ML20205S605

Concludes That Based on Review of Util 851121 Water Hammer event,plant-specific Check Valve Problems Adequately Resolved for Feedwater & Other Sys,Per EDO 860204 Memo

ML20205S605
Person / Time
Site:	San Onofre
Issue date:	06/06/1986
From:	Taylor J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE)
To:	Martin J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V)
References
REF-GTECI-A-01, REF-GTECI-PI, TASK-A-01, TASK-A-1, TASK-OR NUDOCS 8606120694
Download: ML20205S605 (6)

Text

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NUCLEAR REGULATORY COMMISSION g WASHINGTON, D. C. 20555

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June 6, 1986 MEMORANDUM FOR: John B. Martin Regional Administrator Region V FROM: James M. Taylor, Director Office of Inspection and Enforcement

SUBJECT:

STAFF ACTIONS RESULTING FROM THE NOVEMBER 21, 1985 SAN ON0FRE UNIT 1 WATER HAMMER EVENT As directed in the ED0 memorandum dated February 4,1986, IE has reviewed the plant specific aspects of the November 21, 1985 San Onofre Unit 1 (SONGS-1) water hammer event as they relate to the adequacy of the feedwater (and other) check valves to perform their safety function, and concludes, based on this review, that the plant specific check valve problems have been adequately resolved for the feedwater and other systems.

In order to perform this review, IE has participated in meetings with the licensee on February 19, 1986 and March 5, 1986 and responded with specific questions (Enclosure 1); reviewed the licensee's March 2, 1986 submittal and r1sponded with specific questions (Enclosure 2); reviewed the licensees' April 8,1986 submittal and responded with specific questions (Enclosure 3);

reviewed the licensee's May 1, 1986 and May 5, 1986 submittals; performed l

an inspection of MCC-Pacific Valve Company on February 10-14, 1986 (Enclosure 4); performed an inspection of Atwood & Morrill Company on February 10-14, 1986 (Enclosure 5); and performed an inspection of the licensee at the SONGS-1 site on March 17-20, 1986 (Enclosure 6).

These inspections and reviews were performed in order to evaluate:

1. The licensee's engineering report on root cause analysis and proposed corrective actions

2. The adequacy of the check valve design for this application

3. The licensee's Inservice Testing Program and procedures to detect degraded and failed valves

4. The adequacy of check valves in other systems A summary of the results of this review, as documented in the enclosures, is provided below.

8606120694 860606 gDR ADOCK 05000206 PDR

't John B. Martin June 6, 1986 Root Cause Analysis and Corrective Action The Failure Analysis of Swing Check Valves, Revision 1, dated February 24, 1986 was reviewed by the staff and by a consultant (Enclosure 7) and was found to be unacceptable since, among other things, the report failed to properly consider the effects of turbulence on the valve internals. This report was revised and resubmitted as Revision 2 dated April 4, 1986. This revised report properly recognizes that sizing, location, and valve design were contributing factors to the degradation of the valves and, in the staff's opinion, constitutes an acceptable root cause analysis.

In order to correct the identified problems, the licensee has replaced the MCC-Pacific check valves with Atwood & Morrill valves which have been properly sized and designed for this application. Additionally, the three 10 inch check valves have been moved further downstream from the feedwater regulating valves in order to lessen the effect of turbulence. The licensee has conducted flow testing of this configuration to demonstrate satisfactory performance under varying flow conditions. These flow tests have been reviewed and are considered to adequately assure proper performance of the valves (Enclosure 8).

Adequacy of Check Valve Design As discussed in Enclosure 5, the design of the MCC-Pacific check valves was inappropriate for this application since they were high flow, low differential pressure valves with a correspondingly low angle of incidence of the disk in the flow stream. Consequently, when used in a highly turbulent application with marginal flow rates through the valve, the disk was particularly prone to flutter and, consequently, failure. The replacement Atwood & Morrill valves are appropriately sized, located, and designed for this application. They are designed with an integral swing arm / disk and are not prone to the same types of failures seen in the MCC-Pacific check valves.

Adequacy of Inservice Testing (IST) Program for Check Valves The licensee's Inservice Testing program has been reviewed by NRR and their evaluation is substantially complete.

Relief from the testing requirements of the Code was requested by the licensee for the following check valves:

Safety Injection System SIS-003 SIS-004 SIS-010 SIS-303 SIS-304

John B. Martin June 6, 1986 Diesel Generator Cooling Water System DWN-306 DWS-306 DWN-309 DWS-309 Feedwater and Condensate System FWS-438 FWS-439 For the Safety Injection and Diesel Cooling Water systems, the ASME Code requires that the check valves be exercised once every three months. As an alternate test method for these valves, the licensee proposes an inspection of the valve internals and manual full stroking on a sampling basis at each refueling outage.

Relief from the Code required testing frequencies is allowed by 10 CFR 50.55a(g). It is expected that relief will be granted in these cases since disassembly and inspection provides an acceptable testing alternative as proposed by the licensee. For the feedwater pump discharge check valves, the ASME Code requires quarterly verification of the capability to both open and close. Normal feedwater system operation gives a reliable indication that the valves are open. However verification of the valve's ability to close cannot be done quarterly during operation since it would disrupt feedwater flow. As an alternate test method for these valves the licensee has proposed disassembly, inspection of the valve internals, and manual full stroking of each valve at each refueling outage. This test would verify the ability of the valves to both open and close. Relief from the Code-required testing frequency is expected to be granted for these valves since the alternative testing (disassembly) proposed provides a better indication of valve condition than would be provided by a full-stroke flow test or a back-leakage test.

However, even testing performed in full conformance with the ASME Code does not necessarily detect the type of degradation evident in the San Onofre check valves that were found to have failed on November 21, 1985. Because of this inherent inadequacy in the Code criteria for testing, the licensee has committed to using a quantitative leak rate criterion when testing the new Atwood & Morrill valves, except for the feedwater pump discharge check valves discussed above. Also, during the first refueling outage, the licensee will open and inspect the internals of at least one of the new 10 inch Atwood & Morrill check valves inside containment, and at least one of the new 10 inch and 4 inch Atwood &

Morrill valves outside containment.

A Safety Evaluation Report for the Inservice Testing of pumps and valves for San Onofre, Unit 1 is being prepared by NRR providing the details and results of the staff review. An approved IST program, augmented with the additional inspection and testing for the new feedwater system check valves described in the licensee's May 1,1986 submittal, is considered adequate to detect degraded and failed valves.

John B. Martin June 6, 1986 1

Adequacy of Check Valves in Other Systems In order to assure that similar problems did not exist in other systems, the licensee disassembled and inspected every MCC-Pacific check valve in the plant (29 total) - one additional valve failure was discovered; reviewed maintenance histories for all Unit 1 swing check valves (141 maintenance orders) and dis-assembled and inspected any which had experienced problems with the valve internals - no problems were observed; and performed calculations to determine which valves could be expected to be less than fully open during nominal opera-ting conditions, each of these valves (15) was disassembled and inspected - one was determined to be inoperable.

The results of these corrective actions have been reviewed by the staff and have been found to adequately address the operability of check valves in other systems.

In summary, the licensee's submittals of April 8, 1986, May 1, 1986, and May 5, 1986 describe an adequate root cause analysis and corrective action program to assure that check valves will perform their safet," function.

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J mes M. Tay) r, Director Office of Inspection and Enforcement

Enclosures:

1. March 17, 1986 Letter to SCE

2. March 25, 1986 Letter to SCE

3. April 21, 1986 Letter to SCE i

4. MCC-Pacific Valve Inspection Report j

5. Atwood & Morrill Inspection Report l

6. San Onofre Unit 1 Inspection Report i

7. Failure Analysis Review

8. Valve Testing Program Review

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1 June 6, 1986 John B. Martin Adequacy of Check Valves in Other Systems In order to assure that similar problems did not exist in other systems, the j licensee disassembled and inspected every MCC-Pacific check valve in the plant (29 total) - one additional valve failure was discovered; reviewed maintenance histories for all Unit 1 swing check valves (141 maintenance orders) and dis-assembled and inspected any which had experienced problems with the valve internals - no problems were observed; and performed calculations to determine which valves could be expectea to be less than fully open during nominal opera-ting conditions, each of these valves (15) was disassembled and inspected - one was determined to be inoperable.

The results of these corrective actions have been reviewed by the staff and have been found to adequately address the operability of check valves in other systems.

In summary, the licensee's submittals of April 8,1986, May 1,1986, and May 5, 1986 describe an adequate root cause analysis and corrective action program to assure that check valves will perform their safety function.

Origin:f Sfgned Byi James i,1. Taylor James M. Taylor, Director Office of Inspection and Enforcement

Enclosures:

1. March 17, 1986 Letter to SCE

2. March 25, 1986 Letter to SCE

3. April 21,1986 Letter to SCE 4 MCC-Pacific Valve Inspection Report

5. Atwood & Morrill Inspection Report

6. San Onofre Unit 1 Inspection Report

7. Failure Analysis Review

8. Valve Testing Program Review Distribution:

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9 ENCLOSURE 1

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1 g ENCLOSURE 1 1

MAR 171986 Docket No. 50-206 Mr. Kenneth P. Baskin, Vice President Nuclear Engineering Safety and Licensing Department Southern California Edison Company 2244 Walnut Grove Avenue P.O. Box 800 Rosemead, CA 91770

SUBJECT:

REQUEST FOR INFORMATION NEEDED FOR NRC REVIEW 0F NOVEMBER 21, 1985 EVENT AT SAN ON0FRE, UNIT 1 The November 21, 1985 loss of offsite power at San Onofre 1 resulted in the occurrence of a severe water hammer event. This water hammer caused significant damage to the feedwater line to the "B" steam generator and stretched the bolts on a check valve resulting in a feedwater system leak.

Recovery from this event involved complex operator actions and was accomplished without abnormal releases of radioactivity.

The NRC subsequently investigated the circumstances of this event and documented its conclusions in NUREG-1190 (Loss of Power and Water Hammer Event at San Onofre, Unit 1, on November 21,1985), issued in January 1986. The l

investigation concluded that the most significant aspect of the event involved

! the failure of five safety-related check valves in the feedwater system which occurred in less than a year, without detection, and jeopardized the integrity of safety systems.

t As you are aware, on November 21, 1985, the NRC Region V office issued a Confirmatory Action Letter which confirms your commitment to maintain San Onofre Unit 1 in a shutdown condition until concurrence is received from the NRC to return to power. Region V has the overall lead responsibility for NRC staff actions related to facility restart. The purpose of this letter is to request information that the staff needs in order to determine the adequacy of the design and operation of San Onofre Unit 1. Schedules for these responses should be developed with your NRC Project Manager.

l l The reporting and/or recordkeeping requirements contained in this letter

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e MAR 171986

, K. P. Baskin affect fewer than ten respondents; therefore, OMB clearance is not required under P.L.96-511.

Sincerely, Origina1 signed by:

George E. Leaf, '

George E. Lear, Director PWR Project Directorate #1 Division of PWR Licensing-A

Enclosure:

Request for Additional Information l

I l Office: M PAD (n_ PD/ PAD #1 Surname: RDudley*/tg:jm Glear*

Date:

03/]/86 f 03//f/86 t

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l Mr. Kenneth P. Baskin San Onofre Nuclear Generating Station

- Southern California Edison Company Unit No.1 j CC Charles R. Kocher, Assistant Joseph 0. Ward, Chief General Counsel Radiological Health Branch James Beoletto, Esquire State Department of Health Southern California Edison Company Services Post Office Box 800 714 P Street, Office Bldg. 8 Rosemead, California 91770 Sacramento, California 95814 David R. Pigott Mr. Hans Kaspar, Executive Director Orrick, Herrington & Sutcliffe Marine Review Committee. Inc.

600 Montgomery Street 531 Encinitas Boulevard, Suite 105 San Francisco, California 94111 Encinitas, California 92024 Mr. Stephen B. Allman San Diego Gas & Electric Company P. O. Box 1831 San Diego, California 92112 Resident Inspector / San Onofre NPS c/o U.S. NRC P. O. Box 4329 San Clemente, California 92672 Mayor City of San Clemente San Clemente, California 92672 4

Chairman Board of Supervisors County of San Diego San Diego, California 92101 Director Energy Facilities Siting Division l Energy Resources Conservation &

! Development Commission l

1516 - 9th Street Sacramento, California 95814 Regional Administrator, Region V U.S. Nuclear Regulatory Commission i 1450 Maria Lane Walnut Creek, California 94596 l

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e MAR 171986 Distribution:

Docket Files NRC PDR Local PDR PD#1 r/f G. Lear

, P. Shuttleworth l R. Dudley L. Harmon

E. Jordan B. Grimes J. Partlow T. Barnhart (4)

A. Chaffee.(Region V) i G. Zech (IE)

ACRS (10)

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ENCLOSURE REQUEST FOR ADDITIONAL INFORMATION

1. Describe steam generator blowdown isolation features and provide an evaluation of the steam generator blowdown system, including the following:

a. Any proposed features which preclude automatic reinitiation of steam generator blowdown upon reset of the steam generator blowdown isolation signal or appropriate justification for not doing so.

b. Features which allow monitoring status of the steam generator blowdown system including the need for flow monitoring capability or valve position status. Specifically address control room status indication.

2. Describe the current (as modified prior to restart) SONGS-1 main steam and feedwater system design and the basis for the design. Additionally, you should address the following:

a. Specific water hammer design considerations and any instrumentation to indicate impending water hammer conditions. Include in your discussion the basis for concluding that the water hammer originally occurred in the feedwater line and not the feedring. Also, compare your design considerations for water hammer with vendor recommen-dations to prevent water hammer.

b.

Measures piping and taken or to bestructures supporting taken to verify the integrity)of (including feedwater concrete prior to return to service. Also, provide a summary of the results of NDE of pipe weldments and any metallographic examination of feedwater pipe cracks.

c. Results of any reevaluation of existing design of main steam and feedwater systems with respect to potential for loss of h_ eat sink in the event of steam or feedwater system rupture. Include in your (4scussion, as appropriate, consideration of manual and automatic actuation of steam line isolation valves and assurance of steam generator availability to remove decay heat.

3. Provide an evaluation and description of your consideration to provide an uninterruptible power source (UPS) for the Critical Function Monitoring System (CFMS) in order to enhance the plant post-trip review capability.

Describe administrative procedures for resetting the CFMS after troubleshooting.

4 Provide a discussion of the neutral grounding of auxiliary transformer "A." is the neutral grounded through an impedance? If so, what is the value of neutral impedance and of the ground fault current?

5. Provide a description of the relay protection and settings for the auxiliary transformer "A" grounded neutral.

6. Provide an evaluation of the rationale for not loading diesels automatically when power to Class 1E buses is lost from the offsite source.

7. Provide information on Safeguard Load Sequencing System (SLSS) including logic, type, and description of operating modes.

8. Provide information on load sequencing of load groups for loss of station power with discussion of status lamps in the surveillance panels.

9. Provide information on station loss of voltage auto-transfer scheme.

Discuss how the automatic transfer of electrical power recovery is accomplished.

10. Provide information on any fault locating and/or maintenance testing procedures of 4.16 Ky cable circuits at San Onofre nuclear generating plant.

11. Provide a description of the power supply to vital 120V Bus #4. Is the supply to vital 120 volt Bus #4 from 7.5 KVA transformer or unregulated 37.5 KVA transformer? Are the transfer switches associated with the supply to vital 120 volt Bus #4 and the 7.5 KVA and 37.5 transformer manual or automatic?

12. What was the phase-relationship between transformer A and transformer C windings when both transformers were momentarily paralleled?

13. For loss of Bus #4, provide an evaluation of the necessity to scram the reactor.

14. Provide the rationale for not restoring Bus 2C from Bus 1B before manual scramming of the reactor.

15. Discuss any design changes to eliminate spurious SI indication.

16. Discuss interlocks, including basis for interlocks, associated with the l diesel generator output breaker; and provide an evaluation of the appropriateness of these interlocks, i

17. Discuss the basis for maximum permissible time limits on loading of diesel generators following loss of station power.

l 18. Describe provisions made for reconstructing event data following loss of

, station power.

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19. Describe any improvements to be made for labeling of selected control room indicators.

20. Provide an evaluation of the need of an uninterruptible power such as inverter power to vital Bus #4.

21. Provide a report and supporting documentation which addresses the root cause of the November 1985 water hammer event and SCE's proposed corrective actions. Include discussion of the root cause of the check valve failures. ..

22. Provide a determination and supporting documentation of the adequacy of testing programs and procedures, as implemented, to detect degraded and failed safety-related check valves. Describe any QA involvement in the testing programs.

23. Provide a determination and supporting documentation of the adequacy of the design and related testing, maintenance, and inspection programs for the various check valves in the feedwater and other safety-related systems. l

24. Describe any additional sensors, such as acoustic monitors, that will be used to account for uncertainties in the effect of turbulence on feedwater system check valve discs.

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ENCLOSURE 2 1

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ENCLOSURE 2 yAR 2 5 1986 Docket No. 50-206 l

Mr. Kenneth P. Baskin, Vice President ,

Nuclear Engineering Safety and Licensing Department Southern California Edison Company 2244 Walnut Grove Avenue .

PO Box 800 Rosemead, CA 91770

. De'ar Mr. Baskin:

SUBJECT:

REQUEST FOR ADDITIONAL INFORMATION 4

As a result of the March 5,1986 meeting between the staff and Southern California Edison Company, the staff has found that additional information is required related to the Navember 21, 1985 event. Please provide responses to the enclosed questions. Schedules for these responses should be developed with your NRC Project Manager.

The reporting and/or recordkeeping requirements contained in this letter affect fewer than ten respondents; therefore, OMB clearance is not required under P.L.96-511.

Sincerely, E. .

