ML20196C195
| ML20196C195 | |
| Person / Time | |
|---|---|
| Issue date: | 11/29/1988 |
| From: | Cherny F NRC OFFICE OF NUCLEAR REGULATORY RESEARCH (RES) |
| To: | Baer R NRC OFFICE OF NUCLEAR REGULATORY RESEARCH (RES) |
| References | |
| REF-GTECI-B-55, REF-GTECI-PV, TASK-B-55, TASK-OR NUDOCS 8812070217 | |
| Download: ML20196C195 (41) | |
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\,*..../ NOV 2 91988 MEMORANDUM FOR: Robert Baer, Chief Engineering Issues Branch Division of Safety Issue Resolution FROM: Frank C. Cherny, Section Leader Engineering Issues Branch Division of Safety Issue Resolution
SUBJECT:
MINUTES OF OCTOBER 25, 1988 MEETING WITH BWR OWNER'S GROUP RE: TARGET ROCK 2-STAGE SAFETY / RELIEF VALVE SET POINT DRIFT (GENERIC ISSUE B-55 PROGRESS REPORT)
Attached are the attendance list and the handouts of the October 25, 1988, staff meeting with the BWR Owner's Group (BWROG) on the referenced generic issue.
P_re-meeting Background In an attachment to a memorandum dated January 13, 1988, from Guy A. Arlotto to B. M. Morris re: STATUS REPORT-GENERIC IdSUE B-55 "IMPROVE RELIABILITY OF TARGET ROCK SAFETY-RELIEF VALVES." the status of the resolution of this issue, up to that time, was sunnarized. It was noted in that report that setpoint drift resulting from pilot valve disk to seat corrosion bonding in the 2-stage safety / relief valve was the sole remaining concern to be addressed before this generic issue could be considered resolved. The report described that the BWROG had committed to conduct a 2-3 year test program, consisting of both laboratory and reactor testing, on a new pilot valve disk material, PH13-8Mo, which the BWROG had concluded had the potential to be less susceptible to forming a tightly adherent corrosion Land to the Stellite 6B pilot valve seating surface. As discussed in the status ceport, the most significant element of the test program was that, over the 2-3 year testing program, up to 50 percent of the pilot disks in 2-stage SRVs in a number of BWRs would be replaced with PH13-8Mo disks to obtain reactor performance data to compare with that of the existing Stellite 68 disks exposed to the same environtrent.
In the status report, it was indicated that, bastd on the limited operating experience and test data accumulated up to that time, the PH13-8Mo disks were performing acceptably. It was estimated that at le6st an additional 18 months was needed to fully assers the performance of the new disk material.
Meeting of October 25, 1988 The purpose of the most recent meeting on October 25, 1988, was for the BWROG to provide an updated progress report including the latest results of both reactor and laboratory testing. A considerable amount of both types of test data had becone available since the issuance of the January 8,1988, status report. Detailed information presented is shown in the attachments to this memorandum. Some of the more significant items are:
' l 3 E C PDC
2 NOV :: 9 1983
- 1. As of October 1988, reactor comparison test data of PH13-BMo pilot disks versus Stellite 68 disks has been obtained from 5 operating BWRs, repre-senting 4 different utilities and 2 plant cycles from 1 plant. This represents data from a total of 29 SRVs with PH13-8Mo pilot disks and 37 with Stellite 6B disks.
- 2. "As received" comparative test data indicates the performance of the PH13-8Mo disks was cor.sidera'uly better than that of Stellite 68. On 1 plant, 2 SRVs with new disks displayed setpoint drift of rore than 3 percent above normal set pressure, i.e., 4.28 percent and 3.5 percent.
These were 2 out of 8 SRVs with new disks installed on the same plant.
Three of 6 other SRVs with Stellite 6B disks, from the same plant, had i setpoint drifts much greater than 3 percent, ranging up to 10 percent. !
Although not totally clear in the meeting handouts, as reported in NRC Information Notice No. 88-30 on another plant,1 out of 4 SRVs with PH13-8Mo disks tested at higher than 3 percent above normal set pressure (4 percent), and 1 out of 5 SRVs on that plant with Stellite 6B disks tested at 9.3 percent above nominal.
The other 26 SRVs with PH13-8Mo pilot disks all exhibited set point drift ;
of less than 3 percent above nominal set pressure. By comparison, approximately 12 of the 37 SRVs with Stellite 6B disks opened at greater than 3 percent above nominal set pressure.
3 The reactor data accumulated thus far indicates that SRVs with PH13-8Mo disks display an average setpoint drift of about 50 percent less than those with Stellite 6B disks that were exposed to the same environment. l
- 4. Laboratory testing has provided increased insight on the effects of l various environmental conditions on PH13-8Mo in contact with Stellite 68.
However, from examinations of both laboratory samples and reactor test disks, it appears that the laboratory testing performed to date has not '
successfully duplicated the reactor environment.
- 5. The BWROG is generally encouraged by the reactor test date thus far accumulated. However, the BWROG program established in late 1985 requires ,
the accumulation of at least 50 as received set pressure data points from SRVs using PH13-BMo disks to assure that a statistically meaningful data base exists for reaching a final conclusion. Thus, another 20-30 data points must be obtained before the BWROG will be able to reach a final conclusion on the use of PH13-8Mo. The BWROG specifically stated that while the additional data is being obtained, they would not reconnend replacing more than 50 percent of the SRV pilot disks per plant with those of the new material. Obtaining this additional data is expected to take 12-14 more nonths; thus, the schedule for resolution of this issue will have to be $!ipped about 12 months. The schedule for resolution of this generic issue $s approximate, because the operating cycle schedules for the reactors of the participating utilities are governed by factors beyond the scope of the issue.
