Criticality safety assessment of an abandoned plutonium lab

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Discussion Overview

The discussion revolves around the criticality safety assessment of a waste removal plan for an abandoned laboratory that previously handled plutonium. Participants explore various aspects of safely draining and decontaminating a dissolver and sump containing fissile materials and nitric acid, with a focus on theoretical approaches and literature sources relevant to nuclear waste management.

Discussion Character

  • Exploratory
  • Technical explanation
  • Homework-related

Main Points Raised

  • One participant seeks case studies or literature to characterize the waste in the dissolver and sump, and to develop a safe removal plan for fissile materials and nitric acid.
  • Another participant suggests that the original poster is likely working on a hypothetical school assignment rather than a real cleanup, and recommends contacting the USNRC for reliable sources.
  • A different participant raises concerns about radiation levels in the room and the feasibility of remote handling, depending on the burnup of the fuel dissolved.
  • There are considerations regarding the neutralization of nitric acid without causing violent reactions, and minimizing additional waste material.
  • Participants discuss the need for a method to demobilize liquid waste, possibly using cement or grout, and the importance of assessing criticality risks in the liquid waste.
  • Surface decontamination strategies and the characterization of metal chips found in the lab are also mentioned, with a cautionary note about potential critical configurations.

Areas of Agreement / Disagreement

Participants generally agree on the need for careful planning and consideration of safety measures in the waste removal process. However, there are multiple competing views regarding the best approaches and sources of information, and the discussion remains unresolved on specific methodologies.

Contextual Notes

Limitations include the hypothetical nature of the scenario, potential missing assumptions regarding the specific conditions of the laboratory, and the dependence on regulatory guidelines that may vary by country.

Who May Find This Useful

This discussion may be useful for students studying nuclear engineering, environmental science, or related fields, as well as professionals interested in nuclear waste management and safety protocols.

richphys
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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:

https://books.google.co.uk/books?id=f4dJDgAAQBAJ&pg=PA200&dq=nuclear+fuel+dissolvers&hl=en&sa=X&ved=0ahUKEwj6mtueptjaAhWKSsAKHR_LC5cQ6AEIVjAJ#v=onepage&q=nuclear fuel dissolvers&f=false

https://books.google.co.uk/books?id=jQAxAQAAMAAJ&pg=SA2-PA24&dq=plutonium+dissolver+raschig&hl=en&sa=X&ved=0ahUKEwi_6seLqNjaAhXKDMAKHV_tB5QQ6AEIJzAA#v=onepage&q=plutonium dissolver raschig&f=false

THANK YOU
 
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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 occurring 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!
 
richphys said:
Thank you for the replies! Yes it is a university assignment. I'm stuck on another part of it now - possibly calculating critical mass. I made a new thread:

https://www.physicsforums.com/threads/how-to-calculate-critical-mass.946257/

In that case, I'm going to close this thread until your other thread is finished. If you want to reopen it, click on my name and start a conversaion.