Recounting the Windscale Story

The Blog, Histories of Things to Come, includes a post titled Nuclear Leaks 8, Sellafield, aka Windscale. The Nuclear Leaks part of the post title is the give away that the blog is not exactly cheer leading for nuclear power, but there is a good deal to learn here. Most of the story is told through links to a BBC documentary on the Windscale reactor fire. The BBC narrative fingers politicians, in particular British Prime Minister Harold MacMillan as playing a major causal role in the Windscale fire, by pressuring Windscale leadership to go beyond what was safe in reactor operations.

The original Windscale reactors were modeled after the ORNL graphite reactor, the world's first reactor designed to produce plutonium. The graphite reactor was low enough powered to be directly air cooled. That is air was physically blown through the reactor to remove heat. The Graphite reactor operated with natural uranium because enriched uranium was not available at the time it was built. With the uranium spread out through the graphite blocks in the reactor core, a chain reaction could be maintained. The British decided that the Graphite Reactor was safer than the water cooled Hanford Reactors. They wanted to produce nuclear bombs, so they decided to build Plutonium production reactors, using the reliable graphite pile approach.

The two Windscale reactors can be described as primitive. While the leaders of the American reactor building group at the University of Chicago, and in particular Eugene Wigner, had a very good theoretical understanding of what was happening inside a reactor, the British scientists who worked on the Windscale design seem to have been particularly remiss in the failure to appreciate the safety problems associated with this type of reactor. The British scientists had learned from the Americans that when bombarded by neutrons, relatively cool graphite could store a form of energy related to changes in its crystal structure. This energy, discovered by Eugene Wigner, and called Wigner energy, could be released by an increase in heat. The release of Wigner energy increased the heat contained in the nuclear core. In a large reactor the heat release could in turn trigger more Wigner energy releases in the core graphite, thus producing a sudden cascade of core heating.

The air cooled graphite piles operated at low temperatures - under 200 degrees Centigrade. Wigner energy could be released by increasing pile heat to over 250 degrees Centigrade.

Wigner also discovered Xenon-135 poisoning, which creates problems for reactor control. Xenon-135 related control problems can lead to uneven reactor heating and to overheating in some reactor areas. Xenon-135 atoms can put a break on chain reactions if present in large enough numbers in a reactor core. Increased power levels can in turn burn off Xenon and this can lead to a sudden surge in power output.

A further problem relates to the effect of heat on the Windscale fuel capsules. The Windscale reactor was fueled by metallic uranium, encapsulated in aluminum. Uranium swells when exposed to radiation or increased heat. That swelling in turn can burst the aluminum sheathing of the fuel capsule.

Metallic uranium is a pyrophoric substance. However uranium is more likely to burn if it has been powdered or shaved first. Lithium burns spontaneously if heated to about 356°F (180°C), and if Lithium is present in the core of an air cooled reactor it would be a huge fire hazard, especially in the presence of heating to release Wigner energy. If a core was heated to facilitate Wigner energy release, and a lithium containing capsule burst in it, the fire danger would be significant. The Windscale reactor cores housed capsules which contained both lithium and magnesium. Magnesium will not ignite in ordinary air, but it will catch on fire in heated air and of course a lithium fire will heat the air. The Penney Commission on the Windscale fire considered it possible that lithium initiated the fire, but appeared to consider uranium oxidation a more likely suspect. In their investigation of the Windscale fire, the Penney Commission found that capsules had burst by uranium expansion caused by radiation and heat. The expansion forced the aluminum top off the fuel capsule. Once the cap was removed the uranium top would be exposed to O2 in the air and would have begun to oxidize.

The Penney Commission did not focus on the oxidation of Windscale Unit 1 graphite during the October 1957 incident, although it gave a great deal of attention to the presumed release of Wigner energy from that graphite. Thus the Penney Commission was not in a position to determine the role of graphite fire in the Windscale accident.

Fred Pearce in The New Scientist asked,

What had gone wrong?

And answered,

the pile became too hot, cans of uranium split, the exposed uranium oxidized, releasing more heat, and eventually the graphite caught fire.

