New Extraction Methods for Actinides in Urine at SRS

Sherrod L. Maxwell III and David Fauth

Savannah River Site

Recent Applications

• New Column Extraction Applications at SRS– UTEVA method for Pu/U removal for Pu/U oxides (Impurity

assay)

– New UTEVA method for Pu and U-Isotope Dilution Mass spectrometry in mixed oxides (strip Pu separately using 3M HNO3-0.2MHF)

– Actinides in soil using Diphonix Resin-microwave digestion

– Sequential column extraction in Bioassay Lab for Pu, Np, Am, U plus enhanced Sr method using cartridge technology

– Pu, Am in fecal samples using Diphonix Resin-microwave digestion and TEVA+TRU Resin

Actinides in Urine• Current Urine Methods

– Pu-acidified 500 mL samples/evaporated -anion resin

– U-acidified 50 mL samples/evaporated -anion resin

– Pu/Am/Sr- 500 mL calcium phosphate/ TRU + SR Resin

• Need more efficient, consistent, sequential methods with better Th-228 removal; larger aliquots for special urine samples

Bioassay Urine Methods

• New Methods– Expand use of calcium phosphate precipitation (500 ml to 1000+

mL)

– Improve Th-228 removal

– Enhance vacuum column extraction with cartridge work

– Pu (Np when Pu-236 tracer used) on TEVA Resin

– Pu, Np, U, Am using TEVA/TRU column or cartridge technology

– Pu, Np, U, Am, Sr using TEVA/TRU +SR columns or cartridge technology

Bioassay Application

• Advantages– Faster, more consistency, less acid waste (0.9 L

vs. 6 L per batch); reduced labor costs; sequential analysis; better alpha peak resolution

– Better detection limit for uranium-500 mL+ sample (vs. current 50 mL sample size)

– Cartridge technology more efficient; eliminates large sequential load solutions (evaporation steps)

Bioassay Implementation

Status• Implementation over next 3 to 6 months

• Pu, Np-TEVA -implemented-10/99

• Pu, Np, Sr -TEVA /SR cartridge or column

• Pu, Np, Am -TEVA+TRU cartridge or column

• Pu, Np, Sr, U,Am -TEVA+TRU cart. + SR column (add 2nd small TEVA column to ensure complete Th-228 removal)

Challenges

• Optimize nitrate levels for Pu, Np on TEVA and Sr on SR Resin work using cartridges

• Achieve adequate Th-228 removal for Pu/U work

– successful with second 1 ml TEVA column

• Interface with current electroplating practices/evaluate cerium fluoride ppt

• Improved Pu stripping from TEVA Resin (NH4I or Ti+3)

• Ensure adequate Pu, Np reduction w/o Fe+2 to enable TRU cartridge below TEVA for urine samples

Sample Preparation

• Tracer addition (Pu-242 or Pu-236, U-232, Am-243)

• Routine calcium phosphate precipitation

– 3 mmol Ca (120 mg )+ 15 mmol (NH4)2HPO4

• Precipitate/centrifuge/redissolve/ash

• TEVA+TRU: Pu, Np, Am, U, Sr– Redissolve in 6 mL of 5M to 6M HNO3

– Add 6 mL of 2 to 2.5 M Al(NO3)3 -scrubbed using UTEVA – after valance adj., no additional acidity adjustment needed

• TEVA+SR: Pu, Np, Sr– Redissolve in 5 mL of 5M HNO3

– Add 5 mL of 2 to 2.5 M Al(NO3)3 -scrubbed using UTEVA

– after valance adj., add 3 mL 16M HNO3 (adjust acidity to 4.5M )

Sample Preparation (contd.)

