The MSSVs ensure secondary system pressure is limited to within 110% of the design pressure of 1085 psig during the most severe anticipated transient. They also protect against overpressurization of the RCS pressure boundary by providing a heat sink for energy removal when the preferred heat sink is unavailable.

The maximum relieving capacity case is a turbine trip from 100% RTP coincident with a loss of condenser heat sink (no steam bypass to the condenser). Total relieving capacity for all valves on all steam lines is 16.66 x 10⁶ lbs/hr, approximately 110% of the maximum calculated steam flow of 15.12 x 10⁶ lbs/hr at 100% RTP. A minimum of 2 OPERABLE safety valves per OPERABLE steam generator ensures sufficient relieving capacity for the allowable power restriction in Table 3.7-1.

The acceptable power levels for operation with inoperable MSSVs were determined by explicit transient analysis. The limiting anticipated operational occurrence is a loss of external electrical load and/or turbine trip. The transient analysis assumes MSSVs start to open at the lift setpoint with ±3% tolerance plus a 5 psi accumulation ramp to fully open. Inoperable MSSVs are assumed to be those with the lowest lift settings.

For three inoperable MSSVs in one or more steam generators, thermal power must be reduced AND the Power Range Neutron Flux High trip setpoint must be reduced to prevent secondary overpressurization. RCCA Bank Withdrawal at Power analyses demonstrate adequate relief capacity with up to two inoperable safety valves per SG — the OTDT reactor trip plus remaining MSSVs is sufficient to meet secondary pressurization limits.

Following surveillance testing, valves must be reset to within ±1% of the lift setpoint (narrower than the ±3% allowance during operation) to allow for drift.

Amendment No. 259

The AFW system ensures the RCS can be cooled down to less than 350°F from normal operating conditions in the event of a total loss of offsite power.

Verifying each AFW pump’s developed head at the flow test point confirms pump performance has not degraded and that accident analysis assumptions remain valid. Flow and differential head testing is required by ASME Code Section XI. Because it is undesirable to introduce cold AFW into the steam generators while operating, the test is performed on recirculation flow. This confirms one point on the pump design curve (head vs. flow) and is indicative of overall pump performance.

The flow path to each steam generator is ensured by maintaining all manual maintenance valves locked open. A spool piece (length of pipe) may be used as an equivalent to a locked-open manual valve.

LCO 3.0.4.b is NOT applicable to an inoperable AFW train — there is an increased risk associated with entering an applicable MODE with an AFW train inoperable, so mode change with the LCO not met (even after a risk assessment) is prohibited.

Amendment No. 258

The minimum water volume of 200000 gallons ensures sufficient water is available to maintain the RCS at HOT STANDBY conditions for 8 hours with steam discharge to the atmosphere concurrent with a total loss of offsite power. The contained water volume limit includes an allowance for water not usable because of tank discharge line location or other physical characteristics.

Amendment No. 258

The secondary specific activity limit ensures the resultant offsite radiation dose is limited to a small fraction of 10 CFR Part 100 limits in the event of a steam line rupture. The dose calculation includes the effects of a coincident 1.0 GPM primary-to-secondary tube leak in the steam generator of the affected steam line. These values are consistent with the assumptions used in the accident analyses.

MSIV OPERABILITY ensures no more than one steam generator will blow down in the event of a steam line rupture. This restriction is required to: 1) minimize the positive reactivity effects of the RCS cooldown associated with the blowdown, and 2) limit the pressure rise within containment if the rupture occurs inside containment.

If the MSIV closure time during TS surveillance testing (performed at SG pressure between 800 psig and 1015 psig) is ≤5.0 seconds, and the ESF response time (including valve closure) for the MSI signal (Table 3.3-5) is ≤5.5 seconds, then assurance is provided that MSI occurs within 12 seconds under accident conditions where SG pressure may be lower.

Fast closure of the MSIVs is assured at a minimum steam pressure of 170 psia. The MSIV will still close via the steam assist function between 118–170 psia with slightly greater closure times. For steam line ruptures that do not have adequate steam pressure to close the MSIVs (less than 118 psia), the event does not require MSIV closure to satisfy design basis requirements — minimum DNBR remains above the limit and peak containment pressure remains below 47 psig.

