L-07-135, Notification of Potential Part 21 Report Re Poppet Nut and Stem Assembly Degradation on MSIV
| ML072760115 | |
| Person / Time | |
|---|---|
| Site: | Beaver Valley |
| Issue date: | 10/01/2007 |
| From: | Sena P FirstEnergy Nuclear Operating Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| 43679, L-07-135 | |
| Download: ML072760115 (14) | |
Text
1010112007 U.S. Nuclear Regulatory'Comnnmission OperationsCenter Event Report Pqge I General Information or Other (PAR) Event# 43679 Rep Org: FIRSTENERGY NUCLEAR OPERATING CO. Notification Date I Time: 10/01/2007 16:34 (EDT)
Supplier: FIRSTENERGY NUCLEAR OPERATING CO. Event Date I Time: 08/02/2007 (EDT)
Last Modification: 10/01/2007 Region: 1 Docket #:
City: SHIPPINGPORT Agreement State: No County: License #:
State: PA NRC Notified by: PETER SENA III Notifications: RAY POWELL R1 HQ Ops Officer: JOHN KNOKE JERRY DOZIER NRR Emergency Class: NON EMERGENCY PART 21 GROUP EMAIL 10 CFR Section:
21.21 UNSPECIFIED PARAGRAPH PART 21 REPORT - POPPET NUT AND STEM ASSEMBLY DEGRADATION ON MSIV "In accordance with 10 CFR 21.21 (d)(3)(ii), FirstEnergy Nuclear Operating Company (FENOC) is providing the required written notification of a concern regarding the potential for vibration inducted wear on the pilot poppet nut and stem assemblies provided for use in the Beaver Valley Power Station Unit No. 2 (BVPS-2) Main Steam System Isolation Valves [MSIV] that if uncorrected could potentially create a significant safety hazard. FENOC evaluated the concern via a Prompt Operability Determination and concluded that there is reasonable assurance that currently installed valve components at BVPS-2 are operable and plans to replace the affected components during the next BVPS-2 refueling outage."
Valve manufacturer of defective valve components is Weir Valves and Controls USA Inc. in Salem, MA.
The licensee notified the NRC Resident Inspector.
10/01/2007 MON 16:34 FAX [00o2 FENOC RirstEnergy Nuclear OperatingCompany Peter P. Sena II 724-682-5234 Site Vice President Fa: 724-643-8069 October 1, 2007 L-07-135 ATTN: Document Control Desk U. S. Nuclear Regulatory Commission Washington, DC 20555-0001
Subject:
Beaver Valley Power Station, Unit No. 2 BV-2 Docket No. 50-412, License No. NPF-73 10 CFR Part 21 Notification In accordance with 10 CFR 21.21(d)(3)(ii), FirstEnergy Nuclear Operating Company (FENOC) is providing the required written notification of a concern regarding the potential for vibration inducted wear on the pilot poppet nut and stem assemblies provided for use in the Beaver Valley Power Station Unit No. 2 (BVPS-2) Main Steam System Isolation Valves that if uncorrected could potentially create a significant safety hazard. Attachment I provides the details of the notification. FENOC evaluated the concern via a Prompt Operability Determination and concluded that there is reasonable assurance that currently installed valve components at BVPS-2 are operable and plans to replace the affected components during the next BVPS-2 refueling outage.
No new regulatory commitments are contained in this submittal. If there are questions, or additional information is required, please contact Mr. Colin P. Keller Manager, Regulatory Compliance, at (724) 682-4284.
Sincerely, Peter P. Sena III Attachment I - 10 CFR Part 21 Notification Enclosure 1 - 8/2/07 WVC USA Letter Enclosure 2 - 8/14/07 WVC USA Letter
10/01/2007 MON 16:34 FAX I*003 Beaver Valley Power Station, Unit No. 2 10 CFR Part 21 Notification L-07-135 Page 2 C: Ms. N. S. Morgan, NRR Project Manager Mr. D. L. Werklheiser, NRC Senior Resident Inspector Mr. S. J. Collins, NRC Region I Administrator
10/01/2007 MON 16:34 FAX [a004 ATTACHMENT 1.
10 CFR Part 21 Notification Beaver Valley Power Station Unit No. 2 This notification follows the format of and addresses the considerations of 10CFR 21.21 (d)(4)(i)'(viii):
(i) Name and address of the individual or individuals informing the Commission.
Mr. Peter P. Sena, III Site Vice President Beaver Valley Power Station FirstEnergy Corp Nuclear Operating Company (FENOC)
PO Box 4 Shippin'gport, PA 15077 (ii) Identification of the facility, the activity, or the basic component supplied for such facility or such activity within the United States which fails to comply or contains a detet.
Facility:
Beaver Valley Power Station, Unit No. 2 (BVPS-2)
Dockei No: 50-412, License No: NPF-73 Component:
Vendor Designation:
Weir Valves and Controls USA Inc. (formerly Atwood & Morrill Co.)
