activation with constant source

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alexey28
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activation with constant source

Post by alexey28 » Thu Jun 03, 2021 1:19 pm

Hello!
I have an activation task with a constant source. I want to calculate the flux once and then change only the thermal power, taking into account the reactor stops.
Here is a code snippet

Code: Select all

dep daystep 455
set power 0
dep actstep 30
set power 1128000000
dep actstep 695
set power 0
dep actstep 30
Could you please tell me each step on the activation will count with the power that I enter before it?
Since I no longer have transport cycles, will I have the first one considered every time?

Ana Jambrina
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Re: activation with constant source

Post by Ana Jambrina » Thu Jun 03, 2021 3:25 pm

If you run the case with the current depletion history, you would see that you only run a single transport (corresponding with the predictor-corrector depletion scheme) calculation corresponding with the first burnup step. After which, you would deplete the material for the given activation steps (in total 1 pcc burnup step + 3 activation steps). As mentioned in the Wiki: “Transport cycle is run only once with the actstep and acttot options”. In activation burnup mode the cross sections are not updated after the first step (consequently burnup and other neutronics results are not calculated).

In terms of normalization, you can check how the power normalization is applied in the ‘_res.m’ file (data only available for the burnup steps involving a transport cycle), section “Normalized total reaction rates (neutrons)”.

With the current setting, assuming the first step within the depletion history corresponds to 455 days, the normalization is set to zero power: you would obtain an error: “Division by zero”. This error could be avoided if you substitute zero for a very small value, e.g., 1E-10 (if that is what you aim for).

The depletion history corresponds to: from 0 to 455 days (power 0), from 455 to 485 days (power 11.28E+08), from 485 to 1180 days (power 0), from 1180 to 1210 days (power 0). - It seems that you might want to define the initial burnup step power normalization to some nominal value.
- Ana

alexey28
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Re: activation with constant source

Post by alexey28 » Thu Jun 03, 2021 4:17 pm

Ana, Thank you!

Code: Select all

set power 1128000000
dep daystep 455
set power 1E-10
dep actstep 30
set power 1128000000
dep actstep 695
set power 1E-10
dep actstep 30
I thought you should first set the power and then the step.

from 0 to 455 days (power 1128000000), from 455 to 485 days (power 0), from 485 to 1180 days (power 1128000000), from 1180 to 1210 days (power 0)

Could you please tell me if this corresponds to the code above?

Ana Jambrina
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Re: activation with constant source

Post by Ana Jambrina » Thu Jun 03, 2021 4:25 pm

It does. Note that you could set the power to zero for other depletion steps except the first one.
You might want to consider the length of the (first) burnup step and its effect on the depletion calculation.

Some notes:
- regarding a constant source, you could define a source and only deplete the materials involved in the activation sequence (burnup calculation), keeping the irradiation source constant.
- if you set the power to zero, Serpent does not print out the detector output for the given step (similar to decay steps).
- Ana

alexey28
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Re: activation with constant source

Post by alexey28 » Wed Jun 16, 2021 4:08 pm

Ana, Thank you!

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