India's top nuclear bodies on Sunday said they would revisit all safety aspects of atomic plants in the country and analyse the nuclear crisis arising in Japan after the tsunami as it had offered new lessons to fine-tune existing emergency preparedness.

“We will not jump to say that our power reactors will not suffer a similar kind of situation but we are planning to revisit all the safety aspects of our plants after doing a complete analysis of the Japanese incident and share the entire safety means with the public in a transparent way,” said Nuclear Power Corporation of India Ltd. (NPCIL) Chairman and Managing Director S.K. Jain.

This was the general practice adopted by the World Association of Nuclear Operators (WANO) and the NPCIL would closely work with the Department of Atomic Energy and the Atomic Energy Regulatory Board (AERB) to revisit the safety aspects.

“Although the Fukushima incident is the rarest of sequence of combination of events, we will be doing a complete analysis of it as to what might have gone wrong and how,” Atomic Energy Commission Chairman Srikumar Banerjee said.

Japan on Sunday warned of another explosion at the Fukushima plant as it battled hard to avert multiple meltdowns at two of its nuclear reactors damaged by the devastating tsunami triggered by an earthquake.

In the International Nuclear Event Scale, the Three Mile Island accident was at level 5, Chernobyl was at level 7, whereas the current Japanese incident is at level 4.

Mr. Jain said that out of the 20 operating Indian reactors, 18 were Pressurised Heavy Water Reactors, two were Boiling Water Reactors. The two reactors of 1,000 MWe of Russian VVER-1000 type under construction at Kudankulam in Tamil Nadu had Generation-3 plus designs.

Between BWR (Tarapur units 1 and 2 and the Japanese reactors at Fukushima Daiichi) and PHWR there was a big difference as the PHWR reactor had 100 to 200 tonnes of cold moderator, which surrounded all the coolant channels. Calandria was submerged in a cool water of calandria vault (1,000 tonnes). There was a very big heat sink available in PHWRs and secondly, unlike the BWR, the PHWR was also cooled by naturally occurring siphon mechanism. Since the steam generator was located at a higher elevation, directly injecting water from the fire-fighting system into the generator was also available as a supplement, he said.

Unique feature

“The uniqueness of the Indian system is that NPCIL has got centralised online monitoring system of all the power stations which are operating in Mumbai. We have all the emergency control centres where plants' live parameters are online through satellite,” Mr. Jain said.

“Parameters are available for various safety and reactor systems where safety experts can assemble within a few minutes and can do the entire parallel analysis and also in continuous contact with the stations.”

“Design safety, safety analysis capacity are available as a back-up of operating plants, which is unique to India,” Mr. Jain said, adding “it is a big strength.”

“In spite of all these, with an open mind we will be revisiting the safety aspects and share them with the public.”

AERB chairman S.S. Bajaj said: “We do not allow any of the reactors to operate unless all emergency plans are in place. The operators [NPCIL] have to conduct an actual exercise before getting clearance for operation of the plant and also the exercises are repeated every two years.”

High alert

“Even in the rarest of rare scenario, there is enough time for emergency planning of evacuation.” Citing the case of Japan, Mr. Bajaj said that on Friday a high alert was given, on Saturday general emergency was declared and evacuation was done up to 3 km and the radioactive release happened after the emergency precautions were taken.

“Of course, after this incident, new lessons are there for all the nuclear community to improve and fine-tune the existing emergency preparedness. We will review it in the light of the recent Japanese incident,” Mr. Bajaj said.

Meanwhile, seismologists here said all Indian reactors were not on the coast and the Indian coastline was more than 2,000 km away from the Sunda trench where mega earthquakes could occur.

“Hence, similarity analysis of reactor accidents/incidents between the Japanese reactors, which are a few hundred km away from mega subduction zones, and the Indian coastal reactors, which are a few thousand km away from the Sunda trench, should be done objectively,” they said.

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