| Th. A. Mueller, D. Lhuillier, M. Fallot, A. Letourneau, S. Cormon, M. Fechner,
L. Giot, T. Lasserre, J. Martino, G. Mention, A. Porta,3 and F. Yermia |
| Precise predictions of the antineutrino spectra emitted by nuclear reactors is a key ingredient in
measurements of reactor neutrino oscillations as well as of the recent applications to the surveillance
of power plants in the context of non proliferation of nuclear weapons. We report new calculations
including the latest information from nuclear databases and a detailed error budget. The first part of
this work is the so-called ab initio approach where the total antineutrino spectrum is built from the
sum of all -branches of all fission products predicted by an evolution code. Systematic effects and
missing information in nuclear databases lead to final relative uncertainties in the 10 to 20% range.
A prediction of the antineutrino spectrum associated with the fission of 238U is given based on this ab
initio method. For the dominant isotopes 235U and 239Pu, we developed a more accurate approach
combining information from nuclear databases and reference electron spectra associated with the
fission of 235U, 239Pu and 241Pu, measured at ILL in the 80’s. We show how the anchor point of the
measured total -spectra can be used to suppress the uncertainty in nuclear databases while taking
advantage of all the information they contain. We provide new reference antineutrino spectra for
235U, 239Pu and 241Pu isotopes in the 2-8 MeV range. While the shapes of the spectra and their
uncertainties are comparable to that of the previous analysis of the ILL data, the normalization is
shifted by about +3% on average. In the perspective of the re-analysis of past experiments and
direct use of these results by upcoming oscillation experiments, we discuss the various sources of
errors and their correlations as well as the corrections induced by off equilibrium effects. |