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George E. Lear, Director Project Directorate #1 l

Division of PWR Licensing-A

Enclosure:

As Stated cc: See next page 1

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Office: P A j PD/ PAD #1 Surname: RDudley/tg RBa J hoan Gleark Date: 03/; 4/86 03/Jyf86 03 86 03/:Tah86

Mr. Kenneth P. Baskin San Onofre Nuclear Generating Station Unit No. 1 Southern California Edison Company CC Charles R. Kocher, Assistant Joseph 0. Ward, Chief General Counsel Radiological Health Branch James Beoletto Esquire State Department of Health Southern California Edison Company Services Post Office Box 800 714 P Street Office Bldg. 8 Rosemead, California 91770 Sacramento, California 95814 Dpvid R. Pigott Mr. Hans Kaspar Executive Director Orrick, Herrington & Sutcliffe Marine Review Committee Inc.

600 Montgomery Street 531 Encinitas Boulevard, Suite 105 San Francisco, California 94111 Encinitas, California 92024 Mr. Stephen B. Allman San Diego Gas & Electric Company P. O. Box 1831 San Diego, California 92112 Resident Inspector / San Onofre NPS c/o U.S. NRC P. O. Box 4329 ,

San Clemente, California 92672 Mayor City of San Clemente San Clemente, California 92672

- Chairman .

i- Board of Supervisors County of San Diego San Diego, California 92101 l

l Director Energy Facilities Siting Division Energy Resources Conservation &

Development Commission l 1516 - 9th Street i Sacramento, California 95814 Regional Administrator, Region V ,

U.S. Nuclear Regulatory Commission 1450 Maria Lane Walnut Creek, California 94596 -

ENCLOSURE REQUEST FOR ADDITIONAL INFORMATION

1. System Design / Operating Data

a. At steady state 92% rated thermal power (RTP), what are the feed flows (in Ib/hr and gpm), pressures, and temperatures encountered at the feed pump discharge check valves (12") and the steam generator feed line check valves (10")? How was this data obtained?

b. What were the above data at steady state 100% RTP? How was the data obtained?

c. What is the minimum steady state flow rate, along with pressures and temperatures, that these valves encounter?

d. Clearly indicate the source and reliability of the Atwood Morrill valve data used in the redesign calculations.

2. Valve Technical and Performance Requirements

a. What was the design basis for the 10" and 12" valves in terms of flows, port size, obturator weights, pressure, and temperatures for both the MCC-Pacific and Atwood-Morrill valves? How does this differ from actual values?

b. What are the acceptable operating ranges for the new valves and what is the impact on plant / system operations?

. c. What are the maintenance, installation, and operation requirements or guidelines provided by MCC-Pacific and Atwood-Morrill?  ;

d. Will the new valves be mcdified to include operator assists or position indicators?

e. What are the " enhanced" surveillance and maintenance requirements and their basis for the Atwood-Morrill valves? Are they from or concurred by the manufacturer?

f. What are the Atwood-Morrill bonnet and packing torque values?

g. Where is the Atwood-Morrill actual hinge and di,sc combination center l

of gravity?

3. Vibratory Loads

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a. Clarify the method of development of the factor that turbulence loads from upstream components will not exceed 10% of disc weight? ,

b. The ISA Handbook of Control Valves provides recommendations on ,

installation. Why or why can't these locational restrictions be  !

correlated to check valves?

c. Atwood-Morrill recommends not locating check valves within specific distances of turbulence producing components. What is the basis for deviating from these recommendations?

4.- What was the procurement history for the original valves and spare parts?

5. Were other types of valve designs considered for this application (e.g.,

tilting or damped disk)? What is the basis for choosing a swing check design?

6. What flow band can result in a valve disk flutter problem for each of the new valves?

7. Include a discussion on how the auxiliary feedwater operating flow band avoids disk flutter or vibration from other check valves in the main feedwater and auxiliary feedwate,r piping system.

8. Clarify the statement made in handouts used at the January 31, 1986 meeting with the NRC that an error existed in Crane Technical Paper 410 that may have contributed to this problem.

. 9. Submit the results of the re-analysis of the auxiliary feedwater (AFW) initiation timing requirements that determine how quickly the emergency

?. _ diesel generators must be manually loaded in the case of a  ;

- loss-of-offsite power and a single failure of the turbine-driven AFW pump.

10. Document the basis for your conclusions stated in the March 5, 1986 meeting regarding the possible effects on the November 21, 1985 event if the diesel generators had been designed to automatically load upon loss of offsite power.

11. Document the operator actions needed to:

a. Transfer loads from the onsite power sources (diesels) back to an offsite power source when offsite powe'r is recovered, and

b. load '.he diesel generators to provide motive power to the electric-driven auxiliary feedwater pump in case of loss-o,f-offsite power.

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ENCLOSURE 3

ENCLOSURE 3 l i

APR 211986 Docket No.: 50-206 Mr. Kenneth P. Baskin, Vice President Nuclear Engineering Safety and Licensing Department Southern California Edison Company 2244 Walnut Grove Avenue P.O. Box 800 Rosemead, California 91770

SUBJECT:

SAN ONOFRE, UNIT 1 The April 8, 1986 Investigative Report on the San Onofre Unit 1 Water -

Hammer Event of November 21, 1985 has been received by the NRC and is under review. Based upon our review, several items require further information, as discussed in a telephone call on April 16, 1986.

Specific questions are provided in the enclosure to this letter. In order for the NRC review schedule to remain consistent with the current facility restart schedule, a response should be provided by April 30, 1986.

The reporting and/or recordkeeping requirements contained in this letter affect fewer than ten respondents; therefore, OMB clearance is not required under P.L.96-511.

Sincerely, Original sign 8d liti George E.Leagr sy Richard F. Dudley, Jr.

a s > ' f/-f'L, ,o _ ) Project Manager W- 7 / PWR Project Directorate #1 cc's next page Office: PD/P Surname:

[PMudley/jm GLear

/

Date: / /86 f/ /86 l

. I Mr. Kenneth P. Baskin San Onofre Nuclear Generating Station Southern California Edison Company Unit No. 1 ]

CC Charles R. Kocher, Assistant Joseph 0. Ward, Chief General Counsel Radiological Health Branch James Beoletto, Esquire State Department of Health Southern California Edison Company Services Post Office Box 800 714 P Street. Office Bldg. 8 <

Rosemead, California 91770 Sacramento, California 95814 David R. Pigott Mr. Hans Kaspar, Executive Director '

Orrick, Herrington & Sutcliffe Marine Review Committee Inc.

600 Montgomery Street 531 Encinitas Boulevard, Suite 105 San Francisco, California 94111 Encinitas California 92024 Mr. Stephen B. Allman San Diego Gas & Electric Company P. O. Box 1831

• San Diego, California 92112 1 Resident Inspector / San Onofre NPS c/o U.S. NRC P. O. Box 4329 San Clemente, California 92672 Mayor City of San Clemente San Clemente California 92672 Chairman Board of Supervisors County of San Diego San Diego, California 92101 Director Energy Facilities Siting Division Energy Resources Conservation &

Development Commission 1516 - 9th Street Sacramento, California 95814 Regional Administrator, Region V U.S. Nuclear Regulatory Commission 1450 Maria Lane

Wa'.aut Creek, California 94596 l

. ENCLOSURE REQUEST FOR ADDITIONAL INFORMATION f

1. What are the new locations of the 10 inch feedwater system check valves relative to the flow control valve upstream and the block valve downstream? ,

The Isometric Drawings previously provided only show the original locations.

2. With regard to your current IST program, it appears that at least some of the five check valves which failed can be (and have been) tested while the plant is hot. However. relief from the Code has been requested for these valves to only test during cold shutdown. What is the basis for the reduced periodicity of tes. ting these valves in light of the code

, , requirements and the recent failures?

What enhanced testing is plar.ned for each of the new Atwood Morrill check 3.

valves, including any quantitative leak rate criteria, procedures, and how new testing taps will be utilized?

4. Please clarify your commitment with regard to opening and visuall /

l l inspecting the new check valves. Specifically:

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- Which valves will be inspected?

- How often will they be inspected?

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- If valves are noisy in operation, will inspection periodicity be increased?

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5. Since less than 165 gpm through the 10 inch check valves is considered to be severe service by the vendor, what additional actions do you intend to take to assure that operations within this regime (AFW flow) will not unacceptably degrade the valve.

6. Please provide the results of the full scale valve testing performed by Dr. Tullis at Utah State University.  ;

P

7. How do you intend to monitor the performance of these valves during

- startup and operation to determine if they are tapping?

8. In Table 8 of Appendix D, provide the reason for replacement of the -

internals to valve DWN309.

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ENCLOSURE 4

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. gog EHCLOSURE 4 UNITED STATES

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f, j NUCLEAR REGULATORY COMMISSION C W ASHING TON. D. C. 20555

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March 31, 1986 Docket No. 99900075/86-01 Pacific Valves ATTN: Mr. Reid Armstrong Vice President, Engineering 3201 Walnut Street Long Beach, California 90807 Gentlemen:

This refers to the inspection conducted by Mr. James T. Conway of this effice on February 10-14, 1986, of your facility at Long Beach, California and to the discussions of our findings with Mr. Robert Argent and you at the conclusion of the inspection.

The purpose of this inspection was to review manufacturing records and gather data on design changes, recommended maintenance programs and vendor / licensee interface pertaining to swing check valves. Areas exanined during the inspection and our findings are discussed in the enclosed report. Within these areas, the inspection consisted cf an examination of procedures and representative records, interviews with personnel, and observations by the inspector.

During the inspection it was found that the implementation of your QA program failed to neet certain NRC requirenents. Significant items included failures to: (a) cost aonlicable documents to neet the requirements of 10 CFR Part 21; (b) pass on 10 CFR Part 21 reouirements to suppliers /maru'acturers; (c) have sufficient quaHfication records for rendestructive examination nersonnel and auditors; and (d) review and accept vendor procedures. The specific findings and references te the pertinent requirerents are identified in the enclosures te this letter.

The enclosed Notice of Violaticn is sent to ycu pursuant to the provisions of Section 206 of the Eneroy Peorganizatior. Act of 1974 You are reouired to sut'mit to this office within 30 days from the date of this letter a written statement containirg: (1, a cescriotion of steps that have been or wil! De taken to cCerect these items; (?) a description of steps that have been or will be taken to prayer.t recurrence; and (3) the dates your correct 1ve actions and preventive measures were or wil! t,e completed.

Ccnsideration cay b.e given to extending your response tine for good cause shown.

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You are also requested to submit a similar written '.itatenent for each item which appears in the enclosed Notice of Nonconformance. The responses , '~

requested by this letter are not subject to .the clearance procedures _ of the Office .of Management and Budget as requirej by the Paoerwrirk: Reduction Act ~

of 1980, PL 96-511. In accordance with 10 CFR 2.7BO -oi"the.lCor.wission's - ,

regulations, a copy of this letter and the'~ enclosed inspec* ion report '

' - will "

s be placed in the NRC's Fvblic-Qcc.ument Room. _

Should you have any questions concerning this ' inspection, we:will be pleased 'I~ -

to discuss them with yeu.' ,

3-Sincerely, '

Gary G. Zech, Chief Vendor Program Branch , , . , ,

Civision of Quality Assuranc'e, Vendor and Technical Trainin9 Center Programs Office of Inspection and'Enforcemert-

Enclosures:

1. Appendix A-Notice of Violatico -

2. Appendix.R-Nctice of Nonconformance ..  ;

3. -Appendix'C-In;pection 9tpcrt 99900075/86 -

4. Appe,ndix D-I.nspec_ tion Data Sheets (2 pages)

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APPENDIX A Pacific Valves ~

Docket No. 99900075/86-01 NOTICE OF VIOLATION As a result of the inspection conducted on February 10-14, 1986, and in accordance with Section 206 of the Energy Reorganization Act of 1974 and its implementing regulatien 10 CFR Part 21, the following violations were identified and categorized in accordance with the NRC Enforcement Policy (10 CFR Part ?, Appendix C), 49 FR 8583 (March 8, 1984):

1. Section ?1.6 of 10 CFR Part 21 dated May 31, 1984, states, in part,

"(a) Each... corporation... subject to the regulations in this part, shall post current copies of the following documents in a conspicuous position...(1) the regulations in this part, (2) Section 206 of the Energy Reorganization Act, and (3) procedures adopted pursuant to the regulations in this part."

Contrary to the above, copies of Section 206 of the Energy Reorganization Act and Procedure No. QSP-0004 " Identifying and Reporting Defects Under 10 CFR 21" were not posted, and an outdated copy of 10 CFR Part 21 was posted. (86-01-01)

This is a Severity Level V violation (Supplement VII).

2. Section 21.31 of 10 CFR Part 21, dated May 31, 1984, states, in part, "Each... corporation... subject to the reaulations in this part shall assure that each procurement document for a... basic component. ..

specifies, when applicable, that the provisions of 10 CFR Part 21 apply."

Contrary to the above, a review of documentation packages for Section III nuclear swing-type check valves revealed that while 10 CFR Part ?1 was imposed on Paci'ic Valves (PV) by their customers, PV did not specify that 10 CFR Part 21 reauirements would apply on purchase orders 46330N and 46360N to Pacific Southern Foundries, 50396 to Sun-Ray Testing, 49956N to A&G Engineering, 56698N to Poly Cast, and 58159 to Jorgensen Steel.

(86-01-0?)

This is a Severity Level V violation (Supplement VI.

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APPENDIX B Pacific Valves Docket No. 99900079/86-01 NOTICE OF NONCONFORMANCE Based on the results of an NRC inspection conducted on February 10-14, 1986 it appears that certain of your activities were not conducted in accordance with NRC requirements.

Criterion V of Appendix B to 10 CFR Part 50 states: " Activities affecting quality shall be prescribed by documented instructions, procedures, or drawings, of a type appropriate to the circumstances and shall be accomplished in accordance with these instructions, procedures, or drawings. Instructions, procedures, or drawings shall include appropriate quantitative or qualitative acceptance criteria for determining that important activities have been satisfsctorily accomplished."

Norconformances with these requirements are as follows:

1. Section 5.7.1.1 of the Quality Assurance Manual (QAM), Revision 2 states, " Vendor NDE Procedures shall be reviewed and accepted by the QA Department personnel."

Section 5.7.1.2 of the OAM states, in part, " Material Manufacturer's

... heat treat procedure shall be reviewed and accepted by the Welding Engineer."

Contrary to the above, there was no documented evidence that NDE procedure QCS 300, Pevisions K and N; FSP-0900, Revision 0; and FSP-0901. Revision 1; and heat treat procedure FSP-0950, Pevisions 0 and 2 from Pacific Southern Foundries (PSF) were reviewed and approved by PV. (86-01-03)

2. Section 9.2 of STD No. QAS-6, "NDE Personnel Cualification and Certification (Written Practice)," Revision 12 requires that PV's Level III NDE Examiner retain copies of the qualification records of assigned NDE personnel # rom an outside agency.

Section 7.4.2.1 of the QAM, Revision 2 states, in part, " Records of the subcontractor's... qualification...are maintained by the NDE Section."

Section 7.4.1 of the OAM states, in part, "PV personnel performing NDE activities shall be qualified in accordance with SNT-TC-1A 1980...."

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Section 9.6.1 of SNT-TC-1A and Section 7.? of STD No. 0AS-6 recuire that qualification records of the certified individuals be maintained and include a statement indicating satisfactory completion of training in accordance with the employer's written procedure.

Contrary to the above, a review of qualification records for nine NDE personnel, three each from PV, PSF, and Sun-Ray Testing (SRT), revealed the following: (86-01-04)

a. There was no documented evidence that M. Hess from SRT was qualified to a Level III examiner when he qualified PV's J. Sewell to a Level III-liquid penetrant testing in February 1984

b. Qualification records were missing for R. Nielson from PSF who perfortred magnetic particle testing in May 1982.

c. The qualification records of the three PV examiners did not contain a statement indicating satisfactory completion of training in accordance with STD No. QAS-6.

3. Section 5.3.8 of the QAM reouires that vendor audits be performed by qualified PV personnel.

Section 11.5.2 of the QAM requires that audits of vendors for code material and itens be conducted with a qualified lead auditor.

Contrary to the above, it was noted that vendor audits were conducted by M. Merrill in September 1983 and K. Cranek in April 1985, but they were not qualified as auditors until July 1984 and October 1905, respectively. (86-01-05)

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. ORGANIZATION: PACIFIC VALVES LONG BEACP, CALIFORNIA REPOPT INSPECTION INSPECTION N0.: 99900075/86-01 DATE: 2/10-14/86 ON-SITE HOUPS: 28 CORRESPONDENCE ADDRESS: Pacific Valves ATTN: Mr. Reid Armstrong Vice President, Engineering ,

3201 Walnut Street Long Beach, California 90807 ,

ORGANIZATIONAL CONTACT: Mr. Robert Argent, GA Manager TELEPHONE NUMBER: (213) 426-2531 NUCLEAR INDUSTRY ACTIVITY: Approximately 2 percent of valve sales.

ASSIGNED INSPECTOR: .hthy74 3- M- F4 ve Inspection Section (RIS) Date TJ.)lT. Conway, Reac L)

OTHER INSPECTOR (S):

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APPROVED BY: / '

/ D/- / . -v 7 2-/

E. W. Merschoff, Chief, RIS, Vendor Program Branch Oste l

l INSPECTION BASES AND SCOPE:

i A. BASES: 10 CFR Part 21 and 10 CFR Part 50, Appendix B.

B. SCOPE: The purpose of this inspection was to review manufacturing recnrds and gather data on design changes, recommended maintenance programs and vendor / licensee interface pertaining to swing-type check l valves.

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PLANT SIVE APPLICABILITY: Failed swing-type check valves - San Onofre Unit 1 (50-206); Failed stop check valves - Turkey Point Units 3 and 4 (50-250/251).

