T.O. 33B-1-1emits a ‘‘chirp’’ for each dose increment. The radiation is recorded normally in dose increments of 0.25 mR to1 mR units.6.9.12.5.2Some units of this type are equipped with a chirp rate switch allowing the user to select a low or high chirprate. In the low position, each dose increment produces one chirp; in the high position, each incrementproduces about 40 chirps, giving a more immediate audible warning at relatively low exposure rates. Forexample, at an exposure rate of 10 mR/hr, the unit will chirp about every 6 minutes in low position and aboutevery 10 seconds in the high position.6.9.12.5.3The alarm dosimeter has a case usually constructed from aluminum or high impact plastic. The DAD/PAD islightweight (8 ounces or less), has a corrosion-resistant surface coating and operates on a 9-volt alkalinebattery for up to 6 months of normal use.6.9.12.5.4Operation is very simple: turn the unit on. Some units reset the display each time the unit is turned on;others require resetting the display with a reset switch or button. A memory is available on some models,which allows the unit to be turned off without losing the stored dose. This feature permits a single dailyrecording of the wearer’s exposure dose because the dosimeter will continue to monitor exposure to theradiation without having to record each exposure dose if operations are stopped and resumed several times ina day’s operation. Dosimeter reading for each individual shall be entered on the utilization log at the end ofthe workday.6.9.12.5.5Any time a DAD/PAD is used by a different radiographer, it SHALL be reset to zero prior to use. Eachradiographer SHALL wear a single DAD/PAD, which has been reset to zero prior to the start of each day’soperation and calibrated in accordance with specific equipment technical data. A reading may be obtained atany time while working in a radiation area by simply pushing a read button to view the accumulated dose onthe readout display. An emergency situation should be considered to exist whenever a daily accumulateddose of 100 mrem or more is registered on the display of the dosimeter.6.9.12.5.6The Victoreen Model 885 PAD is one example of the alarm dosimeter. It detects gamma and X-rays over arange of 0-999 mR (0-10 mSv) by integrating radiation exposures. It provides both a visual and audibleindication and ‘‘chirps’’ in direct proportion to radiation intensity/dose rate with ‘‘chirps’’ at the rate of onechirp per 0.025 mR. Using one 9V alkaline battery, the PAD will operate for 30 days continuously or for 120days at 8 hours per day. (Low battery indicator notes when battery life drops below 100 hours.) The Model885 PAD must be worn under outer garments when conducting operations during cold weather as it isdesigned to function properly only when the lower operating temperature is above zero degrees Celsius (32degrees Fahrenheit).6.9.12.5.7Eachpersonalalarmingdosimeter/alarmrate-metermust:NOTECalibration of both pocket dosimeters and personnel alarm dosimeters mustbe scheduled so that sufficient quantities remain on hand to support continu-ing radiography operations. Additionally, except in cases of emergency, TLDbadges should not be submitted until replacement badges have been received.a. Be checked to ensure that the alarm functions (sounds) use at the start of each shift.b. Be set to give alarm signals a preset dose rate of not more that 500 mR/hr (5 mSv/hr).c. Require special means to change the preset alarm function.6-131
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