Reaction frequency using multigroup cross-section and inverse-velocity

[cjwiguna]

Greetings all!

According to this thread, inverse-velocity score is a flux-weighted inverse-velocity:

Kinetic Parameter Calculation

All tallies will give you quantities that are “per source particle”. Since each source particle is lost (absorbed or leaked), this means that “per source particle” is really the same thing as “over the total loss rate”. I ran a quick test on the Jezebel benchmark using OpenMC and MCNP and get the following results: MCNP prompt removal lifetime = 3.7435e-9 +/- 2.7119e-12 OpenMC inverse-velocity = 3.73529e-9 +/- 3.84415e-12

Which, if I’m not wrong, means \text{inverse velocity score} = \frac{\phi}{v} for each particles energy (does OpenMC average this value over the filter domain?).

Now, if I tally the flux and a reaction–e.g absorption, over a spatial domain with EnergyFilter for multigroup approach, I can “approximate” the reaction cross-section using this relationship:
\Sigma_{abs}(E_i)\approx\frac{\text{absorption score}}{\phi}\vert_{E_i}

If I want to get the reaction rate per second, can I instead do the following?
\text{Absorption reaction rate}(E_i) = v\Sigma_{abs}\vert_{E_i} = \frac{\text{absorption score}}{\text{inverse-velocity score}}\vert_{E_i}

Thanks in advance!

Best regards,
Chris