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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