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Anti-neutrinos Spectra from Nuclear Reactors
Alejandro Sonzogni
National Nuclear Data Center
Anti-neutrinos #2 - Alejandro Sonzogni
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).
ENDF VII.I Decay Data Sub LibraryA transformation of all relevant data into computer “friendly” files
What’s in there…
Wallet CardsTheory (CGM)
ENSDF
New ENSDF
3817 “materials”g.s. and isomers
What’s it good for …
• Decay heat
• Antineutrino spectra
• Delayed nu-bars (reactor operation)
• Astrophysics ?
• ????
Antineutrino Experiments
Decay of fission fragments
More than 800 nuclides produced in the fission of 235U
Antineutrino Spectrum:
S (E) = Yi x Si(E)
Yi: cumulative fission yields
Si(E): individual spectrum
Anti-neutrinos #8 - Alejandro Sonzogni
Jii
Z,N Nucleus
Jkk Ek
Ik
Z+1,N-1Nucleus
- decay from Level i to level k
a: normalization, d: shape factor, F: Fermi function. The sum spectrum is obtained as:
b: branching ratiosAll nuclear decay data from ENDF/B-VII.1 (December 2011)
Anti-neutrinos #9 - Alejandro Sonzogni
Example, 137Cs
Anti-neutrinos #10 - Alejandro Sonzogni
How to calculate anti-neutrino rates
-
-
(n,)
(n,)
The nuclei in the core form a decay/processing network:
Neglect processing as n << 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
Anti-neutrinos #11 - Alejandro Sonzogni
235U at thermal energies
Detection through inverse decay on proton
Anti-neutrinos from reactors
Reaction threshold : ~1.8 MeV
FluxPrincipal Contributors
235U, 238U, 239Pu, 241Pu
Anti-neutrinos #13 - Alejandro Sonzogni
NNDC calculations on the Daya signal shape
Anti-neutrinos #14 - Alejandro Sonzogni
Nucleus % at 3 MeV
54-Xe-137 3.519
55-Cs-139 3.259
39-Y - 94 3.120
40-Zr- 99 3.010
41-Nb-100 2.916
41-Nb- 98 2.830
39-Y - 92 2.812
41-Nb-101 2.654
Nucleus % at 4 MeV
41-Nb-100 4.872
37-Rb- 92 3.694
39-Y - 96 3.545
52-Te-135 2.994
39-Y - 94 2.897
55-CS-140 2.780
39-Y - 95 2.646
54-Xe-139 2.606
Nucleus % at 5 MeV
37-Rb- 92 9.171
39-Y - 96 7.475
41-Nb-100 6.592
55-Cs-142 4.585
55-Cs-140 4.153
52-Te-135 3.636
39-Y - 99 3.460
38-Sr- 95 3.435
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.
235U(thermal n,f) main contributors to anti-neutrino spectra
51(18) %
a) 2000 ENSDF
95(5) %
b) Update with new data
g.s.
g.s.
One small nucleus, one big effect92Rb
92Rb
Anti-neutrinos #16 - Alejandro Sonzogni
Effects of Valencia TAGS data
Anti-neutrinos #17 - Alejandro Sonzogni
Anti-neutrinos for Applied Purposes
235,238U and 239Pu produce a different signal, in shape, maxima and multiplicity
Anti-neutrinos #18 - Alejandro Sonzogni
100Nb, CFY=5.89E-2, CFY=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
Anti-neutrinos #19 - Alejandro Sonzogni
142Cs, CFY=2.71E-2, CFY=2.803 %
Anti-neutrinos #20 - Alejandro Sonzogni
92Rb, CFY=4.82E-2, CFY=1.398 %
Anti-neutrinos #21 - Alejandro Sonzogni
92Rb, comparison to Rudstam data
Anti-neutrinos #22 - Alejandro Sonzogni
92Rb, comparison to Rudstam data
Anti-neutrinos #23 - Alejandro Sonzogni
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.
Anti-neutrinos #24 - Alejandro Sonzogni
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, ~ 5x10-19 barns
Anti-neutrinos #25 - Alejandro Sonzogni
Some history
In - 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
Anti-neutrinos #26 - Alejandro Sonzogni
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.
Anti-neutrinos #27 - Alejandro Sonzogni
239Pu at thermal energies
Anti-neutrinos #28 - Alejandro Sonzogni
238U at fast energies
Anti-neutrinos #29 - Alejandro Sonzogni
252Cf spontaneous fission
Anti-neutrinos #30 - Alejandro Sonzogni
235U - spectra ratios
The published ILL data is binned at 250 keV. Could we get the 50 keV data?
Anti-neutrinos #31 - Alejandro Sonzogni
239Pu - spectra ratios
Anti-neutrinos #32 - Alejandro Sonzogni
238U - spectra ratios
Anti-neutrinos #33 - Alejandro Sonzogni
252Cf - spectra ratios
More theory needed, but better agreement with higher statistics, cleaner data
Anti-neutrinos #34 - Alejandro Sonzogni
anti-neutrino + proton (water) positron + neutron
Two 511 keV gammas
Captured in Gd
High energy gamma signal
3 near neutrino detectors and 3 far neutrino detectors
Anti-neutrinos #35 - Alejandro Sonzogni
Anti-neutrino SignalUse the anti-neutrino capture on proton:
Reaction has a 1.8 MeV threshold
Anti-neutrinos #36 - Alejandro Sonzogni
Daya Bay Results
Anti-neutrinos #37 - Alejandro Sonzogni
Some recent experimentsDaya Bay
Experiment in China, 6 nuclear power reactors.
Ref: F.P. An et al, Physical Rev. Lett. 108, 171803 (2012)