New and Novel Nondestructive Neutron and Gamma …...Lawrence Livermore National Laboratory New and Novel Nondestructive Neutron and Gamma-Ray Technologies Applied to Safeguards Arden

Lawrence Livermore National Laboratory

New and Novel Nondestructive Neutron and Gamma-Ray Technologies Applied to

Safeguards

Arden D. Dougan, Neal Snyderman, Les Nakae, Dan Dietrich, Phil Kerr, Tzu-Fang Wang, Wolfgang Stoeffl, Stephan Friedrich, Lucian Mihailescu

Presented to the JAEA-IAEA Workshop on Advanced Safeguards Technology for the Future Nuclear Fuel Cycle

This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344 UCRL-PRES-235638

2Lawrence Livermore National Laboratory

Novel Science and Technology Solutions for Safeguards

Compact Compton imager combined with 3D LIDAR for Design

Information Verification

Superconducting gamma-ray

spectrometer for ultra-precise sample

analysis

New Correlated Fast Neutron Counting

technique using Liquid Scintillator Multiplicity

counter and nanosecond timing

Next generation high efficiency neutron

detectors based on pillar technology


Superconducting γ-Ray Spectrometer (Ultra-Spec)

Si3N4

NbAl

Mo

Si Substrate

Mo/Cu thermistor

Sn absorber (0.25mm3)

γ-ray

Energy resolution ΔEFWHM = 2.355 k BT2CSource

Cold fingerwith detector

Refrigerator

Temperaturecontrol

Electronicread-out

HPGe

UltraSpec

90 92 94 96 980

50

100

150

200

250

300

350

Cou

nts

Energy [keV]

Pa Kα1 Pa K

α2

U Kα1

U Kα2

Th Kα1

(↔235U)

234Th (↔238U)

Gamma-ray absorption increases absorber temperature, which is measured with a superconductingthermometer

Low-temperature operationenables ultra-high energy resolution, <80 eV FWHM.

Operating Principle Spectrometer

Results

ApplicationsUltra-high energy resolution greatlyincreases precision of isotope ratio measurements in cases where HPGedetectors are affected by line-overlap.

e.g. MGA for Pu at 100keV, MGA-U for U at 92keV2006


We are developing a compact Compton imager

The Compton camera determines the direction of the gamma ray by tracking its interactions inside a multilayered detector system.Compton imaging provides 180 deg field of view, 2 deg angular resolution (3 cm at 1 m), 2 keV energy resolution, and can image the 186 keV 235U line and the 375 and 414 keV 239Pu lines. It takes 5 min to image 1 g 239Pu in a 6 cm pixel, 2 m away

We have built and tested the first Compton camera to take advantage of the new semiconductor strip detector technology that enables high-spatial-resolution, collimatorless imaging.


Verification of material hold-up and diversion in enrichment plants by combining 3D laser ranging with Compton camera gamma-ray imaging

Combining wide field-of-view gamma-ray imagers with 3D range maps obtained with a Design Information Verification (DIV) lidarscanner improves the fidelity of the gamma-ray image and adds a capability to directly measure isotope hold-up information compared to using laser ranging alone.

Lidar scans will provide the map of objects in the environment. The Compton camera measures the gamma-ray image.

Monte Carlo simulation of the gamma-ray intensity image of Pu-239 hold-up in a pipe elbow.


Measurements demonstrate gamma-ray imaging of materials in pipes

Reconstructed gamma-ray image measurements of a Eu-152 344 keV gamma-ray line source (analog for the Pu-241 414 keV line) hidden in a pipe are shown as contour plots on top of visual panoramic images of the Lab.

Expectation-Maximization Maximum Likelihood (EM-ML) Algorithm

Compton imaging will help inspectors verify plant designs, design changes, diversion of SNM, movement of SNM, hold-up and material accumulation.

Raw Compton image Filtered Back-projections using Spherical Harmonics


Mapping of gamma-ray images onto 3D range maps – side view

A gamma-ray image is back-projected onto the range map – snapshot of the 3D model (side view)

Virtual Scan axis

Gamma-ray imaging axis


New method: Correlated Fast Neutron Counting

Fast neutron counting enables isolation of individual fission events This will enhance the capability to statistically determine the fission isotopes in a mixed TRU stream—Cm versus Pu

With 60 keV active interrogation, we can preferentially fission 239Pu (and 235U) over 242Cm—239Pu and 240Pu dominate in concentration and

fission cross section


Measured Count Distributions

Random Source (AmBe) 2.1K cts/sec

Fission Source

S.F., M=1, eff ~ 3%252 Cf 3.1K cts/sec

06122002_143810-2A, Gate 512, 512 usecs

Tim

es p

er 1

0^6

cycl

es

Number of counts per cycle

100

101

102

103

104

105

106

107

-1.000 1.000 3.000 5.000 7.000 9.000 11.000

datapoisson

06132002_104441-2A, Gate 512, 512 usecs

Tim

es p

er 1

.3 x

10^

8 C

ycle

s

Number of counts per cycle

10-1

100

101

102

103

104

105

106

107

108

-1.000 2.000 5.000 8.000 11.000 14.000

datapoisson

Correlated Fission Source has wider distribution than predicted from Poisson (Random) with the same count rate


Individual Fission Chain Detection

Time Since Start of Burst (s)

Fission chain burst is easily distinguished from cosmic ray background

Measured data from 22 kg bare HEU shell

Neu

tron

Num

ber

Sin

ce F

irst i

n B

urst

Δt I

nter

val

Bet

wee

n C

ount

s

1 μs

100 μs

10 ms

1 s

10 ns

0

10

20

40

0 0.1 0.2 0.3 0.4 0.5

30

+ n Detector• Cosmic Ray Detector


0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0 1 2 3 4 5 6 7 8

Induced Fission Neutron Distributions

U235 inducedPu239 induced

Pro

babl

ility

per F

issi

on

Number of Neutrons per Fission

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0 1 2 3 4 5 6 7 8

Spontaneous Fission Neutron Distributions

Pu240 sponCf252 spon

Pro

babi

lity

per F

issi

on

Number of Neutrons per Fission

• SNM fissions with an expectation of 2-4 neutrons• Finite probability of more (especially with multiplication)

Fission Neutron Distributions


Time Scales: What does timing buy?

