An Investigation into the Reactor Antineutrino Anomaly Through the Lens of Californium-252

Neutrinos were first proposed by Wolfgang Pauli in 1930 to explain the electron spectra following beta-minus decay. The first experimental evidence of their existence took place in 1956 by a team led by Cowan and Reines employing the huge antineutrino flux generated by nuclear reactors. A new generation of reactor experiments, Daya Bay, Double Chooz, NEOS, PROSPECT, RENO, and STEREO, has collected Inverse Beta Decay (IBD) electron antineutrino spectrum data with unprecedented statistics and energy resolution, revealing two unexpected results with respect to the most reliable models (Huber-Mueller), (i) a ~6% deficit, known as the Reactor Antineutrino Anomaly (RAA), and (ii) an excess at ~6 MeV, known as 'the bump'. The RAA is most likely due to modelling issues in Uranium-235, while several hypotheses have been put forward to explain 'the bump'. A relatively inexpensive to test the methods used to predict reactor antineutrino spectra would be to precisely measure the electron spectrum following the spontaneous fission of Californium-252 to obtain the corresponding antineutrino spectrum. In particular, this experiment would also provide a way of understanding the high-energy section of the antineutrino spectrum measured by the Daya Bay collaboration since the corresponding electron spectra for 235,238U and 239,241Pu are unlikely to be measured at energies higher than 9 MeV due to time constraints. Additionally, the data needed for a reliable summation calculation will have to be improved. In this work we perform a comprehensive comparison between the recommended cumulative yields from the ENDF/B-VIII.0 and JEFF-3.3 libraries, with those obtained from the GEF code as well as experimental values. Surprisingly, despite the relevance of 252-Cf in nuclear science and technology, there is a marked disagreement between databases and theory, and a dearth of experimental data for the neutron rich fission products making a sizable contribution to the IBD spectrum.