ML20247C320
| ML20247C320 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 03/24/1989 |
| From: | Gridley R TENNESSEE VALLEY AUTHORITY |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 8903300162 | |
| Download: ML20247C320 (23) | |
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TENNESSEE VALLEY AUTHORITY CH ATTANOOGA, TENNESSEE 37401 SN 1578 Lookout Place MAR 241989 U.S. Nuclear Regulatory Cormission 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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50-328 SEQUOYAH NUCLEAR PLANT (SQN) NOTICE OF VIOLATION (NOV) AND PROPOSED IMPOSITION OF CIVIL PENALTY (NRC INSPECTION REPORT NOS. 50-327/88-35, 50-328/88-35, 50-327/88-55, AND 50-328/88-55)
This letter, including enclosures, is submitted to NRC in accordance with 10 CFR 2.201 and 2.205 in response to NRC's letter of February 23, 1989, which transmitted the subject notice of violation and proposed imposition of civil penalty regarding the SQN shutdown margin (SDM) and reactor coolant system (RCS) overcooling issues.
TVA admits the violations cited in the subject notice of violation (NOV).
TVA ar,knowledges that the SDM issue represented a condition that, if left uncorrected, could have allowed operation prohibited by the technical specifications (TSs).
TVA further acknowledges that overcooling of the RCS in a manner inconsistent with design requirements represents clear departure from good operating principles.
However, TVA believes that there are points meriting consideration relative to our performance in addressing the subject issues.
First, TVA performance prior to the 1985 shutdown is clearly not reflective of current TVA ability and inclination to identify and correct safety deficiencies.
Extensive management and culture changes were needed and accomplished during the extended shutdown.
Second, TVA identified the SDM issue following the first unit 2 trip after the May 1988 restart and promptly resolved the SDM safety issue in June 1988 by instituting requirements for boration. Third, comprehensive corrective actions were initiated to address the RCS overcooling issue and to institute programmatic improvements.
While part of the actions taken to address RCS overcooling were determined to be ineffective, as evidenced by operator response to the November 18, 1988, unit 1 trip, no safety issue resulted because SDM continued to be ensured by boration. Management response to this trip was immediate and thorough, resulting in implementation of additional actions and enhancements to address both specific and programmatic concerns.
TVA believes that these poin h clearly demonstrate current TVA ability, inclination, and commitment ti identify and correct safety deficiencies and trusts that this submittal wf 1, in part, provide the staff with additional 2
perspective consistent with our belief.
i 8903300162 890324 PDR ADOCK 0500 7
An Equal opportunity Employer I
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_2-MAR 241989
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f U.S. Nuclear Regulatory Commission For these reasons, and after careful consideration of-NRC enforcement policy-
. outlined in 10 CFR, Part 2, Appendix C, TVA respectfully requests
-reconsideration or mitigation of the proposed civil penalty' As detailed in enclosure 1 to this submittal,.TVA believes enforcement policy guidelines are applicable and that imposition of a civil penalty is. not needed to achieve the intent of enforcement policy objectives ~.
Pursuant to 10 CFR 2.205, enclosure i provides TVA's answer to the proposed Amposition of civil penalty. Pursuant.to 10 CFR 2.201, enclosure 2 provides TVA's response to the NOV. provides a summary listing of TVA actions taken in response to the subject issues as reference within enclosure 1. provides a summary listing of new commi ments made in this submittal.
Ifyouhaveanyquestionsconcerningthissubmittal,pleksetelephonemeat-(615) 751-2729.
Very truly yours, TENNESSEE VALLEY AUTHORITY R.
ridley, Ma ager Nuclear Licen ng and Regulatory ffairs Enclosures cc: Ms. S. C. Black, Assistant Director for Projects TVA Projects Division U.S. Nuclear Regulatory Commission One White Flint, North 11555 Rockville Pike Rockville, Maryland 20852 Ms. L. J. Watson, Acting Assistant Director for Inspection Programs TVA Projects Division U.S. Nuclear Regulatory Commission Region II 101 Marietta Street, NW, Suite 2900 Atlanta, Georgia 30323 j
Sequoyah Resident Inspector Sequoyah Nuclear Plant 2600 Igou Ferry Road Soddy Daisy, Tennessee 37379
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N ENCLOSURE 1 RESPONSE TO PROPOSED' IMPOSITION OF CIVIL PENALTY-NOS. 50-327/88-35 AND 50-328/88-35 NOS. 50-327/88-55 AND 50-328/88-55 D. M. CRUTCHFIELD'S LETTER TO 0. D. KINGSLEY~
DATED FEBRUARY 23, 1989 Introduction F
TVA has' reviewed the history and chronology of the shutdown margin (SDM) and overcooling issues,.the safety significance of both issues, and TVA's response to the issues.
In light of this review, TVA has also reviewed the general enforcement policy set forth in 10 CFR Part 2,' Appendix C.
It appears that there is particular relevance to section V.B regarding mitigation-factors and section V.G regarding exercise of discretion.
In both sections, NRC's stated objective is to avoid penalizing a licensee' whose current performance is consistent with the objectives of the policy, i.e., identifying, reporting, and correcting violations.
As a result of TVA's review, TVA concludes that its performance in addressing the SDM and cooldown issues merits consideration relative to policy objectives outlined in the NRC enforcement policy. Accordingly, TVA respectfully requests NRC reconsideration of the applicability of discretion to this case and/or mitigation of the proposed civil penalty. The basis for TVA's request is provided as follows.
