ML20057F353
| ML20057F353 | |
| Person / Time | |
|---|---|
| Site: | Waterford  |
| Issue date: | 10/06/1993 |
| From: | Burski R ENTERGY OPERATIONS, INC. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| GL-89-10, W3F1-93-0181, W3F1-93-181, NUDOCS 9310150181 | |
| Download: ML20057F353 (5) | |
Text
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October 6, 1993 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C. 20555 l
Subject:
Waterford 3 SES Docket No. 50-382 License No. NPF-38 Generic Letter 89-10, Supplement 5 Inaccuracy of Motor-Operated Valve Diagnostic Equipment Gentlemen:
t The purpose of this letter is to provide information on the status of the Waterford 3 Motor-Operated Valve (MOV) Program as requested by the NRC staff in Supplement 5 to Generic Letter (GL) 89-10.
t The NRC issued Supplement 5 to Generic Letter 89-10, " Inaccuracy of Motor-Operated Valve Diagnostic Equipment," on June 28, 1993.
The purpose of the supplement was to request that licensees reexamine their MOV Programs to identify measures taken or planned to account for the inaccuracy of various MOV diagnostic systems.
Licensees were directed to provide a summary of these actions or plans and a schedule for the implementation of any incomplete actions.
The supplement also directed that licensees inform the NRC of the particular type of MOV diagnostic equipment in use at the i
facility.
Waterford 3 has taken aggressive action to address concerns related to MOV diagnostic system inaccuracy and its possible effects on MOV operability.
These actions began in anticipation of the final results of the MOV User's Group (MUG) performance validation program for diagnostic equipment.
Before the MUG issued their final report, Waterford 3 began the transition p,f j
from an ITI-MOVATS 2151 diagnostic system to a VOTES diagnostic system for
)0 testing gate and globe valves.
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Generic Letter 89-10, Supplement 5 Inaccuracy of Motor-Operated Valve Diagnostic Equipment W3F1-93-0181 Page 2 October 6,1993 l
The intent of this transition was to avoid the inaccuracy issues surrounding the MOVATS 2151 system entirely.
The majority of the required GL 89-10 dynamic testing was scheduled during the fifth and sixth refueling I
outages (RFOs) in order to satisfy the commitment made in the response to the original Generic Letter.
In light of the aggressive test schedule that resulted from this plan, the questions raised about the performance of the MOVATS 2151 system for testing of gate and globe valves made its continued use unacceptable.
j Waterford 3 used the MOVATS 2151 system with the BART sensor until recently to test butterfly valves in the GL 8 4-10 program. Although this test system was not examined by the MUG's performance validation program,
[
Waterford 3 is transitioning to the VOTES system to conduct GL 89-10 butterfly valve testing.
This transition is intended to avoid possible questions about the MOVATS TMD methodology used in conjunction with the BART sensor.
t The timing of the MOVATS inaccuracy issue was fortunate in one respect:
it j
allowed Waterford 3 to purchase the VOTES system and have it in place in time for it to be used for all of the GL 89-10 required valve testing.
For the purposes of the Generic Letter, Waterford 3 does not intend to take any credit for testing conducted with the M0 VATS system.
'l Having opted to transition to the VOTES system, one final MOVATS issue remained to be addressed:
namely that the magnitude of the MOVATS system inaccuracy suggested that valves that had been set up with the MOVATS equipment might not operate under design basis conditions or, alternatively, might be susceptible to an overthrust condition.
3 In the Spring of 1992, Waterford 3 received NUMARC's report entitled " Final l
Guidance for Responding to Motor-Operated Valve Diagnostic Validation Testing." As you know, the NUMARC guidance described a prioritized approach for' reevaluating existing MOVs whose switch settings had been established based on the MOVATS correlation between spring pack compression and measured thrust. NUMARC recommended that valves within the scope of d
4 Generic Letter 89-10, Supplement 5 Inaccuracy of Motor-0perated Valve Diagnostic Equipment W3F1-93-0181 i
Page 3 October 6,1993 i
IEB 85-03 receive the highest priority and that evaluation of these valves f
t be completed within 60 days.
Remaining MOVs were to be reevaluated based on safety significance within 180 days.
The NUMARC approach was considered to be " generally satisfactory" by the NRC staff.
Waterford 3 performed an evaluation of the 20 IEB 85-03 MOVs to ensure that the "as-left" MOVATS settings were adequate to ensure operability under design basis conditions without creating a potential overthrust condition.
I The engineering evaluation, utilizing the guidance provided in ITI-MOVATS Engineering Report 5.2, concluded that no operability concern existed for j
the 20 IEB 85-03 valves that were set up with the MOVATS system.
Some small potential for overthrusting was found to exist for a few valves. The j
magnitude of the overthrust conditions was judged to be small enough so that it did not pose an immediate concern, especially in light of the fact that the valves were to be tested using the VOTES system just a few months later.
