Windscale plant

In 1942, the Mallinckrodt Chemical Company adapted a diethylether extraction process to purify tons of uranium for the U.S. Manhattan Project [2] later, after an explosion, the process was switched to less volatile extractants. For simultaneous large-scale recovery of the plutonium in the spent fuel elements from the production reactors at Hanford, United States, methyl isobutyl ketone (MIBK) was originally chosen as extractant/solvent in the so-called Redox solvent extraction process. In the British Windscale plant, now Sellafield, another extractant/solvent, dibutylcarbitol (DBC or Butex), was preferred for reprocessing spent nuclear reactor fuels. These early extractants have now been replaced by tributylphosphate [TBP], diluted in an aliphatic hydrocarbon or mixture of such hydrocarbons, following the discovery of Warf [9] in 1945 that TBP separates tetravalent cerium from... 

Following successful pilot-plant tests at Chalk River [N4], the Butex process was adopted for large-scale separation of plutonium, uranium, and fission products from natural uranium irradiated to low bumup at the Windscale plant of the U.K. Atomic Energy Authority [H8]. Even after its use in this application was replaced by the Purex process, the Butex process remained in use at Windscale for primary decontamination of high-bumup fuel until the 1970s. Then an explosion, probably due to reaction of nitric acid vnth solvent, terminated its use. 

The very nature of these requirements leads to a conservative design philosophy and yet, as the second Windscale Plant has proved, the reward is high utilization and longevity, with consequent economic benefits. 

A necessarily brief outline of some of the process features of the second Windscale Plant will illustrate the application of the above prin-... 

Packed columns were used in the first Windscale plant (Sellafield, UK). Pulsed columns were used at Hanford (USA), in the old Eurochemic plant at Mol (Belgium), and are currently in use in the newer La Hague and THORP plants. Mixer-settlers have be used at Savannah River (USA), in the Magnox plant at Sellafield (UK), and at La Hague (France). Centrifugal extractors have bear installed at Savannah River and at La Hague. 

The BEA had been involved from quite early in the study, and had even delayed construction at a site at East Yalland near Barnstaple in Devon to allow borings to be taken in the hope that the new plant would be constructed there. On the other hand, given that the main purpose of the new plant would be to produce plutonium, it made much greater sense to situate it next to the Windscale plant. 

A second source of plutonium, dispersed more locally, is liquid effluent from fuel reprocessing facilities. One such is the fuel reprocessing plant at Windscale, Cumbria in the United Kingdom where liquid waste is released to the Irish Sea(6). Chemical analysis of this effluent shows that about one percent or less of the plutonium is in an oxidized form before it contacts the marine water(7). Approximately 95 percent of the plutonium rapidly adsorbs to particulate matter after discharge and deposits on the seabed while 5 percent is removed from the area as a soluble component ). Because this source provided concentrations that were readily detected, pioneering field research into plutonium oxidation states in the marine environment was conducted at this location. 

Irish Sea, site impacted by Windscale Reprocessing Plant and reference sites, 1977 EPA 1984... 

The rate of dissolution of these reaction products is slow (1.5-2 fig/day per 50-70 mg of solids). Lai and Goya 147) showed that at least 90% of these plutonium aggregates had a diameter <0.01 jum. However, it must be stressed that these forms do not necessarily represent those forms which would be produced as a result of an accidental release from a nuclear power plant or as a result of controlled release from nuclear fuel reprocessing facilities such as those which occur at Windscale in England. 

Windscale II plant in the UK. In this the uranium and plutonium are back-extracted together in a first cycle of decontamination. They are then separated in a second cycle of solvent extraction and independent back-extraction. The factors affecting the choice of flowsheet type have been reviewed and criticality control is an important consideration in the process design.286... 

Huggard, A.J., Warner, B.F. 1963. Investigations to determine the extent of degradation of TBP/odorless kerosene solvent in the new separation plant, Windscale. Nucl. Sci. Eng. 17 638-650. 

Table 2.3 shows the estimated releases of 90Sr, 131I, 137Cs and 144Ce in the Nevada tests, the thermonuclear tests (H tests), the 1957 Windscale accident, the 1957 accident at a separation plant in the Urals... 

A cluster of cases of childhood leukemia has been found in West Cumbria (Forman et al., 1987). As a result, an exhaustive reexamination has been made of the emissions from the Windscale piles and the adjacent Sellafield reprocessing plant, including those before,... 

On 29 September 1957, eleven days before the Windscale accident, there was a chemical explosion in a Soviet plant treating active wastes, situated in the Urals. No mention of the accident was made in Soviet media at the time, but an exiled scientist, Z. A. Medvedev collected information and published it in the west (Medvedev, 1976, 1979). A further study, using Medvedev s data and oblique references to the effects of the disaster in Soviet ecological literature, was made by scientists at Oak Ridge (Trabalka et al., 1980). After the elapse of 32 a,... 

