ML17263A703
| ML17263A703 | |
| Person / Time | |
|---|---|
| Site: | Ginna  |
| Issue date: | 06/16/1994 |
| From: | Andrea Johnson Office of Nuclear Reactor Regulation |
| To: | Mecredy R ROCHESTER GAS & ELECTRIC CORP. |
| References | |
| TAC-M82335, NUDOCS 9406230019 | |
| Download: ML17263A703 (8) | |
Text
UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 June 16, 1994 Docket No. 50-244 Dr. Robert C. Mecredy Vice President, Nuclear Production Rochester Gas and Electric Corporation 89 East Avenue Rochester, New York 14649
Dear Dr. Mecredy:
SUBJECT:
RESOLUTION OF GINNA USE OF BUS CROSS-TIES (TAC NO. M82335)
During an NRC Service Water System Operational Performance Inspection (SWSOPI) in December
- 1991, one of the SWSOPI team concerns was with regard to the plant licensing basis which allows a safeguard bus tie-breaker to be manually closed by operator action.
This connection of the two 480 VAC safeguard busses allows one out of two emergency diesel generator (EDG) sets to feed both busses during postulated accident conditions'.
This action consequently supplies power to a minimum of two service water pumps (one from each distribution train) required during the recirculation phase of a postulated accident.
You responded to this concern by indicating that the procedure was acceptable according to Generic Letter (GL) 91-11.
In the course of a SWSOPI conducted by the NRC staff, the team identified a
difference between the appropriate number of service water system (SWS) pumps that would be needed to be operable as prescribed in the Ginna Technical Specifications (TSs) and that defined in the licensing basis updated final safety analysis report (UFSAR).
The team had identified that the TS required that two of four pumps be operable (one pump operable on each of the two class IE buses),
and the UFSAR required two pumps for the recirculation phase.
Thus, the TS are inconsistent with the licensing basis, given a single failure of a pump, diesel generator, or an electrical bus.
However, this issue could be resolved by: (1) revising the TS to require that two SWS pumps be operable on each class lE bus, or (2) staff acceptance of your submittal regarding the analysis that shows only one SWS pump is required for the recirculation phase of a design basis accident (DBA).
Pending resolution of this issue, the licensee has implemented certain compensatory measures which the staff has evaluated and found acceptable.
You indicated that given the worst-case design basis accident (loss-of-coolant accident with loss of offsite power) and the single failure of a bus of a diesel generator, you would utilize the cross-ties between the two redundant busses such that two pumps could be powered by one diesel generator.
You further indicated that this application was consistent with the following statement contained in GL 91-11:
"These tie breakers could be beneficial under very special conditions (such as a loss of offsite power coincident with a loss of a diesel generator or batteries) by providing the flexibilityto supply power across division boundaries."
By allowing this use of the bus cross-ties, the appropriate number of operable service water pumps would be 200034'40b2300
~ Og000244 Oiq 940bib PDR ADOC P
VRC I:II.E mWTEII COPED
~ >
I
~
~
~ i
~
3une 16, 1994 This completes the staff's activities on TAC No. H82335.
Original signed by Allen R. Johnson, Project Manager Project Directorate I-3 Division of Reactor Projects I/II Office of Nuclear Reactor Regulation
Enclosure:
As stated cc:
See next page DISTRIBUTION:
Docket-File-'RC
& Local PDRs PDI-3 Reading S.
Varga'.
Calvo W. Butler S. Little K. Cotton A. Johnson
J. Linville, RI E.
Imbro C. HcCracken Wermiel P. Kang, three rather than four given a single failure of a pump.
Included as an enclosure is the staff's Safety Evaluation (SE) regarding the "Evaluation of use of Bus Tie Breakers."
As stated in the conclusions of the SE; based on the review of your submittal, adequate time limitations and surveillance requirements exist at Ginna for the proper use of the tie breakers on occurrence of loss of offsite power and failure of one EDG.
This is consistent with the guidance provided-in GL 91-11.
However, the crediting of the tie breaker during the post LOCA recirculation phase does not satisfy the design basis with regard to the single failure criterion.
The licensee has submitted to the
- NRC, a number of analyses which conclude that a single service water pump is adequate during the recirculation phase.
The single failure criterion would be satisfied under current TSs with only one service water pump required during the recirculation phase.
On this basis, we conclude that the use of the tie breaker (52/BT 17-18) during the recirculation phase of a DBA is acceptable until the NRC staff completes its evaluation of single service water pump operation in the recirculation phase.
