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Collaborations Double Chooz, Nucifer and MURE

Time evolution of reactor antineutrino energy spectrum and flux. Collaborations Double Chooz, Nucifer and MURE. Outline. 2 reasons why antineutrino spectrum and flux vary with time : Non equilibrium : U and Pu istope  and  energy spectrum simulations

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Collaborations Double Chooz, Nucifer and MURE

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  1. Time evolution of reactor antineutrino energy spectrum and flux Collaborations Double Chooz, Nucifer and MURE AAP09 - Brazil - M. Fallot et al.

  2. Outline • 2 reasons why antineutrino spectrum and flux vary with time : • Non equilibrium : U and Pu istope  and  energy spectrum simulations • Variation of the fuel isotopic content of a reactor core : • reactor antineutrino spectrum and flux simulation • proliferation scenario (taking into account out of equilibrium effects when rapid power changes) AAP09 - Brazil - M. Fallot et al.

  3. -spectra determinations • Integral -spectra measurements:[A. Hahn et al., Phys. Lett. B, 218, (1989)] • 235U, 239,241Pu targets@ILL, at better than 2% until 8 MeV • Summing individual -spectra:[Tengblad et al. (NPA503(1989)136) 111 nuclei @OSIRIS Studsvik and ISOLDE ]  Conversion- e : global shape uncertainty from 1.3%@3MeV to 9%@8MeV • Measurement only related tothermal fission • Irradiation time dependence(20 min & 1.5 d) Don’t agree with the experimental integral spectra (important errors : 5% at 4MeV, 11% at 5MeV and 20% at 8MeV) Remaining short-lived, high Q, unknown nuclei AAP09 - Brazil - M. Fallot et al.

  4. -spectra determinations • i (t) : relative contributions to the total fission (i=1) • i (E) : -spectra 235U, 239Pu, 241Pu, and 238U (Schreckenbach et al. and P. Vogel • Determination of the-spectra : • Theoretical approach : • Microscopic cal. of trans. mat. elts [H-V. Klapdor, Phys. Rev. Lett., 48, (1982)] • Phenomenological model for unknown nuclei + databases [P. Vogel et al., Phys. Rev. C, 24, (1981)] • Determination of the reactor -spectra : • V. Kopeikin :Resolution of the Bateman equations for selected set of fission products + fission rates from the power plants + neutron capture contributions (ENDF database) • Antineutrino experiment approaches:  Don’t take into account-decay from products of radiative capture of neutron In agreement with Chooz and Bugey data (1.9% on the e flux) AAP09 - Brazil - M. Fallot et al.

  5. Neutron capture, non equilibrium effects V. Kopeikin et al. , arXiv:hep-ph/0110290 « Inthe antineutrino energy range 1.8-3.5 MeV, the relative contribution of the additional radiation during the reactor operating period (Figs. 1, 5) is about 4%, which is somewhat greater than the error of the ILL spectra [5]. » Ratio of the reactor -spectrum obtained by conversion + calculation methods  to the  - spectrum obtained by conversion method only convers. : 1 – the additional contribution from fission product residual  - activity of the previous two reactor cycles; 2 – from neutron capture by fission products; 3 – from increase of fission product  - activity of the current reactor cycle from 1 day to 0.5 year; 4 – the sum (4=1+2+3) AAP09 - Brazil - M. Fallot et al.

  6. Neutron capture, non equilibrium effects  (E,toff) / (E,ton= 1 yr) 0 . 0 4 toff = 1 d 0 . 0 2 S p e n t F u e l P o o l toff = 1yr 0 2 3 2 . 5 3 . 5 Modification of the - and  spectra associated with neutron capture by fission products V. Kopeikin et al. , arXiv:hep-ph/0110290 Addition to the  spectrum: 1, 2 and 3 correspond to the beginning, middle and end of the reactor operatingcycle But also the evolution of the  and  spectra during operating (ON) and shutdown(OFF) periods Solid line is the ratio of the spent fuel pool- spectrum to the reactor spectrum. Dashed lines are the ratios of the reactor - spectrum after the reactor is shut down to the reactor - spectrum at the end of the operating cycle. AAP09 - Brazil - M. Fallot et al.