Mitigation Factors (Section V.B.)
A.
Identification and Reporting Shortly following restart of SQN unit 2 from the extended shutdown, five reactor trips occurred-- May 19, 1988; May 23, 1988; June 6, 1988; June 8,
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1988; and June 9, 1988.
TVA personnel involved in performance of the posttrip SDM calculations on May 19, 19ES, noticed an unexpected reduction in excess SDM following that first trip, and discussions commenced both internally and with the Nuclear Steam Supply System (NSSS) vendor regarding the cause and poss1ble resolution.
It was initially thought that the observed reduction was solely the result of additional conservatism recently added to the xenon tables. Although calculated SDM was well above the technical specification (TS) requirements, a questioning and safety-conscious attitude prompted additional review.
However, because adequate margin existed to the TS limits, this was not an issue that should have prevented restart of the unit.
Following the first reactor trip, TVA management was also questioning the i
cause of observed reactor coolant system (RCS) overcooling from an operational standpoint. Discussions were held among TVA management, the site reactor engineers, and personnel from the corporate fuels organization relative to possible effects of low decay heat.
Telephone inquiries were made to other plants to determine if RCS overcooling existed or had existed and what actions may have been taken to resolve the problem.
Early management concern was evidenced by an operator aid issued on May 24, 1988, regarding isolation of main feed pump governor valves
ENCLOSURE 1
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that had been found to be leaking.
The-operator aid directed isolation of high-and low-pressure steam to both main feed pumps on a unit trip to prevent excessive cooldown of the RCS..At this point, the RCS overcooling was viewed as an operational concern; the tie had not yet been made to the SOM issue and the cooldown " event" itself was considered bounded by the main steam line break accident analysis.
TVA acknowledges that the NRC resident inspectors were que @ ning the RCS cooldown during this same period.
However, TVA does not believe NRC identified either the overcooling issue, the SDM issue, or the tie between the two.
NRC inspectors expressed-concerns to TVA shift personnel regarding the thermal cyclic impact on RCS materials as a result of the cooldowns.
The cooldown below no-load RSC average temperature (Tavg) of the magnitude experienced at SQN does not represent a thermal cyclic concern, and a cooldown in itself does not necessarily represent a safety.
problem from an SDM perspective; the cooldown becomes a problem based on time in life of core, magnitude of the cooldown, and existence of compensating measures (e.g., boration). At the time of the NRC inspector's comments, shirt personnel acknowledged the cooldown as an expected situation for the SQN units; however, TVA management was concerned and was questio11ng the cooldcwn from an operational standpoint. At this time, neither TVA nor NRC had correlated the cooldowns to the SDM issue.
TVA had previously (pre-1985 shutdown) identified the posttrip cooldown issue during startup testing and, based on conditions at that time, had incorrectly considered it acceptable.
1 Following the June 6 trip, SQN reactor engineers began to suspect the observed reduction in excess SOM was caused by more than just the
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additional conservatism in the xenon tables and discussions were reinitiated with the NSSS vendor.
By June 14, 1988, following extensive discussion and evaluation, TVA had determined that conservatism in the xenon tables was only a contributor to the problem and that the root cause of the problem was excessive RCS posttrip cooldown below no-load Tavg.
TVA determined that the potential existed for violating the required SDM L
value during the posttrip cooldown transient at end of life for the SQN 1
cores. A condition adverse to quality report (CAQR) was initiated on June 14, 1988, to document the condition, and further discussions with the NSSS vendor ensued to determine appropriate corrective action. As a result, emergency procedure ES-0.1 was revised on June 18, 1988 (revision 3), to require manual boration, and unit 2 was restarted from the fifth trip on June 19, 1988.
Extensive additional actions were subsequently initiated, as will be later addressed, and TVA reported the condition to NRC in Licensee Event Report (LER) 328/88030 on July 14, 1988.
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ENCLOSURE 1 In summary, TVA identified the SDM issue as a result of a conscientious, questioning attitude _in evaluation of data and aggressive pursuit of the root cause of an unexpected condition.
TVA initially addressed the RCS overcooling as an operational concern until the correlation us made between the cooldown and SDH safety issue. Once established, TVA promptly documented the issues using SQN's approved corrective action program and reported the issues to NRC in accordance with 10 CFR 50.73.
B.
Corrective Actions Unit 2 Trips As previously described, a CAQR was initiated on June 14, 1988, when TVA determined that the potential existed for violating the TS SDM requirement during a posttrip cooldown transient.
In the event of a loss of SDM, TSs require boration to restore SDM; consistent with TSs, ES-0.1 was revised on June 18, 1988 (revision 3), to require manual boration in the event of prescribed RCS cooldowns following reactor trips.
This eliminated the SDM concern and ensured that operation in violation of TSs would not occur. Additionally, ES-0.1 also was revised at this time to require manual control of auxiliary feedwater (AFW) to try to mitigate the cooldown and obviate the need for boration.
Because TVA was operating unit 2 at less than 70-percent power in order to extend core' operation until after unit I restart (scheduled shutdown for refueling was in January 1989), the initial boration requirements provided by the vendor bounded the existing unit 2 core until end of life for 70-percent power operation.
Subsequent revisions were made to first bound unit 2 at end of life, for 100-percent power, and later to bound both units for end of life, 100-percent power operation.
