Hardness radiation effects

In treated water for high-pressure boilers or where radiation effects are important, as in some nuclear projects, impurities are measured in very small units (e.g. g/litre or p.p. 10 ), but for most purposes it is convenient to express results in mg/litre. In water analysis, determinations (except occasionally for dissolved gases) are made on a weight/volume basis but some analysts still express results in terms of parts per million (p.p.m.). The difference between mg/litre and p.p.m. is small and for practical purposes the two units are interchtmgeable. For some calculations, the use of milli-equivalents per litre or equivalents per million (e.p.m.) has advantages but has not found much application. Hardness, whatever the constituent salts, is usually expressed as p.p.m. CaCOs (see Table 2.10). 

In inorganic and organometallic solids, the average electron concentration tends to be high. This means that absorption and extinction effects can be severe, and that the use of hard radiation and very small crystals is frequently essential. Needless to say that the advent of synchrotron radiation has been most helpful in this respect. The weaker contribution of valence electrons compared with the scattering of first-row-atom-only solids implies that great care must be taken during data collection in order to obtain reliable information on the valence electron distribution. 

Collection of diffraction data at liquid-helium temperatures is important to reduce thermal motion and its anharmonicity. Similarly, the use of shorter wavelengths at such low temperatures makes data at higher values of sin 6/X accessible, which facilitates deconvolution of thermal motion and bonding effects. Both very low temperatures and hard radiation are becoming more readily available, and are expected to play a crucial role in future studies. 

Lumpkin, G. R., Chakoumakos, B. C. Ewing, R. C. 1986. Mineralogy and radiation effects of microlite from the Harding pegmatite, Taos County, New Mexico. American Mineralogist, 71, 569-588. 

In real-world applications, the importance of interfaces is hard to overestimate and three chapters are devoted to the effects of radiation at aqueous-solid boundaries. Jonsson focuses on applications within the nuclear industry where basic studies on radiation effects at water-metal interfaces have enabled a proposal for safe storage of spent nuclear fuel. Also with implications for the nuclear industry, Musat et al. document alterations in the radiation chemistry of liquid water confined on the nanoscale. Such nanoconfmed solutions are prevalent in the media proposed and indeed in use for waste storage. In another application, radiation chemistry has successfully been used to produce nanoscale objects such as metallic clusters and nanoparticles, an area summarized by Remita and Remita. 

Oliver WC, McCallum JC, Chakoumakos BC, Boatner LA (1994) Hardness and elastic modulus of zircon as a function of heavy-particle irradiation dose II. Pb-ion implantation damage. Radiation Effects Defects in Solids 132 131-141... 

Hi) Other readions. Although the hydrogenation of ethylene is an obvious reaction for the exploration of radiation effects on catalysts, it has been little used with silica, probably because it is too slow. Unirradiated silica gel appears completely inactive, and irradiation to a dose around 2 x lO ev/gm gave a material producing equilibration in 4 days at room temperature (1 gm catalyst, 200 torr gas mixture in 30 cm ). The half-time can hardly be less than several hours, since an irradiation to 2 X 10 ev/gm gave no detectable increase in activity (69). 

Addition of dimethylformamide makes it possible to achieve essential increase in monoohlorobenzene yield. In this case the total current efficiency of the benzene chlorination products is 9056, 3B-33% substance yield, while the chlorobenzene current efficiency 15%. This effect mi t have been concerned with the enhancement of benzene solubility in the water phase. Furthermore dimethylformamide depresses side processes, concerned v/ith both electrochemical conversion of chlorine, formed on the electrodes and formation of dichlorobenzene. As fair as chlorination of benzene derivatives to the side oliain is concerned, the factors that influence the chemical chlorination (UV and more hard radiation, the presence of different initiators of free radicals formation) favorably affect the isolation of benzyl chloride, o-, m-, p-xylylchloric -. The current efficiency is more than 85%. 

Additional work was performed by Gardner (Refs 92 99) on proplnts for future missions in space. A PBAA AP/Al proplnt, an aluminized double-base proplnt, and a polyurethane—AP/Al proplnt were studied as a function of Co radiation, with a dose rate of 2.54 x 10 R/hr and total doses ranging up to 1.5 x 10 R. The effects were noted on tests with the burning rate, tensile stress, elongation modules and hardness of the three materials. The PBAA proplnt withstood 1.5 X lO R. On the tensile strength, the double base and polyurethane decrease significantly at a dose of 4 x 10 R. On elongation, the double base decreased on stress at max strain after 10 R, while the polyurethane pro-pint decreased on modulus and hardness after a dose of 10 R. Estimates of the radiation effects on polymers are listed in Table 19... 

Radiation effects and oxidation causes changes in the tensile properties of the canning material. Fresh fuel has a can that is very ductile whereas the can of spent high bum-up fuel normally is hard and brittle. 

The concentrations of various substances in water in dissolved, colloidal, or suspended form are typically low but vary considerably. A hardness value of up to 400 ppm of calcium carbonate, for example, is sometimes tolerated in public supplies, whereas 1 ppm of dissolved iron would be imacceptable. In treated water for high-pressure boilers or where radiation effects are important, as in nuclear reactors, impurities are measured in very small units such as parts per billion (ppb) or 1 /ig of contaminant per hter of water. Water analysis for drinldng water supplies is concerned mainly with pollution and bacteriological tests. For industrial supphes a mineral analysis is of more interest The important constituents can be classified as follows [9] ... 

The first complication to be considered is the presence of an electrostatic field during the mass spectrometric study of the reaction. Only few quantitative studies have allowed for the possible contribution of hard collisions to cross-section (25), and the possibility that competitive reactions of the same ion may depend on ion energy is generally neglected in assigning ion-molecule reaction sequences. These effects, however, do not preclude qualitative application of mass spectrometric results to radiation chemistry. 

In addition to emitting electrons, a solid bombarded with ions in the keV range emits electromagnetic radiation from the near infrared to the near ultraviolet, with a photon yield of typically KT4 per incident ion for a metal, and 10 2 to 10 l for insulators. If the primary beam is intense, as in the dynamic SIMS range, and the sample is an insulator, one observes a bright glow at the point where the beam hits the sample. With conductors, the effect is not or hardly observable. 

After a few years of operation there was a significant increase in radiation fields from the primary circuit piping in the Douglas Point generating station. Other water-cooled reactors around the world experienced similar effects. The principal source of the radioactivity was traced to cobalt-60, formed by neutron absorption in the natural cobalt-59 which arose from hard-facing alloys and was also present as an impurity in boiler materials such as HMDnel, and in carbon steel and other structural materials. The mechanism of this radioactivity transport was found to be corrosion of the cobalt bearing materials, transport... 

Monchick [36, 273] has used the diffusion equation and radiation boundary conditions [eqns. (122) and (127)] to discuss photodissociative recombination probabilities. His results are similar to those of Collins and Kimball [4] and Noyes [269]. However, Monchick extended the analysis to probe the effect of a time delay in the dissociation of the encounter pair. It was hoped that such an effect would mimic the caging of an encounter pair. Since the cage oscillations have periods < 1 ps, and the diffusion equation is hardly adequate over such times (see Chap. 11, Sect. 2), this is a doubtful improvement. Nor does using the telegraphers equation (Chap. 11, Sect. 3.3) help significantly as it is only valid for times longer than a few picoseconds. 

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