Integrated System Based on Muon Tomography for Nuclear ... · HPGe, Boron-Coated detectors, 3He...

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O. Kamaev, V. Anghel, A. Erlandson, C. Jewett, S. Livingstone,E. Rand, M. Thompson, B. van der Ende

Canadian Nuclear Laboratories

International Workshop on Numerical Modelling of Non-Destructive Assay Instrumentation and Methods for Nuclear Safeguards

16 – 17 May 2018

Integrated System Based on Muon

Tomography for Nuclear Security and

Safeguards


Challenges in Nuclear Security and SafeguardsObjectives of IAEA safeguards: “the timely detection of diversion of significant quantities of nuclear material from peaceful nuclear activities to the manufacture of nuclear weapons … and deterrence of such diversion by the risk of early detection”.

IAEA Safeguards Glossary

• Prevent or deter the theft of special nuclear material (SNM), detect illicit movement: facility / border security

• Characterise legacy nuclear waste stored within industrial containers: waste management verification / non-proliferation

Detection of shielded illicit radioactive materials, including SNM, is a long standing challenge.


Muon Tomography for Nuclear Safety & Security

Muon Scattering Tomography (MST) technique:

• Muons are highly penetrating and are hard to shield.• Employs the multiple Coulomb scattering of naturally

occurring cosmic-ray muons inside a material.• Allows a passive non-destructive assay of large-volume

objects.• Detects the presence of high-density / high-Z materials.

scattering

angle q

muon

material

Integrated System for detecting radioactive materials:

Motivation? To increase the accuracy and speed of detecting shielded SNM.How? By integrating muon tomography with gamma-ray, neutron detectors:

• Experimental tests with multiple technologies towards integration.• Monte Carlo simulations for lab-scale systems.


Multiple Passive Technologies for SNM DetectionMuon tomography:Is there illicit high-density object?Where is it exactly inside a container?

High resolution gamma spectroscopy:Is radioactive/nuclear material present?What is the source?

Neutron counting:Is it SNM?What is the mass?


Muon Tomography DetectorCosmic Ray Inspection and Passive Tomography (CRIPT) – a scintillator-based MST detector at Canadian Nuclear Laboratories.

UV and blue light is produced by muon’s interactions in scintillators



Position-sensitive super-layer

UV and blue light is produced by muon’s interactions in scintillators



121 x and 121 y bars per super-layer2.0 m x 2.0 m in area


CRIPT Muon Tomography Detector

Deflection in

high-Z target

Target

area

Muon

Spectrometer for

muon momentum

Detector

Layers

5.3 m tall

“A plastic scintillator-based muon tomography system with an integrated muon spectrometer”, Nuclear Instruments and Methods in Physics Research A 798 (2015)


CRIPT Detector: Output

2 hours of data5 cm voxels8 hit threshold

with high-density Pb flaskw/o flask

Images:• Collect enough data in enough voxels and

create an image (we get ~60 muons/s).• Sophisticated image reconstruction algorithm

(Canada Patent 2838656, 2012).• A qualitative result, rather than a quantitative.

Detection parameter:• Evaluated with Geant4 Monte Carlo studies.• Selected parameter: median logarithm of the

scattering density estimate (SDE).


CRIPT Detector: Output

2 hours of data5 cm voxels8 hit threshold

with high-density Pb flaskw/o flask

Images:• Collect enough data in enough voxels and

create an image (we get ~60 muons/s).• Sophisticated image reconstruction algorithm

(Canada Patent 2838656, 2012).• A qualitative result, rather than a quantitative.

Detection parameter:• Evaluated with Geant4 Monte Carlo studies.• Selected parameter: median logarithm of the

scattering density estimate (SDE).• High-density/Z material produces the tail on

the right side of the distribution.


Gamma-ray DetectorWith light or irregular shielding, gamma-rays are easy to detect.High-purity germanium (HPGe) detector:• Relative efficiency: 25% @ 1.3 MeV• Energy resolution: FWHM 1.8 keV @ 1.3 MeV• Endcap diameter: 76 mmUtilized γ-lines from Uranium:• 238U via 234mPa: 1001, 766, 258 [keV].• 235U: 186 keV.

Energy [keV] Time [days]


Neutron DetectorNeutrons are fairly unique to SNM.Boron-lined hybrid 10B/3He (B10+) detector:• A boron-lined neutron detector boosted

with 0.75 atm of 3He.• Detector area: ~ 100 x 20 cm2

• Tubes are placed in a high-density polyethylene box. n

• Based on thermal neutron capture by 10B (3840 barn):n + 10B → 7Li*+ α + 2.3 MeV (94%)

→ 7Li + α + 2.8 MeV (6%)• 3He has a large cross-section for capture of thermal neutrons (25 meV):

n + 3He → 3H + p + 0.765 MeV (5400 barn)


Blind Tests: Typical Setup


Scenario: Verify that SNM content in storage material is intact.

