ML20210T569

Summary of 861211 Meeting W/Util Re Failures Experienced W/ Main Steam Turbine Bypass Flow Line & Corrective Actions to Resolve Problem.Meeting Agenda,Viewgraphs & List of Attendees Encl

ML20210T569
Person / Time
Site:	Fermi, 05000000
Issue date:	01/14/1987
From:	Stefano J Office of Nuclear Reactor Regulation
To:	Office of Nuclear Reactor Regulation
Shared Package
ML20210T193	List: ML20210T187 ML20210T243 ML20210T439 ML20210T483 ML20210T532 ML20210T569 ML20210U435
References
FOIA-87-50 NUDOCS 8702180226
Download: ML20210T569 (15)

Text

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LICENSEE: Detroit Edison Company FACILITY: Fermi-2 SUB.1ECT: MEETING SUMMAD.Y FOR DECEMPER 11, 1986, MEETING ON MAIN STEAM TUPBINE BYPASS FLOW LINE FAILURE On December 11, 1986, members o' the NRR staff met with the licensee to discuss failures experienced with the main steam turbine bypass flow line and corrective actions taken by the licensee to rectify the problems. Enclosure (11 is a copy of the meetina agenda and the slide presentation made by the licensee at the meetino. Enclosure (71 is a list of the meeting participants. Enclosure (3T documents the NRR's staff's position and corrents expressed at the meetine with respect to actions taken by the licensee to identify the root cause of the problen, corrective actions taken as of the date of the meetina, and the follow-on surveillances planned by the licensee.

The meetino was noticed in the PDR by memorandum dated November 76, 1986.

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Enclosures:

As stated 1

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1 l 8702180226 870209 PDR FOIA PUNTENNE87-So pga Id Jl !, - o sEI l

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l Pr. R. Ralph Sylvia Detroit Edison Company Femi-? Facility  !

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Mr. Harry H. Voigt, Esq. Ronald C. Callen LeBoeuf Lamb, Leiby & PacRae Adv. Planning Review Section 1333 New Hampshire Avenue, N. W. Michigan Public Service Commission Washington, D. C. E0036 6545 Mercantile Vay P. O. Box 30221

.lohn Flynn, Esa. Lansing, Michigan 48900 Senior Attorney Detroit Edison Company Regional Administrator, Region III 2000 Second Avenue U. S. Nuclear Regulatory Comission Detroit, Michigan 48226 799 Roosevelt Road Glen Ellyn, Illinois 60137 Mr. Dennis R. Hahn, Chief Nuclear Facilities and Environmental Monitoring Section Office Division of Padiological Health P. O. Box 30035 Lansing, Michigan 48909 Mr. Steve Frost Supervisor-Licensing Detroit Edison Company Femi Unit 2 6400 North Dixie Highway Newport, Michigan 48166 Mr. Thomas Randazzo Director, Regulatory Affairs Detroit Edison Company Fermi Unit 2 6400 North Dixie Highway Newport, Michigan 48166 Pr. Walt Rogers U. S. Muclear Regulatory Comission Resident Inspector's Office 6450 W. Dixie Highway Newport, Michigan 48166 Ponroe County Office of Civil i Preparedness 963 South Raisinville Monroe, Michigan 48161 l

(!PV/d AGENDA Objective of Presentation:

The actions and essential facts surrt>unding the initial reports of leakage on the main steam bypass lines, the corrective actions taken, and the followup measures implemented by Detroit Edison will be the subject of this presentation.

Detroit Edison believes that the root cause of.the problem has been identified and adequately dealt with. Further, that the bypass lines in their current configtration will support normal operations for the 110 year design life of the plant.

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AGENDA i

1. Initial Failu-e of the Main Steam Bypass Lines Initial detection of the leakage Determination of Root Cause

2. Modification of the Bypass Lines Industry experience search Consultants and A/E's Synthesis of the modifications NDE performed

3. Post Construction Testing Hopper report on fatigue life Testing program Results of test data analysis

4. Supplemental Testing Location of additional strain gages defined Testing program Results of testing

5. Service Life of the Lines Operational modes of the syste Extrapolation to a 40 plant life

6. Fesidual Concerns Relative to the Bypass Systm

7. Line Monitoring and Contingency Plans

8. Summary i

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The mainsteam bypass lines are acceptable f or the 40 year normal operating life of the Permi plant due to the following:

1. The lines meet or exceed the e mperical requirements for avoid-ance of acoustically induced pipe vall cracking.

2. The lines meet or exceed the req-uirements of the ANSI B 31.1 code to which they were designed.

3. Two separate rigorus evaluations, which utilize two different methods, predict 100 days of cumulative life in the least desireable range of valve positions.

4. The pipe wall strains measured since the lines were modified show signif-icantly reduced pipe wall strain are present.

5. The bypass line hangers and supports and snubbers meet or exceed the req-ments of the ANSI B 31.1 and AISC codes to which they were designed.

6. The least desireable valve position range is not a hold point in the normal plant operating proceedures.

7. The lines have operated for a peroid of 8 cumulative days in the valve position range of interest with:

a) Minor loosening of clamp nuts, which was resolved.

b) Some snubber clamp and one instance of hanger tube steel cracking which could have occurred during

,' operation of the original

- 3/8" wall line. Also, an analysis of the line shows that the supports could have been removed with no detremental effects.