28" Y Type Globe Valve Model No. 15579-03 Pilot poppet nut and stem assembly BVPSa2 Designation:
Main Steam System Isolation Valves 2MSS-;AOVIQ1A and 2MSS-AOV101C (iii) Identification of the firm constructing the facility or supplying the basic component which fails to comply or contains a defect.
Weir Valves and Controls USA Inc. (WVC USA) 285 Canal St.
Salem. MA 01970-4595
10/01/2007 MON 16:34 FAX [a 065 Attachment 1 10 CFR Part 21 Notification Page 2 of 4 (iv) Nature of the defect or failure to comply and the safety hazard which is created or could be created by such defect or failure to comply.
Nature of defect:
WVC USA has provided information to FENOC that based on vibration induced wear observed on the pilot poppet nut and stem assembly supplied for us6 in the Main Steam Isolation Valves (MSIV) at BVPS-2, a potential exists that may result in a condition that could impact the ability of the affected MSLVs to achieve full closure under design basis accident in the reverse flow direction. The information received from WYC USA is provided as Enclosures I and 2.
Safety hazard which could be created:
The analysis for a postulated main steam system line break accident at BVPS-2 assumes that only the affected steam generator will blowdown.
The concern identified by WVC USA indicates that the reverse flow isolation function of an MSIV may be adversely affected if the vibration induced wear on the pilot poppet nut and stem assembly causes the assembly to lock together. If this were to occur in conjunction with an assumned random single failure, a blowdown of more than one steam generator could occur during a postulated main steam leak break accident and the resultant steam flow would exceed the accident analysis assumptions, thus creating a potential significant safety hazard.
FENOC has evaluated the identified condition, using guidance provided in RIS 2005-20, and in conjunction with the vendor (WVC USA) has concluded that the identified condition is age related and does not impact current plant operation.
(v) The date on which the information of such defect or failure to comply .was obtained.
FENOC received the initial letter from WVC USA on August 2, 2007 and the follow-up letter on August 14, 2007.
(vi) In the caSe of a basic component which contains a defect or fails to comply, the number and location of these components in use at, supplied for, being supplied for, or may be supplied for, manufactured, or being manufactured for one or more facilities or activities subject to the regulations in this part.
10/01/2007 MON 16:35 FAX o006 Attachment I1 10 CFR Part 21 Notification Page 3 of 4 The cdmponents potentially affected at BVPS-2 are the MSIVs on the 'A' and 'Cd' main steam system lines. The presently installed pilot poppet nut and stem assemblies are replacement components that were supplied by WVC USA. FENOC has also received a replacement pilot poppet nut and stem asembly for the 'B' MSIV, however, these parts have not been installkd. The replacement pilot poppet nut and stem assembly design is subject to the concerns identified by WVC USA. The August 2, 2007 WVC USA letter also identifies that South Texas Project Unit Nos. 1 and 2 were riotified by WVC USA as having a similar potential condition. The Beavet Valley Power Station Unit I MSIVs are a different design and are unaffected by the WVU USA notification. FENOC has no other inforniation regarding applicability to other components or facilities.
(vii) The corrective action which has been, is being, or will be taken; the name of the individual or organization responsible for the action; and the length of time that has been or will be taken to complete the action.
After receipt of the infonnation from WVC USA, FENOC entered the concern into the corrective action program. FENOC evaluated the concern via a Prompt Operability Determination, per the guidance in Regulatory Issue Summary 2005-20, and concluded that there is reasonable assurance that cilrrently installed valve components at BVPS-2 in the 'A' and 'C' MSIVs will function as designed. FENOC plans to replace the affected compqnents with a different design that WVC USA developed to reduce vibration inducted wear during the next refueling outage at BVPS-2. These action. will be tracked under the corrective action program. The point of contaw!t for additional information is Mr. Colin P. Keller, Manager, Regulttory Compliance, at 724-682-4284.
(viii) Any advice related to the defect or failure to comply about the facility, activity, or basic component that has been, is being, or will be given to purchasers or licensees, FENOC believes that WVC USA has notified other affected purchasers or licensees of the identified concern, and has no other advice other than what was provided to FENOC in the WVC USA letters provided as enclosures.
10/01/2007 MON 16:35 FAX 0017 Enclosure 1
10/01/2007 MON 16:35 FAX li 0o 8 Weir Valves & Controls USA Inc. Excellent Engineering Solutions 285 Canal SL Yel: 978 744 5690 E v Salem, MA 019704595 iFu 978 741 3626 USA vw.weivlve.cm August 2, 2007 Beaver Valley Power Station P.O. Box 4 Shippingport, PA 15077 I Attn: Manager, Site Ragulatory Compliance Subject Main Steam Isolation Valves tMSIV) Beaver Valley Power Station Unit 2 Gentlemen'.
