Can we have a radioactive release without a panic?

Figure 1. Windscale towers. Calder Hall in the background

After World War II, the British were desperate to get the bomb. They needed weapons grade plutonium. But the Special Relationship with the USA did not include sharing secrets on plutonium production. They were on their own. What they came up with was two enormous, klutzy piles of graphite in northwest England at a place called Windscale. Cartridges containing uranium were pushed into holes in the graphite on one side, pushing the irradiated cartridge already in the hole out the other. The reactors were air cooled. The poorly designed facility experienced continuing problems, stuck and broken cartridges, unexplained temperature excursions, and sporadic leaks.

The graphite was used to slow the neutrons down to create a self-sustaining chain reaction. Unfortunately, the British knew very little about the behavior of graphite under radiation. Under the right conditions, irradiated graphite can store energy, which if not released properly can start a fire. Releasing this energy requires annealing, which is done by increasing the reactor temperature.

On October 8, 1957, Windscale 1 caught fire during an attempted anneal. The fire destroyed the reactor. Radioactive material spewed out of the 410 foot high cooling stack, and spread out over the Cumbrian countryside.

The man most responsible for putting out the fire was Tom Tuohy. In the process, he intentionally exposed himself to large amounts of radiation multiple times. Predictably, top management in the British weapons program attempted to blame the fire on operator error. Tuohy called them "a shower of bastards." The man had a way with words. Tom Tuohy died at age 90. RIP.

In a nuclear power plant release almost all the harm to the public is caused by the four isotopes shown in Table 1. Te-132 decays to iodine-132 with a half-life of 3.2 days. I-132 decays quickly (half-life = 2.3 hours). So it really comes down to cesium and iodine. The concern with iodine is it concentrates in the tiny thyroid gland, multiplying dose rates to that organ by up to a factor of 1000.

Table 1 compares the amounts released at Windscale with those at Three Mile Island. At TMI, almost all the iodine and cesium stayed dissolved in water within the containment. And the gases that were vented passed through a high performance filter. Based on iodine, if we had to put a number on it, we might say the Windscale release was 1500 to 3000 times worse than TMI. For an SNTer, harm goes very roughly as dose rate squared. Using this metric, Windscale was more than a million times more harmful.

Table 1. Four main isotopes at four big releases.

What's interesting about Windscale is the response. Or really the non-response. There was no evacuation, voluntary or involuntary. Plant management was active in the community, had developed good relationships with local officials, and kept them closely informed throughout. Importantly, milk produced in the neighboring area (about 500 square kilometers) was condemned and the farmers compensated.¹ This lasted about six weeks. The auxiliary buildings at Windscale continued to be occupied and operate. Construction on the neighboring Calder Hall site was shut down for a day. Windscale, now called Sellafield, continues to be a center of British nuclear power activity. It is possible to have a release without a panic.

Since radioiodine dominated the release, if we were going to have any effect, it would show up as thyroid cancer in people who were young at the time of the release. McNally et al found a slightly increased thyroid cancer incidence among Cumbrians who were less than 20 at the time, relative to the rest of England.² But they found essentially the same increase in Cumbrians who were born between 1959 and 1963, who had no exposure to the Windscale release. They also found considerable clustering. When the clustering was allowed for, none of the differences were statistically significant.

1. The milk could have been turned into cheese or butter and stored for a month or two, to allow the iodine to disappear. This was considered and rejected on PR grounds.\cite{arnold-1992}

2. McNally, R. and Wakeford, R. and James, P. A Geographical study of thyroid cancer incidence in north-west England following the Windscale nuclear reactor fire of 1957, Journal of Radiological Protection, 2016 , Vol 36, No 4.