IR 05000458/1994003
| ML20059K462 | |
| Person / Time | |
|---|---|
| Site: | River Bend  |
| Issue date: | 01/13/1994 |
| From: | Wester T NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| To: | |
| Shared Package | |
| ML20059K458 | List: |
| References | |
| 50-458-94-03, 50-458-94-3, NUDOCS 9402020107 | |
| Download: ML20059K462 (12) | |
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APPENDIX U.S. NUCLEAR REGULATORY COMMISSION
REGION IV
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Inspection Report:
50-458/94-03 License: NPF-47 Licensee:
Gulf States Utilities P.O. Box 220 (
St. Francisville, Louisiana Facility Name:
River Bend Station i
j-Inspection At:
St. Francisville, Louisiana
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Inspection Conducted: January 3-7, 1994 Inspectors:
M. F. Runyan, Reactor Inspector, Engineering Branch Division of Reactor Safety
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C. J. Paulk, Reactor Inspector, Engineering Branch Division of Reactor Safety Approved:
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T. F. Westerman, Chief, Engineering Branch Date Inspection Summary Areas Inspected:
Routine, announced inspection of motor-operated valve maintenance and testing programs and followup ~ of previously identified items.
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Results:
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.1 The licensee has developed and implemented a maintenance and testing
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program consistent with the commitments to Generic' Letter (GL) 89-10,
" Safety-Related Motor-Operated Valve Testing and Surveillance" (Section 2).
The licensee had issued a trending procedure and was in the process of l
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gathering data (Section 2).
l The licensee's approach to temperature effects on motor-operated valves j
was considered conservative (Section 3.1).
i 9402020107 940127 PDR ADOCK 05000458 G
PDR L.
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-2-The licensee's use of a 0.7 valve factor, a 0.2 stem friction
coefficient, and the assumed margins for load sensitive behavior in the calculation of valve requirements was considered conservative (Section 3.2).
The methodology of applying all conservatisms to the calcula.ted minimum
thrust required, rather than to the measured thrust, was considered nonconservative (Section 3.2).
The licensee decreased many conservatisms in design basis calculations
for short-term disposition of operability evaluations for marginal valves. This included the use of an average value for the stem friction coefficient and not applying any uncertainties to the spring pack curves.
This was considered nonconservative (Section 3.2).
The licensee made an extensive effort to demonstrate an interim
operability status for the GL 89-10 motor-operated valves (Section 3.2).
The remaining uncertainties regarding the operability criteria, and the
operability status of the 39 marginal valves, were considered sufficiently significant to keep the unresolved item open until the test results from RF5 testing can be reviewed (Section 3.2).
Overall, the licensee's engineering organization is actively supporting
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their motor operated valve program and have strengthened their program by use of an outside contractor. Technically, the licensee has some nonconservative elements to their program that will need to be resolved prior to the closure of Generic letter 89-10. Their program appears to be headed in the proper direction and has shown significant improvement (Sections 2 and 3).
t Summary of Inspection Findinas:
Inspection Followup Item _458/9124-01 was closed (Section 3.1).
- Unresolved Item 458/9304-01 was reviewed but not closed (Section 3.2).
- Inspection Followup Item 458/9304-02 was closed (Section 3.3).
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Inspection Followup Item 458/9304-03 was closed (Section 3.4).
- Inspection Followup Item 458/9304-04 was closed (Section 3.5)
Inspection Followup Item 458/9304-08 was closed (Section 3.6).
i Inspection Followup Item 458/9304-09 was closed (Section 3.7).
- Inspection Followup Item 458/9304-10 was closed (Section 3.8).
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Attachmenta
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Attachment - Persons Contacted and Exit Meeting
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l-4-DETAILS 1 PLANT STATUS During this inspection, the plant was operated at 100 percent power.
2 GENERIC LETTER (GL) 89-10 " SAFETY-RELATED MOTOR-OPERATED VALVE TESTING AND l
SURVEILLANCE" (TI 2515/109)
2.1 Backaround On June 28, 1989, the NRC issued GL 89-10, " Safety-Related Motor-Operated Valve Testing and Surveillance," which requested licensees and construction permit holders to establish a program to ensure switch settings for safety-i related motor-operated valves and certain other motor-operated valves in safety-related systems were selected, set, and maintained properly. On
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January 14, 1991, the NRC issued Temporary Instruction (TI) 2515/109, j
" Inspection Requirements for Generic Letter 89-10, Safety-Related Motor-Operated Valve Testing and Surveillance," to provide instructions for the
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inspection of the licensee's motor-operated valve programs.
