The End Of 3He As We Know It

Richard Kouzes

Pacific Northwest National Laboratory

BES Detector Workshop August 1-3, 2012

PNNL-SA-89037

3He Applications   3He is a rare isotope with important uses in:

  Neutron detection " science " national security " safeguards " oil/gas exploration " Industrial applications

  Low-temperature physics   Lung imaging   Missile guidance   Laser research   Fusion

2

Current 3He Supply  By-product of nuclear weapons program

  Tritium decays with 12.4-year half-life to 3He   Tritium was produced for nuclear weapons in reactors   U.S. tritium production ended in 1988 - weapons needs met

through recycling and reductions in the weapons stockpile   Tritium production restarted in U.S. at Watts Bar reactor in

2007 only to support a smaller weapons stockpile   U.S. 3He made available through DOE Office of Science   Russia is only other supplier of 3He   U.S. accumulated 200,000 liters of 3He by the end of 1990s   Demand was ~65k liters/year in 2009   Decay produces ~8,000 liters/year of 3He in U.S.

3

U.S. Government Decisions (2010)  Reduce Demand

  Evaluate performance standards - can 3He per device be reduced   Random movement of existing detectors   Accelerate development and deployment of alternative technologies

 Manage Demand   Suspend deployment of 3He detectors in portal monitors   Highest priority to uses that depend on unique properties   Priority to uses taking advantage of major investments (e.g., SNS)

 Increase Supply   Encourage 3He recycling and reuse   Increase 3He extraction efficiency   3He supply from other countries – Russia, Canada, Korea, India?   Investigate dedicated 3He production from natural sources

4 Information from Steve Fetter, OSTP

New Supplies of 3He?  CANDU Reactors

  Discussions with Canada about possible supply from Ontario Power Generation

  CANDU (like) reactors: Canada (17+3), South Korea (4), India (15+3) Romania (2+3), China (2), Argentina (1), Pakistan (1)

 3He not currently extracted from natural supplies   Primordial abundance of 3He:4He was ~ 140 ppm   Atmospheric abundance of 3He:4He is ~1.4 ppm by volume   About 1/500 fissions releases tritium   Natural-gas has 0.2-8.0% He with 3He:4He of 0.02-0.2 ppm

by volume (fission product + primordial)   Solar wind is 4% He with 3He:4He of ~480 ppm   Lunar soil (0.01-0.05 ppm of 3He)?

5

3He Demand Forecast In 2011

6 Plot From Julie Bentz, National Security Staff

New supply from CANDU and/or Natural Gas?

Workshops

" Problem recognized in 2007 " NNSA (SRNL) " IEEE Nuclear Science Symposium

2010-2012 " AAAS " IAEA

" Safeguards " Science

7

Homeland Security Applications of Neutron Detection

9

Homeland Security Applications " Neutron Detection primarily for plutonium

" Neutron background low; few sources of significant neutrons

" Portal Monitors: one of largest users of 3He " No further allocation for 3He, must use alternatives

10

Mail/ECCF Land Border Maritime Air Cargo

" 332,622 vehicles per day " 57,006 trucks/containers per day

307 Ports of Entry representing 621 border sites to protect

The Challenge: U.S. Ports of Entry

" 2,459 aircraft per day " 580 vessels per day

Over 98% of all containerized cargo is now screened for radiation

11

Border Security Examples

12

RPM Concept of Operations

Primary Detection

Confirm

Secondary Detection

Isolate

Isolation

Identify

Identification of Isotope

Neutron Scan

Respond

Seize/Arrest or Release

Detect

Gamma Detectors – Poly-Vinyl Toluene (PVT) Plastic Scintillators Neutron Detectors – Moderated Helium-3 Gas Tubes

13

Alarms and “Nuisance” Alarms   Few sources of Neutron Alarms (~1/10,000)

  Troxler gauges, well logging sources, nuclear fuel, yellowcake   Nuisance alarms: large gamma ray sources and “ship effect”

