Safety concerns

Print edition : July 02, 2004

Some recent lapses in safety at nuclear installations across the country lead the Department of Atomic Energy to review its safety procedures.

IS the Department of Atomic Energy (DAE) slipping in its record of safety?

On April 17, three employees at the Waste Immobiliation Plant (WIP) at Tarapur in Maharashtra received doses of radiation from a tiny bottle containing a few drops of diluted highly radioactive waste. DAE officials alleged that another employee had "deliberately" placed the bottle on a chair that the three used at different times. The presence of the bottle was detected after instruments kept in the laboratory for measuring radiation registered more than the normal radioactivity.

On March 10, there was a "reactor power rise" in the first unit of the Kakrapara Atomic Power Station (KAPS) in Gujarat because "the operator failed in not tripping the reactor in time". (An operator of a nuclear electricity reactor is a graduate engineer and is akin to a pilot of an aircraft.) According to S.K. Jain, Chairman and Managing Director, Nuclear Power Corporation of India Limited (NPCIL), the operator had made "a mistake" in not tripping the reactor in time. The reactor shut down on its own, with the defence-in-depth mechanism coming into play.

A robotic arm welds a canister in which solid waste has been vitrified into glass at the Waste Immobilisation Plant, Tarapur.-PICTURES BY SPECIAL ARRANGEMENT

The incident prompted NPCIL, which runs 14 nuclear reactors, to conduct refresher courses for operators at Kakrapara and the other nuclear power stations in the country and renew their licences to man the reactors. The Atomic Energy Regulatory Board (AERB), which monitors safety in these nuclear installations, said that though the incident did not lead to any radiation leak or damage the reactor, it "reflected certain weaknesses in the safety culture at the plant and the need for improving the safety practices". NPCIL, as per AERB's directive, shut down the two reactors at Kakrapara, which generate 220 Mwe each, on April 22 and May 21 to carry out modifications.

Jain said that the first unit at Kakrapara was started up on June 5 at 2.39 p.m. after modifications were carried out in the reactor. It was operating at full power. Annual maintenance work was under way in the second reactor, which was also ordered to be shut down by the AERB. "We are doing annual maintenance work in the reactor, taking advantage of its shutdown to carry out modification work," Jain said. The second unit was expected to come on line on June 15.

On January 21, 2003, six employees of the Kalpakkam Reprocessing Plant (KARP), about 50 km from Chennai, were exposed to radiation exceeding the AERB-prescribed annual dosage limit of 2 rem. A leak in a valve separating a high-level radioactive liquid waste tank and a low-level liquid waste tank led to the mixing of the two kinds of wastes and increased radioactivity in the area. There were no monitors to detect the radiation level in the enclosed area. The workers were not wearing the personal thermo luminescent dosimeters, which register the radiation doses received. (Frontline, August 29, 2003).

In the International Nuclear Event Scale, what happened at Kakrapara fell in Level 2, and the one at Kalpakkam between Level 1 and 2. The scale ranges from 1 (anomaly) to 7 (major accident). Any event between 1 and 4 is called an incident, and those above 4 are categorised as accidents. (The Chernobyl disaster was of Level 7 and the Three Mile Island disaster fell in Level 5.)

AERB could not intervene with what happened at WIP, and at KARP because these facilities come under the purview of the Bhabha Atomic Research Centre (BARC), which is a strategic facility. After the May 1998 nuclear tests at Pokhran, Rajasthan, BARC and its satellite facilities were removed from AERB's purview. A BARC Safety Council was set up to oversee safety aspects in them.

BARC has several facilities located near the Tarapur Atomic Power Station (TAPS), which has two reactors of 160 MWe each. The WIP there was commissioned in March 1985. It handles liquid, solid and gaseous radioactive waste material generated in a nearby plant that reprocesses spent fuel from power reactors into plutonium. The liquid waste is stored in huge tanks in underground vaults and the integrity of the tanks and vaults is monitored all the time. The solid waste is vitrified, that is, it is converted into glass by heating, and stored in small capsules underground where the chances of flooding or earthquake are low. The gaseous effluents are treated and released through tall stacks into the atmosphere, which is monitored continuously.

In the April 17 incident at Tarapur, the liquid waste in the bottle, which was found embedded in the chair, contained caesium, strontium and so on. A BARC official alleged that "someone kept it there deliberately". He said: "It was a 10 ml bottle. It is so small and kept in such a way that a person sitting on the chair would not feel it. That is why it remained hidden." He blamed it on "rivalry among employees".

The three persons who sat on the chair received radiation doses ranging from 0.04 rem to 0.3 rem, which was "a very low exposure" compared with the permissible annual dose of 2 rem a year, said a BARC scientist. BARC safety committees were probing the incident.

The March 10 incident at Kakarapara, about 80 km from Surat, was more serious. The two 220 MWe units were operating at 170 MWe each. To take care of emergencies such as station blackout, there are back-up power systems that include uninterrupted power supply (UPS) and diesel generators. The UPS of the first unit had been taken out for maintenance when one of the relays in the unit malfunctioned, leading to over-voltage. This led to the failure of the control rod system (CRS), which controls the reactor's power. The CRS power fuse blew, making the controlling (regulating) mechanism unavailable. And because the operator failed to trip the reactor in such a situation, its power kept increasing from 73 per cent (170 MWe) to 98 per cent (almost 220 MWe).

According to AERB, what saved the day was that the reactor tripped (shut down) automatically on its safety systems. "However," it said, "it reflected certain weaknesses in safety culture of the plant and the need for improving the safety practices." Besides, it said "an erroneous operator action" inhibited a design feature of the reactor power control system. Luckily, the reactor systems remained healthy. There was no leak of radioactivity into the atmosphere.

Jain told Frontline: "When the operator comes to know that the regulation (controlling) part is not available, he should trip the reactor." But he did not. "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." The AERB also felt that the operator's action "was not within the prescribed thinking of safety procedures".

The containment domes of the two reactors of the Kakrapara Atomic Power Station, about 80 km from Surat.-

Jain said there was "a structured, detailed training programme" for the operators. Each and every person associated with the operation of the reactors in the country underwent "rigorous training". After successful completion of this, they were given licences to operate the reactors for three to five years. After that, there was a system of re-licensing. Even the top brass including Station Directors were required to have the AERB's licence. "There is a system of retraining too... which is very rigorous," Jain said.

Jain added: "I have started brainstorming sessions with all Station Directors. We will take stock of the situation whether any policy decision, directive or action of ours, had influenced the operator to behave in a less than conservative fashion. Our approach is that the operators should behave in the most conservative fashion."

Jain asserted that it was "absolutely not" true that the NPCIL was flogging the reactors in its quest to show more capacity and this had led to the incident. He said: "Generally, there is a feeling that operators are `power-driven' and that they don't give weightage to safety. But our people are under instructions to take decisions, which should be in the most conservative direction with regard to safety. I don't have an answer why despite such a directive, such technical requirements, such training, the operator of the first unit behaved in that fashion. That is a mistake and we admit that."

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