Coupling of ASTEC V2.1 and RASCAL 4.3 Codes to Evaluate the Source Term and the Radiological Consequences of a Loss-of-Cooling Accident at a Spent Fuel Pool

Abstract

This paper deals with a general methodology to evaluate the Source Term (ST) and the Radiological Consequences (RC) of a hypothetical Severe Accident (SA) at a Fukushima-like Spent Fuel Pool (SFP) by coupling ASTEC 2.1 and RASCAL 4.3 SA and consequence projections (CP) codes, respectively. The methodology consists of the following sequential steps: the ST provided by a prior simulation performed by ASTEC V2.1 code was used as input to RASCAL 4.3 code to make a RC analysis. This approach was developed as a preparatory study for the Management and Uncertainties in Severe Accident (MUSA) H2020 European Project, coordinated by CIEMAT, where the ENEA's Nuclear Installations safety laboratory is committed to performing an analysis on a Fukushima-like SFP with the aim to apply innovative management of SFP accidents (WP6) to mitigate the RC of the accident itself. To perform the RC studies that could have an impact on Italy, a Fukushima-like SFP was assumed located in one of the Italian cross-border NPP sites. The weather data adopted are both standard and real hourly meteorological data taken from more than one geographical location. The results of the RC for 96 h of ST release in a range of 160 km from the emission point are reported in terms of Total Effective Dose Equivalent (TEDE), Thyroid dose, and Cs-137 total ground deposition. The mitigating effect on ST and on RC of the cooling spray system (CSS) actuated with several pH values (i.e., 4,7,10) was also investigated.