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, ORGANIZATION: PACIFIC VALVES LONG BEACH, CALIFORNIA REPORT INSPECTION NO.- 99900075/86 01 RESULTS: PAGE 2 of 11 A. VIOLATIONS:

1. Contrary to Section 21.6 of 10 CFR Part 21, copies of Section 206 of the Energy Reorganization Act and Procedure No. QSP-0004

" Identifying and Reporting Defects Under 10 CFR 21" were not posted, and an outdated copy of 10 CFR Part 21 was posted. (86-01-01)

2. Contrary to Section 21.31 of 10 CFR Part 21, a review of documen-tation packages for Section III swing-type check valves revealed that while 10 CFR Part 21 was imposed on Pacific Valves (PV) by their customers, PV did not specify that 10 CFR Part 21 require-ments would apply on purchase orders 46330N and 46360N to Pacific Southern Foundries (PSF), 50396 to Sun-Ray Testing (SRT), 49956N to A&G Engineering, 56698N to Poly Cast, and 58159 to Jorgenson Steel.

(86-01-02)

B. NONCONFORMANCES:

1. Contrary to Criterion V of Appendix B to 10 CFR Part 50 and Sections 5.7.1.1 and 5.7.1.2 of the Quality Assurance Manual (QAft), there was no documented evidence that NDE procedure QCS 300, Revisions K and N; FSP-0900, Revision 0; FSP-0901, Revision 1; and heat treat precedure FSP-0950, Revisions 0 and 2 from PSF were reviewed and approved by PV. (86-01-03)

2. Contrary to Criterion V of Appendix B to 10 CFR Part 50, Sections 7.2 and 9.2 of STD No. GAS-6, and Sections 7.4.1 and 7.4.2.1 of the GAM, a review of qualification records for nine NDE personrel, l

three each from PV, PSF, and SRT revealed the following: (86-01-04) l a. There was no documented evidence that M. Hess from SRT was qualified to a Level III examiner when he qualified PV's J. Sewell to a Level III-licuid penetrant testing (PT) in February 1984.

b. Qualification records were missing for R. Nielson from PSF who performed magnetic particle testing (MT) in May 1982.

c. The qualification records of the three PV examiners did r.ot contain a statement indicating satisfactory completion of training in accordance with STD No. QAS-6.

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, ORGANIZATION: PACIFIC VALVES LONG BEACH, CALIFORNIA l 1

REPORT INSPECTION j NO.- 99900075/86-01 RESULTS: PAGE 3 of 11 l I

3. Contrary to Criterion V of Appendix B to 10 CFR Part 50 and Sections 5.3.8 and 11.5.? of the QAM, it was noted that vendor audits were conducted by M. Merrill in September 1983 and K. Cranek in April 1985, but they were not cualified as auditors until July 198a and October 1985, respectively. (86-01-05)

C. OPEN ITEMS:

None.

D. STATUS OF PREVIOUS INSPECTION FINDINGS:

Not addressed during this inspection.

E. OTHER FINDINGS OR COMMENTS:

1. San Onofre Unit No. 1 (50NGS-1) Incident The NRC inspector discussed the five swing-type check valves that failed in the feed water system at SONGS-1 with the V-P Engineering, the Chief Design Engineer and the 0A Manager. Upon learning of the

1. ailed valves, PV sent a Customer Service Representative to the reactor site to get the Serial Number (S/N) of the affected valves.

The tag containing the S/N for the 4" valve was missing, but the S/Ns for the three 10" valves were 47754, 47755, and 47756; and the 12" valve was identified with S/N 48345. The inspector was told that l

manufacturing records did not exist for commercial valves manufactured prior to the first Section III valve fabricated in 1975. The only record was PV's Valve Serial Number Log dated 1957 to 1966. The log contained model numbers along with S/Ns and the date that.a valve underwent hydro testing. A review of this log indicated that the three 10" valves were hydrotested on December 7, 1965, and the 1?"

valve was tested cn December 30, 1965. However, there is no irdication where the valves, which were manufactured as commercial grade WCB, were shipped. The NRC Incident Investigation Team (IIT) that evaluated the event at SONGS-1 was told that the valves were purchased by Bechtel from Atlar. tic Richfield Hanford Ccmpany.

Neither Southern California Edison nor Bechtel contacted PV regard-

ing check valve deteriorations (i.e., discs, hinge supports, ard hinge pirs were replaced in the failed valves at SONGS-1 ir. 1975 and 19771 until January 1986 when Bechtel called PV reouesting spare parts for eight check valves and a proposal for design enhancements for the swing-type check valves. Initially, Bechtel was satisfed with l

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l PACIFIC VALVES l ORGANI7ATION:

LONG BEACH, CALIFORNIA l

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PEPORT INSPECTION NO - 09900075/86-01 RESULTS: PAGF 4 cf 11 PV's proposed changes which included adding stellite to the wear surfaces of the disc and hinge support, enlarging the diameter o#

the hinge pin, and changing the configuration of attaching the disc to the hinge support. However, Bechtel later told PV that they were going to replace the failed valves with Atwood Morrill swing-type check valves which have a one piece disc / hinge assembly.

NUREG-1190 documented the IIT's findings at SONGS-1, and it was noted that the three 10" main feedwater regulator check valves were inspected in 1975 and 1977, and new internals were installed in all three check valves. The NPC inspector was told by PV management that records did not exist to show that spare parts for PV swing-type check valves were ever ordered or shipped to SONGS-1.

2. Swing-Type Check Valves In 1975, PV received their "N" and "NPT" stamps, and to date approximately 226 swing-type check valves have been manufactured to the requirementsSection III, Class 1, 2 & 3 of the ASME Code.

Since the initial nucler check valve was shipped in January 1976, PV has not made any chances in material for individual components or design configuration. Tack welds are not used, and the attachment of the disc to the hinge support is with a nut that is pinned to the threaded stem of the disc.

Since 1970, a copy of PV's Maintenance Manual has been sent to customers with the finished valves. Section C " Pacific Swing Check Valves" of the Manual addresses Installation, Operating Instructions, Maintenance, and Preventive Maintenance. There is a caution not to exceed the pressure and temperature limits of ANSI B16.34, but specific examination periods for maintenance activities are not identified in the Manual.

Starting in 1978, PV cautioned owners in Catalog No. 400 regarding

l. the use of swing check valves in certain environments. Under

" Service P.ecommendations" it was noted that service in systems involving rapid and frequent flow reversals, pulsation or excessively turbulent flow should be avoided; and the location of swing-type check valves away from fittings within the piping system could minimize or eliminate potential problems. It was also recom-mended that suspect problem systems be reviewed with PV before

! selecting and purchasing a particular swing-type check valve. For all the nuclear orders of Section III swing-type check valves, PV could not recall any discussions or correspondence with customers

. ORGANIZATION: PACIFIC VALVES LONG BEACH, CALIFORNIA REPORT INSPECTION Mn - 99900075/86-01 RESULTS: PAGE 5 of 11 pertaining to operational environments within a piping system. The purchase orders (PC) and technical specifications did not identify the specific flow conditions, and the P0 only listed a valve size, model number and class.

For best performance, the catalog also reccmmended that swing-type check valves operate within a flow range sufficient to hold the valve fully open, but not so high that it produces excessive turbulence. To correctly size &* valve, the seat port velocity at the operating flew rate should be calculated, and it should fall within the velocity range noted by the following formula:

55 [< V (fps) $ 240 h Where [ equals the square root of specific volume of ficw medium at operating conditions.  ;

The NRC inspector was told that PV service representatives normally distribute the catalog to their customers.

Feedback from customers pertaining to problems with PV valves is directed to the Field Services organization who maintains a file of customer inquiries or complaints and subsequent action taken by PV.

PV could not identify in their files any inciderts where nuclear or commercial customers had notified PV of swing-type check valve failures and in particular any that were similar to those failures at SONGS-1. It was also noted that PV does not perform any trend analysis en failure data received from their customers.

3. Welding The NRC inspector reviewed the qualification records of seven welders and seven welding procedures used for the narufacture of nine nuclear check valves and related spare parts. A review of Welder Performance Continuity Records and Qualification Test Records of Welder ?!os.10, l 12, 13, 21, 30, 32, and 34 indicated that all the welders were

' qualified to weld with the applicable Welding Precedure Specification (WPS). A review of seven Procedure Qualification Records indicated that the WPSs used to weld the seal rings into the body, to apply the hard-facing on the sealing surfaces and for repair welding were all qualified, and test specimens had been satisfactorily tested by either Continental Testing or Dickson Testing.

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,' CRGANIZATION: PACIFIC VALVES LONG BEACH, CALIFORNIA

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REPORT INSPECTION NO.- 99900075/86--01 RESULTS: PAGE 6 of 11 l

The inspector evaluated the weld material control area. Electrodes i for nuclear work were retained in two furnaces. One furnace (S/N 23916) contained 14 different type rods and was designated 'or the "1st shift." A calibration sticker was on the front door and indicated that Golden State Calibration & Service Company had calibrated the temperature recorder (current reading of 240 F) on December 10, 1985.

The second furnace (S/N 23978) was for "2nd shift" and contained a similar calibration sticker. The second furnace contained six different size rods. Both furnaces were padlocked, and the keys are controlled by the Weld Shop Supervisor.

4 10 CFR Part 21 Procedure QSP-0004 relating to the identification and reporting of defects and failures was reviewed, and the implementation of the procedure in regard to posting requirements was evaluated by inspecting the shop areas. It was noted that an outdated copy of 10 CFR Part 21 was the only document posted in several areas (see Violation 86-01-01). A review of PV P0s to vendors for components used in the manufacture of safety-related nuclear valves revealed that the requirements of 10 CFR Part 21 were not referenced or identified on the following P0s which were stamped " Nuclear:" (See Violation 86-01-02)

- 46330N (Decer.ber 1,1981) and 46360N (January 5,1982) to PSF for castings (body, bonnet, and disc)

- 50396 (October 6, 1982) to SRT for radiographic testing (RT)

- 49956N (August 10, 1982) to A&G Engineering for fasteners

- 56698N (September 10,1984) to Poly Cast fcr hard-coating plasma powder

- 58159 (March 5,1985) to Jorgensen Steel for bar and plate

5. NDE The NPC inspector reviewed the qualificatior and certification records of nine NDE personnel, three each from PV, PSF, and SRT, to determine whether the individuals performing NDE were certified to SNT-TC-1A.

The written practice (STD No. QAS-6) of PV for all phases of training and certifying NDE personnel was also reviewed, and it appeared to be consistent with SNT-TC-1A.

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ORGANIZATION: PACIFIC VALVES LONG BEACH, CALIFORNIA

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REPORT INSPECTION NO.- 99900075/86-01 RESULTS: PAGE 7 of 11 One Level III examiner from SPT performed RT on nuclear valve components in October and December 1982. The other two examiners administered and graded the examinations of PV's J. Sewell to a Level II-RT and MT and a Level III-PT. The qualification records on file at PV for the examiner who performed RT and the Level III-RT and MT indicated that they both met the requirements of SNT-TC-1A.

It was noted that J. Sewell was certified in February 1984 to a level III-PT, but the records en file at PV indicated that Hess was not certified to a Level III-PT until August 1984 (See Nonconformance 86-01-Oda).

The three examiners from PSF performed RT and MT on valve components (body, bonnet and disc) used on Section III swing-type check valves.

With the exception of records for R. Neilson who performed FT in May 1982 of a bonnet on shop job (S/J) No. 1000066N, PV had sufficient records to verify that the other examiners meet the qualification requirements of SNT-TC-1A when they performed a specific NDE (See Nonconformance 86-01-04b).

The NDE examiners from PV included two Level IIIs ard one Level 11 certified to PT. The current Level III at PV was also certified to a Level II in MT and RT in February 1984 With the exception of a missing statement pertaining to training in accordance with STD No.

QAS-6, the records including eye examinations, training, written tests and certifications appeared to satisfy the requirements of SNT-TC-1A (see Nonconformance 86-01-0ac ).

Five NDE procedures were reviewed. Two procedures from PV addressed RT (QSP-0045) and PT (QSP-0047) of valve ccmponents. The RT (QCS-300), PT (FSP-0900), and MT (FSP-0901) of steel castings was covered in PSF procedures. It was noted that the PSF procedures were not reviewed and approved by PV's QA department (see Nonccnformance 86-01-03).

During a walk-through of the RT' station, it was observed that the densitcmeter is calibrated against a density strip (fo. 1498) on an annual basis, but the reference standard (strip) hac not been calibrated since 1981 as docunented on a Density Strip Calibration Report from Dupont.

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. ORGANIZATION: PACIFIC VALVES l LONG BEACH, CALIFORNIA l REPORT INSPECTION NO - 999n0075/86-01 RESULTS: PAGE 8 of 11

6. Audits The NRC inspector reviewed applicable sections of the QAP, two procedures, seven external audit reports and the qualification records of four auditors to assure that items and services were being purchased from qualified vendors, and PV personnel were trained and qualified to perform audits.

PV's activities pertaining to five manufacturers who supplied items for safety related swing-type check valves were evaluated.

Audits were conducted by PV of Poly Cast (one) who supplied hard-coating material, PSF (three) who supplied castings, and SRT (three) who performed NDE. Checklists were used or all the audits which were conducted in 1983,1984, and 1985, and the results were documented in a Vendor Quality System Evaluation report. The other two manufacturers - E.M. Jorgenson (wrought products) and A&G Engineering (fasteners) - were Quality System Certificate (Materials) holders and were not audited by PV.

The QA records for the four personnel who conducted the external audits consisted of Auditor Qualification Records, a written examination addressing material contained in ANSI /ASME NQA-1 and related codes and regulations, and a Record of Lead Auditor Qualification. It was noted that SRT was audited by M. Merrill in September 1983 and K. Cranek in September 1985, but QA records indicated that they were not qualified to lead auditors until July 1984 and October 1985, respectively (see Nonconfornarce 86-01-05).

7. Stop Check Valve Failures - Turkey Point Between November 1985 and January 1986, numerous failures were experienced in stop check valles located in the stean supply system to the auxiliary feedwater pumps at Turkey Point Unit Nos. 3 and 4 The failure mode was degradation of the disc and disc rut assembly due to low stream flow conditions caused by a leaking motor-operated valve (M0V) in the system. In seven valves, the vibration and chattering of the disc assembly resulted in 3 broken disc guide stud which caused the disc to become locked in the valve thus preventing full closure and full opening of the valve. The l

broken stud was also free to travel causing further damage, l

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ORGANIZATION: PACIFIC VALVES LONG BEACH, CALIFORNIA REPORT IMSPECTION NO.- 99900075/86-01 RESULTS: FAGE 9 of 11 The failed valves were ordered by Florida Power & Light (FP&L) on P0 No. 65380-27088P dated May 24, 1983 to be fabricated in accord-ance with specification PTP-1000-4.55.5 and Section III/ Class 2 reouirements of the Code. Twelve carbon steel valves (3" 660S WE-80-X) were manufactured by PV on S/J No. 3A0038N, and the valves were sent to FP&L in October 1983.

With regards to the failures in November 1985, PV's Manager, Field Services (MFS) supervised the replacement of damaged parts in five valves in Unit No. 3. The MFS told the NRC inspector that the spare parts (e.g., disc assembly, seat ring) were identical (material and configuration) to the original components in the valve. When the reactor went operational, the MFS observed the re-worked valves and noted that the internals were still chattering, and the valves were very noisy. It is PV's opinion that the valves are failing because of the turbulence problem caused by the leaking M0V.

8. Nuclear Orders - Check Valves The NRC reviewed the QA records for three nuclear orders and five spare part orders of swing-type check valves. Records consisted of P0s and technical specifications from the customer and PV Cata Packages (DP). Eight P0s, five of which were for spare parts, referenced technical specifications and the requirements of Section III of the Code and 10 CFR Part 21. A DP consisted of A ta Peports for the pressure retaining parts (i.e., body, bonnet, ano disc), Production Work Order (i.e., traveler), hydrostatic test report, certified material test reports (CMTR), heat treet reports with time / temperature charts, casting repair reports, wel. ding and hard facing records, NDE reports, wall thickness measurements, and visual examiration checklists. The CMTRs were for pressure retaining castings, welding material, and fasteners; and the NDE reports were for MT, PT and RT.

The three most recent nuclear orders were from: (a) Stone &

Webster (S&W) on P0 No. 2362.050-651 dated May 7, 1981 for Millstene Unit No. 3; (b) S&W on P0 No. 2282.050-676 dated September 17, 1981 for Millstone Unit No. 3; and Gibbs & Hill (G&H) P0 No. 5021-1-6.6-044 dated October 23, 1984 for Susquehanna.

The May 1981 order from S&W was for carbon steel valves, and the other order was for stainless steel valves. The G&H order was for valves to be installed at the Diesel Generator "E" facility.

O ORGANIZATION: PACIFIC VALVES LONG BEACH, CALIFORNIA REPORT INSPECTION Nn - 00000075/86-01 RESULTS: PAGE 10 of 11 Data obtained on the three nuclear orders is as follows:

S/J No. Quality-Model No. Approx. Date Shipped 1W0066N 2-10" 180-7-WE-X 10/82 1W0163N 10-21" A-180-14-FF-X 11/82 2-3" A-180-14-FF-X 11/82 2-8" G-680-7-WE-X 1?/82 4WO340N 2-10" 380-15-WE-40-X 10/85 Spare part orders for nuclear valves included items such as seat ring, wedge, stem, eyebolt, gasket (bonnet), hinge pin, disc, nut wasner (disc), and segment ring. The five orders were from the following customers and were manufactured under the noted S/J No.:

Customer P0 No. (date) S/J No.

S&W 2362.050-651-30 4WO284N (9/19/85)

S&W 2262.050-676 4W0032N (7/17/84)

Onaha Public 536874 480269N Pcwer District (9/17/84)

Duke Power P25624-73 SW0143N (4/25/85)

Kansas Gas & 53239 5H03690 Electric (11/7/85)

The S/J Instructions for both valve and spare part orders originated in the Project Engineering Department and included requirements fer pressure retaining and non-pressure retaining components, and weld filler metal; list of procedures; and documentation reouired with the shipment.

