ML20138D952
| ML20138D952 | |
| Person / Time | |
|---|---|
| Site: | Peach Bottom  |
| Issue date: | 04/25/1997 |
| From: | James Shea NRC (Affiliation Not Assigned) |
| To: | NRC (Affiliation Not Assigned) |
| References | |
| NUDOCS 9705010314 | |
| Download: ML20138D952 (23) | |
See also: IR 05000277/1996006
Text
_ _ .______ _ _ __. _ __ _ _ .- . _ - -
^
April 25, 1997
NEMORANDUM T0: (Docket 2fUi6
FROM:
Joseph W. Shea, Project Manager (Original signed by)
Project Directorate I-2 i
Division of Reactor Projects - I/II !
Office of Nuclear Reactor Regulation l
SUBJECT: BACKGROUND DOCUMENT REGARDING STATION BLACK 0UT ISSUES, PEACH
BOTTOM ATOMIC POWER STATION, UNITS 2 AND 3
!
The attached document was provided by PECO Energy Company (the licensee) to '
the NRC staff in March'1997. The documents provide the licensee's response to
unresolved inspection items regarding the Station Blackout (SBO) electrical
,
!
tie line that runs from the conowingo Hydroelectric station to the Peach ;
Bottom Atomic Power. Station. These items were identified in NRC inspection j
report 50-277, 278/96-06 as unresolved items 96-06-02 and in inspection report -
50-277, 278/96-07 as unresolved item 96-07-01.
Please place the attached document in the Peach Bottom Atomic Power Station
Docket File and in the Public Document Room (PDR) and Local PDR.
Docket Nos. 50-277/278
Attachment: As stated
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MEMORANDUM T0: Docket File
FROM: Joseph W. Shea, Project Manage /
Project Directorate I-2
Division of Reactor Projects - I/ I
Office of Nuclear Reactor Regulation
SUBJECT: BACKGROUND DOCUMENT REGARDING STATION BLACK 0UT ISSUES, PEACH
BOTTOM ATOMIC POWER STATION, UNITS 2 AND 3
i 1
The attached document was provided by PECO Energy Company (the licensee) to
the NRC staff in March 1997. The documents provide the licensee's response to
unresolved inspection items regarding the Station Blackout (SB0) electrical
tie line that runs from the conowingo Hydroelectric station to the Peach
Bottom Atomic Power Station. These items were identified in NRC inspection
report 50-277, 278/96-06 as unresolved items 96-06-02 and in inspection report ;
50-277, 278/96-07 as unresolved item 96-07-01. '
Please place the attached document in the Peach Bottom Atomic Power Station '
Docket File and in the Public Document Room (PDR) and Local PDR.
Docket Nos. 50-277/278
Attachment: As stated
'
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, Response to PBAPS SBO Line Inspection Open Item URI-96-06-02
i
References
Response to NRC from PECO dated Aug 6.1992
Meeting Minutes from April 13.1993 Meeting with NRC
Response to NRC from PECO dated April 7,1995
Meeting Minutes from May 11.1995 Meeting with NRC
Response to NRC from PECO dated July 13.1995 (TS change)
Letter from NRC to PECO dated August 16.1995
, NUMARC 87-00. sections B.3 and B.13
l Purpose
l
l This paper will provide additional background, discuss the position of PBAPS, described
l decisions made in regards to corrective actions and address generic implications of each
j open item.
!
Issues
The open items are described below and are handled individually in this paper.
(1) The NRC staff did not understand that statements made in the August 6.1992
response were intended to identify that there are times when no Conowingo units
are generating nor used as electrical condensers (spinning reservs). Address the
frequency that Conowingo has at-least one generator operating, at-least one
generator used as an electrical condenser (spinning reserve), and none of the SBO
generators operating.
(2) URI 96-06-02 states that the staff" expected" at least one Conowingo hydro unit
would supply the SBO line loads normally and therefore could be considered an i
operating line. However, with the possibility of no units operating, the system I
'
overall would be in standby and therefore, reliability should be monitored.
l Address measuring reliability given there are times when SBO generating units
! are off-line and how the NUMARC 87-00 guidance for reliability being met?
(3) The August 6.1992 response by PECO states all components of the SBO line
'
would be " capable of withstanding the effects oflikely weather related events that
may initiate the loss of of-site power event"(reference NUMARC 87-00 item
B.3). However. a wooden utility pole is used at the Susquehanna Substation
where the SBO line leaves the breaker and goes underground on the south side of
Rt.1. Address how the use of a wooden utility pole is consistent with the stated
i
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design criteria on weather related events. Also, provide justification of how
wooden utility poles and exposed conductors meet the requirements of NUMARC
item B.3.
