ML23067A176
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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 supp ly 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 Co olant System (RCS) makeup for a small break LOCA.
The ECCS injection mode following a large break LOCA consists o f 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 conditi ons, and heat from fission product decay, hot internals, and the vessel continues to be transferred to the reactor coolant. The blowdown phase of t he transient ends when the RCS pressure falls to a value approachi ng 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 es sentially in adiabatic heatup. The balance of a ccumulator 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 ong oing 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 b ounded 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 th e beginning stages of reflood to fill the downcomer and lower ple num. The injection of the ECCS pumps aids during refill. Reflood and th e following long term heat removal are accomplished by water pumped into th e core by the ECCS pumps.
The accumulators are pressure vessels partially filled with bor ated water and pressurized with nitrogen gas. The accumulators are passiv e components, since no operator or control actions are required i n order for them to perform their function. Internal accumulator tank pres sure is
(continued)
CALLAWAY PLANT B 3.5.1-1 Revision 14 Accumulators B 3.5.1
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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 accumulat or line and is isolated from the RCS by a motor operated isolation valv e 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 accu mulators are adequate for this function is consistent with the LOCA assumption that the entire contents of one accumulator will be lost via th e RCS pipe break during the blowdown phase of the LOCA.
APPLICABLE The accumulators are assumed OPERABLE in both the large and sma ll 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 a re made concerning the availability of ECCS flow. In the early stages of a LOCA, with or without a loss of offsite power, the accumulators provi de the sole source of makeup water to the RCS. The assumption of loss of o ffsite 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 tim ed 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 brea k at the discharge of the reactor coolant pump. During this event, the accumulators discharge to the RC S as soon as RCS pressure decreases to below accumulator pressure.
As a conservative estimate, no credit is taken for ECCS pump fl ow until an effective delay has elapsed. This delay accounts for the di esels starting and the pumps being loaded and delivering full flow. The delay time is conservatively set with an additional 2 seconds to accou nt for SI signal generation. During this time, the accumulators are anal yzed as providing the sole source of emergency core cooling. No operat or action is assumed during the blowdown phase of a large break LOCA.
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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 s mall ANALYSES breaks, the rate of blowdown is such that the increase in fuel clad (continued) temperature is terminated primarily by the accumulators, with p umped 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 un til 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 foll owing a LOCA:
- a. Maximum fuel element cladding temperature is 2200°F;
- b. Maximum cladding oxidation is 0.17 times the total cladding thickness before oxidation;
- c. Maximum hydrogen generation from a zirconium water reaction i s 0.01 times the hypothetical amount that would be generated if a ll 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 con tained accumulator water volume is used. The contained water volume i s the same as the deliverable volume for the accumulators, since the accumulators are emptied, once discharged. For small breaks, a n 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 p ortion 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 specifi ed.
(continued)
CALLAWAY PLANT B 3.5.1-3 Revision 14 Accumulators B 3.5.1
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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 asse mbly insertion. A reduction in the accumulator minimum boron concen tration would produce a subsequent reduction in the available containment sump concentration for post LOCA shutdown and an increase in the max imum sump pH. The maximum boron concentration is used in determinin g the cold leg to hot leg recirculation switchover time and minimum sump pH.
The large and small break LOCA analyses are performed at the mi nimum nitrogen cover pressure, since sensitivity analyses have demons trated 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 pre serves accumulator integrity.
The effects on containment mass and energy releases from the accumulators are accounted for in the appropriate analyses (Ref s. 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 mi nimum conditions required to ensure that the accumulators are available to accomplish their core cooling saf ety function following a LOCA. Four accumulators are required to ensure that 100% of the contents of three of the accumulators will reach th e 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 violate d.
For an accumulator to be considered OPERABLE, the isolation val ve must be fully open, power removed above 1000 psig, and the limi ts established in the SRs for contained volume, boron concentratio n, and nitrogen cover pressure must be met.
(continued)
CALLAWAY PLANT B 3.5.1-4 Revision 14 Accumulators B 3.5.1
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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 dec reases, 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 2200°F.
