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

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


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)


Example, 137Cs


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


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


NNDC calculations on the Daya signal shape


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


Effects of Valencia TAGS data


Anti-neutrinos for Applied Purposes

235,238U and 239Pu produce a different signal, in shape, maxima and multiplicity


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


142Cs, CFY=2.71E-2, CFY=2.803 %


92Rb, CFY=4.82E-2, CFY=1.398 %


92Rb, comparison to Rudstam data


92Rb, comparison to Rudstam data


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.


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


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


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.


239Pu at thermal energies


238U at fast energies


252Cf spontaneous fission


235U - spectra ratios

The published ILL data is binned at 250 keV. Could we get the 50 keV data?


239Pu - spectra ratios


238U - spectra ratios


252Cf - spectra ratios

More theory needed, but better agreement with higher statistics, cleaner data


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-neutrino SignalUse the anti-neutrino capture on proton:

Reaction has a 1.8 MeV threshold


Daya Bay Results


Some recent experimentsDaya Bay

Experiment in China, 6 nuclear power reactors.

Ref: F.P. An et al, Physical Rev. Lett. 108, 171803 (2012)

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

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