ML20082J470
| ML20082J470 | |
| Person / Time | |
|---|---|
| Site: | Shoreham File:Long Island Lighting Company icon.png |
| Issue date: | 11/28/1983 |
| From: | Rigert J LONG ISLAND LIGHTING CO. |
| To: | |
| References | |
| ISSUANCES-OL, NUDOCS 8312020172 | |
| Download: ML20082J470 (29) | |
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LILCO, Novcmber 28, 1983
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UNITED STATES OF AMERICA DOCKETED
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NUCLEAR REGULATORY COMMISSION USNc.;
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' a and Licensina Bo2@d 050 -1 A10:39 Before the Atemic Safety CFFxc.v e ne.
In the Matter of
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C0Ci:EimG '5Mrfe :
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WM:CH LONG ISLAND LIGHTING COMPANY
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Docket No. 50-322 (OL)
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(Shoreham Nuclear Power Station, )
Unit 1)
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AFFIDAVIT OF JOHN A. RIGERT REGARDING THE DETECTION OF PASSIVE MECHANICAL CHECK VALVE FAILURES AT SHOREHAM John A.
Rigert, being duly sworn, deposes and says as fol-lows:
1.
My name is John A.
Rigert.
I am employed by Long Is-land Lighting Company as the Section Head of the Systems Engi-neering Section of the Nuclear Engineering Department.
In this capacity, I supervise the development of Shoreham's In-Service Testing (IST) program for valves.
I have testified before this Board in connection with the litigation of SC Contention 16 --
ATWS, and SC Contention 27/ SOC Contention 3 -- Post-Accident Monitoring.
In addition, I have submitted to this Board two affidavits regarding Snoreham's IST program -- one on April 21, l
1983, the other on June 10, 1983.
My professional qualifica-tions have been previously submitted to the Board.
2.
This affidavit provides the Board with information requested in its Partial Initial Decision regarding the detec-tion of passive mechanical check valve failures at Shoreham.
After the hearing in June 1982 on SC Contention 11 (Passive 8312020172 831128 PDR ADOCK 05000:322 p) 8 PDR i
, Mechanical Valve Failures), NRC Inspection and Enforcement Bul-letin 83-03, " Check Valve Failures in Raw Water Cooling Systems of Diesel Generators," was issued in March 1983.
This Bulletin raised concerns about the adequacy of single direction flow testing to detect check valve failures generally, and specifi-cally those occurring in diesel generator cooling water supply systems.1/
The Board, therefore, has ordered LILCO to provide:
a statement of its basis for concluding that its current IST program will adequate-ly detect and prevent check valve failures such as those described in IE Bulletin 83-03, even though that Bulletin specifically states that normal forward flow testing may not adequately detect such check valve failures.
This statement, in the form of an affidavit or affidavits, shall include a discussion of both whether and why it be-lieves that single direction flow testing will be adequate to detect or prevent "la-tent" check valve failures, such as those described in IE Bulletin 83-03, and what other methodologies does LILCO intend to use to detect or prevent such failures.
Partial Initial Decision at 64.
1/
Although the Bulletin dealt directly only with operating plants, NRC Region I required LILCO, because its IST program had already received a licensing review, to comply with the Bulletin.
Principally, LILCO was required to include diesel generator cooling water supply system check valves in its IST program and to establish verification procedures confirming the integrity of valve internals.
Even prior to the Bulletin, LILCO had already included these check valves in its program and had already specified forward and reverse flow testing for them to establish their integrity.
As required by Bulletin 83-03, LILCO also performed an initial valve integrity verifica-tion and found no evidence of valve failure.
LILCO submitted two written reports to the NRC regarding its compliance with the Bulletin:
SNRC-904 (June 30, 1983) and SNRC-958 (August 31, 1983).
.
- 3.
Shoreham's IST program meets applicable NRC regula-tions and, specifically, the requirement of 10 CFR S 50.55a(g) that.in-service examinations comply with the edition and adden-da of the ASME Boiler and Pressure Vessel Code,Section XI, in effect 12 months prior to the date of issuance of the operating license.
Although the exact provisions applicable to LILCO are unknown until its operating license is granted, certain basic provisions of the Code remain unchanged, and Shoreham's IST program complies with them.
