Radioactive cesium

Approximately 25—30% of a reactor s fuel is removed and replaced during plaimed refueling outages, which normally occur every 12 to 18 months. Spent fuel is highly radioactive because it contains by-products from nuclear fission created during reactor operation. A characteristic of these radioactive materials is that they gradually decay, losing their radioactive properties at a set rate. Each radioactive component has a different rate of decay known as its half-life, which is the time it takes for a material to lose half of its radioactivity. The radioactive components in spent nuclear fuel include cobalt-60 (5-yr half-Hfe), cesium-137 (30-yr half-Hfe), and plutonium-239 (24,400-yr half-Hfe). 

The properties of hydrated titanium dioxide as an ion-exchange (qv) medium have been widely studied (51—55). Separations include those of alkaH and alkaline-earth metals, zinc, copper, cobalt, cesium, strontium, and barium. The use of hydrated titanium dioxide to separate uranium from seawater and also for the treatment of radioactive wastes from nuclear-reactor installations has been proposed (56). 

Barium titanate thin films can be deposited on various substances by treating with an aqueous solution containing barium salts and an alkanolamine-modifted titanate such as TYZOR TE (151). In a similar fashion, reaction of a tetraalkyl titanate with an alkah metal hydroxide, such as potassium hydroxide, gives oxyalkoxide derivatives (KTi O(OR) ), which can be further processed to give alkali metal titanate powders, films, and fibers (152—155). The fibers can be used as adsorbents for radioactive metals such as cesium, strontium, and uranium (156). 

Zirconium phosphate [13772-29-7] also absorbs cesium and other radioactive-decay daughter products, and has been proposed as part of permanent disposal systems for nuclear fuel waste processing. 

It has been suggested that cesium may be useflil in the fixation of radioactive waste in a cesium-based glass and in detoxification procedures for fugitive Cs emissions, such as at Chernobyl, Ukraine. 

NatuiaUy occuiiing cesium and cesium mineials consist only of the stable isotope Cs. The radioactive cesium isotopes such as Cs are generated in fuel rods in nuclear power plants (38). 

Cesium isotopes can be recovered from fission products by digestion in nitric acid, and after filtration of waste the radioactive cesium phosphotungstate is precipitated using phosphotungstic acid. This technique can be used to prepare radioactive cesium metal or compounds. Various processes for removal of Cs isotopes from radioactive waste have been developed including solvent extraction using macrocycHc polyethers (62) or crown ethers (63) and coprecipitation with sodium tetraphenylboron (64). 

Strongly radioactive, short-lived element that can be found in tiny amounts in uranium ores. It arises fleetingly from 235U in its decay chain through actinium (227Ac). Is only of scientific value as it has a maximum half-life of about 22 minutes. Nevertheless, in its short existence it is the atom with the largest diameter (0.270 nm cesium 0.265 nm). 

Pavlotskaya, F. I., Surotkevichiene, R. and Levina, G. P. (1974). State of strontium-90, cesium-137 and cerium-144 in radioactive fallout, page 111 in Nuclear Meteorology, Report No. TT-74-50011, also Report No. CONF-690670, Makhon ko, K. P. and Malakhov, S. G., Eds. (National Technical Information Service, Springfield, Virginia). 

Cadwell, L.L., R.G. Schreckhise, and R.E. Fitzner. 1979. Cesium-137 in coots (Fulica americana) on Hanford waste ponds contribution to population dose and offsite transport estimates. Pages 485-491 in Low-Level Radioactive Waste Management Proceedings of Health Physics Society. Twelfth Midyear Topical Symposium. February 11-15, 1979, Williamsburg, VA. 

Common radioactive material in use today includes the alpha emitters Americium-241 and Plutonim-238 the beta emitters Phosporus-32 and Strontium-90 and the gamma emitters Cesium-137, Cobalt-60, and Iridium-192 [44], These materials are commonly used in smoke detectors, oil exploration, industrial gauges, food and mail irradiation, cancer therapy, industrial radiography, and in research laboratories. 

Another application for adsorption of metal impurities is in the nuclear power industry. Radioactive cesium is one of the compounds that is difficult to remove from radioactive waste. This is because ordinary resins and zeolites do not effectively adsorb radioactive cesium. In 1997, lONSlV lE-911 crystalline silicotitan-ate (CST) ion exchangers were developed and effectively used to clean up radioactive wastes in the Melton Valley tanks at Oak Ridge [268, 269], CST was discovered [270] by researchers at Sandia National Laboratories and Texas A M University, with commercial manufacture carried out by UOP. 

