ML19224B189
| ML19224B189 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 02/25/1977 |
| From: | Metropolitan Edison Co |
| To: | Mullinix W NRC/IE |
| References | |
| 1707, TM-0114, TM-114, NUDOCS 7906140189 | |
| Download: ML19224B189 (4) | |
Text
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DOCUMENT NO:
, h. 7..
OF DOCUMENT PROMDF.D BY COPY MADE ON METROPOLITAN EDISON COMPANY.
Wilda R. Mullinix, IRC G
7906140181 191 141 e
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Revision 2 1707 02/25/77
.s THREE ?.*lLE ISLAND NUCLEAR STATION 2
STATIOi HEALTH PHYSICS PROCEDURE 1707 PLATEAU DETERMIllATI0ft FOR Gpt DETECTORS Table of Effective Pages Page Date Revision Pace Date Revision Pace Date Revision 1.0 02/25/77 2
26.0 51.0 2.0 og/1gf75 1
27.0 52.0 3.0 09/1b/75 1
28.0 53.0 4.0 29.0 54 CONTROLLED COPYss.0 5.0 30.0 o
6.0 31.0 56.0 M
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n: DO \\!OT REMOV$d 11.0 36.0 61.0 12.0 37 0 62.0 13.0 30.0 63.0 14.0 39.0 64.0 15.0 40.0 65.0 16.0 41.0 66.0 17.0 42.0 67.0 18.0 10.0 43.0 68.0 44.0 69.0 20.0 45.0 70.0 21.0 46.0 71.0 22.0 47.0 72.0 23.0 43.0 73.0 24.0 49.0 74.0
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1707 Revision 2 02/25/77 i
THREE MILE ISLAt1D NUCl. EAR STATION STATI0f1 HEALTH PHYSICS PROCEDURE 1707 Plateau Determination for G.M. Detectors 1.0 PURPOSE i
The purpose of this procedure is to list the steps taken to determine i
a Voltage plateau for the GM detectors used with the Hewlett Packard scaler. The optimum operating voltage is determined from this plateau.
2.0 DISCUSSION 2.1 A characteristic plateau curve for the detecting element should be I
determinea monthly.
2.2 The characteristic curve indicates the variation in counting rate with change of applied voltage, all other parameters being held constant.
2.3 A point in the flat area of the curve (plateau) is chosen as the normal operating voltage for the instrument.
3.0 REFERENCES
3.'
ORTEC Manuals for the following units:
2.1.1 Model 456 - High Voltage Supply 3.i.2 Model 719 - Timer l
3.1.3 Model 775 - Counter
(
i 4.0 EOUIPMEi1T l
4.1 Lead shield with open end G.M. tube.
I 4.2 ORTEC model 456 High Voltage Supply i
4.3 ORTEC model 719 Timer 4.4 ORTEC model 775 Counter 4.5 Beta source 4.6 Semi-log graph paper 5.0 PLATEAU DETERMINATION PROCEDURE 191 143 5.1 Insure Cabinet Power supply is on.
-j 5.2 Insure instrument high voltage supply is on.
l.0 I
.i' 09/15/75 1707 Revision 1 5.3 Insure Timer Preset is set to 1.
5.4 Insure Timer Multiplier is set to 100.
5.5 Insure Timer Base is set to 0.01 min.
5.6 Insure Discriminator on model 775 counter is set to 0.1 volt (minimum).
5.7 Allow 15 minutes warm up time.
5.8 Insert Beta Source, activity side up, on shelf in lead shield in geometry to be used for counting sample.
5.9 Depress Reset button on counter.
5.10 Depress Start button on scaler timer.
5.11 Beginning at 700 volts, slowly increase power supply voltage until a count rate is observed on the scaler.
5.12 When counts are observed, round off the high voltage setting to the nearest 50 volts and record as starting voltage.
5.13 Prepare a sheet of semi-iog graph paper labeling the X (horizontal) axis with voltage, and Y (vertical) axis in counts per minute.
A previously obtainea Plateau Curve may be used for reference as necessary.
Record name, date, source used and operating voltage setpoint determined on the semi-log graph paper.
5.14 Repeat 1.0 minute counts at starting voltage setpoint determined in Step 5.12 and at 50 volt increments until a good Plateau Curve, or a maximum of 1200 volts is obtained.
5.15 Record and plot each voltage and its corresponding counts per minute at each step before proceeding to the next step.
6.0 OPERATING VOLTAGE SELECTION
)
6.1 Select from the curve the approximate becinning and ending point of the plateau.
(Normally about 800 to 1200 volts respectively).
2.0 9l lf4
09/15/75 1707' Revision 1 6.2 Take one/ third of the difference between voltages of step 6.1 and add to the beginning voltage.
Round this figure to the nearest 50 volts.
Use this value as the operating voltage setpoint until another plateau determination indicates a different voltage is best for optimum operation.
- 3. 0 191 145 2
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