Russia and the United States were not the only countries involved in the post-World War Two nuclear race as Great Britain was also involved in the research and development of a new and improved, unlimited energy source. Originally, the two Windscale Piles were built in order to develop nuclear weapons, as they seemed to be all the talk since the U.S. dropped two atomic bombs on Japan to end the Second World War. Once countries new it was possible it seemed as if it came down to a ‘kill or be killed’ situation when it came to nuclear power and no one wanted to be left behind. Britain chose to forgo the research of lower-grade uranium-based weapons and jumped straight into the R&D of more powerful yet unstable plutonium-based weaponry. The two reactors were built in the village of Seascale, Cumberland and were known as Windscale Pile 1 and Pile 2 and were housed in large concrete structures located a few hundred feet apart. The initial design for the cooling system called for a constant supply of water to be running through the reactors at all times, this brought up numerous issues with the largest being what would happen if that constant water supply system failed. This would result in the temperatures within the reactors rising at extreme rates and in turn resulting in a catastrophic failure, think Chernobyl. At an alternate location, this issue was dealt with by having a 30-mile road that was provided for the evacuation of the area in case the cooling systems failed; this was not possible at the Windscale location so they had to go with a different cooling system. Instead they decided to go with an air convection based coolant system, which was able to cool the reactors in both Windscale Piles at normal operating conditions.
Early in October in 1957 an operator at Pile 1 realized that the main reactor was heating up more than usual and essentially thought nothing of it but called for a Wigner release. During the Wigner process the temperatures began to fall within the reactor except for in channel 2053 whose temperatures actually started to rise. The next day another Wigner release was ordered and this time all channels heated up evenly which indicated that the process worked to control the reactor. Early on the morning of October 10th operators were suspicious that something unusual was taking place within Pile 1, the events that took place next would confirm their theories. As they preformed another Wigner process, they noticed that they entire core was rising rather than falling and eventually reached over 400ºC. In reaction to this the crew sped up the cooling fans while also increasing airflow to the core of the reactor in order to attempt to cool down the rising temperatures. Once they did this, the radiation detectors within the chimney had detected a release of radiation but the crew assumed that this was just an internal cartridge burst, which at the time was no issue as it has happened in the past. Little to the crews knowledge though, the cartridge actually had caught on fire in channel 2053 which would explain why it was the only channel heating up during the first Wigner process on October 7th.
While the crew thought they were helping the problem by speeding up the fans and increasing airflow, the exact opposite was happening. The increased oxygen that was being fed into the heart of the fire actually ended up spreading the flames into the surrounding fuel channels causing the temperature within the reactor to continue to rise. Once this was known, the operators then were convinced that there was a fire within the reactor itself which enticed Tom Hughes, second in command at the time, to take a closer look into the situation.
“An inspection plug was taken out,” said Tom Hughes in a later interview, “and we saw, to our complete horror, four channels of fuel glowing bright cherry red.”
Now there was no doubt in the minds of the crew on site, the reactor was on fire and it had been for at least 48 hours up to this point. The first response to attempt to battle the fire within was to blow it out using the fans, but once again this only fed into the flames. The next method that was used to extinguish the fire was by using carbon dioxide. They decided to drop 25 tons of liquid carbon dioxide directly on the fire but the fire was so hot that the carbon dioxide had no oxygen to adhere to; they simply just did not have enough carbon dioxide in order to put the blaze out. On October 11th the fire reached maximum temperatures of 1,300ºC and the crew was running out of options as the biological shield around the reactor was in danger of collapsing. The next thought was to use water but the threat posed with this option was that if the molten metal oxidized when the water hit it and striped the oxygen from the water molecules, this would only leave hydrogen within the blaze which, combined with incoming air, could have resulted in an explosion. Faced with a lack of other options they decided to go ahead with this plan. They hauled in 12 fire hoses in order to tame the fire but it proved to be ineffective as the fire continued to rage on within the reactor. The crew was down to their last option, turn the air off completely, the theory was that if there was no abundance of oxygen feeding the flames, it would eventually go out on its own as it ran out of fuel as the Fire Chief on site noticed the fire was sucking in air through the top of the chimney. This worked exactly as he predicted, first the flames subsided and eventually went out in a low burning red ember within the reactor. After the flames died down, water was ran through the reactor for 24 hours straight until the entire structure was cooled down. The reactor tank has been sealed ever since the accident took place as it still contains 15 tons of uranium fuel still left in it, they believed that if it was disturbed it could reignite due to the presence of pyrophoric uranium hydride that was built up during their attempt at putting the fire out with water. The pile is not scheduled for final decompressing until 2037.
The fire released an estimated 740 TBq of Iodine-131, 22 TBq of Caesium-137 and 12,000 TBq of Xenon-133 into the atmosphere that eventually spread across the U.K. and Europe. This was essentially nothing compared to the releases at Chernobyl or Fukushima, as the spread of radioactive material is comparable to that of Three Mile Islands. Experts say that this can be contributed to the presence of chimney scrubbers at the Windscale Plant, which were able to reduce the radioactive content within the smoke that was being released into the atmosphere.
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