Frequency Based on Program Sensitivity - doe-std-1128-98

DOE-STD-1128-98

The rationale for the selected bioassay measurement frequency should also be documented.

It is appropriate to evaluate the probability of intake and to modify the sampling frequency

based on that probability.

The frequency of bioassay measurements should normally not be decreased because

analytical results are below the detection level. The bioassay program should be maintained

to confirm the proper functioning of the overall internal exposure control program and to

document the absence of significant intakes of radionuclides.

5.4.1

Frequency Based on Program Sensitivity

The minimum detectable dose concept refers to the potential dose associated with an

MDA bioassay measurement at a given time interval post-intake. The pattern of

retention of activity in the body, the MDA for a bioassay measurement technique,

and the frequency with which that technique is applied define a quantity of intake

that could go undetected by the bioassay program. An intake of such a magnitude

would not be detected if it occurred immediately after a bioassay measurement and if

it were eliminated from the body at such a rate that nothing was detected during the

next scheduled measurement. The dose resulting from such an intake would be the

MDD for that particular measurement technique and frequency.

Estimates of MDD in terms of CEDE should be documented for each measurement

technique, MDA, and frequency. Retention functions specific to the various chemical

forms and particle size distributions found in the facility should be used. Examples of

MDD tabulations can be found in La Bone et al. (1993) and Carbaugh et al. (1994).

In establishing MDD tables, it is important to consider dose contributions from all

appropriate radionuclides in any mixture, rather than just the dose contribution from

the bioassay indicator nuclide.

5.4.2

Frequency Based on Potential Risk of Intake

As discussed in Section 5.3.2, although plutonium workers are not generally

considered to be at high risk of incurring intakes that might result in CEDEs of 100

mrem or more, any plutonium worker can be considered to have the potential for

such an intake. However, having the potential for intake does not mean that they are

likely to incur an intake.

Workers who have the highest potential risk for an intake are those most closely

working with plutonium or plutonium-contaminated material. Typically, these

workers are glove-box workers, maintenance workers, and operational health physics

surveillance staff. These workers should be on a routine plutonium or americium

bioassay program, including urinalysis and in vivo measurements. Such programs are

relatively insensitive compared to the 100-mrem CEDE goal and are a safety net

intended to catch intakes of significance relative to regulatory limits, rather than

substantially lower administrative levels. Selection of bioassay frequency depends on

the facility experience with potential intakes, the perceived likelihood of intake, and

the MDD of a program. Annual urinalyses and in vivo chest counts are fairly typical.

More frequent (e.g., semi-annual or quarterly) measurements may permit more timely

review of workplace indicators in the event that an abnormal bioassay result is

obtained, but do not necessarily mean a more sensitive program.

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