1. 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 Effort on the simulation of the antineutrino spectrum from reactors M. Fallot - AAP Workshop 2007

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

3. 235 U 239 Pu Days 235 U 239 Pu 238 U 241 Pu Percentage of fissions Where do antineutrinos from reactors come from ? 235 U 239 Pu 238 U 241 Pu E f (MeV)201.7210.0205.0212.4 (MeV)1.461.321.561.44 (E>1.8MeV) 5.58 (1.92) 5.09 (2.38) 6.69 (1.45) 5.89 (1.83) The fission products are neutron-rich nuclei   - decay : M. Fallot - AAP Workshop 2007

4. Standard power plant 900 MW e : Detection through inverse  -decay process on quasi-free proton : Reaction threshold : 1.8 MeV Interaction cross-Section (  E 2 ) : ~ 10 -43 cm -2 [C. Bemporad et al,. Rev. of Mod. Phys., 74 (2002)} Correlation antineutrino flux vs thermal power thermal power Fuel composition, energy spectrum M. Fallot - AAP Workshop 2007 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. Antineutrinos from reactors

5. Simulation of the total e spectrum number of  decays of a given fission fragment at time t, = Isotopic composition, T 1/2 Y n depends on: - Geometry and initial composition of the reactor core - Thermal power and time evolution of the fuel - Cross sections and fission yields spectrum for  decays of a fission fragment(Z,A) -  Y n (Z,A, t) N (E,t) =. S, n (Z,A, E ) -- - M. Fallot - AAP Workshop 2007

6. The e spectra formulation Coulomb corrections Phase space Spectral Shape factor (Well controlled for allowed and forbidden unique transitions) with depends on the  transition : Branching Ratios, End-Points,spin, parity of the mother and daughter nuclei branching ratios  individual spectra S, n (Z,A, E ) =  b n,i (E 0 ). i i P(E 0, E ) i - --  Remaining short-lived, high Q , unknown nuclei M. Fallot - AAP Workshop 2007

7.  Integral  - spectra measurements: [ A. Hahn et al., Phys. Lett. B, 218, (1989)] 235 U, 239, 241 Pu 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 to thermal 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) -spectra determinations M. Fallot - AAP Workshop 2007  Remaining short-lived, high Q , unknown nuclei

8.  In agreement with Chooz and Bugey data (1.9% on the e flux ) -  i (t) : relative contributions to the total fission (  i =1) -  i (E) : -spectra 235 U, 239 Pu, 241 Pu, and 238 U (Schreckenbach et al. and P. Vogel  Don’t take into account  - decay from products of radiative capture of neutron 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: -spectra determinations M. Fallot - AAP Workshop 2007

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

10. M. Fallot - AAP Workshop 2007 Bestiole Database (ROOT and ASCII formats) 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

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

12. [ A. Hahn et al., Phys. Lett. B, 218, (1989)] 235 U : 1.5 days in thermal flux Agreement within 1  up to 8 MeV Expect final error to be comparable to experimental data 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,  E 0,….. ) (Thomas Müller PhD) Relevant for normalization of Dchooz phase 1

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

14. Important fission products for the total beta spectrum between 2 and 4 MeV ALTO, Orsay, France - 235 U fission: 86 Ge - 239 Pu fission: 104 Nb, 109 Tc - 238 U fission: 100 Y, 101 Y, 103 Zr with missing information: T 1/2, J ,  individual spectrum or transition type … 86 Ge: 1.2 10 2 pps 102 Nb: 5.6 10 3 pps 109 Tc: 1.2 10 3 pps 100 Y: 1.3 10 3 pps 101 Y: 3.8 10 2 pps 103 Zr: 1.6 10 3 pps http://ipnweb.in2p3.fr/tandem-alto/alto Expected counting rates for 10 11 fission/sec Electrons beam: 50 MeV, 10  A Photofission of 238 U L. Giot Yields : large discrepancies beetween the databases between ENDFBVI.8, ENDFBVII, JENDL3.3 and JEFF3.1: To be completed with the full computation of correlated errors

15. M. Fallot - AAP Workshop 2007 Evolution of the spectrum shape with time 235 U under monoenergetic n flux (no moderation) : evolution during 1 year To be studied in the reactor framework : under realistic n spectrum Bin per bin comparison with respect to 0.7day -spectrum for 60 time steps during 1 year 0 2 4 6 8 10 12 Energy (MeV)

16. M. Fallot - AAP Workshop 2007 Different conversion procedures o 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 independantly known as a function of the endpoint energy o Our approach : unambiguous conversion but still some discrepancies with very precise data from ILL o K. Schreckenbach : use a set of a few tens of fictive fission product  branches, 3-4% error with weak energy dependance K. Schreckenbach’s suggestion : combine the very precise  spectra data and our branch-by-branch conversion procedure using the ratio then

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

18. M. Fallot - AAP Workshop 2007 Worldwide experimental perspectives 238 U integral  spectrum measurement in Münschen (Niels Haag et al. @Garching ) : meas. in April 2008 235 U/ 239 Pu ratio measurement in Moscow @Kurchatov institute (V. Kopeikin et al.) : planned to be settled in 2008 - 235 U target irradiated by slow neutrons from FRM II - 238 U 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 – high selective  -spectrometer, – 235 U, 239 Pu targets (~10 mg/cm 2 ) 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  10 6 s  1  cm  2 ), – chopper,– shielding.

19. Simulation of Chooz reactors Chooz : 2 PWR - N4 - 2x4.27 GW th - Fuel: enriched Uranium - Moderator/Coolant: Light pressurized Water (155 Bar, 600K) Core Control rods (Instrumentation, Poisons…) Coat (Zircalloy) 205 Fuel Assemblies 264 fuel rods Fuel Assembly (0.2x0.2x4.8) Fuel rod (D: 0.8 cm ; h:4.8 m) (2.1, 2.6, 3.1 % enrichment) B. Guillon Fuel UO 2 pellets reflector Actual geometry simplifications : simplified pins, no 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

21. M. Fallot - DChooz Oxford 19. Sept. 2007 Conclusion & Outlooks Modelization tools : MURE & Bestiole are 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. M ü ller ’ 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 : o on the experimental fissile isotope integral spectra : M ü nschen, Kurchatov o detectors close to reactors : Songs at San Onofre (Los Alamos) Angra (Brazil) Double-Chooz in 2008-2010 (France) : Direct confrontation of our simulation tools Proliferation scenario study (IAEA collaboration) Pertinence of the probe ? 15