Alpha Spectrometry Source Preparation:
Rare Earth Fluoride Microprecipitation$1--
6XPPDU\ RI 0HWKRG Rare earth fluoride microprecipitation is an alternative to electrodeposition for alpha
spectrometry source preparation, which provides adequate alpha peak resolution for most analytical applications, while
greatly reducing the time for sample preparation. Alpha spectrometry sources can often be prepared directly from theeluate used to recover the actinide fraction from the chromatographic column used to separate the actinides from thesample matrix and potentially interfering nuclides. The direct precipitation eliminates the numerous evaporation anddigestion steps normally required for electrodeposition, reducing the alpha spectrometry source preparation time from
3-8 hours to 30-60 minutes and eliminating the emission of corrosive acid fumes through the laboratory fume hoodvents.
Lanthanum, cerium or neodymium carrier and hydrofluoric acid are normally used to produce the rare earth
fluoride precipitate. Ammonium bifluoride may be used instead of HF. Additionally, for laboratories which are restrictedfrom the use of fluoride, Ce(OH)4 precipitation (AN-1807) may be a suitable alternative.
Rare earth fluoride precipitates will nearly quantitatively carry trivalent and tetravalent actinides, while rejecting
pentavalent and hexavalent actinides. Therefore, the addition of TiCl3 is required to reduce U(VI) to U(IV) to prepare
uranium samples. Samples of the other actinides may be further purified from U during the rare earth fluoride
precipitation by the addition of H2O2, which will ensure U(VI) that will not be carried on rare earth fluorides.
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 rare earth 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.
Rare earth fluoride microprecipitation onto Eichrom Resolve Filters produces alpha spectra which are suitable
for most analytical applications. However, electrodeposition may be required for some applications, such as thepreparation of calibration sources and the measurement of nuclides with difficult to resolve alpha peaks.

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Lanthanum, Cerium or Neodymium Carrier (10 mg/mL)
HF(49%)
30% H2O2
Deionized Water
Denatured Ethanol
10-20% TiCl3 (for Uranium fractions)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)
50 mL Centrifuge Tubes
Alpha Spectrometry System
Stainless Steel planchets with two sided tape
Heat Lamp
Vacuum Pump)LJXUH5DUH(DUWK)OXRULGH$OSKD6SHFWURPHWU\6RXUFH3UHSDUDWLRQUranium Samples*(1) Obtain a purified sample of U in a
50 mL centrifuge tube using anappropriate separation method.
Samples are typically in 10-20 mL of
1M HCl or 0.1M ammonium
bioxalate. Other matrices andvolumes should be tested prior toapplication. Concentrations of >0.1M
HNO3 may interfere with uranium
reduction by TiCl3 and lead to poor
recoveries in the rare earth fluoride
precipitation.
(2) Add 0.25 mL of 20% TiCl3 and100 Pg of La, Ce or Nd carrier. Mix.
(3) Add 1 mL 49% HF. Mix well. Wait
15-20 minutes. 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 10-15 mL of
6-9M HCl.
(2) Add 50 Pg of La, Ce or Nd carrier.
Dillute to 30 mL with DI H2O. Mix.
(3) Add 1 mL 49% HF. Mix well. Wait
15-20 minutes. 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 50 Pg of La, Ce or Nd carrierand 0.5 mL 30% H2O2. Mix.
(3) Add 1 mL 49% HF. Mix well. Wait
15-20 minutes. 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 aretypically 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).

(5) Wet filter with
3 mL 80% ethanol
followed by 3 mLDI 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 stainless steel planchet with
2-sided tape.

(2) Add 50 Pg of La, Ce or Nd carrierand 0.2 mL 30% H2O2. Mix.
(3) Add 1 mL 49% HF. Mix well. Wait
15-20 minutes. Proceed to step (4).
(4) Set up Resolve® Filter Funnel onvacuum box.

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

Typical Performance of CeF3 Microprecipitation onto Eichrom Resolve Filters
Nuclide230
Thmg Ce50

Matrix30 mL 4.5M HCl

Yield>95%

Resolution (FWHM)
20-30 keV

238/234UPu

100

20 mL 1M HCl>95%

30-40 keV

50

20 mL 0.1M HCl-0.05MHF-0.01MTiCl3>95%

30-40 keVAm50

15 mL 4M HCl>95%

22-28 keV239
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) ASTM C1163-14, Standard Practice for Mounting Actinides for Alpha Spectrometry Using Neodymium Fluoride
1955 University Lane Lisle, IL 60532, USA+1 (630)963-0320

www.eichrom.com