The TI was divided into two parts. The first was for the inspection of the program development; and the second was for the inspection of the implementation of the program.
The results of the Part 1 inspection were documented in NRC Inspection Report No. 50-458/92-24. The results of the Part 2 inspection for diagnosis of test data were documented in NRC Inspection Report'
No. 50-458/93-04.
During this inspection, the inspectors reviewed test procedures, post maintenance test procedures, maintenance work request packages, and condition reports associated with motor-operated valves since January 1992. The inspectors used the guidance of TI 2515/109, Part 2 to perform this
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inspection.
2.2 Procedures The inspectors found that the following procedures were, in general, acceptable to meet the licensee's commitments to GL 89-10.
CMP-1251
"Limitorque* Model SMC-04 Overhaul," Revision 3; CMP-1252 "Limitorque* Model HBC 0 thru 10 Overhaul," Revision 4;
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CMP-1253 "Limitorque* Motor Operated Valves," Revision 9; CMP-1282 "Limitorque' Model SMB-000 Overhaul," Revision 0; CMP-1283 "Limitorque' Model SMB-00 Overhaul," Revision 0; CMP-1284 "Limitorque* Model SMB-0 thru 4 Overhaul," Revision 0; PEP-0059 " Motor Operated Valve Trending," Revision 0; and PMP-1205 " Motor Operated Valve Routine Maintenance," Revision 8.
The inspectors noted that the licensee was in the process of revising Procedure CMP-1284. The inspectors also found that Procedure CMP-1283 did not
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-5-i contain information provided in Limitorque' Technical Update 89-1.
The licensee informed the inspectors that a contractor was being brought in to assist in the updating of all motor-operated valve related procedures. The procedure upgrade effort was scheduled to be completed before the performance of any work on motor-operated valves during the next refueling outage (scheduled for March-1994).
The inspectors also found that the licensee had developed a trending procedure for the trending of motor-operated valve data.
The procedure was thorough and, when implemented, should provide good information to the licensee. The licensee was in the process of gathering data for trending and evaluation and planned to implement the trending program after the initial testing was completed.
2.3 Maintenance Work Reauests The inspectors reviewed 27 maintenance work requests that had been completed since January 1992 and found that the information provided in the work packages was of sufficient detail to permit an adequate evaluation. No concerns with the work packages reviewed were identified.
It was noted that the licensee had replaced a number of limit and torque switches because they were not environmentally qualified. The-inspectors were
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informed that the components in question were not located in harsh t
environments; however, they were being replaced so that all safety-related motor-operated valves would have the same components.
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2.4 [ondition Reports The inspectors reviewed 19 condition reports that had been completed or issued
since January 1992. The inspectors found the documents to have been well written and of sufficient detail to address the concern. The inspectors did not identify any concerns with the condition reports reviewed.
2.5 Conclusions
The licensee has developed and implemented a maintenance and testing program consistent with the commitments to GL 89-10. Additionally, the licensee had -
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issued a trending procedure and was in the process of gathering data.
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FOLLOWUP (92701)
3.1 (Closed) Inspection Followuo Item 458/9124-01:
Evaluation of l
Temperature Effects on Motor-0perated Valves This item involved the licensee's response to information provided by
Limitorque* concerning torque and current losses experienced by motor-operated j
valve motors operating in high temperature environments. This item was reviewed and left open in NRC Inspection Report 458/93-22.
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-6-During this inspection, the inspectors reviewed Condition Report 93-0310 and related attachments.
The inspectors also discussed the details of the analysis with the licensee's lead engineer for this project. The inspectors determined that the licensee's approach to this issue was conservative and that all significant impacts to motor-operated valve capability due to temperature had been identified and appropriately addressed. Although the analysis was still being refined, the inspectors concluded that the licensee had satisfactorily addressed this item for closure.
3.2 (00en) Unresolved Item 458/9304-01:
Site-Specific Validation of Assumed Ennstants During the previous motor-operated valve inspection, the inspectors had noted that the licensee had made assumptions for valve factor, stem friction coefficient, and load sensitive behavior that had not been justified by analysis of the onsite test results.
Furthermore, preliminary review of the test data suggested that the licensee's assumptions were potentially nonconservative. On the basis of less conservative assumptions, several valves were found to be marginally sized.
