ML20209A118
Text
CHAPTER TABLE OF CONTENTS CHAPTER B 3.5 EMERGENCY CORE COOLING SYSTEMS (ECCS)
Section Page B 3.5.1 Accumulators ...............................................................................................B 3.5.1-1 BACKGROUND ......................................................................................B 3.5.1-1 APPLICABLE SAFETY ANALYSES ......................................................B 3.5.1-2 LCO ........................................................................................................B 3.5.1-4 APPLICABILITY .....................................................................................B 3.5.1-5 ACTIONS ..................................................................................................B 3.5.1-5 SURVEILLANCE REQUIREMENTS .........................................................B 3.5.1-6 REFERENCES .......................................................................................B 3.5.1-7 B 3.5.2 ECCS - Operating ........................................................................................B 3.5.2-1 BACKGROUND ......................................................................................B 3.5.2-1 APPLICABLE SAFETY ANALYSES ......................................................B 3.5.2-3 LCO ........................................................................................................B 3.5.2-6 APPLICABILITY .....................................................................................B 3.5.2-7 ACTIONS ..................................................................................................B 3.5.2-7 SURVEILLANCE REQUIREMENTS .........................................................B 3.5.2-9 REFERENCES .....................................................................................B 3.5.2-13 B 3.5.3 ECCS - Shutdown ........................................................................................B 3.5.3-1 BACKGROUND ......................................................................................B 3.5.3-1 APPLICABLE SAFETY ANALYSES ......................................................B 3.5.3-1 LCO ........................................................................................................B 3.5.3-2 APPLICABILITY .....................................................................................B 3.5.3-3 ACTIONS ...............................................................................................B 3.5.3-3 SURVEILLANCE REQUIREMENTS .........................................................B 3.5.3-4 REFERENCES .......................................................................................B 3.5.3-5 B 3.5.4 Refueling Water Storage Tank (RWST) .......................................................B 3.5.4-1 BACKGROUND ......................................................................................B 3.5.4-1 APPLICABLE SAFETY ANALYSES ......................................................B 3.5.4-2 LCO ........................................................................................................B 3.5.4-4 APPLICABILITY .....................................................................................B 3.5.4-4 ACTIONS ..................................................................................................B 3.5.4-4 CALLAWAY PLANT 3.5-i
CHAPTER TABLE OF CONTENTS (Continued)
Section Page SURVEILLANCE REQUIREMENTS .........................................................B 3.5.4-5 REFERENCES .......................................................................................B 3.5.4-6 B 3.5.5 Seal Injection Flow .......................................................................................B 3.5.5-1 BACKGROUND ......................................................................................B 3.5.5-1 APPLICABLE SAFETY ANALYSES ......................................................B 3.5.5-1 LCO ........................................................................................................B 3.5.5-2 APPLICABILITY .....................................................................................B 3.5.5-3 ACTIONS ..................................................................................................B 3.5.5-3 SURVEILLANCE REQUIREMENTS .........................................................B 3.5.5-4 REFERENCES .......................................................................................B 3.5.5-5 3.5-ii
Accumulators B 3.5.1 B 3.5 EMERGENCY CORE COOLING SYSTEMS (ECCS)
B 3.5.1 Accumulators BASES BACKGROUND The functions of the ECCS accumulators are to supply borated water to replace inventory in the reactor vessel during the later stages of the blowdown phase to the beginning stages of the reflood phase of a large break loss of coolant accident (LOCA) and to provide Reactor Coolant System (RCS) makeup for a small break LOCA.
The ECCS injection mode following a large break LOCA consists of three phases: 1) blowdown; 2) refill; and 3) reflood.
The blowdown phase of a large break LOCA is the initial period of the transient during which the RCS departs from equilibrium conditions, and heat from fission product decay, hot internals, and the vessel continues to be transferred to the reactor coolant. The blowdown phase of the transient ends when the RCS pressure falls to a value approaching that of the containment atmosphere.
In the refill phase of a LOCA, which begins prior to or at the end of the blowdown phase, reactor coolant inventory has vacated the core through steam flashing and spill out through the break. The core is essentially in adiabatic heatup. The balance of accumulator inventory is then available to help fill voids in the lower plenum and reactor vessel downcomer so as to establish a recovery level at the bottom of the core and ongoing reflood of the core with the addition of safety injection (SI) water. The refill phase is complete when the injection of ECCS water has filled the reactor vessel downcomer and the lower plenum of the reactor vessel which is bounded by the bottom of the fuel rods (called bottom of core recovery time).
The reflood phase follows the refill phase and continues until the reactor vessel has been filled to the extent that the core temperature rise has been terminated.
The accumulators function in the later stages of blowdown to the beginning stages of reflood to fill the downcomer and lower plenum. The injection of the ECCS pumps aids during refill. Reflood and the following long term heat removal are accomplished by water pumped into the core by the ECCS pumps.
The accumulators are pressure vessels partially filled with borated water and pressurized with nitrogen gas. The accumulators are passive components, since no operator or control actions are required in order for them to perform their function. Internal accumulator tank pressure is (continued)
CALLAWAY PLANT B 3.5.1-1 Revision 14
Accumulators B 3.5.1 BASES BACKGROUND sufficient to discharge the accumulator contents to the RCS, if RCS (continued) pressure decreases below the accumulator pressure.
Each accumulator is piped into an RCS cold leg via an accumulator line and is isolated from the RCS by a motor operated isolation valve and two check valves in series.
The accumulator size, water volume, and nitrogen cover pressure are selected so that three of the four accumulators are sufficient to partially cover the core before significant clad melting or zirconium water reaction can occur following a LOCA. The need to ensure that three accumulators are adequate for this function is consistent with the LOCA assumption that the entire contents of one accumulator will be lost via the RCS pipe break during the blowdown phase of the LOCA.
APPLICABLE The accumulators are assumed OPERABLE in both the large and small SAFETY break LOCA analyses at full power (Ref. 3). These are the Design Basis ANALYSES Accidents (DBAs) that establish the acceptance limits for the accumulators. Reference to the analyses for these DBAs is used to assess changes in the accumulators as they relate to the acceptance limits.
In performing the LOCA calculations, conservative assumptions are made concerning the availability of ECCS flow. In the early stages of a LOCA, with or without a loss of offsite power, the accumulators provide the sole source of makeup water to the RCS. The assumption of loss of offsite power is required by regulations and conservatively imposes a delay wherein the ECCS pumps cannot deliver flow until the emergency diesel generators start, come to rated speed, and go through their timed loading sequence. In cold leg break scenarios, the entire contents of one accumulator are assumed to be lost through the break.
The limiting large break LOCA is a double ended guillotine break at the discharge of the reactor coolant pump. During this event, the accumulators discharge to the RCS as soon as RCS pressure decreases to below accumulator pressure.
As a conservative estimate, no credit is taken for ECCS pump flow until an effective delay has elapsed. This delay accounts for the diesels starting and the pumps being loaded and delivering full flow. The delay time is conservatively set with an additional 2 seconds to account for SI signal generation. During this time, the accumulators are analyzed as providing the sole source of emergency core cooling. No operator action is assumed during the blowdown phase of a large break LOCA.
(continued)
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Accumulators B 3.5.1 BASES APPLICABLE The worst case small break LOCA analyses also assume a time delay SAFETY before pumped flow reaches the core. For the larger range of small ANALYSES breaks, the rate of blowdown is such that the increase in fuel clad (continued) temperature is terminated primarily by the accumulators, with pumped flow then providing continued cooling. As break size decreases, the accumulators and ECCS centrifugal charging pumps both play a part in terminating the rise in clad temperature. As break size continues to decrease, the role of the accumulators continues to decrease until they are not required and the ECCS centrifugal charging pumps become solely responsible for terminating the temperature increase.
This LCO helps to ensure that the following acceptance criteria established for the ECCS by 10 CFR 50.46 (Ref. 2) will be met following a LOCA:
- a. Maximum fuel element cladding temperature is 2200F;
- b. Maximum cladding oxidation is 0.17 times the total cladding thickness before oxidation;
- c. Maximum hydrogen generation from a zirconium water reaction is 0.01 times the hypothetical amount that would be generated if all of the metal in the cladding cylinders surrounding the fuel, excluding the cladding surrounding the plenum volume, were to react; and
- d. Core is maintained in a coolable geometry.
Since the accumulators empty themselves by the beginning stages of the reflood phase of a large break LOCA, they do not contribute to the long term cooling requirements of 10 CFR 50.46.
For both the large and small break LOCA analyses, a nominal contained accumulator water volume is used. The contained water volume is the same as the deliverable volume for the accumulators, since the accumulators are emptied, once discharged. For small breaks, an increase in water volume is a peak clad temperature penalty. For large breaks, an increase in water volume can be either a peak clad temperature penalty or benefit, depending on downcomer filling and subsequent spill through the break during the core reflooding portion of the transient. The analysis makes a conservative assumption with respect to ignoring the line water volume from the accumulator to the check valve. Values of 6061 gallons and 6655 gallons are specified.
