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UNITED STATES NUCLEAR REGUI.ATORY COMMISSION o
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$ 31 Docket No.:
50-293 MEMORANDUM FOR:
R. Wessaian, Sr. Project Manager Project Directorate 1 3 Division of Reacter he$ects 1/11 FROM:
Faust Rosa, Chief Elect-ical Systems Branch Div b lon of Engineering & Systems Technology
SUBJECT:
EVALUATION OF STATION BLACK 0UT DIESEL GENERATOR ACCED AS PART OF PILGRIM SAFETY ENHANCEMENT PROGRAM Plant Name:
Pilgrim, Unit 1 Utility:
Boston Edison Company Docket No.:
50-293 Licensing Status:
OR Resp. Directorate: PD f!-3/DRSP Review Branch:
SELB/ DEST Review Status:
Complete The er. closed evaluation of the non-safety related diesel generator was prepared by the Electrical Systems Branch / Division of Engineering & Systems Technology.
The addition of this new unit was proposed by Boston Edison Company as part of their Safety Enhancement Program. As stated in the enclosure, we conclude that the proposed design is acceptable and this change can be implemented under the provisions of 10 CFR 50.59.
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Enclosure:
Faust Rosa, Chief As stated Electrical Systems Eranch Divisinn of Engineering & Systems Technology cc:
L. Shao A. Thadani i
J. Knight P. Gill
Contact:
- 0. P. Chopra, SELB/ DEST X29488 7/f',$ \\
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,f Enham. ant r<.l,.w Bot'.a Edison Company will install a t
Stet;on Bia,'r':c (560) diesel generator rated at 2000kW to p
>y related mr 4 of onsite ac power to the 4.16kV safety buse iit will be util'.
- operate one ECCS pump and all other as-so.. '
'is from one safety train aquired for reactor shutdown, without LOCA, when e -
er sources of ac power are unavailable. Boston Edison states that this unit can be made available (manually) from the control roJm within an hour.
This backup power source is being installed to reduce the probability of a station blackout which could lead to core damage and/or containment failure.
The unit is skid mounted and housed in a pre-engineered enclosure to protect it from the environment. The unit is fully self-contained, not dependent on any permanent plant systems (except for a non-safety 480V feed from the plant for diesel generator maintenance loads when the unit is not running) and has a in-dependent fuel tank (no connection with emergency diesel generator fuel sup-plies), and a cooling radiator. The new diesel generator and the two existing en.ergency diesel generators for Pilgrim are ALCO engines. The new unit will be located south of the plant adjacent to the switchyard relay house.
The new diesel generator will be connected between the secondary side of the j
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thutdown transfonner (third source of powir to the safety related buses) and emergencybusesA5andA6(Figure 1). The diesel generator and the existing SMVA shutdown transformer will be connected to the existing safety-related 4.16 kV buses AS and A6 through a new two-breaker 4.16kV bus A8. The diesel generator will be connected to the new switchgear A8 thru breaker #801 and the shutdown transformer will be connected to switchgear A8 thru breaker #802. The outgoing feed from the switchgear A8 will be connected to the existing 4.16kV breaker
- 600 which is in turn connected to breakers #501 and #601 of the safety buses A5 and a6.
In the original design the secondary of the shutdown transformer was directly connected to breaker #600.
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. Breaker #802 which is connected to the shutdown transformer will be kept closed during normal operation to supply power when required to safety buses A5 and A6 thru breaker 600 (normally closed) and breakers 501 and 601 (normally open).
This alignment of breakers is consistent with the present arrangement which maintains shutdown power transformer power available for automatic connection to the emergency buses (via automatic closing of 501 and 601) upon a unit trip, loss of the start-up transformer (preferred source) and failure of the emergency diesel generator. The blackout diesel generator output breaker 801 will be main-tained open during normal operation and will be closed to the safety related buses only during station blackout (loss of all ac power) or test. The diesel generator will be tested at regular intervals, when the plant is operating, for its ability to start and assume load by synchronizing to the shutdown trans-forver during plant operation. During this time breakers 802 (NC), 600 (NC),
501(NO) and 601 (NO) are maintained in their normal line up. The diesel gen-erator will also be tested by energizing safety related loads when the reactor is shut down.
The controls of breakers 801 and 802 are interlocked to prevent interconnection of the 580 diesel generator with the shutdown transformer except for testing of the diesel generator. The diesel generator and the 4.16kV breakers of switchgear A8 are controlled manually either from the main control room or locally from the diesel generator enclosure. Protective relaying is provided to prevent dam-f age to the diesel generator. An independent 125 de system (battery and charge /)
15 provided to supply control power to the diesel generator unit controls and f
associated 4.16kVswitchgearA8(breakers 801and802). Loss of de power will be annunciated in the control room.
In addition, annunciation will be provided in the main control room for diesel generator trouble, diesel generator breaker (801) trip / inoperative and shutdown transformer breaker (802) trip / inoperative.
The diesel generator has an independent sufficient fuel system with capacity to supply rated load for a minimum of one week.
. The cabling for the diesel generator controls and new breakers 801 and 802 will be routed in separate conduit and duct banks from the diesel generator enclosure and switchgear A8 to the control room. The physical separation within the con-trol panels between non-safety related diesel generator control wiring and exist-ing class 1E wiring will be in accordance with R.G. 1.75.
All conduit and cable installed by this design change located within safety related areas will be sup-ported in accordance with seismic 1 criteria.
B.
CONCLUSION The staff has reviewed the information provided by the licensee on its proposed modification to add a new diesel generator at Pilgrim which will power required loads for safe shutdown without a LOCA when all other ac power sources are unavailable (Station Blackout).
It is our understanding that the proposed modi-fication is not intended to satisfy the requirements of the proposed USI A-44, Station Blackout rule at this time. The new diesel generator is a backup to the secondary offsite power source (shutdown transformer) and is manually started.
The unit is fully self-contained and interfaces only with the shutdown trans-former (which is the third power source to the safety buses) and no other system except for a 480 voit ac feed from a non-safety relateo load center. The diesel generator breaker 801 is nonnally open, the new breaker in the secondary of the shutdown transformer is normally closed and the present alignment of breakers f
600, 501 and 601 are not changed by this modification. Therefore,theshutdow[
transfomers ability to supply power to buses A5 and A6 under design basis con-ditions will not be affected. There are no changes to the safety related portion of the emergency service buses as a result of this change.
The control cabling of diesel generator and breakers 801 and 802 are routed in a separate conduit and duct banks from the diesel generator enclosure and switch-gear A8 to the control panels C3 and C5 in the control room. The physical separation between new non-safety wiring and existing class 1E wiring within the l
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. panels will be in accordance with R.G. 1.75 (verbal agreement by the ifcensee).
Therefore, although the licensee has not specifically addressed conformance to R.G.1.75, the acceptance of this design is based upon our understanding that the proposed modification will satisfy R.G. 1.75.
Based on the above, the staff concludes that the addition of the non-safety-related diesel generator at Pilgrim will reduce the probability of station black-out and have no adverse effect on the offsite power syster"s, the Class 1E emer-gency diesel generators or the shutdown transformers and (s therefore, accept-able.
It is also concluded that this modification does not require any Tech.
j Spec, changes or result in an unreviewed safety question per 10 CFR 50.59. The implementation of the design will be verified by Region I, with support from NRR as requested by the Region.
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