ML20136E398
ML20136E398 | |
Person / Time | |
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Issue date: | 10/30/1985 |
From: | Advisory Committee on Reactor Safeguards |
To: | Advisory Committee on Reactor Safeguards |
References | |
ACRS-2360, NUDOCS 8601060536 | |
Download: ML20136E398 (14) | |
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SUMMARY
/ MINUTES OF THE OCTOBER 8, 1985 MEETING '
0F THE ACRS SUBCOMMITTEE ON RELIABILITY ASSURANCE (VALVES)
WASHINGTON, DC A meeting was held by the ACRS Subcommittee on Reliability Assurance on October 8, 1985. The purpose of the meeting was tr ? ii Wre tFo sub-committee's investigation of valve reliability. A risk perspective on valve performance was sought. Notice of this meeting was published on Tuesday, September 24, 1985 in the Federal Register (Attachment A).
Attachment B is a schedule of presentations. Attachment C is a listing of meeting slides and handouts on. file in the ACRS Office. The meeting was entirely open to the public. Richard Major was the cognizant staff member for this meeting.
Participants ACRS NRC STAFF C. Michelson, Chairman E. Brown D. Ward, Member G. Weidenhamer G. Reed, Member J. Vora J. Ebersole, Member K. Seyfrit H. Jones, Consultant I. Jackiw R. Major, Staff P. Wohld M. De, Fellow R. Kiessel J. Flack, Fellow D. Rasmuson J. Jeffries, Fellow J. Page OTHERS Va. Power Toledo Edison R. Nicholls J. Ewald R. Hardwick, Jr. S. Wideman N. Bonner J. Elfstrom, B&W W. Johnson, B&W H. Wise, B&W P. Riehm, KMC A. Charbonneau, M0 VATS Inc.
R. Knowles, MOVATS Inc.
J. Milito, Phila. Electric Co.
B. Curry, Phila. Electric Co. .
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RELIABILITY ASSURANCE (VALVES) 2 October 8, 1985 Meeting P. Slane, Southern Co.
D. Warsing, Limitorque Corp.
D. Carapbell, JBF Associates, Inc.
D. Eissenberg, Oak Ridge National Labs R. Prato, PP&L C. Pindzia, Serch, Bechtel Power Corp.
S. Hart, Duke Power Co.
H. Filacchione, NUS Corp.
J. Nurmi, QATEL D. Fawnley, Ga. Power Co.
Perspective on'the Risk Attributed to Valves Mr. Dale Rasmuson, RES, introduced this topic. He noted that qualita-tive insights gained from PRAs should be viewed as more important than bottom line numbers generated through PRAs. One observation was that research into equipment aging and root equipment failure causes were starting to converge. Other ongoing research includes a reliability assurance effort and a closely related effort that evaluates technical specifications. One result which is proving to be useful is calculating the importance of an individual component in a probabilistic risk analysis. In the case at hand some insight to valve importance was sought through.the ANO-1 IREP study.
Mr. David Campbell, JBF Associates, Knoxville, discussed valve-importance gained from insights from the ANO-1, IREP probabilistic risk assessment. He noted software has been developed for calculating the importance of various component types within nuclear power plant PRAs.
The same methods can be used to calculate the importance of various root causes of failures in PRAs.
In this study valves were broken down into five classes: motor-operated
. valves, air-operated valves, relief valves, check valves, and manual valves. Root causes of failures were not considered in this effort.
i Two measures of importance were used. The first, Fussell-Vesely, is the fraction of the core melt ~ frequency that involves failure of any component in the specified group. Any cut set that contains a specific l
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RELIABILITY ASSURANCE (VALVES) 3 October 8, 1985 Meeting valve failure is used in calculating core melt frequency and the importance of the component. A second measure of importance is Birnbaum's. This is defined as the sensitivity of the core melt frequency to changes in the failure probability of components in the specified group. Both of these methods rank the importance of the various valve types about the same.
In this study motor-operated valves are the most important valve type.
This type has the greatest effect on core melt frequency. The single most important valves are the pressure relief valves in the ANO primary system, but for the rest of the modeled plant sytems motor-operated valves (M0Vs) tend to be most important. An upper bound for contri-bution to core melt frequency for MOVs was given as between 30-35%.
