Early on Friday, October 11, Davey was sent home sick and in pain with the flu. Between 4:00 and 5:00 a.m., the largest tank of carbon dioxide that could be found was expended into the fire, with zero effect. There was nothing to do but start pumping water into the fuel channels, a desperate move. The concept of flooding a graphite reactor with water was so remote, there were no fire-hose taps in the building. The works fire brigade was called in with pumper trucks, and nozzles were jury-rigged to force water through the holes in the loading face and deep into the fuel channels, two feet above the highest point of the fire. The water was turned on just before 9:00 a.m. K. B. Ross, the Director of Operations, dispatched the following message to the Authority Chairman, Sir Edwin Plowden, in London:
Windscale Pile No. 1 found to be on fire in the middle of lattice at 4:30 pm yesterday during Wigner release. Position been held all night but fire still fierce. Emission has not been very serious and hope continue to hold this. Are now injecting water above fire and are watching results. Do not require help at present.
Plowden dashed off a note to the Minister of Agriculture, wisely anticipating trouble with radiation contamination of the dairy farms in the area.
Tuohy was relieved when there was no explosion from the water interacting with the graphite. Watching through the viewing port at the back end of the pile, he could see the water gushing out of the fuel channels and cascading down the pile into the cooling pool at the bottom. The water looked good tumbling down, but still the fire raged out of control. The back of the core remained a wall of flames. He watched for an hour, starting to feel that the situation was hopeless, when he was struck by a brilliant idea. All the men had evacuated the loading face. There was no longer any need for the blowers. He decided to turn them off.
Almost instantly, the flames died away.
This time when Tuohy went up to the crane room to look, the viewing port seemed firmly cemented to the floor. The fire in its dying gasp was sucking oxygen out of the remaining air and causing a vacuum in the reactor core. With no more air forced through the fuel channels, there was no more fire. By noon Tuohy was able to report to Davey that the fire was out and the situation was now under control. Just to make certain of his pronouncement, the water was kept flowing for another 30 hours.
The core of Windscale Pile No. 1 was a total loss. Over 10 tons of uranium were melted and five tons were burned. Very little of the uranium or even the fission products went up the chimney. A brittle oxide crust had formed in the extreme heat of the fire, and the heavy oxides were bogged down in it before they made it to the air outlet. The immediate concern was the volatile fission product, iodine-131. The filter packs, which were no longer called “Cockcroft’s follies,” were not expected to capture any of the 70,000 curies of iodine-131 that were present in the fuel when the fire began, but there was a fortuitous happening. The LM cartridges, containing bismuth oxide meant to activate into polonium-210, burned up, and the light bismuth oxide dust went up the stack and caught in the filters. This and some vaporized lead from the weights in the AM cartridges reacted chemically with the free iodine and captured some of it in the filters. Although 20,000 curies of iodine-131 blew out the top of the stack and over the dairy farms, about 30,000 curies of it were caught in the filters. It was better than no capture at all.[128]
The immediate bad thing about loose iodine-131 is that it falls on the grass, cows eat it, it winds up concentrated in the milk, people drink it, it goes straight to the thyroid gland, and the tightly contained radiation load has a good chance of causing thyroid cancer. The good thing is that it has a short half-life of only eight days. On Sunday night, October 6, the reactor was shut down, iodine-131 production by fission stopped, and the countdown for the decay of the iodine-131 began. By eight days later, half of it was gone. On Saturday it was estimated that 20,000 curies of it were contaminating 200 square miles of territory north of the reactor, but in about 80 days that contamination would drop to 1/1,000 of that level.
However, 20,000 curies divided by 1,000 is 20 curies, and that is still a great deal of radiation. It is 7.4 3 1011 becquerels, or 7.4 3 1011 iodine-131 disintegrations per second, emitting first a 606 kev beta ray and then a 364 kev gamma ray, becoming a stable xenon isotope. The dairy industry in Cumbria was thus in serious trouble. On Saturday morning there was enough active iodine-131 on the grass, 132,000 disintegrations per second per square foot, to rattle a Geiger counter in a most alarming way.
