Disaster monitoring with amateur photographic film and with dental x-ray film.

Abstract

If an atomic disaster were to strike an urban community, it would be of great importance to have some means of reconstructing, at least approximately, the pattern of radiation dose distribution over the different sections of that community. Two recent publications (1, 2) from the Kodak Research Laboratories deal with the problem of radiological monitoring with amateur and commercial photographic roll films manufactured by the Eastman Kodak Company. A study of a similar nature has been carried out at the National Bureau of Standards. The total number of film types investigated was smaller than that covered in the second of the papers cited above, mainly because the investigation was restricted to types that would be widely available in any urban community. The work was not limited, however, to the products of any one film company, but covered all products generally available in drugstores, photographic stores, and dental offices throughout the United States. The data were obtained in a series of laboratory tests and in an actual field exposure to the prompt radiation from the detonation of a nuclear device during the 1955 series of atomic tests at the Nevada Test Site. Exposure in Bulk Tests were performed to determine the feasibility of interpreting dose from films exposed in their original packages. It was found that amateur roll films could be used in the original case, provided the dose interpretation was made from the density on areas not obliterated by the image of the central metal spool, and located in the outer third of the film length. The exposure of dental films in large boxes containing 100 or more films was found to be undesirable, mainly because of the filtering action of the lead backing provided in all tested brands of dental film packets. All work described in this paper was therefore carried out on roll films in the original packages and on single or paired dental film packets. Density-vs.-Exposure Relations Figures 1 and 2 give the density-vs.-exposure relations for six types of amateur black-and-white roll film and for six types of dental x-ray film, obtained with radiation from a Co60 gamma-radiation source. All laboratory processing (solid lines) was done in Kodak Liquid X-Ray Developer for five minutes at 68° F. This type of processing is fairly realistic for dental films, but not for amateur roll films; a spot check was therefore made of the influence of a variation in processing conditions on film response, by sending identically exposed roll films to commercial amateur laboratories for routine processing. The dashed lines in Figure 1 show the results obtained by three different laboratories whose processing technics, though apparently closely controlled, are seen not to be identical.