ML20057E720
| ML20057E720 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 09/17/1993 |
| From: | Ang W NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| To: | |
| Shared Package | |
| ML20057E709 | List: |
| References | |
| 50-361-93-17, 50-362-93-17, GL-89-10, NUDOCS 9310130086 | |
| Download: ML20057E720 (18) | |
See also: IR 05000361/1993017
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U. S. NUCLEAR REGULATORY COMMISSION
REGION V
Report Nos.: 50-361/93-17 and 50-362/93-17
Docket Nos.: 50-361 and 50-362
License Nos.: NPF-10 and NPF-15
Licensee: Southern California Edison Company
Irvine Operations Center
23 Parker Street
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Irvine, California 92718
Facility Name: San Onofre Units 2 and 3
Inspection at: San Onofre, San Clemente, California
Inspection conducted: August 16 through 27, 1993
Inspectors:
C. Myers, Reactor Inspector, Region V
C. Yates, Special Inspections Branch, NRR
Accompanying Personnel:
M. Holbrook, Consultant, Idaho National Engineering
Laboratory
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Approved by:
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W. P. Ang, Chief, Engineering Section
Date Signed
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Inspection Summary
Inspection durina the period Auoust 16 - 27. 1993 (Report Nos. 50-361/93-17
50-362/93-17)
Areas Inspected:
A special announced inspection of the implementation of the licensee's program
to meet commitments to Generic letter (GL) 89-10, . " Safety-Related Motor-
Operated Valve Testing and Surveillance," was conducted during the week of
August 16 through 20, 1993.
In-office review of related licensee documents
and a licensee event report was conducted during the week of August 23 through
27, 1993.
Part 2 of Temporary Instruction 2515/109 and Inspection Module
90712 were used as guidance during the inspection.
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ADOCK 05000361
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Safety issues Manaaement System (SIMS) Item:
SIMS Issue Number GL 89-10 was updated to reflect this TI 2525/109 Part 2
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inspection.
Results:
General Conclusions and Specific Findinas:
- The licensee's program was generally effective in establishing assurance of
design basis capability for the sampled MOVs.
- The licensee was implementing a program consistent with their commitments
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- Inadequate documentation and evaluation of test signature anomalies was a
program weakness.
- Testing at less than design basis flow was not yet justified within the
licensee's GL 89-10 program.
Sionificant Safety Matters:
None.
Summary of Violation or Deviations:
One violation was identified.
Open items Summary:
93-17-01:0 PEN
Violat ion
Failure to Document MOV Test Deficiencies and
Take Prompt Corrective Action
93-17-02:0 PEN
Followup
MOV Program Weaknesses
93-17-03:0 PEN
Unresolved
MOV Operability
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Details
1.0 PERSONS CONTACTED
Southern California Edison ComDanY
- D. Axline, Engineer, Onsite Nuclear Licensing (ONL)
- M. Anderson, Supervisor, Nuclear Engineering Design Organization (NED0)
- D. Brieg, Manager, Station Technical (ST)
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- J. Curran, Program Manager, NED0
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- E. David, Lead Engineer, NED0
- G. Gibson, Supervisor, ONL
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- M. Herschthal, Assistant Manager, ST
- B. Joyce, Maintenance Manager, Units 2 and 3
- R. McPherson, Engineer, Maintenance
- J. Reilly, Manager, Nuclear Engineering 'and Construction
- M. Wharton, Manager, NED0
- R. Zbavitel, Engineer, ST
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Others
- C. Reagan, Resident Inspector
- R. Huey, Enforcement Officer, RV
The inspectors also held discussions with other licensee and contractor
personnel during the course of the inspection.
- Denotes those attending the exit meeting.
2.0 GENERIC LETTER (GL) 89-10 " SAFETY-RELATED MOTOR-OPERATED VALVE
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AND SURVEILLANCE"
On June 28, 1989, the NRC issued Generic Letter (GL) 89-10 which requested
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licensees to establish a program to ensure that switch settings for safety-
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related motor-operated valves (MOVs) were selected, set, and maintained
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Five supplements to the generic letter have been subsequently
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properly.
issued.
NRC inspections of licensee actions implementing commitments to GL 89-10 have been conducted based on guidance provided in Temporary Instruction
(TI) 2515/109, " Inspection Requirements for Generic letter 89-10, Safety-
2515/109 is
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Related Motor-0perated Valve Testing and Surveillance."- TI
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divided into Part 1, " Program Review," and Part 2, " Verification of Program
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Implementation." The Part 1 program review at San Onofre was documented in
NRC Inspection Report 92-02. The current inspection was conducted using Part
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2 of TI 2515/109.
The licensee's program for Units 2 & 3 covered 186 MOVs (104 globe and
butterfly valves, 82 gate valves)._ The gate valve types included 57 WKM split
disk,14 Target Rock parallel disk, six Crane Aloyco solid wedge and five
Westinghou;
%xible wedge types.
