AN-1423

Rapid Determination of Pu, Np,and U in 1-8L Seawater Samples

Summary of Method Plutonium, Neptunium, and Uranium are separated and concentrated from up to 8L
samples of seawater with a hydrous titanium oxide precipitation, enhanced with 5mg of lanthanum and 125mg of ferriciron. A second precipitation with lanthanum fluoride removes additional matrix ions, and Uranium and Pu+Np are
separated from potentially interfering radionuclides in the sample using stacked 2mL cartridges of Eichrom TEVA andTRU Resins. Isotopic U and Pu+Np are measured by alpha spectrometry following cerium fluoride microprecipitation
onto Eichrom Resolve® Filters. Chemical yields are determined by recovery of 232U and 242Pu (or 236Pu if measuring237Np) tracers. Recoveries of 232U average 95 + 6%, while 236Pu average 90 + 9%. Measured values of 238U, 239Pu, and237Np typically agree to within 10% of reference value. A single operator can process batches of 12 samples throughalpha source preparation in 6-8 hours. Alpha spectrometry count times will vary depending on desired detection limitand data quality objectives.
Figure 1. Sample Preparation
Reagents
TEVA Resin, 2mL Cartridges (Eichrom TE-R50-S)
TRU Resin, 2mL Cartridges (Eichrom TR-R50-S)
Nitric Acid (70%)
Hydrochloric Acid (37%)
Hydrofluoric Acid (49%) or Sodium Fluoride
Ammonium Hydroxide (listed as 28% NH3 or 56% NH4OH)
Iron Carrier (50mg/mL Fe, as ferric nitrate)
Lanthanum and Cerium Carriers (1mg/mL)
232U and 242Pu(or 236Pu if meas. 237Np) tracers
Oxalic acid/Ammonium Oxalate
Deionized Water
H2O2(30%)
10% (w:w) TiCl32M Al(NO3)3
Boric acidSulfamic Acid
Ascorbic Acid
NaNO2
Denatured Ethanol
1.25M Ca(NO3)2
Equipment
Vacuum Box (Eichrom AR-24-BOX or AR-12-BOX)
Cartridge Reservoir, 20mL (Eichrom AR-200-RV20)
Inner Support Tubes-PE (Eichrom AR-1000-TUBE-PE)
Yellow Outer Tips (Eichrom AR-1000-OT)
Resolve Filters in Funnel (Eichrom RF-DF25-25PP01)
50mL and 250-500mL Centrifuge Tubes
Centrifuge
Stainless Steel Planchets with adhesive tape
Alpha Spectrometry System
Analytical Balance
Vacuum Pump
Heat Lamp

1-8L Sample of Seawater.
Acidify to pH 2 with 70% HCl.
Add tracers. Mix well.
Add 5mg La, 125mg Fe and10mL 10% TiCl3. Mix well.
Add 5mL 56% NH4OH. Mix well.
Allow precipitate to settle.
Decant supernate to <1L.
Transfer remaining supernate and precipitate to250-500mL centrifuge tubes. Centrifuge
3000rpm for 10 minutes. Decant supernate.
Repeat until all sample processed.
Partially dissolve precipitate in 80mL 1M HCl.
Some solids will remain.
Add 1mg La, 25mg Ca, 5mL 10% TiCl3. Mix.
Add 25mL 49% HF. Mix. Centrifuge. Decant Supernate.
Dissolve precipitate with 5mL 3M HNO3-0.25M boric acid,
7mL 2M Al(NO3)3 and 8mL 7M HNO3.
Load solution to valence adjustment
and TEVA-TRU separation.

Figure 2. TEVA-TRU Separation and Alpha Source Preparation(1) Adjust valence states of actinides
by adding the following reagents inthe order listed (mix between steps):-0.2mL 1.5M Sulfamic acid-0.01mL 50mg/mL Fe carrier-1.5mL 1M Ascorbic acid
-1mL 3.5M NaNO2(2) Precondition stacked 2mL TEVA +TRU cartridges with 5mL 3M HNO3.
(3) Load sample solution at ~1mL/min.
(4) Rinse sample tube with
5mL 3M HNO3. Add tube
rinse to cartridges.
(5) Rinse cartridges with
10mL 3M HNO3.*(20) Rinse filter funnel with 1-2mL
100%ethanol.
(21) Draw vacuum until filter is dry.
(22) Remove filter from funnel
assembly and mount filter on
stainless steel planchet with(13) Add 0.5mL 10% TICl3 to U samples
adhesive tape.
and 0.5mL 30% H2O2 to Pu/Npsamples.
(14) Add 50-100ug Ce carrier to eachsample. Mix well. Add 1mL 49%
HF. Mix well. Wait 15-20 minutes.
(15) Set up Resolve® Filter Funnel
on vacuum box.

TEVA(16) Wet filter with 3mL 80% ethanol
followed by 3mLDI water.

TRU(6) Separate TEVA andTRU cartridges.

(10) Rinse TRU with 20mL
4M HCl-0.2M HF.
(11) Rinse TRU with 12mL 10M HNO3 .
(12) Strip U from TRU with 15mL
0.1M ammonium bioxalate.

(17) Filter sample.

(7) Rinse TEVA with 15mL 9M HCl.
(8) Rinse TEVA with 5mL 3M HNO3.
(9) Strip Pu and Np from TEVA with20mL 0.1M HCl-0.05M HF-0.01M
TiCl3.

(18) Rinse sample
tube with 5mL
DI water andadd to filter.

(23) Dry filter under heat lamp for
3-5 minutes.
(24) Measure actinides by alphaspectrometry.

(19) Rinse filter funnel
with 3mL DI water.

*Adding 50uL of 30% H2O2 to tube rinse can improve Uranium recoveries and decontamination in Pu(Np) fractions.
Analyte
239

Pu

239

Pu

239

Pu

Method Performance Pu, Np and U from Seawater% Tracer Analyte(mBq/L) Analyte(mBq/L)
Volume, L Replicates Tracer Recovery
Reference
Measured2362591 + 9
33.8
32.6 + 1.4
Pu
48% Bias-3.6

1236

86

16.9

16.2-4.1

2

236

87 + 327.8

27.6 + 0.5-0.7

Pu
Pu

237

25236

91 + 917.4

17.7 + 1.5

1.7

237

4

1

236

86

8.7

7.2

-17

23782

236

87 + 34.4

4.2 + 0.4

-4.52451232

99 + 2
86

51.8
25.9

49.3 + 1.5
25.0

-4.8
-3.6

82

232

92 + 596.3

94 + 3-2.4

Np
Np
Np

238

UU238
238

UPu
Pu
Pu
UU232

U

16 hour count times

References1) Sherrod L. Maxwell, Brian K. Culligan, Jay B. Hutchinson, Robin C. Utsey, Daniel R. McAlister, “Rapid determinationof actinides in seawater samples,” J. Radioanal. Nucl. Chem., 300(3), 1175-1189 (2014).
1955 University Lane Lisle, IL 60532, USA+1 (630)963-0320

www.eichrom.com