Radiation Dose Reconstruction for Epidemiologic Uses (1995) / Chapter Skim
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3 Estimating and Confirming the Source Term
3 Estimating and Confirming the Source Term
Pages 16-26
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From page 16... ...
Usually, a scoping study should precede a full description of the source term; the objective of a scoping study is to provide a preliminary assessment of the source term and the magnitude of the estimated exposure to be used in further decision-making. Ideally, the results of a comprehensive source term analysis will contain all of the information needed for exposure or dose calculations, with a spatial and time resolution sufficient for the requirements of the epidemiologic study.
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From page 17... ...
The quality and completeness of the estimates of source terms, based on the physical and chemical characteristics of the source supplemented by historic, operational, and release data and those based on any available independent environmental measurements, vary with the facility or site being evaluated. In some instances it will be sufficient to bound the problem based on source estimates derived from engineering data and then to determine whether the public exposure, evaluated from such data, was great enough to warrant further epidemiologic investigation.
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From page 18... ...
A scoping study would use physical and engineering elements of the process or site and knowledge of operations over time to provide the initial input to a decision about whether to conduct an epidemiologic investigation. By its nature, a scoping study should be a conservative estimate that is used to preclude making an incorrect decision not to investigate the consequences of a particular release, either in terms of individual radiation exposures or as an epidemiologic study.
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From page 19... ...
When exposure reconstruction is indicated for a site or facility, it is essential that the reported source term and the data upon which it is based be removed from the arena of proprietary information, including security classification, if the study is to satisfy public scrutiny and achieve acceptance. This means that decision-makers will need to strike a balance between potentially conflicting goals: protecting proprietary or security information and achieving public confidence in the analysis performed.
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From page 20... ...
Atmospheric releases require specification of the source term from the height, diameter, air flow rate, and temperature in the stack and the contaminant concentrations in the discharged air. Information about the size distribution and chemical form of discharged aerosols and particles is important.
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From page 21... ...
Unlined disposal ponds and settling basins that were used to reduce the quantity of pollutants that reached aquifers or downstream surface water bodies, might have produced contamination of underlying soil layers. Liquid effluent discharge rates and contaminant concentrations are two primary characteristics that should be documented.
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From page 22... ...
Routine reports of release estimates are sometimes available in the files of a facility's health physics or industrial hygiene department. However, it is recommended that the formal reports of effluent releases be validated by examination of the original, handwritten logbooks, files, or analytic data sheets that contain sample mass, activity, or concentration measurements.
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From page 23... ...
Some of the information obtained in source term studies is useful for model development, especially data found in production files, specific process data, purchasing records, materials accountability reports, and logbooks of material use or transfer. In some cases, detailed information on reactor operating cycles and fuel cooling times will be needed to quantify estimates of short-lived nuclides.
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From page 24... ...
Gaps in information should be filled, as far as possible, by extrapolation of release data obtained for comparable operating periods or by reconstruction from other data such as exposure records, environmental monitoring results, or waste shipment records. In some cases steady-state conditions of operations and releases will be sufficiently well established to permit interpolation or extrapolation to undocumented periods.
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From page 25... ...
The same could apply to releases that mostly affected the plant site itself. In a detailed study, completeness of data and comprehensive estimates of reported releases should be the goal of the reported source term; this is ensured by using all relevant data, by investigating all reported events and data gaps, and by determining each release value by as many independent means as possible.
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From page 26... ...
13. The release quantities provided for use in a comprehensive study of the source term should be complete, unbiased estimates of all amounts and forms of relevant materials released to the environment.
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