The La Hague site is a nuclear fuel reprocessing plant at La Hague on the Cotentin Peninsula in northern France, with the Manche storage centre bordering on it. Operated by Orano, formerly AREVA, and prior to that COGEMA (Compagnie générale des matières atomiques), La Hague has nearly half of the world's light water reactor spent nuclear fuel reprocessing capacity.[1] It has been in operation since 1976, and has a capacity of about 1,700 tonnes per year. It extracts plutonium which is then recycled into MOX fuel at the Marcoule site.
It has treated spent nuclear fuel from France, Japan, Germany, Belgium, Switzerland, Italy, Spain and the Netherlands. It processed 1100 tonnes in 2005. The non-recyclable part of the radioactive waste is eventually sent back to the user nation. Prior to 2015, more than 32,000 tonnes of spent nuclear fuel has been reprocessed, with 70% of that from France, 17% from Germany and 9% from Japan.[2]
Background
Spent nuclear fuel roughly consists of three categories. The largest fraction by far is uranium that was present in the fuel from the start and was not affected by the nuclear reactions. Most of this uranium consists of uranium-238, which has a low radioactivity. Other uranium isotopes present in spent fuel in relevant quantities are fissile 235
U, fertile 234
U, and 236
U, which is usually seen as a nuisance as it needs three consecutive neutron absorptions to transmute into fissile 239
Pu. While spent LWR fuel contains more 235
U than natural uranium, the presence of 236
U makes it undesirable as a basis for new fuel.
Around 3-4% of the material consists of fission products that result from the nuclear chain reaction (and energy generation). These are mostly composed of highly radioactive isotopes, as the fission of very heavy uranium (which has a higher neutron excess than stable low mass nuclides) has endowed these with too many neutrons to be stable against beta decay.[3] As with all highly radioactive material, this level of radioactivity decreases relatively rapidly, although storage and shielding will be required for at least hundreds of years.[4] While a large fraction of fission products will have decayed during storage in a spent fuel pool and will have reached a stable or stable for all practical purposes form, about half a dozen each are medium lived and long-lived fission products. None of the former has a half-life in excess of 100 years and most cluster around 30 years or less (90
Sr and 137
Cs have half lives in that range). However, the latter includes very long lived radionuclides like 129
I or 135
Cs. While there are current, former or proposed uses for many of the fission products, the low mass fraction (fission product yields are single digit percentages and only a single digit percentage of spent fuel is fission products) and the difficulty of extraction along with regulatory hurdles have prevented their use on any large scale. In addition to the radiological hazards the fission products present outside a nuclear reactor, they are also problematic inside a nuclear reactor as some of them act as very strong neutron poisons. As such all reprocessing needs to remove at least the strongest neutron poisons from spent fuel to produce usable new fuel. As many strong neutron poisons are lanthanides, which are chemically (and even in some physical properties like melting point and solubility) very similar to actinides, separation requires relatively complex chemical processes.
Third, atom species are present which have a larger mass and atomic number than uranium itself. The majority of this so-called Transuranic waste consists of plutonium isotopes, although other species are also present, such as americium. All elements that aren't uranium or plutonium but heavier than the fission products are collectively known by the industry term minor actinides. The most notable among them are Neptunium, Americium and Curium. The transuranic elements are produced when uranium absorbs a neutron without fissioning. In the case of 235
U this is rarer than fission (but 236
U-ingrowth cannot be discarded over long burnup) but in the case of 238
U this is by far the most common interaction between thermal neutrons and uranium nuclei other than scattering. Those isotopes of uranium that aren't beta stable (mainly 237
U and 239
U) then beta decay (237
U to 237
Np; 239
U ultimately to 239
Pu) giving rise to the "first generation" of transuranics. If the resulting plutonium absorbs further neutrons without fissioning, further transuranic elements are produced from beta decay of beta-unstable isotopes of plutonium.
