ML20058G487
| ML20058G487 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 07/21/1982 |
| From: | Papay L SOUTHERN CALIFORNIA EDISON CO. |
| To: | Engelken R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| References | |
| 10CFR-050.55E, 10CFR-50.55E, NUDOCS 8208030337 | |
| Download: ML20058G487 (4) | |
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Docket No 50-362 50.55(e) Report Southem Califomia Edison Company h6 R O. Box 800 2244 WALNUT GROVE AVENUE ROSEM EAD, CALIFORNIA 91770
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July 21, 1982 Mr. R. H. Engelken, Regional Administrator U. S. Nuclear Regulatory Commission Region V 1450 Maria Lane, Suite 210 Walnut Creek, California 94596-5368
Dear Mr. Engelken:
SUBJECT:
Docket No. 50-362 San Onofre Nuclear Generating Station, Unit 3 In a letter to your office dated June 22, 1982 we identified a condition which we consider reportable in accordance with 10CFR50.55(e).
The condition involves gas radiation monitoring equipment.
Enclosed in accordance with 10CFR50.55(e) are twenty-five (25) copies of a Final Report entitled,
" FINAL REPORT ON THE GAS RADIATION MONITORS."
If you have any questions regarding this report, we would be pleased to discuss this matter with you at your convenience.
Very truly yours, Enclosures cc:
R.C. De Young - (NRC, Director I&E)
A. E. Chaffee (NRC, San Onofre Units 2 and 3):
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8208030337 820721 gf"... !
PDR ADOCK 05000362 S
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o FINAL REPORT ON THE GAS RADIATION MONITORS SAN ONOFRE NUCLEAR GENERATING STATION, UNIT 2 & 3 Introduction This report is submitted pursuant to 10CFR50.55(e).
It describes a condition involving the gas radiation monitoring equip-ment.
One aspect of the condition involves leakage of the detector chamber; the other involves incorrect calibration data.
The gas radiation monitors involved are supplied by General Atomic (GA) and Nuclear Measurement Corporation (NMC).
They will be discussed separately.
I.
NMC GAS RADIATION MONITORS, UNIT 2 A.
Background
During calibration of NMC gas monitors using Kr-85 gas, it was observed that the Kr-85 gas leaks into the detector housing.
Also, when purging Kr-85 out of the detector chamber it was not possible to purge the chamber to a low background level in a reasonable amount of time.
B.
Description of Deficiency The defect of the NMC gas monitors was observed during the high range calibration.
An investigation discovered that there is no gas tight seal between the photo multipler tube (PMT) chamber and the gas samples being monitored.
The leakage of Kr-85 gas into the PMT compartments caused an abnormally high background radiation reading.
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C.
Analysis of Safety Implication The high background radiation reading will cause higher set points which would mask an accident or near accident radiation l
level condition.
Hence it will delay the actuation of the protective l
system which prevents potential offsite radiation.
I
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A Page 2 D.
Corrective Action A nuclear grade sealant, loctite PST No. 58031, was applied to the leak area of the detector assembly.
This sealant can withstand temperbtures of -65 F to 300 F while receiving a total dose of 2 x 10 rads.
All Unit 2 detectors were sealed and tested; and no leakage was observed.
II.
GA WIDE RANGE GAS MONITORS A.
Background
Two problems existed in these monitors:
1.
The calibration and testing results were different from the certified calibration data provided with the detector by GA.
It was discovered that the delivered detector differs from the unit on which the certified calibration data was obtained.
The difference is that a spacer was missing from the Edison detector.
This spacer provided the correct geometry for the detector internals and allowed for correct calibration of the unit.
In addition, the calibration procedure did not identify all radioactive sources to be used in calibrating these units.
2.
The RM-80 microprccessors for each detector re-ceive flow indication signals continuously from the flow meters installed in the effluent stack.
These microprocessors adjust the detector sample flow rate to maintain isokinetic sampling at all times.
The general RM-80 microprocessor flow ve-locity-to-voltage curve does not match that of the t
flow meters over the 1-8 SCFM range.
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'Page 3 1
B.
Description of Deficiency 1.
The installed wide range gas monitor did not meet the calibration-tolerance.
The omission of the spacer in the detectors presented a condition where unqualified and uncertified components were installed.
Additionally, the calibration procedure called for the use of a Cs-137 source, only; the GA certified cali-bration data was obtained by using Cs-137 and Xe-133 as sources.
A Xc-133 source was included in the calibration of the mid and high range detectors, but the results were still unacceptable.
2.
The sample flows were not isokinetic at all
-times. The radiation effluent-rate would be. incorrect.
Hence the-detection of a radioactive leakage could be delayed or missed.
i C.
Analysis of Safety Implications 1.
The accuracy of the detector influenced the timely response to the actuation of the protective system and the discovery of radioactive leakage.
2.
Non-isokinetic sample gathering would affect
-only the gathering of particulate and iodbme. Hence it would result in inaccurate figures of particulates and iodine release to the plant environment and would violate the Technical Specification, per Table 4.11:2.
D.
Corrective Actions 1.
The spacer was replaced, bringing the detector assemblies back into confprmance with the design which was used by GA to obtain the certified calibration data.
General Atomic is developing a design change to correct the design deficiency.
2.
The instruments have been calibrated to obtain the. desired accuracy between sample flow rates 1-3 SCFM.
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