NEA Benchmark Study of the Accident at the Fukushima Daiichi Nuclear Power Station (BSAF) Project

The Benchmark Study of the Accident at the Fukushima Daiichi Nuclear Power Station (BSAF) Project was established in 2012. The objective of the project is to improve severe accident (SA) codes and to analyse the accident progression and current status of units 1 to 3 of the Fukushima Daiichi nuclear power plant (NPP), providing useful information for the decommissioning of these units.

It is hosted by the operating agent, the Institute of Applied Energy (IAE), in collaboration with other Japanese institutions such as, the Japan Atomic Energy Agency (JAEA), the Nuclear Regulatory Authority (NRA) and the Central Research Institute of Electric Power Industry (CRIEPI). It is additionally supported by the Tokyo Electric Power Company (TEPCO), the Nuclear Damage Compensation and Decommissioning Facilitation Corporation (NDF) and other Japanese industry partners. The project brings together international experts to advance the understanding of severe accident phenomena specific to the Fukushima Daiichi NPP accident while also improving the methods and codes for modelling such severe accidents.

A phased approach is applied in the NEA benchmark exercise. The first phase of the BSAF project closed in 2015, and focused on the thermal-hydraulics in reactor pressure vessels (RPVs) and primary containment vessels (PCVs) for the first six days of the accident. The summary report is available here.

The NEA started the second phase of the project, which expands the work scope to include fission product behaviour outside PCVs, lengthening the time span for analyses of accident events to about three weeks after the occurrence of the earthquake. During phase 2, several workshops will be held to allow project participants to discuss their calculation results with other experts and to compare them with other information, such as measured data and investigation results from the Fukushima Daiichi nuclear power plant, for better understanding of the current status of the plant and the progression of the accident.


The second phase runs for 3 years and includes research institutes and governmental organisations from the following 11 countries:

Canada, People's Republic of China, Finland, France, Germany, Japan, Korea, Russian Federation, Spain, Switzerland and United States.

Project period

April 2015 to March 2018


EUR 270 000

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Last updated: 19 December 2017