With-the safety issue thus resolved for continued operation, TVA continued investigating the potential causes for the RCS overcooling below no-load Tavg and possible fixes to either mitigate or eliminate the cooldown. -The cause of the cooldown was determined to be excessive mass loss from the steam generators by the steam dump system, excessive feed of cold AFW to the steam generators from SQN's AFW automatic level control feature, and possible secondary-side steam leaks that could exacerbate the steam generators' mass loss. As previously stated, the initial revision to ES-0.1 (revision 3) included requirements for taking manual control of AFW to control the cooldown.
TVA management was, however, concerned with the problems that could be created by placing an automatic safety system in manual control in a manner that was inconsistent with the system design basis. As a result cf these concerns and because the safety issue had been resolved by the boration requirements, TVA subsequently removed the requirement for manual control of AFW from ES-0.1 (revision 4) while continuing to aggressively pursue with the vendor potential hardware
- r. modifications that could mitigate the cooldewn. This decision was made 1
after careful consideration by site management who were actively involved
.in resolution of these issues.
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ENCLOSURE'l Deta'lled sensitivity studies were being conducted during this time by the-NSSS vendor to determine potential benefits of various hardware modifications. Under consideration were various modifications to the steam dump control' system, modifications to the main feedwater isolation setpoints, and modifications to the.AFW system. Any changes in system design had to be considered relative to benefit, possible impact to accident analysis assumptions, increase in required operator actions, and impact on operator training.
During this period of time, NRC inspectors expressed concern that TVA emergency procedures deviated from the Westinghouse Owners Group (HOG) emergency procedure guidelines that specified manua.1 control of AFW to mitigate RCS posttrip cooldown. Additionally, TVA was learning from the previously described NSSS vendor studies that, regardless of implementation of proposed modification (s), full elimination of the posttrip cooldown would not likely result from the modifications alone,-
i.e., some operator action would be necessary to more fully mitigate the cooldown. Absence of cooldown mitigation would result in continued requirement for immediate boration.
As a result of consideration of the WOG emergency procedure guidelines and modification evaluation results. TVA decided to reinstitute requirements for manual control of AFW in ES-0.1 with wording consistent with that used in the WOG guidelines. TVA committed to NRC to revise ES-0.1 (revision 5) and provide operator training through a training ietter before restart of unit 1 as short-term actions to address the overcooling issue and to provide status of long-term actions, such as plant modifications, to NRC in an October 14, 1988, submittal.
TVA issued a training letter to 1icensed operators describing procedural changes involving manual control of AFW. Additionally, unit i startup operators received simulator training with anticipated procedure changes.
This occurred in advance of actual issuance of revision 5 to ES-0.1 on October 20, 1988, in order to expedite training before unit I restart. Operators from both units participating in annual requalification training also received simulator training using the anticipated procedure changes and later using the actual changes as they were incorporated into ES-0.1.
In summary, following the unit 2 trips, TVA promptly and effectively resolved the SDM safety issue by requiring boration.
TVA also continued to pursue resolution of the RCS overcooling issue through administrative controls and plant modifications.
TVA described these actions to NRC in reports and submittals dated July 14, 1988; August 31, 1988; September 9, 1988; and October 14, 1988; and NRC specifically reviewed the corrective actions for acceptability before unit 1 restart as described in NRC Inspection Report No. 50-327, 328/88-49 and Safety Evaluation Report transmitted by NRC letter to TVA dated September 30, 1988.
1 Unit 1 Trip SQN unit I was restarted on November 6, 1988, and experienced a reactor trip on November 18, 1988, as a result of actuation of the turbine generator neutral overvoltage protective relay.
The SQN Plant Manager
ENCLOSURE 1 i
. ' i arrived in the main control room immediately following the trip and in observing plant recovery and. stabilization noted that RCS overcooling had occurred and that short-term corrective actions initiated to mitigate the cooldown issue had not been effectively implemented.
Discussions among the Plant Manager, Operations superintendent, and' shift operations supervisor were held in the control room, and it was immediately determined that the intended ES-0.1 actions had been misinterpreted. The operator involved in the unit I trip misinterpreted the procedure and delayed taking manual control of AFW to a point in the cooldown transient where mitigation of the cooldown was largely ineffective. While the revisions made to ES-0.1 had been specifically worded to be consistent with WOG guidelines and operator training had been conducted on the simulator before restart, it was determined that the
-procedural wording and one-time simulator training had been inadequate to have changed an ingrained operator mind-set relative to SQN's automatic AFW system.
(Additional details regarding operator actions are provided in TVA's response to violation II contained in enclosure 2.)
It must be noted, however, that the corrective actions under consideration here are those addressing mitigation of the cooldown issue, not (>se addressing the SDM safety issue. Boration requirements were stili schieved during.
the November trip.
It should be noted that the boration source swapped from the boric acid tank to the refueling water storage tank (RWST) following the trip.
ES-0.1 provided flexibility for using either the " normal" or " emergency" boration flow path; however, in either case boration was assumed from the boric acid tank at 20,000 parts per million (ppm). As a result of the RCS overcooling, letdown isolated on low pressurizer level; and ultimately, the charging pump suction swapped from the volume control tank to the RWST as the volume control tank level dropped.
This resulted in a change in boration source from the boric acid tank (containing 20,000 ppm boron) to the RWST (containing 2,000 ppm boron) because the normal boration flow l
path being used was isolated when the volume control tank discharge valves isolated. The operators observed the swapover but recognized equivalent l
boration would be provided from the RWST.
