ML19224B193
| ML19224B193 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 02/25/1977 |
| From: | Metropolitan Edison Co |
| To: | Mullinix W NRC/IE |
| References | |
| 1709, TM-0116, TM-116, NUDOCS 7906140196 | |
| Download: ML19224B193 (5) | |
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TMI DOCUMENTS DOCUMENT NO:
COPY MADE ON OF DOCUMENT PROVIDED BY METROPOLITAN EDISON COMPANY.
Wilda R. Mullinix, NRC 7906140tsq
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s 192 049
Revision 2
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1709 02/25/77 THREE MILE ! ELAND NUCLEAR STATION STATION HEALTH PHYSICS PROCEDURE 1709 PLATEAU DETERMIllATICl4 FOR BECKMAN WIDE BETA
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Table of Effective Pages Paae Date Revision Pace Date Reeision Pace Date Revision 1.0 02/25/77 2
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/r9/77 Approval A
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Cognizant Dept. He:d Cognizant Dept. Head Unit 1 PORC ccmm nds Approval Unit 2 ? ORC f%comnOnds,pproval I
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v 1709 Revision 2 02/25/77 THREE MILE ISLAND NUCLEAR STATION STATION HEALTH PHYSICS PROCEDur.E 1709 Plateau Detennination for Beckman Wide Beta II
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l.0 PURPOSE The purpose of this procedure is to describe in detail the equipment needed and steps to be taken for Plateau Determination on the Beckman Wide Beta II.
2.0 DISCUSSION 2.1 The Beckman Wide Beta II is an automatic counting device for Jetermining alpha, and/or beta radioactivity.
Pure 100% 0xygen Free Methane gas is used with a window detector, and cosmic or noise pulses are auto-matically rejected.
2.2 A plateau determination is used to find the correct operating voltage for the counter. A plateau is the flat portion of the count rate versus voltage curve where changes in operating voltage induce minimum changes in counting rate.
2.3 The Beckman Wide Beta II, a proportional type counter, exhibits two plateaus. On the first one, only alpha particles produce ionization sufficient to register on the scale.
Beta particles are not counted on this plateau. As the high voltage is increased, a second plateau is found.
Both beta and alpha radiations are detected at this higher voltage.
2.4 Plateau determination is normally required at initial start-up, after maintenance and when operation characteristics indicate.
3.0 REFERENCES
I 3.1 Wide Beta II Planchet Counting System Manual
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3.2 Fluke Manual I92 05l 1.0
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09/17/75
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Revision 1 4.0 EQUIPMEflT 4.1 Beta Standard Source
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4.2 Alpha Standard Source 4.3 Fluke-8100A Digital Voltmeter 4.4 Beckman Wide Beta II 4.5 Screw driver 4.6 Graph paper, sem1-log 4.7 Counting gas 5.0 OPERATIfiG If1STR'JCTIONS 5.1 Open gas control valve located behind instrument.
Check that the gas flow reads approximately.2 CFH.
If no gas flow is indicated a gas cylinder refill may be required.
5.2 Wait 30 minutes, open the lower right panel, ano turn the PLATEAU POIflT knob to the OPERATE position.
NOTE:
If the gas supply valve is in the open position and gas flow is indicated as in Step 5.1, eliminate the 30 minute wait time.
5.3 Place the Fluke - 8100A Digital Voltmeter in service by placing the low connector (black wire) into the GROUtlD.
Place the high connector, (red wire) in the HV+100 socket of the Beckman Wide Beta II.
5.4 Position the selector switches as follows:
5.4.1 Set the Af1ALYZER MODE selector knob to ALPHA.
5.4.2 Set the preset filti knob to one (1) minute.
5.4.3 Set the COUtiT MODE switch to flET.
2 5.4.4 Set the OPERATE LOAD switch to LOAD.
5.4.5 Set the RECYCLE switch to SIflGLE SAMPLE REPEAT.
5.5 After the change has stopped, press the CAGE ADVAfiCE button (upper right panel) to bring the changer to the #1 cage position.
I92 052 5.6 Place the alpha source with activity side towards the detector, in 2.0
09/17/75 1709 Revision 1 the planchet holder.
Put the planchet in the changer magazine on the top of #1 cage. This is sample position #10.
5.7 Set the first sample selector and the final sample selector to #10.
5.8 Set ti,9 OPERATE LOAD switch to OPERATE.
5.9 Depress the RESET button, followed by the START button.
5.10 Set the HIGH VOLTAGE switch at 1000 v. and slowly increase the voltage until counts are observed.
5.11 Increa;e the voltage in 50 volt increments and obtain a 1 minute count at each voltage setting.
5.12 Record each voltage value and its corresponding count rate.
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Do not exceed 3550 volts.
5.13 Prepare a sheet of semi-log graph papes by labeling the X axis (horizontal) in voltage increments and Y axis (vertical) in counts / minute increments. A previously obtained Plateau Curve may be used for a reference as necessary. Put the Plateau Curve in the Plateau Curve Log book.
5.14 Insert the Beta standard source in place of the 61pha standard source.
5.15 Repeat steps 5.7 through 5.13, omitting step 5.10.
Record each voltage and corresponding counts / minute and plot these for the beta values.
6.0 OPERATING VOLTAGE SELECTION 6.1 Select from the Count Rate versus Voltage Curve the approximate beginning and ending points of the plateau (flat portion of the curve).
6.2 Take one third of the difference between the beginning point and ending 2
point voltages of Step 6.1 and add to the beginning voltage.
Interpolate I
this value to the nearest 50 volts.
192 0*63
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3.0 1
09/17/75
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1709 Revision 1 fiOTE: Use this value as the operating voltage setpoint until another plateau determination indicates that a different voltage is best for optimum operation.
6.3 Complete Steps 6.1 and 6.2 fo~ toth the Alpha and the Alpha + Beta Plateaus.
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