Methyl Isocyanate C2H3NO

Curious Article No. 27:

Late in the evening of December 2, 1984 things weren’t going at all well at the Union Carbide facility in the central Indian city of Bhopal. Either by mistake or owing to faulty equipment somebody introduced 180 gallons or so of water into a tank containing about 12,000 gallons of methyl isocyanate or MIC. This was a problem because MIC, a chemical used to make Sevin brand pesticide, is highly toxic (50 times more potent than Sarin, of Tokyo subway infamy) and reacts violently with water.

The reaction simmered at first, but at 12:15 forty tons of unreacted MIC and heaven knows what else blasted up and out of the plant’s chimney. Heavier than air, it tumbled to the ground and enveloped the shantytowns hugging the plant. It killed 2000-3000 people outright and sickened 500,000 as they trampled one another to escape. MIC kills most immediately by congesting the lungs with fluid so that the victim suffocates, but short of that it burns the skin and eyes and can lead to permanent disability or blindness.

In light of the plant’s working environment such a disaster was all but inevitable. Valves leaked, indicators froze, hoses were clogged, refrigeration systems to keep volatile chemicals cool were inoperable, an emergency water curtain device was only there in spirit, and a pipe was missing that should have conducted escaping MIC to a flare tower to burn it off. The Bhopal operation had been losing money for years, so Union Carbide India Ltd. had cut its staff to the bone and those who remained were largely unqualified and knew little or nothing about handling MIC and other hazards.

Union Carbide CEO Warren Anderson flew in under the promise of safe passage. Indian authorities reneged when he landed and placed him under arrest for culpable homicide and criminal conspiracy, but for the sake of diplomatic relations they extracted a token $2000 bail and allowed him to leave the country. That was the last they ever saw of him.

Rioting from Indira Gandhi’s assassination was still fresh on everyone’s mind, so many wondered at first if they were witnessing a terrorist attack. For its part Union Carbide blamed the leak on a malcontent whose identity they swore they knew, though they refused to share it with anyone else and continue to do so. Nor will they disclose the precise chemicals involved.

Bhopal itself couldn’t have been more vulnerable. It had no evacuation plans. It had one doctor for every 3500 people, one phone for every 100, only sporadic electricity and running water, and no treatment for sewage let alone toxic waste. Local authorities had never been told about the chemicals UCIL was toying with in their midst. Frantic hospital staffers only learned about the MIC and its properties when they read the papers the following evening.

Union Carbide settled out of court for $470 million, 40% of which their insurance paid for and another 40% they had saved up. In comparison a similar number of stateside silicone breast implant plaintiffs got $3.2 billion. Dow Chemical bought Union Carbide in 2001 and has since declared the Bhopal issue closed. Meanwhile hundreds of tons of industrial chemicals languish in open pits and moldering sacks and tanks on the now-derelict site. Area groundwater and breast milk samples show lead, mercury (20,000 to 6 million times normal), chloroform (which breaks down into phosgene), carbon tetrachloride (1700 times safe levels), and a host of other evils.

The basic idea of a nuclear power plant is that you want to split or fission atoms in your fuel to give off heat, then use that heat to boil water to run a generator. The fuel needs to be radioactive, enough so that neutrons from the fissioning atoms hit other atoms, which fission and shoot off more neutrons to fission more atoms, and so forth. The dioxide form of enriched uranium fits the bill, but to maintain the fission you also need to slow the neutrons down by about a factor of 6000 so they don’t just fly away. For that you use a moderator. Lastly you want to intersperse something with the fuel to throttle its fission or turn it off completely, so you need neutron-absorbing control rods you can push in and out.

By 1986 the Soviet Union had fifteen operational power-generating RBMK-type reactors: ten in what is now Russia, one in Lithuania, and four in Ukraine north of Kiev — Chernobyl, to be precise. RBMKs use graphite bricks for moderator and water for coolant to carry the heat out of the core. Though a 1000-ton concrete slab seals the core, there’s no further containment. Moscow

St. Andrews Church, Kiev Photo: Alexander Noskin

liked RBMK reactors because they were cheap and because they could also breed weapons-grade plutonium while they were at it. Non-Soviet reactors overwhelmingly used water for both their moderator and coolant and had heavy containment structures.

Shortly after midnight of April 26th at Unit 4 in Chernobyl deputy chief engineer Anatoly Dyatlov and a crew including shift chief Aleksandr Akimov and operator Lenya Tuptonov started a test. The plant’s systems ran off the city power grid, so they wanted to see if, in the event of a blackout, the turbines would have enough momentum to continue operating the reactor. This required shifting to manual control, disabling several safety systems, and lowering the reactor’s power to between 700 and 1000 megawatts.

An RBMK reactor gets dangerously unstable at low power but the operators weren’t fully aware of this. Under low power, voids open up in the water as more and more of it turns to steam. That hampers the cooling, but all that graphite moderator which encourages the fission stays put since it’s an integral part of the structure. An RBMK’s control rods in 1986 were also unusual. The first meter was graphite, then there was a space of another meter, and then neutron-absorbing boron nitride the rest of the way up.

When despite everyone’s efforts the power toppled to 30 megawatts, Tuptonov wanted to shut the core down completely to be on the safe side. Not so fast, Dyatlov growled. He wanted him to do just the opposite and pull some control rods to jack the power back up. House rules mandated that at least 28 of the rods be fully inserted at all times. Dyatlov was asking Tuptonov to violate this grossly, so he refused. Akimov stood by him. Dyatlov erupted into a namecalling frenzy and threatened to have them sacked. So Tuptonov complied.

Moments later shop chief Valeri Perevozchenko who was in the area over the reactor core was horrified to see hundreds of fuel rod channel caps, each weighing 770 pounds (350 kg), bouncing up and down. Back in the control room Dyatlov ordered an emergency shutdown. But because the control rods were graphite at the bottoms the power first went up when they pushed them in, rather than down. Then the rods simply froze. The power skyrocketed to 30,000 megawatts. The building shook with a tremendous explosion.

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Text © Peter Blinn 2006