Case Study for a Post‑Accident Situation: Remediation of Areas Affected by the Chernobyl Accident. Annex III

The accident in Unit 4 of the Chernobyl nuclear power plant was the most serious nuclear accident in history. The accident resulted in the release of a mixture of radionuclides into the air over a period of approximately 10 days. The total release of radioactive substances was about 14 EBq¹ (as of 26 April 1986), including 1.8 EBq of ¹³¹I, 0.085 EBq of ¹³⁷Cs and other caesium radioisotopes, 0.01 EBq of ⁹⁰Sr and 0.003 EBq of plutonium isotopes. The radionuclides released were in the form of gases, condensed particles and fuel particles. Fuel particles made up the most important part of the fallout in the close vicinity of the nuclear power plant. Radionuclides, such as ⁹⁵Zr, ⁹⁵Nb, ⁹⁹Mo, ^141,144Ce, ^154,155Eu, ^237,239Np, ^238–242Pu, ^241,243Am and ^242,244Cm, were released in a matrix of fuel particles. More than 90% of the total activity of ^89,90Sr and ^103,106Ru released was in fuel particles. Radiocaesium was the main contributor to radiation dose in the contaminated area around the Chernobyl nuclear power plant, except in the period during and immediately after the accident, when short lived² and intermediate lived³ radionuclides were significant contributors to the exposure of the population. Therefore, the planning and implementation of remediation was based mainly on assessments of ¹³⁷Cs activity concentrations in the environment.