ML16138A782
| ML16138A782 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 10/31/1994 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML16138A781 | List: |
| References | |
| NUDOCS 9411070364 | |
| Download: ML16138A782 (6) | |
Text
UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 207 TO FACILITY OPERATING LICENSE DPR-38 AMENDMENT NO. 207 TO FACILITY OPERATING LICENSE DPR-47 AND AMENDMENT NO. 204 TO 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 December 8, 1993, as supplemented April 20, September 8, and October 25, 1994, Duke Power Company, et al. (the licensee), submitted a request for changes to the Oconee Nuclear Station, Units 1, 2, and 3, Technical Specifications (TS).
The requested changes would make two revisions to Technical Specification (TS) 3.4, "Secondary System Decay Heat Removal" of the Oconee Nuclear Station, Units 1, 2 and 3, plant technical specifications.
The first revision proposes to revise TS 3.4.1 "Emergency Feedwater System" to address the need to bypass the loss of main feedwater (MFW) automatic initiation signal to the emergency feedwater (EFW) system when the (MFW) discharge pressure is below the EFW actuation setpoint. The basis for this revision is to prevent inadvertent actuation of the EFW system during startups and shutdowns. The present TS could also be interpreted to require the licensee to enter a limiting condition for operation (LCO) while following normal startup and shutdown procedures, therefore, clarification was needed.
In the second revision, Duke proposed to remove the operability requirements and surveillance requirements (SR) for the emergency condenser circulating water (ECCW) system as currently specified in TS 3.4.5 and TS Table 4.1-2, respectively. The licensee's basis for removal of the ECCW system from the TSs is that it is not required for decay heat removal to mitigate any design basis events. In a telephone call on October 25, 1994, the licensee agreed to retain surveillance requirements for the portion of ECCW required to support operability of the low pressure service water (LPSW) system.
The EFW system consists of one turbine-driven and two motor-driven EFW pumps with associated-flow paths to the steam generators. Each of the motor-driven pumps.will automatically start o" low steam generator (SG) level in both SGs or a loss of both MFW pumps. Te turbine driven-pump only receives an automatic start signal on a loss of both MFW pumps. The loss of both MFW pumps is sensed by either low MFW turbine control oil pressure or low MFW discharge header pressure. The proposed change would bypass only the automatic start on loss of both MWF pumps signal when the MFW pump discharge pressure is below the actuation trip setpoint. The automatic start of the motor-driven pumps on low level in both SGs would still be available.
9411070364 941031 PDR ADOCK 05000269 P
-2 The ECCW system is actually the condenser circulating water (CCW) system relying on syphon flow in lieu of the CCW pumps and with discharge flow diverted via an emergency discharge line to the Keowee Hydro Plant tailrace.
Normally, the CCW pumps take suction from Lake Keowee and the discharge from the condenser is returned to the Keowee River Arm of Lake Keowee. The CCW system is designed to take advantage of an inherent system syphon effect so that the CCW pumps are required only to overcome pipe and condenser friction losses. Under a loss of power situation, the emergency discharge line (to the tailrace) will automatically open and the CCW system will continue to operate as an unassisted siphon system supplying sufficient water to the condenser for decay heat removal.
This "siphon system" is the ECCW system and is divided into two distinct parts. The "first siphon" supplies suction to the LPSW system and.the "second siphon" provides flow through the main condenser to remove decay heat. The operation of the first siphon is unaffected by the operation of the second siphon. However, operation of the second siphon relies in part on the operation of the first siphon. The distinction between these two "siphons" is important because this distinction essentially forms the basis for the licensee's proposal to remove the ECCW system from the TSs.
The ECCW system includes operation of both siphons with flow through the main condenser. To support removal of the ECCW TS, the licensee states that only the first siphon is required for safe plant shutdown (provides net positive suction head [NPSH] to the LPSW pumps) and is already controlled via FSAR Chapter 16 and the LPSW system TS.
The April 20, September 8, and October 25, 1994 supplements provided additional information that did not change the scope of the December 8, 1994, application and the initial proposed no significant hazards consideration determination.