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- 6. Technical Specification Revisions In addition to discussing the performance of the pilot valve SRV disks, the BWROG discussed a proposal for several changes to SRV setpoint tolerances in plant technical s:.ecifications applicable to most BWR plants, i.e., both plants utilizing the Target Rock 2-stage SRV and others. The details of the proposal are shown in the attached meeting slides entitled "SRV Setpoint Tolerance Program." The proposed changes involve changing the c.arrently used, plus or minus 1 percent of nominal setpoint to plus or minus 3 percent of nominal, for selection of additional valves for testing (ref. ASME/ ANSI-0M-1-1981) and submittal of a "cyclic report." Analyses would be performed to justify a new LCO, higher than plus or minus 3 percent, beyond which an LER per 10CFR50.72 or 10CFR50.73 would be submitted.
The staff emphasized that the proposed Technical Specification Revisions were considered to be outside the scope of Generic Issue B-55 and that the BWROG should interact directly with NRR (Technical Specifications Branch) regarding review and approvals of the proposed revisions.
o F. Cherny, Sect n Leader Engineering Issues Branch Division of Safety Issue Resolution cc: w/ attachment T. Speis J. Rosenthal W. Houston G. Thomas W. Minners K. Desai R. Bosnak C. Hanner R. Baer E. Sullivan L. Shao M. Wegner J. Richardson S. Tingen, RI!
C. Rossi F. Jappe, RII C. Thomas R. Kirkwood W. Hodges H. Ornstein L. Marsh POR E. Butcher
BWROG/NRC MEETING 10/25/88 ROCKVILLE, MD 9:00 INTRODUCTION / PURPOSE CHURNCY (NRC) 9:05 BACKGROUND WARGO (NUSCO) 9:15 SETroINT DRIFT o FIx DESCRIPTION $ZEGLIN (TRC) o INSERVICE EXPERIENCE BOSEMAN (GE) o LAsonAToRY Test REsuLTs HANSON (GE) o MATERIAL SELECTION PANEL COMMENTS JOHNSON (S. LEVY) 10:30 o
SUMMARY
WARGO 10:45 SETPOINT TOLERANCE RELAXATION o BACKGROUND WARGO o OsasCTIVE CoRNWELL (GE) o APPROCH/ SCOPE 11:15
SUMMARY
WARG0 11:30 COMMENTS / CONCLUSIONS CHURNEY 12:00 MEETING CLOSE (102588-MET /GVK1)
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. BWROG / NRC MEETING DCTOBER 25, 1988
. VALVE DESIGN
- 1. SIZE AND BASIC OPERATIONAL REQUIREMENTS
- 2. DESCPIPTION OF OPERATION
. LABYRINTH SEAL "FIX" l
- 1. OBSERVATIONS
- 2. FIELD IMPLEMENTATION OF "FIX' K- t
. SEAT TO Disp'CORROS!ON BONDING "FIX"
- 1. OBSERVATIONS
- 2. MATERIAL SELECTION
- 3. MATERIAL QUALIFICATION
- 4. FIELD IMPLEMENTATION i
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TRC 6x10 MODEL 756/F VALVE DESIGN
. SIZE: 6" INLET x 10" OUTLET SET POINT RANGE: APPROXIMATELY 1060 --- 1160 PSIG SET POINT TOLERANCE: + 1.0% FOR NEW OR REFURBISHED VALVE BLOWDOWN: 3 --- 11% l FLOW CAPACITY: 818,000 TO 950,000 #/HR.
SATURATED STEAM AT 3% AccVMULATION t
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. DESCRIPTION OF OPERATION l
PILOT MAIN PNEUMAT!c OPERATOR NOTE: FURTHER DETAll ON OPERATION FOLLOWS PAGE 4 0F PRESENTATION A.L. SZEGLIN 10/25/88
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TARGET ROCK CORPORATION MODEL 7567F 6x10 MSRV DESCRIPTION AND OPERATION GENERAL THE TARGET ROCK MODEL 7567F PILOT-OPERATED SAFETY / RELIEF VALVE CONSISTS OF TWO PRINCIPLE ASSEMBLIES: A SII.0T STAGE ASSEMBLY AND THE MAIN STAGE ASSEMBLY. TEESE TWO ASSEMBLIES ARE DIRECTLY COUPLED TO PROVIDE A UNITIZED, DUAL FUNCTION SAFETY / RELIEF VALVE. TPE PILOT STAGE ASSEMBLY IS THE PRES-SURE-SENSING AND CONTROL ELEMENT, AND THE MAIN STAGE ASSEMBLY IS A SYSTEM FLUID-ACTUATED FOLLOWER VALVE WHICH PROVIDES THE P R E S SIIR E RELIEF FUNCTION. SELF-ACTUATION OF THE PILOT ASSEM-BLY AT SET PRc 3URE VENTS THE MAIN PISTON CHAMBER, PERMITTING THE SYSTEM PRESSURE TO FULLY OPEN THE MAIN ASSEMBLY, WHICH RESULTS IN SYSTEM DEPRESSURIZATION AT FULL RATED FLOW.
