concentrated with TIOA in toluene.
the actinides in the soil samples. Many individual procedures have been
developed for Np, Pu, Am, and Cm in soil matrices and have been reported in
the literature. Procedures have been also reported for separation of these
elements in groups of two or more. The evolution of these procedures has been
based on the insurance that the actinides have been completely solubilized and
equilibrated with tracer, when added, The method of assay also has influenced
the concentration technique. Virtually all methods involve drying the soil,
charring the organic and humus, and grinding and sieving the sample. However,
in the HASL procedure, Harley (1972), the organic is ground up with the sample
and destroyed by HNO;-HC1 acid when the Pu is leached.
Bernhardt (1976)
evaluated sample collection and analyses techniques for environmental Pu.
The greatest controversy has been connected with the leach method versus
complete dissolution. For large (1 kg) samples, the acid leach has proven to
be the only practical procedure.
Leaching methods have been successful with
Pu activities, particularly when they are not refractory and loosly bound to
the matrix.
Geiger (1959) discussed the relative ease of Al(NOQ 4) 4~-HNO3
leaching of Pu from soils exposed to reactor effluents. Bond and Clark (1958)
discuss efficiency of leaching Rainier and Tamalpais nuclear debris with
groundwater, from the Nevada Test Site, as a function of leaching temperature.
Thomas (1957) reports on leaching with HNO; and HF in the analysis of Bravo
Shot soils. Olafson et ai. (1957) wet ashed New Mexico soils with HNO3~
HC10,-HF and isolated the Pu on a LaF3 carrier. Everett and Drake (1960) have
leached fused Nevada soil samples, covering a wide range of activity, with
HNOg and reported good yields on the leach solution, but measurements on the
residue were not indicated. More recently, Bishop et ai. (1971) tested 50-g
acid leaching and Sill's fusion methods for 72%Pu in soil using tracer techniques with comparable results.
with TLOA-xylene.
They used an HNQ3-HF leach and concentrated
Corley et al. (1971) successfully leached 239Pu from Hanford
surface soil (10-g) using an HC1, HNO, cycle and anion exchange and TTA extraction and evaporated the organic phase directly onto a Pt disc.
Sill (1975)
performed experiments on soils heated to different temperatures and then
leached with various combinations of acids. His plutonium activity balances
showed the fate of sample and tracer Pu for each and the fact that HF had a
large effect on obtaining the true Pu concentration in the soil. The most
referred to leaching techniques are those of Talvitie (1971) for 1-g quantities
and of Chu (1971) for bulk samples. The HASL acid leach has been adapted to
i-kg and 3-kg soils by Major et al. (1972) and is sometimes complicated by
colloid formation. Poet and Martell (1972) used an acid leach but did not use
HF for Am and Pu.
Fowler and Essington (1974) report on a method for plutonium
in soil, the HASL-LASL leach method. This formed the basis for the procedure
described in AEC Regulatory Guide 4.5, Anonymous (1974a), which was stated to
be "acceptable to the Regulatory staff for sampling and analysis of plutonium
in soil with the sensitivity and accuracy needed to adequately monitor plutonium
in soil in the environs of fuel processing and fuel fabrication facilities."
The procedures involved HNO3-HF leaching, a leach with HCl, and complexing
with H3B03. A precipitation of Fe(OH); is made with NaOH, carrying down
undissolved residues which are then treated with HNO, and H3B0, before any
undissolved residue is discarded and the Pu purified by usual anion exchange
techniques.
Hayes et al. (1975) simply leached estuarine soils with HC1 and
550
Bently et al, (1971) used acid leach on
50-g soila followed by HDEHP extraction and a LaF, precipitation and reported
90% yields. Noshkin and Bowen (1973) leached ocean sediments with HNO3.
Koide et al, (1975) applied the acid leach techniques of Talvitie and Wong to
both atmospheric dusts and marine sediments.
Complete dissolution techniques are satisfactory for limited sample sizes.
Crouch and Cook (1956) reported on fusion of irradiated rocks, soil, and
organic matter, and report losses due to fusion insolubles in samples over 250
mg and spattering difficulties, Merritt {1958} fused Chalk River soils with
alkalai hydroxides and carbonates but reported interferences from large amounts
of alkalai.
5111 (1961), and Sill and Williams (1971) have extensively studied
the fusion of refractory silicas and later Sill and co-workers (1974) extended
the method. For soils and air dusts, after a preliminary HF treatment, sequential potassium fluoride and potassium pyrosulfate fusions are performed.
Bretthauer and Hahn (1975) proposed the fusion method as a reference method
for Pu in soil. Butler et al. (1971) use a similar technique on 5-g samples
but extracts with TIOA and then a LaF3 precipitation.
Complete acid dissolutions of soil samples are suitable for samples up to
100 g, at which point the procedure becomes lengthy and uneconomical. Wet
ashing, involving complete acid dissolution, has been found to be the method
of choice by Major et al. (1965a, 1971) and has been applied to soil samples
up to 100 g. HNO3-HC10, was used to destroy the organic matter followed by
HNO;-HF treatment. Residues were separated, dissolved, and recombined and
concentrated by coprecipitation with Fe({OH)3.
The isolation of the other actinides in soil does not differ materially from
that of Pu except in the concentration steps.
Major et al. (1971) used, for
the Nevada soils, a eeries of HF, HNO3-HC1 steps and H3B03 to decompose the
silicon fluorides, and subsequently isolate by anion exchange and HDEHP extraction. Nevissit et al. (1975) reported on complete acid dissolution techniques
similar to the above for both Pu and Am in Bikini soils, They fused any
residues with a NaOH/Naj,CO3 mixture and extracted with TIOA.
Edgington et al.
(1975) applied the methods of Talvitie and Wong to the determination of Pu and
Am in Lake Michigan sediments and extracted the Am with Aliquat 336S.
Kleinberg
(1967), in the LASL collected radiochemical procedures, reporta on individual
and sequential procedures in Nevada soil debris. For Am and Cm samples up to
a few grams, Smith (1967) found LaF, precipitation after dissolution was
satisfactory for 0.1 to 0.3 g soil, but for larger samples, HDEHP extractions
were necessary. Barnes (1967) used anion exchange and elution with dilute
thiocyanate for Cm.
Smith (1967) used Zr and Sr hold back for Np and a LaF
precipitation.
Wolfsberg and Daniels (1967) concentrated the actinides from
250-g dissolved samples, first with TBP and then with HDEHP. S111 et ail.
(1974) applied his fusion method followed by extraction with Aliquat 336
separating out first Am, Cm, and then Np and Pu.