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ATTACIMENT
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. Response to PBAPS Silo Line inspection Open item URI-96-06-02
(4) PECO letter 7/13/95 supporting revising Technical Specifications for 14 days.
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stated the voltage and frequency would be monitored periodically during the time
an EDG was inoperable. Also, in 4/7/95 letter response stated that the voltage and
frequency verifications were used during EDG in-operability to determine
connectability. Address how the periodic voltage and frequency verifications are
performed including a discussion of the location of the associated instruments and
j v locatron of associated displays. .\lso, discuss how this helps determine
l
connectability of the SBO line.
Response to item 1
l
The intent of the August 6.1992 response was to identify that the normal
operating condition at Conowingo includes at least five generators running as
! electrical condensers which would be available as spinning reserves for 33kV 3
'
operation within 5 minutes. Ilowever. there is no commitment to maintain any
units operating or running as electrical condensers except to ensure minimum !
flows are met. Even these minimum flows are not required for certain time I
,
!
periods during winter months and may not be maintained by the operation of SBO
units. Therefore. there is no assurance that there will be an SBO unit spinning at
l
- all times. Conowingo has reported that since January 1,1996, at least one
generator has been operating or spinning to maintain these minimum flows.
However detailed research may not be able to determine the percent of time
l when the combination of units operating or spinning included an SBO supplying
unit because Conowingo does not retain this level of data.
l
The Conowingo Engineer and Plant Operators have stated that when a blackout
l
i occurs. the generating units and condensing units trip. During a blackout, the
l plant will be starting from a " black start" no matter the initial unit condition. In
addition. the 10CFR50.59 Safety Evaluation for Modification 5396 and all
referenced submittals identify that the manual connection time to supply the start-
l up bus is designed as less than one-hour. The ability to meet this commitment
l was proven by modification testing. This evaluation does not identify any
constraints on the initial conditions of the Conowingo units and can be met from a :
l
i complete black (dead) start. Therefore, it is not critical to ensure that an SBO unit
is operating at all times or understand the percentage of time operated or operated
as electrical condensers.
Since it is not critical for SBO operability. " black starting" SBO in one-hour is the
i commitment and the Conowingo plant records are not maintained to provide the
j data requested. we do not believe that an extensive search. which could potentially
l result in inaccurate data. is warranted.
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. Response to PilAPS Silo Line inspection Open item L'RI-96-06-02
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l Response to item 2
It was originally submitted that the SBO system is a normally operating system
per NUMARC 87-00 item B.13. and reliability is not monitored. The availability
is monitored under the Maintenance Rule and includes all equipment from the
,
busses at Conowingo to the PBAPS switchgear(see attachment 1). The SBO line
!
= may'be supplied by the system grid via one of two paths that connect at the
generator output when the generating units are off-line. Therefore. with the SBO
l line energized. the entire SBO system may not be operation.
l
Modification documents address PBAPS ownership of the line from the
Susquehanna Substation output to and including the SBO system at PBAPS. This
contiguration is normally in operation because the line is energized or the
condition is annunciated in the PBAPS Main Control Room. Also,in the
configuration for an operable SBO source it was documented that the generation
would only contribute 1hr/yr of unavailability (defined for an operating source in l
l NUMARC). Therefore. the August 6.1992 response identifies that the goal for j
l
the SBO modification is to supply an SBO "Line" with greater than 95%
i availability. This is supported in the 10CFR50.59 Safety Evaluation for i
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Modification 5396.
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l Because there are times SBO may be supplied by the 220kV grid with no SBO
units operating. the generators are " stand-by" Therefore, we agree with the NRC
concern that reliability should be monitored. However, availability of the
l
normally operating system from the generator output busses to the PBAPS l
l switchgear breaker. should be maintained. NUMARC 87-00. B.13. states that a )
stand-by system maintains reliability of 0.95 per demand. An evaluation of
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overall Conowingo reliability was conducted and the plant. as a whole. has a
- reliability of 0.9946 for greater than 2000 attempted starts from Jan to Oct 1996.
'
There was no historical data retained to give specific SBO unit reliability.