It appeared, therefore, that those motor-operated valves would be rendered inoperable if the parametric assumptions were increased to bound the test results.
The licensee contracted a consultant to assist in addressing this item. The consultant had completed a review of the River Bend test data and had assessed the operability implications of each motor-operated valve in the licensee's GL 89-10 program. The reports documenting this review had been transmitted to the licensee; however, at the time of this inspection, the licensee had not completed its review and approval process. The inspectors reviewed this material in recognition of its draft status. The inspectors reviewed the following reports:
" River Bend Station Test Data Review," November 29, 1993;
" River Bend Station Motor-0perated Valve Margin Sensitivity Study,"
December 29,1993; " River Bend Operability Evaluation," December 29, 1993; and, " White Paper-Stem Factor, Coefficient of Friction, and Load Sensitive Behavior," December 29, 1993.
The inspectors' review of dynamic test data found that the licensee's original assumption of 0.3 for valve factors was not conservative.
In fact, the licensee found that, on the basis of orifice diameter, a 0.7 valve factor was necessary to bound the average apparent valve factor and to account for two,
standard deviations of the test data taken at high differential pressures.
The inspectors considered a 0.7 valve factor to be sufficiently conservative (based on testing completed to date) for disposition of motor-operated valves that cannot be tested at meaningful differential pressures.
The licensee's review of stem friction coefficients was based solely on static testing, with the understanding that any increase in stem-stem nut friction under dynamic conditions would be accounted for by the margin provided for load sensitive behavior. The inspectors noted that the licensee considered a 0.2 stem friction coefficient would bound the static data with sufficient
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-7-margin to account for two standard deviations. The inspectors considered the 0.2 stem friction coefficient assumption to be conservative.
Based on a review of torque switch trip thrust under static and dynamic conditions, the consultant recommended that a margin of 10 percent, in a biased application, and 20 percent, in an unbiased application, be applied to account for load sensitive behavior (and thus incorporate increases in stem friction under dynamic conditions). The unbiased portion of the load sensitive behavior was applied in a square root sum of the squares calculation that also included instrument error and torque switch repeatability. The inspectors considered the assumed margins for load sensitive behavior to be conservative.
Other margins adop%d in the consultant's study included 5 percent for stem lubrication dearcJation (in addition to a 10 percent unbiased margin for this factor) and a 3 percent margin for spring pack relaxation. Torque switch repeatability margin was consistent with Limitorques recommendations, though the licensee may attempt to justify smaller margins on the basis of test results.
The inspectors expressed a concern that the method utilized by the licensee to calculate minimum target thrusts for motor-operated valve testing applied all uncertainties to the calculated minimum required thrust, rather than to the measured thrust. This practice was considered nonconservative since the margin percentages were being applied to a lower quantity and the uncertainties, in general, were associated with the measured thrust. -The licensee stated that the methodology would be modified and that some of the margins would be applied to the measured thrust. The licensee determined that the change in methodology would result in an approximate 2 percent increase in the target thrust amounts.
The inspectors determined that the revised assumptions and margins utilized in predicting motor-operated valve performance were conservative and that this portion of the unresolved item was satisfactorily addressed. The other issue associated with the unresolved item was the operability status of the motor-
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operated valves as currently set up.
For these assessments, many'of the conservatisms were decreased for short-term disposition before actions could be taken during Refueling Outage No. 5 (RF5) scheduled for Spring 1994.
The inspectors reviewed the operability criteria used to disposition 39 motor-operated valves that were designated as being marginal.
The licensee considered a motor-operated valve marginal if it could not meet the design criteria. This design criteria included the desirable margins to make long-term operability assessments.
For these 39 motor-operated valves, a less conservative set of operability criteria was applied to perform a short-term operability assessment. The licensee stated that each of the 39 marginal valves would be addressed during RF5 and would be upgraded to meet the design criteria by the end of the outage.
The inspectors considered the licensee's i
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-8-intention to have each GL 89-10 motor-operated valve meet the design criteria by the end of RF5 to be timely.
The inspectors considered several of the assumptions used to disposition the 39 marginal valves to have been nonconservative, as discussed below:
The operability criteria utilized actuator run efficiency in the open
direction.
Limitorque* has only endorsed the use of pullout efficiency for this case.
The inspectors were informed that this criterion was not used in any of the current motor-operated valve dispositions; therefore, the concern was limited to the possible use of this criterion in future operability assessments.
The inspectors informed the licensee that use of run efficiency in the open direction would require a rigorous justification since this was not a generally accepted assumption.
