ML022960284

Technical Specification Bases (TSB) Change

ML022960284
Person / Time
Site:	Oconee
Issue date:	10/14/2002
From:	Mccollum W Duke Energy Corp
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
Download: ML022960284 (17)

Text

Mk Duke Duke Energy r-F Energy.

Oconee Nuclear Station 7800 Rochester Highway Seneca, SC 29672 W. R. McColumi, Jr.

(864) 885-3107 OFFIcE Vice President (864) 885-3564 FAx October 14, 2002 U.

S. Nuclear Regulatory Commission Washington, D.

C.

20555 Attention: Document Control Desk

Subject:

Oconee Nuclear Station Docket Numbers 50-269, 270, and 287 Technical Specification Bases (TSB) Change Please see attached revisions to Technical Specification Bases (TSB) 3.4.12 "LTOP System" which was implemented on August 15, 2002. This change removes the requirement to have power available to the block valve as long as the block valve is open. Currently, the bases require that power must be available to the block valve in order for the PORV to be OPERABLE. Nothing in the LTOP analysis requires the operator to close the block valve during an LTOP event. If the block valve is open, the PORV should be considered OPERABLE whether or not the block valve has the power available to it or not. contains the new TSB pages and Attachment 2 contains the markup version of the Bases pages.

If any additional information is needed, please contact Larry E. Nicholson, at (864-885-3292).

Veye y yours, W. 9 Collum, Jr., Vice President Oconee Nuclear Site 4 o00

U.

S. Nuclear Regulatory Commission October 14, 2002 Page 2 cc:

Mr.

L. N. Olshan Office of Nuclear Reactor Regulation U.

S. Nuclear Regulatory Commission Washington, D. C.

20555 Mr.

L.

A. Reyes, Regional Administrator U.

S. Nuclear Regulatory Commission - Region II Atlanta Federal Center 61 Forsyth St.,

SW, Suite 23T85 Atlanta, Georgia 30303 Mel Shannon Senior Resident Inspector Oconee Nuclear Station Virgil R. Autry, Director Division of Radioactive Waste Management Bureau of Land and Waste Management Department of Health & Environmental Control 2600 Bull Street

Columbia, SC 29201

LTOP System B 3.4.12 B 3.4 REACTOR COOLANT SYSTEM (RCS)

B 3.4.12 Low Temperature Overpressure Protection (LTOP) System BASES BACKGROUND The LTOP System limits RCS pressure at low temperatures so the integrity of the reactor coolant pressure boundary (RCPB) is not compromised by violating the pressure and temperature (P/T) requirements of 10 CFR 50, Appendix G (Ref. 1). The reactor vessel is the limiting RCPB component for providing such protection. LCO 3.4.3, "ORCS Pressure and Temperature (P/T) Limits," provides the allowable combinations for operational pressure and temperature during cooldown, shutdown, and heatup to keep from violating the Reference 1 limits.

The reactor vessel material is less ductile at reduced temperatures than at normal operating temperature. Also, as vessel neutron irradiation accumulates, the material becomes less resistant to pressure stress at low temperatures (Ref. 2). RCS pressure must be maintained low when temperature is low and may be increased only as temperature is increased.

Operational maneuvering during cooldown, heatup, or related anticipated transients must be controlled to not violate LCO 3.4.3. Exceeding these limits could lead to brittle fracture of the reactor vessel. LCO 3.4.3 presents requirements for administrative control of RCS pressure and temperature to prevent exceeding the P/T limits.

This LCO provides RCS overpressure protection in the applicable MODES by ensuring an adequate pressure relief capacity and a limit on coolant addition capability. The pressure relief capacity requires the power operated relief valve (PORV) lift setpoint to be reduced and administrative controls implemented which assure >_ 10 minutes available for operator action to mitigate an LTOP event. The administrative controls include limits on pressurizer level, limits on RCS pressure when RCS temperature is < 325°F, limits on RCS makeup flow, the number of available pressurizer heater banks, requirements for alarms and restrictions upon use of the High Pressure Nitrogen System.

