ML20196G796
| ML20196G796 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 06/22/1999 |
| From: | TENNESSEE VALLEY AUTHORITY |
| To: | |
| Shared Package | |
| ML20196G793 | List: |
| References | |
| NUDOCS 9907010269 | |
| Download: ML20196G796 (4) | |
Text
3/4.0 ELECTRICAL POWER SYSTEMS BASES 3/4.8.1 and 3/4.8.2 A.C.
SOURCES AND ONSITE POWER DISTRIBUTION SYSTEMS The OPERABILITY of the minimum specified A.C. and D.C. power sources and associated distribution systems during shutdown and refueling ensures that 1) the facility can be maintained in the shutdown or refueling condition for extended time periods and 2) sufficient instrumentation and control capability la available for monitoring and maintaining the unit status.
The requirements of Specification 3.8.2.1 provide those actions to be taken for the inoperability of A.C. Distribution Systems. Accion a of this specification provides an 8-hour action for the inoperability of one or more A.C. boards.
Action b of this specification provides a relaxation of the 8-hour action to 24-hours provided the Vital Instrument Power Board is inoperable BR-12 solely as a result of one inoperable inverter and the board has been energized within 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />.
In this condition the requirements of Action a do not have to be applied. Action b is not intended to provide actions for inoperable inverters, which is addressed by the operability requirenents for the boards, and is included only for relief from the 8-hour action of Action a when only one inverter is affected. More than one inverter inoperable will result in the inoperability of the associated 120 Volt A.C. Vital Instrument Power Board (s) in accordance with Action a.
With'more than one inverter inoperable entry into the actions of TS 3.0.3 is not applicable because Action a includes provisions for multiple inoperable inverters as attendant equipment to the boards.
The Surveillance Requirements for demonstrating the OPERABILITY of the diesel generators are in accordance with the recommendations of Regulatory Guides 1.9 " Selection of Diesel Generator Set Capacity for Standby Power Supplies," March 10, 1971, and 1.108 " Periodic Testing of Diesel Generator Units Use Onsite Electric Power Systems at Nuclear Power Plants,"
Revision.
quat 1977, and 1.137 " Fuel-Oil Systems for Standby Diesel Generators,' Fevision 1, October 1979.
The surveillance requirements for the diesel generator load-run test and the 24-hour endurance and margin test are in accordance with Regulatory Guide 1.9, Revision 3, July 1993, " Selection, Design, Qualification, and Testing of Emergency Diesel Generator Units Used as R177 Class 1E Onsite Electric Power Systems at Nuclear Power Plants."
During the diesel generator endurance and margin surveillance test, momentary transients outside the kw and kvar load ranges to not invalidate the test results.
Similarly, during the diesl generator load-run test, monentary transients outside the kw load range do not invalidate the test results.
Where the SRs discussed herein specify voltage and frequency tolerances, the following is applicable.
6800 volts is the minimum steady state output voltage and the 10 second transient value.
6800 volts is 98.6% of nominal bus voltage of 6900 volts and is based on the minimum voltage required for the diesel generator supply breaker to close on the 6.9 kV shutdown board. The R238 specified maximum steady state output voltage of 7260 volts is based on the degraded over voltage relay setpoint and is equivalent to 110% of the nameplate rating of the 6600 volt motors. The specified minimum and maximum frequencies of the diesel generator are 58.8 Hz and 61.2 Hz, respectively.
These values are equal to i 2% of the 60 Hz nominal frequency and are derived from the recommendations given in regulatory Guide 1.9.
The Surveillance Requirement for demonstrating the OPERABILITY of the Station batteries are based on the recommendations of Regulatory Guide 1.129
" Maintenance Testing and Replacement of Large Lead Storage Batteries for Nuclear Power Plants," February 1978, and IEEE Std 450-1980, "IEEE Recommended Practice for Maintenance, Testing, and Replacement of Large Lead Storage batteries for Generating Stations and Substations."
September 9, 1998 lR209 SEQUOYAH - UNIT 1 B 3/4 8-la Amendment No. 12,137,173,205,2'4 9907010269 990622 PDR ADOCK 05000327 P
~
j 1
5 3/4.5' EMERGENCY CORE COOLING SYSTEMS.
BASES l-i 3/4.5.1 ACCUMULATORS j
i l
The OPERABILITY of each cold leg injection accumulator ensures that a lR144
[.
sufficient volume of borated water will be immediately forced into the reactor core in the event that the RCS. pressure falls below the specified pressure of the accumulators.
For the cold leg injection accumulators, this condition occurs in the event of a large or small rupture.
