A) Windscale Accident

Circulating water

Condensate

Heated water

Working steam

I

HH

SG

Spent 'steam Electric power

fi

G к

\Cooled water^

Tf ▼ TT

Electric power supply lines

Fig.25. Simplified production process diagram of nuclear power plant:

R - nuclear reactor; SG - steam generator; T- steam turbine; G - electric power generator; С - steam condensor; S - switchboard

The fissioning of uranium-235 or plutonium-239 atoms - the pri­mary nuclear fuels - is caused by the impacts of neutrons on these at­oms. The fission process not only produces heat but also several addi­tional neutrons that can cause fissioning of other uranium-235 or pluto­nium-239 atoms. Thus, by proper arrangement of the atoms of the fuel, a sustained chain reaction can be maintained to provide a steady source of heat for operating a power plant. This chain reaction is controlled by regulating the number and the energy of the neutrons as they proceed from one fission reaction to another.

There are various types of nuclear reactors. The major differences between them are the form of the fuel, the methods for controlling the number and energy of the neutrons, and the type of liquid or gas used to remove the heat from the reactor core.

31. Read the texts and find in them the answers to the questions that fol­low.

Throughout the years, accidents causing a release of radioactive material to the environment have occurred. Since World War II all over

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the world large scale nuclear facilities have been built and operated both for civil and defense purposes. Some of the sites on which these facilities were located are heavily contaminated with radioactive sub­stances.

One of the first nuclear reactor accidents of environmental concern was the Windscale accident in October 1957. During the accident the military air-cooled graphite-moderated natural-uranium reactor used for plutonium production caught fire during the liberation of energy in the graphite. Emission from the Windscale lasted for 18 hours. Radioactive material was detectable in many parts of Western Europe but the ma­jority of it was deposited in the United Kingdom.

1. How long did the emission from the Windscale reactor last?

2. What did the emission result in?

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