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Factors Affecting the DIL for Air Sampling
Internal Dosimetry - index
Performance Specifications for a Bioassay Laboratory

and that lapel-type breathing zone air samplers more accurately corresponded to intakes predicted using
the 1966 ICRP lung model and fecal data. He also showed wide variability between breathing zone air
results and general area air results, with median BZ/GA ratios between 3 and 8, and 90 percentile ratios
from 9 to 26.
4.4.4 Supplementing Routine Bioassay Programs When DIL < MDA
DOE's 10 CFR 835.402(c) requires that, with a likelihood for 0.1 rem of HE,50, a worker must be on
a dose evaluation program. There is no requirement that the program be able to detect 0.1 rem of CEDE,
only that it has to detect 5 rems of CEDE, as in 10 CFR 835.402(d).
To gain insight on the question of detection capability, one may examine requirements for external
irradiation. There is the same 0.1-rem threshold for external monitoring, but an additional requirement
that external dosimeters be accredited by the U.S. Department of Energy Laboratory Accreditation
Program (DOELAP). Since 10 CFR 835 is a requirements document, then the standards in the DOELAP
manual (DOE 1986) are requirements. Thus, personnel dosimeters must be able to detect 0.03 rem in
several categories of radiation exposure. The practice for external irradiation is to require not only
detection capability at 30% of the monitoring threshold, but also fairly precise and accurate detection
capability at that level. By analogy, one might consider it desirable for an internal dosimetry program to
be capable of detecting HE,50 values in the same range. However, this is not always practical or even
There is technology shortfall for routine bioassay programs when the DIL is lower than the MDA.
When a bioassay program has DIL < MDA, BZ or personal air monitoring may be implemented to
supplement the routine bioassay program, as illustrated in Example 4.3.
Personal air samples are often more representative that fixed samplers. However, personal air
samplers have a lower flow rate than most fixed air samplers. Example 4.4 shows how averaging of
periodic results can be used to lower the MDC.
4.4.5 A Potential Technology Shortfall for Breathing Zone Air Sampling
Breathing zone air sampling may not be adequate in facilities where 238Pu or another high specific
activity alpha emitter is processed. High specific activity radionuclides usually have shorter half lives
than lower specific activity isotopes. The problem with high specific activity radionuclides arises from
the fact that a small number of particles can be significant from a dose standpoint as illustrated in
Example 4.5. However, as shown in Example 4.6, a similar concern does not exist for isotopes with
lower specific activity, such as 239Pu. Thorough discussions of the problems with detecting and
quantifying intakes using personal air samplers, including accounting for slip correction, are given by
Birchall et al. (1985, 1986, 1987, 1991) and by Scott et al. (1997).
There is historical precedent for a BZ or personal air monitoring program supplemented by an
aggressive fecal sampling program in NRC-licensed plutonium facilities. A facility operated in the 1960s
and 1970s in Parks Township, Pennsylvania, by NUMEC, ARCO, and most recently by Babcock &
Wilcox (Caldwell 1972), which processed reactor-grade plutonium, did not have significant trouble with
the "countable number of particles" problem discussed in Example 4.5.

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