New prompt fission gamma-ray spectral data from ²³⁹Pu(n_th, f) in response to a high priority request from OECD Nuclear Energy Agency

¹ European Commission, Joint-Research Centre, Directorate G, Geel, Belgium
² Extreme Light Infrastructure - Nuclear Physics (ELI-NP) / Horia Hulubei National Institute for Physics and Nuclear Engineering (IFIN-HH), Bucharest-Magurele, Romania
³ Centre for Energy Research, Hungarian Academy of Sciences, Nuclear Analysis and Radiography Department, Budapest, Hungary
⁴ Institut de Physique Nucléaire Orsay (IPN-Orsay), Orsay, France
⁵ Hamburg University, Department of Physics, Hamburg, Germany
⁶ University of Oslo, Department of Physics, Oslo, Norway
⁷ Ghent University, Department of Physics, Gent, Belgium

^a e-mail: Stephan.oberstedt@ec.europa.eu

Published online: 13 September 2017

Abstract

Benchmark reactor calculations have revealed an underestimation of γ-heat following fission of up to 28%. To improve the modelling of new nuclear reactors, the OECD/NEA initiated a nuclear data High Priority Request List (HPRL) entry for the major isotopes (²³⁵U, ²³⁹Pu). In response to that HPRL entry, we executed a dedicated measurement program on prompt fission γ-rays employing state-of-the-art lanthanum bromide (LaBr₃) detectors with superior timing and good energy resolution. Our new results from ²⁵²Cf(sf), ²³⁵U(n_th,f) and ²⁴¹Pu(n_th,f) provide prompt fission γ-ray spectra characteristics : average number of photons per fission, average total energy per fission and mean photon energy; all within 2% of uncertainty. We present preliminary results on ²³⁹Pu(n_th,f), recently measured at the Budapest Neutron Centre and supported by the CHANDA Trans-national Access Activity, as well as discussing our different published results in comparison to the historical data and what it says about the discrepancy observed in the benchmark calculations.