2.0 EVALUATION 2.1 Emergency Feedwater System During a normal plant startup, reactor coolant temperature could be above 250OF while actual MFW discharge pressure is still below the EFW initiation setpoint or reset point (about 100 pounds above setpoint) even though the MFW pumps are running and feeding the steam generators. Under these conditions, an unwanted EFW initiation signal would be generated and EFW would be delivered to the steam generators. The plant startup procedures presently bypass this initiation signal until the actual MFW discharge pressure is above the EFW actuation reset pressure to prevent inadvertent EFW initiation. TS 3.4.1a presently requires three EFW pumps and associated initiation circuitry to be operable before the reactor can be heated above 250 degrees fahrenheit
('F).
The requirement does not define the initiation circuitry to be automatic or manual, however, the ases for 3.4.1 do describe the automatic initiation logic. Therefore, the present TS could be interpreted to be violated whenever the actuation logic is bypassed when reactor coolant temperature is above 250'F.
To correct these conflicting requirements the proposed changes separately address the operability requirements for the manual and automatic functions and revised the TS as follows:
-3 1
TS 3.4.1a will now require that the manual initiation circuitry be operable whenever the EFW pumps are required to be operable, i.e.,
whenever the reactor coolant system is above 250'F. This is basically the same as the existing TS.
2 A new TS 3.4.2 has been added to require the automatic initiation circuitry associated with the loss of the MFW pumps be operable prior to criticality. This eliminates the confusion as to when the automatic function must be operable.
3 Existing TS 3.4.2 has been renumbered to 3.4.3 and revised (TS 3.4.3e) to clarify the required action if the EFW automatic initiation function becomes inoperable. Specifically, the actions are identical to the actions for an inoperable EFW pump, except that cooldown to 250 0F is not required since shutdown to hot shutdown will exit the applicability requirements for the automatic initiation circuitry.
Other minor changes and renumbering have also been made to the EFW system TS for clarification and consistency. The staff has reviewed these minor changes and found them acceptable as they do not have any impact on safety and more accurately reflect the actual EFW system requirements and design.
The change to TS 3.4.1a which addresses only the manual initiation circuitry is acceptable because it basically reflects the existing requirements for the manual initiation circuitry to be operable whenever the EFW pumps are required to be operable. Therefore, this is essentially no change.
The change to add TS 3.4.2 which addresses the automatic initiation function as sensed by the loss of MFW pumps logic is the main thrust of this TS revision. This new TS is also considered to be basically the same as the existing TS except that the operability requirements specify "prior to criticality" rather than "prior to the reactor being heated above 250 0F."
However, the existing TS do not adequately reflect actual plant operating conditions during startup and, therefore, had to be changed to prevent inadvertent EFW system initiation and to prevent violating TS requirements during normal plant startups or shutdowns. The proposed change would require the automatic initiation function as sensed by loss of both MFW pumps to be operable prior to criticality in lieu of prior to reaching 250'F. The bypassing of the automatic initiation function during startup and shutdown is in accordance with the plant design basis as reflected in FSAR Sections 10.4.7 and 16.7.3 which specify that this. function will be bypassed whenever the operating MFW pump(s) discharge pressure approaches the actuation setpoint.
FSAR Section 16.7.3 also requires the EFW automatic initiation low steam generator level-function (motor-driven pumps only) to be operable whenever the reactor coolant system is greatgpthan 250 0F. FSAR Section 16.7.3 further states that adequate time is available for manual initiation of the EFW system whenever plant conditions are such that the automatic initiation function on loss of MFW pumps must be bypassed. The staff agrees that the proposed change, as it reflects the actual plant design basis, is consistent with the FSAR accident analyses which assume power operation as an initial plant condition, and is necessary to prevent inadvertent initiation of the EFW system.
-4 The proposed addition of TS 3.4.3e is the action statement counterpart to the new TS 3.4.2. In the event the automatic actuation function becomes inoperable, the plant must be brought to hot shutdown in lieu of being cooled to below 250*F as presently required by'the existing specifications. The staff concurs with this proposed change because it makes the TS action statement consistent with the new operability requirements of TS 3.4.2 as justified above.
By bringing the plant to hot shutdown conditions, the operability requirements are no longer applicable because the reactor is no longer critical and, therefore, no further action is required.
