The STEREO experiment: neutrino spectrum emitted by the ILL research reactor.

The STEREO experiment is measuring the antineutrino flux emitted by the reactor of the Institut Laue-Langevin (ILL) in Grenoble-France. About 400 antineutrinos per effective day of data taking are currently detected. The target volume, segmented in 6 detector cells, allows for a search of a light sterile neutrino in a way independent of the reactor parameters (see poster by P. Del Amo Sanchez). However the detected spectrum also provides a new reference of antineutrino fission-spectrum, with virtually pure contribution from the ²³⁵U isotope given the very high enrichment of the nuclear fuel. In this poster we will present the calculations performed to compare this upcoming new experimental reference with a predicted spectrum. This includes the determination of the accuracy of the thermal power, the estimation of off-equilibrium effects for typical 50-days long cycles and the neutrinos emitted by the spent fuel stored on site and activated materials. Finally the normalization of the reference beta fission-spectra measured at the ILL in the 80’s will be discussed.