This is probably a factor of one and a half to two above the actual contribution to core melt. A more realistic estimate of contribution to core melt frequency from MOVs is about 15%. This figure represents all cut sets that contain MOV failures, but may indeed contain other component failures. It was suspected that this result would be typical of other results derived from PWR PRAs.
In the J8F study the relative importance of valves in various systems is computed. As a class of valves MOVs are the most important followed by, in order, manual valves, check valves, and air operated valves. The pressure relief valves are very important, contributing in the neighborhood of 10% to core melt frequency.
Mr. Ward suggested areas for further study including:
l What effect would a factor of ten in valve failure frequency have on the overall core melt frequency?
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e RELIABILITYASSURANCE(VALVES) 4 October 8,1985 Meeting There are limitations to the IREP study--common cause failures are an example; what effect does this have on the results of the valve importance study?
What effect would giving credit for recovery from valve failures have on these results?
How generically applicable are these results?
Mr. Campbell expressed his view that failure of MOVs is a significant i (20%) contributor to core melt frequency. He also noted there was plenty of plant experience to indicate that valves are important. l Discussion with Limitorque Corp. - Dan Warsing Mr. Warsing explained that Limitorque has been manufacturing valve activators for the past fifty years. He noted that feedback from users on' field experience is generally poor. Limitorque does offer training programs. One individual at Limitorque presents seminars related to maintenance at various power plants. Basic disassembly and reassembly of the activator is also taught in classes given at Limitorque's Lynchburg, Va. and Chicago facilities.
Limitorque has methods for trying to improve the reliability of the.fr product. A group within the company investigates all field service reports that are received. The aim is to generate product improve-ments. Field service reports are filed by Limitorque field service engineers. There is approximately one and one-half years of data in this system. This data relates to all Limitorque applications.
It was also noted that Limitorque, as a manufacturer, has a difficult time receiving NRC, INPO, EPRI, etc. experience reports. Reports are not routinely copied to Limitorque. These reports on occasion are made available to Limitorque through a third party, usually one of their
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RELIABILITY ASSURANCE (VALVES) 5 October 8, 1985 Meeting customers. At the present time Limitorque does not have a specific reliability target. They can and do respond to specific requirements; however, the marketplace is usually the driving force for improvements.
A problem area was explored by the subcommittee related to overall responsiblity for valve performance. Mr. Warsing explained that there is some lack of communication between valve manufacturers and Limitorque. Each manufacturer adds extra conservatism based on worst case scenarios. At present, there is not one focal point for the entire area of valve reliability.
M0 VATS Experience - Philadelphia Electric Co. - Brian Curry Mr. Curry discussed experience with M0 VATS testing at the Limerick generating station. Mr. Curry has had 13 years of experience with motor-operated valves at the Peach Bottom and Lirarick stations. He began his presentation with a review of the operation of a Limitorque actuator.
At Limerick, M0 VATS was used in combination with other test systems. It was found that many problems thought to be torque-switch related were really mechanical problems. It was also noted the M0 VATS system has not been used to set limit switches.
M0 VATS was valuable in the initial problem determination stage by providing a dynamic record of the actuator operation. After the initial problem identification, problems could frequently be identified by other means. M0 VATS will be used in the future at Limerick if a maintenance activity disturbs a torque switch mounting, spring pack condition, or if the valve stem or stem nut is replaced with a unit manufactured by other than the original manufacturer. It will also be used if a problem occurs that cannot be resolved by analysis. It is felt M0 VATS is a t developing technique that will yield further knowledge of operator and l
valve problems.
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0 RELIABILITY ASSURANCE (VALVES) 6 October 8, 1985 Meeting Mr. Curry believes many valve operator reliability problems are due to the lack of understanding of Limitorque operator operation and training on the part of plant maintenance personnel. Current failure reports on Limitorque operators do not contain enough information to detemine the true root cause of failure.
M0 VATS has identified previously suspected but unverified problems in Limitorque motor operators. It has identified deficiences in valve manufacturer's sizing and setting calculatio's.n Use of M0 VATS by the valve manufacturers should allow more accurate sizing and setting of Limitorque motor operators. Confimation of the'se problems allows identification and correction of problems to be perfomed more easily.
