Activists protest against nuclear power and weapons near Jantar Mantar in New Delhi. File picture

New Delhi, April 14: India will buttress safety at its nuclear power plants and gear them for automatic shutdowns during earthquake-triggered ground movements under a plan pencilled after the nuclear crisis in Japan.

The Nuclear Power Corporation (NPC), which operates India’s 20 commercial nuclear reactors, said it will initiate action to implement the plan which seeks extra safety to tackle a Fukushima-type scenario where all power was lost after reactor shutdowns.

The failure of back-up power at the Fukushima Daiichi nuclear power station in Japan last month led to overheating of the reactor cores and cascaded into hydrogen explosions and radiation leaks into the environment.

The NPC plan which emerged from internal safety audits has also sought an increase in the duration for which the cores of nuclear reactors that have shut down may be cooled with passive systems that require no electric power.

“We already have good safety systems in place at our nuclear plants. With the new steps we’re being super-conservative,” Nalinish Nagaich, executive director of the NPC told The Telegraph.

The safety audits have also recommended the creation of “hook-up” arrangements for adding cooling water inventory to all reactor cooling systems and to support mobile diesel-driven pumping units.

“The hook-ups are interfaces between external systems and the (nuclear) plant — we have an adequate inventory of water, but even if everything else fails, we should be able to supply water through external tankers,” Nagaich said.

All of India’s reactors are designed to handle the seismic events that can occur in their seismic zones — and shut down when ground accelerations exceed specific values. But the safety audits have now recommended that reactors should automatically shut down even if the site experiences ground acceleration that is slightly lower than the current safe operating limits.

For instance, a plant that may be designed to shut down safely at earthquake-triggered ground acceleration of 0.2g may be geared to automatically shut down at 0.15g. “The actual figures will vary from site to site,” Nagaich said.

But the task forces have now suggested that reactors should initiate the shutdown sequence as soon as operators sense seismic waves. The NPC has not specified at what limits of acceleration will this shutdown begin.

The audits have also asked the NPC to establish “hook-up” points to make available water to the spent fuel ponds at the nuclear power stations in Tarapur, Kalpakkam, and Rajasthan.

The NPC said the current water inventory at its nuclear reactors is enough to be sufficient for 10 days, and at some places for up to 30 days. Water is crucial in attempts to cool reactors that have shut down but continue to heat because of radioactive decay.

The NPC said the water reservoirs at its reactors in Kalpakkam are three metres above flood level and located at a considerable distance from the coast. However, additional shore protection measures to reduce the energy of tsunami waves will be carried out at both Tarapur and Kalpakkam, the NPC said.

India’s Atomic Energy Regulatory Board is also independently reviewing safety issues of nuclear plants after the crisis in Fukushima.

The NPC said it will await the results of that review, but will seek to implement the task force’s recommendations immediately.