Equipment Qualification Program Under Accident Conditions for KAPP-3&4 Indian Pressurized Heavy Water Reactors

India’s indigenous nuclear power program is primarily based on the Pressurized Heavy Water Reactors (PHWR). Each of KAPP-3&4 units are of 700 MWe Indigenous PHWRs. Environmental qualification requirements of Equipment and components of a conventional plant and a Nuclear Power Plant (NPP) are different. Even after the Nuclear Reactor is shutdown during normal condition or in accident condition, decay heat is to be continuously removed to maintain the fuel integrity. Hence many safety system and safety related equipment have to operate reliably even after shut down of the reactor during normal condition or in accident condition. To meet the objective of safety functions, safety systems and safety related systems qualify to tolerate service conditions for a specified mission. Environmental parameters such as temperature, pressure, radiation, humidity undergo significant change as a result of bounding DBA. All equipment exposed to these kinds of degraded environment service condition and which is credited with performing a safety function, or which by its failure can impede the execution of safety function, falls within the scope of the Equipment Qualification program. Environmental condition based of bounding design basis accidents is evaluated using different thermal hydraulic computer codes. A parametric study has been performed with location and break sizes and most bounding pressure and condition are generated. Computer Code ‘ATMIKA’ is used calculate mass and energy discharge from break postulated in Primary Heat Transport System or Secondary System, Computer Code “PACSR’ is used to calculate the temperature and pressure inside containment and Computer Code ‘STAR’ and ‘ACTREL’ are used to calculate radiation conditions resulting from these breaks inside reactor building. Equipments are qualified for bounding accident scenario at design stage, for which they are required to perform their intended safety function and margin for qualification as per IEEE-323 standard. The Equipment qualification process confirms that the equipment is capable of meeting, throughout its operational life, the requirements for performing safety functions when subjected to the stipulated environmental conditions.