BVY-92-124, Responds to Violations Noted in Electrical Distribution Sys Functional Insp Rept 50-271/92-81 on 920706-0807.Corrective Actions:Util Will Evaluate Possible Enhancement of Molded Case Circuit Breaker Program
| ML20116C366 | |
| Person / Time | |
|---|---|
| Site: | Vermont Yankee  |
| Issue date: | 10/30/1992 |
| From: | Pelletier J VERMONT YANKEE NUCLEAR POWER CORP. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| BVY-92-124, NUDOCS 9211030340 | |
| Download: ML20116C366 (9) | |
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VERMONT YANKEE NUCLEAR POWER CORPORATION u s
. !' ' Ferry Road, tirattleboro. VT 05301-7002
[ E NGINE i i N3 OFr ICE ga m ,u w o n ;
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October 30,1992 BVY 92124 U.S. Nuclear Regulatory Commission Washingten. D.C. 20555 Attention: Document Control Desk References a) License No. DPR-28 (Docket No. 50-271) b) Letter, USNRC to VYNPC, Electrical Distribution System Functionalinspection of Vermont Yankee, Report Nu. 50-271/92 81 c) USNRC Memorandum, W.F. Kano to S.A. Varga, ' Meeting Minutes from the Staff's IST Review Meeting with Representatives of Vermont Yankee Nuclear Power Corporation held on October 14 and 15,1987 at Region 1 (TAC 57518)*
dated March 30,1988.
d) Vermont Yankee Inservice Testing Program, Rev.12 e) Supplementary information, H.M. Metell, VY, to N. Della Greca, USNRC, faxed August 13,1992 f) NEMA AB41991, ' Guidelines for inspection and Preventative Maintenance of i Molded Case Circuit Breakers Usod in Commercial and Industrial Applications" l g) USNRC Information Notice 92 51, " Misapplication and inadequate Testing of l
Molded Case Circuit Breakers", July 9,1992 h) Maintenance Request 90-2812 0 NUMARC 90-12, " Design Basis Program Guldelines". October 1990 0 SECY 90 365. Taylor to Commissioners,
- Design Document Reconstitution Programs In". lated by Utilnles", October 26,1990 k) EPRI Report, EPRI NP-7410, Vol 3, Breaker Maintenance
SUBJECT:
Response to NRC Electrical Distribution System Function inspection of Vermont Yankee, Report No. 50-271/92-81, Reply to a Notice of Violation
Dear Sir:
This letter responds to Reference b) which Indicates that certain activities were not conducted in full compilance with NRC requirements. The apparent violations were identified in Reference b) as a result of the NRC Electrical Distribution System Functional Inspection conducted during the period July 6 to August 7,1992 and have been classified as severity level IV. This response addresses the o apparent violations. As suggested la Reference b), unresolved items will be addressed under separate cover, 00A011 e1 9211030340 921030 PDR II I 0 ADOCK O!>000271 PDR j
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VERMONT YANKCC NUCLE AR POWCR CORPORATION U.S. Nuclear Regulatory Commission October 30,1992 Page 2 j APPARENT VIOLATION A Section_5.2.4. Molded Caso Circuit Dreakers ltem 92 81 02 10 CRF 50, Appendix B, Critorion XI, requires,in part, that:"a test program shall be established to assure that all testing required to demonstrato that structuros, systems, and components will perform satistsctorily in service is identiflod and performed in accordance with written test ,
procedures which incorporate the requirements and acceptance limits contained in applicable i design documents. The test program shall include, as appropriate, proof tests prior to installation, pro-operational tests, and operational tests during nuclear power plant... operation, of structures, systems and components." Test controlla required by Section XI of the Yankee Atomic Electric Company Operation Quality Assurance Program Manual (YOOAP 1 A).
Contrary to the above, on August 7,1992, Vermont Yankee did not have a test program for safety related molded case circuit broakers to periodically demonstrate that the breakers would trip within the design time-current band. The trip characteristics of most of these breakers had not boon veriflod by test sinto Vermont Yankoo's commercial operation more than twenty years ago.
RESPONSE
Vermont Yank 6e has reviewed the above item and has noted that:
Vermont Yankee faxed sample MCCD (Molded Case Circuit Breakers) design time-current testing data shoots to the NRC on 8/13!92 (Referenco e). VY collected this data during periodic MCC cubicle inspections per procedure OP 5210 "MCC Inspectioi,s". Speelfically this data included manufactures design verification testing of overcurrent trips in the thermal (long time) and instantaneous regions of the manufacturer's time current curves. OP 5210 provides the procedural controls for receipt inspection, initialinstallation and field testing of all ,
molded caso circuit breakers, and serves as Vermont Yankee's pro 0rammatic control for MCCBs.
