ML20078L642
| ML20078L642 | |
| Person / Time | |
|---|---|
| Site: | South Texas  |
| Issue date: | 11/17/1994 |
| From: | HOUSTON LIGHTING & POWER CO. |
| To: | |
| Shared Package | |
| ML20078L636 | List: |
| References | |
| NUDOCS 9411300318 | |
| Download: ML20078L642 (6) | |
Text
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W Attachment F ,
Page 2 of 13 ;
The OPERABILITY of the AC electrical power sources is consistent with the initial assumptions of the Accident analyses and is based upon meeting the design basis of the unit. This results in maintaining at ,
least one train of the onsite or offsite AC sources OPERABLE during !
Accident conditions in the event of:
- a. An assumed loss of all offsite power or all onsite AC power; and ;
- b. A worst case single failure The AC sources satisfy Criterion 3 of NRC Policy Statement.
LCO Two qualified circuits between the offsite transmission network and the onsite Class 1E Electrical Power System and separate and independent DGs.for each train ensure availability of the required power to shut down the reactor and maintain in a safe shutdown condition after an anticipated operational occurrence (AOO) or a postulated DBA.
Qualified offsite circuits are those that are described in the FSAR and are part of the licensing basis for the unit.
Each offsite circuit must be capable of maintaining rated frequency and voltage, and accepting required loads during an accident, while connected to the ESF buses.
Each DG must be capable of starting, accelerating to rated speed and voltage,.and connecting to its respective ESF bus on detection of bus undervoltage. This will be accomplished within [10] seconds. Each DG must also be capable of accepting required loads within the assumed loading sequence intervals, and continue to operate until offsite power can be restored to the ESF buses. These capabilities are required to be met from a variety of initial conditions such as DG in standby with the engine hot, DG in standby conditions, and DG operating in parallel test mode.
The AC sources in one train must be separate and independent (to the extent possible) of the AC sources in the other train. For the DGs, separation and independence are complete.
For the offsite AC sources, separation and independence are to the extent practical. A circuit may be connected to more than one ESF bus, with fast transfer capability to the other circuit OPERABLE, and not violate separation criteria. A circuit that is not connected to an ESF bus is required to have OPERABLE fast transfer interlock mechanisms to at least two ESF buses to support OPERABILITY of that 1 circuit.
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'ISC. 94 \ 94 419. 001 9411300318 941117 ,
PDR ADOCK 05000499 -
P PDR !
Attachment F-
-Page 3 of 13 S
S.PPLICABILITY The AC sources are required to be OPERABLE in MODES 1, 2, 3, and 4 to ensure that:
- a. Acceptable fuel design limits and reactor coolant pressure boundary limits are not exceeded as a result of anticipated operational occurrences (AOOs) or abnormal transients; and
- b. Adequate core cooling is provided and containment OPERABILITY and other vital functions are maintained in the' event of a postulated DBA.
The AC power requirements for MODES 5 and 6 are covered in LCO 3.8.2, "AC Sources-Shutdown."
3.8.1.1 Action a.
To ensure a highly reliable power source remains with one offsite circuit inoperable, it is necessary to verify the OPERABILITY of the remaining required offsite circuit on a more frequent basis. However,
- if a second required circuit fails 4.8 1.1.1.a, the second offsite circuit is inoperable, and Action e, for two offsite circuits inoperable, is entered.
TS 3.8.1.1 Action b.
To ensure a highly reliable power source remains with one diesel generator inoperable, it is necessary to verify the OPERABILITY of the i required offsite circuits on a more frequent basis. However, if a ;
required circuit fails 4.8.1.1.1.a, the offsite circuit is inoperable, and Action c, for one offsite circuit and one diesel generator inoperable, is entered. Action b provides an allowance to avoid ;
unnecessary testing of OPERABLE diesel generators. If it can be determined that the cause of the inoperable diesel generator does not exist on the OPERABLE diesel generators, and is an independently testable component or an inoperable support system, then surveillance '
requirement 4.8.1.1.2.a.2 does not have to be performed.
TS 3.8.1.] Action c.
To ensure a highly reliable power source remains with one offsite circuit and one diesel generator inoperable, it is necessary to verify the OPERABILITY of the remaining required offsite circuit on a more frequent basis. However, if a second required circuit fails 1 4.8.1.1.1.a, the second offsite circuit is inoperable and LCO 3.0.3- !
should be entered. Action c provides an allowance to avoid unnecessary testing of OPERABLE diesel generators. If it can be i determined that the cause of the inoperable diesel generator does not !
exist on the OPERABLE diesel generators, and is an independently I testable component or an inoperable support system, then surveillance l requirement 4.8.1.1.2.a.2 does not have to be performed.
