Contesting the JNPP-related issues raised by Prof Bilham last week, NPCIL’s executive director N Nagaich said that his organisation had considered the issue of seismicity in a comprehensive way — “from historical seismic data point-of-view to specifying and building reactors on conservative basis with ample design margins above what is considered possible risk”.
“The conservative approach used by NPCIL to arrive at the ground motion at Jaitapur very well accommodates even higher-impact possible events with comfortable margins. Seismic aspects of site have adequately been addressed in Indian Nuclear Power Plants, including at Jaitapur,” Nagaich said.
At a Greenpeace India-organised news conference in the city on Thursday last, Bilham, a professor of Geological Sciences at University of Colorado, Bilham had said that an earthquake of a high magnitude of 6-plus on the Richter scale could occur at Jaitapur, and the State-run NPCIL and the Government must take this into account while considering the design of the six 1,650 MW units for this site. Having co-authored a research paper ‘Historical and Future Seismicity near Jaitapur’ in Current Science with Dr Vinod Gaur of the Indian Institute of Astrophysics, Bilham had also said that since JNPP site lay in the in the same “compressional stress regime” that has been responsible for generating both, Latur (6.3) and Koyna (6.4) earthquakes in the past five decades, it could be argued that a “similar sized’ could possibly occur directly beneath the power plant.
In his rebuttal, Nagaich said the various seismo-tectonic studies of the Jaitapur site were taken up during the site selection stage itself i.e. from 2003 to 2005, much before the site was accorded ‘in principle’ approval by the Government of India in 2005.
The studies conducted by various expert agencies during the period included: satellite imagery based lineament map by Geological Survey of India (GSI), Gravity anomaly map study to arrive at sub-surface by Agricultural Meteorology Division (AMD) of Indian Meteorological Department, deep seismic sounding study by Keshava Deva Malaviya Institute of Petroleum Exploration, Dehradun (KDVMIPE) and Microearthquake (MEQ) studies by Koyna Bandhakam Vibhag.
“MEQ studies by Koyna Bandhakam Vibhag from 1970 onwards reveal that all the events are in Koyna Warna Region towards North East of the plant,. MEQ study by National Geophysical Research Institute (NGRI) from 2004 onwards in which the nearest event was of October 10, 2008 of 3.1 magnitude at 44.9 km distance,” Nagaich said.
Nagaich went onto reveal: “Opinions of geological & seismological experts in the country like Dr. J.R. Kayal, former Deputy Director General GSI, Dr SK Biswas, former Director, KDVMIPE and Dr BK Rastogi, Director General, Institute of Seismological Research (ISR) was also taken while arriving at the design basis earthquake. The information from various studies and the process of providing design margins has also been discussed with Dr Gaur (who co-authored a research paper on future seismicity with Bilham)”
Seeking to puncture Bilham’s argument, the NPCIL’s senior official said: “There are no Micro Earthquake (MEQ) events within 44 km of the site, based on expert opinions Assumption of subsurface faults at 0.5 to 50 km for magnitude and depth of focus, such that ground motion at the NPP site gives a spectral shape, which will have a peak ground acceleration (pga) of 0.125 g to 0.3 g for low, moderate, moderate to high seismicity has been made to arrive at the design ground motion at Jaitapur”.
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