Classification of Bioassay Measurements

DOE-STD-1128-98

Guide of Good Practices for Occupational Radiological Protection in Plutonium Facilities

-- Baseline measurements are used to establish a pre-exposure condition, either for a new

employee or as a result of a new work assignment. The standard, Radiological Control

(DOE, 1999a), recommends baseline measurements if workers are considered likely to

receive intakes resulting in greater than 100-mrem CEDE. It is a good practice to

perform such measurements for newly hired employees, intra-company transferees, or

workers transferred from facilities where bioassay measurements may not have been

required. In addition, baseline measurements can verify workers' status for special work

assignments. For plutonium bioassay, baseline measurements made before any

occupational exposure can be expected to yield no detectable results using current

technology.

Exempting workers from baseline bioassay implies accepting any detectable results as

likely attributable to current occupational exposure. However, requiring baseline

measurements can potentially impact the schedule of short-term jobs; the time required

to obtain a chest count and a large-volume urine sample may add a day or two delay to

entry procedures. Moreover, missing a baseline for a long-term employee who will be

placed on a routine bioassay program is not likely to be as troublesome as not obtaining

a baseline for a short-term worker who provides a termination sample that shows

detection of plutonium after the worker has left the site and is difficult to reach for

follow-up.

Routine, or periodic, measurements are performed on a predetermined schedule

(e.g., an annual or quarterly frequency).

Special bioassay measurements are performed as follow-up to unusual routine

results or suspected intakes (See Section 5.9 for recommended internal dosimetry

indicator and action levels).

End of assignment or termination measurements are performed following

completion of specific work or at the time of termination of employment. The

standard, Radiological Control (DOE, 1999a), recommends that workers who

participate in bioassay programs have appropriate termination measurements.

Bioassay classification is important because the purpose of a sample may affect the

collection and analysis or monitoring method chosen. For example, single-void urine

samples are not adequate for routine monitoring of potential plutonium exposure, but

can provide important information for dose-reduction therapy following a suspected

intake; samples representative of excretion over a 24-hour period should be collected for

quantitative intake and dose assessment. The date of sample collection (and possibly the

time of collection) can be very important to special monitoring performed to assess

intake. However, these are much less important with regard to periodic monitoring, for

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