Nuclide filter for IFP method

[OlivaresDarian]

Description

In order to study which isotopes contribute to the $\beta_{eff}$ estimation, a very studied aspect, it could be interesting to add a nuclide filter to the beta_numerator tally.

Its implementation must respect the recursive principle of the IFP method, so it should not study the p.event_nuclide() of the descendant but of the ancestor. This information has to be saved in a similar way as IFP does nowadays with the delayed neutron family.

It is important that the filter should be applied only to IFP calculations.

Compatibility

It has to be applied to the IFP implementation.