LLNL This work was partially performed under the auspices of the US Department of Energy by the University of California, Lawrence Livermore National Laboratory, under contract No. W-7405-Eng-48. Safeguards and Cooperative Monitoring of Reactors With Antineutrino Detectors Adam Bernstein, (P.I.) Jan Batteux Dennis Carr Celeste Winant Chris Hagmann Norm Madden John Estrada (P.I.) Nathaniel Bowden Jim Lund C. Michael Greaves N. Mascarhenas Lawrence Livermore National Laboratory Sandia National Laboratories California Stanford University Giorgio Gratta, Yifang Wang University of Alabama Andreas Piepke Oak Ridge National Laboratory Ron Ellis Collaborators

LLNL Project Timeline Late 2000 Research into 1 kT explosion detection Recognize futility of this effort – publish paper 2000/2001Research into reactor monitoring 2002Begin installation at San Onofre Oct. 2003First data taking Dec. 2003IAEA interest / experts meeting NowOperational for 100 days, 70 events/day Feb 9 th 2004Refueling shutdown Summer events per day

LLNL Properties of Antineutrinos and Antineutrino Detectors Rates near reactors are high  1 ton detector, 24 m from reactor core  Not untypical core thermal power = 3.46 GW  3925 events/day/ton (100% efficient detector) Rate and spectrum are sensitive to the isotopic composition of the core Cost and complexity can be made comparable to that of a few high-end Germanium detectors

LLNL Monitoring Reactors with Antineutrino Detectors A. ~1 cubic meter antineutrino detectors placed a few tens of meters from the reactor core B. Compare measured and predicted total daily or weekly antineutrino rates (or spectrum) to search for anomalous changes in the total fission rate C. Identify changes in fissile content based on changes in antineutrino rate (“the burnup effect”) A. Measured in previous experiments B. Rovno quotes 540 kg +- 1% fissile content from shape analysis

LLNL What Good Is That ? 1. Detecting unauthorized production of plutonium outside of declarations 2.Measuring enrichment of freshly loaded fuel and burn-up or plutonium content of spent fuel destined for reprocessing or storage  shipper-receiver difference 3.Checking progress of plutonium disposition, and ensuring burnup is appropriate to core type 4.Monitoring core conversion An integral, continuous, high statistics, non-intrusive, unattended measurement

LLNL Fission Rates Vary with Time and Isotope U-238 Pu-241  Input fuel enrichment can be changed in PWRs  increased plutonium production even at constant power  Easy to alter for CANDU (online refueling)

LLNL Detected Antineutrino Rates Vary With Isotope

LLNL The Antineutrino Rate Tracks Inventory Changes The total antineutrino rate changes with the relative U/Pu content of the core About 250 kg of Pu is generated during the cycle Rate calculation based on a detailed reactor simulation shows an antineutrino rate change of about 10% through a 500 day equilibrium reactor cycle This “burnup effect” seen and corrected for in past experiments Modern detectors reach 3% precision The change in antineutrino rate directly tracks the fissile inventory even at constant power

LLNL A 1 Cubic Meter Detector, 10 Meters From PWR Core fuel rods with 20 kg Pu replaced with fresh rods (0 kg Pu) assumed 3% systematic error 50% detection efficiency A standard statistical test can identify the switch with > 90% confidence with one month’s data The systematic shift in inventory is reflected by the antineutrino count rate over time Days Counts per day

LLNL Inputs Needed to Predict/Extract an Absolute Antineutrino Measurement 1. Core model with the input parameters: Secondary calorimetric power Pressure Flow rates Boron concentration Inlet temperature  total model error 1% (power dominates) * 2. Antineutrino energy density  error = 3 % 3. Null result from near-reactor oscillation experiments 4. Well understood antineutrino detector (* from “Estimation of Expected Neutrino Signal at Palo Verde”, Lester Miller, Stanford University,unpublished note)

