RS-05-038, Additional Information Supporting the Request for License Amendment Related to Extending the Completion Time for Nuclear System Protection System Inverters
| ML051080395 | |
| Person / Time | |
|---|---|
| Site: | Clinton  |
| Issue date: | 04/18/2005 |
| From: | Jury K AmerGen Energy Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| RS-05-038, TAC MC3035 | |
| Download: ML051080395 (10) | |
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RS-05-038 10 CFR 50.90 April 18,2005 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Clinton Power Station, Unit 1 Facility Operating License No . NPF-62 NRC Docket No . 50-461
Subject:
Additional Information Supporting the Request for License Amendment Related to Extending the Completion Time for Nuclear System Protection System Inverters References : (1) Letter from Keith R. Jury (AmerGen Energy Company, LLC) to U . S . NRC, "Request for Technical Specification Change to Extend Completion Time for Nuclear System Protection System Inverters," dated April 26, 2004 (2) Letter from U. S. NRC to Christopher M. Crane (AmerGen Energy Company, LLC), "Clinton Power Station, Unit 1 - Request for Additional Information (TAC No. MC3035)," dated September 28, 2004 In Reference 1, AmerGen Energy Company, LLC (AmerGen) requested an amendment to the facility operating license for Clinton Power Station (CPS), Unit 1 . The proposed -change revises the Completion Time for Required Action A.1 of Technical Specification (TS) 3.8.7, "Inverters -
Operating," from the current 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> to 7 days for an inoperable Division 1 or 2 Nuclear System Protection System (NSPS) inverter .
The NRC, in support of their review of Reference 1, has provided a request for additional information (Reference 2). This request was related to compensatory measures and equipment history associated with the affected equipment. Attachment 1 provides the requested information. The associated marked up Bases page is provided, for information only, in . The regulatory commitments contained in this letter are summarized in .
April 18, 2005 U. S . Nuclear Regulatory Commission Page 2 AmerGen has reviewed the information supporting a finding of no significant hazards consideration that was previously provided to the NRC in Reference 1 . The supplemental information provided in this submittal does not affect the bases for concluding that the proposed license amendment does not involve a significant hazards consideration .
Should you have any questions related to this information, please contact Mr. Timothy A. Byarn at (630) 657-2804 .
I declare under penalty of perjury that the foregoing is true and correct. Executed on the 18`h day of April 2005.
Respectfully, Keith R. Jury Director - Licensing and Regulatory Affairs AmerGen Energy Company, LLC Attachments:
1 . Additional Information Supporting the Request for License Amendment Related to Extending the Completion Time for Nuclear System Protection System Inverters
- 2. Markup of Proposed Technical Specification Bases Page
- 3. Commitments
ATTACHMENT 1 Additional Information Supporting the Request for License Amendment Related to Extending the Completion Time for Nuclear System Protection System Inverters Request 7 During an extended inverter allowed outage time (AOT), the instrument bus would be powered from the constant voltage transformer. In the event of loss of offsite power (LOOP), the power supply to the instrumentation bus would be dependent upon the emergency diesel generator. As a result, entry into extended A OT concurrent with an EDG routine maintenance could have an impact on plant safety leaving the instrument bus without power. In addition, an entry into the extended inverter A 0 T, concurrent with planned maintenance on another reactor protection system (RPS)Iengineered safety feature actuation system (ESFAS) channel, could potentially result in that channel being in a tripped condition . Provide compensatory measures that would be taken before and during the time the instrument bus inverter is removed for an extended outage. For any compensatory measure proposed, identify how these actions will be documented and controlled at the facility.
Responsel In the license amendment request (Reference 1), it was stated that the change to the Completion Time (CT) is being proposed to support on-line corrective maintenance of the Nuclear System Protection System (NSPS) inverters . AmerGen Energy Company, PLC (AmerGen) understands the risk associated with performance of maintenance on the NSPS inverters during the modes of applicability as documented in Reference 1 . As a result, an emergency diesel generator (EDG) outage or other RIPS or Emergency Core Cooling System (ECCS)/Reactor Core Isolation Cooling (RCIC) System actuation logic maintenance activity would not be planned concurrent with a Division 1 or Division 2 NSPS inverter outage . Section 4 of Attachment 1 to Reference 1 states that for planned maintenance activities, an assessment of the overall risk of the activity on plant safety, including benefits to system reliability and performance, is currently performed prior to scheduled work . The assessment includes the following considerations .
Maintenance activities that affect redundant and diverse structures, systems, and components (SSCs) that provide backup for the same function are minimized.
The potential for planned activities to cause a plant transient are reviewed and work on SSCs that would be required to mitigate the transient are avoided.
Work is not scheduled that has a potential to exceed a Technical Specification (TS)
Completion Time requiring a plant shutdown . Planning for on-line equipment outages typically provides for a 100% contingency time within the TS Completion Time.
For Maintenance Rule Program High Risk Significant SSCs, the impact of the planned activity on the unavailability performance criteria is evaluated.