The operability criteria used a motor rating of 1.1 in combination with
a 1.0 application factor.
Industry testing to date has not sufficiently established motor performance capability to incorporate these assumptions for assessing motor-operated valve operability.
The licensee stated that the motor-operated valves would be reassessed using a 1.0 motor rating. Additionally, the licensee stated that a continuing review of industry data would be conducted to attempt to validate the higher rating. Of the 39 marginal motor-operated valves, only 2 were evaluated using the 1.1 motor rating. One of these two motor-operated valves, IG33*H0VF001, was determined to pass operability criteria using a slightly less conservative valve factor of 0.63.
The inspectors considered this disposition to be acceptable. The other motor-operated valve, 1E51*MOVF068, Reactor Core Isolation Cooling Steam Discharge Containment Isolation Valve, was determined to be potentially inoperable as currently set up using a 1.0 motor rating and a less conservative torque switch repeatability of 3 percent. The problem was that, under degraded voltage conditions, motor gearing capability, when adjusted for instrument uncertainty and torque switch repeatability (4.07E4 N (9148 lbf)) was less than the torque switch setting (4.14E4 N (9338 lbf)), as determined by static testing.
The valve had adequate margin to close against design conditions, but the motor might stall and be damaged in the attempt to actuate the torque switch.
If this were to occur, the motor-operated valve may not be able to be reopened remotely.
The reactor core injection cooling system was out of service at the time of the exit meeting and the licensee stated that the operability of IE51*M0VF068 would be resolved prior to returning the system to an operable status. This motor-operated valve is accessible during power-operations.
The licensee stated that the most likely course of action would be to lower the torque switch setting on an interim basis before additional testing could be conducted during RFS.
The inspectors determined that the licensee's immediate response and intended actions to address this operability concern were satisfactory.
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-9-The inspectors noted that the consultant's analysis had used an average
stem friction coefficient number of 0.13 to assess the operability status of the 11 marginal valves which had not been tested. These assessments were based on generic spring pack information using known torque switch settings. However, no uncertainty was applied to the information taken from the generic spring pack curves. The use of an average value for stem friction coefficient and not assigning error to the spring pack curves was considered nonconservative. The concern was mitigated, however, by the fact that an initial estimate had been made to identify any untested motor-operated valves that were clearly inoperable.
Each of these valves was scheduled to be tested or have torque switch setting changes during the RF5 outage.
The inspectors concluded that the licensee, through its consultant, had made
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an extensive effort to demonstrate an interim operability status of its GL 89-10 motor-operated valves. The evaluation was technically competent and very comprehensive.
The design assumptions to which all motor-operated valves were slated to be in compliance with by the end of the RF5 outage appeared to be conservative.
The remaining uncertainties regarding the operability criteria, and the operability status of the 39 marginal valves, were considered sufficiently significant to keep this unresolved item open until the test results from RF5 testing can be reviewed and until the licensee has made a final decision on its operability criteria.
3.3 (Closed) Inspection Followuo Item 458/9304-02: Motor-Operated Valve Capability at Dearaded Voltaae Conditions During the previous motor-operated valve inspection, the inspectors noted that the licensee was monitoring spring pack displacement during dynamic diagnostic testing, but had not established acceptance criteria related to this measurement. The concern was that this information was not being used to
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confirm the degraded voltage motor gearing capability of the actuator under dynamic conditions. The licensee had previously relied entirely on the static test to verify this capability.
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The licensee revised procedure PEP-0057, " Votes Signature Testing Procedure,"
Revision 1, with Change Notice 93-1375, to require that the spring pack displacement measured with the linear variable differential transformer during dynamic testing was within 0.127 mm (0.005 in) of the displacement measured by
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the V0TES* Torque Cartridge during static testing. The inspectors determined that the licensee had satisfactorily addressed the concern.
3.4 (Closed) Inspection Followuo Item 458/930a-03:
Toroue Switch Repeatability
During the previous motor-operated valve inspection, the licensee had not incorporated the revised torque switch repeatability percentages published by Limitorque* in Maintenance Update 92-02.
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F-10-The inspectors found that Procedure PEP-0057, Revision 1, Change Notice
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93-1375, also implemented the Limitorque* torque switch repeatability numbers.
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The licensee stated that resultant changes to motor-operated valve calculations had been performed.
The licensee indicated that motor-operated valve testing had indicated much better repeatability than the Limitorque*
values and that this information may be used at a later date to justify a tighter tolerance for repeatability.