In accordance with ASME, every safety-related check valve -- a check valve which must function in order to ensure the pr,oper operation of a safety-related system -- is included in Shoreham's IST program.
Also, the flow directions for the in-service testing of check valves were selected to comply with another long standing and enduring pro-vision of ASME XI that " valves shall be exercised to the posi-tion required to fulfill their function unless such operation is not practical during plant operation."
Thus, the type of testing required by ASME is based upon the required valve re-sponse to system flow conditions during system operation.
If a valve must permit forward flow, it is tested for its ability to open either by a forward flow test or by other methods of valve exercising.
If it must prevent reverse flow, it is tested for its ability to close by either a reverse flow test or other methods of valve exercising.
If a valve must both pass forward flow and prevent reverse flow for proper system operation, the valve is tested for its ability to both open and close.
This
, testing satisfies the goal of ASME XI by demonstrating that the valve will perform its intended safety function'-- it does not necessarily detect latent passive mechanical valve failures.
4.
With regard to detection of passive mechanical valve failures, LILCO believes that the adequacy of single direction i
flow testing depends upon the direction.
The reason is that, if a valve has become oisassembled, more than likely it will allow flow in either direction through it.
Forward flow t
testing (or equivslent testing) -- which confirms that a valve will allow flow through it -- would not detect such a failure P
unless the valve disassembly occurred in such a way as to sub-stantially restrict flow.
However, reverse flow testing (or equivalent testing) -- which confirms valve integrity by de-monstrating that a valve will properly close and not allow flow
-- would detect a passive mechanical valve failure because a disassembled valve would probably allow flow through it.
5.
It is important fer present purposes, however, that ASME testing is only oneoof several methods used to determine valve operability.
Frequently, other testing pursuant to ei-ther Shoreham Technical Specificetions or NRC regulations is performed which verifies a valve's integrity.
This testing may be performed in addition to, or in lieu of, ASME testing.
In some instances, system operational parameters are used to de-tect valve failures.
Moreover, for certain valves, the low likelihood of. passive mechanical valve failure simply does not
. justify imposition of detection methods.
6.
Of the 1692/ regular system piping check valves, 50 are presently specified for both forward and reverse flow testing -- testing clearly adequate to detect passive mechani-cal valve failures.
They are in the following systems:
Main l
Steam, Feedwater, Standby Liquid Control, Core Spray, High Pressure Coolant Injection, Reactor Core Isolation Cooling, Radwaste, Service Water (including diesel generator cooling water supply) and Reactor Building Closed-Loop Cooling Water.
7.
LILCO's Nuclear Engineering Department and Storeham's Plant. Staff Technical Support Department, as well as consul-tants to LILCO, have evaluated each of the remaining 119 regu-lar piping system check valves _and the 411 Hydraulic Control Unit (HCU) valves to determine whether there are adequate means of detecting passive mechanical valve failures.
The results of thic evaluation are presented in Attachment 1, which was pre-pared under my direction and supervision.
8.
LILCO's evaluation concludes that adequate means exist to detect passive mechanical check valve failures and that Shoreham's IST program is fully responsive to the generic implications raised by Sulletin 83-03.
This statement is not meant to imply that means to detect latent passive mechanical valve failures exist for each and every single check valve --
indeed, such detection not only would be unnecessary, it would 2/
My June 10, 1983 affidavit erroneously reported that there were 168 regular piping system check valves in the IST program.
. be impossible.
It does mean, however, that LILCO has analyzed each single check valve in the IST program and has determined that overall adequate detection methods exist.
To r~mmarize this affidavit and its attachment, LILCO believes:
that ASME XI testing provides reasonable assurance that a valve will permit proper system operation; that ASME XI reverse flow testing or its equivalent is an adequate means of de-tecting passive mechanical check valve failures; that other testing performed in addition to, or in lieu of, ASME XI testing provides adequate detectability of passive mechani-cal valve failures for certain check valves at Shoreham; that normal system operational parameters provide adequate.detectability of passive mechanical valve failures for certain other valves; that the ASME XI testing, other testing, and normal system operational parameters collectively provide detectability of pas-sive raechanical valve failures for the vast majority of check valves at Shoreham; that passive mechanical check valve fail-ures are unlikely even for check valves in seawater applications because of their de-sign and because special corrosion-resistant materials were used for them; that forward and reverse flow testing for a large portion of the check valves in a sea-water environment provides reasonable as-surance that common mode passive mechanical valve failures will be detected and thus indicate whether other similar valves need to be inspected or tested; that, for the very few valves where normal detection means do not exist, the likeli-hood of passive mechanical valve failures is sufficiently small, because conditions conducive to such failures do not exist, that imposition of detection methods is not necessary; and that for two of the three HCU valves per control rod drive, methods of detecting passive mechanical valve failures exist and that no detection method is necessary for the third valve.
