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Waste and Cleanup Risk Assessment

EPA Radiation Conversion

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EPA Radiation Conversion


Welcome to the EPA's Superfund Counts Per Minute (CPM) calculator. This tool is provided to help calculate the radiation detector reading in counts per minute (cpm) that corresponds to the level of radioactivity in a surface or volume of medium by converting radioactivity in either pCi/cm2 or pCi/g to cpm. The CPM calculator has two major sub calculators based on the field survey scenario: (1) ground-based scanning of surface contamination, and (2) ground-based scanning of volumetric contamination. To ensure proper application of the radiation conversion tool, please see further guidance from the "Area User's Guide", "Volume User's Guide", and 'FAQ" links.


EPA developed the CPM electronic calculator to help risk assessors, remedial project managers, and others involved with risk assessment and decision making at radioactively contaminated sites. The CPM electronic calculator provides a method for correlating real-time survey results, which are often expressed as counts per minute, to contaminant concentrations that are more typically provided in risk assessments or for cleanup levels, usually expressed in pCi/g or pCi/m2, at Superfund sites (those regulated under the Comprehensive Environmental Response, Compensation, and Liability Act of 1980, or CERCLA).

The intent of the CPM calculators is to facilitate more real-time measurements within a Superfund response framework. The CPM calculator may also standardize the process of converting lab data to real time measurements. It will thus lessen the amount of lab sampling that is needed for site characterization and confirmation surveys, but it will not remove the need for sampling.

Field sampling has the potential to be an extremely time-consuming and expensive portion of a radiological site remediation. Collected samples must be shipped to an off-site laboratory or counted in an on-site mobile unit in order to establish areas of contamination and to ensure that acceptable residual levels of contaminants remain. Previously there was no EPA guidance for Superfund sites on correlating count per minute field survey readings back to risk, dose, or other ARAR-based concentrations.

Highlights of this tool are provided here in a poster-style presentation.

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