Our service includes an evaluation of resiliency against natural hazards. Examples of our experience include risk assessment of the accident at the Fukushima Daiichi nuclear power plants and resiliency against tornado missiles.
Seismic Probabilistic Risk Assessment: At the Fukushima Daiichi nuclear power plants, following the 2011 Great Tohoku Earthquake and subsequent tsunami, the Nuclear Regulatory Commission (NRC) established a Near Term Task Force (NTTF). Acting on the recommendations issued by the NTTF, NRC requested the licensees and holders of construction permit under 10 CFR 50, 52, 72 (Code of Federal Regulations, Title 10, Part 50, 52, 72), to reevaluate the seismic hazard and tornado-generated missile protection at their sites against present-day NRC requirements.
The plants were required to perform new seismic probabilistic risk assessments (SPRA) to demonstrate an acceptable level of risk. To support this new SPRA, we helped utilities in the United States by using advanced technologies for reducing excessive unwanted conservatism. For example, we accounted for building-equipment-piping interactions by conducting a coupled dynamic analysis of the Reactor Pressure Vessel (RPV) and its support (nozzle supports and Neutron Shield Tank), together with the primary coolant loop piping, Steam Generator (SG) and its support, Reactor Coolant Pump (RCP) and its support, and Pressurizer and its support including the surge line. Such interactions lead to seismic demands that can be an order of magnitude lower than that evaluated by conventional methodologies.