Portable Survey Instruments - doe-std-1128-98

DOE-STD-1128-98

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 2 π 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.

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