ML20148E034
| ML20148E034 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 01/20/1988 |
| From: | Shelton D TOLEDO EDISON CO. |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| Shared Package | |
| ML20148E029 | List: |
| References | |
| TAC-66967, NUDOCS 8801250547 | |
| Download: ML20148E034 (13) | |
Text
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4 Docket No. 50-345 1
License No. NPF-3 Serial No. 1469 Enclosure Page 1 APPLICATION FOR AMENDMENT TO FACILITY OPERATING LICENSE NO. NPF-3 l
FOR DAVIS-BESSE NUCLEAR POWER STATION UNIT NO. 1 I
Attached is the requested change to the Davis-Besse Nuclear Power 5
Station Unit No. 1 Facility Operating License No. NPF-3.
Also included are the Safety Evaluation, Summary Significant Hazards Consideration and Significant Hazards Consideration.
I The proposed change (submitted under cover letter Serial No. 1469) concerns!
Section 3/4.8.1, Electrical Power Systems. A.C. Sources Specification 1
4.8.1.1.lb.
i By
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D.'C.
Shelton, Vice President, Nuclear s
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Sworn and subscribed before me thip 20th day of January, 1988.
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Notary Public, State of Ohio i
My commission expires 3 !/ I f /
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r 8801250547 8801kM)
PDR ADOCK 05000346 P
PER I
Docket No. 50-346 License No. NPF-3 Serial No. 1469 Enclosure Page 2 The following information is provided to support issuance of the requested change to the Davis-Besse Nuclear Power Station, Unit No. 1 Operating License No. NPF-3 Appendix A Technical Specffications Surveillance Requirement 4.8.1.1.lb.
A.
Time Required to Implement:
This change is to be implemented by the licensee within 30 days following NRC issuance of the License Amendment, or by March 1, 1988, whichever occurs first.
B.
Reason for Change (DCR 88-0004-00): Revise the Teranical Specifications to allow a one-time extension in the 18 month surveillance interval for operability testing of the 13.8 KV bus transfer breakers.
C.
Safety Evaluation:
See attached Safety Evaluation (Attachment No. 1).
D.
Summary Significant Hazards Consideration: See attached Summary Significant Hazards Consideration (Attachment No. 2).
E.
Significant Itazards Consideration:
See attached Significant Hazards Consideration (Attachment No. 3).
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Docket No. 50-346 License No. NPF-3 Scrial No. 1469 Page 1 SAFETY EVALUATION Description The purpose of this safety evaluation is to review a proposed change, the one-time extension in the 18 nonth surveillance interval for operability testing of the 13.8 KV bus transfer, to the Davis-Besse Nuclear Power Station (DBNPS) Unit No. 1 Operating License, Appendix A, Technical Specifications, to ensure that no unreviewed safety questions exist. This safety evaluation is being performed to meet the requirements of 10CFR50.59.
The DBNPS Technical Specifications, Section 3/4.8.1 Electrical Power Systems, A.C. Sources, Surveillance Requirements 4.8.1.1.1 and 4.8.1.2 require the 13.8 KV bus transfer be demonstraced operable by performing certain tests once per 18 months. Technical Specification 4.0.2a provides for a maximum allowable extension of this interval by 25 percent. For any one 18 month interval, this provides D-a maximum 4.5 month extension. Technical Specification 4.0.2b requires that the total combined interval for any three consecutive tests does not exceed 3.25 times the specified time interval. Therefore, the total combined interval for three consecutive tests cannot exceed 58.5 months.
Technicc1 Specification 3.8.1.la requires that two independent circuits between the offsits trarsmission network and the onsite Class 1E distribution system he opert.ble in Modes 1 through 4.
Technical Specification 3.8.1.2a requires that, at a minimum, one circuit between the offsite transmission network and the onsite Class IE distribution system be operable in Modes 5 and 6.
To demonstrate operability of these circuits, Surveillance Requirements 4.8.1.2 (for Modes 5 and 6),
4.8.1.1.la, and 4.8.1.1.lb are performed.