CENERAL DATA VALVE TYPE: P.'OT-OPERATED SAFETY / RELIEF VAuYE SIZE: INLET 6 INCH-1500# (6 INCH BORE)
FLANGED CONNECTION OUTLET 10 INCH-300# FLANCED CONNECTION DESIGN PRESSURE: 1250 PSI DESIGN TEMPERATURE: 5750 F SET PRESSURE ADJUSTMENT RANGE: 1025 TO 1190 PSIG CAPACITY: 818,000 TO 950,000 LB/HR-SATURATED STEAM (DEPENDING ON SET PRESSURE)
OVERALL DIMENSIONS: 36 x 30 x 17-1/2 INCHES WEIGHT: 1100 LB l PILOT ASSE,MBLY OPERATION (SAFETY MODE)
OPERATION OF THE PILOT ASSEMBLY AND MAIN ASSEMBLY IS DESCRIBED IN DETAIL IN THE FOLLOWING SECTIONS. REFER TO FIGURES 1 AND 2 kJR SCHEMATIC ILLUSTRATIONS OF THE VALVE IN CLOSED AND GPEN POSITIONS.
THE PILOT ASSEMBLY OF THE VALVE CONSISTS OF TWO MELATIVEI.Y SMALL, LOW FLOW PRESSURE-SENSING ELEMENTS. THE SPRING-LOADED PILOT DISC SENSES THE SET PRESSURE, AND THE PRESSURE-LOADED STABil.IZER DISC SENSES THE RESEAT PRESSURE. SPRING FORCE (PRELOAD FORCE) IS APPLIED TO THE PILOT DISgBSY MEANS OF THE PILOT ROD. THUS. THE ADJUSTMENT OF THE SPRING PRELOAD FORCE WILL DETERMINE THE SET PRESSURE OF THE VALVE.
ALS 6/3/85
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OPERATION OF THE PILOT ASSEMBLY IS AS FOLLOWS:
DURING ASSEMBLY, THE PILOT SPRING IS ADJUSTED TO PROVIDE A PRELOAD FORCE ON THE PILOT DISC WHICH WILL ESTABLISH THE REQUIRED SET PRESSURE OF THE VALVE. THE SPRING PRELOAD FORCE SEALS THE PILOT DISC TICHTLY TO PREVENT LEAKAGE AT NORMAL OPERATING PRESSURES OR LOWER SYSTEM PRESSURES.
IN OPERATION, AS SYSTEM PRESSURE INCREASES AND REACHES SET PRESSURE, THE SEATING FORCE ACTING ON THE PILOT DISC IS RE-DUCED TO ZERO CAUSING THE PILOT DISC TO LIFT FROM ITS SEAT.
PILOT DISC LIFT RESULTS IN THE DEPRESSURIZATION OF THE MAIN PISTON CHAMBER VOLUME. INITIAL VENTING (DEPRESSURIZATION) 0F THE MAIN PISTON CHAMBER CREATES A DIFFERENTIAL PRESSURE ACROSS THE STABILIZER DISC IN A DIRECTION CAUSING THE STABI-LIZER DISC TO SEAT. SYSTEM PRESSURE ACTING UPON THE STABILIZER DISC VIA THE INTERNAL PORTING MAINTAINS TliE PILOT DISC IN THE "LIFTED" POSITION THEREBY MAINTAINING MAIN PISTON CHAMBER VENTING UNTIL THE REQUIRED DIFFERENTIAL PRESSURE ACROSS THE MAIN PISTON IS ACHIEVED, AT WHICH POINT THE MAIN S1 AGE OPENS.
WHEN SYSTEM PRESSURE HAS DECREASED TO THE VALVE RESEAT PRES-SURE, THE PRESSURE-SENSING STABILIZER DISC WILL UNSEAT PER-MITTING THE PILOT DISC TO RESEAT THIS IN TURN CAUSES MAIN PISTON CHAMBER REPRESSURIZATION, WHICH RESULTS IN CLOSING OF THE MAIN STAGE.
ALS 6/3/85
O e MAIN STAGE ASSEMBLY OPERATION THE MAIN ASJEMBLY OF THE TARGlT ROCK SAFETY / RELIEF VALVE IS BASICALLY A REVERSE (PRESSURE) SEATED, SYSTEM FLUID-ACTUATED ANGLE GLOBE VALVE. ACTUATION OF THE MAIN ASSEMBLY PERMITS DISCHARGE OF FLUID FROM THE PROTECTED SYSTEM AT THE VALVE'S RATED FLOW CAPACITY AND PR^VIDES THE SYSTEM PRESSURE RELIEF FUNCTION OF THE VALVE. THE MAJOR COMPONENTS OF THE HAIN STAGE ARE THE VALVE BODY, DISC / PISTON ASSEMBLY AND PRE-LOAD SPRING.
OPERATION OF THE MAIN STAGE IS AS FOLLOWS IN ITS NORMALLY CLOSED POSITION, THE MAIN STAGE DISC IS TIGHTLY SEATED BY THE COMBINED FORCES EXERTED BY THE PRELOAD SPRING AND THE SYSTEM INTERNAL PRESSURE ACTING OVER THE AREA 0F THE DISC.
NOTE THAT IN THE CLOSED (NO FLOW) POSITION THE STATIC PRESSURES WILL BE EQUAL IN THE VALVE INLET N0ZZLE AND IN THE CHAMBER OVER THE MAIN STAGE. PISTON. THIS PRESSURE EQUALIZATION IS MADE POSSIBLE BY THE INTERNAL PASSAGES PROVIDED 1.e. PISTON RING GAP. VENT HOLE, DRAIN GROOVE AND STABILIZER DISC SEAT. !
WHEN SYSTEM PRESSURE INCREASES TO THE VALVE SET PRESSURE, PILOT STAGE OPE 7ATION WILL VENT THE CHAMBER OVER THE M AIN S** AGE PISTON TO D0'JNSTREAM OF THE VALVE VIA INTERNAL PORTING. THIS VENTING ACTION CREATES A DIFFERENTIAL PRESSURE ACROSS THE MAIN STAGE PISTON IN A DIRECTION TENDING TO UNSEAT THE VALVE. THE MAIN STAGE PISTON IS SIZED SUCH THAT THE RESULTANT OPENING FORCE IS GREATER THAN THE COMBINED SPRING PRELOAL AND SYSTEM PRESSURE SEATING FORCE.