The LTOP approach to protecting the vessel by limiting coolant addition capability requires controls upon RCS makeup flow, the number of available pressurizer heater banks, and requires deactivating HPI, and isolating the core flood tanks (CFTs).

Should one or more HPI pumps inject on an HPI actuation (HPI-ES) or a CFT discharge to the RCS, the pressurizer level and PORV may not prevent overpressurizing the RCS.

BASES REVISION DATED 08/15/02 I OCONEE UNITS 1, 2, & 3 B 3.4.12-1

LTOP System B 3.4.12 BASES BACKGROUND The administrative controls upon pressurizer level provides a (continued) compressible vapor space or cushion (either steam or nitrogen) that can accommodate a coolant insurge and prevent a rapid pressure increase, allowing the operator time to stop the increase. The PORV, with reduced lift setting, is the overpressure protection device that acts as backup to the operator in terminating an increasing pressure event.

With HPI-ES deactivated, the ability to provide RCS coolant addition is restricted. To balance the possible need for coolant addition, the LCO does not require the makeup system to be deactivated. Due to the lower pressures associated with the LTOP MODES and the expected decay heat levels, the makeup system can provide flow with the HPI pumps providing RCS makeup through the makeup control valve.

PORV Requirements As required for LTOP, the PORV is signaled to open if the RCS pressure approaches a limit set in the LTOP actuation circuit. The LTOP actuation circuit monitors RCS pressure and determines when an overpressure condition is approached. When the monitored pressure meets or exceeds the setting, the PORV is signaled to open. Maintaining the setpoint within the limits of the LCO ensures the Reference 1 limits will be met in any event analyzed for LTOP.

When a PORV is opened in an increasing pressure transient, the release of coolant causes the pressure increase to slow and reverse. As the PORV releases steam, the RCS pressure decreases until a reset pressure is reached and the valve is signaled to close. The pressure continues to decrease below the reset pressure as the valve closes.

Administrative Control Requirements Administrative controls are necessary to assure the operator has at least ten minutes available to mitigate the most limiting LTOP event. These administrative controls include the following:

1)

Limits on RCS pressure based on RCS temperature;

2)

Limits upon pressurizer level;

3)

Limits upon makeup flow capability;

4)

OPERABLE Alarms;

5)

Controls upon use of the High Pressure Nitrogen System; and

6)

Restricting the number of available pressurizer heater banks.

BASES REVISION DATED 08/15/02 I OCONEE UNITS 1, 2, & 3 B 3.4.12-2

LTOP System B 3.4.12 BASES BACKGROUND Administrative Control Requirements (continued)

Limiting RCS pressure based on RCS temperature provides a minimum margin to the RCS P/T limit. Restricting RCS makeup flow capability and pressurizer level and controls on the use of high pressure nitrogen limit the pressurization rate during an LTOP event. Restricting the number of available pressurizer heater banks limits the pressurization rate during an LTOP event. Alarms ensure early operator recognition of the occurrence of an LTOP event. The combination of minimum margin to the limit, limited pressurization rate and OPERABLE alarms ensure ten minutes are available for operator action to mitigate an LTOP event.

APPLICABLE Safety analyses (Ref. 3) demonstrate that the reactor vessel can be SAFETY ANALYSES adequately protected against overpressurization transients during shutdown. In MODES 1, 2, and in MODE 3 with RCS temperature exceeding 3250F, the pressurizer safety valves will prevent RCS pressure from exceeding the Reference 1 limits. At nominally 3251F and below, overpressure prevention falls to an OPERABLE PORV, a restricted coolant level in the pressurizer and other administrative controls.

The actual temperature at which the pressure in the P/T limit curve falls below the pressurizer safety valve setpoint increases as vessel material toughness decreases due to neutron embrittlement. Each time the P/T limit curves are revised, the LTOP System will be re-evaluated to ensure that its functional requirements can still be met with the PORV and pressurizer level/administrative controls method.

