ML100550641

Developmental Revision B - Technical Requirements Manual Bases B 3.6 - Containment Systems

ML100550641
Person / Time
Site:	Watts Bar
Issue date:	02/02/2010
From:	Tennessee Valley Authority
To:	Office of Nuclear Reactor Regulation
References
Download: ML100550641 (12)

Text

Ice Bed Temperature Monitoring System B 3.6.1 B 3.6 CONTAINMENT SYSTEMS B 3.6.1 Ice Bed Temperature Monitoring System BASES BACKGROUND The Ice Bed Temperature Monitoring System consists of Resistance Temperature Detectors (RTDs) which are located in various parts of the ice condenser. They serve to verify the attainment of a uniform equilibrium temperature in the ice bed and to detect general gradual temperature rise in the cooling system if breakdown occurs.

Forty-seven RTDs are mounted on ice bed probes which are located throughout the ice bed. These 47 RTDs tie into a temperature scanner unit, located in the Incore Instrument Room. The scanner multiplexes the ice condenser RTD's signals to a Westronics recorder in the Main Control Room. There are also six temperature switches located at various points in the ice bed to serve as backup indication should the scanner unit or recorder fail to operate. These inputs provide an alarm on the control room annunciator panel should the ice bed temperature exceed preset value (Ref. 1). In addition, the 47 RTDs can be read from the local ice condenser temperature monitoring panel.

APPLICABLE The ice condenser is a passive device requiring only maintenance of the SAFETY ice inventory in the ice bed. As such there are no actuation circuits or ANALYSES equipment which are required for the ice condenser to operate in the event of a Loss of Coolant Accident (LOCA). The Ice Bed Temperature Monitoring System serves only to monitor the ice bed temperature. Since the ice bed has a very large thermal capacity, postulated off-normal conditions can be successfully tolerated for a week to two weeks.

Therefore, the Ice Bed Temperature Monitoring System provides an early warning of any incipient ice condenser temperature anomalies. The Ice Bed Temperature Monitoring System is not assumed to be OPERABLE to mitigate the consequences of a DBA or transient. Based on the PRA Summary Report (Ref. 2), the Ice Bed Temperature Monitoring System has not been identified as a significant risk contributor.

(continued)

Watts Bar - Unit 2 B 3.6-1 Technical Requirements (developmental) A

Ice Bed Temperature Monitoring System B 3.6.1 BASES TR TR 3.6.1 states that the Ice Bed Temperature Monitoring System shall be OPERABLE with at least two OPERABLE RTD channels in the ice bed at each of three basic elevations: 10'6", 30'9", and 55' above the floor of the ice condenser, for each one-third of the ice condenser.

The OPERABILITY of the Ice Bed Temperature Monitoring System ensures that the capability is available for monitoring the ice bed temperature. The ice bed temperature may be determined at the local ice condenser temperature monitoring panel as well as in the Main Control Room and the Monitoring System would still be considered OPERABLE.

In the event the Monitoring System is inoperable, the Required Actions provide assurance that the ice bed heat removal capacity will be retained within the specified time limits.

APPLICABILITY The Ice Bed Temperature Monitoring System is required to be OPERABLE in MODES 1, 2, 3, and 4. This corresponds to the Applicability requirements for the ice bed in Technical Specification LCO 3.6.11, Ice Bed.

ACTIONS A.1 With the ice bed temperature not available in the Main Control Room, the ice bed temperature must be determined at the local ice condenser temperature monitoring panel (local panel) every 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />. Since the ice bed has a very large thermal capacity, postulated off-normal conditions can be successfully tolerated for one or two weeks. Therefore, a 12 hour1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> surveillance of the ice bed temperature will give sufficient warning of any incipient ice condenser temperature anomalies.

B.1.1, B.1.2, and B.1.3 With the Ice Bed Temperature Monitoring System inoperable and being unable to determine the ice bed temperature at the local panel, Required Actions B.1.1, B.1.2, and B.1.3 require verification that: the ice compartment lower inlet doors, intermediate deck doors, and top deck doors are closed; the last recorded mean ice bed temperature was less than or equal to 20°F (value does not account for instrument error) and steady; and the Ice Condenser Cooling System is OPERABLE.