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 fr om the RCS (Refs. 6 and 7). Accumulator isolation is only required when the accumulator pressure is greater than or equal to the maximum RC S 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 lim its, 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 Condi tion, the ability to maintain subcriticality or minimum boron precipitation time may be reduced. The boron in the accumulators contributes to the a ssumption that the combined ECCS water in the partially recovered core du ring the early reflooding phase of a large break LOCA is sufficient to k eep that portion of the core subcritical. One accumulator below the min imum boron concentration limit, howev er, 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 b oron in the saturated liquid that remains in the core. Even if the acc umulators 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 sta tus 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 a n
(continued)
CALLAWAY PLANT B 3.5.1-5 Revision 14 Accumulators B 3.5.1
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ACTIONS B.1 (continued)
insignificant effect on core damage frequency. In this Conditi on, the required contents of three accumulators cannot be assumed to re ach the core during a LOCA. Due to the severity of the consequences sh ould 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 o pen the valve, remove power to the valve, or restore the proper water v olume or nitrogen cover pressure ensures that prompt action will be take n to return the inoperable accumulator to OPERABLE status. The Completion Ti m e minimizes the potential for exposure of the plant to a LOCA und er 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 require d 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 c ondition 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 in jection 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 c hange with power removed, a closed valve could result in not meeting accident analyses assumptions. The Surveillance Frequency is based on o perating experience, equipment reliability, and plant risk and is contro lled under the Surveillance Frequency Control Program.
(continued)
CALLAWAY PLANT B 3.5.1-6 Revision 14 Accumulators B 3.5.1
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SURVEILLANCE SR 3.5.1.2 and SR 3.5.1.3 REQUIREMENTS (continued) Borated water volume and nitrogen cover pressure are verified f or each accumulator. Only one set of non-safety channels (1 of 2) is r equired 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.
The boron concentration should be verified to be within require d 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 reliabili ty, and plant risk and is controlled under the Surveillance Frequency C ontrol 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 d iluted since verifying that its boron concentration satisfies SR 3.5.4.3, because the water contained in the RWST is nominally within the accumul ator boron concentration requirements. This is consistent with the recommendation of NUREG-1366 (Ref. 4).
Verification that power is removed from each accumulator isolat ion valve operator when the RCS pressure is > 1000 psig ensures that an ac tive failure could not result in the undetected closure of an accumu lator motor operated isolation valve. If this were to occur, only two accu mulators would be available for injection given a single failure coincident with a LOCA. The Surveillance Frequency is based on operating experie nce, equipment reliability, and plant risk and is controlled under t he Surveillance Frequency Control Program.
REFERENCES 1. FSAR, Chapter 6.
- 2. 10 CFR 50.46.
- 3. FSAR, Chapter 15.
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CALLAWAY PLANT B 3.5.1-7 Revision 14 Accumulators B 3.5.1
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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 coolin g and negative reactivity to ensure that the reactor core is protected after a ny 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 t he loss of secondary coolant accident where primary cooldown could add eno ugh positive reactivity to achieve criticality and return to signif icant power.
There are three phases of ECCS operation: injection, cold leg recirculation, and hot leg recirculation. In the injection pha se, 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 s umps have enough water to supply the required net positive suction head t o the ECCS pumps, suction is switched to the containment sumps for co ld 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 s hifted 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 prec ipitation.
The ECCS consists of three separate subsystems: centrifugal charging (high head), safety injection (SI) (intermediate head), and res idual heat removal (RHR) (low head). Each subsystem consists of two redun dant, 100% capacity trains. The ECCS accumulators and the RWST are a lso 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 RC S following the accidents described in this LCO. The major compo nents of each subsystem are the centrifugal charging pumps, the RHR pumps, (continued)
CALLAWAY PLANT B 3.5.2-1 Revision 16 ECCS - Operating B 3.5.2
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BACKGROUND heat exchangers, and the SI pumps. (Note: The term centrifuga l 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 inje ction 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 interc onnected and redundant such that either train is capable of supplying 10 0% of the flow required to mitigate the accident consequences (Refs. 8 and 9). This interconnecting and redundant subsystem design provides the ope rators 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 s upplies water from the RWST to the ECCS pumps. Separate piping supplie s 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 discha rge 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 b alance the flow to the RCS. This balance ensures sufficient flow to the core t o meet the analysis assumptions following a LOCA in one of the RCS cold le gs.
For LOCAs that are too small to depressurize the RCS below the shutoff head of the SI pumps, the ECCS centrifugal charging pumps suppl y water until the RCS pressure decreases below the SI pump shutoff head. During this period, the steam generators are used to provide part of t he 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 t o supply borated water to the reactor core following increased heat remo val events, such as a main steam line break (MSLB). The limiting design co nditions occur when the negative moderator temperature coefficient is hi ghly negative, such as at the end of each cycle.
