REACTOR MONITORING WITH ANTINEUTRINO DETECTOR

The modern status of neutrino physics allows considering an introduction of antineutrino detection technology for remote on-line monitoring of nuclear reactor operation to reduce the threats of weapons-grade plutonium production. This method, based on the measurement of antineutrino radiation emitted by nuclear fuel during the chain fission reaction, was proposed in Kurchatov Institute and then was confirmed in a number of the experiments which have been carried out at the Rovno NPS (USSR) and recently at the San Onofre NGS (USA). At the moment the collaboration of Russian Institutes (Kurchatov, VNIIA, and others) is developing the new pilot facility for antineutrino detection in order to demonstrate advanced technology for identification of unauthorized reactor regimes. The main goals are the permanent real time monitoring of reactor fission rate, determining of the total amount of plutonium accumulated in the core and fixing of unforeseen reactor shutting down for replacement of fuel. The detector contains ~1 ton target of liquid scintillator, which is penetrated by the transparent tubes - rods of ~2 cm in the diameter filled with stable and transparent Gdloaded solution. Antineutrinos interact within the target via the inverse beta decay reaction on protons, forming a positron and a neutron. The positron is detected inside the scintillator, while the thermalized neutron is captured within the rods by Gd and then detected via emitted gammas. In order to increase the gamma detection efficiency, the target is surrounded by the external layer of scintillator which is working both as the additional detector for gammas from the neutron and as the veto detector for the prompt positron signal. Light signals are detected by PMTs dipped into the liquid none scintillate buffer. Experience of works, simulations and background analysis show, that for the ordinary use conditions, the detector, installed at the distance of 20 m from pressurised light water reactor with the thermal power of 3 GW, will provide the measurement accuracy of the daily power production at the level of 3% and reactor shutting down detection at the 95%C.L. during 2-3 hours.