ML20082S740
| ML20082S740 | |
| Person / Time | |
|---|---|
| Site: | Hope Creek  |
| Issue date: | 04/26/1995 |
| From: | Labruna S Public Service Enterprise Group |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| REF-PT21-95 LR-N95059, NUDOCS 9505030198 | |
| Download: ML20082S740 (13) | |
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f Putsc Service Electric and Gas Company Stanley LaBruna Public Service Electnc and Gas Company P.O. Box 236, Hancocks Bridge, NJ 08038 609-339-1700 ;
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APR 261995 LR-N95059 United States Nuclear Regulatory Commission Document Control Desk Washington, DC 20555 Gentlemen:
10CFR21 NOTIFICATION ANCHOR DARLING VALVE COMPANY SWING CHECK VALVES HOPE CREEK GENERATING STATION DOCKET NO. 50-354 '
l In accordance with the requirements of 10CFR21, Public Service .
I Electric and Gas-(PSE&G) hereby provides the attached report concerning the hinge arms associated with sixteen swing check !
valves manufactured by Anchor-Darling Valve Company. The initial i 10CFR21 notification was provided to the NRC. Operations Center on i March 29, 1995. The attachment fully describes the identified i deficiency and corrective actions planned and implemented. l Please do not hesitate to .*ontact us if there are any questions j regarding this submittal.
Sincerely, f '
l Attachment !
9505030198 950426 PDR ADOCK 05000354 S PDR ,
l j
Document Control Desk 2 LR-N95059 APR 2 61995 C Mr. T. T. Martin, Administrator - Region I U. S. Nuclear Regulatory Commission 475 Allendale Road King of Prussia, PA 19406 Mr. David H. Moran i Licensing Project Manager - Hope Creek
- U. S. Nuclear Regulatory Commission One White Flint North 11555 Rockville Pike Mail Stop 14E21 Rockville,.MD 20852 Mr. R. Summers (SO9)
USNRC Senior Resident Inspector Mr. K. Tosch, Manager, IV NJ Department of Environmental Protection Division of Environmental Quality Bureau of Nuclear Engineering ,
CN 415 Trenton, NJ 08625 l
(
95-4933
LR-N95059 ATTACHMENT 1 I. BACKGROUND In November, 1994, 12" Core Spray Pump "B" discharge check valve 1BEV-015 failed to close during performance of procedure OP-IS.BE-002(Q). Inspection of the valve determined that the valve disc contacted the body in such a way as to pinch the disc causing it to stick in the open position for a short period of time. The valve design includes a butt stop hinge to prevent the disc from contacting the valve body. Based on the inspection, it was determined that the butt stop on the hinge arm was not contacting the valve body to prevent disc-to-body contact (See Enclosure 1 - Schematic from Anchor-Darling Valve Co.,
Williamsport, Pa.). To correct the deficiency, a new butt stop hinge arm, hinge pin and disc were installed, and the valve successfully retested in accordance with the surveillance test procedure.
As a result, PSE&G initiated inspections of Anchor-Darling check valves with a similar hinge style to determine if a generic type deficiency exists. A total of 15 additional valves were identified that may be affected as listed in Enclosure 3. On 1/19/95, 20" Station Auxiliary Cooling System (SACS)"D" pump check valve 1EGV-019 was inspected as a result of the Core Spray check valve failure corrective actions. The inspection revealed that the valve disc was knocking against the valve body in two places with the valve in the open position. Although this valve had not failed, it was apparent that the butt stop feature was inadequate. The valve hinge arm and disc were replaced, and the new ninge arm was modified per the vendor instructions to built up material on the butt end.
On March 29, 1995, PSE&G reported this deficiency to the NRC in accordance with 10CFR21. The inadequate butt stop feature may not preclude disc-to-body contact resulting in disc pin failure or the valves sticking in the open position.
