Elements gaseous radioactive products

A small percentage of the fuel elements in a water-cooled reactor release gaseous fission products to the coolant. The insoluble noble gases are collected and stored for radioactive decay prior to their release to the atmosphere. Calculate the required storage time such that the radioactivity levels of Xe and Kr in the released gas are equal. Assume fissions at constant power only in an average irradiation time of 2 years, and assume that these noble gas radionuclides are released to the coolant in the same proportion as they exist within the fuel. Obtain mass yields from Table 2.9. Twenty-three percent of the fissions at mass 85 produces Ki. 

Nuclear power engineering is the main source of gaseous radioactive wastes. They are released from fuel assemblies, which have become non-gas-tight during the operation, and further from a residual contamination of the surface of fuel elements resulting from the production and from the activation of the primary coolant and its admixtures. The contributions from these sources are remarkably variable, depending on the type of the... 

If we look at the burnt fuel pellets on a microscopic level, we can see that analysis of the material is complicated. The formation of fission products in the pellet causes defects that arise from gaseous fission products like xenon that result in microscopic bubble-like pores. The radioactive decay of short-lived xenon isotopes leads to formation of cesium and other fission products that may be inside these pores. Furthermore, the temperature gradient inside the pellet causes the more volatile fission products to migrate to the cooler parts at the edge of the pellet, while less volatile elements migrate to the center. Total dissolution of a pellet (or better yet, several pellets) can yield a representative sample that can be characterized analytically, but care must be practiced to prevent the loss of gaseous products. 

It had been observed already that the radioactive minerals on heating give off Helium — a gaseous element, characterised by a particular yellow line in its spectium — and it seemed not unlikely that helium might be the ultimate decomposition product of the emanation. A research to settle this point was undertaken by Sir William Ramsay and Mr. Soddy, and a preliminary experiment having confirmed the above speculation, they carried out further very careful experiments. "The maximum amount of the emanation obtained from 50 milligrams of radium bromide was conveyed by means of oxygen into a U-tube cooled in liquid air, and the latter was then extracted by the pump." The spectrum... 

The basic idea in developing quick and efficient methods and techniques for TAEs was immediate, and continuous chemical processing of the nuclear reaction products in gaseous phase to obtain volatile compound(s) of the element under study. These had to be isolated from nonvolatile compounds of other elements and transported to detectors of radioactivity. 

The term radon means the radioactive gaseous element and its shortlived decay products produced by the disintegration of the element radium occurring in air, water, soil, or other media. 

Based on measurements of air filters from 1965 to 1967 and rainwater samples from 1967, the Tc/ Cs ratio seems to be a factor of 10 higher than expected from the fission yield. The anomalous ratios of fission products observed in the atmosphere may partly be explained by fractionation of radionuclides during the detonation process. The precursors of Cs are gaseous or volatile elements, i.e., xenon and iodine, while the precursors of T c are refractory elements, i.e., zirconium and niobium, which are usually incorporated in radioactive particles. Thus, the Tc/ Cs ratio in the atmosphere may decrease with time after detonation due to the deposition of large radioactive particles. For deposited material releases of Tc with time should be expected due to weathering of particles. Howevei we cannot, at this stage, exclude additional sources contributing to releases of Tc to the atmosphere. 

Dorn, Friedrich Ernst (1848-1916) German chemist who discovered the chemically almost inert, but medically dangerous, radioactive gaseous element radon, a noble gas, and showed that it arose as a decay product of radium. 

These exist or existed as intermediate products in radioactive decay series. It does not mean that they are unimportant The gaseous element radon may, as is well known, be present as a dangerous air pollutant in houses built on radioactive ground. Because the element is gaseous the radioactivity can be removed by ventilation. 

Principal gaseous products from fission and radioactive decay are xenon, krypton, and helium. Using the SCALE/ORIGEN program, the whole core inventories of these elements after 10 years of operation were estimated to be 217 g of xenon, 24 g of krypton, and 1 mg of helium. A considerable amount of these elements would be expected to be entrained in the foam. Consequently, a core clad breach due to pressurization is not credible, and consequences of clad mpture would be relatively insignificant as compared to a commercial power reactor. 

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