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. ORGANIZATION: PACIFIC VALVES LONG BEACH, CALIFORNIA

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PEPORT INSPECTION NO.- 99900075/86-01 RESULTS: PAGE 11 of 11 F. PERSONMEL CONTACTED i

• R. Argent, QA Manager

• R. Armstrong, V-P, Engineering J. Sewell, NDE - Level III F. Hernandez, Gage Technician G. Brown, Chief Design Engineer F. O'Brien, Manager - Pesign Engineering R. McConnell, Manager - Field Services G. Hay, Weld Shop Supervisor

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ENCLOSURE 5

go NUCLEAR REGULATORY COMMISSION UNITE] STATES s l wAstoucrow, o.c.meses

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- June 4, 1986 Docket No. 99900049/86-01 Atwood & Morrill Company, Inc.

ATTN: S. N. Shields Vice President, Engir.eering 285 Canal Street Salem, Massachusetts 01970 Gentlemen:

This refers to the inspection conducted by Mr. E. H. Trottier of this office on February 10-11, 1986, of your facility in Salem, Massachusetts and to the discussions of our findings with you and members of your staff at the conclusion of the inspection.

This inspection was performed as a result of the recent failure of five safety related check valves at Unit 1 of the San Onofre Nuclear Generating Station.

Their failure directly led to the rupture of a low pressure feedwater heater and a significant water hammer event in the feedwater system. Although Atwood

& Morrill valves were not involved in this event, they have been ordered as replacements for the affected feedwater system check valves. Accordingly, emphasis was placed on the attributes of Atwood & Morrill's Quality Assurance Program related to check valve design control and application; procurement document control; identification and control of material, parts and components; and control of special processes. Within these areas, the inspection consisted of an examination of procedures and representative records, employee interviews and observations by the inspector.

In accordance with 10 CFR 2.790 of the Comission's regulations, a copy of this letter and the enclosed inspection report will be placed in the NRC's Public Document Room.

Should you have any questions concerning this inspection, we will be pleased to discuss them with you.

Sincerely, W* ary G. Zech, C ief Vendor Program Branch Division of Quality Assurance, Vendor and Technical Training Center Programs Office of Inspection and Enforcement l

prin ADA& M -fQ w.yr-,

% *t ORGANIZATION: ATWOOD & MORRILL COMPANY, INC.

SALEM, MASSACHUSETTS

' INSPECTION INSPECTION REPORT 16 DATE: 2/10-11/86 ON-SITE HOURS:

NO.: 1 CORRESPONDE d M ORESS: Atwood & Morrill Company, Inc.

ATTN: Mr. S. N. Shields Vice President, Engineering 285 Canal Street Salem, Massachusetts ORGANIZATIONAL CONTACT:

Frederick W. Wilson, QA Manager TELEPHONE NUMBER: 617-744-5690 l

NUCLEAR INDUSTRY ACTIVITY: Atwood & Morrill provides special main steam isola-tion valves (Y-pattern globe), turbine extraction steam valves -(bleeder trip),

and general product line valves for gas and fluid systems.

ASSIGNED INSPECTOR: ,{ Odhfo E. H. Trottier, Reactive Inspection Section (RIS) Date i

OTHERINSPECTOR(S): Bruce E. Miller, Consultant Brookhaven National Laboratory APPROVED BY: M d E. T. Baker, Acting Chief, RIS, Vendor Program Branch Date INSPECTION BASES AND SCOPE:

A. BASES: 10 CFR 50 Appendix 8 and 10 CFR Part 21 B. SCOPE: This inspection was conducted to determine whether appropriate t consideration was given to the design, sizing, and location of the Atwood

& Morrill check valves purchased to replace and add to the feedwater system check valves at the San Onofre Nuclear Generating Station, Unit 1.

In addition, this inspection sought general information on check valve design, application, and recommended location in fluid systems.

PLANT SITE APPLICABILITY: San Onofre Nuclear Generating Station, Unit 1, (50-206).

etc(??@! $l>f

ORGANIZATION: ATWOOD & MORRILL COMPANY, INC.

SALEM, MASSACHUSETTS l

REPORT INSPECTION RESULTS: PAGE 2 of 6 NO.: 99900049/86-01 A. VIOLATIONS:

None.

B. NONCONFORMANCES:

None.

C. BACKGROUND:

In the early morning hours of November 21,1985, Unit 1 of San Onofre Nuclear Generating Station (SONGS-1) experienced a temporary loss of inplant and offsite ac power. (Plant emergency diesel generators were available to restore power within one minute, but operating instructions in effect at the time of the incident gave priority to restoring power to the plant from offsite sources.)

In the 21 seconds between the loss of inplant and offsite ac power, only one ac powered feed pump was available for both feedwater trains that supply all three steam generators. The suction piping of the non-running ac feed pump (low pressure feedwater heater train "B") should have been protected from over pressurization by the still-running "A" feed pump. It was not. The 12-inch check valve at the discharge of feed pump "B" had failed to close on reverse flow. Thus, the "B" feedwater flash evaporator failed due to overpressurization. Subsequent investigation found the "A" feed pump discharge check valve also stuck open, two 10-inch check valves stuck open in lines feeding two steam generators, and the 10-inch check valve broken apart in the line feeding the third steam generator.

As part of the measures taken by the utility (Southern California Edison) to prevent recurrence of this incident, Atwood & Morrill check valves were purchased to replace the failed feedwater check valves, plus other existing feedwater system check valves. (In addition, the plant is adding three check valves to the feed system. These also will be supplied by Atwood & Morrill.)

This inspection sought to review the design and operating history of the valves being purchased by San Onofre Nuclear Generating Station, Unit 1, as well as engineering (application) assistance and customer support programs (bulletins, maintenance advice, etc.) provided by Atwood & Morrill.

. . _ . .. .. I

ORGANIZATION: ATWOOD & MORRILL COMPANY, INC.

SALEM, MASSACHUSETTS INSPECTION REPORT .

PAGE 3 of 6 RESULTS:

NO.: 99900040/06-01 D. OTHER FINDINGS AND COMMENTS:

1. Design of SONGS-1 Atwood & Morrill Check Valves All eleven SONGS-1 Atwood & Morrill check valves purchased by SONGS-1 are of essentially the same design. However, the new 12-inch A and 8 feed pump check valves have a 7/32-inch hole drilled in their disks for pressure release. This was found to be required so that automatic valve alignment upstream (feed pump suction source) could occur in a timely fashion to support actuation of the required engineered safety feature systems.

The basic design features of the Atwood & Morrill check valve that differ from other check valves are:

- disk arm, disk arm swing stop ud disk is a one piece casting

- valve seat offset 20* from vertical The method used to limit disk travel (and thus set the full open angle) is to build up the disk arm swing stop. In this check valve design, the disk arm swing stop strikes the inside of the valve body at the curved surface between the bonnet and valve outlet.

2. Application to SONGS-1 Feed System The inspector interviewed the Atwood & Morrill Project Engineer for the SONGS-1 contract. He discussed the many conversations held with SCE staff engineers concerning important variables to be addressed l when considering application of a particular valve to a system. The l

i system variables to be considered are: flow velocity an'd valve l

location.

a. System flow velocity increases at the check valve because the valve's seat bore (minimum flow passage) is usually somewhat smaller than system nominal pipe diameter, and system mass flow rate is a constant. This increase in velocity through the seat bore is an important variable, along with disk size and weight, in holding the valve disk fully open. In a given fluid system, Atwood & Morrill recomends a seat bore diameter that will produce a flow rate between 10 feet per second (minimum) and 40 feet per second (maximum) during normal, extended system operation. (Ten to 30 feet per second is considered an ideal 1

L.z .

ORGANIZATION: ATWOOD & MORRILL COMPANY, INC.

SALEM, MASSACHUSETTS REPORT /'- INSPECTION RESULTS: PAGE 4 of 6 NO.: 9 01

)J '

range of flow velocity). The importance of minimum flow velocity is that it must be sufficient to hold the disk in the full open

(" pinned") position. Maximum flow velocity is important because it signifies a value above which excessive flow turbulence and pressure drop can occur.

Atwood & Morrill engineers worked with Southern California Edison (SCE) engineers to provide check valves whose seat port velocities and flow characteristics were expected to be adequate for the application. Based on preliminary data supplied by SCE for 100% power operation, Atwood & Morrill predicted a seat velocity of approximately 25 feet per second through each of the three 10-inch check valves. (The flow rate through each 12-inch check valve was expected to be similar because of a higher mass flow rate through two, slightly larger valves.) Final system calculations yielded approximately 19.3 feet per second through each 10-inch check valve and 20.5 feet per second through each 12-inch check valve. ~As stated above, these valves are well within the ideal seat bore velocity range recommended by Atwood &

Morrill.

b. Valve location is not a variable that is easily controlled by a company providing replacement valves in an existing plant.

In pursuing this issue with Atwood & Morrill engineers, the inspector was advised that Atwood & Morrill supports industry reconnendations of locating check valves in piping runs such that the nearest system device capable of altering the fluid flow profile is at least five pipe diameters downstream and ten pipe diameters upstream of the check valve, where possible.

Atwood & Morrill engineers cautioned that these are ideal con-

- ditions and are seldom found in application. Beyond making SCE aware of industry reconnendations, piping configuration in a plant already constructed is usually beyond the control of the valve manufacturer. Further, Atwood & Morri11's experience has shown that while the ten pipe diameters upstream - five pipe diameters downstream arrangement may be ideal, Atwood & Morrill

' check valves have performed satisfactorily in decidedly less than optimum conditions for many years.

ORGANIZATION:

ATWOOD&MORRILLCOMPAN)Y,INC.

SALEM, MASSACHUSETTS REPORT INSPECTION NO.: 99900049/86-01 RESULTS: PAGE 5 of 6 1

3. Performance History of SONGS-1 Atwood & Morrill Check Valves The inspector established that while Atwood & Morrill has an adequate Part 21 procedure (Procedure No. 20-67.10, " Reporting of Defects and Noncompliances Under 10 CFR Part 21"), it has not had occasion to put its requirements into effect since 1979. Further, Atwood & Morrill has no formal method or procedure for processing or evaluating field deficiencies. In defense of their seemingly non-existant Part 21 notifications (none in seven years), the inspector was adv.ised that Atwood & Morrill has issued and will continue to issue information notices informing customers of difficulties encountered with valves supplied. These information notices (three since 1980) are sent in lieu of Part 21 notifications, because Atwood & Morrill seldom knows if a valve's application is safety-related. In August and November, 1983, four nuclear customers were notified that NDE had not been performed on valves shipped to them. In March, 1984, six nuclear plants were notified of cracked valve shafts in main steam isolation valves manufactured since 1976. In December, 1984, one nuclear util-ity was advised that an Atwood & Morrill air-operated plug valve shipped to them could be defective. In addition, Atwood & Morrill noted that almost all Atwood & Morrill valve problems brought to their attention turn out to be, on examination, plant installation related.

For example: flow or improper maintenance (pressure disturbances elsewhere in the syste to valve); improper size for application.

4. Maintenance Recommendations Provided by Atwood & Morrill The inspector reviewed examples of instruction manuals shipped with each valve order. The manuals were found to contain .a preventive maintenance section, a general maintenance section, and' pressure seal ring precautions. Preventive maintenance consists of an inspec-tion of bonnet and bearing cover gaskets for deterioration and obvious leaks to be performed, "...during any period of shutdown....;" while general maintenance is to be performed at valve disassembly. For valves with bolted bonnets, 12 steps for disassembly and 7 steps for i reassembly are provided. For valves with pressure seal bonnets, 29 steps for disassembly and 16 steps for reassembly are provided. Valve seat inspection, lapping, and cleaning instructions are found in the disassembly steps. Torque values are provided for pressure retaining bolting and detailed instructions on how to tighten them are provided (typical bolting pattern sequence).

~

ORGANIZATION: ATWOOD&MORRILLCOMPAkY,INC. ,

SALEM, MASSACHUSETTS REPORT INSPECTION 01 RESULTS: PAGE 6 of 6 NO.:

V'

5. 10 CFR 50 Appendix B Program The inspectors reviewed the Atwood & Morrill Appendix B Quality Assurance Program as found in the Atwood & Morrill Quality Assurance Manual. Its content and implementing procedures appeared to be adequate.

E. CONCLUSIONS:

Based on the information reviewed during this inspection, the replacement Atwood & Morrill check valves are properly sized and designed for the in-tended application.

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. / 'o,, UN!IED STATES

.' 8' o NUCLEAR REGULATORY COMMISSION g a WASHING TON, D. C. 20555 1 g*.../

June 6, 1986 Docket No. 50-206 Sosthern California Edison Company ,

ATTN: Mr. Kenneth P. Baskin, Vice President -

Nuclear Engineering, Safety an6 _

Licensing Department 2244 Walnut Grove Avenue.

Rosemead, California 91?70- ,

P~

Gentlemen: -

s

SUBJECT:

NRC INSPECTION OF SAN ONOFRE UNIT 1 s This refers to the inspection conducted by Messrs.z P.' Milano, R. Ccrreia.

E. Trottier, H. Gregg, O. Rothberg, and H. Rockhold of the NRC on March 17-20, 1986, of N tivities authorized by NRC License No. CPR-13, and to the discussion of their findings held with members of your staff at the conclusion of the inspection.

~

Areas examined during this inspection are described in the enclosed inspection report. Within these areas, the inspection consisted of selective examinations of procedures and representative records, interviews with personnel, and observations by the inspectors. s The purpose of this inspection was to review the corrective actions taken to date in response to the November 21, 1985 water hammer event. This report will serve as a portion of the NRC staff's overall review of the check valve related issues of this event. ,

In accordance with 10 CFR 2.790(a), a copy of this letter and the enclosure will be placed in the NRC Public Document Room.

Should you have any questions concerning this inspection, we will be glad to discuss them with you.

Sincerely, it B i n K. Grimes, Dir tor or <v nd o o 7 b Division of Quality ssurance, Vendor and Technical Training Center Programs w'~'7- l/ Office of Inspection and Enforcement

Enclosure:

Inspection Report No. 50-206/86-15 cc w/ enclosure:

D. J. Fogarty, SCE H. B. Ray, SCE (San Clemente)

H. E. Morgan, SCE (San Clemente)

State of California

U.S. NUCLEAR REGULATORY COMMISSION REGION V Report No.: 50-206/86-15 License No.: OPR-13 Licensee- Southern California Edison Company Post Office Box 800 2244 Walnut Grove Avenue Rosemead, California 91770 Facility Name: San Onofre Nuclear Generating Station, Unit 1 Inspection at: San Onofre, San Clemente, California Inspection Conducted: March 17-20, 1986 Inspectors: .D_ . 7 8G Patrick D. Milano, Inspector, Special Projects Inspection Date Section (SPIS) e/w(; . fue. V Z-Es Richard P. Correia, Inspector, SPIS Date

,- ~

%%YL Edouard H. Trottier, Inspector, Reactive Inspection

- 3mmBC Date Section (RIS)

C 8C Date ps.H.I.Gregg,Ipector,RegionI l Also participating in the inspection were:

O. O. Rothberg, NRR H. C. Rockhold, Consultant, EG&G, Idaho

/

/

4 f4 Approved by: .

Gary G. Zech, Chief dor Program Branch Date s o: w u i

I.

SUMMARY

Inspection on March 17-20, 1986 (Report No. 50-206/86-15)

Areas Inspected: An announced inspection by headquarters of activities associated with the design, procurement, operation, and maintenance histories of the MCC-Pacific main feedwater system check valves which had failed, thus contributing to the water hammer event on November 21, 1985. Also, a review was made of the design and procurement activities associated with the Atwood-Morrill replacement check valves and the function of the inser-vice inspection and testing programs. The inspection involved 174 inspec-tor hours by five NRC inspectors and one consultant.

Results: No violations or deviations were identified. This inspection report, in conjunction with inspections of the associated check valve vendors, is intended to serve as a portion of the NRC staff's review of Southern California Edison's response to the check valve related aspects of the November 21, 1985 water hammer event.

t

DETAILS

1. PERSONS CONTACTED Southern California Edison Company (e) W. M. Lazear (e) H. E. Morgan (e/b/x) M. P. Short (e) B. Katz (e/x) D. E. Shull (e/x) W. G. Zinti (e/b) T. A. Mackey, Jr. (e/b/x) D. E. Nunn (e) A. E. Talley (e) C. A. Kargis (e) M. Macoundray e) L. Bajada (e/b/x) L. Rafner e) D. Bruce (e) B. Woods e) P. Cray (e) T. Herring, III e/b/x) C. Chiu (e) V. Salvator b) S. D. Root (b) B. R. Doncil (b) J. Blanco (b) B. Watts (b) J. Yann (b) G. L. Stawniczy (b) H. L. Richter (b) V. A. Gow (x) J. T. Reilly (x) M. A. Wharton (x) R. L. Erickson (x) D. A. Herbst (x) N. Maringas J. Hirsh P. Croy Bechtel Power Corporation, Western Power Division (b) R. Gavankar (b) F. McCluskey (b) J. Statton (b) P. Cruz (b) R. L. Loos (b) R. G. Allen (b) R. Elder, Consultant (b) P. Tulles, Consultant (b) L. Wiedemann (b) J. Hosmer (b) A. Langmo NRC Resident Inspectors F. R. Huey, Senior Resident Inspector A. D'Angelo, Resident Inspector R. C. Tang, Resident Inspector e- Denotes attendees at entrance meeting on March 17, 1986 b- Denotes attendees at Bechtel meeting on March 19, 1986 x- Denotes attendees at exit meeting on March 20, 1986

2. LICENSEE ACTION ON PREVIOUSLY IDENTIFIED ITEMS This subject was not addressed in the inspection.

3. UNRESOLVED ITEMS No unresolved items were identified during this inspection.

4. BACKGROUND During the San Onofre Generating Station, Unit 1 (SONGS 1) construction in the 1960s, swing check valves manufactured by MCC-Pacific Valve Company, purchased by the design agent Bechtel Corporation, were installed in the feedwater system. The original main feedwater system in San Onofre Nuclear Generating Station Unit 1 (SONGS-1) contained eight (8) check valves: one in each of the two (12") main feedwater pump discharge lines; one in each of the three (10") steam generator feed lines and one in each of the three associated (4") by-pass lines. Each steam generator feed line and its associated by-pass line has the check valve located in close proximity to the respective upstream flow control valves. After the water hamer event of November 21, 1985, an inspection of the feedwater system was conducted. Each of the 10" and 12" Pacific check valves were found to have failed or degraded in-service prior to the event. The 4" bypass line check valve in the B line failed as a result of the event.

