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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.
Yasuo Koizumi, Hiroshige Kumamaru, Yuichi Mimura+, Yutaka Kukita, Kanji Tasaka†
Nuclear Technology | Volume 96 | Number 3 | December 1991 | Pages 290-301
Technical Paper | Nuclear Reactor Safety | doi.org/10.13182/NT91-A34590
Articles are hosted by Taylor and Francis Online.
Cold-leg small-break loss-of-coolant accident experiments were conducted for break areas ranging from 0.5 to 10% of the scaled cold-leg flow area using the Large-Scale Test Facility (LSTF). The LSTF is a volumetrically scaled simulator of a Westinghouse-type pressurized water reactor. For all the experiments, the core collapsed liquid level was temporarily depressed when liquid in the primary loop U-bend (crossover leg) was being cleared by steam. For scaled break areas <2.5%, the minimum core liquid level was equal to the lowest elevation of the crossover leg. For break areas >5%, the minimum core level was even lower because differential pressures created by the residual liquid holdup in the steam generator (SG) upflow side affected the core liquid level adversely. This influence of SG liquid holdup on the minimum core liquid level was larger for larger break sizes within the range of these experiments; thus, a more severe core level depression was seen for larger break sizes. Also, for the same break size, the core level depression was more severe when higher core power values were used for the simulation of the postscram core power decay. The RELAP5/MOD2 code reasonably well predicted the major phenomena observed in the experiments; however, several shortcomings were found in interfacial drag calculation for the SG U-tube inlet and the hot-leg outlet to the SG inlet plenum and core.