Quantcast General Performance Criteria for Instruments - doe-std-1128-98_ch10065


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Instrumentation Considerations - doe-std-1128-98_ch10064
DOE Standard Guide of Good Practices for Occupational Radiological Protection In Plutonium Facilities
Portable Survey Instruments - doe-std-1128-98_ch10066

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.
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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