It doesn't appear to be very relevant, looking at different fuel cycles' transients.jaro wrote:It's important to note that there is a significant difference in reactor controllability when using different fuel types in reactors.
For example, the delayed neutron fraction of U233 is small relative to the U235 we normally use: 0.67% versus 1.62%.
Much more important is speed and magnitude of the feedback coefficients, and reactivity reserve (in case of control rod withdrawal accidents)/reactivity insertion possibilities.
MSRs should do well, with light elements like Be, F in the salt and alpha emitters directly inside this light element mixture. After some time the salt becomes a giant neutron source.Besides that, there may also be important sources of delayed neutrons that do not come from fission product decay.
For example, when heavy water moderator is used, we get some delayed neutrons from gamma ray hits on deuterium nuclei.