- Although the EDSFI Inspection Report (Reference b, Page 24. Para. 3) did not acknowledge the design time-current testing, the report did acknowledge the other programmatic testing performed by OP 5210 which included:
- visual irupection,
' mechanical cycling of the breaker,
- measurement of insulation and contact resistance.
Vermont Yankoo wrote OP 5210 in March 1992 ar( >lemented it during the Spring 92 refueling outaga. OP 5210 is primarily based on the t:rril Report NP 7410 (Reference k) on MCCBs, vendor manualinformation and NEMA AB4- 1991 (Reference f). Subsequently, the NRC issued the MCCB Testing Information Notice on July 9,1992 (Referenco g) which endorsed use of NEMA AB41991 and other industry practicos, it can be seen that Vermont
, Yankee pro-actively addressed MCCB inspection / testing prior to the EDSFl and before the NRC Information Notice was issued.
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WRMONT YANKEE NUCLF AR POWER CORPOR ATION ;
U.S. Nucicar Regulatory Commission l October 30,1992 Page 3 The EPRI report on MCCBs (Referenco k) recommends overcurrent trip testing only for thoso MCCBs which exhibit some abnormality during the Inspection / testing process. For Vermont Yankee 235 breakers woro inspected / tested during the Spring 1992 Refueling Outage (/3 of which were safety related) with 47 breakers overcurrent trip tested. This testing showed that all 47 breakers trippod satisfactorily with no failures to trip within the published manuf acturer's tolerance curves.
- A search of NPRDS data showed, Vorrnont Yankee's history of MCCBs failures are less than the Industry average.
Based on the above, Vermont Yankoo has concluded that the intent of 10 CFR 50, Appendix B, Critorion XI has boon met for Motor Control Contor MCCDs. After performing the above review of Vermont Yankoo's program for MCCBs it is felt that we have an adequate program but it might be enhanced if a representativo sample of MCCDs was timo-current testod each cyclo. Vermont Yankee will evaluate this possible program enhancement which would do some lovel of preplanned breaker time-current testing, provido a sampling system which could be expanded or contracted based on testing results, industry experlence and NRC information. Additional details on Vermont Yankoo's MCCB program are provided in Appendix A.
APPARENT VIOLATION B Section 4.2.2 EDO Air Start System item 92 81 01 10 CFR 50.55a, Paragrsph (g)(4)(ll) toquires that inservico examinations of components, inservice test to verify operational readiness of pumps and valvos whose function is required for safety, and system pressure tests must comply with the latest edition and addenda of Section XI of the ASME Code.
The ASME Boller and Pressure Vessel Code, Sotion XI, paragraph IWV 3520 requires, in part:
" Check valvos shall be exercised to the position required to fulfill their function unless such operation is not practical during plant operation... Valves that are normally open during plant operation and whose function is to prevent reversed flow shall be tested in manner that proves that the disk travels to the seat promptly on cessation or reversal of flow."
Contrary to the above, on August 7,1992 the NRC dotorm!ned that two check valves in the l
emergency diosol generator starting air system woro not testod in a manner that proves that the '
I disk travels to the seat prornptly on cessation or reversal of flow.
RESPONSE
l Vermont Yankee has reviewed the above item and has noted that:
The present method of testing EDG (Emergency Diesel Generator) air riart recolver check valves was reviewed, discussed and agreed to by the NRC in Referenco c). Tnese discussions were extensive and recognized the limitations imposed by the installed configuration. On this basis. Vermont Yankee considers 10 CFR 50.55a and ASME Section XI was met,
VERMONT YANKEE NUCLE AR POWER CORPOR ATION U.S. Nuclear Regulatory Commission October 30.1992 Page 4
- Vermont Yankeo agroos with the NRC EDSFI Inspection Team, that the check valve testing could be enhanced beyond that agreed to in Reference c), but would require a hardware change. We noted to the inspectors that this would take engineering and construction resourcos that require management review.
Based on the above, Vermont Yankee agrees to consider the above mentioned hardwaro changes for our 1994 Design and Construct'an Work Scope. If approved, this change could be installed during the first available EDG outage after completion of tho associated design work. Vermont Yankee sees that no other actions are necessary, unless the NRC is changing 'ts positions stated in Referenco c). Additional details on this subject are provided in Appendix B.
