Confessions of an Applied Nuclear Physicist

Glen WarrenPacific Northwest National laboratory

glen.warren@pnnl.gov

Hall C Meeting, JLabAug. 16, 2013

PNNL-SA-97564

OutlineIntroductionPNNL and RDNSNuclear PhysicsLead Slowing Down SpectrometryMaterial Verification for Arms Control

My Job

Apply nuclear physics to solve national security and non-proliferation needs

Specialize in active interrogation: use of beamsLook for ways to exploit nuclear physics to do better measurements

Kinds of Applications:Assay used nuclear fuelConfirm nuclear weapons dismantlementEnvironmental measurement samplesCargo inspection techniquesGeneral radiation detection:

Detector designAlgorithm development

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My View of Differences

Energy ScaleFrom GeV to keV

Applied ResearchClients have questions they want answeredShorter time scales (requires greater flexibility)

Work environmentWork with nuclear physics, particle physicists, chemists, nuclear engineers, chemists, mechanical engineers Strong emphasis on integrated team workNo more night shifts!

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OutlineIntroductionPNNL and RDNSNuclear PhysicsLead Slowing Down SpectrometryMaterial Verification for Arms Control

PNNL’s Past is Linked with Hanford

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National Security and PNNL

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FY12 PNNLBusiness Volume: $1.03 BillionStaff: 4,500

FY12 National SecurityBusiness Volume: $554 MillionDirect Staff (Mission): 1,037Direct Staff (Organization): 781

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RDNS and DSG

RDNS Capabilities•Ultra-low background rad detection•Materials development•Algorithms, modeling & simulation•Active Interrogation

DSG Capabilities• Software

• Electronics• Testing

• Detector design & fabrication

Shared Missions:•Basic Science

•High energy physics•Nuclear physics

•Treaty Enforcement•Nonproliferation

• Interdiction

Nuclear & High-Energy Physics at PNNL

Lepton Number Violation (MAJORANA) - 0nbbDark Matter (MJD, CoGeNT, C4, COUPP, CDMS)Neutrino Mass (Project 8)Heavy Quark Physics (Belle/Belle II)Lepton Flavor Physics (µ2e)http://www.pnnl.gov/physics/

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Treaty Enforcement at PNNL

► CTBT’s three critical components:► International Monitoring System

(IMS)►Seismic activity►Airborne particulates

► International Data Center►Process information from IMS

► On-site inspections► PNNL has become CTBTO’s go-to

source for expertise in radiation detection technology and training

Interdiction Technologies at PNNL

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Multi-Sensor Airborne Radiation Survey (MARS)

►Challenge: Rapidly detecting and identifying radiological materials

► Standoff distances► Wide area► Lightweight, rugged, mobile

►Solution: Multi-sensor Airborne Radiation Survey (MARS)

► Rugged to temperature, humidity and transport conditions

► Energy resolution of 3 keV at 1333 keV► Over 400% photopeak efficiency at

1333 keV compared to 3″×3″ NaI(Tl) detector

► Synchronized GPS data for isotope mapping

OutlineIntroductionPNNL and RDNSNuclear PhysicsLead Slowing Down SpectrometryMaterial Verification for Arms Control

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Fission

ApplicationReactors: “clean” energyNuclear weapons

EmissionsSeparation of nucleus into multiple piecesEmissions per fission

2-3 Fission productsTypically about 2/3 and 1/3 of original A

200 MeV kinetic energyAverage 2-3 neutronsAverage 7-8 g

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Isotopes of Interest

U-235Goes BOOM (fissile)Naturally occurring, but at low concentrationsVery little radiation emissions (186-keV g, very few neutrons)

U-238Benign, unless in nuclear weapon (fissionable)Naturally occurringStrong g emissions (1001-keV g, very few neutrons)

Pu-239Goes Boom (fissile)Produced in reactorsStrong g emissions (375-keV g)

Pu-240Produced in reactorsAccompanies Pu-239Strong neutron emitterRatio of Pu-240/Pu-239 determines quality of material