  7. Developed simulation tools And results on U and Pu isotopes spectra AAP09 - Brazil - M. Fallot et al.

  8. Principle of our strategy exp. spectrum fissile mat. + FY nuclear database models Core geometry neutron flux Two distinct studies Monte-Carlo Simulation : Evolution Code MURE -branch database : BESTIOLE, … -/espectra - decay rates  -  econversion : pas branch by branch method : no additional error • Neutron capture taken into account • Long lived fission products accumulation • Error treatment and propagation • Nuclear database tests weighted  Total e and  - energy spectra with complete error treatment AAP09 - Brazil - M. Fallot et al.

  9. The e spectra formulation S,n (Z,A, E) = bn,i(E0) . - - i P(E0, E) i - i individual spectra branching ratios depends on the transition : Branching Ratios, End-Points,spin, parity of the mother and daughter nuclei with Phase space Coulomb corrections Spectral Shape factor (Well controlled for allowed and forbidden unique transitions) Remaining short-lived, high Q, unknown nuclei AAP09 - Brazil - M. Fallot et al.

  10. Bestiole Database • Collect all available information : • Nuclear Database : ENSDF • Experimental spectra • 111 nuclei @ISOLDE [O. Tengblad et al., Nucl. Phys. A, 503, (1989)] • 950 nuclei : • ~ 10000  branches • ~ 500 -n branches • Tag all relevant information : • Forbiddenness (spin & parity) • Level of approximation (ROOT and ASCII formats) CEA/Saclay/SphN : D. Lhuillier, Th. Müller et al. AAP09 - Brazil - M. Fallot et al.

  11. MURE * Geometry *MCNP Utility for Reactor Evolution, O. Méplan et al. ENC Proceedings (2005) Developed by CNRS/IN2P3/IPNO and LPSC Evolution • Open source code : adapted to antineutrino needs(simple geometry implementation, easy coupling to databases …) • Benchmarked with APOLLO2 code  • Fuel Burnup  • Fission product distributions  • Refined effects : out of equilibrium spectra • Neutron capture on FPs … • Possibility to simulate : • Simple cases : pure U or Pu isotope fissions and associated  spectra • Complexe cases : reactor and associated  spectra proliferation scenario calculations AAP09 - Brazil - M. Fallot et al.

  12. Obtained spectra Rudstam data + Bestiole + JENDL + Qb Rudstam data + Bestiole Données :[A. Hahn et al., Phys. Lett. B, 218, (1989)] X 4% agreement in the range 2 -6MeV with Schreckenbach’s data , higher discrepancy at high energy X simulation errors (cf. Th. Müller’s talk) within the experimental error bars Ratio : (MURE - DATA)/DATA AAP09 - Brazil - M. Fallot et al.

  13. Origins of the discrepancy and solutions b- ? ZAN γ γ Z+1AN-1 γ1 γ2 • Pandemonium effect : use of Ge detectors to measure the decay schemes : underestimate of b branches towards high energy excited states : overestimate of the high energy part of the FP b spectra • Unknown fission products contribute importantly at E>5-6MeV Several tracks to solve these problems : - Use ofGross Theory in existing databases such as JENDL3.3when the considered nuclei have been treated, other models… (QRPA) - Sensitivity tofission yields databases - Inclusion ofexisting TAGS nuclear dataand new measurements - an alternative : the « ratio method » (see Th. Müller’s talk) : relying on the very precise Schreckenbach’s team 235U and 239Pu b spectra measurements + corrections to be applied for time evolution and neutron capture AAP09 - Brazil - M. Fallot et al.