As a final check, a quantitative risk assessment is performed to ensure that the activity does not pose any unacceptable risk . This evaluation is performed using the Level 1 PRA model through use of the online risk assessment tool .
ATTACHMENT I itional Information Supporting the Request for License Amendment Related to Extending the Completion Time for Nuclear System Protection System Inverters These assessments are required in accordance with plant procedure, WC-AA-101, "On-Line Work Control Process" (Reference 2) . Clinton Power Station (CPS) Operations work to ensure that the work does not invalidate Shift Management reviews all emergent the assumptions made during the work management process . As required by plant procedures and stated in Reference 1, prior to starting any work, the work scope and schedule are critically reviewed to assure that nuclear safety and plant operations are consistent with the expectations of management . Individual work activities that potentially affect plant risk are evaluated by the use of system impact matrices, work document job details, plant drawings, or additional means to effectively determine the overall impact to plant risk levels .
AmerGen commits to take the following compensatory actions when a Division 1 or 2 NSPS inverter is inoperable .
Entry into the extended inverter CT will not be planned concurrent with EDG maintenance on the associated train .
Entry into the extended inverter CT will not be planned concurrent with planned maintenance on another RPS or ECCS/RCIC actuation logic channel that could result in that channel being in a tripped condition.
actions These are taken because it is recognized that with an inverter inoperable and the instrument bus being powered by the regulating transformer, instrument power for that train is dependent on power from the associated EDG following a loss of power event.
Therefore, in order to ensure appropriate control over these compensatory actions, AmerGen will describe these two actions in the TS Bases .
In addition, as documented in Section 4 of Attachment 1 to Reference 1, AmerGen will perform the following evaluations as part of the CPS risk management program documented in Reference 2 .
- Evaluate simultaneous switchyard maintenance and reliability.
0 Evaluate concurrent maintenance or inoperable status of any of the remaining three instrument bus inverters for the unit.
0 Evaluate simultaneous emergency diesel generator maintenance.
These commitments, as shown in Attachment 3, will be reflected in the CPS TS Bases and associated plant procedures . Attached is a copy of the marked-up TS Bases page that reflects the above. These Bases changes will be implemented in accordance with TS 5.5.11, "Technical Specifications (TS) Bases Control Program," as part of the
ATTACHMENT I Tonal Information Supporting the Request for License Amendment Related to Extending the Completion Time for Nuclear System Protection System Inverters implementation process for the associated license amendment upon NRC approval of Reference 1 .
Request 2 As stated in Regulatory Guide (RG) 1 . 177, "An Approach for Plant-Specific, Risk-Informed Decision Making Technical Specifications, " a Technical Specification (TS) change may be requested to reduce the unnecessary burdens in complying with current TS requirements, based on operating history of the plant or industry in general. Please provide maintenance (e.g., time to repair) and operating (e.g., constant voltage transformer and inverter failure rates) data for the extended outage .
Response 2 Based on a review of failure data contained in the Institute of Nuclear Power Operations (INPO) Nuclear Plant Reliability Data System (NPRDS) and Equipment Performance and Information Exchange System (EPIX), there have been no forced power reductions or plant shutdowns resulting from a failure of an instrument power (IP) system inverter or a regulating transformer at CPS. There has been one recent instance (in August 2004) in which another plant initiated a plant shutdown required by TS for an inverter failure, however, operability was restored prior to completion of the plant shutdown .
As described in Section 4 of Attachment 1 to Reference 1, the CPS Division 1, 2, 3, and 4 NSPS inverters have an extensive history of maintenance and operational issues since they were installed in 1986 . A review of the Division 1, 2, 3, and 4 NSPS inverter corrective maintenance and elective maintenance records was performed to identify the non-preventive NSPS inverter activities . This review indicated that 37 emergent activities have been completed since installation of the CPS NSPS inverters. The most significant failures occurred during refueling outages, when no generation capability was lost Of these failures, the longest duration to repair an inverter was 174 hours0.00201 days <br />0.0483 hours <br />2.876984e-4 weeks <br />6.6207e-5 months <br /> (7.25 days). This occurred in August 1998 during Clinton's extended sixth refueling outage.
No significant failures have occurred with the regulating transformers . There have been 7 emergent work activities completed on the regulating transformers since they were installed . None of these failures resulted in a production loss or derate . The longest duration for repair was 3 days which occurred in 1997 .
In general, inverter reliability issues have been resolved satisfactorily with the establishment of an adequate maintenance program and refurbishment of the units in 199&1991 As noted in Reference 1, in an effort to allow for rapid response to future catastrophic failures of a divisional NSPS inverter, CPS obtained a spare NSPS inverter in 2001 . In addition, CPS replaced the Division 2 NSPS inverter in the February 2004 refueling outage to correct known deficiencies . Section 4 of Attachment 1 to Reference 1 states that while use of the spare inverter will reduce the time required to repair a failed NSPS inverter, the spare may not be able to be installed and tested in 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.
