Flux Interpretation and Units in SERPENT

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Sasha
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Flux Interpretation and Units in SERPENT

Post by Sasha » Wed Sep 09, 2015 6:58 pm

Dear Jaakko,
I've seen several discussions on the forum regarding neutron flux estimation using detectors and flux units. Excuse me, I still have a few questions (Note: I am using Serpent 2.1.24):

1) TOT_FLUX is the total flux integrated over the geometry and all energy groups. In the User's Manual, it is written that "All flux values are divided by volume" (page 86). I did the following test: I defined a detector for the flux estimation in all volumes, and I specified 1 energy group. Then, I did summation over all bins. If I don’t divide the obtained value by the total volume, I get the same value as TOT_FLUX. Otherwise, if I divide by the volume, the flux values are different. Do I misinterpret anything or there is an inaccuracy in the User's Manual?
The detectors are the following:

Code: Select all

ene 2 3 100 1E-11 20.0
det All1 de 2 du 0 dv 1.0e4
det All2 de 2 du 0 
det All2 provides the same value as TOT_FLUX, det All1 doesn't.

2) Could you please correct me, if my understanding of the flux unites in SERPENT is wrong?

- TOT_FLUX value is in [n/cm^2/s]
- The output from the flux detector after the division by volume also provides flux in [n/cm^2/s]
For example, the following detector provides flux [n/cm^2/s] as a function of energy [MeV] (flux spectrum in other words) for the whole reactor.

Code: Select all

ene 2 3 100 1E-11 20.0
det All de 2 du 0 dv 1.0e4

Thank you very much in advance for your response!
With best regards,
Sasha.

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Jaakko Leppänen
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Re: Flux Interpretation and Units in SERPENT

Post by Jaakko Leppänen » Fri Sep 11, 2015 4:54 pm

The manual is wrong. TOT_FLUX is not divided by volume. Instead, similar to detectors, it is the integral flux, i.e. the value is integrated over space, energy and time. Division by volume gives the volume-averaged flux in units n/cm^2/s.
- Jaakko

Sasha
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Re: Flux Interpretation and Units in SERPENT

Post by Sasha » Fri Sep 11, 2015 5:03 pm

Thank you very much for the clarification!
Sasha.

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