05000336/LER-1990-017-01, :on 901010,discovered That Svc Water Pipe Support Inadequate

:on 901010,discovered That Svc Water Pipe Support Inadequate

ML20197H510
Person / Time
Site:	Millstone
Issue date:	11/09/1990
From:	Bergin J, Scace S NORTHEAST NUCLEAR ENERGY CO., NORTHEAST UTILITIES
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-90-017-01, LER-90-17-1, NUDOCS 9011160033
Download: ML20197H510 (4)

LER-1990-017, on 901010,discovered That Svc Water Pipe Support Inadequate

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability
3361990017R01 - NRC Website

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November 9, 1990 MP-90-1202 Re: 10CFR50.73 i

U.S. Nuclear Regulatory Commission Document Control Desk i

Washington, D.C. 20555

Reference:

Facility Operating License No. DPR-65 Docket No. 50-336 i

Licensee Event Report 90-017-00 Gentlemen:

This letter forwards Licensee Event Report 90-017-00 required to be submitted within thirty (30) days pursuant to 50.73(a)(2)(v) and 50.73(a)(2)(vii).

Very truly yours, NORTHEAST NUCLEAR ENERGY COMPANY

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/ Steph n E.

cace Director, hiillstone Station l

SES/JhiB:ljs Attachment: LER 90-017-00 ce; T. T. hiartin, Region 1 Administrator W, J. Raymond, Senior Resident inspector, hiillstone Unit Nos.1, 2 and 3 G. S. Vissing, NRC Project hianager, hiillstone Unit No. 2 i

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Millstone Nuclear Power Station Unit 2 oi sI ol of of 313 l 6 1lodOl3 TITLE 14)

Sernce Water Pipe Support Inadequac)

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NAME TELEPHONE NUMBER ARE A CODE Joseph M. Bergin. Engineer, Ext. 5352 2l0j3 4l4l7l-l1l7l9l1 COMD ETf ONE tlNE FOA E ACM COMAONEN' F AiLUA! DE SC A1 BED IN TMts AEDOAT I13)

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On October 10, 1990, with the Unit in Mode 6. 0G power and temperature at 90 degrees, it was discosered that a seismic Class I hanger. #60027. did not comply with the requirements of I&C Bulletin 79-02. The anchor bolts on this hanger were being inspected as part of a program being instituted to evaluate the effects of safety water induced corrosion on the seismic intmity of Class I hangers. During this evaluation, hanger

1. 60027 was found w1th degraded anchor bolts. While performing calculations to determine the " As Found" factor of safety for this hanger, an error was found to show that the hanger did not meet the required factor of safety 2 4, The " As Found" factor of safety was calculated and was less than 2. Calculations have shown that section of piping support by this hanger would have failed during the Design Basis Earthquake. During the Operating Basis Event the pipe would have suffered plastic deformation. Failure of this pipe could have affected the abiht) of both Semce Water Headers to satisfy their intended safet) functions. Since the requirement for this hanger is based upon the need to seismicall) qualify a flow restriction orifice and the hanger does not meet this design function, the flow orifice at the branch cr nection of each semce water header has been relocated to an upstream portion of the system. This upstream location is seismically qualified by other hangers and the need for hanger #60027 has been eliminated. Hanger #60027 has been removed.

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Desctmtion of Event On October 10, 1990, with the Unit in Mode 6, O'~c power and temperature at 90 degrees, it was discovered that a seismic Class I hanger. #60027, did not comply with the requirements of 1&C Bulletin 79-02. During the couse cf the Refuehng activities, an evaluauon was being performed to determme the extent of co rosion affects of seismic anchor bolts in areas where they could be subjected to salt water intrusion. This evaluauon required several hangers to be removed from their grout pads and anchor bolts. The hanger #60027 was removed from its grout pad and the "As Found" diameters of its anchor bolts were determined. This data and the original design calculation were thers reviewed by the Engineering staff. This review found that the ongmal design did not compl3 with the requirements of l&C Bulleun 79-02. Further evaluation determmed that this hanger had a remaining factor of safety less than 2.

This hanger supports the Service Water supply from the Facility I and FaciM.,11 Service Water headers to the Sodium Hypochionte skid. The design for this hne incorporate. the use of a flow restncting orifice in each supply hne to hmit flow to acceptable levels, if this lint were to fail dunng a seismic event. The orifice in each line is located between a hanger at ie brtnch pomt on each header and hanger #60027, where the two lines meet at a tee. These imes are designated as seismic Class 11 hnes in the Unit's design. The specification change, from Class I to Class li, occurs at a manual isolation valve in each branch line from the Facihty I and 11 Service Wat:r Headers.

There were no Automatic or manually imtiated safety responses as a result of this event.

11.

Cause of Event

The root cause of this event is personnel error in the placement of a Category I component in a system which is detignated as Class 11 m the Unit's specificauon. This deficiency resulted in this hanger being considered a Class 11 hanger when the 79-02 review was performed and as a result the deficiency in the calculation was not discovered until this hanger inspection program required a review of the origmal calculation.

Annhsis of Event This event is being reported pursuant to the requirements of 10CFR50.73(a)(2)(v) and 50.73(a)(2)(vii) which require tne reporting of events that affect the Unit's ability to remove residual heat. At the time of discovery the manual isolation valves which isolate this portion of the system from the mam headers were closed. Upon discovery thew valves were maintained closed until the flow orifice on each of the headers were relocated.

If the Design Basis Earthquake were to occur with tht hanger in the degraded condition, each of the Service Water Headers could have had a six-inch breach until isolated by closure of the manual isolation valves. This six-inch breach in the discharge piping of the Service Water Pumps would have reduced the flow to vital components to less than that required by the Design Basis.

Based tapon the fact that no seismic event had occurred there was no safety significance to this event.

IV.

Corrective Action

The need for the hanger has been eliminated based upon the relocation of the flow orifice to the upstream side of the manual isolation valve in each line. Based upon this relocation, hanger #60027 is no longer required to meet the design and has been removed from the service water system.

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Ft.gulatory Commission W asmngton DC 20655 aw to th. Pa erwork R.aoction Proi.c1 (3150-0104i Off.ce o' Manament and Budo.1 Wasmneton. DC 70603 F ACILITY NAME (i)

DOCKET NUMBER (2)

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Since this section of piping was upgraded from a seismic Class !! to a seismic Class li 11 is unique in the Unit and no other similar conditions are anticipated. The staff will review a sample lot of hangers in Safety Related Systems at the interface between seismic Class I and Class II. This will serify that hangers which are required for seismic Class I systems are in comphance with the requirements of I&C Bulletin 79-02 V.

Additional Information

Similar LERs 86-01 Ells Code BI - SPT - 0000 i

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