General Performance Criteria for Instruments

DOE-STD-1128-98

Guide of Good Practices for Occupational Radiological Protection in Plutonium Facilities

performed to determine instrument locations. Continuous air monitors may not have

adequate detection capabilities for real-time monitoring at the DAC level. For 239Pu, the

annual limit on intake (ALI) is 4.8 nCi for class W compounds based on the DAC of 2 x

10-12 :Ci/mL, as given in Appendix A to 10 CFR Part 835 (DOE, 1998a). Representative

manufacturers' specifications on the performance level of such a CAM range from 1 DAC in

4 hours (4 DAC-h) to 1 DAC in 8 hours (8 DAC-h) for alarm (with no radon present).

Continuous air monitors typically have had poor large-particle response due to particle loss

during transport to the filter inside the system. Newer alpha air monitors are able to handle

large particles more efficiently. Background levels of radon-thoron decay products may be

present in concentrations up to 50 to 100 times greater than the level of plutonium of

interest. If calibrated properly, alpha CAMs will subtract background levels of radon-thoron

decay products; however, in practice the detection limit for plutonium may be as high as

40 DAC-h in the presence of high radon levels. A new generation of alpha CAMs is able to

compensate for radon more effectively and meet the desired 8 DAC-h alarm level.

Transuranic aerosol measurement units have been developed and adapted to be used in the

workplace. These units avoid preferential plate-out of larger particles by using an in-line

filter. Higher flow rates than those normally used with CAMs may be used. Increased

detection is obtained on a quasi-real-time basis by high-volume air sampling and counting in

a separate vacuum chamber. Detection levels of less than 0.5 DAC-h have been quoted for

these units. It has been demonstrated that high-volume impact samplers used at some

facilities have demonstrated detection capabilities of 0.1 DAC-h in the laboratory and

1 DAC-h in the field. Other monitoring systems that use diffusion, impaction, or electronic

discrimination to reduce the effect of background resulting in an increased detection

capability have also been used and are being improved upon. However, it is suggested that

site-specific testing be performed on any new equipment to ensure compatibility and verify

expected performance. See the Health Physics Manual of Good Practices for the Prompt

Detection of Airborne Plutonium in the Workplace (Mishima et al., 1988) for additional

information on the selection, placement, and operation of plutonium air monitors.

3.5.2 General Performance Criteria for Instruments

Programs for in-plant monitoring of plutonium consist mainly of airborne and surface

contamination surveys and dose rate surveys. The general and specific performance criteria

for the instrumentation needed to conduct these programs are described in ANSI N317-1991

(ANSI, 1980a). Performance specifications are also given in ANSI N323 (ANSI, 1997b),

ANSI N42.17A (ANSI, 1988b), and ANSI N42.17C-1989 (ANSI, 1987c) for portable health

physics instrumentation and IEC Publication 325 (IEC, 1981) for alpha and beta

contamination meters and monitors. Criteria for air monitoring instrumentation are

contained in ANSI N13.1 (ANSI, 1969b), IEC Publication 761-2 and draft IEC Publication

761-6 (IEC, 1983), and ANSI N42.17B-1989 (ANSI, 1987b). Criticality alarm systems are

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