The Hanford Environmental Dose Reconstruction Project A Review of Four Documents (1994) / Chapter Skim
Currently Skimming:
IV. OBJECTIVES AND GOALS OF HEDR
IV. OBJECTIVES AND GOALS OF HEDR
Pages 14-26
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 14... ...
The approach taken in the documents is to rely primarily on releases calculated from daily measurements of operational conditions that are directly related to iodine-131 and other fission-product production. The operational measurements include power levels, fuel loading and unloading, and cooling times between fuel discharges and processing and are comprehensive and complete for calculation of iodine-131 generation and release.
|
From page 15... ...
The measurements are simple, their accuracy in the 1940s was as good as it would be with current techniques, and the committee believes that the daily data were logged dutifully and without bias; i.e., they are complete and an excellent source of information generated by Hanford's workers for determining the source term. A fuel charge was typically left in the reactor for about a month, after which it was discharged from the fuel channel as a total batch after the desired burnup was achieved (as indicated by the operations log)
|
From page 17... ...
cO ~ ~ - ~ ~L - ~ Let l< - r ·' ~ O ~ ~5 ~ ~ · ~ · · ~ o 17 Ct V]
|
From page 18... ...
That is the main reason why most of the iodine-131 releases occurred in 1944 to 1947; cooling times were later extended to about 6 months to allow most of the iodine-131 to decay before processing began. The times between discharge from the reactor and initiation of fuel reprocessing are also in the operations logs for each batch of fuel.
|
From page 19... ...
The dose-reconstruction team appears to have followed up on all potentially missing events suggested by the public and employees at the Hanford site; to our knowledge, no important events of this type have escaped examination, and doses resulting from unaccounted-for releases are not likely to produce a total dose which exceeds the HEDR staffs estimate of the total dose. On the basis of fuel-burnup records and the volatility of iodine during fuel reprocessing, and the volatility of iodine during fuel reprocessing, the authors assumed a constant fraction of iodine losses in the source term.
|
From page 20... ...
An analysis of fuel technology at the time suggests that such releases should have been measurable, although they were no doubt considerably smaller than those due to fuel reprocessing. If available, data on iodine-131 concentrations in the reactor cooling water might be useful in determining associated airborne releases.
|
From page 21... ...
The releases are not likely to be underestimated, inasmuch as the authors took care to account for all fuel changes, operational parameters including measured power levels, fuel cooling times, and residual fractions in process chemicals. The only concern that the committee has is in the paucity of information about the releases of iodine-131 from the reactor themselves although it realizes these are likely to be minor compared with those from reprocessing.
|
From page 22... ...
In the HEDR project, the decision was made to expend more effort on the earlier periods (mid-1940s) , when the largest releases of radionuclides occurred and reliable monitoring data were scarce, than on the later periods, when releases were relatively small and reliable monitoring data were more abundant.
|
From page 23... ...
However, biases that tend to increase the dose estimates have been accepted (for example, in the case of the chemical form to be considered) , and triangular distributions have often been used when lognormal distributions might be more appropriate.
|
From page 24... ...
2. SURFACE-WATER AND GROUNDWATER PATHWAYS Pathways of exposure to contaminated river water include: direct consumption; swimming; boating; shoreline exposures; consumption of resident fish, anadromous fish, and other seafood; and possibly consumption of irrigated crops.
|
From page 25... ...
With respect to the issues of clarity and detail, the committee feels that the information given in the documents regarding water pathways is sparse, but that what is provided is quite clear. DOSE ASSESSMENT Doses will be assessed on the basis of the environmental concentrations of radionuclides in air, soil, and terrestrial foodstuffs for the atmospheric pathways and in water, sediments, and aquatic foodstuffs for the surface-water and groundwater pathways.
|
From page 26... ...
· The decision to exclude the ingestion pathway in the doses received by the populations on site should be justified. · Additional pathways will be included in the assessments if it is determined that such pathways have "the potential to add more than 5% of the total annual dose for any individual at a time when the dose exceeds the TSP guidelines." But those TSP guidelines are not specified in the documents provided to the committee, and it should be indicated whether only the effective dose or the dose to any organ or tissue of the body is considered, as well as how the effective dose was estimated.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.