On April 10, 1995, PSE&G inspected SACS "C" pump discharge check valve 1EGV-013 to ensure sufficient spacing between the valve disc and body when in the open position. Again, disc-to-body contact was identified with no failure (Same as SACS "D" pump check velve). The valve was repaired by weld build-up to the hinge arm butt and reassembled using the original hinge arm, disc and hinge pin.
PSEEG has reviewed the maintenance history of the other similar l check valves. One previous Anchor-Darling check valve (FPCC Pump i
Page 1 of 11 l
LR-N95059 ATTACHMENT 1 (cont'd) discharge check valve 1ECV-007) of similar design was found to have stuck in the open position due to the hinge butt pinching against the body. This occurred on three (3) separate occasions in 1988 and 1989. The final resolution was to grind the hinge butt. No problems have been identified to date with this valve '
since the corrective actions were completed.
II. EVALUATION PSE&G evaluation of this deficiency has identified that fracturing of swing check valve disc pins in the industry has occurred. The failures have been attributed to the direct impact of the valve disc on the body during opening. Repeated occurrences of this impact due to operation and/or disc flutter has contributed to pin failures. Anchor-Darling modified its swing check valve design in the 1980 time frame by adding an extended hinge tail stop to absorb the impact during valve I opening instead of the butt stop design installed in 16 check valves at Hope Creek (See Enclosure 2). This modification addressed the potential pin failure concern. Anchor-Darling has recommended replacement of the older hinge arm design. PSE&G is )
repairing the present hinge arms typically by weld build-up, as I warranted to prevent disc-to-body contact, and is evaluating if ,
replacement of the hinge arms with the new design is required. !
PSE&G has concluded that the deficiency in the hinge arm tolerances that relies on the older butt stop design may not preclude disc-to-body contact (as was the case with the Core Spray and SACS check valves). Variations in the valve body casting profiles that occur during manufacturing or location of the hinge during assembly could also contribute to reduced clearance between the disc and body resulting in contact. Disc- .
to-body contact could result in two types of failure modes of the l check valves; (1) disc pin failure due to fatigue from the direct impact of the disc against the valve body or disc flutter, or (2) the potential for the valves to stick in the open position due to the butt stop or the valve disc becoming wedged against the valve body. The two failure modes create different operational concerns. Disc pin failure could result in disassociation of the valve disc from the hinge. The unattached disc could become wedged in the valve body or down stream piping resulting in the partial or complete blockage of an essential flow path. For the second failure mode, pump runout could occur for parallel pump loops (i.e. Core Spray System) due to failure of the opposite pump discharge check valve to close and the loss of the associated pump. This failure mode could also result in a loss to the Keep Fill systems associated with the Core Spray System and Residual Heat Removal (RHR) System. The Keep Fill systems Page 2 of 11 I
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LR-N95059 ATTACHMENT 1 (cont'd) prevent a potential water hammer event due to pump start that could result in the loss of the loop or piping failure. Based on the above, PSE&G has concluded that the existing hinge arms installed at Hope Creek could be considered a Substantial Safety Hazard as defined by 10CFR21 should similar dimensional tolerance deficiencies exist in the remaining valves that have yet to be inspected. Therefore, this issue is reportable in accordance with 10CFR21.
Engineering Evaluation (EE) H-1-ZZ-MEE-0984 was performed to address the two failure modes above and the specific impact these failures could have at Hope Creek. The EE concluded that the subject deficiency is not considered an immediate operability concern for the fol2_ wing reasons:
Disc Pin Failure No disc pin failures have been identified in the sixteen check valves to date. The disc pins from the "B" Core Spray Pump check valve 1BEV-015, and SACS Pump check valves 1EGV-019 and 1EGV-013 were magnetic particle tested, and no defects were identified.
In each of these three cases, disc-to-body contact or disc flutter were observed. Also, during early 1991, the "B" RHR pump discharge check valve 1BCV-008 was disassembled and visually inspected. No deficiencies were noted with those valve internals at thct time.
