Nuclear Criticality Safety Management

Abstract

NUCLEAR CRITICALITY SAFETY MANAGEMENT Nuclear critical Safety management was established over fifty years ago following several accidents associated with Nuclear weapons research and development numbering well over fifty taking into account previously unreported accidents in the former Soviet Union. An estimated 10% of these accidents occurred in working nuclear reactors, 20% in production plants and 70% in critical facilities. Although, the rate of nuclear accidents has dramatically reduced, the recent reactor accidents of Chernobyl and Toka Mura demonstrate the need for greater safety management measures. The importance of safe handling of fissile materials was recognized at an early stage by the scientific community and other responsible authorities. At that point in time, technology was not sophisticated enough to reliably predict the critical status of fissile materials. The state-of-the-art knowledge in criticality safety has an economic impact, the reduction of uncertainties in safety margins allows improved and more economical designs for manipulation, storage and transportation of fissile materials. Moreover, there are new demands on method development, experimentation and regulation as a result of handling excess fissile materials from the weapons program which have possible civil energy applications. Some criteria for nuclear criticality safety are; designs for criticality safety, method of criticality control and criticality monitoring. A nuclear chain reaction occurs when more than neutron from a fission reaction causes another fission reaction. An uncontrolled chain reaction within a sufficiently large amount of fission fuel (critical mass) can lead to explosive energy release. Nuclear criticality accidents is the occurrence of a self-sustaining neutron chain reaction that is either unplanned or behaves unexpectedly. Enriched uranium and plutonium are capable of supporting self-sustaining neutron chain reaction. Nuclear criticality results in the same reactions that occur in a nuclear reactor were the products are heat, radiation and radioactive materials which are referred to generally as fission products. In the workplace, nuclear criticality accidents last from a fraction of a second up to several minutes, but may persist for a much longer time depending on the specific condition. Since the beginnings of nuclear industry in the early to mid 1940s, there have been 60 known nuclear criticality accidents. These occurred in Argentina, Belgium, Canada, France, Japan, Russia, UK, USA, and Yugoslavia and publicly available data report on them.

Seminar presented by Saiyadi Sulaiman