The RWST constitutes an alternate, qualified boration source, and equivalent boration was provided as a result of a higher flow rate.
Evaluation of the November 18, 1988, trip results identified the need for additional actions to ensure maximum cooldown mitigation benefit would be achieved in the future. TVA's Senior Vice President of Nuclear Power and l
the Vice President, Nuclear Power Production, were extensively involved in the issue evaluation immediately following the trip. While the cooldown for this trip did not represent a safety concern, the cooldown represented a clear departure from TVA's commitment to operate the plants properly (i.e., in accordance with design requirements).
Senior-level meetings were held to discuss the trip response sequence and RCS cooldown and to identify comprehensive actions to address both specific and programmatic issues.
In immediate response to the
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ENCLOSURE 1
, misinterpretation of the procedures following the November 18, 1988, trip, TVA revised ES-0.1 on November 20, 1988 (revision 6), to clarify the intent.
ES-0.1 was also revised to specify use of the " emergency" boration path to prevent potential isolation of the prescribed path should a comparable cooldown occur.
The SQN simulator model was modified to better duplicate the November 18 event, and additional classroom and simulator training was provided to the operators on the revision to ES-0.1 and the bases behind the revision. A special check for training effectiveness was also conducted on December 19, 1988, at the request of senior nuclear power management as further assurance that the operators clearly understood the basis behind the procedure and would properly act to mitigate RCS cooldown following a reactor trip.
In addition to actions to address these specific issues, TVA reviewed the issues and their root causes for any generic implications. While TVA processes were-working to identify and drive this issue to resolution, review for programmatic improvement / enhancements was warranted to provide assurance of prompt identification and correction of similar problems in the future.
Specifically, the fuel reload analysis process has been enhanced by assigning responsibility for the entire process to the Nuclear Fuel organization and through inclusion of a mult1 disciplinary review of the reload core design and safety evaluation.
The SQN posttrip review procedure was revised to provide improved guidance on evaluating trip performance and to enhance the posttrip investigation through an interdisciplinary approach and use of upper-line management in a team concept.
To reverify effectiveness of SQN's postrestart review processes, TVA has 1nitiated an historical review of events since unit 2 restart with particular attention to adequacy of identified corrective action when viewed collectively with other events and to determine if common root causes exist for multiple events. Additionally, an effort is currently underway to enhance SQN's incident investigation and reporting process.
Current processes will be revised to better focus ownership and responsibility, better define appropriate levels of management involvement, and to clearly delineate TVA notification and reporting requirements and timeframes.
These actions and.ders initiated by TVA in response to these inues are summarized in enclosure 3.
The anclosure groups TVA corrective actions into three categories as related to (1) the SDM issue, (2) the overcooling issue, and (3) programmatic assessments / enhancements.
This enclosure clearly illustrates the prompt, extensive, and comprehensive actions initiated by TVA in response to review and resolution of these issues from both specific and programmatic perspectives.
In summary, TVA believes that its actions in response to the SDM safety i
1 issue were timely and successfully prevented operation in violation of TSs. Although not all actions taken were initially effective, actions taken in response to the RCS overcooling issue were extensive and demonstrated licensee initiative to correct problems. Actions taken to address generic implications and root cause of the issues were also extensive, thorough, and appropriate.
ENCLOSURE 1
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.C.
Application of the Enforcement Policy Under the enforcement policy of 10 CFR Part 2, Appendix C, an' enforcement action accompanied by imposition of a civil penalty is intended..to emphasize the need for lasting remedial action and to deter future violations.
The policy specifically provides for mitigation based on licensee identification, reporting, and correction of identified issues.
These mitigation factors are intended to encourage licensee identification, reporting, and correcting of violations and-to minimize potential to provide disincentives for a licensee to identify and correct
'l violations.
TVA believes that its actions taken in response to the subject issues have demonstrated its willingness and ability to aggressively identify and correct problems.
Based upon a review of the subject violations and policy mitigating factors, TVA also believes that both the identification / reporting and corrective action factors should be applied, resulting in total mitigation of the proposed civil penalty.
The policy states that reduction of up to 50 percent may be given when a licensee identifies the violation and promptly reports the violation to NRC. As previously discussed, TVA identified the SDM issue and promptly reported the issue to NRC as required.
The policy also notes that consideration should be given to the opportunity available to discover the violation, the ease of discovery, and the promptness and completeness of any required report.
While TVA acknowledges that an opportunity existed to identify and prevent the violation prior to the extended SQN shutdown, TVA believes consideration of performance prior to the shutdown is not appropriate in this case.
TVA considers that, following restart, opportunity to identify the issue existed from the first unit 2 trip on May 19, 1988. As previously discussed, the SDM problem was noted by TVA personnel immediately following that first trip, and by June 14, 1988. TVA had evaluated all information to establish cause and implications.
Tu issue was reported to NRC by LER 328/88030 within 30 days of determination i
of a potential to operate in a condition prohibited by TSs in accordance with 10 CFR 50.73.
The second relevant mitigstion factor involves corrective actions.
The policy states that the promptness and extent to which the licensee takes corrective action, including actions to prevent recurrence, may result in up to a 50-percent decrease in the base civil penalty.
The policy also notes consideration should be given to the timeliness of corrective action, degree of licensee initiative, and comprehensiveness of the corrective action, such as whether the action is focused narrowly to the specific violation o broadly to the general area of concern.
