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30 July 2010

Answer to Question #731 Submitted to "Ask the Experts"

Category: Radiation Basics — Radionuclides

The following question was answered by an expert in the appropriate field:

How do you convert becqerel quantities to parts per billion, micrograms/litre, or parts per million, milligrams per litre for specific elements?

The conversion from activity concentration dimensions, such as Bq/g, to those of atom concentrations, such as ppm, requires that one first convert activity to atom quantity. To convert activity to atoms, simply using the following formula for the isotope of interest: N = A/L, where N = number of atoms, A = activity (Bq) and L is the decay constant (per second). The decay constant, L, can be directly calculated as the ratio of Ln(2) to the isotope half life. Keeping with consistent units, L = Ln(2)/H, where H is the half life of the isotope in (seconds). Once the atom quantity has been determined, conversion to mass (or mass concentration) is the same as for all other elemental calculations.

Robert L. Coleman
Oak Ridge National Laboratory

Answer posted on 5 March 2001. The information and material posted on this Web site is intended as general reference information only. Specific facts and circumstances may alter the concepts and applications of materials and information described herein. The information provided is not a substitute for professional advice and should not be relied upon in the absence of such professional advice specific to whatever facts and circumstances are presented in any given situation. Answers are correct at the time they are posted on the Web site. Be advised that over time, some requirements could change, new data could be made available, or Internet links could change. For answers that have been posted for several months or longer, please check the current status of the posted information prior to using the responses for specific applications.