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 Post subject: Fission Product Database
PostPosted: Dec 27, 2017 8:02 pm 
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Joined: Jan 16, 2012 7:15 am
Posts: 93
I've created a database of cumulative fission fragment yields, because I couldn't find one on the net. I've been working this a couple years, as a retirement hobby. I thought it would be useful for MSR design. It can help answer a lot of engineering questions on the content of the salt as it ages.

It needs to be vetted by a competent nuclear authority. At this point, having a grad student confirm my methodology would be an improvement in the project’s provenance. The name of my web site suggests its current validity, http://iffydata.org

I hope some of you will check it out and pass along any suggestions you have.


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PostPosted: Dec 29, 2017 4:55 pm 
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Joined: Jan 16, 2012 7:15 am
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The next phase of the project is to predict the evolution of failed fuels. What happens when a fuel nucleus absorbs a neutron but fails to fission? Seeking a one-syllable verb, I say it “plumps” to the next higher isotope of the same element. I’ve read this process is called transmutation, but I’d rather reserve that verb for a change to a new element.

For failed fuel evolution, I’ll again be using the Half-life Equivalent concept. This is iffydata's iffiest concept! Has anyone heard of anything similar? If so, I’ll have to change a lot of text!

My immediate task is to add a bunch of charts to display the consequences of plumping for fission products, particularly the neutron poisons. The web site already has one such chart in the sidebar, for 135-Xe. I assume someone, somewhere has a similar chart, since 135-Xe is so critical. Charts for other neutron poisons would go a long way in validating the Half-life Equivalent concept.

135-Xe is rather simple. The next most poisonous isotope is 157-Gd. It's a bit more interesting because, after a long-while, 156-Gd begins to plump the 157-Gd population. The attached chart shows this increase on the far right.
Attachment:
CapNoCap157-Gd.png
CapNoCap157-Gd.png [ 106.59 KiB | Viewed 207 times ]


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PostPosted: Dec 31, 2017 9:36 am 
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Joined: May 24, 2015 9:43 pm
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Thanks! Even if iffy, the data should be useful for making a nuclear reactor construction game.


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PostPosted: Jan 08, 2018 3:28 pm 
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Joined: Jan 16, 2012 7:15 am
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I’m still developing charts for the evolution of neutron poisons. In the meantime, I have created charts for several decay chains. The charts reflect the exponential time-frame nicely. Short-lived isotopes show up well. (With a more normal treatment of time, they tend to disappear as they evolve to their longer-lived daughters.) These charts demonstrate other aspects of fission product evolution, as well.

Most of the charts show the contribution of each nuclide in the decay chain, that is, the proportion of the population of each nuclide at that atomic weight. The initial yields of the nuclides directly created by the fission event are on the far left. They should sum to the population of the Sink on the far right. Neutron emission might change the sum slightly. Neutron capture can change it a lot.

There are a few growth curves that are not symmetric, as in the orange curve in the example below. I think this is due to having multiple parents, but I’m still working on those charts. Until then, please peruse some more “normal” curves at http://iffydata.org/chain-evolution/


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Chain 83.png
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