This is the classic graphite fire story. The story that has not been told in every recounting of the Windscale fire story. Where did the graphite fire come from? The New Scientist appears to have relentlessly pushed the graphite fire story, includes a 1982 account of a visit by Edward Teller to Harwell in 1948, Upon learning that the British were planning to build a graphite reactor, Teller is alleged to have warned British scientists of the dangers of graphite fires. Teller's warning was part of a standard account of the Windscale fire. No one has produced a contemporary account of Teller's Harwell visit, and the texts of the story are not sure whether or not Teller specifically mentioned a graphite fire, and indeed the operation of human memory as such, that Teller who was concerned about nuclear safety issues in general, did not warn of a reactor fire, but graphite popped into someones memory of the Teller warning after the Windscale event.

Remote inspections of the interior of the Windscale reactor do not demonstrate extensive evidence of graphite burning. The link is too a set of presentation graphics for the Windscale Piles Decommissioning Project. These graphics contain pictures of both damaged and undamaged fuel channels in Windscale Pile 1. Pictures of undamaged fuel capsule, fire damaged cartridges, all show graphite fuel channels which appear to be in good shape. Some oxidation may have taken place in the Pile 1 graphite, but the overall density loss of Pile 1 graphite is similar to the density loss of Pile 2 graphite. Thus conditions inside the reactor offers little evidence that a graphite fire took place, and indeed the fire damage to fuel capsules, suggest that they, and not the core graphite were the cause of the core fire.

The capsules containing lithium and magnesium were intended to produce tritium to be used in the British H bomb program. The decision to use the Windscale reactors for tritium production should have been vetoed for safety purposes. It wasn't. The British nuclear science community was shockingly unconcerned about nuclear safety issues. Not only was the community willing to allow the operation of reactors with unsafe materials in their cores, but they had no safety plans in the event of a major reactor accident.

On October 7, 1957 the Windscale staff began the annealing process expected to prevent the buildup of Wigner energy in Windscale Unit 1. The lithium-magnesium capsules were allowed to remain in the core during the annealing process the reactor despite the hazard they posed. The fans blowing cooling air into the core were turned down as was the reactor power. It was assumed that by decreasing cooling, the core temperature would rise to 250 degrees, enough to trigger a Wigner release. Once the Wigner release was assumed to have begun, the reactor was shut down. But the core heat was believed to drop off too quickly, evidence that the Wigner process had not been successful. At that point the Windscale staff decided to reheat the reactor. The second heating is believed to have some how triggered the fire.

It should not be said, however that the cause of the Windscale fire will never be known, because it would be possible to model the circumstances that gave rise to the fire, and test likely causes. At any rate the fire began to spread through the core as the aluminum sheathing of fuel capsules began to melt exposing more and more uranium to fire heated air. Aluminum is a class 4 flammable solid, and soon the molten aluminum began to add to the conflagration. It was only a matter of time before the fire was to spread to the uranium fuel.

The Windscale staff noted a rise in core temperature after the second attempt to accomplish a Wigner energy release, they tried to use passive cooling by opening core dampers, but the temperature continued to rise. Radioactive materials were observed flowing out the chimney stack.

At this point I will take a break for the day. There is a lot more to the story, and the story should be told. So look for more in the coming days.

Did the Graphite in the Windscape Reactor Burn?

It is not entirely clear what happened in the Windscale reactor fire. The Windscale reactor has not yet been entirely dismantled, so how much damaged was done to its core graphite is still open to question. There is little doubt that metals in the core - Aluminum and Uranium - burned. The hastily prepared 1957 Penney report stated that the Windscale core graphite caught fire, but did it? When The UK Nuclear Safety Advisory Committee (NuSAC) meet in 2009 to examine evidence from the Windscale reactor, it found,

• Inspections have shown that there was NOT a graphite fire: damage to graphite, caused by severely overheated fuel assemblies, was localised.

The NuSAC report added,

Some members of NuSAC may be aware that recent attempts to burn GLEEP graphite (block form) in a high temperature incinerator succeeded only in making it hot.

The findings also stated,

There is evidence in the literature that under certain extreme conditions reactor graphite dust can be made to explode. The Pile 1 project has completed research at
ANNEX A Leeds University which has concluded that although the conditions can be recreated in the laboratory they will not exist in the reactor and the dust explosion hazard can be discounted. As an added precaution the production of fine dusts during dismantling operations will be closely controlled.

It would appear then the NuSAC's findings are completely in support of the General Atomics position that Nuclear Graphite does not burn.