Transients that are capable of overpressurizing the RCS have been identified and evaluated. These transients relate to either mass input or heat input: actuating the HPI System, discharging the CFTs, energizing the pressurizer heaters, failing the makeup control valve open, losing decay heat removal, starting a reactor coolant pump (RCP) with a large temperature mismatch between the primary and secondary coolant systems, and adding nitrogen to the pressurizer. LTOP limits and restrictions take into account the presence of nitrogen and/or air in the RCS during LTOP conditions.

HPI actuation and CFT discharge are the transients that may result in exceeding P/T limits within < 10 minutes in which time no operator action is assumed to take place. Starting an RCP and adding nitrogen to the pressurizer are self limiting events. In the rest, operator action after that time precludes overpressurization. The analyses demonstrate that the time allowed for operator action is adequate, or the events are self limiting and do not exceed P/T limits.

BASES REVISION DATED 08/15/02 I B 3.4.12-3 OCONEE UNITS 1, 2, & 3

LTOP System B 3.4.12 BASES APPLICABLE The following controls are required during the LTOP MODES to ensure SAFETY ANALYSES that transients do not occur, which either of the LTOP overpressure (continued) protection means cannot handle:

a.

Limiting RCS makeup flow capability;

b.

Deactivating HPI-ES;

c.

Immobilizing CFT discharge isolation valves in their closed positions; and

d.

Limiting the number of available pressurizer heater banks.

The Reference 3 analyses demonstrate the PORV can maintain RCS pressure below limits when both makeup flow capability and the number of available pressurizer heater banks is restricted. Consequently, the administrative controls require makeup flow capability and the number of available pressurizer heater banks to be limited in the LTOP MODES.

Since the PORV cannot protect the reactor vessel for engineered safeguards actuation of one or more HPI pumps, or discharging the CFTs, the LCO also requires the HPI-ES actuation circuits be deactivated and the CFTs isolated. The isolated CFTs must have their discharge valves closed and the valve power breakers fixed in their open positions.

Fracture mechanics analyses established the temperature of LTOP Applicability at 3251F. Above this temperature, the pressurizer safety valves provide the reactor vessel pressure protection. The vessel materials were assumed to have a neutron irradiation accumulation equal to 33 effective full power years (EFPYs) of operation for Units 1, 2, and 3.

This LCO will deactivate the HPI-ES actuation when the RCS temperature is < 3250F.

Reference 3 contains the acceptance limits that satisfy the LTOP requirements. Any change to the RCS must be evaluated against these analyses to determine the impact of the change on the LTOP acceptance limits.

PORV Performance The fracture mechanics analyses show that the vessel is protected when the PORV is set to open at < 535 psig. The setpoint is derived by modeling the performance of the LTOP system for different LTOP events.

The PORV setpoint at or below the derived limit ensures the Reference 1 limits will be met.

BASES REVISION DATED 08/15/02 I OCONEE UNITS 1, 2, & 3 B 3.4.12-4

LTOP System B 3.4.12 BASES APPLICABLE The PORV setpoint is re-evaluated for compliance when the revised P/T SAFETY ANALYSES limits conflict with the LTOP analysis limits. The P/T limits are periodically (continued) modified as the reactor vessel material toughness decreases due to embrittlement induced by neutron irradiation. Revised P/T limits are determined using neutron fluence projections and the results of examinations of the reactor vessel material irradiation surveillance specimens. The Bases for LCO 3.4.3 discuss these examinations.

The PORV is considered an active component. Therefore, its failure represents the worst case LTOP single active failure.

Administrative Controls Performance Limiting RCS pressure when RCS temperature is < 325°F provides a minimum margin to the RCS P/T limit. Restricting RCS makeup flow capability, the number of available pressurizer heater banks, pressurizer level, and controls on the use of high pressure nitrogen limit the pressurization rate during an LTOP event. Alarms ensure early operator recognition of the occurrence of an incipient LTOP event. The combination of minimum margin to the limit, limited pressurization rate and OPERABLE alarms ensure ten minutes are available for operator action to mitigate an LTOP event.