The current system repair includes replacement of the Pacific feedwater check valves with Atwood and Morrill swing check valves. The system repair also includes relocation of the (3) 10" check valves farther downstream of the flow control valves and the installation of drain and vent valves to facilitate leak testing. Full scale flow testing of the 10" valves at an offsite facility at representative flow conditions and piping arrangements has been performed. Finally, the system repair includes the installation of (3) additional 10" Atwood and Morrill swing chck valves inside contain-ment, one on each steam generator feedwater line.

Specific details of the design, procurement, installation and failure analysis reviewed during the inspection are presented in the following subparagraphs.

4.1 Review of the original MCC-Pacific (PAC) check valves l

f a. Valve Design The inspection team reviewed the PAC catalog information, corre-spondence interchange between the licensee and the vendor, and the licensee's report entitled " Failure Analysis of Swing Check Valves," Rev. 1. Discussions were held with SONGS 1 and Bechtel personnel. Additionally, several of the failed parts were j examined. The inspection team made the following observations concerning the Facific valve design.

2

The valve is a cast steel body, bolted bonnet design in which the seat plane is approximately 5 from vertical in the disc opening direction. The total disc movement from closed to fully open against its stop would be from the 5 from vertical to a position approximately 5* below horizontal for a total angular displacement of about 80 .

When fully open the disc is nearly out of the flow stream.

This configuration tends to produce a low pressure drop l through the valve. However, there is the possibility of I the disc not seating tightly against its stop due to large  !

internal body bowl passage areas at the disc full open position.

The internal parts making up the disc assembly consist of the disc, a circular cast plate with the seat on one side and a protrusion termed the disc pin on the other side; the hinge which attaches to the disc at the disc pin and to the body by means of the hinge pin; and a disc washer, disc nut and disc nut pin to attach the disc to the hinge. The design has ouilt-in radial clearances between the disc pin and the hir.ge and a longitudinal clearance between the disc, hinge and nut. These clearances allow the disc to close against the seat without an adjustment. However, with this built-in play, the disc is free to rock and rotate when in the open position. This can cause significant wear of the parts as evident frmg the failed parts. Turbulence or specific flow conditions also contribute to the disc to hinge movement.

Additionally, since the disc pin and nut are used as a stop, the striking of the stop against the valve cover tends to create additional clearances.

b. Purchase Specification In a meeting attended by the NRC inspection team, Southern California Edison and Bechtel Power Corporation, the original architect / engineer for SONGS-1, the Bechtel technical staff presented their check valve criteria and methodology used during the 1960's time period; the same period in which SONGS-1 was constructed.- The Eechtel criteria based the selection of the main-feedwater system check valves on the general service conditions required of the valves, the size of the pipe in which the valves were to be placed, the system design pressure and temperature, and engineering judgement and experience. Check valves were preferably located in the piping system in a horizon-tal orientation, and in an area which would allow for maintenance access. These parameters were utilized to produce a cost effec-tive layout and were derived from the designer's judgement and experience. The specific types of valves to be used and the manufacturer selected to supply them were accomplished via a project master valve list and a general valve specification.

The master list was developed based on past experience and industry practice at the time of development. The list contained pressure ratings, material specifications and a mark number which 3

I

designated the type of valve (e.g., globe, gate, swing check, etc.).

In conjunction with the project master valve list, a general valve specification formerly used on a fossil plant project, and each bidder's published product descriptions, vendors were selected for the types of valves required for procurement. No technical information was exchanged between the vendor and the procurement agent for the system in which the check valve would be placed, the location of the check valve in the system relative to other equipment, or flow conditions. No installation specification was available at SONGS-1 which may have been part of the procure-rent package furnished by MCC-Pacific and there was no maintenance or spare parts information.

The licensee provided the available documentation relating to the purchase of the PAC swing check valves. This consisted of:

a general Bechtel specification No. 8AL 560 for cast steel, cast iron, and bronze valves for a fossil plant, the Alamitos Steam Station Units 5 and 6, from which the valves were purchased; the Bechtel piping specification Job No. 3246; a general valve listing, part of No. BAL 560 and several pages of a valve description; and one invoice page A-10335 dated 12/7/65 for a 10" Pacific swing check valve, Mark 222 Figure No. 680-7 WE80.

Specification No. BAL 650 was provided because the one actually utilized was no longer available. Since Specification No. BAL 650 was from the same time period, it was believed to be similar to that used for SONGS-1.

It was determined that the piping system including valves was designed and purchased to ASA B-31.1. The piping specification pressure - temperature service index and valve design rating was 600 psig at 850 F.

Bechtel and the licensee stated that the record retention require-ments of ASME Nuclear codes were not yet in place at the time of construction of this plant. Thus, the licensee's information was limited. t

c. Failure Analysis Report The inspection team reviewed the SONGS 1 report on " Failure l Analysis of Swing Check Valves, Revision 1," dated February 24, 1986. The inspection team concluded that the report provided a general analytical approach for disc lift vs. velocity based on l

an extrapolation of experimental information from another valve vendor. However, the inspection team had concerns about the small contribution the report assigned to turbulence. There was no mention of the built-in clearances of the PAC disc arrangement which would be further affected due to turbulence. Also, there was no knowledge of the thru-porting areas to be able to determine that the disc was against its stop under full flow conditions.

4 m r

e Because of these factors, the inspection team disagreed with the

~

report's premise that the problem occurred solely due to the licensee's recent operation at 92% rated thermal power (RTP) flow conditions. In addition, specific aspects of this failure report were reviewed by an NRC consultant, the results of which are included as Appendix A to this inspection report.

The failure report has been revised and corrected in several I

areas and resubmitted as revision 2 to the NRC. This revised report properly recognizes turbulence as a contributing factor l to the degradation of the valve internals. I l

d. Observations of Failed PAC Valve Parts  !

The inspection team observed the discs from the (3) 10" swing check valves FWS 345, 346, and 398. The seating surface of each disc was in good condition. However, there was considerable wear on the back of the discs, on the lower 180 of the OD and on the anti-rotation bars. There was considerable matching wear on the hinge, and considerable wear of the disc pin hole which resulted in a radial clearance with the disc pin of at least 3/16 inch. There was also considerable wear on the back of the hinge caused by the nut and on the end of the disc pin where it strikes ~the open stop.

From the observed parts it was evident that the disc rocked, fluttered and rotated. Initial clearances were greatly increased by the wear, and the disc became free to rotate past the anti-rotation bars. This wobble of the disc to hinge arm connection probably caused a changing angle of incidence of the disc in the flow stream and compounded the problem with stability at the disc stop.

e. Installed Location of PAC Check Valves l

One of the 12" swing check valves (FWS-438 and 439) was l

installed on each pump discharge and was located downstream I of a long radius elbow. The outlet side was relatively unobstructed. The licensee's initial failure report portrayed this arrangement as having no high upstream turbulence component.

Each of the 10" swing check valves (FWS 345, 346 and 398) was installed approximately two pipe diameter downstream of a double ported top and bottom guided control valve. This arrangement was portrayed in the licensee's revised failure report as a major

! turbulence producing component immediately upstream of these l

check valves.

The inspection team agrees with the conclusions of the revised l

failure analysis that stated there will be strong turbulence effects within the 10" check valves because of the control valve located immediately upstream. The inspection team also agreed that the long radius elbow upstream of the 12" check valves has less of an effect.

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a During a meeting with cognizant SONGS-1 personnel on 3/18/86 the inspector expressed concerns about the close location of the 10" check valves to the control valves. The inspection team pointed out the general valve placement practice of providing a separation between these components of 5 to 10 diameters upstream and 3 to 5 downstream of the check valve.

f. Licensee Check Valve Review Program l

Because of the observed failures with MCC-Pacific check valves in feedwater service, the licensee initiated a program that entailed a visual inspection of all Pacific valves and a sample  ;

inspection of other check valves in turbulent, lower port flow velocity situations.

A total of 29 Pacific check valves were disassembled and inspec-ted. In addition to those failures resulting from the event, one check valve, FWH-437, feedwater heater drain pump check valve, was found with the disc detached due to a disc pin failure.

A sample lot of check valves for inspection was also developed from calculations of system performance which would have subjected the valves to a condition of being less than fully open during operation. The sample consisted of 15 valves which were also found to be in potentially turbulent flow regimes because of being located less than 10 pipe diameters downstream of a turbulence generating device. This inspection resulted in no other valves which exhibited disc detachment. One valve, SDW-002 in the services and domestic water system, was found with excessive corrosion.

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! Finally, the licensee reviewed the plant maintenance orders f

for all SONGS-1 swing check valves. This review identified l

five check valves which had required corrective maintenance for valve internal deficiencies. These valves sere also disassembled and inspected and no deficiencies noted.

4.2 Review of Replacement Atwood and Morrill (AM) Check Valves l

l The proposed modified main feedwater system at SONGS-1 is to contain l eleven (11) check valves: eight direct replacements of the originals and three additional valves which are to be placed one in each of the three steam generator feed lines inside the reactor containment. These replacement check valves were procured from Atwood-Morrill. The three check valves which are downstream of the flow control valves are to be relocated further downstream from the control valves. Bechtel Power Corporation and Southern California Edison have concluded that the turbulence created by the flow control valves was a contributing factor in the failure of the original MCC-Pacific swing check valves.

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Current Bechtel practices and criteria guidance used in the selection

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and location of check valves includes using a tilting disc type of I valve and locating the valve at a distance of 5-10 pipe diameters from a turbulence generating source. The tilting disc check valve design incorporates a shorter swing arc to facilitate opening and closing of the valve and to reduce the radial velocity when the valve closes.

The location criteria of 5-10 pipe diameters away from a turbulence generating source is to allow a majority of the flow turbulence to subside prior to entry into the check valve to prevent banging of the disc into the valve body and/or seat. Bechtel used velocity criteria taken from Crane Technical Paper No. 410. " Flow of Fluids Through Valves, Fittings, and Pipe," to detennine minimum required flows through the i check valves in order to maintain the disc in the full open position l to prevent " dangling" of the disc in the flow-stream.

At a meeting held at the SONGS-1 site, Bechtel engineering managers and staff presented to the NRC inspection team their current design standards for the SONGS-1 check valve replacements. Bechtel sizing and location criteria were compared to Atwood-Morrill sizing and loca-tion criteria. Atwood-Morrill recommends a port velocity of 10-20 ft./

sec., and to avoid velocities of less than 5 ft./sec. or greater than 40 ft./sec. Bechtel has calculated that the flow through the replace-ment check valves will be 22 ft./sec. at 92% rated thermal power.

This value is slightly higher than Atwood-Morrill's recomended value but Bechtel concludes that the slight difference in the actual versus recommended values is acceptable. Atwood-Morrill location criteria for swing-type check valves is to optimally have straight pipe at a distance of 10 pipe diameters upstream and 5 diameters downstream of the valve.

a. Valve Design Based on the review and evaluation of documentation provided by the licensee and Bechtel and additional review of catalog information and the valve drawings, the following was determined:

The valves purchased to replace the Pacific valves and the three new valves are 900# class, cast steel swing check valves with pressure seal bonnet (internal pressure produces a large force on the bonnet which moves tighter against a steep tapered seal ring).

• The seat plane is 20' from vertical in the disc opening direction. The disc movement from closed to fully open against its stop is from the 20* from vertical position to a position 15' below horizontal (a total of 55 angular displacement with the disc partially in the flow stream at full open position). This configuration may produce a l slightly increased flow resistance but the disc should be firmly seated against its stop under most flow conditions as is the accepted practice for check valves.

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The disc assembly is essentially one integral part. The hinge arm is cast integrally with the disc and there are no bolts, nuts or pins. The design utilized close clearance bushings at the hinge pin resulting in little built-in play.

Also, with this type disc assembly there will be no rocking, or rotation of the disc. Adjustment for seating is by means of the rotatable external bearing covers.

Although not classified as a tilting-disc check valve by Atwood-Morrill (AM), their swing-check valves have a shorter disc-hinge swing arc than the MCC-Pacific valves. Bechtel felt that this shorter swing arc is very similar to a tilting disc design and will mitigate check-valve slamming in reverse flow conditions.

b. Purchase Specification The inspection team reviewed the licensee's documentation related to the procurement of the AM swing check valves. This included a review of: (a) portions of the SONGS 2 and 3 specification 50 23-408-1 that was used as the basis for quotations and purchase of the valves; (b) Bechtel purchase memorandum 531 with Bill of Material (BM) requirements that was sent to several vendors for quotations; (c) Bechtel purchase memorandum 532, and subsequent revisions, for purchase of the valves from AM; (d) the initial SCE purchase order No. V 82000603 to AM for the valves, and subsequent change orders; and (e) correspondence interchanges between Bechtel and AM regarding details of the purchase require-ments and several technical issues related to installation loca-tion, flow conditions, expected differential pressure for the 10" l valves outside and inside containment, disc weights, seat angle, port diameters, and the drilling of a hole in the 12" valve discs.

The check valves were purchased as safety-related valves to ANSI B31.1 (1980 Edition). For the replacement valves outside containment, the valves purchased were three (3) 10" 900# valves; two (2) 12" 900# valves; and three (3) 4" 900# valves. The design l

condition for these valves was specified as 1350 psig and 420*F.

! Each valve is to have butt weld ends prepared for schedule 80 pipe.

The (3) new 10" valves inside containment were also specified as 900# but the design condition was 1210 psig and 420 F. These valves are ordered with butt weld ends prepared for schedule l 60 pipe.

l The documentation was found to be acceptable. Several questions were raised by the inspector for which a resolution was required l

and later furnished by the licensee. These items are described l

l in the following paragraphs.

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8 1

• l 4

The replacement outside containment AM valves were purchased as 900# class for a design condition of 1350 psig, 420 F, whereas the old PAC valves were 600# class. The new inside containment AM valves are also 900# class at a slightly lower design condition of 1210 psig, 420*F. The licensee was asked to provide the rationale for the increased pressure class and justification that existing piping and other valves are suitable for both the old and new design conditions. Bechtel, by letter dated March 27, 1986, provided the basis for the original check valve 600# ASA rating as follows: At the time of the 50NGS-1 design, the applicable codes (1962 ASME Section I and 1955 ASA B31.1) permitted either pressure or temperature to exceed design for short periods of time provided the increase and time was within the prescribed limits. Since (1) the plant normal operating conditions of approximately 900 psig at 417 F is well below the 600# ASA rating pressure at temperature capability of 1320 psig at 420 F, and (2) the SONGS-1 design of 1350 psig at 420 F was based on main feedwater pump shutoff conditions that would rarely occur and would be within the permitted code variation limits, the code provisions were met.

The inspection team verified that the 1962 ASME Section I and 1955 ASA B31.1 permitted the above described variations.

During the initial purchase evaluation of the 12" AM check valves a drilled hole was to be placed in the disc at a set location. The final purchase document retained the hole requirement but considerably more latitude was given for its location. The licensee was asked to provide reasons for the latitude in hole location. Bechtel by letter dated March 27, 1986, provided their response that: (1) there was no specific process criteria involved in the hole location, (2) the hole was to be located in a general area similar to the previously installed valves, and (3) the manufacturer AM was given some latitude to allow them to consider the particular disc design l

and disc to seat configuration.

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l Based on an evaluation of the purpose of the hole, the above response addressed the inspectors concerns.

l During the Bechtel presentation concerning these valves, the l

i Bechtel representative stated there were numerous comunications l

with the vendor regarding the valve design and application conditions. The inspection team reviewed the communication inter-changes which basically related to the 10" valve. The licensee was asked for correspondence concerning the other valves (the 12" valve was mentioned). The licensee said they would review this with Bechtel to see that all the correspondence was presented and that the 10" valve may have been the valve with the most bounding conditions. The Bechtel response of March 27, 1986, provided additional AM correspondence information. The response also verified that the 10" valve was of particular concern and that AM evaluated flows and the suitability of the application.

9

The inspector determined that the information provided and the commitment to have AM review the data for all check valves satisfactorily addresses the inspectors concerns regarding information interchanged between the licensee and vendor.

A question was raised concerning the flow coefficient, Cv for the valves of both PAC and AM. The current PAC catalog provides a Cv that appears extremely high. While the AM valves have a somewhat lower Cv, in both cases the numbers appear to be higher than the maximum theoretical value. Further, neither PAC nor AM have a flow test facility to obtain or validate these values emperically. This was not made an open item since the licensee's evaluations did not utilize the vendor's Cv values, and actual flow testing would be performed,

c. Installed Location of AM Check Valves As mentioned previously, the inspection team's concerns about the original close location of the 10" check valves to the control valves was discussed with SONGS-1 personnel on 3/18/86. At that time licensee personnel stated they were not relocating the 10" AM check valves. However, on the following day, 3/19/86, the Bechtel presentation included the subject of relocation of the outside containment 10" check valves to a new location approximately 8 diameters downstream of the control valves to reduce turbulence in these check valves. The licensee said this was the maximum distance available.

