Radiation, effect

Exposure of silicate glasses to high energy radiation usually results in compaction of the glass, with density increases in the order of 1% 

Most studies have dealt exclusively with vitreous silica, which compacts by only a few hundred ppm at doses as great as 10 rad. Some commercial borosilicate glasses compact up to 40 times as much as vitreous silica for comparable radiation doses. Limited data for alkaline earth aluminosilicate glasses suggests that they expand slightly under these same conditions. 

The radiation-induced compaction of vitreous silica can be reversed by saturating the sample with molecular hydrogen prior to irradiation. After irradiation, the sample is found to expand by a few hundred ppm (doses of 10 ° rad). Large quantities of Si-OH and Si-H bonds are formed in the irradiated glasses. Apparently the production of the broken bonds, due to formation of bound hydrogen species, allows the structure to relax and expand, reducing the density. 

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Radiation Effects. Polytetrafluoroethylene is attacked by radiation. In the absence of oxygen, stable secondary radicals are produced. An increase in stiffness in material irradiated in vacuum indicates cross-linking (84). Degradation is due to random scission of the chain the relative stabiUty of the radicals in vacuum protects the materials from rapid deterioration. Reactions take place in air or oxygen and accelerated scission and rapid degradation occur. 

Radiation Effects. The primary effect of radiation is the degradation of large molecules to small molecules. Molecular weight reduction can be... 

Optical Properties and Radiation Effects. Within the range of wavelengths measured (uv, visible, and near-ir radiation), Teflon PFA fluorocarbon film transmits slightly less energy than FEP film (29) (Table 6). In thin sections, the resin is colorless and transparent in thicker sections, it becomes translucent. It is highly transparent to it radiation uv absorption is low in thin sections. Weather-O-Meter tests indicate unlimited outdoor life. 

Nuclear Radiation Effects. Components of a nuclear reactor system that require lubrication include control-rod drives, coolant circulating pumps or compressors, motor-operated valves, and fuel handling devices, and, of course, are exposed to varying amounts of ionising (14). 

Y. Shimizu and co-workers, "Life Span Study Report 11, Part 1, Comparison of Risk Coefficients for Site-Specific Cancer MortaUty," Technical Report RERF-TR-12-87, Radiation Effect Research Foundation, Hiroshima, Japan, 1987. 

Pulsed plasmas containing hydrogen isotopes can produce bursts of alpha particles and neutrons as a consequence of nuclear reactions. The neutrons are useful for radiation-effects testing and for other materials research. A dense plasma focus filled with deuterium at low pressure has produced 10 neutrons in a single pulse (76) (see Deuterium AND TRITIUM). Intense neutron fluxes also are expected from thermonuclear fusion research devices employing either magnetic or inertial confinement. 

A. B. BriU, Eow-Eevel Radiation Effects A.Fact Book, The Subcommittee on Risks ofEow-Eevelloni ng Raidiation, The Society of Nuclear Medicine, New... 

Pentoxifylline is stmcturaHy related to other methylxanthine derivatives such as caffeine [58-02-2] (1,3,7-trimethylxanthine), theobromine [83-67-0] (3,7-dimethylxanthine), and theophylline [58-55-9] (3,7-dihydro-1,3-dimethyl-1 H-piirine-2,6-dione or 1,3-dimethylxanthine), which also show radioprotective activity in some instances, suggesting that methylxanthines as a dmg class may radioprotect through a common mechanism (see Alkaloids). In a retrospective analysis of cervical and endometrial cancer patients receiving primary or adjuvant XRT, no association between caffeine consumption and incidence of acute radiation effects has been found. However, there was a decreased incidence of severe late radiation injury in cervical cancer patients who consumed higher levels of caffeine at the time of thek XRT (121). The observed lack of correlation between caffeine consumption and acute radiation effects is consistent with laboratory investigations using pentoxifylline. 

Space-based solar ceUs are covered with a very thin layer of vitreous siHca to protect against the damaging environment of space such as atomic oxygen, micrometeorites, and radiation effects. Because the siHca is transparent to damaging uv radiation, it is normally coated with a uv-reflective thin film... 

Radiation Effects. Alpha sihcon carbide exhibits a small degree of anisotropy in radiation-induced expansions along the optical axis and perpendicular to it (58). When diodes of sihcon carbide were compared with sihcon diodes in exposure to kradiation with fast neutrons (59), an increase in forward resistance was noted only at a flux about 10 times that at which the increase occurs in a sihcon diode. In general, it appears that sihcon carbide, having the more tightly bound lattice, is less damaged by radiation than sihcon. 