A review of the expected system flow parameters, valve operating characteristics, valve cycle history and the recent inspections ,
of the Core Spray and SACS check valve's disc pins provides reasonable assurance that no disc pin failures are expected to occur in the remaining systems in the near term.
For all of the systems involved, initial startup of a pump typically does not result in a large initial mass flow, and therefore, low disc pin impact loads are expected should disc-to-body contact occur. For the ECCS check valves (Core Spray and RHR), the pumps are started with no discharge paths open other than minimum flow pathways. Since the minimum flow lines are upstream of the discharge check valves, this open path way will not result in the discharge check valves opening until a process ,
flow path is established. Additional increases in pump flow are
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controlled by motor operated valves. In addition, a Keep Fill system is utilized to minimize the initial surge due to pump starts. Therefore, opening of the ECCS check valves is not expected to result in excessive impact loads. The opening of the SACS pump discharge check valves on pump start could yield high disc impact loads. However, no disc pin failures have been observed to date based on the inspections of "C" and "D" pump Page 3 of 11
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l LR-N95059 ATTACHMENT 1 (cont'd) discharge check valves that have experienced disc-to-body contact or disc flutter. Anchor-Darling has suggested a "high confidence" no failure limit of 1,000 cycles for the type of moderate service the check valves normally experience. A conservative estimate on the number of cycles that the Core Spray, SACS and RHR check valves may have seen during the first 10 years of operation at Hope Creek was made based on pump l starts. Each pump start was assumed to result in impact. The maximum number of impacts estimated was 250 based on "A" and "B" RHR check valves. The number of impacts was estimated based on system normal operation, surveillance testing and post maintenance testing, and also includes additional margin for conservatism. The effects of pump start impacts are considered to bound possible disc flutter. For each of these systems, the number of impacts is well below the 1,000 cycle limit provided by Anchor-Darling.
Check Valve Failure in the Open Position This failure mode was evaluated for Hope Creek on the Core Spray, RHR, SACS and FPCC systems to determine the impact on system l operation following a design basis accident. A summary of this evaluation is provided below:
i Core Spray System - Should a single active failure (i.e.,
unavailability of Channel A dc source) be considered concurrently with a check valve failure in the open position in the remaining loop, both loops of the Core Spray system could be inoperable.
The check valve failure in the open position will result in a loss of that loop if the associated pump is no longer running. l This could result in parallel pump runout because of the common header piping configuration. If a Core Spray injection line failure occurred in the remaining loop, both loops could also be inoperable. In both cases, the design of the Emergency Core Cooling Systems (ECCS) would ensure that a sufficient combination of ECCS equipment (i.e., 3 Low Pressure Coolant Injection (LPCI) loops and the Automatic Depressurization System (ADS)) would be available in the event of a Loss of Coolant Accident (LOCA) even if offsite power was not available (See Hope Creek UFSAR Subsection 6.3.1.1.2). The sequence of failures that could result in a loss of both Core Spray loops is considered highly unlikely. Therefore, check valve failures in the open position would not prevent the ECCSs from mitigating a Design Basis Accident (DBA). The Low Pressure Coolant Injection (LPCI) mode of RHR operation in the event of a check valve failure is discussed below.
The Core Spray check valves are normally closed and open only upon ECCS initiation or surveillance testing. The failure of a Page 4 of 11
i LR-N95059 ATTACHMENT 1 (cont'd)
Core Spray check valve in the open position would be readily identified following performance of surveillance testing due to the failure of the Keep Fill system to maintain downstream pressure when the system is not operating. Failure of the valve is only a concern if the pump is initially started, the check valve sticks open, the pump is stopped and cannot be restarted.