During low temperature conditions in the RCS, limitations are p laced 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 16 ECCS - Operating B 3.5.2
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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 s tart immediately in the programmed sequence. If offsite power is no t available, the Engineered Safety Feature (ESF) buses shed selec ted loads and are connected to the emergency diesel generators (EDG s).
Safeguard loads are then actuated in the programmed time sequence.
The time delay associated with diesel starting, sequenced loadi ng, and pump starting determines the time required before pumped flow i s 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 wate r 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 2200°F;
- b. Maximum cladding oxidation is 0.17 times the total cladding thickness before oxidation;
- c. Maximum hydrogen generation from a zirconium water reaction i s 0.01 times the hypothetical amount generated if all of the met al 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 pow er following an MSLB event and ensures that containment temperature limits a re met.
Each ECCS subsystem is taken credit for in a large break LOCA e vent 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 S I pumps are credited in a small break LOCA event. This event establish es the flow
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$33/,&$%/( and discharge head at the design point for the ECCS centrifugal charging 6$)(7< pumps. The SGTR and MSLB events also credit the ECCS centrifug al
$1$/<6(6 charging pumps. The OPERABILITY requirements for the ECCS are
FRQWLQXHG 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 containme nt. 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 ref loods the core.
The effects on containment mass and energy releases are account ed 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 S I 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 maxim um and minimum ranges of potential pump performance. These resistance s and ranges of pump performance are used to calculate the maximum an d minimum ECCS flows assumed in the safety analyses.
The CCP minimum flow SR in FSAR Section 16.5 provides the absol ute minimum injected flow (at zero RCS pressure) assumed in the saf ety analyses (305.25 gpm). The maximum total system resistance defi nes 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 must not be P d Z d Z RCS+[] Q 2()-
d greater than 1.004E-02 ft/gpm2, where Pd is pump discharge pressure in
FRQWLQXHG
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$33/,&$%/( feet, Zd is the pump discharge elevation in feet, Z RCS is RCS water level 6$)(7< elevation in feet, and Qd is the total pump flow rate in gpm.
$1$/<6(6
FRQWLQXHG The SI pump minimum flow SR in FSAR Section 16.5 provides the absolute minimum injected flow (at zero RCS pressure) assumed i n 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 injectio n pump total system resistance must not be greater than P d Z d Z RCS+[] Q 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 recirculati on 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. Th is value of flow includes a nominal 30 gpm of mini-flow. A best estimate increase of 16 gpm when aligned in the reci rculation 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 an d 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 imbal ance 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 uncertaint ies. 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).
FRQWLQXHG
CALLAWAY PLANT B 3.5.2-5 Revision 16 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, individua l components within the ECCS trains may be called upon to mitigate the conse quences of other transients and accidents.
In MODES 1, 2, and 3, an ECCS train consists of a centrifugal cha rging subsystem, an SI subsystem, and an RHR subsystem. Each train includes the piping, instruments, and controls to ensure an OPE RABLE flow path capable of taking suction from the RWST upon an SI si gnal and automatically transferring suction to the containment sump.
During an event requiring ECCS actuation, a flow path is requir ed to provide an abundant supply of water from the RWST to the RCS vi a the ECCS pumps and their respective supply headers to each of the f our cold leg injection nozzles. Either of the CCPs may be considered OPERABLE with its associated discharge to RCP seal throttle valve, BGHV8 357A or BGHV8357B, inoperable. In the long term, the injection flow path may be switched to take its supply from the containment sump and to su pply 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 fai lure can disable both ECCS trains.
As indicated in Note 1, the SI flow paths may be isolated for 2 h ours in MODE 3, under controlled conditions, to perform pressure isolati on 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 375 °F, 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 16 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 fo r 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 performan ce 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 pressur e 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 actuat ion 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 syst em 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 an d 9),
the inoperable components must be returned to OPERABLE status w ithin 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 reliabi lity evaluation (Ref. 5) and is a reasonable time for repair of many ECCS components.
