Experience of territory decontamination

The need for protective actions became evident very soon after the Cher­nobyl accident occurred. Activities for area decontamination were part of an extensive set of short — and long-term environmental countermeasures, applied to protect workers and the public from radiation. These counter­measures involved large amounts of human, economic and scientific resources. According to IAEA (2001), such countermeasures included:

• reduction of radionuclides release from the destroyed reactor (in the early stages of the accident),

• evacuation of population and its resettlement,

• construction of the ‘Shelter’ object (SO),

• decontamination of the soil, buildings and installations,

• disposal of the RAW resulting from the decontamination measures,

• surface and groundwater protection,

• restriction of access to the contaminated areas and the prohibition of economic activity,

• changing the type of forestry and agricultural activities,

• ban or limitation of the consumption of contaminated foodstuffs,

• reduction of radioactive contamination of agricultural products,

• information to the population, social and other supplementary measures.

Large-scale decontamination and clean-up activities were performed between 1986 and 1989 both within the Chernobyl Exclusion Zone, and in the cities and villages of the USSR most contaminated after the Chernobyl accident. This activity was performed usually by military personnel and included removal and disposal of contaminated soil and civil constructions, cutting and disposal of contaminated forests, washing of buildings with water or special solutions, cleaning and washing of roads, and decontamina­tion of open water supplies. The decontamination has produced a huge amount of radioactive waste, which was collected in numerous RWDP and RWTSP and has created a problem for its final disposal. More than 800 waste localization sites were created within ChEZ and 47 outside of it, with a total volume of more then 106m3 . The reliability of these sites is a cause for concern, and the problem needs to be solved in the future. The greatest amount of RAW arose during decontamination of the site of the destroyed unit 4 in the course of the ‘Shelter’ object (SO) construction. The object is classified now as a temporary storage of radioactive waste (RSNU, 1997). The SO, RWDP and RDTSP are described in Section 11.4.3.

The efficiency of various measures for protecting workers and public from radiation was assessed in IAEA (2006) . According to this source, depending on the decontamination technologies used, the dose rate was reduced by a factor of 1.5-15. However, the high cost of these activities hindered their comprehensive application to all contaminated areas. Due to these limitations, the actual effectiveness of the decrease in annual exter­nal dose was 10-20% for the average population and ranged from about 30% for children to less than 10% for outdoor workers.

It should be noted that in many cases the decisions about decontamina­tion in 1986-1989 were of a political nature. In many cases such political decisions were in contradiction with conclusions reached by cost-benefit analysis. Therefore, the resulting effect in reducing the exposure dose was achieved by unnecessarily high costs in human and economic resources.

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