AMIR:ANTINEUTRINO MEASUREMENT OF

ISOTOPES IN REACTORS

Yan-Jie Schnellbachy.schnellbach@liverpool.ac.uk

NuSec Nuclear Security Detection Workshop (15th - 16th April 2019)

ANTINEUTRINO MONITORING AT REACTORS

Anti-neutrino production at reactors: c. 2 x 1021 per GWthermal

Emitted isotropically

Electron anti-neutrino can be detected through inverse beta decay:­ νe + p → e+ + n­ Positron carries energy information: Ee = Eν -1.293­ Neutron some directional information­ Double coincidence signal

Extremely low cross-section (< 10 MeV)­ σ ~ 10-42

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USE AS SAFEGUARDS & NON-PROLIFERATION

Identified as potential tool for non-proliferation:­ Signal directly related to reactor status­Double coincidence allows for background rejection

Many ongoing experiments aimed at that:­ Renaissance of reactor antineutrino experiments­ SONGS1, AIT-Watchman, SoLid, PANDA, NuLat & many more!

All of them use antineutrino events to detect reactor status:­ On/off­ Change in event rate during burn-up

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From: Bowden, NS. “Reactor monitoring andsafeguards using antineutrino detectors” (2008)

[MeV]en

E2 3 4 5 6 7 8

]-1

fiss

ion

-1 [M

eVenN

-210

-110

1U

235

U238

Pu239

Pu241

INFORMATION CARRIED BY ANTINEUTRINO

Antineutrino rate carries reactor power + burn-up information

Antineutrino direction points to reactor­ Very hard to measure: initial direction of IBD neutron­ Thermalisation loses this information­ Possible over long time-periods, not for individual events

Antineutrino energy related to original fission­ Spectrum for each isotope fissioning!­ Effectively carries information about core composition!

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AMIR PROJECT

Investigate the use of spectral information:­Determine the use of spectra­Map rates for extended/multiple reactors­Translate into detector predictions­Combine into a toolkit

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0 1 2 3 4 5 6 7 8 9 10Energy [MeV]

1210

1310

1410

1510

1610

Anti-neutrino flux per isotopeAnti-neutrino flux per isotope

SPECTRA AT REACTORS

Toolkit accepts multiple inputs for isotope spectra:­ Fitted functions (e.g. Mueller et al)­ Tabulated flux predictions with errors­ Working with NNL student (George Holt)

Spectra are for total anti-neutrino emission per MWthermal per second­200 keV bins

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Antin

eutri

nos

[MW

th-1

s-1 ] 235U

238U239Pu241Pu

EXTENDED CORE

Toolkit divides core into 1m x 1m x 1m voxel:­ Each cube is a point source­ Can have its own thermal power and fission fractions

Core map is loaded in via table describing each voxel­ Allows for easy modelling of multiple extended reactors

Toolkit predicts antineutrino flux at each voxel in map:­ Here: a 100m x 100m x 100m example ­ Oscillation can be included, too

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INTERACTION RATE AT DETECTOR

Combined with anti-neutrino cross-section­ Gives anti-neutrino interactions per second per proton

Toolkit can take following detector parameters:­ Total active mass­ Hydrogen density­ Efficiency­ Resolution

Uses it to calculate event rate prediction

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0 1 2 3 4 5 6 7 8 9 10Energy [MeV]

29-10

28-10

27-10

Anti-neutrino interactions per isotopeAnti-neutrino interactions per isotope

Antin

eutri

nos

[pro

ton-

1s-

1 ] 235U238U239Pu241Pu

PREDICTED EVENT RATE

0 1 2 3 4 5 6 7 8 9 10Energy [MeV]

0

10

20

30

40

50

60

70

80

Detector measurementDetector measurementSample detector:­ 1 ton active mass­ Polystyrene­ 20% total efficiency­ 50m distance from 1.5 GWth core (⌀: 20m)

Predicted event rate can also be fitted with:­ Polynomials­ Histogram shapes

This allows determining whether:­ Different models have significant impact on spectral measurement

­ Determination of fission fractions­ Calculate uncertainty of predictions

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Antin

eutri

nos

Pred

ictio

n [w

eek-

1 ]

NEXT STEPS

Apply toolkit to specific case studies:­Different reactor types: AGR, PWR, research reactor­Study specific usage scenarios to make sensitivity predictions

Turn toolkit into library for easy use:­Allow custom voxelization size­Add option to evolve reactor map over time (based on tables + interpolation)­Optimisations for interactive use

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SUMMARY & CONCLUSIONS

Developed toolkit for evaluating reactor near-field detectors

Capable of evaluating multiple extended reactor cores in 3D space

Predicts and fits antineutrino spectra at a customisable detector

Many thanks to the NuSec Network for funding this work!

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