(continued)
CALLAWAY PLANT B 3.5.1-3 Revision 14
Accumulators B 3.5.1 BASES APPLICABLE The minimum boron concentration limit is used in the post LOCA boron SAFETY concentration calculation. The calculation is performed to assure reactor ANALYSES subcriticality in a post LOCA environment. Of particular interest is the (continued) large break LOCA, since no credit is taken for control rod assembly insertion. A reduction in the accumulator minimum boron concentration would produce a subsequent reduction in the available containment sump concentration for post LOCA shutdown and an increase in the maximum sump pH. The maximum boron concentration is used in determining the cold leg to hot leg recirculation switchover time and minimum sump pH.
The large and small break LOCA analyses are performed at the minimum nitrogen cover pressure, since sensitivity analyses have demonstrated that higher nitrogen cover pressure results in a computed peak clad temperature benefit. The maximum nitrogen cover pressure limit prevents accumulator relief valve actuation, and ultimately preserves accumulator integrity.
The effects on containment mass and energy releases from the accumulators are accounted for in the appropriate analyses (Refs. 1 and 3).
Safety analyses assume a B-10 abundance of 19.9 a/o (Ref. 5).
Administrative controls ensure that the reactivity insertion from the accumulators reflects this assumption.
The accumulators satisfy Criterion 2 and Criterion 3 of 10CFR50.36(c)(2)(ii).
LCO The LCO establishes the minimum conditions required to ensure that the accumulators are available to accomplish their core cooling safety function following a LOCA. Four accumulators are required to ensure that 100% of the contents of three of the accumulators will reach the core during a LOCA. This is consistent with the assumption that the contents of one accumulator spill through the break. If less than three accumulators are injected during the blowdown phase of a LOCA, the ECCS acceptance criteria of 10 CFR 50.46 (Ref. 2) could be violated.
For an accumulator to be considered OPERABLE, the isolation valve must be fully open, power removed above 1000 psig, and the limits established in the SRs for contained volume, boron concentration, and nitrogen cover pressure must be met.
(continued)
CALLAWAY PLANT B 3.5.1-4 Revision 14
Accumulators B 3.5.1 BASES (Continued)
APPLICABILITY In MODES 1 and 2, and in MODE 3 with RCS pressure > 1000 psig, the accumulator OPERABILITY requirements are based on full power operation. Although cooling requirements decrease as power decreases, the accumulators are still required to provide core cooling as long as elevated RCS pressures and temperatures exist.
This LCO is only applicable at RCS pressures > 1000 psig. At pressures 1000 psig, the rate of RCS blowdown is such that the ECCS pumps can provide adequate injection to ensure that peak clad temperature remains below the 10 CFR 50.46 (Ref. 2) limit of 2200F.
In MODE 3, with RCS pressure 1000 psig, and in MODES 4, 5, and 6, the accumulator motor operated isolation valves are closed with power removed from the valve operators to isolate the accumulators from the RCS (Refs. 6 and 7). Accumulator isolation is only required when the accumulator pressure is greater than or equal to the maximum RCS pressure for the existing RCS cold leg temperature, as allowed by the P/T limit curves provided in the PTLR. Accumulator isolation allows RCS cooldown and depressurization without discharging the accumulators into the RCS or requiring depressurization of the accumulators.
ACTIONS A.1 If the boron concentration of one accumulator is not within limits, it must be returned to within the limits within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. In this Condition, the ability to maintain subcriticality or minimum boron precipitation time may be reduced. The boron in the accumulators contributes to the assumption that the combined ECCS water in the partially recovered core during the early reflooding phase of a large break LOCA is sufficient to keep that portion of the core subcritical. One accumulator below the minimum boron concentration limit, however, will have no effect on available ECCS water and an insignificant effect on core subcriticality during reflood.
Boiling of ECCS water in the core during reflood concentrates boron in the saturated liquid that remains in the core. Even if the accumulators discharge following a large main steam line break with offsite power available, their impact is minor and not a design limiting event. Thus, 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> is allowed to return the boron concentration to within limits.
B.1 If one accumulator is inoperable for a reason other than boron concentration, the accumulator must be returned to OPERABLE status within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />. This time period has been determined to have an (continued)
CALLAWAY PLANT B 3.5.1-5 Revision 14
Accumulators B 3.5.1 BASES ACTIONS B.1 (continued) insignificant effect on core damage frequency. In this Condition, the required contents of three accumulators cannot be assumed to reach the core during a LOCA. Due to the severity of the consequences should a LOCA occur in these conditions, the 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> Completion Time to open the valve, remove power to the valve, or restore the proper water volume or nitrogen cover pressure ensures that prompt action will be taken to return the inoperable accumulator to OPERABLE status. The Completion Time minimizes the potential for exposure of the plant to a LOCA under these conditions.
C.1 and C.2 If the accumulator cannot be returned to OPERABLE status within the associated Completion Time, the plant must be brought to a MODE in which the LCO does not apply. To achieve this status, the plant must be brought to MODE 3 within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and RCS pressure reduced to 1000 psig within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />. The allowed Completion Times are reasonable, based on operating experience, to reach the required plant conditions from full power conditions in an orderly manner and without challenging plant systems.
D.1 If more than one accumulator is inoperable, the plant is in a condition outside the accident analyses; therefore, LCO 3.0.3 must be entered immediately.
SURVEILLANCE SR 3.5.1.1 REQUIREMENTS Each accumulator isolation valve should be verified to be fully open. This verification ensures that the accumulators are available for injection and ensures timely discovery if a valve should be less than fully open. If an isolation valve is not fully open, the rate of injection to the RCS would be reduced. Although a motor operated valve position should not change with power removed, a closed valve could result in not meeting accident analyses assumptions. The Surveillance Frequency is based on operating experience, equipment reliability, and plant risk and is controlled under the Surveillance Frequency Control Program.
(continued)
CALLAWAY PLANT B 3.5.1-6 Revision 14
Accumulators B 3.5.1 BASES SURVEILLANCE SR 3.5.1.2 and SR 3.5.1.3 REQUIREMENTS (continued) Borated water volume and nitrogen cover pressure are verified for each accumulator. Only one set of non-safety channels (1 of 2) is required for water level and pressure indication. The Surveillance Frequency is based on operating experience, equipment reliability, and plant risk and is controlled under the Surveillance Frequency Control Program.
SR 3.5.1.4 The boron concentration should be verified to be within required limits for each accumulator since the static design of the accumulators limits the ways in which the concentration can be changed. The Surveillance Frequency is based on operating experience, equipment reliability, and plant risk and is controlled under the Surveillance Frequency Control Program. Sampling the affected accumulator within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> after a 70 gallon increase will identify whether inleakage has caused a reduction in boron concentration to below the required limit. It is not necessary to verify boron concentration if the added water inventory is from the refueling water storage tank (RWST) and the RWST has not been diluted since verifying that its boron concentration satisfies SR 3.5.4.3, because the water contained in the RWST is nominally within the accumulator boron concentration requirements. This is consistent with the recommendation of NUREG-1366 (Ref. 4).
SR 3.5.1.5 Verification that power is removed from each accumulator isolation valve operator when the RCS pressure is > 1000 psig ensures that an active failure could not result in the undetected closure of an accumulator motor operated isolation valve. If this were to occur, only two accumulators would be available for injection given a single failure coincident with a LOCA. The Surveillance Frequency is based on operating experience, equipment reliability, and plant risk and is controlled under the Surveillance Frequency Control Program.
REFERENCES 1. FSAR, Chapter 6.
- 2. 10 CFR 50.46.
- 3. FSAR, Chapter 15.
(continued)
CALLAWAY PLANT B 3.5.1-7 Revision 14
Accumulators B 3.5.1 BASES REFERENCES 4. NUREG-1366, February 1990.
(continued)
- 5. RFR-17070A.
- 6. FSAR Section 6.3.2.
- 7. FSAR Section 7.6.4.
CALLAWAY PLANT B 3.5.1-8 Revision 14
ECCS - Operating B 3.5.2 B 3.5 EMERGENCY CORE COOLING SYSTEMS (ECCS)
B 3.5.2 ECCS - Operating BASES BACKGROUND The function of the ECCS is to provide core cooling and negative reactivity to ensure that the reactor core is protected after any of the following accidents:
- a. Loss of coolant accident (LOCA), coolant leakage greater than the capability of the normal charging system;
- b. Rod ejection accident;
- c. Loss of secondary coolant accident, including uncontrolled steam release or loss of feedwater; and
- d. Steam generator tube rupture (SGTR).
The addition of negative reactivity is designed primarily for the loss of secondary coolant accident where primary cooldown could add enough positive reactivity to achieve criticality and return to significant power.
There are three phases of ECCS operation: injection, cold leg recirculation, and hot leg recirculation. In the injection phase, water is taken from the refueling water storage tank (RWST) and injected into the Reactor Coolant System (RCS) through the cold legs. When sufficient water is removed from the RWST to ensure that enough boron has been added to maintain the reactor subcritical and the containment sumps have enough water to supply the required net positive suction head to the ECCS pumps, suction is switched to the containment sumps for cold leg recirculation. After approximately 13 hours1.50463e-4 days <br />0.00361 hours <br />2.149471e-5 weeks <br />4.9465e-6 months <br />, the ECCS flow is shifted to the hot leg recirculation phase to provide a backflush, which would reduce the boiling in the top of the core and any resulting boron precipitation.
