ML20046A651

LER 93-017-01:on 930527,concluded That,Based on 930521 Determination,That Feedwater Isolation Bypass Valves Inoperable Since Pneumatic Positioners & Solenoids Remained in Svc Beyond Qualified Life.Control Scheme Modified

ML20046A651
Person / Time
Site:	South Texas
Issue date:	07/20/1993
From:	Pinzon J HOUSTON LIGHTING & POWER CO.
To:
Shared Package
ML20046A646	List: ML20046A645 ML20046A651
References
LER-93-017, LER-93-17, NUDOCS 9307290167
Download: ML20046A651 (7)

Text

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ERC FORM 366 U.S. NUCLEN! REGULATCCtf COMMISS!(D QPPCOL'ED B7 OMB WO. 3150-0104 (5-92) EXPIRES 5/31/95 ESTIMATED BUROEN PER RESPONSE TO COMPLY BITH I I " LL LICENSEE EVENT REPORT (LER) Eggg"'U"c"g*

c MENS REGARDING BU DEN ST) ATE b THE INFORMATION AND RECORDS MANAGEMENT BRANCH (MNBB 7714), U.S. NUCLEAR REGULATORY COMMIS$10N, (See reverse for required number of digits / characters for each block) WASH]NGTON, DC 20555-0001, AND TO THE PAPERWORK REDUCTION PROJEC1 (3150-0104), OFFICE OF MANAGEMENT AND BUDCET, WASHINGTON, DC 20503.

FACILITY KAME (1) DOCKET NUMBER (2) PAGE (3)

South Texas, Unit 1 05000 498 1 OF 7 TITLE (4) Extension Of FWIBV Positioner and Solenoid Equipment Beyond Oualification Life EVENT DATE (5) LER NUMBE R (6) REPORT DATE (7) OTHE R F ACILITIES INVOLVED (8)

SEQUENTIAL REVIS10N FACILITY KAME DOCKET NUMBER MONTH DAY YEAR YEAR g g MONTH DAY YEAR South Texas, unit 2 05000499 05 27 93 93 -- 017 -- 01 07 20 93 O O OPERATING THM MMT M WBMlHED MWANT T THE RNRW NTS OF 10 CFR D Wck one or nm) (M) 5 20.402(b) 20.405(c) 50.73(a)(2)( i v) 73.71(b)

MODE (5)

POWER 20.405(a)(1)(i) 50.36(c)(1) 50.73(a)(2)(v) 73.71(c) 0 20.405(a)(1)(ii) 50.36(c)(2) 50.73(a)(2)(vii) x OTHER LEVEL (10) 20.405(a)(1)(iii) 50.73(a)(2)(i) 50.73(a)(2)(viii)(A) 20.405(a)(1)(iv) 50. 73(a )(2)( i i ) 50.73(a)(2)(viii)(B) in Text, NRC form '

20.405(a)(1)(v) 50.73(a)(2)(iii) 50.73(a)(2)(x) 366A) Volmtary l

LICENSEE CONTACT FOR 1HIS L ER (12) hAME TELEPHONE NUMBER (include Area Code)

Jairo Pinzon - Senior Engineer (512) S72 - 8027 COMPL ETE ONE LINE FOR EACH COMPONE NT FAltVEE DESCRIBE D IN THIS RE PORT (13)

CAUSE SYSTEM COMPONENT MANUFACTURER CAUSE SYSTEM COMPONENT MANUFACTURER SUPPLEMENTAL REPORT EXPECTED (14) EXPE CT ED MONTH DAY YEAR YES(if yes, complete EXPECTED SUBMISSIDW DATE). X No AT (5 ABS 1RACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines) (16) j On May 27, 1993, Unit 1 was in Mode 5 at 0% power and Unit 2 was defueled in a refueling outage. Plant personnel concluded that, based on a May 21, 1993 determination that the Feedwater Isolation Bypass Valves (FWIBVs) in both units were inoperable since the pneumatic positioners and solenoids had remained in service beyond their qualified life, this event was reportable. STP personnel determined that Technical Specification 3.7.1.7 had been violated during various modes of operation since 1992. The inappropriate extension of the equipment qualification life of the FWIBV positioner and solenoids was the result of incorrectly interpreting design documents. Corrective actions include reviewing other safety-related ,

valves with positioners for similar problems, reviewing other solenoid l valves qualified for service in a harsh environment to determine if similar problems could exist, reviewing safety-related components which have been  !

