This is fun:
The actual thing seems to be:
In July 2008, the ODA told the Environment Agency that it had found 40 cubic metres, about 50 tonnes, of waste that showed radioactive readings up to three times higher than the levels at which waste is treated as exempt. But it argued that when put together with 1,500 cubic metres of material that was \”definitely exempt\” this would bring the whole waste into the exempt category.
Documents obtained under Freedom of Information (FOI) rules reveal that, contrary to government guidelines, waste from thorium and radium has been mixed with very low-level waste and buried in a so-called disposal cell under, or close, to the Olympic stadium.
OK. So, there was some lightly radioactive waste then. The rules are a little more complex than I\’ll make them out to be but roughly speaking, if there\’s less than 500 parts per million thorium then this is \”exempt\” waste. For we\’re talking about stuff that is less radioactive than various granite outcrops around the country like half of Cornwall or Arthur\’s Seat in Edinburgh.
It\’s also true that thorium really isn\’t that radioactive. I once sold a 15 lb bar to a customer and he could have it on a shelf, right next to his computer, for a year and it wouldn\’t even fog his dosimeter at all.
Radium is a slightly different kettle of fish. Much more dangerous….however, there will only be tiny, tiny, quantities there. You tend to find both together when you\’ve got the decay products from uranium and you get hundreds of times more thorium than you do radium.
Of course, when you\’re measuring the Th and Rd together, you tend to measure by the radiation being given off. And the way you do that is measure how much you\’re getting from, say, a kilo, or a litre, of the stuff. Which means that if you do mix stuff which is on the borderline of being exempt with stuff which is definitely exempt then you will get something which will pass these tests. Because you\’ve diluted the radioactive components and brought the total material under the level for exemption.
It\’s possible that these peeps have used the regulations in a way they weren\’t supposed to be used. However, dilution of the radioactive particles to bring them down to under the exempt level seems reasonable enough. We are still talking about stuff which is about as radioactive as general bits of rock lying about the countryside.
Now why they did this is a matter of money, yes. If you\’ve got exempt material you can, as they have done, bury it onsite. You can also send it to standard landfill and pay, perhaps £200 a tonne all told. However, if you\’ve got non-exempt material, but still low level radioactive, then you\’ve got to send it off to the low level waste depositary at West Drigg. There it\’s put into barrels sheathed in concrete and then stored….you can imagine that this is much more expensive.
There\’s a third thing you can do: process that waste and take the thorium and radium out of it. You\’ve then definitely got stuff which is exempt which you can use to level off the site. You\’re talking about 5oo grammes of thorium per tonne waste here (assuming the very top level of exempt material, even after they\’ve mixed it all up) and 7,500 tonnes of mixed material: 4 odd tonnes of thorium (and it would actually be much lower than this: they won\’t have done the mixing to leave it right on the upper limit). The radium would be, at a guess, somewhere around a kew kilos. It\’s not difficult (although boring and expensive) to process all of that with acid and to lift out the actinides (ie, the radioactives) and send them off to the high level repositary at Sellafield and be left with dirt on site. Leaving aside the cost of depositing in that repositary (for unfortunately, no one in the western world uses thorium for anything much anymore: that 15lb bar I sold was something like 80% of all trade in thorium in the US that year) you could do that processing for a few million £. Easily.
So why didn\’t they do that?
Because diluting the radioactive parts is just fine. In fact, if you go looking you can find the guidance to schools which might want to dispose of any thorium they have lying around (used to be reasonably common in chemistry labs). Pour it down the sink with the tap running is the advice. Because you\’ll dilute it sufficiently that you\’re getting to or even below general background radioactivity.
What we\’ve really got here is a bit of that good old hysteria about radiation. The amount in that soil is almost certainly less than you can find by going digging in various parts of the country. But because we\’ve got all wound up about dangerous levels of radioactivity (strangely, much more so about the very little that comes from nuclear power plants than the hugely greater amounts that come from coal fired power stations) wetherefore seem to have absolutely no societal tolerance for amounts equal to what you might find in a vegetable patch near Padstow.