(./
John A.
RigFrt STATE OF NEW YORK)
COUNTY OF NASSAU )
Subscribed and sworn to before me this JJ day of M
7 1983.
L 2-e G NOTARY PUBLIC My Commission Expires on 3/J j/f/
ROSA LEE OLIVEROS Notary Pub.'ic. Ot:tc of New York No. 00 4700:C3 Quali.'ed it: fM:::u C:unty Commission exp:::s !.2.. 30,19,(_
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DETECTION OF PASSIVE MECHANICAL CHECK VALVE FAILURES AT SHOREHAM The purpose of this evaluation was to examine the means of detecting latent passive mechanical check val /e failures at Shoreham to determine whether Shoreham's IST program is respon-sive to the generic implications of Bulletin 83-03 regarding the detectability of such failures.
The program consisted of two phases:
(1) an identification of existing detection meth-ods, and (2) a determination of whether additional detection methods should be imposed.
ASME XI testing as well as other testing performed pursuant to Shoreham Technical Specifications or NRC regulations were examined.
In addition, the evaluation looked at the detection of passive mechanical valve failures by system operational parameters.
In the few instances where nor-mal detection means were not present, the likelihood of passive mechanical check valve failures was examined to determine whether additional detection methods should be imposed.
The following table presents the results of the evaluation.
In summary, it shows that Shoreham has adequate detection of la-tent passive mechanical check valve failures.
A-2 GROUP 1 -- 20 Valves Valve Description of System Identification Valve Function 1M50
- 0139 A,3 RBSVS & CRAC Con-densing Water System 1M50
- 0140 A,B RBSVS & CRAC Con-densing Water System 1M50
- 0178 A,B RBSVS & CRAC Con-densing Water System 1M50
- 0179 A,B RBSVS & CRAC Con-densing Water System 1M50
- 0007 A,B RBSVS & CRAC Con-densing Water Pump Discharge 1M50
- 0008 A,B RBSVS & CRAC Con-densing Water Pump Discharge 1P41
- 0008 A,B RER Heat Exchanger A,B Service Water Outlet 1P41
- 0010 A,B RBCLCW Heat Exchanger A,3 Service Water Outlet 1P41
- 0032 A,B Service Water to RBSVS
& CRAC Condensers 1P41
- 0033 A,B Service Water to RBSVS
& CRAC Condensers Particular attention was given to these valves during the evaluation because they are in a seawater environment and thus, potentially, subject to corrosion that could lead to passive mechanical failures.
The valves that were the subject of Bul-letin 83-03 had similar service conditions.
- However,
A-3 Shoreham's valves are different from those discussed by Bulle-tin 83-03.
All of these valves at Shoreham are Mission " Duo-Chek Style K" check valves.
These insert type check valves are of an entirely different design concept as compared to the swing checks discussed in Bulletin 83-03.
The valve hinges and disks are integrally cast as one piece in the " Duo-Chek" as op-posed to the bolted connection in most swing enecks.
It is this bolted connection that often leads to valve disassembly.
In addition, all internal valve parts are made of Monel and the valve body is of neoprene-lined cast steel.
These materials
'are specially selected for seawater service and are highly re-sistant to corrosion.
Recent inspections by LILCO of two Shoreham service water check valves (IM50 *06V-139A, IM50 *06V-1783) revealed that after approximately three years in service, the valves show no signs of corrosion or other degradation due to the seawater environment.3/
In addition to these 20 check valves, there are another 14 at Shoreham that function in a seawater environment.
These are also of the Mission " Duo-Chek Style K" design.
These 14 valves are tested for both forward and reverse flow.
The testing of 3/
Although the inspection found no evidence of corrosion, it did reveal that a torsion spring which aids in valve disk clo-sure was installed improperly in both valves, resulting in spring failure.