RCS Vent Requirements for Testing With the RCS depressurized, analyses show:

a.

For HPI System testing, a vent of > 3.6 square inches is capable of mitigating the transient resulting from HPI-ES actuation testing in which three HPI pumps inject to the RCS through two injection flow paths.

b.

For CFT Discharge Testing, a vent of > 201 square inches is capable of mitigating the transient resulting for discharge of both CFTs to the RCS.

The capacity of vents of these minimum sizes is sufficient to limit the RCS pressure to <400 psig, which is less than the maximum allowable pressure at minimum RCS temperature.

The RCS vent size will also be re-evaluated for compliance each time P/T limit curves are revised based on the results of the vessel material surveillance.

These vents are passive and not subject to active failure.

The LTOP System satisfies Criterion 2 and Criterion 3 of 10 CFR 50.36 (Ref.6).

BASES REVISION DATED 08/15/02 I OCONEE UNITS 1, 2, & 3 B 3.4.12-5

LTOP System B 3.4.12 BASES LCO The LCO requires an LTOP System OPERABLE with a limited coolant input capability and a pressure relief capability. The LCO requires HPI to be deactivated and the CFTs to be isolated. For pressure relief, it requires the pressurizer coolant at or below a maximum level and the PORV OPERABLE with a lift setting < the LTOP limit.

The PORV is OPERABLE when its block valve is open, its lift setpoint is set at < 535 psig and testing has proven its ability to open at that setpoint, and power is available to the PORV and its control circuit.

An RCS vent path capable of mitigating the most limiting LTOP event (except for HPI-ES actuation or CFT discharge) has a minimum equivalent diameter of 1-3/32 inches, which is equal to the inner throat diameter of the PORV.

Implementation of the following administrative controls assure that >_ 10 minutes are available for operator action to mitigate an LTOP event:

1.

RCS pressure:

• 375 psig when RCS temperature < 220OF

• 525 psig when RCS temperature > 220OF and < 325°F

2.

Pressurizer level is maintained within the following limits:

a.

RCS pressure is > 100 psig:

< 220 inches when RCS temperature < 3250F

b.

RCS pressure is _ 100 psig:

• 310 inches when RCS temperature < 2200F.

< 380 inches while filling or draining the RCS when RCS temperature < 160OF and no HPI pumps are running.

When the RCS pressure is < 100 psig, pressurizer level is normally maintained *220 inches except for certain RCS evolutions. The specified pressurizer level limits provide assurance that at least 10 minutes is available for operator action during those evolutions. The temperature limits are based on operational limits for the evolutions and are used in the analyses to determine allowable pressurizer levels.

3.

Makeup flow is restricted with the HP-1 20 (makeup control valve) travel stop set to < 98.0 gpm for all three units.

BASES REVISION DATED 08/15/02 I OCONEE UNITS 1, 2, & 3 B 3.4.12-6

LTOP System B 3.4.12 BASES LCO

4.

Three audible pressurizer level alarms at < 225 inches, *< 260 (continued) inches, and *315 inches from the temperature compensated pressurizer level indication.

5.

Two audible RCS pressure alarms at 375 psig and 525 psig.

6.

High pressure nitrogen system is administratively controlled to prevent inadvertent pressurization of the RCS.

7.

Core Flood Tank(s) are isolated as required by the LCO by closing the appropriate isolation valve(s) (either CF-1 and/or CF-2), tagging open the valve breaker(s), and tagging the valve(s) in the closed position.

8.

The HPI safety injection flowpaths must be deactivated.

a.

Deactivating Train A of HPI is accomplished by either:

1)

Shutting and deactivating valve HP-26 by tagging open the valve breaker and tagging the valve handwheel in the closed position, shutting valve HP-410 and tagging the valve switch in the closed position.

2)

Deactivating all HPI pumps aligned to HPI train A and tagging the pump breakers open.

b.

