ML20236J733

Forwards Addl Justification for Reducing Inservice Testing Check Valve Disassembly Frequency,Consisting of Insp Results Summary for Eight Valves & Justification for Less Frequent Insps,Per Discussions in 861224 & s.Fee Paid

ML20236J733
Person / Time
Site:	Three Mile Island
Issue date:	11/03/1987
From:	Hukill H GENERAL PUBLIC UTILITIES CORP.
To:	NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
References
RTR-NUREG-1269 5211-87-2197, GL-87-12, IEB-80-12, IEIN-81-09, IEIN-81-9, IEIN-86-101, IEIN-87-023, IEIN-87-23, NUDOCS 8711060256
Download: ML20236J733 (9)

Text

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GPU Nuclear Corporation L u Nuclear  :=orar8o Middletown, Pennsylvania 17057 0191 717 944 7621 TELEX 84 2386 Writer's Direct Olal Number: ,

November 3, 1987 5211-87-2197 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555 Gentlemen:

Three Mile Island Nuclear Station, Unit 1 (TMI-1)

Operating License No. DPR-50 Docket No. 50-289 Inservice Testing (IST) Check Valve Disassembly Frequency The frequency of disassembling certain valves (BS-V30A/B, BS-V52A/B, DH-V14A/B, and MS-V9A/B) for inspection purposes is an issue that was resolved for Cycle 6 operation in .that these valves were disassembled and the inspections were performed to comply with the staff position stated in the NRC's Safety Evaluation Report (SER) dated March 19, 1987. In order to resolve this issue for the balance of the current IST interval, this letter provides the additional information as discussed in GPUN letters dated December 24,1986 and February 19, 1987 to support our justification for disassembling these valves for inspection less frequently than the current NRC position would allow.

GPUN has stated that disassembling these valves on a sampling basis (alternating between the A and the B valve for each valve set) each refueling results in excessive wear and tear on the parts for very little information to be gained. The valve internals for these valves experience an environment where the water chemistry is controlled to minimize corrosion and the valves experience infrequent flow service. Problems related to wear or partial disassembly of check valve internals would be highly unlikely.

In regard to DH-Vl4, the disassembly frequency generates unnecessary radwaste, causes avoidable personnel exposure, and creates unnecessary equipment downtime. This is particularly true for DH-V14A/B where the valve is stroke tested to pass approximately 2/3 of the accident design flow rate each refueling and where disassembling the valve results in removing a train of the Decay Heat Removi , stem from service while the plant is shutdown and decay heat removal e flity is required. Loss of decay heat removal capability has been the su' ,. of numerous NRC documents addressed to licensees including, NUREG-1269, oeneric Letter 87-12,Bulletin 80-12, and Information Notices 81-09,86-101, and 87-23.

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q f' -5211-87-2197 Attachment A provides a summary of _ the disassembly inspection results for these eight valves including the disassembly inspections performed during the Cycle 5 i

-refueling outage.. Attachment'B'provides the detailed justification for less l frequent disassembly inspections, i GPUN believes that the information and conclusions expressed in Attachments A  !

and B provide adequate technical basis for extending these disassembles to a l 10 year frequency. l In accordance with 10CFR170.2, attached is our check for $150.00 as part of the  ;

fee associated with NRC review of this submittal. In order to make plans for maintenance during the next refueling outage, GPUN requests NRC approval by March 1988.

Sincerely, H. D. iukill Vice President & Director, TMI-l HDH/MRK/spb:1016A ,

1 cc: R. Conte I W. Russell J . Stol z

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ATTACHMENT A SHEET 4 of 4 i MS-V9A/B INSPECTIONS / FINDINGS DURING 6R REFUELING The November 18, 1986 disassembly of MS-V9A revealed the following. 1 I

1. Disc stud nut, disc stud washer and disc stud cotter key were missing. l

2. The disc was still in place on the yoke arm (see attached photographs).

The fit between the hole in the yoke arm and the shoulden of the stud was j a sliding friction fit. There was no damage to the disc stud end, stud 1 threads, disc seat or disc seating surfaces. The valve was found operabl e.

