Indian nuclear plants are safe: NPCIL
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Last Updated: Wednesday, April 13, 2011, 22:17
  
New Delhi: Even while maintaining that India's atomic plants are capable of handling extended power loss scenario witnessed during Japan's nuclear crisis, NPCIL on Wednesday announced additional safety measures at all nuclear power plants.

The state-run Nuclear Power Corporation of India Limited (NPCIL) came out with the additional measures after an internal safety assessment of all nuclear reactors by four taskforces it had appointed for the purpose in the wake of the Fukushima nuclear accident in Japan triggered by earthquake and tsunami.

The results of the study were thoroughly reviewed and discussed by experts and the top management at NPCIL today.

The studies have indicated that capabilities exist in all Indian nuclear plants to handle severe natural events, NPCIL Chairman and Managing Director Shreyans Kumar Jain said.

He said the taskforces have come out with recommendations with a view to enhancing the safety levels and build further defence.

"NPCIL proposes to take up implementation of the recommendations of its task forces immediately with requisite approvals from Atomic Energy Regulatory Board, wherever applicable," Jain said.

The NPCIL task forces' recommendations include incorporation of automatic reactor shutdown initiation on sensing seismic activity and increasing passive power source capacity for monitoring and control purposes, for longer durations.

They also suggested making provisions for hook up arrangements for adding cooling water inventory through external sources to all reactor cooling systems, and mobile diesel driven pumping units and augmentation of water inventory and arrangement for transfer of water from the nearby sources, if required.

The task forces suggested incorporating additional shore protection measures at Madras Atomic Power Station, and Tarapur Atomic Power Station, which are located in the coastal regions.

They also recommended additional hook up points for making up water to spent fuel pools at Tarapur Atomic Power Station units 1 and 2, Rajasthan Atomic Power Station units 1 and 2, and Madras Atomic Power Station units 1 and 2.

The task force for the Tarapur Atomic Power Station (TAPS) has recommended advance alert mechanism for tsunami and also to inert the primary containment of the two Boiling Water Reactors with nitrogen.

"The seismic capability of the structures has been found adequate for the seismic zone in which it is located," it said.

It found that the plant was safe for the maximum height of tsunami that can be generated by a quake triggered by the Makran fault, which is located 900 km away near Karachi.

It said additional shore protection measures were also being undertaken which will absorb considerable energy from the tsunami waves.

"Water sources existing at the site in the form of emergency condenser, suppression pool and underground storage tank is adequate to cater to the cooling requirements for extended periods of more than 10 days," the task force said.

The task force for the Rajasthan Atomic Power Station (RAPS) considered the scenario of possible flooding due to a break in the upstream Gandhi Sagar dam.

It found that on-site power will be available in such a scenario.

RAPS-1, built with Canadian assistance, is a Canada-deuterium-uranium (CANDU) type. It became the prototype for the country's indigenous Pressurised Heavy Water Reactors (PHWRs). India completed the RAPS-2 on its own after Canada suspended its assistance following India's 1974 nuclear test.

"A separate, Station Black Out Diesel generator is provided at a height of about three meters above flood level. Water resources available in several tanks at a higher elevation is adequate for the safety systems," the task force found.

At the Madras Atomic Power Station (MAPS), the task force said that the finished floor levels of the buildings were higher than the maximum flood level postulated.

It noted taht MAPS had already handled the Indian Ocean Tsunami in December 2004 successfully and core cooling was maintained without any interruption.

Additional measures in the form of tsunami bunds have been constructed along the shore which will further reduce the intensity of tsunami, it said adding that a tsunami alert system was also available at this station.

"One of the diesel generators and two diesel driven fire fighting pumps are located at a height of about three meters from the flood level. The reservoirs at site which are at a higher elevation and at a considerable distance from the coast and the water contained in the various tanks and suppression pool will cater to the requirements for more than 10 days," it said.

The task force for all the standardized PHWR type of reactors, found that the seismic design was adequate to cater to all seismic events that can occur in the seismic zone in which the plants are located.

"There is also a margin of 1 to 4 meters above flood level postulated for the respective sites. The water inventory at these sites will also suffice for meeting the requirements for a period of more than 10 days and in some cases upto even 30 days. The spent fuel pool water inventory is also assessed to be adequate for more than 10 days," it found.

Standardised PHWRs are located at Narora (two units), Kaiga (four units), Kakrapar (two units) and Tarapur (two units).

Narora-1 had faced the extended black out scenario had during the turbine fire in 1993.

The event was successfully handled to maintain adequate core cooling, it said.

The events at Three Mile Island in the US, and Chernobyl in Ukraine, had brought out many learning points which were studied and incorporated in Indian reactors.

Jain said the Atomic Energy Regulatory Board has also constituted a high level specialist committee to study the implications of the accident at Fukushima and examine the need for enhancing the safety of Indian nuclear power plants.

The committee will also be submitting its report and NPCIL is committed to incorporate all the recommendations made by the committee, Jain said.

PTI


First Published: Wednesday, April 13, 2011, 22:17


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