General Performance Criteria for Instruments

DOE-STD-1128-98

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 discussed in

ANSI/ANS 8.3-1986 (ANSI, 1986a). The criteria discussed in the following

subsections are specified in these standards as referenced.

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