Monitoring SBO system reliability has been initiated and is being maintained
utilizing Conowingo's " attempted start sheets" These are generated by
Conowingo Operations and a copy sent to the PBAPS System Manager. The
SBO units are monitored against the 0.95 demand goal. Records for historical
data are not retrievable. however, the overall plant reliability goal establishes a
high confidence the reliability factor is met to date.
Response to item 3
The above referenced documents commit our SBO design to NUMARC
Appendix B. Item B.3 specifically identities the requirement for protection
against likely weather-related events. Further. NUMARC Appendix B.Me) states
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Response to PilAPS Silo Line Inspection Open item URI-96-06-02
that no single point vulnerability exists that a likely weather-related event or
smgle failure can cause a failure at the emergency AC. preferred or AAC power
supplies. The August 6.1992 response states "all of these components are
capable of withstanding likely weather related events" The substation
configuration and design was supplied by PECO d dDesign
PECO at the Main Office tnote
that this group no longer exists in its original format) and meets stan ar
Energy substation design critena.
The design of the Susquehanna Substation for the SBO line was discussed with
l
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PECO Energy Regional System Design and Equipment and Controls Branch
Engineering. The design packages no longer exist except as shown on design
drawings. The substation design packages of this level (33kV) are not mainta
as permanent record. However. the standard design of d PECO substations
M3 ed :ria which states that the design withstand expecte
to NESC section 25
weather related events, fherefore. the August 6.1992 response that SBO can
withstand likely weather related events is valid.
A letter from the NRC dated April 20.1993, discussed topics from a meeting
This letter doce mts the NRC concern that the equipment at
April 13.1993.Susquehanna and Peach Bottuu v.bstation would not be pro
severe weather. PECO provided additional information on the weather protec
13.1993 meeting,
aspects of the substation equipment.ThisThe presenter at
the substation location were discussed as an additional protective measure.
response also stated that the designh prevents an S
Emergency AC sources the preferred power sources and the AAC source
is highly unlikely that a single weather related event could simultaneously cau
failure of the 220kV lines from Nottingham and Newlinville substations. Muddy
Run generators and substations. or the multiple feeds to the 500kV ring b
of these sources are adequate as power supplies to PB APS start-up sources.
Therefore, the design meets the commitments made during the SBO Line desig
and provides the protection required from likely weather-related events re
in NUMARC 87-00. The original modification documentation did not
specifically address the way in which this comenitment was met. This white
and associated action iuqtw evaluation will document this issues closure.
The Susquehanna Substation consists of exposed aerial bus with ground mo
breakers (similar to 500kV and 220kV substations h at PBAPS). Th
the SBO line I191-00 line is sia an aerial line to a terminal pole within t e
Susquehanna Substation fenced area which cc 1ects to the underground p
of the line (reference attachment 2).
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Respons: a- s PS SBO Line inspection Open item URI-96-06-02
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Response to item 4
!
There is presently no means to identify the frequency of the SBO unit generators
!
at PBAPS ano frequency is not used during declaration of an operable SBO line
(Procedure ST O 51H-200-2). The voltage of the line is venfied in this procedure
and is constantly monitored because the SBO breaker.1005 CB will trip on
undervoltage conditions and subsequently alarms in the PBAPS Main Control
Room. The SBO line is declared inoperable during the time the 1005 CB is open.
, T'ie operability procedure verifies adequate informatic. .vhile SBO is in its
l nosmal operating state to determine its availability and conneetability in the SBO
l mode.
1
During the Technical Specitication change process to gain a 14 day allowable
TSA for plant operation with one Emergency Diesel Generator (EDG) inoperable,
a letter from the NRC to PECO dated April 5.1995. listed nine conditions to be
met. Condition number three was a requirement that " voltage and frequency" he
l verified in declaring the SBO source available. The PECO response. the
l presentation made May 11.1995 and the associated meeting minutes dated June
l 7.1995 supported this request to monitor voltage and frequency in declaring the
l SBO available. However. the amendment letter from the NRC to PECO dated
! August 16.1995 identifies tW rommitment changes made to the Technical
Specifications and bases and A , associated safety evaluation for the 14 day EDG
! TSA. This text of this document does not include condition three or the
! requirement to monitor frequency for verification of the availability of the
!
Conowingo Line. Therefore, we believe the requirement to monitor and
frequency for the availability of the Conowingo (SBO) Line is not a commitment.
During emergency uw a Se SBO line. frequency. via turbine speed, and voltage
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are controlled at Cor ago by their automatic controls and the operations staff.
