Simulation of the loss of the residual heat removal of an integral test facility using computer code Cathare7

Due to the character of the original source materials and the nature of batch digitization, quality control issues may be present in this document. Please report any quality issues you encounter to digital@library.tamu.edu, referencing the URI of the item.Includes bibliographical references: 51-52.Issued also on microfiche from Lange Micrographics.Assessment of the ability of thermal hydraulic codes to correctly predict complex phenomena during reactor transients can be performed only by means of comparison against experimental data. The thermal hydraulic CATHARE V1.3U computer program has been used to simulate International Standard Problem (ISP38) experiment conducted at BETHSY Integral Test Facility located in Grenoble, France. BETHSY is an integral test facility modeling the three-loop, 2775 thermal NM Framatome Pressurized Water Reactor (PWR). Its main objectives are to contribute to the assessment of CATHARE code and of the physical basis of PWR Emergency Operating Procedures. This investigation dealt with experimental simulation of the loss of the Residual Heat Removal System (RHRS) during midloop operation. It involved opening of the pressurizer manway and the steam generator outlet plenum manway simultaneously with switching on the power of heating rods, thus simulating loss of the RHRS. The total power was kept unchanged with the level 138 kW throughout the test. Mass discharge through both manways led to core boiling and uncovery. A gravity feed injection of cold water was actuated in the cold leg when cladding temperature at the top of heating rods reached 250 C. The test was stopped when the primary cooling system was filled back to rnidloop level. The transient was executed on the HP6400 workstation at Texas A&M University. The code predictions underestimated the time of the core uncovery and the actuation of the gravity feed injection due to the ovepredicted mass discharge through steain generator manway during the initial stage of the transient. This was probably caused by CATHARE's miscalculation of the phase separation effect at the hot leg/surge line tee junction and significant water entrainment into the surge line in the beginning of the test. It was found that the model of the upward tee junction needs to be refined for the low pressure range. Overall, the code's predictions were in a qualitative agreement with the experimental data