Determining Reactor Neutrino FluxDetermining Reactor Neutrino Flux

Jun Cao

caoj@ihep.ac.cn

Institute of High Energy Physics, CAS, Beijing

Neutrino 2010, Athens, Jun. 14-20, 2010

2 Reactor Neutrino ExperimentsReactor Neutrino Experiments

The first neutrino observation iThe first neutrino observation in 1956 by Reines and Cowan.n 1956 by Reines and Cowan.

Determination of the upper limiDetermination of the upper limit of mixing angle theta13 to sint of mixing angle theta13 to sin22

221313<0.17 (Chooz, Palo Verde)<0.17 (Chooz, Palo Verde)

The first observation of reactor The first observation of reactor anti-neutrino disappearance at anti-neutrino disappearance at KamLAND in 2003.KamLAND in 2003.

• Precision Experiments on theta13Precision Experiments on theta13 (Daya Bay, Double Chooz, RENO) (Daya Bay, Double Chooz, RENO)

-electron or -electron or -nucleus scattering (TEXONO, MUNU, GEMMA, CvNS)-nucleus scattering (TEXONO, MUNU, GEMMA, CvNS)

• Non-proliferation monitoring (France, US, Russia, Japan, Brazil, Italy)Non-proliferation monitoring (France, US, Russia, Japan, Brazil, Italy)

• Possible 60-km baseline experimentPossible 60-km baseline experiment

3 Reactor Neutrino Flux at a GlanceReactor Neutrino Flux at a Glance

Using PWR (Pressurized Water Reactor) as examples in the following. Using PWR (Pressurized Water Reactor) as examples in the following. (3-4)% U-235 enrichment. > 95% is U-238.(3-4)% U-235 enrichment. > 95% is U-238.

Neutrinos from subsequent Neutrinos from subsequent -decays of fission fragments. -decays of fission fragments.

Neutrino rate,

Palo Verde

Isotope evolvement,

Palo Verde

Neutrino spectra, ILL

More neutrinos from a U-235 fission than Pu-239

Visible spectrum, multipled by inverse -decay (IBD) Xsec.

0.1%

U-235 depletion

Pu-239 breeding

Peak at 4 MeV

Refueling outagePower tripsIsotope evolvement

XU-235, U-238U-235, U-238

Pu-239, Pu-241Pu-239, Pu-241

4 Neutrino Flux CalculationNeutrino Flux Calculation

( ) ( )istopes

i ii

S E f S E

( ) ( ) ( )( )

istopesth

i iii ii

WS E f F S E

f F e

Thermal PowerWth

Thermal PowerWth

Core Simulationfi/F

Core Simulationfi/F

Spectra of Isotopes Si(E)

Spectra of Isotopes Si(E)

E : Neutrino energy

fi : Fission rate of isotope i

Si(E) : Neutrino energy spectra/f

Neutrino Flux

(fi /F): Fission fraction

Wth : Reactor thermal power

ei : Energy release per fission , th i i ii i

W f e F f

Heat balance testOnline calibration

Core configurationThermal power

OperationsTemperature

pressure… …

MeasurementsCalculations

Spent fuel Non-equilibrium

Energy release/fissionEnergy release/fission

Flux

5 Thermal PowerThermal Power

KMEKME, thermal power, , thermal power, Secondary Heat BalanceSecondary Heat Balance Method. Method. The most accurate measurement.The most accurate measurement. Offline measurement, weekly or monthlyOffline measurement, weekly or monthly Generally cited with Generally cited with (0.6-0.7)% uncertainties(0.6-0.7)% uncertainties in literature. in literature.

KITKIT/KDO/KDO, thermal power. , thermal power. Good for analysisGood for analysis.. Primary Heat BalancePrimary Heat Balance OnlineOnline Weekly calibrated to KME power.Weekly calibrated to KME power.

RPNRPN, nuclear power, nuclear power Ex-core neutron flux monitoringEx-core neutron flux monitoring OnlineOnline Safety and reactor operation controlSafety and reactor operation control Daily calibrated to KIT/KDO powerDaily calibrated to KIT/KDO power

0.1% FPKIT KMEP P

1.5% FPRPN KMEP P

6 Core SimulationCore Simulation

Qualified core simulation code is normally licensed, not available for Qualified core simulation code is normally licensed, not available for scientific collaborations.scientific collaborations.