APPARENT VIOLATION C Section 5.4 Fuse Control item 92 81 03 10 CFR 50, Appendix 0. Critorion Ill, requires that measures be established to assure that the design bases, as defined in 10 CFR 50.2, are correctly translated into specification, drawl?gt procedures and Instructions.10 CFR 50.2 defines design bases as tf'at information whicn identifics the specific functions to be performod by a component, and the specific range choson for controlling paramotors as reference bounds for design. Critorion 111 further specillos fMt design changes, including field changes be subject to design control measures commonsuratJ with those applied to the original design.
Ccntrary to the above, on or before August 7,1992, Vermont Yankoo did not have measures, such as instructions, procedures or drawings in all safety related casos, to adoquately identify electrical system fuse types to ensure appropriato replacement.
RESPONSE
Vermont Yankee has reviewed the above item and has noted that the following measures are in place to adequately identify electrical systen fuse types:
Instry_q,tigns and Prpcodures - Vermont Yankee controls fuse replacement by procedure AP 0021, " Work Orders". This procedure, in concert with supporting procedures, specifies strict equipment controls and material replacements, if an exact fuse replacement can not be made, a One for One evaluation is performed using procedure AP 0008, "Orte for One Evaluations",
if a One for One evaluation can not be made, then a design change is initiated by procedure AP 6000, ' Plant Design Change Requests" or AP 6004, " Engineering Design Chango Request
- Sppgifigations l anj;l Drawinag - Vermont Yankee utilizes the Vendor Manual Program, Vendor Specifications, the Procurement Program and controlled drawing information to adoquately identify electrical system fuse types. As noted in the inspection report (Reference b) and Information supplied in Reference e) Vermont Yankee had initiated work in 1989 to further enhanco fuse information listed on drawings that are used by technicians. This work was performed as recommended by Reference 1) and D.
VERMONT YANKEE NUCLE AR POWER CORPORATION U.S. Nuclear Regulatory Commission October 30,1992 Page5 Vermont Yankee also developed a controllod fuse list which listed pertinent fuse information for many commonly accessible fuses 11 was compiled for each panel by wiring diagram review to identify panel fuse location and by field walk downs. An engineering review of each fuso size was performed to verify the fuse size mot the design critoria. Vermont Yankee did not intend to have this list be allinclusive, but to be available as an aid. Maintenance and l&C personnoi, who replace virtually all fuses, have been made aware of the list and may use it or may use appropriato specifications, drarings, Instructions, and procedures as needed. This methodology was demonstrated during the EDSFl when an inspector noted that SLC (Stand.by Liquid Contro!)
fuses were not listed on the fuse list. Vermont Yankee's investigation of an associated Maintenance Request (Reference h) showed the propor Identification of the fuse was provided for SLC fuse replacement. In this example the correct fuse was found within the vendor manual.
Operations personnel replace fuses in urgent situations only, and follow up with a work orcer, The fuse list is a useful tool for these situations. Engineering, by AP 6000, " Plan; 9esign Change Requests
- and AP 6004, " Engineering Design Change Requests" will provide appropria.e drawings, specifications, and procedures for design needs.
The information provided above and in the attached appendices provides a more comprehensive explanation of our programs and practices in the areas of apparent violation than we were able to provide during the inspection period. This information suggests that these areas may not be in violation. Therefore, Vermont Yankee respectfully requests the NRC to reconsider the apparent violations in light of the information provided within this letter. We have found the EDSFI inspection to have been a worth while activity and want to assure you that we are working diligently to address the areas of concern mentioned in the report.
Very truly yours, Vermont Yankee Nuclear Power Corporation pfPR James P. Pelletler Vice President, Engineering cc: USNRC Regional Administrator, Region i USNRC Resident inspector, VYNPS ,.
USNRC Project Manager, VYNPS cw-- r r 'Wa
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i VERMONT YANKEE NUCLE AR POWER CORPORATION APPENDIX A DETAILED RESPONSE TO APPARENT VIOLATION SECTION 5.2.4, MOLDED CASE CIRCUlf BREAKERS ITEM 92 81M This appendix responds to item 92 81-02 via the following subsections:
- Existing Program Description
- Vermont Yankoo Maintenanco Experience with Mo!dod Caso Breakers
- Industry Standards and Practices
- Conclusion EXISTING PROGRAM DESCRIPTION Vermont Yankee's program for periodic testing of molded case breakers is contained in plant procedure OP 5210, MCC Inspoctions, and in Vermont 'vankee's MPAC computerized maintonance program. MPAC speciflos the frequency for inspection o, n4CC cubicles, including molded case breakers. The procedure has specific Instructions for the testing of molded caso breakers which incorporate the recommendations of various manuf acturer's instructions and Industry standards.
