The Karachai Lake

The polluted Karachai Lake, located on the plant's site, covers about an area of about a quarter of a square kilometre and has a volume of about 400,000 cubic metres. Currently the total radiation is estimated at 4.4 Ebq, with specific water activity of ⁹⁰Sr и ¹³⁷Cs being 0.06 and 0,4 GBq/liter, and soil 10 and 50 GBq/litre.

There is an estimated amount of underground water covering 30 square km with a volume of up to 4 million cubic metres. This has a high content of cesium and strontium.

Concrete panels shaped like upside-down glasses have been placed on the bottom of the lake to protect the lake's surface. From above the blocks have been covered with rocks. Currently about 70% of the reservoir's surface has been covered. A chain of drilling holes has been made around Karachai to enable continuous monitoring of soil and subsoil water pollution at various depths and distances.

The 1957 Explosion

Following the explosion at the plant in 1957, about 90 per cent of the radioactive material fell on the plant itself. The cloud, which had completely settled within 11 hours, left a trace 300 km long and between 30 and 50 km wide. This has been named the Eastern Ural Radioactive Trace (VURS). As a result of the accident about 23,000 sq km was exposed to radiation, including 217 homes. About 1,200 people were evacuated, mainly during the first day of the accident. They received radiation of 0.5 Gy. A further, 11,000 people were moved later. They received average doses of 0.2 Gy.

Radioactivity levels have now decreased 15 times since the half-life period is less than a year and most of the area was brought back within safety standards by 1982. Almost all of the land which received initial pollution of up to 4 Curie/km² is currently being used for agriculture.

Research into radioactive ecology and biology is now being carried out in the remaining area, covering some 170 sq km, known as the Eastern Uralian Reserve. One of the world's largest centres of radiological research, a branch of the Biophysics Institute of the Russian Academy of Science, was established in Ozersk in 1953. Research has shown that the greatest impact on human health was in the early years of the plant's operation. This includes radiation sickness, high cancer rates, and thyroid gland disease in children.

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