LILCO is currently inve=tigating the failure to determine how the installation error occurred, how many valves are affected, and the required corrective action.
Our preliminary conclusion based upon a discussion with the manu-facturer is that this failure does not degrade the safety func-tion of the valves.
The spring is not a safety grade component of the valve and the valve will close on reverse flow even withcut the spring.
A-4 these 14 valves (approximately 40% of the check valves in'a seawater environment) serves as an adequate sample for the de-tection cf passive mechanical valve failures.
The forward and reverse flow testing of.these 14' valves would reveal any common mode of passive mechanical failures and indicate the need, if any, for additional inspections.or testing of other similar valves.
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A-5 G2OUP 2 -- 15 Valves Valve Description of System Identification Valve Function 1E41
- 0001 HPCI Suction From Condensate Storage Tank 1E41
- 0011 HPCI Condensate Pump Discharge 1E41
- 0012 HPCI Pump Minimum Flow 1E51
- 0001
-RCIC Suction From Condensate Storage Tank 1E51
- O006 RCIC Condensate Pump Discharge 1E51
- 0024 RCIC Pump Minimum Flow 1R43
- 0200 A,B,C Diesel Fuel Oil Transfer Pump Discharge 1R43
- 0201 A,B,C Diesel Fuel Oil Transfer Pump Discharge 1T48
- 0004 A,B Hydrogen Recombiner Outlet These valves are in systems normally in a standby mode.
In addition to their infrequent operation, the valves are nei-ther in a corrosive nor erosive environment.
Additionally, the system operation will not induce abnormal stresses (e.a.,
ther-mal or vibration) on the check valve internals.
And industry experience shows that there is no history of these check valves
A-6 4
failing.
LILCO~ believes that the forward flow testing of these i
valves performed pursuant to ASME XI is sufficient to demon-3 strate their operability.
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A-7 GROUP 3 -- 12 Valves Valve Description of System Identification Valve Function 1B21
- RV-093 Drywell/ Suppression A,B,C,D,E, Pool Vacuum Breakers E, G, H,3, K, L,M These valves serve as the drywell/ suppression chamber vac-uum relief system.
They are installed in series of two on six downcomer pipes in the suppression chamber and operate automat-ically on differential pressure.
Failures of these valves are detected through various surveillances carried out in accor-dance with Shoreham Technical Specifications.
1)
Technical Specification Surveillance Requirement 4.6.4 is performed in lieu of ASME XI testing on these check valves.
Not only is it more frequently performed than ASME XI testing, it is a better indicator of valve operability.
It re-quires:
i) that each valve be verified closed weekly; ii) that each valve be tested through one complete cycle of full travel monthly; and iii) that operability of positions indicator be veri-fied monthly by observation of expected valve movement during the cycling test.
The position indication used to verify valve position is monitored remotely in the concrol room and is of actual disk
A-8 position.
The remote indicator is actuated by plunger-type switches on the valve that complete the electrical circuits to the indicators when the valve is fully closed.
On the inboard valves, the switch is actuated by a lever attached to the main shaft.
On the outboard valves, the switch is actuated directly by the disk.
These valves are normally closed and are continu-ously monitored in the control room.
Open position of the valve is indicated through use of a rotary switch on each valve that is actuated when the valve reaches full open position.
The valve open switches are actuated by a lever attached to the main shaft.
2)
If the surveillance described in Item 1 shows the valve position indicator to be inoperable, Technical Specifica-tion 3.6.4c requires that a drywell floor pressure decay test 4
be performed once every 15 days.
This test will also be per-formed during refueling outages.
It verifies valve integrity by demonstrating that acceptable pressure differential across the drywell floor has been maintained without make-up nitrogen having been provided to the drywell.
If the pressure differen-tial is not being maintained at this level, it indicates that either a valve or some other penetration is leaking.
Immediate action would be taken to find the cause.