The disc stud washer was found in the MS-V6 (downstream control valve for the Turbine Driver (EF-U1) for the Turbine Driven Emergency Feedwater Pump, (EF-P1), during the SM Eddy Current Test Outage. The SM Eddy Current Test Outage was approximately six months prior to the November, 1986 disassembly of MS-V9A. Viewed from the side, the washer was bent in an "S" shape and was oblong. On November 20, 1986 the disc nut was found downstream of MS-V10B. The nut was in good condition. However, upon trial re-assembly the fit between the nut and the stud was very loose (approximately 1/16" of axial and radial play). This may have allowed the cotter key (1/8" diameter and 2-1/2" long) to take the load rather j than the threads. Eventually the cotter key may have fatigued and it may 3 have broken into several pieces. This loose thread fit was determined to be manufacturing defect, not a problem caused by wear. A review of the machinery history file indicated that MS-V9A had never been disassembled prior to November 18, 1986.

A search (drain valves, steam trap and steam chest / governor valve of EF-U1) for the missing cotter key was made but it was not found. As j stated above, the washer was found during the SM Eddy Current Test Outage ]

and EF-P1 had been operated satisfactorily on Main Steam at least five j times with the cotter key missing.

In addition, Test Procedure 636/1, Full EF-P1 flow to the OTSG's was '

performed in October,1985. Therefore, it was concluded that either the cotter key was never installed by the valve manufacturer or it is not in a location where it will do damage. A new cotter key was installed in MS-V9A and the nut was welded to the disc stud.

For MS-V9A and B, GPUN's IST Program Submittal dated December 24, 1986 states, "If degradation is found which would make the valve's full stroke capability questionable, then the other valves (MS-V9A or B) would be disassembled and inspected during the same outage". Therefore, MS-V98 was disassembled. MS-V98 was found operable. See attached photographs. s l No unusual corrosion, loose parts or wear was found. The fit between the l nut and the stud was somewhat loose but not as loose as MS-V9A. As a j precaution the disc nut was welded to the disc stud. )

Because the disc nuts were welded on both MS-V9A and 98, and because of '

' the infrequent and short term flow through these valves (for monthly IST and quarterly electrical surveillance testing only), a recurrence of any i valve internals degradation would be extremely unlikely.

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ATTACHMENT B- SHEET 1 of 2- i s .:

VALVE DISASSEMBLY REPORT CONCLUSIONS l

1 NRC has addressed a number of check valve failures-in recent IE Bulletins and IE Information Notices. INP0 has issued Significant Event Reports and Significant Operating Experience Reports concerning check valve failure.

Also, INPO is working to solve industry generic problems with check valves.

The mode of. failure indicated in a large percentage of these failures is partial disassembly' (disc.may become a loose part) of the' check valve internals caused by ' corrosive / abrasive wear; inadequate' design of locking mechanisms, flow induced disc chatter resulting in damage ~ to the valve internals, o.r poor quality control during assembly. j l

LACK OF CORROSION / ABRASION CONCERNS,

]

All of the DH and BS valves listed in Attachment A are used in borated water service, are'of stainless steel construction ,and therefore are not f

' susceptible to general corrosive attack. MS-V9A/B are carbon steel but are located in a controlled chemistry environment. Abrasive wear can also be ruled out for these' valves since high purity. borated water and main steam do I not contain appreciable quantities of abrasives nor are these valves subject j to extended periods of flow.

]

LACK 0F ANY LOCKING DEVICE CONCERN

. Check valve failures have been attributed to inadequate design of locking

-devices or poor quality control during valve assembly. Attachment A discusses j this type of _ failure for MS-V9A and this failure mode has been eliminated for ]

MS-V9A and B. The BS and DH check valves are in , standby service and seldom,- i if ever, - see ~ flow. Consequently, they h. ave shown no problems or potential l problems with locking devices during any. previous inspection.

FATIGUE / MISAPPLICATION CONCERNS Fatigue fracture of the disc stud or other internal parts have also caused failure. Another cause of failure is valve misapplication. In this context, misapplication refers to selection of a valve that is too large or too small for system flow conditions, selection of the wrong type of valve, locating check valves in areas of highly turbulent flow or incorrect orientation of valves in the system (e.g., vertice versus horizontal). Since the check valves discussed herein are in standby service, fatigue / misapplication problems would not be likely to occur. More frequent disassembly of the l valves would not add significantly enhanced knowledge of the valve condition i because there would' be so little operation and opportunity for exercise / wear subsequent to the last disassembly.