Odd-numbered isotopes of plutonium are fissile, which in the case of spent fuel usually means 239
Pu and 241
Pu. As the half life of 241
Pu is "only" around 14 years and the decay product 241
Am is non-fissile, it is desirable to bring spent fuel to a reprocessing facility as fast as feasible. However, dry cask storage and especially currently used methods of transporting spent fuel can only be employed after decay heat has dropped below a certain value. As such interim storage in spent fuel pools is still necessary. Plutonium recovered via reprocessing is mixed with either depleted uranium, natural uranium or uranium recovered in reprocessing at suitable ratios to obtain a new fuel, called MOX-fuel ("mixed oxide" fuel due to containing uranium dioxide and an oxide of plutonium). While further 238
U is "bred" into 239
Pu in a reactor running on MOX-fuel, on balance more fissile material is "consumed" than "produced" as more 239
Pu is convered to non-fissile 240
Pu than 240
Pu is converted to 241
Pu. Furthermore, some 241
Pu is converted into non-fissile 242
Pu upon encountering a neutron and 243
Pu beta decays into non-fissile 243
Am before being able to fission. Thus spent MOX-fuel contains an isotopic mixture of plutonium with undesirable properties and is usually not reprocessed further. Spent MOX-fuel also contains higher proportions of Americium and Curium (albeit only negligible amounts of Neptunium) and even higher atomic weight elements. If extracting those elements is desired, spent MOX-fuel is a better source than spent "first generation" LWR fuel.
Operations
Spent fuel treatment plants seek to separate the three aforementioned categories into fractions that are as pure as possible. In nuclear reprocessing plants about 96% of spent nuclear fuel is recycled back into uranium-based and mixed-oxide MOX fuels.
One of the main workhorses for the separation of spent nuclear fuel is the PUREX process, which is able to separate the plutonium and other transuranics from the remainder of the spent fuel. The uranium and plutonium are separated in turn in a series of (additional) complex chemical operations. The uranium will become uranyl nitrate and the plutonium will be converted into plutonium oxide. The latter will be used to produce fresh fuel called MOX – mixed oxides of uranium and plutonium, which can be used as "fresh" fuel in nuclear reactors.[5] The uranium fraction is very low in radioactivity and can be stored in specialized warehouses.[4]
Long-term storage of radioactive waste requires the stabilization of the waste into a form that will neither react nor degrade for extended periods. Decades of research efforts have shown that a viable way to do this is through vitrification. High temperature treated ("calcined") fuel separation fractions are fed into an induction heated furnace with fragmented glass. The resulting glass contains the waste products which are bonded to the glass matrix. The fission products, which make up around 4% of the spent fuel mass, are the ones that are vitrified in this glass, as they are not used for any other purpose, and when mixed together are highly radioactive.[6] In practice, because of limits to separation of the three categories, a small amount of transuranic isotopes will be present in this material.
History
The La Hague site was built after the Marcoule site originally for producing plutonium for military purposes. In 1969 the French military, having had a sufficient supply of plutonium for weapons, had no further use of the reprocessing centre. The factory directed its efforts toward civil operations, and with the reduction of 350 people from the plant's workforce, its military connections ended.
This shift to civil uses was supported by Valéry Giscard d'Estaing and strengthened by the 1973 oil crisis.