ENCLOSIIRE (2)

DECEMBER 11, 1986 MEETING WITH DECO RE:

MAIN STEAM TtIRBINE BYPASS LINE FLOW-INDilCED VIBRATIDN MAME DPGANIZATION John Stefano NRC - Project Manager P. Wavne Houston NRR - Division of BVR Licensino John Tsao NRR - DRL/En Thomas Randazzo Detroit Edison Frank Aposti Detroit Edison Duane Danielson NRC - RIII John Jacobson NRC - RIII J. J. Harrison NPC - RIII, Chief Eng. Rranch Pob Hermann NRC - DRL/Section Chief EB E. G. Adensar NRC - DDL/8WD-3 Stephanie Murphy NIRS - 1616 P. St. NW, #160 D. G. La Grance NRC - DBL /ER T. Yano Stone F: Webster Steve Frost Detroit Edison Gene Preston netroit Edison Lawrence Sir.pkin Detroit Edison Pavid Spiers Detroit Edison John Conroni Detroit Edison David Hocper Hopper 8. Assoc.

Johseph Cohen ne troit Edison i

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%....+/ N li ppyi Docket No.: 50-341 MEMORANDUM FOR: Elinor G. Adensam, Director /

Project Directorate No. 3 Division of BWR Licensing FROM: Gus C. Lainas, Assistant Director Division of BWR Licensing

SUBJECT:

FERMI UNIT 2: MAIN STEAM BYPASS LINE FAILURE (TAC #63376) i Introouction In September 1985, Detroit Edison (DECO) discovered through-wall cracks in two main steam bypass lines at Fermi Unit 2. Subsequently, DECO replaced both lines with a thicker wall pipe, redesigned some of the pipe supports, and analyzed the piping vibration. DECO has identified the root cause of the problem to be acoustically induced flutter of the pipe wall. On December 11, 1986 a meeting was held in Bethesda, Maryland for DECO to present their assess-ment of the problem and corrective actions that they have taken to resolve

the issue. The Engineering Branch and Region III staff have evaluated this

! issue from the viewpoint of sound engineering practices rather than from assessment of meeting license requirements since the lines in question are a

! part of balance of plant. The assessment by the staff is to critique Deco on the basis of performance for this issue as an indicator of how they might address a similar problem in the " safety-related" part of the plant.

Both bypass lines (the West line and East line) are made of 30 inch diameter

- carbon steel pipe (API SL Grade B) and are reduced to 24 inch diameter at the inlet to condenser. The cracks were found at various locations on the pipe surface including, pipe support lug attachments, small test connections, and flow measurement orifices. DECO replaced the original 0.375 inch thick pipe with a 1.0 inch thick pipe for the 30-inch diameter section and 1.25 inch

thick pipe for the 24-inch diameter section. Deco also eliminated all pipe weld attachments. As a part of the modification, Deco conducted a test program j to obtain as-built stresses and strains at various locations of the lines and contracted Hopper and Associates and Stone and Webster to predict the service life of the pipe using the test data. After resolutions of disagreements l

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Contact:

4. Tsao x29408 l

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Elinor G. Adensam regarding the fatigue life of the pipe predicted by the two contractors, Deco concluded that the west line is acceptable if cumulative operation with bypass valve position between 30% and 45% opened for a period not to exceed 100 days, and that the east line can be operated indefinitely.

Discussion and Evaluation The staff believes the licensee has properly identified the root cause of this vibration as acoustically induced pipe wall fluttering resulting from high pressure drop across the bypass dump valve seat. The dump valve opening is about 9 inches whereas the pipe opening is 28 inches. The supersonic steam entering the pipe is choked at the valve exit. When the steam is expanded into the larger pipe, the flow becomes turbulent and generates the acoustic j vibrations.

i The modification that has been perfonned by the licensee has not been success-i ful in elminating the acoustically induced vibration from the piping system.

, The arguments presented by the licensee on alternative designs and why they could not be implemented at the facility appear plausible. However, in the design of the modification, it does not appear that sufficient considerations were given to this system with its inherent vibration problem. For instance, several supports on the system have cracked and nuts on clamps have fallen off. We understand that fillet welds rather than full penetration welds were used in the support design. Although this practice would meet the usual code requirements for supports of this type for power pipings, we believe that the fillet welds, with their inherent stress raisers, were not appropriate for i

this application. Further, no special care appears to have been taken by the licensee to preclude loosening of bolting in the system. As with the supports, no special considerations were taken with regard to the circumferential weldments in the piping. Weldments were made using backing rings. This type of joint is less desirable than an full penetration weldment made without a backing ring.

A joint made without a backing ring would not only have been more readily I

inspectable but also would have been less likely to provide a site for potential fatigue crack initiation. With regard to inspection, volumetric examinations

• i of the girth weld following fabrication could have provided added assurance that discontinuities from fabrication would not be present to serve the fatigue l crack initiation sites. Also, no volumetric inservice inspection has been proposed to monitor if service-induced degradation has occurred.

CONCLUSION The staff concludes that the licensee has been triorough and effective in identifying the root cause of the pipe vibration. However, the modification which is admittedly a compromise because of physical limitations and cost appear to have been done without going significantly beyond what the applicable ASME Codes would require. The licensee has attempted to reduce some stress raisers but has neglected quite a few others. Further, non-destructive inspections per-formed in past and those proposed by the licensee for the future are minimal.

l l

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JAN 1 2 E"I Elinor G. Adensam -

3-Had this problem occurred in the " safety-related" part of the facility, the staff would have expected the licensee to have been more attentive to design, fabrication and inspection factors discussed above.

This completes our action on this TAC.

$. py Gus C. Lainas, Assistant Director Division of BWR Licensing cc: R. Bernero W. Houston G. Lainas J. Stefano E. Adensam B. D. Liaw R. Hermann J. Jacobson, R III D. Danielson, R III i

J. Harrison, R III J. Tsao

Contact:

J. Tsao X-29408 l

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