Probabilistic Risk Assessments (PRA), which are conducted with the aim of assessing the safety of nuclear power plants in a systematic and rational manner, are categorized into three levels: level 1 PRA for assessing the plant core damage frequency (CDF) using reliability analysis techniques; level 2 PRA for determining the amount and frequency of radioactive substances released into the atmosphere due to the containment vessel failure following core damage; and level 3 PRA for assessing the extent of impact on public individuals and populations caused by the release of radioactive substances. JANUS has many experiences in Japan for conducting analysis at levels 1, 2 and 3 PRA.
JANUS also conducts surveys related to risk base management, and is involved in the sale of software packages and associated training.
Level 1 PRA
JANUS has experience in conducting level 1 PRA analysis and assessments on full plant scale in Japan, as well as reliability analysis and assessments using the fault tree model.
JANUS also has international experience surveying the development of PRA technologies, utilization of risk information for the operation and management of nuclear power plants and safety regulations through partnerships with overseas agencies. JANUS sells WinNUPRA, which is support tool for conducting level 1 PRA.
JANUS provides analysis and assessment services, as well as analysis support tools related to the operation and management of facilities in Japan, such as nuclear power plants that utilize risk information.
JANUS applies Reliability Centered Maintenance (RCM) assessment methods to certain parts of nuclear power plants in Japan, and has experience with assessing the effectiveness of such methods. General-purpose software used for analyzing RCM on PCs has been jointly developed with chemical companies in Japan, and JANUS sells and provides training for that RCM software. JANUS also sells Safety MonitorTM, an effective risk management tool that is developed and installed in America.
Level 2 PRA
Level 2 PRA for nuclear power plants addresses accident progression within reactor vessels and containment vessels following a severe accident, and covers the role of handing over the accident source-term to the subsequent level 3 PRA.
JANUS played a central role during the development project of Japan Atomic Energy Research Institute’s (current Japan Atomic Energy Agency) THALES core meltdown accident analysis code system, and also has a wealth of knowledge and experience with severe accident impact analysis using codes other than THALES.
Level 3 PRA
In addition to source-term information from the results of level 2 assessments, level 3 PRA requires organizing various data and setting of various parameters, including a year’s worth of weather data (wind direction, wind speed, atmospheric stability, amount of rainfall) in the area where the assessed plant is located, population data of surrounding areas, the ratio of land, agricultural parameters, model parameters for considering emergency exposure mitigative action, and health impacts of radiation exposure.
JANUS provides a full range of advanced services required for level 3 PSA using the MACCS2 code in Japan, including organizing various environmental data, conducting analysis, and organizing and reviewing results.