Online Monitoring of the Osiris Reactor with the Nucifer Neutrino Detector

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 an new tool to assess both the thermal power and the fissile content of the whole nuclear core and could be used by the Inter- national Agency for Atomic Energy (IAEA) to enhance the Safeguards of civil nuclear reactors. Deployed at only 7.2m away from the compact Osiris research reactor core (70MW) 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 0.85m3 detector remotely operating at a shallow depth equivalent to 12m 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 40760 electron antineutrinos, the mean number of detected antineutrinos is 281 +- 7(stat) +- 18(syst) electron antineutrinos/day, in agreement with the prediction 277(23) electron antineutrinos/day. Due the 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.Comment: 22 pages, 16 figures - Version

Temporal variability in the relationships between precipitation, discharge and suspended sediment concentration in a small Mediterranean mountain catchment

Relationships between discharge and suspended sediment are very complex in most Mediterranean catchments. In the case of the Arnás catchment (Central Spanish Pyrenees), with a long history of human activity, the main factors that explain the variability of suspended sediment concentration (SCC) during floods are the peak flow and the intensity of precipitation. A cluster analysis distinguishes four types of floods according to different characteristics of precipitation, discharge, suspended sediment transport and antecedent moisture conditions. G1 and G2 floods occur under dry conditions (which prevail most of the year), with moderate rainfall and low precipitation intensity; the discharge and suspended sediment response are very fast but limited in intensity. This suggests that the origin of water and sediment is restricted to areas located very close to the channel. G3 floods also occur under dry conditions, although during intense rainfall events; then the response in both discharge and suspended sediment is very high, showing an enlargement of the contributing areas. Under very wet conditions (G4 floods) relatively moderate precipitation produces a very high response in discharge, but suspended sediment concentration records moderate values due to the effect of dilution when the entire catchment is contributing. © IWA Publishing 2007