RHR - The RHR system is designed with four independent loops l without the pump discharge piping cross-connected. A check valve l failure in the open position will not prevent the loops from performing their intended design function. Upon ECCS initiation, the LPCI mode of RHR operation will result in all four RHR pumps starting. As is the case with Core Spray, a single active l component failure (i.e. unavailability of Channe' A de source) would result in the loss of one LPCI loop. Three LPCI loops would be available to mitigate the event. If a piping failure was assumed in the RHR system instead of the Core Spray system, the remaining Core Spray loop would be available as discussed above (See Hope Creek UFSAR Subsection 6.3.1.1.2). Although it could be postulated that a combination of RHR and Core Spray failures in conjunction with a check valve failure in the open position could result in less ECCSs per UFSAR Section 6.3.1.1.2, it is considered highly unlikely based on engineering evaluation including Probabilistic Risk As.nessment (PRA).
Long term containment cooling is performed using either the "A" or "B" RHR loops. Long term cooling is provided through either the "A" or "B" RIIR pumps and is initiated after approximately 10 minutes following ECCS initiation. Either pump provides adequate flow to accomplish this design function. Pump flow is not terminated to align the RHR pumps for long term cooling. Vessel makeup is accomplished using either 1 RHR loop or Core Spray loop. A sequence of failures that could result in the ability to provide vessel makeup is considered highly unlikely.
The RHR check valves would be normally closed and open only upon ECCS, Shutdown Cooling initiation or surveillance testing. The failure of a RHR check valve in the open position would be readily identified following performance of surveillance testing due to the failure of the Keep Fill system to maintain downstream pressure when the system is not operating. Failure of the valve is only a concern if the pump is initially started, the check valve sticks open, the pump is stopped and cannot be restarted.
SACS - The consequences of a failed open SACS pump check valve is similar to that of the Core Spray System. Loss of pump flow may occur in the parallel pump if the opposite pump is stopped with Page 5 of 11
LR-N95059 ATTACHMENT 1 (cont'd) its discharge check valve stuck in the open position. This pump would trip resulting in the loss of that SACS loop. However, this would result in automatic swap over to the other SACS locr to provide the required cooling. Only one SACS loop with one pumn is required to operate and safely shutdown the plant. A sin gle active failure along with a postulated piping failure in the redundant train is not considered credible per HC UFSAR Sec t' on 3. 6.1.1. SACS check valves associated with pumps "C" and
" D' e .v'e been repaired to prevent disc-to-body contact.
FPCC - The bases for concluding that a failure of the FPCC check valver does not constitute a Substantial Safety Hazard in accordance with 10CFR21 as described in UFSAR Section 9.1.3.
To date, there have been two check valves that have stuck in the open position due to disc-to-body contact (FPCC pump discharge check valve 1ECV-007 in 1989 and Core Spray pump discharge check valve 1BEV-015 in November, 1994). Because the failures to date l have been attributed to deficiencies and casting variations that may reduce clearance between the disc and body, it is expected that the failure mode would be random in nature. Multiple failures of check valves in the open position is considered highly unlikely during a single event. Check valve 1ECV-007 was repaired in 1989 to prevent disc-to-body contact.
Therefore, it is concluded that the subfoct deficiency is not considered an immediate operability concern while inspection and repair of the hinge arms is ongoing.
III. CORRECTIVE ACTIONS The overall schedule for completion of valve inspection, and repair or parts replacement for the remaining valves is no later than prior to startup following Refueling Outage # 7 (Spring, 1997), with specific valves presently scheduled to be completed sooner based on relative risk.
Prior to completion of these corrective actions, the following actions will ensure continued valve operability:
- ECCS pump discharge check valves operability will be determined by either routine quarterly surveillance tests (which evaluate system flows and idle pump status), or by the ability of the ECCS Keep-Fill Systers to maintain downstream pressure when the system is not operating.
I I
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LR-N95059 ATTACHMENT 1 (cont'd) {
- SACS pum* discharge check valves operability will be determined by either routine quarterly surveillance tests (which evaluate system flows and idle pump status), or by verification of appropriate system flows during routine system realignments.
- Although not considered a Substantial Safety Hazard, FPCC pump !
discharge check valves operability will be determined by !'
verification of appropriate system flows during routine system realignments.
If the above testing methodology identifies a new check valve failure, the surveillance and/or verification frequency will be evaluated to ensure continued operability.
