Evaluation of the natural phenomena hazards as part of safety assessments for nuclear facilities

In reassessing the overall safety of existing nuclear facilities, the effects of Natural Phenomena Hazards (NPH), for which the facilities may not have been designed, must also be taken into account. An NPH evaluation approach is outlined, which is based on a combination of detailed facility walk through screenings, use of existing structural analyses, and a minimum of new analysis. The method is applied to a low hazard nuclear laboratory complex, and the results of the NPH evaluation are factored into the overall safety analysis. It is found, that in spite of some seismic vulnerabilities and expected facility damage, the resulting radioactive material releases have only minor impact on the on-site worker and negligible effects off-site. Hence, the facility risks are acceptable and continued operations are justified. (author). 12 refs., 2 figs., 1 tab