Neutron Test Sources Po210+Be or U238+Be?

This area is for discussions involving any fusion related radiation metrology issues. Neutrons are the key signature of fusion, but other radiations are of interest to the amateur fusioneer as well.
Dan Knapp
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Re: Neutron Test Sources Po210+Be or U238+Be?

Post by Dan Knapp » Sat Jan 12, 2019 7:49 pm

Dennis stated in an earlier reply that a neutron source could be rented. I don't think one could rent a neutron source without an NRC license. Can he be more specific about this? Was he referring to the Polonium alpha source that Staticmaster leases?

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Richard Hull
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Re: Neutron Test Sources Po210+Be or U238+Be?

Post by Richard Hull » Sun Jan 13, 2019 5:14 am

I am sure he was. No single person can get an NRC license for a home neutron source.

Richard Hull
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Fusion is the energy of the future....and it always will be
Retired now...Doing only what I want and not what I should...every day is a saturday.

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Dennis P Brown
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Re: Neutron Test Sources Po210+Be or U238+Be?

Post by Dennis P Brown » Sun Jan 13, 2019 12:14 pm

Unless rules have changed, the commercial polonium source was available for rental (6 months.) But it was three years ago I looked into it. So, they might not allow it anymore. The neutron flux wasn't dangerous at all. I even saw someone use one to calibrate their neutron detector selling He tubes on ebay. Again, a few years ago so the rules might have changed - still, they didn't discus with me any licence requirement when I discussed ordering one. Again, times might have changed or they forgot to mention that and that would then come up later. I can only talk about what happen when I talked to the company to order one. Then, of course, didn't since I obtained a fusor level power supply. As for who rented it, I assumed (now) it was the Polonium alpha source that Staticmaster leases.

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Richard Hull
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Re: Neutron Test Sources Po210+Be or U238+Be?

Post by Richard Hull » Sun Jan 13, 2019 9:16 pm

Polonium is not a neutron source..... Period! Any polonium source over 300uCi (static master) must be controlled leased as a large anti-static alpha source. Each year it must be re-leased as the old source is dead, per se and an exchange unit is sent out to the end user and the old one must be returned to the original seller. No license is required when on lease.

You are not leasing a neutron source.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
Retired now...Doing only what I want and not what I should...every day is a saturday.

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Re: Neutron Test Sources Po210+Be or U238+Be?

Post by John Myers » Sun Jan 13, 2019 9:45 pm

Sealed sources and/or exempt amounts don't require a license for the person receiving it. I just spent a little time on the NRC site and I don't see anything specific to neutron sources that prevents a licensee from distributing a sealed neutron source to the public.

Dan Knapp
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Re: Neutron Test Sources Po210+Be or U238+Be?

Post by Dan Knapp » Sun Jan 13, 2019 11:28 pm

There is no exempt quantity for any neutron source. I spent some time a year or so ago interacting with the NRC on this issue. We were talking with the NRC people about petitioning for establishment of an exempt quantity for Californium-252 (the most commonly used neutron source). This was involved with a company that sells Cf-252 sources. They take back decayed sources from customers, which becomes a nuisance for them in that they have to track them forever. If there were an exempt quantity of Cf-252, they could easily get rid of the decayed sources (sell them as exempt test sources, give them away for a tax writeoff, or even just discard them). The problem is that Cf-252 doesn't just emit neutrons; it is also an alpha source. This is not normally an issue with a Cf-252 neutron source, which is contained in a double welded stainless steel capsule, but for the purpose of establishing an exempt quantity of the isotope, the alpha production becomes the limiting thing. I don't recall the exact numbers, but if you consider that 50 microcuries is a typical exempt amount, the amount of Cf-252 to yield 50 microcuries of neutrons would be many times that amount in terms of alpha activity. If you consider an exempt amount of Cf-252 in terms of alpha activity, it is such a small amount that the neutron flux is uselessly small. We gave up on the issue. Unless someone discovers a new isotope that emits a neutron as a fission fragment with no other radiation production, there will never be an exempt quantity for a neutron emitter.

A Cf-252 source that has decayed to the point of no longer being useful for its original purpose, can still be useful as a test source if one has the required NRC license. But even a general license like a University, for example, would typically have is not sufficient and must still be amended to cover a neutron source. Life is unfortunately never simple. The only neutron test source an amateur is ever likely to be able to have access to would be one improvised from the aforementioned polonium antistatic device with a piece of beryllium.

There is one exception I know of if you by some chance happen to be VERY good friends with a major paving contractor. The big operators use pavement moisture measuring instruments that contain a neutron source (typically Americium/Beryllium). These are very strictly controlled by the NRC for obvious reasons. A paving contractor, unless you are a VERY close friend, is not likely to even admit that they own one; so don't bother asking unless you have a very close friend in the business.

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