Neutron Activation of Uranium (Redux)

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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Jon Rosenstiel
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Neutron Activation of Uranium (Redux)

Post by Jon Rosenstiel » Fri Mar 26, 2021 9:27 pm

Previous work from Carl Willis and myself…
viewtopic.php?f=13&t=5846&p=38723&hilit=uranium#p38723
viewtopic.php?f=13&t=5860&p=34304&hilit=uranium#p34304

As expected, this latest attempt turned up the anticipated 74 KeV gamma from U-239. But what also turned up (completely unexpected) were several short-lived fission products. Amongst those short-lived fission products were what Carl suspected he was seeing, 15.2-minute Rb-89. Wow, fantastic work on Carl’s part.

Activation specifics: 5.788 grams of Carl’s ammonium diuranate (yellowcake) was baked in the neutron oven for one-hour at 7.0E+06 n/s TIER. This was the first time I had run the water-cooled cube fusor that long and that hard. (55 to 56 kV at around 9 mA) TIER at the start of the one-hour run was 7.1E+06 n/s at a temperature of 34 C. At the end of the run TIER had dropped to 6.9E+06 n/s and temperature had crept up to 41 C. After activation the yellowcake was transferred to my hpGe spectrometer for a 3000 s count. (For comparison purposes a 3000 s “background” count was done just prior to activation.

Jon Rosenstiel
Attachments
Ammonium Diuranate.jpg
Yellowcake
Neutron oven.jpg
Neutron oven
0 to 1600.png
Spectra
Spectra, expanded.pdf
Figured some may like to see a little more detail.
(514.53 KiB) Downloaded 63 times

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Mark Rowley
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Re: Neutron Activation of Uranium (Redux)

Post by Mark Rowley » Fri Mar 26, 2021 11:04 pm

Absolutely fantastic work Jon. And the 1hr run at such a high output level has to be a record on its own.

Regarding the gamma spec, are any of those telltale peaks something that would show on a NaI(TI) based system?

Mark Rowley

Jon Rosenstiel
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Re: Neutron Activation of Uranium (Redux)

Post by Jon Rosenstiel » Sat Mar 27, 2021 2:51 am

I was really impressed at how stable she ran. I did minutely readjust the throttle valve a few times during the run, mainly because I didn’t want the hv to creep up the slightest... have already gone through too many feedthroughs. I have some quartz tubing, one of these days I’m going to try my hand at constructing the David feedthrough.

Seems like this would be pretty tough to do on a NaI detector.

JonR

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Richard Hull
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Re: Neutron Activation of Uranium (Redux)

Post by Richard Hull » Sat Mar 27, 2021 5:09 am

Jon , the "pace setter", ever out in front. Fabulous work Jon! My jaw dropped as I read the details on the run and marveled at your gamma spec. You pack the gear to do this and I will add this to your Elite Fusioneer blurb. Wish I coulda' been there swilling a strong root beer watching the long run and musing with you as you minded the controls. Excellent work.....As I say all too often..."you be da' man!"

You are correct with that crowded spectrum and smaller peaks for the fission products, an NaI spectrum would have had a couple of bumps in places combining all the fission products. The few dollars and the hassle you spent on the LN2 to get that spectrum was money and time very well spent.

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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