The inspectors concluded that the
licensee had satisfactorily addressed this concern.
- 3.5 (Closed) Inspection Followuo Item 458/9304-04: Enaineerina Chances to Oriainal Desian Basis Calculations During the previous motor-operated valve inspection, the inspectors observed that licensee testing personnel had changed the maximum expected differential pressure of a motor-operated valve without concurrence from engineering. The change was based on differential pressures observed during the performance of a test which was thought to fully mimic the design basis condition. The inspectors agreed that maximum expected differential pressure changes could be
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based on test results; however, engineering should be involved in the process of revising the maximum expected differential pressures.
By Change Notice 93-1375 to Procedure PEP-0057, the licensee established a formal procedure to account for changes to the maximum expected differential pressure. This included engineering's participation in revising the maximum expected differential pressure calculation. The inspectors concluded that the licensee had satisfactorily addressed this concern.
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3.6 (Closed) Inspection Followuo Item 458/9304-08: Weakness in Static and Dynamic Test Acceptance Criteria During the previous motor-operated valve inspection, the inspectors noted that the licensee did not provide for a documented check of diagnostic traces for anomalies that may indicate erratic behavior, or imminent failure, of a motor-operated valve.
By Change Notice 93-1375 to Procedure PEP-0057, the licensee added the acceptance criterion that the diagnostic traces be reviewed for abnormalities.
If found, the abnormalities must be documented and justified in the comments section. The licensee had reviewed the entire population of completed i
diagnostic traces for any existing abnormalities in accordance with the revised procedure. The inspectors concluded that the licensee had satisfactorily addressed this concern.
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3.7 (Closed) Inspection Followuo Item 458/9304-09:
Review of Diaanostic Traces During the previous motor-operated valve inspection, the inspectors noted that some of the peak thrust measurements on diagnostic traces were outside the i
V0TESS best-fit straight-line calibration range. The concern was that Liberty
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Technology (V0TES* vendor) had not identified a method to account for the
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uncertainty associated with these measurements.
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Since the previous inspection, the licensee had employed a new technique published by Liberty Technology to use the curve-fit analysis for calibration
traces without a recognizable zero point. Through use of this method and review of all remaining best-fit, straight-line calibrations, the licensee had determined that no thrust information outside current best-fit, straight-line
calibration ranges was being used. The inspectors concluded that the licensee had satisfactorily addressed this concern.
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3.8 (Closed) Inspection Followuo Item 458/9304-10: Trainino on Proper Methodolooy of Usino V0TESS Software
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During the previous motor-operated valve inspection, the inspectors identified several errors that had been made in marking diagnostic traces.
In response, the licensee stated that additional training would be conducted on the proper l
methodology of using the VOTES * software.
During this inspection, the inspectors reviewed the course sfilabus, student l
handouts, and attendance lists for training that was conducter in July,
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August, and September 1993. The inspectors determined that tfis training met
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the need to assure proper marking of diagnostic traces.
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ATTACHMENT 1 PERSONS CONTACTED 1.1 Licensee Personnel R. Biggs, Supervisor, Quality Assurance J. Blakely, Director, Predictive Programs L. Borel, Senior Mechanical Engineer 0. Bulich, Director, Licensing E. Ewing, Assistant Plant Manager, Maintenance J. Fisicaro, Manager, Safety Assessment and Quality Verification T. Gates, Engineer, Licensing K. Gladrosul, Director, Quality Assurance J. Hamilton, Manager, Engineering T. Leonard, Manager, Systems Engireering D. Lorfing, Supervisor, Licensing J. Miller, Director, Nuclear Engineering H. Sellman, Plant Manager J. Shippert, Assistant Plant Manager, System Engineering D. Steinsiek, Senior Mechanical Engineer K. Suhrke, Manager, Site Support R. Thweat, Senior Engineer J. Venable, Assistant Plant Manager, Operations 1.2 NRC Personnel C. Skinner, Resident Inspector W. Smith, Senior Resident Inspector The personnel listed above attended the exit meeting.
In addition to the personnel listed above, the inspectors contacted other personnel during this inspection period.
2 EXIT MEETING An exit meeting was conducted on January 7, 1994. During this meeting, the inspectors reviewed the scope and findings of the report. The licensee acknowledged the inspection findings presented at the exit meeting and documented in this report. The licensee did not identify as proprietary any
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information provided to, or reviewed by, the inspectors.
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