ONCE THE MAIN STAGE DISC STARTS TO OPEN. THE SEATINO F0ECE IS RAPIDLY REDUCED, ALLOWING THE MAIM DISC TO OPEN WITH ITS CHARACTERISTIC "POP OPEN" ACTION TO THE FULLY OPEh POSITION.
WHEW SYSTEM PRESSUP5 HAS BEEN REDUCED TO DESIGN RESEAT PRESSURE, THE PILOT DISC RESEATS PERMITTING REPRESSURIZATION OF THE MAIN PISTON CHAMBER. FLOW OF SYSTEM FLUID THROUGH THE MAIN STAGE ,
PISTON RING GAP AND STABILIZER SEAT THEN REPRESSURIZES THE l CHAM 3ER OVER THE PISTON. MAIN ST/.GE DESIGN IS SUCH THAT THE REPRESSU21ZATION OF THE PISTON CHAMBER EQUALIZES SYSTEM PRESSURE FORCES PERMITTING THE PRELOAD SPRING AND FLOW FORCES TO CLOSE THE MAIN STAGE. ONCE CLOSED, THE ADDITIONAL SYSTEM FLUID SEAT-ING FORCE, OUE TO SYSTEM PRESSURE ACTING ON THE MAIN STAGE DISC, 6 SEATS THE MAIN STAGE TIGHTLY.
ALS ,
6/3/85 1
l PNEUMATIC ACTUATOR OPERATION (RELIEF MODE) l A REMOTELY CONTROLLED AIR OPERATOR IS FITTED TO THE PILOT STAGE ASSEMBLY TO PROVIDE SELECTIVE CPERATION OF THE VALVE AT SYSTEM PRESSURES RANGING FROM 50 PSIC TO VALVF SET PRES-SURE. THIS IS A DIAPHRAGM TYPE PNEUMATIC ACTUATOR WHICH MUST BE ACTUATED TO OPEN THE VALVE. IT IS ACTUATED BY MEANS OF A SOLENOID CONTROL VALVE WHICH ADMITS PLANT AIR TO THE AIR OPERATOR PISTON CHAMBER AND STROKES THE AIR OPERATOR STEM, IN TURN STROKING THE PILOT DISC VIA THE PILOT ROD. THE MAIN STAGE THEN CPENS AS DESCRIBED IN PREVIOUS PARAGRAPHS. DE-ENERGIZING THE SOLENOID VENTS THE AIR OPERATOR DIAPHRAGM CHAMBER CAUSING THE AIR OPERATOR STEM TO RETURN TO ITS UN -
STROKED POSITION. THE PILOT STAGE THEN RESEATS IF SYSTEM PRESSURE IS AT THE VALVE DESIGN RESEAT PRESSURE OR LOWER.
RESEAT OF THE PILOT STAGE, WHICH IS AS PREVIOUSLY DESCRIBED, IN TUWi CAUSES RESEAT OF THE MAIN STAGE AS DESCRIBED THEREIN.
ALS 6/3/85
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A.L. SZEGLIN 10/25/88
TRC 6X10 MSRV LABRINTH SEAL 'FIX' l'
- 1. OBSERVATIONS:
+ A) THE SET POINTS NOTED DURING AS FOUND RECERTIFICATION TE; TING WOULD BE HIGH AND TREND D0ti1 WARDS AFTER THE FIRST CYCLE. THIS WAS ATTRIBUTED TO ABNORMALLY HIGH FRICTION IN THE LABYRINTH SEAL AREA. (EXAMPLE NP 1100 SET POINTS 1145, 1130, 1140, 1125)
B) LAB)RINTH SEAL AREAS WERE INSPECTED, CLEARANCES WERE NOTED TO BE BELOW DESIGN HINIMUMS AND WEAR PATTERNS WERE ABNORMAL.
- 2. FIELD IMPLEMENTATION 0F 'FIX' A) VALVES DISASSEMBLED B) LABYRINTH SEAL CLEARANCES MEASURED C) LABYRINTH SEAL AREA POLISHED AS NECESSARY TO ADJUST CLEARANCE AND FINISH l D) LABYRINTH SEAL AREA LUBRICATED WITH 'DAG 156' E) VALVE RE ASSEMBLED AND TESTED F) LABYRINTH SEAL CHECKED AT REGULAR VALVE REBUILD INTERVALS r
A.L SZEGLIN 10/25/88 ,
TRC 6X10 MSRV CORROSION BONDING 'FIX'
- 1. OBSERVATIONS:
A) THE SET POINT NOTED DURING THE AS FOUND RECENTRIFICATION TESTING OF THE FIRST CYCLE WOULD BE HIGH AND SUBSEQUENT CYCLES ROUGHLY WITHIN SPECIFICATION SET POINT REQUIREMENTS, (EXAMPLE NP 1100. SET POINTS, 1145, 1105 AND 1109)
B) CORROSION BONDING NOTED AT DISC / SEAT INTERFACE.
- 2. MATERIAL SELECTION A) BASED ON THE INPUT OF THE 'HATERIALS SELECTION PANEL", AS WELL AS DISC / SEAT MATERIAL EVALUATION TESTS ON ELEVEN DISC / SEAT COMBINATIONS (TOTAL OVER 5,000 STiAM CYCLES) IT WAS DETERMINED THAT PH13 8MO WAS THE MOST SUIT ABLE CANDIDATE OF THE MATERIALS INVESTIGATED FOR THE PILOT DISC.
