Rapid Determination of Np/Pu
in 20-50g Soil Samples

AN-1435
Summary of Method Plutonium and Neptunium are separated and concentrated from 20-50 gram soil samples.
Samples are leached with HNO3 and HCl. The leachates are evaporated to dryness, and sequential precipitations withFe/Ti-hydroxide and LaF3 facilitate matrix removal. Pu-Np are separated on 2mL cartridges of Eichrom TEVA resin. PuNp are measured by alpha spectrometry following CeF3 microprecipitation onto Eichrom Resolve® Filters. Chemicalyields of the 236Pu tracer ranged from 82-96%. Measured values typically agreed to within 10% of reference values.
Sample preparation for batches of 12 samples can be completed by a single operator in <8 hours.
Figure 1. Sample Preparation
Reagents
TEVA Resin, 2mL Cartridges (Eichrom TE-R50-S)
Iron carrier (50mg/mL Fe, as ferric iron nitrate)
236Pu tracer
NH4OH (28% NH3 or 56% NH4OH)
La carrier (10mg/mL)
Ce carrier (1mg/mL)
Deionized Water
2M Al(NO3)3
10% (w:w) TiCl3
HNO3 (70%)
HCl (37%)
HF (49%) or NaF
Boric acid
H2O2 (30%)
NaNO2Denatured ethanol
Sulfamic Acid
Ascorbic Acid

Dry 20-50g soil at 110°C. Blend and Size.
Aliquot sample to 600mL glass beaker. Add 236Pu.
Add 1.5mL 70% HNO3 and 0.5mL 37% HCl pergram of sample. Heat to 80°C on hotplate.
Transfer liquid to 250mL centrifuge tube.
Add 20mL 70% HNO3 to beaker. Warm beaker.
Transfer liquid to same 250mL centrifuge tube.
Repeat once.
Centrifuge 3500 rpm, 10 min.
Transfer leachate to 600mL beaker.
Evaporate to dryness.

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)
600mL Glass beakers
Stainless Steel Planchets with adhesive tape
Alpha Spectrometry System
50mL and 250mL Centrifuge Tubes
Centrifuge
Heat Lamp
Hot Plate
Analytical Balance
Vacuum Pump

Dissolve residue in 20mL 1M HCl. Warm if necessary.
Dilute samples to 180mL.
Add 5mg La, 125mg of Fe, and 20mL 10% TiCl3.
Mix. Add 25mL 56% NH4OH. Mix.
Centrifuge 3500 rpm. 5min. Decant supernate
Partially dissolve in 60mL 1.5M HCl.
Solids will remain. Dilute to 170mL.
Add 3mg La and 20mL 10% TiCl3. Mix.
Add 22mL 49% HF. Mix.
Place in ice bath for 10min.
Centrifuge 3500 rpm. 5min. Decant supernate.
Dissolve solids in 6mL 3M HNO3-0.25M H3BO3,8.5mL 7M HNO3, and 8mL 2M Al(NO3)3. Warming
samples can improve dissolution.

Figure 2. Actinide Separation on TEVA - TRU - DGA and Source Preparation
Cool samples to room temp. Fix(7) 50ug Ce carrier. Mix.
Add 1mL 49% HF. Mix.
valence by adding: (mix between steps)
Wait 15-20 minutes.
-0.5mL 1.5M sulfamic acid-40uL 50mg/mL Fe carrier-1.5mL 1M ascorbic acid (Wait 3 min) (8) Set up Resolve® Filter Funnel on-1mL 3.5M NaNO2vacuum box.
(1) Precondition 2mL TEVA,cartridges with 5mL 8M HNO3.

TEVA(2) Load Sample.
(3) Rinse centrifuge tube
with 5mL 6M HNO3.*
Add to TEVA.
(4) Rinse cartridges with:-15mL 3M HNO3-20mL 9M HCl-5mL 3M HNO3.
(5) Strip Pu/Np from TEVA with 20mL
0.1M HCl-0.05M HF-0.03M TiCl3.

(6) Add 0.5mL 30% H2O2 to eachsample for additional uranium
decontamination during CeF3 ppt.

(14) Remove filter from funnel
assembly and mount filter on
stainless steel planchet with 2sided tape.

(9) Wet filter with
3mL 80%ethanol
followed by
3mL DI water.

(15) Dry filter under heat lamp for
3-5 minutes.
(16) Measure actinides by alpha
spectrometry.

(10) Filter sample.
(11) Rinse sample tube with 5mL DI
water and add to filter.
(12) Rinse filter funnel with 3mL DI
water and 2mL 100% ethanol.
(13) Draw vacuum until filter is dry.

*Adding 50uL 30% H2O2 to the tube rinse can improve Uranium decontamination.
236

Pu

239

Pu

239

238

Pu

Pu

238

237

Pu

239

Np

237

Np

238

237

Tracer Reference Measured Pu Reference Measured Pu Reference Measured Np
Sample, g replicates % Yield (mBq)(mBq) %Bias (mBq)(mBq) %Bias (mBq)(mBq) %Bias116.3
118+7
1.5
63.2
67+4
6.0
37.0
39+4
5.4
206
89+6
1.69
2.1+0.4 24
25.3
25+2-1.2
37.0
35+2-5.4
20
696+73050

6682+688+5116.3
116.3

121+5114+3

4.0-2.0

63.2
63.2

68+564+2

7.6
1.3

37.0
37.0

39+4
21+11

5.4-43

References
1) Sherrod L. Maxwell, Brian K. Culligan, Gary W. Noyes, “Rapid separation method for 237Np and Pu isotopes in large
soil samples,” Applied Radiation and Isotopes, 69(7), 917-925 (2011).
1955 University Lane Lisle, IL 60532, USA+1 (630)963-0320

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