The inspection consisted of a detailed review of the licensee's documentation
of their GL 89-10 activities for selected MOVs in Units 2 and 3.
The
inspectors selected a sample of MOVs from an information matrix provided by
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The inspectors selected MOVs that appeared to have mar'ginal
the licensee.
actuator capacity and thrust settings compared to calculated requirements.
The selected
The sampled MOVs included a variety of valve and actuator sizes.
MOVs included examples of testing under various differential pressure
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conditions.
For each MOV selected, the inspectors reviewed the design basis calculation of
design flow, temperature, and the maximum expected differential pressure
(MEDP), the sizing and switch setting calculations, the diagnostic test data
package, and the diagnostic traces using M0 VATS (Motor Operator Valve Analysis
and Test System, ITI-MOVATS) Version 3000 software. The .following MOVs were
selected for review:
Shutdown Cooling Flow Isolation Valve
CCW from Emergency Cooling Unit E399 Containment Isolation Valve
2HV-9353 Shutdown Cooling Recirculation Valve
2HV-9378 Shutdown Cooling Pump Suction Valve
3HV1705 Auxiliary Feedwater Discharge Control Valve
The selected MOVs included four gate valves and one globe valve, all with
Limitorque actuators. No butterfly valves were selected. The sample MOVs
were configured as shown below:
Actuator
Closure Control
Valve Size (inches) and Vendor
SMB-1
14" Aloyco Gate
SB-00
10" WKM Split-Disk Gate
SMB-00
8" WKM Split-Disk Gate
SB-1
8" WKM Split-Disk Gate
SMC -000
4" WKM Globe
A summary of the test data for the sampled valves is provided in Attachment 1.
The inspectors concluded that the implementation of the licensee's MOV program
Concerns
was adequate for the sampled MOVs with the exception of 3HV-4705.
associated with the implementation of the GL 89-10 program for 3HV-4705 are
discussed in Paragraph 2.3.h.
Generally, the program appeared to implement
the licensee's commitments to the generic letter.
2.1 Desian-Basis Reviews
The inspectors reviewed the licensee's program description, "MOV Program
Response for Generic Letter 89-10," Rev. 2, dated January 10, 1992, Design
Standard MS-123-125, " Generic letter 89-10 Motor-0perated Valve Program," Rev.
24, 1993, and the licensee's calculations for thrust and torque
1, dated May
requirements. The calculations documented the maximum expected differential
pressure (MEDP, alternately referred to as the design-basis differential
pressure), design flow conditions, design temperature, and other design
parameters for each of the MOVs selected for review.
The calculations
appeared to acceptably address these design basis parameters for the selected
MOVs.
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2.1.a Pressure Locking and Thermal Binding
The inspectors found that the licensee had established an action plan to
address pressure locking and thermal binding.
Through discussions with licensee personnel, the inspectors determined that
the licensee had evaluated the potential for pressure locking and thermal
The licensee identified a total of 27 MOVs which met
binding of gate valves.
their review screening criteria for valves susceptible to pressure locking and
thermal binding. The licensee planned to issue their evaluation in Technical
Paper TP-9 in Appendix XIII of their Design Standard MS-123-125.
The inspectors found the licensee's preliminary analysis indicated that the
operability of all of the susceptible MOVs could be justified by analysis.
The inspectors found the
The licer.see planned no hardware corrective actions.
licensee's evaluation to be incomplete and a potential program weakness.
Further review of Technical Paper TP-9 and the licensee's corrective actions
will be addressed in a followup inspection of program weaknesses (93-17-02:
OPEN)
2.2 MOV Sizina and Switch Settina
2.2.a Calculation Method
The inspectors reviewed the licensee's " Design Standard" and calculations for
MOV sizing and switch settings.
The inspectors found that the licensee had established specific procedures for
conducting calculations within their GL 89-10 program.
The licensee's
calculations for the sampled valves appeared to be adequate. The inspectors
independently calculated the minimum thrust for opening and closing the
valves. No significant errors were identified by the inspectors.
The inspectors noted the following features of the licensee's method.
(1) Valve Factor Assumption (VF) -
(Valve factor was defined as the
ratio of the stem thrust to the differential pressure force acting on the
valve disk.) The licensee assumed a valve factor of 0.4 for all gate
valves and 1.1 for globe valves.
(2) Stem Friction Coefficient Assumption (C0F) - In calculating
actuator output thrust capability, the licensee assumed a stem friction
coefficient of 0.20.
