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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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Time evolution of reactor antineutrino energy spectrum and flux Collaborations Double Chooz, Nucifer and MURE AAP09 - Brazil - M. Fallot et al.
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.
-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.
-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.
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 . » 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.
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.
Developed simulation tools And results on U and Pu isotopes spectra AAP09 - Brazil - M. Fallot et al.
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.
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.
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.
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.
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.
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.
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
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.
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.
Antineutrino energy spectrum and flux reactor simulations, « gross » proliferation scenarios AAP09 - Brazil - M. Fallot et al.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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
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.
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.
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.
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.
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.
Backup Slides AAP09 - Brazil - M. Fallot et al.