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History Repeats itself - Seawater was used to put out fires at worlds first Nuclear Power Station CALDER HALL.

 
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03/15/2011 09:25 PM
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History Repeats itself - Seawater was used to put out fires at worlds first Nuclear Power Station CALDER HALL.
Posting the below as I've not seen anyone point to the parallels of the fire at the worlds first commercial Atomic power plant at the Windscale Atomic Works in Cumbrian, England.

Obviously the tech was completely different at the Windscale plant in 1957, but seawater was used in a last ditch attempt to put out fires and cool the reactor

The German Bremen University confirmed that radioactive contamination by Americium-241 found in some soil samples taken by Greenpeace 11.5 km south of Sellafield, were 400 times higher than those taken 11 km from Chernobyl. 51 years on, the villagers of Seascale still live with the ramifications of the accident at Pile 1 of the Windscale Works Atomic Energy Factory.

[link to en.m.wikipedia.org]


There was no doubt that the reactor was now on fire, and had been for almost 48 hours. Reactor Manager Tom Tuohy[4] donned full protective equipment and breathing apparatus and scaled the 80 feet to the top of the reactor building, where he stood atop the reactor lid to examine the rear of the reactor, the discharge face. Here he reported a dull red luminescence visible, lighting up the void between the back of the reactor and the rear containment. Red hot fuel cartridges were glowing in the fuel channels on the discharge face. He returned to the reactor upper containment several times throughout the incident, at the height of which a fierce conflagration was raging from the discharge face and playing on the back of the reinforced concrete containment—concrete whose specifications required that it be kept below a certain temperature to prevent its disintegration and collapse.[5]

Initial fire fighting attempts

Operators were unsure what to do about the fire. First, they tried to blow the flames out by putting the blowers onto full power and increasing the cooling, but this fanned the flames. Tom Hughes and his colleague had already created a fire break by ejecting some undamaged fuel cartridges from around the blaze and Tom Tuohy suggested trying to eject some from the heart of the fire, by bludgeoning them through the reactor and into the cooling pond behind it with scaffolding poles. This proved impossible and the fuel rods refused to budge, no matter how much force was applied. The poles were withdrawn with their ends red hot and, once, a pole was returned red hot and dripping with molten metal. Hughes knew this had to be molten irradiated uranium and this caused serious radiation problems on the charge hoist itself.

"It [the exposed fuel channel] was white hot," said Hughes' colleague on the charge hoist with him, "it was just white hot. Nobody, I mean, nobody, can believe how hot it could possibly be."

Carbon dioxide

Next, the operators tried to extinguish the fire using carbon dioxide. The new gas-cooled Calder Hall reactors on the site had just received a delivery of 25 tonnes of liquid carbon dioxide and this was rigged up to the charge face of Windscale Pile 1, but there were problems getting it to the fire in useful quantities. The fire was so hot that it stripped the oxygen from what carbon dioxide could be applied.

"So we got this rigged up," Hughes recounted, "and we had this poor little tube of carbon dioxide and I had absolutely no hope it was going to work."

The use of water

On the morning of Friday 11 October, when the fire was at its worst, eleven tons of uranium were ablaze. Temperatures were becoming extreme (one thermocouple registered 1,300°C) 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. Faced with a lack of other options, the operators decided to go ahead with the plan. About a dozen hoses were hauled to the charge face of the reactor; their nozzles were cut off and the lines themselves connected to scaffolding poles and fed into fuel channels about a metre above the heart of the fire.

Tom Tuohy then ordered everyone out of the reactor building except himself and the Fire Chief. All cooling and ventilating air entering the reactor was shut off. Tuohy once again hauled himself atop the reactor shielding and ordered the water to be turned on, listening carefully at the inspection holes for any sign of a hydrogen reaction as the pressure was increased. Tuohy climbed up several times and reported watching the flames leaping from the discharge face slowly dying away. During one of the inspections, he found that the inspection plates—which were removed with a metal hook to facilitate viewing of the discharge face of the core—were stuck fast. This, he reported, was due to the fire trying to suck air in from wherever it could.

"I have no doubt it was even sucking air in through the chimney at this point to try and maintain itself," he remarked in an interview.

Finally he managed to pull the inspection plate away and was greeted with the sight of the fire dying away.

"First the flames went, then the flames reduced and the glow began to die down," he described, "I went up to check several times until I was satisfied that the fire was out. I did stand to one side, sort of hopefully," he went on to say, "but if you're staring straight at the core of a shut down reactor you're going to get quite a bit of radiation."

Water was kept flowing through the pile for a further 24 hours until it was completely cold.

The reactor tank itself has remained sealed since the accident and still contains about 15 tonnes of uranium fuel - which, due to the presence of pyrophoric uranium hydride formed in the original water dousing, could still reignite if disturbed. "Nobody has touched it for almost 50 years because of a fear that it could either catch fire again or go critical and explode."[6] The pile is not scheduled for final decommissioning until 2037.

Further witness testimony from workers at Windscale.

[link to www.no2nuclearpower.org.uk]





GLP