Based on the present schedule, all surveillance requirements are anticipated to be satisfied within ti.e interval specified by the Technical Specifications, including the 25 percent extension allowed by 4.0.2a, with the exception of 4.8.1.1.lb.
Surveillance Requirement 4.8.1.1.lb, Demonstrate OPERABLE at least once per 18 months during shutdown by transferring (manually and automatically) unit power supply to each of the 345 KV transmission lines.
Surveillance Requirement 4.8.1.1.lb was last performed on April 14, i986. Therefore, in order to meet the Technical Specifications surveillance interval, including the 25 percent extension, and maintain an operable status, a 345 KV transfer test must be performed by March 1, 1988 (the 3.25 interval comes due on 7/24/98). As stated above, the
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L Docket No. 50-346 License No. NPF-3 i
Serial Np. 1469 Attachmei,t 1 Page 2 i
Technical Specifications require the plant to be in a shutdown condition to verify operability. This implies, and recent review veriffes, that performance of this test while the reactor is at power could potentially challenge (should a failure occur) plant safety systems, which is t
undesirable. Performance of this Surveillance Test in Modes 1 through 4 would force entry into several Limiting Conditions for Operation Action Statements due to the loss of Electrical Distribution train independence. This maicos performance of this test while at power I
undesirable, Consequent 2y, this,would require a plant shutdown and cooldown prior to the fifth refueling outage, now scheduled to commence on March 11, 1988.
This safety evaluation presents technical justification for a one-time extension of the 18 month surveillance schedule of the 13.8 KV bus transfer test. This extension wculd be applicable to Surveillance Requirement 4.8.1.1.lb.
Surveillance Requirement 4.8.1.2, which defines operability requirements for che 345 KV circuits in Modes 5 and 6, also i
references this section of 4.8.1.1.1.
The 13.8 KV bus transfer test, i.e., Surveillance Requirement 4.S.1.1.lb, is proposed to be completed no later than April 1, 1988.
While this deferral would exceed the maximum single interval allowed by Technical Specifications, it would still allow compliance with the three consecutive tests interval. The extension would be peroitted by adding a footnote to Section 4.8.1.1.1b which reads:
- The 18 month surveillance, which is due on March 1, 1988, may be delayed until April 1, 1988.
Systems Affected j
7 Offsite A.C. Electrical Power Sources Documents Affected Davis-Besse Nuclear Power Station Operating License, Appendix A:
l Technical Specifications Davis-Besse Surveillance Test ST 5080.02 Independent Offsite AC Sources Bus Transfer Safety Function of Affected System
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The offsite A.C. power supply system provides a reliable, redundant i
source of power to the on-afte A.C. porer distribution system when the
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normal source of A.C. power (the Davis-Besse turbine generator) is j
unavailable due to planned shutdown or a transient which results in a turbine trip. The 345 KV transmission lines feed the startup I
transformers, which af ter stepping down the incoming power from 345 KV to j
13.8 KV, feed breakers on the 13.8 KV AC busses. From this point, the g
i power is then distributed throughout the facility.
The relaying of the r
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Docket No. 50-346 License No. NPF-3 Serial No. 1469 Page 3 system is set up so that open a turbine generator trip, the 13.8 KV busses are fast transferred to the offsite power source, vhich was preselected by the reactor operator in the control room.
If the preselected power supply is not available, the 13.8 KV bus goes dead, the corresponding emergency diesel generator (EDG) automatically starts and picks up the essential (safety related) loads. The 13.8 KV bus will not shift to the alternate startup transformer.
If a 13.8 KV bus is being I
supplied from a startup transformer and the offsite source fails, the l
13.8 KV bus will fast transfer to the alternate startup tranaforrer, if l
preselected by the operator. This is the capability demonstration which is being deferred. This transfer logic can be manually controlled and l
overridden for unusual circumstances. The capability to transfer betwaen l
offsite power supplies was not assumed to exist in USAR Chapter 15
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analyses. These analyses were based on mitigating accidents with l
equipment powered from the EDGs, not offsite power.
If one of the offsite power supplies is not available in Modes 1 through 4, the unit enters r Technical Specification Limiting Condition for Operation.