(3) Load Sensitive Behavior Assumption (LSB) - A thrust margin of 20-
25% was incorporated in the setpoint calculations to address possible MOV
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load sensitive behavior (also known as " rate of loading"). The thrust
margin was a percentage in excess of the minimum calculated required
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thrust. The licensee developed a criteria for their LSB margin which was
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the ratio of the stem factors for C0Fs of 0.15 and 0.20. (Stem factor was
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a calculated parameter derived from the stem screw dimensions and an
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assumed C0F.)
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Minimum Thrust Setooint - The' minimum required thrust.setpoint
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included a 15% allowance for diagnostic equipment inaccuracy and torque
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switch repeatability.
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(5) Stem tubrication Deoradation - The licensee had included a 10%
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thrust margin in the setpoint calculation to account for degradation
between periodic verification testing.
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(6) Motor Control Loaic - The licensee used the following three types
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of motor control logic depending'on the valve type: torque seating, limit
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seating and soft seating.
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Torque seating was the predominant method for flex wedge gate
valve and all globe valves. Using torque seating, the torque switch
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a.
activates at a preset actuator output torque-to stop the motor
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during valve seating. With torque seating motor control, the-torque
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switch was adjusted to achieve the specified thrust setpoints.
b. . Limit seating was used for sealing certain double disk gate
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valves after flow cutoff. Using limit. seating, a position switch
opens near the end of the valve stroke to stop the motor during
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valve seating. Although the torque switch remained in series with-
the limit switch using this control logic, the torque switch was-
bypassed for the entire valve stroke and did not serve as backup
overload protection. . Using limit seating motor control, the limit
switch was adjusted to achieve specified thrust setpoints.
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c.
According to the licensee's Engineering. Department, " soft
seating" was used as a variation of torque seating for several gate
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valves. The licensee defined soft seating as torque seating after
the flow cutoff has been achieved. With this control logic, the
torque switch was bypassed (similar to limit seating logic) for the
After flow
majority of the closing stroke until flow cutoff.
cutoff, the torque switch controlled the wedging force and the final
seating thrust. The licensee achieved this control logic by wiring
the torque switch in parallel with the limit switch. The licensee
considered that this control logic provided adequate control. for
sealing valves with leak tightness criteria while minimizing high
inertial loads. Using soft seating motor control, the torque switch
was adjusted to achieve specified thrust setpoints.
The inspectors found that the licensee's Design Standard MS-123-125,
Revision 1, did not accurately. describe the licensee's use of soft
seating as a motor control logic. According to.the-licensee's
maintenance department, when this logic was used with Limitorque Model SB
actuators (which incorporate a' compensating spring to reduce inertia-
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loads), the limit switch rather than the torque switch was adjusted to
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achieve the specified thrust setpoints. The licensee ~ acknowledged the
inconsistency in the use of. soft seating motor control logic between
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their engineering and maintenance departments and committed to clarify
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the intended use of soft seating in a revision to design standard MS-123-
125. The inspectors found the licensee's proposed actions to be
adequate.
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2.2.b.
Diagnostic System Inaccuracy
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The licensee's diagnostic equipment included Teledyne strain gages mounted on
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the valve stem and MOVATS data acquisition "" ,re/ hardware. The licensee
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assumed that 10% inaccuracy in thrust dete /
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combination. The
uncertainty associated with this diagnosti;
H, " dual component accuracies
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licensee based their assumption on aaalysis u
and the performance of the complete Teledyne sys y 'uring the Motor-0perated
Valve User's Group (MUG) diagnostic equipment vahs.io.n test program.
Furthermore, the licensee initiated their own effort to validate the 10%
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assumption through a program similar to the MUG validation test program.
inspectors found the licensee's efforts in this area to be adequate.
2.2.c.
Torque Switch Repeatibility
In the determination of thrust measurement inaccuracy, the inspectors found
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that Revision 1 of Design Standard MS-123-125 did not incorporate the torque
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switch repeatability values specified in Limitorque Maintenance Update 92-2.
The design standard directed the use of 10% thrust measurement inaccuracy due
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to torque switch repeatability for all cases.
Limitorque Maintenance Update
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92-2 identified certain cases where a 20% inaccuracy was applicable.
Licensee
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personnel stated that the 20% repeatability allowance was applicable to some
GL 89-10 MOVs and that reviews of dynamic test results were being conducted to
identify those cases where the 20% value would be applicable.
The licensee
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stated that thrust calculations would be revised, as necessary. Further, the
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licensee indicated that they will revise the design standard to incorporate
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the new repeatability value. The inspectors foun .he proposed licensee
action to be adequate.
2.2.d.
Open Torque Switch Bypass Setting
The inspectors noted that in the Nuclear Engineering Design Organization
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(NEDO) review of the test data, the open torque switch bypass setting (OTSB)
was determined as a percentage of the total actuator operation time. However,
the inspectors noted that the acceptance criteria for the OTSB was specified
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as a percentage of the valve stroke length. The inspectors found that the
licensee's design standard allowed parameters othr.r than stroke length to be
the basis f
the setpoint specification provided that the resulting
specificat
tas an equivalent amount of stem travel.