  14. decay database testing and fission yields Rudstam et al. data JENDL total JENDL exp. (ENSDF) BESTIOLE exp. (ENSDF) BESTIOLE beta-n branches (ENSDF) 83As 142Cs 89Br Yields from JENDL3.3 Yields from ENDFB Yields from JEFF31 85As • Treatment of Pandemonium with JENDL3.3 : Gross Theory spectra [K. Takahashi and M. Yamada 1969] -> comparer JENDL avec JEFF3 et ENDFBVII • Different databases for fission yields : important input for MURE simultion : Ratio : (MURE - DATA)/DATA With beta spectra from : BESTIOLE + JENDL Gross Theory + Q approx. 235U AAP09 - Brazil - M. Fallot et al. M. Fallot et al. ND2007, L. Giot et al. Physor 2008

  15. Evolution of the spectrum shape with time 0 2 4 6 8 10 12 Energy (MeV) • 235U under monoenergetic n flux (no moderation) : evolution during 1 year Bin per bin comparison with respect to 0.7day -spectrum for 60 time steps during 1 year To be studied in the reactor framework : under realistic n spectrum AAP09 - Brazil - M. Fallot et al.

  16. World-wide initiatives • 238U - spectrum integral measurement in Münschen (Niels Haag et al. @Garching ) : March-April 2009 (now !!!) • 235U/239Pu ratio measurement in Moscow @Kurchatov institute (V. Kopeikin et al.) • Measurements of Pandemonium nuclei : Total Absorption Spectrometry collab. (Valence group) TAS measurements @ Univ. Jyvaskyla Using large 4 scintillation detectors, aims to detect the full -ray cascade rather than individual -rays New Surrey-Valencia Total Absorption Spectrometer 12 BaF2 Crystals D. Jordan, PhD Thesis AAP09 - Brazil - M. Fallot et al.

  17. Antineutrino energy spectrum and flux reactor simulations, « gross » proliferation scenarios AAP09 - Brazil - M. Fallot et al.

  18. Scenarios and reactors of interest for IAEA ? International expert meeting organized by the Department of New Technologies of IAEA, October 26-28. 2008 : • An antineutrino measurement is directly related to the fission process in the reactor core. • An antineutrino measurement can provide in real time information on isotopic fission rates, which can be related to the thermal power and fissile inventory of the reactor. • PWRs : PWR (full core) simulation and simple refuelling scenario studies • BWR, FBR, CANDU reactors : channel simulation, simplistic refuelling scenario study • Research reactor / isotope production reactors Pth >10MWth : started OSIRIS simulation for Nucifer, and high flux ILL reactor simulation • Future reactors (PBMRs, Gen IV reactors, ADS, especially reactors using carbide, nitride, metal or molten salt fuels. • PWRs • BWR, FBR, CANDU reactors • Research reactor/isotope production reactors Pth >10MWth • Future reactors (PBMRs, Gen IV reactors, ADS, especially reactors using carbide, nitride, metal or molten salt fuels. AAP09 - Brazil - M. Fallot et al.

  19. Chooz-B reactors (I, II) • 2 core N4 series : 4.27GWth • Moderator/coolant • pressurized borated water (155 bars) • 560 K < TH2O< 620 K • (ρ= 0.7 g.cm-3 ) 13 m 4,8 m • Fuel • enriched UO2 pellet : 1.8, 2.4 and 3.1 % • (ρ= 10.85 g.cm-3 ) • 700 K < TUO2< 1400 K 3,8 m 9 mm 13 mm 4,5 m AAP09 - Brazil - M. Fallot et al.

  20. Assembly PWR N4 : Chooz-B (I, II)-like reactor Core 214 mm Fuel element 214 mm • Zircaloy structure • 24 ‘guide’ tubes • (poison, instrumentation,..) • 3(4) enrichment zones • Refueling 1/3(4) 11 months • 317 pellets / h = 4.2 m • Zircaloy coating/ 0.6 mm • 3 Enrichments : • (1.8, 2.4, 3.1 %.) 264 205 12.6 mm 12.6 mm PWR : full core simulation. Approx. : No control rod reactor driving yet : constant power, Boron diluted into water and mean keff =1 AAP09 - Brazil - M. Fallot et al.

