File:PhysRevLett.122.232501.pdf

English: We report a fuel-dependent reactor electron antineutrino (¯νe) yield using six 2.8 GWth reactors in the Hanbit nuclear power plant complex, Yonggwang, Korea. The analysis uses 850 666 ¯νe candidate events with a background fraction of 2.0% acquired through inverse beta decay (IBD) interactions in the near detector for 1807.9 live days from August 2011 to February 2018. Based on multiple fuel cycles, we observe a fuel 235U dependent variation of measured IBD yields with a slope of (1.51±0.23)×10−43  cm2/fission and measure a total average IBD yield of (5.84±0.13)×10−43  cm2/fission. The hypothesis of no fuel-dependent IBD yield is ruled out at 6.6σ. The observed IBD yield variation over 235U isotope fraction does not show significant deviation from the Huber-Mueller (HM) prediction at 1.3 σ. The measured fuel-dependent variation determines IBD yields of (6.15±0.19)×10−43 and (4.18±0.26)×10−43  cm2/fission for two dominant fuel isotopes 235U and 239Pu, respectively. The measured IBD yield per 235U fission shows the largest deficit relative to the HM prediction. Reevaluation of the 235U IBD yield per fission may mostly solve the reactor antineutrino anomaly (RAA) while 239Pu is not completely ruled out as a possible contributor to the anomaly. We also report a 2.9 σ correlation between the fractional change of the 5 MeV excess and the reactor fuel isotope fraction of 235U.