The purpose of this complex system is to ensure that an adequate A.C.
pcwer supply is always available to power the minimum equipment assumed to operate in the Updated Safety Analysis Report (USAR).
System
'lexibility, coupled with the Emergency Diesel Generators (EDCs),
provides the capability to supply power to essential plant electrical equipnent. The Technical Specification Surveillance Requirement causes verification that redundancy and reliability greater than that assumed in the USAR analyses exists. This verification is accomplished by manually and automatically transferring the 13.8 KV busses between offsite power sources while in Mode 5 or 6.
Effects on Safety The purpose of the Surveillance Test is to verify that the transfer capability is still operable, and deferring the demonstration of transfer capability between offsite sources while the plant is at power has no adverse effect on plant safety. The operability of the 13.8 KV breakers' manual transfer capability has been demonstrated several times since the last performarce of the Surveillance Test in April 1986. Additionally, the ability to perform an automatic fast transfer from the nornal source (D-B turbine generator) to the selected offsite source (startup transformer 01 or 02) has been demonstrated several times.
This has occurred as a result of several plant trips. While one of the breakers failed during the September 6, 1987 trip, follow-up post maintenance testing demonstrated its operabill.ty. During the unit trip on December 7, 1987, the 13.8 KV busses automatically transferred to the correct offsite power supplies. The basis of the Surveillance Requirement interval is to verify operability prior to exceeding the equipment's mean tire between failures.
In this case, an acceptable system function has been demonstrated within this interval.
The portions of the manual and automatic transfer capabilities, which have been called upon to operate, have operated properly during these plant trips and, therefore, provide confidence in the system's capability to properly functicn during power operation.
Dochet No. 50-346 License No. NPF-3 Serial No. 1469 Page 4 After the plant is shut down, the normal power supply (the turbine generator) to the 13.8 KV busses is no longer available. Consequently, the ability to select (either automatically or manually) between the offsite power sources is highly desirable, but not necessary for plant safety, since any scenario involving a loss of offsite power (including the failure of the offsite power supply transfer scheme addressed herein) will cause the EDGs to start. Even if one of the EDGs fails, redundancy ensures the minimum equipment assumed to function in the USAR will be powered. In addition, since the plant would already be in a shutdown condition, the amount of time available for operators to take manual action prior to occurrence of a significant threat to public health and safety developing is greatly extended.
Consequently, deferring the demonatration of operability to a time when the plant is in a stable shutdown condition has no adverse effect on plant safety.
Mhite it can be concluded that deferral of this Surveillance Test does tot impact plant safety, this testing will be perfermed as soon as persible after the plant is placed in a stable shutdown condition.
Unreviewed Safety Ouestion Review The one time deferral of operability verification of the 345 KV offsite power riupply transfer capability until April 1, 1968:
Does not increase the probability of an accident previously evaluated in the USAR because the manual and automatic transfer capability will still be available when required. Deferral of the test has no impact on the probability of a loss of offsite power, Joad rejection or station blackout (10CFR50. 59 (a) (2) (1)).
Does not increase the consequences of an accident previously evaluated in the USAR because adequate power sources which are known to be operable are available. Consequently, all the conclusions of the accident analyses in the USAR, including single failure assumptions, are still valid (10CFR50.59(a)(2)(1)).
Does not increase the consequences of a malfunction of equipment impor tant to safety since the system has demonstrated sufficient operability to be able to cope with malfunctions and still meet the r
assumptions made in the USAR accident analyses, including single failure analyses (10CFR50.59(a)(2)(1)).
Does not create a possibility for an accident of a different type than any evaluated previously in the USAR since a failure to transfer between offsite power supplies is a previously analyzed event. No new types of accidents are created (10CFR50.59(a)(2)(1)i.
1 Docket No. 50 346 License No. NFF-3 Serial No. 1469
-Attachment 1 Page 5 1
Does not create a possibility _for a malfunction of equipment of a different type than any evaluated previously in the USAR because no 4
physical changes are being made which could create any new failure modes (10CFR50.59(a)(2)(ii)).