Corrective actions t (en to resolve the SDM concern were prompt and effective (boration requirements implemented in June 1988) in preventing operation in violat ans of TSs. Although some of the initial actions taken to address tt RCS cooldown issue were determined to be inadequate,
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ENCLOSURE'1
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. extensive actions were taken both before and after the November 18, 1988, trip to address this-issue with extensive management involvement. As previously described and additionally depicted in enclosure 3, actions.
taken to address broader programmatic issues were equally extensive and demonstrate clear licensee initiative to assess and. enhance programmatic 3
areas that could affect licensee ability to identify and correctly resolve
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issues in the future.
Exercise of Enforcement Discretion (Section V.G)
Under the current enforcement policy, NRC has noted certain Severity Level III situations where it is appropriate to apply enforcement discretion and thereby to refrain from issuing any NOV and/or civil penalty.
This discretion is intended to further encourage licensee identification, reporting, and correction of violations.
TVA has reviewed both the overall intent of this enforcement policy and the specifig prescribed situations where discretion is considered appropriate and believes that such discretion may be warranted in the present case.
Example V.G.2 describes situations similar to that involved at SQN. The example involves nonwillful violations, identified by the licensee, and based on licensee activities / performance before an extended shutdown, such as that experienced at SQN.
This provision of the enforcement policy reflects the reasonable premise that applying current enforcement action for preshutdown performance is not needed or consistent with the NRC regulatory purpose.
TVA performance prior to the 1985 shutdown is clearly not reflective of current TVA ability and commitment to identify and correct safety deficiencies.
Extensive management and culture changes were needed and accomplished during the shutdown. TVA draws attention to this example to clarify the period of time for which TVA's performance in addressing the SDM and cooldown issues should reasonably be considered for enforcement consideration, i.e., restart forward.
Example V.G.3 describes the situation where a Severity Level III violation was identified by the licensee, comprehensive corrective actions were initiated in a reasonable time, and the violation was not reasonably preventable by the licensee as a result of previous regulatory concern or prior notice of the problem involved. As previously discussed, the issue was identified by TVA, and extensive actions were initiated to resolve both specific and programmatic issues.
From a restart-forward perspective, it is not reasonable to expect TVA to have identified or prevented the problem prior to the first trip when the problem could be observed.
At that point, the SDM issue was identified, and action was subsequently taken that prevented future potential for operation in violation of TSs.
Conclusion from TVA's own review of the subject issues and enforcement basis, it is readily seen that the issues involved are complex and involve events over a i
significant period of time.
TVA believes that imposition of a civil penalty i
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should be reflective of current licensee overall performance associated with j
the issue, including consideration of whether.a licensee's current performance L.
is consistent with the objectives of the enforcement policy in identifying, reporting,- and correcting problems.
4 TVA identified the SDM' problem as a result of a conscientious and questioning attitude, promptly_ initiated investigation into the cause and implications, promptly achieved resolution.of the saft.ty. issue by imposing immediate l
boration requirements, and promptly reported the issue to NRC in accordance H
with 10 CFR 50.73.
TVA initiated and.' implemented extensive actions in attempt I
to mitigate future RCS cooldowns,. initiated and implemented.various programmatic enhancements to address broader perspectives than the specific issues, and promptly made readjustments to corrective actions where assessment of effectiveness proved to be wa~ ranted.
TVA feels that these actions directly parallel enforcement policy mitigation criteria and demonstrate TVA's commi-tment to identification and resolution of problems consistent with enforcement policy objectives.
For these reasons, TVA respectfully requests mitigation of the proposed imposition of civil penalty or application of enforcement discretion as provided for in 10 CFR, Part 2,_ Appendix C.
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ENCLOSURE 2 RESPONSE TO NRC NOTICE OF VIOLATION
'NOS. 50-327/88-35 AND 50-328/88-35 N05. 50-327/88-55 AND 50-328/88-55
.D. M. CRUTCHFIELD'S LETTER TO 0. D. KINGSLEY DATED FEBRUARY 23, 1989 Violation I "10 CFR 50.'59, Changes, Tests, and Experiments, allows a licensee to make changes in a facility, as described in the' safety. analysis report, without prior Commission approval, provided the change does not involve an unreviewed safety question.
In part, a change is deemed to involve an unreviewed safety question.if the probability of occurrence or the consequences of an accident or malfunction of equipment important to safety previously evaluated in the safety analysis report may be increased, or if the margin of safety as. defined in the basis for any technical specification is reduced.
Sequoyah Final Safety Analysis Report (FSAR), Sections 7.7 and 15.1, require, in part, that-the feedwater control systems prevent the average reactor coolant temperature (Tavg) from dropping below the 547*F programmed no-load temperature following a reactor trip to ensure that adequate shutdown margin is maintained.
Contrary to the above, the feedwater control system failed to perform as described in the FSAR in that during the reactor trips of May 19, 23, and June 6, 1988 Tavg dropped below the 547 F programmed no-load temperature needed to assure adequate. shutdown margin.
This would result in an end-of-life-condition for the subject cores which would have violated the Technical Specification limit for shutdown margin after a reactor. trip, and increased the probability of occurrence and consequences of an accident previously evaluated and, therefore, an unreviewed safety question.
There was no evaluation supporting this deviation from the FSAR pursuant to 10 CFR 50.59(b), and this change was implemented without prior Commission approval as required by 10 CFR 50.59(a)."
Admission or Denial of the Alleged Violation (Violation I)
TVA admits the violation.
