Welcome

Welcome to the EPA's Superfund Counts Per Minute (CPM) calculator. This tool is provided to help calculate the potential radiation detector reading, in counts per minute (CPM), that corresponds to a measured level of radioactivity in either pCi/cm² or pCi/g. Surface and volumetric contamination are converted to CPM by separate processes utilizing Monte Carlo N-Particle (MCNP) derived conversion factors. The CPM calculator is capable of converting activity in soil, steel, glass, drywall, concrete, and wood to CPM. To ensure proper application of the radiation conversion tool, please see further guidance from the User's Guide and FAQ pages. In addition, Users of the CPM at a CERCLA site should consult with EPA Headquarters, Stuart Walker at Walker.Stuart@epa.gov (202-566-1148), David Kappelman at Kappelman.David@epa.gov (513-487-6540), and Jack Burn at Burn.James@epa.gov (334-270-3437).

The EPA has prepared a fact sheet for the general public that describes CPM uses, CPM calculator operation, and situations (e.g. land uses, contaminated material, radiation detectors) available for assessment. Additionally, this fact sheet describes the CPM calculator in greater detail for EPA staff.

The CPM calculator results were previously verified. The documentation from these may be seen on the Internal Verification page. The CPM calculator was previously peer reviewed and the documentation of those peer reviews may be seen here. The CPM calculator results were previously validated/corroborated. The documentation from these may be seen on the Electronic Corroboration and Physical Corroboration pages.

The CPM calculator was previously peer reviewed and the documentation of those peer reviews may be seen here.

Introduction

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 to 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 calculator 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 only acceptable residual levels of contaminants remain. Previously, there was no EPA guidance for Superfund sites on correlating CPM field survey readings back to risk, dose, or other ARAR-based concentrations.

Related CERCLA Calculators and Guidance

The CPM calculator requires target activity concentrations that may be based on preliminary remediation goals (PRGs) or dose compliance concentrations (DCCs). PRGs and DCCs can be calculated from the following EPA tools recommended for Superfund sites:

• the PRG Calculator for radionuclide cancer risk for soil, water, biota, and air,
• the DCC Calculator should be used to assess radionuclide dose for soil, water, biota, and air,
• the BPRG Calculator for radionuclide cancer risk inside buildings,
• the BDCC Calculator for radionuclide dose inside buildings,
• the SPRG Calculator should be used to assess radionuclide cancer risk for hard outside surfaces,
• the SDCC Calculator for radionuclide dose for hard outside surfaces, and
• the RVISL Calculator for radon in air, groundwater, and soil gas.

It should also be noted that calculating a PRG or DCC doesn't address noncancer toxicity nor potential ecological risk. Of the radionuclides generally found at CERCLA sites, only uranium has potentially significant noncancer toxicity. When assessing sites with uranium as a contaminant, it may also be necessary to consider the noncancer toxicity of uranium. Additional screening levels can be calculated from the following EPA tools:

• the RSL calculator for chemical hazard and cancer risk for soil, water, and air,
• the WTC for uranium inside buildings, and
• the VISL Calculator for chemical contaminants in air, groundwater, and a soil gas.

Sites with radiological contaminants in sensitive ecological settings may also need to be evaluated for potential ecological risk. EPA's guidance "Ecological Risk Assessment Guidance for Superfund: Process for Designing and Conducting Ecological Risk Assessment" contains an eight step process for using benchmarks for ecological effects in the remedy selection process.

Below is a table that summarizes the existing EPA online calculators for assessing risks from chemicals and radionuclides at Superfund sites.