Flux output unit

[Mohammad Hashemi]

Dear All, 

What is the exact unit of the flux output in OpenMOC? Is it track length per second or can it be already divided by the volume of the domain and therefore can be per square centimeter ?

Best regards

Mohammad 

 

[Guillaume Giudicelli]

I think I replied in private but I guess it did not show up here, so for the future onlooker:

The flux has no units, it is normalized so that the fission source integrates to 1 over the whole domain. 

To have the right unit for flux, you need to renormalize the fission source to the reactor power, so multiply the flux by the power. 

It will be volume averaged. 

Best,

Guillaume

[Tanvir]

Hi Guillaume,

Could you explain why multiply the flux value by the power gives the traditional flux unit(n/cm2.sec)?

Best

Tanvir

[Guillaume Giudicelli]

Correction to the previous answer:

Le mar. 27 avr. 2021 à 08:11, Guillaume Giudicelli <guillaume....@gmail.com> a écrit :

Hi Tanvir

So the current normalization of the flux is 

sum_g ( (nu sigma_f)_g phi_g) = 1

The 'normalization' of the flux in a reactor is 

sum_g ( (kappa sigma_f)_g phi_g) = Power.  with kappa the energy produced by fission

So it's a little more involved than that actually. You can use the python API to compute that later sum and re-normalize the flux. 

Or you can use an approximate values for kappa, like 200MeV/fission.

Best,

Guillaume

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[Tanvir]

Hi Guillaume,

If possible, Could you give me a small python file for such a problem?

Best

Tanvir

[Guillaume Giudicelli]

Hi Tanvir

I don't have that handy. If you make such a utility to compute the normalization factor, it'd be helpful to make a PR to add it to the python API. 

Best,

Guillaume

[Kevin McLaughlin]

Hello,

A follow up question for this thread: how is the normalization done for purely fixed source calculations? Thanks!

Best,
Kevin

[AB C]

Excuse me, I'd like to ask two more questions

①If, as you say : sum_g ( (nu sigma_f)_g phi_g) = 1

Can we get the real flux(n/cm2.sec) by this way : phi_g(n/cm2.sec)=phi_g(normalized)*P*nu/kappa

②By the way , is the normalization in all regions ? That is to say : sum_fsr[ sum_g ( (nu sigma_f)_g phi_g) ] = 1