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AERB detects flaws at nuclear plants

Sanjay Jog  |  Mumbai 

Regulatory inspections of nuclear power plants and research facilities have revealed there have been deviation from technical specifications and other regulatory stipulations, deficiencies and degradations in safety-related systems and procedural inadequacies.

The Atomic Energy Regulatory Board (AERB), which carried out 47 regulatory inspections, comprising 25 scheduled and 22 special inspections in 2011-12, observed there were shortcomings in safety design and safety support systems based on operating experience, including generic deficiencies.

The board has made a strong case for improvement in procedures and design by the respective nuclear power plants. It observed at Narora Atomic Power Station 1 & 2, continuous monitoring of healthiness and availability of seismic trips circuits did not exist. The unavailability of this trip due to loss of power supply or discontinuity in the wiring remain unnoticed till the next surveillance test. The scheme in this regard was under AERB's review with the designers of Nuclear Power Corporation.

Further, the air handling unit of main control room at the Madras Atomic Power Station (MAPS) was missing. This is provided generally in the standardised pressurised heavy water reactor design. MAPS was asked to implement the design and auto closure of the main and emergency airlock doors. Some of the area radiation monitors of Rajasthan Atomic Power Stations (RAPS) 3 & 4 were given power supply from class IV in place of class II. RAPS was asked to restore power supply to these monitors according to the original design. NPC-run Tarapur 3 & 4 Kaiga 3 & 4, Rajasthan 3 & 4, Kakrapar 1 & 2 and Rajasthan 2 were asked to expedite issue of approved in service inspection manual.

AERB observed the revision of emergency preparedness manual for NAPS, KAPS 1 & 2 and MAPS was pending and NPC and these stations were asked to complete the revision of these manuals at the earliest.

AERB observed that at MAPS emergency diesel generators were prevented from auto start during the surveillance resulting in the unavailability of diesel generating (DG) sets on demand. Based on the regulatory inspection recommendations, MAPS has discontinued the practice of disabling DGs during surveillance test of station batteries.

The scheme is all set to allow construction of toilets as part of the changed guidelines. Thus, MPLADS funds is expected to help fund the material component of such projects.

NPC official told Business Standard, "Safety has been of a paramount importance and it will not be compromised. NPC regularly follows AERB's directives and accordingly upgrades safety applications at the nuclear power plants."

Meanwhile, AERB has mentioned that comprehensive reassessment of safety against external events and emergency mitigation measures carried out by NPC at all 20 nuclear power plants with the generation capacity of 4,780 MW. Of the 20 plants 19 are developed and owned by NPC while one by Department of Atomic Energy. NPC has completed the safety assessment of all operating nuclear plants and identified measures to deal with severe external conditions.

However, AERB has asked NPC to carry out analysis for severe accident conditions and develop guidelines for operator to take appropriate actions for such accident conditions. In this regard, NPC is considering implementation of provisions such as hydrogen recombiners and containment venting scheme for mitigating the consequences of the unlikely event of severe accident.

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First Published: Tue, September 04 2012. 00:36 IST