Need a lot of information from the power plant as inputs, such as Need a lot of information from the power plant as inputs, such as configurations, fuel composition, operations (control rods movement, configurations, fuel composition, operations (control rods movement, Boron dilution, etc), inlet temperature, pressure, flow rate, etc.Boron dilution, etc), inlet temperature, pressure, flow rate, etc.

Fission fractionsFission fractions, as a function of burn-up, could be a by-product of the , as a function of burn-up, could be a by-product of the refueling calculation, refueling calculation, provided by the power plantprovided by the power plant..

Burn-up is the amount of energy in Mega Watt Days (MWD) released from unit initial mass (ton) of Uranium (TU).

For small power variation, fission fraction can be gotten without redoing the simulation.

Provided by CNPRI

7 Spectra of IsotopesSpectra of Isotopes

Lack of data of the Lack of data of the -decays of the complex fission fragments, theoretical -decays of the complex fission fragments, theoretical calculation on the neutrino spectra of isotopes carries large uncertainties.calculation on the neutrino spectra of isotopes carries large uncertainties.

ILL measured the ILL measured the spectra of fissioning of U-235, Pu-239, and Pu-241 by spectra of fissioning of U-235, Pu-239, and Pu-241 by thermal neutrons, and converted them to neutrino spectra. Normalization ethermal neutrons, and converted them to neutrino spectra. Normalization error rror 1.9%,1.9%, shape error from 1.34% at 3 MeV to 9.2% at 8 MeV. shape error from 1.34% at 3 MeV to 9.2% at 8 MeV.

U-238 relies on theoretical calculation, 10% uncertainty (U-238 relies on theoretical calculation, 10% uncertainty (P. Vogel et al., PRC2P. Vogel et al., PRC2

4, 1543 (1981)4, 1543 (1981)). Normally U-238 contributes (7-10)% fissions.). Normally U-238 contributes (7-10)% fissions.

K. Schreckenbach et al. PLB118, 162 (1985)

A.A. Hahn et al. PLB160, 325 (1985) Shape verified by Bugey-3 dataNormalization improved to 1.6%

8 Energy Release per FissionEnergy Release per Fission

Isotopes Energy (MeV)

U-235 201.7±0.6

U-238 205.0±0.9

Pu-239 210.0±0.9

Pu-241 212.4±1.0

M.F. James, J. Nucl. Energy 23, 517 (1969)

Slightly varied for different cores due to Slightly varied for different cores due to neutron captureneutron capture. Uncertainties in (0.30-. Uncertainties in (0.30-0.47)%.0.47)%.

Kopeikin et al, Physics of Atomic Nuclei, Vol. 67, No. 10, 1892 (2004)

9 U-238 (n,U-238 (n,) Reaction) Reaction

Besides fission products, U-238(n,Besides fission products, U-238(n,)U-239 reaction contributes to neutrin)U-239 reaction contributes to neutrino yield. It is o yield. It is below inverse-below inverse- decay threshold decay threshold (1.8 MeV) but it is importa (1.8 MeV) but it is important to low energy neutrino-electron scattering experiments (TEXONO, MUnt to low energy neutrino-electron scattering experiments (TEXONO, MUNU).NU).

10 Non-equilibrium IsotopesNon-equilibrium Isotopes

ILL spectra are derived after 1.5 days exposure time. Long-lived fissioILL spectra are derived after 1.5 days exposure time. Long-lived fission fragments have not reached equilibrium. Contribute only to low enern fragments have not reached equilibrium. Contribute only to low energy region.gy region.

In Chooz paper it is estimated to be In Chooz paper it is estimated to be ~0.3%~0.3% and is ignored, comparing t and is ignored, comparing to other errors.o other errors.

Six chains have been identified, with half lives from 10h to 28y. (Six chains have been identified, with half lives from 10h to 28y. (KopeiKopeikin et al.) kin et al.)

90Sr 90Y

Fission Fission

89Sr neutron capture

89Y neutron capture

neutron capture

neutron capture

28.78y

0.546MeV

64.1h

2.284MeV

X.C. Ruan et al. (CIAE)

Ratio to all neutrinos

Ratio to neutrinos in 2-4 MeV

Weighted by inverse- decay Xsec.

11 Spent FuelSpent Fuel

Spent fuel stored temporarily adjacent to the core, could be up to 10 years.Spent fuel stored temporarily adjacent to the core, could be up to 10 years. Similar to non-equilibrium contributions, long-lived fragments in spent Similar to non-equilibrium contributions, long-lived fragments in spent

fuel will emit neutrinos.fuel will emit neutrinos.

