05000423/LER-1995-001, :on 950202,SWS Pipe Expansion Joint Discovered to Be Improperly Bolted.Caused by Loss of Work Control.Joint Properly Bolted

:on 950202,SWS Pipe Expansion Joint Discovered to Be Improperly Bolted.Caused by Loss of Work Control.Joint Properly Bolted

ML20080L823
Person / Time
Site:	Millstone
Issue date:	02/27/1995
From:	Mcguinness R, Miller D NORTHEAST NUCLEAR ENERGY CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-95-001, LER-95-1, MP-95-070, MP-95-70, NUDOCS 9503030009
Download: ML20080L823 (4)

LER-1995-001, on 950202,SWS Pipe Expansion Joint Discovered to Be Improperly Bolted.Caused by Loss of Work Control.Joint Properly Bolted

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2) 10 CFR 50.73(a)(2)(ii) 10 CFR 50.73(a)(2)(v), Loss of Safety Function
4231995001R00 - NRC Website

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~.fl N:rtherst nope Ferry ad. (noute 156), waterford, cr 06385 p Nuclear Energy Millstone Nuclear Power Station

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RO. Box 128 Waterford, Cr 06385-0128 (203)444 -4300 Fax (203) 444-4277 The Northeast Utilities System Donald B. Miller Jr.,

Senior Vice President - Millstone Re: 10CFR50.73 (i) 10CFR50.73 1

10CFR50.73 Febraury 27, 1995 MP-95-070 U.S. Nuclear Regulatory Commission e-Document Control Desk Washington, D.C. 20555

Reference:

Facility Operating Ucense No. NPF-49 Docket No. 50-423 Licensee Event Report 95-001-00 This letter forwards Licensee Event Report 95-001 -00 required to be submitted within thirty (30) days pursuant to 10CFR50.73(a)(2)(l),50.73(a)(2)(ii), and 50.73(a)(2)(v).

Very truly yours, NORTHEAST NUCLEAR ENER COM ANY Oh1 Donald B. Miller, Jr.

Senior Vice President - Millstone Station DBM/RLM:ljs Attachment: LER 95-001 -00 cc:

T. T. Martin, Region l Administrator P. D. Swetland, Senior Resident inspector, Millstone Unit Nos.1,2, and 3 V. L. Rooney, NRC Project Manager, Millstone Unit No. 3 000000 388328883o!8ssLs f3?'

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Millstone Nuclear Power Station Unit 3 05000423 1OF3 TITLE (4)

Service Water System Train "B" Expansion Joint Inoperable Due to Work Control During Plant Construction EVENT DATE (5)

LER NUMBER (6)

REPORT DATE (7)

OTHER FACILITIES INVOLVED (8) raCW NAME DOCKET NUMBER sE g g REgsg uours o4y ygan Mourn oAv YEAR vEAR p g 05000 FACa.nv NAuE oOCKcr NuuseR 02 02 95 95

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NAME TELEPHONE NUMBER (indud. Area Cod )

Robert L McGuinness, Senior Engineer (203) 447-1791 Ext. 6855 COMPLETE ONE LINE FoR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (13)

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On February 2,1995, with the plant in MODE 1 at 100% power, a pipe expansion joint in the "B" train of the Service Water System (SWP) was discovered to be improperly bolted. The affected pipe supplies service water to one of two Containment Recirculation Spray (RSS) heat exchangers in the "B" train. Immediate operator actions were taken to conservatively declare the affected SWP "B" train and Diesel Generator (EDG) inoperable, and also to isolate and declare the "B* train RSS heat exchangers inoperable. Corrective action was taken to restore proper bolting of the expansion joint, inspect other joints, and return the affected equipment to oporable status.

Technical Specifications require two trains of SWP, two trains of RSS, and two operable EDGs. It was estimated that the incorrect bolting could have existed from pressure testing during plant construction. Since there were periods of time in plant history when the "A" train of SWP, RSS, or EDG was also inoperable (for surveillance, etc.),

there were historical occasions when the plant could have been in a condition prohibited by Technical Specifications; or outside the design basis; or that cculd have resulted in the loss of a safety function.

The condition involved moderate safety significance. No component failures or loss of safety systems occurred.

It was conservatively estimated that the condition could have resulted in SWP pipe stresses that would exceed allowablo stresses for the worst case design basis load combinations. A pipe rupture, combined with a design basis accident, would have resulted in a loss of flow to one of four RSS heat exchangers, and a reduction in flow to one EDG and another RSS heat exchanger.

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Descriotion of Event On February 2,1995, with the plant in MODE 1 at 100% power, a pipe expansion joint in the "B" train of the Service Water System (SWP) was discovered to be improperly bolted. The affected pipe supplies service water to one of two Containment Recirculation Spray (RSS) heat exchangers in the "B" train. A designer was performing a field walkdown for a future modification, when the bolting discrepancy was identified.

