ML20070M523
| ML20070M523 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 03/15/1991 |
| From: | Medford M TENNESSEE VALLEY AUTHORITY |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9103210266 | |
| Download: ML20070M523 (5) | |
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. o IM Tene.e vm Afya, nm uaw tec cuwow twwe mu Mm6 O Med'o'd vu Nawo tuues Asune 1 weg wm s.e MAR 151991 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 Tennescoo Valley Authority
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50-328 SEQUOYAH NUCLEAR PLANT (SQN) - NRC INSPECTION REPORT NOS. 50-327, 128/90-32, REVISED RESPONSE TO NOTICE OF VIOLA 1/0N (NOV) 50-327, 328/90-32-03 Enclosed is TVA's revised responso to B. A. Wilson's letter to
- 0. D. Kingsley, Jr., dated November 1, 1990, which transmitted the subject NOV regarding failure to follow SQN's posttrip review procedure.
In our initial response TVA committed to clarify the requirements for taking the reactor critical in parallel with ongoing secondary side investigations. This clarification was incorporated into an extensivo revision, which included merging of two procedures and reformatting to comply with TVA's writer's guido.
Broader interpretation difficulties were encountered in the use of this new procedure following a Unit 2 turbino trip on January 3, 1991 (LEE 50-328/9100;); and an overall upscade in the posttrip review portion of the procedure was initiated utilizing industry experience and Institute of Nucicar power Operations guidance. The upgraded proceduro, issued on February 22, 1991, provides clearer and more detailed instructions for overall conduct and documentation of posttrip reviews; the requirements.for restart of either the reactor or turbine are further clarified.
TVA's responso is being revised to provido details of this revision to the posttrip review procedure.
The changes from TVA's original responso are designated by vertical bars.
The enclosure provides TVA's revised response to the NOV.
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If you have any questions concerning this submittal, please telephone M. A. Cooper at (615) 843-8422.
Very truly yours, TENNESSEE VALLEY AUTi!0RITY
()>}j;/yb1 $?'$l?l44-Mark 0. Medford Enclosures cc (Enclosures):
Ms. S. C. Black, Deputy Director j
Project Directorate 11-4 i
U.S.-Nuclear Regulatory Commission One White Flint, North 11555-Rockville Pike Rockville, Maryland -20852 Mr. J. N. Donohow, Project Manager U.S. Nuclear Regulatory Commission One White Flint, North-11555 Rockville Pike Rockville, Maryland 20852 f
NRC Resident Inspector Sequoyah Nuclear Plant 2600 Igou Ferry Road Soddy Daisy, Tennessee 37379 Mr.=B. A._ Wilson, Project Chief-U.S. Nuclear _Regulotory Comndssion-Region II 1
_101 Marietta Street, NW, suite 2900 Atlanta, Georgia 30323 f
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ENCLOSURE REVISED RESPONSE TO NRC INSPECTION REPORT NOS. 50-327/90-32 AND 50-328/90-32 B. A. WILSON'S LETTER TO 0. D. KINGSLEY, JR.,
DATED NOVEMBER 1, 1990 Violation 50-327. 32S/90-32e03 Technical Specification 6.8.1 requires that procedures recommended in Appendix A of Regulatory Guide 1.33, Revision 2, be established, implemented and maintained. This includes maintenance, operating.
surveillance, administrative, and fuel handling procedures.
Administrative Instruction AI-18.78, Post-trip Review, requires a root cause determination to be complete and the Post-Trip Review to be approved by the Plant Operations Review Committee prior to restart.
Contrary to the above, the requirements of AI-18.79 vere not implemented in that a root cause of a reactor trip was not identified in the Post-trip Review Report and approved by the Plant Operations Review Committee prior to restart of Unit 1 on September 19, 1990.
Thir is a Severity Level IV violation (Supplement I)
Admlesion or Denial of the Alleged Violation TVA admits the violation.
Reason for the Violation During the investigation of the turbine trip and reactor trip on September 19, 1990, it was determined that the reactor and the reactor protection systems performed as expected and' that-the root cause of the reactor trip was not related to the reactor side of the plant, but was associated with the cause of the turbine trip.
It wa6 determined that the turbine trip was a result of a transformer-sudden pressure relay operation, indicating that the problem was with the main transformers. Key parameters were reviewed to verify that no other anomalies existed.
These included parameters, such as feedwater flow, steam flow, pressurizer level and pressure, reactor coolant system (RCS) temperature, and auxiliary feedwater pe rfo rmance.. The reactor trip was reported in accordance with 10 CFR 50.73 in Licensee Event Report 50-327/90022.
