Determination of the type and amount of fission products released in a nuclear reactor accident

In case of an accident in a nuclear reactor, it is very important to evaluate promptly the magnitude and composition of release of fission products, in order to take the adequate emergency measures. The present study describes a method of rapid determination of the type and amount of fission products released in a nuclear reactor accident, by measuring the released radioactivity at specific high γ ray energy levels (2.4 to 6.6 MeV). The specificity of some fission products (e.g. 84Br) characterized by emission of high energy γ rays, makes possible the rapid determination of the group of fission products released (halogens, volatiles or solids) and the estimation of the amount of release of critical fission products such as 131I, 90Sr and 137Cs. The method allows the detection of the release, both at the source and in the environment, in airborne material and on deposition surfaces, and at different time delays from occurrence of an accident, varying from zero time up to several days. Other advantages and limitations of the method are discussed. (author)