Possible accident scenarios related to the Spent Fuel Pool operating events

Abstract

After the accident in Fukushima Daiichi NPP, the Nuclear Energy Agency Committee on the Safety of Nuclear Installations (OECD/NEA CSNI) initiated activities to address some technical issues. As a one of results, the Status report on Spent Fuel Pools (SFPs) under Loss of Cooling Accident Conditions was created. To give a valuable contribution to the post-Fukushima accident decision making process, brief summaries were produced on:

 - The status of SFP accident and mitigation strategies;

 - Assessment of current experimental and analytical knowledge about loss of cooling accidents in SFPs and their associated mitigation strategies;

- The strengths and weaknesses of analytical methods used in codes to predict SFP accident evolution and assess the efficiency of different cooling mechanisms for mitigation of such accidents;

- Identification of additional research activities required to address gaps in the understanding of relevant phenomenological processes, where analytical tool deficiencies exist, and to reduce the uncertainties in this understanding.

The final report was approved by OECD/NEA CSNI in December 2014 with the reference NEA/CSNI/R(2015)2 and it is available for download on the OECD website http://www.oecdnea. org/nsd/docs/2015/csni-r2015-2.pdf. Joint Research Centre of European Commission took the leading role in creation of the chapter about possible accident scenarios, past accidents and precursor events. Evaluations of past events where SFP cooling has been lost show that malfunctions of the SFP cooling system are in most cases caused by inoperable cooling pumps. The other important causes are inadvertent diversion of coolant flow and Loss of ultimate heat sink. This paper is providing short general report overview and more details about JRC contribution.