Volume of vessel (free volume V) Shape of vessel (area and aspect ratio) Type of dust cloud distribution (ISO method/pneumatic-loading method) Dust explosihility characteristics Maximum explosion overpressure P ax Maximum explosion constant K ax Minimum ignition temperature MIT Type of explosion suppressant and its suppression efficiency Type of HRD suppressors number and free volume of HRD suppressors and the outlet diameter and valve opening time Suppressant charge and propelling agent pressure Fittings elbow and/or stub pipe and type of nozzle Type of explosion detector(s) dynamic or threshold pressure, UV or IR radiation, effective system activation overpressure Hardware deployment location of HRD suppressor(s) on vessel... 

This accident has the potential to seriously injure 50 people because of blast overpressure and thermal radiation effects. 

In order to compute the thermal radiation effects produced by a burning vapor cloud, it is necessary to know the flame s temperature, size, and dynamics during its propagation through the cloud. Thermal radiation intercepted by an object in the vicinity is determined by the emissive power of the flame (determined by the flame temperature), the flame s emissivity, the view factor, and an atmospheric-attenuation factor. The fundamentals of heat-radiation modeling are described in Section 3.5. 

Radiation effects, as well as combustion behavior, were measured. LNG and refrigerated liquid propane cloud fires exhibited similar surface emissive power values of about 173 kW/m. ... 

Zeeuwen et al. (1983) observed the atmospheric dispersion and combustion of large spills of propane (1000-4000 kg) in open and level terrain on the Musselbanks, located on the south bank of the Westerscheldt estuary in The Netherlands. Thermal radiation effects were not measured because the main objective of this experimental program was to investigate blast effects from vapor cloud explosions. 

Radiation effects from a flash fire are now fully determined if vapor cloud composition, as well as the geometry of the flame front (dependent on time), is known. Vapor cloud composition is, of course, place- and time-dependent, and the shape of flame front will greatly depend on cloud shape and ignition site within the cloud. The total radiation intercepted by an object equals the surmnation of contributions by all successive flame positions during flame propagation. This is an impossible value to compute with the simplified approach just described. Because there are many uncertainties (e.g., cloud composition, location of ignition site) which greatly influence the final result, a conservative approach is recommended for practical applications ... 

The curve, however, seems to indicate the tendency of a fireball s emissive power to rise as its diameter grows. The results of the experiments described above reveal that the fireball properties of greatest influence on radiation effects are ... 

Radiation effects from a fireball of the size calculated above, and assumed to be in contact with the ground, have been calculated by Pietersen (1985). A fireball duration of 22 s was calculated from the formula suggested by Jaggers et al. (1986). An emissive power of 350 kW/m was used for propane, based on large-scale tests by British Gas (Johnson et al. 1990). The view factor proposed in Section 6.2.5. 

In this chapter, applications of the calculation methods used to predict the hazards of BLEVEs, as described in Chapter 6, are demonstrated in the solution of sample problems. Fire-induced BLEVEs are often accompanied by fireballs hence, problems include calculation of radiation effects. A BLEVE may also produce blast waves and propel vessel fragments for long distances. The problems include calculations for estimating these effects as well. Calculation methods for addressing each of these hazards will be demonstrated separately in the following order radiation, blast effects, and fragmentation effects. 

A liquefied propane tank truck whose volume is 6000 U.S. gallons (22.7 m ) is involved in a traffic accident, and the tank truck is engulfed by fire from burning gasoline. The tank is 90% filled with propane. Assume that all of the propane will contribute to the fireball. Radiation effects are calculated below blast and fragmentation effects for this problem will be calculated in Sections 9.2 and 9.3, respectively. 

This appendix is a summary of the woiit published in the so-called Green Book (1989). Possible effects of explosions on humans include blast-wave overpressure effects, explosion-wind effects, impact from fragments and debris, collapse of buildings, and heat-radiation effects. Heat-radiation effects ate not treated here see Chapter 6, Figure 6.10 and Table 6.6. 

The response of humans to var> ing doses of radiation is a field tlmt has been widely studied. The obscr ed radiation effects can be categorized as stochastic or nonstochastic effects, depending upon tlie dose received and tlie time period over which such dose was received. Contrary to most biological effects, effects from radiation usually fall under tlie category of stochastic effects. The nonstochastic effects can be noted as having three qualities a minimum dose or tlucshold dose must be rcceii ed before the particular effect is obsen ed the magnitude of the effect increases as the size of the dose increases and a clear, casual relationship can be determined between the dose and the subsequent effects. 

The response of humans to varying doses of radiation is a field that has been widely studied. The observ ed radiation effects can be categorized as... 

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). 

Neutron Radiation. See under Radiation Effects on Explosives, Propellants and Pyrotechnics... 

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