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Radiological Dose Assessment for the PublicOverviewRadiation Dose OverviewRadiation can damage living cells because of its ability to deposit energy as it passes through living matter. Energy deposited in the cell can result in cell damage, cell death, and, rarely, cell mutations that survive and can cause cancer. Because energy deposition is how radiation causes cell damage, radiation doses are measured in the quantity of radiation energy deposited per unit mass in the body. Different types of radiation carry different amounts of energy and are multiplied by adjustment factors for the type of radiation absorbed. Radiation affects different parts of the body with different degrees of effectiveness, but we need to report the "effective" dose the whole body has received. The term "effective dose equivalent" (EDE), also referred to as dose, is the "effective" dose calculated to have been received by the whole body, generally from an external radiation source. To calculate this dose we sum the doses to individual organs or tissues. Long-lived radionuclides that a body inhales or ingests continue to deposit energy in the body and give doses for a long time after their intake. To account for this extended dose period, we also calculated a "committed effective dose equivalent" (CEDE), also referred to in this report as "dose." The CEDE gives the total dose, integrated over 50 years, that would result from radionuclides taken into the body from short-term exposures. Calculated doses generally include the contributions from internally deposited radionuclides (CEDE) and from radiation exposures received from sources outside the body (EDE) all under the general term "dose." RegulationsRegulations & RequirementsFederal government standards limit the dose that the public may receive from Laboratory operations. The Department of Energy (DOE Order 5400.5 1990) public dose limit from DOE operations to any individual is 100 mrem per year received from all pathways (i.e., all ways in which people can be exposed to radiation, such as inhalation, ingestion, and direct exposure). The dose received from airborne emissions of radionuclides is further restricted by the dose standard of the Environmental Protection Agency (EPA) of 10 mrem per year, which is codified in the Code of Federal Regulations (40 CFR 61); see Appendix A. These doses are in addition to exposures from normal background, consumer products, and medical sources. PathwaysPathways and ScenariosThe objective of our dose calculations is to calculate and report incremental (above background) doses caused by LANL operation. Therefore, we don't include dose contributions from radionuclides present in our natural environment or from radioactive fallout unless we identify LANL as a source for some of these radionuclides. Our assessments are intended to be realistic but conservative enough to demonstrate with a high degree of certainty that larger doses did not occur. Annual radiation doses to the public are evaluated for three principal exposure pathways: inhalation, ingestion, and external (also referred to as direct) exposure. We calculate doses that the population as a whole within 80 km may have received and also doses to specific hypothetical individuals within that population as shown below.
MethodologyGeneral MethodologyAdditional information is available regarding the methodologies we follow in our radiological dose calculations. |
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