Leak-rate tests for the N S Savannah were initially conducted at pressures lower than those encountered in a maximum credible accident, requiring extrapolation to predict the release of radioactivity. Improved test procedures have reduced extrapolation errors by making it possible to increase the test pressure to 60 lb/in.2 Leak rates determined by both absolute and reference methods show close agreement. The most extensive Savannah containment tests are described. These tests showed that the most significant leakage was through the containment electrical penetrations. Replacement of the original penetration fittings with an improved design using hermetically sealed conductors is eliminating this leakage. Significant leaks were also detected at the seats of valves forming a single containment barrier. Installation of double valves and valves using seats with teflon inserts is eliminating this leakage.