The Hindu : National : `There was no radiation leak at KAPS'

Online edition of India's National Newspaper
Monday, Apr 26, 2004

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National

`There was no radiation leak at KAPS'

By T.S. Subramanian

COIMBATORE, APRIL 25. The incident of `reactor power rise' in the first unit of the Kakrapar Atomic Power Station (KAPS), Gujarat, took place because "the operator had failed in not tripping the reactor" in time, according to S.K. Jain, Chairman and Managing Director of the Nuclear Power Corporation of India Limited (NPCIL). "A global analysis" of the incident had been done in an "overall way." The NPCIL was doing "a micro-level analysis" and "the incident is being totally simulated on the computer," he said. Despite the incident, the fuel was sound and there was no radiation leak, he added.

The Atomic Energy Regulatory Board (AERB), entrusted with keeping a tab on safety in nuclear power facilities in the country, asked the NPCIL on April 22 to stop operating the reactor. But the incident took place on March 10.

Mr. Jain told The Hindu on April 24 from Mumbai that KAPS's two units of 220 MWe each were operating at 170 MWe each on March 10 because the hydel generation of the State Electricity Board was good. The reactors had various power supply systems for reactors' controls and there were back-up power systems, including the uninterrupted power supply (UPS) and huge diesel electricity generators, to take care of emergencies. When the UPS was taken out for maintenance, one of the relays malfunctioned, he said. So there was over-voltage, which led to the failure of the control rod system (CRS).

The rods are used for controlling the reactor power and their movement is as per commands from the automatic reactor power control system. When the CRS power fuse blew up, the regulation (controlling) part was not available because there was positive reactivity. The reactor power kept increasing to 94 per cent and the reactor tripped immediately, the CMD said.

Answering a question on the AERB's observation that the incident "reflected certain weaknesses in safety culture at the plant and the need for improving safety practices" and "erroneous operator action," Mr. Jain said "when the operator comes to know that the regulation part is not available, he should trip the reactor." He should have taken this action. But his perception was different because the reactor was operating at 70 per cent power, not 100 per cent and he did not trip the reactor. "His judgment is not in line with the worst scenario safety culture. He may say the fuel is sound. As per our unambiguous approach, safety comes first," he said.

After ensuring back-up power supply and fine-tuning all operations, the reactor was started up within two days. "We also promptly informed the AERB about the entire incident," he said. The AERB wanted more information and the NPCIL gave it to the AERB. A global analysis — in an overall way — of the incident was done, Mr. Jain added. "But the AERB was not satisfied because the incident cannot be repeated mathematically at the macro-level. Though there was no radiation leak into the atmosphere, the AERB said that unless this understanding is there, the unit should be down as a matter of abundant caution. So we have shut down the reactor." He stressed the NPCIL had "respect for all safety standards and safety is the overriding factor with us."

Sources in the DAE wondered why the AERB ordered the reactor to be shut down on April 22 — after a gap of 42 days — when the incident took place on March 10. "Was not the reactor safe during that period," they asked.

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