Add support for spontaneous fission yield (sfy) #8
Description
In the past, fission yields were only given for neutron-induced fission (so-called nfy — neutron-induced fission yields). Nowadays and for example since JEFF-3.1, these fission yields are also given for spontaneous fission (so-called sfy — spontaneous fission yields). These spontaneous fission yields are today not taken into account in the production of Draglib.
Before embracing any development, it would be useful to evaluate their importance. For example, it would be possible to replace neutron-induced fission yields (nfy) by spontaneous fission yields (sfy), for the 3 isotopes present since JEFF-3.1 (Cm242,244, Cf252) in a depleting PWR cell. Attention could be focused on differences of reactivity (and their decompositions with DUO module), decay heat and fission products concentrations.