How can I calculate
Prompt neutron life time
Effective Neutron generation time
in OpenMC?
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If I add some artificial 1/v capture cross-section material,
Which material should I choose? Is it B-10?
What will be the value of “Atom density” ?
How can I create linear–linear interpolated continuous capture cross-sections of that artiificial material?
How can I use CLUTCH method in this case? Can I get some example ?
Tallying the “inverse-velocity” score will give you the flux-weighted prompt removal lifetime. There is currently no way to tally the effective generation time, and we don’t have any sensitivity methods like CLUTCH implemented in the main branch (although this is being worked on by students at MIT).
Best,
Paul
Got it. Thanks for your help.
Tallying the “inverse-velocity” score will give you the flux-weighted prompt removal lifetime.
The inverse-velocity tally does not give the prompt removal lifetime directly (the units alone show that).
Comparing the integral for inverse velocity with the ones in LA-UR-03-198 “MCNP — A General Monte Carlo N-Particle Transport Code, Version 5 Volume I: Overview and Theory” show that whereas the integral ratio for inverse velocity has the flux-weighted inverse velocity over the total flux, in MCNP the removal lifetime is the same flux-weighted inverse velocity but over the total loss rate.
What is the correct way to compute the removal lifetime from the inverse velocity using the tally outputs that OpenMC provides?
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
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Hi Paul, has there been any updates recently to get the neutron generation time ?