R144 The limits on accumulator volume, boron concentration and pressure ensure
.that the assumptions used for accumulator injection in the safety analysis are met.
The limits in the specification for accumulator nitrogen cover pressure are analysis limits and do not include instrument uncertainty.
The cold leg BR-accumulator volume (level) values in the limiting'co-dition for operation, 13 TS 3/4.5.1, are the operating limits. The analysis limits bound the operational limits with instrument uncertainty applied.
The minimum boron concentration ensures that the reactor core will remain suberitical during the R159 post-LOCA (loss of coola'nt accident) recirculation phase based upon the cold leg accumulators' contribution to the post-LOCA sump mixture concentration.
The accumulator power operated isolation valves are considered to be
" operating bypasses" in the context of IEEE Std. 279-1971, which requires that bypasses of a protective function be removed automatically whenever permissive conditions are not met..In addition, as these accumulator isolation valves fail to meet single failure criteria, removal of power to the valves is required.
The limits for operation with an accumulator inoperable for any reason except boron concentration not within limits minimizes the time exposure of the R196 plant to a LOCA event occurring concurrent with failure of an additional accumulator which may result in unacceptable peak cladding temperatures. Under l
these conditions, the full capability of one accumulator is not available and prompt action is required to place the reactor in a mode where this capability is not required.
For an accumulator inoperable due to boron concentration not l
within limits, the limits for operation allow 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> to return boron concentration to within limits. This is based on the availability of ECCS l
water not being affected and an insignificant effect on core subcriticality during reflood because boiling of ECCS water in the core concentrates boron in the saturated liquid.
l 3/4.5.2 and 3/4.5.3 ECCS SUBSYSTEMS i
1 The OPERABILITY of two independent ECCS subsystems ensures that L
sufficient emergency core cooling capability will be available in the event of l
a LOCA assuming the loss of one subsystem through any single failure consideration.
Either subsystem operating in conjunction with the accumulators j
l is capable of supplying sufficient core
- cooling to limit the peak cladding i
temperatures within acceptable limits for all postulated break sizes ranging L
from the double ended break of the largest RCS cold leg pipe downward.
In addition, each ECCS subsystem provides.long term core cooling capability in the recirculation mode during the accident-recovery period.
i t
January 25, 1999 SEQUOYAH - UNIT 1 B 3/4 5-1 Amendment No. 155, 140, 192 i
I L
f 1
i 3/4.8 ELECTRICAL POWER SYSTEMS 1
l BASES l
l I
3 /4. 8.1 AND 3 /4. 8. 2 A.C.
SOURCES AND ONSITE POWER DISTRIBUTION SYSTEMS The OPERABILITY of the minimum specified A.C. and D.C. power sources and associated distribution systems during shutdown and refueling ensures that
- 1) the facility can be maintained in the shutdown or refueling condition for extended time periods and 2) sufficient instrumentation and control capability is available for monitoring and maintaining the unit status.
The requirements of Specification 3.8.2.1 provide those actions to be taken for the inoperability of A.C. Distribution Systems. Action a of this specification provides an 8-hour action for the inoperability of one or more A.C. boards. Action b of this specification provides a relaxation of the 8-i hour action to 24-hours provided the Vital Instrument Power Board is inoperable solely as a result of one inoperable inverter and the board has been energized BR-13 within 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />.
In this condition the requirements of Action a do not have to be applied. Action b is not intended to provide actions for inoperable inverters, which is addressed by the operability requirements for the boards, and is included only for relief from the 8-hour action of Action a when only one inverter is affected. More than one inverter inoperable will result in the j
inoperability of the associated 120 Volt A.C. Vital Instrun.ent Power Board (s) in accordance with Action a.
With more than one inverter inoperable entry into the actions of TS 3.0.3 is not applicable because Action a includes provisions for multiple inoperable inverters as attendant equipment to the boards.
The Surveillance Requirements for demonstrating the OPERABILITY of the diesel generators are in accordance with the recommendations of Regulatory Guides 1.9 " Selection of Diesel Generator Set Capacity for Standby Power j
Supplies", March 10, 1971, 1.108 " Periodic Testing of Diesel Generator Units Used as Onsite Electric Power Systems at Nuclear Power Plants," Revision 1, August 1977, and 1.137 " Fuel-Oil Systems for Standby Diesel Generators,"
Revision 1, October 1979.
The surveillance requirements for the diesel
'i generator load-run test and the 24-hour endurance and margin test are in accordance with Regulatory Guide 1.9, Revision 3, July 1993, " Selection, Design, Qualification, and Testing of Emergency Diesel Generator Units Used as Class 1E Onsite Electric Power Systems at Nuclear Power PIMnt."
