Simulation of the SPE-4 small-break loss-of-coolant accident using RELAP5/MOD 3.1

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.A small-break loss-of-coolant accident experiment conducted at the PMK-2 integral test facility in Hungary is analyzed using the RELAP5/MOD3.1 thermal-hydrauhc code. The experiment simulated a 7.4% break in the cold leg of a VVER-440/213-type nuclear power plant as part of the International Atomic Energy Agency's Fourth Standard Problem Exercise (SPE-4). One distinguishing characteristic of this type of power plant 'LS the horizontal steam generator. Nineteen countries participated in the exercise, with Texas A&M representing the U. S. Blind calculations of the exercise are presented, and the timing of various events throughout the transient is discussed. A post-test analysis is performed in which the sensitivity of the calculated results is investigated. RELAP5 predicts most of the transient events well, although the predicted time of occurrence of several events during the accident scenario is adversely affected by an underprediction of system pressure. A few problems are noted, particularly the failure of RELAP5 to predict dryout in the core even though collapsed liquid level fell below the top of the heated portion. A discrepancy between the predicted primary mass inventory distribution and the experimental data is identified. Finally, the primary and secondary pressures calculated by RELAP5 fell too rapidly during the latter part of the transient, resulting in rather large errors in the predicted timing of some pressure-actuated events