Severe Accident Analysis Conclusions

MELCOR was the first of the severe accident analysis codes to undergo a formal peer review process. One of the major conclusions of the recent MELCOR Peer Review [2] was the need for a more comprehensive and more systematic program of MELCOR assessment. A systematic program of code assessment provides a number of benefits, including ... 

As a brief conclusion to this section, let us recall that the global safety objectives are fully transposable to the MSFR reactor. The difficulty lies, among other things, in the identification of severe accidents for this type of reactor. Thus a core melt in the case of solid-fueled reactors is central to present safety studies and has no immediate equivalent in a Uquid-fiieled reactor. A safety analysis for the MSFR must then proceed from the fundamentals of nuclear safety. 

Trend analysis can be confused or invalidated by a sample that is too small. If the charting or analysis is limited only to major incidents, there will often be too few within a period to arrive at meaningful conclusions. For example, a facility with one thousand employees may experience only one or two serious incidents per year, and several years worth of data would be needed to make any meaningful statistical analysis. Minor incidents and near misses can be as useful in trend analysis and preventive prediction as major incidents. All process incidents should be reported, classified, and investigated as appropriate. The severity of an incident is frequently more a function of chance than actual fundamental system differences among accidents and near misses. 

Large-scale experimental releases of fission product activity are clearly ruled out because of the implications on the safety of the public, described in Section V,F, as are also the smaller scale releases referred to earlier in Section V. Therefore, for verification of our conclusions we have to rely on limited experience from those few accidents that have occurred and that have released fission products (see Section I,D), but much more on our store of knowledge of all the factors involved, i.e., types of reactor accidents (Section II) through fission product release (Section III) and dispersion of a release in the atmosphere (Section IV), to analysis of the radiation and radiobiological hazards and risks to exposed members of the population. In view of these several steps involved in the estimation of hazard, it is reassuring that the many different authors who have written on the topie reach conclusions which are generally similar and differ only in limited areas. 

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