PSE&G is also considering the development and implementation of a '
Design Change Package (DCP) to install an extended tail stop design to absorb the impact during valve opening instead of the butt stop design presently installed in the 16 affected valves at Hope Creek.
It is also noted that a review of selected additional hinge arms '
in storage showed either no tail stop or the non-functional older hinge arm tail stop. The hinge arms that contained a small non-functional tail stop appear to be part of the older design although not reflected on the design drawings. The hinge arms may be used during valve repair, and modified as necessary to !
ensure proper valve function.
1 Page 7 of 11
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PARTS LIST PART '
DESCRIPTION MATERIAL NO. QTY.
SA216-WCB i 1 1 WELD ENDS BODY
'2 1 SEAT RING W/ STELLITE SAIO6-B _ .
DISC W/ STELLITE SA216-WCB 3 1 1 HINGE A216-WCB 4
SET SCREW COMMERCIAL STEEL 5 1 - i 6 1 HIllGE PIN A564 -630-1075 BONNET GASKET 2)* 22.Inj 304SS W/ ASBESTOS 7 1 8 1 BONNET SA515-70 1 9 20 BONNET NUTS SA194-2H ;
10 20 BONNET STUDS is D1A. ' SA193-87 l 11 1 HINGE SUPPORT A216-WCB P 2 SL'~' ORT CAPSCREWS A574 12 i
2 DOWEL PINS A108 14 .
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. DISC WASHER STAIHLESS STEEL 16 1 17 1 DISC NUT - A276-410T l 18 1 DISC NUT PIN STAINLESS STEEL SE.TscREW coMMER\ CAL 61EES. l 19 i rey 3 a u l
. 0 ENCLOSURE. 2 13.ussos, SWING CHECK Anchor / Darling's swing check valves provide the most economical reverse flow protection for normal applications.
STANDARD MOUNTING ALTERNATE MOUNTING With body penetration. Leakage os prevented by using a blond
-) flance with spiral-wound gasket,
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f, rather than a pipe plug.
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9 Extended hinge, which takes up normal
% flow impact. Prevents dosc contact with body e No bodypenetration e Hunge mounted on pads, readily accessible for '
l adjustment and replacement TT1
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Clear waterway design, NO * *L
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thtt minimizes pressure . , , , , , ,,,,,,,,, _ ,, _ ,_,
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Crowned sealong surface achieves precise unit
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inclined seat to provode assurance of closure even on loading fora toghtsealwith monamni force .
the absence of reverse flow.
APPOCAtlONS: ,
. g e Where tight sealing is required.
e Where pressure drop must be kept to a minimum, e Where water hammer occurrence does not present a problem.
- Where flow is relatively constant. ;
Seat Rings are seal welded to
- ,,*'ny'8' ,",',, ',,
, g ,*, $ o#[ e Can be installed in horizontal as well as in vertical lines replacement. (with flow upward).
e Easy to maintain.
Page 10 of 1.t
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LR-N95059
\
L ENCLOSURE 3 LIST OF AFFECTED ANCHOR-DARLING CHECK VALVES SACS PUMP DISCHARGE CHECK VALVES (20", 150#)
1EGV-010 1EGV-013 1EGV-016 1EGV-019 CORE SPRAY PUMP DISCHARGE CHECK VALVES (12", 300#)
1BEV-013 !
1BEV-014 1BEV-015 1BEV-016 l RHR PUMP DISCHARGE CHECK VALVES (18", 300#)
1BCV-002 i 1BCV-008 1BCV-099 1BCV-105 FPCC PUMP DISCHARGE CHECK VALVES (6", 150#) i 6
1ECV-007 !
1ECV-040 l I
FPCC FILTER DEMIN OUTLET CHECK VALVES (8", 150#) l 1ECV-015 f FPCC FILTER DEMIN OUTLET RETURN TO TORUS CHECK VALVES (6", 150#) ;
T 1EEV-007 i
l Page 11 of 11 1