PERALS® Short CourseSimpleAlpha Assay

ORDELA, Inc.

Dr. Dale Ensor,

Tennessee Tech UniversityWayne Graves, Product Manager

Introduction & Overview -PERALS® Short Course

� Introductions

� PERALS® Demo

� Chemistry– Alpha Liquid

� Instrumentation�Theory of operation

�Tips & techniques

�Troubleshooting

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– Alpha Liquid Scintillation theory; solvent extraction & scintillators

– Lab techniques & applications

– Troubleshooting

�Troubleshooting

�Lab work

� Round Table Discussion

� Feedback& Exit

Schedule, Day 1

� Morning– 0830...1000 Chemistry &

Instrumentation Demo (Just watch & ask questions!)

� Afternoon – Separate into two groups;

Group A to laboratory & Group B to use PERALS® instrument

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questions!)

– 1000 …Break

– 1015…1115 Chemistry Presentation

– 1130… Lunch -Your choice

PERALS® instrument

– Group B counts Group A’s samples!

– Break, as required

– Answer questions in remaining time

Schedule, Day 2

� Morning– Switch groups; repeat as

in previous afternoon

– Break, as required

Group A counts Group

� Afternoon– Chemistry &

Instrumentation Presentations, as time & interest allows

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– Group A counts Group B’s samples!

– 1130…1230 Lunch -Bring in ???

interest allows

– Break, as required

– Round Table Discussion, Summary, Feedback!

PERALS® Instrument Demo

� Pulse Shape (Timing) output

� Pulse Shape Discriminator (PSD) setting

� Use of 137Cs Source to set PSD

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Use of Cs Source to set PSD

� Pulse Height (Energy) output

� Energy resolution

� Quench; chemical & color, two most common causes

PERALS® Demonstration

� Instrument ease of use

� Chemistry often shorter & simpler

� Use with anyMCA

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� Use with anyMCA

� Quick set up

� Accurate

� Repeatable results

� Minimal training required

Vocabulary (Instrument)

� Gain control

� Pulse Shape Discriminator (PSD) control

� Display control

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� Pile Up control

� Pulse Height output

� Gate output

� Pulse Shape output

Instrumentation Lab

� Instrument, MCA set-up & calibration– Timing (includes setting PSD) & Energy, 226Ra

counting reference sample

– Count 234,238U sample with above setting

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– Count 234,238U sample with above setting

� PSD setting determination

� Repeatability study, 241Am

� Count new chemistry lab samples

Niche Application

Silicon Surface Barrier SpectrometryResolution: 20-150 keV;

Efficiency: 15 - 30%

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Gas-flow Proportional CounterResolution: NoneEfficiency: 35%

PERALS® Alpha SpectrometerResolution: 200-250 keV;

Efficiency: 99.7%

PERALS® System

PERALS® Alpha SpectrometerModel 8100AB

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Internal HVPS(Recommended Option)

Nim Bin/Power Supply(Only +/-12, 24 volts required)

Multi-channel Analyzer(MCA)

Sample Chamber Detail

� Advantages– 99.7% Efficiency

� Special coating normalizes PMT response

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response

� Silicon oil matches refractive index of glass

– Elimination of recoil & cross contamination

– No sample repositioning problems

PERALS® Circuit Diagram

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PERALS® Instrument Advantages

� Near 100% Counting Efficiency

� Low Instrument Background; 0.001

� No Sample Self-Absorption

� No Cross-Contamination

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Background; 0.001 dpm

� Alpha (ONLY!)

� 99.95%Beta/gamma Rejection

� No Recoil Problems

Contamination

� Small Footprint; ideal for mobile labs

� Standalone (+12 v dc or 110/220 v ac) model available, too!

PERALS® Chemistry Advantages

� Shorter, simpler procedures

� Element-specific (often)

� More concentrated samples

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� Analyze samples on other systems, too!– Pour samples into planchet, flame, count on

alpha/beta proportional counter

– Same as above, except count on alpha spectrometer

PERALS® System Advantages

� High counting efficiency (99.7%) with good (99.95%)

beta/gamma

� Improved throughput

� Reduced turnaround

� Generally shorter sample preparation &

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beta/gamma background rejection and low (as low as

0.001 dpm) instrument

backgrounds

sample preparation & counting times

� Minimal technician training

� Use with existing MCAs & software

Liquid Scintillation Counting

� In General:– Good Counting Technique - Alphas & Betas

– High Alpha Counting Efficiency

4 π Counting Geometry

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– 4 π Counting Geometry– Good Figure of Merit - E2/B

