Kinetic parameter evaluation --update

User Support
1

Dear community members,

I would like to draw your attention in evaluating kinetic parameter like, delayed neutron fraction (\beta_{eff}) and prompt neutron lifetime (l_p) using perturbation
free techniques. Refer the literature [1]. With some success I’m able to calculate the l_p for some of the known experimental values [2].

Regarding \beta_{eff} the MCNP community evaluate this parameter using the method called prompt method, where they used the relation;
[
\beta_{eff} = 1 - k_p/k_{eff}
]
Where k_eff is the fundamental eigenvalue and the k_p is the prompt eigenvalue taking only prompt neutron into consideration. In MCNP this easy with using the totnu card.

My question is whether we have any such option in OpenMC or the developer can mention locations in the source code where some modifications could be done to evaluate
k_p only.

With regards
Ajay RAWAT

[1] Perturbation-independent methods for calculating research reactor kinetic parameters, ANL0RERTR0TM-30.
[2] Tonoike, Kotaro, et al. Journal of nuclear science and technology39.11 (2002): 1227-1236.

2

Hi Ajay,

Right now there is no option in OpenMC that is equivalent to MCNP’s TOTNU option. There was some work on implementing adjoint-weighted tallies which would provide a more accurate way to calculate kinetics parameters like beta-effective. However, I’m not sure when it will make it into the mainstream code.

That being said, changing the source so that only prompt neutrons are generated is quite trivial – see here for a diff showing what lines would need to be changed. Let me know if you run into any trouble with it.

Best regards,
Paul

3

Dear Paul,

Thankyou for the reply.

Merry X-mas and a Happy New Year in advance.

with regards
Ajay RAWAT