Individual isotope detector

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Manitee
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Individual isotope detector

Post by Manitee » Sun Feb 17, 2013 6:40 am

Hi, I am trying to find a way to look at the captures, fissions, and neutron productions within the entire reactor and also within individual isotopes in my fuel material which is called fuel.

Is it possible to do this? I have tried using the following:

For total captures in the reactor i've tried using a detector for example:

det capturetotal de grida dr -2 void

and then for an individual isotope, say pu239, Ive used:

mat pu239 1.0 94239.09c 1.0
det capturepu239 de grida dm fuel dr -2 pu239

I believe this is not correct as the values for captures i get within individual isotopes is much higher than the total i get for the reactor.

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Jaakko Leppänen
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Re: Individual isotope detector

Post by Jaakko Leppänen » Sun Feb 17, 2013 12:20 pm

When you replace the material entry in the detector response with 'void', the code scores the local macroscopic reaction rate (total capture in this case). This means that also the material denisty is defined locally at each collison point. When the material is given, the density is fixed. The reason why your second detector gives much higher values is that the atomic density in material pu239 is very high (1.0).

Also note that positive and negative response numbers are handled differently. Positive numbers refer to microscopic and negative numbers to macroscopic reaction rates. The density of the response material is therefore ignored when calculating microscopic rates, and the material must consist of a single nuclide.
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Manitee
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Re: Individual isotope detector

Post by Manitee » Sun Feb 17, 2013 5:43 pm

ah I think i understand. I wish to get macroscopic reaction rates for each isotope.

So if I wish to compare capture rates for each isotope within the fuel, I can use:

mat pu239 X 94239.09c 1.0
det capturepu239 de grida dm fuel dr -2 pu239

where X is the atomic density of pu239 i have defined in my fuel material. This would take the cross section of pu239 at X atomic density, and use the flux information within the fuel material to find the reaction rate?

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Jaakko Leppänen
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Re: Individual isotope detector

Post by Jaakko Leppänen » Sun Feb 17, 2013 9:33 pm

That's correct. If you didn't use atomic densities in the input, you can find the exact values used by Serpent in the .out output file.
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jesse.johns
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Re: Individual isotope detector

Post by jesse.johns » Thu Dec 19, 2013 2:34 am

I apologize for resurrecting an old post, but I figured it would be appropriate to ask the question here.

I would like to find the reaction rates for nuclides during a burnup calculation. So, with each step the nuclide inventory will change, which require me to change the "X" manually as given by the previous post. Is there a way around this to ensure that the inventory is current with the burnup step?

Thanks.

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Jaakko Leppänen
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Re: Individual isotope detector

Post by Jaakko Leppänen » Mon Dec 23, 2013 8:27 pm

There is no automated way to do it, but if you set the nuclide density of the detector material to 1 (i.e. X = 1 in the previous example), you will get the microscopic reaction rate, which you can multiply by the density printed in the _dep.m file.
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Re: Individual isotope detector

Post by keckler » Sat Dec 21, 2019 11:09 pm

I am wondering, is there a reason why there cannot be a detector option similar to the 'dm' or 'dc' options which enables the user to select a particular isotope? For instance, as pointed out in the previous posts, to calculate the reaction rate in Pu239 within a fuel material, a new material needs to be set up with the proper density for Pu239 in that particular material. This is another external step that the user is required to do, which may be prone to error. But clearly Serpent already knows what the proper density is for that isotope within each material of the geometry, so it would seem trivial for there to be an option in the detector cards to only tally over a given isotope. For example:

det capturepu239 dm fuel diso 942390

where 'iso' is the flag indicating which isotope to score the tallies over.

This would be a very handy feature that could reduce opportunities for errors and make the inputs cleaner. It would also make it possible to tally the isotopic reaction rates over multiple materials when a detector uses the sum function (i.e. dt -4). Is there some reason why this cannot be implemented into the code?

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