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David Lhuillier, CEA-SaclayCEA - Saclay1 Thermal Power with Neutrinos Motivation - Principle Absolute and relative accuracy Mini-detectors, running exp and projects. Slide 2 David Lhuillier, CEA-SaclayCEA - Saclay2 Standard power measurements: n counters: very large dynamic, high sensitivity to relative changes. But flux distortions lead to complex translation into P th number. Heat evacuated by coolant: depends on flow profile and turbulences. P th /P th ? Getting an argued answer turns out to be a challenge ( or maybe Michel didnt try hard enough, he contacted only 12 potential speakers)... Neutrino approach: very complementary, mostly independent syst errors. Interest for absolute measurement and low frequency remote monitoring using simple and low cost detectors. Prototype of ~1m 3 mini-detector to establish achievable precision. Motivations Slide 3 David Lhuillier, CEA-SaclayCEA - Saclay3 Leading Order Approach 235 U Z=N Z N Fission of 235 U 36 56 Fission products evolve toward stability via decay chains Rb 37 92 38 92 Sr e e (no threshold) Slide 4 David Lhuillier, CEA-SaclayCEA - Saclay4 Leading Order Approach flux = direct image of P th Kamland, PRL 90 (2003) 021802 ocsillate: P( e e ) = P(E,L) But no significant flux distortion with E = few MeV and L = few 10m Sensitive to weak interaction only, almost no int. with matter 10 -17 barn Reactor core spectrum Slide 5 David Lhuillier, CEA-SaclayCEA - Saclay5 e Detection e + p e + + n Prompt e + signal E prompt = E - M n -M p +m e Delayed n capture after thermalization inverse process: Threshold: M n -M p + M e = 1.8 MeV & Slide 6 David Lhuillier, CEA-SaclayCEA - Saclay6 e Detection ( det = 50%) Flux int. rate 1.8 MeV threshold Huge flux compensate tiny cross section. Miniature detector very close to reactor core can reach pretty high counting rate: 1t target @ 25m of 1GW e reactor 1% stat on total flux within 5.5 days Slide 7 David Lhuillier, CEA-SaclayCEA - Saclay7 Going to NLO Fuel burn-up: Slide 8 David Lhuillier, CEA-SaclayCEA - Saclay8 Fissile Isotopes spectra Fission fragments from 239 Pu heavier in the light hump 235 U 239 Pu A corresponding energy spectra are different Slide 9 David Lhuillier, CEA-SaclayCEA - Saclay9 Fissile Isotopes spectra 235 U 239 Pu E / fission201.7 MeV210.0 MeV (E >1.8 MeV) 2.94 MeV2.84 MeV / fission (E >1.8 MeV) 1.921.45 3.2 10 -43 cm 2 2.76 10 -43 cm 2 All curves normalized to same number of fissions For a constant P th, the of neutrino flux from pure 235 U would be 1.6 times larger than the one from pure 239 Pu ! Slide 10 David Lhuillier, CEA-SaclayCEA - Saclay10 e flux vs Time Fractional # of fission Time 235 U 238 U 239 Pu 241 Pu 070%6%20%4% 1 year49%6%40%5% 1 year cycle of a PWR reactor @ P e = 0.9 GW 10% (only) decrease over 1 year Depends on fuel history, detection thresholds & resol. k(t) independent of P th for a given reactor (?) 1/3 fresh fuel, 1/3 one year old, 1/3 two years old 35% constant E resolution P th = cst ! Normalized to T=1day Slide 11 David Lhuillier, CEA-SaclayCEA - Saclay11 e spectrum shape vs Time Set clever cuts and weights to reduce (P th ) or enhance (non-prolif) sensitivity to burn-up? Margin reduced by stat loss at high E and background at low E. Get isotopic composition and then P th from energy shape only? Does current knowledge of e energy spectra allow to get rid of fuel history? Slide 12 David Lhuillier, CEA-SaclayCEA - Saclay12 Integral Measurements @ ILL Target foil ( 235 U, 239 Pu, 241 Pu) in thermal n flux High resolution spectrometer ILL research reactor (Grenoble, France) S total = S 235U + S 239PU + S 241PU + S 238U Spectra assumed to be at equilibrium after 1 day of irradiation Possible check of deviation from equilibrium and improvement of e - conversion procedure using detailed simulation. (see M. Fallots talk) e-e- e-e- Reference for previous reactor experiments K. Schreckenbach et al. Phys. Lett. B160 (1985) 325. +3% norm. error Slide 13 David Lhuillier, CEA-SaclayCEA - Saclay13 Stand Alone Measurement P. Huber & T. Schwetz, Phys.Rev. D70, 053011 (2004). Fuel composition assumed constant during data taking and extracted only from shape of total spectrum. Almost perfect detector. # of e events 1 error Slide 14 David Lhuillier, CEA-SaclayCEA - Saclay14 Stand Alone Measurement No! : input of fuel composition, even with few % accuracy, improves a lot the above stat convergence. Same