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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.
Kevin T. Clarno, Yassin A. Hassan
Nuclear Technology | Volume 141 | Number 2 | February 2003 | Pages 142-156
Technical Paper | Thermal Hydraulics | doi.org/10.13182/NT03-A3356
Articles are hosted by Taylor and Francis Online.
In order to analyze the benefits of the multidimensional hydrodynamic modeling capability of the RELAP5-3D system code for the VVER-1000 nuclear power plant (NPP), a three-dimensional (3-D) model of the core, downcomer, and lower plenum has been created to replace the NPP one-dimensional (1-D) counterparts in a complete plant model. This multidimensional model has been validated with plant operational data and other computer simulations of a thermal-hydraulic transient. The simulated transient considered was a large-break loss-of-coolant accident (LB LOCA).A validated, 1-D control model of the NPP, for the study of the effects of mixed oxide fuel, was modified to include a standard fuel loading of UO2. The development of the 3-D sections of the reactor vessel consisted of ensuring geometrical fidelity with the design of the modeled plant, the Balakovo Unit 4 NPP in Saratov, Russia. A stable operational steady state was obtained and the calculated plant conditions compared well with the design values of the Balakovo plant. Transient results verified that the simulated thermal-hydraulic conditions of the multidimensional model agreed well with both the control and analyses that have been performed separately from this study.It was found that the multidimensional model has shown a reduction in the calculated hot-spot peak-clad temperature (PCT) during the blowdown stage of a LB LOCA and an increase in PCT during the reflood stage. A preliminary uncertainty analysis of the PCT during blowdown stage was performed using a response surface method of the Code Scaling, Applicability, and Uncertainty Method and a significant number of relevant input variables. From the preliminary analysis, the PCT reduction during blowdown appears to be significant, but a further, more detailed analysis should be performed, along with an uncertainty analysis of the PCT during the reflood stage.The enhanced depiction of the flow patterns and temperature distributions in the transient situation allowed the user further understanding of the thermal-hydraulic conditions throughout the transient. The developed model proved to be suitable for analysis of the VVER-1000 plant, but to further the applicability of the model, a 3-D kinetics model of the neutronics and 3-D hydrodynamic models of the horizontal steam generators should be included.
