Normalization of tallies

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1

Hello everyone,

I am currently studying the performance of Serpent 2 and OpenMC and I am struggling to compare certain values.
I find very different flux and power so I searched information about normalization in both codes but it is not very clear to me. Could anyone tell me how both codes differ in this matter?

Thanks.
Juliette

2

Hello Juliette,
Perhaps Paul’s this reply might help you

3

Hello @fsabab,

My question is actually more about the different methods of normalization in OpenMC.
How many are there? What are their differences and how can I change them? For example, in Serpent2, there are 4 ways of calculating the deposited energy (“set edepmode” command in Serpent2 : Input syntax manual - Serpent Wiki).

What I am trying to do is explain the huge differences I encountered across tallies for the same system between Serpent2 and OpenMC.

Here is my code :
##################################################

Materials definition

mat = openmc.Material()
mat.add_nuclide(‘Ga69’,2.0517e-2)
mat.add_nuclide(‘Ga71’,1.3615e-2)
mat.add_nuclide(‘Pu239’,9.1951e-1)
mat.add_nuclide(‘Pu240’,4.3465e-2)
mat.add_nuclide(‘Pu241’,2.8975e-3)
mat.set_density(‘g/cm3’,15.61)

materials = openmc.Materials([mat])

materials.export_to_xml()

Geometry defintion

sphere = openmc.Sphere()
inside = -sphere
sphere.r = 6.39157
sphere.boundary_type = ‘vacuum’

fuel = openmc.Cell()
fuel.fill = mat
fuel.region = inside

geometry = openmc.Geometry([fuel])

geometry.export_to_xml()
#############################################
The exact same specifications and the same database (ENDF B VII.1) are used for both codes.

And here are the tallies results :

OpenMC :

flux 4.6985563774625545 0.00012531146042234445
inverse-velocity 3.741619004300651e-09 1.7010891996524724e-13
heating 55506645.00148293 1436.9080313350564
k_combined 1.0008284918766601 2.4688889916300313e-05
beta eff 0.002045324880571339 1.0802094095533329e-08

Serpent2 :

impKeff 1.000857 4.182993652567228e-05
totPower 65965093.75000001 2720.8168904348677
totFlux 4.69654775 0.0001713967881097879
adjIfpAnaBetaEff 0.0018457935 7.719006695098435e-06
adjIfpLifetime 2.8785955e-09 1.0152401509507941e-12

How can we explain the differences, especially between the power/heating and inverse-velocity/lifetime ?

Thank you for your help.

4

There are the following types of normalization according to this documentation

  1. For fixed source problems, the openmc.Source.strength value has to be specified
  2. For eigenvalue problems, there are several following ways
    • using the heating-local score.
    • kappa-fission or fission-q-recoverable scores along with an estimate of the extra heating due to neutron capture reactions.
    • Calculate the overall fission rate and then used a fixed Q value to estimate the heating rate.

Regarding, energy deposited modes in OpenMC, you can follow this link
I’m not sure about the difference occurring in the power/heating and inverse-velocity/lifetime parts. Perhaps, someone else may be able to help you in this case. I hope this helps.

5

Thank you for your help ! I think I figured it out for power.