Friday, June 09, 2006

A bad week for Nuclear!

Sellafield looks set to face an unlimited fine over a major leak of radioactive material, after pleading guilty to to breaches in safety regulations. A broken pipe was discovered at the Thermal Oxide Reprocessing Plant (THORP) last year which had allowed a solution containing 20 tons of uranium and 350 pounds of plutonium in concentrated nitric acid to leak out over a period of about nine months. It was said at the time that the volume was equal to that of an Olympic sized swimming pool. No wonder the public gets nervous when such stories hit the press - though not the headlines, as I recall. Apparently nobody had noticed this. British Nuclear Group (BNG) pleaded guilty, but Andrew Carr, speaking on its behalf, said that the leak presented no risk either to health and safety or to the environment. Since local magistrates could only fine BNG up to a maximum of £15,000 ($27,000), they referred the case to Carlisle Crown Court, where the case is to be heard on July 8. On account of the leak, THORP remains closed, which so far has cost BNG £50,000,000 in terms of its salary bill and in lost revenue, and the situation looks set to prevail for a good while longer than the three months originally predicted to retrieve the liquid waste and to repair the facility.
Sellafield is located in the charming county of Cumbria, also known as the Lake District, where I have often been on walking holidays. The original "atomic station" was opened by Her Majesty the Queen in the mid 1950's, and in 1957 there was a serious fire which spread radioactive contamination widely. I recall as a "radiation worker" in the 1980's that we had to wear a "film badge" which consisted of a plastic wrist-band on which was a clear layer of plastic under which could be seen a small quantity of sodium iodide crystals. The principle was that exposure to radiation would liberate iodine which could be determined by titration against sodium thiosulphate, so providing a measure of the level of radiation exposure. One man who worked at Windscale in 1957 contracted cancer in later years and went after Sellafield (after the name was changed) for compensation. There was a television programme on the subject, and I recall him saying that on entering a particular room "[his] badge went black" (from the iodine), so the amount of radiation he received must have been enormous. I don't recall the outcome, but I believe that he died before the case could be brought to a conclusion, as often seems to happen in such cases of compensation claim, due to the long mechanical windings of the legal process.
It would appear, however, that 49 years on parts of Cumbria are still affected by the radiation leaked from the Windscale fire, which peppered England and Wales with radioactive contamination, and left "hot-spots" over Cumbria. Although the incident pales by comparison with Chernobyl, it remains the west's worst nuclear accident, and was a greater threat to life than the partial melt down at Three Mile Island. In a relatively small upland area to the south east of the Windscale site, the vestiges of the 1957 incident contribute around 60% of the total caesium-137 that can be detected there; however, and interestingly, in the west of Cumbria it is caesium-137 from Chernobyl which remains dominant. In the east of the county, it is fallout from atmospheric nuclear tesing in the 1960's that is responsible for most of the caesium-137 now detected in the soil. Despite all of this, Cornwall notably is far more radioactive than is Cumbria, due to the high but natural level of radon which emanates from the granitic rock formed in the particular geology of that region.
Nuclear waste continues to be a thorny issue, as I suspect it will for some time, at least until pressures of other resources are such that we have too many other prevailing problems to bother about it too much any more. However, while we do continue to worry about it, security specialists have given a warning that the U.K. government is being a little tardy about securing our nuclear waste, which they claim, is vulnerable to terrorist attack, and the paper targets especially the liquid nuclear waste from the reprocessing operations at Sellafield. So, THORP is in the gunsights once again, it would seem. In addition to the uranium and plutonium "stored" at Sellafield, there is apparently about 40 times the amount of caesium-137 there as was released by Chernobyl. I guess that puts an element of scale on the matter, although the two things are not strictly comparable. Sellafield already has a no-fly zone overhead, and RAF fighters have instructions to "scramble" if an aircraft were to enter the zone. There are a score of other security measures emplaced, some introduced after the World trade Centre attack on 9/11 (2001), and the site is under armed guard, so I guess it is quite well protected in fact.
I have noted in previous postings my thoughts about exactly what language should be used to write an equivalent of "DANGER HIGH LEVEL NUCLEAR WASTE", so that that particular fact might instantly be recognised in say, 10,000 years from now, by when it is doubtful that modern English will be an understood language, except by scholars possibly. In 1993, the U.S. gathered a team of "experts": an anthropologist, an astronomer, an archeologist, an environmental designer, a linguist and a materials scientist, to decide upon the best design for the Waste Isolation Pilot Plant (WIPP) in New Mexico, a nuclear waste depository housed in a salt mine half a mile underground. The design was required to convey various messages, along the lines of: "this place was made by humans", "this place is repulsive and dangerous to us" and "this is a place of danger, the danger is to the body and can kill". The message was to be carried by various architectural artifacts, statues etc., with messages written in the current U.N. languages, leaving space for further tongues to be added as they developed, and current languages had been lost from memory.
The problem at Sellafield is on a smaller scale than this, and Ben Russell of Nirex (the U.K. company responsible for radioactive waste management) noted that in the 50's and 60's "...they really didn't know if the world would be around in the next generation, so passing on the information wasn't a priority. Now we have to concentrate on preserving our records for the next 10 generations and beyond."
Since any U.K. deep waste depository is not likely to be opened for another thirty years, I guess there is still time to find the right signs.


Anonymous said...

"Since any U.K. deep waste depository is not likely to be opened for another thirty years, I guess there is still time to find the right signs."

Either that, or destroy the material that requires long-term isolation. That can be done, and quite well in my opinion, with the right type of reactor.

Professor Chris Rhodes said...

A very good point - i.e. in a thorium reactor (of the right kind). Thus the material could be destroyed usefully in such a way as to provide energy - an additional bonus.

Anonymous said...

Yes, the particular reactor I had in mind would dissolve the transuranic wastes from Sellafield (such as Pu-239, Pu-240, Am-241) in a chloride salt to promote a very hard neutron spectrum. That would quickly destroy the transuranics through fission. The fission products generated would be highly radioactive, but would decay to background levels of radiation in ~300 years, unlike the tens of thousands of years required for transuranics to decay away.

The excess neutrons (beyond those needed to maintain criticality) would be captured in a "blanket" of thorium chloride and be used to transmute that thorium to uranium-233, which would then be used to "start" many liquid-fluoride thorium plants.

The reason for this arrangement is two-fold. Liquid-fluoride thorium reactors will have a thermal neutron spectrum, which is not very effective for destroying these transuranics (since they were formed in a thermal spectrum in the first place). Also, fluoride reactors can "break-even" in their thorium conversion, but they can't make any "extra" to start new fluoride reactors. But the chloride reactors could make a lot as they destroy transuranic waste.

Anonymous said...

any idea how the compensation claim for radioactive exposure wen?

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