ML19270H541
| ML19270H541 | |
| Person / Time | |
|---|---|
| Site: | Three Mile Island  |
| Issue date: | 09/19/1972 |
| From: | VICTOREEN, INC. |
| To: | |
| Shared Package | |
| ML19270H523 | List: |
| References | |
| PROC-720919, NUDOCS 7911040175 | |
| Download: ML19270H541 (8) | |
Text
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INSTRUCTION MANUAL
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MODEL S48-8 ' - FIELD CALIBRATOR KIT
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DETECTOR CABLE RECEPTACLE V;
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oo o h. $ h.!it Figure 1. 2. ode! 818-31 zelu Calib:ation :;it
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SECTION I GENERAL DESCilIPTION
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1-3. DESCitlPTION. ..- ,
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, %c 848-8 Field Calibration Kit is a portable, self-contained unit designed to provide a quick convenient means of checidng the calibration of the Victorcen 845 Area Monitoring System with Imown gamma radiation ficids. .
A scaled radiation source, in conjunction with reproducible geometry, assures constant,
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The 100 me,137Cs source is encapsulated in welded stainless stccl and scaured inside a rotating coction of the source shield. Exposure of the source to the 847-1 Detector requires first unlocking the shield with a key. The shield is then rotated and held against a spring return so that the source cannot be left in the exposed position.
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%c rotating shield has low and high range positions, providing average flux fields of approximately 500 mil /hr and 5000 mR/hr, respectively. The exact fields are given on 137 CS decay curves individually plotted and supplied with cach unit.
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The shiciding, while light enough to satisfy the requirement of hand portability, is sufficient to reduce radiation levels one foot from any surface of the unit to less than S mR/hr with the source in the closed position. These levels are maintained in the
. rear 100 (towards the operator) when the source is fully exposed.
Eccause of the short time constant of the S45 Arca Monitoring System, a few seconds of source exposure arc all that is needed to check calibration, and adjust if necessary.
, Thus, the need Tor area posting and roping off during a calibration is elimina'ed, when the unit is used properly by a responsible operator. '
. While careful ad conscientious attention to safe operating procedures when handling
. any radiation source are presupposed, the incorporation of several safety features in the 848-R practically climinates the possibility of inadvertant personnel exposure.
1-2. SPECIFIC /tTIONS. Length: 13-1/4 inches (33.G cm).
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Width: 8-7/8 inches (22.5 cm). Height: G-5/8 inches (1G. S cm).
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Weight: 24 pounds (11 KG). . Source: 100 me, 137Cs scaled in welded stainless steel capsule (Amerrham-Scaric, Model X.7 Capsule). , 1-3. RADI ATION LEVELS.
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- a. External; one foot from any ex!crior surface, less then S mn/hr, wi'h scur:c in closed position,
- b. Extern '., in front 1 SOU (away from operator),
Less than 100 mR/hr bevend 2 fceld . "*
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Less tN" E mM/hr E~Ed 3 0 feehj
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' c. Inside dctcctor motmting hole; when measured with the Victorcen S17-1 Detector,
, Approximately 50 mH/hr*, Source in closed position Approximately 500 mR/hr*, Source in intermediate position
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Approximately 5000 mR/hr*, Source in open position ,
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*The exact levels for cach individual calibrator to be supplied o;i decay curves affixed to the calibrator. ,
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1-4. SAFETY FEATURES. . . a.' . Lead sourec shielding is wholly contained in steel and brass container, to prevent molten lead from flowing away from source during a hot fire.
- b. TlIc source is mounted in- steel-brass part of rotating shield,- and will-remain in -
place should lead become molten. .
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- c. The rotating shield is held in the closed position by two parallcl acting helical springs, either one of which has enough torque to rotcte the shield closcd, in case the other breaks (redundancy). Thus, the source cannot be left in the open position.
- d. The rotating shield is locked closed by a key-type lock. The lock must be in the locked position for the key to be removed.
- c. A special welded latch assembly assures that the scource cannot be locked in the open or any intermediate position.
