ML20209B730
| ML20209B730 | |
| Person / Time | |
|---|---|
| Site: | Byron, Braidwood  |
| Issue date: | 06/30/1999 |
| From: | Krich R COMMONWEALTH EDISON CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| Shared Package | |
| ML20209B737 | List: |
| References | |
| NUDOCS 9907080004 | |
| Download: ML20209B730 (13) | |
Text
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., Commonwealth Edison Company 9 1400 Opus Place Downers Grove, 11, 60515-5701 g
June 30,1999 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555 Byron Station, Units 1 and 2 Facility Operating License Nos. NPF-37 and NPF-66 NRC Docket Nos. STN 50-454 and STN 50-455 Braidwood Station, Units 1 and 2 Facility Operating License Nos. NPF-72 and NPF-77 NRC Docket Nos. STN 50-456 and STN 50-457 l
Subject:
Request for Technical Specifications Change, Correction to Limiting Condition for Operation 3.8.5, "DC Sources - Shutdown" 1 Pursuant to 10 CFR 50.90, we propose to amend Appendix A, Technical Specifications (TS), of Facility Operating License Nos. NPF-37, NPF-66, NPF-72 and NPF-77, for Byron Station, Units 1 and 2, and l
l Braidwood Station, Units 1 and 2. The proposed changes provide correction to the Limiting Condition 1 for Operation (LCO) associated with TS Section 3.8.5, "DC Sources - Shutdown." Additionally, an admireistrative change is being proposed to delete various references to AT&T batte%s in TS Section 3.8, ' Electrical Power Systems," for Braidwood Station only.
The proposed amendment corrects an oversight that occurred in TS 3.8.5 "DC Sources - Shutdown,"
during the implementation of the improved Standard TS. This change removes the requirement from LCO 3.8.5.b, to have at least one cross-tie breaker open. The cross-tie breaker requirement will apply only to LCO 3.8.5.a, as originally intended by the old TS. This change clarifies that the source of DC
- electrical power required by LCO 3.8.5.b for a Unit in Mode 5, Mode 6 or during the movement of j irradiated fuel assemblies, may be cross-tied to the opposite Unit when required by LCO 3.8.10, I
" Distribution Systems - Shutdown." Additionally attached for information only are the proposed TS Bases changes.
An administrative change to the Braidwood Station TS is also included to delete reference to AT&T batteries in LCO 3.8.4,"DC Sources - Operating," LCO 3.8.5, "DC Sources - Shutdown," LCO 3.8.6, I
" Battery Cell Parameters," and LCO 3.8.9, " Distribution Systems - Operating," since all AT&T batteries have been replaced with Ch& awer Systems, Inc. (C&D) batteries. Again, attached for information only are the proposed TS Bases changes associated with this administrative change.
990N000004 30- \
PDR ADOCK 05000454 P PDR_ g ,
A Unicom Company e Us] ;1 l
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L June 30,1999 U. S. Nuclear Regulatory Commission
. Page 2 Also included with this change is the removal of the Allowed Outage Time extension approved for Braidwood Station with TS Amendment Number 99. The activity addressed by TS Amendment Number 99 is complete, and the extension no longer applies.
We request approval of this amendment prior to the start of Byron Station Unit 2 refueling outage, which is scheduled to begin October 23,1999.
This proposed amendment request is subdivided as follows:
- 1. Attachment A gives a description and safety analysis of the proposed changes.
- 2. Attachments B-1 and B-2 include the marked-up TS pages with the requested changes indicated for Byron Station and Braidwood Station, respectively.
Attachments B-3 and B-4 include the associated typed pages with the proposed changes incorporated for Byron Station and Braidwood S'ation, respectively.
Additionally attached for information on!y are the associated TS Bases page changes.
- 3. Attachment C describes our evaluation performed using the criteria in 10 CFR 50.91(a)(1), which provides information supporting a finding of no significant hazards consideration using the standards in 10 CFR 50.92(c).
