Radiological Dose Assessment Methodology

General Methodology

Our radiological dose calculations follow methodologies recommended by federal agencies to determine radiation doses.

The general process for calculating doses from ingestion or inhalation is to multiply the concentration of each radionuclide in the food product, water, or air by the amount of food or water ingested or air inhaled to calculate the amount of radioactivity taken into the body. Then, we multiply this amount by the dose conversion factors from Federal Guidance Report No. 11 (EPA 1988) to calculate the dose from each radionuclide. We sum these amounts to give the total dose from each pathway, such as ingestion and inhalation, throughout the year.

Where local concentrations are not known but source amounts (amounts released from stacks or from diffuse emission sources) are known, we calculate the doses at receptor locations using an EPA approved computer model, CAP88.. The model combines source-term information with meteorological data to estimate where the radioactive material went. By determining air concentrations in all directions around the source, the model can then calculate doses at any location. The models are also capable of calculating how much of the airborne radioactive material finds its way into nearby vegetation and animal material.

Direct doses from radiation sources external to the body are measured by thormoluminescent dosimeters (TLDs) placed in the environment as part of the DPRNET process.