T.O. 33B-1-1a.The 440 (Table 6-22), SM-400 and the VR-10 are similar in size, appearance and specifications. Allare 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 0-300mR/hr.c.The instruments are, for practical purposes, energy independent from 15 keV to 1.2 MeV withtheirfrontcapsremoved.d.The batteries for the 440 and VR-10 consist of our ‘‘D’’ f lashlight cells. Each instrument weighsapproximately 5-1/2 pounds and its overall dimensions are 10 long, 4 wide and 7 high. The SM 400uses 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 areconnected, permitting the operator to check the battery condition. Although instruments such as the440 can accurately measure low levels of X-ray emissions and scattering, care must be exercised toassure that the upper limit is not exceeded.f.The SM-400 end cap contains a lever-operated alpha/beta check source to verify instrument operationeach time it is used.6.9.10.4.2RecommendedNewInstruments:6.9.10.4.2.1VictoreenModel450PSurveyMeter.The Model 450P is a lightweight portable survey meter designed to measure X radiation above 25 keV. It hasa 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) onthe highest scale and has a programmable ‘‘f lash alarm’’ which causes the display to pulsate at a rate of onceper second when the measured dose rate exceeds a preset limit. The detector is a 300-cc ionization chamberpressurized 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. Formaximum sensitivity, the Model 450P survey meter should be perpendicular to the ground plane whenmaking measurements rather than being parallel to the ground.6.9.10.4.2.2VictoreenModel450Band450-CHPSurveyMeters.The Model 450B and 450-CHP Survey Meters are similar instruments that detect gamma and X-rayradiation above 7 keV. Both have a five decade operating range measuring from 0-5mR/hr (0-50 mSv/hr) to0-50 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 aset of two new 9-volt batteries. The Models 450B and 450 CHP should always be used with the cap off whenmeasuring X-ray and gamma radiation with energies below 200 keV due to energy response variation.6.9.10.4.2.3VictoreenModelRPO-50SurveyMeter.The Model RPO-50 Survey Meter is an excellent replacement for the older instruments listed in the abovetable. It has similar controls compared to the SM-400, and Victoreen 440, but has significantly improvedperformance characteristics. It detects gamma and x-ray radiation above 7 keV. The Model RPO-50 has fouroperating ranges, measuring from 0-5mR/hr (0-50 mSv/hr) to 0-5 R/hr (0-. 05 Sv/hr). The detector is a 349-ccair ionization chamber that has a 493-mg/cm2 bakelight wall and a 3.5 mg/cm2 window. It operatescontinuously for about 3000 hours on a set of four new 9-volt batteries. It is environmentally sealed and haslimited RF shielding, permitting its use in demanding environments. The Model RPO-50 should always beused with the cap off when measuring X and gamma radiation with energies below 200 keV due to energyresponse variations.Change 36-127
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