RELAP5 analysis of PKL, main steam line break test

The calculation results have been compared to the experimental results. It was concluded that the most important events during the test are reproduced relatively well by the model. The calculated coolant temperature in the core is higher than in the experiment. The minimum temperature is about 5% higher than measured. The secondary pressures in SG-1, 3, and 4 is in very good agreement with the experimental value, but in the SG-2, the depressurization is calculated to be slower than in the experiment. The different SG-2 behavior is caused by slightly different initial conditions. This fact indicates that RELAP5 results may, in some cases, be extremely sensitive to the initial conditions and this should be investigated in the future. With respect to the initial objective of the present analysis, it is concluded that the RELAP5 code is validated against the PKL test G3.1 with the developed model and within acceptable margins.