3 He Neutron Detection Alternatives for Radiation Portal Mo

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3 He Neutron Detection Alternatives for Radiation Portal Mo




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Presentations text content in 3 He Neutron Detection Alternatives for Radiation Portal Mo

Slide1

3He Neutron Detection Alternatives for Radiation Portal Monitors

Richard KouzesKen Conlin, James Ely, Luke Erikson, Azaree Lintereur, Emily Mace, Edward Siciliano, Daniel Stephens, David Stromswold, Renee Van Ginhoven, Mitch WoodringPacific Northwest National LaboratoryWork Supported by DOE, DOD, DHS, PNNLIAEA 3He WorkshopMarch 22-24, 2011

PNNL-SA

-77910

Slide2

2

The 3He Problem

National security and science applications have driven up demand for 3He for neutron detectionCurrently, 3He comes solely from the processing of tritiumNo significant production of new tritiumProduction of tritium solely for 3He need is cost prohibitiveReserves of 3He have been consumedProjected 3He Supply ~10-20 kL/y (U.S.& Russia)Demand for 3He was ~65 kL/y – now reducedNothing matches all of the capabilities of 3HeAn alternative is needed now

2

3

He Tubes

Slide3

3He Applications

3He is a rare isotope with important uses in:Neutron detection sciencenational securitysafeguards oil/gas explorationIndustrial applicationsLow-temperature physicsLung imagingMissile guidance Laser researchFusion

3

Slide4

3He Characteristics

3He is excellent for neutron detectionLarge thermal neutron capture cross-sectionInert gasGood gamma ray rejection

4

Slide5

3He Demand Forecast: FY09

5

Data From Steve Fetter, OSTP

Supply

Projected demand ~65 kL/

y

- Projected Supply ~10-20 kL/

y

Slide6

3He Demand Forecast: FY1

6

Plot From Julie Bentz, National Security Staff

Slide7

7

Border Security Examples

Over 1400 RPM systems deployed in US

About 3000 RPM systems deployed worldwide

Neutron and gamma ray detection

Slide8

8

Alarms and “Nuisance” Alarms

Few sources of Neutron Alarms (~1/10,000)Troxler gauges, well logging sources, nuclear fuel, yellowcakeNuisance alarms: large gamma ray sources and “ship effect”Gamma Ray Nuisance Alarms (~1/100)agricultural products like fertilizerkitty litterceramic glazed materials aircraft parts and counter weightspropane tanksroad saltwelding rodsore and rocksmoke detectorscamera lensestelevisionsmedical radioisotopes

Troxler Gauge

Slide9

Requirements for Neutron Detection for National Security

Plutonium emits detectable quantities of neutronsNeutron background arises from cosmic ray produced secondaries and is a very low rate (~1000 times smaller than gamma ray background)Neutron alarms initiate a special Operating ProcedureFast and slow neutron detection required with flat responseAbsolute efficiency per panel: єabs = 0.11% or 2.5 cps/ng 252CfGamma ray discrimination of better than 10-6Maintain neutron detection efficiency in presence of gamma rays: gamma absolute rejection ratio (0.9 < GARRn < 1.1)Meet all ANSI N42.35/N42.38 requirements

9

Slide10

Requirements for Alternative Neutron Detection for National Security

Physically fit in the volume currently occupied by the neutron detection assembly in existing systemsElectronics compatible with existing systemThermal and fast neutron detectionNon-responsive to gamma raysRugged, reliable, and accurateSafeInexpensiveReadily available commercially now

10

Slide11

Alternative Neutron Detectors

Proportional Counter AlternativesBF3 filled proportional countersBoron-lined proportional countersScintillator-based AlternativesCoated wavelength shifting fibers/paddlesScintillating glass fibers loaded with 6LiCrystalline: LiI(Eu), LiF(W), Li3La2(BO3)3(Cr)Liquid scintillatorSemiconductor Neutron Detectors in DevelopmentGallium arsenide, perforated semiconductor, boron carbide, boron nitride, pillar-structured detectorsHigh efficiency, but limited in sizeOther: doped glasses, Li-foil ion chamber, Li phosphate nanoparticles, fast neutron detectors

11

Slide12

Existing Commercial Alternative Neutron Detectors

Proportional Counter AlternativesBF3 filled proportional countersBoron-lined proportional countersScintillator-based AlternativesPlastic fiber/paddle light-guides coated with ZnS scintillator and 6Li neutron absorberScintillating glass fibers loaded with 6LiSystems from 9 vendors tested

12

Slide13

Boron-based Detectors

“Straw tube”

designs (Proportional Technology)

Multi-chamber

boron lined approachesLND Centronic

BF

3 (LND)

Boron

lined (Reuter Stokes)

Slide14

BF

3 Proportional Counters

14

Neutrons captured by the

10

B (>90%) yields

α

+

7

Li

Gas pressure must be low (0.5 to 1.0 atm.) to operate at reasonable voltages (2000-2500 V)

Cross-section ~70% that of

3

He

Advantages

Inexpensive direct replacement for

3

He

Better gamma-neutron separation than

3

He

Disadvantages

BF

3

is toxic, difficult to purify, degrades over time, and is corrosive to the gas enclosure

Subject to strict DOT shipping regulations

Requires the use of multiple tubes to meet capability

Requires changes to electronics

Slide15

Boron-Lined Proportional Counters

15

Similar detection mechanism to BF3 (yields α + 7Li)Boron in matrix on walls; more signal amplitude spread AdvantagesNew prototypes promise needed efficiencyBetter gamma-neutron separation than 3HeDirect tube replacement for 3HeOnly minor electronics changes

