ML050880413

Tech Spec Pages for Amendments 343, 345 and 344, Minimum Pressurizer Heater Capacity

ML050880413
Person / Time
Site:	Oconee
Issue date:	03/28/2005
From:	NRC/NRR/DLPM
To:
Olshan L N, NRR/DLPM, 415-1419
References
TAC MC1105, TAC MC1106, TAC MC1107
Download: ML050880413 (7)

Text

I Pressurizer 3.4.9 3.4 REACTOR COOLANT SYSTEM (RCS) 3.4.9 Pressurizer LCO 3.4.9 The pressurizer shall be OPERABLE with:

a. Pressurizer water level < 285 inches; and

b. A minimum of 400 kW of pressurizer heaters OPERABLE and I capable of being powered from an emergency power supply.

APPLICABILITY: MODES 1 and 2, MODE 3 with RCS temperature > 3250F.

ACTIONS CONDITION REQUIRED ACTION COMPLETION TIME A. Pressurizer water level A.1 Restore level to within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> not within limit. limit.

B. Required Action and B.1 Be in MODE 3. 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> associated Completion Time of Condition A not AND met.

B.2 Be in MODE 3 with 18 hours2.083333e-4 days <br />0.005 hours <br />2.97619e-5 weeks <br />6.849e-6 months <br /> RCS temperature

< 325 0F.

C. Capacity of pressurizer C.1 Restore pressurizer 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> heaters capable of heater capability.

being powered by emergency power supply less than limit.

(continued)

OCONEE UNITS 1, 2, & 3 3.4.9-1 Amendment tlos. 343, 345, & 344 l

- I Pressurizer 3.4.9 ACTIONS (continued)

CONDITION REQUIRED ACTION COMPLETION TIME D. Required Action and D.1 Be in MODE 3. 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> associated Completion Time of Condition C not AND met.

D.2 Reduce RCS 18 hours2.083333e-4 days <br />0.005 hours <br />2.97619e-5 weeks <br />6.849e-6 months <br /> temperature to

< 325 0F.

SURVEILLANCE REQUIREMENTS SURVEILLANCE FREQUENCY SR 3.4.9.1 Verify pressurizer water level < 285 inches. 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> SR 3.4.9.2 Verify capacity of required pressurizer heaters 18 months and associated power supplies are 2 400 kW.

I OCONEE UNITS 1, 2, & 3 3.4.9-2 Amendment Nos. 343, 345, & 344 I

Pressurizer B 3.4.9 BASES BACKGROUND maintained with a loss of offsite power. Consequently, the-emphasis of this (continued) LCO is to ensure that the essential power supplies and the associated heaters are adequate to maintain pressure for RCS loop subcooling with an extended loss of offsite power.

A minimum required available capacity of 400 kW ensures that the RCS I pressure can be maintained. Unless adequate heater capacity is available, reactor coolant subcooling cannot be maintained indefinitely. Inability to control the system pressure and maintain subcooling under conditions of natural circulation flow in the primary system could lead to loss of single phase natural circulation and decreased capability to remove core decay heat.

The 400 kW of heater capacity exceeds the capacity required to be powered by the Standby Shutdown Facility (SSF) per the Technical Specification 3.10.1 BASES. The 400 kW limit is not unit specific and was conservatively established to bound future increases Inpressurizer ambient heat loss.

APPLICABLE In MODES 1 and 2, the LCO requirement for a steam bubble is reflected SAFETY ANALYSES implicitly in the accident analyses. No associated safety analyses are performed in lower MODES. All analyses performed from a critical reactor condition assume the existence of a steam bubble and saturated conditions in the pressurizer. In making this assumption, the analyses neglect the small fraction of noncondensible gases normally present.

Safety analyses presented In the UFSAR do not take credit for pressurizer heater operation; however, an Implicit initial condition assumption of the safety analyses Isthat the RCS is operating at normal pressure.

The maximum level limit Isof prime interest for the startup accident and Loss of Main Feedwater (LOMFW) event. Conservative safety analyses assumptions for the startup accident indicate that it produces the largest Increase of pressurizer level caused by an analyzed event. Thus this event has been selected to establish the pressurizer water level limit. For pressurizer levels > than 285 inches, the LOMFW event may be more limiting.

Evaluations performed for the design basis large break loss of coolant accident (LOCA), which assumed a higher maximum level than assumed for the startup accident, have been made. The higher pressurizer level OCONEE UNITS 1, 2, &3 B 3.4.9-2 Amendment Nos. 343, 345, & 344 l

Pressurizer B 3.4.9 BASES APPLICABLE assumed for the LOCA is the basis for the volume of reactor coolant SAFETY ANALYSES released to the containment. The containment analysis performed using (continued) the mass and energy release demonstrated that the maximum resulting containment pressure was within design limits.

The requirement for emergency power supplies is based on NUREG-0737 (Ref. 2). The intent is to allow maintaining the reactor coolant in a subcooled condition with natural circulation at hot, high pressure conditions for an undefined, but extended, time period after a loss of offsite power.

While loss of offsite power is an initial condition or coincident event assumed in many accident analyses, maintaining hot, high pressure conditions over an extended time period is not evaluated as part of UFSAR accident analyses.

The maximum pressurizer water level limit satisfies Criterion 2 of 10 CFR 50.36 (Ref. 1). Although the heaters are not specifically used in accident analysis, the need to maintain subcooling in the long term during loss of offsite power, as indicated in NUREG-0737 (Ref. 2), is the reason for providing an LCO.

LCO The LCO requirement for the pressurizer to be OPERABLE with a water level

• 285 inches ensures that a steam bubble exists. Limiting the maximum operating water level preserves the steam space for pressure control. The LCO has been established to ensure the capability to establish and maintain pressure control for steady state operation and to minimize the consequences of potential overpressure transients. Requiring the presence of a steam bubble is also consistent with analytical assumptions.

