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DOE-STD-1128-98
Guide of Good Practices for Occupational Radiological Protection in Plutonium Facilities
General follow-up actions to abnormal bioassay measurements should include data checks, timely
verification measurements, work history reviews, and performance of special in an in vivo
measurements or excreta sample analyses for intake and dose assessments.
5.7.1 In Vivo Count Results
In an in vivo plutonium or americium measurements are generally relatively insensitive with
regard to levels of occupational exposure concern. This applies particularly to routine chest
or lung counting, skeleton counting, and liver counting. For that reason, any detection of
plutonium or americium should be investigated. The investigation should address the
validity of the measurement by reviewing the spectrum and its associated background
subtraction. These reviews are particularly important if the result is near the Lc. Follow-up
to a positive result should include a confirming measurement. Ideally, this should be an
immediate (same day) recount of equal or higher sensitivity. The farther removed in an in
time a verification measurement is from the original measurement, the more important it
becomes to factor in an in potential lung clearance in an in comparing the two
measurements. A follow-up measurement taken 30 days after an initial high-routine may
not be capable of providing verification if the material of concern exhibits class W behavior.
Chest-wall thickness has a significant impact on chest counting. Corrections are commonly
made using a height-to-weight ratio or ultrasonic methods (Kruchten and Anderson, 1990).
Corrections may be required to address apparent detection in an in one tissue resulting from
photon crossfire from another tissue. For example, chest counting is performed primarily to
estimate activity in an in the lung. Yet, there is substantial bone over the lungs (rib cage,
sternum) and behind the lungs (vertebrae). Plutonium and americium are both bone-seeking
radionuclides which will deposit on those bone surfaces and can interfere with chest
counting. It is possible for a person having a systemic burden of plutonium from a wound in
an in the finger to manifest a positive chest count from material translocated to the skeleton,
axillary lymph nodes, or liver (Carbaugh et al., 1989; Graham and Kirkham, 1983; Jeffries
and Gunston, 1986). Interpreting such a chest count as a lung burden can render dose
estimates somewhat inaccurate.
When comparing in an in vivo measurements made over many years, it is important to make
sure that the measurements are, in an in fact, comparable. One consideration is to make sure
that corrections have been consistently applied to all similar measurements. It is not unusual
for measurement systems to be replaced or to change the algorithms used for calculating
results over time. Step changes in an in data can occur and should be addressed in an in
monitoring long-term detectable trends (Carbaugh et al., 1988).
5-26


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