ML19261F207

RO 76-42/1P:on 761122,leakage Found in B Decay Heat River Water Underground Pipe,Requiring Work on Stress Cracks. Caused by Pipe Misalignment Due to Improper Installation

ML19261F207
Person / Time
Site:	Three Mile Island
Issue date:	12/07/1976
From:	Arnold R METROPOLITAN EDISON CO.
To:
References
GQL-1683, NUDOCS 7910250626
Download: ML19261F207 (4)

Text

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% ORIGIN AL NU NC LAC 31FI E D One 5!Med Ocepy DE5CRIPTION E N C LOSU R E l Licensee Event '.e, ort (no 50-259/76-42/IP) on 11/22/'6 concernin; a crach in the "3" Jaca" !!aa: iver 'Ja ter Under ,rOund Pi ?c.

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'f POST OFFICE BOX 542 READING PENNSYLVANI A 19603 TELEPHONE 215 - 929-3601 December 7, 1976 GQL 1683 -

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Mr. J. P. O'Reilly, Director Office of Inspections and Enforcement, Region I _ _ .

U. S. Ieuclear Regulatory Cennission -

631 Park Avenue King of Prussia, PA 19L06

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Dear Sir:

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y Dceket :To. 50-289 T-Operating License IIc. DPR-50 In acecrdance with the Technical Specifications of our Three Mile Island !iuclear Station Unit 1 'TMI-1), we are reporting the following reportable occurrence.

Ecvever, as stated in the conversation with 3. Davis this report is ene day late.

(1) Report iumber: 76 h2/1P (2a) Required Repcrt Date: 12/6/76 (2b) Date of Occurrence: 11/22/76 (3) Facility: Three Mile Island :Iuclear Station - Unit I (k) Identification cf Cccurrence:

Title:

A Crack in the "3" Decay Heat River Water Underground Pipe.

Type: A reportable occurrence as defined by Technical Specificatica 6.9 2.A (9) in that the "3" Decay Heat River Water undergrcund pump discharge line leaked, thus requiring ccrrective reasures to prevent cperatien in a manner less conservative than assumed in the accident analysis in the FSAR cr Technical Specification 3.3 bases.

(f ) Ccnditions' Frier to Cecurrence:

Power Ccre O Elec 0 .

RC Flev 0 RC Pressure RC Tenp.

80 psig 850 F

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PRZR I.evel lh5 inches FRZR Temp. 3150 F M( Db

J. P. O'Reilly GQL 1683 (6) Descriptien of Occurrence:

The "B" Decay Heat River Water undergrcund piping cracked i==ed!.ately cutside the Intake Pu=p and Screen Ecuse vall joint. During the replace-ment of this pipe, it was discovered through investigatiens that the failure was attributable to settlement of the elbow thrust bicek which resulted in cisalign=ent of the pipe.

Further inspection of the adjacent 20" Reactor Building Energency Cccling Rive Water "A" line revealed that the bell fitting en the vall joint was crac:ed. The adjacent 30" Uuclear Services River Water line was drained and refilled as an adjunct to its inspection; upon refilling seepage vas observed frc= the cla .; bar veld on the pipe spigot fitting at the vall joint.

(7) Designaticn of Apparent Cause of Cccurrence:

The cause of this cccurrence has been determined to be due to stress resulting frc= misalign=ent of the pipe caused by improper installaticn.

Review of the original surveyors data indicated that the pipe had been installed in a level condition. It was then concluded that the pipe failure had been due to an apprcximate four (h) inch settlement of the thrust blocx arcund the Decay Heat River Water "B" pipe elbow. Measure-ment of the elevations of the Reactor Building Energency Ccoling River Water "A" thrust block and the Nuclear Services River Water Thrust bicek and soil density reasurements confirmed that the soil cc=paction in the vicinity of the thrust blocks in the backfilled area North of the Intake Pump Ecuse was poor and that settlement had cecurred in all three (3) blocks . This settlement has resulted in cracks in all three (3) pipes due to misalign-

=ent stresses.

(3) Analysis of Occurrence:

It has been determined that this cccurrence did not constitute a threat to the her.lth & safety of the public in that :

1) Only one (1) Decay Heat River Water pump and discharge line is necessary to supply sufficient emergency ecoling water in the event of a less-of-coolant accident and the redundant DR-PlA flevpath was verified as cperable.

2) The Reacter Building Energency Cooling River Water "A" line was near failure, however, this system was not requirea to be cperable since the unit was in a cold shutdcun condition. If the piping would have failed during an operating basic earthquake as a result of its stressed condition a redundant pump and flev path would be available to provide sufficient cooling water capacity.

3) The Reactor Building Spray System also provides additional redundancy since it possesses full post-accident cooling capability independent of the Reactor Building E=ergency Cccling System.

h) The leakage disecvered on the Nuclear Services River Water line was

=inor in nature and would have had nc effect en normal syst,e= cperation.

J. P. O'Reilly GQL 16c3 (9) Ccrrective Action:

The planned cutage was extended to allev for the folleving changes :

1) Replacement of the failed 2k" cencrete Decay Heat River Water "3" line frc= the vall joint to the elbev.

2) Replacecent of the 20" Reacter Building Emergency Cooling "A" line frcs the vall joint to the elbev and including replacement of the failed vall joint bell fitting.

3) Weld repair of the leaking section of clamp bar veld at the vall joint spigot fitting of the 30" Nuclear Services River Water line.

h) Raisi:, of the 30" Nuclear Services River Water elbev thrust bleek to its ' built" elevation by foundation grcut injecticn.

5) The elbcv joints nearest the vall joints on the three river water lines were freed frc= their encasement in the concrete of the thrust biceks to provide additional flexibility ^f these pipes to accept angular displacements.

6) An evaluation of the design laycut of similar River Water piping and thrust blocks en the Scuth side of the Intake Purp Ecuse augnented by tests of the core berings, evaluatien of soil Ocepaction results by the Architect-Engineer, and Generation Engineering review of criginal installation procedures and evaluation of the longer piping runs to the thrust block which has at least one (1) additional flexible joint per line resulted in the conclusien that the under-grcund piping en the Scuth side of the Intake House are not as susceptible to the thrust bicek settling probles.

Long Ter=: Long ters resolution cf this problem includes:

1) Installation of "scunding rod" tubes en the three (3) thrust blocks to allev periedic surveillance cf the elevatien of these thrust blocks to detect any future settling.

2) An engineering review and evaluation of the feasibility of a chemical grout injecticn under the base of the thrust biccks to provide a scre solid and permanent fcundation which vill resist or eliminate future settling prcblems.

(10) Failure Data:

Piping: Reinforced Concrete Water Pipe, steel cylinder type SP-5, prestressed in acecrdance with AWUa C-301-6h of 20", 2k" and 30" diameters.

Joints: Earnessed clamp joint bell and spiget design.

Manufacturer: Price 3rcthers Co.. Dayten, Chio Similar Events:

Ucne S'ncerely, )kh\

4 R. C. krnold

' lice Fresident