10-9

(ns)10-6

(μs)10-3

(ms)

Time (s)

Individual Fission

Fission Chains (metal)

Neutron Thermalization Time(3He/10B detectors, reactors)

Liquid Scintillator/Stilbene Detection Time

Liquid Scintillator is fast (nanoseconds) can detect individual fissions even in high count rate environments


High source count rate requires new technologies

With our new Liquid Scintillator array and nanosecond timing data acquisition

We have demonstrated isolation of fission chains in Pu


Discrimination of neutrons and gamma-rays with liquid scintillator

105 discrimination of neutrons and gamma-rays above 500 keV neutron energy

Neutrons

Tail

Rat

io

2” lead between 252Cf and stillbenedetector


• Use low-energy neutrons to induce fission in 235U and 239Pu

• Detect fission neutrons— Liquid Scintillator detectors— Pulse-shape discrimination— High-energy neutrons— Low background

Proof-of-ConceptSystem

Diagram

Active interrogation

60 keV neutrons preferentially fission 235U and 239Pu over 242CmThe fission cross section for 238U is even smaller


60-keV neutron interrogation

Induce fission in Pu— Detect high-energy fission neutrons

with Liquid Scintillator Detectors— Pulse-shape discrimination separates

fission neutrons and gamma rays− Energy Threshold detectors− Neutron beam energy well below

detector energy threshold

Low-energy neutron interrogation provides a rapid signature for the

presence of 235U

Single 3”x3” Detector

Single 3”x3” Detector

60-keV neutrons from proton beam

RFQ: 7Li(p,n)


Low Energy Neutron Interrogation with fast scintillator detection

Only SNM Pu, 235U readily fission from low energy neutronsMeasuring with fast scintillator preserves neutron energy Detector can be made invisible to interrogation BeamChanges in Fast Neutron Signature can help distinguish Neutron Source (e.g. Cm from Pu, HEU from LEU or DU) Fast Neutron Detection allows Pulsed Interrogation with Portable D-D or D-T generators.


Solid-state neutron detectors

LiF, 10B solid state neutron detectionUbiquitous neutron detectionLow power consumptionInsensitive to gammasPreamplification for each detector, signals can be transmitted via wire or wirelessPreamplifier performs as well as commercial unit 14%

15%

LLNL preamp Commercial preamp


Nanotechnology can lead to dramatic improvements in radiation detection

3D matrix of semiconductor nano-crystals

• Tuning the size of the nano-crystals will allow optimal scintillator-photodetector match.

3D semiconductor pillars surrounded by a boron-10 matrix

• Tuning the size of the pillars will lead to improved efficiency.

For neutron detection

For gamma-ray detection

The ability to control semiconductor dimensions at the nano/micro-scale can potentially lead to the next generation radiation detectors.

The ability to control semiconductor dimensions at the nano/micro-scale can potentially lead to the next generation radiation detectors.

Radiation Scintillation

Radiation electrons/holescollected

20Option:UCRL# Option:Additional Information

Lawrence Livermore National Laboratory

Pillar device for high efficiency neutron detection

Simulations indicate this 3-D structure will increase efficiency towards 85+% / cm2 !

Device geometry: etch depth → capture neutron

fluxpitch → alpha particle range

Simulations indicate this 3-D structure will increase efficiency towards 85+% / cm2 !

Device geometry: etch depth → capture neutron

fluxpitch → alpha particle range

10B efficiently produces α particles

But….Most α particles do not reach the detector!Limited efficiency: 2-5%/cm2 (@ thermal)

10B efficiently produces α particles

But….Most α particles do not reach the detector!Limited efficiency: 2-5%/cm2 (@ thermal)

10B+n → 7Li(0.84MeV) + α(1.47MeV)(Q=2.31MeV, σ=3571b)

10B+n → 7Li(1.01MeV) + α(1.78MeV)(Q=2.79MeV, σ=269b)

94 %

6%

Z1RR

A

B Z2

+, -Electron-hole pairsD

etec

tor

C

onve

rter

Neutrons

Charged particles(α, 7Li)10Boron

+

-

Etch

ed d

epth

Neutrons

Si

10B

+, -Electron-hole pairs

Charged particles(α, 7Li)

Planar 2D Design LLNL Pillar 3D Design

pitch


Next generation high efficiency detectors based on pillar technology

Neutron detection efficiency can be as high as 50%Can be filled with 10B, LiF or threshold fission materials


Applications for solid-state neutron detectors

“Smart tags” for tracking material flowMonitor centrifuge hallStorage area, transport through pipes, etc.Ubiquitous detection

Next steps: Need to do simulations and measurements to demonstrate this capability for specific Safeguards regimes

New and Novel Nondestructive Neutron and Gamma …...Lawrence Livermore National Laboratory New and Novel Nondestructive Neutron and Gamma-Ray Technologies Applied to Safeguards Arden

Documents