Due to actuator and
valve lost
- tion and unseating time, the inspectors observed that a time
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based determination of OTSB was non-conservative and not an equivalent measure
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of stem travel.
However, the licensee also enlaated the OTSB setting to
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assure that peak unseating forces occurred within the bypass period.
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inspectors found no examples where this nonconservative basis for satisfying
the acceptance criteria resulted in the an inadequate setting.
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The licensee acknowledged the inconsistency in their determination of the OTSB
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setting and committed to clarify the required setting in a revision to the
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design standard. The inspectors found the proposed licensee actions to be
adequate.
2.2.e.
AC Motor Torque Derating due to High Temperature
The inspectors noted that the licensee had not addressed Limitorque's report
of a potential 10 CFR 21 condition, " Reliance 3 Phase L. C. Actuator Motors
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(Starting Torque at Elevated Temperatures)," dated May 13, 1993. The
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notification addressed the effect of elevated temperature on the output of AC
The licensee identified that a 10% temperature correction factor had
motors.
been applied to MOVs that could experience a post-accident temperature equal
to, or greater than 200f. However, the inspectors noted that the licensee had
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not addressed MOVs that normally operate in ambient temperatures above 104F.
The Limitorque information indicated that some output degradation would occur
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at temperatures as low as 104F. The licensee was conducting a study
addressing the Limitorque report. The licensee study was scheduled for
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ccmplction by October 1, 1993. The inspectors found the proposed licensee
actions to be adequate.
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2.2.f.
Calculation Assumptions Found to be Non-conservative
The inspectors reviewed nonconformance report (NCR) 9308066, dated 8/16/93.
In the NCR, the licensee identified that the test data for MOV 2HV-9378
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indicated an open running load of 2271 pounds force (lbf) which exceeded the
The licensee
maximum value of 2250 lbf assumed in the design calculation.
determined that their packing load calculation method for Chesterton packing
was not conservative. Using a revised Chesterton packing equation, the
licensee re-calculated the maximum running load to be 4460 lbf. The NCR
concluded that, after revision of the setpoint calculation, no calculational
requirements were exceeded by the test data. The inspectors found that the NCR
did not address the generic implication of the non-conservative calculation
for other valves which had not been tested.
The licensee indicated that feedback of test data to revise their calculations
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will be conducted as part of their final data reconciliation evaluation at the
conclusion of their test schedule. The inspectors found that the licensee was
not incorporating a generic review of the adequacy of their calculational
assumptions as part of their evaluation of test' data following each refueling
Without a generic review of the test, the inspectors were concerned
outage.
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that consistently non-conservative test results would not be promptly
identified. Furthermore, the implications of the generic applicability on
MOVs which would not be practicable to test, but which used the same setpoint
The licensee
calculation method, would not be evaluated in a timely manner.
acknowledged the inspector's concern and committed to initiate generic
evaluation of test data following the U3C7 outage.
The lack of timely generic
review of test results is further discussed in Paragraph 2.3.f.
The
inspectors considered the lack of timely generic review of test data to
The inspectors
validate calculational assumptions to be a program weakness.
considered the proposed licensee actions to be adequate. The licensee actions
will be confirmed during a followup inspection of program weaknesses (93-17-
02: OPEN)
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2.2.g.
Lack of Testing at Design Basis Flow Rates
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The inspectors reviewed a summary of all GL 89-10 testing performed by the
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licensee. and notad that a majority of the differential- pressure tests, did not
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achieve maximum expected flow (MEF) conditions. Further, the percentage of
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MEF attained during testing was sometimes much less than the percentage of the
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maximum' expected differential pressure (MEDP). For example, MOV 2HV-6371 was
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tested at 91% MEDP but only 16% MEF. MOV 2HV93-53 was tested at 93% MEDP but
only 21% MEF. The inspectors were concerned that testing under low flow
conditions may. not be conservative. The licensee did not include a
consideration of flow rate in the test acceptance criteria or their
calculations. The inspectors emphasized that the licensee should justify all
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testing performed at less than design basis differential pressure and flow.
The licensee acknowledged the inspectors' concern and identified that they are
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following industry developments in this area. The licensee committed to
established adequate justification for their treatment ~ of flow. effects. The
inspectors found the licensee proposed actions to be adequate.
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2.3.
Testino and Data Analysis
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2.3.a.
Changes in. Diagnostic Equipment
For design basis testing conducted through March, 1992, including the Cycle 6
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refueling outages in Units 2 and 3, the licensee used the MOVATS 3000 system
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as its primary diagnostic system using the MOVATS thrust measuring device
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(TMD) which measured spring pack displacement as the basis for thrust
determination. In addition, stem mounted strain gages were also used as
supplemental stem thrust data.
