ML17037B620
| ML17037B620 | |
| Person / Time | |
|---|---|
| Site: | Nine Mile Point  |
| Issue date: | 07/14/1977 |
| From: | Rhode G Niagara Mohawk Power Corp |
| To: | Lear G Office of Nuclear Reactor Regulation |
| References | |
| Download: ML17037B620 (16) | |
Text
U.S. NUCLEAR REGULATORY CO ION NRC FORM 196 I2.76)
~ g NRC DISTRIBOTION FoR PART 50 DOCKET MATERIAL DOC T NUMBER FILE NUMBER TO:
Mr. George Lear FROM:
Niagara Mohawk Power Company
- Syracuse, New York Gerald Ko Rhode DATE OF DOCUMENT 7/14/77 DATE RECEIVED 7/18/77 E
ER RIGINAL COPY DESCRIPTION gc-O~ 6 ONOTORI2ED NCLASSIFIED PROP INPUT FORM ENCI OSURE NUMBER OF COPIES RECEIVED gpggg REMOVE Consists of information on degreded voltage conditions for emergency power systems
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ACKNPWLEDG<>,
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PLANT NAME. Nine Mile Point Unit No, 1
RJL 7/18/77 FOR ACTION/INFORMATION ENVIRHNMENTAL MANAGER CEN ING ASS'XSTANT:
ASSIGNED AD:
Ve MOORE LTR BRANCH CHIEF:
PROJECT MANAGER:
LICENSING ASSISTANTS Bi HARLESS INTERNALD ISTRI BUTION
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'AM SAFETY HEINEMAN EDER ENGINEERING PLANT SYSTEMS TEDESCO BENAROYA IPPOLITO OPERATING REACTORS SITE SAFETY 8c ENVIRON ANALYSIS DENTON 8c MULLER ENVIRO TECH ERNST BALLARD BLOOD TIC VA CHECK AT I LTZMAN BERG EXTERNALDISTRIBUTION
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NSIC'AER BUTLER GRIME GAMMILL 2
SITE ANALYSIS VOLLMER BUNCH Je COLLINS KREGER CONTROL NUMBER REG IV J
HANCHETT 16 CYS ACRS SENT CA GO Y NRC FORM 195 (2.75) 771990248
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NIAGARAMOHAWKPOWER CORPORATION
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MOHAWK 300 ERIE BOULEVARD. WEST SYRACUSE, N. Y. I3202 July 14, 1977
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'irector of Nuclear Reactor Regulation Attn:
Mr. George Lear, Chief Operating Reactors Branch $ 3 U.
S. Nuclear Regulatory Commission Washington, D.
C.
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~I SoctI2I Re:
Nine Mile Point Unit 1 Docket No. 50-220 DPR-'6'3
'entlemen:
Your letter of June 2,
1977 requested information concerning undervoltage protection at Nine Mile Point Unit 1.
The enclosure
"'to this letter addresses itself to the staff positions on degraded voltage conditions for emergency power systems'.
Proposed technical specifications are 'being forwarded under separate cover.
Ver'y truly yours, NIAGARA MOHAWK POWER CORPORATTON Ge aid K.
ode Vice President-gineering MGM/szd Enclosure 77i990243
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Enclosure EMERGENCY POWER SYSTEMS
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Introduction The onsite 'emergency power systems for Nine Mile Point Unit 1 has been reviewed to assess the susceptibility of redundant safety-related electrical equipment to:
Sustained degraded voltage conditions at the offsite power source; and Interaction of the offsite and onsite emergency power systems.
References 1 and 2 contain analyses which indicated that voltage levels at safety related buses have been optimized for all con-ditions throughout the anticipated ranges of v'oltage variations fox off-site power sources'.
This has been accomplished by the addition of'a second level of undervoltage protection, as described 'in.those submittals.
1.
Letter dated October 18, 1976 from G.
K. Rhode to George Lear 2.
Letter'ated Novembex 30, 1976 from G.
