Uranium isotopic analysis

TIMS has been used for many years as the benchmark technique especially for uranium isotope analysis. Instrumental improvements have enabled ICP-MS to approach the accuracy and precision obtained by TIMS in measuring data. In addition, due to time consuming sample preparation steps and the need for a large volume of urine, the method has been replaced by the more powerful ICP-MS in many laboratories. An interlaboratory analytical exercise on the determination of natural and depleted uranium in urine was carried out by different ICP-MS instruments, by thermal ionization mass spectrometry (TIMS) and instrumental neutron activation analysis. TIMS has also been employed to determine fg quantities of Pu and °Pu in bioassay samples (such as human urine and artificial urine), ° in an interlaboratory comparison for the analysis of the Pu and Pu/ °Pu atomic ratios in synthetic urine by TIMS and AMS as reported in reference. ... 

Singh and Wrenn (1988) describe a method for uranium isotopic analysis of air filters. Air filters are ashed, redissolved, and co-precipitated with iron hydroxide and calcium oxalate. The uranium is further purified by solvent extraction and electrodeposition. An alpha spectroscopy detection level of 0.02 dpm/L for in solution was reported (Singh and Wrenn 1988). 

The uranium content of a sample can be determined by fluorometry, alpha-spectrometry, neutron activation analysis (NAA), (IAEA 2000), or inductively coupled plasma mass spectrometry (ICP-MS) (Baglan etal. 1999). For uranium, isotope analysis may be carried out using ICP-MS (Uchida etal., 2000). In most cases, measurements of environmental levels or biological materials require preliminary sample preparations such as ashing and dissolution in acid, followed by either solvent extraction or ion exchange (PUvio and... 

The primary sample bottle is transferred to the operator s laboratory and mounted on a subsampling station O Fig. 63.10). The UFg is liquefied and a subsample of 1 to 5 g is collected again from the liquid phase (ANSI 1972 ISO 1996b) into a finger tube ( Fig. 63.11), which is weighed and shipped to the inspectorate laboratory. If the subsample is not issued from homogeneous liquid phases, only the uranium isotopic analysis will provide a meaningful result. In such a case, it is recommended to skip the elemental uranium assay. 

C1457 standard test method for determination of total hydrogen content of uranium oxide powders and pellets by carrier gas extraction Uranium isotopic analysis by mass spectrometry... 

Detection systems. Prior to the past decade, most instruments used for uranium-series analysis were single-collector instruments, for which ion beams of the various isotopes are cycled onto a single low-intensity detector, usually with electronics operating in pulse counting mode (Chen et al. 1986 Edwards et al. 1987 Bard et al. 1990 Goldstein et al. 1989 Volpe et al. 1991 Pickett et al. 1994), in order to measure the low-intensity ion beams of °Th, Pa, Pa, Ra and Ra. Daly detectors and... 

SIMS techniques have occupied somewhat of a narrower niche in uranium-series analysis, but have significantly improved Th isotope analysis relative to TIMS for chemically separated samples. The major improvement relative to TIMS is an improvement by about an order of magnitude in efficiency or sample size requirements for silicates. For uranium and/or thorium rich minerals such as carbonates and zircons, both SIMS and laser-ablation MC-ICPMS have been used for the direct in situ analysis of U and Th isotopes (Reid et al. 1997 Stirling et al. 2000) on very small (pg to ng levels of total U and Th) samples, at 10-100 pm scale resolution. 

Turekian, K. K., Chan, L. H., The Marine Geochemistry of the Uranium Isotopes, 230Th and 231Pa, In Activation Analysis in Geochemistry and Cosmochemistry, Universitetsforlaget, Oslo, 311-320 (1971). 

Of all the different mass spectrometric techniques for isotope analysis (such as ICP-MS, LA-ICP-MS, TIMS, GDMS, AMS, SIMS, RIMS and isotope ratio mass spectrometry of gases), the greatest proportion of pubhshed papers today concern ICP-MS with single and multiple ion collection.19 Due to its benefits, ICP-MS has now become a widely accepted method for isotope analysis and allows isotope ratios to be measured in a short time with good accuracy and precision.9,19,75 78 As discussed above, as a powerful and universal tool, ICP-MS has opened up new applications for isotope ratio measurements of elements with a high first ionization potential, which are difficult to analyze with TIMS (such as Mo, Hf, Fe). Of all the heavy metals studied, uranium was favoured by ICP-MS and LA-ICP-MS. 