It was understood that the facility would be used to reprocess the uranium sold to Taiwan in the 1980s and a number of politicians and experts from Taiwan listed the La Hague site in the course of securing the deal. France later reneged on the agreement and the nuclear material sold to Taiwan remains unreprocessed and is stored in temporary cooling ponds.[7]
On 5 October 2002, an INES Level 1 incident occurred at La Hague. A sub-contractor working at the plant suffered skin contamination while rinsing equipment in the plutonium purification workshop.[8]
Controversy surrounding radioactive releases
Greenpeace has been campaigning since 1997 for the shutdown of the site, which they claim dumps "one million litres of liquid radioactive waste per day" into the ocean; "the equivalent of 50 nuclear waste barrels", claiming the radiation affects local beaches,[9][10] although official figures are to the contrary.[11]
Greenpeace have protested by creating roadblocks and chaining themselves to vehicles transporting materials to and from the site.[12][13] However the leader of Greenpeace France, Yannick Rousselet, has since stated that they have ceased attempting to criticize the reprocessing plant on technical grounds, COGEMA having succeeded at performing the process without serious spills that have been frequent at other such facilities around the world. In the past, the antinuclear movement argued that COGEMA would not succeed with reprocessing.[14] Eric Blanc, deputy director of the processing plant, says that although the plant does intentionally release radioactive material, the annual dose in the vicinity of the facility is less than 20 microsieverts per year, which is equivalent to the dose of cosmic radiation received during a single transatlantic flight, and therefore within regulation.[14] The AREVA NC website emphasizes that they are committed to keeping the dose below 30 microsieverts per year.[15]
One radionuclide, whose release is very difficult to avoid if aqueous processes (such as PUREX) are employed, is Tritium. Tritium behaves chemically nigh-identical to other isotopes of hydrogen and thus filtering it out of water is very energy consuming and cumbersome. In 2018 about 31.2 grams (1.10 oz) of tritium were discharged to the local environment. This quantity is about an order of magnitude lower than the amount of tritium naturally contained in the English Channel if one in 1018 atoms of hydrogen in that body of water is tritium.
See also
- Sellafield, a similar facility in the United Kingdom
References
- ^ Kok, Kenneth D. (2010). Nuclear Engineering Handbook. CRC Press. p. 332. ISBN 9781420053913.
- ^ Emmanuel Jarry (6 May 2015). "Crisis for Areva's plant as clients shun nuclear". Moneyweb. Reuters. Retrieved 6 May 2015.
- ^ http://ch302.cm.utexas.edu/nuclear/radioactivity/selector.php?name=band-stability
- ^ a b "Treatment and Conditioning of Nuclear Wastes - World Nuclear Association".
- ^ "Orano la Hague".
- ^ "Vitrification: The Workhorse of Nuclear Waste Management". 18 June 2019.
- ^ Turton, Michael. "Notes from central Taiwan: Taiwan's spent nuclear fuel problem". www.taipeitimes.com. Taipei Times. Retrieved 14 March 2021.
- ^ "NUCLEAR SAFETY: WORKER CONTAMINATED IN INCIDENT AT LA HAGUE PLANT". Europe Environment. 2002-12-13. Archived from the original on 2016-05-06. Retrieved 2015-05-02 – via Highbeam Research.
- ^ "Greenpeace installs webcam at the end of France's nuclear reprocessing discharge pipe 'to open the eyes of Governments'". Greenpeace website archive. 2000-06-26. Archived from the original on 2007-06-14. Retrieved 2007-08-26.
- ^ "Areva NC discharge pipe - Collection of related press releases". Greenpeace website archive. Archived from the original on 2007-08-28. Retrieved 2007-08-26.
- ^ "La Hague - France Nuclear Forces". GlobalSecurity.org. Retrieved 2007-08-26.
- ^ Naegelen, Jacky (2004-10-07). "US Bomb-Grade Plutonium Convoy to Cross France". Reuters. Archived from the original on 2007-08-03. Retrieved 2007-08-26.
- ^ "Greenpeace blocks top secret transport of plutonium in France, revealing global proliferation threat is not in Iraq". Greenpeace International. 2003-02-19. Archived from the original on 2007-12-02. Retrieved 2007-08-26.
- ^ a b Fairley, Peter (February 2007). "IEEE Spectrum: Nuclear Wasteland". Archived from the original on 2007-02-16. Retrieved 2007-08-26.
- ^ "Zero impact commitment". AREVA NC. Retrieved 2007-08-26.[dead link]