The staff has also reviewed the proposed revised Bases for the above TS changes and concludes that they adequately reflect the design basis and operation of the EFW system and are also consistent with the proposed corresponding changes to the existing technical specifications. The proposed new bases are, therefore, acceptable to the staff.
2.2 Emergency Condenser Cooling Water System The licensee has proposed-to eliminate TS 3.4.5 (and its Bases) which presently requires the ECCW system to be operable whenever the reactor coolant system temperature is greater than 250.F. An allowed outage time of seven days is specified for loss of system function. The licensee contends that the original design basis for the ECCW system was to provide decay heat removal through the condenser in the event of a complete loss of offsite and onsite power. Section 10.4 of the staff's original Safety Evaluation Report (SER),
dated December 29, 1970, supports the licensee's contention that the design basis for the ECCW system was to accommodate a complete loss of all ac power.
This was a design basis that was unique to Oconee at the time of licensing.
The staff confirmed this licensing basis in an April 30, 1984 Safety Evaluation related to a TS change for the ECCW system. Subsequently, the licensee provided other means to cope with a complete loss of ac power in order to meet the Station Blackout (SBO) Rule, 10 CFR 50.63.
Following an SBO, the preferred method of coping would rely on the ECCW system and the turbine-driven emergency feedwater (EFW) pump to conserve makeup inventory and to maintain chemistry in the secondary system. However, because of certain limitations, this method is not credited to meet the SBO rule. The credited method, and therefore the method required to be available for coping with SB0, is the standby shutdown facility (SSF). The SSF auxiliary service water (ASW) system is capable of providing lake water to the steam generators under SBO conditions and meets all the requirements of the SBO rule. In the December 3, 1992 Supplemental Safety Evaluation for SBO at Oconee, the staff concluded that the SSF was acceptable with respect to coping with an SBO.
The staff, therefore, concludes that the ECCW system is no longer required to be in the TS because it is not reqy,4med to cope with a complete loss of ac power.
During its review, the staff questioned how the operability of the LPSW pumps would be assured without reliance on the ECCW system to provide a NPSH following design basis events involving the loss of the CCW pumps. In its April 20, 1994 response, the licensee clarified the operation of the "first" siphon and demonstrated that it would not be affected by removal of the ECCW system from the TS. Administrative controls are provided in FSAR Chapter 16
-5 system from the TS. Administrative controls are provided in FSAR Chapter 16 where selected licensee commitments are identified. Section 16.9.7, Keowee Lake Level, specifies a number of required actions in the event the lake level falls below certain levels. The actions associated with the first siphon flow puts the plant in a.24-hour LCO via the LPSW TS 3.3.7 if only one siphon source is available (LPSW does not meet the single failure criterion) and requires a plant shutdown (via TS 3.0) if no siphon source is available (LPSW system is declared inoperable). In addition, the licensee stated in the September 8, 1994 supplement that the "first" siphon mode of operation is tested during the LPSW System Flow Test. In the October 25, 1994 supplement, the licensee provided a clarification of the testing performed and stated that LPSW pump suction would not be aligned to this siphon during the flow test, but adequate suction flow for the LPSW system would be verified. In a telephone call on, October 25, 1994, the licensee agreed to include surveillance test requirements in TS Table 4-1-2 for the "first" siphon.
Based on the inclusion of the requirements in FSAR Chapter 16, and the surveillance requirements-for the "first" siphon, the staff concludes.that adequate controls are in place to verify LPSW system operability and the ECCW system TS is, therefore, not required for LPSW operability.
Based on its review the staff concludes that the proposed changes to the EFW system TS are consistent with the system design basis, plant operating procedures, and the FSAR accident analysis. The proposed changes are also necessary to avoid confusion in interpreting the EFW TS and prevent inadvertent initiation of the EFW system during startups and shutdowns.
The staff also concludes that the proposed change to eliminate the ECCW system from the TS is consistent with the current licensing basis which does not rely on operation of the ECCW system for any design basis events, including a complete loss of ac power, i.e., SBO.
The staff, therefore, concludes that the proposed changes to TS 3.4 related to the EFW and ECCW systems are acceptable and should be approved.
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. 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 individ
[1or 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 (59 FR 39584 dated August 3, 1994).
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.
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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 Contributor: William T. LeFave Date: October 31, 1994