– Poor Alpha Spectral Resolution

– Marginal Alpha Background

– Problematic Beta/Gamma Crosstalk

Alpha/Beta/Gammas in LSC

� Beta/Gamma Interactions… x10 Light Output Vs Alpha Particles

� Pulse Rise Time Same for Alpha/Beta/

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Gammas

� Pulse Decay Time x10 Longer for Alphas Vs Beta/Gamma

� It is this decay difference that makes possible Pulse Shape Discrimination (PSD)

Pulse Shape Discrimination

� Based on Alpha Particles Producing Pulses with Long Decay Times Vs Betas & Gammas

Simple, 15 - 30 second Adjustment on

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� Simple, 15 - 30 second Adjustment on PERALS®

� 99.95% Beta/Gamma Rejection Possible

PSD Setting Procedure

� To set the PSD use a 226Ra, or other, counting reference sample

� Connect the Pulse Shape Outputon the PERALS

PSD set too high, resulting in loss of alpha counts!

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Outputon the PERALS to the MCA input

� Start acquisition; while holding down the Displayswitch, move the PSD controlto set it

Figure 3. Multichannel Analyzer (MCA) spectrum obtained from the Pulse Shape Output on the PERALS® front panel. A high setting of the Pulse Shape Discriminator, such that it overlaps the alpha peak, results in a low measurement of the alpha pulses as some of the counts are rejected and lost.

PSD Setting Procedure

� Set the PSD in the centerof the valley between the two peaks, or even left of

Here, the PSD is set too low and into the beta/ gamma region; alpha assays will be high using this setting.

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peaks, or even left of center, in samples with well-separated peaks

� If in doubt, set just to the right of the beta/gamma peak

Figure 5. A spectrum obtained from the Pulse Shape Output on the PERALS® front panel. The PSD is set too far to the right; beta and gamma counts are not properly rejected in this situation, resulting in dramatically increased background under the alpha peaks in the pulse height output.

PERALS® Spectra

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Extractive Scintillators

� Synergistic Combination of Extractant and Scintillator to Concentrate, and often Separate, Element of Interest

Extractants - bis-2-ethylhexyl phosphoric

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� Extractants - bis-2-ethylhexyl phosphoric acid, Primary, Tertiary amines, Others….

� Diluent - Toluene, DIN (~75%)

� Energy Transfer Agent (~20%)

� Scintillator (PBBO) (~5%)

Routine Maintenance & Checks

� Change silicon oil when timing resolution degrades >10% (about once a month with constant use)

Use soft plastic dropper and position towardthe

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– Use soft plastic dropper and position towardthe photomultiplier tube face

� Efficiency check …

� Counting reference sample count …

� Other …

Tips & Techniques

� Use 137Cs source (from 1-10 µCi) to set the PSD for low-level samples

� Change silicon oil

� Check energy & timing resolution

� Troubleshooting

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samples– Even better, use

DataMap & DataView

– Recheck PSD aftereach count!

– Expand scale to set PSD, ROIs

� Troubleshooting– NIM Bins

– HVPS

Summary

� Chemistry & Instrumentation

– Theory

– Applications

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– Applications

– Troubleshooting

� Apply this training to develop/refine your own specific procedures

� Tell us what you think!

PERALS® WIP Overview

� New Applications– Sequential U, Th, Ra

from soils (in process)

– Polonium analysis in

– ASTM D6239 Uranium in Drinking Water Method

� Training Available

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– Polonium analysis in lead and solders

– Effect of different extractive scintillators on pulse height response

– PERALS® for betameasurements

– PERALS® Short Course

� Presentation

� Discussion & Questions Period

Work in Progress - Overview

� Goal: U, Th, Ra in soil with microwave dissolution & a single extraction– “Total Alpha” for soils

Use commonly available lab equipment (no

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– Use commonly available lab equipment (no platinum crucibles!)

