Search

The primary purpose of this study is to establish the methods for determination of total growth of 222Rn daughters and 222Rn exposure of the workers at desired places of mines. This paper presents a comprehensive review of the types of radiation hazards associated with underground uranium mining. The mathematical modelling of the growth of 222Rn daughters for a horizontal tunnel is also derived in this paper. Further, an example of the determination of inhalation exposure of miners in a cut-and-fill stope mine is provided in this paper. A critical analysis of the literature review revealed that the radiological hazards associated with low-grade uranium ore are primarily owing to inhalation of 222Rn and its daughters. The total growth of 222Rn daughters are found to be 0.468 μJ/m3 that are calculated based on the reported values of 222Rn release rate from mine walls, blasting materials, fill materials, and the percolating water. Further, it also revealed that the radon contamination of intake air was the significant contributory factor in the radiation exposure of uranium mine workers. [ABSTRACT FROM AUTHOR]

Longwall technology is one of the principal underground coal mining methods widely used around the globe which is not fully emerged in India. However, since the introduction of first self-advancing powered roof supports, there has been mixed experience of longwall technology. History of failure of some longwall panels desponded the success stories of others. Majority of longwall downtimes and/or failure had been attributed due to poor cavability of roof, inadequate capacity of supports, lack of knowledge on longwall caving mechanisms, less than adequate strata monitoring systems, etc. Strata around coal seams in India are dominated by competent beds, which do not normally cave in immediately after face advance, rather it remains in hanging condition for certain length and break into large discrete blocks. This type of caving mechanics is irregular and complex. Fracturing of competent bed in the immediate roof zone is certain to manifest itself on face as heavy load on supports, bleeding of hydraulic legs of supports, aggressive face spall and guttering in gate roads and in worst conditions longwall face stoppage and sometimes even structural failure of supports as the severity may be. This paper presents a case study of strata behavioural experiences gained while extracting a deep and wide longwall panel overlain by 3.0 to 3.5m coal roof as immediate roof and 20 to 28m thick competent sandstone bed as main roof with high capacity longwall equipment. While extracting the panel the precise strata monitoring and trigger action response plans are prepared and implemented successfully for negotiating all the strata control hindrances. [ABSTRACT FROM AUTHOR]

Emanation of radon from rock surfaces in underground uranium mines is a continuous process and its magnitude depends on several factors such as radium content, porosity, moisture content and mineralogical characteristics of the ore. The radon gas entering into mine atmosphere starts decaying into its daughter products, which attach themselves to the dust particles in mine atmosphere. Inhalation of radon and its daughters are recognized as the primary cause of health hazard to the miners. Thus, accurate estimation of radon emanation is essential to control the radiation levels within the safe limits and protect the miners from radiation hazards. This paper presents an overview of different sources of radon in underground uranium mines. It also discusses the prediction of radon emanation rate in underground uranium mines based on diffusion theory and growth of radon daughters. [ABSTRACT FROM AUTHOR]

This paper presents a comparative study of Rn emanation from the ore and backfill tailings in an underground uranium mine located at Jaduguda, India. The effects of surface area, porosity, Ra and moisture contents on Rn emanation rate were examined. The study revealed that the bulk porosity of backfill tailings is more than two orders of magnitude than that of the ore. The geometric mean radon emanation rates from the ore body and backfill tailings were found to be 10.01 × 10 and 1.03 Bq m s, respectively. Significant positive linear correlations between Rn emanation rate and the Ra content of ore and tailings were observed. For normalised Ra content, the Rn emanation rate from tailings was found to be 283 times higher than the ore due to higher bulk porosity and surface area. The relative radon emanation from the tailings with moisture fraction of 0.14 was found to be 2.4 times higher than the oven-dried tailings. The study suggested that the mill tailings used as a backfill material significantly contributes to radon emanation as compared to the ore body itself and the Ra content and bulk porosity are the dominant factors for radon emanation into the mine atmosphere. [ABSTRACT FROM AUTHOR]

Seasonal variation of 222Rn levels was studied in the dwellings in U-Cu mineralized area of East Singhbhum, Jharkhand, India. Copper mining and processing industry is operational in this area for the last hundred years. Copper minerals of this region contain a significant fraction of uranium and the decay products. To measure the activity concentration of 222Rn, LR-115, type-II solid-state nuclear plastic track detector was used in an indigenously developed radon dosimeter cup. A higher value of 222Rn activity concentration was recorded in some of the dwellings in the mineralized zone. The results at different locations adjoining the facilities show that the 222Rn activity concentration varies to a great extent following an approximate log-normal distribution. The observed range varied from 29.1 and 314.6 Bq m-3 with an overall geometric mean of 72.3 Bq m-3 and geometric standard deviation 1.67. Further, in poorly ventilated dwellings 222Rn levels were higher compared to the properly ventilated houses. The peak activity concentration of 222Rn was recorded during winter (December- February). Appreciably lower activity concentration of radon was observed during summer and rainy seasons. The results reflect that the levels are higher than the global average indoor activity concentration of 40 Bq m-3 (UNSCEAR-1993) for 222Rn, but are comparable to the studies carried out in similar types of geological formations. [ABSTRACT FROM AUTHOR]