  Gamma Ray Nuisance Alarms (~1/100)   agricultural products like fertilizer   kitty litter   ceramic glazed materials   aircraft parts and counter weights   propane tanks   road salt   welding rods   ore and rock   smoke detectors   camera lenses   televisions   medical radioisotopes

Troxler Gauge

Requirements for Neutron Detection for National Security

" Plutonium emits detectable quantities of neutrons " Neutron alarms initiate a special Standard Operating Procedure " Neutron background arises from cosmic ray produced

secondaries - 1000 times smaller than gamma ray background " Physically fit in the volume currently occupied by the neutron

detection assembly in existing systems " Fast and slow neutron detection required with flat response " Absolute efficiency per panel: єabs = 0.11% or 2.5 cps/ng 252Cf " Minimum gamma ray discrimination ratio of better than 10-6 " Maintain neutron detection efficiency in presence of gamma

rays: gamma absolute rejection ratio (0.9 < GARRn < 1.1) " Meet or exceed all ANSI N42.35/N42.38 requirements

14

Alternatives to 3He for Neutron Detection

Alternative Neutron Detectors  Proportional Counter Alternatives

  BF3 filled proportional counters   Boron-lined proportional counters

 Scintillator-based Alternatives   Coated wavelength shifting fibers/paddles   Scintillating glass fibers loaded with 6Li   Crystalline: LiI(Eu), LiF(W), Li3La2(BO3)3(Cr), CLYC   Liquid scintillator

 Semiconductor Neutron Detectors   High efficiency, but limited in size   Gallium arsenide, perforated semiconductor, boron carbide,

boron nitride, pillar-structured detectors

 Other: doped glasses, Li-foil ion chamber, Li phosphate nanoparticles, fast neutron detectors

16

Proportional Counters n

n

p

t 3He

Boron-lined

α

7Li e

e

10B Based Alternatives

18

" Neutrons captured by 10B yields α + 7Li

" BF3 " Equivalent or better gamma discrimination than 3He " Cross-section ~70% that of 3He " Operates at low pressure (~1 atm) for reasonable HV " Requires multiple tubes for 3He replacement " BF3 is corrosive (hazardous gas): shipping regulations

" Boron-lined proportional/straw tubes " Thin layer on tube wall to collect reaction products in proportional gas " Surface area limited, lower (<0.5) efficiency per tube than BF3

" Requires configuration with many tubes " Safe, operates at low pressure (<1 atm)

Boron-Based Detectors

“Straw tube” designs (Proportional Technology)

Multi-chamber boron lined approaches (LND) (Centronic)

BF3 (LND)

Boron lined (Reuter Stokes)

  Pulse height spectra of 3He tube in the presence of a large gamma source for five-minute integration period

  Multichannel analyzer limited to 1280 counts in each channel, cutting off noise peaks.

1

10

100

1000

10000

100000

1000000

10000000

0 50 100 150 200 250

Channel Number

Cou

nts

in 3

00 s

econ

ds

Closed10 mR/hr20 mR/hr40 mR/hr100 mR/hr200 mR/hr400 mR/hr

1

10

100

1000

10000

0 20 40 60 80 100 120

Channel

Counts

Closed10 mR/hr20 mR/hr40 mR/hr100 mR/hr200 mR/hr400 mR/hr

BF3 3He

3He and BF3 Gamma Ray Sensitivity

  Insensitive to 60Co gammas (~10-8)   Good neutron efficiency with gamma discriminating

threshold

Boron-Lined Gamma Ray Sensitivity

0.0E+00

2.0E-07

4.0E-07

6.0E-07

8.0E-07

1.0E-06

1.2E-06

1.4E-06

1.6E-06

1.8E-06

2.0E-06

0.05 0.25 0.45 0.65 0.85 1.05 1.25 1.45 1.65 1.85

Coun

ts pe

r emi

tted

neru

tron

per 1

0keV

Energy Bins (MeV)