Disadvantages

Co

unting

efficiency is lower than that of either

3

He or BF

3

M

ore variation in pulse height

R

equires

the use of multiple tube

assembly

to meet efficiency requirement

Slide16

ZnS + 6Li-coated Light-guide Detectors

Paddles or fibers coated with ZnS scintillator mixed with

6

Li

AdvantageComparable performance to 3He tube(s)DisadvantagesGamma-ray discrimination as tested required improvement for fiber versionPossible significant change to electronics

Coated Paddles(Symetrica)

Coated Fibers (IAT)

Coated Paddles (SAIC)

Slide17

6Li Loaded Glass Fibers

17

6Li-enriched lithium silicate glass fibers doped with cerium (Bliss et al. 1995, PNNL) Neutron capture on 6Li produces charged particles that cause Ce ions to fluoresce (observed by photomultiplier tubes)AdvantagesComparable performance to one 3He tubeFibers can be formed into different shapesDisadvantagesLess gamma-ray discrimination than 3HePossible significant change to electronics

Slide18

PNNL Neutron Detector Testing

Measurements of neutron efficiency have been carried out at PNNL for standard deployable RPM systems.Testing of alternatives: 3He at pressures of 1.0, 2.0, 2.5 and 3 atmospheres BF3 filled proportional counter tubes Boron-lined proportional counters ZnS-6Li coated plastic fibers/paddles Glass fibers loaded with 6Li

18

Slide19

Detection efficiency

(cps/ng) for shielded source Uncertainty primarily due to uncertainty in source activity

ASP spec

RPM spec

ANSI N42.35

BF

3

Results

Slide20

Modeled with MCNPGood qualitative agreement with data

Boron-lined Neutron Detection

Slide21

Insensitive to

60Co gamma rays (~10-8)Good neutron efficiency with gamma ray discriminating threshold

Boron-Lined Gamma Discrimination

Slide22

Neutron

and gamma pulse from IAT system

Differences in pulse shape allow for pulse-shape discrimination

Neutron Pulse

Gamma Pulse

ZnS + 6Li-coated Fiber Signal

Slide23

All options will require hardware and software modifications

Summary of Technology Testing

TechnologyEfficiencyGamma Rejection VoltageComments3He    Gold standardBF3    Hazardous gasHigh operating voltage Boron-lined   Meets requirementsCoated Plastic Paddles    Meets requirementsCoated Plastic Fiber   As tested, efficiency requirement not quite metGlass Fiber   Issues with neutron and gamma ray efficiency Only small version tested.

Does Not Meet Requirement

Meets Requirement

Slide24

Conclusions

Applications for

3

He are diverse

Demand is greater than supply

The national security need for an alternative is immediate

Four alternative neutron detection technologies have been tested

Alternatives for RPM systems can meet the technical requirements for

national security applications

Slide25

Support

Work supported by:

DOE NNSA

DoD

DHS DNDO

PNNL

Thank you!

Slide26

26

Backup

Slide27

3He Supply

3He not currently extracted from natural supplies Primordial abundance of 3He:4He is 1:100001.4 ppm by volume atmospheric He 0.2 ppm by volume natural-gas He (fission product)Lunar sourcesBy-product of nuclear weapons programTritium was produced for nuclear weapons in reactorsTritium production in U.S. ended in 1988 since weapon needs met through reductions in weapon stockpile, recycleTritium production restarted in U.S. in 2007 only to support smaller stockpileTritium decays with 12.4-year half-life to to 3HeSeparated 3He made available by DOE SC/NP Isotope ProgramU.S. accumulated 200,000 liters of 3He by the end of 1990s Decay produces ~8000 liters/year of 3He in U.S.

27

Slide28

Estimate of Supply and Demand

28

Data from Steve Fetter, OSTP

Slide29

3

He

Five Year Usage: All Applications

Data from

Linde

Electronics and

Specialty

Gases

From Ron Cooper, ORNL

Slide30

3He Demand – AAAS Study

Neutron Scattering: 120,000 liters over the next five yearsHomeland Security: Historically large1000 – 2000 liters / year for 5 yearsDropping to zero once alternative technologies become availableMedical Imaging: 2000 liters / yearCryogenics: 2500 – 3000 liters / yearOil and gas exploration: 2000 liters / yearDOE “emergency response assets”: few 1000 liters / yearOther fields: each require a few hundred liters / year

30

Slide31

TypeGRRGARRnεDetail3HeBT 10-81.03.13Single 3 atm tubeBF3BT 10-8NM1.6Single tube, 3 tubes = 3.0Boron-lined PCBT 10-8NM0.16Single tube, 3 tubes = 0.25Boron-lined MTPCBT 10-71.013.01Full volumeBoron-lined MTPCBT 10-81.010.98Single tubeBoron-lined MTPCBT 10-81.060.1212” tube, scaled to 3 tubes =~1.5Straw tubes (B-lined)BT 10-81.04.0Full volumeCoated Plastic Fiber10-81.032.0~ Full volumeCoated Plastic PaddleBT 10-71.010.9Small system, scaled by 4x =~3.5Lithium Glass Fiber10-71.310.32Middle setting (0.18*volume)

Comparative Results

GRR = Gamma Ray Rejection

GARRn = Gamma Absolute Rejection Ratio

BT = Better Than

PC

= proportional counter

MTPC = multi-tube (or multi-chamber) proportional counter


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