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DOE-HDBK-1184-2004
efforts will probably not be straightforward, and conservatism must be used to
ensure that the hazards associated with ITPs are adequately addressed to provide
an adequate level of protection to DOE workers. If the analyses cannot definitively
identify the ITP species, identity of the ITP species may be based on process or
historical knowledge.
In all cases, a conservative approach should be used in identifying STC-
contaminated samples. If the combination of factors identified below (facility
history, radioanalytical identification of tritium, particle species identification) leads
to a conclusion that the presence of STCs is likely, then the appropriate controls
should be implemented consistent with this manual.
For ITPs, a scanning electron microscope (SEM) may be used to identify the
presence of particles that are likely hosts for tritium atoms. In combination with
conventional radioanalysis using LSC, an estimate of the gross ITP contamination
levels may be obtained. This technique does have limitations however. While the
LSC can definitively establish the levels of tritium emissions, and the SEM can
definitively establish the presence and size of possible host particles, it is difficult to
establish a direct correlation between the detected tritium emissions and the
particulate levels. That is, it is not possible to state with any degree of certainty
what fraction of the detected emissions arise from ITPs versus that fraction that
arises from the more common tritium forms that may also be present. The
presence of likely host particles does not definitely prove the presence of tritium
within those particles.
The presence, of but not the amount of, ITPs may also be inferred by performance
of multiple LSC analyses of individual samples, and trending the results to evaluate
the change in observed tritium activity as the tritium atoms are released from the
host material in the sample. (The observed tritium activity increases because the
betas emitted by the tritium molecules that have been released from the metal
particle are not absorbed by the metal particle.) This method may only be effective
for those ITPs where the tritium is released from the host particle over a time period
ranging from a few hours to a few weeks. If the tritium binds to the host material
very tightly, the growth in observed activity will not be apparent over any reasonable
time interval between repetitive sample analyses. If the ITP species is soluble, then
all of the captured tritium may be released into the counting solution before the
sample is counted. Because the lack of an effect does not mean ITPs are not
present, the use of this method depends on reliable knowledge of the strength of
the bond between the tritium and the host material in the ITPs expected to be
present in the work area. Information on dissolution is contained in Appendix D. If
tritium is likely to be present in both ITP and conventional forms, efforts should be
undertaken to differentiate between the different species so that the appropriate
controls (e.g., based on applicable limiting values) may be applied. One approach
is to count a survey or air filter sample in LSC cocktail. This measurement gives a
value for ITP plus HTO content. Addition of fresh water to the cocktail followed by
evaporation (thus removing HTO from the sample) and then recounting the sample,
provides a value for ITP alone. Other approaches at differentiating between the
species may include attempts at ITP dissolution, following by sample counting to
detect changes in analysis results due to particle dissolution and subsequent
increase in detected tritium atom disintegrations. The accuracy of this approach is
dependent on knowledge of the specific species present, the fraction of tritium
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