ML22335A511
| 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
Attachment 2 to ULNRC-06781 Page 1 of 15 Proposed TS Bases Changes (Markups) to ULNRC-06781 Page 2 of 15 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 secondary 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 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 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 flow to ensure mixing, prevent stratification, and produce gradual reactivity 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 Mitigation System (BDMS). With no reactor coolant loop in operation in either MODES 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
Attachment 2 to ULNRC-06781 Page 3 of 15 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 controlled 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 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />.
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 Volume Control System mixing tee is not permitted, operation of CVCS resin vessels configured with resin for Cooling water for the RHR dilution during normal operation is not permitted, and operation of the loops is provided by the purge line associated with flushing the CVCS letdown radiation monitor is Component Cooling Water not permitted when no RCS loop is in operation. Note that CVCS resin System. The heat sink for the vessels include the resin vessels of its subsystem the BTRS.
Component Cooling Water 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 />, System is the Service Water provided that the other loop is OPERABLE and in operation. This permits System or Essential Service periodic surveillance tests to be performed on the inoperable loop during Water System, as determined the only time when these tests are safe and possible.
by system availability and plant operational constraints An OPERABLE RHR loop is comprised of an OPERABLE RHR pump during MODE 5. Specifically, capable of providing forced flow to an OPERABLE RHR heat exchanger.
one train of the Service Water RHR pumps are OPERABLE if they are capable of being powered and are System may serve as the able to provide flow if required.
heat sink for one of the two Electrical power source and distribution requirements for the RHR loops required RHR loops, provided are as specified per LCO 3.8.2, AC Sources - Shutdown; LCO 3.8.5, that one train of the Essential DC Sources - Shutdown; LCO 3.8.8, Inverters - Shutdown, and LCO Service Water System serves 3.8.10, Distribution Systems - Shutdown, consistent with the Bases for as the heat sink for the other those Technical Specifications for reduced requirements during shutdown RHR loop. 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 to ULNRC-06781 Page 4 of 15 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 required 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 prevented.
Suspending the introduction of coolant, into the RCS, with boron 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 operations.
Introduction of reactor makeup water into the RCS from the Chemical and Volume Control System mixing tee is not permitted, operation of CVCS (continued)
CALLAWAY PLANT B 3.4.8-3 Revision 13 to ULNRC-06781 Page 5 of 15 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 loops 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 (BDMS). The immediate Completion Time reflects the importance of maintaining operation for heat removal. The action to restore must continue 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.
SR 3.4.8.2 Verification that a second RHR pump is OPERABLE ensures that an additional pump can be placed in operation, if needed, to maintain decay heat removal and reactor coolant circulation. Verification is performed by verifying proper breaker alignment and power available to the RHR pump.
The Surveillance Frequency is based on operating experience, equipment reliability, and plant risk and is controlled under the Surveillance Frequency Control Program.
SR 3.4.8.3 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 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 (continued)
CALLAWAY PLANT B 3.4.8-4 Revision 13 to ULNRC-06781 Page 6 of 15 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 depend on plant and system configuration, such as standby versus operating conditions.
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 accumulated gas (i.e., the system is sufficiently filled with water), the Surveillance may be declared met. Accumulated gas should be eliminated or brought within the acceptance criteria limits.
RHR System locations susceptible to gas accumulation are monitored, and if gas is found, the gas volume is compared to the acceptance criteria for the location. Susceptible locations in the same system flow path which are subject to the same gas intrusion mechanisms may be verified by monitoring a representative subset of susceptible locations. Monitoring may not be practical for locations that are inaccessible due to radiological or environmental conditions, the plant configuration, or personnel safety.
For these locations alternative methods (e.g., operating parameters, remote monitoring) may be used to monitor the susceptible location.
Monitoring is not required for susceptible locations where the maximum potential accumulated gas void volume has been evaluated and determined to not challenge system OPERABILITY. The accuracy of the method used for monitoring the susceptible locations and trending of the results should be sufficient to assure system OPERABILITY during the Surveillance interval.
The Surveillance Frequency is controlled under the Surveillance Frequency Control Program. The Surveillance Frequency may vary by location susceptible to gas accumulation.
REFERENCES 1. FSAR Section 15.4.6.
CALLAWAY PLANT B 3.4.8-5 Revision 13 to ULNRC-06781 Page 7 of 15 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 controls 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 normal unit operations. A single train will provide the required temperature 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 the system to perform its design function. Redundant detectors and controls are provided for control room temperature control. The CRACS is designed in accordance with Seismic Category I requirements. The CRACS is capable of removing sensible and latent heat loads from the control 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 required to be OPERABLE to ensure that at least one is available, assuming a single failure disabling the other train. Total system failure could result in the equipment operating temperature exceeding limits in the event of an accident.
(continued)
CALLAWAY PLANT B 3.7.11-1 Revision 10
Attachment 2 to ULNRC-06781 Page 8 of 15 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 refrigeration compressors, heat exchangers, cooling coils, fans, and associated temperature control instrumentation. In addition, the CRACS must 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 flowpath 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 control Cooling water for the room temperature will not exceed equipment operational requirements.