This testing includes visualinspection, mechanical testing of the breaker by cycling the breaker handle a minimum of five timos to verify proper latching and opening of the breaker with the handle end by manually actuating the trip shaft, measurement of insulation and contact resistance, and overcurrent inp testing in the thermal ('wg time) and instantaneous regions of the manuf acturer's curves. This procedure was In place and was being utillred in the testing of breakers at the time of the EDSFl Inspection. Therefore, Yvmont Yankee did have a test program for safety related molded case circuit breakers to demonstrate that the breakers would trip within the design time-current band.
Vermont Yankee periorms breaker visualinspection, mechanical operation, and opSrability testing every third operating cycle. Vermont Yankee perfmms overcurrent trip testing of breakers 1) upon receipt inspection,
- 2) upon installation into an apolbetion, and 3) whenever the breaker is suspect for any reason during periodic inspection because of abnormalltles observed in the visualinspection, during mechanical or operational tects.
VERMONT YANKEE MAINTdNANCE EXPERIENCE WITH MOLDED CASE DREAKERS Vermont Yankee, although having hundreds of molded case breakers installed in the plant, does not have a history of breakers prematurely tripping or drifting from the published curvos. The vast majority of breaker failures experienced have been mechanical in nature such as a failure to latch when closing the breaker. As an example of recent experience, of the 235 breakers tested last outage (73 of which were safety related), 47 were overcurrent trip tested. All 47 breakers trip tested satisfactorily with no fwlures or trips outside of published tolerances of manufacturer's curves, Vermont Yankee's experience with molded case breakers does not Indicate a need to increase the frequency of overcurrent testing. This is based on the number of breaker overcurrent device failures experlonced during testing under the currcnt program. Vermont Yankee does not believe increassag the frequency of overcurrent testing is justifies from an experience perspective.
Because Vermont Yankee's program does test breakers periodically under OP 5210 and because Vermont Yankee performs overcurrent trip tests of breakers upon rece8pt inspection and initiallnstallation, and then retests those breakers which show any sign of degradation, Vermont Yankee believes adequate assurance is provided that the breaker will perform its safety function.
VERMONT 'rANKEE NUCLEAR POWER CORPORATION Although it is true that a significant number of breakers in the plant have not been overcurrent trip tested since originalinstallation, the testing that has been performed on these breakers (visual and mechanical testing and post maintenance testing) does not reveal a reason 13 suspect the breakers are degraded.
INDUSTRY STANDARDS AND PRACTICES There i ' Mensu!In tta industry as to wY minimum scope and frequency of testing is necessary to prove the abeg , a breaker to perform its safety funcuon. There also is no established firm technical basis to justify a required scope and frequency of testing in the industry.
There are a number of guidelines arid reports which address the subject and provide recommendations but none firmly establish a requirgd frequency or scop or provide any sound engineering basis for that requireme6t. The following are examples of industry documents which address the testing of molded case breakers:
a EPRI Report EPRI NP-7410 Vol 3, Breaker Maintenance, providas the most in depth discussion of the subject and makes a recommendation in scope and frequency. Nyever, it falls short of providing a sound engineering basis for the recommendation in fact, ira document states in Section 3.0, Periodicity and Program Development Guidelines, that their recommendations are submitted as a baseline and that every plant should adjust the test frequency on the basis-of their experience. It also recognizes that the number of MCCBs at a p; ant are many and resources are limited. It states that "If the program is too aggressive, fewer resources may be avaliaUs for other necessary programs."
b) NEMA Standard AB-4, Guideline for inspection and Preventive Maintenance of Molded Case Breakers used in Commercial and Industrial Applications, addresses scope but does not address a required frequency. In section 4, Preventive Maintenance, it states ?when inspections determine an abnormal condition and indicate possibility of damage, it may be necessary to perform certain maintenance steps. This section is intended to assist the user in performing the a atops." The overcurrent testing of breakers is not included in the scope of this section. The program at Vermont Yankee exceeds this guidance since at Vermont Yankee overcurrent testing is performed if abnormal conditions are identified. .OP 5210 was written based heavily on the contents of this standard for the scope of testing.