The ECCS consists of three separate subsystems: centrifugal charging (high head), safety injection (SI) (intermediate head), and residual heat removal (RHR) (low head). Each subsystem consists of two redundant, 100% capacity trains. The ECCS accumulators and the RWST are also part of the ECCS, but are not considered part of an ECCS flow path as described by this LCO.
The ECCS flow paths consist of piping, valves, heat exchangers, and pumps such that water from the RWST can be injected into the RCS following the accidents described in this LCO. The major components of each subsystem are the centrifugal charging pumps, the RHR pumps, (continued)
CALLAWAY PLANT B 3.5.2-1 Revision 14
ECCS - Operating B 3.5.2 BASES BACKGROUND heat exchangers, and the SI pumps. (Note: The term centrifugal charging (continued) pump or CCP refers to the safety-related ECCS charging pumps only (PBG05A and PBG05B). The normal charging pump or NCP (PBG04) does not serve an ECCS function and is tripped by a safety injection signal.) The pumps in the three ECCS subsystems have miniflow protection as discussed in References 11 and 12. Each of the three subsystems consists of two 100% capacity trains that are interconnected and redundant such that either train is capable of supplying 100% of the flow required to mitigate the accident consequences (Refs. 8 and 9). This interconnecting and redundant subsystem design provides the operators with the ability to utilize components from opposite trains to achieve the required 100% flow to the core.
During the injection phase of LOCA recovery, a suction header supplies water from the RWST to the ECCS pumps. Separate piping supplies each subsystem and each train within the subsystem. The discharge from the ECCS centrifugal charging pumps combines prior to entering the boron injection header and then divides again into four supply lines, each of which feeds the injection line to one RCS cold leg. The discharge from the SI and RHR pumps divides and feeds an injection line to each of the RCS cold legs. Throttle valves and flow orifices are utilized to balance the flow to the RCS. This balance ensures sufficient flow to the core to meet the analysis assumptions following a LOCA in one of the RCS cold legs.
For LOCAs that are too small to depressurize the RCS below the shutoff head of the SI pumps, the ECCS centrifugal charging pumps supply water until the RCS pressure decreases below the SI pump shutoff head. During this period, the steam generators are used to provide part of the core cooling function.
During the recirculation phase of LOCA recovery, RHR pump suction is transferred to the containment sump. The RHR pumps then supply the other ECCS pumps.
The centrifugal charging subsystem of the ECCS also functions to supply borated water to the reactor core following increased heat removal events, such as a main steam line break (MSLB). The limiting design conditions occur when the negative moderator temperature coefficient is highly negative, such as at the end of each cycle.
During low temperature conditions in the RCS, limitations are placed on the maximum number of ECCS pumps that are capable of injecting into the RCS. Refer to the Bases for LCO 3.4.12, "Cold Overpressure Mitigation System (COMS)," for the basis of these requirements.
(continued)
CALLAWAY PLANT B 3.5.2-2 Revision 14
ECCS - Operating B 3.5.2 BASES BACKGROUND The ECCS subsystems are actuated upon receipt of an SI signal. The (continued) actuation of safeguard loads is accomplished in a programmed time sequence. If offsite power is available, the safeguard loads start immediately in the programmed sequence. If offsite power is not available, the Engineered Safety Feature (ESF) buses shed selected loads and are connected to the emergency diesel generators (EDGs).
Safeguard loads are then actuated in the programmed time sequence.
The time delay associated with diesel starting, sequenced loading, and pump starting determines the time required before pumped flow is available to the core following a LOCA.
The active ECCS components, along with the passive accumulators and the RWST covered in LCO 3.5.1, "Accumulators," and LCO 3.5.4, "Refueling Water Storage Tank (RWST)," provide the cooling water necessary to meet GDC 35 (Ref. 1).
APPLICABLE The LCO helps to ensure that the following acceptance criteria for the SAFETY ECCS, established by 10 CFR 50.46 (Ref. 2), will be met following a ANALYSES LOCA:
- a. Maximum fuel element cladding temperature is 2200F;
- b. Maximum cladding oxidation is 0.17 times the total cladding thickness before oxidation;
- c. Maximum hydrogen generation from a zirconium water reaction is 0.01 times the hypothetical amount generated if all of the metal in the cladding cylinders surrounding the fuel, excluding the cladding surrounding the plenum volume, were to react;
- d. Core is maintained in a coolable geometry; and
- e. Adequate long term core cooling capability is maintained.
The LCO also limits the potential for a post trip return to power following an MSLB event and ensures that containment temperature limits are met.
Each ECCS subsystem is taken credit for in a large break LOCA event at full power (Refs. 3 and 4). This event establishes the requirement for runout flow for the ECCS pumps, as well as the maximum response time for their actuation. The ECCS centrifugal charging pumps and SI pumps are credited in a small break LOCA event. This event establishes the flow (continued)
CALLAWAY PLANT B 3.5.2-3 Revision 14
ECCS - Operating B 3.5.2 BASES APPLICABLE and discharge head at the design point for the ECCS centrifugal charging SAFETY pumps. The SGTR and MSLB events also credit the ECCS centrifugal ANALYSES charging pumps. The OPERABILITY requirements for the ECCS are (continued) based on the following LOCA analysis assumptions:
- a. A large break LOCA event, with a loss of offsite power and a single failure disabling one ECCS train; and
- b. A small break LOCA event, with a loss of offsite power and a single failure disabling one ECCS train.
During the blowdown stage of a LOCA, the RCS depressurizes as primary coolant is ejected through the break into the containment. The nuclear reaction is terminated either by moderator voiding during large breaks or control rod insertion for small breaks. Following depressurization, emergency core cooling water is injected into the cold legs, flows into the downcomer, fills the lower plenum, and refloods the core.
The effects on containment mass and energy releases are accounted for in appropriate analyses (Refs. 3 and 4). The LCO ensures that an ECCS train will deliver sufficient water to match boiloff rates soon enough to minimize the consequences of the core being uncovered following a large LOCA. It also ensures that the ECCS centrifugal charging and SI pumps will deliver sufficient water and boron during a small LOCA to maintain core subcriticality. For smaller LOCAs, the ECCS centrifugal charging pump delivers sufficient fluid to maintain RCS inventory. For a small break LOCA, the steam generators continue to serve as the heat sink, providing part of the required core cooling.
The safety analyses make assumptions with respect to: (1) both the maximum and minimum total system resistance; (2) both the maximum and minimum branch injection line resistance; and (3) the maximum and minimum ranges of potential pump performance. These resistances and ranges of pump performance are used to calculate the maximum and minimum ECCS flows assumed in the safety analyses.
The CCP minimum flow SR in FSAR Section 16.5 provides the absolute minimum injected flow (at zero RCS pressure) assumed in the safety analyses (305.25 gpm). The maximum total system resistance defines the range of minimum flows (including the minimum flow SR), with respect to pump head, that is assumed in the safety analyses. Therefore, the CCP total system resistance P d + Z d - Z RCS Q must not be 2
d greater than 1.004E-02 ft/gpm2, where Pd is pump discharge pressure in (continued)
CALLAWAY PLANT B 3.5.2-4 Revision 14
ECCS - Operating B 3.5.2 BASES APPLICABLE feet, Zd is the pump discharge elevation in feet, ZRCS is RCS water level SAFETY elevation in feet, and Qd is the total pump flow rate in gpm.
ANALYSES (continued) The SI pump minimum flow SR in FSAR Section 16.5 provides the absolute minimum injected flow (at zero RCS pressure) assumed in the safety analyses (455.6 gpm). The maximum total system resistance defines the range of minimum flows, with respect to pump head, that is assumed in the safety analyses. Therefore, the safety injection pump total system resistance P d + Z d - Z RCS Q must not be greater than 2
d 0.414E-02 ft/gpm2, where Pd is pump discharge pressure in feet, Zd is the pump discharge elevation in feet, ZRCS is RCS water level elevation in feet, and Qd is the total pump flow rate in gpm.
The CCP maximum total pump flow SR in FSAR Section 16.5 ensures the maximum injection flow limit of 550 gpm is not exceeded. This value of flow is comprised of the total flow to the four branch lines of 461 gpm and a seal injection flow of 87 gpm plus 2 gpm for instrument uncertainties. A best estimate increase of 17 gpm when aligned in the recirculation phase (maximum flow of 567 gpm) is discussed in References 8 and 9.
The SI pump maximum total pump flow SR in FSAR Section 16.5 ensures the maximum injection flow limit of 675 gpm is not exceeded. This value of flow includes a nominal 30 gpm of mini-flow. A best estimate increase of 16 gpm when aligned in the recirculation phase (maximum flow of 691 gpm) is discussed in References 8 and 9.
The test procedure places requirements on instrument accuracy (20 inches of water column for the ECCS charging branch lines and 10 inches of water column for the safety injection branch lines) and setting tolerance (30 inches of water column for both the ECCS charging and safety injection branch lines) such that branch line flow imbalance remains within the assumptions of the safety analyses.
The maximum and minimum potential pump performance curves, in conjunction with the maximum and minimum flow SRs, the maximum total system resistance, and the test procedure requirements, ensure that the assumptions of the safety analyses remain valid.
