ML20246F703
| ML20246F703 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 05/05/1989 |
| From: | Fox C TENNESSEE VALLEY AUTHORITY |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 8905150062 | |
| Download: ML20246F703 (8) | |
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1 TENNESSEE VALLEY AUTHORITY 1
CH ATTANOOGA. TENNESSEE 37401 SN 157B Lookout Place MAY 051989 U.S. Nuclear Regulatory Commission ATTN:- Document Control Desk Washington, D.C.
20555 Gentlemen:
In the Matter of
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Docket Nos. 50-327 Tennessee Valley Authority
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and 50-328 SEQUOYAH NUCLEAR PLANT -
SUMMARY
OF MEETING ON RECENT UNIT 2 REACTOR TRIPS, APRIL 23,.1989 TVA and NRC met on April 23, 1989, at the Power Training Center to discuss problems and corrective actions associated with the three unit 2 reactor trips that occurred during restart from the refueling outage. An analysis of all Sequoyah' reactor trips since restart of unit 2 in early 1988 was performed to identify common elements. Short-term and long-term corrective actions were identified in the areas of Operations, Maintenance, and Nuclear Engineering.
A simulator visit was conducted. At the conclusion of the meeting, NRC indicated overall agreement with the analysis and corrective actions.
TVA was asked to submit a summary of the information and commitments.
contains a summary of the information presented at the meeting.
contains a summary of the commitments.
If you have any questions, please call M. J. Burzynski at (615) 843-6422.
Very truly yours, TENNESSEE VALLEY AUTHORITY
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C. H. Fox, r., Vic P esident and Nuclear Technical Director Enclosures cc: See page 2 06 "
I 8905150062 890505 PDR ADOCK 05000327 P
PDC An Equal Opportunity Employer
l i i U.S. Nuclear Regulatory Commission A4/Of 051989 cc (Enclosures):
Ms. S. C. Black, Assistant Director for Projects TVA Projects Division U.S. Nuclear Regulatory Commission One White Flint, North J
11555 Rockville Pike Rockville, Maryland 20852 Mr. B. A. Wilson, Assistant Director for Insoection Programs TVA Projects Division U.S. Nuclear Regulatory Commission Region II 101 Marietta Street, NW, Suite 2900 Atlanta, Georgia 30323 Sequoyah Resident Inspector Sequoyah Nuclear Plant 2600 Igou Ferry Road Soddy Daisy, Tennessee 37379 l
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ENCLOSURE 1 TVA/NRC MEETING
SUMMARY
SEQUOYAH UNIT 2 REACTOR TRIPS Introduction TVA and NRC met on April 23, 1989, at the Power Training Center to discuss the problems and corrective actions associated with the three Sequoyah unit 2 reactor trips that occurred during restart from the unit 2 cycle 3 refueling outage.
The meeting was held to address NRC concerns that the recent reactor trips at unit 2 appeared to be similar to the reactor trips experienced during unit 2 restart in early 1988.
The TVA presentation included an analysis of all Sequoyah reactor trips since restart in early 1988 and a discussion of the short-term and long-term corrective actions identified in the areas of Operations, Maintenance, and Nuclear Engineering. A visit to the Sequoyah simulator was also included on the agenda.
Analysis of Sequoyah Reactor Trips TVA conducted a review of 11 reactor trips that have occurred at the Sequoyah
' units since restart.
The review addressed five unit 2 restart reactor trips, three unit I reactor trips, anc three unit 2 cycle 4 startup trips.
The general results indicated that nine reactor trips involved feedwater.
Five of the nine reactor trips involved full or partial feedwater interruptions that
-were caused by testing, maintenance, or equipment failures.
Four of the nine reactor trips involved feedwater control problems during startup.
TVA concluded that six of the feedwater-related reactor trips have relevant similarities.
Four common elements were identified during further review of the six similar reactor trips. One common element was an Operations philosophy that accepted known equipment problems.
Several startups were attempted with feedwater bypass valve controller problems.