Deactivating Train B of HPI is accomplished by either:

1)

Shutting and deactivating valve HP-27 by tagging open the valve breaker and tagging the valve handwheel in the closed position, shutting valve HP-409 and tagging the valve switch in the closed position.

2)

Deactivating all HPI pumps aligned to HPI train B and tagging the pump breakers open.

9.

Pressurizer heater bank 3 or 4 must be deactivated.

Operational parameters identified in TS 3.4.12 and this TS Bases include allowances for instrument uncertainty.

APPLICABILITY This LCO is applicable in MODE 3 when any RCS cold leg temperature is

< 3250F, and in MODES 4, 5 and 6 when an RCS vent capable of mitigating the most limiting LTOP event is not open. The Applicability BASES REVISION DATED 08/15/02 I OCONEE UNITS 1, 2, & 3 B 3.4.12-7

LTOP System B 3.4.12 BASES APPLICABILITY temperature of 3250F is established by fracture mechanics analyses.

(continued)

The pressurizer safety valves provide overpressure protection to meet LCO 3.4.3 P/T limits above 3251F. With the vessel head off, overpressurization is not possible. With an RCS vent capable of mitigating the most limiting LTOP event open, an LTOP event (including HPI-ES actuation or CFT discharge) is incapable of pressurizing the RCS above the RCS P/T limits.

A RCS vent Ž 3.6 square inches is capable of mitigating a HPI-ES actuation of three pumps through two flow paths to the RCS. A RCS vent

> 201 square inches is capable of mitigating a discharge of both CFTs.

LCO 3.4.3 provides the operational P/T limits for all MODES. LCO 3.4.10, "Pressurizer Safety Valves," requires the pressurizer safety valves OPERABLE to provide overpressure protection during MODES 1, 2, and 3 above 3251F.

The Applicability is modified by two Notes. Note 1 states that CFT isolation is only required when the CFT pressure is more than or equal to the maximum RCS pressure for the existing RCS temperature, as allowed in LCO 3.4.3. This Note permits the CFT discharge valve surveillance performed only under these pressure and temperature conditions.

Note 2 permits the PORV to be inoperable when no HPI pumps are running and RCS pressure is < 100 psig. PORV operability is not required when RCS pressure is < 100 psig and HPI pumps are not operating since credible LTOP events progress relatively slowly, thus giving the operator ample time to respond.

ACTIONS A.1 With the HPI activated, immediate actions are required to deactivate HPI.

Emphasis is on immediate deactivation because inadvertent injection with one or more HPI pump OPERABLE is the event of greatest significance, since these events cause the greatest pressure increase in the shortest time.

The immediate Completion Times reflect the urgency of quickly proceeding with the Required Actions.

B.1, C.1, and C.2 An unisolated CFT requires isolation within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> only when the CFT pressure is at or more than the maximum RCS pressure for the existing temperature allowed in LCO 3.4.3.

,BASES REVISION DATED 08/15/02 I B 3.4.12-8 OCONEE UNITS 1, 2, & 3

LTOP System B 3.4.12 BASES ACTIONS B.1, C.1, and C.2 (continued)

If isolation is needed and cannot be accomplished in 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />, Required Action C.1 and Required Action C.2 provide two options, either of which must be performed in 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />. By placing the unit in MODE 4 with the RCS temperature > 200°F, the CFT pressure of 650 psig cannot exceed the LTOP limits if both tanks are fully injected. Depressurizing the CFTs below the LTOP limit of 373 psig also prevents exceeding the LTOP limits in the same event.

The Completion Times are based on operating experience that these activities can be accomplished in these time periods and on engineering judgement indicating that a limiting LTOP event is not likely in the allowed times.

D.1, E.1, and E.2 With the PORV inoperable, overpressure relieving capability is lost, and restoration of the PORV within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> is required.