SR 4.7.1.5 testing is performed prior to opening MSIVs for power operation. Only one valve is opened at a time with the other three remaining closed, ensuring isolation capability is maintained. A postulated failure of the tested valve in the open position would result in blowdown of a single SG — consistent with the accident analysis assumptions for a major secondary system pipe rupture (UFSAR Section 15.4.2).

Revised by letter dated 6-19-2003

The limitation ensures that pressure-induced stresses in the steam generators do not exceed the maximum allowable fracture toughness stress limits. The limits of 70°F and 200 psig are based on average steam generator impact values taken at 10°F and are sufficient to prevent brittle fracture.

The CCW loops are independent of each other — each has separate controls and power supplies, and the operation of one does not depend on the other. The system consists of two safeguards mechanical trains supplied by three pumps powered from separate vital buses.

This complement of equipment assures adequate redundancy for a single active component failure during the injection phase and either a single active failure or passive failure during the recirculation phase. The redundant cooling capacity, assuming a single failure, is consistent with the assumptions used in the accident analyses (separation of loops as required by the single-failure analysis).

An OPERABLE CCW loop consists of one mechanical train and one CCW pump.

S20-04

The service water system ensures sufficient cooling capacity for continued operation of safety-related equipment during normal and accident conditions. The redundant cooling capacity of this system, assuming a single failure, is consistent with the assumptions used in the accident analyses to maintain conditions within acceptable limits.

S20-04

The limitation on flood protection ensures that facility protective actions will be taken and operation will be terminated in the event of flood conditions. The limit of elevation 10.5 ft Mean Sea Level is the elevation above which facility flood control measures are required to provide protection to safety-related equipment.

Background: The CREACS provides a protected environment from which occupants can control the unit following an uncontrolled release of radioactivity, hazardous chemicals, or smoke. It ensures: 1) ambient air temperature does not exceed the allowable continuous duty rating for equipment and instrumentation, and 2) the control room remains habitable during and following all credible accident conditions.

The CREACS consists of two independent redundant trains, one from each unit, that recirculate and filter the air in the Control Room Envelope (CRE). Each train consists of a prefilter, HEPA filter, activated charcoal adsorber section (principally for iodine removal), and fans. CREACS is a shared system between Unit 1 and Unit 2 supplying a common CRE.

Upon receipt of a Safety Injection or High Radiation actuation signal, one 100% capacity fan in each unit’s CREACS operates in pressurization mode with outside air supplied for CRE pressurization. One fan from each train auto-starts; a standby fan auto-starts on failure of the running fan. Each CREACS train has two 100% capacity fans — any one of the four fans is sized to provide the required CRE pressurization flow.

Outside air is supplied from the non-accident unit’s emergency air intake through the cross-connected supply duct (determined by which unit received the accident signal). The CREACS is designed to maintain a habitable environment for 30 days of continuous occupancy after a DBA without exceeding 5 rem TEDE.

Normal air supply to the CRE is isolated upon actuation signal; ventilation air is recirculated through the filter trains. Pressurization of the CRE minimizes infiltration of unfiltered air. CREACS will be manually initiated in recirculation mode only in the event of a fire outside the CRE, a toxic chemical release, or testing.

LCO: Two independent and redundant trains are required OPERABLE so at least one is available if a single active failure disables the other. Total system failure could result in exceeding 5 rem TEDE to CRE occupants in the event of a large radioactive release. The CRE boundary must be maintained such that CRE occupant dose does not exceed the licensing basis consequence analysis values, and occupants are protected from hazardous chemicals and smoke.

The CRE boundary may be opened intermittently under administrative controls (doors, hatches, floor plugs, access panels). A dedicated individual stationed at the opening must be in continuous communication with operators and have a method to rapidly restore the CRE boundary.

