Hypothetical Method for Gamma Dose Rate Assessment to Conditioned Radioactive waste Container

Abstract

Metallic solid radioactive waste class low level - short lived Radioactive Waste (LL-SL RW) is the main type of radioactive waste generated from decommissioning operations. Transport, storage and disposal regulations require for gamma emitting radioactive waste (mainly by 137 Csisotope), that the dose rate in the proximity of the container should stand below a certain threshold. Also, the conditioning technique (using cementation technique) based on certain matrix with specific ratios should be able to attenuate the gamma radiation activity to the minimum level or to acceptable dosage rate at distance of 1m from the container. In this paper ,in absence of suitable labs for waste package assessment ,hypothetical method present to assess dose rate in safe way, assumption based on metallic waste pieces contaminated with ( 137 Cs), were conditioned with cement matrix and contained in carbon steel drum volume 220 liter ,60cm diameter then dose rate measurement applied in vicinity of the container. Instead of real contaminated metallic waste, ( 137 Cs,D ∘ =20mR/hr) gamma radioactive point source was positioned in different places in front of cross section of the cemented free metallic waste and gamma dose rates were measured on the outer side of the drum sample using NaI dose meter device. The readings showed good attenuation of gamma radiation activity (low dose rates), efficiency of the cement matrix to decrease the dose rate of ( 137 Cs,0.662Mev) gamma radiation lower to acceptable values and with waste acceptance criteria and regulation.