The surveillance flow and differential pressure requirements are the Safety Analysis Limits and do not include instrument uncertainties. These instrument uncertainties will be accounted for in the surveillance test procedure to assure that the Safety Analysis Limits are met.
The ECCS trains satisfy Criterion 3 of 10CFR50.36(c)(2)(ii).
(continued)
CALLAWAY PLANT B 3.5.2-5 Revision 14
ECCS - Operating B 3.5.2 BASES (Continued)
LCO In MODES 1, 2, and 3, two independent (and redundant) ECCS trains are required to ensure that sufficient ECCS flow is available, assuming a single failure affecting either train. Additionally, individual components within the ECCS trains may be called upon to mitigate the consequences of other transients and accidents.
In MODES 1, 2, and 3, an ECCS train consists of a centrifugal charging subsystem, an SI subsystem, and an RHR subsystem. Each train includes the piping, instruments, and controls to ensure an OPERABLE flow path capable of taking suction from the RWST upon an SI signal and automatically transferring suction to the containment sump.
During an event requiring ECCS actuation, a flow path is required to provide an abundant supply of water from the RWST to the RCS via the ECCS pumps and their respective supply headers to each of the four cold leg injection nozzles. Either of the CCPs may be considered OPERABLE with its associated discharge to RCP seal throttle valve, BGHV8357A or BGHV8357B, inoperable. In the long term, the injection flow path may be switched to take its supply from the containment sump and to supply its flow to the RCS hot and cold legs.
During cold leg recirculation operation, the flow path for each train must maintain its designed independence to ensure that no single failure can disable both ECCS trains.
As indicated in Note 1, the SI flow paths may be isolated for 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> in MODE 3, under controlled conditions, to perform pressure isolation valve testing per SR 3.4.14.1. The flow paths are readily restorable from the control room.
As indicated in Note 2, operation in MODE 3 with ECCS pumps made incapable of injecting, pursuant to LCO 3.4.12, "Cold Overpressure Mitigation System (COMS)," is allowed for up to 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> or until the temperature of all RCS cold legs exceeds 375F, whichever comes first.
LCO 3.4.12 requires that certain pumps be rendered incapable of injecting at and below the COMS arming temperature and time is needed to restore the pumps to OPERABLE status.
Management of gas voids is important to ECCS OPERABILITY. The ECCS is OPERABLE when it is sufficiently filled with water to perform its specified safety function.
(continued)
CALLAWAY PLANT B 3.5.2-6 Revision 14
ECCS - Operating B 3.5.2 BASES (Continued)
APPLICABILITY In MODES 1, 2, and 3, the ECCS OPERABILITY requirements for the limiting Design Basis Accident, a large break LOCA, are based on full power operation. Although reduced power would not require the same level of performance, the accident analysis does not provide for reduced cooling requirements in the lower MODES. The ECCS centrifugal charging pump performance is based on a small break LOCA, which establishes the pump performance curve and has less dependence on power (minimum ECCS large break LOCA assumes the same CCP flow rates as the small break LOCA analysis). The SI pump performance requirements are based on a small break LOCA. MODE 2 and MODE 3 requirements are bounded by the MODE 1 analysis.
This LCO is only applicable in MODE 3 and above. The SI signals on low pressurizer pressure and low steam line pressure may be blocked manually in MODE 3 below the P-11 interlock (pressurizer pressure below 1970 psig). There are no blocks of the safety injection signal on containment pressure - High 1, and this signal is required throughout MODE 3. The manual safety injection signal and automatic actuation logic and relays in the SSPS cabinets are required to be OPERABLE during MODES 1-4. Below MODE 3, manual action is sufficient to mitigate a loss of coolant, and the emergency core cooling system functional requirements are relaxed as described in LCO 3.5.3, "ECCS -
Shutdown."
In MODES 5 and 6, plant conditions are such that the probability of an event requiring ECCS injection is extremely low. Core cooling requirements in MODE 5 are addressed by LCO 3.4.7, "RCS Loops -
MODE 5, Loops Filled," and LCO 3.4.8, "RCS Loops - MODE 5, Loops Not Filled." MODE 6 core cooling requirements are addressed by LCO 3.9.5, "Residual Heat Removal (RHR) and Coolant Circulation - High Water Level," and LCO 3.9.6, "Residual Heat Removal (RHR) and Coolant Circulation - Low Water Level."
ACTIONS A.1 With one or more trains inoperable and at least 100% of the ECCS flow equivalent to a single OPERABLE ECCS train available (Refs. 8 and 9),
the inoperable components must be returned to OPERABLE status within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. The 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> Completion Time is based on an NRC reliability evaluation (Ref. 5) and is a reasonable time for repair of many ECCS components.
(continued)
CALLAWAY PLANT B 3.5.2-7 Revision 14
ECCS - Operating B 3.5.2 BASES ACTIONS A.1 (continued)
An ECCS train is inoperable if it is not capable of delivering design flow to the RCS. Individual components are inoperable if they are not capable of performing their design function or supporting systems are not available.
The LCO requires the OPERABILITY of a number of independent subsystems. Due to the redundancy of trains and the diversity of subsystems, the inoperability of one component in a train does not render the ECCS incapable of performing its function. Neither does the inoperability of two different components, each in a different train, necessarily result in a loss of function for the ECCS. The intent of this Condition is to maintain a combination of equipment such that 100% of the ECCS flow (injection and recirculation phases) equivalent to a single OPERABLE ECCS train remains available. This allows increased flexibility in plant operations under circumstances when components in opposite trains are inoperable.
An event accompanied by a loss of offsite power and the failure of an EDG can disable one ECCS train until power is restored. A reliability analysis (Ref. 5) has shown that the impact of having one full ECCS train inoperable is sufficiently small to justify continued operation for 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />.
Reference 6 describes situations in which one component can disable both ECCS trains. With one or more component(s) inoperable such that 100% of the flow equivalent to a single OPERABLE ECCS train is not available, the facility is in a condition outside the accident analysis.
Therefore, LCO 3.0.3 must be immediately entered.
B.1 and B.2 If the inoperable train(s) cannot be returned to OPERABLE status within the associated Completion Time, the plant must be brought to a MODE in which the LCO does not apply. To achieve this status, the plant must be brought to MODE 3 within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and MODE 4 within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />. The allowed Completion Times are reasonable, based on operating experience, to reach the required plant conditions from full power conditions in an orderly manner and without challenging plant systems.
(continued)
CALLAWAY PLANT B 3.5.2-8 Revision 14
ECCS - Operating B 3.5.2 BASES (Continued)
SURVEILLANCE SR 3.5.2.1 REQUIREMENTS Verification of proper valve position ensures that the flow path from the ECCS pumps to the RCS is maintained. Misalignment of these valves could render both ECCS trains inoperable. Securing these valves in position by removal of power by the use of control hand-switches ensures that they cannot change position as a result of an active failure or be inadvertently misaligned. These valves are of the type, described in Reference 6, that can disable the function of both ECCS trains and invalidate the accident analyses. The Surveillance Frequency is based on operating experience, equipment reliability, and plant risk and is controlled under the Surveillance Frequency Control Program. In accordance with Reference 7, EMHV8802A (or EMHV8802B) can be stroked open for testing in MODES 1-3 provided that:
- a. EMHV8821A (or EMHV8821B) is closed first, with power removed and the motor circuit breaker racked out, and remains closed until EMHV8802A (or EMHV8802B)is reclosed.
Closure of EMHV8821A or EMHV8821B isolates the associated SI pump from its cold leg injection path rendering that train inoperable; however, the opposite train is prevented from exceeding runout flow conditions which would occur if the opposite pump were connected to both cold leg and hot leg injection paths. The inoperable trains pump is then placed in pull to lock to prevent unanalyzed hot leg injection via its associated 8802 valve. Although one SI train would be rendered inoperable, more than 100% of the ECCS flow equivalent to a single OPERABLE ECCS train would be available, and the plant would be in CONDITION A.1 with a 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> restoration time rather than entering LCO 3.0.3.
SR 3.5.2.2 Verifying the correct alignment for manual, power operated, and automatic valves in the ECCS flow paths provides assurance that the proper flow paths will exist for ECCS operation. This SR does not apply to valves that are locked, sealed, or otherwise secured in position, since these were verified to be in the correct position prior to locking, sealing, or securing. A valve that receives an actuation signal is allowed to be in a non-accident position provided the valve will automatically reposition within the proper stroke time. This SR does not require any testing or (continued)
CALLAWAY PLANT B 3.5.2-9 Revision 14
ECCS - Operating B 3.5.2 BASES SURVEILLANCE SR 3.5.2.2 (continued)
REQUIREMENTS valve manipulation. Rather, it involves verification, through a system walkdown (which may include the use of local or remote indicators), that those valves capable of being mispositioned are in the correct position.
This SR does not apply to valves that cannot be inadvertently misaligned, such as check valves and relief valves. Additionally, vent and drain valves are not within the scope of this SR.
The Surveillance is modified by a Note which exempts system vent flow paths opened under administrative control. The administrative control should be proceduralized and include stationing a dedicated individual at the system vent flow path who is in continuous communication with the operators in the control room. This individual will have a method to rapidly close the system vent flow path if directed.
