Some aspects of permissible leak rate specification for TAPS primary containment system

The Tarapur Atomic Power Station was designed by the General Electric (GE) Company, U.S.A. The GE considered four specific Design Basis Accidents (DBAs) to demonstrate that the design of the primary containment system is capable to keep the leaks within specifications laid down for leak rate. The DBAs considered were: (1) control rod drop accident with reactor vessel head closed, (2) refuelling accident with reactor vessel head open, (3) primary steam line rupture accident outside reactor building and (4) Loss of Coolant Accident (LOCA) in the dry well. The assumptions made in the analyses of the above DBAs are critically examined. Estimate of fission products release, particularly of iodine, by GE is examined in detail and lacunas in the estimate are pointed out. Acceptable release in emergency values of iodine and permissible leak rate from primary containment for release as evaluated by GE are given. Areas in which detailed analyses will be useful in estimating acceptable leak rate specifications are indicated. (M.G.B.)