Evaluation of the gravimetric tetraphenylarsonium method for the determination of Tc(VII)

Solubility losses in the gravimetric tetraphenylarsonium method for determining pertechnetate have been evaluated. Liquid scintillation counting was used to measure the beta(-) activity of (99)Tc in the filtrate, and indicated solubility losses of about 1% in analyses yielding 40-50 mg of precipitate. The solubility product Of (C(6)H(5))(4)AsTcO(4) is estimated to be (8.6 +/- 0.2) x 10(-10) at room temperature (24-25 degrees ) and K(sp) for (C(6)H(5))(4)AsReO(4) at approximately 21-23 degrees is estimated at (2.6 +/- 0.3) x 10(-9). Both values are satisfactory for gravimetric purposes, but to keep solubility losses within 1% at least 40mg of (C(6)H(5))(4)AsTcO(4) or 80 mg of (C(6)H(5))(4)AsReO(4) should be obtained (assuming 20 ml of solution, 20-30% excess of precipitant and 6 or 7 washes with 5-ml portions of distilled water).     

A substoichiometric radioisotope dilution study using210Pb

A radioisotope dilution procedure has been developed which permits the determination of lead over a concentration range of 0.1 to 10 ppm. Samples in an ammoniacal cyanide/sulfite medium are labelled with²¹⁰Pb, followed by addition of substoichiometric amount of dithizone. The Pb/HDz/₂ formed is extracted into CH₂Cl₂, and aliquot portions are taken for liquid scintillation counting. Count rate is plotted vs. the reciprocal of the lead concentration, yielding a straight line. An average error of ±3.5% is estimated, based on a linear least squares fit.     

Systematics of (p,p′) and (p, α) spectra from 14 MeV proton bombardment of medium-A targets

Differential cross sections have been measured between 30° and 150° for the (p, p′) and (p, α) reactions induced by 14 MeV protons in the following targets: ³⁵Mn, ³⁶Fe, ⁵⁸Ni, ⁵⁹Co, ⁶²Ni, ⁶³Cu and ⁶⁴Zn. The results have been compared with the spin-dependent statistical theory and good agreement was obtained for the (p, α) reactions with a level density parameter a = (0.138±0.008)A MeV^?1. This value is substantially lower than that obtained in a spin-independent analysis of the same data. The agreement of the (p, p′) spectra with theory is poor and it is found that a 15–40% contribution from precompound emission is required. The emission of low-energy protons from the (p, np) reaction was observed in all cases and comparison of the cross sections with these of the corresponding (p, n) reactions yields information on the competition between γ-ray and proton emission.     

Determination of cadmium in sewage sludge by differential pulse anodic stripping voltammetry

A procedure was developed for the determination of cadmium in sewage sludge by differential pulse anodic stripping voltammetry. A sodium peroxide fusion carried out in zirconium crucibles was found to give satisfactory results, based on analysis of standard reference materials. Samples collected from the municipal sludge lagoon in Fort Wayne, Indiana were found to have cadmium abundances ranging from 120 to 250 ppm, with most samples falling in the 120 to 170 ppm range. Interference from zinc is easily eliminated by carrying out the deposition step at -0.95 V vs. Ag/AgCl. Lead-to-cadmium ratios as high as 50:1 (ppm basis) have no effect on the height of the cadmium peak.     

Effect of container adsorption on the210Pb/210Bi secular equilibrium relationship in spiked aqueous solutions

The radioactive boric acid wastes generated from the nuclear power plants have been solidified with cement. One of the properties required for solidified radioactive wastes is resistance to leaching. The leachability of¹³⁷Cs from solidified waste specimens prepared by various formulation has been studied according to the proposed ANS 16.1 Standard Leach Test. For the evaluation of radiological safety in the solidified radioactive waste disposal, the leachability indices have been determined from the leaching test data. The results have turned out to be 5.97–7.60, depending on formulation and solidifying matrix.     

Separation of the radioelements210Pb−210Bi−210Po by spontaneous deposition onto noble metals and verification by Cherenkov and liquid scintillation counting

A method for the separation of²¹⁰Pb,²¹⁰Bi and²¹⁰Po using spontaneous deposition has been developed. The²¹⁰Bi and²¹⁰Po are simultaneously removed by deposition onto nickel foil (copper and tin could also be used but less effectively) while the²¹⁰Po is separated from²¹⁰Bi, after dissolution of the nickel foil, by deposition onto silver foil. The effectiveness of each separation was evaluated by adding aliquot portions of each solution to a cocktail and counting with a liquid scintillation counter. Water was used as the medium to observe the Cherenkov count of the sample solution.     

A container adsorption study of cadmium using109Cd spiking and liquid scintillation counting

¹⁰⁹Cd may be used as a radiolabel in tracer studies of Cd(II) because of the ease and efficiency with which it may be counted by liquid scintillation counting. It has been found that ppm solutions of Cd²⁺, spiked with¹⁰⁹Cd, may be stored for at least 200 d, in either amber glass or polypropylene containers, without measurable container adsorption, at pH's of 5 or less. At pH's above 5, there is some evidence of container adsorption, particularly in the case of polypropylene containers. Amber glass is recommended if pH's between 5 and 7 must be used for storage.     

Liquid scintillation and Cherenkov counting characteristics of109Cd

When¹⁰⁹Cd is placed in a liquid scintillation counter, 146±1 counts are obtained for every 100¹⁰⁹Cd nuclides which undergo decay. Thus, the average efficiency for each of the two steps in the decay process is 73%. In examining the distribution of energy among the windows available, it was noted that the distribution pattern is quite similar to that of¹⁴C. An average Cherenkov counting efficiency, in water, was found to be 0.0258±0.0005%. Both 0.010M K₂Cr₂O₇ and CHCl₃ quench the count rate, particularly in the lower energy channel, where count rates are suppressed by up to a factor of 20.     

The role of210Pb in evaluating container adsorption of Pb(II) from dilute aqueous solutions

Solutions of Pb²⁺ at ppb to ppm levels were tagged with²¹⁰Pb and then counted from time to time over a period of one year to measure the extent of container adsorption. All count rates for samples which were acidified with HNO₃ were at least 90% of their initial values, even after one year of storage. Amber glass containers proved to be superior to polypropylene for 0.1 and 1.0 ppm Pb²⁺ solutions; but below 0.1 ppm, polypropylene was superior. For non-acidified samples, the count rate dropped rapidly within the first two months, and then declined more gradually thereafter, with polypropylene generally superior.     

The role of Cherenkov and liquid scintilation counting in evaluating the anion-exchange separation of210Pb−210Bi−210Po

Using as eluent a sequence of 3M HCl, 12M HCl, and 8M HNO₃, a mixture of²¹⁰Pb,²¹⁰Bi, and²¹⁰Po may be clearly separated on a column of Dowex 1×2−100 anion exchange resin. A Cherenkov count in H₂O and the variation in count rate with time confirm that the nuclides emerge in the order²¹⁰Pb→²¹⁰Bi→²¹⁰Po. If 12M HCl is replaced by 1.5M H₂SO₄/2.3 M Na₂SO₄, a clean separation also results, but recovery of²¹⁰Po becomes considerably more difficult. All three nuclides are readily detectable by liquid scintillation counting, with the efficiency for²¹⁰Pb in the 60–70% range. The Cherenkov aqueous counting efficiency for²¹⁰Bi is ∼14–15%.