classified as non-safety to determine generic implications, and modifying I the pneumatic control scheme of the FWIBV to ensure closure of the valves independent of the positioner upon de-energization of the safety-related solenoid valves. Further evaluation determined that the qualified life of the FWIBV positioners and solenoids had, in fact, not been exceeded and no  !

violation of Technical Specifications occurred.

NkC FOAM 366 (542) 9'307290.167 9307po DR ADOCK 05000498 PDR LE R-93 \L93017R1.U1

NRC FORM 3664 U.S. C28 CLEAR REeJLATOV COMMISSIC APPROVED BY OMB Wo. 3150-0104 (5-92) EXP!RES 5/31/95 ESTIMATED DURDEN PER RESPONSE TO COMPLY WITH THis INFORMATION COL LECTION REQUEST: 50.0 HRS.

FORWARD COMMENTS EECARDING BURDEN ESTIMATE TO THE LICENSEE EVENT REPORT (LER) INFORMATION AND RECORDS MANAGEMENT BRANCH (MNBB TEXT CONTINUATION 7714), U.S. NUCLEAR REGULATORY COMMISSION, WASHINGTON, DC 20555-0001 AN3 TO THE PAPERWORK REDUCTION PROJECT (31$0-0104), OFFICE OF MANAGEMENT AND BUDCFT, WASHINGTON, DC 20503.

FACILITY NAME (1) DOCKFT NUMRTR (?) LFR WUMBER (6S PACF (3)

YEAR SEQUENTIAL REVISION South Texas, Unit 1 05000 498 2 OF 7 93 -- 017 -- 01 TEXT (if more space is reouired. use additional copies of Not Form 366A) (17)

DESCRIPTION OF EVENT:

On May 27, 1993, Unit 1 was in Mode 5 at 0% power and Unit 2 was defueled in a refueling outage. Plant personnel concluded that, based on a May 21, 1993 determination that the FWIBVs in both units were inoperable since the pneumatic positioner and solenoids had remained in service beyond their qualified life, this event was reportable. STP personnel determined that Technical Specification 3.7.1.7 had been violated during various modes of operation since 1992. Technical Specification 3.7.1.7 requires that each FWIBV be operable while in Modes 1, 2 ar_d 3.

POSITIONERS On May 21, 1993, as a result of an investigation to resolve a FWIBV valve position indication issue, an STP engineer noted that the FWIBV positioner EQ documentation stated that the positioners were classified as non-safety related. The STP engineer questioned the basis of the quality classification, since he understood that the positioners were required to function to close the FWIBV during a Main Feedwater isolation.

The FWIBV positioners were classified, procured and installed as safety related components under the original Main Feedwater system design. However, based on an Architect Engineer's memorandum stating that STP pneumatic positioners do not perform any safety functions and threefore are not subject to EQ requirements, STP Engineering downgreded the FFI?T positioners to non-safety related and extended their life 1.0 40 years cm September 16, 1986. No hardware changes were made as a result of the change in classification.

Further review of the plant design documentatiin acnfirmed that the positioners do perform a safety function during a Mr.>r Feedwater isolation, and therefore, the EQ requirements should have been raintained. Based on these findings, a new qualified life calculation was amediately performed.

A review of the FWIBV positioner EQ report revealed that replacement of the positioner's sensitive parts is required every four yairs based on a maximum continuous operating temperature of 300F and a thres. ,ld radiation dose of 10E6 rads. This replacement interval is based on a worst case effect (under an assumed bounding maximum operating temperature or radiation exposure) to the age-sensitive materials in the positioner. Since the design basis radiation dose for a postulated accident in the Isolation Valve Cubicle at STP is less than the threshold radiation limit, operating temperature is the limiting factor for qualified life of positioners at STP. However, no precise measurement or estimate of positioner operating temperature was available.

