The most interesting releases for safety evaluations

This chapter deals with some simple and quick methods for the evaluation of the dispersion in the environment of gaseous releases (gases, volatile products, aerosols and particulates). Chapter 7 describes some methods for evaluating the health consequences of releases. 

There are three steps in the evaluation of the consequences of accidents  

The gaseous releases which are dealt with here, are the most relevant ones for the evaluation of the immediate accident consequences and for the preparation of short-term emergency plans. Solid and liquid releases are less important for a nuclear power station because the radioactive products released to the environment are mainly gaseous and have high velocity (which may cause adverse consequences outside the plant). However, liquid releases have to be taken into account under some circumstances. The situation, then, is very different from many non-nuclear process plants where the prevailing accidental release from the point of view of the consequences may frequently be the release of flammable or toxic liquids. 

The radioactive isotopes which could in theory be released during an accident from a nuclear power station are listed in Table 2-1. In practice, however. 

In some cases, the safety reports used for licensing evaluate only the releases of the above listed isotopes, even if this practice doesn t satisfy many specialists. Ultimately, it is totally unsatisfactory when the consequences of releases evaluated in this manner are relatively close to the limits fixed for them in the design criteria. 

---