The second common element involved the fact that dynamic tuning was not performed for the feedwater bypass valves during all startup attempts. A third common element was the fact that the standard startup methods were not specific or correct for all feedwater control transfer evolutions.
The procedures allowed either manual or automatic bypass valve control without specific guidance. The procedures incorrectly allowed automatic main valve control during turbine load reductions below 20 percent turbine power. The fourth common element involved insufficient follow-through on posttrip recommendations on feedwater controls.
TVA did not learn enough from the unit I startup experience.
Feedwater bypass valve tuning was not formally integrated inta the startup process.
The standard startup method was not completely proceduralized in that manual bypass valve control was routinely used without specific guidance.
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Operations Performance Several contributing factors were identified that affected Operations performance.
In some cases, there was a willingness to proceed with material deficiencies. Operating procedures contained some generalities that allowed too many alternatives for feedwater operation.
The team approach to plant evolutions.was applied inconsistently.
Preparations for plant evolutions are generally slow and methodical; however, performance becomes rushed at times.
TVA has identified a number of improvements that address these contributing factors. Prior to restarting unit 2, TVA will revise general operating instruction (G0I) 2 to incorporate industry feedwater startup experience, add guidelines for each crew member, control the use of manual bypass control, add cautionary statements prior to important feedwater evolutions, and add hardware operability requirements for important feedwater evolutions.
Two special startup crews will be selected and trained on the new startup methods. These crews will be used for the unit 2 startup feedwater evolutions.
To ensure that all normal crews become proficient at the standard startup methods, TVA will incorporate the standard feedwater startup method into certification training by August 14, 1989, and requalification training by May 19, 1989.
TVA will also add specific training on control loop design and operation into the certifichtlon training by August 14, 1989, and requalification training by December 1,1989.
TVA will also review operating procedures to incorporate team concepts or test director requirements for important, critical tasks.
This effort will be completed by June 30, 1989.
TVA has a number of activities planned to improve the Operations philosophy at Sequoyah.
First, TVA will revise administrative instruction (AI) 30 by June 30, 1989,. to identify the role of senior Operations management support in f
the main control room during important plant evolutions.
Second, TVA will develop specific management requirements by June 30, 1989, to reinforce the desired operational philosophy. And third, TVA is developing a long-range I
plan to get Operations management more involved with industry top performers and INP0 evaluations.
This plan will be developed by May 30, 1989.
Maintenance Overall, restart proceeded with minimal outstanding equipment deficiencies.
For example, the number of outstanding control room work orders (12) was the lowest in Sequoyah unit 2 history and well below the startup goal of 20.
However, feedwater system discrepancies identified during startup were not worked expeditiously and corrected prior to proceeding with power escalation.
TVA also found that the feedwater bypass valve dynamic calibration methodology to support power escalation did not reflect current industry experience.
Several maintenance program enhancements are planned to improve performance.
TVA will develop a dynamic calibration methodology for feedwater controls, incorporating industry experience, prior to restarting unit 2.
TVA will
. provide feedwater flow indication over the full range and install temporary enhanced steam generator level recorders prior to restarting unit 2.
To ensure proper preparation of the feedwater system for startup from future refueling outages, TVA will-establish a comprehensive checklist of feedwater equipment checks, calibrations, and testing activities for the unit I cycle 4 refueling outage.
Nuclear. Engineering As a result of the reactor trips, TVA reviewed the design of the feedwater system.
No outstanding design deficiencies were identified that required resolution prior to restarting unit 2.
In particular, TVA performed an evaluation of differences between the analog feedwater bypass controller used for unit 2 and the digital feedwater bypass controller used for unit 1.
From an engineering perspective, there are negligible differences in response time as compared with the overall system response time, which is dominated by the mechanical / pneumatic valve interface. Westinghouse Electric Corporation performed an independent evaluation of controller differences and did not recommend one controller over the other.
There was no overriding operator preference for either controller.
TVA is conducting a number of feedwater system studies to identify areas for improvement. A multidiscipline review (Nuclear Engineering, Operations, and Maintenance) will be conducted of the integrated feedwater control system.