M0 VATS use will be contined at Limerick; training programs are being based on the knowledge gained from M0 VATS. M0 VATS also adds reliability through the indirect method of teaching operators how to identify motor operator problems.
PECO owns their M0 VATS equipment.
Mr. Curry felt there was an interface problem between Limitorque and valve manufacturers. He though a users group might help correct this problem.
M0 VATS Experience - Virginia Power - R. Hardwick R. Nicholls The M0 VATS system was first described to Virginia Power in 1983.
Currently Virginia Power has a service contract with MOVATS to assist their maintenance department with motor-operated valve problems. The major attraction of this system was that, as found, conditions of the motor operator could be documented. A review of this documentation i
could help in determining any necessary corrective actions.
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RELIABILITYASSURANCE(VALVES) 7 October 8, 1985 Meeting With the specific information that can be presented as a thrust / switch actuation signature a number of degradations can be identified. These include: valve mechanical ~ wear, operator mechanical degradation, operator gear wear, motor electrical degradation, improperly set bypass switches, improperly set torque switches, backseating conditions, excessive stroke time, inadequate load available to operate valve under accident or design conditions, improper alignment of operator to valve,
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excessive packing loads, and thermal overload trip setpoints.
From 1983-85 M0 VATS assisted in the corrective maintenance effort on a total of 35 MOVs. The M0 VATS experience provided added insight on motor-operated valve maintenance and additional details to maintenance procedures.
It was also noted that a rotating equipment signature analysis program is under way for the North Anna Station and is planned for the Surry Station.
Evaluation of the Motor Operated Valve Analysis and Test System (M0 VATS) - Oak Ridge Report Introduction and Brief Review of NRC Research Related to Va've Reliability - J. Vora, G. Weidenhamer, RES J. Vora, RES, explained that approximately $400,000 is being spent on research related to aging characterization qualification and degradation monitoring in FY 1985. This number will increase through FY86 and FY87 to $500,000 and $650,000 respectively. He noted that as far as the evaluation of MOVATS is concerned the objective of this program is to
, learn exactly what the equipment can provide about safety-related MOV operational readiness above and beyond currently used ASME Section 11 l methods.
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RELIABILITY ASSURANCE (VALVES) 8 October 8, 1985 Meeting Dr. Vora also noted that a report on PORV and block valve experience will be available in several weeks.
Dr. Weidenhamer, RES, discussed work associated with valve operability and reliability being conducted in the mechanical / structural engineering branch. Budgeting for this work is a little over $1 million per year through FY88.
Oak Ridge Presentation - David Eissenberg (ORNL)
Dr. Eissenberg described the nuclear plant aging research (NPAR) program related to motor-operated valve research which has been under way for about two years. The objective of this study was to demonstrate technology for maintaining operational. readiness of motor-operated valves important to safety, The approach has been to characterize how and why MOVs fail in nuclear plant service. It has been to identify and evaluate methods for detecting and trending time-dependent degradation (aging) and other abnormalities that can lead to MOV failures. A technical basis was developed for recommending when and what maintenance actions should be taken based on diagnostics.
Recently, NUREG/CR-4234, Volume 1, Aging and Service Wear of Electric Motor-0perated Valves Used in Engineered Safety Feature Systems of
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Nuclear Power Plants, was published. This study looked at MOV design and technical specification surveillance requirements. It recommends maintenance practices, identified aging-related failures, and identified measurable parameters. Some results of this study include: the predominant causes of failures are torque or limit switch misadjustments or failures, and motor failures; and maintenance practices tended to be aimed at restoring operability rather than identifying and correcting the degradation or abnonnality.
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RELIABILITY ASSURANCE (VALVES) 9 October 8, 1985 Meeting In-situ testing of MOVs in nuclear power plants has been conducted using M0 VATS signature analysis. The objective of this work was to (1) evaluate the capability of M0 VATS to provide useful diagnostic information for determining operatforal readiness of MOVs beyond that currently provided by ASME Section XI and (2) to identify and characterize types of abnormalities found in some selected operational MOVs. M0 VATS was hired as a subcontractor and tested 36 valves at four nuclear plants. These valves were considered operational by the utilities.
