Potassium-40 content in male radiation workers at Narora Atomic Power Station

749 radiation workers at NAPS, aged 20 to 59 years, were monitored by using Shadow Shield Whole Body Counting System, having NaI (Tl) crystal coupled with 4K Multi Channel Analyser (MCA), to determine the 40K activity in the body and assess internal dose due to naturally occurring 40K. These subjects belonged to 18 different states with nearly 54% from Uttar Pradesh. The data have been grouped for analysis in vegetarian and non-vegetarian. The paper describes the calibration details of whole body counter for 40K using water phantom. The frequency distribution of natural potassium content (g K kg-1 body weight) is found to be normally distributed with the peak occurring for 1.70-1.90g K kg-1 grouping. The average natural potassium content per unit body weight (g K kg-1) (average 40K activity kBq kg-1) for vegetarian, non-vegetarian and all subjects taken together is found to be 1.84 (57.66), 1.92 (60.20) and 1.88(58.86) respectively. The data obtained could be expressed as a linear relationship C= A+Bx, where 'C' is the potassium content per unit body weight in g K kg-1of body weight and 'x' is the age of the subject, in years. The coefficient A and B for vegetarian, non-vegetarian and all subjects taken together are found to be 1.89 and -0.002, 2.18 and -0.008 and 2.03 and -0.005 respectively. The data obtained for all these groups was also fitted in a linear relationship between the activity due to 40K(kBq) and the ratio of weight to height, W/H (kg cm-1). The average annual dose from 40K for the subjects is evaluated as 165.42±37.91μSv. (author)