- 4. Attachment D provides information supporting the environmental assessment.
This proposed amendment has been reviewed and approved by the Byron Station and Braidwood Station Plant Operations Review Committee and the Nuclear Safety Review Board in accordance with the requirements of the Quality Assurance Program.
Comed is notifying the State of Illinois of this application for amendment by transmitting a copy of this letter and its attachments to the designated State Official.
Should you have any questions relative to this submittal, please contact Mr. J. A. Bauer at (630) 663-7287.
Respectfully, c . /
R. M. Krich Vice President - Regulatory Services Attachments:
Affidavit Attachment A: Description and Safety Analysis for Proposed Changes Attachment B-1: Marked-up Page for Proposed Changes for Byron Station Attachment B-2: Marked-up Pages for Proposed Changes for Braidwood Station L s
e June 30,1999 U. S. Nuclear Regulatory Commission Page 3 Attachment B-3: Incorporated Proposed Changes, Typed Page, for Byron Station Attachment B-4; incorporated Proposed Changes, Typed Pages, for Braidwood Station !
Attachment C: Information Suppoiling a Finding of No Significant Hazards Consideration l Attachment D: Information Supporting an Environmental Assessment j cc: Regional Administrator- NRC Region lli NRC Senior Resident Inspector - Byron Station NRC Senior Resident inspector - Braidwood Station Office of Nuclear Facility Safety - IDNS ;
i 1
l I
STATE OF ILLINOIS }
COUNTY OF DUPAGE )
IN THE MATTER OF )
COMMONWEALTH EDISON (COMED) COMPANY ) Docket Nos.
BYRON STATION - UNITS 1 and 2 ) STN 50-454 and STN 50-455 BRAIDWOOD STATION - UNITS 1 and 2 ) STN 50-456 and STN 50-457
SUBJECT:
Request for Technical Specifications Change, Correction to Limiting Condition for Operation 3.8.5, "DC Sources - Shutdown" l AFFIDAVIT I affirm that the content of this transmittalis true and correct to the best of my knowledge, information and belief.
D R. M. Kafeff/
Vice President - Regulatory Services l
Subscribed and sworn to before me, a Notary Public in and for the State above named, this day of R 19
/
\ l RQM A~ Notary Public l/ -
d TINA M TAMAYO-SANTOLIN h NOTARY PUBUC, ST ATE OF ILUNols d MY COMMI684)N EXPIRES:04/
t,':::::::::::-'m w- :- 19/00 1
Page 1 of 1 Attachment - Affidavit J
{ ,
e ATTACHMENT A Proposed Changes to Technical Specifications for Byron Station, Units 1 and 2, and Braidwood Station, Units 1 and 2 DESCRIPTION AND SAFETY ANALYSIS FOR PROPOSED CHANGES A.
SUMMARY
OF PROPOSED CHANGES Pursuant to 10 CFR 50.90, we propose to amend Appendix A, Technical Specifications (TS), of )
Facility Operating License Nos. NPF-37, NPF-66, NPF-72 and NPF-77, for Byron Station and )
Braidwood Station. The proposed amendment corrects an oversight that occurred in Limiting ,
Condition for Operation (LCO) 3.8.5, "DC Sources - Shutdown," during the implementation of l the Improved Standard TS. This change removes the requirement from LCO 3.8.5 item b to have at least one cross-tie breaker open. The cross-tie breaker requirement will apply only to LCO 3.8.5 item a, as originally intended by the old TS. This change clarifies that the source of DC electrical power required by LCO 3.8.5 item b for a Unit in Mode 5, Mode 6 or during the movement of irradiated fuel assemblies, may be cross-tied to the opposite Unit when required by LCO 3.8.10, " Distribution Systems - Shutdown."