Am with a half-life of ti = 432 a has to be determined in waste and environmental samples by mass spectrometry. The determination of 238Pu (ti 88 a) at the trace level is difficult in the presence of uranium due to isobaric interference with 238 U+ in mass spectra measured by ICP-MS or LA-ICP-MS. Therefore the application of a sensitive and selective technique such as RIMS or AMS is advantageous. The determination of 238Pu for plutonium isotope analysis in irradiated... 

Resonant and non-resonant laser post-ionization of sputtered uranium atoms using SIRIS (sputtered initited resonance ionization spectroscopy) and SNMS (secondary neutral mass spectrometry) in one instrument for the characterization of sub-pm sized single microparticles was suggested by Erdmann et al.94 Resonant ionization mass spectrometry allows a selective and sensitive isotope analysis without isobaric interferences as demonstrated for the ultratrace analysis of plutonium from bulk samples.94 Unfortunately, no instrumental equipment combining both techniques is commercially available. 

The nuclear area is one that has been heavily dependent upon isotope ratio mass spectrometry performed by thermal ionization. Applications in this area are among the major reasons for the continued push to analyze smaller and smaller samples. There are two primary reasons for this (1) maximum practicable reduction of the hazards associated with radioactivity and (2) presence of often only a very small amount of the target element available. Areas addressed include evaluation of uranium enrichment processes [86], isotopic analysis of transuranium elements (all elements through einsteinium have been analyzed) [87], and environmental monitoring for release of uranium and other actinides [88,89]. This last area has received renewed emphasis in the wake of the Gulf War [90]. 

Determine counting efficiency of the proportional detector in Step 5 for three 3,000-s periods to measure alpha particles and beta particles. Record in Data Table 7.2. Also perform overnight count (50,000 s) for alpha-particle spectral analysis of the planchet to identify the uranium isotopes and any other radionuclides and to determine their relative amounts from their alpha-particle energy spectra and record results in Data Table 7.2. Count alpha- and beta-particle background in proportional counter and alpha-particle spectral background in spectrometer for at least the same periods. 

In the above analysis we have neglected the plutonium decay products and their associated hazards. All of Pu, Pu and Pu decay to much longer lived and less hazardous uranium isotopes. However, Pu (originally present to 1% in reactor plutonium) decays through Ra, and Pu (originally present to 12%) decays through Both radium and neptunium are of high radio-... 

Figure 6.5a illustrates part of a real mass spectrum of a radioactive waste solution in the mass range 180-250 u measured by double-focusing sector field ICP-MS (ELEMENT, Thermo Fisher Scientific) at low mass resolution. In this mass spectrum, atomic ions of Re at mass 185 u and 187 u with isotope abundances of 37.4% and 62.6%, respectively (Re was used for Tc precipitation), ReO+, ReOj and ReOj+ ions were detected. In particular, the ReOj and ReOjH ions appearing at the mass range 233-236 u affected the isotope analysis of uranium due to isobaric interferences. 

Mass spectrometric techniques play a dominant role for the determination of transuranium elements in bulk samples as well as in microparticles. The radioactive element most frequently investigated by inorganic mass spectrometry is uranium. The determination of the concentrations and the precise isotopic analysis of naturally occurring radioactive elements (e.g. Th and the decay nuclides) by inorganic mass spectrometry as terrestrial... 

The report estimated a lifetime risk of excess bone sarcomas per million people of 1.5 if soluble uranium isotopes were ingested at a constant daily rate of 1 pCi/day (0.037 Bq/day). The number of bone sarcomas that occur naturally in a population of a million people is 750. However, no quantitative risk coefficient estimates for developing human exposure protection benchmarks were provided in this report. In addition, the BEIR IV analysis was presumably based on generic short-lived alpha-emitting sources, such as radon that have a higher potential for inducing cancer, and not on radionuclides with relatively longer radioactive half-lives like and Perhaps more importantly, the BEIR IV report... 

---