Thermal mixing tests in a semiannular downcomer with interacting flows from cold legs: International Agreement Report

Abstract

This report describes the test facility and test program for studying thermal mixing of high-pressure injection (HPI) water in the two-fifths scale model of three cold legs, semiannular downcomer and lower plenum of a pressurized water reactor. This test series has been carried out by mutual agreement on the pressurized thermal shock (PTS) information exchange between the US Nuclear Regulation Commission and Imatran Voima Oy. The test facility was originally designed to model the Finnish Loviisa plant but it was redesigned and modified for this test program. The facility can be operated at atmospheric pressure with loop and HPI flows from different cold legs in the area of interest to PTS. Transparent materials were used to allow flow visualization during the tests. The choice of transparent materials limit the upper temperature to 75/sup 0/C. The full buoyancy effect was induced by salt addition and the HPI temperature was used as a tracer. The test matrix consists of 20 tests. The varied parameters were flow rates and the number and configuration of cold legs with HPI and loop flows. Four tests were done with decreasing loop flow temperature to simulate primary flows during steam line breaks.