- 3. MATERIAL QUALIFICATION (PRIOR TO BEING INSTALLED IN BWR SYSTEMS)
A) THREE (3) SAMPLE PILOT DISCS FRCH DIFFERENT HEATS WERE EVALUATED FOR PERFORMANCE AT TARGET ROCK CORPORATION (TRC) ON STEAM AND FOUND ACCEPTABLE (HORE THAN 700 TOTAL CYCLES ACCUMULATED).
- 4. FIELD IMFLEMENTATION OF 'FIX' A) IT WAS DETERMINED THAT UP TO 50% OF THE NUMBER OF REQUIRED VALVES CAN BE MODIFIED WITH PH13 8MO DISCS.
B) VALVES ARE NORMALLY Mi)!FIED DURING REFURBISHMENT AFTER AS FOUND TESTING.
A.L. SZEGLIN 10/25/88
o o i
The Owners Group sponsored investigations of Set Point Drift of Target Rock Two Stage Safety Relief Valves identified two contributing mechanisms.
- 1. The first mechanism is attributed to mechanical friction in the labrinth seal section of the valve.
Labyrinth seal friction is caused by closu running clearances in the pilot section.
Set point drift from this mechanism can be identified by analyzing steam pressure traces of a valve on a test stand. The magnitude of this mechanism is on the order of 5-74 of set point. It is experienced on a small percentage of valves tested at WYLE laboratories.
- 2. The second mechanism is attributed to corrosion at the pilot seat interface.
Similarly, Set Point drift from corrossion can be j identified by analysing steam pressure traces of a j valve on a test stand. Corrosion induced drift is airo 2
experienced on a small percentage of valves and is on the order of **% of setpoint.
l OWNERS GLOUP SPONSORED ACTIONS
- 1. Industry wide inspections of the labrinth seal.
- 2. An advisory panel of metalurgists and engineers was established to evaluate and select disc materials.
- 3. candidate materials were performance tested in a manner j similar to orginal qualification tests.
l One material emerged a this time as a likely
, replacement for Stellite 6B. PH13-8Mo was made available for field use, <= 1/2 of installed discs to i be PH13-8Mo.
- 4. Safety Relief valves were monitored to aquire all data associated with actuation in the field or "as received" i
at WYLE Labs.
- 5. Laboratory testing of PH13-8Mo was initiated to generally confirm asuumptions about the nature of PH13-8Mo and accelerate the process of replacement material installation. The anticipated result of simple bene.h
> tests in the labs at San Jose was to provido clear I evidence of exceptional performance of PH13-8Mo with I respect to Stellite 6B.
t I
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1
SUMMARY
t
- 1. Field and as received data has provided additional ,
assurance that valve performance is improved. .
- 2. Test resbita evoked more tests and at times delayed the installation of PH13-8Mo in the field. Delt,ying the dquisition of .ield data in a true BWR environment.
Test results also provoked evaluation of many facets of corre.csion mechanisms, test dusign, test interferences, valve materials, valve geometry, steam and condensate !
characteristics which ultimatnty mproved confidence in. .
the replacement material.
Target Rock Two Stage SRV's and the Ow..ers Group Today ,
- 1. In plant data has no significant anomolies related to
! demands on the valve from transients, or "as received"
) testing.
- 2. Laboratory testing has provided background details abe't the ei'f ects of a variety of environmental c."dicions on PH13 Ao in contact with Stellite 6.
PH13-8Mo has exhibited characteristic which would enhance the performanco of the velve with respect to I Stellite 6B discs based on assumed conditions prosent ,.
j in the topworks of a valve.
Additional field data is required prior to increasing the fraction of PHl.' 9Mo in the field
- 3. t r :ommend continued installation of PH13-8Mo disc at
.es percent of the population as valves become ,
available during normal availabilities and continued l
field data aquisition. !
a j i i
J I
)
n _.
t TRC TWO-STAGE SRV SET POINT DRIFT ISSUE IN-SERVICE EXPERIENCE o TEN (10 0F 14) BWR POWER PLANTS WITH TARGET ROCK 2-STAGE SRVs HAVE EITHER INCORPORATED OR ARE CURRENTLY PLANNING INSTALLATION OF PH13-8MO PILOT DISCS INTO UP
, TO 50% OF THEIR INSTALLED SRVS. THIS BWROG PRUDENT TECHNICAL APPROACH WAS TAKEN TO OBTAIN ACTUAL IN-SERVICE EXPERIENCE TO DEMONSTRATE THE GENERIC BWR RESOLUTION OF THE RECOMMENDED FIX. THE IN-SERVICE ,
EXPERIENCE APPROACH PROVIDES FOR:
ACTUAL SRV PERFORMANCE DATA FROM MULTI-PLANT OPERATING ENVIRONMENTS.
CONTROL GROUPS TO PROVIDE DIRECT AND IMMEDIATE SET POINT PERFORMANCE DATA COMPARISON SHOULD THERE BE A TRANSIENT.
