ULNRC-06781, Attachment 2 - Proposed TS Bases Changes (Markups)
| ML22335A511 | |
| Person / Time | |
|---|---|
| Site: | Callaway  |
| Issue date: | 12/01/2022 |
| From: | Ameren Missouri, Union Electric Co |
| To: | Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML22335A507 | List: |
| References | |
| ULNRC-06781 | |
| Download: ML22335A511 (1) | |
Text
Proposed TSBases Changes (Markup s)
RCS Loops - MODE 5, Loops Not Filled B 3.4.8
B 3.4 REACTOR COOLANT SYSTEM (RCS)
B 3.4.8 RCS Loops - MODE 5, Loops Not Filled
BASES
BACKGROUND In MODE 5 with the RCS loops not filled, the primary function of the reactor coolant is the removal of decay heat generated in the fuel, and the transfer of this heat to the component cooling water via the residual heat removal (RHR) heat exchangers. The steam generators (SGs) are not available as a heat sink when the loops are not filled. The se condary function of the reactor coolant is to act as a carrier for the soluble neutron poison, boric acid.
In MODE 5 with loops not filled, only RHR pumps can be used for coolant circulation. The number of pumps in operation can vary to suit the operational needs. The intent of this LCO is to provide forced flow from at least one RHR pump for decay heat removal and transport and to require that two paths be available to provide redundancy for heat removal.
During RHR system operation, heat is removed from the RCS by circulating reactor coolant through the RHR heat exchangers whe re the heat is transferred to the Component Cooling Water System. The heat sink for the Component Cooling Water System is in turn normally prov ided by the Service Water System or Essential Service Water System, as determined by system availability.
APPLICABLE In MODE 5, RCS circulation is considered in the determination of the time SAFETY available for mitigation of the accidental boron dilution event. The flow ANALYSES provided by one RHR loop is adequate for decay heat removal.
The operation of one RCP in MODES 3, 4, and 5 provides adequate f low to ensure mixing, prevent stratification, and produce gradual r eactivity changes during RCS boron concentration reductions. The reactivity change rate associated with boron reduction will, therefore, be within the transient mitigation capability of the Boron Dilution Mitigatio n System (BDMS). With no reactor coolant loop in operation in either MO DES 3, 4, or 5, boron dilutions must be terminated and all dilution sources isolated.
The boron dilution analysis in these MODES takes credit for the mixing volume associated with having at least one reactor coolant loop in operation. LCO 3.3.9, "Boron Dilution Mitigation System (BDMS),"
contains the requirements for the BDMS.
RCS loops in MODE 5 (loops not filled) satisfies Criterion 4 of 10CFR50.36(c)(2)(ii).
(continued)
CALLAWAY PLANT B 3.4.8-1 Revision 13 RCS Loops - MODE 5, Loops Not Filled B 3.4.8
BASES (Continued)
LCO The purpose of this LCO is to require that at least two RHR loops be OPERABLE and one of these loops be in operation. An OPERABLE loop is one that has the capability of transferring heat from the reactor coolant at a contro lled rate. Heat cannot be removed via the RHR System unless forced flow is used. A minimum of one running RHR pump meets the LCO requirement for one loop in operation. An additional RHR loop is required to be OPERABLE to meet single failure considerations.
Note 1 permits all RHR pumps to be removed from operation for 1hour.
The circumstances for stopping both RHR pumps are to be limited to situations when the outage time is short and core outlet temperature is maintained at least 10°F below saturation temperature. The Note prohibits boron dilution with coolant at boron concentrations less than required to assure the SDM of LCO 3.1.1 is maintained or draining operations when RHR forced flow is stopped. Introduction of reactor makeup water into the RCS from the Chemical and V olume Control System mixing tee is not permitted, operation of CVCS resin vessels configured with resin for dilution during normal operation is not permitted, and operatio n of the purge line associated with flushing the CVCS letdown radiation monitor is not permitted when no RCS loop is in operation. Note that CVCS resin vessels include the resin vessels of its subsyste m the BTRS.
Note 2 allows one RHR loop to be inoperable for a period of 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />, provided that the other loop is OPERABLE and in operation. This permits periodic surveillance tests to be performed on the inoperable l oop during the only time when these tests are safe and possible.
