EXECUTIVE SUMMARY
This report constitutes a review of four documents developed by the Battelle, Pacific Northwest Laboratories as part of the Hanford Environmental Dose Reconstruction (HEDR) project:
-
PNWD 1983, HEDR Modeling Approach, by D. B. Shipler and B. A. Napier, July 1992 (3 pages).
-
PNWD 2023, Parameters Used in the Environmental Pathways (DESCARTES) and Radiological Dose (CIDER) Modules of the Hanford Environmental Dose ReconstructionIntegrated Codes (HEDRIC)for the Air Pathway, by S. F. Snyder, W. T. Farris, B. A. Napier, T. A. Ikenberry, and R. O. Gilbert, September 1992 (184 pages).
-
PNWD 2033, Iodine-131 Releases from the Hanford Site, 1944 through 1947, Vol. 1, Text and Vol. 2, Data, by C. M. Heeb, October 1992 (362 pages).
The reports provide data and procedures for determining the annual and cumulative releases of iodine-131 (PNWD 2033, Vol. 1 and PNWD 2033, Vol. 2), techniques for modeling environmental movement of radionuclides (PNWD 1983), and parameters for calculating doses (PNWD 2023). The committee evaluated the four documents with emphasis on completeness of data, quality control, uncertainty analysis, model validation, clarity and detail, and issues of public involvement. Although the committee's overall impression of the reports was favorable, specific concerns were identified regarding omissions that should be addressed, quality control, and dose calculations.
The committee concluded that the reports are comprehensive, well-documented, and sound for source-term determinations but could be improved by inclusion of additional information for dose modeling. An example would be that further justification of the
exclusion of onsite groundwater pathways, including surface runoff, and onsite ingestion pathways should be provided. The computer code DESCARTES, which is used to calculate the environmental concentrations of the radionuclides of interest, is not adequately described. It is mentioned that some pathways will be selected if particular criteria are not met, but the nature of these alternative pathways and the criteria are not described. Although up to 12 radionuclides are considered in the atmospheric pathways, the radionuclide-specific parameter values used in DESCARTES are given only for iodine-131. The types of annual dose that will be calculated, the manner in which individual doses are to be validated, and the expected uncertainty estimates associated with the doses should be specified.
The estimated release of iodine-131 in 1944-1947 was 685 kCi, which was calculated from daily measurements of operating characteristics directly related to rates of production and release of iodine-131 and other fission products. Stack-monitoring data are not available to document those substantial releases with direct measurements. However, the committee believes that the overall release calculated from operational measurements is complete and is not underestimated, especially inasmuch as there was no reduction for off-gas losses of iodine-131.
The document on iodine release (report PNWD 2033) is very comprehensive and describes an important phase of the overall project. Some questions remain regarding completeness of the data, the possible role of iodine-129, and the use of distribution functions. The iodine-129 releases were not addressed; these were not a substantial source of human radiation exposure, but the long half-life of iodine-129 might afford an opportunity to validate the iodine-131 exposure models by measuring environmental iodine-129.
The modeling approach described in the documents was considered to be conventional and sound. However, details regarding validation need to be provided, and selections of model parameters need to be documented and supported, especially where selected parameter values differ substantially from literature values. Some of the pathways
discussed are probably of minimal importance, and a consistent screening analysis applied to all streams and pathways might be necessary to keep the project manageable.
The committee reviewed the management of HEDR activities. A Technical Steering Panel (TSP) with broad technical representation has been integral to the scope and content of the HEDR project. It is mentioned that TSP guidelines for annual doses for any individual exist, but these guidelines are not presented in the reports. Some concern was expressed regarding potential conflicts arising from having staff from Battelle, Pacific Northwest Laboratories assess past activities that involved persons who were employees of Battelle Memorial Institute and in some cases previous employees of the General Electric Company. However, the committee did not observe any indication of bias in the studies it reviewed. Finally, the committee recommends that careful consideration be given to how the final results of the project will be evaluated and presented to the public, that public involvement in HEDR be discussed more fully in the reports, and that all doses and quantities of radioactive materials be expressed in both SI units and English units. The committee would like to see the final HEDR reports before making a definitive judgment.
