A devised light absorption method for measuring fast neutron fluences and gamma doses in mixed radiation fields using a cellulose acetate detector

Abstract

A simple and direct method for measuring 14.3 MeV neutron fluences and high doses of gamma radiation has been achieved through measuring the induced coloration in cellulose acetate after being exposed to pure gamma rays and neutrons. A characteristic absorption band with different intensities in the wavelength range between 260 and 320 nm was observed when the sample was exposed to gamma radiation. Two other absorption bands in the wavelength ranges of 220–260 nm and 260–300 nm were observed after irradiating the sample with 14.3 MeV neutrons. Two empirical formulae for calculating the neutron fluence in the range 10 9−1.2×10 11 n/cm 2 have been achieved. The formulae are found to fit the experimental date within ±4%. An empirical formula for calculating the gamma doses in the range 0.3–60 MRad has been achieved and found to fit the experimental data within ±2%. This method enabled the measurement of neutron fluence and gamma doses in mixed fields with an accuracy of about ±14% for neutrons and ±23% for gamma rays. The fading of the intensity of the irradiation induced absorption bands in cellulose acetate, after storage for periods up to one month at a temperature of 35°C and relative humidity 30% have been investigated.