Reason for the Violation (Violation I)
Subsequent to the performance of the 1982 startup tests and prior to the 1985 SON extended shutdown, TVA did not correctly assess the potential significance of the identified RCS posttrip cooldowns and perform a 50.59 evaluation of the deviation from performance described in the FSAR.
While the posttrip cooldown was identified during startup testing, it was not determined to constitute a safety concern e.nd was incorrectly considered acceptable.
Following the unit 2 trips (after restart from the extended outage), TVA personnel identified unexpected reductions in excess ^DM and began investigating to determine the cause. Adequate margin still existed with respect to the TSs SDM requirement; therefore, it was not an issue that should have prevented restart of the unit.
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'd ENCLUSURE 2
' Corrective Steps That Have Been Taken and Results Achieved (Violation I)
Five unit 2 trips occurred--May 19,1988; May 23,1988; June 6,1988; June 8, 1988; and June 9, 1988.
The SDM issue was identified by-TVA following the first trip.
TVA initially thought the observed reduction was solely the result of additional conservatism in vendor-supplied xenon tables, and discussions were initiated with the. vendor to address these concerns.
By-
- June 14,1988, after extensive evaluation, TVA determined that the problem was being caused by the excessive RCS cooldown below no-load Tavg. TVA determined that the potential existed for violating the TSs SDM requirement if a posttrip cooldown transient at end of core life had occurred (additional details
.regarding issue identification are provided in enclosure 1).
A CAQR was initiated on June 14, 1988, to document and resolve the issue.
In the event of a loss of' required SDM, TSs and operating experience would require boration to restore SDM; emergency procedure ES-0.1 was revised on June 18, 1988 (revision 3), to immediately require manual boration in the event of a reactor trip if RCS temperature dropped to prescribed levels.
This
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eliminated the SDM concern and ensured that TS requirements would not be l
violated at end of core life.
In addition, ES-0.1 was also revised to require manual control of AFW as an' attempt to mitigate the cooldown and obviate'the need for boration.
This revision-to ES-0.1 was evaluated pursuant to 10 CFR 50.59.
This evaluation verified that, with the required boration, compliance with the TSs would be ensured and that an unreviewed safety question would not exist in the event of RCS cooldowns of the magnitude previously experienced at SQN.
The initial revision of ES-0.1 specified boration requirements that bounded 70-percent power operation for the unit 2 core until end of life (TVA planned to operate unit 2 at less than 70-percent power in order to extend core operation until after unit I restart). Subsequent revisions to ES-0.1 (revisions 4 and 5) were made to bound both SQN units at end of core life and 100-percent power.
(These additional revisions to ES-0.1 also made changes regarding manual control of AFH. Details of those changes and actions taken to mitigate the cooldowns are further described in TVA's response to violation II.)
Corrective Steps That Will Be Taken to Avoid Further Violations (Violation I)
The FSAR, section 7.7, is being revised for submittal in the 1989 annual update to address administrative controls (boration) that are required if the steam dump and feedwater control system cool the RCS to below the core design i
allowable cooldown temperature.
SQN's posttrip review procedure has been strengthened to provide a new systematic approach to posttrip plant performance evaluation with specific consideration of performance compared to FSAR requirements / assumptions.
The fuel reload analysis process has been enhanced by assigning responsibility for the entire process to the Nuclear Fuel organization and through inclusion of a mult, disciplinary review of the reload core design and safety evaluation.
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1 ENCLOSURE 2
-3 In addition, TVA has recently initiated a 50.59 programmatic improvement effort focused at standardizing implementing procedures, clearly defining and increasing safety evaluation performer qualifications, and enhancing 50.59 training contents and requirements.
TVA is currently completing an extensive SQN FSAR verification program that-has been previously described in submittals to NRC.
This program verified FSAR requirements and statements against the SQN design. Any identified discrepancies have or will be evaluated in accordance with 10 CFR 50.59.
SQN's program to ensure future changes to the SQN design and facility from that described in the FSAR are properly evaluated was also enhanced as part of this corrective action effort.
P,eview for potential FSAR changes has been integrated into the design change process, and the process to initiate and complete actud FSAR updates has been standardized and enhanced.
-Sensitivity to deviations from the FSAR has been heightened over the past several years as a result of various review efforts and program enhancements.
l
_ TVA's corrective action program and implementing procedures specifically define "FSAR discrepancies" and direct issuance of a_CAQR and performance of a 50.59 evaluation for identified discrepancies.
Date When Full Compliance Will Be Achieved (Violation I)
TVA has achieved full compliance.
Violation II "10 CFR Part 50, Appendix B, Criterion XVI, Corrective Action, requires that measures be established to assure that conditions adverse to quality such as failures, malfunctions, deficiencies, deviations, defective material and equipment, and non-conformances are promptly identified and corrected.
Contrary to the above, licensee corrective actions which included procedure changes and operator training as outlined in TVA's October 5 and October 14, 1988 letters to the NRC to prevent excessive post-trip reactor cooldowns were not adequately implemented as demonstrated by the excessive cooldown following the November 18, 1988 Unit i reactor trip. This excessive cooldown resulted, in part, due to insufficient training in manual auxiliary feedwater (AFW) control and unclear instructions for manual AFW control in emergency operating procedure ES-01, Reactor Trip Response."
Admission or Denial of the Alleged Violation (Violation II)
TVA admits this violation.
