ML15218A171
| ML15218A171 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 08/28/1998 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML15218A170 | List: |
| References | |
| NUDOCS 9809030269 | |
| Download: ML15218A171 (6) | |
Text
UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 2055-0001 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO.
230 TO FACILITY OPERATING LICENSE DPR-55 DUKE ENERGY CORPORATION OCONEE NUCLEAR STATION, UNIT 3 DOCKET NO. 50-287
1.0 INTRODUCTION
By letter dated July 16, 1998, Duke Energy Corporation (the licensee) submitted a request for changes to the Oconee Nuclear Station (ONS), Unit 3, Technical Specifications (TS). The requested changes would extend, on a one-time basis, during Operating Cycle 17, certain specified TS surveillances that are required to be performed at a frequency of 18 months from the maximum allowed frequency of 22 months, 15 days, to a maximum of 24 months. The following surveillances are involved: (a) Standby Shutdown Facility (SSF) Reactor Coolant System (RCS) Pressure Instrument Calibration; (b) SSF RCS Pressurizer Level Instrument Calibration; (c) SSF RCS Makeup Pump Flow Instrument Calibration; (d) Reactor Protective System (RPS) RCS Flow Instrument Calibration; (e) RPS RCS Pressure Instrument Calibration; and (f) Low Pressure Injection System Pump Discharge Valves LP-17 and LP-18 Manual Cycle.
To implement the change, a reference would be added to Table 4.1-1, Items 8, 9, 10, and 11; Specification 4.5.1.2.1.b.(1); and Table 4.20-1, Items 1, 2, and 4 that allows a one-time extension to 24 months for the frequency of the respective surveillances for Oconee Unit 3, during Operating Cycle 17.
2.0 DESCRIPTION
During the present operating cycle (Cycle 17), two forced outages and one prolonged shutdown of Oconee Unit 3 caused plant management to extend the operating cycle to October 13, 1998, which delayed the start of the next refueling outage. As a result of the schedule change, the schedule for performing TS surveillances was reviewed to ensure compliance with the TS. This review indicated that seven instrument channel calibrations and a manual stroke test of two valves were required to be completed before the start of the refueling outage. The TS requires that they be performed on an 18-month frequency and they cannot be performed during reactor operation.
For surveillances that are required to be performed on an 18-month frequency, TS 4.0.2 allows a maximum interval of 22 months, 15 days. Therefore, for example, the maximum interval will be exceeded on August 31, 1998, for the SSF RCS pressure instrument calibration surveillance. The interval from the previous instrument calibration date to the date of the unit shutdown of October 13, 1998, results in a maximum allowed interval of 22 months and 15 days being exceeded by 1 month, 13 days. The following table summarizes the TS surveillances that are affected.
9809030269 980828 PDR ADOCK 05000287 P
-2 Description of Component and TS Section Surveillance Added Time 4.20.2 (a),
SSF RCS Pressure Instrument Loops A 1 Month, 12 Days Table 4.20-1, item 1 and B Calibration 4.20.2 (a), Table SSF RCS Pressure Instrument Calibration 1 Month, 13 Days 4.20-1, item 4
4.20.2 (a),
SSF RCS Makeup Pump Flow Instrument 1 Month, 12 Days Table 4.20-1, item 2 Calibration 4.1.1, Table Reactor Protective System (RPS) RCS 26 Days 4.1-1, item 10 Flow Instrument Calibration for Channels C and D 4.1.1, Table 4.1-1, RPS RCS Pressure Instrument Calibration 23 Days items 8, 9 and 11 for Channels C and D 4.5.1.2.1, item b(1)
Low Pressure Injection System Pump 6 Days Discharge Valves LP-17 and LP-18 Manual I Cycle SSF Instrumentation The SSF provides the capability to shut down the three Oconee nuclear reactors from outside the main control room in the event of a fire, flood, or sabotage event. The SSF provides additional "defense-in-depth" backup to safety-related systems and is designed to maintain hot shutdown conditions on all three units for 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> following these events. It is designed to maintain RCS inventory, maintain RCS pressure, remove decay heat, and maintain shutdown margin. The SSF is provided with instrumentation to monitor several RCS parameters that include the SSF RCS Pressure and SSF Pressurizer (PZR) Water Level.
TS Table 4.20-1 specifies the frequency and type of surveillance for SSF instrumentation.
TS Table 4.20-1, item 1 (SSF RCS Pressure), item 2 (SSF RC Makeup Pump - Discharge Flow), and item 4 (SSF PZR Water Level) have a specified calibration frequency of 18 months.
The maximum allowable frequency of 18 months is defined in TS 4.0.2 as 22 months and 15 days.
