Radiation Safety Questions

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.
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Dennis P Brown
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Re: Radiation Safety Questions

Post by Dennis P Brown »

That is great news! Can't wait for your success and I hate to say this, but obstacles are always the case unless one goes all turnkey; bureaucratic issues are, of course, the worse.
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Anze A Ursic
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Re: Radiation Safety Questions

Post by Anze A Ursic »

I just talked to someone "on the inside" over ZOOM today and I may have jumped the gun. It appears as though the standard procedure whenever new radiation producing equipment is introduced, is to throw the entire radiation safety book at it. Granted, usually this equipment is extremely powerful X-ray or neutron sources (some of these on the order of ~10^12 n/s), so I understand now they were just following procedure. Upon talking and explaining exactly what my project is and my procedure, I will just have to take a 1 hour in person training on how to detect and measure radiation. They will also provide lead bricks and possibly borated poly, as well as survey meters and dosimeters. The original email was quite daunting and it truly felt as though the project died with it (there is no way I could've done 26 separate radiation trainings in 2 months or many of the other requirements), but it seems as though they are actually incredibly excited to help and see what we can do with it and they are even looking through the relevant SOPs to see if there is any way to alleviate more requirements to help me out.
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Liam David
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Re: Radiation Safety Questions

Post by Liam David »

Great to hear! Hopefully the rest goes smoothly.
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Dennis P Brown
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Re: Radiation Safety Questions

Post by Dennis P Brown »

Agree, really great news. I did mentioned you can get these people on your side by explaining details to them. I am happy to see it worked and they too, are excited and interested* in your project.

* In the good way!
Alexander Ziemecki
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Re: Radiation Safety Questions

Post by Alexander Ziemecki »

Anze A Ursic wrote: Mon Mar 28, 2022 6:11 pm However, from my understanding, the relatively low neutron rates (<10^6 n/s) and short exposure time (<2 min) would yield no such problem. But to appease the safety folks, I figured a few bags of Borax or maybe a few cases of water with some Borax dissolved in them surrounding this thing may not be a bad idea, but again, any input is great.

The other thing, of course, is X-rays. I have done the relevant calculations and per the picture below, we will be separated from the fusor by about ~3.4m (11ft) of air, ~6mm of steel (our chamber is roughly 0.25" thick) and about ~0.3m (1 ft) of reinforced concrete. Again, based on the calculations I have done, with the Intensity = Intensity_0 * exp(-(mu/rho)*distance) approximation, I found that the steel and concrete alone would shield >99% of the produced X-rays at 40kV and even the 11ft or so of air separation is more than many others have in their setup from what I have read.
Would you be able to upload the math you did? I'd like to compare your math to my own - i'm having a similar problem.

Thanks,
Alex Ziemecki
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Richard Hull
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Re: Radiation Safety Questions

Post by Richard Hull »

In a fusor in continuous operation, the x-rays are the only nasty thing to worry about. No need to calculate anything at all if you are in do mode with an accurate ion chamber. Do and shield accordingly.

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
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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Anze A Ursic
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Re: Radiation Safety Questions

Post by Anze A Ursic »

Alex, this is what I had written down at the time. Whether it is correct or not, I cannot say and currently do not have time to go through all of my reports. That being said, anyone is welcome to tell me whether what I did was right or wrong. I'd love to get some feedback. I'm an electrical engineer so I had to learn about shielding and stuff on my own and in a very short period of time so I'm sure I've made mistakes along the way.

X_0 is just the original dose, which I don't believe I ever accurately calculated.

Anze
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Anze A Ursic
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Re: Radiation Safety Questions

Post by Anze A Ursic »

Richard, I didn't see your response since it was on page 2 of this thread. I agree, but do understand that without my "calculations", nothing would've moved. My setup was in a basement of a university building with classrooms above it, asking the safety folks to just measure as we go was completely dismissed. Believe me, I've tried...
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Richard Hull
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Re: Radiation Safety Questions

Post by Richard Hull »

Your point is well taken. This was not your fusor in your space. It was their fusor in their space. They ruled all things from the first bolt turning through the fusion process. They wanted assurances on paper. (feel good state) Real measurements come last.

I was involved with Virginia Commonwealth Universities fusor build at their request. This started in 2014. They acquired thousand of dollars in brand new vacuum and electronic gear. By 2015 all was ready and then came the cease and desist order! They had a CHP come in and ordered special shielding for the room installed. New funding and the finished work demanded a massive review of the project. I went into hold mode until 2018 when the go ahead came. I found all the seniors I had trained had graduated. Some of the gear had disappeared. (God only knows where)
The real tragedy came when I found out that the fabulous new 3He tube of 2015 was gone and a search came up empty. A totally unsuitable formal neutron counter was borrowed with the lowest range at 50mrem full scale.

Long story short, they did fusion that moved the needle just off zero. Once they achieved fusion, the head of the department who pushed the fusor effort moved to the IAEA in Europe and all ended within months of success.

The worst efforts are college efforts and are mostly still born.

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
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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