Linked Life Data

12018744

Source:http://linkedlifedata.com/resource/pubmed/id/12018744

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
3
pubmed:dateCreated
2002-5-20
pubmed:abstractText
The Bevatron of the Lawrence Berkeley National Laboratory operated with no permanent shielding-roof from 1954 to 1962. Neutron fluences measured at the laboratory perimeter reached a maximum in 1959, and were reported as an annual dose equivalent of 8.1 mSv (54% of the then operative radiation limit). The addition of temporary local shielding and improved operational techniques subsequently led to a steady decline in dose equivalent at the laboratory perimeter. A permanent concrete shielding-roof was constructed in 1962. In those early years of operation the reported dose equivalent, H, was derived from a measured total neutron fluence, phi, and an estimated spectrum-weighted fluence to dose equivalent conversion coefficient, (g), where H= (g) phi. The uncertainty in H was almost entirely due to the uncertainty in (g). While the measurements of phi were accurate the estimates of (g) were quite crude and depended upon measurements of average neutron energy, on assumptions about the shape of the neutron energy spectrum, and primitive values of fluence to dose equivalent conversion coefficients for monoenergetic neutrons. These early reported dose equivalents were known to be overestimated. This paper has reappraised the dose equivalents in the light of better information now available. Environmental neutron spectra have been calculated which more accurately correspond to the operational conditions of the Bevatron in the 1950s and early 1960s. than did those spectra available at that time. A new fluence to dose equivalent conversion function based on the latest data and for isotropic irradiation geometry was developed. From these two parameters better estimates of the coefficient (g) were determined and compared with the earlier values. From this reappraisal it is shown that the early reported dose equivalents were conservative by a factor of at least five.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:status
MEDLINE
pubmed:issn
0144-8420
pubmed:author
pubmed:issnType
Print
pubmed:volume
98
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
269-82
pubmed:dateRevised
2006-11-15
pubmed:meshHeading
pubmed:year
2002
pubmed:articleTitle
A reappraisal of the reported dose equivalents at the boundary of the University of California Radiation Laboratory during the early days of Bevatron operation.
pubmed:affiliation
Ernest Orlando Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, Non-P.H.S.