in search of… the lost art of analytical radiochemistry

In Search of…The Lost Art of Analytical Radiochemistry

…The Last Crusade

David S. Sill

Radiological and Environmental Sciences Laboratory Department Of Energy

60th RRMC, Knoxville, TN October 27– 31 2014

Radiochemistry Fundamentals

Analytical Radiochemistry

“The responsibility of an analytical radiochemist is to accurately determine the analyte of interest in the sample being submitted for analysis.”

D.S. Sill

Accurate Analytical Results

Must Guarantee Complete and Total Dissolution of the Sample

Must Guarantee Isotopic Exchange of the Tracer with the Analyte of Interest

And if you do…

Accurate Analytical Results Are Almost Guaranteed.

Initial Dissolution of the Sample

Most Important Part of Any Analytical Procedure…and also

The Most Neglected Part of Most Analytical Procedures…

Total Dissolution vs. Leaching Techniques

Analyte of interest must be in an ionic form to undergo subsequent chemical separations

“Clear” Does Not Mean Dissolved

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Pu-238 Pu-239 Pu-238 Pu-239 Pu-239

MaS12 MaS18 MaS24

Perc

ent R

ecov

ery

Total Dissolution vs Leaching

Leached

Fused

Two Variables One Equation DilemmaThe Second Most Important Concept

Sample Analysis vs. Evaluation of Laboratory Performance

Sample Unknown Act + Lab Unknown Performance Accuracy Result Unknown

Sample Known Act + {Lab Performance} Accurate Result ?

Laboratory Known Performance + {Unknown Sample} Accurate Result

Properties PE Material Must Have:

Known Activities (NIST) - Not Analyzed No Laboratory Bias Smaller Uncertainties

Address Real World Analytical Issues Sample Matrix Chemical Form of the Nuclide Chemical Interferences / Separations

Homogeneous - At Some Sample Size, At Some Precision

Natural Matrix StandardsRadionuclides Deposited Naturally And Randomly

Activity and Nuclides Present are Random

Can’t Guarantee Homogeneity Pu, Cs

Unknown Chemistry of Nuclide Soluble vs Insoluble

“Known” Values Include Lab’s Bias Uncertainty is always larger than NIST standards

Proper Use of PE Material

Evaluate: Accuracy, Detection Limit, False Positives

Real Samples Should Never be Used to Evaluate Laboratory Performance.

“Round Robin” Intercomparisons are of Little Value.

Precision Does Not Infer Accuracy.

Use of Internal Laboratory Control Sample Does Not Infer Accuracy on Real Samples

Fusions Routinely Used at RESL

Potassium Fluoride – KF, KHF2 Dissolves Siliceous Material – Volatizes Silica as SiF4↑ Dissolves Metal Oxides and Minerals Sulfate System – Pt Dish

Pyrosulfate – S2O7-2

Does Not Dissolve Silica Dissolves Metal Oxides Sulfate System – Glass or Pt Dish

Lithium Metaborate – LiBO2 Dissolves Siliceous Material – Soluble Silicate – SiO2 ↓ Dissolves Metal Oxides and Minerals Nitrate System – Pt Dish

Potassium Fluoride Fusion

Fusion in Pt @ 858°C – Ionic Salt – High [F-] Volatizes Silica as SiF4

No Dissolution of Pt “Precursor” to a Pyrosulfate Fusion Flux Turns Alkaline with Time Due to Loss of HF

SiO2 or H3BO3 can be used to Acidify Flux

KF + SiO2 → [K2SiF6] + H2SO4 → SiF4↑+ HF ↑ + K2SO4

Pyrosulfate Fusion

Does Not Dissolve Siliceous Materials Fusion Can Be Performed in Glass Will Dissolve Pt Rapidly at High Temperatures Little Dissolution of Pt at Low Temperatures Na+ vs. K+

Reversible Reaction / Easily Prepared Precipitation of Anhydrous Metal Salts – Very Insoluble

Na2SO4 + H2SO4 → NaHSO4 → Na2S2O7 → Na2SO4 + SO3

Preparation of Pyrosulfate

Na2SO4 + H2SO4 → 2NaHSO4 → Na2S2O7 → Na2SO4 + SO3 ↑

O O O O‖ ‖ ‖ ‖

-O—S—OH..HO—S—O- → -O—S—O—S—O-

‖ ‖ ‖ ‖ O O O O

Lithium Metaborate Fusion

LiBO2 can be prepared easily from H3BO3 and LiOH Dissolves Siliceous Materials – Soluble Si Reprecipitation of SiO2 can occur w/high [H+] Dissolves Metal Oxides and Minerals No Dissolution of Pt Surface Tension and KI Transposed to a Nitrate System Excellent for Samples Containing High [Ca+2] and [PO4

-3]

OH OH| |

Li+ -OH + HO – B – OH Li+ -O – B – OH Li+ -O – B=O

Common Analytical Problems: Pu SolubilityOnce Soluble Always Soluble ? No

Hydrolysis of Large +3 and +4 Elements

Heating a Salt Containing an Anion of a Volatile Acid(Cl-, NO3

-, etc.)

