Advances Towards Readily Deployable Antineutrino Detectors for

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• Advances Towards Readily Deployable Antineutrino
  Detectors for
• Reactor Monitoring and Safeguards

Belkis Cabrera-Palmer Sandia National
Laboratories June 9, 2009
Sandia is a multiprogram laboratory operated by
Sandia Corporation, a Lockheed Martin Company,
for the United States Department of Energys
National Nuclear Security Administration under
contract DE-AC04-94AL85000.
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Antineutrino Detectors for Reactor Monitoring and
Safeguards
Project Team
Lawrence Livermore National Laboratory
Adam Bernstein Nathaniel Bowden Steven Dazeley
Jim Lund Dave Reyna Lorraine Sadler Scott
Kiff Belkis Cabrera-Palmer
Publications Bernstein JAP 91, 04672,
2002 Bowden NIMA 572, pp. 985, 2007 Bowden JAP
103, 074905, 2008 Bernstein JAP 105, 064902, 2009
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Outline

• Antineutrino detector for reactor monitoring and
  safeguards (power and fuel evolution)
• Technology demonstrated with underground detector
• Going aboveground handling increased backgrounds
• Tight shield for background reduction
• Particle ID for background rejection

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Detected antineutrino rates from reactors are
reasonable for cubic meter scale detectors
Detected rates are quite reasonable
Reactors emit huge numbersof antineutrinos

• 6 antineutrinos per fission from beta decay of
  daughters
• 1021 fissions per second ina 3,000-MWt reactor

• 1017 antineutrinos per square meter per second at
  25-m standoff
• 6,000 events per ton per day with a perfect
  detector
• 600 events per ton per day with a simple detector
  (e.g., SONGS1)

About 1022 antineutrinos are emitted persecond
from a typical PWR unattenuated and in all
directions
Example detector total footprint with shielding
is 2.5 meter on a side at 25-mstandoff from a
3-GWt reactor
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Antineutrino Detectors for Reactor Monitoring

• Different antineutrino spectra from 235U and
  239Pu
• The isotope fuel composition changes during the
  reactor fuel cycle 235U is consumed and 239Pu is
  produced
• ? Detected antineutrino rate is sensitive to the
  isotopic composition of the core

Detector and reactor constants
Fuel composition dependent
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Antineutrino Detectors for Reactor Safeguards

• Antineutrino detectors are particularly useful
  for Reactor Monitoring and Safeguards because
• provide real-time quantitative information about
  core power and isotopic composition while reactor
  online
• report reactor status independent of operator
  declarations
• continuous, non-intrusive, remote, unattended
  monitoring

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Antineutrino detector deployed at SONGS(San
Onofre Nuclear Generating Station, a PWR)

• Since 2003, we have deployed several
  nonproliferation detectors at SONGS
• We have demonstrated that antineutrino based
  reactor monitoring is possible using devices that
  are automated, non-intrusive, simple and
  appropriate for reactor environment

25 m

• Tendon galleries are an ideal location
• Rarely accessed for plant operation
• Close to core, but outside containment
• Provides 10s m.w.e. overburden
• Flux 1017 n / s m2

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Antineutrino below-ground detector SONGS1

• 0.64 tons of Gadolinium-doped liquid
  scintillator, water shielding, plastic muon veto
• Automatic (relative) calibration using background
  gammas

• ne p g e n

inverse ?-decay

• Positron
• immediate
• 1- 8 MeV (incl 511 keV gs)
• Neutron
• Delayed capture in Gd, t 28 ms
• g cascade 8MeV

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Antineutrino below-ground detector SONGS1

• Hourly averaging of data allows for detection of
  a reactor scram within 5 hours at 99.9
  confidence

See NIM A 572 (2007) 985, J. Appl. Phys. 103,
074905 (2008)
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Antineutrino below-ground detector SONGS1

• Daily and weekly averaging allows relative power
  tracking

Daily 8 Relative uncertainty Weeky 3
Relative uncertainty
See NIM A 572 (2007) 985, J. Appl. Phys. 103,
074905 (2008)
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Antineutrino below-ground detector SONGS1

• Long term monitoring-fuel composition

• Removal of 250 kg 239Pu, replacement with 1.5
  tons of fresh 235U fuel

See NIM A 572 (2007) 985, J. Appl. Phys. 103,
074905 (2008)
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Why an aboveground detector?

• Underground antineutrino detection has been
  demonstrated
• Not all PWR have available underground location
• Having no overburden requirement vastly increases
  range of possible locations for safeguards
  applications

Challenge Increased background due to cosmic rays
Our initial goal Report reactor on/off
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Backgrounds
aboveground

• Positron
• immediate
• 1- 8 MeV (incl 511 keV gs)
• Neutron
• captured after thermalization (if Gd, t 28 ms )
• Released energy depends capture agent
  (if Gd, 8MeV)
• ? eliminate other events with similar time
  structure

correlated
uncorrelated
signal inverse ?-decay
background event
Aboveground increase in fast/slow neutron
interactions due to increase in cosmic-ray flux,
hadronic and muonic components.
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Aboveground Bckgrnd Reduction tight shielding

• Goal Reduce flux of incoming particle
• Shield designs for aboveground
• 45 cm High Density Polyethylene on all sides
• Hermetic Muon Veto
• Interior Volume 1.5x1x1.5m
• Fits within a 20 container

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Aboveground Bckgrnd Rejection Particle ID

• Goal reject signal-like bckgrnd events
• Ideal identify one or both of inverse beta-decay
  products
• Alternatively, identify a bckgrnd-generating
  particles (e.g., protons)

Since the expected signal rate is 100/day, a
3-sigma background is 1000/day (to observe
reactor on/off in a week.) We estimate a total
background due to fast neutrons that recoil, and
perhaps capture, of 5,000 50,000 / day !!!
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Aboveground Candidate Particle ID technologies
Identification of inverse ?-decay products (e,n)
Inorganic Scintillator (LGB) with neutron capture
agents 6Li natGd(11BO3)3Ce, mixed with plastic
scintillator ? identifies thermal neutron
capture in 6Li via PSD
Under investigation
6Li mixed inorganic scintillator paint ZnS(Ag) ?
identifies thermal neutron capture in Li via
PSD ? segmentation to identify pair (e-like,n)
Gd-doped segmented liquid scintillator ?
segmentation identifies pair (e-like,n)
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Aboveground Candidate Particle ID technologies

• Organic liquid scintillator
• identifies protons via PSD
• not preferred in reactor environment due to
  flammability

Need to isolate proton recoils (e)-like events
since segmentation might not reject them
Under consideration to prove aboveground
detection
Gd-doped Water Cerenkov detector ? Insensitive
to proton recoils
Initial demonstration done new deployment in
fall 2009
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Conclusions

• Our SONGS1 detector has demonstrated feasibility
  of antineutrino detectors for reactor monitoring
• Aboveground capability is a must and we are
  working to demonstrate it
• Cosmogenic backgrounds (mainly fast neutrons) are
  the main challenge for aboveground detector
• Aboveground detection will require some
  combination of
• - Tight shielding (active and passive)
• - Particle identification (via material or
  geometry)
• - Background insensitivity