Three Mile Island's recent fourth anniversary was an occasion to rehash what many commentators call the worst nuclear-reactor accident on record in the Western world. They picked the wrong accident and the wrong anniversary.
They forget the fire in one of two military reactors at Britain's Windscale plutonium facility in 1957. Three Mile Island (TMI) resulted in no public danger. The Windscale fire spread dangerous radioactive material over Britain to an extent that only now is beginning to be appreciated.
The lesson of TMI was that lax management, inadequate regulation, and poor operator training were a potential danger within the civilian nuclear power system of the United States. The lesson now emerging from the Windscale incident is the danger of excessive military secrecy that hides vital information from regulators responsible for public safety.
As far as TMI is concerned, both the presidential commission chaired by John G. Kemeny and the Nuclear Regulatory Commission's panel found there was no significant radioactive contamination. The only radioactive materials released were chemically inert gases. These quickly dispersed. They could not be absorbed by plants, humans, or other animals. There was no danger of a meltdown. Even had this occurred, the plant's foundation would have contained the fuel, allowing it to resolidify without contaminating the environment. There was no danger of a hydrogen explosion. Although hydrogen did accumulate at the top of the reactor vessel, its presence inhibited release of oxygen, which is needed for hydrogen to burn or explode.
In short, TMI dramatized important management and regulatory shortcomings, but presented no public danger. The Windscale fire was quite different. It released radioactive iodine, which accumulates in human thyroid glands. It now appears that other dangerous radioactive material - polonium - also was released.
Radio-iodine contamination was admitted at the time, although its threat was minimized by officials. Milk from cows grazing over some 500 square kilometers in the vicinity of Windscale was destroyed. This was officially represented as erring on the cautious side. However, Britain's National Radiological Protection Board (NRPB) now disagrees.