The Surveillance Frequency is based on operating experience, equipment reliability, and plant risk and is controlled under the Surveillance Frequency Control Program.
SR 3.5.2.3 ECCS piping and components have the potential to develop voids and pockets of entrained gases. Maintaining the piping from the ECCS pumps to the entrained gases. Preventing and managing gas intrusion and accumulation is necessary for proper operation of the ECCS and may also prevent water hammer, pump cavitation, and pumping of noncondensible gas into the reactor vessel. In conjunction with or in lieu of venting, Ultrasonic Testing (UT) may be performed to verify ECCS pumps and associated piping are sufficiently full of water.
The design of the ECCS centrifugal charging pump is such that significant noncondensible gases do not collect in the pump. Therefore, it is unnecessary to require periodic pump casing venting to ensure the centrifugal charging pumps will remain OPERABLE.
Selection of ECCS locations susceptible to gas accumulation is based on a review of system design information, including piping and instrumentation drawings, isometric drawings, plan and elevation drawings, and calculations. The design review is supplemented by system walkdowns to validate the system high points and to confirm the location and orientation of important components that can become sources of gas or could otherwise cause gas to be trapped or difficult to remove during (continued)
CALLAWAY PLANT B 3.5.2-10 Revision 14
ECCS - Operating B 3.5.2 BASES SURVEILLANCE SR 3.5.2.3 (continued)
REQUIREMENTS system maintenance or restoration. Susceptible locations depend on plant and system configuration, such as standby versus operating conditions.
The ECCS is OPERABLE when it is sufficiently filled with water.
Acceptance criteria are established for the volume of accumulated gas at susceptible locations. If accumulated gas is discovered that exceeds the acceptance criteria for the susceptible location (or the volume of accumulated gas at one or more susceptible locations exceeds acceptance criteria for gas volume at the suction or discharge of a pump),
the Surveillance is not met. If it is determined by subsequent evaluation that the ECCS System is not rendered inoperable by the accumulated gas (i.e., the system is sufficiently filled with water), the Surveillance may be declared met. Accumulated gas should be eliminated or brought within the acceptance criteria limits.
ECCS locations susceptible to gas accumulation are monitored, and if gas is found, the gas volume is compared to the acceptance criteria for the location. Susceptible locations in the same system flow path which are subject to the same gas intrusion mechanisms may be verified by monitoring a representative subset of susceptible locations. Monitoring may not be practical for locations that are inaccessible due to radiological or environmental conditions, the plant configuration, or personnel safety.
For these locations alternative methods (e.g., operating parameters, remote monitoring) may be used to monitor the susceptible location.
Monitoring is not required for susceptible locations where the maximum potential accumulated gas void volume has been evaluated and determined to not challenge system OPERABILITY. The accuracy of the method used for monitoring the susceptible locations and trending of the results should be sufficient to assure system OPERABILITY during the Surveillance interval.
The Surveillance Frequency is controlled under the Surveillance Frequency Control Program. The Surveillance Frequency may vary by location susceptible to gas accumulation.
The Surveillance Frequency is based on operating experience, equipment reliability, and plant risk and is controlled under the Surveillance Frequency Control Program.
(continued)
CALLAWAY PLANT B 3.5.2-11 Revision 14
ECCS - Operating B 3.5.2 BASES SURVEILLANCE SR 3.5.2.4 REQUIREMENTS (continued) Periodic surveillance testing of ECCS pumps to detect gross degradation caused by impeller structural damage or other hydraulic component problems is required by the ASME Code. This type of testing may be accomplished by measuring the pump developed head at only one point of the pump characteristic curve. The ECCS pumps are required to develop the following differential pressures on recirculation flow: 1) ECCS centrifugal charging pumps 2400 psid; 2) safety injection pumps 1445 psid; and 3) RHR pumps 165 psid. This verifies both that the measured performance is within an acceptable tolerance of the original pump than or equal to the performance assumed in the plant safety analysis. SRs are specified in the applicable portions of the Inservice Testing Program, which encompasses the ASME Code. The ASME Code provides the activities and Frequencies necessary to satisfy the requirements.
SR 3.5.2.5 and SR 3.5.2.6 These Surveillances demonstrate that each automatic ECCS valve actuates to the required position on an actual or simulated SI signal or on an actual or simulated RWST Level Low-Low 1 Automatic Transfer signal coincident with an SI signal and that each ECCS pump starts on receipt of an actual or simulated SI signal. The containment recirculation sump to RHR pump isolation valves (EJHV8811A/B) automatically open upon receipt of an actual or simulated RWST Level Low-Low-1 Automatic Transfer signal coincident with an SI signal. In addition to testing that automatic function, SR 3.5.2.5 demonstrates that the RWST to RHR pump suction isolation valves (BNHV8812A/B) are capable of automatic closure after the EJHV8811A/B valves are fully open. The valve interlock functions are depicted in Reference 10. This Surveillance is not required for valves that are locked, sealed, or otherwise secured in the required position under administrative controls. The Surveillance Frequency is based on operating experience, equipment reliability, and plant risk and is controlled under the Surveillance Frequency Control Program. The actuation logic is tested as part of ESF Actuation System testing, and equipment performance is monitored as part of the Inservice Testing Program.
SR 3.5.2.7 The correct position of throttle valves in the flow path is necessary for proper ECCS performance. These valves have mechanical stops to allow proper positioning for restricted flow to a ruptured cold leg, ensuring that the other cold legs receive at least the required minimum flow. The Surveillance Frequency is based on operating experience, equipment (continued)
CALLAWAY PLANT B 3.5.2-12 Revision 14
ECCS - Operating B 3.5.2 BASES SURVEILLANCE SR 3.5.2.7 (continued)
REQUIREMENTS reliability, and plant risk and is controlled under the Surveillance Frequency Control Program. The ECCS throttle valves are set to ensure proper flow resistance and pressure drop in the piping to each injection point in the event of a LOCA. Once set, these throttle valves are secured with locking devices and mechanical position stops. These devices help to ensure that the following safety analyses assumptions remain valid:
(1) both the maximum and minimum total system resistance; (2) both the maximum and minimum branch injection line resistance; and (3) the maximum and minimum ranges of potential pump performance. These resistances and pump performance ranges are used to calculate the maximum and minimum ECCS flows assumed in the LOCA analyses of Reference 3.
SR 3.5.2.8 Periodic inspections of the containment sump suction inlet ensure that it is unrestricted and stays in proper operating condition. The Surveillance Frequency is based on operating experience, equipment reliability, and plant risk and is controlled under the Surveillance Frequency Control Program.
REFERENCES 1. 10 CFR 50, Appendix A, GDC 35.
- 2. 10 CFR 50.46.
- 3. FSAR, Sections 6.3 and 15.6.
- 4. FSAR, Chapter 15, "Accident Analysis."
- 5. NRC Memorandum to V. Stello, Jr., from R. L. Baer, "Recommended Interim Revisions to LCOs for ECCS Components," December 1, 1975.
- 7. RFR-14801A.
- 8. ULNRC-2535 dated 12-18-91 (for SI and RHR pumps) and ULNRC-04583 dated 12-13-01 (for CCPs).
(continued)
CALLAWAY PLANT B 3.5.2-13 Revision 14
ECCS - Operating B 3.5.2 BASES REFERENCES 9. OL Amendment No. 68 dated 3-24-92 (for SI and RHR pumps and (continued) OL Amendment No. 150 dated 5-2-02 (for CCPs).
- 10. FSAR, Figure 7.6-3.
- 11. FSAR, Section 5.4.7.2.2.
- 12. FSAR, Section 6.3.2.2.
CALLAWAY PLANT B 3.5.2-14 Revision 14
ECCS - Shutdown B 3.5.3 B 3.5 EMERGENCY CORE COOLING SYSTEMS (ECCS)
B 3.5.3 ECCS - Shutdown BASES BACKGROUND The function of the ECCS in MODE 4 is to provide core cooling to ensure that the reactor core is protected after a small break loss of coolant accident (SBLOCA). In MODE 4, the required ECCS train consists of two sperate subsystems: centrifugal charging (high head) and residual heat removal (RHR) (low head).
The ECCS flow paths consist of piping, valves, heat exchangers, and pumps such that water from the refueling water storage tank (RWST) can be injected into the Reactor Coolant System (RCS) following a SBLOCA.
During low temperature conditions is in RCS, limitations are placed on the maximum number of ECCS pumps that are capable of injecting into the RCS. Refer to the Bases for LCO 3.4.12, Cold Overpressure Mitigation System (COMS), for the basis of these requirements.
The ECCS components in MODE 4 provide the cooling water necessary to meet GDC 35 (Reference 1).
APPLICABLE Due to the stable conditions associated with operation in MODE 4 and the SAFETY reduced probability of occurrence of a SBLOCA, the ECCS operational ANALYSES requirements are reduced. It is understood in these reductions that certain automatic safety injection (SI) actuation is not available. In this MODE, sufficient time exists for manual actuation of the required ECCS to mitigate the consequences of a SBLOCA.
