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The human factor in licensing and operating the next generation of nuclear plants
As human factors specialists working at the intersection of human performance and nuclear operations, we are witnessing one of the nuclear sector’s most significant transitions in decades. The emergence of small modular reactors, microreactors, and other advanced designs is reshaping the industry’s landscape. Digital instrumentation and controls, passive safety systems, and increased automation are creating opportunities for greater safety margins and more flexible operation. These same features also fundamentally redefine what it means to “operate” a nuclear plant. Interactions among human roles, automation, and passive systems shape how people maintain awareness, exercise judgment, and intervene when necessary. These developments affect both operational realities and the regulatory foundations on which nuclear safety is built.
Gerardo Martinez-Guridi, Pranab Samanta, Tsong-Lun Chu, Ji-Wu Yang
Nuclear Technology | Volume 131 | Number 3 | September 2000 | Pages 297-318
Technical Paper | Reactor Safety | doi.org/10.13182/NT00-A3118
Articles are hosted by Taylor and Francis Online.
Following a loss-of-coolant accident (LOCA) in a nuclear power plant (NPP), the loss of electric-power generation, as might be precipitated by the unit tripping, may cause switchyard- and grid-instability with a subsequent loss-of-off-site power (LOOP). The LOOP usually is delayed by a few seconds or longer. This accident is called a LOCA with consequential LOOP, or a LOCA with delayed LOOP (abbreviated as LOCA/LOOP). NPPs are designed to cope with simultaneous LOCA and LOOP. The U.S. Nuclear Regulatory Commission (NRC) identified this issue as generic safety issue (GSI) 171, "Engineered Safety Feature Failure from a Loss-Of-Off-Site Power Subsequent to a Loss-of-Coolant Accident." NRC subsequently dropped GSI-171 and considers it resolved. We present the probabilistic risk analysis of the LOCA/LOOP scenario that was conducted as part of NRC's resolution of GSI-171. We analyze and quantify the core damage frequency (CDF) associated with this accident. Event/fault trees are developed covering the progression of the accident to core damage. We used engineering evaluations and judgments to estimate probabilities for the conditions identified in a LOCA/LOOP scenario and to obtain a bounding evaluation of the CDF. We show that the contribution of such an accident to CDF depends on electrical-load sequencing and shedding capabilities; plants with adequate capabilities incur a minimal additional contribution to risk. No single plant design is known to be vulnerable to all the conditions; only some of the conditions may apply to some plants.