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Bioassay Compared to and Contracted With Workplace Air Monitoring
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Internal Dosimetry - index
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Investigation Level and Derived Investigation Level


DOE-STD-1121-98
equivalent in a year, or 50 rems committed dose equivalent to an organ or tissue other than the eye). In
light of this requirement, there are three distinct situations for internal dosimetry programs:
1.
Adequate technology. In this situation, routine bioassay measurements can show not only
compliance with 10 CFR 835.202, but can be used to assess doses when HE,50 # 100 mrem (the
investigation level). An example of an "adequate technology" situation, that is, where there is
no technology shortfall, is a routine urinalysis program for 3H or a routine in vivo counting
program for 137Cs: in each case, the MDA is less than the DIL.
2.
Technology shortfall for routine bioassay. In this situation, the DIL is less than the MDA for
practical routine bioassay, but special bioassay, triggered by workplace indicators, is available
on short notice that can be used to show compliance with 10 CFR 835.402(d). An example of a
"technology shortfall for routine bioassay" situation is a state-of-the-art internal dosimetry
program for plutonium supplemented by vigorous workplace monitoring and controls.
3.
No practical bioassay. In this situation, no bioassay method is available for the radionuclides
in question, and no bioassay program, either routine or special, can show compliance with 10
CFR 835.202. An example of a "no practical bioassay" situation is routine worker exposure to
the short-lived decay products of radon and thoron, in which no bioassay program can
demonstrate compliance with the limits. In the "no practical bioassay" case, the only recourse
in showing compliance with 10 CFR 835.202 is using representative air monitoring, tracking
worker exposure in DAC-h or working level months (WLM), and performing dose assessments
on the basis of the air monitoring results.
For the short-lived progeny of radon and thoron, worker stay times and measurements of potential
alpha energy concentration (PAEC) can be converted to potential alpha energy exposure (PAEE) in
WLM. Alternatively, worker stay times and radon concentration measurements, with knowledge or
assumption of the equilibrium factor, can be converted to equilibrium equivalent DAC-h or to PAEE in
WLM.
4.2 REFERENCE LEVELS AND DERIVED REFERENCE LEVELS
A reference level is a predetermined value of a quantity that triggers a specified course of action
when exceeded or expected to be exceeded. Reference levels may be dose-based or intake-based.
Derived reference levels are the measurement values for particular bioassay or air sampling results that
correspond to a more general reference level under specifically defined circumstances. Some suggested
reference levels are described below:
Verification Level, LV - The level of unexpected intake or dose at or above which an attempt
should be made to determine if the intake is real. For example, this is the level at which special
follow-up measurements should be obtained to confirm a high routine result. Below this level,
it may be assumed, routine results are valid and default assumptions can be used to calculate
and assign intake and dose.
Investigation Level, IL - The level of intake or dose (specified in the IDG as 100 mrem) at or
above which a bioassay or air monitoring result should be investigated. The intent of this level
is to investigate the circumstances and, to the extent reasonable, to determine actual conditions
and parameters for dose evaluation, rather than use default assumptions. An investigation may
31


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