I Does not reduce the margin of safety as defined in the basis for any Technical Specification because adequate operability of the A.C.
power system has been demonstrated to ensure sufficient power will be available to supply the safety related equipment of the facility and to allow the mitigation and control of accident conditions within the facility as assumed in the USAR (10CFR50.59(a)(2)(iii)).
Conclusion l
Consequently, it is concluded that deferral of demonstrating the capability to automatically transfer between the 345 KV offsite power j
supplies to no later than April 1, 1988 does not create an unreviewed safety question.
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Docket No. 50-346 License No NPF-3 Serial No. 1469 Page 1
SUMMARY
SIGNIFICANT HAZARDS CONSIDERATION Description of Amendment Request: This amendment request proposes a one-time extension of 30 days to the 13.8 KV Bus transfer 18-month surveillance interval to demonstrate operability. This is accomplished by transferring (manually and automatically) the unit power supply to each of the 345 KV transmission lines. This requirement is contained in Technical Specifications (TS) Section 4.8.1.1.lb and is referenced in TS 4.8.1.2 for Modes 5 and 6 operation.
Basis for Proposed No Significant Hazards Consideration Determination:
The purpose of the change is to allow operation of the Davis-Besse Nuclear Power Station until the fifth refueling outage before performing the testing.
The present schedule, including the allowable extension 1
permitted by TS, would require the 13.8 KV bus transfer to be tested on March 1, 1988. The extension would allow entry into the scheduled refueling outage without requiring a prior unscheduled outage.
Since the last surveillance interval, the operability of the 13.8 KV breaker manual transfer capability has been demonstrated several times during routine electric system operations. Additionally, the ability to perform an automatic fast transfer from the normal power source (auxiliary j
transformer) to the selected offsite source (startup transformers) has l
been demonstrated several cimes as a result of plant trips. While one of the breakers failed during the September 6, 1987 plant trip, follow-up post maintenance testing demonstrated its operability. During the unit trip on December 7, 1987, the 13.8 KV busses automatically transferred to the correct offsite power supplies.
The proposed extension is within the requirement of TS 4.0.2b, which requires that the last three consecutive tests have a combined interval j
of not more than 3.25 times the nominal 18 month interval.
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The safety significance of the extension is in consideration of extending the 18 month test (including TS allowed extensions) by 30 days and the confidence that the 13.8 KV bus transfer breakers will perform their i
functior. with the extension of time.
However, based on the above considerations justifying the extension and that an unscheduled outage just prior to the scheduled refueling outage is not desirable, it is concluded that: The extension will not result in a significant increase in the probability or consequences of a previously evaluated accident nor will it create the possibility of a new or dif ferent kind of an accident.
A significant reduction in the margin of safety is not involved.
Therefore, the proposed amendment is determined not to involve a sig-nificant hazards consideration.
Docket No. 50-346 License No. NPF-3 Serial No. 1469 Page 1 4
SIGNIFICANT HAZARDS CONSIDERATION i
Description The purpose of this Significant Hazards Consideration is to revir> a proposed change, the one-time extension in the 18 month surveillance interval for operability testing of the 13.8 KV bus transfer, to the Davis-Besse Nuclear Power Station (DBNPS) Unit No. 1 Operating License, Appendix A, Technical Specifications, to ensure that no Significant Hazards Consideration exists. This significant hazards consideration is being performed to meet the requirements of 10CFR50.92.
The DBNPS Technical Specifications, Section 3/4.8.1 Electrical Power Systems, A.C. Sources, Surveillance Requirements 4.8.1.1.1 and 4.8.1.2 require the 13.8 KV bus transfer be demonstrated operable by performing certain tests once per 18 months. Technical Specification 4.0.2a i
provides for a maximum allowable extension of this interval by 25 percent.
For any one 18 month interval, this provides for a maximum 4.5 l
month extension. Technical Specification 4.0.2b requires that the total combined interval for any three consecutive tests not exceed 3.25 times I
s the specified time interval. Therefore, the total combined interval for
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three consecutive tests cannot exceed 58.5 months.
I Technical Specification 3.8.1.la requires that two independent circuits j
between the offsite transmission network and the onsite Class 1E dis-tribution system be operable in Modes 1 through 4.