As a result, positioner qualified life was re-calculated to be five years based on a conservatively assumed maximum continuous operating temperature less than 212F. Since the Unit 1 FWIBV positioners qualified life expired on June 6,1992, HL&P conservatively concluded that the Unit 1 positioners had LER-93\L93017R1.U1

NRC FORM 366A U.S. CELEAR REGULATORY COMMISSIC APPROVED BY OMB CD. 3150-0104 (5-92) EXPIRES 5/31/95 ESTIMATED BURDEN PER ttESPONSE TO COMPLY WITH THl$

. INFORMATION COLLECTION REQUEST: 50.0 HRS.

FORWARD COMMENTS REGARDING BURDEN EST! MATE TO THE LICENSEE EVENT REPORT (LER) INr0RMAt!ON AND RECORDS MANAGEMENT BRANCH (MNBB TEXT CONTINUATION 7714), u.S. NUCLEAR REGULA10RY COMMISSION, WASHINGTON, DC 20555-0001 AND TO THE PAFERWORK REDUCTION PROJECT (31$0-0104), OFFICE OF LMANAGEMENT AND BUDGET, WASHINGTON, DC ?0503.

FACllITY NAME (1) DOCKET NUMRER (2) LFR WlMBER (61 PAGE (3)

YEAR SEQUENTIAL REVISION Nuu m Nuw m South Texas, Unit 1 05000 498 3 OF 7 93 -- 017 -- 01 TEXT (If mor e space is reauire<t use additional copies of ARC Form 366A) (17)

DESCRIPTION OF EVENT: (Cont'd) been technically inoperable for 1. 5 years. The Unit 2 FWIBV positioners were found to be operable since they had not yet exceeded a five year life.

As a result of the new life calculations, service requests (SRs) were written to install a modification to the pneumatic control scheme of the FWIBV to ensure closure of the valves, independent of the positioner, upon de-energization of the safety-related solenoid valves. Since the positioner would no longer be required to perform a safety function, the requirement for EQ was deleted.

HLLP continued to evaluate the operability of the positioners. The installed configuration of the positioner has it attached to the FWIBV valve operator yoke. Subsequently, a heat transfer calculation was developed which demonstrated that the maximum yoke temperature during plant operation is 162F.

While actual positioner temperature would be less than 162F because of air flow cooling and because of the limited heat transfer capability of the positioner / yoke attachment, a conservatively assumed positioner operating temperature of 162F was used to calculate a qualified life of over 8 years.

As a result, HL&P has concluded that the FWIBV positioners were within their qualified life and there was no operability concern relative to the positioner.

A five step plan wcs established to address the gencric implication of the declassification of the FWIBVs safety-related positioners and solenoids. This plan included reviews of the classification of all Valtek valve positioners,  !

positioners provided for safety-related valves, and Heating, Ventilating and l Air Conditioning system dampers. This plan also provided for reviews of active parts declassified by use of Technical Evaluations for proper consideration of system / component operation, a sample of EQ packages for proper consideration of system / component operation, and reviews of EQ for solenoids which are normally energized but were evaluated as normally de-energized.

This review resulted in identifying twelve additional valves per unit where failure of the positioner could cause the valve to be mispositioned. Further review revealed the valves are located in a mild environment and do not require periodic replacement. Other solenoids of the same model used with the FWIBVs were identified and action taken to replace them. These additional solenoids were on non-safety related Steam Generator Augmented Blowdown valves, which do not have a qualified life limitation.

LER-93\L93017R1.U1

i i

'NRC FORM 366A U.S. Q) CLEAR RECULATC3Y CDtMISSION APPROVED BY OMB NO. 3150-0104 (5-92) ,

EXPIRES 5/31/95 ESilMATED BURDEN PE2 DESPONSE TO COMPLY WITH THIS i INFORMATION COLLECTION REQUEST: 50.0 HRS.