The new inside containment 10" f.M check valves are to be installed with essentially no upstream or downstream obstruction. However, under conditions of auxiliary feed flow of only 50-200 gpm, there is an uncertainty by the vendor of the 10" check valve ability to satisfactorily function. In a letter to the licensee from AM dated 2/20/86, the vendor stated that flows of 165 gpm or less are considered severe service which could result in seat damage from the disc oscillating closed. Consequently, the licensee included low flow testing in his full scale testing program discussed below. Based on the results of this testing and the

! connitment by the licensee to open and inspect one of each set of valves during the next refueling outage, the installation location and valve capability are considered adequate.

d. Full Scale Testing Southern California Edison (SCE) and Bechtel Power Corporation have conducted and are continuing to conduct testing of the new Atwood-Morrill check valves. SCE feels that testing the valves under conditions which simulate the feedwater system flow conditions at SONGS-1 has verified proper operation of the valves, has verified back-up calculations generated by SCE and Bechtel for the feed-water flow conditions, and will provide data on wear to facilitate anticipated maintenance of the replacement valves.

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l The first phase is complete and consisted of performance tests  !

. through a 10" AM valve at the low flow ranges representative of l the auxiliary feedwater flows. Determinations were made regarding the stability and ability to function of these large 10" valves at low flows. Flow rates were then increased to the higher normal feedwater system ranges to determine where the disc seats against its open stop. A discussion of these tests is provided as Appendix B.

The second phase of this research is a long term wear study for these valves under anticipated operational conditions.

Under a cover letter dated May 5, 1986, SCE provided the final report of the performance tests conducted at the Utah Water Research Laboratory. The tests indicated that the valves would experience tapping during a range of flow rates. However, the intensity of the tapping was not believed to be severe enough to cause damage to the disc or body. The test conducted at low AFW flow rated indicated that the valve would be stable.

e. Industry History with Atwood & Morrill Check Valves During the inspection, the actions that SCE performed in review-ing the available history that the industry has encountered with valves similar to those being installed were reviewed. This information included that available from the Institute for Nuclear Power Operations (INP0), USNRC IE Bulletins and Information Notices, and direct contacts with utility maintenance representa-tives where the valves were being utilized.

The SCE Industry Surveillance Evaluation Group (ISEG) performs the reviews of the received NRC and INP0 information along with support from the affected departments to determine the applica-bility to SONGS. If applicable, the information is transmitted as an action request to the applicable department, and ISEG tracks the request until a response is provided.

Because of the event, the SCE Reliability staff perfdrmed a more detailed review of the INP0 and Nuclear Plant Reliability Data System (NPRDS) data on the Atwood-Morrill check valves.

From this review, SCE found that there were a total of 558 Atwood-Morrill check valves in the industry, with 179 reported failures. The majority of the reported failures were in check valves which had been in air and steam service. SCE therefore concluded that they would expect no major problems with the Atwood-Morrill check valves which they were placing on the feedwater system at SONGS-1. The information obtained from the NPRDS data on Atwood-Morrill valves was to be used as an enhancement to SONGS-1 maintenance of the valves in question in that SCE felt that they could better determine expected problems rather than waiting for problems to arise.

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As a check to NPRDS data, the licensee contacted a number of

. utilities that utilized Atwood-Morrill check valves. These contacts confirmed the NPRDS conclusions of no trends in failure of the type of valves proposed for use.

5. Control of Purchased Material, Equipment and Services As part of the review of San Onofre's control of purchased material, equipment and services (Criterion VII of Appendix B to 10 CFR 50) receipt inspection documents associated with the purchase of eight Atwood-Morrill check valves (2 - 12 inch, 3 - 10 inch, and 2 - 4 inch) were examined.

All receipt inspection documents associated with the subject check valves were found in Receiving Inspection Data Report (RIDR) No. RS0-1235-86, dated February 13, 1986. As reviewed by the inspection team, RIDR was found to contain: Certificate of Compliance attesting to conformance to B16.34 (1977), ASME Section IX, and Bill of Material Revision 9; Certified Material Test Reports, hydrostatic seat leakage and operational test resJlts; final inspection data sheets; and an instruction manual. In addition, a Document Discrepancy Notice was completed to substantiate that the Certified Material Test Report for 12 inch check valve S/N 1-15487-02 arrived without the required heat numbers. (The CMTR had been torn in transit.) All receipt documents appeared to be in order.

6. Document Control To verify proper control of the instruction manual for the new Atwood-Morrill valves, the inspection team pursued the review and approval status of the manual that was included in the RIDR package. According to the SCE Corporate Document Management (CDM) System, the Atwood-Morrill instruction manual was received (via Bechtel Power Corporation) on February 24, 1986. After initial processing, the manual was sent to the Configuration Control Group. Following review by Configuration Control, a copy of the manual and two configuration control forms (183 and 184) were sent to the following SONGS departments on March 25, 1986: Operations, Maintenance Engineering, Maintenance Support and System Descriptions. (Information on Form 183 is prepared by Configuration Control and is intended as a "first cut" of procedures, drawings, lesson plans and schedules that may need to be revised as a result of'information found in the instruction manual.) According to Configuration Document Change Control for Proposed Facility Changes, 50123-XIV-4.2, Form 184 should be returned by affected departments confirming their intention to make appropriate revisions to applicable documents. When all revisions are completed, the "open item" produced by receipt of the Atwood-Morrill instruc-tion manual will be closed on the San Onofre Commitment Register (SOCR).

Documents associated with the proposed facility change are to be sent to Corporation Document Management for archiving when the facility change is complete and associated SOCR items are " closed."

7. Check Valve Maintenance The maintenance practices utilized for the failed feedwater check valves were reviewed. It was found that the maintenance of check valves falls mostly in the category of corrective maintenance with little preventive maintenance being performed. For the failed valves, maintenance activities amounting 12

to opening the valve and inspecting the valve internals were conducted

. during the refueling outages in 1979 and 1980. Since no unusual wear was noted, the installation of anti-rotation lugs was believed to have solved a previous disc detachment problem. No records of subsequent inspection of these valves was noted.

Specific maintenance procedures are not utilized for the work on check valves.

However, the detailed steps to be accomplished during the maintenance activity are described on the Maintenance Order per the General Maintenance Procedure.

The steps are generally prepared in accordance with the requirements in the Installation, Operation, and Maintenance (IOM) Manual. In the case of the MCC-Pacific valves, the licensee did not have a copy of the IOM prior to the event. During the inspection, the recently received IOM was reviewed and found not to contain any information that would have had a bearing on the failures. The IOM did not contain requirements for dimensional measurements or seat contact checks.

8. Inservice Inspection and Testing Implementation of the San Onofre Unit 1 Inservice Inspection and Testing Program was reviewed for compliance with the ASME Boiler and Pressure Vessel Code,Section XI.

Implementation of the program was found to be, in general, consistent with the requirements of the Code. The plant records of the testing performed under the program were reviewed. Those records made available for review indicated that the testing of the safety-related check valves had been performed for the previous five to seven years. It was observed that five check valves in the safety injection system are identified as never receiving a full stroke exercise or a disassembly to verify condition and freedom of movement of the internals. These valves are numbered SIS-003, -004, -010, l -303, and -304. Relief from the ASME XI requirements, however, had been I requested for these valves and will be further reviewed by the NRC staff.

Additionally, there are other check valves where relief had been granted because of the inability to test them during plant operation. The failed feedwater system check valves were in this category. This category is generally tested during periods of cold shutdown and/or refueli.ng outages.

As indicated in the licensee's Failure Report, the A and B feedwater line check valves were last tested in February 1985 and the C line valve was tested in October 1984. In May 1985 the test procedure was changed to require the leak rate test to be performed after steam generator pressure is established. This was prepared to compensate for leak test failures that had been encountered when the tests were performed with the plant in cold shutdown. Although the vibration in the B feedwater line had been attributed to either the gate or check valve, SCE did not avail themselves of the opportunities for testing between May 1985 and the event.

The Operations Surveillance Procedures for performance of routine testing of valves identified in the IST program were reviewed to determine if the testing directed by these procedures could satisfactorily verify the opera-bility of the safety-related valves. The procedures appear to adequately l

13 I

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verify the operability of the valves at the time of the test in the direction

- of the intended safety function. However, check valves were not tested in both the open and closed position when the valve had only one intended safety function. Although this degree of testing is not required by the ASME Code, good engineering practice would, in most instances, require test-ing in both directions to assure full operability of the valve.

The testing being performed as required by the Code does not detect the degradation of check valves. Because of the failure of the feedwater check valves, the licensee has committed to the development of a quantitative leak rate criteria for these five valves. The previous procedural requirement provided no direct limits on the operator performing the leak test to verify that the valves are closed. The leak rate that was considered acceptable for the test was left to the operator's discretion.

During the inspection, the licensee was asked to explain why the quantitative criteria was restricted to the feed system check valves. A response to this question was not obtained. In addition, this proposed leak test acceptance criteria will amount to a normclized measured leak rate. The licensee intends to perform the test at any pressure and, by use of a standard scaling technique, obtain a normalized leak rate. This leak rate test will be used to determine the operability of the valves. Subsequent to the inspection, the licensee's proposed leak rate criteria and testing procedures were reviewed by the staff and found to be acceptable. In addition, the licensee agreed to, within the next six months, determine whether additional check valves warrant a quantitative leak check.

Interviews with licensee personnel concerning the mechanism for tracking the performance of the valve tests, especially those identified for conduct during cold shutdowns, indicated that an adequate method exists for ensuring

! the test is performed and failures are identified for additional testing and I maintenance. The records for calendar year 1985 were reviewed and found to I be satisfactory.

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O G

APPENDIX A

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Room 7-044, MIT

- Cambridge, Mass. 02139 1 April 1986 Mr. Charles L. Malezney EG4G Idaho, Inc.

P.O. Box 1625 Idaho Falls, ID 83415

Dear Chuck,

This is the letter report reviewing the " Failure Analysis of Swing Check Valves," Reference 3, by Chiu and Kalsi. The accident is described in Reference 4 The question which you asked is as follows:

"Is the approach taken to model the local turbulence effects sufficient to account for all the expected effects (e.g. cavitation and vortex shedding) j on the valve discs for the old valves and the replacement valves such that is can be expected that the replacement valve discs will be held firmly .

against the open stop for the postulated flow conditions? If not, provide a discussion of the uncertainty resulting from this analytical approach."

In order to understand the problem better, I hired an undergraduate, Jennifer Snopkowski, to build and run an apparatus to see how swing check values performed. The work was performed during spring break. Her report is included. I worked closely with her and have run the apparatus many times rayself and now feel I have a good understanding of how these valves perform. The details of the apparatus and procedure are in the enclosed report. The important results are as follows.

The velocity at which the check valve is pegged can be calculated very well using the formula and constant (K = 2.22) given in Chiu and Kalsi (3) on the top of page B-3. See Figure. (There is a power (2) missing as an exponent for Y in the second equation. The formula was used correctly, however.) We find that the value calculated with that formula does not work if the number of pipe L/D's lying between the flow control valve and the check valve is less than 6. That is for the region 0 < L/0 < 6

the turbulence and vortex shedding due to the upstream disturbance dominate the pipe turbulence, and the valve chatters. I think no check valve should be placed closer than 6 L/D from the nearest upstre'am disturbance. For short L/D's the valve chatters at velocities which are much greater than that given by the formula which is cited above. See Figure 6 of the Snopkowski report.

With a modest safety factor, say 1.2, I think the minimum velocity values calculated by the formula cited above are acceptable as long as the valve is more than 6 L/D's downstream of any disturbance.

In order to use the check valves in a region which is closer than 15 L/D's to the upstream disturbance, it is necessarv either to run an experiment or to do a pretty complete dynamic analysis. I don't think we know enough at this time to do an analysis. I'd like to describe how one should be done citing the references which apply and pointing out the weaknesses if one is done by South California Edison and if they choose to .

present it. An analysis based on a random vibration model is presented in Appendix E of Reference (3). It is a good start but needs more work. Let me begin with the exciting force.

l A blunt object, like a cylinder, in cross flow sheds vortices, Reference 7. If these are close to a natural frequency of a structure downstream from the blunt object vibrations can be excited. We don't know what values of Strouhol number apply to the flow control valves illustratd in Figures 1, 2, 3, and 4 of Reference (3). Random vibration theory might apply, but we_ don't have the precise PSD's needed for the geometries of__

interest. A convincing dynamic analysis must be based on data taken in the appropriate geometry.

I tried, in the library, to find some measurements of turbulence in jets or the wakes of blunt objects and found some in References (5) and (6). The values are much greater than those we find in pipe flow, but frequencies are not given. Fluctuating velocities are of the order of 50%

of pipe velocity, in some places, rather than the 10% we find in pipe flow, Reference (8). It isn't clear to me, either, whether this problem is

better modeled as randce vibration or as a forced vibration described by the appropriate Strouhol number. That question can only be settled by experiment.

In our experiments, the cate moved up and down, tapping the stop lightly. It was certainly not periodic but rather would show a cluster of four or five impacts then a delay of several seconds or so before the next cluster of taps. I'm not sure how that should be modeled. This kind of turbulence is ch- acteristic of jets (5).

Let us now turn our attention to modeling the gate response. In order to determine this, it is necessary to be able to calculate an effective mass, the spring cons .3nt and the damping factor.

I believe that Reference (3) did not consider the induced or virtual l mass of the water. At least on Page D-1, the mass calculated for the valve gate does not appear to include it. Reference (1) describes virtual mass, .

and Reference (20) gives the values for many shapes of interest, though not, of course, for our valve. The contribution to the mass could be appreciable for a gate in a pipe. For a disc of radias r oscillating in an infinite pool, the virtual mass is equal to the mass of the water contained in the volume (8/3) r 3 This mass is about 20% of that of the disc itself.

The calculation for the spring constant given on page D-1 of Reference (3) does not include the gravity force acting on the disc. Whether it enters in an important way depends, I think, on how wide open the valve is.

It should be included, however. For a wide open valve, it would be an almost constant force and probably does not play an important role.

Our experiments indicated that the gate on the 2" valve we tested was overdamped as long as it was in water. A rough scaling of the damping ratio to a larger valve does not tell use whether the valve is over or under damped though one would expect the valve to be more heavily damped that the damping ratio of 5% assumed in Reference (3). It might be that

there is no resonance because the gate is overdamped for all positions.

I think calculating the damping of the valve is quite difffcult.

Using drag on a pivoting disc might yield an answer good to a factor (2),

, however. I think it is far more heavily damped than the value implicit in a critical damping ratio of 5% which is mentioned on page E-1 of Reference (3). That is a very conservative assumption.

Let us assume that we can overcome all these problems; how do we determine how long the valve will last? It is impossible to start or turn off the flow without the valve hitting the stop a few times. The question is how much is tolerable. In principal, I guess one could get the PSD of the vibration amplitude, calculate the kinetic energy of the gate at each impact and determine the damage done if all that kinetic energy went into yielding the stop or stud or both. I think that is a very conservative procedure.

Perhaps a factor, much less than 1, could be found in the literature for the " efficiency" of the impact so that one could justify reducing the damage per impact. I suspect that measurements of the right kind have been

• made, but I didn't look for them.

In summary, I think you can confidently license the plant if the l following conditions are met:

1. The L/D from the nearest upstream fitting to the gate is greater than 6.

2. The velocity is greater than 1.2 times the velocity calculated from the formula at the top of page B-3 of Reference 3.

If the check valve is closer than 6 L/D's to the nearest upstream fitting, I don't think we know enough to predict whether the installation is safe or not.

If cavitation occurs, the collapse of the resulting vapor bubbles could be quite violent, and I don't think anyone could say whether the l

l

. valve was safe. I don't see why either the check valve or the flow control valve upstream should ever cavitate, during normal operatuton, however.

If an experiment to determine the flow velocity at which the valve is pegged is run full scale with the appropriate upstream geometry but cold  ;

and the valve performs satisfactorily, I think you can scale that experiment and comfortably if cense the plant. For L/D's less than 6, I find such a test the only convincing justification to license an j installation.

I don't think we can calculate whether a valve is safe when the L/D to the nearest upstream disturbance is less than 6 with what we know now.

If you have any questions, feel free to call; I'd be glad to answer them. If you come through Boston, stop by and I can demonstrate our experiment for you. I'm going to make this one of the experiments in our senior undergraduate lab and hope to have it running for several years. .

Sincerely, I

!l.Peter Griffith Consultant t

PG/jg t

\ - - - - . . . . _ . . . - _ - _ _ _-_ _ .

References

1) Milne-Thomoson, L.M., Theoretical Hydrodynamics, 2nd edition, McMillan Co., New York,1950, p. 229.

2) Patton, Kirk T., " Tables for Hydrodynamic Mass Factors for Translational Motion," ASME paper 65-WA/UNT-2,1965.

3) Chf u, C. and Kalsi, M.S., " Failure Analysis of Swing Check Valves,"

Feb. 24, 1986 revision.

4) " Loss of Power and Water Hammer Event at San Onofre, Unit 1, on November 21, 1985, NUREG-1190, January 1986.

5) Rouse, H., Advanced Mechanics of Fluids, J. Wiley & Sons,1959, p. 496.

6) Hinze, J.0., Turbulence, McGraw-Hill,1959, p.404

7) Bleyins, R.D., Flow-Induced Vibration," Van Nostrand Reinhold Co.,

1977, p. 15.

8) Schlicting, H., Boundary Layer Theory, Pergammon Press,1955, p. 576.

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A*(24)

s Check Valve Dynamics

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Jennifer Snopkowski Peter Griffith 1 April 1986 Abstract A two inch diameter check valve was tested in water to find the range of velocities and L/D's from an upstream disturbance when the valve was always (1) pegged, (2) swinging and hitting (tapping), and (3) swinging free. The formula for pegging from the Chiu-Kalsi report was found to predict the pegged velocity quite well when the flow was fully developed (i.e. L/D > 6).

For L/D < 6, the valves tapped at velocities well above that given by the Chiu-Kalsi formula. Tapping was found to persist down to about half the maximum tapping velocity for fully developed flow, independent of L/D from an upstream disturbance.