It was noted that the M0 VATS system is better than ASME Section XI in determining operational readiness. It is felt that operational readiness can be predicted more directly from monitoring and trending abnormalities leading to failure. (ASME Section XI does not measure operational readiness.) M0 VATS can provide information regarding operational readiness beyond that obtained by Section XI tests by identifying and quantifying incorrect adjustments which can cause failures under some anticipated operating condi.tions, i.e., incorrect setting of limit switch, and degradations which can lead to failure if allowed to continue, i.e., bent stem.
Some drawbacks to the M0 VATS system include: some degradations can not be detected by M0 VATS signatures, signatures at ambient conditions may not provide information about perfonnance under operating conditions, periodic testing during shutdown may not be sufficiently frequent to detect degradation, and manual installation and removal of the test device can lead to excessive radiation exposure.
Davis-Besse Event of June 9,1985, Complete Loss of Main and Auxiliary Feedwater with Emphasis on Valve Performance - J. Page, MEB, NRR Mr. Page noted that, following loss'of main feedwater, auxiliary feedwater was unavailable because the isolation valves had improperly L- _ _ ._. . _ __
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RELIABILITY ASSURANCE (VALVES) 10 October 8, 1985 Meeting set ifmit and torque switches and would not reopen after an inadvertent actuation. In addition, lack of delta pressure testing contributed to the failure problem on some valves and an unknown phenomenon caused increased opening torque requirement in one case. Correction actions include setting the bypass limit switches at 20% of full disk travel using MOVATS and increasing open torque switch settings to maximum which precludes valve damage.
The PORV at Davis-Besse stuck open during the third actuation. It is suspected that foreign material was caught in the pilot disk and seat.
The Staff noted the PORY had not been stroke tested since September 1, 1982. This could have contributed to valve degradation.
A number of main steam safety valves failed +o perform adequately; they chattered. A number of these valves are being laboratory tested to determine causes for their failure.
One of two air-operated atmospheric vent valves failed to reseat. An electrical control system problem is suspected as the cause.
A turbine bypass valve that was in service had failed (disk separated from stem) prior to the accident. During the accident the valve was damaged further (valve yoke casting broken).
Nuclear Industry Valve Qualification Process - J..Jeffries, ACRS Fellow Mr. Jeffries explained several reasons why the nuclear industry valve :
qualification process might be fragmented. These include (1) poten-tially inadequate valve specifications, (2) the absence of a valve prob- ;
lem evaluation center, (3) the absence of an industry oversight working group responsible for directing a coordinated engineering effort examining valve problems, (4) insufficient intercomunication, (5) absence of a full-scale test facility, (6) lack of adequate valve
RELIABILITYASSURANCE(VALVES) 11 October 8, 1985 Meeting maintenance criteria, and (7) the inability or unwillingness of anyone to build and maintain a testing facility. He noted other industries rely on full-scale testing of valves. INP0 was suggested as a central coordinator for vilve problem.
Final Session:
The subcommittee decided to present a compilation of their findings to the full ACRS during the January 1986 general meeting. Chaitaan Michelson requested two hours of Connittee time. Currently, Mr. Michelson intends to draft a . report sunnarizing the subcommittee's findings.
The meeting was adjourned at 5:30 p.m.
NOTE: A complete transcript of the meeting is on file at the NRC i Public Document Room at 1717 H Street, N.W., Washington, D.C.
i' or can be obtained at cost from Ace Federal Reporters, Inc.,
444 North Capitol St., Washington, D.C. 20001.
[ Telephone: (202) 347-3700]
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._38730 Feder:1 Register / Vol. 50 No.-185 / Tussdzy, SeptImbIr 24,1985 / N: tic:s A .
Advisory Committee on Reactor Dated September 28,1985.
Safeguards, Subcommittee on
- Morton W. IJbarkia, scheduled meeting to be advised of any
. changes in schedule, etc., which may Reliakitity Assurance (Valies); Meeting Assistant becutive Directorfor Project have occurred.
Review. ,
The ACRS' Subcommittee on Dated: September 18,1985.
Reliabihty Assurance (Valves) will hold p Doc.85-22a20 nled S-23 as; a;45 am)
Morton W.tabarkin, a meeting on October 8,1985, Room sa m ecaos m a ,
3,,j,,,,,3,,,,j,, pj,,,,,,f,,p,,j,, 1 1167,1717 H Street. NW, Washington, Revie r.