Weir Valves & ControlA USA, Inc. (WVC) has completed an evaluation (requested by BVPS) of wear and vibration damage to a 1pilot poppet nut and stem for one of the subject valves.
I WVC has concluded that the vibration and wear evident on the above mentioned parts may result in a condition that could irrpact the ability of the MSIV to achieve full closure under design basis accident in the reverse flow direction.)
Refer to the attached Sketches 132 & 3. Specifically, the valve design relies on a sliding axial fit between the valve stem (pca), pilot poppet nut (pc2) and pilot poppet (pc 6) so that during reverse flow closure, sufficient steam flow Is provided to the top side of the main poppet (pc3) through the pilot seat to allow full closure of the main poppet and sub:%quent eating of the skirt seal (pc4). This function is designed to be accomplished by the reverse steam floe forcing the pilot poppet towards the open position throughout the main valve stroke.
As designed, the sprirg (pc5) is intended to generally bias the pilot poppet towards the closed position, but the spring force is insfficient to provide complete closure and tight shut off of the pilot poppet.
Because of the wear and vibration damage, a condition may exist where the stem and pilot poppet nut become locked togetijer thus not allowing a sliding axial fit (see Sketch 3). Upon closure of the MSIV in this condition, the stem, pilot poppet nut and pilot poppet (pc6) will move axially as one piece and seat the pilot poppet against the mlin poppet thus preventing flow of steam into the top of the main poppet as described above. Without sufficient steam flow into the top side of the main poppet, the required pressure balance is not achieved and the valve actuator closure force may be insufficient to fully close the main poppet and seat the skirt seal. When the irrt seal is properly seated, a net pressure load exists acting in the direction to seat the main poppet.
WVC believes the da&Iage described is a result of fluid born vibrations transmitted from unstable steam flow-WVC is providing thi notification to BVPS for evaluation regarding further notifications that may be required by regulatory requirenents. A similar notification Is being sent to STP Nuclear Operating Company as such notification applies toiSTP Units 1 & 2.
Please contact the urldersigned should you require additional information.
yours,
co PILOT 1AA SKETCH 1 VALVE EACKSEATEB OPEN
H.'
- PILOT POPPE NUT
_*,* - STEM° S TEM/PILOT POPPET NUT LOCKED NOT ALLOWING SLIDING AXIAL FIT s PILOT POPPET NUT
- STEM STEM!PILFOT PO1PPET NUT UNLO]CKED]
A.LLOWING SLID]ING AXIAL FIT SKETCH 3
MAIN PODPPE'T MA SKIRT PILOT POPPET NUT PILOT POPPET z
C SKETCH 2 VALVE CLOISED
.-4
10/01/2007 MON 16:36 FAX [a 012 Enclosure 2
10/01/2007 MON 16:37 FAX (Oa01 Weir Valves & Controls USA Inc. Excellent Engineering Solutions 285 Canal St. TIpl: 978 744 5690 Salem, MA 01970-4595 Fx: 978 741 3626. U i lm USA w~w.welrvally.P=, av T o1 WOMiTr,.Ikv,1
- ,l August 14, 2007 i Beaver Valley Power Station PO Box 4 1 Shippingport, PA 15077 Attn: Manager, iSite Regulatory Compliance Mail Stop !BV-A Ref: WVC USA letter August 2, 2007 Gentlemen:
WVVC USA perso6nel have performed additional evaluation of the condition described in the referenced letter.! This letter is intended to provide further information relative to that evaluation.
VVVC USA examined and inspected the as-found condition of the following parts removed from the degraded MPIV:
Pilot popp*el nut Pilot poppet Spring I Stem i Pilot popret cap In addition, technical discussions were held to better understand the operation of the valve including fit up arid functioning of the valve parts described above.
Based on these 4ddltional Inspections and evaluations WVC USA believes that, while the potential exists for the pilot poppet nut and stem to lock together as described in the reference letter, there has been no actual known case of this happening.
I We believe that there is reasonable assurance that the valve will perform its safety related closure under design basis accident based on the following:
While !there is a possibility that the pilot poppet and stem may lock together it is apparbnt from examination of the as-found parts that significant relative motion must take Rlace between these two parts to allow for that condition to exist. This is not likely lo occur in service.
The valve was diagnostically stroke tested In the as-found condition prior to the last outag6 and no anomalies were noted in the resulting data attributable to this condition.
10/01/2007 MON 16:37 FAX Qo 14 BVPS MSIV lettr, pg. 2 August14,2007
- The ondition described appears to be time related and given that the valve ran for two f 'el cycles it is likely that the current valve will operate for one fuel cycle without delet erious effects.
Very truly yo~ws.
Samuel N. 4lsields Samuel N. 4~ields, VP Engineering
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cc: MA Manolews, Mail Stop BV-IPAR Carmen V. Mancuso, Mail Stop BV-OEB-3 WVC: KI McManus fv, Milburn S1 Sullivan Macdonald