An OPERABLE RHR loop is comprised of an OPERABLE RHR pump capable of providing forced flow to an OPERABLE RHR heat exchanger.
RHR pumps are OPERABLE if they are capable of being powered and a re able to provide flow if required.
Electrical power source and distribution requirements for the RHR loops are as specified per LCO 3.8.2, AC Sources - Shutdown; LCO 3.8.5, DC Sources - Shutdown; LCO 3.8.8, Inverters - Shutdown, and LCO 3.8.10, Distribution Systems - Shutdown, consistent with the Bases for those Technical Specifications for reduced requirements during shutdown conditions, subject to the provisions and limitations described in the Bases.
Management of gas voids is important to RHR System OPERABILITY.
The RHR System is OPERABLE when it is sufficiently filled with water to perform its specified safety function.
(continued)
CALLAWAY PLANT B 3.4.8-2 Revision 13 RCS Loops - MODE 5, Loops Not Filled B 3.4.8
BASES (Continued)
APPLICABILITY In MODE 5 with loops not filled, this LCO requires core heat removal and coolant circulation by the RHR System.
Operation in other MODES is covered by:
LCO 3.4.4, "RCS Loops - MODES 1 and 2";
LCO 3.4.5, "RCS Loops - MODE 3";
LCO 3.4.6, "RCS Loops - MODE 4";
LCO 3.4.7, "RCS Loops - MODE 5, Loops Filled";
LCO 3.9.5, "Residual Heat Removal (RHR) and Coolant Circulation - High Water Level" (MODE 6); and LCO 3.9.6, "Residual Heat Removal (RHR) and Coolant Circulation - Low Water Level" (MODE 6).
Since LCO 3.4.8 contains Required Actions with immediate Completion Times, it is not permitted to enter LCO 3.4.8 from either LCO 3.4.7, "RCS Loops - MODE 5, Loops Filled" or from MODE 6 unless the requirements of LCO 3.4.8 are met.
ACTIONS A.1
If only one RHR loop is OPERABLE and in operation, redundancy for RHR is lost. Action must be initiated to restore a second loop to OPERABLE status. The immediate Completion Time reflects the importance of maintaining the availability of two paths for heat removal.
B.1 and B.2
If no required RHR loops are OPERABLE or in operation, except during conditions permitted by Note 1, all operations involving introduction of coolant, into the RCS, with boron concentration less than requi red to meet the minimum SDM of LCO 3.1.1 must be suspended and action must be initiated immediately to restore an RHR loop to OPERABLE status and operation. Boron dilution requires forced circulation from at least one RCP for proper mixing so that inadvertent criticality can be preven ted.
Suspending the introduction of coolant, into the RCS, with boro n concentration less than required to meet the minimum SDM of LCO 3.1.1 is required to assure continued safe operation. With coolant added without forced circulation, unmixed coolant could be introduced to the core, however coolant added with boron concentration meeting the minimum SDM maintains acceptable margin to subcritical operatio ns.
Introduction of reactor makeup water into the RCS from the Chem ical and Volume Control System mixing tee is not permitted, operation of CVCS (continued)
CALLAWAY PLANT B 3.4.8-3 Revision 13 RCS Loops - MODE 5, Loops Not Filled B 3.4.8
BASES
ACTIONS B.1 and B.2 (continued)
resin vessels configured with resin for dilution during normal operation is not permitted, and operation of the purge line associated with flushing the CVCS letdown radiation monitor is not permitted when the RCS lo ops are not filled or when no RCS loop is in operation, consistent with Required Action C.1 of LCO 3.3.9, Boron Dilution Mitigation System (BDM S). The immediate Completion Time reflects the importance of maintainin g operation for heat removal. The action to restore must continu e until one loop is restored to OPERABLE status and operation.
SURVEILLANCE SR 3.4.8.1 REQUIREMENTS This SR requires verification that one loop is in operation. Verification may include flow rate, temperature, or pump status monitoring, which help ensure that forced flow is providing heat removal. The Surveillance Frequency is based on operating experience, equipment reliability, and plant risk and is controlled under the Surveillance Frequency Control Program.