D.C. Advisory Committee on Reactor p Doc.sw2a21 nIed m us am]
The entire meeting will be open to Safeguards, Subcommittee on Safety ****C"'**'*"
public attendance. Philosophy, Technology, and Criteria; The agenda for the subject meeting " 9 shall be as follows: Advloory Committee on Reactor The ACRS Subcommittee on Safety Safeguards, Subcommittee on State of Tuesday, October 8,1965-dJO o.m. Philosophy Technology, and Criteria Nuclear Power Safety; Weeting untilthe conclusion of business. will hold a meeting on October 9,1985.
N %e Subcommittee will continue Room 1167,1717 H Street. NW, The ACRS Subcommittee on State of discussions on valve reliability. A risk W Nuclear Power Safety will hold a .
perspective on valve performance will , , pm eting will be open to meeting on October 9,1985 Room 1187,
, be sought Also to be studied is the pu aed 1717 H Street, NW, Washington. DC.
}, impor*ance of valves from a safety enda for he subject meeting ne entire meetin standpoint. shall be as follows: public attendance. g will be open to Oral statements may be presented by Irednesday, Octobers, 1965-120p.m. The agenda for the subject meetig
, , members of the public with the untilthe conclusion ofbusiness. shall be as follows:
The Subcommittee will continue the trednesday October 9,1985-&JOo.m.
aancurrence of the Subcommittee review of the two. year trial use of the Chairman; written statements will be . untilthe conclusion ofbusmess proposed Safety Goal Policy, the future The Subcommittee will discuss the accepted and raade to the Committee, use of safety goals, and containment draft report on the " State of Nuclear Recordings will be permitted only during performance guidelines. Power Safety"in preparation by the those portions of the meeting when a Oral statements may be presented by Subcommittee, transcript is being kept, and questions members of the public with the may be asked only by members of the Oral statements may be presented by concurrence of the Subcommittee members of t5e pubhc with the . -
Subcommittee,its consultants, and Staff. Chairman; written statements will be concurrence of the Subcommittee Persons desiring to make oral accepted and made available to the
, Chairman: written statements will be statements should notify the ACRS staff Committee. Recordings will be permitted accepted and made available to the member named below as far in advance only during those portions of the Committee. Recordings will be permitted t as is practicable so that appropriate meeting when a transcript is being kept, only during those portions of the 1 crrangements can be made. and questions may be asked only by meeting when a transcript is being kept.
During the initial portion of the members of the Subcommittee,its and questions may be asked only by i meeting. the Subcommittee, along with consultants, and Staff. Persons desiring members of the Subcommittee,its
! cny ofits consultants who may be to make oral statements should notify l present, may exchange preliminary the ACRS staff member named below as consultants. and Staff. Persons desiri to make oral statements should notify
- views regarding matters to be farin advance as is prawticable so that the ACRS staff member named below as g considered during the balance of the approprite arrangerients can be made. far in advance as is practicable so that -
meeting. During the initial portion of the appropriate arrangements can be made.
i t meeting, the Subcommittee, along with During the meeting, the Subcommittee The Subcommittee will then hear any of its consultants who may be i
presentations by and hold discussions will exchange views regarding matters -
- present, may exchange preliminary Pertaining to the draft Subcommittee with representatives of the NRC Staff, views regarding matters to be its consultants, and other interested report on the state of nuclear power I considered during the balance of the safety.
persons regarding this review meeting.
Further information regarding topics The Subcommittee will then hear The Subcommittee will then hear presentations by and hold discussions ta be discussed, whether the meetings Pfesentations by and hold discussions with representatives of the NRC Staff,
- has been cancelled or rescheduled, the w:th representatives of the NRC Staff, its consultants, and other interested
,j Chairman's ruling on requests for the, its consultants, and otherinterested persons regarding this review.
