Possible accident scenarios related to the Spent Fuel Pool operating events

Following the 2011 accident at the Fukushima Daiichi NPP, the Nuclear Energy Agency Committee on the Safety of Nuclear Installations (NEA CSNI) decided to prepare the "Status Report on Spent Fuel Pools under Loss-of-Cooling Accident Conditions". The report presents a brief assessment of prevention and mitigation strategies, and current experimental and analytical knowledge of SFP accident. It reveals 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. It also identifies 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 report is intended to provide decision makers with a better understanding of causes of described events which could be the basis for implementation of improvements to minimize risk of fuel damage. Understanding accident progression and circumstances can also help in definition of mitigation strategy. The Joint Research Centre (JRC) of European Commission played a leading role in creation of the chapter about possible accident scenarios, past accidents and precursor events. This paper is providing short general overview of report with more details about JRC contribution for a wider dissemination of the report. The main objective of this paper is to describe the most dominant failure mechanisms and some specific scenarios which could lead to fuel damage in SFP. 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.

STRUCIC Miodrag; 

2016-07-06

Croatian Nuclear Society

JRC102251