The posttrip review report (PTRR), Revision 0, included the above information and concluded that it was safe to restart the reactor.
Further, the PTRR required that' the cause for the transformer sudden pressure relay operation be determined before the generator was to be synchronized.
A revision to the PTRR would be made at that time and reviewed by Plant Operations Review Committee (PORC) before synchronizing the generator.
Discussions in the PORC meeting indicated that moisture and corrosion of the terminals in the gas relay had been identified as the possible cause 01 the gas relay actuation, resulting in the turbine trip.
It was concluded that because the cause for the reactor trip was known not to involve the reactor side of the plant (i.e.,
turbine = trip), and that there were no anomalies noted during or following the trip f rom the reactor protection systems, the reactor could be taken critical while work on the transformer proceeded.
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Administrative Instruction (AI) 18.78, " Post Trip Review Report," Section 5.0,
" Responsibilities " states that PORC shall review the PTRR for, " root causes of all plant anomalies that have been identified or all possible troubleshooting avenues have been exhausted." It is also stated in Section 5.0 that the Plant Manager shall be responsible for overall unit operation. The approval of the PTRR by the Plant Manager shall serve as his authorization that (1) all of the actions identified to be accomplished before rectart are complete or a justification has been provided for each incomplete item, and (2) the unit may restart. Approval of the PTRR by the Plant Manager shall be documented on the cover sheet of the PTRR.
Section 6.0, " Instructions," states that plant restart shall be authorized only upon completion of the posttrip review by PORC and the Plant Manager.
Restart shall be authorized by the Plant Manager only after assurance that associated plant anumalies bave been resolved or justification has been provided for satisfactory mode progression with each open item.
It was the interpretation of PORC and the Plant Manager that because the cause of the reactor trip was limited to the turbine side of the plant and there were no anomalies en the reactor side, AI-18.78 did not prohibit restart of the reactor while repairs were being nede to the transformer.
Also, on September 19, 1990, PTRR, Revision 1, was presented to PORC. The results of the investigation revealed that the relay operation had resulted from moisture and corrosion of the terminals in the gas relay on the spare transformer, which we.s being used as the "A" phase transformer. This information was not included in Revision 0 to the PTRR, but had been discussed in the previous PORC meeting..
Upon further review of this event and the results of a subsequent Unit 2 turbine trip (LER 50-328/91001), which occurrod on January 3, 1991, it has been determined that lack of clarity and detail in the site governing procedures directly. contributed to this violation.
Corrective Steps That Have Been Taken and Results Achieved PORC reviewed Revision 1 to the PTRR on September 19, 1990, which included the results of the investigation on the transformer sudden pressure relay operation.
-The previous procedure governing posttrip reviews, AI-18.78, was replaced by Site Standard Practice (SSP) 12.7 " Incident Investigations and Root Cause.
Analysis," which covers both posttrip reviews and routine. incident investigations. During the merging of these procedures, the PTRR portion was reworked in an attempt to streamline the process.
When the PTRR portion of this new procedure was utilized for the first time to evaluate a Unit 2 turbine trip that occurred on-January 31, 1991, deficiencies were identified including a lack of clarity with regard to the requirements necessary for plant-restart. An overall upgrade of the PTRR process was initiated utilizing industry experience and Institute of Nuclear Power Operations (INPO) guidelines. The upgraded procedure, issued on February 22, 1991, provides clearer and more detailed instructions for overall conduct and documentation of posttrip reviews the requirements for restart of either the reactor or turbine are f urther clarified.
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After performing a detailed review of plant response to the transient, start-up permission will be requested by the shift operations supervisor and shift technical advisor, reviewed by PORC, and approved by the Plant Manager when one of the following conditions are met 1.
The cause of the event and anomalies noted have been identified and corrected or 2.
The cause of the event and anomalies noted have been corrected or are restricted to secondary side components that can be fully isolated from the primary side and no potential challenge to safety systems exists.
Based on these conclusions, the reactor can be restarted and operated safely. Start-up may proceed to a step in the start-up sequence specilled in the PTRR, which cannot be initiated until corrective actions are
-completed and the Duty Plant Manager grants permission to proceed.
Corrective Steps That Will Be Taken To Avoid Further Violations i
This revision has established a standardized method of reviewing the transients' associated with reactor and turbine trips and clarified the basis for reactor and turbine ristart decisions.
Utilization of this procedure should prevent:further violations.
Date When Full Compliance Will be_ Achieved SQN is'in-full compliance. TVA considers that the current site procedure providas enhanced processes and controls for conduct of PTRRs and will ensure appropriate basis is established for restart and power escalation.
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