The PBAPS Design Review Board for the SBO modification determined from the
design that " frequency recovery is a normal function of Conowingo" and
" frequency deviations are within the margins specified". During the line-up for
SBO. the substation is configured such that the grid is not interconnected and the
l generator voltage and frequency become critical for operating PBAPS loads. The
! modification acceptance testing verified the ability to start required loads at
,
PBAPS while isolated from the grid and maintaining adequate generation and
! freguncy control.
1
The voltage and frequency measurements in the normal operatinc configuration
do not have a bearing on the availability or connectabilit'y of the SBO line in the
emergency operating configuration. These readings. taken with the substation
- contigured to a normal line-up. only verify grid frequency and not necessarily the
frequency with a generator providing sole power to the PBAPS SBO equipment.
The critical parameter under non-emergency operatms, conditions is that the SBO
breakers. transformer, switches and generating units are available for connection
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Response to PBAPS SHO Line inspection Open item URI-96-06-02
and that the line is still capable of suppiying the loads. The above referenced ST
adequately verities these constraints. The frequency and voltage output in an
SBO line-up is automatically controlled by generation control equipment at
Conowingo. Conowingo operations uses turbine speed. which is indicated in the
. Conowingo Control Room for each unit being operated. to manually check
generator frequency and this is indicated in each units startup procedure.
Because it is believed that there is no frequency commitment and the above
, opembility verification procedure adequately checks for SBO availability and
connectability, the requirement for checking frequency during normal operations
is not applied.
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_ _ _ _ _ - _ . . _ _ _ _ _ _ _ _ _ - - _ _ _ _ _ - _ _ _ _ _ _ - _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ - _ _ _ _ - _ _ _ .
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Atracem ewT 2.
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llesponse to PBAl'S Silo Line inspection Open item U111-96-06-02
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Susauchanna Substation at Conowinao
Breakers
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Wooden Utility Poles
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NUM ARC 87-00
Appendix II ,
11.3 Components and subsystems shall be protected against the effects oflikely
weather-related events that may initiate the loss of off-site power event.
Protection may be provided by enclosing AAC components within structures that
conform with the Uniform Building Code, and burying exposed electrical cable
run between buildings (i.e. connmions between AAC power source and the !
shutdown busses).
11.13 The non-class 1E AAC system should attempt to meet the target reliability and
availability goals specified below, depending on normal system state. In this
context, reliability and availability goals apply to the overall AAC system rather
than individual machines, where a syste m may compromise more than one AAC -
power source.
a. Systems Not Normally Operated (Standhv Systems)
System reliability should be maintained at or above 0.95 per
demand, as determined in accordance with NSAC-108
methodology (or equivalent).
b. Systems Normally Operated (Online Systems)
Availability: AAC systems normally online should attempt to be
available to its associated unit at least 95% of the time the
reactor is operating.
Reliability: No reliability targets or standards are established for
online systems.
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SBO Line Monitorine
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Maintenance llule Monitoring;
+ Availability:
. The 191-00 line. inclusive of all equipment from the 213 and 307 disconnect
switch as Susquehanna substation to the 252-0316 breaker normally open
- breaker at the 2SU switchgear at PBAPS. This includes the 30601 breaker
feeding the substation light and power (L&P) sources. A failure of the breaker
to trip or a fault in which the breaker fails will cause CB #1005 to trip.
Because of the resultant bus undervoltage, an SBO trouble alarm is
l annunciated in the PBAPS Main Control Room (MCR).
. At least one of the two redundant lines from the output of the Conowingo
generators. the 1BE. 2BW and 6B busses. to the 215 CB and 325 CB
including the #12 and #10 transformers respectively. At least one of these .
lines is required to support SBO and must be energized to maintain the St30
line operable. The 220kV lines may provide power to these busses but the
busses and equipment to the SBO line must remain operable to support normal
operation of the SBO line. Also, the equipment is checked daily by
Conowingo operations to ensure connectability.
- Reliability:
. The 252-0316 breaker, which is normally open. is monitored by functional
failures and maintenance preventable functional failures to determine the
reliability of the breaker to close when required. This breaker will need to be
l closed to provide power the 2SU switchgear when SBO is reuqired.
NUM AllC 87-00 Monitorine:
. Reliability:
!
. The Conowingo generators are monitored for reliability against the NUMARC
! suggested 95% criteria. The number of actual starts, which includes the
ability to load the busses described aoove, versus the number of attempted
starts is monitored or each SBO generator.