Portions of the SSF RCS PZR Water Level instrumentation and SSF RCS Pressure instrumentation surveillance must be performed from inside the containment. The location of the SSF RCS Pressurizer Level instrumentation and the high dose rate that would be received preclude performance of this surveillance at power.
Considering the previous SSF instrument calibration dates and the need to operate until October 13, 1998, the maximum allowed interval of 22 months and 15 days would be exceeded by 1 month and 13 days.
The licensee performed a review of the procedure used to calibrate and verify proper operation of Loops A and B SSF Reactor Coolant Pressure Instrumentation, the SSF PZR Water Level Instrumentation, and the SSF Reactor Coolant Makeup Pump - Discharge Flow instrumentation
-3 during the previous two performances. This review did not indicate any adverse trends and found that the instrumentation remained within allowable tolerances.
According to the licensee, the as-found data for these surveillances was well within the specified tolerance of the procedures. There is no indication of significant calibration drift to suggest a degradation of this instrumentation due to a surveillance extension of up to 24 months would occur. A review of historic instrument drift for these instruments indicates that a 6-month extension beyond the normal 18-month surveillance interval would not result in drift beyond their allowable tolerances. Therefore, the licensee has a high level of confidence that a one-time extension of the calibration frequency to a maximum of 24 months would result in an extremely low probability of instrument drift beyond the allowed tolerances.
Reactor Protective System (RPS) Instrumentation The RPS monitors parameters related to safe operation and trips the reactor to protect the reactor core from fuel rod cladding damage. It also assists in protecting against RCS damage caused by high system pressure by limiting energy input to the system through reactor trip action.
The RPS inputs to the system are provided to monitor reactor flux, various RCS parameters, Reactor Building pressure, Main Turbine trip and loss of Main Feedwater. This portion of the proposed amendment addresses the RCS pressure and flow instrumentation only.
The RPS has four independent input channels for monitoring RCS pressure and four independent input channels for monitoring RCS flow. RCS flow is an input to the Flux/Imbalance/Flow trip and provides operators with flow indication for each RCS Loop.
RCS pressure is an input to the High RCS Pressure trip, Low RCS Pressure trip, Shutdown Bypass High Pressure trip, and the Variable Low RCS Pressure trip. The proposed amendment involves only Channels C and D of the RCS pressure and flow instrumentation since Channel A and Channel B calibrations for both the RCS pressure and flow instruments will remain within the allowable surveillance frequency.
TS Table 4.1-1 includes the frequency and type of surveillances required for RPS instrumentation. TS Table 4.1-1, item 8 (High Reactor Coolant Pressure), item 9 (Low Reactor Coolant Pressure), item 10 (Flux-Reactor Coolant Flow Comparator), and item 11 (Reactor Coolant Pressure Temperature Comparator) have a specified interval between tests of 18 months. Therefore, the maximum allowable interval between the surveillances is 22 months and 15 days.
It is undesirable to calibrate the RPS RCS flow and pressure instrument channels with the reactor at power due to the potential for a reactor trip during these calibrations. Considering the previous RPS instrument calibration dates and the need to operate until October 13, 1998, the maximum allowed interval of 22 months and 15 days would be exceeded by 26 days for the earliest due date.
The licensee reviewed the procedure used to calibrate and verify proper operation of the Channel C RPS RCS flow instrumentation, the Channel D RPS RCS flow instrumentation, the
-4 Channel C RPS RCS pressure instrumentation, and the Channel D RPS RCS pressure instrumentation during the previous two performances of these procedures and determined that there was no indication of adverse trends and the instruments were within allowable tolerances.
According to the licensee, the RPS RCS instrumentation is highly reliable based on performance history. Additional confidence in the continuing accuracy of the instrumentation is achieved by performance of an Instrument Channel Check each shift (i.e., twice per day). The Instrument Channel Check verifies acceptable performance of each instrument channel by observation of its behavior and/or state. This verification includes comparison of output and/or state of each of the four independent instrument channels for RCS flow and the four independent channels for RCS pressure. The licensee has found no indication of significant calibration drift that would suggest a degradation of this instrumentation would occur due to a surveillance extension of up to 24 months. A review of historic instrument drift for these instruments conducted by the licensee has indicated that a 6-month extension to the normal 18-month surveillance interval would not result in drift beyond their allowable tolerances.
Therefore, there is a high level of confidence that a one-time extension of the calibration frequency to a maximum of 24 months is not expected to result in instrument drift beyond the allowed tolerance.
