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Anti-neutrinos Spectra from Nuclear Reactors

Anti-neutrinos Spectra from Nuclear Reactors. Alejandro Sonzogni National Nuclear Data Center. ENDF/B VII.1 Decay Data Sub-Library. Most recent …. Q values -- Audi 2011 mass update ENSDF data (when complete) else Wallet Cards (2011)

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Anti-neutrinos Spectra from Nuclear Reactors

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  1. Anti-neutrinos Spectra from Nuclear Reactors Alejandro Sonzogni National Nuclear Data Center

  2. ENDF/B VII.1 Decay Data Sub-Library Most recent … • Q values -- Audi 2011 mass update • ENSDF data (when complete) else Wallet Cards (2011) • Atomic data -- Evaluated Atomic Data Library (LLNL) – includes X-rays and Auger electrons • TAGS data • Electron conversion -- BrIcc • Theoretical calculations for neutron-rich nuclei using beta-strength functions (Moller) and CGM (Kawano) More details in Nuclear Data Sheets 112, 2887 (2011).

  3. ENDF VII.I Decay Data Sub Library A transformation of all relevant data into computer “friendly” files

  4. What’s in there… 3817 “materials” g.s. and isomers Wallet Cards Theory (CGM) ENSDF New ENSDF

  5. What’s it good for … • Decay heat • Antineutrino spectra • Delayed nu-bars (reactor operation) • Astrophysics ? • ????

  6. Antineutrino Experiments

  7. Decay of fission fragments More than 800 nuclides produced in the fission of 235U Antineutrino Spectrum: S (E) =S Yi x Si(E) Yi: cumulative fission yields Si(E): individual  spectrum

  8. b- decay from Level i to level k Jipi Ik Z,N Nucleus Jkpk Ek Z+1,N-1Nucleus a: normalization, d: shape factor, F: Fermi function. The sum spectrum is obtained as: b: branching ratios All nuclear decay data from ENDF/B-VII.1 (December 2011)

  9. Example, 137Cs

  10. (n,g) (n,g) b- b- How to calculate anti-neutrino rates The nuclei in the core form a decay/processing network: Neglect processing as Fns << l and consider an equilibrium situation: Then the anti-neutrino rate per fission is: Used by Vogel et al, 1981, ENDF/B-V We’ll repeat the calculations using the fission yields from ENDF/B-VII.1

  11. 235U at thermal energies

  12. Anti-neutrinos from reactors Principal Contributors Flux 235U,238U, 239Pu, 241Pu Detection through inverse  decay on proton Reaction threshold : ~1.8 MeV

  13. NNDC calculations on the Daya signal shape

  14. 235U(thermal n,f) main contributors to anti-neutrino spectra With TAGS: 140Cs. 96Y seems is good shape. We’ll look at some of the other nuclides and if available, compare it to Rudstam data.

  15. One small nucleus, one big effect 92Rb a) 2000 ENSDF 51(18) % g.s. b) Update with new data 92Rb 95(5) % g.s.

  16. Effects of Valencia TAGS data

  17. Anti-neutrinos for Applied Purposes 235,238U and 239Pu produce a different signal, in shape, maxima and multiplicity

  18. 100Nb, CFY=5.89E-2, DCFY=16.883 % The GS to GS transition is not well determined. It could be up to 75%. BNL plans to submit a proposal to CARIBU. Would include other Nb nuclides

  19. 142Cs, CFY=2.71E-2, DCFY=2.803 %

  20. 92Rb, CFY=4.82E-2, DCFY=1.398 %

  21. 92Rb, comparison to Rudstam data

  22. 92Rb, comparison to Rudstam data

  23. Summary The next generation of experiments using anti-neutrinos from nuclear reactors have just published their first results. More to come in the next few years. There is a close link between basic nuclear structure research and the calculation of anti-neutrino spectra.

  24. Why nuclear reactors? Nearly 1,000 different fission fragments (materials) are produced in the fission of an actinide nuclide. Most of them are neutron rich, undergoing beta-minus decay: Nucleus(Z,A)  Nucleus(Z+1,A) + e- + anti-neutrino In an equilibrium situation, we obtain about 6 anti-neutrinos/second per fission, or ~1020 anti-neutrinos per reactor. Anti-neutrinos interact through weak interaction, very small cross sections, s ~ 5x10-19 barns

  25. Some history In b- decay, the electron energy is a continuum distribution linking two nuclear levels (quantum). Another particle must be involved n  p + e- + anti-neutrino (Fermi, 1934) First detection in 1956 by Cowan and Reines (LANL) using neutrinos from a nuclear reactor in SRS: anti-neutrino + p  n +e+ The positron created two 511 keV gammas and the neutron was captured in Cd, releasing a gamma cascade

  26. More history In 1962, Leon Lederman and collaborators (BNL) discovered the muon neutrinos: Finally, in 1975 the Tau lepton and in 2000 the Tau neutrino were discovered. In the late 1960’s Ray Davies (BNL) measured the flux of neutrinos coming from the Sun, observing a deficit. Neutrino oscillations were formalized to explain this problem.

  27. 239Pu at thermal energies

  28. 238U at fast energies

  29. 252Cf spontaneous fission

  30. 235U b- spectra ratios The published ILL data is binned at 250 keV. Could we get the 50 keV data?

  31. 239Pu b- spectra ratios

  32. 238U b- spectra ratios

  33. 252Cf b- spectra ratios More theory needed, but better agreement with higher statistics, cleaner data

  34. 3 near neutrino detectors and 3 far neutrino detectors anti-neutrino + proton (water) positron + neutron Captured in Gd Two 511 keV gammas High energy gamma signal

  35. Anti-neutrino Signal Use the anti-neutrino capture on proton: Reaction has a 1.8 MeV threshold

  36. Daya Bay Results

  37. Some recent experiments Daya Bay Experiment in China, 6 nuclear power reactors. Ref: F.P. An et al, Physical Rev. Lett. 108, 171803 (2012)

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