Criticality safety assessment of an abandoned plutonium lab

I'm assessing criticality safety of a waste removal plan for a (theoretical) abandoned russian laboratory. In the laboratory plutonium was recovered from fuel rods. The room is mainly empty except for a dissolver, a sump below the dissolver and spilled metal chips on the floor. The dissolver contains fissile material, nitric acid and debris at the bottom. It can be filled from the top and has a tap at the bottom. The sump is filled with raschid rings and contains boron and plutonium nitrate.

I need to come up with a plan to drain and decontaminate safely the dissolver and sump so the room is ready for demolition. There are no roads in the arctic so any waste must be stored appropriately.

Basically, i'm in need of some case studies or literature so I can make a reasonable attempt at a plan.

My main questions are:

What can I use to accurately characterise the waste in the dissolver and sump?
How do I remove the fissile materials and nitric acid safely from the dissolver and sump?
What do I use to store the wastes?

Some random sources of information I have found: fuel dissolvers&f=false dissolver raschig&f=false

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Insights Author
Gold Member
Since your profile says that you are an undergrad, I presume that this assignment is a school hypothetical and not that you are the lead engineer on a real life cleanup; correct?

I think your best source is USNRC, not Google, not PF. If you can't find it on their web site, I suggest trying to make personal contact. They may be glad to provide unclassified published sources for you to look at (glad because they might recruit you as a future NRC employee).

If USNRC is politically incorrect, I think you could do the same with regulators in Sweden, Switzerland, France, the UK, Canada and other countries.


This isn't my direct area, but here are some things to think about.

1. What is the radiation readings in the room? Can you even get in there, or does everything have to be done remotely?
If they were dissolving spent fuel with a high burnup, everything would be remote. If it was lower burnup fuel, you might be able to get close.

2. You need to figure out a way to neutralize the acid without making a violent reaction. You also want to add as little extra material as possible to reduce the overall waste.

3. You need a way to demobilize the liquid waste. Probably some type of cement/grout. Liquid waste is very difficult to handle and store long-term.

4. Is there any chance of a criticality occuring in the liquid? If so, you will need to add neutron absorbers.

5. You will need to figure out a way to decontaminate all the surfaces and/or figure out a binding agent to keep the radioactivity from flaking off during destruction. Read the recent news about Hanford to see how NOT to do this :)

6. You need to characterize the "metal chips". Could this be fuel? If so, high radioactivity and possible critical configuration.

Good luck!


Insights Author
Gold Member

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