HINIMIZING VARIABLES BETWEEN ACTUAL IN-SERVICE CONDITIONS AND OTHER APPROACHES. ,
4
+
i
TRC TWO-STAGE SRV SET POINT DRIFT ISSUE o TEN (10 0F 14) BWR POWER PLANTS WITH TARGET ROCK 2-STAGE SRVs HAVE EITHER IllCORPORATED OR ARE CURRENTLY PLANNING INSTALLATION OF PH13-8MO PILOT DISCS INTO UP TO 50% OF THEIR INSTALLED SRVS. THIS BWROG PRUDENT TECHNICAL APPROACH WAS TAKEN TO OBTAIN ACTUAL IN-SERVICE EXPERIENCE TO DEMONSTRATE THE GENERIC BWR RESOLUTION OF THE RECOMMENDED FIX. THE IN-SERVICE EXPERIENCE APPROACH PROVIDES FOR:
ACTUAL SRV PERFORMANCE DATA FROM MULTI-PLANT OPERATING ENVIRONMENTS.
CONTROL GROUPS TO PROVIDE DIRECT AND IMMEDIATE SET 1 POINT PERFORMANCE DATA COMPARISON SHOULD THERE BE A TRANSIENT.
- MINIMIZING VARIABLES BETWEEN ACTUAL IN-SERVICE CONDITIONS AND OTHER APPROACHES.
.e
. ?.?l.
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Attacheent.,
IN-SERVICE EXPERIENCE OF PH13-8MO (T0 JANUARY 1987)
N0. OF TOTAL NO. OF SRY IN-SERVICE C!MLLENGES PLANT OF YALVES W/PH13-8MO SINCE TO DATE REMARXS Hatch 1 11 5 May 86 2)a Satisfactory operation b
Hatch 2 11 5 Dec. 86 l) Satisfactny operation CI tisfactory Brunswick 2 11 6 June 86 2 i Farmi 2 15 8 Aug. 86 None Hope Creek 14 1 Aug. 86 None j Notes: a) January 1987, all eleven valves lifted. (Peak pressure within 31 of '
highest setpoint.)
b) January 1987,10 of 11 lifted (one Stellite valve did not lift-peak pressure within 15 of highest setpoint).
j c) All valves required to actuate (including some using PH13-8Mo) lifted automatically. Others did not lift due to low peak transient pressures, j
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% ORIFT HISTOGRAM OF SRV DRIFT FOR VALVES WITH @H13-8 DISCS
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% ORIFT HISTOGRAM OF SRV DRIFT FOR VALVES WITH STELLITE DISCS 4
, REV. 2 10/88 TRC TWO-STAGE SRV AS-RECEIVED SETPOINT DATA
SUMMARY
FOR PLANTS WITH PH13-8Mo DISCS PLANT / QTY AVERAGE STD QTY STUCK DlSC MATERIAL VALVES DRIFT M) Diy Dlici HATCH 1/
PH13-8Mo 5 0.08 1.66 0 STELLITE 6B 6 0.85 2.97 1 HATCH 2/
PH13-8Mo 5 1.03 1.48 'O STELLITE 6B 6 1.77 1.51 1 HATCH 1/
PH13-8Mo 5 -0.48 1.94 0 p j,17 STELLITE 6B 6 0.34 1.29 0) fol $$
BRUNSWICK 2/
PH13-8Mo 4 1.16 2.28 0 STELLITE 6B 5 2.28 4.25 1 HOPE CREEK /
PH13-8Mo 2 1.03 0.70 0 STELLITE 68 8 3.33 1.99' 1 FERMI 2/
PH13-8Mo 8 1.79 1.80 2 11ELLITE 6B 6 4.46 4.71 _1 l
i JJB-1
TRC TWO-STAGE SRV SET POINT DRIFT DATA
SUMMARY
FOR PLANTS WITH PH13-8Mo DISCS OBSERVATIONS o SRVs WITH PH13-8Mo DISCS HAVE A SIGNIFICANTLY LESS PROPENSITY FOR SET POINT DRIFT THAN SRVS WITH STELLITE 6B DISCS.
I AVERAGE DRIFT IS APPROX. 50% LESS STANDARD DEVIATION IS APPROX. 30% LESS o SRVs WITH PH13-8Mo DISCS HAVING "AS-RECEI"ED" SET POINT DRIFT GREATER THAN 3% WERE NOTED ON JUST ONE PLANT.
TWO (2) 0F THE EIGHT (8) SRVS INSTALLED WITH j PH13-8Mo DISCS HAD SET POINT DRIFT GREATER THAN 3%.
1 l
o MAGNITUDE WAS 4.28% (S/N 333) AND 3.5% (S/N 391)
)l RESPECTIVELY.
! l o WHEREAS (3) THREE OF THE EIGHT (8) SRVs WITH l STELLITE 6B DISCS HAD SET POINT DRIFTS OF UP TO l i
10%.
l l \
BOTH PH13-8Mo SRVS WITH THE GREATER THAN 3% SET j POINT DRIFT LEAKED PRIOR TO SRV ACTUATION SUCH THAT
) A N2 (STUCK DISK) DIAGNOSTIC TEST WAS NOT !
PERFORMED.
- l '
l !
l')/88 l JJB-2 :
I r
,,,o -
l TRC TWO-STAGE SRV SET POINT DRIFT DATA
SUMMARY
I FOR PLANTS WITH PH13-8Mo DISCS l t
. o OVERALL
SUMMARY
OF THE IN-SERVICE SRV SET POINT ;
! PERFORMANCE RESULTS OBTAINED TO DATE INDICATES i THAT: ,
- THE PH13-8Mo PILOT DISC APPEARS TO MITIGATE
) EXCESSIVE SET POINT DRIFT (>3%) DUE TO .
CORROSION INDUCED BONDING EXPERIENCED WITH THE !
