Monthly variation of gamma dose rate measured in indoor air of buildings of Bangladesh was found to vary cosinusoidally through a period of 1 year. Significant seasonal variations were observed. Maximum dose rate, however, was observed in January and a minimum in July. Dose rate in January was 32% higher than the annual average, whereas dose rate in July was 50% lower. Seasonally varied ventilation and air exchange rates of the houses might play an important role in the observed variation. The average reduction with respect to winter dose was 59% in summer. Because of lower ventilation and air exchange rates between indoor and outdoor atmosphere, it is expected that the indoor dose rate would be higher in basements than that of upper floors. Monthly dose rate was also found to be influenced by the meteorological conditions. Correlations between dose rate and temperature (r2=0.85), rainfall (r=-0.83) and atmospheric pressure (r=0.92) were obtained, but no significant correlation (r=-0.45) was seen between dose rate and humidity. The results show that the seasonal variations of indoor dose rates should be taken into account to estimate annual effective dose equivalent.
Radiation effects on the uranium retention property of degraded n-dodecane by acidic radiolysis in the Purex process were studied. The absorbed dose of n-dodecane varied from 24.04 to 2403.69 kGy (5 to 500 Wh/dm3) . When the absorbed dose exceeded 48.07 kGy (10 Wh/dm3), the uranium (UO22+) was retained in degraded n-dodecane even without TBP as extractant. An empirical correlation of the uranium retention was also derived. This correlation is a very effective one because it can especially be used for the prediction of the amount of retained uranium in the degraded n-dodecane. Data obtained through this work should be useful for the process design under solvent degradation conditions in nuclear fuel processing facilities especially in reused solvent.