Key Dampers:

• Fan outlet dampers: 1(2)CAA15 and 1(2)CAA16 — open on fan operation
• Return air isolation damper: 1(2)CAA17 — administratively open during single-train operation
• CAACS outside air intake isolation dampers: 1(2)CAA40, 1(2)CAA41, 1(2)CAA43, 1(2)CAA45
• CAACS exhaust isolation dampers: 1(2)CAA18 and 1(2)CAA19 — normally closed, prevent outside inleakage
• CREACS air intake dampers: 1(2)CAA48, 1(2)CAA49, 1(2)CAA50, 1(2)CAA51 — control logic auto-opens the intake farthest from the radiation source based on which unit’s SSPS or RMS signal is received
• CAACS/CREACS interface isolation dampers: 1(2)CAA14 and 1(2)CAA20 — normally open, isolate CREACS from CAACS during emergency

Actions: With one CREACS train inoperable, align for single filtration train operation within 4 hours and restore within 30 days. Single-train alignment requires the unit with the operable train to be in Chilled Water LCO 3.7.10.a configuration (not 3.7.10.c). With CRE boundary inoperable, implement mitigating actions immediately; verify exposures within limits within 24 hours; restore within 90 days.

Surveillance: Each CAACS normal air intake has two radiation detector channels. A minimum of one out of two detectors in either intake initiates CREACS pressurization mode. With two detector channels inoperable on a unit, CREACS must be placed in pressurization or recirculation mode. Movement of irradiated fuel assemblies is NOT permitted when in recirculation mode (auto-initiation capability is defeated for high radiation).

Amendment No. 297

The Auxiliary Building Ventilation System (ABVS) consists of two major subsystems designed to control building temperature during normal and emergency operation and to contain airborne contamination by maintaining slightly negative pressure during a LOCA:

1. Exhaust system — once-through filtration exhaust to contain particulate and gaseous contamination per 10 CFR 20. Consists of three 50% capacity fans powered from vital buses, designed for continuous operation to control building pressure at -0.10” Water Gauge with respect to atmosphere.
2. Supply system — once-through air supply to maintain building temperatures within acceptable limits. Consists of two 100% capacity fans powered from vital buses. For TS LCO purposes, one supply fan must be administratively removed from auto-start on an actuation signal but must remain OPERABLE.

Normal alignment: Two exhaust fans and one supply fan. During cooler seasons, both supply fans may be secured and exhaust fans reduced to one (sufficient to maintain negative pressure).

Emergency alignment: At least two of three exhaust fans and one supply fan. During a Safety Injection, all three exhaust fans and one supply fan will auto-start. If access/egress becomes difficult with three exhaust fans running, one exhaust fan should be secured.

The system also provides a flow path for containment purge supply and exhaust during Modes 5 and 6. Either the Containment Purge system or the ABVS with suction from containment atmosphere (with associated radiation monitoring) must be available whenever movement of irradiated fuel is in progress in containment with the equipment hatch open.

OPERABILITY ensures that air potentially containing radioactive materials leaked from ECCS equipment following a LOCA is monitored prior to release from the plant via the plant vent. Auxiliary building exhaust air filtration system functionality is NOT required to meet LCO 3.7.7. ABVS is discussed in UFSAR Section 9.4.2.

Amendment No. 252

The removable contamination limitation (including alpha emitters) is based on 10 CFR 70.39(c) limits for plutonium. This ensures leakage from byproduct, source, and special nuclear material sources will not exceed allowable intake values.

Sealed sources are classified into three groups according to their use, with surveillance requirements commensurate with the probability of damage. Sources that are frequently handled are tested more often than those that are not. Sealed sources continuously enclosed within a shielded mechanism (e.g., within radiation monitoring or boron measuring devices) are considered to be stored and need not be tested unless removed from the shielded mechanism.

Amendment No. 209

All snubbers are required OPERABLE to ensure structural integrity of the RCS and all other safety-related systems is maintained during and following a seismic or other event initiating dynamic loads. Snubbers excluded from the program are those installed on non-safety-related systems, and only if their failure (or failure of the system they are installed on) would have no adverse effect on any safety-related system.

The program for examination, testing, and service life monitoring is performed in accordance with ASME BPV Code Section XI or the OM Code and applicable addenda as required by 10 CFR 50.55a, except where the NRC has granted specific written relief or authorized alternatives.

Amendment No. 284