RECENT RESEARCH IN HIGH-LEVEL GAMMA DOSIMETRY
Many radiation chemistry and radiation-effects studies are conducted at radiation doses 100-fold or more higher than the maximum dose which can be measured with existing dosimetry systems. When raiation sources for which the intensity varies in an unpredictable manoer are used, the determination ef total dose by periodic measurement of dose rate is a tedious and, often, inaccurate method. Dose measurementa woutd be greatiy simplified if a dosimeter capable ef measuring integrated doses in the range 10/sup 6/ to 10/sup 9/ rads or higher were available. This paper deals with a study of systems which appear promising for use in this high-dose range. Among the types of radiation-induced processes studied for high-level dosimetry are color changes in dyes, depolymerization ef polymeric materials, coloration of glasses, and evolution of hydrogen irom organic mnterials. On the basis ef information available in the literature several dyes which appeared to be promising for high-level dosimetry were selected for investigation. The best results were obtained with methyl yellow which exhibits a linear and reproducible optical density change as a funotion of radiation dose up to a dose ef aboct 1 x 10//sup 8/ rads. The extent of radiationinduced degradntion of polymers was determined by viscosity changes ef solutions prepared from the irradiated materials. Maximum deses which can be measured with several polymers are about 5 x 10 /sup 6/ rads with polyisobutylene, 2 x 10/sup 7/ rads with Lucite, and 1 x 10/sup 8/ rads with Parapol S-50, a copolymer of styrene and isobutylene. Several glass systems were studied by measuring optical density as a function of radiation dose. The two most promising glasses studied are Corning, Code 8892 and a special high-antimony glass. The maximum doses which can be measured with these glasses has not yet been determined. However, exposures up to 3 x 10/sup 8/ rads have indicated a linear change in optical density as a fanction of dose. The radiationinduced coloration has shown no evidence ef saturation at the highest doses studied. The possibility of utilizing the hydrogen evolved from an organic material as a means ef measuring radiation dose was investigated. Various organic materials were irradiated in contact with metal oxide films. The hydrogen formed is available for partial reduction of the metal oxide. The extent ef reduction is reflected by changes in the electrical resistance ef the film. Only a few of the nomerous possible combinations of organic and metal oxides materials have been studied. A tin oxide-paraffin system has given best results to date. This system has been irradiated to doses of more than 1 x 10/sup 8/ rad. The electrical resistance of the tin oxide decreased as a function ef radiation dose and no evidence of saturation was observed at the highest doses used. (auth)
- Research Organization:
- Battelle Memorial Inst., Columbus, Ohio
- NSA Number:
- NSA-12-014932
- OSTI ID:
- 4305931
- Report Number(s):
- A/CONF.15/P/2001
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
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