During the R164 diesel generator endurance and margin surveillance test, momentary transients outside the kw and kvar load ranges do not invalidate the test results.
Similarly, during the diesel generator load-rua test, momentary transients i
outside the kw load range do not invalidate the test results, Where the SRs discussed herein specify voltage and frequency tolerances, the following is applicable.
6800 volts is the minimum steady state output voltage and the 10 second transient value.
6800 volts is 98.6% of nominal bus voltage of 6900 volts and is based on the minimum voltage required for the R224 diesel generator supply breaker to close on the 6.9 kV shutdown board. The specified maximum steady state output voltage of 7260 volts is based on the degraded over voltage relay setpoint and is equivalent to 110% of the nameplate rating of the 6600 volt motors. The specified minimum and maximum frequencies of the diesel generator are 58.8 Hz and 61.2 Hz, respectively. These values j
are equal to i 2k of the 60 Hz nominal frequency and are derived from the i
recommendations given in regulatory Guide 1.9.
l The Surveillance Requirement for demonstrating the OPERABILITY of the Station batteries are are based on the re ;ommendations of Regulatory Guide 1.129 " Maintenance Testing and Replacement of Large Lead Storage Batteries for Nuclear Power Plants," February 1978, and IEEE Std 450-1980, "IEEE Recommended Practice for Maintenance, Testing and Replacement of Large Lead Storage Batteries for Generating Stations and Substations."
September 9, 1998 SECUOYAH - UNIT 2 B 3/4 0-la Amendment No. 123, 164, 195, 224 lR195 i
i
y 3/4.5 EMERGENCY CORE COOLING SYSTEMS BASES j
3/4.5.1 ACCUMULATORS The OPERABILITY of each cold leg injection accumulator ensures that a lR131 sufficient volume of borated water will be immediately forced into the reactor core in the event the RCS pressure falls below the pressure of the accumulators.
For the cold leg injection accumulators this condition occurs in the event of a large or small rupture.
R131 The limits on accumulator volume, boron concentration and pressure ensure that the assumptions used for accumulator injection in the safety analysis are met.
The limits in the specification for accumulator nitrogen cover pressure are analysis limits and do not include instrument uncertainty. The cold leg BR-accumulator volume (level) values in the limiting condition for operation, 14 i
TS 3/4.5.1, are the operating limits. The analysis limits bound the i
op*. rational limits with instrument uncertainty applied.
The minimum boron concentration ensures that the reactor core will remain suberitical during the post-LOCA (loss of coolant accident) recirculation phase based upon the cold accumulators' contribution to the post-LOCA sump mixture concentration.
BR-3 The accumulator power operated isolation valves are considered to be
" operating bypasses" in the context of IEEE Std. 279-1971, which requires that bypasses of a protective function be removed automatically whenever permissive conditions are not met.
In addition, as these accumulator isolation valves fail to meet single failure criteria, removal of power to the valves is required.
The limits for operation with an accumulator inoperable for any reason except boron concentration not within limits minimizes the time exposure of the R184 i
plant to a LOCA event occurring concurrent with failure of an additional accumulator which may result in unacceptable peak cladding temperatures.
Under these conditions, the full capability of one accumulator is not available and prompt action is required to place the reactor in a mode where this capability is not' required.
For an accumulator inoperable due to boron concentration not within limits, the limits for operation allow 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> to return boron concentration to within limits. This is based on the availability of ECCS water not being affected and an insignificant effect on core suberiticality during reflood because boiling of ECCS water in the core concentrates boron in the. saturated liquid.
3 /4. 5. 2 and 3 /4. 5. 3 ECCS SUBSYSTEMS The OPERABILITY of two independent ECCS subsystems ensures that sufficient emergency core cooling capability will be available in the event of a LOCA assuming the loss of one subsystem through any single failure consideration.
Either subsystem operating in conjunction with the accumulators is capable of supplying sufficient core cooling to limit the peak cladding temperatures within acceptable limits for all postulated break sizes ranging from the double ended break of the largest RCS cold leg pipe downward.
In addition, each ECCS subsystem provides long term core cooling capability in the recirculation mode during the accident recovery period.
With the RCS temperature below 350*F, one OPERABLE ECCS subsystem is acceptable without single failure conrideration on the basis of the stable reactivity condition of the reactor and the limited core cooling requirements.
January 25, 1999 SEQUOYAH - UNIT 2 B 3/4 5-1 Amendment Nos. 131, 184