An administrative change to the Braidwood Station TS is also included to delete reference to AT&T batteries in LCO 3.8.4, "DC Sources - Operating," LCO 3.8.5, "DC Sources - Shutdown,"
LCO 3.8.6, " Battery Cell Parameters," and LCO 3.8.9, " Distribution Systems - Operating," since i all AT&T batteries have been replaced with Charter Power Systems, Inc. (C&D) batteries. Also included with this change is the removal of the Allowed Outage Time (AOT) extension approved for Braidwood Station with TS Amendment Number 99. The activity addressed by TS Amendment Number 99 is complete, and the extension no longer applies. We request i approval of this amendment prior to the start of Byron Station, Unit 2 refueling outage (i.e.,
B2RO8), which is scheduled to begin October 23,1999.
The proposed changes are described in detailin Section E cf this Attachment. The marked-up TS and Bases pages are shown in Attachment B.
B. DESCRIPTION OF THE CURRENT REQUIREMENTS LCO 3.8.5, "DC Sources - Shutdown," requires that for a unit in Mode 5, Mode 6 or during the movement of irradiated fuel assemblies, two DC sources must be operable when required by LCO 3.8.10 " Distribution System - Shutdown." Neither of these sources can be supplied by the opposite unit via the cross-tie. A Note modifies this LCO, stating that closing the cross-tie is permissible to supply the opposite unit if the opposite unit is in Mode 1,2,3, or 4, and the opposite unit's battery charger is inoperable.
C. BASES FOR THE CURRENT REQUIREMENTS The LCO Section of the Bases for B3.8.5 states, "The DC electrical power subsystems with:
Page 1 of 8 Attachment A - Description and Safety Analysis
r:
gp _
- a. i at least one subsystem consisting of a battery and battery charger;
- b. when the redundant division of the Class 1E DC electrical power distribution subsystem t is required by LCO 3.8.10, the other subsystem consisting of either a battery or a l charger; and
- c. the corresponding control equipment, and interconnecting cabling within the division (s) are required to be OPERABLE to support required division (s) of the distribution systems
- required OPERABLE by LCO 3.8.10, " Distribution Systems - Shutdown." This ensures the availability of sufficient DC electrical power sources to operate the unit in a safe manner, and to mitigate the consequences of postulated events during shutdown (e.g., fuel handling accidents).
Furthermore, at least one unit cross-tie breaker per division is required to be open to maintain independence between the units."
The Background Section of the TS Bases for B 3.8.4 states, "The cross-tie between 125 VDC ESF buses 111 and 211 and the cross-tie between 125 VDC ESF buses 112 and 212 are each provided with two normally locked open, manually operated circuit breakers. No interlocks are provided since the interconnected buses are not redundant. However, if one battery is inoperable, procedural and administrative controls are used to limit the connected load to 200 amps [ Byron) based on not exceeding the OPERABLE battery capacity. These controls ensure that combinations of maintenance and test operations will not preclude the system capabilities to supply power to the ESF DC loads. The provisions of administratively controlled, manually actuated, interconnections between the nnn-redundant Class 1E DC buses increases the overall reliability and availability of the DC systems for each unit in that it provides a means for manually providing power to a DC bus at a time when it would otherwise have to be out-of-service (e.g., to perform a battery discharge test during an outage, to replace a damaged cell, etc.). Cross-tie breaker closed alarms are also provided to alert the operator when the units are cross-tied." For Braidwood Station, the connected load is administratively limited to 100 amps for AT&T batteries (200 amps for C&D batteries), when DC buses are cross-tied and one
- battery is inoperable.
D. NEED FOR REVISION OF THE REQUIREMENT We are submitting this amendment request to correct an oversight that occurred in LCO 3.8.5, "DC Sources - Shutdown," during the implementation of the Improved Standard TS. This change will allow the use of the DC cross-tie breakers to supply power from the operating unit to one DC bus on the unit in Mode 5, Mode 6 or during the movement of irradiated fuel assemblies. LCO 3.8.5 currently requires two sources of DC power when required by LCO 3.8.10, however, neither source is permitted to be powered via the DC cross-tie breakers.