In certain cases with limited stem access,
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yoke mounted strain gages were also used as thrust measurements. The stem
strain gages were analytically calibrated per manufacturer's recommendations
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and were not in-situ calibrated as part of the licensee's testing. The
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supplemental strain gage data was not used to satisfy setpoint thrust
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requirements. The inspectors did not review the supplemental data obtained
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during this testing.
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For design basis testing conducted after March,1992, including the Unit 2
Cycle 7 refueling outage, the licensee ccntinued to use the M0 VATS diagnostic
system but changed to the use of stem mounted stain gage data as the primary
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basis for their thrust determination. The stem mounted strain gages were
calibrated in-situ. TMD data continued to be used in cases where strain gage
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data wrs unavailable.
2.3.b.
Timeliness of Data Review
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The inspectors reviewed the licensee's MOV test procedure S023-V-3.29,
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Revision 0, " Motor Operated Valve Differential Pressure Test". The inspectors
noted the test procedure did not require evaluation of the MOV diagnostic . .
signature data prior to returning the MOV to service in an operational mode in
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which the MOV was required to be operable. The inspectors found that the
acceptance criteria for the design basis test stated that the valve was
considered operable pending NEDO review if it stroked satisfactorily during
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the test. The inspector found that for Cycle 6 testing, the time for
completion of the NEDO review had not been specified.
For Cycle 7 testing,
the licensee completed the NEDO review of the test data by close of breakers
following the outage.
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The inspectors noted that in their October 29, 1992 response to the licensee's
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notification of an extension of their schedule, NRR emphasized the following
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condition: "SCE should ensure that adequate acceptance criteria are prepared
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for MOV test results to demonstrate that the MOVs tested und.3r the GL 89-10
program can perform their design-basis functions."
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Subsequent to the exit meeting on August 20, 1993, the licensee committed to
formally require the completion of the NEDO review prior to close of breakers.
In _ addition, the licensee committed to include specific acceptance criteria in
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the CL 89-10 test procedures to evaluate design basis capability based on the
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test data. The licensee planned to establish a design basis screening
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criteria using an extrapolation of the test data.
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The inspectors found the previous lack of specific test acceptance criteria
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for determining design basis capability and the untimely completion of NEDO reviews of the test data to be a program weakness.
The proposed licensee
action appeared adequate. The licensee's actions will be confirmed during a
followup inspection of program weaknesses (93-17-02: OPEN).
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2.3.c.
Design-Basis Capability
The inspectors reviewed the licensee's Design Standard MS-123-125, Appendix
VI, Part II, "GL 89-10 Motor-0perated Valve (MOV) Test Data Reconciliation,"
the static test results and the dynamic test results for the following valves:
VALVE
CLOSE MAX. D/P
CLOSE TEST D/P
% MAX D/P
204 psid
110 psid
54%
87 psid
79 psid
91%
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135 psid
180 psid
133%
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The inspectors reviewed the selected dynamic test data using the industry
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standard equation, the valves' mean seat diameters, and the dynamic test
conditions. The inspectors found that the licensee's test data indicated that
gate valve factors ranged from 0.52 up to 0.73.
Based on the inspectors'
review, the licensee's valve factor assumption of 0.4 for the three gate
valves did not bound the test data. However, the thrust margin allocated for
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load sensitive behavior effects appeared conservative for the sample group and
no operability concerns were identified.
2.3.d.
Independent Review
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The inspectors noted that the licensee had implemented an independent review
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of the diagnostic traces including a qualitative assessment of the trace
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characteristics, but this review had not been formalized as a part of the
generic letter program.
In addition, the licensee had not identified any
methods for resolution of potential conflicts between the original test
analysis and the subsequent test review. The licensee committed to implement
a procedure covering the independent review activity by the next Unit 3
refueling outage. The inspectors observed that the procedure was in draft at
the time of the inspection. The inspectors found the proposed licensee
actions to be adequate.
2.3.e.
Auditability of Diagnostic Traces
During their review of the diagnostic traces, the inspectors noted a concern
regarding the auditability of the licensee's records using the MOVATS 3000
diagnostic software. The traces did not identify where the licensee analyst
":croed" the trace.
Critical events in the trace were not specifically
identified. To check for the proper selection of data from the traces, the
inspectors had to reconstruct the licensee's analysis.
The inspectors pointed
out tiiat better documentation of reference points and events would also assist
the licensee's qualitative assessment effort. The licensee acknowledged the
inspectors' observation and agreed to review their methods in order to improve
auditability of their diagnostic traces.
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2.3.f.
Generic Review of Test Data
The inspectors reviewed the results of recently completed U2C7 design basis
testing. The inspectors observed that 11 of the 17 gates valves tested (65%)
displayed valve factors in excess of the licensee calculational assumptions.
