Preliminary validation of the coupling between a primary system and a containment code

The present report describes the preliminary assessment of the coupling methodology adopted to link a nuclear reactor thermal-hydraulic primary system code to a containment system code, set up in the frame of task LP2- E.1 of the AdP PAR2008-09 assigned to CIRTEN. The coupled codes are the RELAP5 Mod3.3 patch 3 and the Gothic version 7.2b(QA). The RELAP5 code was provided to the University of Pisa by ISPRA together with the FORTRAN source program, while the executable version of the Gothic code and limited rights to use it for the purposes of the present work were acquired from Numerical Applications, Inc. (NAI). A companion report describes the choices made in the coupling of the two codes. Different test cases were defined and run in order to check the capabilities of the coupled codes. The considered cases are simple enough to grant the possibility to clearly ascertain if the flow of information between the two codes is correct enough, in the limits of the scope of the present work. The simplest cases involve the injection or extraction of water and/or noncondensable gases into or from Gothic volumes by two different junctions; a sample pressurised water blowdown case from a vessel is also considered, with and without gravity driven injection of water to the vessel. The analysed calculation cases provide adequate confidence in the adequacy of the performed coupling work, though future improvement of the coupling strategies can be envisaged on the basis of what already discussed in the companion report.