Fission products

Physics

Yield (engineering)

Isotope

Fission

Anomaly (physics)

Radiochemistry

Neutron

Nuclear physics

Chemistry

Condensed matter physics

Fission product yield

Thermodynamics

Physical Review Letters

We report a fuel-dependent reactor electron antineutrino (ν¯e) yield using six 2.8 GWth reactors in the Hanbit nuclear power plant complex, Yonggwang, Korea. The analysis uses 850 666 ν¯e 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 U235 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 U235 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 U235 and Pu239, respectively. The measured IBD yield per U235 fission shows the largest deficit relative to the HM prediction. Reevaluation of the U235 IBD yield per fission may mostly solve the reactor antineutrino anomaly (RAA) while Pu239 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 U235.Received 26 June 2018Revised 16 May 2019DOI:https://doi.org/10.1103/PhysRevLett.122.232501Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Funded by SCOAP3.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasFissionNuclear reactionsNuclear reactorsParticle interactionsNuclear PhysicsParticles & Fields

Fuel-Composition Dependent Reactor Antineutrino Yield at RENO