Occupational Intakes of Radionuclides Part 1 - ICRP

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DRAFT REPORT FOR CONSULTATION
difficulties in assessing intakes from PAS measurements were considered by Whicker
(2004). Breathing zone measurements can vary significantly as they can be affected
by measurement conditions such as orientation of the sampler with respect to source,
on which lapel (right or left) the sampler is worn, design of the air sampling head,
particle size, local air velocities and directions, and sharp gradients in and around the
breathing zone of workers.
(263) Britcher and Strong (1994) reviewed the use of PAS as part of the internal
dosimetry monitoring programmes for the Calder Hall reactors and the Sellafield
nuclear fuel reprocessing facility in the U.K. It was concluded that samplers can be
used to obtain satisfactory estimates of intake for groups of workers. However, for
individuals, the correlation between assessments using PAS and biological samples
was poor and the authors cast doubt on the adequacy of PAS for estimating annual
intakes of individual employees at the levels of exposure encountered in operational
environments. The authors also questioned whether, for environmental monitoring,
PAS offered any advantages over static air sampling programmes. The same lack of
correlation between PAS and bioassay sample-based intake estimates was also seen
for known acute exposures (Britcher et al, 1998).
(264) A uranium exposure study was conducted by Eckerman and Kerr (1999) to
determine the correlation between uranium intakes predicted by PASs and intakes
predicted by bioassay at the Y12 uranium enrichment plant in Oak Ridge, USA. This
study concluded that there was poor correlation between the two measurements.
(265) Static air samplers are commonly used to monitor workplace conditions, but
can underestimate concentrations in air in the breathing zone of a worker. Marshall
and Stevens (1980) reported that PAS:SAS air concentration ratios can vary from less
than 1 up to 50, depending on the nature of the work. Britcher and Strong ( 1994)
concluded from their review of monitoring data for Magnox plant workers in the U.K.
that intakes assessed from PAS data were about an order of magnitude greater than
those implied by SAS data. SAS devices, however, can provide useful information on
radionuclide composition, and on particle size, if used with a size analyzer such as a
cascade impactor.
(266) Overall, the use of PASs and SASs can be an important part of a
comprehensive workplace monitoring programme and is able to provide an early
indication of risk of exposure. Experience of the use of PASs and SASs indicates that
body activity measurements and/or excreta analysis are to be preferred for the
assessment of individual intakes of airborne radionuclides and doses.
(267) However, for some transuranic radionuclides, body activity measurements and
urine analysis can only quantify exposures sufficiently reliably above a few mSv
unless sensitive mass spectrometric techniques for the analysis of bioassay samples
are available. For the detection of lower exposures, a combination of monitoring
methods is then likely to be needed, which could include air sampling and faecal
analysis.
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