New Fecal Method for Plutonium and Americium at SRS

Sherrod L. Maxwell III and David Fauth

Savannah River Site

Background

• SRS Incident in FB-Line (9/1/99)

• Need for Improved Fecal Analysis for Pu and Am

– Complete dissolution of any plutonium oxide present– Effective Th-228 removal

• Completed FB-Line incident samples

• Successful routine operation

New Approach

• Old method:– residual undissolved solids in final nitric acid solution– solids contained some activity

• New approach: – Use HNO3-HF dissolution/multiple digestions– Apply Diphonix Resin technology used successfully for large soil

samples– Digest Diphonix using SRS microwave method– Apply Eichrom sequential column method

Actinide Retention on Diphonix Resin

Ref: E. Philip Horwitz et al.,Separation Science and Technology, 32, 1, (1977)

% Bias Plot for EML Soil Standards

-60.0

-40.0

-20.0

0.0

20.0

40.0

60.0

Pu238 Pu239 Pu238 Pu239 Pu238 Pu239 Am241 U234 U238

% B

ias

Leached Fused Acceptable Lower % Acceptable Upper %

EML9403 EML9509EML9403 EML9509 EML9609EML9609 EML9609EML9609EML9609

Performance on Large Soil Samples

Pu, Am on DIPHONIX RESIN

• Redissolve in 0.5M to1M HCL-0.1M to 0.2M HF• Redissolve any solids that precipitate in 0.5M HCL-O.25M H3BO3

• Add 1.5M Ascorbic Acid (Reduce Fe)• Load HCl-HF and HCl- H3BO3 fractions separately

Rinse 210mL 0.5MHCLRinse 1

20mL 0.5MHCL-0.25M HF

Rinse 320mL water

2.4 mL Diphonix Resin

Method Digestion Details

• Microwave Digestion of Diphonix Resin– Microwave to 190C for 15 minutes in 10 mL 16M HNO3

– Change disk/microwave to 200C for 20 minutes in 10 mL 16M HNO3

– Change disk/ microwave to 215 C for 25 minutes in 10 mL 16M HNO3

– Add 3.5 mL 30wt% H2O2 & microwave to 21O C for 10 minutes in 10 ml 16M HNO3

• Final wet ashing of Resin– Ash with 30wt% H2O2 four times

– Ash with HNO3 + H2O2 one time, or until does not get any whiter

Pu, Am Column Separation

• Preparation for Pu, Am column separation– Dissolve in 6 mLs of 5M to 6M HNO3

– Add 6 mLs 2 to 2.5M aluminum nitrate

– Solution ready for TEVA + TRU Resin column extraction

• Preparation for Pu, Am column separation

– Valence adjustment for Pu1) Add 1 mL 1.5M ferrous sulfate + 1 mL 1.5M ascorbic

acid, wait 3 min.

2) Add 1 mL 3.5M to 4M sodium nitrite

Pu, Am Column Separation

• Separate Pu using TEVA column– Th removal 9M HCl+8M HCl

– Use 2nd 1 mL TEVA column to remove all Th-228

– High retention/good clean-up

• Separate Am using TRU column – Collect load plus rinse from 1st TEVA column

– Evaporate to dryness

– Redissolve in 15 mls 3 M HNO3

– Add 2 mLs 1.5M sulfamic acid + 5 mls 1.5M ascorbic acid

– Load to TRU resin

Pu, Am ON TEVA + TRU RESIN (FECAL METHOD)

Pu on TEVA RESIN(2nd Column to Remove all Th-228)

• Redissolve in 7.5mL 3M HN03 + 1mL 2.5M Al(NO3)3

• Add 0.5mL 1.5M Ferrous Sulfate + 1mL 1.5M Ascorbic Acid• Add 1mL 3.5M Sodium Nitrite• Add 1mL 16M Nitric Acid

Th Removal2mL 9MHCI/8mL

8MHCIRinse

10mL 3MHN03

Pu Elution15mL

0.10MHC1 - 0.05MHF - 0.1M NH4l

1mL TEVA Resin

Method Validation

• Analysis of multiple sample blanks– Complete dissolution– High tracer recovery– Good Th-228 removal

• Analysis of artificial fecal sample spiked with Pu oxide from DOE RESL-Idaho– Test plan to validate versus known Pu levels

TEVA+TRU Pu/Am Tracer RecoveriesFecal samples : 1.5-4 grams ash/ Pu-242 spike= 1.26 dpm

TEVA column+ 2nd 1 mL TEVA column

%Pu-242 Recovery %Am-243 Recovery

Fecal blank 1A 75.3 91.5Fecal blank 1B 68.5 103.1Fecal blank 2 72.1 81.5

Fecal blank 3 A 75.6 89.2

Fecal blank 3 B 79.3 95.8

Fecal blank 4 78.4 100.8

Avg. 74.9 93.7

Column Reagent blank 74.4 90.8

Column Reagent blank 82.8 89.8

Avg. 78.6 90.3

Assay of of DOE-RESL Fecal Standards

RESL RESL SRS Measured Bias vs. RESL % Std. Dev.

Stds. Ref. Values Values Values Bewteen Dups. Picocuries Picocuries 1 std. dev

SR-194

#1 1.860 -14.7%

#2 1.841 -15.6%

SR-194 Pu-239 2.18 Avg 1.850 -15.1% 1.0%

#1 2.405 -12.8%

#2 2.608 -5.5%

SR-194 Am-241 2.76 Avg 2.507 -9.2% 10.1%

SR-234

#1 2.062 -3.2%

#2 2.139 0.4%

SR-234 Pu-239 2.13 Avg 2.101 -1.4% 3.9%

#1 2.488 -7.8%

#2 2.335 -13.5%

SR-234 Am-241 2.70 Avg 2.411 -10.7% 7.7%

DOELAP Bias Criteria: -25% to +50% DOELAP Standard Deviation Criteria:<40%

% Bias Plot for DOE-RESL Standards

-80.0

-60.0

-40.0

-20.0

0.0

20.0

40.0

60.0

80.0

Pu-239 Pu-239 Pu-239 Pu-239 Am-241 Am-241 Am-241 Am-241

% B

ias

% Bias Acceptable Lower % Acceptable Upper %

SR-194 #1 SR-194 #2 SR-194 #2SR-194 #1SR-234 #1 SR-234 #2 SR-234 #1 SR-234 #2

Sr in Fecal Samples

Approach

• Collect rinses from Diphonix columns

• Evaporate/Dissolve in 8M HNO3

• Separate on Sr-Resin

Preliminary Results

• 90% recovery on spiked samples

• Good precision on DOELAP samples

DOELAP SR RESULTS

Samples Blanks Spike Spike Spike

Added MeasuredRecovery

(pCi) (pCi) (pCi) (pCi) (%)

1) 258 0.98 194.5 178.5 91.8

2) 285 0.78 178.7 91.9

3) 287 1.32

4) 244 0.44

5) 254

6) 253

Avg. 263 0.88 178.6

Stdev 6.9% 41.6% 0.11%

Summary

• New fecal method dissolves Pu oxide using HNO3

-HF• Column loading from HCl-HF sample solutions

with no visible solids• High recovery/accurate results/good Th-228

removal• Sr-90 can also be assayed