Special Bioassay as Supplements to Routine Bioassay Programs

DOE-STD-1128-98

Plutonium facility decommissioning projects may present a different set of

challenges for worker protection. In particular it is likely that clean up of areas will

involve more plutonium that is not contained than is the case during normal

operations. In addition, the workers involved may be relatively transient as the

project progress through phases requiring different craft labor mixes. This being the

case, more frequent bioassay may be necessary to provide good assurance that dose

limits are not exceeded. As discussed in Section 5.3.1, it is likely that program

administrators will require a baseline measurement prior to the start of work and

another at the termination of work. However, if the worker moves between tasks, it

may be difficult to determine the source of an uptake without intermittent bioassay.

In such cases, the use of breathing zone air samplers may be appropriate.

5.4.3

Special Bioassay as Supplements to Routine Bioassay Programs

Special bioassay programs for workers with known or suspected acute inhalation

intakes of plutonium or other alpha-emitting radionuclides should include both urine

and fecal sampling. Special bioassay measurements should be initiated for each

employee in a contaminated work area when surface contamination is detected by

routine surveillance if it is possible that the contamination resulted in a CEDE of 100

mrem or greater. Excreta samples should not be collected where they may be

contaminated by external sources of plutonium. Ideally, total urine and feces should

be collected for about a week following intake. This permits a sensitive assessment of

potential intake and internal dose. Longer term special samples collected at various

times from a month to a year following intake can help to discriminate between

ingestion, class W inhalation, and class Y inhalation. See Section 5.9 for indicator

levels where special bioassay should be considered.

5.4.4

Long-term Follow-up Bioassay Programs

Following an intake a long-term follow-up bioassay program may be required for a

worker to compare the actual excreta or in vivo results with those projected by the

evaluation. This is important to verify the accuracy of intake and dose assessments.

The frequency and duration of a special program is dependent upon the projected

values; it is suggested that as long as a worker continues to have detectable bioassay

results, he or she should continue to be monitored. It is particularly important to have

good baseline data and projections for individuals who return to plutonium work. The

ability of a bioassay program to distinguish between an established, elevated baseline

and a new potential intake is important in the continued monitoring of workers once

an intake has occurred. Because of statistical fluctuations in low-level plutonium and

americium measurements, it can be very difficult to identify a new intake by routine

bioassay if a worker has an elevated baseline.

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