Therefore, when the associated charger for a DC bus is out of service for maintenance or testing, a temporary charger must be used in order for certain activities to continue, as permitted by the previous TS. If a battery on the shutdown unit became inoperable and the bus
. was required by LCO 3.8.10, the cross-tie to the opposite unit could be closed, but certrin activities on the shutdown unit could not continue, as permitted by the previous TS. The associated charger alone could be used in this case, but this option would require a temporary alteration. It was subsequently realized that the added flexibility and reliability of powering a DC i source using the DC cross-ties is desired for maintenance on the DC subsystems on the Page 2 of 8 Attachment A - Description and Safety Analysis
I ..
4 i i i
shutdown unit, as was permitted by the TS in effect before conversion to the Improved Standard Technical Specifications (Amendment 106 for Byron Station, Amendment 98 for !
Braidwood Station). l This amendment request also resolves an inconsistency between LCO 3.8.5 and LCO 3.8.4, Condition C. This Condition addresses an operating unit's DC bus that is cross-tied to the opposite unit's associated DC bus, which has an inoperable source (i.e., battery or battery I charger), when the opposite unit is in Mode 5, Mode 6, or defueled. This provision is included explicitly to accommodate maintenance and/or testing of the shutdown unit's DC subsystems. l The administrative change to the Braidwood Station TS is included to delete various references to AT&T batteries in LCO 3.8.4, "DC Sources - Operating," LCO 3.8.5, "DC Sources -
Shutdown," LCO 3.8.6, " Battery Cell Parameters," and LCO 3.8.9, " Distribution Systems - 1 Operating," since all AT&T batteries have been replaced with C&D batteries. Also included with this change is the removal of the Allowed Outage Time extension approved for Braidwood Station with Amendment 99. The activity addressed by Amendment 99 is complete, and the extension no longer applies.
l E. DESCRIPTION OF THE PROPOSED CHANGES The proposed change will allow one required source of DC for a unit in Mode 5,6 or during the movement of irradiated fuel assemblies, to be provided by the DC bus cross-ties from the opposite unit, or by the associated battery and either the associated charger or a temporary charger, or the associated charger alone. This change removes the requirement from LCO 3.8.S item b to have at least one cross-tie breaker open. The cross-tie breaker requirement will apply only to LCO 3.8.5 item a. Thus, the DC source referenced by LCO 3.8.5 item b will no longer have the limitation regarding the DC cross-ties. The second source of DC power may then be provided by closing the cross-ties to the opposite unit, by the associated battery and either the associated charger or a temporary charger, or by the associated charger alone, in order to satisfy the requirements of the LCO. The Applicability, Actions, and Surveillance Requirements associated with LCO 3.8.5 will remain unchanged. The impact of this change on plant operations is described below. To facilitate review, a simplified diagram of the DC Electrical Power System at the Byron and Braidwood Stations is provided in Figure 1.
The first case to be discussed is where one unit is shutdown in Mode 5, Mode 6 or moving irradiated fuel assemblies, and the other unit is operating in Mode 1,2,3, or 4, and one of the shutdown unit's DC source (i.e., battery or charger) becomes inoperable either for maintenance or as a result of a failure. When the bus with the inoperable source is cross-tied to the opposite unit, the change to LCO 3.8.5 will allow shutdown unit evolutions to continue, as long as the cross-tied bus is the bus credited for LCO 3.8.5, item b. However, the operating unit will be in LCO 3.8.4, Condition C, and the associated Required Actions must be performed. With the l shutdown unit's battery and charger out of service for maintenance or otherwise inoperable, the
! operating unit will be required to supply allloads on the shutdown unit's cross-tied bus should l
an event occur on the shutdown unit. Therefore, LCO 3.8.4, Required Action C.1 specifies that the possible loading on the shutdown unit's DC bus be verified to be less than or equal to 200 amps once per 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />. Limiting the load to 200 amps ensures that the operating unit's DC subsystem will not be overloaded in the event of a concurrent event on the operating unit.