(continued)

Watts Bar - Unit 2 B 3.6-2 Technical Requirements (developmental) A

Ice Bed Temperature Monitoring System B 3.6.1 BASES ACTIONS B.1.1, B.1.2, and B.1.3 (continued)

The Completion Time of 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> and every 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> thereafter to perform Required Actions B.1.1 and B.1.3 and 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> to perform Required Action B.1.2 is reasonable and based upon the typical time necessary to perform the Required Actions. These Required Actions, along with the high thermal capacity of the ice bed, ensure that the ice bed will remain below critical temperatures while the Monitoring System is inoperable.

B.2.1 and B.2.2 With the Ice Bed Temperature Monitoring System inoperable and being unable to determine the ice bed temperature at the local panel, either the Monitoring System or the local monitoring panel must be restored to OPERABLE status within 30 days. A Completion Time of 30 days is given, provided that Required Actions B.1.1, B.1.2, and B.1.3 are met.

These Required Actions, along with the high thermal capacity of the ice bed, ensure that the ice bed will remain below critical temperatures during the 30 day Completion Time. Also, the six alarmed temperature switches (which provide an alarm at 25°F) will continue to monitor the ice bed temperature. If the Ice Condenser Cooling System becomes inoperable before the Ice Bed Temperature Monitoring System is OPERABLE, then Required Action C must be performed.

C.1.1 and C.1.2 With the Ice Bed Temperature Monitoring System inoperable and being unable to determine the ice bed temperature at the local panel and with the Ice Condenser Cooling System not satisfying the minimum components OPERABILITY requirements of Required Action B.1.3, Required Actions C.1.1 and C.1.2 require verification that: the ice compartment lower inlet doors, intermediate deck doors, and top deck doors are closed; and that the last recorded mean ice bed temperature was less than or equal to 15°F (value does not account for instrument error) and steady. The Completion Time of 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> and every 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> thereafter to perform Required Action C.1.1 and 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> to perform Required Action C.1.2 is reasonable and based upon the typical time necessary to perform the Required Actions. These Required Actions, along with the high thermal capacity of the ice bed, ensure that the ice bed will remain below critical temperatures while the Monitoring System and Ice Condenser Cooling System are inoperable.

(continued)

Watts Bar - Unit 2 B 3.6-3 Technical Requirements (developmental) A

Ice Bed Temperature Monitoring System B 3.6.1 BASES ACTIONS C.2.1, C.2.2, and C.2.3 (continued)

With the Ice Bed Temperature Monitoring System inoperable and being unable to determine the ice bed temperature at the local panel and with the Ice Condenser Cooling System not satisfying the minimum components OPERABILITY requirements of Required Action B.1.3, the Ice Condenser Cooling System, Ice Bed Temperature Monitoring System or the local temperature monitoring panel must be restored to OPERABLE status. A Completion Time of 6 days is given, provided that Required Actions C.1.1 and C.1.2 are met. These Required Actions, along with the high thermal capacity of the ice bed, ensure that the ice bed will remain below critical temperatures during the 6 day Completion Time. Also, the six alarmed temperature switches (which provide an alarm at 25°F) will continue to monitor the ice bed temperature.

D.1 and D.2 If the Required Action and associated Completion Time of Condition A, B or C is not met, the integrity of the ice bed may be threatened. Therefore, the plant must be placed in a MODE in which the TR does not apply.

This is done by placing the plant in MODE 3 in 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and MODE 5 in 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />. The allowed Completion Times are reasonable based on operating experience to reach the required plant conditions from full power conditions in an orderly manner and without challenging plant systems.

TECHNICAL TSR 3.6.1.1 SURVEILLANCE REQUIREMENTS Performance of a CHANNEL CHECK on the Ice Bed Temperature Monitoring System once every 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> ensures that a gross failure of instrumentation has not occurred. A CHANNEL CHECK is a comparison of the parameter indicated on one channel to a similar parameter on other channels. It is based on the assumption that instrument channels monitoring the same parameter should read approximately the same value. Significant deviations between the instrument channels could be an indication of excessive instrument drift in one of the channels or of even something more serious. The Surveillance Frequency, about once every shift, is based on operating experience that demonstrates the rarity of channel failure. Thus, TSR 3.6.1.1 ensures that loss of function will be identified within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />.