Pending completion of this evaluation, the licensee plans to keep in place those compensatory measures referred to above.
- P PDI-3: P
- DE:EELB
- RSIB NAME:.:::::::::;::~:::;-'::::i-,':;,'.:,;:..',':,:.:":5,;:;,:::;:: SLittle KCotton AJohnso CBerlinger EImbro iOFFICE""i;""'.4ilsg':5'"
- SPLB I
94 V'4 94 5 24 94 PDI-3 5 25 94
,:;:NAME:::!:,:;::::,:;:::;:,.;:::.:::,::::,:::,.:9(~:,:::::::,";!".::,:::.'::. CHcCracken WButler i;:DATE:::::::::,::::i::.:i::,"!:::.!aC!,;::,'::::
06/10 94 4 94 OFFICIAL RECORD COPY DOCUMENT NAME: A:iCLOSEOUT.TAC
dune 16, 1994 three rather than four given a single failure of a pump.
Included as an enclosure is the staff's Safety Evaluation (SE) regarding the "Evaluation of use of Bus Tie Breakers."
As stated in the conclusions of the SE; based on the review of your submittal, adequate time limitations and surveillance requirements exist at Ginna for the proper use of the tie breakers on occurrence of loss of offsite power and failure of one EDG.
This is consistent with the guidance provided in GL 91-11.
However, the'crediting of the tie breaker during the post LOCA recirculation phase does not satisfy the design basis with regard to the single failure criterion.
The licensee has submitted to the
- NRC, a number of analyses which conclude that a single service water pump is adequate during the recirculation phase.
The single failure criterion would be satisfied under current TSs with only one service water pump required during the recirculation phase.
On this basis, we conclude that the use of the tie breaker (52/BT 17-18) during the recirculation phase of a DBA is acceptable until the NRC staff completes its evaluation of single service water pump operation in the recirculation phase.
Pending completion of this evaluation, the licensee plans to keep in place those compensatory measures referred to above.
This completes the staff's activities on TAC No. H82335.
Enclosure:
Safety Evaluation cc w/enclosure:
See next page All R. John on, Project Hanager Proje
'torate I-3 Division of Reactor Projects I/II Office of Nuclear Reactor Regulation
Dr. Robert C. Hecredy R.E. Ginna Nuclear Power Plant CC:
Thomas A. Hoslak, Senior Resident Inspector R.E.
Ginna Plant U.S. Nuclear Regulatory Commission 1503 Lake Road
- Ontario, New York 14519 Regional Administrator, Region I U.S. Nuclear Regulatory Commission 475 Allendale Road King of Prussia, Pennsylvania 19406 Hs.
Donna Ross Division of Policy Analysis
& Planning New York State Energy Office Agency Building 2 Empire State Plaza
- Albany, New York 12223 Charlie Donaldson, Esq.
Assistant Attorney General New York Department of Law 120 Broadway New York, New York 10271 Nicholas S. Reynolds Winston
& Strawn 1400 L St.
N.W.
Washington, DC 20005-3502 Ms. Thelma Wideman
- Director, Wayne County Emergency Hanagement Office Wayne County Emergency Operations Center 7370 Route 31
- Lyons, New York 14489 Hs. Nary Louise Heisenzahl Administrator, Honroe County Office of Emergency Preparedness ill West Fall Road, Room ll Rochester, New York 14620
~
~S AE0(
- 0O I
0
+~
gO
++*++
UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 2055&0001 SAFETY EVALUATION BY THE OFFICE 0 NUCLEA REACTOR REGULATION LU IO OF USE OF BUS IE BR AKE G INN UC OWE LAN DOC E
NO. 50-24
- 1. 0 INTRODUCTION The NRC staff performed a Service Water System Operational Performance Inspection (SWSOPI) for Rochester Gas and Electric (RG&E) Corporation at the R.E. Ginna Nuclear Power Plant (Ginna).
The inspection team identified that if either emergency diesel generator (EDG) failed during a recirculation phase of design basis accident (DBA), the bus tie breaker would be used to connect the redundant safety busses in order to supply power from the remaining EDG.
This is needed in order to obtain two service water (SW) pumps required under the licensing basis and Technical Specification (TS).
The staff evaluated whether the use of the tie breaker is appropriate under this condition and whether it conforms with the guidance provided in Generic Letter (GL) 91-11 regarding interlocks and limiting condition for operations (LCOs) for Class lE tie breakers.