TSC-94\94-319.001 I
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. Attachment F Page 4 of 13
-TS 3.8.1.1 Action d.
Provides assurance that a loss of offsite power, during the period that a diesel generator is inoperable, does not result in a complete-loss of safety function of critical systems. In this condition the remaining OPERABLE diesel generators and rifsite circuits are adequate to supply electrical power to the onsite Class 1E Distribution System.
Thus, on a component basis , single failure protection for the -
required feature's function may be lost; 1.owever, function has not been lost. Discovering one required dierel generator inoperable 1 coincidentLwith one or more inoperable 2equired support or supported l features, or both, that are associated with the operable diesel !
generator, results in starting the completion time for the required action. Additionally, the completion time takes into account the ,
capacity and capability of the remaining AC sources, and the low j probability of a DBA occurring during the period. j TS 3.8.1.1 Action e.
Operation may continue for a period that should not exceed 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.
This level of degradation means that the offsite electrical power system does not have the capability to effect a safe shutdown and to mitigate the effects of an accident; however, the onsite AC sources have not been degraded. This level of degradation generally corresponds to a total loss of the immediately accessible offsite
, power sources. With both of the required offsite circuits inoperable, l sufficient onsite AC sources are available to maintain the unit in a safe shutdown condition in the event of a DBA or transient.
TS 3.8.1.1 Action f.
With two or three of the standby diesel generators inoperable, there is insufficient or no remaining standby AC sources. Thus, with an assumed loss of offsite electrical power, insufficient standby AC sources are available to power the minimum required ESF functions. )
Since the offsite electrical power system is the only source of AC power for this level of degradation, the risk associated with continued operation for a very short-time could be less than that associated with an immediate controlled shutdown (the immediate ,
shutdown could cause grid instability, which could result in a total I loss of AC power). Since any inadvertent generator trip could also result in a total loss of offsite AC power, however, the time allowed for continued operation is severely restricted. The intent here is to avoid the risk associated with an immediate controlled shutdown and to minimize the risk associated with this level of degradation.
TSC 94\94 - M 9. 001
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Attachment F Page 5 of 13 Surveillance Recuirements The AC sources are designed to permit inspection and testing of all :
important areas and features, especially those that have a standby function, in accordance with 10 CFR 50, Appendix A, GDC 18. Periodic component tests are supplemented by extensive functional tests during refueling outages (under simulated accident conditions). The Technical Specification Surveillance Requirements (SRs) for demonstrating the OPERABILITY of the standby diesel generators are in accordance with the recommendations of Regulatory Guide 1.108, '
Regulatory Guide 1.137, as addressed in the FSAR and NUREG 1431.
Where the SRs discussed herein specify voltage and frequency tolerances, the following is applicable. The minimum steady state output voltage of 3744 is 90% of the nominal 4160 V output voltage.
This value, which is specified in ANSI C84.1, allows for voltage drop-to the terminals of 4000 V motors with minimum operating voltage specified as 90% or 3600 V. It also allows for voltage drops to motors and other equipment down through the 120 V level where minimum operating voltage is also usually specified as 90% of name plate rating. The specified maximum steady state output voltage of 4576 V is less than the maximum operating voltage of 4756 specified for 4000 (
V n otors. It ensures that for a lightly loaded distribution system, the voltage at the terminals of 4000 V motors is less than the maximum rated operating voltages. The specified minimum and maximum t frequencies of the standby diesel generators are 58.8 Hz and 61.2 Hz, respectively. These values are equal to plus or minus 2% of the 60 Hz nominal frequency and are derived from the recommendations given in Regulatory Guide 1.108 and NUREG 1431.
SR 4.8.1.1.1.a This SR ensures proper circuit continuity for the offsite AC electrical power supply to the onsite distribution network and availability of offsite AC electrical power. The breaker alignment verifies that each breaker is in its correct position to ensure that distribution buses and loads are connected to their preferred power source, and that appropriate independence of offsite circuits is maintained. The 7 day Frequency is adequate since breaker position is ,
not likely to change without the operator being aware of it and ,
because its status is displayed in the control room.