(continued)

Watts Bar - Unit 2 B 3.6-4 Technical Requirements (developmental) A

Ice Bed Temperature Monitoring System B 3.6.1 BASES (continued)

REFERENCES 1. Watts Bar FSAR, Section 6.7.15, "Ice Condenser Instrumentation"

2. WCAP-11618, "MERITS Program-Phase II, Task 5, Criteria Application," including Addendum 1 dated April, 1989.

Watts Bar - Unit 2 B 3.6-5 Technical Requirements (developmental) A

Inlet Door Position Monitoring System B 3.6.2 B 3.6 CONTAINMENT SYSTEMS B 3.6.2 Inlet Door Position Monitoring System BASES BACKGROUND Ninety-six limit switches monitor the position of the lower inlet doors.

Two switches are mounted on the door frame for each door panel.

The position and movement of the switches are such that the doors must be effectively sealed before the switches are actuated. A single annunciator window in the control room gives a common alarm signal when any door is open. Open/shut indication is also provided at the lower inlet door position display panel located in the Main Control Room. For door monitoring purposes, the ice condenser is divided into six zones, each containing four inlet door assemblies, or a total of eight door panels.

The limit switches on the doors in any single zone are wired to a single light on the inlet door position display panel such that a closed light indicates that all the doors in that zone are shut and an open light indicates that one or more doors in that zone are open (Ref. 1). The display panel is considered the Inlet Door Position Monitoring System.

Monitoring of inlet door position is necessary because the inlet doors form the barrier to air flow through the inlet ports of the ice condenser for normal unit operation. Failure of the Inlet Door Position Monitoring System requires an alternate OPERABLE monitoring system to be used to ensure that the ice condenser is not degraded.

APPLICABLE Proper operation of the inlet doors is necessary to mitigate the SAFETY consequences of a loss of coolant accident or a main steam line break ANALYSES inside containment. The Inlet Door Position Monitoring System, however, is not required for proper operation of the inlet doors, nor is it considered OPERABLE as an initial condition for a DBA. Hence, the Inlet Door Position Monitoring System is not a consideration in the analyses of DBAs. Based on the PRA Summary Report in Reference 2, the Inlet Door Position Monitoring System has not been identified as a significant risk contributor.

(continued)

Watts Bar - Unit 2 B 3.6-6 Technical Requirements (developmental) A

Inlet Door Position Monitoring System B 3.6.2 BASES (continued)

TR The Inlet Door Position Monitoring System provides the only direct means of determining that the inlet doors are shut. Since an open door would allow heat input that could cause sublimation and mass transfer of ice in the ice condenser compartment, the Inlet Door Position Monitoring System must be OPERABLE whenever the ice bed is required to be OPERABLE. This ensures early detection of an inadvertently opened or failed door, allowing prompt action before ice bed degradation can occur.

APPLICABILITY The Inlet Door Position Monitoring System is required to be OPERABLE in MODES 1, 2, 3 and 4. This corresponds to the Applicability requirements for the ice bed.

ACTIONS A.1 and A.2 If the Inlet Door Position Monitoring System is inoperable in MODE 1, an alternate OPERABLE monitoring system must be used to ensure that the ice condenser is not degraded. This is done by confirming the Ice Bed Temperature Monitoring System is OPERABLE with the ice bed temperature 27°F (value does not account for instrument error). This Action must be completed within 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> and each 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> thereafter.

The Frequency of 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> is based on the fact that temperature changes cannot occur rapidly in the ice bed because of the large mass of ice involved. Since this is an indirect means of monitoring inlet door position, operation in MODE 1 may continue for a maximum of 14 days in this condition. If the ice bed temperature increases to above 27°F, the ice bed must be declared inoperable in accordance with Technical Specification 3.6.11, "Ice Bed".

