ML19207A562
| ML19207A562 | |
| Person / Time | |
|---|---|
| Site: | Midland |
| Issue date: | 07/31/1979 |
| From: | Hood D Office of Nuclear Reactor Regulation |
| To: | Rubenstein L Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 7908210049 | |
| Download: ML19207A562 (5) | |
Text
9$AO JUL 311979 MEETING NOTICE DISTRIBUTION Docket File J. Knight 6
S. Hanauer Local PDR R. Tedesco TIC S. Pawlicki LWR #4 File F. Schauer NRR Reading K. Kniel H. Denton T. Novak
. Case Z. Rosztoczy
- 9. Crutchfield R. Bosnak D. Bunch R. Satterfield P. Butler R. Mattson F. kosa R. DeYoung V. Moore D. Muller W. Kreger D. Ross M. Ernst D. Vassallo R. Denise D. Skovholt R. Ballard W. Gammill B. Youngblood F. Williams W. Regan J. Stolz G. Chipnian R. Baer R. Houston
- 0. Parr J. Collins S. Varga G. Lear I
P. Collins M. Spangler T. Speis V. Benaroya W. Haass R. Jackson C. Heltemes L. Hulma,'
ACRS (16)
H. Ornstein L. Crocker J. LeDoux, IE H. Berkow IE Region m Project Manager D.
Hood Principal Staf f
Participants:
Attorney, ELD Om Chopra IE (3)
SD (7)
Licensing Assistant M.
Service Receptionist L. Rubenstein L. Soffer l
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NUCLEAR REGULATORY COMMISSION
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,s, m y JUL 311979 Docket Nos.: 50-329 50-330 MEMORANDUM FOR:
L. S. Rubenstein, Acting Chief, Light Water Reactors Branch No. 4, Division of Project Management FROM:
Darl S. Hood, Project Manager, Light Water Reactors Branch No. 4, Division of Project Management
SUBJECT:
MEETING NOTICE REGARDING SEQUENCING OF EMERGENCY LOADS FOLLOWING A LOSS OF C.;FSITE POWER Date & Time:
Thursday, August 23, 1979 8:30 a.m.
Location:
Room P-110, Phillips Building, Bethesda, Maryland
Purpose:
To discuss the design for Midland Plant, Units 1 & 2, for sequencing emergency loads in the events of a loss of offsite power.
Participants:
NRC Om Chopra, D. Hood Consumers Power Company J. Pastor, et. al.
Bech'cel
~
Darl S. Hood, Project Manager Light Water Reactors Branch No. 4 Division Of Project Management Enclosure (s):
0040.112 0040.85 cc: See next page 81}is323 f9 M
Consumers Power Company ccs:
Michael I. Miller, Esq.
Mr. S. H. Howell Isham, Lincoln & Beale Vice President Suite 4200 Consumers Power Company One First National Plaza 212 West Michigan Avenue Chicago, Illinois 60603 Jackson, Michigan 49201 Judd L. Bacon, Esq.
Consumers Powcr Company 212 West Michigan Avenue Jackson, Michigan 49201 Mr. Paul A. Perry Secretary Consumers Powr Corapany 212 W. Michigan Avenue Jackson, Michigan 49201 Myron M. Cherry, Esq.
One IBM Plaza Chicago, Illinois 60611 Mary Sinclair 5711 Summerset Drive Midland, Michigan 48640 Frank J. Kelley, Esq.
Attorney General State of Michigan Environmental Protection Division 720 Law Building Lansing, Michigan 48913 Mr. Wendell Marshall Route 10 Midland, Michigan 48640 Grant J. Merritt, Esq.
Thompson, Nielsen, Klaverkaap & James 4444 IDS Center 80 South Eighth Street Minneapolis, Minnesota 55402 Mr. Don van Farove, Chief Division of Radiological Health Department of Public Health P. O. Box 33035 Lansing, Michigan 48909
Responses to NRC Questions Midland 1&2 Question 040.112 (8.3)
Your response to Q040.85 is incomplete.
The use of a single load sequencer in your design for the connection of emergency safety features loads to the emergency buses when power is being supplied either from offsite or from the diesel generators is unacceptable as documented because it does not provide independence between the offsite power source and the onsite power sources to meet the requirements of GDC 17.
Therefore, we require that you either provide a separate sequencer for offsite and onsite power or a detailed analysis to demonstrate that there are no credible sneak circuits or common failure modes in the sequencer design that could render both onsite and offsite power sources unavailable.
In addition, provide information concerning the reliability of your sequencer and reference design detailed drawings.
Response
Subsection 8.3.1.1.3 has been revised to provide reliability data for the sequencer.
The following is provided to support the existing system design,which utilizes one sequencer per the ESFAS channel.
18 After an accident signal, the sequencer is enabled upon the receipt of a power-available signal from the undervoltage relays located at the safety-related buses.
The relay, bus, and sequencer are all part of the same safety-related redundant load gr;up.
The power source to this load group may be either offsite or onsite.
If a separate sequencer were provided so that one could be used to sequence the safety-related loads on offsite power and the other could be used to sequence safety-related loads on onsite power, it would be incorporated as an integral part of the same redundant load group of the existing sequencer.
As a result, the power supplies for the separate sequencing systems would be derived from the same load group power source, and the sequencers would be electrically interconnected.
As such, no independence or significant increase in reliability would be achieved by the addition of another sequencer.
It is our positi.on that the existing design implements all applicable criteria with more than sufficient assurance of proper operation and independence.
/
Revision 1B Q&R 8.3-25 2/ 93.'32D
Responses to NRC Questions Midland 1&2 Question 040.85 (8.3)
/'
Subsection 8.3.1.1.2 of the FSAR states that, "If preferred power is available to a 4.16kV Class lE bus following a LOCA, the loads are sequentially started." Provide your basis and justification i
for sequencing safety loads when preferred power is available during the accident.
Provide a comparison on a bus-by-bus basis for all emergency buses of the voltage and motor starting transients associated with sequences versus instantaneous leading for the condition of grid voltage at the low end of its normal range and maximum plant auxiliary load.
Provide a description of what would be required to remove this nonstandard design feature from your design and the associated safety implications, if any.
15
Response
The decision to sequence the idle safety-related loads on an ECCAS signal with preferred power available was made early in the electrical system design.
This was done in consideration of possible voltage regulation problems which could result in the plant auxiliary power system.
Additionally, this scheme simplified the logic which initiates the ECCAS sequencer which starts all the required safety-related loads well within the time restraints required to provide for a safe plant shutdown.
Note that there is no load shed initiated in this situation.
The running loads are unaffected and the only loads that are sequenced are the required additional idle safety-related lcads as identified in Table 8.3-1.
Present system analysis indicates that, under certain diverse loadings, proper voltcge regulation can be maintained during a simultaneous start of all idle safety-related loads from the preferred offsite power source.
However, under worst case 21 loadings during starting transients, proper voltage regulation cannot be maintained.
Therefore, load sequencing from the offsite preferred power supply is required.
A design change that would implement simultaneous starting on an ECCAS signal with preferred power available would involve the following:
Additional logic for initiating the ECCAS sequencer when a.
preferred power is not available b.
Additional logic to start "CCAS functions when preferred power is available Q&R 8.3-18 Revision 21 5/79 808.326
Responses to NRC Questions Midland 1&2 It is our position that this design change is unnecessary because 3,
the present design satisfies safety system requiremunts.
-)
Q&R 8.3-18a Revision 21 5/79 808.Td7
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