Detector reading

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Husamkh
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Detector reading

Post by Husamkh » Tue Mar 10, 2020 5:48 pm

Hello.
I am using serpent for depletion calculations and I am tallying the fission rate. at the EoC I set the power to zero to simulate decay mode. after that I get zero detector output for the last two burn up steps. do you know how could I solve this problem. I tried to place an extra dummy BU step at the end of the cycle, but this is putting extra computation effort and cost. so is there any other possible solution for that problem ? here is my input example.

set power 3983.0E6

dep daytot
50.000
100.000
150.000
200.000
300.000
400.000
490.000

set power 0.0

dep daytot
511.00



and the detector card:

det Radial_pow
dr -6 void
dx -177.44277 177.44277 17
dy -177.44277 177.44277 17

thanks.

Ville Valtavirta
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Re: Detector reading

Post by Ville Valtavirta » Wed Mar 11, 2020 11:52 am

I'm sorry, why are you not actually using decay mode for the simulation?

If you explicitly want to do burnup instead of decay, I would advice using a very low power instead of zero. I.e. something like 1e-6 Watt.

-Ville

Husamkh
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Re: Detector reading

Post by Husamkh » Sat Mar 21, 2020 1:10 pm

Actually I also tried the decay mode but this also gave me a zero flux reading for the last depletion step. the trivial solution I made was to place a dummy step at the end of the depletion cycle ( like 480.0001 day ) that works but it increases the total calculation time and I thought there might be another possible way or I might be doing something wrong. Nevertheless, this might be also a bug in the serpent and btw currently I am using Serpent 2.129.


thanks.

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Jaakko Leppänen
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Re: Detector reading

Post by Jaakko Leppänen » Sat Mar 21, 2020 1:26 pm

If you are not using decay steps, the zero detector results come from normalization. When you set power to zero, all your detector results are also multiplied by zero.
- Jaakko

hartanto
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Re: Detector reading

Post by hartanto » Sun Jun 07, 2020 12:22 pm

Hello,

I also have a similar question regarding this issue. Let's say

dep daytot
50.000 -> index 1
100.000 -> index 2
150.000 -> index 3
200.000 -> index 4
300.000 -> index 5
400.000 -> index 6
490.000 -> index 7

set power 0.0

dep daytot
511.00 -> index 8

If we do the fission power tally, I recall in the previous Serpent (not sure which version, it has been a long time ago), the detector result was available and it was not zero at t=490 days or input_det7.m file. However, in the latest Serpent 2 I used, it provided me zero values. I wonder why the fission power by the detector is not available because the power is not zero at t=490 days.

Many thanks for your support.

Ville Valtavirta
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Re: Detector reading

Post by Ville Valtavirta » Mon Jun 08, 2020 10:08 am

Hi,

the way you specify your depletion history means that you are using one power until 490 days and then the total power of 0.0 from 490 days to 511 days. Serpent evaluates the neutronics solution for 490 days as the starting point for the depletion interval between 490 and 511 days and since the power (and flux) is zero for that interval, you will get zero results for the starting point of that interval.

Do you want two solutions for time point 490 days, one with full power and one with zero power?

If you want to deplete with zero power (and zero flux), but still want nonzero detector results for power and flux, it is probably best to simulate this using a very very low power level, e.g. 1e-6 Watt or similar.

-Ville

hartanto
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Re: Detector reading

Post by hartanto » Mon Jun 08, 2020 2:35 pm

Thank you for your reply.

If I would like to get the detector results at 490 days with full power condition, can you recommend me the best way to obtain that?

Is it such as below?

dep daytot
50.000 -> index 1
100.000 -> index 2
150.000 -> index 3
200.000 -> index 4
300.000 -> index 5
400.000 -> index 6
490.000 -> index 7
490.001 -> index 8

set power 0.0

dep daytot
511.00 -> index 9

Many thanks.

Ville Valtavirta
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Re: Detector reading

Post by Ville Valtavirta » Tue Jun 09, 2020 12:58 pm

If I wanted to get detector results at full power at 490 days I would simply do

dep daytot
50.000 -> index 1
100.000 -> index 2
150.000 -> index 3
200.000 -> index 4
300.000 -> index 5
400.000 -> index 6
490.000 -> index 7

set power 1e-10

dep daytot -> index 8
511.00

and simply scale the detector results for step 8 with (full_power/1e-10).

Your approach will also give you the results, but will require at least one additional transport solution, so I wouldn't use it myself.

-Ville

hartanto
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Re: Detector reading

Post by hartanto » Wed Jun 10, 2020 1:59 pm

Thank you.

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