If restoration cannot be completed within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />, either Required Action E.1 or Required Action E.2 must be performed. Required Action E.1 requires increasing RCS temperature within 23 hours2.662037e-4 days <br />0.00639 hours <br />3.80291e-5 weeks <br />8.7515e-6 months <br /> to exit the Applicability of the specification. With RCS temperature > 3250F, the CFTs are not required to be isolated. Required Action E.2 requires the RCS be depressurized to less than 100 psig within 35 hours4.050926e-4 days <br />0.00972 hours <br />5.787037e-5 weeks <br />1.33175e-5 months <br />. With reactor pressure < 100 psig more time is available for operator action to mitigate an LTOP event.

These Completion Times also consider these activities can be accomplished in these time periods. A limiting LTOP event is not likely in these times.

F.1 and G.1 With Administrative Controls that assure > 10 minutes are available to mitigate the consequences of an event not implemented, the capability for operator action to mitigate an LTOP event may be lost. In this circumstance, compensatory measures must be established to monitor for initiation of an LTOP event. Establishing a dedicated operator within 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> to monitor for initiation of an LTOP event is sufficient to compensate for inoperability of makeup flow restrictions, having too many pressurizer heater banks available, inoperability of required alarms, or deviation from pressure, temperature or level limits. Establishing a dedicated operator is not sufficient to compensate for not deactivating HPI or isolating CFTs. If the Required Action and associated Completion Time of Condition F is not met, the RCS must be depressurized and an BASES REVISION DATED 08/15/02 I OCONEE UNITS 1, 2, & 3 B 3.4.12-9

LTOP System B 3.4.12 BASES ACTIONS F.1 and G.1 (continued)

RCS vent path capable of mitigating the most limiting LTOP event must be established within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />. These Completion Times also consider that these activities can be accomplished in these time periods. A limiting LTOP event is not likely in these periods.

H.1 and H.2 With administrative controls which assure > 10 minutes are available to mitigate the consequences of an LTOP event not implemented and the PORV inoperable; or the LTOP System inoperable for any reason other than cited in Condition A through G, the system must be restored to OPERABLE status within one hour. When this is not possible, Required Action H.2 requires the RCS depressurized and vented within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />.

One or more vents may be used. A vent path capable of mitigating the most limiting LTOP event is specified. Because makeup may be required, the vent size accommodates inadvertent full makeup system operation.

Such a vent keeps the pressure from full flow of the makeup pump(s) with a wide open makeup control valve within the LCO limit.

The Completion Time is based on operating experience that these activity can be accomplished in this time period and on engineering judgement indicating that a limiting LTOP transient is not likely in this time.

SURVEILLANCE SR 3.4.12.1 and SR 3.4.12.2 REQUIREMENTS Verifications must be performed that HPI is deactivated, and the CFTs are isolated. These Surveillances ensure the minimum coolant input capability will not create an RCS overpressure condition to challenge the LTOP System. The Surveillances are required at 12 hour1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> intervals. The 12 hour1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> intervals are shown by operating practice to be sufficient to regularly assess conditions for potential degradation and verify operation within the safety analysis.

SR 3.4.12.3 Verification that the pressurizer level is less than the volume necessary to assure >_ 10 minutes are available for operator action to mitigate an LTOP event by observing control room or other indications ensures a cushion of sufficient size is available to reduce the rate of pressure increase from potential transients.

BASES REVISION DATED 08/15/02 I OCONEE UNITS 1, 2, & 3 B 3.4.12-10

LTOP System B 3.4.12 BASES SURVEILLANCE SR 3.4.12.3 (continued)

REQUIREMENTS The 30 minute Surveillance Frequency during heatup and cooldown must be performed for the LCO Applicability period when temperature changes can cause pressurizer level variations. This Frequency may be discontinued when the ends of these conditions are satisfied, as defined in plant procedures. Thereafter, the Surveillance is required at 12 hour1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> intervals.

These Frequencies are shown by operating practice sufficient to regularly assess indications of potential degradation and verify operation within the safety analysis.

SR 3.4.12.4 Verification that the PORV block valve is open ensures a flow path to the PORV. This is required at 12 hour1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> intervals.

The interval has been shown by operating practice to be sufficient to regularly assess conditions for potential degradation and verify operation is within the safety analysis.