  21. Neutronics inputs σ(n,f) 235U σ(n,γ) 235U σ(n,f) 238U σ(n,γ) 238U • A matter of neutronics : neutron flux & interaction cross sections (n,x) Fast neutrons Fission spectrum ~2MeV Slow neutrons thermalisation ~0.025eV Epithermal domain +moderator 1eV<En<1MeV Burnup effect • Φ~3,5 .10 14n.cm-2.s-1|<En> ~0.7MeV • Systematic effects : • Temperature : Thermalisation & Doppler effect • Neutron Absorbant : Bore AAP09 - Brazil - M. Fallot et al.

  22. Systematic effects 0 K 1800 K • Doppler effect : • Thermalization : Tfuel ➚⇒ Resonant captures➚ • Thermal bump displacement : • Criticity control with soluble boron : • Cbore adjusted at each time step t , <keff (t+1)>= 1 • Boron Cross sections  1/v • Harder neutron spectrum AAP09 - Brazil - M. Fallot et al.

  23. Systematic effects • Systematic study : • T moderator : 300, 600,... 1200K • T fuel : 300, 600,.... 1500 K • Boron Concentration : 0, 500,... 3000 ppm mass. n, En, keff( <>, Inventory, Nf/s. Studied effects : of the order of 2% or lower on main fission rates (exc. 238U) Also studied : - self-shielding effect on inventories and fission rates, - influence of the Monte-Carlo seed AAP09 - Brazil - M. Fallot et al.

  24. PWR refueling simulation 6.4% Folded by Nucifer response @25m : Constant power simulation of N4 PWR Constant power : 4.27GWth Boron concentration 1000ppm Mean keff = 1 Antineutrino rate/s in Nucifer Preliminary PWR refuelled every year : 250kg 239Pu retrieval 900kg 235U adjunction AAP09 - Brazil - M. Fallot et al.

  25. Filling all control rods with 238U Folded by Nucifer response @ 25m : Fission rates 238U inventory Preliminary 25*205 control rods : +11.5t 238U => 238U mass increase of 10% Preliminary 235U and 239Pu fission rates change by -5.5% and +2.5% resp. 235U : +150kg 239Pu :+100kg 235U and 238Pu inventory Antineutrino rate/s in Nucifer Preliminary Preliminary Antineutrino flux : Change of 0.5% ! Because of 238U fission rate increase +6-8% : mimick 235U AAP09 - Brazil - M. Fallot et al.

  26. Removal of the control rods Preliminary Normal refuelling 1.3% Replacement of the control rods Corresponds to 65kg 239Pu removal, without changing 238U and 235U masses as rods are replaced by fresh Unat Amount of 238U stays ~ the same, so no compensation by 238U of 235U and 239Pu fission rates variations AAP09 - Brazil - M. Fallot et al.

  27. CANDU reactor specifications (CANada Deuterium Uranium) • Heavy water as moderator and coolant and natural uranium as fuel • Spatial separation of coolant (in force tubes) and moderator (between force tubes) moderator • On-line refuelling : Plutonium proliferation Calandria • Antineutrino flux and spectra : refuelling and 239Pu proliferation scenarii Force tubes V.M. Bui PhD, Collaboration with A. Nuttin (LPSC) (*)A. Nuttin, Physor-2006, Study of CANDU Thorium-based Fuel Cycles by Deterministic and Monte Carlo Methods. AAP09 - Brazil - M. Fallot et al. http://canteach.candu.org

