ML19210A217

Abnormal Occurrence 50-289/75-22:on 750711,leaks Found in Socket Weld Joints of Makeup Pump Suction Vent Line MU-PIA Leading to Valve MU-V156A.Caused by Improper Spacing Between Moving Anchor & First Pipe Restraint

ML19210A217
Person / Time
Site:	Three Mile Island
Issue date:	07/21/1975
From:	Arnold R METROPOLITAN EDISON CO.
To:
Shared Package
ML19210A218	List: ML19210A217 ML19210A222
References
NUDOCS 7910240932
Download: ML19210A217 (4)

Text

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NRC _ STRIBUTION FOR PART 50 DOCK M ATERI AL (TEMPORARY FORM)

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NRC 1 signed SENT LOCAL PDR XX CLASS UNCLASS PROPINFO ;NPUT NO CYS REC'D DOCKET NO:

XXX 1 50-289 DESCRIPTION: Ltr advising of Abnormal ENCLOSURES:

Occurrence A0-50-289/75-22 on 7-11-75 re socket weld joint leaks in the suction vent line for the Make-Up Pump (MU-PIA).. , .

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Division of Reactor Licensing -s _r-U.S. Nuclear Regulatory Commission b Washington, D.C. 20555

Dear Sir:

Docket No. 50-289 Operating License No. DPR-50 In accordance with the Technical Specificctions of our Three Mile Island Nuclear Station Unit 1 (TMI-1) , we are reporting the following abnormal occurrence.

(1) Report Number: A0 50-289/75-22 (2a) Report Date: July 21, 1975 (2b) Occurrence Date: July 11, 1975 (3) Facility: Three Mile Island Nuclear Station Unit 1 (4) Identification of Occurrence:

Title:

Socket weld joint leaks in the suction vent line for the Make-Up Pump (MU-PlA).

Type: An abnormal occurrence as defined by the Technical Specifications, paragraph 1.8e, in that leaks from this Make-Up Pump suction line constituted abnormal degradation of a system boundry designed to contain radioactive materials.

(5) Conditions Prior to Occurrence:

Power: Core: 100%

Elect.: 870 W e }4]h 2kb 7827

RC Flow: 140 x 106 lb/hr RC Pressure: 2155 psig RC Temp.: 579 F PRZP Level: 240 inches PRZR Temp.: 6500F (6) Description of Occurrence:

On July ll,1975, during a routine inspection of the Auxiliary Building, two leaks were discovered in socket weld joints of the Make-Up Pump (MU-PLA) suction vent line leading to valve MU-V156A.

One leak on this vent line was a crack in the weld joint adjacent to the 6 inch diameter Make-Up Pump suction line. The other leak was a pinhole crack in the weld joint of a 900 elbow fitting on this same vent line.

Immediately upon discovery, these leaks were isolated.

(7) Designation of Apparent Cause of Occurrence:

Installation procedures specify 80 inches to be the minimum space between a moving anchor and the first pipe restraint. This specification allows sufficient flexibility in the pipe between the moving anchor and the first pipe restraint to prevent cyclic f atigue failure. For the vent line only 23 inches of space between anchor and restraint existed allowing cyclic stresses to cause f atigue f ailure of the weld joints on this line. Therefore, the apparent cause of this occurrence is installation / construction.

(8) Analysis of Occurrence:

It has been determined that this occurrence did not represent a threat to the health or safety of the public, in that

a. only two Make-Up Pumps are required for normal system operation,

b. the effected pump was immediately isolated, and

c. no detectable increase in radiation levels were observed.

(9) Corrective Actions:

In addition to the immediate corrective action listed above, long term corrective actions were to:

a. modify the restraints to conform to the instr.11ation specifi-cations, and

b. inspect and verify that similar conditions did not exist on "B" and "C" Make-Up Pumps.

1 A 7 6 'c) 4 o'

The Plant Operations Review Committee and Station Superintendent have reviewed and approved the above listed corrective actions.

(10) Failure Data:

Pipe: 3/4 inch diameter Schedule 40S ASTM A 312, type 304 Stainless C teel Socket Welds .

Similar Occurrences: None Since rely ,

W R. C. Arnold Vice President RCA/CWS/cas cc: Of fice of Inspection and Enforcement , Region 1 File: 20.1.1/7.7.3.5.1 1,476 247