(continued)
CALLAWAY PLANT B 3.5.2-7 Revision 16 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 th e 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 reli ability analysis (Ref. 5) has shown that the impact of having one full E CCS 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 disa ble both ECCS trains. With one or more component(s) inoperable suc h 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 statu s 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 16 ECCS - Operating B 3.5.2
BASES (Continued)
SURVEILLANCE SR 3.5.2.1 REQUIREMENTS Verification of proper valve position ensures that the flow pat h from the ECCS pumps to the RCS is maintained. Misalignment of these val ves could render both ECCS trains inoperable. Securing these valves in position by removal of power by the use of control hand-switche s ensures that they cannot change position as a result of an active failu re or be inadvertently misaligned. These valves are of the type, descri bed in Reference 6, that can disable the function of both ECCS trains a nd 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 accordanc e 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 un til EMHV8802A (or EMHV8802B)is reclosed.
Closure of EMHV8821A or EMHV8821B isolates the associated SI pump from its cold leg injection path rendering that train inoperabl e; however, the opposite train is prevented from exceeding runout flow cond itions which would occur if the opposite pump were connected to both cold leg and hot leg injection paths. The inoperable trains pump is th en placed in pull to lock to prevent unanalyzed hot leg injection via its as sociated 8802 valve. Although one SI train would be rendered inoperable, mor e 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.
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 posi tion, since these were verified to be in the correct position prior to lock ing, 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 te sting or
(continued)
CALLAWAY PLANT B 3.5.2-9 Revision 16 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 d r ai n v al v es 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 ind ividual at the system vent flow path who is in continuous communication with the operators in the control room. This individual will have a met hod to rapidly close the system vent flow path if directed.
The Surveillance Frequency is based on operating experience, eq uipment reliability, and plant risk and is controlled under the Surveil lance Frequency Control Program.
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. Prevent ing 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 nonconden sible gas into the reactor vessel. In conjunction with or in lieu of venting, Ultrasonic Testing (UT) may be performed to verify ECCS pumps a nd associated piping are sufficiently full of water.
The design of the ECCS centrifugal charging pump is such that s ignificant noncondensible gases do not collect in the pump. Therefore, it is unnecessary to require periodic pump casing venting to ensure t he 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 16 ECCS - Operating B 3.5.2
BASES
SURVEILLANCE SR 3.5.2.3 (continued)
REQUIREMENTS system maintenance or restoration. Susceptible locations depen d on plant and system configuration, such as standby versus operating cond itions.
The ECCS is OPERABLE when it is sufficiently filled with water.
Acceptance criteria are established for the volume of accumulat ed gas at susceptible locations. If accumulated gas is discovered that e xceeds 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 accumula ted gas (i.e., the system is sufficiently filled with water), the Surve illance 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 person nel safety.
For these locations alternative methods (e.g., operating parame ters, remote monitoring) may be used to monitor the susceptible locat ion.
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 trendi ng of the results should be sufficient to assure system OPERABILITY durin g 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, eq uipment reliability, and plant risk and is controlled under the Surveil lance Frequency Control Program.
(continued)
CALLAWAY PLANT B 3.5.2-11 Revision 16 ECCS - Operating B 3.5.2
BASES
SURVEILLANCE SR 3.5.2.4 REQUIREMENTS (continued) Periodic surveillance testing of ECCS pumps to detect gross deg radation caused by impeller structural damage or other hydraulic compone nt problems is required by the ASME Code. This type of testing ma y be accomplished by measuring the pump developed head at only one p oint 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 p ump 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 s ignal 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 Automati c Transfer signal coincident with an SI signal. In addition to t esting that automatic function, SR 3.5.2.5 demonstrates that the RWST to RH R pump suction isolation valves (BNHV8812A/B) are capable of auto matic 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 secur ed in the required position under administrative controls. The Surveilla nce Frequency is based on operating experience, equipment reliabili ty, and plant risk and is controlled under the Surveillance Frequency C ontrol Program. The actuation logic is tested as part of ESF Actuatio n System testing, and equipment performance is monitored as part of the INSERVICE TESTING PROGRAM.
The correct position of throttle valves in the flow path is nec essary for proper ECCS performance. These valves have mechanical stops to allow proper positioning for restricted flow to a ruptured cold leg, ensuring that
(continued)
CALLAWAY PLANT B 3.5.2-12 Revision 16 ECCS - Operating B 3.5.2
BASES
SURVEILLANCE SR 3.5.2.7 (continued)
REQUIREMENTS the other cold legs receive at least the required minimum flow. The Surveillance Frequency is based on operating experience, equipment reliability, and plant risk and is controlled under the Surveil lance 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 devi ces help to ensure that the following safety analyses assumptions remain valid:
(1) both the maximum and minimum total system resistance; (2) bot h the maximum and minimum branch injection line resistance; and (3) the maximum and minimum ranges of potential pump performance. Thes e resistances and pump performance ranges are used to calculate t he maximum and minimum ECCS flows assumed in the LOCA analyses of Reference 3.