I. Introduction Check valves used in a reactor feed-water delivery system are designed to prevent the backflow of steam. Failure of the check valves can' result in a j water hammer, causing severe damage to the feed-water system. An actual l water hammer occurrence due to check valve failure occurred and is reported in reference 4 of the letter.

A diagram of one of the check valve installations in the system which experienced failure is shown in Figure 1. The failure is a result of repeated tapping of the check valve against the stop. This tapping is caused by disturbances in the flow over a certain range of velocities.

The purpose of this experiment was to find out what the range of

• elocities was which caused an experimental check valve to tap against the stop. This report compares the maximum water velocity at which tapping occurred with an analytical method developed by Chiu and Kalsi given in reference 3 of the cover letter.

The folicwing question, presented in the work statement will be addressed:

i "Is the approach taken to model the local turbulence effects sufficient to

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account for all expected effects (e.g. cavitation and vortex shedding) on the valve disks for the old valves and the replacement valves such that it can be expected that the replacement valve disks will be held firmly against the open stop for the postulated flow conditions? If not, provide a discussion of the uncertainty resulting from this analytical approach." The results reported here are the basis for the recommendations in the cover letter.

II. Apparatus and Experimental Procedure The apparatus was set up as shown in Figure 2. A diagram of the experimental system is given in Figure 3. The check valve was placed downstream of a plastic insert simulating a valve which was used to produce a disturbance in the flow. A tracing of the insert is shown in Figure 3. The distance L shown on the diagram was varied to test the effects of L/D change on the range of critical flow velocities. In this apparatus, D is the inside diameter of the pipe and is equal to 2.062 inches. The plastic insert was removed to determine a range for an asympotoic value of L/D.

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The check valve used in the experiment is shown in Figure 4 The total

. weight of the gate, including the arm, was .471 lb,. The details are given on Figure 4 To take this picture, the bonnet on the check valve was removed and replaced

- with a plastic window which w(s screwed into the thread originally holding the bonnet. It was easy to see wbsre the gate was through this window and whether it was pegged or not. The window is visible in the photographs of Figure 2 and Figure 5. Figure 5 shows the gate pegged and is photographed thrcugh the window. The windows at the ends of the horizontal run shown on Figure 1 were not needed.

III. Results A plot of flow velocity versus L/D is given in Figure 6. The area used in the velocity calculations was based on pipe diameter and is equal to 3.34 in 2. The lower half of the graph shows points where the valve oscillated in the flow without tapping the stop. It can be seen that the transition to velocities where tapping begins is not dependent on L/D. Above this transition velocity, the valve repeatedly tapped against the apen stop.

The frequency and intensity of the tapping increased with increasing 4

velocity.

The transition where the valve no longer taps aginst the stop but is pegged against it is an important one. If the. velocity is kept above this transition velocity, the valve will 'be held stationary against the stop by the flow, and there is little possibility for failure. At L/D values above 6, the velocity at which the valve was pegged is fairly constant. The far right of the graph of Figure 6 shows the minimum tapping velocity for a fully developed flow. Below an L/D of 6, however, the pegging velocity dramatically increases and is off scale for L/D values less than about 3.

The frequency of tapping is high and the severity of oscillations large for the low L/D values.

The analytical method mentioned in the Introduction and found in Reference 2 was followed for the equipment used in this experiment. The calculations are given in Appendix A. The minimum velocity needed to keep the valve pegged was determined using this method. It was 6.75 ft/sec and is shown in

Figure 6. This valve clearly behaves as predicted for L/D values greater

. than 6. Below this value, however, this method fails.

An attempt was made to find the approximate damping ratio experfmentally by disturbing the gate and watching it respond. As far as could be seen, this gate was more than critically damped. One could not see any overshoot at all for any gate position. The measurement was entirely visual however and hardly one of high precision. Nonetheless, this gate appears heavily damped and one would not expect it to display any resonance due to vortices or turbulence generated at the disturbance upstream.

When there was no disturbance upstream, the tapping was easy to hear. It

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could be heard more easily through a screwdriver held against the body of the check valve with the handle held against the ear. With the disturbance upstream, however, the flow noise overwhelmed the tapping and I (PG) couldn't hear the tapping at all even though I could see the valve swinging and hi tti ng.

IV. Conclusions

1. The velocity at which the valve gate is always pegged is well predicted by the Chiu-Kalsi formula for a fully developed flow. This means the L/D is greater than 6 for the distance from ar upstream disturbance to the ga te.

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2. When the L/D is less than 6 from the nearest upstream disturbance to the gate, the valve taps for velocities much greater than that calculated using that formula.

3. The valve swings free without tapping for velocities equal to about half of that given by the Chiu-Kalsi formula.

4 The gate in the 2" ID valve used in these experiments appeared to be heavily damped for all positions. No resonance was observed or expected.

5. The fact that a formula developed for a valve of a 4.iailar type but of a different geometry works so well it leads one to think it would work on other valves too.

Appendix A. Pegging Velocity Calculations The Chiu-Kalsi formula from the top of PB-3 of reference (3) of .the letter is:

.5 W.)(b)(g) .5 y ,"(W

. K p A sin2 g ,

In this formula V = velocity, [f t/sec]

W = mass of gate plus arm = .471 lb m W, = mass of arm = .164 lb, b = bouyancy factor = .883 .

2 g = acceleration of gravity = 32.2ft/sec k = empirical constant = 2.21 3

o = density of water = 62.3 lb,/ft A = pipe area = 3.34 in2 = l0232 ft2 6 = angle of valve from the horizontal when pegged = 16.0*

The resulting minimum pegging velocity is

• V e 6.75 ft/sec This formula is derived from a force balance on the gate where the jet force holds the gate up against gravity which is tending to make it fall off the stop. It is the maximum tapping velocity. The constant 2.21'given as K above was determined from the minimum acceptable operating velocity provided by one of the valve manufacturers.

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NOTES: 1. MAJull TURBULENCE COMPONENTS ( PRESSURE liEDtJCING CONTROL VALVE. AND AN EXPANDER)

IMMEDIATELY UPSTREAM.

2. ONI_Y IxD STRAIGHT PIPE LENGTH AFTER tIIGti 1URBULENCE COMPONENTS.

4 FIGURE 1. 10" GOO # CHECK VALVE INSTALLATION (1:WS - 345, 346, 398)

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APPENDIX B i

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Report on Check Valve Testing ,

Performed at Utah Water Research Laboratory ,

For Southern California Edison Co.

During The Week of March 31, 1986 Herb Rockhold o

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- The week of March 31, 1986, Dr. Paul Tullis and associates of Utah State University performed a series of tests on a 10" Atwood-Morrill check valve at dn> Utah Water Research Laboratory (UWRL) in Logan, Utah for Southern California Edison Co. (SCE) operators of the San Onofre Unit One (

Nuclear Station. This report is a summary of the tests performed and does

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not intend to draw any conclusions since the data obtained from the tests was retained by Dr. Tullis and will be published in a report by him for SCE. .

The check valve test configuration for the first test had the 10" l Atwood-Morrill check valve located in a straight run of horizontal 10" l pipe with greater than 10 pipe diameters of straight pipe upstream and greater than 5 diameters of straight pipe downstream of the check valve.

The water ht shs 5.50C was supplied to the test assembly by a reservoir initially at about 10.5 psi to supply low flow, and by a centrifugal pump rated at 1500 gpm at 70 feet of head driven by a 100 horsepower motor-for the hicker flowrates. The flowrates through the check valve was measured by w r ring the quanti?.y of water passed through the valve in specific time itervals. The flowrates were also measured with a flow orifice, j l

however, this was expected to be inaccurate at low flowrates. The check valve was equipped with an accelerometer located on the valve body located. l approximatley where the valve disk would make contact. The accelerometer"  ;

was coupled to an acoustic amplifier feeding a speaker to provide '

relatively clear audible monitoring of the check valve internal moving parts. The check valve noise was also monitored with a simple stethoscope.

At flowrates up to 2600 gpm equivalent plant flows (corrected for

• water density, velocity, etc., to produce the same forces on the check l valve disk that would be experienced at plant operating conditions) the noise level was primarily background flow and pump noise. Near 2600 gpm equivalent plant flow gentle tapping of the valve disc against the valve body was distinctly heard and this gentle tapping continued up to ,

approximately 3000 gpm equivalent plant flow. Flowrates greater than 3000

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gpm equivalent plant flow produced very little if any distinguishable l

tapping attributable to valve disc to body contact. This test was l performed to simulate the plant conditions for the check valves to be located in the feedwater headers inside the containment at SONGS-1. This test tends to indicate little or no problems can be expected from these check valve'due to flow induced vibrations resulting from location in the pipe.

The second test performed at the UWRL on the 10" Atwood-Morrill check valve involved locating the check valve downstream of the feedwater regulating valve as installed at the 50NGS-1 facility. The check valve was located approximately 86 inches downstream of the feedwater regulating valve in a straight run of 10 inch pipe with greater than 5 pipe diameters of straight 10 inch pipe downstream of the check. The feedwater regulating valve is a Fisher 8 inch spool type, double seated, balanced plug valve located 52 inches downstream of a 10 inch 900 elbow. The flow through the test assembly was provided by a centrifugal pump rated at 4500 gpm at 140 feet of head driven by a 200 horsepower motor with the flowrate controlled by a combination of the pump discharge pressure regulating valve and a flow control ball valve located approximately 1

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twenty feet downstream of the check valve. This flow control configuration was utilized to minimize the cavitation in the feedwater regulating. valve which was set at sw60% open to correspond with the setting du?ing 94% power operation of the SONGS-1 plant. The ficwrate through the test assembly was measured by a flow orifice and a catch tank with level instrumentation. Differential pressure across the check valve was also monitored. At approximately 2300 gpm equivalent plant flow distinct valve disc tapping began and continued through the maximum flowrates obtained during this test (approximately 6000 gpm). The tapping ,

J of the disc on the valve body was distinct however, Dr. Tullis and Bill Rahmeyer of Utah State and Edgar Bottom of Atwood-Morrill felt the )

magnitude and frequency of tapping at all flowrates would not be detrimental to the valve or significantly reduce its service life.

The third test performed on the 10" Atwood-Morrill check valve was intended to simulate the conditions that the 8 main feedwater pump .

2 discharge check is exposed to at SONGS-1. This test configuration involves a scaling factor of approximately 10/12 since the actual plant check valve is a 12 inch check of the same design as the 10 inch check utilized in the lab. Additionally, since the actual plant conditions utilize a multi-stage centrifugal feedwater pump just upstream of the chack, the lab test configuration utilized a short radius 8 inch elbow and two 8 inch by 10 inch reducers to simulate the turbulence produced by the feedwater pump.

The test configuration was established with an orifice plate with the center hole 10.0 inches in diameter (slightly iteger than pipe inside diameter) located in a vertical run of 10 inch pipe 16 inches above an 8 e inch to 10 inen reducer. The 8 inch outlet of this reducer was welded to a short radius 8 inch elbow and this was then welded directly to another 8 inch to 10 inch reducer. Flow then traveled through a short, approximately 12 inch, section of straight 10 inch pipe into a long radius 10 inch elbow into another short section of straight 10 inch pipe then into the check valve. Flow from the check valve immediatley entered a 10 inch T with the straight thru outlet welded closed with a flat plate, therefore the flow turned 900 down out of the T directly into another long radius 10 inch elbow. From this point the flow traveled a long straight run of 10 inch pipe (greater than 10 pipe diameters) to a ball type flow control valve and into the instrumented tank for flowrate measurement.'

Once flow was established in the test assembly and increased to approximately 3600 gpm equivalent plant flow, there was no noticeable noise attributable directly to the check valve. At equivalent plant flows of 3653 and 5321 gpm gentle tapping of the check valve was detected however, the magnitude was low at about one to two taps per second. At an equivalent plant flow of 6283 gpm very little tapping was noticed (about once per 10 seconds). When reducing flow to approximatley 4900 gpm near continuous tapping was noticed (about 4 to 5 Hz) of relativsiy low amplitude.

After performance of the previous testing the flow was stopped and the orifice plate was changed to an orifice plate with 33 one inch holes drilled cheu the 1 inen thick aluminum disc with the inlet side of the 2

1 holes radiused 1/4" to provide reasonable smooth flow upstream of the pump simula device. Again various flow rates were established through the test as ly and light tapping began at approximately 3762 gpm and continuedkuntil a maximum of 6005 gpm was established. Although the tapping continued throughout this flowrate range the tapping was less severe than that noticed in the configuration with the check valve located just downstream of the feedwater regulating valve. The temperature of the test water was measured at 6.50C.

This series of tests indicates the check valves located downstream of the feedwater regulating valve and at the feedwater pump discharge are in a severe turbulence region in the system and are never firmly backseated during plant operation.

During the test with the check valve located downstream of the .

feedwater regulating valve it was noticed that the sound of tha check valve disc tapping against the valve body appeared to be comming from a spot approximately 10 to 12 inches downstream of the actual contact aret.

This tends to explain the opinion of the SCE staff that the noise during the July 1985 event was comming from the downstream block valve rather than the check valve that was later found failed during the November, 1985 water hammer event investigation.

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Prof. Peter Griffith 77 Massachusetts Ave.

Room 7-044 Cambridge, MA 02139

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Dr. Charles llalezney i EG4G Idaho, Inc. )

P.O. Box 1625 Idaho Falls, 10 83415 l

Dear Chuck,

This is the review of the final Report " Performance Tests on the Feed Water Chect Valves for the San Onofre Unit 1 Nuclear Power Plant, Phase A" by J. Paul Tullis and William J. Rahmeyer dated April 1986.

I have no disagreements with their measurements or interpretation ~ of them. Because the tests were run in low pressure, low temperature water and applied to high temperature, high pressure water, some extrapolation of the test results is needed. Let me touch on two issues that must be extrapolated, the maximum tapping velocity, and the cavitation limits.  !

A small extrapolation of the tapping velocity measured is necessary because the water density in the test is higher than in the application.

Equation (3) of the report does this and I agree with the use of this equation in this problem. It is just what I would have done. Used with a modest safety factor, say 1.2, these test car. be used to set the minimum velocity at which these values are allowed to run during steady operation.

In later work, they might want to correct the buoyant force of the gate for

• the different water density but that is a trivial improvement. In any case, the valves should not be installed with less than 6 L/O's to the nearest upstream disturbance.

The other extrapolation was for the cavitation index. This is given as equation 4. This is a commonly accepted formulation for extrapolating cavitation data taken at one condition to another. (See Streeter, V.L.,

" Handbook of Fluid Dynamics," First edition, McGraw-Hill,1961, pp.12-17.)

The value at which cavitation occurs can be greater than the value calculated for this valve 1.34, and is a function of geometry. Though I see no reason for alarm, it would be good, in subsequent tests, to see if there is any cavitation. I, frankly, find it hard to believe any valve manufacturer would design a valve that would cavitate under design conditions. It would greatly reduce the life of the valve. The cavitation index of 1.34 is large enough so that there may be no cavitation at all.

The fact that this valve failed only when operated at less than design velocity for a year after apparently operating for years et the design velocity makes me think that cavitation is no problem. The valve should cavitate most at its maximum velocity. If it worked for years at full load I fail to see how cavitation could cause problems at part load. In the phase two tests, however, I think finding the cavitation limits for this system of flow control valve an new check valve is a worthwhile goal. I think this problem can be laid to rest once and for all. My guess is that you will never have cavitation in the operating range for the valve.

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• l They could take this valve into the cavitating range by increasing the water temperature or, perhaps, decreasing the back pressure. I would like

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to see one of those things done.

4 There one ites that I would like to raise that might be settled in the phase experiments. The description of the tapping in this report makes it heet for me to believe that it could cause the damage that led to the valve's failing. Whether the severe damage in the San Onofre installation was due to the check valves closeness to other fittings or the design of the check valves themselves is not clear. I'd like to see that settled. I would also like to see some damage measurements made so that an inspection schedule can be set up and approximate times at which the valves can be run at less than design velocity determine.

Let me now sunmarize my findings.

1) The tests and extrapolation procedures used to define the allowable conditions for the Atwood and Morrill swing check velves are both satisfactory.

2) I would like to see the flow limits presented in this report checked against the minimum velocity formula in Chiu and Kalsi report to see what an allowable safety factor for the Chiu and Kalsi formula is. This would help you evaluate other installations.

3) I would like to see the cavitation limits determined for this flow control valse-check valve installation. I suspect you have no cavitation under normal operating conditions, and this is no problem. One measurement.would show this.

4) I would like to see some kind of deformation or wear measurement made so that the life of the valves when they are tapping could be estimated. I'm not sure how to do this but using a soft stop, made of lead perhaps, would give accelerated wear and allow use to estimate the life. Probably penetration hardness is the scaling parameter. This would tell us how often to inspect the valves and how long, during startup for instance, we could run at reduced velocity.

If you have any questions, I'd be glad to talk to you. Enclosed is an invoice for the time I spent on this review.

i Sin rely, D .

(3 eter Griffith Consultant PG/jg B*21

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1 ENCLOSURE 7 a

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. ENCLSOURE 7

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. Room 7-044, MIT Cambridge, Mass. 02139 1 April 1986 Mr. Charles L. Nalezney EGSG Idaho, Inc.

P.O. Box 1625 Idaho Falls, ID 83415

Dear Chuck,

This is the letter report reviewing the " Failure Analysis of Swing Check Valves," Reference 3, by Chiu and Kalsi. The accident is described in Reference 4 The question which you asked is as follows:

i "Is the approach taken to model the local turbulence effects sufficient to account for all the expected effects (e.g. cavitation and vortex shedding) on the valve discs for the old valves and the replacement valves such that is can be expected that the replacement valve discs will be held firmly against the open stop for the postulated flow conditions? If not, provide a discussion of the uncertainty resulting from this analytical approach."

1 In order to understand the problem'better, I hired an undergraduate, Jennifer Snopkowski, to build and run an apparatus to see how swing check values performed. The work was performed during spring break. Her report is included. I worked closely with her and have run the apparatus many times myself and now feel I have a good understanding of how these valves perform. The details of the apparatus and procedure are in the enclosed report. The important results are as follows.