The actual valve factors ranged from 0.09 to 2.52 and averaged 0.65.
The
licensee had assumed a valve factor of 0.4 in its setpoint calculations.
Furthermore, the inspectors observed that ten of the valves tested were WKM
split disk gate valves. Seven of the ten WKM valves [iO%) displayed valve
factors greater than the 0.4 value which the licensee had assumed. The valve
factors ranged from 0.09 to 0.65 and averaged 0.54.
The inspectors noted that
57 of the 82 gates valves (70%) in the licensee's GL 89-10 program are WKM
split disk valves. The inspectors were concerned that the licensee's generic
gate valve factor assumption of 0.4 did not appear to be conservative for this
type of valve in light of the consistently high valve factors demonstrated
during testing.
The calculated thrust requirements and setpoints for WKM
valves not yet tested were still based on the original 0.40 valve factor.
The inspec. tors observed that the licensee's test data reconciliation evaluated
the dynamic test data only on a valve-by-valve basis.
According to the
licensee, a later functional margin review will be performed that will revise
individual thrust calculations where the original assumptions were not
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conservative. The inspectors noted that the licensee's design standard,
Attachment 6A, " Functional Margin Review", did not specifically require an
assessment of the generic implications of the test data that was applicable to
other untested valves of the same type or manufacturer.
The inspectors found
the lack of a timely generic review of test data to be a weakness in the
licensee's program.
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The licensee acknowledged the inspectors' concern and committed to begin their
functional assessment of the Cycle 7 data following the completion of the U3C7
outage. The licensee stated that their functional assessment will evaluate
the generic implications of the high valve factors observed during the Cycle 7
testing. Another example of the lack of timely generic review of test data is
discussed in Paragraph 2.2.f.
2.3.g.
Linear Extrapolation
To determine design basis capability from ter .ing at less than design basis
conditions, the licensee linearly extrapolated the measured thrust necessary
to overcome differential pressure from test conditions to design basis
conditions. Where possible, the licensee conducted dynamic testing of each
valve at three different differential pressures in an effort to develop a
justification for their linear extrapolation method. The licensee planned to
justify its method of extrapolation within their schedule for the completion
of their GL 89-10 program.
2.3.h.
Inadequate Documentation of Abnormalities
The inspectors identified several abnormal features in the diagnostic traces
that were reviewed. However, .the inspectors found that only a small
percentage of these anomalies were specifically documented and evaluated by
the licensee. The inspectors were concerned because the qualitative aspects
of the diagnostic signatures affected both the validity of the initial
acceptance of the MOV test and the future capability to trend M0V mechanical
problems.
For example, the inspectors noted that the March 1992 diagnostic thrust
signature for 3HV-4705 displayed significant abnormal cyclic thrust loading at
the initiation of the closing stroke. This condition was unusual during a
portion of the valve stroke normally requiring only minimal thrust to overcome
packing load and stem ejection force. The unusual trace feature was not
identified or evaluated by the licensee in the test procedure. The inspectors
were concerned that the anomaly potentially indicated improper operation of
the MOV due to internal actuator degrthtion, bent valve stem or excessive
packing load. The licensee stated that, although unusual, .they considered the
irregularity to be a repeatable characteristic of the valve signature which
was inconsequential to the proper valve operation.
The inspectors emphasized
the need to document the evaluation of the qualitative characteristic for
future reference in review of the same abnormality.
3
At the exit meeting, the licensee identified that they had completed a review
the signatures of all MOVs which had been design basis tested during Cycle 6
outages. The licensee provided the inspectors a list of the qualitative
anomalies identified during their review. Through further discussions with
'
the licensee, the inspectors found that the licensee did not consider any of
the anomalies to. affect either the immediate operability or the design basis
capability of the MOV as determined from the test data. The list of 75 MOVs
identified anomalies in 53 of the signatures, including the following
anomalies:
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Excessive spring pack gap (up to 0.124 inch)
Potential stem misalignment
Hammering
Potential internal damage
Potential bent stem
Potential loose worm bearing or stem rotation
The licensee identified that four of the MOVs had been reworked during the
U2C7 outage as a result of the observed deficiencies and that eight additional
MOVs were scheduled to be reworked during the upcoming U3C7 outage.
The
licensee stated that due to concerns regarding the test data obtained from the
Cycle 6 testing, they were considering repeating the design basis testing
during the Cycle 8 outages.
The inspectors were concerned about extensive amount of deficiencies wh'ich the
licensee identified existing in many of the MOVs following the design basis
testing. The inspectors noted that in the licensee's setpoint calculations,
the licensee assumed the valve and actuator were in good working condition.
