Agenda - 11-17-1998 - 5a - Laserfiche WebLink

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25 Chapter 10 Solving the ~Vucleer Waste Dispos211 Crisis Defense-in-Depth The nuclear pug+•er industry in the United States applies a defense-in-depth approach to safety. Defense-in-depth relies on design features to pro~•ide assur- ance that (a) the frequency of major accidents is as logy as reasonably achie~•able. (b) the consequences from a major accident are mitigated to the greatest extent reasonably achievable, and (c) the public and the environment are protected even if a major accident ~~ith substantial radiological release occurs. The primary fac- tors in real estate may be "location, location, and location," but in nuclear safety they are "prevention, mitigation, and containment." Collectively, these defense- in-depth principles maintain the inherent risks acceptable lo~v, thereby pru~•iding the solid foundation for safe nuclear energy in this country. For an example of how defense-in-depth ~~•orks, nuclear po~~•er plants are designed to withstand a loss-of-coolant accident. The design basis LOCH involves the pustulated instantaneous break in the largest diameter pipe con- nected to the reactor pressure vessel. To satisfy the Eirst defense-in-depth pnnci- ple, the piping connected to the reactor pressure vessel is designed, constructed, and inspected to exacting standards that ensure its integrih•. The chances of a pipe failing are therefore extremely unlikely. Yet, defense-in-depth assumes that the pipe fails an«.•av and requires design provisions to mitigate its conse- quences. To satisfy the second defense-in-depth principle. the eme ~ency systems fur nuclear pu~•er plants are designed. constructed, and tested against rigorous cri- teria that ensure adequate makeup water is supplied to the reactor pressure ~•es- se! to compensate for the reactor coolant loss in a LOCH, thus preventing fuel damage from inadequate core cooling. The conditional probability of fuel dam- age given an initiating pipe break is therefore extremely lo~~•. Yet, defense-in- depth assumes that fuel damage occurs anvw•av and requires design provisions to contain the radioactivity released from the cure. Tu satisfy the third defense-in-depth principle, the containment sv~tems f~~r nuclear power plants ire des:~ned. constructed, <ind tested to ensure that radioactive material resulhn~ from a pustulated reactor care damage e~ ent is nut released to the em•trunment. The cund:nunal probability of sa~n:ficant radiuac- tn•ity release :yen In .ucuient :nyulytn~ reactor care damage :s therefore extremely lu~.•. i5~