A. I.1. INTRODUCTION

This section covers plant life management in general at Indian PHWRs. Plant life management of PHWRs in India generally follows the practices identical to CANDU reactors as given in Chapter 3. Nuclear Power Corporation of India Ltd (NPCIL) conducts PLiM exercise at its plants as per requirements specified in NPCIL HQI-7005 and Atomic Energy Regulatory Board safety guide SG-O-14. These guidelines cover the requirements that are essentially based on the information available from national and international experiences, IAEA (For example IAEA Technical Reports Series No.338, IAEA-TECDOC-1188, IAEA-TECDOC-1037, IAEA — TECDOC-540). Within the operating license, the Indian Regulatory Body — Atomic Energy Regulatory Board (AERB) grants initial authorization for a specified period which may range from five to nine years and renewal of authorization for further specified periods after assessment of safety.

For renewal of authorization, comprehensive safety review of plants is required considering the cumulative effects of plant ageing and irradiation damage, results of in-service inspection, system modifications, operational feedback & status of performance of safety system etc. AERB Safety Guide on Renewal of Authorization for operation of Nuclear Power Plants SG-O — 12 covers the requirements.

This process of safety review for renewal of authorization is carried out several times periodically during the design life of the NPPs. This comprehensive safety review is termed as periodic safety review (PSR). For this purpose, standard categorization of systems, structures and components SSCs into following four categories has been made. The health of all the systems is reported as part of PSR based on the ageing management applicable to each SSC.

Major critical SSCs Limiting plant life. Critical SSCs Important SSCs Other SSCs

A. I.1.1. SCREENING OF SSCs

A. I.1.1.1. Category 1 — Major critical SSCs limiting plant life

The major critical components are those of which integrity & functional capabilities have to be ensured during plant operation & shutdown conditions. These have the highest safety significance. These components are non replaceable and control the plant life. For Examples: Calandria, Endshield components, Calandria tubes, Incore components for reactivity mechanisms, Moderator system piping (inside Calandria Vault).

A. I.1.1.2. Category 2 — Critical SSCs

These components are required for plant operation & shutdown condition. They have high
safety significance as major critical components. Usually they are difficult to replace due to

radiation exposure, long shut down period and high cost. Examples: PHT system piping and equipments, pressure tubes, steam generators, primary coolant pumps, PHT feeders, ECCS system piping and equipments, Shut down cooling, moderator cooling heat exchanges and pumps.