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Station Blackout Open Items
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l + L RI 96-06-02
o L open items were createc during July 4,1996
l
l Inspection Team Wa kdown
!
i + L RI 96-07-01
!
o SBO was not incluc ed in the original scope of
,I the Maintenance Ru e
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-- - -- _ - - _ - -
-
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+k. UR196-06-02 - Sta
ssue 1: The NRC staff did not understand that there are times when
the Conowingo units may not be operated as generating units or as
spinning reserves.
o Original intent to describe the normal operations at Conowingo usually
consist of five generators operating as a minimum as electrical condensers
or spinning reserves
'
o Committed to maintain floivs, however not required during some periods
o Conowingo does not keep detailed enough records to determine"theMA g
po >:4
,
amount of time units were operated in which configuration
oyse
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o For designed Blackout (all AC power lost): p
+ All units and reserves trip,[1ouse generatorhtarts then SBO units started per
procedures
+ Can be completed within required I hour time
+ Because from " black start", no need to ensure spinning unit available
Because we meet start within I hour no matter condition and records are
difTicult to retrieve, no extensive research is warranted
,
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- URI 96-06-02 - Station Blackout Review July 9,1996
.
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+1/ssue 2: The staff expected at least one SBO generator to be supplying
loads normally. Address reliability because these are standby per
a Original submittal described normally operating and availability
monitored.
+ Includes all equipment from gen bus to PBAPS switchgear
+ 2 paths exist to feed bus from 220kV and SBO " system" may not feed bus
a Mod does address PB ownership from substation to PBAPS only
+ Normally energized from Conowingo or 220kV
+ Generation only contributes to 1% unavailability per year
+ Aug 6 response, safety evaluation and documents reference availability
o Agree that SBO reliability should be monitored per NUMARC 87-00
+ llowever, maintain availability of operating system from gen output busses to
PBAPS switchgear per existing monitoring under Maintenance Rule
+ Add monitoring of SBO generator reliability per existing Conowingo
performance indicators
,
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_ _ _ _ . _ _ _ _ _ . _ . . _ _ _ _ _ _ _ _ _ _ _ . _ _ _ _ . _ _ _ _ _ _ _ _ _ _ _ _ ____._.__________m_ _ . _ _ _ _ _ _ _ _ _ _ _ _ . _ - . _ . _ _ _ _ _ _ _ _ . . _ _ _ _ . _ _ _ . _ . _ _ _ _ _ _ _ _ _ _ _ . _ . _ _ _ _ _ _ _ _ _ _ _ . _ _ _ _ . . _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ . _ _ _ . _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ -,----~m,= = = = - - - - * - -- ~ . -
--- - -- -_- ----- - - - - - - - - - - - - - - - - - - _ - - - - - _ - - - - - - - --- -_- - - _ - - - - - - - _ - -- - _-- - _ - - - - -_-
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1[ URI 916-06-02 - Station Blackout Review July 9,1996
l _
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3 onitoring History and Plan
! o Jan to Oct 1996 from Plant Data Pls
+ Greater than 2000 starts
) + Overall plant reliability of 0.9946
+ No data for specific SBO units maintained at Conowingo
+ Gives confidence in SBO unit reliability
o Continuing SBO reliability monitoring has been initiated
l
+ Includes SBO specific data
4
+ SBO units have been maintained greater than 95% goal per NUMARC 87-00
Overall 24 month average reliability has been greater than 99%
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!
