On this day in 1957, Britain was host to a nuclear reactor accident of potentially disastrous level. Due to its flawed design resulting from bureaucratic mismanagement and unrealistic demands.
On October 10, 1957 the graphite core of a British nuclear reactor at Windscale Cumbria, caught fire, releasing substantial amounts of radioactive material. The event, known as the Windscale fire, was considered the world's worst nuclear accident until the Three Mile Island accident in 1979. Then both were dwarfed by the Russian Chernobyl disaster in 1986.
The Windscale site was home to Britain's first two nuclear reactors - the Windscale Piles - which were constructed to produce plutonium and other materials for the UK's nuclear weapons programme.
The UK was in a desperate race to produce a working thermonuclear weapon, in an attempt to re-establish the 'special relationship' with the U.S., and resume to sharing of nuclear secrets. This led the British government and the military to increase demands on Windscale to produce increasing amounts of material. As a result of these demands, the safety margins of the radioactive materials inside the reactor were being eroded to dangerous levels.
Fire broke out at atomic pile number one during a routine maintenance exercise called a Wigner release. This involves overheating the reactor to allow graphite to heat up in a controlled situation to release the energy that builds up when graphite is irradiated. This procedure is known as "annealing".
But on the 10th of October, an unsuccessful Wigner release was followed immediately by a second, creating such high temperatures that one of the fuel element channels started to burn.
The fuel melted, fuel cans burst, uranium was ignited and radioactive contamination was spewing into the
atmosphere. Chimney filters which had been fitted as a last minute afterthought blocked some but not all
First, they tried to blow the flames out by putting the blowers onto full power and increasing the cooling, but predictably this simply spread the conflagration.
Next, the operators tried to extinguish the fire using carbon dioxide sourced from the adjacent Calder Hall
reactors. But the heat generated by the fire was so extreme that the oxygen was stripped from the carbon atoms and added to the blaze.
On the morning of Friday October 11 and at its peak, 11 tonnes of uranium were ablaze. Temperatures were becoming extreme (one thermocouple registered 1,300 degrees Celsius) and the biological containment around the stricken reactor was now in severe danger of collapse.
Faced with this crisis, the operators decided to use water. This was incredibly risky: molten metal oxidises in contact with water, stripping oxygen from the water molecules and leaving free hydrogen, which could mix with incoming air and explode, tearing open the weakened containment.
Hoses were rigged on scaffold poles to the charge face of the reactor and turned on. Water was kept flowing through the pile for a further 24 hours, but it was not untill the fans were turned off as well that the fire was extinguished completely.
The fire itself released an estimated 20,000 curies (700 terabecquerels) of radioactive material into the nearby countryside, although recent reworking of contamination data has shown national and international contamination to have been much higher than previously estimated.
The reactor was unsalvageable; where possible, the fuel rods were removed, and the reactor bio shield was sealed and left intact. Approximately 6,700 fire-damaged fuel elements and 1,700 fire-damaged isotope canisters remain in the pile. Windscale Pile no. 2, though undamaged by the fire, was considered too unsafe for continued use. It was shut down shortly afterward.
In the aftermath of the accident, the true scale of the event was concealed from the public, and the majority of the blame was apportioned to the plant operators. For 50 years, the official record on the accident has been that the very men who had averted a potentially devastating accident were to blame for causing it.
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