Answer to Question #5680 Submitted to "Ask the Experts"
The following question was answered by an expert in the appropriate field:
I did a preliminary survey of background radiation levels of Vypeen Island (one of the islands situated in Kerala, India). We conducted an ambient gamma exposure survey using micro-R-survey meter UR 705. We measured the gross alpha activity of that island using the alpha counting system CS-201 manufactured by Pla Electro Appliances. From the ambient gamma exposure survey we found out that the dose rate on that island varies from 60.9 nGy/hr to 182.7 nGy/hr with a mean value 127.02 nGy/hr. We found out that the gross alpha activity on that island varies from BDL (below detectable level) to 5892.26 Bq/kg with a mean value 1083.97 Bq/kg.
Right now, sitting in my home in western New York state, my dose-rate meter (a Ludlum Model 19) has a reading of about 70 nGy/hr. As I go around the city, I get readings that range from about 50 to 150 nGy/hr. Rochester is not a high-background radiation area—the underlying geology is primarily limestones and sandstones that have fairly low levels of natural radionuclides. Based on that, I would venture to suggest that the readings you are getting are fairly normal.
A few years ago, when I visited the high-background radiation area in Ramsar, Iran, I had readings of about 22 microGy/hr. The soils in this area had 226Ra activity concentrations of about 6,000 pCi/gm (about 16,000 Bq/gm), with decay progeny in equilibrium—this gives a gross alpha radioactivity concentration of about 50,000 or 60,000 Bq/gm.
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