Verification that a second RHR pump is OPERABLE ensures that an additional pump can be placed in operation, if needed, to maint ain decay heat removal and reactor coolant circulation. Verification is performed by verifying proper breaker alignment and power available to the R HR pump.
The Surveillance Frequency is based on operating experience, equipment reliability, and plant risk and is controlled under the Surveil lance Frequency Control Program.
RHR System piping and components have the potential to develop voids and pockets of entrained gases. Preventing and managing gas intrusion and accumulation is necessary for proper operation of the RHR loops and may also prevent water hammer, pump cavitation, and pumping of noncondensible gas into the reactor vessel.
Selection of RHR System locations susceptible to gas accumulati on is based on a review of system design information, including pipin g 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
(continued)
CALLAWAY PLANT B 3.4.8-4 Revision 13 RCS Loops - MODE 5, Loops Not Filled B 3.4.8
BASES
SURVEILLANCE SR 3.4.8.3 (continued)
REQUIREMENTS and orientation of important components that can become sources of gas or could otherwise cause gas to be trapped or difficult to remove during system maintenance or restoration. Susceptible locations depen d on plant and system configuration, such as standby versus operating cond itions.
The RHR System 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 RHR System is not rendered inoperable by the accumulat ed 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.
RHR System locations susceptible to gas accumulation are monitored, and if gas is found, the gas volume is compared to the acceptan ce criteria for the location. Susceptible locations in the same system flow path which are subject to the same gas intrusion mechanisms may be verifie d 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.
REFERENCES 1. FSAR Section 15.4.6.
CALLAWAY PLANT B 3.4.8-5 Revision 13 CRACS B 3.7.11
B 3.7 PLANT SYSTEMS
B 3.7.11 Control Room Air Conditioning System (CRACS)
BASES
BACKGROUND The CRACS provides temperature control for the control room.
The CRACS consists of two independent and redundant trains that provide cooling of recirculated control room air. Each train consists of a prefilter, self-contained refrigeration system (using essential service water as a heat sink), centrifugal fans, instrumentation, and control s to provide for control room temperature control. The CRACS is a subsystem to the CREVS, described in LCO 3.7.10, providing air temperature control for the control room.
The CRACS is an emergency system, which also operates during no rmal unit operations. A single train will provide the required temp erature control to maintain the control room 84°F. The CRACS operation in maintaining the control room temperature is discussed in the FSAR, Section 9.4.1 (Ref. 1).
APPLICABLE The design basis of the CRACS is to maintain the control room SAFETY temperature for 30 days of continuous occupancy.
ANALYSES The CRACS components are arranged in redundant, safety related trains.
During normal or emergency operations, the CRACS maintains the temperature 84° F. A single active failure of a component of the CRACS, with a loss of offsite power, does not impair the ability of th e system to perform its design function. Redundant detectors and controls are provided for control room temperature control. The CRACS is de signed in accordance with Seismic Category I requirements. The CRACS i s capable of removing sensible and latent heat loads from the con trol room, which include consideration of equipment heat loads and personnel occupancy requirements, to ensure equipment OPERABILITY.
The CRACS satisfies Criterion 3 of 10 CFR 50.36(c)(2)(ii).
LCO Two independent and redundant trains of the CRACS are req uired to be OPERABLE to ensure that at least one is available, assuming a s ingle failure disabling the other train. Total system failure could result in the equipment operating temperature exceeding limits in the event o f an accident.
(continued)
CALLAWAY PLANT B 3.7.11-1 Revision 10 CRACS B 3.7.11
BASES
LCO The CRACS is considered to be OPERABLE when the individual (continued) components necessary to maintain the control room temperature are OPERABLE in both trains. These components include the refriger ation compressors, heat exchangers, cooling coils, fans, and associat ed temperature control instrumentation. In addition, the CRACS mu st be operable to the extent that air circulation can be maintained. Isolation or breach of the CRACS air flow path can also render the CREVS flo wpath inoperable. In these situations, LCO 3.7.10 would also be applicable.
APPLICABILITY In MODES 1, 2, 3, 4, 5, and 6, and during movement of irradiated fuel assemblies, the CRACS must be OPERABLE to ensure that the contr ol room temperature will not exceed equipment operational requirements.
