Supplementing Routine Bioassay Programs When DIL

DOE-STD-1121-98

and that lapel-type breathing zone air samplers more accurately corresponded to intakes predicted using

the 1966 ICRP lung model and fecal data. He also showed wide variability between breathing zone air

results and general area air results, with median BZ/GA ratios between 3 and 8, and 90 percentile ratios

from 9 to 26.

4.4.4 Supplementing Routine Bioassay Programs When DIL < MDA

DOE's 10 CFR 835.402(c) requires that, with a likelihood for 0.1 rem of HE,50, a worker must be on

a dose evaluation program. There is no requirement that the program be able to detect 0.1 rem of CEDE,

only that it has to detect 5 rems of CEDE, as in 10 CFR 835.402(d).

To gain insight on the question of detection capability, one may examine requirements for external

irradiation. There is the same 0.1-rem threshold for external monitoring, but an additional requirement

that external dosimeters be accredited by the U.S. Department of Energy Laboratory Accreditation

Program (DOELAP). Since 10 CFR 835 is a requirements document, then the standards in the DOELAP

manual (DOE 1986) are requirements. Thus, personnel dosimeters must be able to detect 0.03 rem in

several categories of radiation exposure. The practice for external irradiation is to require not only

detection capability at 30% of the monitoring threshold, but also fairly precise and accurate detection

capability at that level. By analogy, one might consider it desirable for an internal dosimetry program to

be capable of detecting HE,50 values in the same range. However, this is not always practical or even

feasible.

There is technology shortfall for routine bioassay programs when the DIL is lower than the MDA.

When a bioassay program has DIL < MDA, BZ or personal air monitoring may be implemented to

supplement the routine bioassay program, as illustrated in Example 4.3.

Personal air samples are often more representative that fixed samplers. However, personal air

samplers have a lower flow rate than most fixed air samplers. Example 4.4 shows how averaging of

periodic results can be used to lower the MDC.

4.4.5 A Potential Technology Shortfall for Breathing Zone Air Sampling

Breathing zone air sampling may not be adequate in facilities where 238Pu or another high specific

activity alpha emitter is processed. High specific activity radionuclides usually have shorter half lives

than lower specific activity isotopes. The problem with high specific activity radionuclides arises from

the fact that a small number of particles can be significant from a dose standpoint as illustrated in

Example 4.5. However, as shown in Example 4.6, a similar concern does not exist for isotopes with

lower specific activity, such as 239Pu. Thorough discussions of the problems with detecting and

quantifying intakes using personal air samplers, including accounting for slip correction, are given by

Birchall et al. (1985, 1986, 1987, 1991) and by Scott et al. (1997).

There is historical precedent for a BZ or personal air monitoring program supplemented by an

aggressive fecal sampling program in NRC-licensed plutonium facilities. A facility operated in the 1960s

and 1970s in Parks Township, Pennsylvania, by NUMEC, ARCO, and most recently by Babcock &

Wilcox (Caldwell 1972), which processed reactor-grade plutonium, did not have significant trouble with

the "countable number of particles" problem discussed in Example 4.5.