Two Boiling Water Reactors (BWR) of 210 MWe each at Tarapur Atomic Power Station, Units-1&2 (TAPS-1&2) were commissioned in the year 1969. The safety related civil structures at TAPS had been designed for a seismic coefficient of 0.2g and other structures for 0.1g. The work of seismic re-evaluation of the TAPS-1&2 has been taken up in the year 2002. As two new Pressurized Heavy Water Reactor (PHWR) plants of 540 MWe each, Tarapur Atomic Power Project Units-3&4 (TAPP-3&4), are coming up in the vicinity of TAPS-1&2, detailed geological and seismological studies of the area around TAPS-1&2 are available. The same free-field ground motion as generated for TAPP-3&4 has been used for TAPS-1&2. The seismic re-evaluation of the plant has been performed as per the procedure given in IAEA, Safety Reports Series entitled “Seismic Evaluation of Existing Nuclear Power Plants”, and meeting the various codes & standards, viz., ASME, ASCE, IEEE standards etc. The Safety Systems (SS) and Safety Support Systems (SSS) are qualified by adopting detailed analysis and testing methods. The equipment in the SS and SSS have been qualified by conducting a walkdown as per the procedure given in Generic Implementation Procedure, Dept. of Energy (GIP–DOE), USA. The safety systems include the systems required for safe shutdown of the plant, one chain of decay heat removal and containment of activity. The safety support systems viz., Electrical, Instrumentation & Control and systems other than SS & SSS have been qualified by limited analysis, testing and mostly by following the procedure of walkdown. The paper brings out the details of the work accomplished during seismic re-evaluation of the two units of BWR at Tarapur.

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