• Lead flask:

(4.3 cm thick)

Setup: DU inside Lead Flask

Units: inches

10 minutes of data• CRIPT: shows a barrel-like object placed in the center.• HPGe: observed a hint of 238U via 1001 keV γ-line.• B10+: null result consistent with background.

• 55-gallon drum with 2 stacked concrete blocks inside.• High-density polyethylene (HDPE), tungsten rod, fake

metal CANDU fuel bundle, metal objects, sand bags .• Depleted uranium (DU) slugs, ~6 kg in total, were added

during tests – not known to “blind” analysers.


Setup: DU inside Lead Flask2 hours of data:• HPGe: still observed a hint of 238U.

Estimated min detection time: 10 hours.• CRIPT: observed an anomaly (high-density/Z spot) in horizontal

slices at ~55 cm vertical position.Integral of SDE is 341 ± 18 vs. 319 ± 18 (reference case).

• B10+: clear signal of 22.2 ± 3.0 cpm.Estimated min detection time: 82 minutes.Estimated NU/DU mass: 21.5 ± 4.0 kg.

reference test


Setup: DU inside Lead Flask

20 hours of data from CRIPT:• Confirmed an anomaly (high-density/Z spot).

Clear difference between “test” and “reference” cases.Reference case: a cavity within high-density material is seen.Test case: cavity is filled with SNM.

reference test


Setup: LEU inside textile containerScenario: Undeclared, illicit nuclear material inside shipping container with textile.

• Heavy fabric completely filling plywood box.• Low-enriched uranium (LEU) container, 0.5 kg total

weight, was placed into the middle of the box during tests – not known to “blind” analysers.

10 minutes of data• CRIPT: using 4-cm voxels scanning volume appears as

low-density.• HPGe: clear signal of 73.2 ± 0.9 cpm rate for 1001 keV

γ-ray with a background of 5 – 8 cpm.Estimated min detection time: 0.3 minutes.Estimated enrichment: 5.2 ± 1.7 % of 235U.

• B10+: null result with 7.8 ± 10.2 cpm corrected for background.


Setup: LEU inside textile container2 hours of data• CRIPT: small high-density/Z material was observed

directly in the center.Integral of SDE is 2 vs. 0 (reference case).

• B10+: null result consistent with background. Estimated mass of 235U: 3.7 kg.

20 hours of data from CRIPT

reference test

test


Integrated Monte Carlo Simulation Framework

• Can include CRIPT, PVT plastic scintillator panels, HPGe, Boron-Coated detectors, 3He tubes.

• Flexible number of gamma-ray, neutron detectors.

• Capable of simulating and detecting coincident signals.

Simulated integrated system based on muon tomography with multiple gamma, neutron detectors

Modular object-oriented framework to support the detection of SNM.• Build upon the Geant4 toolkit

Standard G4 physics lists High-precision neutron physics lists

• Includes FREYA from LLNL Fission Library package for emission of correlated fission secondaries.


Benchmark/Validation of Integrated Monte Carlo

Experimental setup

Simulation setup

“Small Lead Flask shielding” experiment

Simulated response of PVT panels to neutrons

1H capture

35Cl capture

• Good agreement between experiment PVT measurements with PuBe n-source and simulations.

• Currently assessing performance of the integrated SNM detection system using developed MC simulation framework.


MC Characterization of 10B/3He Detector

B.M. van der Ende et al., “Use of SRIM and Garfield with Geant4 for the characterization of a hybrid 10B/3He neutron detector”, Nuclear Inst. and Methods in Physics Research, A 894 (2018)

Pulse height spectra from measurement vs. Garfield + SRIM simulation

• Geant4 MC simulation agrees with 252Cf measurements to within 6.4%.

• Extended MC model by simulating raw pulses with Garfield and SRIM.

• Developed tools can be applied to modelling of any gas-based prop. counterfor neutron detection.


Summary• A passive system based on muon tomography, neutron detection, and gamma-ray

spectrometry for non-destructive assay can address detection of shielded illicit radioactive materials, including SNM, - a long standing challenge. Facility / Border Security Non-proliferation / Waste Management Verification.

• CRIPT, a muon tomography system with unique capability of measuring muon momentum, is in operation at Canadian Nuclear Laboratories.

• Passive neutron and gamma-ray systems were added: Confirm the clear presence of SNM Identify a radioactive source, estimate enrichment Provide an estimate for the mass of SNM.

• Experimental tests with multiple technologies towards integration were performed.• Integrated MC simulation framework was developed and validated - finalizing

performance assessment.


Backup Slides


CRIPT Detection Time

60 second scan, 90% success rate with ~1% false alarm rate... But, that is lead in empty container, work continues....

50/50 guess

“A plastic scintillator-based muon tomography system with an integrated muon spectrometer”, Nuclear Instruments and Methods in Physics Research A 798 (2015)

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