SR 4.8.1.1.1.b Transfer of each 4.16 kV ESF bus power supply from the normal offsite circuit to the alternate offsite circuit demonstrates the OPERABILITY !
of the alternate circuit distribution network to power the shutdown ,
loads. The 18 month Frequency of the Surveillance is based on engineering judgment, taking into consideration the unit conditions required to perform the Surveillance, and is intended to be consistent with expected fuel cycle lengths. Operating experience has shown that -
the components usually pass the SR when performed at the 18 month TSC-94\94-319.v01
. Attachment F Page 6 of 13 Frequency. Therefore, the Frequency was concluded to be acceptable from a reliability standpoint.
SR 4.8.1.1.2.a.1 This SR provides verification that the level of fuel oil in the fuel tank is at or above the required level.
SR 4.8.1 J.2.a.2 This SR helps to ensure the availability of the standby electrical ~
power supply to mitigate DBAs and transients and to maintain the unit in a safe shutdown condition.
To minimize the wear on moving parts that do not get lubricated when the engine is not running, these SRs are modified by a Note (Note 2) to indicate that all DG starts for these Surveillances may be preceded by an engine prelube period and followed by a warmup period prior to loading.
For purposes of this testing, the DGs are started from standby-conditions. Standby condition for a DG mean that the diesel engine coolant and oil are being continuously circulated and temperature is :
being maintained consistent with manufacturer recommendations. i In order to reduce stress and wear on diesel engines, some manufactures recommend a modified start in which the starting speed of DGs is limited,. warmup is limited to this lower speed, and the DGs are gradually accelerated to synchronous speed prior to loading. In addition, the modified start may involve reduced fuel (load limit). -
These start procedures are the intent of Note 3, which is only applicable when such modified start procedures are recommended by the ,
manufacturer.
Once per 184 days the DG starts from standby conditions and achieves required voltage and frequency within 10 seconds. The 10 second start ,
requirement supports the assumptions of the design basis LOCA analysis in the FSAR.
The 10 second start requirement is not applicable (see Note 3) when a modified start procedure as described above is used.
The normal 31 day Frequency for SR 3.8.1.2 (see Table 4.8-1, " Diesel Generator Test Schedule, " in the accompanying LCO) is consistent with Regulatory Guide 1.108. The 184 day Frequency in Note 3 is a reduction in cold testing consistent with Generic Letter 84-15. These Frequencies provide adequate assurance of DG OPERABILITY, while minimizing degradation resulting from testing.
TSC-94\94-319.001
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a Attachment F Page 7 of 13 SR 4.8.1.1.2.a.3 i
This Surveillance verifies that the DGs are capable of synchronizing ;
with the offsite electrical system and accepting loads greater than or i equal to the equivalent of the maximum expected accident loads. A .
minimum run time of 60 minutes is required to stabilize engine temperature, while minimizing the time that the DG is connected to the ,
offsite source. l The load band is provided to avoid routine overloading of the DG, !
Routine overloading may result in more frequent teardown inspections in accordance with vendor recommendations in order to maintain DG OPERABILITY.
I his SR is modified by two Notes. Note 4 indicates that diesel engine I cuns for this Surveillance may include gradual loading, as recommended ;
by the manufacturer, so that mechanical stress and wear on the diesel +
engine are minimized. Note 6 states that momentary transients, because of changing bus loads, do not invalidate this test.
l A successful DG start under SR 4.8.1.1.2.a.2 must precede this test to credit satisfactory performance. l SR 4.8.1.1.2.b i
Microbiological fouling is a major cause of fuel oil degradation.
There are numerous bacteria that can grow in fuel oil and cause ,
fouling, but all must have a water environment in order to survive.
Removal of water from the fuel oil tanks once every 31 days eliminates ;
the necessary environment for bacterial survival. This is-the most
- effective means of controlling microbiological fouling. In addition, it eliminates the potential for water entrainment in the fuel oil l during DG operation. Water may come from any of several sources, including condensation, ground water, rain water, contaminated fuel oil, and breakdown of the fuel oil by bacteria. Frequent checking for and removal of accumulated water minimizes fouling and provides data regarding the watertight integrity of the fuel oil system. .The Surveillance Frequencies are established by Regulatory Guide 1.137. i This SR is for preventative maintenance. The presence of water does not necessarily represent failure of the SR, provided the accumulated water is removed during the performance of this Surveillance.
SR 4.8.1.1.2.c l r
The requirements will be controlled and adminfs".ered by the Diesel i Fuel Oil Testing Program located in sectic:- r7 of Administrative !
Controls. >
i, TSC- 94 \94 - 319. 001
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