The facts that Windscale Pile No. 1 was able to achieve criticality and maintain it could give one with a religious bent the belief that God was on the side of the United Kingdom. Or, perhaps the Devil was. Driving it was like trying to steer the RMS Titanic around an iceberg. The core was so big, the peak of the neutron flux curve could be put just about anywhere in the massive block of graphite by artistic positioning of the controls, but it was ponderously slow to respond to control movements, and the instrumentation was a bit numb. The pile would not do anything quickly, and the dangers of a sudden runaway or an explosion were nonexistent.
An hour after the beginning of Tuesday, October 8, the pile seemed to be running cool, reading between 50° and 80 °C in the graphite. One thermocouple indicated 210 °C, and this was obviously where the annealing process had begun. An anneal would always start somewhere and then spread out slowly, hopefully infecting the entire pile. The operators ran in the controls to shut it down, letting it cook, and sat back to watch it happen. For some odd reason, two uranium thermocouples read 250 °C. Uranium does not anneal; only graphite. Ian Robertson, the pile physicist on duty, had the flu, and he went home to collapse in bed at 2:00 a.m. The anneal seemed well in hand by the operating crew.
Robertson came back on duty at 9:00 the next morning, sick as a dog, to find that the temperature was not spreading the way it was supposed to, and the operators had decided to reheat the reactor by bringing it back to criticality. In a couple of hours they had it back running at low power, but something was not right. One uranium thermocouple showed a sudden temperature rise to 380 °C. What’s that all about? This type of reactor was run by the graphite temperature and not necessarily by the neutron counts, and it was meandering all over the place, from 328° to 336 °C. Pile No. 1 had its own quirks, but meandering was not one of them. Something was amiss, but the annealing had to proceed. The fission process was shut down again at 7:25 P.M. Robertson was starting to get woozy, and the operating crew insisted that he go home.
By Wednesday morning, things seemed to have calmed down. The crew shut the inspection ports atop the core and turned on the shutdown fans to give it some air and bring the wayward temperatures down. At about midnight, the temperature readings off the graphite thermocouples started to go wild.
It was now early Thursday morning. One thermocouple in the middle of hole 20–53, 20 rows up from the bottom and 53 across, was reading extremely high at 400 °C. Air dampers were opened. In 15 minutes the temperature rose to 412 °C. It did not make sense. At 5:10 a.m. the dampers were opened again, and this time the smokestack radiation monitor indicated a bit of radioactivity in the filter. At about the same time, the stack on Windscale Pile No. 2, which was running plutonium production at balls-to-the-wall power, indicated increased radioactivity. Obviously a fuel cartridge had burst in No. 2. They really should do something about that.
Attempts to bring the annealing under control continued. Air dampers were opened and closed again, with no expected results. By 1:30 P.M., the stack radiation was unusually high, and it was clear that there was a problem. The uranium temperature was at 420 °C and rising quickly. The Pile Manager, Ron Gausden, was called in. He gave instructions to open the dampers, turn on the shutdown fans, and try to bring down this temperature. Obviously, a fuel cartridge had broken open and fission products were collecting in the stack filter. The Christmas trees, which were parked off to the side at the back of the core, would not work with the pile at this elevated temperature, so they could not identify the broken cartridge. The temperatures were not going down, and at 2:30 P.M. Gausden told the operators to turn on the main blowers. He picked up the phone to call Tom Hughes and share the excitement.
The Windscale operation was critically understaffed, particularly for this running emergency to produce bomb material. Of the 784 professional posts, 52 were vacant. Hughes had worked at Windscale since 1951 as the Assistant Works Manager in charge of the chemical group. He was also Acting Works Manager for the entire site and had just been assigned a third post as Works Manager for the pile group. His response to the call from Gausden would mark his first visit to an actual pile.
Huw Howells, the Health Physics Manager, was already there to inquire about radiation coming out of the stack. With a short rundown of the situation in the control room, Hughes and Howells decided to call H. Gethin Davey, the Works General Manager with bad news about Pile No. 1. A crew from the control room rode the lift to the refueling platform and pressed the UP button to take them to row 20 on the loading face and have a peek behind plug 53.[127]
The loading face was a bio-shield, built to protect workers who could stand there and push fuel into the graphite pile behind the shield with long poles. When not in use, each hole was plugged with a metal cylinder. A worker pulled out the plug in 20–53 and looked in the hole. Normally, it would take a flashlight to illumine the black-as-carbon fuel channels to see what was inside, but in this case a bright red glare greeted them. All five holes behind the plug were glowing.
The pile was on fire, and it had been burning since Tuesday. Windscale Pile No. 1, running too fast in the dark, had crashed into its iceberg.
Gausden ordered the crew to make a firebreak by removing all the fuel around the burning channels. Easier said than done. Even some fuel cartridges that were not on fire were so swollen from the high temperature, they would not budge. The men dressed out in rubber suits, full-mask respirators, gloves, and dosimeters to monitor their radiation exposures. It was going to be a long night. They started dumping fuel into the cooling pool in back of the core, pushing it out with the heavy rods. It was hot, difficult work, but the main blowers put positive air pressure behind the loading face, and clean, cool air blew out the loading holes and onto the men. The airflow was all that made the work possible.
The graphite on the front of the pile below where the men were ejecting fuel was now a mass of flames, and the highest temperature reading had passed 1,200 °C. At 5:00 P.M. on Thursday, Davey picked up his phone and rang his deputy, Tom Tuohy. “Come at once,” he said. “Pile No. 1 is on fire.”
Tuohy was at home caring for his wife and children, who were all down with the flu, and when he got off the phone he instructed them to please keep all the windows closed and not to leave the house.
Tom Tuohy, excitable, bubbly, and auburn-haired, was born at the eastern end of Hadrian’s Wall in northern England in a town named Wallsend in 1917. He studied chemistry at Reading University, worked for the Royal Ordnance Corps during the war, and had joined the nuclear effort in 1946. He arrived at the stricken pile in minutes and went straight to the loading face. He saw men struggling to punch the fuel out the back of the pile and got a grim impression of the situation. They were pulling back rods that were glowing yellow on the ends and dripping molten uranium. Back in Davey’s office he found a knot of scientists arguing over using carbon dioxide or argon to quench the fire. By 7:00 P.M. he decided to get a better look. He took the stairs to the crane room and lifted an inspection plate so he could see the front of the reactor. It was glowing. He went back at 8:00 P.M. and found flames shooting from the fuel channels, colored yellow by the sodium in the construction workers’ sweaty handprints on the graphite blocks. At 11:30 he pried up the viewing port, which was becoming quite warm, and saw blue flames hitting the concrete wall many feet behind the back of the pile, and a new fear gripped him. The flames were hot enough to ionize the nitrogen in the air. Not only could the hot flames burn through the concrete wall, but he was not certain about the floor under him staying put much longer.
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An interesting bit of trivia from B. J. Marsden of the Nuclear Graphite Research Group at the University of Manchester: the refueling platforms at the Windscale reactors, called “charging hoists,” were airplane elevators salvaged from WWII aircraft carriers.