Reason for the Violation (Violation II)
As previously discussed, TVA had revised ES-0.1 (revision 3) following the unit 2 trips to require manual boration on a reactor trip to ensure that adequate SDM was maintained in the event of a posttrip cooldown below no-load l
i ENCLOSURE-2 i
k Tavg. This eliminated the potential for SDM safety concerns and would prevent operation in violation of TSs in the event of a significant RCS cooldown below no-load Tavg at end of core: life.
In addl. ion TVA revised ES-0.1 to require manual control of AFW following a reactor trip, in attempts to mitigate the RCS cooldown below no-load Tavg.
As previously described in enclosure 1, a subsequent revision was made to ES-0.1 (revision 4) on July 16, 1988, which removed the provision for manual control of AFW. This was done as a result of TVA management concern with the-problems that could be created by placing an automatic safety system in manual control in a manner inconsistent with the system design basis.
When the decision was made to reinstate manual AFW control, TVA was sensitive to NRC's concerns regarding TVA's previous deviation from the WOG guidelines (i.e.,
absence of manual AFH control) and accordingly revised ES-0.1 (revision 5) to be consistent with wording contained in those guidelines.
The procedure required maintaining manual control of total AFW to greater than 440 gallons per minute (gal / min) until narrow-range level is greater than 25 percent in at least one steam generator.
SQN's AFH system is an automatic system that is designed to deliver full flow from two 100-percent, motor-driven pumps (440 gal / min each) and one 200-percent, turbine-driven pump (880 gal / min) with flow not throttled by level control valves untti associated steam generator levels reach 33 percent.
The intent of the procedure revision was to take manual control and throttle flow to slightly greater than 440 gal / min immediately following a trip.
4 TVA issued a training letter t0 licensed operators describing procedural changes involving manual control of AFH and conducted operator simulator training requiring manual control of AFW to be taken as temperature dropped below 547 degrees F.
While procedure revisions were not finalized at that time, trair,ing commenced with anticipated procedural changes to expedite completion.
(Additional details regarding operator training are provided in enclosure 1.)
In addition, the basis for the new requirement was explained.
Operators satisfactorily completed thi', simulator training before unit I restart. NRC reviewed the revised procedures and witnessed simulator training in order to assess adequacy for unit i restart; NRC found those actions to be acceptable.
Following the November 18, 1988, unit I trip, the operator initiated and delivered adequate boration to address any SDM concerns.
It should be noted that the boration source unexpectedly swapped from the boric acid tank to the RHST following the trip.
ES-0.1 (revision 5) provided flexibility for using either the " normal" or " emergency" boration flow path; however, in either case boration was assumed from the boric acid tank at 20,000 ppm. As a result of the RCS overcooling, letdown isolated on low pressurizer level, and ultimately, the charging pump suction swapped from the volume control tank to the RHST as volume control tank level dropped. This resulted is a change in boration source from the boric acid tank (containing 20,000 ppm boron) to the RHST (containing 2,000 ppm boron) since the normal boration flow path being used was isolated when the volume control tank discharge valves isolated.
The operators observed the swapover but recognized that equivalent boration would be provided from the RHST.
The RHST constitutes an alternate, qualified boration source, and equivalent boration was provided as a result of a higher flow rate.
I
o.
ENCLOSURE 2'
, Attempts to mitigate the RCS cooldown were ineffectively implemented following the unit I trip.
The operator incorrectly interpreted the procedure in such a way that the AFW system should be allowed to remain in automatic control and deliver full system flow rate until the level' in at least one steam generator reached 25 percent; at that time, manual control would be taken.
By the time the level recovered to 25 percent and the operator took manual control, the RCS cooldown to 522 degrees F could not be prevented.
In hindsight, TVA has determined that the original procedure change was inadequate and initial training insufficient. While the procedures had been revised consistent with WOG guidelines and training had been completed, it was determined that additional efforts were needed, especially to change an ingrained operator mind-set with regard to SQN's automatic AFW system.
Before these issues were identified, operators had always been trained to allow the automatic AFW system to provide system design flow rates that were-much greater than 440 gal / min to expedite rapid restoration of levels. -The operator's primary concern was to ensure minimum flow of 440 gal / min, with higher flow rates being all the better. With this type of mind-set, the operator interpreted the procedure to observe flow rate to each steam generator at greater than 440 gal / min and not require any throttling of flow until the steam generator level was returned to 25 percent.
The procedure did not specify an upper limit of flow to ensure the intent was clearly defined. Although the intent of the procedural requirement had been addressed in prerestart simulator training, the one-time training was not adequate to have changed ingrained operator mind-set.
Corrective Steps That Have Been Taken and Results Achieved (Violation II) l After the unit I trip, which occurred on November 18, 1988, ES-0.1 was promptly revised on November 20, 1988 (revision 6).
ES-0.1 was revised (revision 6) to clarify the method for taking manual control of AFW by clearly specifying a minimum total flow of 440 gai/ min to all steam generators and an upper limit of 500 gal / min total flow to all steam generators untti the level in at least one steam generator is greater than 25-percent narrow range.
Senior-level management was extensively involved in assessing the root cause of the posttrip cooldown and in directing prompt and comprehensive corrective actions. Additional classroom and simulator training was promptly conducted for operators on the new procedures to fully address the intent and basis for the procedural requirements and to emphasize practical application on the simulator. The simulator software was remodeled to more closely reflect actual plant response and to better duplicate the November 18 event.
In addition, a special training evaluation was conducted to determine the effectiveness of the ES-0.1 training. One operating shift crew was notified 1
after shift turnover to report to the training center without revealing the I
exact nature of the request.
