# Calculation of "Prompt neutron lifetime" and neutron generation time using Openmc

**URL:** <https://openmc.discourse.group/t/calculation-of-prompt-neutron-lifetime-and-neutron-generation-time-using-openmc/5543>\
**Category:** User Support\
**Created:** [May 22, 2025, 11:04am UTC](https://openmc.discourse.group/t/calculation-of-prompt-neutron-lifetime-and-neutron-generation-time-using-openmc/5543 "2025-05-22T11:04:07Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![s\_rahman\_wave](https://avatars.discourse-cdn.com/v4/letter/s/b5ac83/32.png) [@s\_rahman\_wave](https://openmc.discourse.group/u/s_rahman_wave)\
**Post date:** [May 22, 2025, 11:04am UTC](https://openmc.discourse.group/t/calculation-of-prompt-neutron-lifetime-and-neutron-generation-time-using-openmc/5543/1 "2025-05-22T11:04:07Z")

</div>

Can anyone assist me by saying step by step of calculating prompt neutron lifetime and neutron generation time in openmc. If i get any exact code as example ,this will be much more helpfull

---

<div class="post-metadata">

**Author:** ![s\_rahman\_wave](https://avatars.discourse-cdn.com/v4/letter/s/b5ac83/32.png) [@s\_rahman\_wave](https://openmc.discourse.group/u/s_rahman_wave)\
**Post date:** [May 22, 2025, 11:27am UTC](https://openmc.discourse.group/t/calculation-of-prompt-neutron-lifetime-and-neutron-generation-time-using-openmc/5543/2 "2025-05-22T11:27:55Z")

</div>

Is this how i have to calculate prompt neutron lifetime.

inv\_vel\_tally\_result = sp.get\_tally(name=‘inverse\_velocity\_tally’)  
inv\_vel\_mean = inv\_vel\_tally\_result.mean[0][0][0]  
flux\_tally\_result = sp.get\_tally(name=‘flux\_tally’)  
flux\_mean = flux\_tally\_result.mean[0][0][0]

prompt\_neutron\_lifetime = inv\_vel\_mean / flux\_mean