  28. Simulation inputs A bundle A channel Moderator Calandria tube coolant Annular gas CO2 37pins Force tube Mirror 1 2 3 Pool Irradiated fuel 4 5 1’ Fresh fuel • Force tube →channel of 12 fuel bundles • Refuelling of a channel 2/3 fresh fuel and 1/3 irradiated fuel Different simulation steps : • Fit boundary mirror dimensions to obtain the CANDU moderation ratio • 1 bundle + mirror→ full reactor, homogeneous, infinite (no leak) • Temperature dependance : T= 300 K for all components Tfuel= 1200 K Tcool= 600 K Tmod= 300 K • Spatial dependance of the neutron flux Dwell time : 200d • Dwell time def. :threshold 1.05 (A. Nuttin* et al.) : leaks : 3000pcm, absorptions (Boron and impurities) : 2000pcm. Correct mean temperatures AAP09 - Brazil - M. Fallot et al.

  29. Channel simulation & gross diversion scenario • 3 channels (12 bundles) simulations with 100d, 200d and 300d refueling periods Inventory @ refuelling period 100d • X-checks : collaboration with A. Nuttin et al., Physor 2006 Conf. Proc. , comparison between MURE and deterministic code DRAGON • Principle : refuel faster some channels to take Pu away and refuel slower the same number to mask diversion • Isotopic Vector Plutonium: Pu of military quality (VP>90%) Inventory @ refuelling period 200d • 2 “full core” refuelling scenarii - Standard : 400 channels refueled @200 days - Proliferant : 200 channels refueled @ 100d + 200 channels refueled @ 300d to mask diversion Inventory @ refuelling period 300d AAP09 - Brazil - M. Fallot et al.

  30. A gross proliferation scenario e in Nucifer (Hz) +…+ Adding 400 channels with history shifted by 1 day « Normal refueling »  : 0.02588 Hz => 2236 per day in Nucifer 400 channels (~ CANDU600-like) refueled every 200d, @ 2 channels per day :adequation between dwell time, daily number of refuelled channels and total number of channels : flat profile of the flux 0 100 200 300 400 Folded with Nucifer response @ 25m for 1 channel with different refueling periods : Preliminary 200d 300d 100d 0 100 200 300 0 100 200 300 400 0 100 200 300 400 Time (days) Time (days) Time (days) Fits and sums Time (days) AAP09 - Brazil - M. Fallot et al.

  31. Core refuelled @ 100d and 300d 0 100 200 300 400 0 100 200 300 400 Time (days) Time (days) 200 channels refuelled every 100d, 200 channels every 300d, @ 2 channels per day Folded by Nucifer response @ 25m : 0.02588 Hz => 2236 per day 0.02497 Hz => 2157 per day +660kg 235U after 200x100d + 200x300d -430kg 239Pu including 152kg from 100d channels +600kg 235U after 400x200d -464kg 239Pu Fission rates : Normal refuelling : 54.1% 235U - 45.9% 239Pu Diversion scenario : 60,1% 235U - 39,9% 239Pu 3.5% discrepancy in the antineutrino rate !!! Nucifer reaches 1% statistic precision after 1 day AAP09 - Brazil - M. Fallot et al.

  32. Conclusions and outlooks • A set of performant tools (MURE+BESTIOLE+databases…) to compute the antineutrino energy spectrum and flux under various conditions : experiment and reactor simulations • Neutron capture and long-lived fission products contributions to the spectrum : need to be evaluated carefully and compared with Kopeikin’s et al. results • Simulation of different kinds of reactors, including Chooz-B ones for the Double Chooz experiment • First gross proliferation scenarios studied, with PWR and CANDU reactors, including the response of the Nucifer detector placed at 25m from the cores • Nucifer sensitivity in 239Pu content : ~+-65kg <=> 1% change in the measured antineutrino flux by Nucifer @25m of a PWR core, 1% statistical accuracy reached in 4days by Nucifer in these conditions AAP09 - Brazil - M. Fallot et al.

  33. Backup Slides AAP09 - Brazil - M. Fallot et al.

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