Experimental Constraints on Neutrino Spectra Following Fission

We discuss new initiatives to constrain predictions of fission neutrino spectra from nuclear reactors. These predictions are germane to the understanding of reactor flux anomalies; are needed to reduce systematic uncertainty in neutrino oscillation spectra; and inform searches for the diffuse supernova neutrino background. The initiatives include a search for very high-$Q$ beta decay components to the neutrino spectrum from the Daya Bay power plant; plans for a measurement of the $\beta^-$ spectrum from $^{252}$Cf fission products; and precision measurements of the $^{235}$U fission neutrino spectrum from PROSPECT and other very short baseline reactor experiments.