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__________.__._.__._._._____..___.______.___________._.___.___._____._______..____________m___-_.__m. ._ __
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URI 96-06-02 - Station Blackout Review July 9,1996
ssue 3: Providejustification of how the wooden utility poles at the
Susquehanna substation meet NUMARC guidance for severe sveather
protection
o Item B.3 states "likely" weather related events and B.8(e) states no single
point exists which could fail emergency AC, preferred and AAC power
o Regional System Design (PECO Energy)
+ Design per NESC section 25 - 1993
_ States it must withstand expected weather related events
o April 13 Meeting discussions involved the protection of the Susquehanna
and PBAPS substation from severe weather
+ Presenter recalled discussions of design, distance and location
+ Unlikely that a single weather related event effect Nottingham, Graceton,
Newlinville, all 500 kV bus feeds near the 3SU transformer and Muddy Run
o Therefore, design meets guidance in NUMARC 87-00 but mod
documentation and meeting minutes did not properly close the issue
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+
, -- _ - , , , , . _ - _ , . _ , . - , . . . , _ _ _ _ , _ , . . . _ _- ..,. .-_
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- URI 96-06-02 - Station Blackout Review July 9,1996
+1[ o Issue 4: PECO letter supporting Tech Spec change to 14 dah's stated
voltage and frequency be monitored to determine if SBO available
+ No means to identify frequency
+ Voltage monitored from CB #1005 and alarms MCR on UV
+ Procedure verifies availability and connectability of SBO
+ Emergency configuration:
_ Frequency controlled by Conowingo automatic controls
- PBAPS design review board stated " frequency recovery is a normal
function of Conowingo"
,
- Grid is not tied to Susquehanna bus or generating busses
+ Normal configuration:
Grid connected to Susquehanna bus and generating busses (220kV)
Frequency would not be a true verification of generator performance
-
_ Critical parameters are alignment and availability for connecting per
procedure as verified by daily procedure and CB #1005 UV trip
s
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\" URI 96-06-02 - Station Blackout Review July 9,1996
+/
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o Confusion around commitments during EDG Tech Spec change
+ Letter to PECO from NRC identified Frequency and Voltage to be checked for
SBO availability
'
+ PECO response during presentation per meeting minutes supported this
i
+ Amendment to Tech Specs issued by NRC did not identify Condition 3
. discussed in above or the frequency of the units
.,
o Conclusion:
! + Not sure commitment to monitor frequency or voltage for SBO to be available
+ A frequency check does not verify that SBO is available or connectable
+ Frequency is a normal Conowingo controlled function satisfactorily tested to
control loads at PBAPS
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URI 96-07-01 - Station Blackout Maintenance Rule
+k ackground
o Causes SBO was not originally in the scope of the Maintenance Rule
-
+ Procedures and design change procedures not implemented during time frame
of modification installation
+ No reviews of changes between initial scoping and procedural changes being
implemented
+ SBO modification was in progress during initial Maintenance Rule (MR)
scoping
o Multiple opportunities existed to identify SBO in MR scope
+ Engineering reviews, implementation team mtgs, Expert Panel Reviews
+ Additional opportunity in pilot MR periodic assessment where summary mods
were reviewed but SBO was not identified
i
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t/<- URI 96-07-01 - Station Blackout Maintenance Rule
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o SBO scoping questions answered YES for MR
+ Scope includes 34.5kV switchgear to 13kV breaker 252-0316
+ Equipment not directly maintained by PBAPS is not directly in MR
-
1 MPFF criteria - no identified system MPFFs
_ Availability >99% based on SBO historical data
+ Only major unavailability during bus PM work
- Additionally, availability covers efrom gen output busses to PBAPS
g + Only one of two paths needed from generator busses
V + Either 220kV or generating units from busses
Generators are monitored under NUMARC guidance for reliability but
not covered under maintenance rule
o Although originally not in MR, SBO still monitored for availability
+ Operations logs (including TRMS) identified CB #1005 due to any line UV
+ System Operations provided info that 99% availability maintained
+ SBO history searched in PIMS and no FFs or MPFFs found
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_ -_ --- _ _ _ - - _ --- ------- - ----
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-URI 96-07-01 - Station Blackout Maintenance Rule
4
+1 o Trips of SBO CB #1005 count as unavail to monitor power supply
+ Trips have resulted from 33kV line trips
+ During emergency,33kV loads are disconnected at substation
+ All trips reviewed and are not functional failures
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o System Scoping Generic Implications
+ Complete rescoping by System Managers
. go + Master Equipment List (CRL) reviewed at component level and ensured
-
g uf6- design changes that could be missed were captured
O .
w+"}O y o Mod Generic Implications
c'
e
+ Mod procedures revised to address MR during process
4
+ Station Document Checklist revised in June 1995 for MR reviews
+ Review of all interim mods (6/94 to 6/95) completed
+ Post 6/95 mods to Risk Significant system review completed
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. _ . _ _ _ _ _ . _ . - - _ . . _ _ _ _ _ _ - - - - - - _ - _ - - _ _ - _ _ _ _ _ _ - - - _ _ . - _ _ . . - _ - _ . _ _ - _ - _ _ _ _ _ _ - - _ _ _ _ - - _ - _ - . _ _ _ _ _ . - . - _ . - - - - - - - _ _ . _ _ _ _ . _ _ _ - _ _ _ _ - _ - _ - n. , ,- ~ , , , - - - - - -- -