RELAP5/MOD.2 Post Test Analysis and Accuracy Quantification of Lobi Test BL-34

The present document deals with the Relap5/Mod3.2 analysis of the small break LOCA experiment BL-34 performed in LOBI/MOD2 facility. LOBI/MOD2 was a PWR simulator (Integral Test Facility) installed at JRC (Joint Research Center) in Ispra Establishment (1). Volume scaling and core power scaling factors are 1/712, with respect to the KWU Siemens 1300 MWe (3900 MWt) standard reactor. The experiment is originated by a small break in the cold leg (2" equivalent break area in the plant) without the actuation of the high pressure injection system. Low pressure injection system actuation occurs after core dry-out and accumulators intervention is foreseen when primary pressure falls below 4 MPa. The Relap5 code has been extensively used at University of Pisa; the nodalization of LOBI facility has been qualified through the application of the version Relap5/Mod2 to the same experiment and another test performed in the same facility. Sensitivity analyses have been addressed to the influence of several parameters (like discharge break coefficient, time of accumulators start etc.) upon the predicted transient evolution. Qualitative and quantitative code calculation accuracy evaluation has been performed