Letter Report: Review of the Identification of Radionuclides Released from the Hanford Nuclear Reservation's Facilities to the Columbia River (2002) / Chapter Skim
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Letter Report
Letter Report
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Smith: May 2S, 2002 As you kr~ow, the Centers for Disease Control and Prevention (CDC) asked the National Research Council's Committee on an Assessment of CDC's Radiation Studies from DOE Contractor Sites to evaluate a draD report titled A Risk-based Screening Analysis for Radionuclides Released to the Columbia River from Past Activities at the U
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Review all the available HEDR Project documents related to the published Columbia River dose calculations and select the best available information related to the quantities of each of the eight radionuclides listed above that were released to the Columbia River between 1944 and 1972. The contractor shall NOT develop any new information on estimates of the radionuclide releases to the Columbia River without the approval of the project of ficer.
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However, when the committee sought to examine the basic data used to derive RAC's findings, it encountered many discrepancies between RAC's values and designations and those in the HEDR documents, which are the source of the basic information. For example, as a result of an error in the computer code, six of the eight reactors are misidentified and the reactors are placed in the wrong locations, and they start and stop releasing at the wrong times (see Appendix B for details)
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As written on page 10 of the RAC report: "To allow a relative ranking it is important that the parameter values used to characterize the exposure pathways and the radionuclides are selected in a consistent manner to avoid biasing the results. Assigning realistic values is preferred because it is difficult to define parameter values with the same degree of conservatism consistently." That statement notwithstanding it does not seem to have been followed for the fish pathway.
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As for data sources, page 27 states that "Monthly release quantities to the Columbia River for a subset of the radionuclides examined from all reactors are provided in Heeb and Bates (1994) and compiled in a Microsoft Excel spreadsheet.
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In addition, the fish ingestion pathway analysis indicates that about 90% of the risk arises this way; actual data on concentrations of radionuclides in fish, which exist, should have been used to validate, or at least benchmark, the model instead of depending entirely on analysis to determine the major effect factor. To go from water-sample analysis through the food chain into fish and into risk when the concentration in the water varies from place to place and time to time and when what the fish fed on and where is Ken own yields a less than credible result that merits a "reality check" against the available data.
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and to compare the estimated risks from the two sources. Another way that RAC could provide more realism in discussing the risks would be to perform calculations of parallel scenarios that used approximate central estimates of the population exposures based on the median or modal values for the various parameters that went into its models and present them as an alternative, pointing out the greater likelihood that most people's exposures would have been closer to the central estimates than to the upper bound estimates.
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For those reasons, the findings in the draft RAC report are suspect, and the committee believes that a careful and thorough revision of the report is needed. If you desire further elaboration on the comments above or in the accompanying appendixes, please do not hesitate to call or write either Dr.
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