I FORWARD CCMMENTS REGARDING BURDEN ESilMATE TO THE 1 LICENSEE EVENT REPORT (LER) INFORMATION AND RECORDS MANAGEMENT BRANCH (MNBB l TEXT CONTINUATION 7714), U.S. NUCLEAR REGULATORY COMMISSION, j WASHINGTON, DC 20555-0001 AND TO THE PAPERWORK i REDUCTION PROJECT (31$0-0104), OFFICE OF MANAGEMENT AND BUDCET, WASHINGTON, DC 20503.

FAClllTY NAME (1) DOCKET Nt#tBER (2) LER NUMBER (65 PAGE (3)

YEAR SEQUENTIAL REVISION ]

South Texas, Unit 1 05000 498 4 OF 7 93 -- 017 -- 01 TEXT (if more space is reouired, use additional copies of NRC Form 366A) (17)

DESCRIPTION OF EVENT: (Cont'd)

SOLENOIDS I

On May 28, 1993, as part of the continuing investigation of the FWIBV issues, an STP engineer reviewing the Equipment Qualification Calculation Package (EQCP) for the FWIBV safety-related solenoids, questioned the assumptions used in determining their qualified life. Calculation E-89-ASCO, Revision 3, indicated that the solenoids are only energized during feedwater heatup and not during normal operation resulting in a qualified life of forty years.

Review of the logic drawings for these valves showed that there are three solenoids for each FWIBV. One non-Class 1E solenoid is controlled by a main control board handswitch and is normally de-energized. The other two Class 1E solenoids are each controlled by a combination of the Main Feedwater Isolation Valve control switches and a Feedwater Isolation signal from the Solid State Protection System. A review of the design documents showed that these two safety-related solenoids are energized during normal plant '

operations. As a result of recalculating the life of the solenoids in the normally energized state using worst case design basis assumptions, the '

qualified life was determined to be 2.5 years. As a result, HL&P conservatively concluded that the FWIBV solenoids qualified life expired in l December 1989 for Unit 1 and June 1991 for Unit 2.

As with the positioners, HL&P continued to evaluate the operability of the FWIBV solenoids. The solenoid coil had been the limiting component in the j qualified life calculation. After several discussions with ASCO's technical representatives, STP engineering determined that the failure of the solenoid's coil did not prevent the valve from performing its safety function. Solenoid '

coil failure would result in the FWIBV failing in the required position. As l a result, the solenoid's qualified life was re-calculated based on the next most limiting component and the new qualified life was determined to be over 30 years. Therefore, HL&P has concluded that the FWIBV solenoids were within their qualified life. Further, HL&P has concluded that the FWIBVs were operable at all times because the FWIBV positioners and solenoids were within their qualified life.

Although the FWIBV solenoids were proven to be operable, other solenoid valves qualified for service in a harsh environment were reviewed to determine if a similar condition could exist where an incorrect assumption that the solenoid was de-energized when they were actually energized was made. The review included ASCO, Valcor and Target Rock solenoids. This review resulted in a reduction in qualified life for the Preheater Bypass valves and the Main Steam Bypass valves ASCO solenoids. Although their qualified lives have been reduced, they have not yet expired.

LER-93\L93017R1.U1 l

'NRC FOR'M 366A U.S. CDCLEAR REGJLATO Y COMMISSI C APPROUED BY OMB C3. 3150-0104 (542) ,

EXPIRES 5/31/95 ESilMATED BURDEN PER RESPONSE TO COMPLY WITH THIS INFORMATION COLLECTION REQUEST: 50.0 HRS.

FORWARD COMMENTS REGARDING BURDEN EST! MATE TO THE LICENSEE EVENT REPORT (LER) INFORMATION AND RECORDS MANAGEMENT BRANCH (MNBB TEXT CONTINUATION m 4), U.S. NUCLEAR REGULATORY COMMISSION, WASHINGTON, DC 20555-0001, AND TO THE PAPERWORK REDUCTION PROJECT (3150 0104), OFFICE OF MANAGEMENT AND BUDGET, WASHINGTON, DC 20503.

FACILITY NAME (1) DOCKET NLMBER (2) LER MMFIER (61 PAGE (3)

YEAR SEQUENT 14L REVISION South Texas, Unit 1 05000 498 5 OF 7 93 -- 017 -- 01 TEXT (If more sDece is reovired, use additional copies of NRC Form 366A) (17)

CAUSE OF EVENT:

In both cases, the erroneous qualified life extensions of the FWIBV l positioners and solenoid valves were the result of incorrectly interpreting design documents.