The LCO helps to ensure that the following acceptance criteria for the ECCS, established be 10 CFR 50.46 (Reference 2), will be met following a SBLOCA:
- a. Maximum fuel element cladding temperature is < 2200°F;
- b. Maximum cladding oxidation is < 0.17 times the total cladding thickness before oxidation;
< 0.01 times the hypothetical amount generated if all of the metal in the cladding cylinders surrounding the fuel, excluding the cladding surrounding the plenum volume, were to react; (continued)
CALLAWAY PLANT B 3.5.3-1 Revision 13
ECCS - Shutdown B 3.5.3 BASES APPLICABLE d. Core is maintained in a coolable geometry; and SAFETY ANALYSIS e. Adequate long term core cooling capability is maintained.
(continued)
WCAP-12476, Revision 1 (Reference 3), provides the results of a generic probabilistic risk assessment showing that a break with an equivalent diameter greater than 6-inches is not a credible MODE 4 scenario.
Reference 3 also presents a generic bounding thermal-hydraulic analysis for the MODE 4 SBLOCA based on limiting representative plant parameters with the accumulators isolated. The assumed ECCS availability is based on one OPERABLE ECCS train consisting of a centrifugal charging subsystem and an RHR subsystem.
The generic thermal-hydraulic analysis for the limiting MODE 4 SBLOCA in Reference 3 is supplemented by a plant-specific evaluation (Reference
- 4) which demonstrates that the minimum safeguards ECCS flow from one centrifugal charging pump (CCP) and one RHR pump in Table 2 of Reference 4 can satisfy the MODE 4 small break LOCA ECCS flow requirements given in Table 4-7 of Reference 3 provided that:
- 1. ECCS flow from one centrifugal charging subsystem can be established within 10 minutes of recognition of the event;
- 2. Flow from one RHR subsystem into two or more cold leg injection nozzles (i.e., RHR cross-tie valves EJHV8716A/B either open or closed) can be established within 30 minutes of recognition of the event; and
- 3. Decay heat loads are not exceeded at MODE 4 entry as required by FSAR Section 16.5.3 (Reference 5).
Only one train of ECCS is required for MODE 4. This requirement dictates that single failures are not considered during this MODE of operation. The ECCS trains satisfy Criterion 3 of 10CFR50.36(c)(2)(ii).
LCO In MODE 4, one of the two independent (and redundant) ECCS trains is required to be OPERABLE to ensure that sufficient ECCS flow is available to the core following a DBA.
In MODE 4, an ECCS train consists of a centrifugal charging subsystem and an RHR subsystem. Each train includes the piping, instruments, and controls to ensure an OPERABLE flow path capable of taking suction from the RWST and transferring suction to the containment sump.
(continued)
CALLAWAY PLANT B 3.5.3-2 Revision 13
ECCS - Shutdown B 3.5.3 BASES LCO During an event requiring ECCS actuation, a flow path is required to (continued) provide an abundant supply of water from the RWST to the RCS via the ECCS pumps and their respective supply headers to a minimum of two cold leg injection nozzles. In the long term, this flow path may be switched to take its supply from the containment sump and to deliver its flow to the RCS hot and cold legs.
This LCO is modified by a Note that allows an RHR subsystem to be considered OPERABLE during alignment and operation for decay heat removal, if capable of being manually realigned (remote or local) to the ECCS mode of operation and not otherwise inoperable. This allows operation in the RHR mode during MODE 4.
Management of gas voids is important to ECCS OPERABILITY. The ECCS is OPERABLE when it is sufficiently filled with water to perform its specified safety function.
APPLICABILITY In MODES 1, 2, and 3, the OPERABILITY requirements for ECCS are covered by LCO 3.5.2.
In MODE 4 with RCS temperature below 350F, one OPERABLE ECCS train is acceptable without single failure consideration, on the basis of the stable reactivity of the reactor and the limited core cooling requirements.
In MODES 5 and 6, plant conditions are such that the probability of an event requiring ECCS injection is extremely low. Core cooling requirements in MODE 5 are addressed by LCO 3.4.7, "RCS Loops -
MODE 5, Loops Filled," and LCO 3.4.8, "RCS Loops - MODE 5, Loops Not Filled." MODE 6 core cooling requirements are addressed by LCO 3.9.5, "Residual Heat Removal (RHR) and Coolant Circulation - High Water Level," and LCO 3.9.6, "Residual Heat Removal (RHR) and Coolant Circulation - Low Water Level."
ACTIONS A Note prohibits the application of LCO 3.0.4.b to an inoperable ECCS centrifugal charging pump subsystem when entering MODE 4. There is an increased risk associated with entering MODE 4 from MODE 5 with an inoperable ECCS centrifugal charging pump subsystem and the provisions of LCO 3.0.4.b, which allow entry into a MODE or other specified condition in the Applicability with the LCO not met after performance of a risk assessment addressing inoperable systems and components, should not be applied in this circumstance.
(continued)
CALLAWAY PLANT B 3.5.3-3 Revision 13
ECCS - Shutdown B 3.5.3 BASES ACTIONS A.1 (continued)
With no ECCS RHR subsystem OPERABLE, the plant is not prepared to respond to a loss of coolant accident or to continue a cooldown using the RHR pumps and heat exchangers. The Completion Time of immediately to initiate actions that would restore at least one ECCS RHR subsystem to OPERABLE status ensures that prompt action is taken to restore the required cooling capacity. Normally, in MODE 4, reactor decay heat is removed from the RCS by an RHR loop. If no RHR loop is OPERABLE for this function, reactor decay heat must be removed by some alternate method, such as use of the steam generators. The alternate means of heat removal must continue until the inoperable RHR loop components can be restored to operation so that decay heat removal is continuous.
With both RHR pumps and heat exchangers inoperable, it would be unwise to require the plant to go to MODE 5, where the only available heat removal system is the RHR. Therefore, the appropriate action is to initiate measures to restore one ECCS RHR subsystem and to continue the actions until the subsystem is restored to OPERABLE status.
B.1 With no ECCS centrifugal charging subsystem OPERABLE, due to the inoperability of the CCP or flow path from the RWST, the plant is not prepared to provide high pressure response to Design Basis Events requiring SI. The 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> Completion Time to restore at least one ECCS centrifugal charging subsystem to OPERABLE status ensures that prompt action is taken to provide the required cooling capacity or to initiate actions to place the plant in MODE 5, where an ECCS train is not required.
C.1 When the Required Actions of Condition B cannot be completed within the required Completion Time, a controlled shutdown should be initiated.
Twenty-four hours is a reasonable time, based on operating experience, to reach MODE 5 in an orderly manner and without challenging plant systems or operators.
SURVEILLANCE SR 3.5.3.1 REQUIREMENTS The applicable Surveillance descriptions from Bases 3.5.2 apply.
(continued)
CALLAWAY PLANT B 3.5.3-4 Revision 13
ECCS - Shutdown B 3.5.3 BASES (Continued)
REFERENCES 1. 10 CFR 50, Appendix A, GDC 35.
- 2. 10 CFR 50.46
- 3. WCAP-12476, Revision 1, Evaluation of LOCA During Mode 3 and Mode 4 Operation for Westinghouse NSSS, November 2000.
- 4. Westinghouse letter SCP-10-31, Transmittal of Mode 4 Small Break LOCA (SBLOCA) RHR Flow Evaluation for Callaway (SCP)
- Phase 3 - Revision 1, May 11, 2010.
- 5. FSAR Section 16.5.3.
CALLAWAY PLANT B 3.5.3-5 Revision 13
RWST B 3.5.4 B 3.5 EMERGENCY CORE COOLING SYSTEMS (ECCS)
B 3.5.4 Refueling Water Storage Tank (RWST)
BASES BACKGROUND The RWST supplies borated water to the Chemical and Volume Control System (CVCS) during abnormal operating conditions, to the refueling pool during refueling, and to the ECCS and the Containment Spray System during accident conditions.
The RWST supplies both trains of the ECCS and the Containment Spray System through a common suction supply header during the injection phase of a loss of coolant accident (LOCA) recovery. A motor operated isolation valve is provided in each pump suction branch line off the common header to isolate the RWST from the ECCS once the system has been transferred to the recirculation mode. The recirculation mode is entered when pump suction is transferred to the containment sump following receipt of the RWST Level Low - Low 1 Automatic Transfer Signal coincident with an SI signal. Use of a single RWST to supply both trains of the ECCS and Containment Spray System is acceptable since the RWST is a passive component, and passive failures are not required to be assumed to occur coincidentally with Design Basis Events.
The switchover from normal operation to the injection phase of ECCS operation requires changing centrifugal charging pump suction from the CVCS volume control tank (VCT) to the RWST through the use of isolation valves. Each set of isolation valves is interlocked so that the VCT isolation valves will begin to close once the RWST isolation valves are fully open. Since the VCT is under pressure, the preferred pump suction will be from the VCT until the tank is isolated. This will result in a delay in obtaining the RWST borated water. The effects of this delay are discussed in the Applicable Safety Analyses section of these Bases.
During normal operation in MODES 1, 2, and 3, the safety injection (SI) and residual heat removal (RHR) pumps are aligned to take suction from the RWST.
The ECCS pumps are provided with recirculation lines that ensure each pump can maintain minimum flow requirements when operating at or near shutoff head conditions.
When the suction for the ECCS and Containment Spray System pumps is transferred to the containment sumps, the RWST flow paths must be isolated to prevent a release of the containment sump contents to the RWST, which could result in a release of contaminants to the atmosphere and the eventual loss of suction head for the ECCS pumps.
