ML20084L179

Ao:During Jet Pump Insps Completed on 740415,discrepancies Noted Re Missing Restrainer Gate Bolts,Keepers,Keeper Welds & Gate Wedge,Possible Vertical Movement of Gate Wedge Prior to Installation & Bolt Assemblies Failure

ML20084L179
Person / Time
Site:	Quad Cities
Issue date:	04/25/1974
From:	Kalivianakis N COMMONWEALTH EDISON CO.
To:	Oleary J US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20084L155	List: ML20084L154 ML20084L157 ML20084L179 ML20084L184
References
NJK-74-42, NUDOCS 8305200316
Download: ML20084L179 (7)

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April 25, 1974 3 Mr. John F. O' Leary, Director Directorate of Licensing Regulation U. S. Atomic Energy Commission Washington, D. C. 20545 Re ference: Quad-Cities Nuclear Power Station, Unit 1 Docket No. 50-254, DPR-29, Appendix A Sections 1.0.A.4, 6.6.B.l.a De ar Mr . O ' Leary : .

The purpose of this letter is to inform you of the details or the rincings rrom J et pump inspecrions perrormea on wuaa- -

Cities Unit 1. Initial inspections were completed on April 15, 1974. The initial findings were discussed with Region III Regulatory Operations personnel on April 16, 1974 and were reported to you and to the Region III Directorate of Regula-tory Operations byr telegram that same day. On April 24, 1974 the findings and plans to date were discussed with Commission personnel at the station.

PROBLEM AND INVESTIGATION INITIAL INSPECTION With Unit 1 in the cold shutdown mode during refueling opera-tions, a cheduled jet pump inspection was performed. This inspection was carried out with the aid of an underwater tele-vision car. era and video tape unit. The details of the inspection are listed below. Refer to Figures 1 and 2 for location of the components.

1) Inspection of the tack welds on the jet pump beam bolt keepers and a check of beam pocket fits.

2) Observation of the beam bolt assembly while applying 200 ft-lbs. of torque to the beam bolt in both the clock-wise and counterclockwise directions, respectively.

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3) Inspection of the restrainer gate and wedge positions and restrainer bolt tack welds.

Upon completion of the above inspections on all twenty jet pumps, the following discrepancies were noted:

1) While applying up to 200 ft-lbs. of torque to the beam bolts, movement was detected on three bolt assemblies, namely numbers 10, 13, and 16. They thus failed the test.

2) Three restrainer gate bolts and keepers were found to be completely sheared and missing. Two of these were from jet pump 5; one was from jet pump 6.

3) Thirty of thirty-seven remaining restrainer bolt keeper welds were found to be either missing or cracked.

4) The restrainer gate wedge on jet pump 5 was missing.

5) The restrainer gate on jet pump 18 showed signs of wear in the vicinity of the wedge indicating possible vertical movement of the wedge prior to the inspection.

SUBSEQUENT INSPECTION A subsequent inspection was made of the jet pump inlet riser braces for jet pumps 5 and 6. This inspection showed the brace to vessel welds to be intact.

RECOVERY OF MISSING PARTS From the above inspections, the following parts were determined to be missing: ,

1) Three restrainer gate bolt heads.

,2) Three restrainer gate bolt head keepers.

3) One wedge.

4) 'One wedge spring.

I Attempts to locate and retrieve the missing parts produced the following results:

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1) One restrainer gate bolt head was retrieved.

2) Two restrainer gate bolt head keepers were retrieved.

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3) One wedge was retrieved in three pieces; the wedge, the wedge bale, and the wedge spring.

4) One additional wedge bale was retrieved.

EVALUATIONS AND CORRECTIVE ACTIONS An extensive plan has been developed by the station and the General Electric Company to repair the discrepancies noted above. Details of this plan are described below.

Beam Bolts All beam bolts (20) for the twenty jet pumps will be com-pletely detensioned and then retensioned. The procedure to be used will be one previously used at Quad-Cities Station for jet pump repairs but modified from the tensioning pro-cedure used for the original installation. The modified procedure includes observing the beam bolt for rotation '

while being tensioned. The retensioned beam bolts will then be rewelded with two tacks per bolt.

Restrainer Gates All restrainer gate assemblies (20) for-the twenty jet pumps will be replaced with new assemblies. These new assemblies will be installed, properly tensioned and re-strained, and the keepers welded with one tack per bolt.

(Total of 40 bolts).

Riser Braces The riser braces on all ten jet pump inlet risers (1 riser per 2 jet pumps) will be completely inspected by using the underwater television camera. This inspection will primarily check the brace to vessel wall welds for integrity.

Jet Pumps 5 and 6 Jet pumps 5 and 6 will be removed from their normal posi-tion and raised to a position for more complete viewing.

A complete inspection of these jet pumps will be performed.

l Recovery of Missing Parts Attempts will be made to locate and retrieve the parts that are still missing. These include two restrainer gate bolt heads and one restrainer gate bolt head keeper. Additionally, an attempt will be made to determine the source of the extra wedge bale .

o o Mr. 'J . F . O ' Le ary April 25, 1974 Metallurgical Inspection of Retrieved Parts All parts retrieved from the vessel to date were sent to the General Electric Company on April 23, 1974. These parts will be examined at their Vallecitos Nuclear Center to determine the possible causes or reasons for the failures.

The above actions are scheduled to begin approximately April 30, 1974 and tentatively be accomplished by June 3,1974.

SAFETY EVALUATION The jet pumps are designed to withstand the combined loadings from differential pressure and temperature, dead weight, fluid movement, seismic acceleration and vibration without failure or loss of integrity. Even though there were significant failures of jet pump restraints and fasteners, there were no jet pump failures _or loss of. integrity. Particularly there were no failures of any jet pump nolddown components. There were thus no unsafe conditions existing during previous periods of reactor power . operation.

CAUSES, The cause of the failed restrainer gate bolt keeper tack welds and the apparent lack of preload on the beam bolts _ is presently being attributed to construction and-installation deficiencies.

The apparent cause of the failed restrainer bolts and the missing and possibly moved restrainer gate wedge is probably excessive vibration as a result of the deficient installation.

CUMULATIVE EXPERIENCE The problems discovered on this inspection of Unit 1 are similar to those discovered during inspections related to a jet pump failure on Quad-Cities Unit 2 in August 1972. At that time a jet pump assembly had become dislodged from its normal posi-tion and rotated in the vessel. At that time extensive inspec-tions and repairs were performed on all Unit 2 jet pumps and they have since operated satisfactorily. The details of that occurrence were reported to A. Giambusso by F. Palmer's letter of August 30, 1972. We are confident that the planned repairs to the Unit 1 jet pumps will be as successful as the repairs made on Unit 2.

We note that a previously reported failure of flow instru-mentation for jet pump number seven on Unit 1 nou appears to have a reasonable explanation and could be related to these current failures. That failure was reported to A. Giambusso by B. Stephenson's letter of December 4,1972. That failure

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.. G Mr . J . F . O ' Le ary April 25,1974 has now been located as a severed' instrument line at the point where the line is attached for support to jet pump number six.

It appears that this failure could have been caused by ex-cessive vibration of jet pump six due to the failed restraints.

It appears that all jet pump problems that have been experi-enced at Quad-Cities Station can probably be traced to faulty craft installation and workmanship during the initial installa-tion of both units.

The station and General Electric Company are still involved in discussions and planning to resolve all the deficiencies related to this abnormal occurrence. The results of the future inspections and planned repairs will be reported to you in a timely manner.

Very truly yours, COMMONWEALTH EDISON COMPANY QUAD CITIES NUCLEAR POWER STATION

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