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Oxidation of combustible wastes in molten salt baths is being considered as an alternative to incineration. This paper examines the oxidation of cyanide ions (present in molten carbonate bath) by molecular oxygen as a function of the total gas mixture (O2−Ar) flow rate, input gas composition (vol % O2 in O2−Ar mixtures), melt composition (initial mol % CN- in CN-−CO3 2- baths), and melt temperature. The melts were sampled for the presence of CN-, CNO-, NO2 -, and NO3 - while the gas streams were sampled for N2, N2O, NO, NO2, CO, and CO2. While cyanide destruction proceeds rapidly (>90% loss of CN- at 486 standard cm3 per min, 40 vol % O2, and 1243 K), NO2 and CO emissions remain within the limits of air quality standards. Under all conditions CN- and CNO- were the major components, while NO2 - and NO3 - were the minor components of the melt. The amount of CNO- present in the melt after any period of reaction was always smaller than the amount of CN- lost from the melt during the same time period. The CO + CO2 content of the gas was always much larger than the NO + NO2 content. The CO/CO2 ratio was always small while the NO/NO2 ratio was always large. While N2 content was larger than the NO + NO2 content, no N2O was ever detected. Material balance indicated that most of the nitrogen input to the system remained unaccounted after the reaction. Significance of the data are discussed.

A walk-in type 222Rn calibration chamber of volume 22.7 m3, which has traceability to international standards, is established at the Centre for Advanced Research in Environmental Radioactivity, Mangalore University, India. It has a human–machine interface communication system, a programmable logic controller and sensor feedback circuit for controlling and data acquisition of relative humidity (RH) and temperature (T). An innovative method for the generation of desired 222Rn concentration (a few hundred Bq m−3 up to about 36 kBq m−3) using soil gas as a source was adopted. Leak rates of 222Rn from the chamber for the mixing fan ON and OFF conditions were determined to be 0.0011 and 0.00018 h−1 respectively. With the exhaust system fully turned on, the maximum clearance rate of the chamber was 0.58 ± 0.07 h−1. Excellent spatial uniformity in 222Rn concentration in the chamber was confirmed (with a mean value of relative standard deviation < 12%) through measurements at 23 locations using CR-39 film-based passive devices. Demonstration of calibration applications was performed using charcoal canister and PicoRad vials as the 222Rn adsorption devices. The study shows that gamma spectrometry is a convenient alternative approach to liquid scintillation analysis of PicoRad vials for 222Rn measurement.

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