Radiation case histories

This chapter describes the main features of vapor cloud explosions, flash fires, and BLEVEs. It identifies the similarities and differences among them. Effects described are supported by several case histories. Chapter 3 will present details of dispersion, deflagration, detonation, ignition, blast, and radiation. 

We turn now to concrete examples of the interplay between photochemical and radiation chemical techniques in the form of case histories taken mainly from our work at Brookhaven National Laboratory. 

Appelman has reviewed the case history of HOF, the recently isolated non-existent molecule, which may well be the reactive species formed when F2 reacts with water. The photoelectron spectrum of this unstable compound has been obtained by Berkowitz et al using He I resonance radiation. Three bands were observed which could be interpreted by analogy with the diatomic halogens and with the recently reported CIF. The first (adiabatic) ionization potential was found to be 12.69 0.03 eV, in close agreement with the photoionization value of 12.7 0.01 eV. 

Occupational skin cancer is most commonly associated with SCC. Statistics and studies on SCC may underestimate the incidence rate of this disease because of its long latency period. Case history must be assessed carefully in order not to miss the exposure to an occupational carcinogen 20-30 years before. SCC is particularly dangerous due to its ability to metastasize and spread to the lymph nodes (Headington 1978). Occupational SCC is mainly induced from chemical carcinogens. However, results for occupational nonsolar radiation exposure for SCC are limited and... 

Carpenter et al. (1988) carried out a nested case-control study of cancer of the central nervous system among workers at two nuclear facilities located in Tennessee (United States). They identified 89 cases (72 males and 17 females) who had died between 1943 and 1979. Four controls, living at the time the case was diagnosed, were matched to each case. Job history records were scrutinized by an industrial hygienist to assess potential exposure to each of 26 chemicals or chemical groups. Toluene, xylene (see this volume) and 2-butanone (methyl ethyl ketone) were evaluated as one chemical group the matched relative risk was 2.0 (95% confidence interval (Cl), 0.7-5.5 n = 28) in comparison with unexposed workers. Almost all cases had had low exposure, according to the classification used and there was no dose-response trend. The authors stated that the relative risks w ere adjusted for internal and external exposure to radiation. 

Paleontology has shown that the history of life has been full of adaptive radiations, processes in which an ancestral taxon gave rise to descendant taxa which diverged by adapting to different environmental conditions. Some adaptive radiations have been explained with the mechanism of phyletic gradualism, while others are better described by punctuated equilibria, but in all cases they are classical processes of adaptation to the environment by natural selection. 

Photochemistry has expanded enormously since those first days. A serious percentage of the papers in any single volume of the Journal of the American Chemical Society, for instance, can rightly fall in its purview. The emergence of the laser and the evolution of theoretical methods strongly influenced research. With new computational methodology almost no intermediate lives too short a time to be detected and its dynamics characterized. The fundamental objective of our field, elucidation of the history of a molecule that absorbs radiation, is now within reach in even the most complicated cases. We hope that the series continues to reflect the frontiers of photochemistry as it evolves into the future. 

The last chapter in the geologic history of the ice-free valleys is concerned with the geochemical evolution of the lakes and ponds several of which contain dense brines overlain by layers of dilute water under a permanent cover of ice. These lakes and the associated meltwater streams give the ice-free valleys the appearance of oases on a very cold continent buried under snow and ice. The water in the lakes is warmed by solar radiation that penetrates 4 m of permanent ice and up to 60 m of water in the case of Lake Vanda. 

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