This review will also include a human factors review. The target completion date for this study is July 14, 1989. A study will be done of the main feed pump turbine speed control system.
The target completion date for this study is July 14, 1989. A study of the main feedwater control valve and bypass valve flow characteristics will be done.
The target completion date for this study is May 12, 1989.
The results of these studies will be reviewed by TVA management, and the results will be submitted to NRC by September 1,1989.
TVA has a number of engineering changes planned that affect feedwater system i
performance. Prior to restarting unit 2, TVA will revise the main feed pump i
setpoint program to improve low-power control characteristics and change the control point for manual bypass valve control to increase the operating margin to the trip setpoint.
TVA will standardize the feedwater bypass valve controllers by startup after the unit 2 cycle 4 refueling outage.
TVA will install human factored, enhanced steam generator level recorders for startup feedwater control by startup from the cycle 4 refueling outage for each unit.
TVA will install the Eagle 21 protection set by startup from the cycle 4 refueling outage for each unit. Also, TVA will install the Westinghouse l
Owners Group startup trip reduction package (steam generator setpoint trip l
time delay and environmental allowance modifier) by startup from the cycle 5 refueling outage for unit I and the cycle 4 refueling outage for unit 2.
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Summary
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TVA has reviewed the Sequoyah reactor trip history since restart in early 1988. A number of improvements have been identified for Operations.and Maintenance A number of design improvements are planned for future refueling outages.
TVA believes that these actions will have a very significant effect l
on reducing the number of startup-related feedwater reactor trips.
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ENCLOSURE 2
SUMMARY
OF COMMITMENTS Nuclear Operations
- 1. - Revise G01-2 prior to restarting unit 2 to incorporate industry feedwater startup experience, add guidelines for each crew member, control the use of manual bypass control, add cautionary statements prior to important feedwater evolutions, and add hardware operability requirements for important feedwater evolutions.
(Complete) 2.
Select and train startup crews for unit 2 restart.
(Complete) 3.
Review operating procedures to incorporate team concept or test director requirements for important, critical tasks by June 30, 1989.
4.
Develop a plan by May 30, 1989, to get Operations management more
' involved with industry top performers and.in INP0 evaluations.
5.
Revise AI-30 by June 30, 1989, to identify role of senior Operations management support in the main control room during important plant evolutions.
6.
Develop specific management requirements to reinforce desired operational philosophy by June 30, 1989.
7.
Incorporate control loop design and operation into certification training by August 14, 1989.
8.
Incorporate standard feedwater startup methods into certification tralning by August 14, 1989.
9.
Incorporate control. loop design'and operation into requalification training by December 1, 1989.
10.
Incorporate standard feedwater startup methods into requalification training by May 19, 1989.
Maintenance
- 11. Develop dynamic calibration methodology for feedwater controls, incorporating industry experience, prior to restarting unit 2.
(Complete)
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- 12. Provide feedwater flow indication over the full range and temporary enhanced steam generator level recorders prior to restarting unit 2.
(Complete)
- 13. Establish comprehensive checklist of feedwater equipment checks, calibrations, and testing activities for unit I cycle 4 refueling outage.
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Engineering 14.
Revise main feed pump speed control setpoint program and feedwater bypass valve control point prior to restarting unit 2.
(Complete)
- 15. Complete engineering studies for an integrated feedwater control system review, main feed pump turbine speed control system, and main and bypass feedwater control valve characteristics.
Results of the studies will be submitted to NRC by September 1, 1989.
- 16. Standardize feedwater bypass valve controllers by startup from the unit 2 cycle 4 refueling outage.
17.
Install the Eagle 21 protection set by startup from the cycle 4 refueling outage for each unit.
18.
Install human factored, enhanced steam generator level recorders for
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startup feedwater control by startup from the cycle 4 outage for each unit.
19.
Install the Westinghouse Owners Group startup trip reduction package (steam generator setpoint trip time delay'and environmental allowance modifier) by startup from the cycle 5 refueling outage for unit 1 and the cycle 4 refueling outage for unit 2.
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