The inspectors found that the list of deficiencies did not appear to support
the design assumption. The inspectors found the lack of timely evaluation of
anomalies to be a weakness in the licensee's program.
An example of this
program weakness is discussed in Paragraph 2.3.1.
2.3.i.
Failure of 3HV-4705
Subsequent to design basis testing in March 1992, MOV 3HV-4705 failed to open
under no flow conditions during routine testing in May,1993. The valve was
the auxiliary feedwater (AFW) discharge control valve from the turbine driven
AFW pump to steam generator E088. The valve was normally closed and required
to open on an emergency feedwater actuation signal (EFAS). The inspectors
revieved NCR 93050059, dated 5/20/93, which documented the test failure and
licensee's subsequent root cause investigation.
According to the NCR, the licensee's investigation of the as-found condition
of the MOV identified the following conditions:
1.
The valve actuator stalled during repeated attempts to open the valve
electrically.
2.
Maintenance personnel observed the actuator move to take up slack
.
with the shaft.
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3.
No opening movement of the shaft was observed during repeated
attempts to open the valve electrically.
4.
Maintenance personnel lubricated the stem with castor oil but were
unable to open the valve manually.
5.
Maintenance personnel unseated the val've manually using a 14"
extension (cheater) on the handwheel of the actuator, hearing a small
" pop" when the valve unseated.
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6.
Subsequently manual and electrical operation showed no unusual
conditions.
While no single root cause was identified, the licensee concluded that the
probable cause of the failure was due to misalignment of the actuator / valve
and internal degradation of the actuator.
The licensee considered that the
i
following maintenance related deficiencies conditions contributed to the
failure:
1.
The yoke-to-bonnet fastener (yoke nut) was found to be loose,
'
allowing 3/8 inch upward movement of the actuator.
2.
The valve stem anti-rotation device lock nut was found loose.
3.
The actuato~r grease was found in a degraded condition.
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4.
The top and bottom thrust bearings were found corroded.
5.
The bronze worm gear was _ worn, and the steel worm was corroded.
6.
The top thrust bearing cover plate was warped.
The inspectors noted that some of the causal factors identified by the
licensee were qualitative characteristics identifiable in diagnostic traces as
unusual indications. However, the inspectors could not conclude that the
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specific conditions found by the licensee after the failure were evident in
the March, 1992 data. The inspectors considered that the abnormal qualitative
characteristics of the earlier data appeared to indicate abnormal actuator or
valve operating conditions. The inspectors further noted that interference
between the anti-rotation device and the yoke was subsequently identified and
eliminated by the licensee in August,1993, after further review of the
signatures by Engineering.
The abnormalities in the thrust signature were
eliminated when the misalignment was corrected.
This failure to identify and document the qualitative deficiencies in the Gl.
89-10 test data for 3HV-4705 and take prompt corrective actions is an apparent
,
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violation of 10 CFR Part 50, Appendix B, Criterion XVI, Corrective Action (ENF
93-17-01).
In discussions with licensee representatives, the inspectors disagreed with
the licensee interpretation of the failure mode for 3HV-4705. The inspectors
4
were concerned that the valve disk appeared to have been jammed in its seat.
The licensee hypothesized that the stem / stem nut misalignment caused the stem
nut to jam on the stem resulting in only torque being a] plied to the stem with
no thrust. The licensee did not consider the valve to aave overthrusted when
previously closed.
The licensee considered the reported " pop" to have
resulted from unlocking the stem / stem nut and not unseating of the valve.
The licensee considered the observed actuator degradation to have resulted
from environmental conditions due to heavy rains and the outdoor location of
the valve.
The licensee considered that accelerated degradation and
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progressive misalignment occurred after March,-1992, and resulted in the
failure in May, 1993. The licensee disagreed with the inspectors'
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observations that the March 1992 diagnostic trace indicated that the
degradation and misalignment had existed during the earlier testing.
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The licensee stated that the qualitative characteristics of the diagnostic
signature had been evaluated informally by Maintenance personnel following the
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The
GL 89-10 testing and had been judged to be acceptable at that time.
licensee acknowledge the lack of documentation of their evaluation. The
licensee identified that a-formal procedure for signature analysis would be.
issued prior to testing during the U3R7 outage.
2.4 Periodic Verification of MOV Caoability
'
.
Through discussions with licensee personnel, the inspector found that the
licensee planned to perform periodic verification of MOV capability every
third refueling outage as recommended by GL 89-10. However, the licensee had
not yet established a program for.the periodic verification. The licensee-
planned to use static testing .only for periodic verification. The licensee
stated that they would justify the adequacy of their periodic verification
program.
2.5 MOV Failures. Corrective Action and Trendina
The licensee had recently issued Engineering Procedure S0123-V-3.4, "MOV Data
Trending." The inspectors reviewed the procedure and found that the licensee
was implementing general trending of M0V data although specific
characteristics and action levels were not yet designated.