Alpha & Li Currents from B-lined Tube w/ 252Cf in Pig 2m from RSP

Alpha Current Into GasLi7 Current Into GasTotal Current Into Gas

3He

6Li Based Alternatives

22

" Neutron capture by the 6Li yields α + 3H " Glass fibers

" 6Li-enriched lithium silicate glass fibers doped with cerium which fluoresces (Bliss et al. 1995, PNNL)

" Good efficiency (per unit surface area or neutron module) " Gamma-ray sensitive: discrimination with PSD

" Coated wavelength shifting fibers " ZnS scintillator material mixed with 6Li coating " Good efficiency (per unit surface area or neutron module) " Coating gamma-ray sensitive:

Good discrimination with PSD

ZnS+6Li

ZnS Plus 6Li

plastic light guide

plastic light guide

n

α

t PMT

photons

Concept of layers of light guide and scintillator

ZnS + 6Li-coated Light-guide Detectors  Paddles or fibers coated with ZnS

scintillator mixed with 6Li  Advantage

  Comparable performance to 3He tube(s)  Disadvantages

  Gamma-ray discrimination as tested required improvement for fiber version

  Possible significant change to electronics

Coated Paddles (Symetrica)

Coated Fibers (IAT) Coated Paddles (SAIC)

Testing

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 (LND) " Boron-lined proportional counters (GE RS, LND, Centronic,

Proportional Technology) " ZnS-6Li coated wavelength-shifting plastic fibers/paddles

(IAT, Symetrica, SAIC) " Glass fibers loaded with 6Li (Nucsafe)

26

Testing At PNNL: Requirements

" Absolute efficiency per neutron module: " єabs = order of 0.11% efficiency per emitted neutron " Equivalent to 2.5 cps/ng 252Cf at 2 meter standoff

" Minimum gamma ray discrimination ratio of 10-6

" Maintain neutron detection efficiency in presence of

gamma-rays " GARRn: Gamma Absolute Rejection Ratio (neutron) " Neutron efficiency measured with gammas / without gammas " Value needs to be within 10% (0.9 < GARRn < 1.1)

27

All options will require hardware and software modifications

Summary of Technology Testing

Technology

Efficiency

γ-discrim.

Comments

3He Gold standard

BF3 Hazardous, high operating voltage, more space

Boron-lined Meets requirements

Coated Plastic Paddles /Fibers

Meets requirements

Glass Fiber Issues with neutron and gamma ray efficiency

Modeling and Simulation

" Simulation guides investigation into alternatives and optimized configurations " 3He and BF3 tubes straightforward to model (reaction

counting) " Boron-lined tubes more complicated, reaction product

tracking required for accurate simulations " Requires newer versions of MCNPX " Models developed and verified with different approaches

" Reaction counting in LiF/ZnS appears to be consistent with measurements using a scaling factor

29

Modeled Pulse-Heights for B-Lined Tube Reaction Products

30

Measured Response of GE Reuter Stokes Detector

31

Conclusions  Applications for 3He are diverse with demand > supply   There are no known alternative for some applications  Alternatives being deployed for national security  A lot of work remains to be done   Four alternative neutron detection technologies tested:

" Boron lined tube technology meets requirements " BF3 meets requirements but hazardous gas " LiF/ZnS coated material technology meets requirements " Glass fiber technology needs improved gamma ray separation

 Model and simulation has been applied to alternatives   Focus shifting to other applications

" Backpacks and handhelds " Safeguards

32

Acknowledgements

" Support for this work came from: " US Department of Energy: NA-22 & NA-24 " The US Department of Defense " The US Department of Homeland Security " PNNL

33

Backup

34

3He Demand Forecast In 2009

35 Data From Steve Fetter, OSTP

Supply

Projected demand ~65 kL/y - Projected Supply ~10-20 kL/y

36

The Global View

20 foot Shipping Container Traffic Per Year Megaport Deployments