Modelling for safe nuclear operation in the USA
The United States of America is the world’s largest producer of nuclear power, accounting for more than 30% of worldwide nuclear generation of electricity. In 2018, the country’s nuclear reactors produced 807 billion kWh or about 20% of total electrical output. There are three reactors under construction that are expected to come online in 2020. To help with construction and operating licences for the three new builds, a joint RSK–Radiation Safety & Control Services, Inc. team travelled to Texas and Maryland.
RSK specialists wrote sections of the final safety analysis reports and environmental reports relating to groundwater issues for the Calvert Cliffs Unit 3, South Texas Project Unit 3 and South Texas Project Unit 4 sites. Additionally, we responded to queries from the US Nuclear Regulatory Commission. Our report writing included a description of the regional, local and site-specific geological progression; the geological units and their hydrogeologic properties; and the regional and local current and projected use of groundwater and potential impacts such as lowered water levels, land subsidence and intrusion of brackish water owing to new withdrawals during operation of the new units.
A site-specific conceptual model defined the hydrogeologic parameters that would control the transport of liquid radionuclides if an accidental release to the environment were to occur. The concentrations of specific radionuclides were estimated from an assumed accidental release that might be transported to the site boundary in groundwater and surface water, considering the effects of advection, adsorption, dispersion, dilution and radioactive decay within the contaminant flow path.
Work is ongoing; however, the detailed groundwater monitoring programmes will be implemented throughout the operating period of the plants to evaluate changes in groundwater levels and flow paths. This will indicate changes in groundwater radiochemical quality that may indicate an undetected spill or leak of radionuclides and allow the design of an effective plan for managing any unintended release into the environment.