Alpha Spectrometry Source Preparation:
Cerium Hydroxide Microprecipitation$1--
6XPPDU\ RI 0HWKRG Cerium hydroxide microprecipitation is an alternative to rare earth fluoride microprecipitationand electrodeposition for alpha spectrometry source preparation. Microprecipitation provides adequate alpha peak
resolution for most analytical applications, while greatly reducing the time for sample preparation relative toelectrodeposition. Alpha spectrometry sources can often be prepared directly from the eluate used to recover theactinide fraction from the chromatographic column used to separate the actinides from the sample matrix and potentiallyinterfering nuclides. The direct precipitation eliminates the numerous evaporation and digestion steps normally required
for electrodeposition, reducing the alpha spectrometry source preparation time from 3-8 hours to 30-60 minutes andeliminating the emission of corrosive acid fumes through the laboratory fume hood vents.
Cerium hydroxide is an alternative to rare earth fluoride microprecipitation for labs looking to avoid the use ofhydrofluoric acid. Cerium hydroxide precipitates will nearly quantitatively carry actinides in all oxidation states.
Therefore, the additional U decontamination of Th, Np/Pu and Am/Cm samples achieved by the rare earth fluoride
precipitation will not occur using the cerium hydroxide precipitation. The cerium hydroxide precipitate has a yellow color,
providing visual confirmation of the collection of the precipitate on the Resolve Filter and easy identification of thesurface of the filter containing the precipitate.
Cerium carrier, hydrogen peroxide and a pH indicator are added to each sample fraction from the appropriate
separation method. After mixing to distribute the carrier, ammonium hydroxide is added to adjust the pH. The optimal
pH and the appropriate pH indicator will depend on the actinide metal ion being collected. U and Th show the highest
recovery from pH 5-7, utilizing the bromocresol purple pH indicator. However, U and Th recoveries do not decrease dramatically if the pH is increased to 8-10. Am and Pu/Np recoveries are most consistent utilizing thymol blue, with a color
change from pH 8-10. The higher pH range is important to ensure high recoveries of Am. Since Pu and Np are often
measured together, with a single 236Pu yield tracer, it is important that their recoveries are very similar. The pH of 8-10 isimportant to ensure similar recoveries of Pu and Np. At lower or higher pH, Np recovery can diverge significantly fromPu. [2]Eichrom’s Resolve Filters (RF-DF25-25PP01) are manufactured specifically for alpha spectrometry source
preparation. The manufacture and quality control procedures ensure a uniform surface for the collection of the rareearth fluoride precipitate, reducing self attenuation of the alpha emissions, which can degrade peak resolution. Otherfilter membranes may not be suitable for alpha source preparation or may require the addition of substrate to achieveadequate resolution.
Sources prepared by microprecipitation precipitation typically sit closer to the detector in alpha spectrometry
systems than electrodeposition sources. The difference in distance from the source to the detector can lead to a 5-10%
higher efficiency for the measurement of microprecipitation sources. Since most laboratories calibrate their alpha
spectrometry systems with electrodeposited sources, the efficiency difference must be considered when determining
the absolute recovery of the chemical yield tracers.

5HDJHQWV
Cerium Carrier (10 mg/mL)
30% Hydrogen Peroxide (H2O2)
Ammonium Hydroxide (NH4OH)
Deionized Water
Denatured Ethanol
Bromocresol Purple
Thymol Blue(TXLSPHQW

