Post on 18-Dec-2021
transcript
Consortium for Verification Technology
Fissile material experiments at the Device Assembly Facility
CVT Workshop – October 20, 2016
Michael Hamel1, Pete Chapman2, Michael Streicher1
1University of Michigan2North Carolina State University
Consortium for Verification Technology
Campaign objectives
• July 11-21, 2016, CVT and CNEC conducted experiments with Cat-I SNM at DAF for a second time
• Provided CVT and CNEC students, post-docs, and faculty with the opportunity to conduct hands-on experiments with Category I (weapons usable) special nuclear material (SNM)
• Included a neutron generator for active interrogation of HEU
2
Consortium for Verification Technology
Device Assembly Facility
• Located within the Nevada National Security Site, 90 minutes northwest of Las Vegas
• Operated by NSTec for the NNSA
• Houses the National Criticality Experiments Research Center
• Supports critical and subcritical measurements of WGPu, HEU, and Np
3
Las Vegas
DAF
Consortium for Verification Technology
• North Carolina State University– Prof. John Mattingly, Jonathan Mueller, Pete Chapman
• Princeton University– Prof. Alex Glaser, Sebastien Phillipe, Benjamin Reimold
• University of Illinois– Prof. Clair Sullivan, Mark Kamuda
• University of Michigan– Prof. Igor Jovanovic, Michael Streicher, Bennett
Williams, Jason Nattress, Lazar Supic, Michael Hamel
• Oak Ridge National Laboratory– Jason Newby
• Los Alamos National Laboratory– Jesson Hutchinson, Donnette Lewis, et al.
CVT campaign participants
4
Consortium for Verification Technology
Sources
• SNM sources– BeRP ball: 4.5-kg WGPu metal sphere
– Thor core: 4.1-kg WGPu metal disk
– Rocky Flats shells: 13.7-kg HEU metal shells
– Neptunium: 6.1-kg metal sphere
• Interrogating Sources– AmLi
– DD neutron generator
– DT neutron generator
5
Rocky Flats shells with AmLi
Assembly of Rocky Flats shells
Consortium for Verification Technology
• Neutron coded aperture imager (ORNL/SNL)
• Bubble detectors array (Princeton)
• NaI, CsI scintillators (Illinois)
• Dual particle imager (Michigan)
• One dimension transmission imager (Michigan)
• Polaris and Orion CZT imagers (Michigan)
Instruments
6
Consortium for Verification Technology
Dual-particle imager• Combined Compton and neutron
scatter camera• Two-plane design
– Front Plane: EJ-309 liquid organic scintillators
– Back Plane: EJ-309 and NaI(Tl)
• Separate neutron and photon signals
7
NaI(Tl)EJ-309
Back PlaneFront Plane
Neutron Image Photon Image
Consortium for Verification Technology
AmLi experiment
8
Top View6.25×104 n/s AmLi
in 1” lead pig
Aluminum table
Dual-Particle Imager
116 cm
13.7 kg HEU
Measurement time: 850 min
DPI
13.7-kg HEU
Consortium for Verification Technology
AmLi experiment
• Most neutron emitted by AmLiare less than 1.5 MeV
• Threshold of DPI ensures measured neutrons are from induced fission
9
Neutron Image Photon Image
Neutron Spectrum
Photon Spectrum
Consortium for Verification Technology
DT experiments
10
Top ViewTarget
Generator tube
Aluminum table
Dual-Particle Imager
155 cm28 cm
13.7 kg HEU
13.7-kg HEU
DT generatorDPI
Consortium for Verification Technology
DT experiments
• Generator emitted 14.1 MeV neutrons
• Operated at 300 Hz with a 10% duty cycle
• 333 μs pulse length
• Digitized start of veto signal and vetoed based on pulse arrival times
• 335,700 ns after start of pulse
11
Neutrons per Second
No Veto With Veto
698 0.0048
Neutron Image:No Veto
Consortium for Verification Technology
DT experiments
12
HEU
HEU with poly moderator
DT Generator position
Consortium for Verification Technology
Identifying Fissile Assemblies in Fast Neutron Images
13
Consortium for Verification Technology
Neutron Coded Aperture Imager (NCAI)
14
Consortium for Verification Technology
2015 DAF Campaign Update• Passive measurements of
bare BeRP ball (WGPu)• Used Time-Correlated
Pulse-Height (TCPH) analysis to identify fissile assemblies
• Neutrons depositing more energy than predicted by their time-of-flight indicate fission chain reactions
