ML16138A734
| ML16138A734 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 05/11/1992 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML16138A735 | List: |
| References | |
| NUDOCS 9205260271 | |
| Download: ML16138A734 (7) | |
Text
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NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 195TO FACILITY OPERATING LICENSE DPR-38 AMENDMENT NO. 195TO FACILITY OPERATING LICENSE DPR-47 AND AMENDMENT NO. 191TO FACILITY OPERATING LICENSE DPR-55 DUKE POWER COMPANY OCONEE NUCLEAR STATION, UNITS 1. 2. AND 3 DOCKET NOS. 50-269, 50-270, AND 50-287
1.0 INTRODUCTION
By letter dated April 28, 1983, the NRC staff transmitted a safety evaluation report (SER) to the Duke Power Company (the licensee) in which it concluded that the design of the Oconee Nuclear Station's Standby Shutdown Facility (SSF) was acceptable. However, the staff requested that the licensee provide Technical Specifications (TS) for the operability of the SSF components to ensure that the SSF will meet its intended safety function. By letter dated July 26, 1985, the licensee submitted proposed changes to the Oconee Nuclear Station, Units 1, 2, and 3 TS for the SSF.
In a letter of January 23, 1987, the NRC staff reviewed the submittal and concluded that the proposed SSF TS outage time limit of 60 days was unacceptable because the licensee relies on the SSF for mitigating design basis events such as fires, flooding, and sabotage'. The staff suggested revising the limiting conditions for operation (LCO) of the proposed TS to make them equivalent to those of a safety-related system specified in the standard technical specifications (STS). In a letter of August 14, 1987, the licensee proposed revised SSF TS to address the staff's concerns on the 60-day outage time. In a submittal of August 12, 1988, the licensee added requirements for the hot leg temperature of the reactor coolant system (RCS) to the operability and surveillance requirements for instrumentation, as originally proposed in its submittals of July 26, 1985, and August 14, 1987.
The NRC staff sent a request for additional information (RAI) dated September 20, 1988, after reviewing the licensee's August 14, 1987, submittal.
The staff requested the following information:
- 1. The required mode of operation for the reactor during scheduled and unscheduled SSF outage times,
- 2. The impact that the failure of Keowee Hydroelectric Station and other emergency power sources will have on the capability of the SSF to perform its intended safety functions, 9205260271,920511 PDR ADOCK 05000269 I
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- 3. The rationale for deleting the originally proposed compensatory measures in the revised SSF TS proposal, and
- 4. The rationale for allowing an additional 7-day hot shutdown period before being required to enter Cold Shutdown mode, which is not provided in the Oconee TS for other similar safety systems.
Upon reviewing the licensee's response of November 28, 1988, to these concerns, the NRC staff issued a letter of February 21, 1990, in which it requested the licensee to clarify the following issues:
- 1. The allowed outage time of the SSF power system for planned reasons when the normal standby power supply (Keowee Hydroelectric Station) is out of service for planned or unscheduled inoperability and one or more of the units are in a condition requiring SSF operability,
- 2. Justification for including a 45-day combined special inoperability period for any SSF systems other than the SSF power system, and
- 3. The compensatory measures used between the 7th and 14th day of the proposed hot standby period when the SSF systems could still be required to be functional.
On August 21, 1990, the licensee submitted the requested information.
On September 17 and 18, 1990, the NRC staff met with the licensee to clarify previous concerns. Following the meeting, the licensee provided the staff with an amended TS submittal, dated March 5, 1991. The licensee also submitted SSF and diesel generator availability records in letters of August 1 and August 12, 1991.
The NRC staff reviewed these submittals, including the most recent submittals of March 5, 1991, and April 9, 1992, to verify that the SSF TS would meet the requirements for safe shutdown. This SER does not address acceptability of the TS for station blackout (SBO).
As a separate activity, the staff will review the TS requirements for using the SSF for a station blackout (SBO) to verify that these requirements comply with the SBO rule and associated guidance. The August 14, 1987, August 12 and November 28, 1988, August 21, 1990, March 5, 1991, March 24 and April 9, 1992, letters provided clarifying information that did not change the initial proposed no significant hazards consideration determination.
2.0 EVALUATION The SSF is a single train system consisting of a seismically designed, reinforced concrete structure and the components and systems contained therein. These components and systems provide an alternative and independent means to achieve and maintain hot shutdown in one, two, or three of the Oconee
-3 units for approximately 3 days following a loss of normal ac power. The SSF was designed to provide Oconee Nuclear Station with a means to meet the safe shutdown requirements for fire protection, turbine building flooding, and physical security. The licensee will operate the SSF only if installed normal and emergency systems become inoperable. The licensee personnel must manually actuate the SSF subsystems. The SSF is not designed to meet the single failure criterion but is designed to ensure that failures do not cause failures or inadvertent operation in existing plant systems. If one or more major subsystems and components become inoperable, they could cause the SSF to become inoperable.
The SSF includes the following major subsystems:
(1) The auxiliary service water (ASW) system. This high volume system consists of one high head ASW pump and is designed to provide sufficient coolant to the steam generator to ensure that each of the three units has adequate decay heat removal during loss of normal ac power and normal emergency feedwater system. The ASW system receives its supply of water from the Unit 2 buried condenser recirculating water (CCW) piping.
