# Kinetic Parameter Calculation

**URL:** <https://openmc.discourse.group/t/kinetic-parameter-calculation/596>\
**Category:** User Support\
**Created:** [April 22, 2020, 2:13am UTC](https://openmc.discourse.group/t/kinetic-parameter-calculation/596 "2020-04-22T02:13:49Z")\
**Posts on this page:** 7\
**Page:** 1

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**Author:** ![Pranto](https://yyz2.discourse-cdn.com/free1/user_avatar/openmc.discourse.group/pranto/32/489_2.png) [@Pranto](https://openmc.discourse.group/u/Pranto)\
**Post date:** [April 22, 2020, 2:13am UTC](https://openmc.discourse.group/t/kinetic-parameter-calculation/596/1 "2020-04-22T02:13:49Z")

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How can I calculate

> > Prompt neutron life time  
> > Effective Neutron generation time

in OpenMC?

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**Author:** ![Pranto](https://yyz2.discourse-cdn.com/free1/user_avatar/openmc.discourse.group/pranto/32/489_2.png) [@Pranto](https://openmc.discourse.group/u/Pranto)\
**Post date:** [April 22, 2020, 10:26am UTC](https://openmc.discourse.group/t/kinetic-parameter-calculation/596/2 "2020-04-22T10:26:08Z")

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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 ?

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**Author:** ![paulromano](https://yyz2.discourse-cdn.com/free1/user_avatar/openmc.discourse.group/paulromano/32/486_2.png) [@paulromano](https://openmc.discourse.group/u/paulromano)\
**Post date:** [April 29, 2020, 1:19pm UTC](https://openmc.discourse.group/t/kinetic-parameter-calculation/596/3 "2020-04-29T13:19:55Z")

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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

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**Author:** ![Pranto](https://yyz2.discourse-cdn.com/free1/user_avatar/openmc.discourse.group/pranto/32/489_2.png) [@Pranto](https://openmc.discourse.group/u/Pranto)\
**Post date:** [April 29, 2020, 8:11pm UTC](https://openmc.discourse.group/t/kinetic-parameter-calculation/596/4 "2020-04-29T20:11:18Z")

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Got it. Thanks for your help.

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**Author:** ![careysub](https://avatars.discourse-cdn.com/v4/letter/c/5f9b8f/32.png) [@careysub](https://openmc.discourse.group/u/careysub)\
**Post date:** [February 26, 2021, 8:12pm UTC](https://openmc.discourse.group/t/kinetic-parameter-calculation/596/5 "2021-02-26T20:12:13Z")

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> 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?

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**Author:** ![paulromano](https://yyz2.discourse-cdn.com/free1/user_avatar/openmc.discourse.group/paulromano/32/486_2.png) [@paulromano](https://openmc.discourse.group/u/paulromano)\
**Post date:** [March 2, 2021, 12:36pm UTC](https://openmc.discourse.group/t/kinetic-parameter-calculation/596/6 "2021-03-02T12:36:44Z")

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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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**Author:** ![zouzou974](https://avatars.discourse-cdn.com/v4/letter/z/3ab097/32.png) [@zouzou974](https://openmc.discourse.group/u/zouzou974)\
**Post date:** [July 5, 2024, 8:55am UTC](https://openmc.discourse.group/t/kinetic-parameter-calculation/596/7 "2024-07-05T08:55:45Z")

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Hi Paul, has there been any updates recently to get the neutron generation time ?
