Portable Survey Instruments - STD-1128-98master0078

DOE-STD-1128-98

Guide of Good Practices for Occupational Radiological Protection in Plutonium Facilities

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

subsections are specified in these standards as referenced.

3.5.2.1 Portable Survey Instruments

ANSI N317 (ANSI, 1980a) discusses several criteria related to the performance of

portable survey instruments; these include the following requirements:

-- The overall accuracy shall be within 20%, and the precision shall be within

10% at the 95% confidence level.

-- The response time (i.e., the time for the instrument reading to go from zero to

90% of full scale) shall be < 10 seconds on the most sensitive scale and

< 2 seconds at readings of 100 mrem/h, 100 mR/h, and 500 dpm or greater.

(This criterion is unrealistic with current neutron instrument capabilities.

Response time is typically 30 to 60 seconds.)

-- The instrument shall be able to maintain accuracy and precision for a minimum

of 24 hours of continuous operation.

-- The instrument shall have a minimum battery lifetime of 200 hours of

continuous operation.

ANSI N42.17A (ANSI, 1988a) specifications differ slightly.

-- The response of the instrument shall not change by more than 15% from a

reference value taken at 20C over the anticipated temperature range for

operation.

-- The instrument system shall function within specifications over all anticipated

combinations of temperature and humidity (e.g., 15 to 65C, 40% to 95%

relative humidity).

Photon survey instruments should meet the accuracy requirements stated in ANSI

N317 (ANSI, 1980a) over the energy range of 0.01 to 1.25 MeV. The angular

response of this type of instrument should be within 15% over a 2B steradian

frontal direction using at least two photon sources with energies ranging from 0.06

to 1.25 MeV. Experience has shown that this response specification is not met by

most instruments at lower energies due to attenuation of the photon. The energy

dependence should be within 15% over the range of very low energy to 1.25 MeV

and the operating range should be from 0.5 mR/h to at least 5000 mR/h.

3-18