Strontium nuclides

The significance of these two strontium nuclides warrants reliable procedures for their analysis. Leaching methods [ 11,12,18] for the determination of radiostrontium in soil are applied to large-size samples for higher sensitivity but they assume that the strontium can be easily solubilised. This assumption is not needed in the procedure described, since the sample is decomposed completely. Also, the procedure can be used to analyze leached residues to check the completeness, and thus the reliability, of leaching procedures when higher sensitivities are needed. 

Half-lives span a very wide range (Table 17.5). Consider strontium-90, for which the half-life is 28 a. This nuclide is present in nuclear fallout, the fine dust that settles from clouds of airborne particles after the explosion of a nuclear bomb, and may also be present in the accidental release of radioactive materials into the air. Because it is chemically very similar to calcium, strontium may accompany that element through the environment and become incorporated into bones once there, it continues to emit radiation for many years. About 10 half-lives (for strontium-90, 280 a) must pass before the activity of a sample has fallen to 1/1000 of its initial value. Iodine-131, which was released in the accidental fire at the Chernobyl nuclear power plant, has a half-life of only 8.05 d, but it accumulates in the thyroid gland. Several cases of thyroid cancer have been linked to iodine-131 exposure from the accident. Plutonium-239 has a half-life of 24 ka (24000 years). Consequently, very long term storage facilities are required for plutonium waste, and land contaminated with plutonium cannot be inhabited again for thousands of years without expensive remediation efforts. 

The abundances of krypton and xenon are determined exclusively from nucleosynthesis theory. They can be interpolated from the abundances of neighboring elements based on the observation that abundances of odd-mass-number nuclides vary smoothly with increasing mass numbers (Suess and Urey, 1956). The regular behavior of the s-process also provides a constraint (see Chapter 3). In a mature -process, the relative abundances of the stable nuclides are governed by the inverse of their neutron-capture cross-sections. Isotopes with large cross-sections have low abundance because they are easily destroyed, while the abundances of those with small cross-sections build up. Thus, one can estimate the abundances of krypton and xenon from the abundances of. v-only isotopes of neighboring elements (selenium, bromine, rubidium and strontium for krypton tellurium, iodine, cesium, and barium for xenon). 

Therefore, the preliminary investigation described herein examined several aspects of the behavior of the equilibrium distribution coefficients for the sorption of rubidium, cesium, strontium, barium, silver, cadmium, cerium, promethium, europium, and gadolinium from aqueous sodium chloride solutions. These solutions initially contained one and only one of the nuclides of interest. For the nuclides selected, values of Kp were then... 

Therefore, based on available literature, the following sorption results were expected (l) as a result of the smectite minerals, the sorption capacity of the red clay would be primarily due to ion exchange associated with the smectites and would be on the order of 0.8 to I.5 mi Hi equivalents per gram (2) also as a result of the smectite minerals, the distribution coefficients for nuclides such as cesium, strontium, barium, and cerium would be between 10 and 100 ml/gm for solution-phase concentrations on the order of 10"3 mg-atom/ml (3) as a result of the hydrous oxides, the distribution coefficients for nuclides such as strontium, barium, and some transition metals would be on the order of 10 ml/gm or greater for solution-phase concentrations on the order of 10 7 mg-atom/ml and less (U) also as a result of the hydrous oxides, the solution-phase pH would strongly influence the distribution coefficients for most nuclides except the alkali metals (5) as a result of both smectites and hydrous oxides being present, the sorption equilibrium data would probably reflect the influence of multiple sorption mechanisms. As discussed below, the experimental results were indeed similar to those which were expected. 

For the nuclides studied (rubidium, cesium, strontium, bariun silver, cadmium, cerium, promethium, europium, and gadolinium) the distribution coefficients generally vary from about 10 ml/gm at solution-phase concentrations on the order of 10 mg-atom/ml to 10 and greater at concentrations on the order of 10 and less. These results are encouraging with regard to the sediment being able to provide a barrier to migration of nuclides away from a waste form and also appear to be reasonably consistent with related data for similar oceanic sediments and related clay minerals found within the continental United States. 

The results of the release measurements are given in Table I as a function of temperature and annealing time. For the unirradiated samples, typical release data for the metallic nuclides are included for comparison. The data clearly show that the releases of iodine and xenon have been unaffected by irradiation. The releases of barium and strontium, on the other hand, have been enhanced by a factor of about five at 8.5% FIMA and 10 at 24% FIMA. These data are interpreted in the... 