� Option #1: Two separate extractions; one for U, Th and a second for Ra using ALPHAEX® and RADEX®

Alphas in Tested SoilsTable I

Concentration of Alpha-emitting Nuclides (Bk/g) andEnergies in Standard Soils

Isotope Energy Rocky Flats Peruvian Soil QAP 9503 (Mev) Soil #1

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226Ra 4.76 0.043228Th 5.42 0.07 0.04230Th 4.69 0.044 0.04232Th 4.01 0.069 0.043234U 4.77 0.039 0.030235U 4.40 0.0016238U 4.19 0.039 0.032238Pu 5.50 0.00017 0.032239Pu+240Pu 5.15 0.008 0.000008 0.006241Am 5.48 0.0013 0.000004 0.032

CEM Microwave

DigestionSolution Filter Aliquot

Separatory Funnel

Solvent

Soil

H3BO3 + H2O

Precipitate

ALPHAEX®

NaOH to pH 1 - 3

Organic: Take 1 mL for counting Actinides

Aqueous

Analysis Flow Chart

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Solution 2RADAEX®

NaOH to pH 11 - 13

Separatory Funnel

Organic: Take 1 mL for counting Ra

Aqueous: Discard

Figure 3. Flow Chart for the analysis of soils by m icrowave digestion and extractive scintillation alpha s pectrometry

Figure 1 - Alpha Spectra

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Figure 2 - Ra-226 & Progeny

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Results:

� Recoveries– U, Th Initial Recoveries >90% from fluoride-

free digestions

– U, Th Initial Recoveries 50 to 60% from

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– U, Th Initial Recoveries 50 to 60% from fluoride digestions

– Radium recovery - working to improve - ~30% with fluoride digestions

� Paper to be presented in San Diego, Ca next month

Alphas in Soils

� A procedure has been developed for determining the concentrations of alpha-emitting actinide elements in soils. The procedure consists of completely dissolving the soil samples by means of microwave heating with a hydrofluoric (HF) acid - containing solution. After pH adjustments, the aqueous aliquots are extracted with, successively, two different organic extractive scintillators, one based on a branched

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different organic extractive scintillators, one based on a branched primary amine and the other on an alkyl phosphoric acid. The organic phases are analyzed by alpha liquid scintillation spectrometry using the PERALS® method. This method allows for counting the alpha particles without interference by beta and gamma rays and its only limitation is that energy peaks closer than 200 keV cannot be separated (e.g. 230Th and 234U). The whole analytical procedure is quite simple and precise and, depending on the actinide concentration and the accuracy required, can also be rapid. Results from standard reference materials soils will be presented.

Polonium Analysis in lead/solder

25 mLconc. HCL

90 mLH2O

30%H2O2

Extract w/

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100 mLcompleted

volume

Dissolve Sample

1 - 2 gsamplelead or solder

Extract w/2 mL CLUREXtm

Take Half of Sample

Flow Chart for analysis of Polonium in lead and sol der alloysby extractive scintillation PERALS ® Alpha Spectrometry

Extractive Scintillators

� IIIIs it important to use the same extractive

scintillator for your samples and your counting

reference samples?

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� Yes! Different extractive scintillators have varying

spectral responses, or scintillations, when excited

by alpha particles. This varying light output results

in differing energy responses, resulting in peak

shifts to either higher or lower energies. If not

quantified, these shifts can lead to errors.

238U in URAEX®

extractive scintillator;

count rate = 272 dpm.

Peak energy = 3.9MeV

Figure 1

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238U in THOREX®

extractive scintillator;

count rate = 274 dpm.

Peak energy = 4.1MeV

Figure 2

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238U in ALPHAEX®

extractive scintillator;

count rate = 273 dpm.

Peak energy = 4.8MeV

Figure 3

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Peak energy = 4.8MeV

PERALS® Beta Background

� ~ 320 counts per 10,000 seconds, unshielded and with glass culture tubes (.03 cps)

~ 150 counts per 10,000 seconds with 2”

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� ~ 150 counts per 10,000 seconds with 2” lead shielding and glass culture tubes

� ~ 30 counts per 10,000 seconds, with 2” lead shielding and Teflon counting tubes

PERALS® Beta Background

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Practical Applications

� ASTM-Approved Uranium in Drinking Water Procedure

� U, Th in soil; a mobile lab application

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� U, Th, Ra in soil with a single extraction - a work in progress

�226Ra in soil with

ASTM Uranium in Drinking Water

� New, Very Fast Procedure

� Resolve 238U and 234U Alpha Energy Peaks

� Traceable, with 232U (Recoveries >95%)

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Traceable, with U (Recoveries >95%)

� MDA < 1 pCi/L for 200 mL Samples

� Less than 1% Interferences from Other Radionuclides

� Screening Procedure even FASTER!

� ASTM Method # D 6239

Cost Analysis- One Example: Thorium & Uranium in Soil Application

� Problem: Clean up of Uranium Mill Tailings Sites

– 230Th (T1/2= 77000

– Mobile lab is ideal solution

� In General:

– Faster sample

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– Th (T = 77000 years) results in ingrowth of 226Ra (T1/2= 1600 years)

– Analysis must be done on-site for timely results

– Faster sample preparation

– Faster turnaround times

– Improved throughput

– Little training required

Cost Analysis- One Example: Thorium & Uranium in Soil Application

� In Specific:

– Turnaround time reduced from 14 days to only4 hours!

