information showed that recycling used fuel in the USA using the COEX aqueous process (see
Developments of PUREX below) would be economically competitive with direct disposal of used fuel. A $12 billion, 2500 t/yr plant was considered, with total capital expenditure of $16 billion for all related aspects. This would have the benefit of greatly reducing demand on space at the planned Yucca Mountain repository.
Boston Consulting Group gave four reasons for reconsidering US used fuel strategy which has applied since 1977:
- Cost estimates for direct disposal at Yucca Mountain had risen sharply and capacity was limited (even if doubled)
- Increased US nuclear generation, potentially from 103 to 160 GWe
- The economics of reprocessing and associated waste disposal have improved
- There is now a lot of experience with civil reprocessing.
Soon after this the US Department of Energy said that it might start the GNEP (now IFNEC) program using reprocessing technologies that "do not require further development of any substantial nature" such as COEX while others were further developed. It also flagged detailed siting studies on the feasibility of this accelerated "development and deployment of advanced recycling technologies by proceeding with commercial-scale demonstration facilities."
In 2007 the US Nuclear Regulatory Commission’s Advisory Committee on Nuclear Waste and Materials published a report on
Background, Status, and Issues Related to the Regulation of Advanced Spent Nuclear Fuel Recycle Facilities, which canvassed the advantages of reprocessing US civil spent fuel. The report states: “The DOE’s current program for implementing SNF recycle contemplates building three facilities: an integrated nuclear fuel recycle facility, an advanced reactor for irradiating Np, Pu, Am, and Cm, and an advanced fuel cycle research facility to develop recycle technology. The first two of these are likely to be NRC-licensed.” The report is a thorough overview of reprocessing but does not provide conclusions or recommendations.
The NRC report points out how the Purex process had been greatly improved since its military origins, but still suffered the drawback of producing a separated pure plutonium stream. It points to the virtues of the UREX processes.
mce-anchorReprocessing today – PUREX
All commercial reprocessing plants use the well-proven hydrometallurgical PUREX (plutonium uranium extraction) process, which separates uranium and plutonium very effectively. This involves dissolving the fuel elements in concentrated nitric acid. Chemical separation of uranium and plutonium is then undertaken by solvent extraction steps (neptunium – which may be used for producing Pu-238 for thermo-electric generators for spacecraft – can also be recovered if required). The Pu and U can be returned to the input side of the fuel cycle – the uranium to the conversion plant prior to re-enrichment and the plutonium straight to MOX fuel fabrication.
Alternatively, some small amount of recovered uranium can be left with the plutonium which is sent to the MOX plant, so that the plutonium is never separated on its own. This is known as the COEX (co-extraction of actinides) process, developed in France as a 'Generation III' process, but not yet in use (see next section). Japan's new Rokkasho plant uses a modified PUREX process to achieve a similar result by recombining some uranium before denitration, with the main product being 50:50 mixed oxides.
In either case, the remaining liquid after Pu and U are removed is high-level waste, containing about 3% of the used fuel in the form of fission products and minor actinides (notably Np, Am, Cm). It is highly radioactive and continues to generate a lot of heat. It is conditioned by calcining and incorporation of the dry material into borosilicate glass, then stored pending disposal. In principle any compact, stable, insoluble solid is satisfactory for disposal.
UNQUOTE
Office of Nuclear Energy Strategic Vision
(20min delay)