2.0
~EVALUATIO The safety bus system for Ginna consists of four Class 1E 480 V busses (14, 16, 17, and 18).
Emergency power to busses 14 and 18 is provided by EDG 1A, and emergency power to busses 16 and 17 is provided by EDG 1B.
Busses 17 and 18 can be connected by closing the bus tie breaker (52/BT 17-18).
Similarly busses 14 and 16 can be connected by closing the bus tie breakers (52/BT 14-16).
This configuration is part of the licensing basis of the Ginna plant (newer designs have been required to provide two bus tie breakers in series).
Busses 17 and 18 each supply power to two SW pumps (total of four SW pumps).
Our review of TS 3.3.4. l.a indicates that two SW pumps (one from each of the redundant busses 17 and
- 18) are required to be operable for reactor conditions above cold shutdown.
The licensing basis (table 9.2-5 of the Updated Final Safety Analysis Report (UFSAR)) also requires a
minimum of two SW pumps during the recirculation phase.
The licensing basis also requires conformance of the design to the single failure criterion (see Recommended Action IV of GL 89-13, Service Water System Problems Affecting Safety-Related Equipment).
With only one pump per bus
- operable, the single failure criterion is met for failure of an EDG through use of the bus tie breaker (52/BT 17-18).
However, this criterion is not met for a bus fault type of failure, because the bus tie breaker cannot be used in this case (both passive and active electrical failures must be assumed see footnote (2) in 10 CFR Part 50, Appendix A).
The argument posed by the licensee in the UFSAR that Ginna
was designed for conformance to the criteria that preceded the general design criteria and that these criteria precluded consideration of passive electrical failures is not valid; and in any event, this argument is irrelevant since the catastrophic failure of a breaker (an active component) on the bus must be considered a bus fault which would prevent use of the tie breaker.
- Also, a failure of one of the two available pumps would not meet single failure even though power to both busses would be available.
The bus tie breakers require special consideration (such as administrative controls to remove breakers from their cubicles or otherwise lock them open)
- because, when left closed, they could compromise the independence of the redundant safety-related busses and may prevent loading of both EDGs.
Over the years, the staff has found that in some plants the tie breaker had been left closed inadvertently for a substantial period of time.
To resolve this concern, under the resolution of Generic Issue (GI)-49 "INTERLOCKS AND LCOs FOR CLASS 1E TIE BREAKERS" and pursuant to 10 CFR 50.54(f),
GL 91-11, the staff requested all licensees to provide a written response to certify whether procedures exist which contain time limitations and surveillance requirements for tie breakers.
By letter dated February 3,
- 1992, RGKE provided its response regarding how tie breakers at Ginna conform to GL 91-11 guidance.
Based on the above response, the staff has evaluated the appropriateness of using the tie breaker (52/BT 17-18) at Ginna during a
SW recirculation phase of DBA.
The licensee's response states that:
1.
the above tie breaker is maintained in the test position which would prevent its closure electrically and mechanically to the bus.
Mith the breaker racked in (connected to the bus),
the control scheme is designed such that:
the bus tie breaker can only be closed if either bus 17 and 18 is deenergized from its normal and emergency sources.
Once the tie breaker is closed.
the diesel generator breaker and normal supply breakers of the previously deenergized bus cannot be closed without first opening the tie breaker.
2.
the current Specification 3.7.2.1.a.2 of TS requires that the tie breaker remains open when the plant is not in cold shutdown condition (above 200 degrees F).
Also the TS surveillance 4.6.3.a.3 requires that the tie breaker be verified at least once per 7 days that it remains open when the plant mode is above 200 degrees F.
3.
the continuous monitoring of the tie breaker position is annunciated in the control room.
- 3. 0 CONCLUSION Based on our review of the licensee's submittal, we find that adequate time limitations and surveillance requirements exist at Ginna for the proper use of the tie breakers on occurrence of loss of offsite power and failure of one
On this basis, we conclude that the use of the tie breaker (52/BT 17-18) during the recirculation phase of a DBA is acceptable.
Additionally, the plant does not meet its design basis in regard to the single failure criterion.
However, this issue can be resolved by: (1) revising the TS to require that two SWS pumps be operable on each Class 1E bus, or (2) verifying by analysis that only one SWS pump is required for the recirculation phase of a DBA.
Principal Contributor:
Peter Kang 504-2779 Date:
April 13, 1992