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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.
Wilfried Pfingsten
Nuclear Technology | Volume 140 | Number 1 | October 2002 | Pages 63-82
Technical Paper | Radioactive Waste Management and Disposal | doi.org/10.13182/NT02-A3324
Articles are hosted by Taylor and Francis Online.
In the vicinity of a cementitious nuclear waste repository, mineral reactions will change the hydraulic conditions and the parameters describing radionuclide transport with time during the cement degradation phase. Porosity changes due to mineral and cement reactions will influence permeability and diffusivity. Formation water rich in CO2 will lead to calcite precipitation in the water-conducting zones surrounding the cementitious waste repository. This will have an impact on the radionuclide release from the cementitious repository into the host rock environment. The sequentially coupled flow, transport, and chemical reaction code MCOTAC is used to include such processes in the modeling. A porosity-permeability relation and a porosity-diffusivity relation are used for describing cement degradation and related secondary mineral precipitation and their coupling to reactive transport modeling. Two-dimensional model calculations are used to predict the temporal evolution of transport parameters for radionuclides within a "small-scale" near field of a cementitious waste repository. Reduced solute transport is calculated in the repository near field due to porosity and permeability changes at the rock-repository interface. Within the small-scale porous medium approach, coupling of chemical reactions and hydrodynamic parameters indicates a self-sealing barrier at the host rock-repository interface for several scenarios. This barrier might persist for very long times and effectively contain radionuclides within the engineered repository system. Taking into account flow path and barrier-specific heterogeneity will be a further step to improve the understanding of coupled processes in the vicinity of a real cementitious near field.
