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Establishing bounding internal dose estimates for thorium activities at Rocky Flats.

Authors
Ulsh-BA; Rich-BL; Chew-MH; Morris-RL; Sharfi-M; Rolfes-MR
Source
Health Phys 2008 Jul; 95(1):81-88
NIOSHTIC No.
20034084
Abstract
As part of an evaluation of a Special Exposure Cohort petition filed on behalf of workers at the Rocky Flats Plant, the National Institute for Occupational Safety and Health (NIOSH) was required to demonstrate that bounding values could be established for radiation doses due to the potential intake of all radionuclides present at the facility. The main radioactive elements of interest at Rocky Flats were plutonium and uranium, but much smaller quantities of several other elements, including thorium, were occasionally handled at the site. Bounding potential doses from thorium has proven challenging at other sites due to the early historical difficulty in detecting this element through urinalysis methods and the relatively high internal dose delivered per unit intake. This paper reports the results of NIOSH's investigation of the uses of thorium at Rocky Flats and provides bounding dose reconstructions for these operations. During this investigation, NIOSH reviewed unclassified reports, unclassified extracts of classified materials, material balance and inventory ledgers, monthly progress reports from various groups, and health physics field logbooks, and conducted interviews with former Rocky Flats workers. Thorium operations included: (1) an experimental metal forming project with 240 kg of thorium in 1960; (2) the use of pre-formed parts in weapons mockups; (3) the removal of Th-228 from U-233; (4) numerous analytical procedures involving trace quantities of thorium; and (5) the possible experimental use of thorium as a mold coating compound. The thorium handling operations at Rocky Flats were limited in scope, well-monitored and documented, and potential doses can be bounded.
Keywords
Dose-response; Dosimetry; Occupational-exposure; Exposure-assessment; Employee-exposure; Work-environment; Work-practices; Workplace-monitoring; Metal-mining; Metal-workers
Contact
Brant A. Ulsh, NIOSH, 4676 Columbia Pkwy,Mailstop C-46, Cincinnati, OH 45226
CODEN
HLTPAO
CAS No.
7440-29-1
Publication Date
20080701
Document Type
Journal Article
Email Address
bau6@cdc.gov
Fiscal Year
2008
NTIS Accession No.
NTIS Price
Issue of Publication
1
ISSN
0017-9078
NIOSH Division
OCAS
Source Name
Health Physics
State
OH; CA
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