SPES-2. AP600 integral test facility results. Confirmatory plant behaviour and RELAP5/MOD2.5 code assessment

The present paper discusses the first results of a simulation activity on the Westinghouse AP600 reactor carried-out at ENEL (The Italian Electricity Board), utilizing both the SPES-2 test facility and the RELAP5/MOD2.5 computer code. The AP600 is a medium size (600 MWe) new generation reactor developed by Westinghouse whose safety is ensured by means of dedicated passive systems performing the functions of water injection, RPV depressurization and containment heat removal. SPES-2 facility located at SIET Laboratories in Piacenza (Italy) is a full height, full pressure 1/395 volume scale simulation of the AP600 NSSS. RELAP5/MOD2.5 is a well known thermal hydraulic code developed at Idaho National Engineering Laboratories and made available by US NRC; it has been widely used and qualified all over the world. In order to qualify the analytical code, an extensive simulation work on SPES-2 experimental tests by a detailed RELAP5/MOD2.5 model of the facility has been performed. Here the comparison between experimental results of the 2'' cold leg break test and the corresponding RELAP5/MOD2.5 analysis is reported. A good agreement between experimental and analytical results has been found, achieving a good assessment of the RELAP5/MOD2.5. (author)