A-9 GROUP 4 -- 24 Valves Valve Description of System Identification Valve Function IB31
- 0002 A,B Recirculation Pump Seal Purge Isolation 1C11
- 1028 A,B Recirculation Pump Seal Purge Isolation 1C51
- 0867 Tip Indexer Purge Isolation 1E11
- 3144 RHR (Steam Condensing
- 3145 Mode) Leak-Off Isolation (HPCI Steam Line Drain) 1E11
- 0047 RHR Sample Isolation
- 0048 1P42
- 0037 series RBCLCW Drywell Cooler (8 valves)
Isolation 1P50
- 0695 A,B Instrument Air to Drywell Isolation 1P50
- 0698 A,B Instrument Air to Suppression Pool Isolation' 1P50
- 0603 Service Air to Drywell Isolation IT48
- 0016 A,B PASS Containment Air Sample Isolation These valves are subject to Appendix J Type-C leak-rate testing because they serve as containment isola': ion valves and, therefore, must have a high degree of leak-tight integrity.
.The Appendix J Type-C leak-rate test, which is a reverse flow test, will detect passive mechanical failures, such as internal disassembly of a valve, because if a valve has failed there
A-10 will be excessive leakage from-the containment through the valve.
Industry experience-has shown that-it is effective at detecting passive mechanical failures.
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R-11 GROUP 5 -- 6 Valves Valve Description of System Identification Valve Function IC41
- 0007-A,B Standby Liquid Control Pump Discharge 1 Ell-
- 0035 A,B,C,D RER Pump Minimum Flow As a' result of an on-going review of its IST program, LILCO has determined that these check valves perform a safety-1 related function in both the open and close positions.
There-fore, these valves will be subject to both forward and reverse flow testing.
A-12 GROUP 6 -- 3 Valves Valve Description of System Identification Valve Function 1E11
- 0030 RHR Vessel Head Spray 1P50
- 0702 A,B Instrument Air System As a result of its review, LILCO has determined that these check valves do not serve a safety-related function in either the forward or reverse direction.
These valves will not be subject to ASME XI testing and will be deleted from Shoreham's IST program.
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A-13 GROUP 7 -- 8 Valves Valve Description of System.
Identification Valve Function IE11
- 0020 A,B,C,D RHR Pump Discharge 1E21
- 0013 A,B Core Spray Pump Discharge 1E41
- 0013 HPCI Pump Discharge 1E51
- 0012 RCIC Pump Discharge The position-and operability of these check valves are continuously monitored by the associated loop fill system moni-toring instrumentation.
Valve failures are detectable because the system piping would begin to drain resulting in an alarm in the control room.
Either a high loop level. pump flow alarm or a low loop level pump discharge pressure alarm, or both, would be activated.
A-14 i
GROUP 8 -- 9 Valves Valve Description of System Identification Valve Function 1E11
- 0037 A,B RHR Loop Fill Injection 1E21
- 0015 A,3 Core Spray Loop Fill Injection 1E41
- 0018 HPCI Loop Fill Injection 1E41
- 0026 HPCI Loop Fill Injection 1E51
- 0016 RCIC Loop Fill Injection 1E51
- 0008 RCIC Loop Fill Injection 1E51
- 0010 RCIC Loop Fill Injection The loop level system, due to a blockage in the loop fill injection line occurring from a valve disassembly, would not provide adequate make-up water to the associated system.
This failure would be identified during performance of monthly tech-nical specification tests required to verify water inventory of the systems.
A-15 GROUP 9 -- 6 Valves Valve Description of System Identification Valve Function 1E41
- 0002 HPCI Suction From Suppression Pool 1E51
- 0002 RCIC Suction From Suppression Pool 1G33
- 0036 A,B RWCU/FW Isolation 1G33
- 0050 A,B RWCU/FW Isolation During the first refueling outage, these valves will be equipped with external mechanical actuators for manual exercis-ing of the valves.
Thereafter, during ASME XI testing, the op-erator will be able to detect a valve failure by either:
1) measuring the total travel of the disk from its seat to its travel stop on the upper valve body, or 2) noting the amount of resistance when the valve is stroked.
A broken or detached disk would offer little, if any, resistance.
A-16 GROUP 10 -- 2 Valves Valve Description of System Identification Valve Function 1E41
- 0021 HPCI Turbine Exhaust Check 1E51
- 0020 RCIC Turbine Exhaust Check These check valves serve as containment isolation valves and are, therefore, subject to Appendi:t J Type-C leak-rate testing, described on Pages A-9 and A-lO above, in addition to their quarterly forward flow test.