Radioactive particles have been identified in connection with accidental releases from nuclear installations under high- and low-temperature conditions, in particular in releases from the accident in Unit 4 at Chernobyl (Loshchilov et al., 1992 Devell et al., 1986 Raunemaa et al., 1988) in 1986 and releases from the Windscale piles both during the fire in 1957 (Arnold, 1992) and earlier during the normal operation of the plant (Jakeman, 1986). 

Sources and Amounts of Plutonium in the Environment. Since 1945 approximately 3300 kg of plutonium has been injected into the environment, mostly (>90Z) from atmospheric explosions of nuclear weapons. This corresponds to about 380 kCi total alpha radioactivity. The addition to this amount by releases from nuclear power operations is much smaller the major continuing addition is ca. 0.1 kCi per month released to the Irish Sea from the British nuclear reprocessing plant at Windscale. About 2/3 of the plutonium from nuclear explosions would be formed into highfired oxides which would be rather inert chemically. However, the remainder, created during the explosion as single atoms via the U(n, J ) U(28 ) Pu... 

A solvent extraction process similar to Purex using TBP was developed by the Commissariat a I Energie Atomique [Gl] for use in the French plutonium separation plant at Marcoule. Since then, the Purex process has replaced the Butex process at Windscale [W3], has been used in the Soviet Union [Sll], India [S7], and Germany [S3], and by now is the universal choice for separation of uranium and plutonium from fission products in irradiated sUghtly enriched uranium. Fuel from the liquid-metal fast-breeder reactor (LMFBR) is also reprocessed by the Purex process, with modifications to accommodate the higher concentrations of plutonium and fission products. 

Design of the HAW tanks at the AGNS plant. The AGNS plant design [L2] is similar to that at Windscale [Wl]. The design is based on a bumup of 27,000 MWd/MT and a heat rate of 15.5 kW/MT of heavy metal for waste from 150-day-cooled fuel and of 7.9 kW/MT for waste from 1-year-cooled fuel. The waste will arrive at the tank facility with a specific volume of 1100 liters/MT heavy metal. The volume will be reduced to 550 liters by in-tank evaporation. 

ITie British HARVEST process. Another vitrification process is the HARVEST process (C3, M3], an improved version of the former FINGAL process. It is a pot process or, in the categories of this chapter, a liquid-feed/in-can melting process. A full-scale, fully radioactive plant is scheduled to be in operation at the Windscale site in 1986. 

Nuclear fission provides about 20% of the electricity generated within the UK. Economic womies about the decommissioning of old nuclear stations, and major accidents in Windscale UK (1957), Three Mile Island USA (1979) and Chernobyl Ukraine (1986) have caused many people to question whether or not more nuclear plants should be built. This is a photograph of the fourth reactor at the Chernobyl nuclear power plant where an explosion resulted in the world s worst nuclear accident. 

British Nuclear Fuels pic (BNFL) provide a complete nuclear fuel cycle service with its sites at Springfields (AGR/Magnox Fuel Fabrication) near Preston and Sellafield (MOX Fuel Fabrication and Reprocessing) in Cumbria. BNFL also generates electricity using Magnox Reactors at Sellafield (Calder Hall) and Chaplecross in Scotland. This paper provides an overview of the Windscale Vitrification Plant (WVP) and reviews the major safety issues associated with vitrification operations. The practicalities of vitrification of Pu using the current WVP process are briefly discussed. 

The Windscale Vitrification Plant vitrifies high level (highly active) liquid waste arising from reprocessing operations at Sellafield. The plant operates two identical vitrification lines with a current combined throughput of 350 product containers per year. A third line is currently under construction and will commence operation in the year 2000. The key safety function of the plant is to convert mobile material into a solid immobile form which can be more easily managed, stored, and transported. 

The Safety Case produced for the Windscale Vitrification Plant in 1994 included a detailed and comprehensive assessment of fault conditions in the plant using HAZOP and Probabilistic Risk Assessment techniques. The Safety Case identified a number of major hazards. These major hazards, along with the protective measures, Operating Rules, and Safety Mechanisms designed to prevent these hazards or to mitigate them are briefly described below. 

The HLW feed to the Windscale Vitrification Plant and the vitrified product are highly radioactive, direct doses at 3-4 m from a product container exceed 40 Svh. The Windscale Vitrification Plant has therefore been designed with appropriate levels of shielding and remote handling systems to minimize the potential for significant direct dose to operators. 

Safety of the Windscale Vitrification Plant is demonstrated by a safety case, which is required by the UK Regulators to justify continued operation, key items of safety equipment, and key operating procedures identified within the Safety Case. 

Routine doses to the work force and members of the public resulting from the operation of the Windscale Vitrification Plant are significantly below UK statutory limits. 

WVP Windscale Vitrification Plant (also vitrification plant or process)... 

---