Page 134 - Radiochemistry and nuclear chemistry

120 Radiochemistry and Nuclear Chemistry

The explosion and fire in one of the power reactors at Chernobyl, Soviet Union, in 1986,
was a more severe accident (w167 and 22.3). For several days large amounts of fission
products and actinides were ejected and spread over large areas of the former USSR and
Europe, see Figure 5.8. Almost 20 % of the fission products came down over Scandinavia,
causing a deposition > 120 kBq 137Cs/m 2 over the city G~vle in Sweden (170 kin north
of Stockholm). The plume spread down over Central Europe, causing very uneven
deposition due to wind pattern and local rains: e.g., Munich, Germany, received < 25 kBq
137Cs and 0.2 kBq 9~ per m 2, while Mainz (400 km away) received 180 Bq 137Cs and
-.0.001 Bq 90St per m 2, see also w
In 1957 an explosion occurred in a nuclear waste storage facility (probably due to
reactions between organic matter and nitrate) at Kyshtym south of Sverdlovsk, USSR,
leading to the contamination of approximately 1600 km 2 of land by 8 x 1016 Bq fission
products, causing local contaminations exce~ing 101~ Bq/m 2 (2 x 108 9~ and 137Cs). The
area is still uninhabitable, see also w

5.10.3. Releases from nuclear power plants

All nuclear power plants are carefully controlled by the national radiation protection
boards, and strict limits for releases are set. Usually it is quite easy for the power plants
to meet these requirements. These releases are small compared to the natural radioactivities
and mostly negligible in the far field, see w167 and 21.8.

5.10.4. Other anthropogenic additions

In 1975 the London Dumping Convention set limits to dumping of nuclear waste in the
Oceans to places far of shipping trades and fishing areas and at depths > 4000 m. Earlier
dumping had been common practice by the nuclear powers even in narrow (the British
Channel) and shallow (up to 50 m) waters to get rid of large volumes of low level
long-lived waste. Officially reported dumpings were made as early as in 1946 and continued
in the Pacific and the North Atlantic until 1982 and in the Barents and Kara seas even later.
East of the British Islands the U.K. has dumped 665 TBq, France 134 TBq and other
countries together some 35 GBq. In total some 45 PBq have been dumped at 46 different
sites, mostly at depths of 1400 - 6500 m. Measurements reveal that in some cases
radioactive nuclides are leaking out from the containers, causing bottom contamination at
the site; however, the radionuclides are rapidly diluted as they are carried away by bottom
currents.
Recently it was disclosed that the former USSR made huge dumps of nuclear waste in the
waters east of Novaya Semlya: some 10 000 containers and 13 nuclear reactors (8 still
containing fuel), mainly from nuclear submarines. In some places the waste is at very
shallow waters (some 30 m). The total activity is estimated to > 60 PBq. The waste will
ultimately leak out and spread with westerly currents towards the Barents Sea and the North
Atlantic. However, the releases are expected to be rapidly diluted to harmless
concentrations.