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SUBATECH : S. Cormon, M. Fallot, L. Giot, B. Guillon, J. Martino

Effort on the simulation of the antineutrino spectrum from reactors. SUBATECH : S. Cormon, M. Fallot, L. Giot, B. Guillon, J. Martino. CEA/DAPNIA/SPhN : D. Lhuillier, A. Letourneau, T. Mueller CEA/DAPNIA/SPP : M. Cribier, T. Lasserre. M. Fallot - AAP Workshop 2007. Outline.

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SUBATECH : S. Cormon, M. Fallot, L. Giot, B. Guillon, J. Martino

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  1. Effort on the simulation of the antineutrino spectrum from reactors • SUBATECH : S. Cormon, M. Fallot, L. Giot, B. Guillon, J. Martino • CEA/DAPNIA/SPhN : D. Lhuillier, A. Letourneau, T. Mueller • CEA/DAPNIA/SPP : M. Cribier, T. Lasserre M. Fallot - AAP Workshop 2007

  2. Outline - Introduction : different existing determinations - Presentation of our approach - Some results - Complementary on-going studies - Conclusion and Outlooks 2 M. Fallot - AAP Workshop 2007

  3.   - decay: • The fission products are neutron-rich nuclei 235U 239Pu Percentage of fissions 239Pu 238U 241Pu 235U Days Where do antineutrinos from reactors come from ? M. Fallot - AAP Workshop 2007

  4. Antineutrinos from reactors [C. Bemporad et al,. Rev. of Mod. Phys., 74 (2002)} • Standard power plant 900 MWe : • Detection through inverse -decay process on quasi-free proton : • Reaction threshold :1.8 MeV • Interaction cross-Section ( En2):<> ~ 10-43cm-2 Correlation antineutrino flux vs thermal power • For a fixed fuel composition (k=cste), the e flux is directly proportionnal to the thermal power. • For a constant thermal power (Wth=cste), the e flux as well as the e energy spectra depend on the fuel composition. Fuel composition, energy spectrum thermal power M. Fallot - AAP Workshop 2007

  5. - Yn(Z,A, t) N(E,t) = . S,n (Z,A, E) - - Yn depends on: - Geometry and initial composition of the reactor core - Cross sections and fission yields - Thermal power and time evolution of the fuel Simulation of the total e spectrum -  spectrum for decays of a fission fragment(Z,A) number of decays of a given fission fragment at time t, = Isotopic composition, T1/2 M. Fallot - AAP Workshop 2007

  6. S,n (Z,A, E) = bn,i(E0) . - - i P(E0, E) i - i The e spectra formulation 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 M. Fallot - AAP Workshop 2007

  7. -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 @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 M. Fallot - AAP Workshop 2007

  8. -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 (ENSDF 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) M. Fallot - AAP Workshop 2007

  9. exp. spectrum fissile mat. + FY nuclear database models Core geometry neutron flux Principle of our strategy Two distinct studies Monte-Carlo Simulation : Evolution Code MURE -branch database : BESTIOLE, … -/espectra - decay rates weighted  Total eand -energy spectra with complete error treatment M. Fallot - AAP Workshop 2007

  10. Bestiole Database • Collect all available information : • Nuclear Database : ENSDF • Experimental spectra • 111 nuclei @ISOLDE [O. Tengblad et al., Nucl. Phys. A, 503, (1989)] • Theoritical/phenomenological models • 950 nuclei : • ~ 10000  branches • ~ 500 -n branches • Tag all relevant information : • Forbiddenness (spin & parity) • Level of approximation (ROOT and ASCII formats) M. Fallot - AAP Workshop 2007

  11. Time evolution of the fuel composition MCNP Utility for Reactor Evolution : evolution code on neutron transport MC code MURE: O. Méplan et al., ENC Proceedings (2005) http://lpsc.in2p3.fr/gpr/MURE/html - Neutron flux automatically adjusted to total power parameter - To take into account the neutron capture influences on the absolute normalisation and also the shape of theespectrum V. Kopeikin et al., Phys. Atom. Nucl. 67 (2004) 1963 - Proper calculation of the released energy per fission in the core V. Kopeikin et al., hep-ph/0410100 M. Fallot - AAP Workshop 2007

  12. 235U : 1.5 days in thermal flux Agreement within 1 up to 8 MeV Expect final error to be comparable to experimental data [A. Hahn et al., Phys. Lett. B, 218, (1989)] • Remaining : • Unknown nuclei start to contribute importantly from 6-7MeV : Short-lived, high Q: others databases, nuclear models, measurements,……. • Propagate all errors and compute correlations (bin-per-bin) • Significant gain in sensitivity to shape distortions because most errors • induce large correlations (Y, BR, E0,…..) (Thomas Müller PhD) • Relevant for normalization of Dchooz phase 1 M. Fallot - AAP Workshop 2007