B.1 If the Required Action and associated Completion Time for Condition A are not met or if the Inlet Door Position Monitoring System is inoperable in MODES 2, 3, or 4, the Inlet Door Position Monitoring System must be restored to OPERABLE status within 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br />. The 48 hour5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> Completion Time is based on the fact that, with the very large mass of ice involved, it would not be possible for the temperature to increase to the melting point and a significant amount of ice to melt in a 48 hour5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> period.

(continued)

Watts Bar - Unit 2 B 3.6-7 Technical Requirements (developmental) A

Inlet Door Position Monitoring System B 3.6.2 BASES ACTIONS C.1 and C.2 (continued)

If the Required Action and associated Completion Time of Condition B cannot be met, the plant must be placed in a condition where OPERABILITY of the Inlet Door Position Monitoring System is not required. This is accomplished by placing the plant in MODE 4 within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and MODE 5 within 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />. The allowed Completion Times are reasonable, based on operating experience, to reach the required MODES from full power in an orderly manner and without challenging plant systems.

TECHNICAL TSR 3.6.2.1 SURVEILLANCE REQUIREMENTS Performance of the CHANNEL CHECK for the Inlet Door Position Monitoring System once every 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> ensures that a gross failure of instrumentation has not occurred. A CHANNEL CHECK is a comparison of the parameter indicated on one channel to a similar parameter on other channels. It is based on the assumption that instrument channels monitoring the same parameter should read approximately the same value. Significant deviations between the two instrument channels could be an indication of excessive instrument drift in one of the channels or of something even more serious. Performance of the CHANNEL CHECK helps to ensure that the instrumentation continues to operate properly between each TADOT. The dual switch arrangement on each door allows comparison of open and shut indicators for each zone as well as a check with the annunciator window. An alternate to the use of the annunciator window as the channel check, is to perform a continuity check of the same circuit used by the annunciator window. This continuity check will confirm if one or more inlet door zone switch contacts are closed which would represent an open inlet door. The Surveillance Frequency, about once every shift, is based on operating experience that demonstrates the rarity of channel failure. Thus, TSR 3.6.2.1 ensures that loss of function will be identified within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />.

(continued)

Watts Bar - Unit 2 B 3.6-8 Technical Requirements (developmental) A

Inlet Door Position Monitoring System B 3.6.2 BASES TECHNICAL TSR 3.6.2.2 SURVEILLANCE REQUIREMENTS TSR 3.6.2.2 is the performance of a TADOT every 18 months. It checks (continued) trip devices (limit switches) that provide actuation signals directly.

The 18 month Frequency was developed considering the plant conditions needed to perform TSR 3.6.2.2. The 18 month Frequency is also acceptable based on consideration of the design reliability (and confirming operating experience) of the equipment.

TSR 3.6.2.3 TSR 3.6.2.3 requires verification that the monitoring system correctly indicates the status of each inlet door as the door is opened and reclosed during its Technical Specification testing. This provides ongoing operational testing of the indicating system. The Frequency coincides with the Technical Specifications testing performed.

REFERENCES 1. Watts Bar FSAR, Section 6.7, "Ice Condenser System."

2. WCAP-11618, "MERITS Program-Phase II, Task 5, Criteria Application," including Addendum 1 dated April, 1989.

Watts Bar - Unit 2 B 3.6-9 Technical Requirements (developmental) A

Lower Compartment Cooling System B 3.6.3 B 3.6 CONTAINMENT SYSTEMS B 3.6.3 Lower Compartment Cooling (LCC) System BASES BACKGROUND The Lower Compartment Cooling (LCC) fans provide non-safety related cooling for the lower compartment spaces after all accidents, except those that initiate a Phase B Containment Isolation Signal (Ref. 1), when the non-safety related cooling coils and cooling water supply are available. LCC fans perform a safety related air recirculation function in the lower containment pocketed (dead ended) spaces after a main steam line break (MSLB) to prevent the formation of localized hot spots which could exceed the qualification temperatures of equipment required to operate post accident. The LCC fans are not required to operate during or after a loss of coolant accident (LOCA).

After an MSLB, one LCC train will be manually started a minimum of 1 1/2 hours, but less than 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />, after the accident to ensure that the dead ended compartment temperatures are kept below the environmental qualification limit. Each train consists of two 50% capacity fans, backdraft damper, instrumentation and controls, and associated ductwork. Each train is powered from separate class 1E power sources.