The LCO requires a minimum of 400 kW of pressurizer heaters OPERABLE and capable of being powered from an emergency power supply. As such, the LCO addresses both the heaters and the power supplies. The minimum heater capacity required is sufficient to maintain the system near normal operating pressure when accounting for heat losses through the pressurizer insulation. By maintaining the pressure near the operating conditions, a wide margin to subcooling can be obtained in the loops. The design value of 400 kW will require the use of twenty-nine heaters rated at 14 kW (nominal) each. The amount needed to maintain pressure is dependent on the insulation losses, which can vary due to tightness of fit and condition.

OCONEE UNITS 1, 2, & 3 B3.4.9-3 Amendment Nos. 343, 345, & 344 I

Pressurizer B 3.4.9 BASES APPLICABILITY The need for pressure control is most pertinent when core heat can cause the greatest effect on RCS temperature, resulting in the greatest effect on pressurizer level and RCS pressure control. Thus Applicability has been designated for MODES 1 and 2. The Applicability is also provided for MODE 3 with RCS temperature > 3250F. The purpose is to prevent solid water RCS operation during heatup and cooldown to avoid rapid pressure rises caused by normal operational perturbations, such as reactor coolant pump startup. The temperature of 3250 F has been designated as the cutoff for applicability because LCO 3.4.12, "Low Temperature Overpressure Protection (LTOP) System," provides a requirement for pressurizer level < 3250F. The LCO does not apply in MODE 4, 5 or 6 since either pressurizer level is under the control of LCO 3.4.12, "Low Temperature Overpressure Protection (LTOP) System," or the RCS is open to the containment atmosphere.

In MODES 1, 2, and 3, there is the need to maintain the availability of pressurizer heaters capable of being powered from an emergency power supply. In the event of a loss of offsite power, the initial conditions of these MODES give the greatest demand for maintaining the RCS in a hot pressurized condition with loop subcooling for an extended period. For MODE 4, 5, or 6, it is not necessary to control pressure (by heaters) to ensure loop subcooling for heat transfer when the Decay Heat Removal loops are in service, and therefore the LCO is not applicable.

ACTIONS A.1 With pressurizer water level in excess of the maximum limit, action must be taken to restore pressurizer operation to within the bounds assumed in the analysis. This is done by restoring the pressurizer water level to within the limit.

The 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> Completion Time is considered to be a reasonable time for draining excess liquid.

B.1 and B.2 If the water level cannot be restored, reducing core power constrains heat input effects that drive pressurizer insurge that could result from an anticipated transient. By shutting down the reactor and reducing reactor coolant temperature to at least MODE 3 with RCS temperature < 3250F, the potential thermal energy of the reactor coolant mass for LOCA mass and energy releases is reduced.

OCONEE UNITS 1, 2, & 3 B 3.4.9-4 Amendment Nos. 343, 345, & 344 l

e Pressurizer B 3.4.9 BASES ACTIONS Twelve hours is a reasonable time based upon operating experience to (continued) reach MODE 3 from full power without challenging unit systems and operators. Further pressure and temperature reduction to MODE 3 with RCS temperature

• 3250F places the unit into a MODE where the LCO is not applicable. The 18 hour2.083333e-4 days <br />0.005 hours <br />2.97619e-5 weeks <br />6.849e-6 months <br /> Completion Time to reach the nonapplicable MODE is reasonable based upon operating experience.

C.1 If the power supplies to the heaters are not capable of providing 400 kW, or the pressurizer heaters are inoperable, restoration is required in 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />.

The Completion Time of 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> is reasonable considering the anticipation that a demand will not occur in this period.

D.1 and D.2 If pressurizer heater capability cannot be restored within the allowed Completion Time of Required Action C.1, the unit must be brought to a MODE in which the LCO does not apply. To achieve this status, the unit must be brought to MODE 3 within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> and to MODE 3 with RCS temperature < 3250 F within the following 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />. The Completion Time of 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> is reasonable, based on operating experience, to reach MODE 3 from full power conditions in an orderly manner and without challenging unit systems. Similarly, the Completion Time of 18 hours2.083333e-4 days <br />0.005 hours <br />2.97619e-5 weeks <br />6.849e-6 months <br /> to be in MODE 3 with RCS temperature < 3250F is reasonable based on operating experience to achieve power reduction from full power conditions in an orderly manner and without challenging unit systems.

SURVEILLANCE SR 3.4.9.1 REQUIREMENTS This SR requires that during steady state operation, pressurizer water level is maintained below the nominal upper limit to provide a minimum space for a steam bubble. The Surveillance is performed by observing the indicated level. The 12 hour1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> interval has been shown by operating practice to be sufficient to regularly assess the level for any deviation and verify that operation is within safety analyses assumptions. Alarms are also available for early detection of abnormal level indications.

SR 3.4.9.2 The SR verifies the power supplies are capable of producing the minimum power and the associated pressurizer heaters are at their design rating.

(This may be done by testing the power supply output and heater current, OCONEE UNITS 1, 2, & 3 B3.4.9-5 Amendment flos. 343, 345J & 344 *I

Pressurizer B 3.4.9 BASES (continued)

SURVEILLANCE- or by performing an electrical check on heater element continuity and REQUIREMENTS resistance.) The Frequency of 18 months is considered adequate to (continued) detect heater degradation and has been shown by operating experience to be acceptable.

REFERENCES 1. 10 CFR 50.36.

2. NUREG-0737, November 1980.

OCONEE UNITS 1, 2, & 3 B 3.4.9-6 Amendment Nos. 343, 345, & 344 l