ML19224B150
| ML19224B150 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 02/14/1977 |
| From: | Metropolitan Edison Co |
| To: | Mullinix W NRC/IE |
| References | |
| 1759, TM-0136, TM-136, NUDOCS 7906140120 | |
| Download: ML19224B150 (9) | |
Text
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Wilda R. Mullinix, NRC 790614012e
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.tuision 1 02/14/77 THREE MILE ISLAND NUCLEAR STATION STATION HEALTH PHYSICS PROCEDURE 1739 OPERATION OE. CONDENSER-R METER Table of Effective Pages Paae Date Revision Page Date R evision Pace Date Revision 1.0 02/14/77 1
26.0 51.0 2.0 2/13/74 0
27.0 52.0 29.'O'd'eTROU F~D COPY 3.0 2/13/74 0
28.0 c 53.0 4.0 2/13/74 0
54.0 5.0 2/13/74 0
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30.0 )lD i ;CI 55.0
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6.0 2/13/74 0
56.0 7.0 2/13/74 0
32.0 57.0 32:n h!OT RE..OVE 58.0 M
8.0 2/13/74 0
9.0 34;O
59.0 10.0 35.0 60.0 11.0 36.0 61.0 12.0 37.0 62.0 13.0 38.0 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 43.0 68.0 19.0 44.0 69.0 20.0 45.0 70.0 21.0 46.0 71.0 22.0 47.0 72.0 23.0 48.0 73.0 24.0 49.0 74.0 25.0 50.0 75.0
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189 079
Revision 1 02/14/77 THREE MILE ISLAND NUCLEAR STATION STATION. HEALTH PHYSICS PROCEDURE 1759 Operation of Condenser-R Meter 1.0 PURPOSE The purpose of this procedure is to explai,- the function and operation of the condenser-R meter.
2.0 DISCUSSION 2.1 The condenser-R meter is used for measuring integrating radiation doses.
Its calibration is directly traceable to NBS data.
2.2 The chamber consists of a polystyrene capacitor connected in parallel with an ionization chamber.
With the chamber inserted in the bayonet-type socket of the condenser-R meter, contact is made to the body and central electrode of the chamber. The chamber is charged by operation of the charger controls, and the charge is measured by the electrometer.
The charger electro-meter unit of the condenser-R meter charges the ionization chamber to a predetermined voltaqe as indicated by the "0" position of the electrometer. When the active volume, or thimble portion of the chamber is placed in a gamma field, the air in thimble
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is ionized in proportion to the gamma intensicy.
The ions, or charged particles, are attracted to the oppositely charged electrode of the chamber.
Ion migration to the electrodes reduces the charge held by the capacitor, thus reducing the potential '
differences across the electrodes.
The electrometer measures this potential, and by careful calibration, the scale reading for this potc tial is made equivalent to the gamma dosage to which the
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1759 2/13/74 Revision 0 chamber has been subjected.
This exposure is read directly on the scale in Roentgens.
In order that the chamber will have the same response over a wide range of energies, it has been designed so that the thickness and composition of the wall and electrode materials produce air-equivalent energy response.
2.3 Figure 1759-1 is a simple drawing of the string electrometer used in the model 570 condenser-R meter.
The charge is applied to the horseshoe type of electrometer construction which eliminates the need for any ad ustment of the string by the user.
The string J
is a platinum coated quartz fiber, and is soldered at each end to the horseshoe support. The deflecting electrode is a long screw which projects from the side of the electrometer housing.
This screw is adjusted so that the quartz fiber movement is linear with potential across the scale.
Because the charge on the quartz fiber and the deflecting electrode are opposite in sign, an electro-static attractive force results.
This force moves the quartz loop toward the deflecting electrode, against the spring action of the quartz loop itself. The attractive force is proportional to the charge, and the movement of the quartz fiber is proportional to the force. This principle is utilized to form a direct reading voltage indicator, or string electrometer.
The movement of the string is optically magnified and its relative position appears as a fine shadow line on the illuminated scale viewed through the microscope.
Calibration is accomplished by varying the magnification of string movement.
The scale reads directly in roentgens.
Figure 1759-2 shows enlarged view of scale.
189 081 i
2.
1759 2/13/74 Revision 0 3.0 REFEREt1CES 3.1 Condenser-R meter instruction manual.
4.0 EQUIPMENT 4.1 Condenser-R meter 4.2 Condenser-R meter chamber 4.3 110 Volt AC power supply 5.0 OPERATION INSTRUCTIONS 5.1 Charging 5.1.1 Turn instrument on by turning knurled control "A" (see Figure 1759-4) toward zero set.
Indicating light on front of instru-ment will glow red.
5.1.2 Remove the black plastic guard from the thimble end of the chamber.
5.1.?
Remove the chamber cap from the chamber (ste Figure 1759-3).
5.1.4 Remove the dust cover from the bayonet-type socket of the con-denser-R meter.
5.1.5 Insert the chamber in the bayonet-type socket of the instrument in the following manner.
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(A) Position chamber in socket so that contact locking pin fits into guide.
(B) Press and turn chamber in socket, spring acticn locking device will hold chamber in place.
The chamber is now making contact.
5.1.6 Turn knurled control "B" (Figure 1759-4) toward " CHARGE" against stop.
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5.1.7 Hold control "B" toward charge against stop, and at the same time look into the viewing microscope and rotate control "A"
until hair line reaches the "0" position and then release the 3'
189 082
1759 2/13/74 Revision 0 charging wheel "B".
5.1.8 Remove the chamber from the socket.
5.1.9 Replace the chamber cap over the connection end of chamber.
5.1.10 Replace dust cover over bayonet-type socket of the instrument.
5.2 The chamber may now be exposed to measure gamma dosage. The chamber may be operated in any position and by the use of a timing device, the average gamma radiation may be determined in Roentgens.
5.3 Reading
To read remcve the chamher cap.
- 5. Position chamber in bayonet-type socket of the condenser-R meter so that contact pin does not mate with pin guide, then insert chamber into socket until contact pin stops outside the bayonet-type socket of the instrument.
With chamber in this position the contact pin fuctions as a stop and avoids accidental discharge.
5.3.2 Adjus' the electrometer to "0" as before (5.1.6 and 5.1.7) by operation of controls "A" and "B".
5.3.3 Insert chamber completely into bayonet-type socket so that contact is made (5.1.5).
5.3.4 Read the gamma dosage directly on the scale corresponding to the value engraved on the chamber.
189 083 4.0 J
Revision 0 MICROSCCPE LENS SCALE-SH ADOW OF STRING (See Figure 1759-2)
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