Periodic inspections of the containment sump suction inlet ensure that it is unrestricted and stays in proper operating condition. The S urveillance Frequency is based on operating experience, equipment reliabili ty, and plant risk and is controlled under the Surveillance Frequency C ontrol 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 16 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 16 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 c ore 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 (RW ST) can be injected into the Reactor Coolant System (RCS) following a S BLOCA.
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 necessa ry 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 operati onal 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 fo llowing 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 clad ding 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 equi valent 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 d i c ta t e s that single failures are not considered during this MODE of ope ration. 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 suct ion 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 requir ed to (continued) provide an abundant supply of water from the RWST to the RCS vi a the ECCS pumps and their respective supply headers to a minimum of two cold leg injection nozzles. In the long term, this flow path m ay 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 he at removal, if capable of being manually realigned (remote or loca l) to the ECCS mode of operation and not otherwise inoperable. This allo ws 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 350°F, 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 r equirements.
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. Ther e is an increased risk associated with entering MODE 4 from MODE 5 w ith 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 a fter 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 immediat ely 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 h eat 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 alter nate method, such as use of the steam generators. The alternate mea ns of heat removal must continue until the inoperable RHR loop components can be restored to operation so that decay heat removal is cont inuous.
With both RHR pumps and heat exchangers inoperable, it would be unwise to require the plant to go to MODE 5, where the only avai lable heat removal system is the RHR. Therefore, the appropriate action i s 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 Even ts 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 on e 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 require d.
C.1
When the Required Actions of Condition B cannot be completed wit hin the required Completion Time, a controlled shutdown should be initi ated.
Twenty-four hours is a reasonable time, based on operating expe rience, 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 an d Volume Control System (CVCS) during abnormal operating conditions, to the refu eling pool during refueling, and to the ECCS and the Containment Spra y 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 inject ion phase of a loss of coolant accident (LOCA) recovery. A motor o perated isolation valve is provided in each pump suction branch line of f the common header to isolate the RWST from the ECCS once the system has been transferred to the recirculation mode. The recirculat ion mode is entered when pump suction is transferred to the containment sum p 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 r equired 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 f rom 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 injectio n (SI) and residual heat removal (RHR) pumps are aligned to take suction from the RWST.
The ECCS pumps are provided with recirculation lines that ensur e each pump can maintain minimum flow requirements when operating at o r near shutoff head conditions.
When the suction for the ECCS and Containment Spray System pump s 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 at mosphere 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 coo ling capacity when the transfer to the recirculation mode occurs. Improper b oron concentrations could result in a reduction of SDM or excessive boric acid precipitation in the core followi ng the LOCA, as well as excessive caustic stress corrosion of mechanical components and systems inside th e 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 pr ovides ANALYSES containment cooling and depressurization, core cooling, and rep lacement inventory and is a source of negative reactivity for reactor sh utdown (Ref. 1). The design basis transients and applicable safety analyses concerning each of these systems are discussed in the Applicabl e 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 volum e 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 del ivered.
The minimum boron concentration is an explicit assumption in the main steam line break (MSLB) analysis to ensure the required shutdow n capability. The minimum boron concentration limit is an important assumption in ensuring the required shutdown capability. The m aximum boron concentration is an explicit assumption in the inadverten t ECCS actuation analysis, although it is typically a non-limiting event and the results are very insensitive to boron concentrations. The maxi mum
(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 th e 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 in terlock between the VCT and RWST isolation valves, and the results show that the departure from nucleate boiling design basis is met. The d elay 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 afte r 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 necessar y to assure subcriticality. The large break LOCA is the limiting ca se 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 soluti on recirculated within containment after a LOCA. This pH level minimizes the evolution of iodine and minimizes the effect of chloride an d caustic stress corrosion on mechanical systems and components.