Technical Speci-fication 3.8.1.2a requires that, at a minimum, one circuit between the offsite transmission network and the onsite Class 1E distribution system be operable in Modes 5 and 6.
To demonstrate operability of these l
4 circuits, Surveillance Requirements 4.8.1.2 (for Modes 5 and 6), 4.8.1.1.la, and 4.8.1.1.lb are performed.
Based on the present schedule, all surveillance requirements are anticipated to be satisfied within the interval specified by the Technical Specifications, including the 25 percent extension allowed by 4.0.2a, with the exception of 4.8.1.1.1b.
Surveillance requirement 4.8.1.1.lb, Demonstrate OPERABLE at least 4
once per 18 months during shutdown by transferring (manually and automatically) unit power supply to each of the 345 KV transmission j
lines.
Surveillance Requirments 4.8.1.1.lb was last performed on April 14, 1986. Therefore, in order to meet the Technical Specifications surveillance interval, including.he 25 percent extension, and maintain l
an cperable status, a 345 KV transfer test must be performed by March 1, 1988 (the 3,25 interval comes due on July 24, 1988). As stated above, the 1
Dochee No. 50-346 License No. NPF-3 Serial No. 1469 Page 2 Technical Specifications require the plant to be in a shutdown condition to verify operability.
This implies, and recent review verifies, that performance of this test while the reactor is at power could potentially challenge (should a failure occur) plant safety systems, which is undesirable. Performance of this Surveillance Test in Modes 1 through 4 would force entry into several Limiting Conditions for Operation Action Statements due to the loss of Electrical Distribution train independence. This makes performance of this test while at power undesirable. Consequently, this would require a plant shutdown and cooldown prior to the fifth refueling outage, now scheduled to commence on March 11, 1988.
This safety evaluation presents technical justification for a one-time extension of the 18 month surveillance schedule of the 13.8 KV Bus transfer test.
This extension would be applicable to Surveillance Requirement 4.8.1.1.lb.
Surveillance Requirement 4.8.1.2, which defines operability requirements for the 345 KV circuits in Modes 5 and 6, also references this section of 4.8.1.1.1.
The 13.8 KV bus transfer test, i.e., Surveillance Requirement 4.8.1.1.1b, is proposed to be completed no later than April 1, 1988.
While this deferral vould exceed the maximum single interval allowed by Technical Specifications it would still allow compliance with the three consecutive tests interval. The extension would be permitted by adding a footnote to Section 4.8.1.1.lb which reads:
- The 18 month surveillance, which is due on March 1, 1988, may be delayed until April 1, 1988.
Systees Affected Offsite A.C. Electrical Power Sources Documents Affected Davis-Besse Nuclear Power Station Operating License, Appendix A:
Technical Specifications Davis-Besse Surveillance Test ST 5080.02 Independent Offsite AC Sources Bus Transfer Safety Function of Affected System The offsite A.C. power supply system provides a reliable, redundant source of power to the on-site A.C. power distribution system when the normal source of A.C. power (the Davis-Besse turbine generator) is unavailable due to planned shutdown or a transient which results in a turbine trip. The 345 KV transmission lines feed the startup transformers which, af ter stepping down the incoming power from 345 KV to 13.8 KV, feed breakers on the 13.8 KV AC busses.
From this point, the power is then distributed throughout the facility. The relaying of the 4
Dochet No. 50-346 License No. NPF-3 Serial No. 1469 page 3 system is set up so that upon a turbine generator trip, the 13.8 KV busses are fast transferred to the offsite power source, which was preselected by the reactor operator in the control room.
If the preselected power supply is not available, the 13.8 KV bus goes dead, and the corresponding emergency diesel generator (EDG) automatically starts and picks up the essential (safety related) loads. The 13.8 KV bus will not shift to the alternate startup transformer.
If a 13.8 KV Fus is being supplied from a startup transformer and the offsite source fails, the 13.8 KV bus will fast transfer to the alternate startup transformer, if preseleted by the I
operator. This is the capability demonstration which is being deferred.
I This transfer logic can be manually controlled and overridden for unusual circumstances. The capability to transfer between offsite power supplies
- was not assumed to exist in USAR Chapter 15 analyses. These analyses were based on mitigating accidents with equipment powered frcm the EDGs, not offsito power.
