Rapid Fusion Method for
Refractory Th, U, and Pu in Soils

AN-1608-10
Summary of Method U, Th and Pu are separated and concentrated from 1-2 gram soil samples. Samples arefused with NaOH at 600°C in zirconium crucibles. The fusion cakes are dissolved in water, transferred to 250mL
centrifuge tubes and precipitated sequentially with Fe/Ti-hydroxide and lanthanum fluoride to facilitate matrix removal.
U, Th, and Pu are separated on stacked 2mL cartridges of Eichrom TEVA and TRU resins. U, Th, and Pu are measured
by alpha spectrometry following CeF3 microprecipitation onto Eichrom Resolve® Filters. Batches of 12-24 samples canbe prepared for alpha spectrometry in less than 8 hours. Method ruggedness has been demonstrated with successful
analysis of high fired refractory material from MAPEP 30 soil standards. For one gram soil samples and 16 hour counttimes, MDA for this method is ~500uBq/g.
Figure 1. Sample Preparation
Reagents
TEVA Resin, 2mL Cartridges (Eichrom TE-R50-S)
TRU Resin, 2mL Cartridges (Eichrom TR-R50-S)
Iron carrier (50mg/mL Fe, as ferric iron nitrate)
242Pu, 232U and 229Th tracers
Oxalic acid/Ammonium oxalate
La carrier (10mg/mL) Ce carrier (1mg/mL)
Deionized Water
1.25M Ca(NO3)22M Al(NO3)3
3.2M (NH4)2HPO4
10% (w:w) TiCl3
HNO3 (70%)
HCl (37%)
NaOH
HF (49%) or NaF
Boric acid
H2O2 (30%)
NaNO2Denatured ethanol
Ascorbic Acid

1-2g finely ground soil + tracers in zirconium crucible.
Place in Furnace at 250oC. Ramp to 600oC. Heat 30 min.
Cool. Add 15g NaOH. Fuse at 600°C for 15-20 minutes.
Dissolve fusion cake with 2x 50mL H2O. Transfer to 250mL c-tube.
Add 10mL 3M HNO3 to crucible. Heat to dissolve residue.
Transfer to same 250mL c-tube.
Add 150mg Fe and 5mg La to c-tube. Dilute to 180mL.
Add 2mL 1.25M Ca(NO3)2, 3mL 3.2M (NH4)2HPO4,10mL 10% TiCl3. Mix. Cool in ice bath for 10 min.
Centrifuge 10min. Decant Supernate.

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 250mL Centrifuge TubesCentrifuge
Heat Lamp
Muffle Furnace
Hot Plate
Analytical Balance
250mL Zirconium crucibles with zirconium lids
Stainless Steel Planchets with adhesive tape
Alpha Spectrometry SystemVacuum Pump

Partially dissolve precipitate in 80mL 1.5M HCl.
Some solids will remain. Dilute to 170mL.
Add 1mg La, 0.5mL 1.25M Ca, and 6mL 10% TiCl3.
Mix. Add 25mL 49% HF. Cool in ice bath for 10 min.
Centrifuge 10min. Decant Supernate.
Dissolve precipitate in 10mL 3M HNO3-0.25M Boricacid, 6mL 7M HNO3, and 8.5mL 2M Al(NO3)3.
Warming samples can help complete dissolution.
Cool samples to room temperature.
Fix valence states. Mix between each addition of:
20uL 50mg/mL Fe
1.5mL 1M ascorbic acid1mL 3.5M NaNO2.

Figure 2. Actinide Separation on TEVA - TRU - DGA* and Source Preparation(1) Precondition stacked 2mL
TEVA and TRU cartridges
with 10mL 3M HNO3.
(2) Load sample solution.

(10) Rinse TRU cartridge with:- 5mL 8M HNO3TEVA- 20mL 4M HCl-0.2M HF-0.002M TiCl3- 10mL 8M HNO3

(3) Rinse sample tube with
5mL 3M HNO3 + 30uL 30%
H2O2. Add to cartridges.

TRU(4) Rinse cartridges w/
10mL 3M HNO3.
(5) Separate TEVA-TRU cartridges.
(6) Rinse TEVA cartridge
with10mL 3M HNO3.
(7) Strip Th with 15mL 9M HCl.
Dilute to 30mL. Add 0.5mL 30%
H2O2 and 40ug Ce.
(8) Rinse TEVA with:- 5mL 9M HCl- 5mL 3M HNO3
(9) Strip Pu (and Np) from TEVAwith 20mL 0.1M HCl-0.05MHF0.01M TiCl3. Add 0.5mL 30% H2O2and 50ug Ce. Mix.

(11) Strip U from TRU with 15mL of
0.1M ammonium bioxalate.

(19) Draw vacuum until filter is dry.
(20) Remove filter fromfunnel assembly andmount filter on stainlesssteel planchet with 2-sided tape.

(12) Add 100ug Ce and 0.5mL 10% TiCl3(13) Add 1mL 49% HF to all samples.
Mix well. Wait 15-20 minutes.
(14) Set up Resolve®
Filter Funnel onvacuum box.
(15) Wet filter with3mL 80% ethanolfollowed by 3mLDI water.

(21) Dry filter under heat lamp for
3-5 minutes.

(16) Filter sample.
(17) Rinse sample tube with 5mL DI
water and add to filter.
(18) Rinse filter funnel with 3mL DI
water and 2mL 100% ethanol.

(22) Measure actinides by alpha
spectrometry.

Method Performance
Sample1g Soil
1g Soil

replicates12121g Soil

% tracerrecovery86 + 886 + 8

mBq/g
reference
83.0
81.0

mBq/g
measured
85 + 380 + 2% bias+3+2analyte
238
U234
Utracer
232
U232
U12228

Th229Th91 + 651.1

50 + 2+41g Soil

12230

Th229

Th

91 + 696.2

98 + 6+51g Soil

12232

Th239
Pu229ThPu

91 + 648.8

50 + 3+6242

91 + 676.8

79 + 3+4Pu

91 + 696.0

98 + 5+41g Soil
1g Soil

33239

Pu

242

References
1) Maxwell, Hutchinson, McAlister, “Rapid Fusion Method for the Determination of Refractory Thorium and Uranium
Isotopes in Soil Samples” Analytica Chimica Acta, 701(1), 112-118 (2015).
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