15
Consortium for Verification Technology
2015 DAF Campaign Update
16
BeRP
252Cf
Consortium for Verification Technology
2016 DAF Campaign
• Active measurements of Rocky Flats HEU shells
• AmLi, DD and DT generator drivers
• Used energy or time cuts to identify fissile assemblies
17
Consortium for Verification Technology
AmLi Sources
18
• 4x AmLi sources• ~ 105 n/s• Rocky Flats shells 1-24• 15 hour run time
Consortium for Verification Technology
AmLi Sources
• No cuts needed
19
Consortium for Verification Technology
D-D Generator
20
• 300 Hz• 10% duty cycle• ~ 106 n/s• Rocky Flats shells 1-24• 100 minute run time
Consortium for Verification Technology
D-D Generator
21
Consortium for Verification Technology
D-D Generator Energy Cut (Edep > 2.75 MeV)
22
Consortium for Verification Technology
D-T Generator
23
• 300 Hz• 10% duty cycle• ~ 107 n/s• Rocky Flats shells 1-24• 1 hour run time
Consortium for Verification Technology
D-T Generator
24
Consortium for Verification Technology
D-T Generator Time Cut (t > 333 ns)
25
Consortium for Verification Technology
Fast Neutron Images of Fissile Assemblies
• 2016 DAF Campaign Conclusions– AmLi drivers may be used without cuts– D-D generators may be used with energy cuts
• Best to operate in continuous mode• Some tritium still present
– D-T generators may be used with time cuts• Must be used in pulse mode with veto
• Future Work – Perform simulations of 2015 DAF Campaign scenario
to investigate lower bound of multiplication for which a TCPH-filtered image successfully identifies a multiplying assembly
26
Consortium for Verification Technology
M
“Black Box” Complete Source Characterization
27
Digital CZT array
γ,x-ray
nfast
nthermal
Z?
Consortium for Verification Technology
• Orion Prototype Digital CZT Array System
• Objects:– Rocky Flats Shells– BeRP Ball– Thor Core (2015)– Np Sphere (2016)
28
0 100 200 300 400 500 600 7000
1
2
3
4
5
6
7
8
9
10
11x 105
Energy (keV)
Coun
ts p
er 0
.25
keV
bin
0.63 %
Corrected Count Map57Co Coded Aperture Shadow
Consortium for Verification Technology
Rich Spectral Information Comparable with HPGe
29
Thor Core Measurement
*Compared with ORTEC Micro-Detective (5 cm x 3.3 cm)
n113Cd 114Cd
IC e-γ
γ
γ
500 550 600 650 700 7500
1
2
3
4
5
6
Energy (keV)
Cou
nts
per m
inut
e pe
r keV
BarePoly Sphere Steel + Poly
Unique Thermal Neutron Signature!
Consortium for Verification Technology
Rich Spectral Information Comparable with HPGe
• Energy resolution sufficient to estimate 240Pu
• Use spectral data to identify shielding
30
140 160 180 200 220 240
101
102
Energy (keV)
Cou
nts
per 0
.5 k
eV b
in p
er m
inut
e
Bare HEUIron shielded HEU
U
Consortium for Verification Technology
Spectral-Based Shielding Identification
31
Consortium for Verification Technology
Final Shielding Identification Results• Demonstrated on Pu, U, and Np sources
32
0 5 10 15 20 250
20
40
60
80
100
Z N
umbe
r
Mass Thickness (g / cm2)
Peak AttenuationSmall Angle ComptonTrue Value
Consortium for Verification Technology
SNM Orientation through Gamma-ray Imaging
33
Consortium for Verification Technology
Fast Neutron Detection
34
0 50 100 150 2000
20
40
60
80
100
120
Energy (keV)C
ount
s pe
r min
ute
per 0
.5 k
eV b
in
Module 1
0 50 100 150 2000
20
40
60
80
Energy (keV)
Cou
nts
per m
inut
e pe
r 0.5
keV
bin
Module 3
0 50 100 150 2000
20
40
60
80
100
Energy (keV)
Cou
nts
per m
inut
e pe
r 0.5
keV
bin
Module 2
0 50 100 150 2000
20
40
60
80
100
120
Energy (keV)
Cou
nts
per m
inut
e pe
r 0.5
keV
bin
Module 4
Cf-252Cs-137
• Nuclear recoil in high-Z materials generate very few electron-hole pairs
• Energy depositions less than 20 keVeeare candidates
• Many experiments have confirmed fast neutron detection– See upcoming IEEE
NSS conference
Consortium for Verification Technology
Fissile material experiments at the Device Assembly Facility
CVT Workshop – October 20, 2016
Michael Hamel1, Pete Chapman2, Michael Streicher1
1University of Michigan2North Carolina State University