(continued)
CALLAWAY PLANT B 3.5.4-1 Revision 10
RWST B 3.5.4 BASES BACKGROUND This LCO ensures that:
(continued)
- b. Sufficient water volume exists in the containment sump to support continued operation of the ECCS and Containment Spray System pumps at the time of transfer to the recirculation mode of cooling; and
- c. The reactor remains subcritical following a LOCA.
Insufficient water in the RWST could result in insufficient cooling capacity when the transfer to the recirculation mode occurs. Improper boron concentrations could result in a reduction of SDM or excessive boric acid precipitation in the core following the LOCA, as well as excessive caustic stress corrosion of mechanical components and systems inside the containment.
APPLICABLE During accident conditions, the RWST provides a source of borated water SAFETY to the ECCS and Containment Spray System pumps. As such, it provides ANALYSES containment cooling and depressurization, core cooling, and replacement inventory and is a source of negative reactivity for reactor shutdown (Ref. 1). The design basis transients and applicable safety analyses concerning each of these systems are discussed in the Applicable Safety Analyses section of B 3.5.2, "ECCS - Operating"; B 3.5.3, "ECCS -
Shutdown"; and B 3.6.6, "Containment Spray and Cooling Systems."
These analyses are used to assess changes to the RWST in order to evaluate their effects in relation to the acceptance limits in the analyses.
The RWST must also meet volume, boron concentration, and temperature requirements for non-LOCA events. The volume is not an explicit assumption in non-LOCA events since the required volume is a small fraction of the available volume. The deliverable volume limit is set by the LOCA and containment analyses. For the RWST, the deliverable volume is different from the total volume contained since, due to the design of the tank, more water can be contained than can be delivered.
The minimum boron concentration is an explicit assumption in the main steam line break (MSLB) analysis to ensure the required shutdown capability. The minimum boron concentration limit is an important assumption in ensuring the required shutdown capability. The maximum boron concentration is an explicit assumption in the inadvertent ECCS actuation analysis, although it is typically a non-limiting event and the results are very insensitive to boron concentrations. The maximum (continued)
CALLAWAY PLANT B 3.5.4-2 Revision 10
RWST B 3.5.4 BASES APPLICABLE temperature ensures that the amount of cooling provided from the RWST SAFETY during the heatup phase of a feedline break is consistent with safety ANALYSES analysis assumptions; the minimum temperature is an assumption in both (continued) the MSLB core response and inadvertent ECCS actuation analyses, although the inadvertent ECCS actuation event is typically non-limiting.
The MSLB analysis has considered a delay associated with the interlock between the VCT and RWST isolation valves, and the results show that the departure from nucleate boiling design basis is met. The delay has been established as 27 seconds, with offsite power available, or 39 seconds without offsite power. This response time includes 2 seconds for electronics delay, a 15 second stroke time to open the RWST valves, followed by a 10 second stroke time to close the VCT valves after the RWST valves are fully open.
For a large break LOCA analysis, the minimum water volume limit of 394,000 gallons and the lower boron concentration limit of 2350 ppm are used to compute the post LOCA sump boron concentration necessary to assure subcriticality. The large break LOCA is the limiting case since the safety analysis assumes that all control rods are out of the core. The limits on contained water volume and boron concentration of the RWST also ensure a minimum equilibrium sump pH of 7.1 for the solution recirculated within containment after a LOCA. This pH level minimizes the evolution of iodine and minimizes the effect of chloride and caustic stress corrosion on mechanical systems and components.
The upper limit on boron concentration of 2500 ppm is used to determine the maximum allowable time to switch to hot leg recirculation following a LOCA. The purpose of switching from cold leg to hot leg recirculation is to avoid boron precipitation in the core following the accident.
In the containment backpressure portion of the ECCS analysis, the containment spray temperature is assumed to be equal to the RWST lower temperature limit of 37F (Ref. 3). If the lower temperature limit is violated, the containment spray further reduces containment pressure, which decreases the rate at which steam can be vented out the break and increases peak clad temperature. The upper temperature limit of 100F is used in the small break LOCA analysis and containment OPERABILITY analysis. Exceeding this temperature will result in a higher peak clad temperature, because there is less heat transfer from the core to the injected water for the small break LOCA, and higher containment pressures due to reduced containment spray cooling capacity. For the containment response following an MSLB, the lower limit on boron concentration and the upper limit on RWST water temperature are used to maximize the total energy release to containment.
(continued)
CALLAWAY PLANT B 3.5.4-3 Revision 10
RWST B 3.5.4 BASES APPLICABLE Safety analyses assume a B-10 abundance of 19.9 a/o (Ref. 2).
SAFETY Administrative controls ensure that the reactivity insertion from the RWST ANALYSES reflects this assumption.
(continued)
The RWST satisfies Criterion 2 and Criterion 3 of 10CFR50.36(c)(2)(ii).
LCO The RWST ensures that an adequate supply of borated water is available to cool and depressurize the containment in the event of a Design Basis Accident (DBA), to cool and cover the core in the event of a LOCA, to maintain the reactor subcritical following a DBA, and to ensure adequate level in the containment sump to support ECCS and Containment Spray System pump operation in the recirculation mode.
To be considered OPERABLE, the RWST must meet the water volume, boron concentration, and temperature limits established in the SRs.
APPLICABILITY In MODES 1, 2, 3, and 4, RWST OPERABILITY requirements are dictated by ECCS and Containment Spray System OPERABILITY requirements. Since both the ECCS and the Containment Spray System must be OPERABLE in MODES 1, 2, 3, and 4, the RWST must also be OPERABLE to support their operation. Core cooling requirements in MODE 5 are addressed by LCO 3.4.7, "RCS Loops - MODE 5, Loops Filled," and LCO 3.4.8, "RCS Loops - MODE 5, Loops Not Filled."
MODE 6 core cooling requirements are addressed by LCO 3.9.5, "Residual Heat Removal (RHR) and Coolant Circulation - High Water Level," and LCO 3.9.6, "Residual Heat Removal (RHR) and Coolant Circulation - Low Water Level."
ACTIONS A.1 With RWST boron concentration or borated water temperature not within limits, they must be returned to within limits within 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />. Under these conditions, neither the ECCS nor the Containment Spray System can perform its design function. Therefore, prompt action must be taken to restore the tank to OPERABLE condition. The 8 hour9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> limit to restore the RWST temperature or boron concentration to within limits was developed considering the time required to change either the boron concentration or temperature and the fact that the contents of the tank are still available for injection.
(continued)
CALLAWAY PLANT B 3.5.4-4 Revision 10
RWST B 3.5.4 BASES ACTIONS B.1 (continued)
With the RWST inoperable for reasons other than Condition A (e.g., water volume), it must be restored to OPERABLE status within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />.
In this Condition, neither the ECCS nor the Containment Spray System can perform its design function. Therefore, prompt action must be taken to restore the tank to OPERABLE status or to place the plant in a MODE in which the RWST is not required. The short time limit of 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> to restore the RWST to OPERABLE status is based on this condition simultaneously affecting redundant trains.
C.1 and C.2 If the RWST cannot be returned to OPERABLE status within the associated Completion Time, the plant must be brought to a MODE in which the LCO does not apply. To achieve this status, the plant must be brought to at least MODE 3 within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and to MODE 5 within 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />.
The allowed Completion Times are reasonable, based on operating experience, to reach the required plant conditions from full power conditions in an orderly manner and without challenging plant systems.
SURVEILLANCE SR 3.5.4.1 REQUIREMENTS The RWST borated water temperature should be verified to be within the limits assumed in the accident analyses band. The Surveillance Frequency is based on operating experience, equipment reliability, and plant risk and is controlled under the Surveillance Frequency Control Program.
The SR is modified by a Note that eliminates the requirement to perform this Surveillance when ambient air temperatures are within the operating limits of the RWST. With ambient air temperatures within the band, the RWST temperature should not exceed the limits.
SR 3.5.4.2 The RWST water volume should be verified to be above the required minimum level in order to ensure that a sufficient initial supply is available for injection and to support continued ECCS and Containment Spray System pump operation on recirculation. The Surveillance Frequency is (continued)
CALLAWAY PLANT B 3.5.4-5 Revision 10
RWST B 3.5.4 BASES SURVEILLANCE SR 3.5.4.2 (continued)
REQUIREMENTS based on operating experience, equipment reliability, and plant risk and is controlled under the Surveillance Frequency Control Program.
SR 3.5.4.3 The boron concentration of the RWST should be verified to be within the required limits. This SR ensures that the reactor will remain subcritical following a LOCA. Further, it assures that the resulting sump pH will be maintained in an acceptable range so that boron precipitation in the core will not occur and the effect of chloride and caustic stress corrosion on mechanical systems and components will be minimized. The Surveillance Frequency is based on operating experience, equipment reliability, and plant risk and is controlled under the Surveillance Frequency Control Program.
REFERENCES 1. FSAR, Chapter 6 and Chapter 15.
- 2. RFR-17070A.
- 3. FSAR Section 6.2.1.5 and Table 15.6-11.