Immediate operator actions were taken to declare the "B" SWP train and "B* Diesel Generator inoperable, and also to isolate and declare the "B" train Containment Recirculation Spray (RSS) heat exchangers inoperable. No actual component failures or loss of safety systems occurred. Later during the same shift, the affected expansion joint and associated RSS heat exchanger were Isolated, and all other equipment and systems were returned to operable status.

The design of the expansion joint requires sixteen studs and nuts on the flanges on each end of the expansion joint. However, the as-found condition had eight proper studs on each flange, and an additional eight threaded rods (approximately 30 inches in length) had been installed through the flanges at each end of the expansion,oint. The nuts on these threaded rods were tightened at the flange surfaces at each end of the expansion, oint, thereby precluding the joint from expanding or contracting. The threaded rods had apparently been installed to prevent expansion joint movement during pressure testing of the associated pipe during plant construction.

Corrective action was taken to restore the proper botting of the expansion joint, inspect otherjoints, and return the affected equipment to operable status.

II.

Cause of Event

The cause of the condition was apparently a loss of work control following the hydraulic pressure test of a portion of the SWP prior to preoperational system tumover. The condition was not evident because of an installed shroud and insulation.

Ill.

Analysis of Event

This condition is reported as a condition prohibited by the Technical Specifications; a condition outside the design basis of the plant; and a condition that could have resulted in the loss of a safety function.

Technical Specifications require two trains of SWP two trains of RSS, and two operable EDGs. At the time 1

of discovery on February 2,1995, it was immediately determined that the condition was a violation of Technical Specifications, reportable under 10CFR50.73.

The condition was reviewed by engineering, following the initial discovery The preliminary review determined that the condition existed for a period of time prior to discovery. The review conservatively estimated that the combination of seismic and design basis loads would result in stresses at the bolted expansion joint, that could result in a failure of the pipe supplying one of the four RSS heat exchangers.

There are two 50% capacity heat exchangers in each RSS train. It was also estimated that the incorrect bolting of the expansion joint could have existed from plant construction, when the SWP was hydrostatically tested.

4 Since there were periods of time in plant history when the "A" train of SWP RSS, or EDG was inoperable l

(for survoi!Iance or other reasons), there were historical occasions when the plant could have been in a condition prohibited by the Technical Specifications; or outside the design basis of the plant; or in a condition that could have resulted in the loss of a safety function. Accordingly, based on the engineering review, the historical condition was reported as a prompt report under 10CFR50.72.

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Millstone Nuclear Power Station h8E YEAR T

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The condition involved moderate safety significance. There were no actual failures of piping or systems.

The inccrrect bolting of the expansion joint did not cause any degradation in service water supplied to any safety related equipment. It was conservatively estimated that the incorrect bolting of the expansion joint could have resulted in SWP pipe stresses that would have exceeded Code allowable stresses for the worst case design basis load combinations. A SWP pipe rupture from a seismic event, combined with a design -

basis accident, would have resulted in a loss of flow to one of the four RSS heat exchangers, a reduction in flow to another heat exchanger, and a reduction in flow to one of the EDGs.

The redundant components in the 'A' train ;ystems would have performed the required safety functions unless they were unavailable (due to single failure, testing, etc.). Also the the postulated pipe rupture causing a loss of service water to one of the four RSS heat exchangers, would not cause an actual loss of the other "B* train systems supplied with service water, but it was estimated that there would be a small reduction in flow that would not significantly affect their functions.

IV.

Corrective Action

immediate operator actions were taken to declare the affected "B" SWP train and diesel generator inoperable, and also to isolate and declare the "B" Containment Recirculation Spray (RSS) heat exchangers inoperable. After isolating the affected expansion joint and heat exchanger, the other equipment and systems were retumed to operable status. Corrective action was taken to restore the proper bolting of the expansion joint. The threaded rods were removed one at a time and proper studs and nuts were installed in accordance with the original design. The remaining expansion joints in the area were inspected and no other problems were noted. It was determined that additionalinspections of other SWP expansion joints were not needed since the joints on pump discharges and two of the four joints on the EDG heat exchangers wero previously replaced with no similar problems.

Subsequent to repairs, the affected heat exchanger was returned to operable status. No additional actions were necessary to prevent recurrence, because this was determined to be an isolated occurrence from plant construction. Current work control requirements minimize the potential for a recurrence in any future work on expansion joints.

V.

Additional Information

There have been no other reported events involving expansion joints. The closest similar condition was reported in LER 93-012-01. It involved plywood dams left in the 'A' train of the Service Water System during a refueling outage, which potentially rendered that train inoperable. The cause was inadequate work planning and inadequate verbal communication. The corrective actions strengthened the materiel exclusion program and work control requirements for any ongoing or future work. These actions would not have identified or prevented the hydrostatic test bolting on the service water expansion joint that is reported in the current LER because it was an isolated plant construction item.

Ells _Codna System Component Service Water System - BI Expansion Joint - EXJ