ACTIONS A.1
With one CRACS train inoperable, action must be taken to restore OPERABLE status within 30 days. In this Condition, the remainin g OPERABLE CRACS train is adequate to maintain the control room temperature within limits. However, the overall reliability is reduced because a single failure in the OPERABLE CRACS train could result in a loss of CRACS function. The 30 day Completion Time is based on the low probability of an event requi ring control room isolation and the consideration that the remaining train can provide the required protection.
B.1 and B.2
In MODE 1, 2, 3, or 4, if the inoperable CRACS train cannot be re stored to OPERABLE status within the required Completion Time, the uni t must be placed in a MODE that minimizes the risk. To achieve this status, the unit must be placed in 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 in MODE5 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, b ased on operating experience, to reach the required unit conditions from full power conditions in an orderly manner and without challenging u nit systems.
C.1. C.2.1, and C.2.2
In MODE 5 or 6, or during movement of irradiated fuel, if the ino perable CRACS train cannot be restored to OPERABLE status within the re quired Completion Time, the OPERABLE CRACS train must be placed in operation immediately. This action ensures that the remaining train is OPERABLE, that no failures preventing automatic actuation will occur, (continued)
CALLAWAY PLANT B 3.7.11-2 Revision 10 CRACS B 3.7.11
BASES
ACTIONS C.1.1, C.1.2, C.2.1, and C.2.2 (continued)
and that active failures will be readily detected.
An alternative to Required Action C.1 is to immediately suspend activities that present a potential for releasing radioactivity that might require isolation of the control room. This places the unit in a condi tion that minimizes accident risk. This does not preclude the movement o f fuel to a safe position.
D.1 and D.2
In MODE 5 or 6, or during movement of irradiated fuel assemblies, with two CRACS trains inoperable, action must be taken immediately t o suspend activities that could result in a release of radioactiv ity that might require isolation of the control room. This places the unit in a condition that minimizes risk. This does not preclude the movement of fuel to a safe position.
E.1
If both CRACS trains are inoperable in MODE 1, 2, 3, or 4, the CR ACS may not be capable of performing its intended function. Therefore, LCO 3.0.3 must be entered immediately.
SURVEILLANCE SR 3.7.11.1 REQUIREMENTS This SR verifies that the heat removal capability of the CRACS air conditioning units is adequate to remove the heat load assumed in the control room during design basis accidents. This SR consists of verifying the heat removal capability of the condenser heat exchanger (ei ther through performance testing or inspection), ensuring the proper operation of major components in the refrigeration cycle and verification of unit air flow capacity. The Surveillance Frequency is based on operating experience, equipment reliability, and plant risk and is contro lled under the Surveillance Frequency Control Program.
REFERENCES 1. FSAR, Section 9.4.1, Control Building HVAC.
CALLAWAY PLANT B 3.7.11-3 Revision 10 RHR and Coolant Circulation - Low Water Level B 3.9.6
B 3.9 REFUELING OPERATIONS
B 3.9.6 Residual Heat Removal (RHR) and Coolant Circulation - Low Water Level
BASES
BACKGROUND The purpose of the RHR System in MODE 6 is to remove decay heat and the stored thermal energy of the reactor coolant system, as req uired by GDC 34, to provide mixing of borated coolant, and to prevent bor on stratification (Ref. 1). Heat is removed from the RCS by circulating reactor coolant through the RHR heat exchangers where the heat is transferred to the Component Cooling Water System (The heat sink for the Component Cooling Water System is in turn normally provided by the Servic e Water System or Essential Service Water System, as determined by system availability). The coolant is then returned to the RCS via the RCS cold leg(s). Operation of the RHR System for normal cooldown decay heat removal is manually accomplished from the control room. The he at removal rate is adjusted by controlling the flow of reactor coo lant through the RHR heat exchanger(s) and the bypass lines. Mixing of the reactor coolant is maintained by this continuous circulation of reactor coolant through the RHR System.
APPLICABLE If the reactor coolant temperature is not maintained below 200 °F, boiling of SAFETY the reactor coolant could result. This could lead to a loss of coolant in the ANALYSES reactor vessel. Additionally, boiling of the reactor coolant could lead to boron plating out on components near the areas of the boiling a ctivity. The loss of reactor coolant and the subsequent plate out of boron w ill eventually challenge the integrity of the fuel cladding, which is a fission product barrier. Two trains of the RHR System are required to be OPERABLE, and one train in operation, in order to prevent this challenge.
