subatech : s. cormon, m. fallot, l. giot, b. guillon, j. martino cea/dapnia/sphn : d. lhuillier, a....

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

Outline

- Presentation of our approach

- Conclusion and Outlooks

- Introduction : different existing determinations


- Some results

- Complementary on-going studies

235U239Pu

Days

235U

239Pu

238U 241Pu P

erc

en

tag

e o

f fi

ssio

ns

Where do antineutrinos from reactors come from ?

235U 239Pu 238U 241Pu

Ef (MeV) 201.7 210.0 205.0 212.4

<E > (MeV) 1.46 1.32 1.56 1.44

<N>

(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

€

ZA X → Z +1

AY + e- + ν e - decay :


€

2800 MWth

200 MeV× 6 ν e • Standard power plant 900

MWe :

€

~ 5 ⋅1020 ν e /s

• Detection through inverse -decay process on quasi-free proton :

Reaction threshold : 1.8 MeV Interaction cross-Section ( E

2) : <> ~ 10-43cm-2

€

e + p → e+ + n

[C. Bemporad et al,. Rev. of Mod. Phys., 74 (2002)}

Correlation antineutrino flux vs thermal power

€

N Eν( ) α 1+ k(E

ν) ( )W th

thermal power

Fuel composition, energy spectrum

•


• 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

Simulation of the total e spectrum

number of decays of a given fission fragment at

time t,

= Isotopic composition, T1/2

Yn 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)

- Yn (Z,A, t)N(E,t) = . S,n (Z,A, E)- -

-


The e spectra formulation

Coulombcorrections

Phase spaceSpectral Shape factor(Well controlled for

allowed and forbidden unique

transitions)

€

P(E0

i, E

ν ) = F(Z , E) ⋅ pE(E0

i − E)2 ⋅Sν (E)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) = bn,i(E0) . i

i P(E0, E)

i -- -

Remaining short-lived, high Q, unknown nuclei


Integral -spectra measurements: [A. Hahn et al., Phys. Lett. B, 218,

(1989)] 235U, 239,241Pu 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


Remaining short-lived, high Q, unknown nuclei

In agreement with Chooz and Bugey data (1.9% on the e flux)

€

N (Eν , t ) ≈ α f

f

∑ (t) ⋅ρ f (Eν )- i (t) : relative contributions to the total fission (i=1) - i (E) : -spectra 235U, 239Pu, 241Pu, and 238U (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


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

€

Yi Z , A , t( ) /e spectra

€

Sν ,i Z , A , Eν ( )

Two distinct studies

€

Nν (Eν , t ) = Yn Z , A , t( ) ⋅

n

∑ Sν ,n Z , A , Eν ( )


fissilemat. + FY

neutron flux

Core geometry nuclear

database

exp. spectrum

models


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

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



[A. Hahn et al., Phys. Lett. B, 218, (1989)]

235U : 1.5 days in thermal flux

Agreement within 1up 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, E0,…..) (Thomas Müller PhD)

Relevant for normalization of Dchooz phase 1


239Pu : 1.5 days in thermal flux

Important fission products for the total beta spectrum between 2 and 4 MeV

ALTO, Orsay, France

- 235U fission: 86Ge

- 239Pu fission: 104Nb, 109Tc

- 238U fission: 100Y, 101Y, 103Zr

with missing information: T1/2, J, individual spectrum or transition type …

86Ge: 1.2 102 pps

102Nb: 5.6 103 pps109Tc: 1.2 103 pps100Y: 1.3 103 pps

101Y: 3.8 102 pps103Zr: 1.6 103 pps

http://ipnweb.in2p3.fr/tandem-alto/alto

Expected counting rates for 1011 fission/sec

Electrons beam: 50 MeV, 10 A

Photofission of 238U

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


Evolution of the spectrum shape with time

235U 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 -spectrumfor 60 time steps during 1 year

0 2 4 6 8 10 12

Energy (MeV)


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 <Z> 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

€

Rsim =S

sim(E ν )

S βs im (E β + me c 2 + δCoulomb )

€

SRéel =Rsim ×S

BI LL


235U/239Pu ratio

Ratio of the beta-spectra from the thermal neutron fission products of 235U

and 239Pu

0 1 2 3 4 5 6 7 8

1.0

1.5

2.0

2.5

1

2 34

5

6

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 normalisationNo absolute normalisation


Worldwide experimental perspectives

238U integral spectrum measurement in Münschen (Niels Haag et al. @Garching ) : meas. in April 2008

235U/239Pu ratio measurement in Moscow @Kurchatov institute (V. Kopeikin et al.) : planned to be settled in 2008

- 235U target irradiated by slow neutrons from FRM II- 238U 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,

– 235U, 239Pu targets (~10 mg/cm2) 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 (5106 s1cm2),

– chopper,– shielding.

Simulation of Chooz reactors

• Chooz: 2 PWR - N4 - 2x4.27 GWth - Fuel: enriched Uranium - Moderator/Coolant: Light pressurized Water (155 Bar,

600K) Core

Control rods (Instrumentation, Poisons…)

Coat (Zircalloy)

205 Fuel Assemblies264 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 UO2 pellets

reflectorActual geometry simplifications : simplified pins, no reflector

Mirror symmetry (1/8 of core) : full core simulation !!



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

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. Müller’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 : Münschen, Kurchatovo 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 ?

€

e

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subatech : s. cormon, m. fallot, l. giot, b. guillon, j. martino cea/dapnia/sphn : d. lhuillier, a....

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