If one of the offsite power supplies is not available in Modes 1 through 4, the unit enters a Technical Specification Limiting Condition for Operation.
The purpose of this complex system is to ensure that an adequate A.C.
power supply is always available to power the minimum equipment assumed to operate in the Updated Safety Analysis Report (USAR).
System flexibility, coupled with the Emergency Diesel Generators (EDGs),
provides the capability to supply power to essential plant electrical equipment. The Technical Specifications Surveillance Requirement causes verification that redundancy and reliability greater than that assumed in the USAR analyses exists. This verification is accomplished by manually and automatically transferring the 13.8 KV busses between offsite power sources while in Mode 5 or 6.
Effects on Safety ThepurposeoftheSurvokilanceTest is to verify that the transfer capability is still oparable, and deferring the demonstration of transfer capability between offsite sources while the plant is at power has no adverse effect on plant safety. The operability of the 13.8 KV breakers' manual transfer capability has been demonstrated several times during routine electric system operations since the last performance of the Surveillance Test in April 1986. Additionally, the ability to perform an automatic fast transfer from the normal source (D-B turbine genrator) to the selected of fsite source (startup transformer 01 or 02) has been demonstrated several times. This has occurred as a result of several plant tripr,.
While one of the breakers failed during the September 6, 1987 trip, follow-up post maintenance testing demonstrated its oper-ability. During the unit trip on December 7, 1987, the 13.8 KV busses automat!.cally transferred to the correct offsite power supplies.
The Surveillance Requirement requires operability verification within an 18 month interval not to exceed 25%.
In this case, an acceptable system function has been demonstrated within this interval. The portions of the mancal and automatic transfer capabilities which have been called upon to operate have operated properly during these plant trips and therefore, provide confidence in the system's capability to properly function during power operation.
Docket No. 50-346 License No. NPF-3 Serial No. 1469 Page 4 After the plant is shutdown, the normal power supply (the turbine generator) to the 13.8 KV busses is no longer available. Consequently, the ability to select (either automatically or manually) between the offsite power sources is highly desirable, but not necessary for plant safety, since any scenario involving a loss of offsite power (including the failure of the offsite power supply transfer scheme addressed herein) will cause the EDGs to start.
Even if cne of the EDCs fails, redundancy ensures the minimum equipment assumed t.
function in the USAR will be powered.
While it can be concluded that deferral of this Surveillance Test does not impact plant safety, this testing will be perforced af ter the plant is placed in a stable shutdown condition and no later than April 1, 1988.
Significant Hazards Consideration The proposed change does not involve a significant hazards consideration because the operation of the Davis-Besse Nuclear Power Station, Unit No. 1, in accordance with this change would:
1.
Not involve a si nificant increase in the probability or F
consequences of an accident previously evaluated (10CFR50.92 (c) (i)).
The probability or consequences of an accident previously evaluated is not increased because the manual and automatic transfer capability will still be available and deferral of the surveillance test has no impact on the probability of a loss of offsite power, load rejection or station blackout. Also, adequate power sources which are known to be operable (e.g.
Emergency Diesel Generators) are available.
2.
Not create the possibility of a new or different kind of accident from any accident previously evaluated (10CFR50. 92 (c) ( 2)).
The proposed Technical Specifications change will not create the possibility of a new or different kind of accident from any previously evaluated because proper operability of the 13.8 KV transfer bus is still assured and the failure codes are the j
saee as previously analyzed.
There is no change to the operational limits or physical design of the 13.8 KV transfer bus, j
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Docket No. 50-346 License No. NPF-3 Serial No. 1469 Page 5 3.
Not involve a significant reduction in the margin of safety (10CFR50. 92 (c) (3)).
The proposed Technical Specifications change does not involve a significant reduction in the margin of safety because the assumptions in the USAR analyses are unchanged and the con-sequences of a malfunction of the 13.8 KV bus transfer is within the bounds previously analyzed.
Conclusion Therefore, it is concluded that the proposed Technical Specifications change does not involve a significant hazards consideration.
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