power accuracy asymptote can then be reached within few days. Already useful to electricity companies? (let me know) Is N evt >10 5 mandatory? Best absolute accuracy currently achievable ~3% Slide 15 David Lhuillier, CEA-SaclayCEA - Saclay15 Improve Absolute Accuracy (?) N N fission P th /fission Dominant error ~3% det x m tg x effects + Measure N x det x m tg over full 50 days cycle(s), with virtually pure 235 U spectrum. Chemical analysis or spectroscopy of removed fuel could provide N fissions at 2% level? Would shunt all complex stuff about n flux evolution and fission. Non negligible experimental effort but 1% improvement on P th could be a big deal Calibration measurement at research reactor, e.g. ILL-Grenoble: Controlled at David Lhuillier, CEA-SaclayCEA - Saclay16 Monitoring All correlated errors cancel out Dominated by effective statistical convergence after cuts and background subtraction Looks promising: 1% stat should be achievable within few days @ 25m from P th >1GW reactor. Comparable or higher accuracy already provided by other methods but provide a remote non-intrusive monitoring with limited knowledge of fuel evolution. Portable mini-detector could cross-calibrate different reactors, possibly of different types. Ultimately limited by control of background and detector stability. Slide 17 David Lhuillier, CEA-SaclayCEA - Saclay17 Miniature Detectors Slide 18 David Lhuillier, CEA-SaclayCEA - Saclay18 15 cm steel chamber Kurchatovs Pioneers PWR Rovno reactor (Russia) 1.3 GW th Liquid scintillator active shielding Plastic scintillator active shielding 50 cm Boron Polyethylene chambers ~1m 3 of mineral oil + 0.5 g/l Gd d= 0.78 g/cm 3 84 PMT, det ~50% (see V. Sinevs talk) H 2 O 3 He WINDROSS 1986 Slide 19 David Lhuillier, CEA-SaclayCEA - Saclay19 Kurchatovs Pioneers Detector rate per 10 5 s Days Reactor power in % of 1375 MW Rate per 10 5 sec n /(1+k) = W th =0.733 0.005 evt./MW th Experimental burn-up curve Proportionality to P th after burn-up correction Clear signal P th and burn-up monitoring Slide 20 David Lhuillier, CEA-SaclayCEA - Saclay20 Sandia/ LLNL (see N. Bowdens talk) SONGS detector deployed at the San Onofre Nuclear Generating Station 3.4 GW th ~10 21 /s 3800 int. expected per day in 1m 3 liq. scint. target Low cost and robust detector Automated, non intrusive measurement Slide 21 David Lhuillier, CEA-SaclayCEA - Saclay21 Sandia/ LLNL Removal of 250 kg 239 Pu, replacement with 1.5 tons of fresh 235 U fuel Reactor Power (%) Remarkable monitoring of reactor operation. 20 mwe overburden: large induced correlated background. Spoiling stat. convergence ~450 evts/day after cuts Slide 22 David Lhuillier, CEA-SaclayCEA - Saclay22 Double Chooz Inspired Detector CEA-DSM-DAPNIA (T. Lasserres proposal) Slide 23 David Lhuillier, CEA-SaclayCEA - Saclay23 GEANT4 Simulation based on the GLG4Sim & DCGLG4Sim packages Chimney scint. volume (8 liters) Chimney : 12 mm Acrylics vessel Buffer liquid (1.5 m 3 min. oil, L~50m) Steel/Lead Shielding (100 mm) Buffer Vessel (Stainless steel + surface) Monolithic Target Volume (1.86 m 3 Gd_scint, L~5m) Target Vessel: 12 mm Acrylics vessel 17 PMTs (8) 2.4 m 1.6 m Geometry Slide 24 David Lhuillier, CEA-SaclayCEA - Saclay24 Full detector from above 17 PMTs, side view 17 PMTs, Top view Visible photon (2 eV) single track Target liquid 20% PXE+80%dodecane 0.1% Gd-doped Scintillator Fluors: 6 g/l PPO, 25 mg/l Bis-MSB d=0.8, 7000 photons/MeV, L~5 m PMTs 2 rings of 12 and 5 8 modules Full PMT optical Model implemented R( ,), A( ,), T( ,) Acrylics: 8 mm (L~5 m, cutoff David Lhuillier, CEA-SaclayCEA - Saclay26 No position reconstruction because highly reflective Buffer surface Energy response E e+ > 2.5 MeV p.e.> 1000 e ~ 85 % E n > 4 MeV p.e. > 1800 n ~ 79 % Time cut coincidence time of 100 s t ~ 97% Global efficiency tot ~ e x Gd x n x t ~ 0.57 Detector Efficiency Quenching from Birks law d(E quenched) = dE / (1 + kB dE/dx) 8 MeV Gd peak (Only) Capture efficiency Gd ~ 88% induced positrons induced Gd capture Slide 27 David Lhuillier, CEA-SaclayCEA - Saclay27 2 fixed fuel compositions (in fraction of fission per isotope) 235 U=0.66 239 Pu=0.24 238 U=0.08 241 Pu=0.02 235 U=0.47 239 Pu=0.37 238 U=0.08 241 Pu=0.08 Kolmogorov-Smirnov statistical test. Nul Hypothesis: the two burn-up induce identical p.e. spectra ~28500 events ~5 days of data taking (including efficiencies) Photoelectron Hits spectrum KS prob. 0.05 (shape ony)