T.O. 33B-1-1
a.
The 440 (Table 6-22), SM-400 and the VR-10 are similar in size, appearance and specifications. All
are authorized for use during NDI radiographic operations.
b.
The dial of the meter is calibrated in mR/hr and measures X or gamma radiation up to 300 mR/hr.
The instrument has 5 range selections: 0-3 mR/hr, 0-10 mR/hr, 0-30 mR/hr, 0-100 mR/hr, and 0-300
mR/hr.
c.
The instruments are, for practical purposes, energy independent from 15 keV to 1.2 MeV with their
front caps removed.
d.
The batteries for the 440 and VR-10 consist of our ‘‘D’’ f lashlight cells. Each instrument weighs
approximately 5-1/2 pounds and its overall dimensions are 10 long, 4 wide and 7 high. The SM 400
uses two ‘‘D’’ f lashlight cells and weighs approximately 5 pounds. Its overall dimensions are 10 long,
4.5 wide and 7 high.
e.
When the selector switch is OFF, the batteries are disconnected and the meter is short-circuited,
making the instrument inoperative. With the switch in the battery position the batteries are
connected, permitting the operator to check the battery condition. Although instruments such as the
440 can accurately measure low levels of X-ray emissions and scattering, care must be exercised to
assure that the upper limit is not exceeded.
f.
The SM-400 end cap contains a lever-operated alpha/beta check source to verify instrument operation
each time it is used.
6.9.10.4.2
Recommended New Instruments:
6.9.10.4.2.1
Victoreen Model 450P Survey Meter.
The Model 450P is a lightweight portable survey meter designed to measure X radiation above 25 keV. It has
a five decade operating range from 0-500 mR/hr (0-5 mSv/hr) on the lowest scale to 0-5 R/hr (0-50 mSv/hr) on
the highest scale and has a programmable ‘‘f lash alarm’’ which causes the display to pulsate at a rate of once
per second when the measured dose rate exceeds a preset limit. The detector is a 300-cc ionization chamber
pressurized to 6 atmospheres. The Model 450P measures exposure, exposure rate, and can be used to ‘‘freeze’’
the maximum exposure rate encountered and displays results on an illuminated analog/digital display. For
maximum sensitivity, the Model 450P survey meter should be perpendicular to the ground plane when
making measurements rather than being parallel to the ground.
6.9.10.4.2.2
Victoreen Model 450B and 450-CHP Survey Meters.
The Model 450B and 450-CHP Survey Meters are similar instruments that detect gamma and X-ray
radiation above 7 keV. Both have a five decade operating range measuring from 0-5mR/hr (0-50 mSv/hr) to
0-50 R/hr (0-0.5 Sv/hr). The detector for both instruments is a 349-cc air ionization chamber that has a 200-
mg/cm2 bakelight wall and a 1.7 mg/cm2 mylar window. They operate continuously for about 200 hours on a
set of two new 9-volt batteries. The Models 450B and 450 CHP should always be used with the cap off when
measuring X-ray and gamma radiation with energies below 200 keV due to energy response variation.
6.9.10.4.2.3
Victoreen Model RPO-50 Survey Meter.
The Model RPO-50 Survey Meter is an excellent replacement for the older instruments listed in the above
table. It has similar controls compared to the SM-400, and Victoreen 440, but has significantly improved
performance characteristics. It detects gamma and x-ray radiation above 7 keV. The Model RPO-50 has four
operating ranges, measuring from 0-5mR/hr (0-50 mSv/hr) to 0-5 R/hr (0-. 05 Sv/hr). The detector is a 349-cc
air ionization chamber that has a 493-mg/cm2 bakelight wall and a 3.5 mg/cm2 window. It operates
continuously for about 3000 hours on a set of four new 9-volt batteries. It is environmentally sealed and has
limited RF shielding, permitting its use in demanding environments. The Model RPO-50 should always be
used with the cap off when measuring X and gamma radiation with energies below 200 keV due to energy
response variations.
Change 3
6-127