OutlineIntroductionPNNL and RDNSNuclear PhysicsLead Slowing Down SpectrometryMaterial Verification for Arms Control

Motivation: Direct Measurement of Pu Isotopes in Used Fuel

Measurement of Pu is necessary for:Quantifying material input at reprocessing facilityIndependent verification of burnup to support criticality calculations for fuel storageResolving used fuel shipper-receiver differenceMaintaining continuity of knowledge

Traditional assay methods: Indirectly measure Pu and carry ~10% uncertainty

Lead Slowing Down Spectrometry (LSDS)NDA technique for direct measurement of Pu in used fuel assembliesOur Focus: Develop algorithm to extract fissile isotopic masses from simulated LSDS measurement data

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Background: LSDS Principles

Using fission resonance structure to assay fuel

1.E-02

1.E-01

1.E+00

1.E+01

1.E+02

1.E+03

1.E+04

1.E+05

0 1 10 100 1000

Energy (eV)

Fiss

ion

cros

s-se

ctio

n (a

rbitr

ary

units

) .

Pu-239

U-235

cross sections are off-set for clarity

0.1

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Isotope Responses = x(t)Sensitive to interrogation

neutrons

LSDS for Fuel Assay

dEEEtxifissiondetectorsi )()(

fissilei

fissionfuel dEEEtyi

)()(

Fuel Assembly

Isotopic Fission Chambers(239Pu, 241Pu, 235U)

Threshold Fission Chambers(238U, 232Th)

Assay Signal = y(t) Sensitive to fission neutrons

n

nn

2ottkE

t = neutron slowing-down time

eVE 1.0keV10 %30FWHM

Constants to and k

2 m × 1 m of Pb

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OutlineIntroductionPNNL and RDNSNuclear PhysicsLead Slowing Down SpectrometryMaterial Verification for Arms Control

Material Verification

Material verification in the arms control contextprocess by which monitor verifies that an item is consistent with a declarationgoverned by an agreement

Example of items to be evaluatedassembled weaponsweapon componentsdisassembled materialsnon-treaty limited items

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Operating Environment

Host or inspected partyowns the item to be inspectedabsolute protection of sensitive informationsafetyas a result

host controls equipmenthost either provides the equipment or touches it last

Monitor or inspecting partymust confirm that item inspected has the declared properties

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Constraints

From the host perspectiveAbout to reveal secrets about your national crown jewels … big risks

From the monitor perspectiveExpected to verify the measurement is working as intended when you do not control the equipment … hard, really hard

There are possible solutions to help address some of these problems

joint designrandom selectionincorporating certification and authentication throughout the design process

Measurement systems are driven more by these constraints than by physics

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Information Barrier

Raw data from measurements on sensitive items often contain sensitive information

e.g., complete HPGe spectrum would enable the evaluation of Pu isotopics, which is sensitive to the Russians

Information barrier limits information that goes into and out of the system

Limitspossible operator inputfilter line voltageelectromagnetic cage for shieldingoutput information

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Attributes

The evaluation of an attribute is a non-sensitive characteristics of a measured item that can be determined from potentially sensitive measurements

Examplemeasure the gamma-ray spectrum from a sampleextract the ratio 240Pu/239Pu from that spectrumwhether that ratio exceeds a threshold is then the evaluation of the attribute

Examples of attributespresence of 239Pumass of 239Pu above a thresholdage of PuU enrichment above a threshold

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239Pu and 240Pu Ratio

Measure g from 239Pu646 keV line from 239Pu642 keV line from 240Pu

Measured in previous AMS

EquipmentHPGe detector

Assumptionsadequate amount of 240Pu present to measurehomogenous mixture of 239Pu and 240Pu

Gamma-ray spectrum for a Pu-bearing item (Taken from: Arms Control and Nonproliferation Technologies, 2001)

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SummaryPNNL

Mission-driven lab with diverse efforts

RDNSBasic and applied researchStaff have diverse backgrounds

Applied Nuclear PhysicsMany nuclear physics-related problems to address