ANALYSIS OF EVENT:

Upon discovery of the inappropriate extension of the EQ life the FWIBVs were conservatively declared inoperable. Further evaluation of the operability of the positioners and solenoids revealed that, in fact, the EQ life had not been exceeded and thus, were not inoperable. Had the FWIBV, in fact, been inoperable, the events described in this report would represent an operation or condition prohibited by Technical Specification 3.7.1.7 and would have been reportable pursuant to 10CFR50. 7 3 (a) (2) (i) (B) . Based on the above '

considerations, there is no safety significance from this event. I CORRECTIVE ACTIONS:  !

l l

1. The Preventive Maintenance (PM) activities for EQ replacement for the PWIBV solenoids have been reactivated. ,

1

2. A review of other safety-related valves with positioners was performed to l identify similar concerns. A group of twelve Chilled Water valves was  !

identified with a similar configuration; however, these valves are not located in a harsh environment and no periodic parts replacement is required to maintain the qualification. Further investigation revealed that the EQ of the Chilled. Water valve positioners have not been altered.

l

3. A modification to revise the pneumatic control scheme of the FWIBVs to ensure closure of the valves independent of the positioner upon de-energization of the safety-related solenoid valves, has been developed.

This modification has been implemented in Unit 1 and will be implemented by the end of the current refueling outage in Unit 2. j l

4. A review of other solenoid valves qualified for service in a harsh I environment was performed to determine if a similar problem existed. This review included ASCO, Valcor and Target Rock solenoid valves. This review resulted in a reduction in qualified life for the Preheater Bypass valve and Main Steam Bypass valve ASCO solenoids. Although reduced, their qualified lives, have not yet expired. EQ PM activities will be developed to ensure replacement prior to expiration.  !

LER-93\L93017R1.01

'WRC FORM 366A U.S. CUCLEAR RECULATC2Y COMMISSIC2 APPROVED BY OMB WO. 3150-0104 ,

(5-92) ,

EXP!RES 5/31/95  !

l ESTIMATED BURDEN PER RESPONSE TO COMPLY WITH TH]S I INFORMATION COLLCCTION REQUEST: 50.0 HRS.

FORWARD COMMENTS REGARDING BURDEN ESTIMATE TO THE LICENSEE EVENT REPORT (LER) thF0RMATION AND RECORDS MANAGEMENT BRANCH (MNBB TEXT CONTINUATION 7714), U.S. NUCLEAR REGULATORY COMMISSION, l WASHINGTON, DC 20555 0001, AND TO THE FAPERWORK REDUCTION PROJECT (3150-0104), OFFICE OF MANAGEMENT AND BUDGET, WASHINGTON, DC 20503.

FACItITY NAME (1) DOCKET NUMBER (?) LFR NUMBER (61 PAGE (3)

YEAR SEQUENTIAL REVISION j

" " " " " " I South Texas Unit 1 05000 498 6 OF 7 93 -- 017 -- 01 TEXT (11 mre sr> ace is recuired, use additional copies of ARC Form 366A) (17)

CORRECTIVE ACTIONS: (Cont'd)

5. Information regarding the positioner and solenoid events has been provided to Engineering personnel as lessons learned. In addition, Engineering personnel were sensitized on the need for attention to detail with regard to EQ and verifying assumptions.

6. To address generic implications, a five-step review process was developed to evaluate the part reclassifications and EQ issues indicated as a result of this LER. This review has not resulted in any additional plant safety issues. As a result of this review, the sample scope has been expanded.

This additional review will be completed by July 21, 1993. Based on this additional review, corrective actions and recurrence control measures will be developed as necessary.

bpDITIONAL INFORMATION:

1 The FWIBV positioners are manufactured by Valtek and are model number 80R.

The FWIBV solenoids are manufactured by ASCO and are model numbers 206-832-4VF, NP831655E, and NP8321A2E/A6E.

