Radiation irradiator attacks

All patients from the site of an irradiator attack should be evaluated for radiation sickness, and a health physicist or medical physicist should be consulted to attempt to determine the radiation dose to each patient. If the patient is conscious, it is essential to get as much information as possible about their exact location, travel paths, and the amount of time they spent in each place near the site of the irradiator. For example, if an irradiator is placed in an elevator, persons working on the 50th floor of a high-rise will generally receive more radiation dose than patients on lower levels. On the other hand, a person who has a nonstop ride to an upper level may receive fewer doses than one whose trip to the 10th... 

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. 

When a PVC film is exposed to the UV-visible radiation of an incandescent lamp in the presence of pure chlorine, at room temperature, the chlorine content of the polymer increases from 56.8 % initially to over 70 I after a few hours of irradiation (8). As the reaction proceeds, the rate of chlorination decreases steadily as shown by the kinetic curves of figure 2, most probably because of the decreasing number of reactive sites on the polymer chain that remain available for the attack by chlorine radicals. 

The importance of OH radicals in atmospheric chemistry is the basis of another reactivity scale for organics that do not photolyze in actinic radiation (Darnall et al., 1976 Wu et al., 1976). This scale is based on the fact that, for most hydrocarbons, attack by OH is responsible for the majority of the hydrocarbon consumption, and this process leads to the free radicals (H02, R02) that oxidize NO to N02, which then leads to 03 formation. Even for alkenes, which react with 03 at significant rates, consumption by OH still predominates in the early portion of the irradiation before 03 has formed. It has therefore been suggested that the rate constant for reaction between OH and the... 

For low radiation doses, peroxides accumulate almost linearly with dose. However, after a certain dose has been reached, their concentration tends to level off. This conclusion can be derived from the observed change in the rate of graft copolymerization initiated by polymers subjected to increasing doses of preirradiation in air. Figure 2 illustrates this effect in the case of grafting acrylonitrile onto polyethylene (2). The drop in the yield of peroxide production presumably results from the efficient radiation-induced decomposition of these peroxides. Peroxides are known to decompose under free radical attack, and selective destruction of peroxides under irradiation has been established experimentally (8). This decomposition can become autocatalytic, and sometimes the concentration of peroxides may reach a maximum at a certain dose and decrease on further irradiation. Such an effect was observed in the case of poly (vinyl chloride). Figure 3 shows the influence of preirradiation dose on the grafting ratio obtained with poly (vinyl chlo-... 

Track-etch membranes were developed by the General Electric Corporation Schenectady Laboratory [3], The two-step preparation process is illustrated in Figure 3.4. First, a thin polymer film is irradiated with fission particles from a nuclear reactor or other radiation source. The massive particles pass through the film, breaking polymer chains and leaving behind a sensitized track of damaged polymer molecules. These tracks are much more susceptible to chemical attack than the base polymer material. So when the film is passed through a solution... 

Many groundwaters are contaminated with the cleaning solvents trichloroethylene (TCE) and perchloroethylene (PCE). They are two of the most common organochlorine compounds found in Superfund sites. Radiation-induced decomposition of TCE in aqueous solutions has been the subject of several recent studies [15-20]. In most of the referenced studies, the complete destruction of TCE was observed. Dechlorination by a combination of oxidative and reductive radiolysis was stoichiometric. Gehringer et al. [15] and Proksch et al. [18] have characterized the kinetics and mechanism of OH radical attack on TCE and PCE in y-ray-irradiated aqueous solution. Trichloroethylene was readily decomposed in exponential fashion, with a reported G value of 0.54 pmol J-1. A 10 ppm (76 pM) solution was decontaminated with an absorbed dose of less than 600 Gy. For each OH captured, one C02 molecule, one formic acid molecule and three Cl- ions were generated. These products were created by a series of reactions initiated by OH addition to the unsaturated TCE carbon, which is shown in Eq. (45) ... 

Radiotherapeutics attack cancer by causing radiation damage to DNA in cells. The requirements differ from those for drug delivery because the radiotherapeutic can act at a distance and does not have to separate from the delivery particle. Radiotherapeutics can be selected to provide action over a range of distances, from tens of nanometers to hundreds of microns. Three radiotherapy modalities can be identified. Brachytherapy, most often used with beta-emitters, uses tightly enclosed radioactive material that is brought in close proximity to the tumor. A second modality is intravenous injection so that the radiopharmaceutical binds to the outside of the tumor cells or is taken up by the cell and irradiates from within. The third approach uses a carrier loaded with the radiotherapeutic that is transported to the vicinity of the target cells, and then released. 

Ceramic membranes are quite important since microporous ceramics are the principal barrier in UFe separation. Similar devices are used for microfiltration membranes and to a lesser extent for ultrafiltration. Homogeneous films are transformed into microporous devices by irradiation followed by selective leaching of the radiation damaged tracks, by stretching (Cortex is one welldmown example), or by electrochemical attack on aluminum. A few membranes are made by selective leaching of one component from a solid, as in membranes derived from glass or by selective extraction of polymer blends. 

During irradiation of methanol-water mbctures, formaldehyde is formed in yields proportional to the number of alcohol molecules exposed to radiation. Excess of the dimer (ethylene glycol) was formed—no doubt as a result of attack by free radicals formed during the primary radiolysis of water. 

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