The choice of a particular leak testing method and technique depends on the degree of leak tightness and service requirement of the components. Helium leak testing under vacuum provides the utmost sensitivity and is best suited for testing of critical components like, Control Rod Drive Mechanism (CRDM) components, uranium fuel sub-assemblies and delicate bellows, to a sensitivity 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 and discusses the results.