K. Rhode to George Lear
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Position 1 - Second Level of Under-or-Over Voltage Protection With a Time Dela Two levels of undervoltage protection exist at Nine Mile Point Unit 1.
'The fixst level is associated with Loss of Offsite Power'.
The second level of undervoltage protection was installed during the 'Spring 1977 refue].ing outage.
The relays installed for this second level of protection have inverse time and"iast reset characteristics.
Detailed information regarding items a-d of this, position have prev'iously been discussed in Refexences 1 and 2.
This is summarized below:
Reference 1 included a voltage px'ofile analysis from which the set points and time delays were chosen in order'hat voltage 'requirements for safety related lo'ads were 'maintained.
The time delay as described in Reference
'2 is such that emexgency core cooling will be available within the zequired 35 seconds as xequired by the FSSAR.
In addition, the "inverse time at fast reset charactex'istics of the undervoltage relays will minimize the 'efiect of short duration distur-bances from reducing the availability of offsite power sources'.
They also ensure that failuxes of safet'y related systems will not occur.
These relays also will automatically txip the off-site power sources'hen set point and time delays have been exceeded.
The coincident logic along with the associated trip set points and time delays pxecludes spurious offsite powez trips.
The new rel'ays were 'des'igned to meet the applicable requixements of IEEE-279, 1971, in accordance with Item e of this position.
Proposed Technical Specificati,ons which include limiting conditions for operation, surveillance 'requirements fox first and second levels of undervoltage 'protection are being for-waxded under sepax'ate cover.
These include trip set points with minimum and maximum limits.
Compliance with General Design Criteria 17 "Electric Power Systems" for Nine Mile Point Unit.l is summarized as follows:
"An onsite electxical power system and an offsite electrical power system are pxovided to permit functioning of structures,
- systems, and components important to safety.
The safety
~ function for each system provides'ufficient capacity and capability to ensure that (1) specified acceptable fuel design limits and design conditions of the reactor coolant pressure boundary are 'not exceeded as a res'ult of anticipated oper-ational occurrerices'nd (2) the core is cooled and the containment integrity and other'ital functions are maintained in the event of postulated accidents.
Two completely independent and redundant emergency diesel-generator systems are provided as well as two completely separate and independent Station battery systems.
Two 115-kv transmission lines 'fxom remote generating stations feed the 115-kv reser've
'bus at Nine Mile Point.
In the event of permanent fault on one line, the other line has the necessary capacity to supply all the powex required to ensure that acceptable fuel'nd reactor coolant pressure boundary design limits are 'not exceeded during anticipated operational occurrences.
Two phy'sica'lly independent circuits are provided from the 115-kv bus to the 'res'exve 'station-service transformers.
Each of the on-site 'power'ystems are 'tested according to the Technical Specifications, to ensure their capability to perform their intended safety function.
Loss of power from one 'source 'will not cause loss of power from one of the other'ources'.
The Niagara Mohawk System is designed such that the 115-kv transmission system will not be lost if Nine Mile Point Unit No.
1 goes off the line."
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position 2 - Interaction of Onsite Power Sources with Load Shed Feature Justification for retaining the load shed feature at
.gine Mile Point Unit 1 is discussed in Reference 1.
In addition, testing was performed after installation of the
.second level of under'voltage protection.
Results of this testing verified that the system operated within the design
'requirements.
Proposed Technical Specification changes are being submitted under separate cover'.
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Position 3
Onsite Power Source Testin Technical Specification Surveillance Requirement 4.6.3.a requires a simulation of a loss-of-coolant: accident during each major refueling outage.
Operator Surveillance Test No.
R2 "Loss of Coolant and Emergency Diesel Generator Simulated Automatic Initiation Test" verifies the following:
1)
On loss of off-site power that the engineered safeguard loads axe shed from the emergency buses and 2) that the diesel generators start automatically and sequentially pick up the engineered safe-guard loads.
The load shedding feature for the emergency diesels at Nine Nile Point Unit 1 remains intact throughout operation as described in Reference l.
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