Given these facts the assertion that there was a core graphite fire at Chernobyl ought also to be revisited.

On the History of Nuclear Safety

One of the follies of my youth was to spend a couple of years being trained as a Historian of Ideas. This gives me an unusual perspective as a nuclear blogger. I had a couple of guest posts on Harry's Place last year. In my second post, I discussed the positive secondary benefits of using nuclear power as an energy source. My post attracted an inordinate number of anti-nuclear responses. One of my most vociferous critics was an English woman who was chemist.

My Harry's place critic focused on a number of events in the history of the British nuclear adventure. It is clear that everyone who was doing nuclear science in the 1950's cut corners, and covered up problems, and no one more so than the British. The Windscale fire was a major nuclear accident, and the British covered up quite a lot of the problems. My critic however, chose to attribute to something she called "the nuclear industry" all of the characteristics, of what was a quasi-military nuclear production establishment of the cold war 1950's.

My father did some research on the Windscale accident, because he was researching the movement of radioisotopes in the environment after a nuclear accident. Lots of radioisotopes had escaped into the environment because of Windscale, so Windscale was high on nuclear safety researchers interest list in the early 1960's. Several things about the Windscale reactors, and the 1957 Windscale fire. First the design if the Windscale piles was primitive by American standards. They were graphite piles designed to produce bomb grade plutonium. unlike the Hanford Reactors, which were water cooled, the Windscale reactors were air cooled. The X-10 reactor was the only American air cooled graphite reactor. Eugene Wigner had rejected the use of air or gas cooling in the Hanford reactors. The British did not have a Wigner, and ended up up with an unsafe reactor design.  In addition to being badly designed, the Windscale reactors were poorly instrumented, and the British were having increasing problems managing the reactors graphite moderator.  Those problems had significant safety implications, which the British failed to identify and analyze.

Thus the history of the Windscale fire must include questions about why the British had in the late 1940's chosen a production reactor design that was already considered obsolete in the United States by the time it went into operation, and why they chose to manage it the way they did.  The combination of the reactor design and the management style adopted by the British made an accident in the Windscale reactors quite probable.  Of course there was a coverup because culpability for the accident ran to the top of the British Government and military.   

The history of nuclear safety is both a history of ideas and a socio-political history. The two are intertwined. My British critic on Harry's Place, however, took an ahistorical viewpoint. She refused to place the Windscale reactor fire into the historic context of the British states management of cold war related technology.  It was her view that if something was true of nuclear technology at one time, in one place, it was true everywhere and always. Thus what was characteristic of the Windscale reactors was true of every reactor. And the management of the consequences of the Windscale fire by the British government is characteristic of all aspects of nuclear safety at any time and in any place.

Ahistoric views of the development of any technology are profoundly unsophisticated. Technologies evolve in socio-economic and historical contexts, and attitudes towards technological issues like safety, are in no small measure related to the context in which the technology evolves.  Knowledge evolves and with that evolution comes a greater appreciation for risk and understanding of methods of controlling risk,.  As knowledge evolves it can begin to change the social and political context, thus altering public attitudes and beliefs.  

A historian would, of course, note changes in attitude toward nuclear safety, developing research, on safety, the introduction of new safety concepts, conflicts within the research community, and conflicts over safety involving scientists, interest groups, self styled experts, research funders, policy makers, and policy implementation establishments. Partisans in a conflict might well take a less nuanced view. My British critic from Harry's Place surely took and extremely unsophisticated view that reduced the history of nuclear safety to a simple narrative of good verses evil, With "the nuclear industry" embodying evil, and the critic fantasizing herself to be a warrior on the side of good. This fantasy has characterized the anti-nuclear movement since the 1970's. At its heart then the anti-nuclear movement, to the extent it rejects a historical view of nuclear safety, is wedded to a fantasy politics of identity.

I have pointed out in Nuclear Green, that nuclear critic Ralph Nader's sister Claire had a professional association with with Alvin Weinberg and had discussed nuclear safety issues with Weinberg. Claire Nader undoubtedly passed on the substance of her discussions with Weinberg to her brother, who was later to talk directly with Weinberg about safety issues. The Nader's were both treated with respect by Weinberg. In turn Ralph Nader should hsve known of Weinberg's expertise both on reactor design and on nuclear safety issues. Nader also know of Weinberg's struggle with Chet Hollifeld and Milton Shaw. Thus Nader had no reason to doubt Weinberg commitment to nuclear safety. Nader could have undoubtedly used Weinberg's knowledge in a fight for nuclear safety. Instead Nader made hiscause the fight against nuclear power.

