ML19296D781
| ML19296D781 | |
| Person / Time | |
|---|---|
| Site: | Brunswick  |
| Issue date: | 02/26/1980 |
| From: | Furr B CAROLINA POWER & LIGHT CO. |
| To: | James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| Shared Package | |
| ML19296D782 | List: |
| References | |
| IEB-79-27, NUDOCS 8003130185 | |
| Download: ML19296D781 (6) | |
Text
CP&L Carohna Power & Light Company
-h;-f;jd February 26, 1980 e.
rv FILE: NG-3513(B)
SERIAL: NQ-80-272 Mr. James P. O'Reilly, Director U. S. Nuclear Regulatory Commission Region II 101 Marietta Street, Suite 3100 Atlanta, Georgia 30303 BRUNSWICK STEAM ELECTRIC PLANT, UNIT NCS.1 & 2 LICENSE NOS. DPR-71 AND DPR-62 DOCKET NOS. 50-325 AND 50-324 RESPONSE TO IE BULLETIN 79-27
Dear Mr. O'Reilly:
In response to your letter of November 30, 1979, transmitting IE Bulletin 79-27, concerning loss of non-class IE instrumentation and control power system bus during operation, Carolina Power & Light Company submits the following response for the Brunswick Steam Electric Plant:
The electrical distribution system is designed to furnish adequate power to plant systems which support normal power production concurrently with those plant systems which are necessary to assure operation in a safe manner.
These safety systems include the Engineered Safety Systems, their support systems, and the Safe Shutdown Systems which are needed for the prompt and safe shutdown and cooldown of the units and to maintain the reactor in a safe condition.
Redundant of f-site and on-site power sources and distribution systems assure reliable supplies.
These power sources and distribution systems are sufficient in number and are of such electrical and physical independence that no single credible event can negate all power.
Ty.ree cources of power are available to the plant to support its operation:
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Off-site AC, power through the qwitchyard
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On-site AC power from the emergency diesel generators On-site DC power from the plant batteries 8003130 M 5 411 Fayetteville Street e P. O. Box 1551
- Raleigh, N. C 27602
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i Mr. James P. O'Reilly February 26, 1980 Power from these sources is distributed throughout the plant by four distribution systems as shown in Figures 1 - 3:
Auxiliary AC power (4KV, 480V,120V)
Emergency AC power (4KV, 480V,120V)
Emergency DC power (125/250V, 24/48V)
Vital AC power (120V)
The auxiliary buses are powered by the off-site sources through the switchyard. They, in turn, are the normal sources of power to the emergency buses. The emergency buses can also be powered by the emergency diesel generators automatically in the event of a loss of off-site power. The DC buses are powered by emergency batteries which are kept charged by battery chargers fed from the emergency buses.
The vital bus is powered by either of two UPS systems. Each can be powered by one of the emergency DC buses or directly from an emergency AC bus.
Indirect informat.on on the status of the UPS equipment supplying power to the 120 VAC vital bus is available.
This information consists of bus voltage indicators, bus feeder breaker status indicators, bus undervoltage annunciators, or bus feeder breaker trip annunciators.
la.
Table 1 specifies the information available in the control room to indicate the status of the electrical buses in the plant. Direct information concerning the status of all 4KV buses, 480V buses, the emergency 120V AC buses, and the DC buses is available.
There are additional annunciators on MCC feeder,bteakers, logic power sources, and power supplies for, pritical feeds 'to ECCS and safe shutdown equipment and, pstrumentation to inform the operator of their failure.
Ib.
The reactor can be brought to a cold shutdown condition by either of two general procedures. The normal method is used when the main condenser is available as a heat sink and uses both, balance of plant as well as some safety related equipnient for the cooldown. Due to the variety of equipment used, this method makes use of equipment and instrr'entation supplied by most of the different types of buses. The alternate means of bringing the reactor to a cold shutdown condition is used when the condenser is lost
Mr. James P. O'Heilly February 26, 1980 as a heat sink, off-site power is lost, or there is an accident.