The velocity at which the check valve is pegged can be calculated very well using the formula and constant (K = 2.22) given in Chiu and Kalsi (3) on the top of page' B-3. See Figure. (There is a power (2) missing as an exponent for V in the second equation. The formula was used correctly, however.) We find that the value calculated with that formula does not fl work if the number of pipe L/D's lying between the flow control valve and the check valve is less than 6. That is for the region 0 < L/D < 6

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the turbulence and vortex shedding due to the upstream disturbance dominate the pipe turbulence, and the valve chatters. I think no check valve should be placed closer than 6 L/0 from the nearest upstream disturbance. For short L/D's the valve chatters at velocities which are much greater than that given by the formula which is cited above. See Figure 6 of the Snopkowski report.

With a modest safety factor, say 1.2, I think the minimum velocity values calculated by the formula cited above are acceptable as long as the valve is more than 6 L/D's downstream of any disturbance.

4 In order to use the check valves in a region which is closer than 6 L/O's to the upstream disturbance, it is necessarv either to run an experiment or to do a pretty complete dynamic analysis. I don't think we know enough at this time to do an analysis. I'd like to describe how one should be done citing the references which apply and pointing out the weaknesses if one is done by South California Edison and if they choose to .

present it. An analysis based on a random vibration model is presented in Appendix E of Reference (3). It is a good start but needs more work. Let

, me begin with the exciting force.

A blunt object, like a cylinder, in cross flow sheds vortices, i

Reference 7. If these are close to a natural frequency of a structure downstream from the blunt object vibrations can be excited. We don't know what values of Strouhol number apply to the flow control valves illustratd in Figures 1, 2, 3, and 4 of Reference (3). Random vibration theory might apply, but we_ don't have the precise PSD's needed for the geometries of__

interest. A convincing dynamic analysis must be based on data taken in the appropriate geometry.

I tried, in the library, to find some measurements of turbulence in jets or the wakes of blunt objects and found some in References (5) and (6). The values are much greater than those we find in pipe flow, but frequencies cre not given. Fluctuating velocities are of the order of 50%

of pipe velocity, in some places, rather than the 10% we find in pipe flow, Reference (8). It isn't clear to me, either, whether this problem is 1

= _ _ - - __ - . - _ _ _ - - _ _ . - - _ _ _ _

better modeled as random vibration or as a forced vibration described by the appropriate Strouhol number. That question can only be settled by ,

experiment.

In our experiments, the gate moved up and down, tapping the stop lightly. It was certainly not periodic but rather would show a cluster of four or five impacts then a delay of several seconds or so before the next cluster of taps. I'm not sure how that should be modeled. This kind of turbulence is characteristic of jets (5).

Let us now turn our attention to modeling the gate response. In order ,

to determine this, it is necessary to be able to calculate an effective mass, the spring constant and the damping factor.

l I believe that Reference (3) did not consider the induced or virtual mass of the water. At least on Page 0-1, the mass calculated for the valve gate does not appear to include it. Reference (1) describes virtual mass, .

and Reference (20) gives the values for many shapes of interest, though not, of course, for our valve. The contribution to the mass could be 3

appreciable for a gate in a pipe. For a disc of radias r oscillating in an infinite pool, the virtual mass is equal to the mass of the water contained in the volume (8/3) r 3 This mass is about 20% of that of the disc itself.

The calculation for the spring constant given on page 0-1 of Reference (3) does not include the gravity force acting on the disc. Whether it enters in an important way depends, I think, on how wide open the valve is.

It should be included, however. For a wide open valve, it would be an almost constant force and probably does not play an important role.

Our experiments indicated that the gate on the 2" valve we tested was overdamped as long as it was in water. A rough scaling of the damping ratto to a larger valve does not tell use whether the valve is over or under damped though one would expect the valve to be more heavily damped that the damping ratio of 5% assumed in Reference (3). It might be that

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. there is no resonance because the gate is overdamped for all positions.

I think calculating the damping of the valve is quite difficult.

Using drag on a pivoting disc might yield an answer good to a factor (2),

however. I think it is far more heavily damped than the value implicit in

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a critical damping ratio of 55 which is mentioned on page E-1 of Reference (3). That is a very conservative assumption. .

Let us assume that we can overcome all these problems; how do we determine how long the valve will last? It is impossible to start or turn off the flow without the valve hitting the stop a few times. The questjon is how much is tolerable. In principal, I guess one could get the PSD of ,

the vibration amplitude, calculate the kinetic energy of the gate at each impact and determine the damage done if all that kinetic energy went into yielding the stop or stud or both. I think .that is a very conservative procedure.

Perhaps a factor, much less than 1, could be found in the literature for the " efficiency" of the impact so that one could justify reducing the

, damage per impact. I suspect that measurements of the right kind have been made, but I didn't look for them.

In sumary, I think you can confidently license the plant if the l following conditions are met:

1. The L/D from the nearest upstream fitting to the gate is greater

! than 6.

2. The velocity is greater than 1.2 times the velocity calculated from the formula at the top of page B-3 of Reference 3.

If the check valve is closer than 6 L/D's to the nearest upstream fitting, I don't think we know enough to predict whether the installation is safe or not.

If cavitation occurs, the collapse of the resulting vapor bubbles could be quite violent, and I don't think anyone could say whether the l

valve was safe. I don't see why either the check valve or the flow control valve upstream should ever cavitate, during normal operatulon, h.owever.

If an experiment to determine the flow velocity at which the valve is pegged is run full scale with the appropriate upstream geometry but cold  ;

l and the valve performs satisfactorily, I think you can scale that experiment and comfortably if cense the plant. For L/D's less than 6, I find such a test the only convincing justification to license an 4 installation.

I don't think we can calculate whether a valve is safe when the L/D to the nearest upstream disturbance is less than 6 with what we know now.

If you have any questions, feel free to call; I'd be glad to answer them. If you come through Boston, stop by and I can demonstrate our experiment for you. I'm going to make this one of the experiments in our senior undergrcJuate lab and hope to have it running for several years. .

> Sincerely.

? .

6Peter Griffith /

Consul tant PG/jg

References

1) Milne-Thompson, L.M., Theoretical Hydrodynamics, 2nd edition, McMillan Co., New York,1950, p. 229,

2) Patton, Kirk T., " Tables for Hydrodynamic Mass Factors for Translational Motion," ASME paper 65-WA/UNT-2,1965.

3) Chiu, C. and Kalsi, M.S., " Failure Analysis of Swing Check Valves,"

Feb. 24, 1986 revision.

4) " Loss of Power and Water Hammer Event at San Onofre, Unit 1, on November 21, 1985, NUREG-1190, January 1986.

5) Rouse, H., Advanced Mechanics of Fluids, J. Wiley & Sons,1959, p.196.

6) Hinze, J.0., Turbulence, McGraw-Hill, 1959, p.404,

7) Bleyins, R.D., Flow-Induced Vibration," Van Nostrand Reinhold Co.,

1977, p. 15.

8) Schlicting, H., Boundary Layer Theory, Pergammon Press,1955, p. 576.

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A*(24)

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t .

Check Valve Dynamics

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Jennifer Snopkowski Peter Griffith 1 April 1986 Abstract A two inch diameter check valve was tested in water to find the range of velocities and L/D's from an upstream disturbance when the valve was always (1) pegged, (2) swinging and hitting (tapping), and (3) swinging free. The formula for oegging from the Chiu-Kalsi report was found to predict the pegged velocity quite well when the flow was fully developed (i.e. L/D > 6).

For L/D < 6, the valves tapped at velocitie: well above that given by the Chiu-Kalsi formula. Tapping was found to persist down to about half the maximum tapping velocity for fully developed flow, independent of L/D from an upstream disturbance.

4 l

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I. Introduction Check valves used in a reactor feed-water delivery system are designed to prevent the backflow of steam. Failure of the check valves can result in a water hammer, causing severe damage to the feed-water system. An actual water hammer occurrence due to check valve failure occurred and is reported in reference 4 of the letter.

A diagram of one of the check valve installations in the system which experienced failure is shown in Figure 1. The failure is a result of repeated tapping of the check valve against the stop. This tapping is caused by disturbances in the flow over a certain range of velocities.

The purpose of this experiment was to find out what the range of velocities was which caused an experimental check valve to tap against the stop. This report compares the maximum water velocity at which tapping occurred with an analytical method developed by Chiu and Kalsi given in reference 3 of the cover letter.

The following question, presented in the work statementiwill be addressed:

"Is the approach taken to model the local turbulence effects sufficient to account for all expected effects (e.g. cavitation and vortex shedding) on the valve disks for the old valves and the replacenient valves such that it can be expected that the replacement valve disks will be held firmly against the open stop for the postulated flow conditions? If not, provide a discussion of the uncertainty resulting from this analytical approach." The results reported here are the basis for the recommendations in the cover letter.

II. Apparatus and Experimental Procedure The apparatus was set up as shown in Figure 2. A diagram of the experimental system is given in Figure 3. The check valve was placed downstream of a plastic insert simulating a valve which was used to produce a disturbance in the flow. A tracing of the insert is shown in Figure 3. The distance L shown on the diagram was varied to test the effects of L/D change on the range of critical flow velocities. In this apparatus, D is the inside diameter of the pipe and is equal to 2.062 inches. The plastic insert was removed to determine a range for an asympotoic value of L/D.

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. l The check valve used in the experiment is shown in Figure 4 The total

- weight of the gate, including the arm, was .471 lb,. The details are given on Figure 4 To take this picture, the bonnet on the check valve was removed and replaced with a plastic window which was screwed into the thread originally holding the bonnet. It was easy to see where the gate was through this window and whether it was pegged or not. The window is visible in the photographs of Figure 2 and Figure 5. Figure 5 shows the gate pegged and is photographed through the window. The windows at the ends of the horizontal run shown on Figure 1 were not needed.

III. Results A plot of flow velocity versus L/D is given in Figure 6. The area used in the velocity calculations was based on pipe diameter and is equal to 3.34 in 2. The lower half of the graph shows points where the valve oscillated in the floe without tapping the stop. It can be seen that the transition to velocities where tapping begins is not dependent on L/D. Above this transition velocity, the valve repeatedly tapped against the open stop.

The frequency and intensity of the tapping increased with increasing veloci ty.

The transition where the valve no longer taps aginst the stop but is pegged against it is an important one. If the velocity is kept above this transition velocity, the valve will be held stationary against the stop by the flow, and there is little possibility for failure. At L/D values above 6, the velocity at which the valve was pegged is fairly constant. The far right of the graph of Figure 6 shows the minimum tapping velocity for a fully developed flow. Below an L/D of 6, however, the pegging velocity dramatically increases and is off scale for L/D values less than about 3.

The frequency of tapping is high and the severity of oscillations large for the low L/D values.

The analytical method mentioned in the Introduction and found in Reference 2 was followed for the equipment used in this experiment. The calculations are given in Appendix A. The minimum velocity needed to keep the valve pegged was determined using this method. It was 6.75 ft/sec and is shown in

Figure 6. This valve clearly behaves as predicted for L/D values greater o than 6. Below this value, however, this method fails.

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An attempt was made to find the approximate damping ratio experimentally by disturbing the gate and watching it respond. As far as could be seen, this gate was more than critically damped. One could not see any overshoot at all for any gate position. The measurement was entirely visual however and hardly one of high precision. Nonetheless, this gate appears heavily damped and one would not expect it to display any resonance due to vortices or turbulence generated at the disturbance upstream.

When there was no disturbance upstream, the tapping was easy to hear. ,I t ,

could be heard more easily through a screwdriver held against the body of the check valve with the handle held against the ear. With the disturbance upstream, however, the flow noise overwhelmed the tapping and I (PG) couldn't hear the tapping at all even though I could see the valve swinging and hitting.

IV. Conclusions

1. The velocity at which the valve gate is always pegged is well predicted by the Chiu-Kalsi formula for a fully developed flow. This means the L/D is greater than 6 for the distance from an upstream disturbance to the gate.

l 2. When the L/D is less than 6 from the nearest upstream disturbance to the l gate, the valve taps for velocities much greater than that calculated using tha t. formula.

3. The valve swings free without tapping for velocities equal to about half of that given by the Chiu-Kalsi formula.

3 4 The gate in the 2" 10 valve used in these experiments appeared to be heavily damped for all positions. No resonance was observed or expected.

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5. The fact that a formula developed for a valve of a similar type but of a dif'erent geometry works so well it leads one to think it would work on othei valves too.

1 4

e Appendix A. Pegging Velocity Calculations The Chiu-Kalsi formula from the top of PB-3 of reference (3) of the letter is:

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(W .5 W )(b)(g) .5 y, .

- KpA sin2 g ,

In this formula V = velocity, [f t'/sec]

W = mass of gate plus arm = .471 lb m

W, a mass of arm = .164 lb, b = bouyancy factor = .883 *

= 2 g acceleration of gravity = 32.2ft/sec k = empirical constant = 2.21 3

o =

density of water = 62.3 lb,/ft A = pipe area = 3.34 in2 = .0232 ft2 6 = angle of valve from the horizontal when pegged = 16.0*

The resulting minimum pegging velocity is V = 6.75 ft/sec This formula is derived from a force balance on the gate where the jet force holds the gate up against gravity which is tending to make it fall off the stop. It is the maximum tapping velocity. The constant 2.21 given as K above was determined from the minimum acceptable operating velocity provided I

by one of the valve manufacturers.

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NOTES: 1. MAJOR TURBULENCE COMPONENTS ( PRESSURE HEDUCING CONTROL VAL.VE. AND AN EXPANDER) 1MMEDIATELY UPSTREAM.

2. ONI_Y IxD STRAIGHT PIPE LENGTH AFTER iIIGIi 1URBULENCE COMPONENTS.

FIGURE 1. 10" GOO # CHECK VALVE INSTALLATION (1 WS - 345 346, 398)

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ENCLOSURE 8

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ENCLOSURE 8 Prof. Peter Griffith 77 Massachusetts Ave. i Room 7-044 Cambridge, MA 02139 1

Dr. Charles Nalezney 1

. EG4G Idaho, Inc.

P.O. Box 1625 Idaho Falls, ID 83415

Dear Chuck,

)

This is the review of the final Report " Performance Tests on the Feed Water Check Valves for the San Onofre Unit 1 Nuclear Power Plant, Phase A" by J. Paul Tullis and William J. Rahmeyer dated April 1986.

I have no disagreements with their measurements or interpretation of them. Because the tests were run in low pressure, low temperature water and applied to high temperature, high pressure water, some extrapolation of the test results is needed. Let me touch on two issues that must be extrapolated, the maximum tapping velocity, and the cavitation limits.

A small extrapolation of the tapping velocity measured is necessary because the water density in the test is higher than in the application.

Equation (3) of the report does this and I agree with the use of this equation in this problem. It is just what I would have done. Used with a .

modest safety factor, say 1.2, these test can be used to set the minimum velocity at which these values are allowed to run during steady operation.

In later work, they might want to correct the buoyant force of the gate for f the different water density but that is a trivial improvement. In any I case, the valves should not be installed with less than 6 L/D's to the l nearest upstream disturbance.

The other extrapolation was for the cavitation index. This is given as equation 4. This is a commonly accepted formulation for extrapolating cavitation data taken at one condition to another. (See Streeter, V.L.,

" Handbook of Fluid Dynamics," First edition, McGraw-Hill,1961, pp.12-17.)

The value at which cavitation occurs can be greater than the value calculated for this valve 1.34, and is a function of geometry. Though !

l see no reason for alarm, it would be good, in subsequent tests, to see if there is any cavitation. I, frankly, find it hard to believe any valve manufacturer would design a valve that would cavitate under design conditions. It would greatly reduce the life of the valve. The cavitation index of 1.34 is large enough so that there may be no cavitation at all.

The fact that this valve failed only when operated at less than design velocity for a year after apparently operating for years at the design velocity makes me think that cavitation is no problem. The valve should cavitate most at its maximum velocity. If it worked for years at full load I fail to see how cavitation could cause problems at part load. In the phase two tests, however, I think finding the cavitation limits for this system of flow control valve an new check valve is a worthwhile goal. I think this problem can be laid to rest once and for all. My guess is that you will never have cavitation in the operating range for the valve.

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. They could take this valve into the cavitating range by increasing the

, g water temperature or, perhaps, decreasing the back pressure. I would like di to see one of those things done.

There is one item that I would like to raise that might be settled in l the phase two experiments. The description of the tapping in this report makes it hard for me to believe that it could cause the damage that led to the valve's failing. Whether the severe damage in the San Onofre installation was due to the check valves closeness to other fittings or the design of the check valves themselves is not clear. I'd like to see that <

settled. I would also like to see some damage measurements made so that an I inspection schedule can be set up and approximate times at which the valves can be run at less than design velocity determine.

Let me now summarize my findings.

1) The tests and extrapolation procedures used to define the allowable conditions for the Atwood and Morrill swing check valves are both satisfactory.

2) I would like to see the flow limits presented in this report checked against the minimum velocity fannula in Chiu and Kalsi report to see what an allowable safety factor for the Chiu and Kalsi formula is. This would help you evaluate other installations.

3) I would like to see the cavitation limits determined for this flow control valve-check valve installation. I suspect you have no cavitation under normal operating conditions, and this is no problem. One measurement would show this.

4) I would like to see some kind of deformation or wear measurement made so that the life of the valves when they are tapping could be estimated. I'm not sure how to do this but using a soft stop, i

made of lead perhaps, would give accelerated wear and allow use to I estimate the life. Probably penetration hardness is the scaling parameter. This would tell us how often to inspect the valves'and how long, during startup for instance, we could run at reduced velocity.

I If you have any questions, I'd be glad to talk to you. Enclosed is an invoice for the time I spent on this review.

l Sinc rely, D .

/>A Peter Griffith Consultant PG/jg B*21 4

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