The crew was subjected to a reactor trip l
simulator scenario and subsequent questioning on ES-0.1 procedure bases.
The evaluation concluded that the crew performed satisfactorily.
ENCLOSURE 2-l As a result of detailed vendor sensitivity studies, TVA has implemented two plant modifications intended to partially mitigate the RCS-cooling after a reactor trip.
The-first modification involved changes to the steam dump control system program to reduce the rate of heat removal from the steam generators immediately following a reactor trip.
The second modification involved decreasing the feedwater isolation setpoint such that the warmer main feedwater is supplied to the steam generators for a slightly longer time before swapping to'the cooler AFH.
These modif; cations have been implemented-on both units.
Review of operator performance and RCS temperature data from two unit 1 trips that occurred after implementation of these corrective actions indicates that the RCS overcooling problem has been significantly reduced as a result of proper operator manual control of AFH and implementation of the described physical plant modifications. Again, the SDM safety issue was and continues to be effectively resolved by manual boration.
Corrective Steps That Hill Be Taken to Avoid Further Violations (Violation II)
To further ensure continued effectiveness of these actions, TVA is in the process of adding a posttrip cooldown scenario to the annual requalification training program.
The shift operating crews have been formally evaluated during week one of 1989 requalification training in their performance during this specific scenario. Additional training to licensed shift operators on the previously described plant modifications will be included in the 1989 requalification training program as well.
TVA has additionally instituted a process to require training instructors to evaluate control room activities on a monthly basis, including " quizzing" of operators with specific focus on evaluation of training topic effectiveness.
.This effort, combined with verification and validation processes, should assist in identifying situations where training / procedures could be misinterpreted or where training topics require periodic reinforcement.
Date When Full Compliance Hill Be Achieved (Violation II)
TVA has achieved full compliance.
Violation III "10 CFR Part 50, Appendix B, Criterion V, Instructions, Drawings, and Procedures, requires that activities affecting quality shall be prescribed by documented instructions, drawings, or procedures of a type appropriate to the circumstances and shall be accomplished in accordance with those instructions, drawings, or procedures.
Instructions, drawings, or procedures shall include appropriate quantitative or qualitative acceptance criteria for determining that important activities have been satisfactorily accomplished.
Contrary to the above, AI-18, Reactor Post-Trip Review Procedure, established to identify and correct conditions adverse to quality occurring during a l
reactor trip, failed to provide sufficient guidance and acceptance criteria to
t' ENCLOSURE 2
' evaluate plant performance. The procedure did not compare actual post-trip parameters with FSAR values. Consequently, the post-trip reviews performed following the May 19, 23 and June 6, 1988 reactor trips were inadequate to identify and correct the reactor coolant system over cooling problem.
Collectively, these violations are categorized as a Severity Level III Problem (Supplement I).
Civil Penalty - $50,000 (assessed equally among the violations)."
Admission or Denial of the Alleged Violation (Violation III)
TVA admits the violation.
Reason for the Violation (Violation III)
TVA's procedure for conducting the posttrip review process, Administrative Instruction (AI) 18, " Plant Reporting Requirements," required licensee assessment of plant trip response and assessment of acceptability for restart but did not include criteria against which observed performance should be evaluated.
Corrective Steps That Have Been Taken and Results Achieved (Violation III)
TVA issued a separate procedure, AI-18.78, " Post Trip Evaluation Report," on October 20, 1988, to direct the posttrip evaluation previously performed under AI-18, File Package 18, Part B, " Reactor Trip Report."
This new procedure facilitates the posttrip review by providing a systematic safety assessment that determines the sequence of events before and throughout the trip, the root causes of the trip, and recommendations for corrective actions required to ensure that anomalies associated with the safe operation of the plant are resolved before restart. Operator / personnel performance is evaluated in terms of expected performance and human factors as part of the root cause analysis.
This instruction provides for an interdisciplinary approach for posttrip investigation and review using upper-line management in a team concept. A designated upper-line management individual serves as the investigation team leader, directing the investigation process and providing a high level of management oversight during the review process itself.
The posttrip evaluation report continues to be reviewed and approved by the Plant Operations Review Committee.
The safety assessment of plant response as part of the transient is addressed in detail by the posttrip investigation team using this instruction.
This is done by providing an evaluation of the actual response versus the designed
]
response as described in the FSAR.
Specifically, the requirements using a designated set of parameters are as listed below:
l D
ENCLOSURE 2
, I 1.
Describe actual response.
2.
Compare with FSAR design response. Does actual response fall within the bounds of design response (qualitative assessment)?
3.
Compare with previous trips of similar conditions if anomalies are noted.
4.
Note equipment failures and relationship to plant response.
5.
Note any failures to meet TS parameters / conditions.
6.
Overall conclusion must be made for acceptable plant restart--may require safety evaluation.
Corrective Steps That Have Been Taken to Avoid Further Violations No additional corrective actions are required.
Date When Full Compliance Will Be Achieved TVA has achieved full compliance.
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EP I
I I
ENCLOSURE 4 COMMITMENTS 1.
An effort is currently underway to enhance SQN's incident investigation and reporting process. SQN will implement resulting process revisions and enhancements by June 1, 1989.
2.
TVA will revise FSAR, section 7.7, to address administrative controls (boration) that are required if the steam dump and feedwater control system cool the RCS to below the core design allowable cooldown temperature.
The revision will be submitted to NRC as part of the 1989 annual update.
i i