During the past two years, two LERs have been submitted to the NRC which were related to Equipment / Environmental Qualification problems. These LERs are as follows:

o Unit 1 LER 93-016 regarding a Technical Specification violation due to Circuitry for the Steam Generator Power Operated Relief Valves and Reactor Coolant System Subcooling Margin monitor being inoperable.

o Unit 2 LER 93-008 regarding a Technical Specification violation due to a f ailure to maintain Environmental Qualification of a Residual Heat Removal Motor Operated Valve.

o Unit 2 LER 93-010 regarding a failure of an Essential Cooling Water traveling screen drive coupling.

The following information is with regard to an event that was discovered on April 21, 1993, in which the FWIBV was thought to be open when a Maintenance technician may have observed pointer movement on the stem clamp during 1 maintenance work on the FWIBV. The technician believed that since the perceived pointer movement on the stem clamp was sudden, the valve stem had moved and the valve had been partially open. HL&P conservatively concluded I that the event was reportable because the plant had operated in various modes with the valve inoperable contrary to Technical Specifications. The valve was thought to be open since April 25, 1992. Further investigation determined that the valve, in fact, was closed as required during this time period.

LER-93\L93017R1.U1

v NRCFhRM366A U.S. t:JCLEAR RECULATC27 (XMMISSIC2 APPROVED BY OMB NO. 3150-0104 (5-92) ,

EXPIRES 5/31/95 ESilMATED BURDEN PER RESPONSE TO COMPLY WITH THIS INFORMATION COLLECTION REQUEST: 50.0 HRS.

FORWARD COMMENTS RECARD!bG BURDEN ESTIMATE TO THE LICENSEE EVENT REPORT (LER) INr0RMATION AND RECORDS MAhAGEMENT BRANCH (MNBB TEXT CONTINUATION 7714), u.S. NUCLEAR REGULATORY COMMISSION, WASHlWGTON, DC 20555-0001 AND TO THE PAPERWORK REDUCTION PROJECT (31$0-0104), OFFICE OF MANAGEMENT AND BUDGET, WASHINGTON. DC 20503.

FACILITY kAMF (1) DOCKFT NUMBER (?) (ER NUMBER (61 PACE (3)

SEQUENTIAL REVISION YEAR South Texas, Unit 1 05000 498 7 OF 7 93 -- 017 -- 01 TEXT (If more space is reovired, use additional copies of KRC Form 366A) (17)

ADDITIONAL INFORMATION: (Cont'd)

On May 22, 1993, Fisher Service Company performed a series of diagnostic tests to determine the overall operating condition of the valve. The tests verified that the valve stroke, packing friction, and seat load were within specifications, but did indicate minor resistance in the upper portion of the stroke. This resistance did not prevent or hinder the valve from stroking.

Fisher felt that the resistance could be from galling in the stem guide area ,

or packing material buildup on the stem of the valve. The actuator spring rate, total travel, and bench settings were within specifications. On May 25, 1993, the FWIBV was disassembled and an inspection performed by Engineering ,

and Maintenance personnel revealed signs of normal wear except for thread damage on the upper 5/8 in. of the actuator stem and valve plug stem. There were no indications of any sticking or binding in the valve actuator or body. i On May 26, 1993 the Valtek vendor was brought in to inspect the valve.

Valtek's inspection concurred with HL&P's finding.

This determination is based on the following: l o The I&C technician was not certain he witnessed valve sten movement. '

1 o Valve travel is limited by plug motion between seat and backseat which was j measured to be 1.672 inches. The limit switch settings were found approximately 1.5 inches apart, indicating that the valve had been stroking fully.

l-o No physical evidence was found upon inspection of the valve components I which could have caused or indicated mechanical binding of the valve.

o The discovered thread damage on the actuator stem and valve plug stem at the point of overlap suggests that when the valve stem clamp was loosened for maintenance, the valve actuator stem moved downward while the valve plug stem was stationary due to the valve plug being seated. This also accounts for the observed pointer movement.

HL&P has analyzed Fisher's diagnostic test and Valtek's report. On the basis of this report and HL&P's investigations, HL&P has determined that the valve was, in fact, not open and this event is no longer reportable.

LE R-93\L93017R1.U1