STELLITE 6B PILOT DISC TO STELLITE 6 PILOT SEAT i
INTERFACE.
o THE DATA IS FROM 5 PLANTS, 4 DIFFERENT f UTILITIES, AND 2 PLANT CYCLES FROM 1 PLANT. j o THE INFORMATION IS BASED UPON 29 SRVS ,
CONTAINING THE PH13-8MO DISC AND 37 SRVS ;
CONTAINING THE STELLITE 6B DISC. ,
ANOTHER 20 TO 30 MORE PH13-8Mo SRV OATA POINTS l SHOULD BE OBTAINED FROM AT LEAST 4 MORE PLANTS AND 3 l DIFFERENT UTILITIES TO ASSURE: l I
o STATISTICAll,Y MEANINGFUL SAMPLE BASIS. '
o REPEATABILITY AT MORE THAN ONE UTILITY.
l l
10/88 i JJB-3 I
1 1
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'f
================================ l AUTOCLAVE TESTING AT GE SAN JOSE <
================.""==============E J
ORIGINAL OBJECTIVES OF AUTOCLAVE TESTING i
OBTAIN CORROSION STICKING DATA COMPARING PH13-8MO AND 3
STELLITE PILOT DISCS IN WATER AUTOCLAVE TESTS l l
DEVELOP A HIGHER CONFIDENCE LEVEL FOR AN EARLIER i
CLOSURE OF THE SET POINT DRIFT ISSUE l
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l l GRH OCTOBER 25, 1988 !
i i
__ . _ _ _ . _ _ ___._._____,.______,,__.__,m..,.____.__.,, _
, _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ . _ , - . ~ - - _ . ,
l
. +
'. =============================================
IMPORTANT OBSERVATIONS FROM AUTOCLAVE TESTING
=================================
0 OXIDE BONDING WAS VERIFIED AS A MECHANISM FOR STICKING OF DISKS i 0 EFFECT OF Q3IDE COATING PH13-8MO DEVEL.0PS APROTECTIVE OXIDE WHICH CAN PREVENT STICKING.
STELLITE DOES NOT APPEAR TO DEVELOP A PROTECTIVE OXIDE BUT CONTINUES TO STICK AFTER SUSTANTIAL OXIDE IS FORMED, O THE CONCENTRATION OF OXYGEN APPEARS TO BE AN IMPORTANT VARIABLE IN LOW OXYGEN WATER (6 TO 8 PPM)
PH13-8MO STICKS WITH LOADS UP TO 177 POUNDS, WHEREAS STELLITE STICKS WITH VERY LOW LOADS l (5 LBS MAX) (4# = 1\ DRIFT APPX)
FOR PLANT VALVES THIS BEHAVIOR IS REVERSED, WE BELIEVE THIS MAY BE CAUSED BY HIGHER OXYGEN LEVELS IN THE VALVE i
i STUDIES OF THE VALVE DESIGN AND EXAMINATION OF DISCS EXPOSED TO IN SERVICE VALVE CONDITIONS SHOW THAT OXYGEN LEVELS IN PLANT l VALVES ARE HIGHER THAN WAS USED IN THESE TESTS. OXYGEN IS ESTIMATED TO BE 20 PPM OR HIGHER IN PLANT VALVES 1
0 CONTAMINANTS APPEAR TO HAVE AN EFFECT ON STICKING 0 E&iED ON THESE FINDINGS PH13-8MO CONT'NUES__T0_LOOK PROMISING GRH OCTOBER 25, 1988
j- sEM No._ /3 8/
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10,000 l l PRE-OXIDATION IN STEAM PRL-OXIDATION IN WATER I IlOURS I:Ot!RS l - GRil OCTOBER 25, 1988 e
. .~
i i o ' ENVIRONMENTAL CONDITIONS IN THE VALVE l
=======================================
DIFFERENCES IN AUTOCLAVE TESTS VERSUS FIELD RESULTS TRIGGERED A REVIEW OF POTENTIAL DIFFERENCES BETWEEN THE TEST ENVIRONMENT AND THE VALVE ENVIRONMENT .
- IF ONE EXAMINES THE ARRANGEMENT OF THE IN-SERVICE DISC AND SEAT RELATIVE TO THE STEAM ENTRY IT BECOMES APPARENT THAT THE CHAMBER WHICH HOUSES THESE COMPONENTS IS DEAD ENDED AND IS EQUIVALENT TO AN ACCUMULATOR FOR NONCONDENSIBLE GASES, ONE OF WHICH IS OXYGEN. THEREFORE IF THE PILOT SEAT INTERFACE IS NOT LEAKING THE CHAMBER WILL CONTINUE TO INCREASE IN OXYGEN CONTENT UNTIL IT REACHES EQUILLIBRIUM THE SEM EXAMINATION PERFORMED ON THE HATCH STELLITE DISC WHICH WAS EXPOSED TO REACTOR CONDITIONS CLEARLY SHOWS MORE OXIDATION THAN WAS PRESENT ON STELLITE DISCS EXPOSED TO THE 8 PPM OXYGEN IN THE AUTOCLAVE. THIS FURTHER ARGUES THAT THE OXYGEN LEVEL IS HIGl!ER IN SERVICE.
1 GRH OCTOBER 25, 1988 l
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i , . . .' , . . . . . .. 1 a . V.L 1LL .'.'. q '. 2 . J 1 I I. FIGURE 10. APPEARANCE OF OXIDES ABOVE AND BELOW THE SEAT FOR STELLITE DISC, 1000X, SEM 1 1 a
~ o BWR Owners 8 Group SRV Setpoint Tolerance Program t
t l SCOPE: Discussion of SRV Setpoint Toleranco Program Being Considered by BWROG Members i F OBJECTIVE: Outline Prograa / Discuss Alternatives Understand NRC Perspective Page 1
4
+ 0 BWR Owners' Group
, SRV Setpoint Tolerance Progran ,
BACKGROUND L [ CURRENT SRV TECHNICAL SPECIFICATIONS (TYPICAL) i o Limiting Condition for Operation on Safety Mode Actuation ; t 1090 psig i 1% (X Valves) ~ l 1100 psig i 1% (Y Valves) l 1110 psig i 1% (2 Valves) l J 4 ! O Surveillance Requirements (imposed and implied): i i I Current "As-Received" Testing
- Acceptance Criterion for Setpoints f 4 !