The RHR System is retained as a Specification because it meets Criterion 4 of 10 CFR 50.36(c)(2)(ii).
LCO In MODE 6, with the water level < 23 ft above the top of the reactor vessel flange, both RHR loops must be OPERABLE.
Additionally, one loop of RHR must be in operation in order to provide:
- a. Removal of decay heat;
- b. Mixing of borated coolant to minimize the possibility of criticality; and
(continued)
CALLAWAY PLANT B 3.9.6-1 Revision 13 RHR and Coolant Circulation - Low Water Level B 3.9.6
BASES
LCO c. Indication of reactor coolant temperature.
(continued)
An OPERABLE RHR loop consists of an RHR pump, a heat exchanger, valves, piping, instruments and controls to ensure an OPERABLE flow path and to determine the RCS temperature. The flow path starts in one of the RCS hot legs and is returned to the RCS cold legs. An OPER ABLE RHR loop must be capable of being realigned to provide an OPERA BLE flow path. In addition, management of gas voids is important t o RHR System OPERABILITY. The RHR System is OPERABLE when it is sufficientlly filled with water to perform its specified safety function.
The standby RHR train may be aligned to the Refueling Water Storage Tank to support filling or draining the refuel pool or for the performance of required testing as long as the motor-operated valves EJHV8716A and EJHV8809A are maintained OPERABLE for Train A OPERABILITY and EJHV8716B and EJHV8809B are maintained OPERABLE for Train B OPERABILITY during refuel pool draining. These respective valv es plus EJHV8840 must be maintained OPERABLE during refuel pool filling. The standby RHR train may be considered OPERABLE with BN8717 (RHR return to RWST) open as long as it can be isolated by EJHV8716A or B and EJHV8809A or B can be opened to realign the pump discharge to the RCS cold legs. Caution must be exercised whenever BN8717 is open to ensure the operating RHR train's EJHV8716 valve is maintained closed.
This is to prevent draining the RCS to the RWST. See Reference 3.
Electrical power source and distribution requirements for the R HR loops are as specified per LCO 3.8.2, "AC Sources - Shutdown"; LCO 3.8.5, "DC Sources - Shutdown"; LCO 3.8.8, "Inverters - Shutdown," and LCO 3.8.10, "Distribution Systems - Shutdown," consistent with the Bases for those Technical Specifications for reduced requirements during shutdown conditions, subject to the provisions and limitations described in the Bases.
APPLICABILITY Two RHR loops are required to be OPERABLE, and one RHR loop must be in operation in MODE 6, with the water level < 23 ft above the top of the reactor vessel flange, to provide decay heat removal. Requirem ents for the RHR System in other MODES are covered by LCOs in Section 3.4,
Reactor Coolant System (RCS), and Section 3.5, "Emergency Core Cooling Systems (ECCS)." RHR loop requirements in MODE 6 with the water level 23 ft are located in LCO 3.9.5, "Residual Heat Removal (RHR) and Coolant Circulation - High Water Level." Additional RHR loop requirements in MODE 6 with the water level 23 feet above the top of the reactor vessel flange are located in FSAR 16.1.2.1, Flow Path-Shutdown Limiting Condition For Operation.
(continued)
CALLAWAY PLANT B 3.9.6-2 Revision 13 RHR and Coolant Circulation - Low Water Level B 3.9.6
BASES
APPLICABILITY Since LCO 3.9.6 contains Required Actions with immediate Completion (continued) Times related to the restoration of the degraded decay heat rem oval function, it is not permitted to enter this LCO from either MOD E 5 or from LCO 3.9.5, "RHR and Coolant Circulation-High Water Level" unless the requirements of LCO 3.9.6 are met.
ACTIONS A.1 and A.2
If less than the required number of RHR loops are OPERABLE, action shall be immediately initiated and continued until the RHR loop is restored to OPERABLE status and restored to operation in accordance with the LCO or until 23 ft of water level is established above the reactor vessel flange. When the water level is 23 ft above the reactor vessel flange, the Applicability changes to that of LCO 3.9.5, and only one RHR loop is required to be OPERABLE and in operation. An immediate Complet ion Time is necessary for an operator to initiate corrective action s.
