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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.
Rafael Macian, Paul Coddington, Paul Stangroom
Nuclear Technology | Volume 142 | Number 1 | April 2003 | Pages 47-63
Technical Paper | RETRAN | doi.org/10.13182/NT03-A3373
Articles are hosted by Taylor and Francis Online.
Subcooled and saturated nucleate boiling are important physical processes in boiling water reactors (BWRs) under operating and transient conditions and in pressurized water reactors (PWRs) under transient conditions. Good predictions of such processes by system codes such as RETRAN-3D are, therefore, important from a safety and operational point of view.For this reason, and continuing the validation efforts carried out in the STARS Project at Paul Scherrer Institute, data from experiments in a uniformly heated tube carried out by Bartolomey et al. have been used to assess the subcooled and saturated nucleate boiling models in RETRAN-3D. These experiments were performed at high (~15-MPa) and medium (~7-, 4-, and 3-MPa) pressures. The heat flux (2210 to 420 kW/m2) and mass flux (2123 to 405 kg/s m2) were selected to cover a range of values spanning operating and transient situations in both BWRs and PWRs.This paper reports on the results obtained with both the four- and five-equation RETRAN-3D flow models. The results show that both models used in RETRAN-3D provide good estimates of subcooled and saturated nucleate boiling in heated tubes. The four-equation model, which makes use of the Electric Power Research Institute void fraction profile fitting model for the reactivity feedback only, shows the best performance for high mass fluxes, whereas the five-equation model, which directly computes the vaporization rate, performs better at low mass fluxes and relatively high heat fluxes.In addition to the results from RETRAN-3D, results obtained with the system code RELAP-5 are included in the plots and used to support the conclusions and to perform a comparative analysis of the methods used by the codes.
