A55 Exposure from major accidents

There have been accidents in using nuclear energy or radioactive elements. In medical and diagnostic practice accidents may occur (a few hundreds of all types each year), and usually have serious consequence. The probability that any member of the public be involved is, however, very small, and, by and large, the consequences do not affect the public.

Weapons production and transportation have resulted in several accidents, but the collective dose committed is small. The two most serious accidents in nuclear weapons production were at Kyshtym, in the former USSR, and at the Windscale plant at Sellafield (UK), both in 1957. The first accident caused a collective dose of 2,500 man Sv over the next 30 years. The Sellafield accident caused a total collective dose in Europe (including England) of about 2,000 man Sv.

The two most important accidents in power plants were those at Three Mile Island and Chernobyl [UNSCEAR, 2000; World Nuclear Association website], although the Chernobyl installation produced energy only as a byproduct, the plant being chiefly a plutonium-producing facility, and although what happened can hardly be defined as an accident. At Three Mile Island the containment system, missing at Chernobyl, prevented a large amount of fission fragments from spreading in the environment: the total collective effective dose was <40manSv, with the maximum dose to nearby individuals <1mSv. The Chernobyl accident had much more serious consequences. It caused the death of 30 people among the rescue workers within a few weeks, less than 60 to date, and 1,800 cases of thyroid cancer in the children exposed; no other health impact has been detected up to the year 2000. The worldwide average annual effective dose per person due to the Chernobyl accident, estimated for the year 2000, is 0.002 mSv, down from its peak 0.04 mSv in 1986 [UNSCEAR, 2000]. Note that cancer rates went up by 3% in the affected area, but the children who contracted thyroid cancer had a 99% survival rate rather than 80-85% previously estimated [Nature, 2005]. In fact, according to a report by the Chernobyl Forum released in 2006, poverty and mental-health problems pose a much greater threat to the local community than radiation (see also [Del Rossi and Bruno, 2008]).

A different type of accident occurred about 20 years ago in Taiwan. Recycled steel, accidentally contaminated with radioactive 60Co ended up in construction steel for more than 180 buildings, occupied by about 10,000 persons from periods ranging from 9 to 20 years. The radiation dose received averaged about 0.4 Sv, for a total collective dose of 4,000 person Sv. The observed cancer rate of these people was 3.5 per 105 person-years; congenital heart malformations among children, during the same period were 1.5 x 10~3. These figures were recently compared with the averages over Taiwan's general population, which are 116 cancers per 105 person-years and 23 malformations x 10~3. The conclusions, see [Chen et al., 2004] seem thus to indicate that a "moderate" dose of radiation is beneficial. This finding should be, and

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