These conclusions were later validated by V0TES testing during the j
fifth refueling outage:
evaluation of the valid as-found data indicated that no overthrust or operability concerns existed for the 20 IEB 85-03 val ves.
[
Having reviewed the most safety-significant MOVs, Waterford 3 opted to rely on field testing to determine the condition of the remaining susceptible
-l val ves. As-found values for switch settings were obtained with the' VOTES system during RF05 for each of the susceptible MOVs.
Evaluation of the valid as-found data for these valves indicated that no overthrust or operability concern existed that was related to the previous MOVATS l
settings. Since the refueling outage ended on November 9, 1992, the l
susceptible MOVs were evaluated by field testing within the 180 day period l
suggested in the NUMARC guidance.
With the transition to the VOTES system nearly complete for the start of RF05 testing in September 1992, Waterford 3 learned via the VOTES Users l
Group of new concerns that had been raised regarding the accuracy of the l
VOTES system.
Specifically, three factors were identified that could affect the thrust values obtained with the system.
These factors included:
(1) the possible use of improper valve stem material constants, (2) the l
failure to account for a torque effect when the V0TES equipment is calibrated by measuring strain in the threaded portion of the valve stem, and (3) various hardware deficiencies.
The first two factors are critical l
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Generic Letter 89-10, Supplement 5 Inaccuracy of Motor-0perated Valve Diagnostic Equipment W3F1-93-0181 Page 4 October 6 -1993 to system accuracy because the V0TES system estimates the thrust based on-the strain measured in the valve yoke.
The V0TES system requires that the operator input an accurate value:for the ratio of-Young's modulus, E, divided by Poisson's ratio, p for a given stem material. The problem for users of the V0TES system is that these material parameters, although commonly available, vary depending on the source of the information.
Based on the results of their internal material study-j (which had also been reviewed and approved by Kalsi Engineering), the V0TES manufacturer, Liberty Technologies, provided correct ratios for E/
for the various Waterford 3 valve stem materials; these values were used for Waterford 3's RF05 MOV testing.
The second problem identified with the V0TES system was caused by torque-induced stem diameter changes for certain stem geometries.
Liberty Technologies discovered that, under certain conditions, the decrease in the stem diameter could result in a VOTES thrust reading that was lower than the actual thrust at the valve and could result in an overthrust condition.
To address this issue, Waterford 3 personnel walked down accessible valves to verify design data for the stem thread, lead, and diameter and to identify possible calibrator locations. -0n the basis of this information, Liberty Technologies provided torque correction factors for susceptible valves. Waterford 3 personnel used these correction factors to adjust the i
maximum thrust limits by hand calculations.
Waterford 3 has since reanalyzed RF05 as-left static and dynamic test data with VOTES software version 2.31, which included an automatic correction for the torque-related problem.
No operability problems were identified.
Finally, none of the hardware-related problems identified by Liberty 1
Technologies applied to Waterford 3's VOTES equipment.
One issue related to diagnostic system inaccuracy remtins Eto be addressed at Waterford 3.
During the Phase 2 MOV Program inspection (50-382/93-06),
it was noted that torque measurements had not been adjcsted for diagnostic system inaccuracy.
Instead, a margin was applied to the torque measurement
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i Generic letter 89-10, Supplement 5 Inaccuracy of Motor-Operated Valve Diagnostic Equipment W3F1-93-0181 Page 5 October 6, 1993 based on the use of pullout efficiency in place of running efficiency in the closing direction and the use of a 10 percent margin in excess of the nominal torque rating allowed by Limitorque for inertial torque.
On the basis of an informal estimate of torque measurement inaccuracy provided by Waterford 3 personnel, the inspectors performed a preliminary review of the effect-of applying torque measurement uncertainty to the test data; the inspectors did not identify any instances that would suggest that an operability problem existed. As reflected in Inspection Report 93-06, Waterford 3 intends to account for torque measurement uncertainties in the MOV Program by the end of 1993.
r To summarize, Waterford 3 has kept abreast of emerging industry concerns regarding diagnostic equipment inaccuracy through active participation in various industry groups. Where such action has been warranted, Waterford 3 has taken prompt and aggressive corrective actions to ensure that switch settings for motor-operated valves within the scope of Generic Letter 89-10 have been properly set. Waterford 3 is confident that these actions, in conjunction with other aspects of the motor-operated valve program, will ensure the continued operability of +he plant's motor-operated valves.
If you have any questions concerning this response, please contact T.W. Gates at (504) 739-6697.
Very truly yours, P
-4td)f -
t) JI (j(.7 R.F. Burski Director Nuclear Safety RFB/TWG/ssf Attachment cc:
J.L. Milhoan (NRC Region IV), D.L. Wigginton (NRC-NRR),
R.B. McGehee, N.S. Reynolds, NRC Resident Inspectors Office i
-m.
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