ML20236E452
| ML20236E452 | |
| Person / Time | |
|---|---|
| Issue date: | 03/24/1986 |
| From: | Vollmer R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE) |
| To: | Shao L, Taboada A NRC |
| Shared Package | |
| ML20236E258 | List: |
| References | |
| FOIA-87-666 NUDOCS 8710290226 | |
| Download: ML20236E452 (5) | |
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NUCLEAR REGULATORY COMMISSION WASHINGTON,D.C. 20555 y' 8 l
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NOTE TO:
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j' Attcched are some pictures we requetted from
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t I talked to Southern California Edison as requested by Al and they are looking into the To take possibility of our. setting a sample. care of question j
makeup we would like, please have Al prepare 1
letters either from us as Chairmen PRC or from
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that we could keep proprietary if necessary.
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g Edison Lets
- Date.
March 19, 1986 i
I To:
Officers, Managers and Organizational Unit Heads
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i Harry Tauber fj' From:
Subject:
Monroe Power Plant Fipe Rupture 1
l As the effort continues.to determine the cause of the N?oe Power
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Plant Unit No. I hot reheat pipe rupture. numerous requests have been received by Detroit Edison for information relative to the cause.
It is in the best interest of the Company to limit the amou".t of infor-mation that is released to only that which is factual and celesively correct.
Attached is a statement that has been prepared to provide factual information known at this time relative to the Monroe pipe failure.
This can be provided to outside agencies, utilities, or any other entity outside of the Company.
No other information of any kind related to this incident should be provided at this time.
All requests for additional information relative to the Monroe situ-l ation should be directed to Mr. J. C. Guillaumin, the Project Manager.
Only Mr. Guillaumin or Mr. J. H. Erps of the Legal Department are authorized to respond to inquiries.
Att.
Distribution:
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..On Thursday, January 30, 1986, a failure ' occurred in the north hot reheat line of Unit No. 1 at Detroit Edison's Monroe Power Plant. The four units at Monroe are base loaded ag 750 Mw (net).
Design main steam temperature and pressure are 1006 reheat temperature and pressure are 1002,F and 3800 psi. Design hot F and 750 psi.
Normal full g
load operating hot reheat temperature and ' pressure are 1000 F and 730 psi.
The hot reheat piping is ASTM 105-66 Class 1 Grade 2-1/4Cr-1 Mo electric fusion welded pipe.
The outside diameter is 32 inches with 1.505 inch minimum walg.
Purchase specifications called for the pipe to be annealed at 1700 F.
The longitudinal and circumferential welds were to be '100 percent radiographer.
The pipe was manufactured by National Annealing Box Company and fabricated by Dravo Corporation.
The plant was designed by Detroit Edison.
Unit No. I was operating at near full load (757 Mw gross) under normal, steady state, conditions at the time of the failure.
Since initial. commercial operation in 1971, Unit No. I has operated nearly 97,000 hours0 days <br />0 hours <br />0 weeks <br />0 months <br />. A review of over 72,000 hourly. temperature and pressure readings indicate only 9 fiours of operation outside of the present l
code stress margins.
The-f ailure, a " fish mouth" type rupture twenty feet in length, occurred in the north reheat line.
The rupture was approximately 1
6 feet at its widest point.
The failure followed the longitudinal weld seam in a 39 foot horizontal spool piece just above the turbine room floor.
It arrested at a circumferential weld at the downstream end of the failed pipe spool.
The seam weld was oriented in the six o' clock position, and the force of the steam released broke several pipe supports and bent elbows and pipe sections on both sides of the failed piece. The failed pipe section is 19 inches higher than normal at the rupture.
Seventeen people were injured as a result of the rupture.
Some of them were hospitalized for several days.
None of the injuries was considered to be serious, and all of the injured personnel were released from the hospital by Monday, February 3,1986.
In order to. assure safe operating conditions,0the hot reheat temp-erature and pressure have been reduced to 950 F and 470 psi on the remaining 3 operating units until more information is available relative to the cause of the failure.
The hot reheat lines on Units No.1 and 2 are being inspected from the outside diameter along their entire length.
Magnetic particle, ultrasonic, replication, radio-graphic and metallographic procedures are being utilized.
Management and technical investigation teams have been assembled to detennine the cause of the Unit No. I failure.
Discussions have been held with several other utilities, consultants and agencies to gather information relevant to the failure.
Preliminary results indicate that the rupture followed the base metal to weld metal interface (fusion zone) along one side of the longitudinal weld seam.
The fracture surface is oxidized.
Non-metallic inclusions were found in the weld area.
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Samples from the fracture surface and from the failed section of pipe have been removed and are 'being tested to determine chemical and mechanical properties'as input to establishing the cause and mechanism of failure.
The remainder of the hot reheat lines on Unit No. I are being examined from the outside diameter, utilizing magnetic particle,
. replication, and ultrasonic techniques-to assure pipe integrity.
At this time, it is not possible to release additional detailed infor-mation until the investigation has been completed.
.All inquiries should be directed to J. C. Guillaumin Detroit Edison Engineering Research.
i JCG 3/13/86 l
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