Vacuum Box (Eichrom AR-24-BOX or AR-12-BOX)
Yellow Outer Tips (Eichrom AR-1000-OT)
Resolve Filters in Funnel (Eichrom RF-DF25-25PP01)
Stainless Steel planchets with two sided tape
Alpha Spectrometry System
50 mL Centrifuge Tubes
Heat Lamp
Vacuum Pump)LJXUH&HULXP+\GUR[LGH$OSKD6SHFWURPHWU\6RXUFH3UHSDUDWLRQUranium Samples(1) Obtain a purified sample of U in a50 mL centrifuge tube using anappropriate separation method.
Samples are typically in 10-20 mL of
1M HCl.
(2) Add 25-50 Pg of Ce carrier,
0.2 mL of 30% H2O2 and bromocresol
purple. Mix.
(3) Adjust to pH 5-7 (blue/purplecolor). Mix well. Proceed to step (4).
Thorium Samples(1) Obtain a purified sample of Th ina 50 mL centrifuge tube using anappropriate separation method.
Samples are typically in 20 mL of
6-9M HCl.
(2) Add 25-50 Pg of Ce carrier,
0.2 mL of 30% H2O2 and bromocresol
purple. Mix.
(3) Adjust to pH 5-7 (blue/purplecolor). Mix well. Proceed to step (4).
Pu/Np Samples(1) Obtain a purified sample of Pu/
Np in a 50 mL centrifuge tube using
an appropriate separation method.
Samples are typically in 15-20 mL of
dilute HCl-HF with a reducing agent.

(2) Add 25-50 Pg of Ce carrier,
0.2 mL of 30% H2O2 and thymol blue.
Mix.
(3) Adjust to pH 8-10 (light bluecolor). Mix well. Proceed to step (4).
Am/Cm, An(III), and Ln(III) Samples(1) Obtain a purified sample of Am/Cm, An(III) or Ln(III) in a 50 mL
centrifuge tube using an appropriate
separation method. Samples are
typically in 15-20 mL of 0.1-4M HCl.
Samples with high native rare earth
content will require removal of rareearths using TEVA-SCN (AN-1806).
(2) Add 25-50 Pg of Ce carrier,
0.2 mL of 30% H2O2 and thymol blue.
Mix.
(3) Adjust to pH 8-10 (light bluecolor). Mix well. Proceed to step (4).

(4) Set up Resolve® Filter Funnel onvacuum box.
(5) Wet filter with 3 mL 80% ethanol
followed by 3 mL DI water.
(6) Filter sample.
(7) Rinse sample tube with 5 mL DIwater. Add to filter.

(8) Rinse funnel
with 3 mL DI waterand 2 mL ethanol.
(9) Draw vacuum
until filter is dry.
(10) Remove filter
from funnel. Mountfilter on stainlesssteel planchet with
2-sided tape.

(11) Dry filter under heat lamp for
3-5 minutes.
(12) Measure actinides by alpha
spectrometry.
*Results in Table 1 are for typicalsample matrix from separationmethod. Performance with othermatrices or volumes should beverified prior to implementation.

Typical Performance of Ce(OH)4 Microprecipitation onto Eichrom Resolve Filters
pHmg CeMatrix

Yield

Resolution (FWHM)

230

Th

5-7

25

20 mL 9M HCl

95-99%

25-35 keV

238/234

5-7
8-10

25
25

20 mL 1M HCl
93-97%
20 mL 0.15M HCl-0.05M KF-0.04M Rongalite 89-93%

25-35 keV
25-35 keV

8-10
8-10

25
25

20 mL 0.15M HCl-0.05M KF-0.04M Rongalite 86-92%
15 mL 4M HCl
91-95%

25-35 keV
25-35 keV

NuclideUNp237

239

PuAm

241

5HIHUHQFHV1) Claude W. Sill, “Precipitation of Actinides as Fluorides or Hydroxides for High-Resolution Alpha Spectrometry,”
Nuclear and Chemical Waste Management, 7, 201-215 (1987).
2) Hiromu Kurosaki, Rebbeca J. Mueller, Susan B. Lambert, Govind R. Rao, “Alternate method of source preparation
for alpha spectrometry: no electrodeposition, no hydrofluoric acid,” J. Radioanal. Nucl. Chem., 311, 323-329 (2017).
1955 University Lane Lisle, IL 60532, USA+1 (630)963-0320

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