B.1
If no RHR loop is in operation, there will be no forced circula tion to provide mixing to establish uniform boron concentrations. Susp ending positive reactivity additions that could result in failure to meet the minimum boron concentration limit is required to assure continu ed safe operation. Introduction of coolant inventory must be from sour ces that have a boron concentration greater than that required in the RCS for minimum refueling boron concentration. This may result in an overall reduction in RCS boron concentration, but provides acceptable m argin to maintaining a subcritical operation. Administrative controls a re placed on refueling decontamination activities (See Bases for LCO 3.9.1).
B.2
If no RHR loop is in operation, actions shall be initiated immediately, and continued, to restore one RHR loop to operation. Since the uni t is in Conditions A and B concurrently, the restoration of two OPERABLE RHR loops and one operating RHR loop should be accomplished expeditiously.
(continued)
CALLAWAY PLANT B 3.9.6-3 Revision 13 RHR and Coolant Circulation - Low Water Level B 3.9.6
BASES
ACTIONS B.3 (continued)
If no RHR loop is in operation, all containment penetrations pr oviding direct access from the containment atmosphere to the outside atmosphere must be closed within 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />. With the RHR loop requirements not met, the potential exists for the coolant to b oil and release radioactive gas to the containment atmosphere. Closing containment penetrations that are open to the outside atmospher e ensures that dose limits are not exceeded.
The Completion Time of 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> is reasonable at water levels abo ve reduced inventory, based on the low probability of the coolant boiling in that time. At reduced inventory conditions, additional actions are taken to provide containment closure in a reduced period of time (Refere nce 2).
Reduced inventory is defined as RCS level lower than 3 feet belo w the reactor vessel flange.
SURVEILLANCE SR 3.9.6.1 REQUIREMENTS This Surveillance demonstrates that one RHR loop is in operation and circulating reactor coolant. The flow rate is determined by th e flow rate necessary to provide sufficient decay heat removal capability a nd to prevent thermal and boron stratification in the core. The Surv eillance Frequency is based on operating experience, equipment reliability, and plant risk and is controlled under the Surveillance Frequency Control Program.
Verification that the required pump is OPERABLE ensures that an additional RHR pump can be placed in operation, if needed, to maintain decay heat removal and reactor coolant circulation. Verificati on is performed by verifying proper breaker alignment and power avail able to the required pump. The Surveillance Frequency is based on operating experience, equipment reliability, and plant risk and is contro lled under the Surveillance Frequency Control Program.
RHR System piping and components have the potential to develop voids and pockets of entrained gases. Preventing and managing gas intrusion and accumulation is necessary for proper operation of the RHR l oops and (continued)
CALLAWAY PLANT B 3.9.6-4 Revision 13 RHR and Coolant Circulation - Low Water Level B 3.9.6
BASES
SURVEILLANCE SR 3.9.6.3 (continued)
REQUIREMENTS may also prevent water hammer, pump cavitation, and pumping of noncondensible gas into the reactor vessel.
Selection of RHR System locations susceptible to gas accumulation is based on a review of system design information, including pipin g 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 system maintenance or restoration. Susceptible locations depen d on plant and system configuration, such as standby versus operating cond itions.
The RHR System 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 RHR System is not rendered inoperable by the accumulat ed 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.
RHR System locations susceptible to gas accumulation are monitored, and if gas is found, the gas volume is compared to the acceptan ce criteria for the location. Susceptible locations in the same system flow path which are subject to the same gas intrusion mechanisms may be verifie d 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.
(continued)
CALLAWAY PLANT B 3.9.6-5 Revision 13 RHR and Coolant Circulation - Low Water Level B 3.9.6
BASES
SURVEILLANCE SR 3.9.6.3 (continued)
REQUIREMENTS The Surveillance Frequency is controlled under the Surveillance Frequency Control Program. The Surveillance Frequency may vary by location susceptible to gas accumulation.
REFERENCES 1. FSAR, Section 5.4.7.
- 2. Generic Letter No. 88-17, "Loss of Decay Heat Removal."
- 3. RFR-15632A.
CALLAWAY PLANT B 3.9.6-6 Revision 13