Numerous studies by other workers (I, 10) have shown that the releases of iodine and the noble-gas fission products from pyrolytic carbon-coated fuel particles are controlled by diffusion of these nuclides through grain boundaries, cracks, and defects in the isotropic pyrolytic carbon coating. When coatings are intact, however, the release of these fission product nuclides is low. However, the pyrolytic carbon coating constitutes only a delaying barrier to the metallic nuclides barium and strontium through which they diffuse with diffusion coefficients of the order of 10 9 cm.2/sec. (at — 1400°C.). The steady-state release of these metallic nuclides is controlled instead by diffusion out of the fuel kernel,... 

The most important chemical parameter affecting the deposition and subsequent mobility of radioactive aerosols, such as the nuclides 90Sr and 137Cs examined in this study, is their solubility in rainwater. If these aerosols are dissolved in precipitation, the main factor in their transport is the movement of the rainwater, not the transport of insoluble aerosol particles. Huff and Kruger (2) examined the solubility products of strontium and chemically similar compounds which may carry trace amounts of 90Sr, and they estimated that strontium should be soluble in precipitation. Solubility tables also indicate that cesium compounds likely to exist in precipitation should be soluble. It was noted that the possibility did exist that some of the fission product "Sr and 137Cs might be bound within the structure of insoluble natural aerosols or nuclear weapon debris. 

There are special extractants to extract each class of radionuclides crown ethers for cesium and strontium and phosphine oxides, carbamoylmethylphosphine oxides, and diamides for actinides, etc. It is unrealistic to have a single extractant that can extract all target nuclides with nearly the same effectiveness. So, a promising technical decision is to mix extractants for different radionuclides and extract them simultaneously. 

Modifications to this process can be made to effect recovery of neptunium, americium, curium, californium, strontium, cesium, technetium, and other nuclides. The efficient production of specific transuranic products requires consideration of the irradiation cycle in the reactor and separation of intermediate products for further irradiation. 

The chemical properties of the radiation source. When a radioactive nuclide is ingested into the body, its effectiveness in causing damage depends on its residence time. For example, f Kr and gSr are both /3-particle producers. However, since krypton is chemically inert, it passes through the body quickly and does not have much time to do damage. Strontium, being chemically similar to calcium, can collect in bones, where it may cause leukemia and bone cancer. 

The assay of low-level strontium-90 in biological and radiotoxicological samples requires time-consuming and laborious techniques because both the nuclide Sr and its daughter Y are pure beta-ray emitters. Therefore, the radiostrontium must be completely separated from other radionuclides prior to the beta-ray counting. 

The extraction of transuranic elements has been made by co-precipi-tation in several ways (5,6). We use either one of two methods, depending on what other nuclides are also sought in the sample. The first method is co-precipitation with 0.5-1.0 g iron as hydroxide at pH 9-10 using ammonium hydroxide while the second method is co-precipitation with calcium and strontium oxalate at pH 5-6 using oxalic acid. There are about 22 g calcium and 0.44 g strontium in 55 1. of open-ocean seawater. Because Sr is usually measured in the same seawater sample, we normally add 2 g strontium to that which is naturally present. 

A radioisotope battery is one of the choice for energy source of meteorological obseiwation and development of undersea and space[l]. We have considered a strontium-90 (half-life 28.8y) heat-source model of a radioisotope battery and improved it in two aspects—radiation dose reduction and improvement of thermal conductivity—adding graded structure to the model[2]. The present study reports the dose reduction of bremsstrahlung photons from -ray of - "Sr and its daughter nuclide yttrium-90. The calculation was carried out by a continuous energy Monte Carlo code, MCNP 4A[3]. 

Rosner G, Hotzl H, Winkler R. 1990. Simultaneous radiochemical determination of plutonium, strontium, uranium, and iron nuclides and application to atmospheric deposition and aerosol samples. Fresenius J Anal Chem 338 606-609. 

Some radioactive nuclides are especially damaging because they tend to concentrate in particular parts of the body. For example, because both strontium and calcium are alkaline earth metals in group 2 on the periodic table, they combine with other elements in similar ways. Therefore, if radioactive strontium-90 is ingested, it concentrates in the bones in substances that would normally contain calcium. This can lead to bone cancer or leukemia. For similar reasons, radioactive cesium-137 can enter the cells of the body in place of its fellow alkali metal potassium, leading to tissue damage. Non-radioactive iodine and radioactive iodine-131 are both absorbed by thyroid glands. Because iodine-131 is one of the radioactive nuclides produced in nuclear power plants, the... 

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