Risk assessment and numerical analysis of short-term accident scenarios in a nuclear fuel storage vault

Abstract

Analysis of various accident scenarios is vital for the safety assessment of nuclear fuel storage facilities. The accidents in the storage vault due to loss of cooling are generally considered highly uncertain since the accident progression is slow (in comparison to reactors) and allows time for remedial activities to the operator. In the present work, numerical simulations of different accident scenarios have been carried out for a short duration to understand the situation better. Thermal aspects of accident conditions such as failure of the suction blower, drying of cooling water at the chiller, and combined effect of both accidents were investigated. The airflow inside the ventilated enclosures due to the failure of the blower and the rise in inlet air temperature is analyzed numerically. The temperature distributions inside the vault and the rise in temperature of the sub-assemblies and magazines have been studied. The key mechanisms of heat transfer, which take part in nuclear fuel storage vault for post-accident conditions, were identified. The study will be helpful to classify various accident conditions based on their thermal implications and the model developed can be used to design passive cooling systems.

Keywords:

• Blackout
• computational fluid dynamics (CFD)
• decay heat
• natural convection
• nuclear fuel storage
• temperature distribution

Acknowledgement

One of the authors gratefully acknowledges the Department of Atomic Energy (DAE) for DGFS fellowship. The authors are thankful and sincerely acknowledge the support and motivation received from Dr. B. Venkatraman (Director), Indira Gandhi Centre for Atomic Research, Kalpakkam, Tamil Nadu, India.