FLOW INDUCED WEAR CONCERNS )

l Flow induced chatter was stated as the cause for some of the failures at the other plants. All'of the valves listed on Attachment A have been disassembled 1 at least once and have not exhibited any damage due to chatter. These valves have been in service for more than 10 years.

l _ - _ - _ - _-_ __-

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l-l ATTACHMENT B SHEET 2 of 2 l

l The valves listed in Attachment A are not expected to experience wear due to a valve chatter since they see infrequent or static (standby) service. TMI-1 i service and experience provide the bases to conclude that disc chatter will  !

not cause these valves to fail. I SYSTEM OPERABILITY CONCERNS DURING VALVE INSPECTIONS 1

When the RCS is below 250*F, Technical Specification (T.S.) 3.4.2 requires two j of the four means of decay heat removal to be operable. The four means of j decay heat removal are: i l

1. Decay Heat Removal String "A" j

2. Decay Heat Removal String "B"

3. RCS Loop "A", its OTSG and its Emergency Feedwater flowpath

4. RCS Loop "B", its 0TSG and its Emergency Feedwater flowpath During refueling outages, the RCS and 0TSG's are required to be drained down (due to geometry, the draindown includes both RCS loops and both OTSG's) for long periods of time for RC pump seal work and 0TSG eddy current testing. The- j requirement to maintain two operable means of decay heat removal ensures that j a single failure does not result in a complete loss of decay heat removal j capability. Limited reduction in redundancy is allowed for preventative or j corrective maintenance by T.S. 3.4.2.3c which states decay heat removal means may be reduced to one for seven days. However, TMI-l desires to maximize the time that two dec'ay heat removal systems are available. It is believed that disassembling DH-Vl4A or B each refueling takes away one train of decay heat  ;

removal for no significant benefit and reduces safety especially since DH-V14A 1 and B are proved to pass at least 2/3 of their accident design flow rate each refueling by the performance of Surveillance Procedure 1303-11.54. We can l envision no credible failure of valve internals that would cause these valves, l in this application, to significantly restrict flow. l

SUMMARY

OF CONCLUSIONS For DH-V14A/B, BS-V30A/B, BS-V52A/B and MS-V9A/B a frequency of inspection of every 10 years for one of each valve pair will provide more than adequate assurance that the valves will provide no unintended flow restriction  ;

post-accident.

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PHOTOGRAPH INDEX ,

,, i All photographs show the "as found" co'ndition t p

-PHOTO. NO. VALVE' DATE ' DESCRIPTION 1 .BS-V30B 02/10/87 Bonnet assembly.

2 .BS-V308- 02/10/87 Bonnet assembly' showing dise nut capture wire, m 3 BS-V308 02/10/87 Bonnet assembly. No wear on hinge pin or- i hinge pin hole.

4- SS-Y30B 02/10/87 Body showing disc seating surface.

5 BS-V52A 03/05/87 Bonnet assembly. )

6 BS-V52A 03/05/87 Bonnet assembly showing disc nut capture pin.

'7 BS-V52A 03/05/87 Bonnet assembly showing no hinge pin wear..

8 BS-V52A 03/05/87 Body showing disc seating surface.

9 MS-V9A. 11/18/86 Closed position showing missing disc nut, washer and cotter key. Disc held in-place by the friction fit between disc stud shoulder and hole in disc arm.

10 MS-V9A 11/18/86 Open position showing missing disc nut, washer and cotter key.. Disc held in place by the friction fit between disc stud shoulder and hole in disc arm. .j 11 MS-V9A' 11/18/86 Disc.

12 MS-V9A 11/18/86 Disc arm.

13 MS-V9A 11/18/86 Bonnet with cast disc stop.

14 MS-V9A 11/18/86 Disc showing seating surface.

15 MS-V98 11/20/86 Closed position showing disc, disc arm, nut, washer and cotter key in place.

16 MS-V98 11/20/86 Open position . showing disc, disc arm, nut, washer and cotter key in place. '

17 MS-V98 11/20/86 Bonnet with cast disc stop.

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v, POSTCARDS ,

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THI'S PACKAGE CONTAINS POSTCARDS OPPOSING UTILITY REQUEST FOR EXEMPTION FROM 10CFR50,-APP E REQUIREMENTS FOR FULL PARTICIPATION  !

EXERCISE OF EMERGENCY RESPONSE PLAN, i

DUE TO THE ABNORMAL SIZE OF THESE POSTCARDS SUBMITTED THROUGH THE NRC, PROCESSING ONTO DCS MICROFICHE WAS NOT CONDUCTED.

COPIES OF THESE POSTCARDS ARE AVAILABLE THROUGH THE PUBLIC DOCUMENT ROOM 0F THE NUCLEAR REGULATORY COMMISSION, LOCATED AT 1717 H STREET, N.W., WASHINGTON, D.C..  ;

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NUMBER OF 0:TCAki;5 ACCESSION NUMBER 7 // 0 #Z l

DOCKET NUMBER: 05000400 l

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