Thus, these valves will re-ceive both forward and reverse flow testing.
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A-17 GROUP 11 -- 8 Valves Valve Description of System Identification Valve Function 1G41
- 0003 A,B Fuel Fool Cooling Pump Discharge IM50
- 0019 A,B RBSVS/CRAC Chilled Water Pump Discharge IM50
- 0020 A,B RBSVS/CRAC Chilled Water Pump Discharge 1P42
- 0036 A,B RBCLCW Heat Exchange Return to Pump Suction These check valves are in regularly operating systems dur-ing all modes of plant operation.
Failures are detectable be-cause the operator in the control room is provided with indica-tion of system parameters and alarms in the control room that alert an operator of a degraded system condition (e.g.,
- flow, pressure, temperature) resulting from a valve failure.
A-18 l
GROUP 12 -- 6 Valves Valve Description of i
System Identification Valve Function 1
1R43
- 0208 A,B,C Diesel Air Start Receiver 1R43
- 0209 A,B,C Diesel Air Start Receiver l
These. valves are reverse flow tested pursuant to ASME XI.
j 1
In addition, their position is continually monitored by the diesel generator air starting system status.
A failure of any one of the valves to close would be indicated to the operator in the control room by:
- 1) inability of air storage tanks to maintain pressure, and 2 ) continuous or abnormally frequent air compressor operation.
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A-19 GROUP 13 -- 411 Valves Valve Description of System Identification Valve Function 1C11 F114 (137 total)
Scram Discharge Riser IC11 F115 (137 total)
Charging Water Riser 1C11 F138 (137 total)
Cooling Water Riser These valves are in the hydraulic control units for the control rod drives.
Passive mechanical failures of these check valves are of such low probability that existing tests ade-quately demonstrate check valve reliability.
This conclusion is based on several factors.
1)
Design.
The special ball-type design (see Figure 1) was chosen for Shoreham because of the inherent high reliability of this design as proven by experience throughout the years.
The design is simple in that the only moving part is a ball itself.
The ball simply " rolls" within its machined body cavity either vertically up or down (depending upon flow conditions).
This rolling action eliminates sticking problems associated with other check valve designs.
Additionally, stellite material was chosen for the ball and its seating sur-faces.
This extremely hard material is the best available and is resistant to corrosion and erosion.
2)
Experience.
Industry experience has proven the reliability of these valves -- in decades of reactor-years of
A-20 operation not a single check valve failure has been identified.
In fact, GE indicated that for this type of valve the maximum leakage rate that has been experienced throughout the industry is 0.6 gpm, which indicates that there has been no gross valve failure.
This leakage rate was established by accumulator back leakage test required by Technical Specifications.
3)
Adequacy of Existing Tests.
a.
Valve (F114).
The CRD Scram Insertion Time Test demonstrates the proper operation of the scram discharge check valve (F114) because the valve is located in the only flow path of the scram exhaust water.
If this valve were to fail (block flow) it would be identified immediately because the control rod would not insert.
However, failure of this valve is not expected due to its design described previously.
The valve will be subject to a large pressure differential (reactor pres-sure on one side of and atmosphere pressure on the other) when a scram is initiated.
This pressure differential will easily overcome a potentially stuck valve.
b.
Valve (F115).
Each individual HCU accumulator is continually charged by water from its associated charging water subheader.
Each charging water subhsader is equipped with a check valve (F115).
The safety-related function of the F115 valves is to close on reverse flow in order to maintain scram water inventory and pressure within the accumulator and to en-sure that scram water flow is not diverted back into the charg-ing water header when a scram is initiated.
For this reason,
A-21
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Technical Specification Surveillance Requirement 4.1.3.5 re-t quires that each charging water subheader check valve be tested for. verification of reverse flow closure during refueling out-ages.. Testing will be performed by depressurizing the header and monitoring the individual accumulator pressure and alarm to verify that the valves have closed on reverse flow.
c.
Valve (F138).
There are no normal means to detect latent passive mechanical failures of this valve.
None is needed.
During the licensing review of Shoreham's IST program, General Electric verified that the CRD system can maintain op-i erating requirements upon failure of these valves.
GE per-formed a detailed analysis and' reported that leakage from these valves presents no risk to the safe shutdown of the reactor.
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