Online monitoring of the Osiris reactor with the Nucifer neutrino detector

Abstract

Originally designed as a new nuclear reactor monitoring device, the Nucifer detector has successfully detected its first neutrinos. We provide the second shortest baseline measurement of the reactor neutrino flux. The detection of electron antineutrinos emitted in the decay chains of the fission products, combined with reactor core simulations, provides a new tool to assess both the thermal power and the fissile content of the whole nuclear core and could be used by the International Agency for Atomic Energy (IAEA) to enhance the Safeguards of civil nuclear reactors. Deployed at only 7.2 m away from the compact Osiris research reactor core (70 MW) operating at the Saclay research centre of the French Alternative Energies and Atomic Energy Commission (CEA), the experiment also exhibits a well-suited configuration to search for a new short baseline oscillation. We report the first results of the Nucifer experiment, describing the performances of the ∼ 0.85 m 3 detector remotely operating at a shallow depth equivalent to ∼ 12 m of water and under intense background radiation conditions. Based on 145 (106) days of data with reactor ON (OFF), leading to the detection of an estimated 40 760 νe, the mean number of detected antineutrinos is 281 ± 7(stat) ± 18(syst) νe/day, in agreement with the prediction 277 ± 23 νe/day. Due to the large background no conclusive results on the existence of light sterile neutrinos could be derived, however. As a first societal application we quantify how antineutrinos could be used for the Plutonium Management and Disposition Agreement. arXiv:1509.05610v4 [physics.ins-det]

Prospects for improved understanding of isotopic reactor antineutrino fluxes

“…A number of HEU-based experiments have thus far not demonstrated the level of background rejection necessary to achieve the 1∶1 signal-to-background ratio (S:B) assumed in this study [46,55,57]. On the other hand, other short-baseline efforts have either already achieved a S:B ratio far surpassing 1∶1 at LEU reactors [56] or have presented prototype-and Monte Carlo-based evidence to support their achievement of a S:B of 1∶1 or higher at HEU reactors [35,37].…”

“…Measurement of IBD detection rates dN=dt has enabled a variety of reactor antineutrino experiments to generate one or multiple IBD yield values σ f spanning a wide range of fission fractions. Some experiments have utilized highly enriched 235 U-burning reactors to measure σ f for a single set of fission fractions [5,[43][44][45][46][47]. Other experiments reporting σ f measurements have utilized commercial low-enriched uranium reactors experiencing substantial fission fraction variations over the course of their fuel cycles.…”

“…For the purpose of simplicity, finite core and detector sizes, variations in IBD rates due to nonequilibrium conditions in the reactors, and IBD contributions from spent or nonfissioning nuclear fuel are not considered; it is expected that corrections for these effects will result in negligible changes to statistical or systematic uncertainties in the IBD yield measurements. It is further assumed that any systematic uncertainties due to background estimation and subtraction are also negligible; demonstration of highprecision cosmogenic background reduction for shortbaseline reactor experiments utilizing continuous monitoring of fast neutron and muon rates has been previously demonstrated [46].…”

Reactor fuel fraction information on the antineutrino anomaly

“…We use the data listed in table 1 of ref. [12] of the following experiments: Bugey-4 [13], Rovno91 [14], Bugey-3 [15], Gosgen [16], ILL [17,18], Krasnoyarsk87 [19], Krasnoyarsk94 [20,21], Rovno88 [22], SRP [23], Nucifer [24], Chooz [25], Palo Verde [26], Daya Bay [27], RENO [28], and Double Chooz [29]. The Daya Bay data in ref.…”

Getting the most neutrinos out of IsoDAR

“…Most of these proposals search for sterile neutrinos in the disappearance channel ν e → ν e . Experiments using reactor neutrinos are at an advanced stage [26]: some have completed runs [27], are already running [28][29][30], have a running prototype detector module [31], or are under construction [32].…”