The upper limit on boron concentration of 2500 ppm is used to de termine the maximum allowable time to switch to hot leg recirculation f ollowing 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, t he containment spray temperature is assumed to be equal to the RWST lower temperature limit of 37 °F (Ref. 3). If the lower temperature limit is violated, the containment spray further reduces containment pre ssure, which decreases the rate at which steam can be vented out the b reak and increases peak clad temperature. The upper temperature limit of 100°F is used in the small break LOCA analysis and containment OPERABILITY analysis. Exceeding this temperature will result in a higher p eak 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. F or the containment response following an MSLB, the lower limit on boro n 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 LO CA, 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 Sy stem 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 c an 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 res tore the RWST temperature or boron concentration to within limits was de veloped considering the time required to change either the boron concentration or temperature and the fact that the contents of the tank are stil l 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 S ystem 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 ho ur 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 h ours.
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 wit hin the limits assumed in the accident analyses band. The Surveillance Frequency is based on operating experience, equipment reliabili ty, and plant risk and is controlled under the Surveillance Frequency C ontrol 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 b and, the RWST temperature should not exceed the limits.
The RWST water volume should be verified to be above the requir ed minimum level in order to ensure that a sufficient initial supp ly is available for injection and to support continued ECCS and Containment Spr ay System pump operation on recirculation. The Surveillance Frequ ency 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.
The boron concentration of the RWST should be verified to be wi thin 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 i n the core will not occur and the effect of chloride and caustic stress co rrosion on mechanical systems and components will be minimized. The Surveillance Frequency is based on operating experience, equipment reliabili ty, and plant risk and is controlled under the Surveillance Frequency C ontrol 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 func tion 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 c entrifugal 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 injecti on path following an accident. This limit is based on safety analysis assumptions that are required because RCP seal injection flow is not isolat ed during SI.
APPLICABLE All ECCS subsystems are taken credit for in the large break los s of SAFETY coolant accident (LOCA) at full power (Ref. 1). The LOCA analys is ANALYSES establishes the minimum flow for the ECCS pumps. The ECCS cent rifugal 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 t otal system resistance; (2) both the maximum and minimum branch injection line resistance; and (3) the maximum and minimum ranges of poten tial pump performance. These resistances and ranges of pump perform ance 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 uncertain ties.
The Bases for LCO 3.5.2, "ECCS - Operating," contain additional discussion on the safety analyses. The steam generator tube rup ture 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 o f 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 subcritica l. For smaller LOCAs, the ECCS centrifugal charging pumps alone deliver sufficient fluid to overcome the loss and maintain RCS inventor y. 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 ensu re 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 re sistance, a pressure and flow must be known. The flow line resistance is e stablished 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 o ne ECCS centrifugal charging pump (CCP) operating at 550 gpm on its max imum 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 Techn ical 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 di fference from BGPT0120 to the pressurizer steam space pressure as a func tion 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 p ressure drop from BGPT0120 to the seal injection connection. In additi o n, 2 p s i d i s added to accommodate instrument uncertainty in the pressure dro p measurement. An additional 4 psid has been conservatively adde d to the required pressure differential to allow for seal injection filt er 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 allow s for post-surveillance filter change out with no differential pressure re striction.
Once set, the throttle valves are secured with locking devices and mechanical position stops. These devices help to ensure that t he following safety analyses assumptions remain valid: (1) both th e maximum and minimum total system resistance; (2) both the maximum and minimum branch injection line resistance; and (3) the maximu m and minimum ranges of potential pump performance. These resistance s 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 the se 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 oper ator 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 min imizes the potential exposure of the plant to a LOCA with insufficient injection flow and provides a reasonable time to restore seal injection f low 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 require d 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 pl ant safety systems or operators. Continuing the plant shutdown beg un 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 in jection throttle valve position, and hence, proper seal injection flow, is maintained.
The seal water injection throttle valves are set to ensure prop er flow resistance and pressure drop in the piping to each injection po int in the event of a LOCA.
The seal injection flow line resistance is established by adjus ting 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. Thi s accident analysis limit is met by positioning the valves so tha t 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 di fference from BGPT0120 to the pressurizer steam space pressure as a func tion 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 p ressure drop from BGPT0120 to the seal injection connection. In additi o n, 2 p s i d i s added to accommodate instrument uncertainty in the pressure dro p measurement. An additional 4 psid has been conservatively adde d to the required pressure differential to allow for seal injection filt er 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 allow s for post-surveillance filter change out with no differential pressure re striction.
Once set, these throttle valves a re 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 unti l 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 c orrectly. 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