persons regarding this review,
- cpportunity to present oral statements Further information regarding topics cnd the time allotted therefor can be Further information regarding topics to be discussed, whether the meeting cbtamed by a prepaid ielephone call to to be discussed, whether the meeting has been cancelled or rescheduled, the *
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the cognizant ACRS staff m ember, Mr. has been cancelled or rescheduled. the Chainnan's ruling on requesta for the
.j Richard Major (Telephone :02/634-1414) Chairman's ruling on requests for the opportunity to present oral statementa
- between 8
- 15 a.m. and 5
- 00 mm. Persons opportunity to present oral statements and the time allottre J erefor can be
,i planning to attend this merdng are and the time alloted therefor can be urged to contact the above named obtained by a prepared telephone callthe to cognizant obtainedACRS by a prepa.o telephone call to }
staff member, Mr.
the cognizant ACRS staff member, Dr. ;
Individual one or two da,s before the' Anthony Cappucci (telephone 202/834- t scheduled meeting to be advised ofbetween ariy ' Richard Savio (telephone 202/634-3267) - 3287) between 8:15 a.m. and 8:15 a.m. and 5 00 p.m. Persons I changes in schedule. r.tc., which may ' planning to attend this meeting are Persons planning to attend this m'eeting 1 l have occurred. - - are urged to contact the above named 5
urged to contact the above named
- 'f; a. - individual one or two days before the t
- individual one or two days before the scheduled meeting to be advised of any 9
- ATTACHMENT A
B OCT/8/ AGENDA:JdAN4
. REV.
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TENTATIVE SCHEDULE MEETING 0F THE ACRS SUBCOMMITTEE ON
- ' RELIABILITY ASSURANCE (VALVES)
OCTOBER 8, 1985 WASHINGTON, D.C.
8:30 AM 1. . Chairman's Introduction ,
8:40 AM 2. Perspective on the Risk Attributed to Valves (I hr,30 min)
- a. Introduction and brief description of reliability assurance research - G. Burdick, RES
(10 min) 10:20 AM 3. Discussion by Limitorque - D. Warsing (1 hr)
- Field experience
- Methods to improve reliability
- Experience with M0 VATS system
'11:20 AM 4 Experience of M0 VATS Users (2 hrs)
- a. Philadelphia Electric - Brian Curry 12:20 PM ***
LUNCH ***
1:20 PM b. Virginia Power - Robert Nicholls 2:20 PM 5. Evaluation of the Motor-Operated Valve (I hr, 30 min)
Analysis and Test System (M0 VATS)
- Oak Ridge Report a) Introduction and brief review of NRC research related to valve reliability - J. Vora (tentative) '
b) Oak Ridge Presentation (Ihr) 3:50 PM *** 8REAK * * * (10 min) 4:00 PM 7.. Davis-Besse Event of June 9,1985 Complete (30 min)
Loss of Main and Auxiliary Feedwater with emphasis on valve performance - Joel Page, MEB 4:30 PM 8. Discussion.of Valve Experience in (30 min)
Other Industries - J. Jeffries, ACRS Fellow 5:00 PM ADJOURN ATTACHMENT B l
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ATTACHMENT C MEETING HAND 0UTS AND SLIDES OCTOBER 8, 1985 RELIABILITYASSURANCE(VALVES)
WASHINGTON, D.C.
- 1. Slides, Valve Importances from the AN0-1 IREP, D. Campbell, JBF Associates, 8 slides.
- 2. Slides, Experience with MOVATS, Brian Curry, PECo, 4 slides.
- 3. Slides, Experience in the Use of the M0 VATS System, R. Hardwick and R. Nicholls, Virginia Power, 21 slides.
- 4. Slide, DET/RES Programs, dit VORA - G. Weidenhamer, NRC/RES, I slide.
- 5. Slides, Aging Characterization and Detection of Defects in Valves, J. Vora, EEICB/DET/RES, 7 slides.
- 6. Slides, Nuclear Plant Aging Research (NPAR) Program, Motor-0perated Valve Research, D. M. Eissenberg, Oak Ridge National Laboratory, 33 slides.
- 7. Slides, Davis-Besse Motor-0perated Valve Failures, J. Page, MEB, NRR, 5 slides.
- 8. Draft IE Bulletin No. 85-XX: Motor-0perated Valve Common Mode i
Failures During Plant Transients Due to Improper Switch Settings.
- 9. AE0D/S503, Evaluation of Recent Valve Operator Motor Burnout Events, Special Study Report, AE0D, September 1985 - E. Brown.
Subject:
EPRI Valve Related Research, dated Oct. 1, 1985.
t ATTACHMENT C l
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