Ratio to neutrinos in 2-4 MeV

Ratio to all neutrinos

Day 0Day 1Day 2Day 3Day 4Day 5Day 10Day 20Day 30

top

bottom

Energy Spectra

X.C. Ruan et al.

Contribution from one batch spent fuel

It may accumulate to several percent at 2-3 MeV.

Weighted by IBD Xsec.

12 Uncertainties from Past ExperimentsUncertainties from Past Experiments

Parameter Relative error

Reaction cross section 1.9 %

Number of protons 0.8 %

Detection efficiency 1.5 %

Reactor power 0.7 %

Energy released per fission 0.6 %

Combined 2.7 %

R=1.012.8%(stat) 2.7%(syst)

CHOOZ, Eur. Phys. J. C27, 331 (2003)

• Neutrino spectra (1.9% 1.6% with Bugey data)

• Inverse -decay cross section (0.2%)

• Fission fraction fk (~5%)

• Non-equilibrium fragments (0%)

KamLAND,PRL94:081801, 2005.

Palo Verde, PRD62, 072002

Parameter Relative error

Neutrinos/fission 1.4 %

Power, target, distance 1.5%

Combined 2.1 %

Power contributes ~0.7%

13 Power UncertaintiesPower Uncertainties

Chooz 0.6%, Palo Verde 0.7%.Chooz 0.6%, Palo Verde 0.7%. Motivation of power uprates by the power plants Motivation of power uprates by the power plants Study the power unce Study the power unce

rtainties and improve the instrumentation.rtainties and improve the instrumentation. Uncertainties of secondary heat balance is dominated by the flow rate.Uncertainties of secondary heat balance is dominated by the flow rate.

Venturi flow meterVenturi flow meter. Most US reactors. Uncertainty is often 1.4%. It ca. Most US reactors. Uncertainty is often 1.4%. It can be as low as n be as low as 0.7%0.7% if properly calibrated and maintained, but sufferin if properly calibrated and maintained, but suffering from g from foulingfouling effects, which could grow as high as effects, which could grow as high as 3%3% in a few years. in a few years.

Orifice plateOrifice plate. France EDF reactors. Typically . France EDF reactors. Typically 0.72%.0.72%. No fouling effec No fouling effects. Could be improved to 0.4% with lab tests.ts. Could be improved to 0.4% with lab tests.

Note: Above flow meter uncertainties are at 95% C.L. as defined in ISNote: Above flow meter uncertainties are at 95% C.L. as defined in ISO 5167. Unless specified, the thermal power uncertainty given by O 5167. Unless specified, the thermal power uncertainty given by the power plant is also at 95% C.L.the power plant is also at 95% C.L.

UltrasonicUltrasonic. Start to use in some US and Japan reactors. Type I TT . Start to use in some US and Japan reactors. Type I TT 0.40.45%,5%, Type II TT Type II TT 0.2%0.2% (Djurcic et al.) (Djurcic et al.)

14 An exampleAn example

EPRI document prepared by EDF, EPRI document prepared by EDF, Improving Pressurized Water Reactor Improving Pressurized Water Reactor Performance Through Instrumentation:…… (2006)Performance Through Instrumentation:…… (2006)

For N4 reactor (Chooz type) with 4 steam generators:For N4 reactor (Chooz type) with 4 steam generators:

If not assuming the discharge coefficients of the 4 orifice plates are independent, If not assuming the discharge coefficients of the 4 orifice plates are independent, the power uncertainty at the power uncertainty at 68.3% C.L. will be 0.37%.68.3% C.L. will be 0.37%.

Empirical formula and uncertainty specified in ISO 5167-1-2003.

Correlated or Uncorrelated for the 4 flow meters?

Orifice Plate

15 Another ExampleAnother Example

Daya Bay and Ling Ao reactors (EDF, 2.9GWDaya Bay and Ling Ao reactors (EDF, 2.9GW thth) are all calibrated with SAPE) are all calibrated with SAPE

C system, an EDF C system, an EDF portableportable high precision secondary heat balance test system high precision secondary heat balance test system with its own sensors, databases, and data processing, of uncertainty with its own sensors, databases, and data processing, of uncertainty 0.45%.0.45%. Li Ling Ao KME is predicted to have an uncertainty of ng Ao KME is predicted to have an uncertainty of 0.48%0.48% (95% C.L.) (95% C.L.)

