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Windscale: Britain’s Biggest Nuclear Disaster – Part 01

5 Unknown Nuclear Disasters: Chernobyl Is Far from the Only One, Chernobyl is not the world’s only nuclear disaster, there are plenty of others to keep you up at night., Interesting Engineering, By  Marcia Wendorf, 2 Aug 19

The Windscale Fire

Less than two weeks after Kyshtym, a fire broke out in Unit 1 of the two reactors at the Windscale facility located in what is now known as Sellafield, Cumbria UK.

The two reactors were created because of Britain’s need for an atomic weapon following World War II. Determining that a uranium enrichment plant would cost ten times as much to produce the same number of atomic bombs as a nuclear reactor, the decision was made to build a nuclear reactor that would produce plutonium.

The cores of the reactors were comprised of a large block of graphite, with horizontal channels drilled through it for the fuel cartridges. Each cartridge consisted of a 12-inch-long (30 centimeters) uranium rod encased in aluminum.

The reactor was cooled by convection through a 400-foot (120 m) tall chimney. When Winston Churchill committed the UK to create a hydrogen bomb, the fuel loads at Windscale were modified to produce tritium, but this also meant that the core became hotter.

On the morning of October 10, 1957, the core began to uncontrollably heat, eventually reaching 400 degrees C. Cooling fans were brought in to increase the airflow, but just worsened the problem. It was then that operators realized that the core was on fire.

Workers tried dousing the core first in carbon dioxide, then in water, but both proved ineffective. What finally worked was cutting off air to the reactor building, which starved the fire.

The fire caused the release of radioactive radionuclides across the UK and Europe, including an estimated 740 terabecquerels (20,000 curies) of iodine-131, 22 TBq (594 curies) of caesium-137 and 12,000 TBq (324,000 curies) of xenon-133.

By comparison, the 1986 Chernobyl explosion released far more, and the Three Mile Island accident in 1979 in the U.S. released 25 times more xenon-135 than Windscale, but less iodine, caesium, and strontium. The atmospheric release of xenon-133 by the Fukushima Daiichi nuclear disaster was similar to that released at Chernobyl, and thus, high above what the Windscale fire released.

There were no evacuations of the surrounding area, but it has been estimated that the incident caused 240 additional cancer cases. For a month after the accident, milk coming from 500 square kilometers (190 sq mi) of the nearby countryside was destroyed.

The reactor tank has remained sealed since the accident and still contains about 15 tons of uranium fuel. The reactor core is still slightly warm due to continuing nuclear reactions. It is not scheduled for final decommissioning until 2037. On the International Nuclear Event Scale, Windscale ranks at level 5………. https://interestingengineering.com/5-unknown-nuclear-disasters-chernobyl-is-far-from-the-only-one