ML20205M912
| ML20205M912 | |
| Person / Time | |
|---|---|
| Site: | 07001489 |
| Issue date: | 07/16/1984 |
| From: | Bassett A GOODYEAR ATOMIC CORP. |
| To: | |
| Shared Package | |
| ML20205M785 | List: |
| References | |
| 81768, MSE-HP-239, NUDOCS 8811030358 | |
| Download: ML20205M912 (5) | |
Text
_____
Number:
MFDICAL, SAFETY. AND ENVIRONMENT p,
cocoytaa sto4K ConrotAT10N pg, g
07-16-84
""N'"
HEALTH PHYSICS PROCEDURE 1
of $
USE OF LUDLUM MODEL 12 COUNT RATE METER VITH THE MODEL
SUBJECT:
44-9 PANCAKE G-M PROBE I.
PURPOSE To instruct Industrial Hygiene and H e a. l t h Physics personnel on the proper maintenance,
- storage, and use of this instrument in order to ensure reliable performance.
II.
SCOPE This instrument combines the Ludlum Model 12 Count Rate Meter and Model 44-9 Pancake G-M Probe to make a portable radiation count rate meter.
T probe has a 1.75 inch 2 )h e d ia me te r mica window (2 mg/cm and the probe housing, including the handle and window protector, is aluminum.
The meter has four response scale (Xi, X10, X100, and X1000) and top-mounted high voltage, amplifier gain, calibration, and fsat/ slow response controls.
One interconnecting cable and two "D"
cell batteries are also requirud.
The batteries provide for 100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br /> of continuous operation.
O III.
REFERENCE Instruction Manual Model 12 Count Rate Meter, Ludlum Measurements, Inc., Swe e twa ter, Texas.
IV.
DEFINITIONS None V.
R E Q U _I _R E M E N T S Adequate procedures for all aspects of the Goodyear Atomic Corporation'.
Industrial Hygiene &
Health Physica Health Protection Program are required by the Department of Energy as part of the overall Industrial Hygiene and Health Physics Quality Assurance Program.
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c PREPARED BY:
APPROVED BY:
REVIEWED BY:
Su pen tsor, Admmutra to r, Ind. H)skne &
Medical A.C. Frcett Health liinks Safety. & Env.
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07-16-84 HEALTH PHYSICS PROCEDURE 8'
2 of 5 USE OF LUDLUM MODEL 12 COUNT RATE' METER WITH THE MODEL
SUBJECT:
44 9 PANCAKE C-M PROBE VI.
RESPONSIBILITIES A.
When maintenance, recalibration, or repair of this instrument is
- required, it is the surveyor's re s ponsibili ty to attach a tag designating the 1:-*e1 of c on tamina ti on on the instrument.
It is then to be sent to the Section
- Head, Environmental Surveillance Monitoring Services of the Industrial Hygiene and Health Physics Department (IHHP).
B.
All Instrument Maintenance Personnel The Instrument Maintenance Department has the responsibility for repairing and calibrating this instrument.
After the instrument has been calibrated, a label bearing the date by which the instrument must be returned to Instrument Maintenance for recalibration is affixed to the instrument.
VII.
PROCEDURE A.
Equipment Requized 1.
Ludlum Model 12 Count Rate Meter.
2.
Ludlum Model 44-9 Pancake C-M Probe.
3.
One series "C" teflon coated interconnecting cable.
l B.
Principles of Operation 1.
A high voltage supply develops +900 volts across the G-H tube, giving it the proper operating voltage.
When gamma rays or particulate radiation interact in the G-M tube, ion pairs are formed and tremendous amplification of charge takes place by a process known as "Townnend Avalanche."
For every initial ion pair formed, thousands of additional ion pairs are formed as the initial electron from the first ion pair accelerates towards the collecting electrode.
- Thus, sizable nega tive voltage pulses are generated by a single, initial ionizing event.
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MEDICAL. SAFETY, AND ENVIRONMENT
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HEALTH PHYSICS PROCEDURE N'
3 of 5 USE OF LUDLUM MODEL 12 COUNT RATE METER WITH THE MODEL
SUBJECT:
44 9 PANCAKE G-M PROBE 2.
The negative detector pulses are amplified by the amplifier, and all I91ses above a threshold level are detected by the discriminator and shaped by the ra te me ter.
The pulses from the ra te meter are then conditioned by the meter
- drive, converting the pulses to an average current, which drives the meter, the reading of which is proportional to the detector pulse ra te.
The meter is calibrated so that count rates can be read directly in cpm units.
C.
Equipment Limitations 1.
The maximum detection limit is 500,000 cpm.
2.
The minimum detectable count rate (including background) is 100 cpm.
3.
Ambient temperature should not be below -55'c or over 75'C where this instrument is used.
4.
Dead time losses become significant at 20,000 cps.
D.
Safety Considerations None E.
Maintenance and Storage 1.
No specific storage requirements.
2.
All electronic maintenance is to be performed by the Instrument Maintenance Department.
This does not include emergency ba ttery and cable replacement.
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V HEALTH PHYSICS PROCEDURE I'8' 4
or 5 USE OF LUDLUM MODEL 12 COUNT RATE METER WITH THE MODEL
SUBJECT:
44 9 PANCAKE C-M PROBE F.
Calibration and Performance Check 1.
When the Range Switch is in the BAT position, the c ond i tion of the batteries is indicated by the needle de fle c ti on on the count rate meter.
Deflection past the BAT TEST mark indicates approximately 2.2 volts necessary for operation.
l 2.
Turn the Range Switch to the a ppropria te response l
scale, and turn the F/S toggle switch to the S or F position for slow or fast meter response.
3.
Place the detector window of the probe directly over I
an approved check source.
Read the count rate from the meter face and multiply this number by the scale multiplier to get the actual count rate.
The reading should agree within plus or minns 20% of those obtained on previous performance checks.
If
- not, return the instrument to the Section Head, O
Environmental Surs**.11ance Monitoring
- Services, Industrial Hygiene & Health Physics.
4.
All calibration on this instrument is to be performed by the Instrument Maintenance Department.
G.
S e t-Up and Use 1.
Re pea t s tep s 1
-3 in Section VII, F.
pigstic bag having a 2.
Cover the probe window with a 10 mg/cm Pass the probe density thickness of 5 window over the suspected surface con ta mina tion and select an appropriate response scale.
Record the count rate.
This is the count rate atttibutable to gamma and pene tra ting beta radiation.
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HEALTH PHYSICS PROCEDURE Pas
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3.
Invert the probe and remonitor the same surface.
l Subtract the reading obtained with the probe inverted from the reading obtained in step 2.
This will give the count ra te a ttribu table to pene tra ting l
be ta radiation.
Record the beta count ra te.
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4.
For gross con tamina tion monitoring, remove the plastic bag and repeat s tep 2.
The count ra te found j
y)'
with the de tee tor window unshielded is due to a mixed field of be ta, alpha, and gamma radiation.
- p,
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Avoid monitoring dirty or greasy areas when the de tec tor window is unshielded as appreciable self-g/ h ll'f,'
a b s orp tion will occur and mask the alpha and weak
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beta radia tions.
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