  13. 239Pu : 1.5 days in thermal flux M. Fallot - AAP Workshop 2007

  14. Photofission of 238U 86Ge: 1.2 102 pps Electrons beam: 50 MeV, 10 A 102Nb: 5.6 103 pps 109Tc: 1.2 103 pps Expected counting rates for 1011 fission/sec 100Y: 1.3 103 pps 101Y: 3.8 102 pps 103Zr: 1.6 103 pps Important fission products for the total beta spectrum between 2 and 4 MeV with missing information: T1/2, J,  individual spectrum or transition type … - 235U fission: 86Ge To be completed with the full computation of correlated errors - 239Pu fission: 104Nb, 109Tc - 238U fission: 100Y, 101Y, 103Zr ALTO, Orsay, France http://ipnweb.in2p3.fr/tandem-alto/alto • Yields : large discrepancies beetween the databases between ENDFBVI.8, ENDFBVII, JENDL3.3 and JEFF3.1: L. Giot

  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 M. Fallot - AAP Workshop 2007

  16. Different conversion procedures • K. Schreckenbach : use a set of a few tens of fictive fission product  branches , 3-4% error with weak energy dependance • P. Vogel : revisited recently the conversion procedure from integral  data to  data [arXiv:] : 1% error quoted ! • fine subdivision of the electron spectrum • converted  spectrum binned in bins several times larger than width of the original bins • optimum average nuclear charge <Z> independantly known as a function of the endpoint energy • Our approach : unambiguous conversion but still some discrepancies with very precise data from ILL K. Schreckenbach’s suggestion :combine the very precise  spectra data and our branch-by-branch conversion procedure using the ratio then M. Fallot - AAP Workshop 2007

  17. 235U/239Pu ratio No absolute normalisation No absolute normalisation 235 (E ) / 239 (E ) Energy E, MeV Ratio of the beta-spectra from the thermal neutron fission products of 235U and 239Pu 1 (■)  Schreckenbach, Hahn etal. 1985, 1989 (exp.); 2  Tengblad etal. 1989, normalized per fission (calc.); 3  Klapdor etal. 1982 (calc.); 4  Vogel etal. 1981 (calc.); 5(∆)  Borovoy etal. 1981 (exp.); 6  Kopeikin 1980 (calc.); All errors are given at 68% CL. M. Fallot - AAP Workshop 2007

  18. Worldwide experimental perspectives • 238U integral  spectrum measurement in Münschen (Niels Haag et al. @Garching) : meas. in April 2008 • - 235U target irradiated by slow neutrons from FRM II • - 238U target irradiated by fast neutrons in identical setup • gamma- suppressing e -telescope • Calibration : comparing experimental data from this U235 measurement with the well known data from former experiments [Schreckenbach et. al.] • Measurement of relative γ-intensities of the same long living fission- products of both isotopes (Ge-Detector) -> relative number of fission products determined • - Conversion from β - to antineutrino-spectrum • 235U/239Pu ratio measurement in Moscow @Kurchatov institute (V. Kopeikin et al.) : planned to be settled in 2008 – high selective -spectrometer, – 235U, 239Pu targets (~10 mg/cm2) with cover, and cover without targets (each of them occupy of 1/3 circle) – disc from plastic (D  60 cm, rotation rate  15 s–1), – capture of neutron flux,– neutron flux (5106 s1cm2), – chopper,– shielding. M. Fallot - AAP Workshop 2007

  19. B. Guillon Simulation of Chooz reactors • Chooz: 2 PWR - N4 - 2x4.27 GWth • - Fuel: enriched Uranium • - Moderator/Coolant: Light pressurized Water (155 Bar, 600K) Core Fuel Assembly Fuel rod (0.2x0.2x4.8) (D: 0.8 cm ; h:4.8 m) 205 Fuel Assemblies 264 fuel rods Coat (Zircalloy) Fuel UO2 pellets (2.1, 2.6, 3.1 % enrichment) Control rods (Instrumentation, Poisons…) Actual geometry simplifications : simplified pins, no reflector reflector Mirror symmetry (1/8 of core) : full core simulation !! M. Fallot - AAP Workshop 2007

  20. Reactor simulation • Full reactor simulation with MURE (N4 geom.) during 2days Comparison with spectrum built from Huber and Schwetz ‘s fits weighted by the fission rates given by MURE : Good agreement between reactor spectrum from MURE and reactor spectrum built thanks to the fitted exp. data M. Fallot - AAP Workshop 2007

  21. Proliferation scenario study (IAEA collaboration) Pertinence of the probe ? 15 Conclusion & Outlooks • Modelization tools :MURE&Bestioleare being developed • Bestiole : Unknown exotic nuclei  Experiment measurements ?  Models : phenomenologically “à la Vogel” under study @SUBATECH • MURE : Simulation close to be completedcomparison to data, benchmarks… • Sensibility study & Uncertainties propagation (T. Müller’s PhD @ SPhN) • Conversion procedure combing Schreckenbach’s data and our simul • Three applications :Double-Chooz absolute normalization (Phase I)   Thermal power…………………………………   Fuel composition………………………………? • Worldwide experimental effort : • on the experimental fissile isotope integral spectra : Münschen, Kurchatov •  detectors close to reactors : • Songsat San Onofre (Los Alamos) • Angra(Brazil) • Double-Chooz in 2008-2010 (France) : Direct confrontation of our simulation tools M. Fallot - DChooz Oxford 19. Sept. 2007

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