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PostPosted: Mar 30, 2008 11:11 am 
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Not sure if this is poor form for a first post, but here goes.

I had a bit of a look thru the document repository (after downloading all four gigabytes of it - that was an interesting exercise) and didn't come up with much, so please excuse me if I've overlooked something.

After said look thru, one thing that bugged me was how the gaseous FP heat load on the carbon beds varied with holdup time and size and geometry of holdup tank(s).

So, pursuant to an effort to answer that via modelling:

Per MW(th), at steady state, what's the fission product inventory entering the gaseous FP holdup tank per (second)?

Do I handle increased holdup time as simply more holdup tanks of the same size, scale up existing tanks, or some combination?

Plug or mixed flow?

Can I get away with assuming that everything stays gaseous?


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PostPosted: Mar 30, 2008 12:16 pm 
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Sounds like you're working on some kind of project.

We discussed FP heat load management briefly here.

.


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PostPosted: Mar 30, 2008 5:29 pm 
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In other words, a subtle hint to bugger off, go back and take a closer look. :oops:

I was actually looking for a specific inventory - how many Ci of each fission product so I can figure out, given their half lives, how that FP mix (and associated heat load) varies over time and ultimately to steady state, with varying holdup times and tank geometries.


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PostPosted: Mar 30, 2008 5:48 pm 
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As I recall, people who do those kinds of studies use the ORIGEN code.

A typical result is shown here:

Image

.


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PostPosted: Mar 30, 2008 5:57 pm 
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Thanks anyway - is a start.


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PostPosted: Mar 30, 2008 8:04 pm 
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Thanks for the great table Jaro, I was hoping to find something like that. It does show that Xenon and Krypton, the main two fission gases that a liquid salt reactor needs to collect and store only have significant decay heats for a few days.


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PostPosted: Mar 30, 2008 8:35 pm 
Looks like (in reference to the problem of keeping the salt hot while removing undesirables) Iodine would be a prime candidate to leave in. All the isotopes beta decay to Xenon, which would then be removed of course; collectively they generate a fair amount of heat over a broad spectrum of half lives, and Iodine should be compatible with Fluoride salt.


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PostPosted: May 18, 2008 9:26 pm 
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If anyone wants to see what xenon-135 "looks like" to a thermal neutron, compared to a rather "big" fissile absorber like Pu-239 (or even Am-242m), here you go:


Attachments:
xenonXsection.gif [11.06 KiB]
Downloaded 459 times
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PostPosted: May 31, 2008 10:52 pm 
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Hey, does anyone ever talk much about what krypton-87 poisoning might mean in a reactor? I was plotting out the absorption cross-sections in my radionuclide simulation, and it said that krypton-87 had a thermal neutron absorption cross-section of 12600 barns, and a half-life of 1.3 hours. The fission yield at atomic mass 87 was pretty significant as well.

Sounds like it could do things like xenon-135 in a real reactor. Anyone ever heard of Kr-87 being an issue in reactor control?


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PostPosted: Jun 01, 2008 12:16 am 
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It's so overshadowed by Xenon and Samarium thats it is basically ignored.


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PostPosted: Jan 18, 2010 3:14 pm 
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In reading ORNL 4541 they provide a good amount of detailed information on the off-gas processing system.

There is one thing they said that puzzles me. They said the off-gas contains oxygen from fluorine burn-up but they made no mention of neon. In //www.nndc.bnl.gov/sigma/index.jsp?as=19&lib=endfb7.0&nsub=10 I see the (n,gamma) is much higher (100x) than (n,alpha) so I'm confused. It seems like:


19F + n (n,gamma) => 20F (11 sec beta) => 20Ne (stable) should be the dominate reaction.

19F + n (n, alpha) => 16N + alpha (7 seconds) => 16O + alpha should be around 1% of the reactions.

Am I missing something here?


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PostPosted: Jun 13, 2016 8:26 am 
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This material looks promising for capturing the Xe and Kr in an off-gas processing system: http://phys.org/news/2016-06-material-potential-nuclear-fuel-recycling.html

The article just considers reprocessing applications using used LWR solid fuel rods, but of course it should be great for a MSR. I wonder if this MOF will work better than the charcoal beds that are normally considered for this application.


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PostPosted: Jun 13, 2016 8:56 am 
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That would have other interesting applications in industry - for example it could significantly reduce the cost of xenon gas production, which would allow a number of interesting industrial uses to develop that are currently hampered by the very high price.

It will bear watching at the very least.


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PostPosted: Jun 13, 2016 5:33 pm 
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Lars wrote:
In reading ORNL 4541 they provide a good amount of detailed information on the off-gas processing system.

There is one thing they said that puzzles me. They said the off-gas contains oxygen from fluorine burn-up but they made no mention of neon. In //www.nndc.bnl.gov/sigma/index.jsp?as=19&lib=endfb7.0&nsub=10 I see the (n,gamma) is much higher (100x) than (n,alpha) so I'm confused. It seems like:


19F + n (n,gamma) => 20F (11 sec beta) => 20Ne (stable) should be the dominate reaction.

19F + n (n, alpha) => 16N + alpha (7 seconds) => 16O + alpha should be around 1% of the reactions.

Am I missing something here?


Would the neon be an issue? It is noble and small x-section and thus not a corrosion nor neutronicity issue, right?

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PostPosted: Jun 15, 2016 5:45 am 
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Jim L. wrote:
This material looks promising for capturing the Xe and Kr in an off-gas processing system: http://phys.org/news/2016-06-material-potential-nuclear-fuel-recycling.html

The article just considers reprocessing applications using used LWR solid fuel rods, but of course it should be great for a MSR. I wonder if this MOF will work better than the charcoal beds that are normally considered for this application.


Very promising indeed - but not sure about in on-line reprocessing:
Quote:
To figure out where the discrepancy came from, the researchers modeled what happened to SBMOF-1 at 300 degrees Celsius. Unexpectedly, the pores squeezed in on themselves.


The Xenon freshly removed from a MSR is very hot - in both sense of the word. Cooling it to 100C may be difficult. Potentially it could replace the "second hold up tank".


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