(2) The portable pumping system. This system is designed to provide a backup supply of water to the SSF ASW system if the CCW piping fails and causes a loss of CCW siphon flow from Unit 2.
(3) The reactor coolant (RC) makeup system. This system consists of three independent pumps. One pump is provided for each of the three units to supply coolant to the reactor coolant system (RCS) if normal makeup systems become unavailable. This system has sufficient capacity to compensate for normal RCS leakage and shrinkage which results from going from a hot power operation to hot shutdown. The RC makeup system obtains its coolant from the spent fuel pool, thus ensuring a supply of borated water.
(4) The electrical power system. This system provides normal independent emergency sources of ac and dc electrical power, their associated electrical distribution systems, and various support systems. The SSF standby power supply consists of an independent diesel generator unit rated at 3500 kw, 0.8 PF, 4160 volts. The dc power supply consists of two 125v dc batteries and associated chargers, two dc distribution centers, and a dc power panel board.
This system is designed to provide an uninterruptible source of power for the SSF equipment controls and instruments.
(5) The SSF associated instrumentation. The SSF panel provides accurate and reliable information to ensure safe plant operation and shutdown conditions for all three units. Monitoring capability is provided for needed plant parameters to achieve and maintain hot shutdown conditions in all three units for approximately 3 days.
The licensee is proposing the following TS for Section 3.18, "Standby Shutdown Facility," to ensure that the operability of the SSF components is compatible with fire, flooding, and security assumptions used in the design.
-4 3.18.1, Summary of the limiting conditions for operation requirements for SSF subsystems 3.18.2, "SSF Auxiliary Service Water System" 3.18.3, "SSF Portable Pumping System" 3.18.4, "SSF Reactor Coolant Makeup System" 3.18.5, "SSF Power System" 3.18.6, "SSF Associated Instrumentation" 3.18.7, LCO requirements for 45 day special inoperability periods 3.18.8, LCO requirements for allowing changing mode(s) of operation while in action statement The licensee is proposing the following surveillance requirements (SRs) for Section 4.20, "Standby Shutdown Facility:"
4.20.1, "SSF Pumps and Valves" 4.20.2, "SSF Instrumentation" 4.20.3, "SSF Electrical Power Systems" The LCO defined in TS 3.18.2 through 3.18.6 require that any inoperable system must be restored to operable status within 7 days or that one of two options must be followed:
(1) the affected unit shall be in hot shutdown within the next 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />, and below 250'F within the following 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, or (2) the 45-day special inoperability period as defined in-TS 3.18.7 may be used to extend the outage time of the SSF inoperable subsystem.
The licensee may use the 45-day special inoperability period to extend the outage time of an SSF subsystem(s).
Each Oconee unit has a 45-day special inoperability period. Certain subsystems, such as the RC makeup system, affect only one unit. If one of these systems is inoperable for 8 days, the licensee must reduce the 45-day special inoperability period by 8 days for that unit alone. Other subsystems, such as the diesel generator (DG) affect all units. If one of these systems is inoperable for 8 days, the licensee must reduce the 45-day special inoperability period for each unit by 8 days.
If any unit uses its entire 45-day special inoperability period before the end of the year, the licensee will be required to shut down that unit if a subsystem is inoperable for more than 7 days. In the August 21, 1990, and November 28, 1988, submittals, the licensee described its method for calculating the 45-day combined special inoperability periods in TS 3.18.2 through 3.18.6.
-5 In providing justification for the 45-day special inoperability period, the licensee stated that the need to remove the DG for preventive maintenance and draining of the Unit 2 CCW intake piping are necessary to ensure the long term reliability of the SSF. To perform major activities such as these, the licensee may need more than the 7-day outage time allowed in the LCO. Thus, the licensee would need the 45-day special inoperability provision to avoid shutdown of all three units unnecessarily. The licensee also stated that high radiation levels or problems with operating systems prevent it from performing repairs to certain SSF subsystems, such as the RC makeup pump or associated instrumentation during operation. Therefore, a special inoperability period allows some flexibility in scheduling shutdowns and other activities associated with such repairs. In the submittals of August 1 and 12, 1991, the licensee provided summaries of SSF availability records to support the 45-day special inoperability period. The licensee also stated that it anticipates approaching the end of the 45-day special inoperability period only when it drained the Unit 2 CCW intake piping, which is done once every 3 years. The staff reviewed the availability records and found that the Oconee SSF has only been unavailable for a period greater than 7 days twice since 1985. On August 8, 1985, the licensee had made the SSF unavailable for 7.5 days while making modifications to a diesel oil drain line. On May 22, 1989, the SSF became unavailable for 30.6 days while the licensee drained the Unit 2 CCW intake piping to inspect it and apply a coating. In the August 14, 1987, submittal, the licensee stated that it will perform the scheduled preventive maintenance on the SSF DG, SSF ASW pump, and SSF makeup pump when it drains the Unit 2 CCW piping, if practical, to decrease the outage of the SSF.
