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ATS YG –excursion to Great Britain April 14th-18th 2004

Kari Kuusisto
Finnish Youth for Nuclear Energy, vice chairperson

Kari Kuusisto and Calder Hall.I had the opportunity to participate ATS YG (Finnish Nuclear Society Young Generation) excursion to Great Britain in April 2004. I was specifically interested in the journey, as the programme included a thorough visit to a nuclear power production’s “evil’s nest”, Sellafield. That is a name, which makes the blood of nuclear energy opponents coagulate.

From Manchester Airport the journey continued straight away to Capenhurst, where Urenco fuel enrichment plant is located. On the same area there are old plants that work based on gas diffusion. The plants are owned by BNFL (British Nuclear Fuels), but they have been out of service since 1982. In the plant UF6 (uranium hexafluoride) is transformed into gaseous form and by spinning it in centrifuges Uranium-235 and Uranium-238 are separated from each other. Heavier U238 moves to the outer edges of the centrifuge and can therefore be separated. The temperature gradient is maintained vertical inside the centrifuge, which causes increase in U235-content at the lower section. The centrifuges have magnetic bearings, because no other mechanical structure could bear such a speed of rotational motion. After the enrichment uranium hexafluoride is converted into uranium dioxide (UO2). Finally, ceramic fuel is compressed into pellets, which are grouped in zircon pipes. The technique used by BNFL is the most environmental friendly of current techniques.

The plant is not large, because it manages only one work phase and the pressurized tanks are taken elsewhere to be used in fuel production. The plant employs 500 people. The functioning of it helped to make clear why huge electricity wires are lead to the plant: the process consumes loads of electricity. On our way there I thought that the electricity comes from the plant.

Springfields. Springfields.

On the second day we travelled to Springfields, where nuclear fuel is being produced for Magnox-, AGR- (Advanced Gas-Cooled Reactor) and some pressure water reactors. The process itself is multi-phased and difficult to understand. However, it was awesome to watch from one meter distance, as the loader loads fuel elements into AGR-capsules with his woollen gloves. AGR is a British reactor type. Fifteen reactors of that kind have been constructed since 1963, all of which are operated by British Energy.

In Springsfield there is also development work made, which was introduced us in the laboratories. BNFL is responsible for an international project, which aims at developing a so called High Temperature Gas-Cooled Modular Reactor (HTGMR). It involves using TRISO-particles (tristructual isotrophic) in an HTGR-reactor (High Temperature Gas-Cooled Reactor). The nucleus of TRISO-particles consists of low-enriched uranium dioxide (UO2). The other options are thorium or plutonium, of which the latter would probably interest the nuclear weapon states. TRISO-particles are found in fuel elements, which are typically spherical and 6 centimetres in diameter. The uppermost shell of it is a half-centimetre graphite layer, which covers the actual fuel matrix. That too is graphite and includes TRISO-particles.

Fuel elements and AGR-capsules. Fuel elements and AGR-capsules.

Considering radiation safety, the HTGMR-reactors are safe and cost-effective to operate. However, considering safety, high temperature and vast amount of graphite in the nucleus set their own demands to the maintenance of a plant. Other good features are easy adjustability of power and effortless nuclear waste disposal. Therefore, for us in Finland it is useful to keep up with the course of events in this sector as well, because we already have comprehensive district heating systems in our towns.

Springfields.

Sellafield is quite a Disneyland for people involved in nuclear energy. Almost everything related to fuel life-span can be found there, apparently activities related to military purposes as well. Great Britain has been sued to Court of Justice of the European Communities, because inspectors have not been permitted to go everywhere in the Sellafield area. The area employs as many as 11,000 people.

First we got to visit Calder Hall, which is the first nuclear power plant in commercial use. In the Soviet Union, Obninsk (107 kilometres from Moscow), there was an operating plant before that, but as the society based on real socialism did not have markets, the plant was not in commercial use either. Later Obninsk has become a real Silicon Valley of Russia, as after the nuclear physicists several IT-professionals and the most important international companies have become aware of it. Earlier its main product and the top secret were nuclear reactors used in submarines.

In 1953, it was Winston Churchill himself, who made the decision about building the first four reactors in Calder Hall. Three years later, October 17th 1956 its first reactor was inaugurated by Queen Elizabeth II. The reactors were of the first generation Magnox-type and gas-cooled. Carbon dioxide works as a cooler in them and graphite as moderator. Natural uranium packed in magnesium shells is used as fuel. Hot gas boils water in steamers and the steam in secondary circuit rotates the generators.

There have been altogether 26 Magnox-reactors, of which 18 are still in use. They are located in seven separate plant locations. Reactors were also built to Latin in Italy and Tokaimura in Japan, but those reactors are not operational any more. In Calder Hall one can concretely understand that nuclear power production cannot be paralysed via computer viruses, as the production is fully manual. The interior reminds us of the good old James Bond –films, because the cranes and generators are pink, light yellow and blue.

Calder Hall. Calder Hall.

The finest of Sellafield’s (earlier Windscale) plants is the THORP (Thermal Oxide Reprocessing Plant), which was completed in 1992 and licensed in 1997. The premises with electric glass doors were excellent indeed. In THORP it is possible to get closest to high-active waste considering peacetime security provisions. We were standing on lids, under which there is 1.5 metres concrete capsule that isolates powerful radiation, but one can still feel the warmth when touching the lids. The plant also produces so-called MOX-fuel (Mixed Oxide Fuel). MOX-fuel includes 5 percent plutonium generated in the reactor, which can also be exploited. Since 1963, 400 tons of MOX-fuel has been safely loaded into licensed reactors. In Europe there are over thirty reactors of that kind. In reprocessing some gas and fluid waste that are difficult to manage are also generated.

At its best there have been seven operational plants in the area, but now there is only one. Instead, nuclear material is shipped to be reprocessed in Sellafield from all over the world. Naturally the area has an own harbour in the Irish Sea, so it is no use planning sabotaging railway- or highway transportations! The material is so expensive that it is shipped all the way from Japan to Sellafield. Therefore, reprocessing does not seem very profitable financially, although it is technically well-working and safe.

Springfields.British Museum is responsible for the Sellafield Visitors centre’s operation: information is thus spread by an independent organisation. The Sparking Reaction –animation, which is targeted mainly to elementary school pupils, made it clear which form of energy one should support in modern world. There were stuff from the whole history of nuclear energy on display in the Visitors Centre, and a rather naive Tshernobyl -control room, in which an unstable reactor could somehow be kept on track by pressing different buttons. If one did not press the buttons on a regular basis, the reactor went critical. In Western countries that reactor type could not have even been licensed at 60’s, although Greenpeace and its various partners have repeatedly and mistakenly so claimed.

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Last modified May 5th 2008