MAVRIC Secondary Photon and Activation from Shielding Material

[Zeyu Chen]

Dear all,

         I have two questions related to the mechanism of MAVRIC/MONACO.

         1) Taking the example of shielding neutron with a layer of Boron. I know from my simulation that secondary photons are generated in the simulation. 

             However, I'm not where exactly these photons come from. For example, I believe SCALE calculates gammas from (n,γ) reaction from Boron, but does SCALE also consider the photons created by (n,α) reaction?

         2) Activated shielding materials can undergo decay. Their decay products may also undergo reactions that create photons.

             I know that ORIGEN can do this type of analysis, but can this type of analysis be achieved in MAVRIC calculation?

Thank you,

Zeyu Chen  

[Cihangir]

Dear Zeyu,

See my responses to your questions below.

1) Yes, MAVRIC will generate gammas from all possible gamma production reactions (e.g. inelastic scattering, fission, radiative capture, and other particle production reactions including (n,α), (n,p), (n,t), etc.)

2) You can use energy distributions of neutrons and gammas from ORIGEN via i) using "origensBinaryConcentrationFile" distribution type, or ii) "origensDiscreteGammas" type.  Please refer to the SCALE Manual for how to use these distributions.

Cheers,

Cihangir

[Zeyu Chen]

Dear Cihangir,

    for question 2, currently I am using source distributions from ORIGEN already (or maybe .f71 files from criticality calculation).

    Please correct if I made a mistake:

    Currently I applied the source distribution in a "source region" using .f71 file as an input.

    Neutrons may activate some of the shielding material and that material could decay. Does the decay products participate in the shielding calculation?

    Or maybe consider this example(although not an activation example): 

    consider neutron hitting a Boron Layer. SCALE calculates the gamma from "10B(n,α)7Li" reaction as you replied above. 

    Does SCALE also consider photons created by (n,γ) from 7Li? Because Li was not defined initially in the geometry, and my source from .f71 is only applied in the source region and not in shielding material.

Thank you,

Zeyu Chen

[Cihangir]

Q) Does the decay products participate in the shielding calculation?

A) It is typically the total energy spectra for neutron and gamma requested from the ORIGEN .f71 files. ORIGEN includes all decay products when and their contribution to the total energy spectra. However, MAVRIC only imports the energy spectra and not the produced isotopes from the decay reactions. 

Q) Does SCALE also consider photons created by (n,γ) from 7Li? 

A) No, MAVRIC will not sample any Li-7 reactions since it is not in the compositions provided in the input. You need to provide the exact composition at any given time to MAVRIC in order to account for (n,γ) reaction gammas. You can find out the composition/concentration of materials in ORIGEN calculations by looking at the ORIGEN output file (by enabling printing in the options) directly or use Fulcrum or OPUS with the generated f71 file.

Cheers,

Cihangir

[Zeyu Chen]

Hello Cihangir,

       Thank you, I think that answers my question.

Best,

Zeyu Chen