We reinvestigate the effects of nucleon-nucleon interactions on the se
mileptonic weak processes that control the neutrino physics in a super
nova core. We find clear evidence that any spin or isospin dependent i
nteractions act to reduce the weak interaction rates. Taking the effec
ts of the single pion exchange force as an example, we find large redu
ctions over the whole range of conditions that prevail from the inner
core to the neutrino photosphere.