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- f. The key itself is part of a special wclded assembly. The key is welded to a rod
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which in turn, is welded to a disc. In operation, the 817-1 Detector is first placed ia its mounting hole in the calibrator. The key is then inserted into the lock, whercupon
' the disc reaches over a flange on the detector. The detcetor now cannot be removed from the calibrator without first removing the key. Thus, at the end of each field calibration, it is automatically assured that the calibrator source is closed, locked -
and the key removed. These safety features almost entirely climinate the possibility of the calibrator being inadvertantly left in an unsafe condition. SEC'nON H - OPERATION
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I . 2-1. PROCEDURE. , 1.* Remove 847-1 Detector from wall mounting bracket. .
- 2. If convenient, calilarator may now be mounted on this same bracket. -
'3. Insert detector, snytll diameter section down, into mounting hole in calibrator.
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- 4. " Note reading on remote meter.
- 5. Insert key ft.lly into lock. DO NOT TIJRN YET.
G. Slowly rotate source knob until it stops. (With key in lock, internal source n m will push the latch out of the way, and slide down the edge of the latch assembly until it cames to the bend). Thi:. is the intermediate 1,asition,
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- 7. Note reading < remote meter,
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- 8. Now rotate key the rest of the eay by hand.
- 9. Rotato sourco lalob to final stop. This is the open position.
- 10. Note reading on remote meter.
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- 11. All meter readings should be within
- one minor division of intensity shown on
. decay chart. If adjustment is needed, remove detector bottom to get at calibration potentiometers and repeat the above procedure. .
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NOTE .
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A. Source Exposure may be minimized by familiarizing one's self with
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the intensities on the decay chart and expected meter indications before
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, exposing source.
B. With the sourec in open position, there is no beam shiciding in the ' front hemisphere of the calibrator. IIced the warning decal on the top
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of the casc for radiation levels. The source need be oper. for only a few seconds. to check the 845 System calibration, because of its fast response time, and therefore inadvertant personnel exposure a few
- feet away will probably be minor. For instance, n ten second exposure two icct from the end of the calibrator (approximately 100 mR/hr) will give only 0.3 mR. Ilowever, the momentary beam MAY cause an indication or alarm on other nearby monitoring channels. This, as
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well as possible personnel exposure, should be kept in mind when planning g your calibration procedure.
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. SECTION III
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MAINTENANCE .
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3-1 WIPE TESTING. * ~ The AEC generally requires source wipe testing at intervals NOT TO EXCEED six months.
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The 848-8 source may be wipe tested with a long-handled Q-Tip type cotton swab
,. moistened in alcohol. Rotate the source to the open position. Insert the Q-Tip in the hole in the shield inside the large detector mounting hole. This will contact the re-
,, taining screw holding the cource in place. 'At this point DON'T DAWDLE ! The exposure rate at the center of the detector hole is about 2 mR per second. -
Also wipe around the rotating shield shaft where it penetrates the bearing blocks. This can be accomplished from beneath the calibrator.
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3-2. FACTORY CALIBRA TION.
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The calibrator itself is standardized at Victorcen by inserting a standard 017-1 Detecr,
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the ion chambers of which are read out on a conventional pico-ammeter, rather than the GIS System readout (this affords better readability and accuracy). The sensitiv; tics of this standard detector have been determined by expvaurc to uniferm calibran . fields of 137Cs. The effec:2ve fields in !M calihr.@r are then c!culated, r- i..k. 7 all instrument maccuracic; inta neccen luchi k . uurate to itNa 152.
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ACCESSORY
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MODEL sis-5--55 RE2.!OTE ?. ETER
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. DESCIU PTJON . , The S48-S-55 Remote Aicter is used with the sis-S Field Calibration Kit to checi: cali- " b' ration of the S45 Arca nadiation hIonitoring Systems, when rem 6te meters are not already included in the individual channels.
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- It consists of an eight decado meter and case with a connecting cable and box receptacle.
It may be permanently b':lted directly to the top of the calibrator case through mounting holcs already' existing for this purpose.
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OPERATION
, 1. Disconnect cable from 817-1 Detector and plug into the receptacle on the meter.
- 2. Plug the cable coming from the meter into the 847-1 Detector.
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Since connection is not directly made from the cable to the body of the connectors, the screw threads on the receptacle and cable plug of the remote meter have been climinated, to facilitato connecting and disconnecting.
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- Figure ?. hiounting Arrangcment of-Detector in Calibrator
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