Low Pressure Injection (LPI) System Pump Discharge Valves LP-17 and LP-18 The LPI system provides post-accident core cooling injection for larger RCS break sizes. The LPI system removes decay heat from the reactor core and sensible heat from the RCS during the later stages of normal plant cooldown. Two redundant trains of LPI are provided with pumps and heat exchangers outside the containment. The containment penetration for each LPI flow path through the containment wall to the RCS is isolated by a motor operated valve (MOV) located outside the containment and a check valve located inside the containment. The containment isolation MOVs (LP-17 and LP-18) located outside the containment and the check valves located inside the containment isolate the high pressure RCS from the lower design pressure of the LPI system during normal operation. Therefore, LP-1 7 and LP-1 8 must be maintained operable and closed during normal operation and must be capable of being opened and closed by their motor operators during post-accident events. For certain scenarios, they must be capable of being manually opened in the event of a failure. As a result, testing of the valves can only be performed during Cold Shutdown conditions when the RCS pressure is below the design pressure of the LPI system piping.
Technical Specification 4.5.1.2.1, item b.(1), specifies that the LPI system pump discharge valves be cycled manually every 18 months to verify their operability. Therefore, the maximum allowable interval between tests is 22 months and 15 days. Considering the previous manual stroke test date for the valves and the need to extend the operating cycle until October 13, 1998, the maximum allowed interval would be exceeded by 6 days.
The licensee performed a review of the procedure used to perform the last two tests of LPI system pump discharge valves and determined that they were manually opened with no evidence of restriction or binding. Additionally, the last 4 years of maintenance history for valves LP-1 7 and LP-1 8 was reviewed by the licensee and no record of valve problems that
-5 would suggest difficulties would be encountered in manually opening these valves as a result of the 6-day surveillance interval extension requested by this amendment was found.
Therefore, according to the licensee, the LPI system pump discharge valves have been demonstrated to be reliably capable of being manually opened. A review of industry operating experience with similar valves and actuators did not find any failures of a type that would prevent the valves from being manually cycled. Based on the past performance of these valves and the short duration of the requested extension, the licensee has determined that no adverse effects on the manual operability of the valves is expected to result from the extension.
Therefore, the one-time extension of the manual cycle test frequency to a maximum of 24 months is not expected to result in degradation of the capability to manually open the valves.
3.0 EVALUATION Periodic surveillance requirements were not intended to adversely affect safe plant operation simply because a specified surveillance interval does not coincide with plant operating schedules. Normally, variations in schedules can be accommodated through the existing TS.
Specifically, TS 4.0.1 is an administrative control that ensures surveillance tests are performed within the specified interval, but it provides for an allowable tolerance (25 percent) for performing surveillances beyond the normal surveillance interval. This tolerance provides operational flexibility to allow for scheduling and performance considerations while still ensuring that the reliability of the equipment or system associated with the surveillance is not significantly degraded beyond that obtained from the nominal specified surveillance interval. However, circumstances can develop wherein the relief provided by TS 4.0.1 is inadequate, but good cause for additional relief can be demonstrated by the licensee.
Such is the case here. The licensee has provided compelling evidence that the change in the refueling schedule was not undertaken for a reason or in a manner adverse to safety, that reasonable assurance exists that equipment associated with the subject surveillances will not be degraded significantly by the requested interval extensions, and that good cause exists for granting the extensions. The surveillance interval extensions proposed by the licensee would result in a slightly diminished confidence in the reliability that would be provided by the required TS surveillance intervals, but the licensee has satisfactorily addressed this concern.
Based on its review of the information supplied by the licensee, the staff has determined that the requested one-time extension is acceptable for ONS Unit 3, Operating Cycle 17, since the extension is of short duration and the instruments have shown no adverse trends that questions their reliability or ability to perform their required function.
4.0 STATE CONSULTATION
In accordance with the Commission's regulations, the South Carolina State official was notified of the proposed issuance of the amendment. The State official had no comments.
-6
5.0 ENVIRONMENTAL CONSIDERATION
The amendment changes surveillance requirements. The NRC staff has determined that the amendment involves no significant increase in the amounts, and no significant change in the types, of any effluents that may be released offsite, and that there is no significant increase in individual or cumulative occupational radiation exposure. The Commission has previously issued a proposed finding that the amendment involves no significant hazards consideration, and there has been no public comment on such finding (63 FR 40555 dated July 29, 1998).
Accordingly, the amendment meets the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9). Pursuant to 10 CFR 51.22(b), no environmental impact statement or environmental assessment need be prepared in connection with the issuance of the amendment.
6.0 CONCLUSION
The Commission has concluded, based on the considerations discussed above, that: (1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, (2) such activities will be conducted in compliance with the Commission's regulations, and (3) the issuance of the amendment will not be inimical to the common defense and security or to the health and safety of the public.
Principal Contributor: David E. LaBarge Date:
August 28, 1998