Required Action C.1 is modified by a Note, which only requires Required Action C.1 to be Page 3 of 8 Attachment A - Description and Safety Analysis L
performed when the opposite unit has an inoperable battery. Required Action C.2 requires the associated cross-tie breaker to be opened within seven days and ensures that measures are being taken to restore the inoperable battery or battery charger, and reestablish independence of the DC subsystems. In this condition, the requirements for the operating unit will ensure the use of the cross-tie for the shutdown unit is restricted to less than or equal to seven days.
These provisions exist in the current TS, and existed in the TS in place prior to the conversion to the Improved Standard TS. If the DC bus on the shutdown unit that is cross-tied is the bus credited in LCO 3.8.5 item a, then the operating unit will be in LCO 3.8.4 Condition C (as described above), and the shutdown unit will be in LCO 3.8.5 Condition A, and the associated Required Actions must be performed. LCO 3.8.5 Required Action A.1 specifies that the shutdown unit either immediately declare the affected required features inoperable, or immediately follow Required Actions A.2.1 through A.2.5 to: suspend core alterations, suspend movement of irradiated fuel assemblies, initiate action to sw. pend positive reactivity additions, initiate action to restore required DC electrical power subsj J. ems to OPERABLE status, and declare affected Low Temperature Overpressure Protection features inoperable. These actions minimize probability of the occurrence of postulated events, and ensure actions are immediately taken to restore the required DC electrical power subsystem.
The second case to be discussed is where both units are shutdown, and a shutdcen unit's DC l source (i.e., battery or charger) becomes inoperable either for maintenance or as a result of a failure. When the bus with an inoperable source is cross-tied to the opposite unit, the change to LCO 3.8.5 will allow the shutdown unit with the inoperable source to continue evolutions, as j long as the cross-tied bus on the unit with the inoperable source is the bus credited for LCO 3.8.5 item b. The other shutdown unit will be in LCO 3.8.5 Condition B, and the associated Required Actions must be performed. With a shutdown unit's battery and charger out of service for maintenance or othenvise inoperable, the unit-specific DC subsystem will be required to supply all loads on the opposite unit's cross-tied bus should an event occur on the opposite unit. !
Therefore, LCO 3.8.5 Required Action B.1 specifies that the possible loading on the opposite unit's DC bus be verified to be less than or equal to 200 amps once per 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />. Limiting the ;
load to 200 amps ensures that the unit-specific DC subsystem will not be overloaded in the event of a concurrent event on the units. LCO 3.8.5 Required Action B.1 is modified by a Note,
)
which only requires Required Action B.1 when the opposite unit has an inoperable battery.
LCO 3.8.5 Required Action B.2 requires the associated cross-tie breaker to be opened within seven days and ensures that measures are being taken to restore the inoperable battery or battery charger, and reestablish independence of the DC subsystems. These provisions exist in the current TS, and existed in the TS in place prior to the conversion to the improved Standard TS. If one of the cross-tied buses is the bus credited in LCO 3.8.5 item a, then that shutdown unit will be in LCO 3.8.5 Condition A, as described above, and the unit with the I operable DC sources will be in LCO 3.8.5 Condition B, as described above. If both of the cross-tied buses are the buses credited in LCO 3.8.5 item a, then both shutdown units will be in LCO 3.8.5 Condition A, as described above, and the unit with the operable DC sources will be in LCO 3.8.5 Condition B, as described above.
