High sensitivity leak testing for critical nuclear components

Quality Assurance on leak tightness performance of systems and components that handle hazardous, toxic/radioactive fluids is to be ensured through a well chosen leak testing method. It is very much essential for components and systems used in such applications to be subjected to high sensitive leak testing methods capable of detection of leaks of the order of 10−11 Pa.m3/sec. due to the fact that a minutest leakage to the environment is likely to pose serious consequences. The choice of a particular leak testing method and technique depends on the degree of leak tightness required and the service requirements of the components. Mass spectrometer leak detection method is the only technique which possesses matching sensitivity requirements for the purpose of ensuring the leak tightness of this magnitude, thus well suited for testing of critical components required for Fast Reactor, Cryogenic systems, ultrahigh and high vacuum applications etc. Large number of components required for such applications have been subjected to a very stringent leak tightness requirements with a sensitivity of the order of 10−13 Pa.cu.m/sec.This paper outlines the approach, planning and execution of helium leak testing of a few critical components with varying complexities. The details of the difficulties experienced, particularly in attaining higher vacuum and suggestions to achieve highest sensitivity are also discussed.