Information Notice 1986-10, Feedwater Line Break

Feedwater Line Break

ML042330664
Person / Time
Issue date:	11/10/1988
From:	Rossi C E Office of Nuclear Reactor Regulation
To:
References
IN-86-106, Suppl 3
Download: ML042330664 (3)

UNITED STATES NUCLEAR REGULATORY

COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D.C. 20555 November 10, 1988 NRC INFORMATION

NOTICE NO.86-106, SUPPLEMENT

3: FEEDWATER

LINE BREAK

Addressees

All holders of operating

licenses or construction

permits for. nuclear power reactors.

Purpose

This supplement

to Information

Notice (IN)86-106 is intended to provide ad-dressees with additional

information

about a potential

problem that resulted in thinning of secondary

system piping at both units of an operating

nuclear power station and the catastrophic

failure of a main feedwater

suction pipe.It is expected that recipients

will review the information

for applicability

to their facilities

and consider actions, as appropriate, to avoid similar problems.

However, suggestions

contained

in this information

notice do not constitute

NRC requirements;

therefore, no specific action or written response is required.Discussion:

IN 86-106, Supplement

1, was issued on February 13, 1987, to provide addi-tional information

regarding

the catastrophic

feedwater

line break at Surry Power Station, Unit 2. Results of the licensee's

failure analysis and the NRC technical

panel conclusions

concerning

the pipe break failure mechanism were discussed

in Supplement

1. Supplement

2 addressed

system interactions.

During the September

1988 outage, the Surry licensee discovered

that pipe wall thinning had occurred more rapidly than expected.

On the suction side of one of the main feedwater

pumps, an elbow that was installed

during the 1987 re-fueling outage lost 20 percent of its 0.500 inch wall in 1.2 years. In ad-dition, wall thinning is continuing

in safety-related

main feedwater

piping and in other non-safety-related

condensate

piping.On the basis of partial inspection

results, the licensee indicated

that the broad area thinning rate for the replacement

piping, installed

during the last refueling

outage, is roughly 60 mils/year.

The maximum localized

thinning rate is 90 mils/year.

These rates were higher than the 20 to 30 mils/year rate estimated

previously.

The estimated

rate of 20 to 30 mils/year

was based on a single measurement

and an assumption

that wall thinning had been 1:; 1 CW^F D032 4 IN 86-106, Supplement

3 November 10, 1988 progressing

linearly since initial full-power

operation

was achieved.

This new rate of wall thinning, which is based on a second data point, indicates that significant

wall thinning may have coincided

with a reduction

in feed-water dissolved-oxygen

concentration

subsequent

to steam generator

replacement.

The lower rate of wall thinning associated

with a higher feedwater

dissolved- oxygen concentration

is consistent

with the low rates of erosion/corrosion

reported in IN 88-17, "Summary of Responses

to NRCB 87-01, 'Thinning

of Pipe Walls in Nuclear Power Plants'," for boiling water reactors (BWRs), which typically

operate at a feedwater

dissolved-oxygen

concentration

of approxi-mately 30 ppb. The licensee is continuing

its failure analysis to determine the cause(s) of the increase in the estimated

pipe wall thinning rate. Because the measured rate of pipe wall thinning is in excess of the previously

esti-mated rate, the scheduled

frequency

of future inspections

may need to be reexamined

to ensure that code-allowable

wall thickness

is maintained.

Additional

information

pertaining

to erosion/corrosion

in feedwater-condensate

system piping can be found in IE Information

Notice Nos.86-106; 86-106, Supple-ment 1; 87-36, "Significant

Unexpected

Erosion of Feedwater

Lines"; 88-17; and NRC Bulletin 87-01, "Thinning

of Pipe Walls in Nuclear Power Plants." No specific action or written response is required by this information

notice.If you have any questions

about this matter, please contact the technical

contact listed below or the Regional Administrator

of the appropriate

regional office.s'azt1 Charles E. Rossi, Director Division of Operational

Events Assessment

Office of Nuclear Reactor Regulation

Technical

Contact: Paul Wu, NRR (301)492-0826 Attachment:

List of Recently Issued NRC Information

Notices

Attachment

IN 86-106, Supplement

3 November 10, 1988 LIST OF RECENTLY ISSUED NRC INFORMATION

NOTICES Information

Date of Notice No. Subject Issuance Issued to 88-86 88-85 88-84 88-83 88-82 88-81 Operating

with Multiple Grounds in Direct Current Distribution

Systems Broken Retaining

Block Studs on Anchor Darling Check Valves Defective

Motor Shaft Keys in Limitorque

Motor Actuators Inadequate

Testing of Relay Contacts in Safety-Related

Logic Systems Torus Shells with Corrosion and Degraded Coatings in BWR Containments

Failure of Amp Window Indent Kynar Splices and Thomas and Betts Nylon Wire Caps During Environmental

Quali-fication Testing Unexpected

Piping Movement Attributed

to Thermal Stratification

Misuse of Flashing Lights for High Radiation

Area Controls 10/21/88 10/14/88 10/20/88 10/19/88 10/14/88 10/7/88 10/7/88 10/7/88 All holders of OLs or CPs for nuclear power reactors.All holders of OLs or CPs for nuclear power reactors.

-All holders of OLs or CPs for nuclear power reactors.All holders of OLs or CPs for nuclear power reactors.All holders of OLs or CPs for BWRs.All holders of OLs or CPs for nuclear power, test, and research reactors.All holders of OLs or CPs for PWRs.All holders of OLs or CPs for nuclear power reactors.88-80 88-79 88-69, Supp 1 Movable Contact Finger Binding in HFA Relays Manufactured

by General Electric (GE)9/29/88 All holders of OLs or CPs for nuclear power reactors.OL = Operating

License CP = Construction

Permit