AmerGen has estimated that a repair or replacement of an inverter would take Page 3 of 4
ATTACHMENT 1 dditional Information Supporting the Request for License Amendment Related to Extending the Completion Time for Nuclear System Protection System Inverters approximately 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, and therefore, an allowed outage time of 7 days for completing corrective maintenance and post-maintenance testing is judged to be adequate .
References Letter from Keith R. Jury (AmerGen Energy Company, LLC) to It S . NRC, "Request for Technical Specification Change to Extend Completion Time for Nuclear System Protection System Inverters," dated April 26, 2004
- 2. Exelon Procedure WC-AA-101, "On-Line Work Control Process," Revision 10
ATTACHMENT 2 p of Proposed Technical Specification Bases Page CLINTON POWER STATION, UNIT 1 FACILITY OPERATING LICENSE NO. NPF-62 Additional Information Supporting the Request for License Amendment Related to Extending the Completion Time for Nuclear System Protection System Inverters REVISED TECHNICAL SPECIFICATION BASES PAGE (For Information Only)
B 3.8-71
Inverters-Operating B 3 .8 .7 BASES APPLICABILITY Inverter requirements for MODES 4 and 5 are covered in the (continued) Bases for LCO 3 .8 .8, "Inverters-Shutdown ."
ACTIONS With a required inverter inoperable, its associated uninterruptible AC bus is inoperable if not energized .
LCO 3 .8 .9 addresses this action ; however, pursuant to LCO 3 .0 .6, these actions would not be entered even if the uninterruptible AC bus were de-energized . Therefore, the ACTIONS are modified by a Note stating that ACTIONS for LCO 3 .8 .9 must be entered immediately . This ensures the uninterruptible bus is re-energized within 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> .
AA-1 Required Action A .1 allows to fix h inoperable inverter and return it to service . The limit is This risk has to be balanced against the risk of an immediate shutdown, along with the potential challenges to safety systems that such a shutdown might entail . When the uninterruptible AC bus is powered from its onstant voltage source, it is relying upon interruptible AC electrical power sources (offsite and onsite) . The Y'! e G.t ~y 5ws uninterruptible inverter source to the uninterruptible AC buses is the preferred source for powerin g instrumentation rip setpoint devices .
4-o es s With one or more Division 3 or 4 inverters inoperable, the ssociated Division 3 ECCS subsystem may be incapable of 4x 11 performing intended function and must be immediately declared inoperable . This also requires entry into v1s ~ Ue applicable Conditions and Required Actions for LCO 3 .5 .1, "ECCS -Operating ."
. i r.vev4e, -s P e
C .1 .1, C .1 .2, and C .2 With one RPS solenoid bus inverter inoperable it may be incapable of providing voltage and frequency regulated power (continued CLINTON B 3 .8-71 Revision No . 1-1
Insert 1 (Bases page B 3.8-71) :
With a required inverter inoperable, the following compensatory actions will be taken :
1 . Entry into Required Action A.1 will not be planned concurrent with Emergency Diesel Generator (EDG) maintenance on the associated train.
- 2. Entry into Required Action A.1 will not be planned concurrent with planned maintenance on another RPS or ECCS/RCIC actuation logic channel that could result in that channel being in a tripped condition .
These actions are taken because it is recognized that with an inverter inoperable and the instrument bus being powered by the regulating transformer, instrument power for that train is dependent on power from the associated EDG following a loss of offsite power event.
In addition to the above, the following evaluations will be performed as part of the CPS risk management program whenever inverter maintenance is required .
1 . Evaluate simultaneous switchyard maintenance and reliability.
- 2. Evaluate concurrent maintenance or inoperable status of any of the remaining three instrument bus inverters for the unit.
- 3. Evaluate simultaneous EDG maintenance.
ATTACHMENT 3 Commitments LIST OF COMMITMENTS The following table identifies those actions committed to by AmerGen Energy Company, LLC (AmerGen), in this document . Any other statements in this submittal are provided for information purposes and are not to be considered commitments.
COMMITMENT Due Date/Event Revise TS Bases section 18.7 and the applicable Upon implementation procedure(s) to reflect the following evaluations as part of of the License the risk management program . Amendment
" Evaluate simultaneous switchyard maintenance and reliability.
" Evaluate concurrent maintenance or inoperable status of any of the remaining three instrument bus inverters for the unit .
" Evaluate simultaneous emergency diesel generator maintenance .
(2) Revise TS Bases section 3 .8 .7 to incorporate the Upon implementation following compensatory actions that should be taken of the License when a Division 1 or 2 NSPS inverter is inoperable . Amendment
" Entry into Required Action A.1 will not be planned concurrent with EDG maintenance on the associated train.
" Entry into Required Action A.1 will not be planned concurrent with planned maintenance on another RIPS or ECCS/RCIC actuation logic channel that could result in that channel being in a tripped condition .