4 tests on Ling Ao KME show differences from 0.031% to 0.065%. 4 tests on Ling Ao KME show differences from 0.031% to 0.065%. Why?Why? Used the same orifice plates but different pressure transmitters.Used the same orifice plates but different pressure transmitters. It proves that the uncertainty is dominated by It proves that the uncertainty is dominated by discharge coefficient.discharge coefficient. Ling Ao KME is in very good agreement with SAPEC.Ling Ao KME is in very good agreement with SAPEC.

Thermal power

Uncertainty Analysis

(MW)

(MW)

Difference (MW)

Difference

Test 1 Test 2 Test 3 Test 4

16 Uncertainties of fission fractionUncertainties of fission fraction

Depends on the simulation code. Only slightly on the inputs (has not been Depends on the simulation code. Only slightly on the inputs (has not been checked on other simulation code.)checked on other simulation code.)

Compare Compare measuredmeasured and and calculatedcalculated concentration of fuel isotopes, sampled concentration of fuel isotopes, sampled at different burn-up. Part of the qualification of the code.at different burn-up. Part of the qualification of the code.

Lester Miller thesis, ROCSOne analysis of Apollo 2.5

17 Uncertainties of fission fractionUncertainties of fission fraction

Assuming the neutron flux in simulation isn’t affected by the small Assuming the neutron flux in simulation isn’t affected by the small variations, fission rate variations, fission rate concentration. concentration.

Due to the constraint of the total power, 5% error on simulated isotope Due to the constraint of the total power, 5% error on simulated isotope concentrations corresponds to concentrations corresponds to ~0.5%~0.5% uncertainty on the detected uncertainty on the detected rate via rate via IBD reaction.IBD reaction.

Djurcic et al. J. Phys. G: Nucl. ParDjurcic et al. J. Phys. G: Nucl. Part. Phys. 36 (2009) 045002t. Phys. 36 (2009) 045002

Djurcic et al. collected 159 analDjurcic et al. collected 159 analyses for various codes and varioyses for various codes and various reactors in US and Japan. In us reactors in US and Japan. In average, the simulated concentraverage, the simulated concentration of isotopes have uncertaination of isotopes have uncertainties ties U235: ~4%U235: ~4% Pu-239: ~5%Pu-239: ~5% U-238: ~0.1%U-238: ~0.1% Pu-241: ~6%Pu-241: ~6%

18 IBD Event Rate UncertaintiesIBD Event Rate Uncertainties

Greatly simplified calculation of IBD rate uncertainties.Greatly simplified calculation of IBD rate uncertainties. Single reactor + single detectorSingle reactor + single detector

2 2 2 2 2 2 2/ 2 / 2 (2.02%)W f e s c

2 2 2 2 2 2 2(2.07%)W f e s c WW: thermal power ~ 0.4% (1 sigma), : thermal power ~ 0.4% (1 sigma),

ff: average uncertainties due to 5% fission fraction uncertainty ~ 0.5% : average uncertainties due to 5% fission fraction uncertainty ~ 0.5%

ee: average energy release per fission ~0.4%: average energy release per fission ~0.4%

ss: spectra normalization : spectra normalization 1.92%. 1.92%. Assuming U-238 contribute 8%.Assuming U-238 contribute 8%.

cc: IBD cross section = 0.2%: IBD cross section = 0.2%

Single detector + two reactors (equal distance)Single detector + two reactors (equal distance)

2 20.05 0.05 0.05 0.64% 0.03%unc W f

Near-far detectors + multiple reactors. All correlated errors (common to all Near-far detectors + multiple reactors. All correlated errors (common to all reactors) will cancel out. Uncorrelated errors will reduce depending on the reactors) will cancel out. Uncorrelated errors will reduce depending on the configuration, e.g. to 0.05.configuration, e.g. to 0.05.

19 SummarySummary

Before 80’s, the reactor neutrino flux uncertainties ~10%. With a lot of efforts, especially by ILL, Bugey, Chooz, Palo Ver

de etc., it is improved to 2-3%. More accurate thermal power, and more detailed study on errors. A global picture of uncertainties of fission rate from core simul

ation. Small corrections from spent fuel and non-equilibrium contribut

ions. No new data for neutrino spectra of fuel isotopes, which is domi

nant for a single detector experiment. Thus for single detector experiments, it is still ~2%.

Next theta13 experiments with near-far relative measurements will suffer little from reactor flux uncertainties (~0.1%), while complex correlation analysis should be done.

Thanks!

21 Non-proliferation MonitoringNon-proliferation MonitoringBowden, LLNL, 2008