3 Safety Actuation not to exceed i 1% of Nameplate Value l . l l t Minimum of one-half of Installed SRVs must be tested each cycle ( I I Additional valves tested it criteria is not met l
\
l, [ i ) I 4 Testing performed following completion of cycle f i ' I Page 2 l l 1 i 1
.. s BWR Owners' Group SRV Setpoint Tolerance Progran l ACTIol45 DISULTING FROM TES; EAILURES O SRV Test results exceeding i 1% requires Reporting under 10CFR50.72 or 10CFR50.73 to addresst Cause of Test Failure Safety Implications Valve Corrective Action Taken (e.g., Refurbishment / Replacement) 0 SRV Recertification (before returning to service) Must meet i 1% Tolerance Criterien CURRENT SITUATION O Large population of SRVs do not meet i 1% Criteria (During As-Received Tests) 0 1 1% Criteria applits to new SRVs and SRVs being returned to Service BASIS FOR CHNAGING CRITERIA 0 1 3% Tolerance is appropriate for In-Service Valves O ANSI /ASME OM-1-1981 reconnends 3% as SRV in-service setpoint acceptance criterio.i 0 ASME Code, Section XI, 1986 Edition, Incorporates ANSI /ASME OM-1 as a Requirement Page 3
BWR Own3ra' Grcup SRV Setpoint Tolerance Program PROPOSED TEqlDiLQAL SPECIFICATION MODIFICATIOLS 0 Limiting condition for operation i All SRVs $ XXXX psig i where XXXX psig is an Upper safety Limit (approximately 1200 psig)
- Determined by Plant specific Evaluation
- Dependent on 8 of SRVs and Capacity 0 surveillance Requirements (Typical):
1090 psig i 3% (X Valves) 1100 psig i 3% (Y Valves) 1110 psig i 3% (Z Valves) Minimum of One-half of Valves must be Tested each cycle Two Additional valves (for each failure) must be tested if criterion (above) is not met setpoint not to exceed + 3 % of Nameplate O setpoint Requirement before Returning to Service Setpoint Actuations not to exceed i 1 % of Nameplate o Adminisurative Requiremens ..pecifying cycle-by-cyle submittal of Report" for Valve Test Results which exceed 3% tolerance but are below upper limit LCO value. Page 4
a
,, . o .t BWR Owners' Group 3
SRV Setpoint Tolerance Program i l l CURRENT TECHNICAL SPECIFluATIONS i I ! I ; I ; L in Toleragg ^ i Ar-Received Testing Additional Testing Return to Service . Licensing Event Reports , , I , ? 1 PROPOSED TECHNICAL SPECIFICATIONS i 1 \ f ! t i J i j --
.I -
l 7 .
.I .
) - i in Tolerance 34 Tolerance Ueeer Limit I r As-Received Testing l Additional Testing ; Return to Service cyclic Reports Licensing Event l Reports . { 1 f Page 5 i l
BWR Owners' Group SRV Setpoint Tolerance Program BENEFITS 0 Hore Realistic LCO/ Surveillance Requirements o No change to current return-to-service (reset) criteria (remains at 11%) 0 In-service Setpoint Acceptance criterion changed from 1% to 3%
- 0. Acceptance Criterin for Additional Valve Testing upon Failures changed from 1% to 3%
0 Man-Rem reduction due to a reduction in the number of SRVs requiring testing and refurbishment 0 Upper Safety Limit Concept Reduces and Simplifies Raports Preparation and Review Process. Therefore, Event Reports are more meaningful. Safety concerns associated with valve actuation up to
, upper limit are pre-addressed / reviewed.
O Reporting Modificationst
- LERs required for valves exceeding upper LCO limit
- Cyclic reports for valves below upper limit but above 3%
- No reports for SRVs not exceeding the + 3% Tolerance Limit (most valves expected to meet this criterion, thus fewer LERs will require preparation and review)
Page 6
c- - . - ;.--
.. o
) BWR Owners' Group
. SRV Setpoitit Tolerance Program SRV SETPOINT TOLERANCE PROGRAM (PROPOSED)
TWO PART PLAN PROPOSED: 0 Generic Studies / Licensing Topical Report (Expected submittal Dater Mid 1989) 0 Plant Specific Study / fech spec submittal GENERIC SCOPE: ; 0 Establish Typical Transient Response j (for 3 Product lines, i.e. , l BWR3/4 with Dresser /Three Stage Target Rock l BWR3/4 with Two Stage Target Rock Valves, and l BWR5/6 with Crosby /Dikkers Generic Conclusions Applicable to all Product Lines) 0 Evaluate Effect Ont ! Vessel overpressure Response Puel Thermal Limits : LOCA/ECCS Performance I
- High Pressure Make-up System operability 0 Licensing Topical Report would include
- Purpose / Background of Evaluations (
Results/ Conclusions of Generic Studies [ Identification of areas to be addressed on a plant i specific basis (e.g., SRV discharge line loads)
- Specify plant specific report format
- Discussion & Summary of Application of ASKE i Specifications [
- Proposed Technical Specification Modification Format (s)
Page 7 ;
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