ML20009C167
| ML20009C167 | |
| Person / Time | |
|---|---|
| Site: | McGuire  |
| Issue date: | 05/06/1981 |
| From: | Parker W DUKE POWER CO. |
| To: | James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| Shared Package | |
| ML20009C168 | List: |
| References | |
| NUDOCS 8107200339 | |
| Download: ML20009C167 (3) | |
Text
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Vict PRESIDENT Tg(gpwchg; Anga 7C4 Strau Paoouctio=
May 6, 1981 373..e 3 fl Obe 0 $
Mr. James P. O'Reilly, Director U. S. Nuclear Regulatory Commission S
Region II
@f 101 Marietta Street, Suite 3100
.Ja, 3
Atlanta, Georgia 30303 10}l JUL 171981 >
Re: McGuire Nuclear Station Unit 1 Docket No. 50-369 QUhg,7
Dear Mr. O'Reilly:
8 g
Please find attached Reportable Occurrence Rtport
-43.
This report concerns Channel II of the Negative Steam Line Pressure Rate for S/G 'A' being declared inoperable.
This incident was considered to be of no signi-ficance with respect to the health and safety of the public.
Ve truly yours,
', N w - l0 William O. Parker, Jr.
RWO:pw Attachment cc: Director Mr. Bill Lavallee Office of Management & Program Analysis Nuclear Safety Analysis Center U. S. Nuclear Regulatory Commission P. O. Box 10412
^
Washington, D. C.
20255 Palo Alto, CA 94303 4
8107200339 810506 PDR ADOCK 05000369 S
d' j
i McGUIRE NUCLEAR STATION INCIDENT REPORT Report Number:
81-43 Report Date: April 19, 1981 Occurrence rate: April 10, 1981 Facility:
McGuire Unit 1, Cornelius, N. C.
Identification of Occurrence:
Channel II of the Negative Steam Line Pressure Rate for Steam Generator (S/G) "A" was declared inoperable.
Conditions Prior to Occurrence: Mode 3, Hot Standby Description of Occurrence:
On April 10, 1981 at 1110 hours0.0128 days <br />0.308 hours <br />0.00184 weeks <br />4.22355e-4 months <br />, the Shift Supervisor noticed that the pressure gauge for S/G "A" Steam Line Pressure Channel II did not respond with the other two pressure gauges (Channels I and IV) as the steam pressure was increasing.
This channel was declared inoperable.
This was therefore a reportable incident pursuant to Technical Specification 3.3.2.4d.
Apparent Cause of Occurrence:
The lower stem assembly (plunger) of the Dragon Instrument Root and Manifold Valve is spring loaded (compressed) when closed and provided with a disc for seating.
The valve stem and the plunger are separated by a seal diaphragm to prevent leakage.
When the valve stem is rotated upward, the loaded spring will push the plunger up against the diaphragm allowing the valve to open.
The root valve on the S/G "A" Pres-sure Transmitter was torqued closed such that when it was opened (valve stem cranked up), the plunger did not lif t off the seat because the disc was j
stuck.
The spring was not strong enough to push up the stuck plunger even l
with the aid of system pressure.
(Once plunger is out, usually by tapping the valve, it will not close back unless it is done manually because the spring will hold it up.)
This caused the pressure gauge in the Control Room to read zero.
Analysis of Occurrence: Upon entering Mode 3 on April 10, 1981, the Reactor Coolant System pressure was being raised when the Shift Supervisor noticed that pressure gauge for S/G "A" Steam Line Pressure Channel II in the Con-trol Room was reading zero.
The other two gauges on the same steam line were reading above zero pressure.
Channel II loop was immediately declared in-operable and then placed in the tripped position.
Personnel had previously received a work reques to perform a preventive maintenance periodic test on this channel. When they were notified that the instrument was not working properly, they used the same work request to correct the problem.
The transmitter was aligned and the calibration was completed on April 10, 1981.
t Report Number 81-43 Page 2 Safety Analysis:
Each of the 4 main steam lines is provided with three (3) independent channel instruments to monitor steam line pressure and provide control cf the stop valve.
If one channel in any steam line is inoperable, then one out of the three indicators on that steam line is out of agreenent with the other two.
The stop valves did not close automatically because it would require at least 2/3 channel actuation for main steam line isolation to occur.
Therefore, the S/G "A" Steam Line Pressure Channel II being in-operable did not affect the plant's safe operation and the health and safety of the public.
If valid signals had occurred on the two operable channels, the stop valves would have closed.
Corrective Action: The Shift Supervisor requested personnel to place the affected channel in the trip position immediately upon declaring it in-operable.
(This was done by placing the loop in the TEST position.) The Dragon valve was tapped and the plunger 11ftc.d off its seat. The affected channel was. calibrated and declared operable on April 10, 1981 at 2025 hours0.0234 days <br />0.563 hours <br />0.00335 weeks <br />7.705125e-4 months <br />.
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