India Scientist Ties Water Leak to Gas Disaster

NEW DELHI —  Water entering an underground storage tank probably caused last month’s Bhopal gas disaster in which more than 2,000 people died, a top-level Indian government scientist was reported as saying Friday.

The Press Trust of India said Dr. S. Varadarajan, scientific adviser to the government, told a meeting of the Indian Science Congress in Lucknow that the water set off a violent runaway reaction in liquid methyl isocyanate stored in the tank at a pesticide factory owned by Union Carbide Corp.

“Just half a kilogram of water (about one pint) entered the underground methyl isocyanate tank . . . triggering a runaway reaction that probably pulled the entire tank from the ground causing cracks on its concrete shield,” the news agency quoted him as saying.

He said 30 of the 45 tons of methyl isocyanate stored in the stainless steel tank escaped into the atmosphere, while the rest was polymerized and turned into a plastic-like mass by the reaction.

The lecture by Varadarajan, chief of the Council of Scientific and Industrial Research, who led the government team that investigated the tragedy, was the first official account of the reason for the Dec. 3 disaster, the world’s worst industrial accident.

Varadarajan said the small amount of water was enough to react with phosgene gas, normally added to methyl isocyanate to inhibit polymerization. That reaction liberates hydrochloric acid, which easily polymerizes methyl isocyanate.

Varadarajan said that phosgene, the basis for mustard gas used in World War I, is added to methyl isocyanate to stop it from polymerizing and turning into plastic. He said the reaction between the water and phosgene probably triggered the initial process. Enormous heat is released during the polymerization, so the rest of the methyl isocyanate became gas and escaped after rupturing a safety valve, Varadarajan said in his lecture.

Varadarajan gave no indication as to how water entered the tank.

Varadarajan also reported:

--The liquid-level controls on the faulty tank did not work during the accident.

--The scientific investigative team he is heading was not convinced of the company’s claim that a safety device called a “scrubber” was turned on during the accident. The mechanism is filled with caustic soda, a chemical that neutralizes escaping methyl isocyanate.

--The cooling system for the tank, designed to control chemical reactions, was inefficient.

Varadarajan said the investigation is continuing but a full understanding of what happened will be possible only after the leaky tank is opened up later this month.

In Bhopal on Friday, thousands of victims of the gas disaster signed up for free legal aid while others staged a demonstration to back demands for faster relief payments.

The Press Trust of India reported that about 6,000 gas victims had registered with the Madhya Pradesh Legal Aid and Advice Board at four camps set up by the government.

Hundreds of survivors of the leak staged a sit-down demonstration outside the residence of the state’s chief minister, Arjun Singh. Tempers frayed among the demonstrators when they failed to meet Singh. Police were firm but gentle with the protesters, calming them twice when they threatened to storm Singh’s residence.

On Thursday, gas victims marched through Bhopal, accusing Singh’s government of negligence and demanding relief allowances, jobs for unemployed survivors, pensions for widows and shelter for children orphaned by the disaster.

Official aid to the victims was suspended last week pending an investigation of exactly who was eligible for relief.