In the submittal of March 5, 1991, the licensee also proposed TS 3.18.8, which was previously proposed in the August 14, 1987, and August 21, 1990, submittals.
Proposed TS 3.18.8 would allow the licensee to heatup a unit above 250 0F, to maintain it critical, or to restart it, if the SSF or any of its major subsystems is in a degraded mode or a special inoperability period allowed by TS 3.18.2 through 3.18.6. The licensee had not provided justification for TS 3.18.8. Thus, in a submittal of April 4, 1992, the licensee justified the mode change LCO based on the following:
(1) SSF events are of very low probability; (2) once the SSF is degraded, it usually affects all three units; (3) a unit heating up above 250'F places few additional requirements on the SSF beyond those already required for the operating units; and (4) the remote shutdown TS for many other plants contain similar provisions in the exceptions to LCO 3.0.4.
The NRC staff has reviewed the licensee's submittals requesting the 45-day special inoperability period under TS 3.18.7 and find the period acceptable based on the restrictive and justifiable needs for exceeding normal LCO outage limits provided in TS 3.18.2 through 3.18.6. The licensee has shown, through availability records, that the maximum unavailable period has been 30.6 days, which marginally exceeds the STS limit of 30 days. The licensee can use the special inoperability period of 45 days during certain events such as concurrent maintenance or maintenance of other systems during the same calendar year which require more than 7 days, thus reducing the possibility of
-6 unnecessary shutdown of one or more Oconee units. The LCO in TS 3.18.2 through 3.18.6 include an allowable inoperability period of 7 days for the SSF subsystems. This provision is compatible with the STS for emergency feedwater and other safety-related systems. The licensee's proposed LCO in TS 3.18.8 for allowing mode changes (to heat the reactor above 250'F, maintain it critical, or restart it while the SSF is degraded or during a special inoperability allowed by TS 3.18.2 through TS 3.18.6) is acceptable since this LCO is similar to those previously approved by the staff (such as for Catawba) and is consistent with LCOs for other systems which perform similar functions.
Therefore, the staff finds that the proposed SSF TS are acceptable because (1) they generally conform with the STS guidelines, and (2) the licensee has prudently used the proposed 45-day special inoperability period under TS 3.18.7.
SR 4.20.1 defines the surveillance testing requirements for the SSF pumps and valves. SR 4.20.1 states that all inservice testing of ASME (American Society of Mechanical Engineers) Code Class 1, 2, and 3 pumps and valves in the SSF shall be performed in accordance with Section XI of the ASME Boiler and Pressure Vessel Code, and applicable addenda as required by Part 50 of Title 10 of the Code of Federal Regulations (10 CFR Part 50).
All of the SSF pumps and valves will be tested in accordance with the above criteria with the exception of the portable pump system, which is not safety-related. This portable pump will be tested on a 2-year frequency for developed head and flow, using calibrated test instrumentation. SR 4.20.2 defines the frequency and type of surveillance required for the SSF instrumentation. Table 4.20.1 lists the frequency in which the SSF instrumentation is to be checked and calibrated.
In its rationale for the instrumentation surveillance requirements, the licensee stated that the surveillance requirements are based on the experience in operating both conventional and nuclear systems. Process system instrumentation errors induced by drift should remain within acceptable tolerances if the licensee calibrates these instruments at the specified intervals. SR 4.20.3 defines the surveillance tests to be performed monthly, quarterly, and after maintenance to verify the operability of the DG.
The NRC staff finds that the surveillance requirements are acceptable because they are similar to the surveillance requirements of other similar types of equipment within technical specifications, manufacture recommendations, and appropriate NRC guidelines.
In 1983, the NRC staff found the SSF design acceptable to meet the safe shutdown requirements for fire protection, turbine building flooding, and physical security. The staff reviewed the proposed TS for these issues but did not consider station blackout (SBO).
The NRC staff concludes that the licensee's proposed TS 3.18, "Standby Shutdown Facility," is acceptable because it (1) generally meets the intent of the STS, (2) is similar to TS previously approved by the staff for other systems which perform similar functions, and (3) provides a 45-day special inoperability period that is restrictive and will be used with proper justification to ensure the long term reliability of the SSF.
-7 The elements in SR 4.20, "Standby Shutdown Facility," are acceptable in that they are similar to the corresponding TS for similar plants, add conservatism, and are supported by additional surveillance procedures as appropriate.
3.0 STATE CONSULTATION
In accordance with the Commission's regulations, the South Carolina State official was notified of the proposed issuance of the amendments. The State official had no comments.
4.0 ENVIRONMENTAL CONSIDERATION
The amendments change requirements with respect to installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20 and change surveillance requirements. The NRC staff has determined that the amendments involve 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 amendments involve no significant hazards consideration, and there has been no public comment on such finding (50 FR 43024). Accordingly, the amendments meet 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 amendments.
5.0 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 amendments will not be inimical to the common defense and security or to the health and safety of the public.
Principal Contributors: J. Raval, SPLB F. Burrows, SELB S. Flanders, SPLB L. Wiens, PDII-3 Date:
May 11, 1992