LLNL 3.46 GWt reactor Antineutrino detector in “tendon gallery” with / s per m 2 Installation/testing begun May 2002 The Site, Detector, Signal, Backgrounds  data taking began in late September 2003

LLNL The Underground Experimental Site 20 meter concrete/rock overburden 24 meters from core

LLNL Cutaway Diagram of the LLNL/Sandia Antineutrino Detector Gd-doped Currently operational: 2 cells instrumented with 4 pmts; 0.32 tonnes of Gd- scintillator; quasi-hermetic muon veto hermetic water shield

LLNL The antineutrino interacts with a proton producing… – A 1-7 MeV positron – A few keV neutron – mean time interval 28  sec Both final state particles deposit energy in a scintillating detector over 10s or 100s of microsecond time intervals (depending on the medium) Both energy depositions and the time interval are measured Detection of Antineutrinos

LLNL Backgrounds 1. Muon generated neutrons create “correlated” events  fast neutron  proton knock-on  thermalization and capture within time window  energies and time correlation can mimic the antineutrino 2. Neutron and gamma “singles” can fall within the time coincidence window defining the antineutrino event gammas from surroundings neutrons from S.F., activated nuclei from surroundings muon-induced neutrons Background rate ~ a few dozen per day

LLNL Four Variables Define the Antineutrino Signal VariableEff.  T  > 100 (  sec) 95% the time between a muon veto and a cube signal 10 <  Tcube < 100 (  sec) 70% the time between the two energy depositions mean = 28  sec 3 < E prompt < 10 (MeV) 62% (analytic formula) The prompt, positron-like signal (including annihilation gammas) < E1 < 7 MeV, peak at ~3 MeV 4 < E del < 12 MeV 68% (MC) the delayed, neutron-like signal from Gd gamma cascade “geometry cut”~80% Events with large asymmetries in PMT energy distribution within a cell 1280 events per day  68 events per day (now)  over 800 (with simple upgrades) 100% efficiency  5% efficiency  30% efficiency and 2x volume

LLNL Event Candidates Since the Last Muon antineutrino-like backgrounds (spallation and capture) more likely to occur near a muon  T  > 100  sec Cut on time since last muon:

LLNL 2. Interevent time Interevent time distribution well fit by e -  t/ 28  sec (Capture time set by 0.1% Gd concentration in scintillator) 10 <  Tcube < 100  sec Cut on interevent time:

LLNL Conclusions 1) That antineutrinos can track burnup and plutonium inventory is firmly established by prior experiments and shortly confirmed by us 2) Detector deployment essential for demonstrating practical utility and potential 3) Main challenges: Controlling detector systematic effects (spectrum error, fiducial error, event containment…) Shrinking footprint (coherent scatter, better IVB detector) Transforming a delicate physics instrument into a robust cooperative monitoring device Must compare to existing safeguards methods and demonstrate that the benefit is worth the cost of deployment

LLNL Literature on Applied Antineutrino Physics Reactor Monitoring Bernstein, A., Wang, Y., Gratta, G., West, T., Nuclear Reactor Safeguards and Monitoring with Antineutrino Detectors, J. Of Appl. Phys V.91, Num. 7, p 4672, April 2002Nuclear Reactor Safeguards and Monitoring with Antineutrino Detectors, Klimov, Yu. et al. The remote measurement of power and energy release using a neutrino method, Inst. Obshch. Yad. Fiz, Russia, At. Energ., (1994) 76(2) 130-5, CODEN:AENGAB; ISSN: Detection of Antineutrinos for Non-Proliferation M.M. Nieto, A. C. Hayes, C. M. Teeter, W. B. Wilson,W. D. Stanbro, arXiv:nucl-th/ v1 9 Sep 2003  Conclusion: power and isotopic measurement at m is feasible Explosion Detection A.Bernstein, T. West V. Gupta, An Assessment of Antineutrino Detection as a Tool for Monitoring Nuclear Explosions, Science & Global Security, Volume 9 pp 235, April 2001  Conclusion: 1 kT remote detection is not feasible