ORALS

Solid State Nuclear Track Detectors have existed on earth, moon and other solidified species (e.g. meteorites) due to cooling down of insulation material in space in the form of minerals (mica, quartz, etc.). Passive radon monitoring using SSNTDs was initiated by three American scientists namely, R. L. Fleisher , R. M. Walker and P. B. Price [1, 2] and ultimately, patented by Becker [3, 4]. Typical organic materials used for radon dosimetry are made of bisphenol-A polycarbonate (Lexan, Makrofol), cellulose nitrate (LR-115, CN-85) and polyallyl di-glycol carbonate (PADC or CR-39). Bare mode Single cup diffusion chamber and Twin cup dosimeters for estimation of indoor 222Rn/220Rn concentrations have become obsolete today owing to their several drawbacks such as unwanted interferences from progeny, atmospheric turbulence effects and negative 220Rn concentrations. To overcome these technical limitations, a new pin-hole based 222Rn/220Rn discriminating dosimeter with single entry face was designed by Sahoo et al. [5]. It is one of the most versatile devices in mixed field environment of 222Rn and 220Rn. Numerous dosimetric, radiobiological and epidemiological studies have been carried out by many researchers to establish guideline values for various radionuclides, identify regions of concern develop biokinetic models, and project national baseline values. This study summarizes some important studies conducted in India by our group at NIT Jalandhar. Keeping toxic nature of uranium in mind, a survey of groundwater consumed by inhabitants is also conducted. A comprehensive analysis of uranium burden in a human adult is done by determining natural uranium concentration. The annual effective doses are computed both age-wise and organ-wise. Internal organ/tissue doses give an insight of radioactive targets which may act as bio-indicators of uranium toxicity in human body. The transfer coefficients of different body organs are calculated using hair compartment model of uranium and compared with those obtained using ICRP’s biokinetic model [6]. The results of the study not only fulfil an environmental cause but also, a social cause to identify regions of concern, regions of negligible uranium concentrations and those for which data is currently unavailable, but nevertheless, may become prospective uranium sites and should be investigated.

References:
[1] Fleischer RL, Price PB, Walker RM, The Ion Explosion Spike Mechanism for Formation of Charged Particle Tracks in Solids: Journal of Applied Physics, 36 (1965b) 3645-3652
[2] Fleischer RL, Price PB, Walker RM, Nuclear Tracks in Solids: Principles and Applications (1975): University of California Press Berkeley.
[3] Becker KH, Alpha particle registration in plastics and its applications for radon and neutron personal dosimetry: Health Physics 16 (1969). 113-123.
[4] Becker KH, Personal radon monitor (1970): U.S. Patent, 3: 505-523.
[5] Sahoo et al., A new pin-hole discriminated 222Rn/220Rn passive measurement device with single entry face: Radiation Measurements.58 (2013) 52-60.
[6] Jakhu R, Mehra R, Mittal HM, Exposure assessment of natural uranium from drinking water: Environmental Science: Processes and Impacts (2016), 18(12) 1540-1549.