SR 3.4.12.5 A CHANNEL FUNCTIONAL TEST is required within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> after decreasing RCS temperature to < 3251F and every 31 days thereafter to ensure the setpoint is proper for using the PORV for LTOP. PORV actuation is not needed, as it could depressurize the RCS.

The 12 hour1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> Frequency considers the unlikelihood of a low temperature overpressure event during the time. The 31 day Frequency is based on industry accepted practice and is acceptable by experience with equipment reliability.

SR 3.4.12.6 Verification that administrative controls, other than limits for pressurizer level, that assure > 10 minutes are available for operator action to mitigate the consequences of an LTOP event are implemented is necessary every 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />. This verification consists of a combination of administrative checks for alarm availability, verification that pressurizer heater bank 3 or 4 is deactivated, appropriate restrictions on pressurizer level, controls for High Pressure Nitrogen, etc., as well as visual confirmation using available indications that associated physical parameters are within limits.

BASES REVISION DATED 08/15/02 I OCONEE UNITS 1, 2, & 3 B 3.4.12-11

LTOP System B 3.4.12 BASES SURVEILLANCE SR 3.4.12.6 (continued)

REQUIREMENTS The Frequency is shown by operating practice sufficient to regularly assess indications of potential degradation and verify operation within the safety analysis.

SR 3.4.12.7 The performance of a CHANNEL CALIBRATION is required every 18 months. The CHANNEL CALIBRATION for the LTOP setpoint ensures that the PORV will be actuated at the appropriate RCS pressure by verifying the accuracy of the instrument string. The calibration can only be performed in shutdown.

The Frequency considers a typical refueling cycle and industry accepted practice.

REFERENCES

1.

10 CFR 50, Appendix G.

2.

Generic Letter 88-11.

3.

UFSAR, 5.2.3.7.

4.

10 CFR 50.46.

5.

10 CFR 50, Appendix K.

6.

10 CFR 50.36.

BASES REVISION DATED 08/15/02 I OCONEE UNITS 1, 2, & 3 B 3.4.12-12

LTOP System B 3.4.12 BASES LCO The LCO requires an LTOP System OPERABLE with a limited coolant input capability and a pressure relief capability. The LCO requires HPI to be deactivated and the CFTs to be isolated. For pressure relief, it requires the pressurizer coolant at or below a maximum level and the PORV OPERABLE with a lift setting < the LTOP limit.

The PORV is OPERABL.E;when its block valve is open, its lift setpoint is set at *535 psig and testing has proven its ability to open at that setpoint, and power is available to the tz

',alves m t, r

,-,tl AFoRV 4

&vsc4rol e'rc An RCS vent path capable of mitigating the most limiting LTOP event (except for HPI-ES actuation or CFT discharge) has a minimum equivalent diameter of 1-3/32 inches, which is equal to the inner throat diameter of the PORV.

Implementation of the following administrative controls assure that > 10 minutes are available for operator action to mitigate an LTOP event:

1.

RCS pressure:

< 375 psig when RCS temperature < 220OF

< 525 psig when RCS temperature > 220°F and < 325°F

2.

Pressurizer level is maintained within the following limits:

a.

RCS pressure is > 100 psig:

• 220 inches when RCS temperature _< 325°F

b.

RCS pressure is _< 100 psig:

• 310 inches when RCS temperature _< 2200F.

9 380 inches while filling or draining the RCS when RCS temperature _ 160°F and no HPI pumps are running.

When the RCS pressure is _< 100 psig, pressurizer level is normally maintained *220 inches except for certain RCS evolutions. The specified pressurizer level limits provide assurance that at least 10 minutes is available for operator action during those evolutions. The temperature limits are based on operational limits for the evolutions and are used in the analyses to determine allowable pressurizer levels.

3.

Makeup flow is restricted with the HP-120 (makeup control valve) travel stop set to < 98.0 gpm for all three units.

OCONEE UNITS 1, 2, & 3 B 3.4.12-6 Ameidrnent iob. 307, 307, &