APPLICABLE The LCC fans recirculate air in the lower compartment spaces after an SAFETY MSLB. Under these circumstances, the intact Reactor Coolant System ANALYSES piping will serve as a long term heat source. After the ice is melted, the heat from the Reactor Coolant System (RCS) will result in a gradual temperature increase in the sub-compartments of the lower containment.

If the recirculation of air should fail during or after the accident, the Containment Spray System and Air Return Fan System can be started to provide the necessary containment cooling. The temperatures in the sub-compartments of the lower containment are not input to the safety analyses. Containment area temperatures have not been identified as significant risk contributors.

(continued)

Watts Bar - Unit 2 B 3.6-10 Technical Requirements (developmental) B

Lower Compartment Cooling System B 3.6.3 BASES (continued)

TR The TR specifies the equipment which needs to be OPERABLE in order to ensure that air can be circulated in the sub-compartments if an accident should take place. At least one LCC train must be placed in operation after the accident. The LCC fans do not perform a cooling function, which means that the coils and the secondary cooling water circuits need not be OPERABLE. However, secondary side failures which could impair the operation of the fans and the circulation of the air must be prevented.

APPLICABILITY The flow of air to the sub-compartments is necessary following an MSLB where the RCS represents a major heat source in lower containment.

Based on the temperature of the RCS, this could be in MODES 1 through 4. In MODES 5 and 6, the probability for an accident is small and, in any case, the heat capacity of the RCS is limited and, therefore, not able to heat up the lower compartment spaces to such an extent that equipment could degrade. The specification is therefore only applicable in MODES 1, 2, 3 and 4.

ACTIONS A.1 With one fan inoperable, the inoperable fan must be restored to OPERABLE status within 7 days. During this period, the remaining three fans are available to circulate the air in the lower compartments of the containment. However, only two fans are necessary to prevent the hot spots. Hence, there is one spare fan available. The 7 day Completion Time is based on the low probability of an event requiring emergency fan operation, the availability of one fan more than required, and the availability of alternate cooling means.

B.1 With two fans inoperable the plant has still adequate fan capacity to circulate air if an accident should take place. However, in this case no spare capacity is available. Hence, it is required to restore at least one fan to OPERABLE status within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. With one fan restored, three fans will be OPERABLE and Condition A must be entered. This will allow another 7 days to restore the last inoperable fan to OPERABLE status. The 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> Completion Time in Condition B is based on the low probability of an event requiring fan operation simultaneous with further fan deterioration, and the availability of alternate cooling means.

(continued)

Watts Bar - Unit 2 B 3.6-11 Technical Requirements (developmental) A

Lower Compartment Cooling System B 3.6.3 BASES ACTIONS C.1 and C.2 (continued)

If the Required Actions of A.1 and B.1 cannot be completed within the required Completion Time or if more than two fans are inoperable, the plant must be placed in a MODE in which the TR does not apply. This is done by placing the plant 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 within an additional 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />. The allowed Completion Times are reasonable, based on operating experience, to reach the required plant conditions from full power conditions in an orderly manner and without challenging plant systems.

TECHNICAL TSR 3.6.3.1 SURVEILLANCE REQUIREMENTS During normal operation, three of the four LCCs operate to remove heat from the lower compartments of the containment. This means that three of the four fans are operating at all times. Hence, this gives certainty that at least three fans are OPERABLE. The test is for the fan that has not been in operation during the preceding 31 days and to verify that all fans can be manually started from the control room. The 15 minutes running test is optional for fans that have been running the previous 31 days, or will be running after the Surveillance has been carried out.

REFERENCES 1. Watts Bar FSAR, Section 6.2.2, "Containment Heat Removal Systems."

2. Thomas E. Murley (NRC) letter to W. S. Wilgus, dated May 9, 1988, forwarding the NRC Staff review of the "Nuclear Steam Supply System Vendor Owners Groups' Application of the Commission's Interim Policy Statement Criteria to the Standard Technical Specifications."

Watts Bar - Unit 2 B 3.6-12 Technical Requirements (developmental) B