It makes use of emergency and safe shutdown systems which are all safety related. These systems and the necessary instrumentation are powere.d f rom the emergency AC and DC buses only. Since these are classified as safety-related, they are seismically qualified and have redundant, independent subsystems so that a single failure of a subsystem will not result in the inability to place the reactor in cold shutdown.
ofpladt The auxiliary buses supply power to balance equipment and some of its instrumentation, so while their loss might result in the loss of the condenser as a heat sink and feedwater for makeup to the reactor, it would not impact the ability to use the safe shutdown systems to bring the reactor to a cold shutdown condition. Shutdown by the safe shutdown systems would not be unusual, as that is the method expected to be used in the event of an accident.
While some balance of plant instrumentation is powered by the auxiliary buses, most is powered from the vital bus which is independent.
Loss of the vital bus (UPS) was the subject of the CP&L
- report, "UPS Design and Operation Evaluation,"
(Attachment 2).
It discusses the fact that UPS supplies pouer to most balance of plant instrumentation and to loads which require a source of uninterrupted power to maintain sustained plant operation and monitoring, and that its operation is not necessary to bring the reactor to cold shutdown. Although it feeds a few safety related and some reactor instruments, they are not necessary to shut down the reactor as other suitable indications are available which are powered by other buses.
Loss of the vital bus might result in the loss of the condenser as a heat sink but would not prevent the use of the safe shutdown or emergency systems.
,jp The emergency +AC buses supply power to most of the safety-related equipment and its instrumentation, including some of the safe shutdown equipment and some of the reactor instrumentation. These buses and the shutdown systems and associated instrumentation they supply are redundant and independent, so the loss of a bus or a whole division would not hinder the safe shutdown of the unit with the remaining systems.
The enclosed sections of the CP&L report,
" Analysis of Safe Shutdown Capability," (Attachment 1) examine the impact of the loss of any of the emergency buse,s
Mr. James P. O'Reilly February 26, 1980 cnd shows that the unit could still be brought safely to cold shutdown.
The emergency DC buses supply power to the remaining safety related instruments and to equipment not fed from any AC buses. These loads include annunciators, ECCS initiation and containment isolation logic, electrical distribution system breaker operation, and HPCI/RCIC equipment and instrumentation.
Planned plant modificat.ans will result in new analog reactor level and pressure instrumentatipn, in addition tc the existing, powered from the emergency AC and vital Ar bases. Just as with the emergency AC buses, the DC buses and the shutdown equipment and instrumentation they supply are redundant and independent so the loss of a bus or division would not prevent the safe shutdown of the unit with the remaining systems.
Ic.
The " Analysis of Safe Shutdown System" study recommended three modifications which have already been implemented.
No problems were identified by the review for this IE Bulletin so no additional modifications are planned.
2.
A review of emergency procedures, including procedures required to achieve a cold shutdown condition, that will be used by control room operators upon loss of power to each class 1E and non-class IE bus supplying power to safety and non-safety related instrument and control systems has been completed.
The review indicated that our procedures adequately cover the concerns addressed in Item 2 of this bulletin.
3.
IE Bulletin 79-27 asked for a review of the failure of 120 volt vital AC power supplies. This is the subject of a study completed at BSEP in November,1979. A copy of the study, "UPS Design and Operation Evaluation," is included with this response as Attachment 2.
The study concludes that:
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- 9 V The poss. /ible transients which could result from the a.
loss of UPS are bounded by those analyzed in the FSAR.
b.
Its failure does not affect the overall safe response of the plant to any operating transients, and the purrent design and reliability of the systems are
, acceptable.
O
Mr. James P. O'Reilly
-5 February 26, 1980
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Annunciator procedures exist to instruct the operator on appropriate corrective actions.
d.
An emergency instruction has been developed for complete loss of the UPS Systems.
The diversity and redundancy of buses and instrumentation, the existence of backup power sources for the vital bus and the emergency AC and DC buses, and the design of the emergency buses to safety class and seismic standards all serve to assure the reliability of the electrical distribution system for supplying power to equipment and instrumentation. Even if any portion of the electrical distribution system is lost, the plant can be brought to a cold shutdown condition with existing procedures and alternate or redundant instrumentation.
The operator is warned of problems or loss of all significant portions of the electrical distribution system by instrumentation in the control room. The loss of those small portions of the system for which the operator is not warned would have limited impact and can be accommodated using alternate equipment or other commonly used shutdown procedures.
We trust that this inf o rma tion satisfies the request of IE Bulletin 79-27.
Yours very truly, B. J. Furr Vice President Nuclear Operations RMP/JSB/CSB/jmb*
cc:
Mr. N. C. Moseley
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