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Dear Reader,

It has come to my attention that an accident has occurred at Hanford, for those of you who do not know Hanford is an early nuclear site in the USA in Washington. At this site plutonium was produced, the plutonium used in world war two for nuclear bombs was made there inside the reactors.

I will not pretend that the site is in great condition, there are some serious problems with the way that radioactive waste was stored on the site. What happened was in the early days that neutron irradiated uranium was dissolved in nitric acid. This fuel solution was then processed to recover the uranium.

The first process used was the bismuth phosphate process which I regard as a very dirty process which generates a vast amount of secondary waste. The mixture of plutonium and everything else in a mixture of nitric and sulfuric acids had the oxidation state of the plutonium adjusted with nitrous acid.

Then the plutonium was precipitated using bismuth phosphate, this process separated the plutonium from the uranium and the vast majority of the fission products. The waste solution from this process was then made alkaline with sodium hydroxide before being placed in large steel tanks. The problem with the Hanford site is that it has many different radioactive waste stores and different buildings, so it is not a simple site. But I think that the single skinned tanks containing the alkaline waste are the worst thing on the site.

It is not clear exactly what has happened at the site today, but I think that the worst case accident could never be as bad as Chernobyl. The majority of the radioactivity is inside the tanks. There is a program of tank emptying, the contents of the tanks are being removed and then conditioned to reduce the threat that it poses. A good review of the site can be seen here.

I know that in the Soviet Union that a high level waste tank at Mayak exploded (Kyshtym accident). Here ammonium nitrate and acetates are thought to have reacted violently in the waste store thus ejecting waste from the tank. At Hanford ammonium nitrate and acetates were not present in the waste. Thus the waste in the tanks is more chemically stable. The waste does form some hydrogen as a result of the radiolysis of water. But the hydrogen is a less scary fuel than the ammonium nitrate / acetates.



One Response

  1. Hi Mark, this site from DOE gives continuous updates:

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