They produce distinctive colored flames when burned lithium = crimson sodium = yellow potassium = violet rubidium = purple cesium = blue and the color of francium s flame is not known. Many of francium s characteristics have not been determined owing to the fact that it is rare and all of its many radioactive isotopes have short half-lives. 

ISOTOPES Cs-133 is the only stable isotope of cesium, and it makes up all of the naturally occurring cesium found in the Earth s crust. In addition to Cs-133 there are about 36 radioactive isotopes of Cs, most of which are artificially formed in nuclear reactors. All are produced in small numbers of atoms with relatively short half-lives. The range of Cs isotopes is from Cs-113 (amu = 112.94451) to Cs-148 (amu = 147.94900). Most of these radioisotopes produce beta radiation as they rapidly decay, with the exception of Cs-135, which has a half-life of 3x10 yr, which makes it a useful research tool. Cs-137, with a half-life of 33 years, produces both beta and gamma radiation. 

In 1960 the International Committee of Weights and Measures selected radioactive cesium-137 (with a half-life of about 33 years) as the standard for measuring time. They equated the second with the radiation emitted by a Cs-137 atom that is excited by a small energy source. Thus, the second is now defined as 9,192,631,770 vibrations of the radiation emitted by an atom of Cs-137. There are about 200 atomic clocks around the world that collaborate their efforts to maintain this extremely accurate clock that never needs winding or batteries. 

Francium s atoms are the largest and heaviest of the alkali metals in group 1 (lA). It is located just below cesium on the periodic table, and thus it is assumed to be an extremely reactive reducing agent even though it is the most scarce of the alkali metals. Its most stable isotope (Fr-223) exists for about 21 or 22 minutes. No one has figured out how to refine francium from natural minerals (ores) because the atoms of the most stable isotope found in nature (Fr-223) are scattered very thinly over the Earth s crust. All of the other 30 isotopes are produced for study by nuclear decay of other radioactive elements. 

Cesium is used as a getter in electron tubes. Other applications are in photoelectric cells ion propulsion systems heat transfer fluid in power generators and atomic clocks. The radioactive Cs-37 has prospective applications in sterilization of wheat, flour, and potatoes. 

Some radioactive metals (e.g., cesium) are highly volatile under Q-CEP operating conditions. Predrying may be required for liquids with high water contents. Solids may require shredding or milling prior to treatment. Extensive treatment of off-gases is required. 

Process pH, sodium, calcium, and nitrate concentrations, plugging of the ion exchange column, lot variance, and the presence of binders can affect process efficiency. lonsiv IE-911 does not remove anionic radioactive ions such as technetium. The resins are designed for one-time use and must be replaced when loaded. The waste acceptance criteria at the resin disposal facility may limit the loading of the CST resin. Size constraints of the cesium removal system (CRS) may limit system flow rates. 

Researchers claim that lonsiv TIE-96 can remove 99.9% of the plutonium, strontium, and cesium from waste solutions, allowing for wastes to be divided into separate low-level and high-level radioactive waste streams, where they can be safely and efficiently processed for disposal. 

Sediments in the Mississippi River were accidentally contaminated with a low-level radioactive waste material that leaked from a nuclear power plant on the river. Pore water concentrations of radioactive compounds were measured following the spill and found to be 10 g/m over a 2-mm depth. The water contamination was 30% radioactive cesium ( Cs), with a half-life of 30 years, and 70% radioactive cobalt ( °Co), with a half-life of 6 years. Objections by the local residents are preventing clean-up efforts because some professor at the local state university convinced them that dredging the sediments and placing them in a disposal facility downstream would expose the residents to still more radioactivity. The state has decided that the sediments should be capped with 10 cm of clay and needs a quick estimate of the diffusion of radioactive material through the clay cap (Figure E2.8.1). If the drinking water limit (10 g/m ) is reached at mid-depth in the cap, the state will increase its thickness. Will this occur ... 

Relevant Data. For radioactive cesium and cobalt, =1 x. 10 and 10, respectively. Assume Pb/e= 6 g/cm for clay under low compressive force. The coUoidal concentration in the interstitial water is 10 mg/m ( o.g/L). The foUowing assumptions wiU help to achieve our estimate ... 

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