ML100550641
| 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 (continued)Watts Bar - Unit 2 B 3.6-1 Technical Requirements (developmental) A B 3.6 CONTAINMENT SYSTEMS
B 3.6.1 Ice Bed Temperature Monitoring System
BASES BACKGROUND The Ice Bed Temperature Monitori ng 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
SAFETY ANALYSES The ice condenser is a passive device requiring only maintenance of the ice inventory in the ice bed. As such there are no actuation circuits or
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 moni tor 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 M onitoring 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.
Ice Bed Temperature Monitoring System B 3.6.1 BASES (continued)
Watts Bar - Unit 2 B 3.6-2 Technical Requirements (developmental) A TR TR 3.6.1 states that the Ice B ed 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 w ould 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.
Ice Bed Temperature Monitoring System B 3.6.1 BASES (continued)
Watts Bar - Unit 2 B 3.6-3 Technical Requirements (developmental) A 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.
Ice Bed Temperature Monitoring System B 3.6.1 BASES (continued)Watts Bar - Unit 2 B 3.6-4 Technical Requirements (developmental) A ACTIONS (continued)
C.2.1, C.2.2, and C.2.3
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
SURVEILLANCE
REQUIREMENTS TSR 3.6.1.1
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 />.
Ice Bed Temperature Monitoring System B 3.6.1 BASES (continued)
Watts Bar - Unit 2 B 3.6-5 Technical Requirements (developmental) A 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.
Inlet Door Position Monitoring System B 3.6.2 (continued)Watts Bar - Unit 2 B 3.6-6 Technical Requirements (developmental) A 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 OPER ABLE monitoring system to be used to ensure that the ice condenser is not degraded.
APPLICABLE
SAFETY ANALYSES Proper operation of the inlet doors is necessary to mitigate the consequences of a loss of coolant accident or a main steam line break
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.
Inlet Door Position Monitoring System B 3.6.2 BASES (continued)
(continued)Watts Bar - Unit 2 B 3.6-7 Technical Requirements (developmental) A TR The Inlet Door Position Monitoring Sy stem 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.
Inlet Door Position Monitoring System B 3.6.2 BASES (continued)Watts Bar - Unit 2 B 3.6-8 Technical Requirements (developmental) A ACTIONS (continued)
C.1 and C.2
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
SURVEILLANCE
REQUIREMENTS TSR 3.6.2.1
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 />.
Inlet Door Position Monitoring System B 3.6.2 BASES Watts Bar - Unit 2 B 3.6-9 Technical Requirements (developmental) A TECHNICAL SURVEILLANCE
REQUIREMENTS (continued)
TSR 3.6.2.2
TSR 3.6.2.2 is the performance of a TADOT every 18 months. It checks
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.
Lower Compartment Cooling System B 3.6.3 (continued)Watts Bar - Unit 2 B 3.6-10 Technical Requirements (developmental) B B 3.6 CONTAINMENT SYSTEMS
B 3.6.3 Lower Compartment Cooling (LCC) System
BASES
BACKGROUND The Lower Compartment Cooling (L CC) 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 ar e 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
SAFETY ANALYSES The LCC fans recirculate air in the lower compartment spaces after an MSLB. Under these circumstances, the intact Reactor Coolant System
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.
Lower Compartment Cooling System B 3.6.3 BASES (continued)
(continued)Watts Bar - Unit 2 B 3.6-11 Technical Requirements (developmental) A 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.
Lower Compartment Cooling System B 3.6.3 BASES Watts Bar - Unit 2 B 3.6-12 Technical Requirements (developmental) B ACTIONS (continued)
C.1 and C.2
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
SURVEILLANCE
REQUIREMENTS TSR 3.6.3.1
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."