Solubility Of Some Hydroxides

Compound Ksp pH for ppt. of OH

NaOH Soluble 50%, 12.5M solution

Ca(OH)2 E-6 11

Fe(OH)2 E-16 5

Fe(OH)3 E-38 3

Pu(OH)4 E-55 << 2

SrCO3 E-10SrSO4 E-7

Laboratory Issues

Co-57 False Positive TestingEu-152 added as Interference

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MaS29 - 39% A RdF30 - 62% A

Labo

rato

ries

Not Acceptable

Acceptable

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Natural Uranium

U-238

U-235

U-234

U-232

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Depleted Uranium

U-238

U-235

U-234

U-232

Fractionation of Radionuclides from Non-Acidified Water Samples

1-L Water Samples – Not Acidified Spiked with NIST Traceable Radionuclides Delay Between Dispensing Aliquots Aliquot Sizes: 200 mL, 300 mL, 500 mL Entire 1-L PP Bottle Dissolved and Analyzed

Pu-239

Days Result - pCi Total Found Total Added5 0.82 ± 0.03 (200mL)

12 0.54 ± 0.02 (300mL)

19 0.26 ± 0.01 (500mL)

Bottle 4.17 ± 0.13 5.79 ± 0.19 5.91 ± 0.12

Pu-238


12 1.02 ± 0.02 (300mL)

19 0.12 ± 0.01 (500mL)

Bottle 2.89 ± 0.13 7.1 ± 0.3 7.35 ± 0.15

Am-241


12 2.29 ± 0.02 (300mL)

19 0.08 ± 0.01 (500mL)

Bottle 1.95 ± 0.13 8.6 ± 0.4 8.95 ± 0.18

Current State Of The Analytical Art

Accurate analytical results are difficult to obtain on a routine and reliable basis.

Laboratories continue to use “Leaching Techniques” even though experimental evidence demonstrates that incomplete sample dissolution is the major cause of the inaccurate results being routinely reported.

Analytical problems are not isolated to one analysis area.

Certified Reference Material – CRM

What Worse Than Not Having a CRM ?

Having a CRM that: Has an Inaccurate Reference Value Is Inhomogeneous Does Not Test the Real World Analytical Conditions that

Need to be Tested

Elite Analytical Infrastructure and Methods Verification of Each Reference Value Homogeneity Testing Traceability to NIST

Analytical InfrastructureRadiological Traceability Program

National Institute of Standards and TechnologyA

nalyze PT Material

Prepare PT Material

Prep

are

PT M

ater

ial

Ana

lyze

PT

Mat

eria

l

Radiological & Environmental Sciences Laboratory

Introducing Bias Experimental Value vs Known Value

Nuclide Expt’l ResultsCs-137 2.98 +/- 0.13 E+3 2.95 +/- 0.13 E+3 (Fusion) 3.01 +/- 0.13 E+3 2.99 +/- 0.13 E+3

3.04 +/- 0.13 E+3 2.89 +/- 0.13 E+3

Mean: 2.98 +/- 0.05 E+3 Known Value: 3.31 +/- 0.06 E+3

Cs-137 3.39 +/- 0.14 E+3 3.28 +/- 0.13 E+3 (HF) 3.15 +/- 0.13 E+3 3.21 +/- 0.13 E+3

3.35 +/- 0.16 E+3 3.25 +/- 0.14 E+3

Mean: 3.27 +/- 0.09 E+3 Known Value: 3.31 +/- 0.06 E+3

~100mg Aliquots - pCi/g

Inhomogeneous “Standards”and

The Particle Problem

Different 1-g Aliquots of the "Same Sample"(Pu-239 pCi/g)

70 +/- 475 +/- 436 +/- 3

670 +/- 30490 +/- 2511 +/- 1

“Known” ~ 2000 pCi/g

Soil “Standard” Prepared From NIST SolutionsIndividually Spiked 10g Sample - Pu239

Experimental (pCi/g) Sample Size Total Act/Aliquot12.3 +/- 0.6 3.5 g 43.1 +/- 0.27.8 +/- 0.4 3.5 g 27.3 +/- 1.43.9 +/- 0.2 3.0 g 11.7 +/- 0.6

“Known” 7.6 +/- 0.3 pCi/g Total Act. Found 82 +/- 4 pCiTotal Act Added 76 +/- 3 pCi

Interlaboratory Comparisons

1g Soil Samples / Ra-226

1.64 +/- 0.45 pCi/g5.5 +/- 0.2

2.48 +/- 0.050.00 +/- 0.018. 6 +/- 2.5

1.05 +/- 0.281.72 +/- 0.04

2.0 +/- 0.33.3 +/- 1.7

Mean: 3 +/- 3

Duplicate Samples Used For PE Purposes

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Cs-137

Co-60

"Duplicate" for H-3 Analysis

Co-60

15 min

Duplicate Samples Used For PE Purposes

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Cs-137

Co-60

"Duplicate" for Sr-90 Analysis

Co-60

RESL Certified Reference MaterialsWhy?

Long history of producing CRM’s for internal use.

Numerous requests for unique CRMs that are not available anywhere else.

Soil, Vegetation, Water, Air Filters Fish, Kelp, Bone, Wheat, Milk Dehydrated Eggs – Actinide / Sr-90 Sausage – Co-60 Oil Exploration / Fracking – Ra-226

Verification ResultsCRM Cement 0813

Nuclide Known Expt’lAm-241 4.91 ± 0.13 E1 4.8 ± 0.2 E1Pu-238 4.89 ± 0.12 E1 4.88 ± 0.17 E1Pu-239 4.91 ± 0.13 E1 4.85 ± 0.17 E1U-238 5.05 ± 0.11 E1 5.0 ± 0.2 E1U-234 6.67 ± 0.15 E0 6.9 ± 0.3 E1Cm-244 6.75 ± 0.11 E1 ? ± ?

Sample Size 100mg pCi/g

Questions ?

in search of… the lost art of analytical radiochemistry

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