Analysis of the Reactor Antineutrino Spectrum Using Gamma Rays

Recent electron anti-neutrino measurements have shown a spectral bump in the 5 to 7 MeV region that is not predicted by the β- conversion method based on the high-resolution iron-core electron spectrometer (BILL) measurements. Using the summation method along with the ENDF/B.VII.1 fission yield library and ENSDF decay data library, Dwyer and Langford have pointed out that several specific beta-decaying nuclides are a possible source for this bump. To explore this possibility, 253 nanogram of Uranium 235 sample was irradiated using HFIR for 30 seconds. Subsequently, the gamma ray spectrum was measured for 30 seconds using an ORTEC P-type 44% relative efficiency HPGE. The strongest gamma ray emitted from each of the suggested nuclides has been quantified using a non-linear peak fitting method. The expected yields were calculated using the JEFF-3.3 fission yield library and ENDSF decay data library. The measured gamma ray yields were shown to be within 2-sigma of the expected values for 96-Y, 100-Nb, 95-Sr, 140-Cs and 93-Rb. These results indicate that the spectral bump produced by the summation method could be due to incorrect fission yield values in ENDF/B.VII.1.