Dosimetry ferrous sulfate

In the radiation grafting work, experiments were performed in spent fuel element and cobalt-60 facilities of the Australian Atomic Energy Commission, dose rates being determined by ferrous sulfate dosimetry (G(Fe)= 15.6). For the specific irradiations, which were carried out in quadruplicate, small strips (5 x 4cm) of cellulose (Whatman No. 41, W.R. Balston Pty. Ltd., double acid-washed chromatography grade) were equilibrated at 65% relative humidity for 24 h at 23 °C, folded into test tubes (16 x 1.2 cm), monomer solution (6ml) added to the tubes which were then lightly stoppered. After irradiation, the strips... 

Irradiations were performed with cobalt-60 y-rays from a 1000-curie source. The sealed ampoules were either irradiated in air at 20 °C. or in a water thermostat at different temperatures. Dosimetry was based on the oxidation of ferrous sulfate in 0.8N sulfuric acid, using G(Fe3+) = 15.5. 

Irradiation. All irradiations were performed at the University of Maryland with a 25,000 curie cobalt 60 gamma source. The absorbed dose rate of 1.2 Mrad per hr was determined by ferrous sulfate dosimetry. All samples were irradiated under secondary electron equilibrium conditions. Following irradiation, all samples irradiated in vacuum were annealed in vacuum at 380 K for 24 hours this treatment reduces the long-lived radical concentration to undetectable levels. 

Dosimetry. The intensity of the flux at the sample site was measured periodically with a ferrous sulfate dosimeter, using GFe(iii) = 15.5. Energy absorbed in liquid samples was based on this dosimetry and was corrected for the electron density of the samples. To determine energy absorbed in the vapor samples, nitrous oxide was irradiated, at comparable electron densities, in the vessel used for the hydrocarbons the G value for nitrogen production was taken to be 11.0 (7). 

The radiation cells were made from 9-mm. o.d. borosilicate glass tubing. The concentration of nitrous oxide was calculated by assuming that the amount in the gas phase was negligible since the solutions filled approximately 90% of the cells. The samples were thermostatted at 35°C. and irradiated for one hour in a G0Co y-ray facility at a dose rate of approximately 1.3 X 1019 e.v. liter1 sec."1. Ferrous sulfate dosimetry was used. Since we wished to compare different alkanes, samples were prepared in pairs one sample of the pair always contained cyclohexane and the other some other alkane. Each sample of each pair contained the same amount of nitrous oxide. 

Whatever the source of radiation used, the dose delivered to the biological samples is determined by the time of exposure to radiations. Thus the dose delivered by the radiation source must be measured with precision. Dosimetry can be performed with a ferrous sulfate solution (Fricke and Morse, 1927), thermoluminescent dosimeters, bleaching of films (Hart and Fricke, 1967), Perspex dosimetry (Berry and Marshall, 1969), or calibration with standard enzymes (Beauregard et al., 1980 Beauregard and Potier, 1982 Lo et al., 1982). In many laboratories, control enzymes with known D37 are added to protein preparations as internal standards so that any variation between experiments could be corrected for. Because of the better precision of dose rate in Gammacell irradiators, this precaution is not necessary. 

Dosimetry is the measurement of absorbed dose. The unit of absorbed dose is the gray (Gy). Because dose is a measure of absorbed energy, calorime-try is the fundamental method of measurement. However, calorimetry suffers from being insensitive, complex, slow and highly demanding in technical skills and experience. Primary dose measurement is usually done with substances that are chemically changed quantitatively in response to the amount of radiation absorbed. For most purposes the standard primary system is the Fricke or ferrous sulfate dosimeter. In this system, which consists of a solution of ferrous sulfate in dilute sulfuric acid, ferrous ions Fe are oxidized by absorbtion of radiation to ferric ions Fricke dosimeters are usually presented in glass... 

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