Pretest Calculations of Phase A of ISP-42 (PANDA) Using the GOTHIC Containment Code and Comparison with the Experimental Results

The pretest calculations of phase A of the International Standard Problem 42 (ISP-42) using the GOTHIC containment code are presented in this paper, together with the comparison with the experimental results.

The focus of the analyses presented is on the mixing process in the drywells (DWs), initially filled with air, during the initial steam purging transient. Consequently, a large effort has been made to capture the flow pattern produced by the jet created by the steam injection, including in the model a large number of nodes for the three-dimensional (3-D) representation of the two vessels. The influence of the nodalization of the DWs on the calculation was investigated by means of two additional models using one volume for each of the DWs and a 3-D calculation using a much coarser mesh, respectively.

Since the fluid in the DWs was well mixed and stratification occurred only below the injection level, all the models could predict very accurately the global variables such as pressure and temperature. The 3-D simulation also reproduced the wall and gas temperature distributions fairly well. The only (inferred) discrepancy with the test was the overprediction in the upward deflection of the buoyant steam jet.