A new approach to reactor safety goals in the framework of INES

By extending a framework of the International Nuclear Event Scales (INES) widely used throughout the world, the author proposes a new concept of reactor safety goals that facilitates engineering applications, while removing some of the uncertainties often encountered in implementing safety goals. The INES criteria specified in releases are translated into doses by performing dispersion calculations for a typical site to estimate radiological consequences to the public. Quantitative health objectives that incorporate lessons learned from radiological consequences of the Chernobyl accident are deployed into master risk curves. More attention is paid to immediate noble gas releases occurring in the early phase of severe accidents, as well as the delayed release of iodine and cesium that can cause wide spread land contamination. The land contaminated with radioactive iodine around Chernobyl and the subsequent ingestion of iodine through pasture-cow-milk pathways is said to have induced many of the thyroid cancer cases. By monitoring more frequent incidents with/without release, a set of master risk curves can be used to assess the operating performance of plants in a safety space delineated by three regions (acceptable, tolerable, unacceptable). It is concluded that another Level 5 or beyond radiological consequence, especially the potential land contamination by 137Cs would be a disaster and is totally unacceptable.