This was new, untrod territory in the nuclear business, in which a private industry would have to be shut down because of an unfortunate situation in the government-owned, secret, dangerously handled fissile-isotope-production endeavor. There were no safety standards; no maximum limit for the amount of radiation to which a toddler should be subjected in its otherwise wholesome cow’s milk. The government did the right thing and bought every pint of contaminated milk. It was poured away into ditches, and the countryside smelled of sour milk for quite a while.[129] After a year, not a trace of iodine-131 could be found in the farmland. One good thing about radiation contamination is that it improves with age.
Neither Windscale reactor would ever be started up again, and there would be no more open-looped, air-cooled reactors built anywhere in the world. Pile No. 2, which was in perfect operating condition, was shut down permanently five days after the fire was stopped, and as much remaining fuel as could be moved was carefully taken out of the wrecked Pile No. 1 and processed to remove the plutonium. Unusable radioactive debris was dumped offshore into the Irish Sea. The cores of both reactors were sealed off with concrete, and the buildings were used for several decades as offices, labs, workshops, and for bulk storage. The 6,700 damaged fuel cartridges and 1,700 AM and LM cartridges in Pile No. 1 will be removed by remote-controlled robots by 2037. The core is still a bit warm. The name Windscale, carrying bad karma, was buried and the site was renamed Sellafield. It is now owned by the Nuclear Decommissioning Authority (NDA).
The people who worked at Windscale in 1957 and who participated in the cleanup operations have been studied, looking for radiation-caused diseases. Statistical analysis indicates that the widespread radiation release should have caused 240 thyroid cancers, but no correlation has been found. The last accounting in 2010 could find no evidence of health effects from the radiation release back in 1957. Tom Tuohy, who stood alone in the most hazardous conditions of radiation exposure at the height of the Windscale fire, died in his sleep on March 12, 2008, at the advanced age of 90 years.[130]
Bill Penney, the man whose relentless demands for more tritium, plutonium, and polonium-210 had caused Pile No. 1 to be overworked to the point that it burned down, was assigned as the chairman of the inquiry committee. On October 26, 1957, 16 days after the fire was put out, he submitted his report to the Chairman of the United Kingdom Atomic Energy Authority. His committee found the operating staff at fault for causing the fire. During the annealing process, they had reapplied nuclear heating to the reactor too soon after the first try. He did not point out that the fire had started in hole 20–53 when the overheated lithium in a Mark III AM cartridge diffused through the aluminum and set fire to the adjoining fuel, and he assigned no responsibility to himself or to the questionable engineering of the isotope production cartridges.[131] In retrospect, the Windscale piles were a disaster waiting to happen. Panic-containment photos were released showing contented cows grazing in the grass with the Windscale chimneys looming in the background.
128
There was also a great deal of radioactive xenon-133 gas released at Windscale, 16 times more than the iodine-131. This sounds terrible to the general public, but xenon-133 has zero body burden and it cannot react chemically with anything, unlike iodine-131. Animal body chemistry has no use for xenon. The xenon-133 floats away and decays to stable cadmium with a half-life of 5.24 days. There is no xenon filter, and radioactive xenon escapes regularly from every nuclear power plant in the world.
129
There are also reports that the milk was diluted with water and then dumped into the Irish Sea. It seems a bit odd to dilute it with water before pouring it into the ocean, and the aroma of decomposing milk was mentioned in local newspapers. It’s possible that farmers who were not found to have contaminated milk disposed of it anyway on their own initiatives, but more likely they took advantage of the inflated milk prices and sold it.
130
See an interesting British documentary on the Windscale fire from 2007 at http://www.youtube.com/watch?v=ElotW9oKv1s&feature=relmfu. Some important technical details are garbled, and the recreated scenes of men working at the loading face are seriously wrong.
131
The actual cause of the Windscale fire remains a controversial and unresolved topic. It is probable that it was started in an isotope channel by one of the many AM cartridges, which were the most temperature-sensitive components in the entire pile. There was one isotope channel for every four fuel channels, and when you opened an access plug, the isotope channel was in the center, with four fuel channels surrounding it. The first man to open plug 20–53 reported that “it was glowing bright red, and so were the four channels around it.” It is often assumed that the center hole was a fuel channel, but clearly he was referring to the isotope channel behind 20–53.