ML20008G187
| ML20008G187 | |
| Person / Time | |
|---|---|
| Site: | Susquehanna  |
| Issue date: | 06/17/1981 |
| From: | Curtis N PENNSYLVANIA POWER & LIGHT CO. |
| To: | Grier B NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| References | |
| REF-PT21-81-458-000 10CFR-50.55E, 81-458, 81-458-000, PLA-844, PT21-81-458, PT21-81-458-000, NUDOCS 8107020414 | |
| Download: ML20008G187 (3) | |
Text
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PPaL TWO NORTH NINTH 3TREET, ALLENTOWN, PA.18101 PH o N E: 1215) 770 5151 Y'$si3 f
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NORMAN W. CtJRTIS Vice President.Engineenng & Construction. Nuclear p'
no.sssi June 17, 1981 Mr. Boyce H. Grier
,p7 Director, Region I fs'-
A N U. S. Nuclear Regulatory Commission
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631 Park Avenue King of Prussia, PA 19406
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INTERIM REPORT OF A DEFICIENCY RELATING TO
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ROSEMOUNT MODEL 1151 AND 1152 PRESSURE TRANSMITTERS ERs 100450/100508 FILES 821-10/900-10 PLA-844
Dear Mr. Grier:
Th'is 1&tter serves to provide the Commission with an interim report of a deficiency involving the failure of Zener diodes in the referenced Rosemount pressure transmitters. The deficiency was originally reported by I
telephone to NRC Region I Reactor Inspector, Mr. L. Narrow, in a telephone conversation with Mr. A. Sabol of PP&L on April 10, 1981.
Mr. Narrow was advised that the condition was being evaluated for reportability under the provisions of 10 CFR 50.55(e).
The deficiency involves the failure of the diodes which could result in erroneous outputs from the pressure transmitters. A description of the problem, its cause, safety implications and the corrective action planned is j
attached as an interim report pursuant to the requirements of 10 CFR 50.55(e).
Since the details of this report provide information relevant to the i
reporting requirements of 10 CFR 21, this correspondence is considered to l
also discharge any formal responsibility PP&L may have for reporting in compliance thereto.
We expect to issue a final report on the deficiency prior to November, 1981.
We trust the Commission will find this report to be satisfactory.
Very truly yours,
)bd N. W. Curtis Vice President-Engineering & Construction-Nuclear
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Mr. Boyce H. Grier June 17, 1981 FLWesab Attachment cc:
Mr. Victor Stello (15)
Directer-Office of Inspection G Enforcement U. S. Nuc3 ear Regulatory Commission Washington, D.C. 20555 Mr. G. Mcdonald. Director (1)
Office of Management Information & Program Control U. S. Nuclear Regulatory Commission Washington, D.C. 20555 Mr. Gary Rhoads U. S. Nuclear Regulatory Cocuission P.O. Box 52 Shickshinny, PA 18655 e
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7, Attachment to PLA-844 DESCRIPTION OF THE PROBLEM Rosemount has identified a potential diode failure on the amplifier board of pressure transmitter Models 1151 and 1152 with output codes A and D.
The Zoner diodes (IN2620) are noted to become unstable between production and the end of the normal product life. At low output signals this instability will appear as noise with a magnitude of up to 4% of the sianal value.
CAUSE Rosemount has determined that moisture trapped in the diode during manufacturing is the probable cause of this instability. The water trapped in the diode creates a condition conducive to gold migration which may result in internal shorting. This failure of the diode would result in a fixed 12 to 14 mA transmitter output.
SAFETY IMPACT Bechtel Engineering has identified 40 safety related transmitters of SSES which may conta 5 the defective diodes. Four of tliese transmitters are used to monitor the pressure in the supply lines of containment instrument gas to the ADS (Automatic Depressurization System) steam relief valves. The normal line pressure is 150 psig. The transmitters transmit a 4-20 mA signal corresponding to a 0-250 psig to their respective pressure switchen The switches will actuate on a low pre'ssure signal of 147 psig which opens the solenoid valves.
These solenoid valves release the compressed nitrogen from the instrument gas bottles to maintain the 150 psig line pressure. When the diode fails, the fixed output of the transmitter will have the possibility of masking the low pressure signal to the pressure switch. The solenoid valve will not open automatically on low instrument gas pressure to maintain the line pressure to operate the ADS steam relief valves. A failure of the Zener diode in these transmitters thus impairs the intended safety functions of the Containment Instrument Gas System.
Therefore the condition is considered reportable under the provisions of 10 CFR 50.,55(e).
CORRECTIVE ACTION PLANNED Since Rosemount pressure transmitters have been provided under both the General Electric and Bechtel scope of supply, appropriate corrective action for the defective transmitters is planned as follows:
1.
Bechtel will request that General Electric take action to insure that defective Rosemount pressure transmitters provided under the GE scope of supply will be replaced or repaired.
2.
Bechtel will either replace or repair the defective pressure transmitters previded under their scope of supply.
Bechtel NCR7565 currently identifies and controls the defective Rosemount pressure transmitters. A final report will be issued prior to November, 1981 detailing the specific corrective actions taken.
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