Suitability of On-Line Leak Tests for CANDU Single-Unit Containment Buildings

Abstract

Since these tests are only done every five years, it is possible that CANDU reactor containment buildings are checked for integrity a leak could develop and go undetected until the next test. A leak every five years. An on-line test could be performed more often and test that could be performed during plant operation would allow more thereby reduce the chances of long term unavailability of the frequent tests. Frequent tests would ensure the continued reliability containment system. of the containment system. A test procedure which accounts for operational factors is proposed. A theoretical error analysis is performed to study the effect of test parameters on the accuracy and sensitivity of the test. It is found that leak rates greater than 5% per day can be detected in less than one day. Leak rates at the target 0.5% per day require tests longer than five days and the leak detection is complicated by operations factors. A test of two to three days will allow the detection of a 1% per day leak. It is also shown that a system modification which draws instrument air from inside the reactor building would allow the detection of a 0.50k per day leak rate in less than twelve hours. Annual tests performed during shutdown at a pressure of 62 kPag would detect a 0.5% per day leak rate in 5 hours.