2.6 Schedule
The inspectors reviewed the licensee's schedule for completion of their GL 89-
10 testing. The inspectors found the licensee's test progress to be
consistent with their committed schedule. According to the licensee, the
Cycle 6 valves may be retested during the cycle 8 outages. The licensee
,
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considered that all repeat testing could be completed within the their
)
committed schedule. The inspectors found the licensee's progress to be
)
adequate.
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2.7 OA Involvement
The inspectors reviewed the following licensee surveillance reports conducted
by the licensee's site quality assurance group:
SOS-063-92
MOV Design Change Evaluation
SOS-072-92
Conduct of Testing
S05-282-92
Technical Review and Evaluation of
Reference Design Documents
SOS-140-93
MOV Program Evaluation
The inspectors found the surveillances to be comprehensive with substantive
findings.
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The inspectors concluded that the licensee was implementing their GL 89-10
Siished by their
program through the testing and design control measures cThe inspectors found s
quality assurance program.
oversight and implementation of the licensee's program.
One violation was identified in Paragraph 2.3.i.
3.0
IN-0FFICE REVIEW 0F llCENSEE EVENT REPORT (LER) 93-03 (90712)
The inspectors reviewed LER 93-03, dated June 28, 1993.
In the LER, the
licensee identified that three safety related MOVs in Unit 3 had been
determined to be inoperable for a period of 14 months.
This was a condition
Two of the MOVs were
prohibited by the licensee's Technical Specifications.
component cooling water (CCW) supply valves for the containment emergency
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cooling unit which were required to open on receipt of a containment cooling
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The other MOV was a pressurizer steam sample
actuation signal (CCIS).
isolation valve which was required to close on a containment isolation action
signal (CIAS). The licensee declared the valves inoperable in June 1993 after
The
evaluating test data obtained from GL 89-10 testing in March, 1992.
licensee concluded that the test data indicated that the switch settings for
the valves were non-conservative.
After declaring the valves inoperable, the licensee took corrective actions to
secure the valves in their safety related positions until the switch settings
could be adjusted during an outage.
The inspectors found that the licensee had taken appropriate corrective
,
actions after declaring the valves inoperable. However, the inspectors found
that the licensee's evaluation of the GL 89-10 test data had not been timely.
The valves had been tested under differential pressure conditions 14 months
earlier in March 1992. The valves had been returned to service following the
testing without adequate evaluation of the data to assure design basis
capability. Another example of this lack of timely data evaluation regarding
M0V 3HV-4705 is further discussed in Paragraph 2.3.i.
Evaluation of the test data and licensee's basis for determining the
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operability of the MOVs will be an unresolved item pending inspector review of
the test data for these valves (UNR 93-17-03: OPEN)
4.0 UNRESOLVED ITEMS
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Unresolved items are matters about which more information is required in order
to ascertain whether they are acceptable items, items of noncompliance er
deviations. An unresolved item is discussed in Paragraph 3.0 of this report.
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4
5.0 EXIT MEETING
1
An exit meeting was conducted on August 20, 1993. During this meeting, the
The licensee
inspectors reviewed the scope and findings of the inspection.
The licensee did not identify as
acknowledged the inspectors' findings.
proprietary any information provided to or reviewed by the inspector.
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Additional discussions of the results of the inspection were held by phone
during the week ending August 27, 1993.
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Attachment 1
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APPENDIX A.
SAN ONOFRE GATE VALVE DATA
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Diagnostics: Teledyne Strain Gages /MOVATS System
VALVE
VAIAT SIZE
nTT
DYNAMIC
Srm
14AD"
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NUMBER
&
CONDTTIONS
VALVE
FRICTION
SENStr!VE
l
MANLTACTURER
FAC'IOR*
CODTICIENT
BEIIAVIOR
14*
110 psid (Close)
0.73. (Close)
0.19 (Dynamic)
4.0%
!
Aloyco
110 psid (Open)
0.18 (Static)
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Gate
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10"
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79 psid (Close)
0.53 (Close)
0.12 (Dynamie)
6.0%
WKM
79 psid (Open)
0.11 (Static)
Split-Disk Gate
2HV 0353
8'
180 psid (Close)
0.52 (Close)
0.13 (Dynamic)
2.4%
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WKM
180 psid . (Open)
0.13 (Static)
,
Split-Disk Gate
'B*
S0% MEDP,
unavailabic
unavailab!c
unavailable
WKM
43% MEF
Split-Disk Gate
}
4*
unavailable
unavailable
unavailable
unavailable
WKM
,
Globe
- The dynamic valve factors listed were calculated by the licensee using a mean seat diameter.
~ A negative number indicates that the thnast observed at CST during the dynamic test was greater than the thrus
at CST during the statie test.
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