Valence options to adjust Pu and Np for TEVA:

A. 1) 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

For TRU cartridge below TEVA (no iron added) :

B. 1) Add 0.5 mL 1.5M sulfamic acid , 2mL 1.5M ascorbic acid, wait 3 to 5 min.

2) 2 mL 4 M sodium nitrite, ensuring excess nitrite

Pu, Np on TEVA RESIN (URINE)

TEVA Pu Tracer Recoveries

500 mL urine sample/ Pu-242 tracer= 1.25 dpm / One TEVA Column Fe+AA/+NO2

%Recovery (CeF3 microprecipitation) % Recovery (Electroplating* )

1) 110 1) 84.4

2) 93.3 2) 72.4

3) 92.6 3) 69.3

4) 95.2 4) 69.6

5) 101.5 5) 79.8

6) 99.3 6) 84.5

7) 97.7 7) 79.1

8) 115.4 8) 85.5

9) 107.9 9) 84.8

10) 106.8 10) 77.0

11) 101.6 11) 82.5

12) 102.6

Avg. = 102.0% Avg. = 79.0

*Add 4 mL 0.02M H2SO4 to enhance F removal during solution cleanup for plating

TEVA- Np Spike Recoveries

500 mL urine sample/ Np-237 spike= 1.40 dpm

Single TEVA column Valence adj. : Fe+AA/+`NO2

% Np-237 Recovery (electroplating)

1) 101.6

2) 99.5

3) 71.3 4) 104.5

5) 85.8

6) 78.3

7) 85.9 8) 81.3

9) 77.8

10) 75.3 11) 91.9

12) 105.3

Avg. = 88.2%

Pu, Np/Am, U, Sr on TEVA/TRU RESIN (URINE)

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

TEVA (w/ 2nd Col.) -Pu Tracer Recoveries

500 mL urine sample/ Pu-242 tracer= 1.25 dpm

With 2nd 1 mL TEVA Column to ensure complete Th-228 removal when U-232 added

1+2: Fe+AA/+NO2

3-7: SA+AA/NO2

%Recovery (CeF3 microprecipitation) % Recovery (Electroplating* )

1) 93.2 1) 66.0

2) 90.0 2) 75.4

3) 84.1 3) 72.7

4) 90.0 4) 71.0

5) 86.0

Avg. = 89.3% 6) 80.9

7) 73.0

Avg. = 75.0%

TRU Resin -Am Tracer Recoveries500 mL urine sample/ Am-243 tracer= 1.55 dpm / TRU cartridge after TEVA SA+AA/+NO2 / load TEVA and TRU at same time/remove TRU cart./elute Am

% Am-243 Recovery (Electroplating* )1) 93.2

2) 92.1

3) 107.4

4) 70.3

5) 102.4

6) 103.0

7) 100.2

8) 103.3

9) 102.6

10) 94.7

Avg. = 96.9%

TRU Resin-U Tracer Recoveries

500 mL urine sample/ U-232 tracer= 0.554 dpm / TRU cartridge after TEVA SA+AA/+NO2 / load TEVA and TRU at same time/remove TRU cart./elute U

% U-232 Recovery (Electroplating* )

1) 97.9

2) 74.1

3) 85.6

4) 102.9

5) 90.6

6) 83.1

7) 57.7

8) 81.0

9) 80.4

10) 93.3

Avg. = 84.7%

Pu/Sr On TEVA/SR RESIN (URINE)

TEVA-Pu/Sr Cartridge Recoveries

• 500 mL urine sample Sr-90 spiked in samples: 206 dpm

Measured dpm % Sr-90 Spike Recovery

171 83.0

172 83.5

155 75.2

160 77.7

173 84.0

160 77.7

159 77.2

Avg 164.3 79.8

Sr-90 Spiked after precipitation:

Measured dpm % Sr-90 Spike Recovery

184 89.3%

188 91.3%

Avg 186 90.3 %

Summary

• New implementation of rapid column methods in bioassay lab will result in significant time/cost savings

• Pu and Np together with Pu-236 tracer

• Better Th-228 removal using 2nd 1 mL TEVA col. when U-232 tracer added

• Pu, Np and Sr on TEVA+Sr cartridge

• Pu, Np and Am, U on single two stage TEVA-TRU column with Sr-90 on SR Resin after evaporation