Nader posed for the public as a good little guy, who fought against evil incarnate, represented by such evil forces as "the nuclear industry". Unfortunately this absurd story was bought be an increasingly simple minded media, that wanted to interpret every story for the public as a matter of good verses evil.  Good verses evil was easy to sell to ther public, and drew eyes and ears to the media that told the stories.   Stories with shades of gray were complicated. They required a lot of thinking and a lot of information.  Thinking and information lost readers and viewers. In order to understand the history of nuclear safety in America, we must understand the increasing incompetence and corruption of what past for the mainstream news media during the last third of the 20th century.

There were some bad actors in the nuclear safety story, and Ralph Nader turned out to be one of them. The television networks, and the press were simply too lazy to get the whole story, so the media was content to sell the Saint Ralph line.

Nader tells stories about himself, in which he claims to be a saint of knowledge.  For example, Nader claims that in 1964 he attended a conference at the Oak Ridge National Laboratory. Over lunch Nader claims that he began asking nuclear engineers some questions. "They couldn't answer them, or the answers weren't satisfactory," Nader claims. "'What could happen if a system goes wrong?' Nader asked. They avoided any such descriptions or said, 'we've got defense in depth' -- and other jargon."  "Defense in Depth" is of course an effective operational concept, that was proven to be effective at Three Mile Island.  By describing a discussion of things things that he did not understand as jargon, Nader revealed his lack of understanding of nuclear safety.   As Gomer Pile  use to say, "surprise, surprise surprise."  There were of course, other people at ORNL who could have the answered Nader's 1964 questions,  or at least would have known the answers within the state of knowledge. If Ralph Nader wanted people who could answer his questions about what could go wrong in reactors and under what conditions, he could have talked tp George Parker, or he could have talked to my father. Needless to say, Nader did not seek out nuclear safety experts to answers to his questions. Certainly Alvin Weinberg would and could have answered Nader's questions about nuclear safety, and made himself available to Ralph and his sister Claire. It is quite possible that Nader talked to someone in Oak Ridge who did not answer his question, or alternatively gave Nader an answer that Nader did not understand.  Had Nader sought out answers about nuclear safety in 1964, he would have found them, but Nader wanted answers that made nuclear scientist look bad, not in truth.

Nader was not interested in truth, he was looking for witnesses for his drama which would feature Saint Ralph fighnting an evil dragon "the nuclear Industry." People, like Alvin Weinberg, George Parker, and my father were much to dangerous to rely on as witnesses.  George Parker might start talking about how improbable it would be for most radioisotopes to escape from Light Water Reactors. My father might have started talking about how coal fired power plants and natural gas furnaces were delivering more radioisotopes to the environment than reactors were. Such people might blow Nader's cover, night reveal that Nader was only concerned about radiation coming from reactors. If natural gas delivered radioactive gases to American homes, the Saint Ralph and the nuclear dragon drama might fall apart. People might start asking why does Saint Ralph ignore the Natural Gas Dragon, that is brining radioactive gas to the lungs of so many Americans. If people knew that Alvin Weinberg had been fired over nuclear safety, he might steal attention from Saint Ralph. Weinberg was so dangerous to Nader's because he actually understood reactors, and safety, and his integrity was unquestionable unlike Saint Ralph's. Thus Nader's account of the history of nuclear safety, is self serving and dishonest.

Thus in the case of my British Harry's Place critic, the history of nuclear safety was something to be ignored. Nuclear power is a manifestation of something called "the nuclear industry", an evil despicable entity that transends time and space. "The Nuclear Industry" is always and everywhere the same, thus it cannot evolve, it cannot change, and has no history.  Thus it is impossible to speak of something called the history of nuclear safety.

For Ralph Nader the history of nuclear safety exists to promote his own reputation. Nader has maintained for over a generation that reactors are always and everywhere unsafe. Thus Nader also  believes in a mythic "nuclear industry" which also exists outside of time and space. There is for Nader a history of nuclear safety, which is his account of his own struggle to slay the nuclear dragon.