CRACS trains is provided by the Service Water System or Essential ACTIONS A.1 Service Water System, as determined by system With one CRACS train inoperable, action must be taken to restore availability and plant OPERABLE status within 30 days. In this Condition, the remaining operational constraints OPERABLE CRACS train is adequate to maintain the control room temperature within limits. However, the overall reliability is reduced during MODES 5 and 6.
because a single failure in the OPERABLE CRACS train could result in a Specifically, in MODES 5 loss of CRACS function. The 30 day Completion Time is based on the and 6, and during low probability of an event requiring control room isolation and the movement of irradiated consideration that the remaining train can provide the required protection.
fuel, one train of the Service Water System may serve as the heat sink for B.1 and B.2 one of the two required In MODE 1, 2, 3, or 4, if the inoperable CRACS train cannot be restored CRACS trains, provided to OPERABLE status within the required Completion Time, the unit must that one train of the be placed in a MODE that minimizes the risk. To achieve this status, the Essential Service Water 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 MODE 5 System serves as the heat within 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />. The allowed Completion Times are reasonable, based sink for the other CRACS on operating experience, to reach the required unit conditions from full train. power conditions in an orderly manner and without challenging unit systems.
C.1. C.2.1, and C.2.2 In MODE 5 or 6, or during movement of irradiated fuel, if the inoperable CRACS train cannot be restored to OPERABLE status within the required 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 to ULNRC-06781 Page 9 of 15 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 condition that minimizes accident risk. This does not preclude the movement of 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 to suspend activities that could result in a release of radioactivity 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 CRACS 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 (either 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 controlled 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 to ULNRC-06781 Page 10 of 15 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 required by GDC 34, to provide mixing of borated coolant, and to prevent boron 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 Service 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 heat removal rate is adjusted by controlling the flow of reactor coolant 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 activity. The loss of reactor coolant and the subsequent plate out of boron will 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
Attachment 2 to ULNRC-06781 Page 11 of 15 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 Cooling water for the RHR path and to determine the RCS temperature. The flow path starts in one of loops is provided by the the RCS hot legs and is returned to the RCS cold legs. An OPERABLE Component Cooling Water RHR loop must be capable of being realigned to provide an OPERABLE System. The heat sink for the flow path. In addition, management of gas voids is important to RHR System OPERABILITY. The RHR System is OPERABLE when it is Component Cooling Water sufficientlly filled with water to perform its specified safety function.
System is the Service Water System or Essential Service The standby RHR train may be aligned to the Refueling Water Storage Water System, as determined Tank to support filling or draining the refuel pool or for the performance of by system availability and required testing as long as the motor-operated valves EJHV8716A and plant operational constraints EJHV8809A are maintained OPERABLE for Train A OPERABILITY and during MODE 6. Specifically, EJHV8716B and EJHV8809B are maintained OPERABLE for Train B one train of the Service Water OPERABILITY during refuel pool draining. These respective valves plus EJHV8840 must be maintained OPERABLE during refuel pool filling. The System may serve as the heat standby RHR train may be considered OPERABLE with BN8717 (RHR sink for one of the two return to RWST) open as long as it can be isolated by EJHV8716A or B required RHR loops, provided and EJHV8809A or B can be opened to realign the pump discharge to the that one train of the Essential RCS cold legs. Caution must be exercised whenever BN8717 is open to Service Water System serves ensure the operating RHR train's EJHV8716 valve is maintained closed.
as the heat sink for the other This is to prevent draining the RCS to the RWST. See Reference 3.
RHR loop.
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.
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. Requirements 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 to ULNRC-06781 Page 12 of 15 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 removal function, it is not permitted to enter this LCO from either MODE 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 Completion Time is necessary for an operator to initiate corrective actions.
B.1 If no RHR loop is in operation, there will be no forced circulation to provide mixing to establish uniform boron concentrations. Suspending positive reactivity additions that could result in failure to meet the minimum boron concentration limit is required to assure continued safe operation. Introduction of coolant inventory must be from sources 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 margin to maintaining a subcritical operation. Administrative controls are 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 unit 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 to ULNRC-06781 Page 13 of 15 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 providing 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 boil and release radioactive gas to the containment atmosphere. Closing containment penetrations that are open to the outside atmosphere 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 above 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 (Reference 2).
Reduced inventory is defined as RCS level lower than 3 feet below 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 the flow rate necessary to provide sufficient decay heat removal capability and to prevent thermal and boron stratification in the core. The Surveillance Frequency is based on operating experience, equipment reliability, and plant risk and is controlled under the Surveillance Frequency Control Program.
SR 3.9.6.2 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. Verification is performed by verifying proper breaker alignment and power available to the required pump. The Surveillance Frequency is based on operating experience, equipment reliability, and plant risk and is controlled under the Surveillance Frequency Control Program.
SR 3.9.6.3 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 (continued)
CALLAWAY PLANT B 3.9.6-4 Revision 13 to ULNRC-06781 Page 14 of 15 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 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 system maintenance or restoration. Susceptible locations depend on plant and system configuration, such as standby versus operating conditions.
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 accumulated gas (i.e., the system is sufficiently filled with water), the Surveillance may be declared met. Accumulated gas should be eliminated or brought within the acceptance criteria limits.
RHR System locations susceptible to gas accumulation are monitored, and if gas is found, the gas volume is compared to the acceptance criteria for the location. Susceptible locations in the same system flow path which are subject to the same gas intrusion mechanisms may be verified by monitoring a representative subset of susceptible locations. Monitoring may not be practical for locations that are inaccessible due to radiological or environmental conditions, the plant configuration, or personnel safety.
For these locations alternative methods (e.g., operating parameters, remote monitoring) may be used to monitor the susceptible location.
Monitoring is not required for susceptible locations where the maximum potential accumulated gas void volume has been evaluated and determined to not challenge system OPERABILITY. The accuracy of the method used for monitoring the susceptible locations and trending of the results should be sufficient to assure system OPERABILITY during the Surveillance interval.
(continued)
CALLAWAY PLANT B 3.9.6-5 Revision 13 to ULNRC-06781 Page 15 of 15 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