The third case to be discussed is where one unit is shutdown in Mode 5, Mode 6 or moving irradiated fuel assemblies, the other unit is operating in Mode 1,2,3, or 4, and one of the operating unit's DC battery chargers becomes inoperable either for maintenance or as a result of a failure. In this case the operating unit is in LCO 3.8.4 Condition A, and the associated Required Actions must be performed. LCO 3.8.4 Required Action A.1 provides for restoration of electrical power to the associated DC bus by use of the cross-tie capability to the opposite Page 4 of 8 Attachment A - Description and Safety Analysis
unit. The two hour Completion Time allows adequate time to evaluate the cause for battery charger failure, to determine whether the opposite unit's DC bus is available for support, and to perform the cross-tie procedure. LCO 3.8.4 Required Action A.2 requires the battery charger to be restored to OPERABLE status within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> in order to reestablish the independence of DC subsystems, while providing a reasonable amount of time for repairs. By limiting the cross-tied conditions of the operating unit to 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, the likelihood of an event occurring which could place either unit in jeopardy is minimized. In this condition, the requirements for the operating unit will ensure the use of the cross-tie for the shutdown unit is restricted to less than or equal to 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />. If the cross-tied DC bus on the shutdown unit is the bus credited in LCO 3.8.5 item b, then shutdown unit evolutions may continue. If the cross-tied DC bus on the shutdown unit is the bus credited in LCO 3.8.5 item a, then the shutdown unit will be in LCO 3.8.5 Condition A, as described above.
The final case to be discussed concerns the use of a temporary charger on a shutdown unit, which may be used only in conjunction with the associated battery. If the DC bus on the shutdown unit credited in LCO 3.8.5 item b is using a temporary charger, then shutdown unit evolutions may continue without restriction. If the DC bus on the shutdown unit credited in LCO 3.8.5 item a is using a temporary charger, then the shutdown unit will be in LCO 3.8.5 Condition A, as descr$ed above.
The TS in effect prior to the implementation of the improved Standard TS, LCO 3/4.8.2.1, "DC Sources Operating," and LCO 3/4.8.2.2, "DC Sources Shutdown," previously allowed operation as proposed by this change. Per LCO 3/4.8.2.2, only one DC bus on a shutdown unit was required to be operable with the associated DC bus cross-ties open. No reference was made in LCO 3/4.8.2.2 to the second DC bus on the shutdown unit. Since no reference was made to the second DC bus, it was permissible to use the cross-ties from the opposite unit as a source of power for that DC bus. In the first case discussed above, where one unit is shutdown in Mode 5 or 6, and the other unit is operating in Mode 1,2,3, or 4, and one of the shutdown unit's DC source (i.e., battery or charger) becomes inoperable, and a DC bus was cross-tied, the action requirements for the operating unit per LCO 3/4.8.2.1 limited the time in this condition to seven days, and if the battery was inoperable on the shutdown unit, also limited the current on the cross-tie to 200 amps. These actions are the same as the current requirements, LCO 3.8.4, Required Actions C.1 and C.2, as described above. If the cross-tied bus on the shutdown unit was the one required to be operable per LCO 3/4.8.2.2, then actions equivalent to the requirements of LCO 3.8.5 Required Actions A.1 and A.2.1 through A.2.5, as described above, were required. In the second case discussed above, where both units are shutdown, and a shutdown unit's DC source (i.e., battery or charger) becomes inoperable either for maintenance or as a result of a failure, again the action requirements of LCO 3/4.8.2.2 limited the time in the cross-tied condition to seven days, and if the inoperable source was a battery, then current on the cross-tie was also limited to 200 amps. These actions are the same as the current requirements, LCO 3.8.5, Required Actions B.1 and B.2, as described above. If the cross-tied bus was the one required to be operable per LCO 3/4.8.2.2, then actions equivalent to the requirements of LCO 3.8.5 Required Actions A.1 and A.2.1 through A.2.5, as described above, were required. In the third case discussed above, where one unit is shutdown in Mode 5 or 6, the other unit is operating in Mode 1,2,3, or 4, and one of the operating unit's DC battery chargers becomes inoperable either for maintenance or as a result of a failure, then the action requirements of LCO 3/4.8.2.1 required the shutdown unit to supply the operating units DC bus within two hours, but limited the time in this condition to 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> for the operating unit.