CALLAWAY PLANT B 3.5.4-6 Revision 10
Seal Injection Flow B 3.5.5 B 3.5 EMERGENCY CORE COOLING SYSTEMS (ECCS)
B 3.5.5 Seal Injection Flow BASES BACKGROUND This LCO is applicable to Callaway since the plant utilizes the ECCS centrifugal charging pumps for safety injection (SI). The function of the seal injection throttle valves during an accident is similar to the function of the ECCS throttle valves in that each restricts flow from the centrifugal charging pump header to the Reactor Coolant System (RCS).
The restriction on reactor coolant pump (RCP) seal injection flow limits the amount of ECCS flow that would be diverted from the injection path following an accident. This limit is based on safety analysis assumptions that are required because RCP seal injection flow is not isolated during SI.
APPLICABLE All ECCS subsystems are taken credit for in the large break loss of SAFETY coolant accident (LOCA) at full power (Ref. 1). The LOCA analysis ANALYSES establishes the minimum flow for the ECCS pumps. The ECCS centrifugal charging pumps are also credited in the small break LOCA analysis. This analysis establishes the flow and discharge head at the design point for the ECCS centrifugal charging pumps. The safety analyses make assumptions with respect to: (1) both the maximum and minimum total system resistance; (2) both the maximum and minimum branch injection line resistance; and (3) the maximum and minimum ranges of potential pump performance. These resistances and ranges of pump performance are used to calculate the maximum and minimum ECCS flows assumed in the safety analyses.
The CCP maximum total pump flow SR in FSAR Section 16.5 ensures the maximum injection flow limit of 550 gpm is not exceeded. This value of flow is comprised of the total flow to the four branch lines of 461 gpm and a seal injection flow of 87 gpm plus 2 gpm for instrument uncertainties.
The Bases for LCO 3.5.2, "ECCS - Operating," contain additional discussion on the safety analyses. The steam generator tube rupture and main steam line break event analyses also credit the ECCS centrifugal charging pumps, but are not limiting in their design. Reference to these analyses is made in assessing changes to the Seal Injection System for evaluation of their effects in relation to the acceptance limits in these analyses.
This LCO ensures that seal injection flow will be sufficient for RCP seal integrity but limited so that the ECCS trains will be capable of delivering (continued)
CALLAWAY PLANT B 3.5.5-1 Revision 14
Seal Injection Flow B 3.5.5 BASES APPLICABLE sufficient water to match boiloff rates soon enough to minimize SAFETY uncovering of the core following a large LOCA. It also ensures that the ANALYSES ECCS centrifugal charging pumps will deliver sufficient water for a small (continued) break LOCA and sufficient boron to maintain the core subcritical. For smaller LOCAs, the ECCS centrifugal charging pumps alone deliver sufficient fluid to overcome the loss and maintain RCS inventory. Seal injection flow satisfies Criterion 2 of 10CFR50.36(c)(2)(ii).
LCO The intent of the LCO limit on seal injection flow is to make sure that flow through the RCP seal water injection line is low enough to ensure that sufficient ECCS centrifugal charging pump injection flow is directed to the RCS via the injection points (Ref. 2).
The LCO is not strictly a flow limit, but rather a flow limit based on a flow line resistance. In order to establish the proper flow line resistance, a pressure and flow must be known. The flow line resistance is established by adjusting the RCP seal water injection throttle valves such that the analyzed ECCS flow to the RCP seals is limited to 89 gpm with one ECCS centrifugal charging pump (CCP) operating at 550 gpm on its maximum pump curve. This accident analysis limit is met by positioning the valves so that the flow to the RCP seals is within the limits of Technical Specifications Figure 3.5.5-1 for a given differential pressure between the charging pump discharge header and the RCS pressurizer steam space pressure.
The seal injection flow curve is presented with the pressure difference from BGPT0120 to the pressurizer steam space pressure as a function of total seal injection line flow. A flow measurement instrument uncertainty of 0.25 gpm per loop was accounted for in the calculation of the pressure drop from BGPT0120 to the seal injection connection. In addition, 2 psid is added to accommodate instrument uncertainty in the pressure drop measurement. An additional 4 psid has been conservatively added to the required pressure differential to allow for seal injection filter change out.
Requiring as an initial condition that the filter used for each surveillance have a differential pressure less than or equal to 4 psid allows for post-surveillance filter change out with no differential pressure restriction.
Once set, the throttle valves are secured with locking devices and mechanical position stops. These devices help to ensure that the following safety analyses assumptions remain valid: (1) both the maximum and minimum total system resistance; (2) both the maximum and minimum branch injection line resistance; and (3) the maximum and minimum ranges of potential pump performance. These resistances and pump performance ranges are used to calculate the maximum and minimum ECCS flows assumed in the LOCA analyses of Reference 1.
(continued)
CALLAWAY PLANT B 3.5.5-2 Revision 14
Seal Injection Flow B 3.5.5 BASES LCO The centrifugal charging pump discharge header pressure remains (continued) essentially constant through all the applicable MODES of this LCO. A reduction in RCS pressure would result in more flow being diverted to the RCP seal injection line than at normal operating pressure. The valve settings established at the prescribed differential pressure result in a conservative valve position should RCS pressure decrease.
The limit on seal injection flow must be met to render the ECCS OPERABLE. If these conditions are not met, the ECCS flow will not be as assumed in the accident analyses.
APPLICABILITY In MODES 1, 2, and 3, the seal injection flow limit is dictated by ECCS flow requirements, which are specified for MODES 1, 2, 3, and 4. The seal injection flow limit is not applicable for MODE 4 and lower, however, because high seal injection flow is less critical as a result of the lower initial RCS pressure and decay heat removal requirements in these MODES. Therefore, RCP seal injection flow must be limited in MODES 1, 2, and 3 to ensure adequate ECCS performance.
ACTIONS A.1 With the seal injection flow exceeding its limit, the amount of charging flow available to the RCS may be reduced. Under this Condition, action must be taken to restore the flow to below its limit. The operator has 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> from the time the flow is known to be above the limit to correctly position the manual seal injection throttle valves and thus be in compliance with the accident analysis. The Completion Time minimizes the potential exposure of the plant to a LOCA with insufficient injection flow and provides a reasonable time to restore seal injection flow within limits. This time is conservative with respect to the Completion Times of other ECCS LCOs; it is based on operating experience and is sufficient for taking corrective actions by operations personnel.
B.1 and B.2 When the Required Action cannot be completed within the required Completion Time, a controlled shutdown must be initiated. The Completion Time of 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> for reaching MODE 3 from MODE 1 is a reasonable time for a controlled shutdown, based on operating experience and normal cooldown rates, and does not challenge plant safety systems or operators. Continuing the plant shutdown begun in Required Action B.1, an additional 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> is a reasonable time, based on operating experience and normal cooldown rates, to reach MODE 4 where this LCO is no longer applicable.
(continued)
CALLAWAY PLANT B 3.5.5-3 Revision 14
Seal Injection Flow B 3.5.5 BASES (Continued)
SURVEILLANCE SR 3.5.5.1 REQUIREMENTS Verification that the manual seal injection throttle valves are adjusted to give a flow within the limit ensures that proper manual seal injection throttle valve position, and hence, proper seal injection flow, is maintained.
The seal water injection throttle valves are set to ensure proper flow resistance and pressure drop in the piping to each injection point in the event of a LOCA.
The seal injection flow line resistance is established by adjusting the RCP seal water injection throttle valves such that the analyzed ECCS flow to the RCP seals is limited to 89 gpm with one ECCS centrifugal charging pump (CCP) operating at 550 gpm on its maximum pump curve. This accident analysis limit is met by positioning the valves so that the flow to the RCP seals is within the limits of Technical Specifications Figure 3.5.5-1 for a given differential pressure between the charging pump discharge header and the RCS pressurizer steam space pressure.
The seal injection flow curve is presented with the pressure difference from BGPT0120 to the pressurizer steam space pressure as a function of total seal injection line flow. A flow measurement instrument uncertainty of 0.25 gpm per loop was accounted for in the calculation of the pressure drop from BGPT0120 to the seal injection connection. In addition, 2 psid is added to accommodate instrument uncertainty in the pressure drop measurement. An additional 4 psid has been conservatively added to the required pressure differential to allow for seal injection filter change out.
Requiring as an initial condition that the filter used for each surveillance have a differential pressure less than or equal to 4 psid allows for post-surveillance filter change out with no differential pressure restriction.
Once set, these throttle valves are secured with locking devices and mechanical position stops. The Surveillance Frequency is based on operating experience, equipment reliability, and plant risk and is controlled under the Surveillance Frequency Control Program.
As noted, the Surveillance is not required to be performed until 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> after the RCS pressure has stabilized within a 20 psig range of normal operating pressure. The RCS pressure requirement is specified since this configuration will produce the required pressure conditions necessary to assure that the manual seal injection throttle valves are set correctly. The exception is limited to 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> to ensure that the Surveillance is timely.
(continued)
CALLAWAY PLANT B 3.5.5-4 Revision 14
Seal Injection Flow B 3.5.5 BASES (Continued)
REFERENCES 1. FSAR, Sections 6.3 and 15.6.5.
- 2. 10 CFR 50.46.
CALLAWAY PLANT B 3.5.5-5 Revision 14