Fuel-Composition Dependent Reactor Antineutrino Yield at RENO

Bak, G. (Institute for Universe and Elementary Particles, Chonnam National University, Gwangju 61186, Korea) ; Choi, J. H. (Institute for High Energy Physics, Dongshin University, Naju 58245, Korea) ; Jang, H. I. (Department of Fire Safety, Seoyeong University, Gwangju 61268, Korea) ; Jang, J. S. (GIST College, Gwangju Institute of Science and Technology, Gwangju 61005, Korea) ; Jeon, S. H. (Department of Physics, Sungkyunkwan University, Suwon 16419, Korea) ; Joo, K. K. (Institute for Universe and Elementary Particles, Chonnam National University, Gwangju 61186, Korea) ; Ju, K. (Department of Physics, KAIST, Daejeon 34141, Korea) ; Jung, D. E. (Department of Physics, Sungkyunkwan University, Suwon 16419, Korea) ; Kim, J. G. (Department of Physics, Sungkyunkwan University, Suwon 16419, Korea) ; Kim, J. H. (Department of Physics, Sungkyunkwan University, Suwon 16419, Korea) ; Kim, J. Y. (Institute for Universe and Elementary Particles, Chonnam National University, Gwangju 61186, Korea) ; Kim, S. B. (Department of Physics and Astronomy, Seoul National University, Seoul 08826, Korea) ; Kim, S. Y. (Department of Physics and Astronomy, Seoul National University, Seoul 08826, Korea) ; Kim, W. (Department of Physics, Kyungpook National University, Daegu 41566, Korea) ; Kwon, E. (Department of Physics and Astronomy, Seoul National University, Seoul 08826, Korea) ; Lee, D. H. (Department of Physics and Astronomy, Seoul National University, Seoul 08826, Korea) ; Lee, H. G. (Department of Physics and Astronomy, Seoul National University, Seoul 08826, Korea) ; Lee, Y. C. (Department of Physics and Astronomy, Seoul National University, Seoul 08826, Korea) ; Lim, I. T. (Institute for Universe and Elementary Particles, Chonnam National University, Gwangju 61186, Korea) ; Moon, D. H. (Institute for Universe and Elementary Particles, Chonnam National University, Gwangju 61186, Korea) ; Pac, M. Y. (Institute for High Energy Physics, Dongshin University, Naju 58245, Korea) ; Park, Y. S. (Institute for Universe and Elementary Particles, Chonnam National University, Gwangju 61186, Korea) ; Rott, C. (Department of Physics, Sungkyunkwan University, Suwon 16419, Korea) ; Seo, H. (Department of Physics and Astronomy, Seoul National University, Seoul 08826, Korea) ; Seo, J. W. (Department of Physics, Sungkyunkwan University, Suwon 16419, Korea) ; Seo, S. H. (Department of Physics and Astronomy, Seoul National University, Seoul 08826, Korea) ; Shin, C. D. (Institute for Universe and Elementary Particles, Chonnam National University, Gwangju 61186, Korea) ; Yang, J. Y. (Department of Physics and Astronomy, Seoul National University, Seoul 08826, Korea) ; Yoo, J. (Institute for Basic Science, Daejeon 34047, Korea) (Department of Physics, KAIST, Daejeon 34141, Korea) ; Yu, I. (Department of Physics, Sungkyunkwan University, Suwon 16419, Korea)

12 June 2019

Abstract: 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)×1043 cm2/fission and measure a total average IBD yield of (5.84±0.13)×1043 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)×1043 and (4.18±0.26)×1043 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.


Published in: Physical Review Letters 122 (2019)
Published by: APS
DOI: 10.1103/PhysRevLett.122.232501
License: CC-BY-4.0



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