These actions are the same as the current requirements, LCO 3.8.4, Required Actions A.1 and Page 5 of 8 Attachment A - Description and Safety Analysis
A.2, as described above. If the cross-tied bus on the shutdown unit was the one required to be operable per LCO 3/4.8.2.2, then actions equivalent to the requirements of LCO 3.8.5, '
)
Required Actions A.1 and A.2.1 through A.2.5, as described above, were required. In the final case discussed above, operation with the use of a temporary charger on a shutdown unit was permitted because only one DC bus was required to be operable, and DC source requirements for the second DC bus were not mentioned. Therefore, a temporary charger could always be ,
used on the second DC bus: This discussion demonstrates that the TS in effect prior to the implementation of the improveo Technical Specifications allowed operation in the manner proposed by this change. Thus the proposed change is considered an administrative correction to restore allowances inadvertently eliminated during the conversion to the improved Technical Specifications.
An administrative change to the Braidwood Station Technical Specifications is also included in this proposed amendment. In LCO 3.8.4, Required Action C.1, and in LCO 3.8.5, Required Action B.1, the change deletes "5100 amps for AT&T ($ 200 amps for C&D)" and replace it with "5 200 amps." Other changes to LCO 3.8.4 include the deletion of Condition D, which only applied during the replacement of AT&T batteries, renumbering of Condition E to Condition D and removing Required Action E.2, which only. applied during the replacement of the AT&T batteries, and renumbering of Condition F to Condition E. Whenever Conditions are renumbered, the associated Required Actions are also renumbered. In Surveillance y Requirement (SR) 3.8.4.1, SR 3.8.4.7, and SR 3.8.4.8 references to AT&T batteries are removed. In LCO 3.8.6, " Battery Cell Parameters," Table 3.8.6-1, " Battery Cell Parameters Requirements," all references to AT&T batteries are removed. In LCO 3.8.9, " Distribution Systems - Operating," Required Action C.2 is deleted, because it only applied during the replacement of the AT&T batteries. Braidwood Station has replaced all AT&T batteries with C&D batteries, and thus the reference to AT&T batteries is no longer applicable and the AOT extension granted under TS Amendment Number 99 is no longer applicable, and are celeted as administrative changes.
F. SAFETY ANALYSIS OF THE PROPOSED CHANGES The Byron Station and Braidwood Station Updated Final Safety Analysis Report (UFSAR) section 8.3.2.1.1 states that "the interconnection between each unit's Class 1E 125-Vdc systems, via the cross-tie, is limited by procedural and administrative controls. These controls ensure that combinations of maintenance and test operations will not preclude the systems capabilities to supply power to the ESF d-c loads. The criteria specifying the allowable combinations of maintenance and test operations are governed by the plant technical specification. The provisions of administratively controlled, manually actuated, interconnections between the non-redundant Class 1E d-c buses affects (i.e., increase) the overall reliability and availability of the d-c systems for each unit in that it provides a means for manually providing power to a d-c bus at a time when it would otherwise have to be out-of service (e.g., to perform a battery discharge test during a refueling outage, to replace a damaged cell, etc.)."
The Background Section of the TS Bases for B 3.8.4 states "the cross-tie between 125 VDC ,
ESF buses 111 and 211 and the cross-tie between 125 VDC ESF buses 112 and 212 are each !
