![]() Because of the fundamental change in design philosophy, moisture injection tests were carried out during commissioning to demonstrate that performance matched design. Unit 4 was the first one to be converted during the full scale pressure tube replacement programme. Experience with Unit 3 has shown that dew point monitoring of pressure tube leaks was particularly subject to gas leaks and surface adsorption effects. It is concluded that these tests do not represent AGS conditions that are to be expected in the event of a real pressure tube leak.ĭetection of pressure tube leaks relying on moisture beetles onlyĪ major decision was made for Pickering NGS A Annulus Gas System (ACS) that detection of a pressure tube (PT) leak should be achieved by using only moisture beetles and that dew point monitors would provide 'early warning' without status to shut down the reactor. In this paper the historical development and current status of this leak detection capability is reviewed and the use of moisture injection tests as a verification procedure is critiqued. ![]() In all currently operating CANDU reactors, worldwide, this LBB requirement is met via continuous dew point measurements of the CO gas circulating in the reactor's Annulus Gas System (AGS). In the event of a pressure tube leak from a small through-wall crack during CANDU reactor operations, there is a regulatory requirement - referred to as Leak Before Break (LBB) - for the licensee to demonstrate that there will be sufficient time for the leak to be detected and the reactor shut down before the crack grows to the critical size for fast-uncontrolled rupture. It is concluded that these tests do not represent AGS conditions that are to be expected in the event of a real pressure tube leak.Įnergy Technology Data Exchange (ETDEWEB) ![]() In all currently operating CANDU reactors, worldwide, this LBB requirement is met via continuous dew point measurements of the CO_2 gas circulating in the reactor's Annulus Gas System (AGS). International Nuclear Information System (INIS) CANDU pressure tube leak detection by annulus gas dew point measurement. ![]()
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