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c) The Draft USNRC Generic Letter (which has never been issued) addresses only the overcurrent
- testing of the instantaneous device and consequences of premature tripping due to misapplied breakers or improper trip testing. This letter basically adopted the testing methods of NEMA AB-4. The document stated " addressees are not expected to initiate a comprehensive retesting program to reverify the instantaneous trip feature of MCCBs with safety functions involving this function except for individual MCCB testing in those specific cases in which (1) premature tripping of installed MCCBs is experienced during testing or operations, or (2) other specific information if obtained which may impugn the operability of particular installed safety related MCCBs or the suitability of previously tested, warehoused MCCBs, for installation in safety related applications." Vermont Yankee's program follows this philosophy of testing in the case of (1) or (2) above, d) USNRC Information Notice 92-51, Misapplication and inadequate Testing of Molded Case Cl cult Breakers, was issued instead of the Generic Letter. This Notice, which states the suggestions contained in the Notice are not NRC requirements, addresses the same issues as the generic letter in an abbreviated format. It clso endorses NEMA AB-4 but complicates the matter by waming that application of the manufacturers tolerances "may r.ot always ensure that the MCCBs meet plant specific breaker coordination, circuit protection or technical specification requirements."
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VERMONT YANKEE NUCLE AR POWER CORPOR ATION The Information Notice does not provide any NRC requirements concerning frequency of testing of the overcurrent devices but simply states that testing per Industry recommended practices should provide reasonable assurance that the MCCBs instantaneous trip performance is acceptable for safety related appications.
CONCLUSION The Vermont Yankee program and testing philosophy is consistent with the intent of NRC Information Notice 92 51 to provide reasonable assurance that premature tripping does not occur and that the circult breaker will perform its intended (protection) function. It is also consistent with Section 6.0, Requested Actions, of the proposed Generic Letter, " Premature tripping and inadequate Testing of the Instantaneous Trip Feature of Molded-Case Circuit Breakers MCCBs and Testing of their instantaneous Trip Feature."
Molded case breaker maintenance history at Vermont Yankee does not reveal a significant history of breakers which failed due to trip device malfunction and does not support a conclusion that the existing Vermont Yankee program is inadequater. As in any program, enhancements should be considered. Vermont Yankee will consider a program enhancement which would do some sampling of breaker time-current testing and provide a sampilng sy3 tem which could be expanded or contracted based on test results, industry exporlence and future NRC information.
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VERMONT YANKEE NUCL.E AR POWER CORPOR ATION APPENDIX B DETAILED RESPONSE TO APPARENT VIOLATION B - SECTION 4.2.2u EDG AIR START SYSTEM ITEM 92-81-01 This appendix addresses the adequacy of testing the EDG Air Start System Receiver Check Valves, V72 80A-D. The testing cited is pvrformed undct the Vermont Yankee Inservice Testing (IST) Program
,m (Reference d). The present Second-Interval IST Progrcm is written in accordance with the requirements of
- W Section XI, Division 1, of the ASME Boller and Pressure Vessel Code,1980 Edition through and including "D Winter 1980 Addenda. This is in compliance with 10 CFR 50.55a. Testing requirements for check valves are a provided in Paragraph IWV-3520, with the exercising procedure provided in Paragraph IWV 3522 of Section XI.
g.- In preparation of th's response, Vermont Yankee performed detailed reviews of both the safely function
'%( of check valves V72 80A D and the present testing methods. These reviews indicated that check valves V72-W- 80A-D have a safety function only in the closed position and that the cited testing methods are not in full compliance with the requirements of Paragraph IWV 3522.
Reverse flow testing to prove th11 the check valve disk travels to the seat promptly on cessation or ,
reversal o" flow is not practicable due to the existing system configuration. Allowance for this case is provided in 10CFR50.55a(f)(4), which states that "Throughout the service life of a bolling or pressurized water-cooled nuclear power facility, pumps and valves which are classified as ASME Code Class 1, Class 2, and Class 3 must meet the inservice test requirements, except design and access provisions, set forth b Section XI of editions of the ASME Boller and Pressure Vessel Code and Addenda.,.to the extent practical within the limitations of dasign, goometry and materials of construction of the component." [ emphasis ;dded]
Vermont Yankee and the NRC after extensive discussions, considered the cited testing method to be as effective as the geometry currently permits.
To clearly state this position, Vermont Yankee agrees that relief from the IWV 3522 requirements shouid have been submitted in accordance with 10CFR50.55a(a)(3) and (f). However, Vermont Yankee believes the intent of 10CFRb0.55a was met through the NRC review and appreval of the cited testing method as documented in Reference (c). Reference c) provides questions asked by the NRC relating to IST, and the -
corresponcing enswers. NRC Ouestion No. V7 5 deals specifically with check valves V72 80A-D. The "R' designation on the responso c'enotes that the item was considered resolved and Vermont Yankee's position adequate.
In addition, as part of the preparation of the Vermont Yankee Third Interval IST Program presently underway, Vermont Yankee will review the need for relief from the updated Code requirements and the feasibility of enhanced testing methods.
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