provided with two normally locked open, manually operated circuit breakers. No interlocks are provided since the interconnected buses are not redundant. However, if one battery is inoperable, procedural and administrative controls are used to limit the connected load to 200 Page 6 of 8 Attachment A - Description and Safety Analysis
amps based on not exceeding the OPERABLE battery capacity. These controls ensure that combinations of maintenance and test operations wil! not preclude the system capabilities to supply power to the ESF DC loads.- The provisions of administratively controlled, manually actuated, interconnections between the non-redundant Class 1E DC buses increases the overall reliability and availability of the DC systems for each unit in that it provides a means for l manually providing power to a DC bus at a time when it would otherwise have to be out-of-service (e.g., to perform a battery discharge test during an outage, to replace a damaged cell, etc.). Cross-tie breaker closed alarms are also provided to alert the operator when the units are cross-tied." For Braidwood Station, the TS Bases currently state that the connected load is administratively limited to 100 amps for AT&T batteries (200 amps for C&D batteries), when DC buses are cross-tied and one battery is inoperable. However, the reference to AT&T batteries is being removed as part of this change. As stated in Reference 2, if a fault occurs on one of the DC buses during the time that the two buses are cross-tied, the fault will not cascade to the other bus because a breaker exists on either side of the cross-tie. These breakers are coordinated with the DC bus main breakers to assure that the cross-tie will isolate before the battery would be isolated.
-In Refuence 1, we requested an amendment to the Byron Station TS in part to allow use of the DC br.ttery cross-tie when one unit is in operation and one unit is shutdown. In Attachment A of Reference 1, an independent analysis of the Byron Station DC electrical system in this configuration demonstratea that operation was acceptable as long as current flowing to the
- shutdown unit was administratively limited to 63 amps. In Reference 2, we requested an amendment to the Braidwood Station TS to allow use of the DC battery cross-tie when one unit is in operation and one unit is shutdown. In Reference 3 for Byron and Reference 4 for Braidwood, the NRC concluded that these changes were acceptable. In Reference 5 for Byron Station and Reference 6 for Braidwood Station, the current limit was revised to 200 amps because new higher capacity C&D batteries were installed. In Reference 7 for Byron Station and Reference 8 for Braidwood Station, the NRC also found these changes to be acceptable.
Thus as discussed in Section E of this Attachment, the previous TS clearly allowed operation in the manner proposed by this change.
Therefore, it is concluded that operation with a DC cross-tie closed is within the design bases of the plant and preserves the ability to mitigate the consequences of any accident or transient.
The limitation to not use the DC cross-tie, during shutdown conditions in order to maintain independence between the units, was an oversight introduced during the conversion to the Improved Standard TS. This amendment will correct that oversight. )
G. IMPACT ON PREVIOUS SUBMITTALS We have reviewed the proposed Amendment request regarding its impact on any previous
.submittals and have determined that there is no impact on any previous submittals.
H. SCHEDULE REQUIREMENTS We request approval of this Amendment prior to the start of the Byron Station, Unit 2 refueling outage (i.e., B2RO8) scheduled to begin October 23,1999.
j Page 7 of 8 Attachment A - Description and Safety Analysis i
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- 1. REFERENCES 1
- 1. Letter from R.E. Querio (Comed) to B. Stephenson (NRC) transmitting TS Amendment Request, dated July 15,1986.
- 2. Letter from S. C. Hunsader (Comed) to T. E. Murley (NRC) transmitting TS Amendment Request, dated December 3,1987.
- 3. Letter from L. N. Olshan (NRC) to D. L. Farrar (Comed) issuing TS Amendment No. 5 to Byron Station, dated December 12,1986.
- 4. Letter from S. P. Sands (NRC) to L. D. Butterfield (Comed) issuing TS Amendment No.
5 to Braidwood Station, dated January 27,1988.
I
- 5. Letter from K. L. Graesser (Comed) to NRC Document Control Desk transmitting TS ;
Amendment Request for 125-volt de batteries, dated April 7,1997. l
- 6. Letter from T. J. Tulon (Comed) to NRC Document Control Desk transmitting TS
- Amendment Request for replacing the 125-volt de AT&T batteries, dated January 14, 1998.
- 7. Letter from G. F. Dick (NRC) to I. Johnson (Comed), issuing TS Amendment No. 93 to Byron Station, dated April 7,1997.
- 8. Letter from S. N. Bailey (NRC) to O. D. Kingsley (Comed), issuing 'S Amendment No.
94 to Braidwood Station, dated August 18,1998.
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l Page 8 of 8 Attachment A - Description and Safety Analysis
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