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Palomares and the H-bombs

Dear Reader,

Now some doomsayers may have tried to tell you that once radioactivity appears in soil that you should give up all hope, also on the otherhand some false prophets of insincere reassurance will just tell you to stop worrying and that “everything will be OK”. My advice is not to trust either of these two false friends.

The story of the air crash which involved four H-bombs has popped up again, the BBC report that the local people in Spain are fifty years after the air crash unhappy about what has been done.

The BBC report suggests that the local farmers have a problem getting a good price for their produce at market. I would like to point something out.

The plutonium in the H-bombs would have been in the form of the metal, during the accident this would have been burnt into plutonium dioxide. Now the thing to note about plutonium dioxide is that it is very hard to dissolve in acid, also it is not mobile in soil. Any plutonium which was in a water soluble form is likely to have bonded to the soil minerals thus making it impossible for plants to absorb it via their roots.

M.I. Sheppard and D.H. Thibault, Health Physics, 1990, 59, 471 to 482 gives the binding constants for most metals to the four common soil types. It lists for plutonium the following Kd values.

Sand, 150 L/kg

Loam, 1200 L/kg

Clay, 5100 L/kg

Organic, 1900 L/kg

This means in a bucket containing a mixture of clay type soil and water that the plutonium content of the soil (Bq per kilo) will be 5100 times higher than the plutonium content of the water (Bq per litre).

Hence when 1000 Bq of plutonium is added to a litre of water mixed with a kilo of clay type soil, then the soil will absorb 999.8 Bq of plutonium while 0.2 Bq of plutonium will stay in the water. This calculation is for a static batchwise experiment but it will help experts in the field make predictions about the mobility of plutonium solutions in soil.

Another good bit of news is the fact any plutonium dioxide in the dust will not be well absorbed if it is swallowed (dust on the surface of the food), so orally the plutonium dioxide is not a great threat to life and limb. If you were to swallow a well sintered particle of plutonium dioxide it will pass unchanged through your digestive system.

However plutonium dioxide in the lungs is very dangerous to a persons health, I think that a key thing to do in Spain is to keep the plutonium in the most contaminated soils from entering the air as a dust. I think that the ban on building, farming or walking in the contaminated area is a good idea. But I think that it might be a good idea to pour concrete or asphalt onto the worst hot spots to try to fix the soil to keep it from becoming mobile again.

One of the problems with plutonium is that the colloidal particles of clay can make the plutonium mobile, while the plutonium does not move freely through the soil in aqueous solution the colloidal particles can move through the cracks in the soil. Thus sealing the soil would help to stop the plutonium from reaching the surface again in the form of dust.

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