– Analysis time = 16 hours per 8 samples,

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– Analysis time = 16 hours per 8 samples, excluding quality control samples

– MDA for 1 g soil sample, 300 s count time = 52 Bq kg-1 (1.4 pCi g -1 )

– Analysis Costs, $30.00for Thorium and $0.24for Uranium, respectively, per sample!

226Ra in soil - < 24 hr Turnaround

� $125,000 Award

� And, they were the only lab who chose to bid on the contract! (Ask for your FREE

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copy of our 226Ra Application Note)

� Samples may be analyzed in 4 to 8 hours for a single sample

222Rn in Water

� Obtain water sample; acidify if necessary

� Transfer to scintillation vial

� Add RADONS®; shake for 5 minutes

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Add RADONS ; shake for 5 minutes

� Transfer 1 mL to special radon counting vial

� Wait for 20 minutes for 218Po to ingrow

� Count on the PERALS®!

Solubility Testing of Actinides on Breathing Zone Air Samples

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Dr. Robert MetzgerPERALS® Workshop VIII

November 1998

Frisch-Grid Alpha Spectrometry

� Efficiency 90+%

� Resolution 40 keV FWHM; limited by sample self-absorption

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sample self-absorption

� Large area, 10” diameter, alpha spectrometry

� Background 0.25 cpm

� Rapid sample prep

� NO chemistry

Frisch-Grid Counter

� Alpha Spectrometry with NO chemical preparation� Analyze soils, air filter samples, smears & swipes,

liquids

� 30 minute sample prep on soils; much less on other

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� 30 minute sample prep on soils; much less on other type samples

� Resolution limited by self-absorption;

Frisch-grid Soil Sample Prep

� Dr. Bill Burnett, Florida State University, Infinite Thickness Soil Sample “Pucks”

� Repeatable, Archival Samples

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� Easy to Store, Transport, Ship

� Consistent Resolution - Limited by Sample Self-Absorption

Frisch-Grid Detail

� Advantages– Alpha efficiency >90%

– Low background

Routine Maintenance & Checks

� Change silicon oil when timing resolution degrades >10% (about once a month with constant use)

Use soft plastic dropper and position towardthe

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– Use soft plastic dropper and position towardthe photomultiplier tube face

� Efficiency check …

� Counting reference sample count …

� Other …

Tips & Techniques

� Use 137Cs source (from 1-10 µCi) to set the PSD for low-level samples

� Change silicon oil

� Check energy & timing resolution

� Troubleshooting

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samples– Even better, use

DataMap & DataView

– Recheck PSD aftereach count!

– Expand scale to set PSD, ROIs

� Troubleshooting– NIM Bins

– HVPS

Direct Counting of Soil Wafers Direct Counting of Soil Wafers -- An Improved An Improved Total Alpha/Beta Screening AnalysisTotal Alpha/Beta Screening Analysis

Bill Burnett , Roger WongFlorida State University

Sue ClarkWashington State UniversityWashington State University

Brian CrandallWestinghouse Savannah River Company

Summary of Frisch-grid Work

�Uniform and durable soil “wafers” may be prepared easily without generating waste;

�A systematic relationship exists between the estimated total activity of standard soils and estimated total activity of standard soils and net α and β cpm;

�The Frisch Grid has advantages for ααααmeasurements: (i) increased sensitivity; and (ii) spectral information.

Bill Burnett, et. al.

8600A Ultra-low Background Counter

� Ultra-low background, large area, window-less, gas-flow proportional counter

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proportional counter

� 0.004 ααααlphas/hr/cm2� 1008 cm2 active area

� Count 12” x 12” samples

8600A Benefits

� Markets:– Primary-

Semiconductor Manufacturers

� Competitive Advantages– Windowless; almost

2π counting efficiency

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– Secondary- Suppliers to Semiconductor Manufacturers

– Tertiary- Other low-background users?

2π counting efficiency– No sample adjustment

required

– Low P-10 gas consumption; ~50 ccm

– Count 12” diameter samples

Summary

� PERALS® Chemistry & Instrumentation

– Theory

– Applications

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– Applications

– Troubleshooting

� Apply this training to develop/refine your own specific procedures

� Other ααααlpha measurement techniques� Tell us what you think!