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Rendements de fission

Rendements de fission. Experimental program on PFNS measurements at the CEA in Bruyères le Ch â tel. T. Granier, B. Laurent, A. Chatillon. Historical. Bertin et al. Historical measurements PFNS measurements for fission of 238 U and 235 U induced by fast neutrons 0.6 MeV and 7 MeV

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Rendements de fission

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  1. Rendements de fission Experimental program on PFNS measurements at the CEA in Bruyères le Châtel T. Granier, B. Laurent, A. Chatillon

  2. Historical Bertin et al. Historical measurements PFNS measurements for fission of 238U and 235U induced by fast neutrons 0.6 MeV and 7 MeV Fission chamber method

  3. Recent history and present • Experiments at Los Alamos with FIGARO (CEA-NNSA collaboration) • Comprehensive measurements in the 1-200 MeV region (white neutron source) • First experimental evidence of the dip in <E> at opening of 2nd chance • Results on <E> and nu bar vs En in 1-200 MeV published for 238, 235, presented to conf for 237Np • Preliminary results for 239Pu: spectra and <E>

  4. The FIGARO instrument in the fission configuration 45° 20 neutron detectors 135° Collimated Neutron beam CEA multifoil Fission Chamber Up to 180 deposits, ~400 mg of actinide

  5. PFNS measurements at Figaro 239Pu(n,f) PFNS Preliminary (analysis by A. Chatillon)

  6. PFNS measurements at Figaro 239Pu(n,f) <E> for E in 0.6-7 MeV - Preliminary (analysis by A. Chatillon) Model: BRC09 B. Morillon <E> (MeV) Neutron Energy (MeV)

  7. TiT or TiD target Fission chamber p or d beam ~0.5 m flight path n shielding (Li paraffin) N-γshadow bar Lead shielding Paraterphenyl detector New measurement program at Bruyères • PFNS ~0.2 – 6 MeV using fission chambers • 4 MV Van de Graaff in Bruyères le Chatel • (quasi) Mono energetic neutrons (p+Li, p+T, d+D, d+T) 0.5, 2.5, 4, 6, 14 MeV • Fission chambers containing from 100 to 4000 mg of actinides • Neutron detectors: Paraterphenyl, NE213 • Neutron time of flight measurement, flight path ~50 cm • Detection efficiency: 252Cf measurements, simulations

  8. New measurement program at Bruyères • PFNS 0.5 – 10 MeV using passive targets • 4 MV Van de Graaff in Bruyères le Châtel • Mono energetic 500 keV neutrons from p+Li reaction • Passive sample • Neutron detector: NE213 calibrated at PTB • Neutron time of flight measurement, flight path ~200 cm • Detection efficiency: 252Cf measurements, simulations Li target Actinide sample p beam ~2 m flight path N-γshadow bar n shielding (Li paraffin) Lead shielding NE213 detector

  9. PFNS measurement test in Bruyères

  10. Number of counts TDC channel PFNS measurement test in Bruyères

  11. PFNS measurements • Actinides for which we have fission chambers • 238U, 235U, 237Np, 239Pu, 232Th • Statistics expected below 800 keV: 1000 fission neutrons (1 week) • Measurement plan - Year 1 Start with non fissile actinides: 238U or 237Np • Year 2 Measurements on 235U and 239Pu • Year 3 Measurements on 235U and 239Pu

  12. Additional material

  13. Neutron detectors TOF 2 / ~1 m TOF 1 / ~22 m Fission Chamber Pulsed neutron Beam (1-~200 MeV) Experiment Principle • Double time of flight • Incident n energy (22 m) • Fission n energy (~1 m) • Typical resolution: • Incident: 1% at 2 MeV 15% at 200 MeV • Fission: 15% at 800 keV 50% at 8 MeV • Detection efficiency obtained by measuring known PFNS (252Cf spont. Fiss.) • Total efficiency ~ 1 % • Neutron/gamma discrimination on pulse shape

  14. PFNS measurements at Figaro BRIC calculation (H. Duarte, BIII) 239Pu(n,F), En=50 MeV Normalized Total Neutron spectrum Fragment evap. Neutron yield per MeV Pre-equilibrium Prefission evap. Region of investigation (Watt domain) Neutron energy (MeV)

  15. Published results on <E> for 238U & 235U • BRIC (BRIEF): MC Intra-Nuc. Cascade code (H. Duarte, PRC 75, 024611), includes evaporation and fission models • Red curve: experimental angular cuts + Watt fit over 0.7-7 MeV (same as experimental analysis)

  16. <E> (MeV) Results on 237Np • Data analysis: J. Taieb • Presented by J. Taieb at ND-2007, Nice • Results to be published • <E> obtained from fits of Watt parameters • Red curve: eval. by V. Maslov

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