ML20004F342
| ML20004F342 | |
| Person / Time | |
|---|---|
| Site: | Prairie Island  |
| Issue date: | 06/08/1981 |
| From: | Mayer L NORTHERN STATES POWER CO. |
| To: | Office of Nuclear Reactor Regulation |
| References | |
| GL-81-04, GL-81-4, NUDOCS 8106180185 | |
| Download: ML20004F342 (5) | |
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Northem States Ps., Company 414 Nicollet Mall Minneapoks. Menesota 55401 Telopnone (612) 330 5500 2A I !9/
June 8, 1981 U'
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Director of Nuclear Reactor Regulation U S Nuclear Regulatory Commission
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Washington, DC 20553 9,
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Y PRAIRIE ISLAND NUCLEAR GENERATING PLANT O
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Docket Nos. 50-282 License Nos. DPR-42 A
50-306 DPR-60 Response to Generic Letter 81-04 Assessment of Procedures and Training Programs for Station Blackout In a letter dated February 25, 1981 from Darrell G Eisenhut, Director, Division of Licensing, USN.lC (Generic Letter 81-04), we were requested to provide an assessment of our existing and planned facility procedures and training programs with respect to station blackout events. This letter also stated that the following actions and important considerations should be included in our evaluation:
a.
Maintenance of heat removal capability and inventory control with available equipment, b.
Basis for estimated time available to restore AC power.
c.
Actions required to restore offsite AC power in the event of loss of grid.
d.
Actions required to restore of fsite power when caused by onsite equipment failure.
Actions required to restore emergency onsite AC power, including e.
diesel r enerator loading sequence considerations.
f f.
Consideration of emergency lighting requirements for the duration of the event.
g.
Precautions to prevent consequential equipment damage due to the r.eturn of 4C power.
h.
Definition of specific operator training requirements for the loss of all AC power event.
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l NORTHERN STATES PCWER COMPANY Director of NRR June 8, 1981 Page As previously reported to the Commission in a letter dated April 9,1981 from Robert W Jurgensen, Chairman, Westinghouse Owners Group, to Darrell G Eisenhut, Director, Division of Licensing, USNRC, (OG-56), generic loss of all AC power procedural guidelines will be completed and submitted for NRC review by September 1, 1981. These guidelines, when available, will address items (a), (b), and (g).
Item (h) will be partially addressed through an Owners Group Seminar covering loss of all AC procedures and training to be held in October,1981 following completion of the procedural guidelines. We believe that appropriate Prairie Island procedural changes and training can be completed within six months after the planned seminar.
Our assessment of items (c), (d), (e), and ( f) is presented below:
c.
Actions Required to Restore Of fsite AC Power in the Event of Loss of Grid It is estimated that the maximum time that would be required to re-energize the 345-KV transmission system into the Prairie Island substa-tion would be two hours. This time would, of course, depend greatly on the means by which power were restored. Northern States Power has several (presently nine) gas turbine and jet engine driven generators that have the capability of being started in the absence of AC station auxiliary power.
If remote start of all of the units from the system control center was unsuccessful and operators were required to travel to the generator sites to start the units, a maximum of two hours would elapse.
At the other extreme, system interties could conceivably be reclosed to restore the 345-KV system in a much shorter time; possibly less than 30 minutes.
A review of the most probable system contingencies which would result in the separation of the Northern States Power system and conscquent loss of all generation has been completed. Recommendations resulting from this review are under consideration.
d.
Actions Required to Restore Offsite Power When Caused by Onsite Equipment Failures Nonsafeguards - During normal power operation, the 4KV buses are connected to the unit auxiliary transformers. When an auxiliary trans-former fails or a unit trips, the auxiliary load is transferred to the startup trans former.
If this transformer or both of its sources fail, the non-safeguards buses remain deenergized until an established procedure for backfeeding through the unit auxiliary trans f'rmer can be completed.
Backfeeding is the standard procedural response at Prairie Island for restoration of offsite power to the non-safeguards buses, when the startup transformer source is lost. The estimated maximum time to establish a backfeed condition is four hours per unit.
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NORTHERN STATES POWER COMPANY Director or NRR June 8, 1981 Page Safeguards - During normal operations the plant safeguards buses are supplied by three offsite sources, two per bus.
If the primary offsite source for a safeguards bus is lost, automatic transfer to the secondary offsite source occurs.
In addition, there is an automatic bus tie breaker between two of the offsite sources, which would close except in the event of a fault on one of the buses.
The safeguards load transfers to an emergency onsite source only if offsite sources for the bus have failed. The safeguards buses can receive power from the unit auxiliary transformers by an established manual switching procedure.
Therefore, even if extensive damage occura to normal offsite safeguards sources, offsite AC can be restored to the safeguards buses as soon as backfeeding of the unit auxiliary transformer can be established, and power is available in the substation, e.
Actions Required to Restore Emergency Onsite AC Power, Including Diesel Generator Loading Sequence Considerations Prairie Island has two dieael-generators, each of which is capable of supplying the full engineered safeguards load for one unit plus concurrent hot shutdown load for the second unit. Each diesel generator has a DC control system which is supplied by a battery charged b3 the safeguard system. Each diesel has starting air receivers and an air compressor which is powered by a safeguards bus served by the diesel-generator output.
The diesels may be started and controlled either automatically or manually, in accordance with established procedures.
If a sr irting attempt fails, a shutdown relay must be reset before a second attempt is made.
If the starting air for one diesel is exhausted, the starting air tanks can be cross-connected such that additional air is supplied from the other diesel's supply.
The Westinghouse Owner's Group is planning to provide additional informa-tion relating to loading sequence and unavailability of AC power considera-tions.
Emergency procedures will be reviewed and revised accordingly when the owner's group study is complete, f.
Consideration of Emergency Lighting Requirements for the Duration of the Event The Prairie Island normal lighting system is supplemented by three emergency lighting systems.
There is a 125 VDC system for each unit which provides emergency lighting to the turbine building, auxiliary building, and containment. Powee is automatically transferred from an l
interruptible AC source to the emergency DC source upon loss of power.
The emergency lighting in the control room is provided by a 12 VDC system. This system is served by a dedicated battery and charger, i
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NORTHERN STATES POWER COMPANY Director of NRR June 8, 1981 Page and is energized automatically upon loss of normal AC lighting.
There is also an array of strategically placed portable emergency lights.
These ate maintained on a trickle charge. The operations, maintenance, and periodic testing of these emergency lighting systems is performed in accordance with established plant procedures.
Please contact ua if you have any questions related to the information we have provided.
L 0 Mayer, PE llanager of Nuclear Support Services LOM/DMM/jh cc J G Keppler NRC Resident Inspector G Charnoff Attachment
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'A UNITED STATES NUCLEAR REGULATORY COMMISSION NORTHERN STATES POWER COMPAhT PRAIRIE ISLAND NUCLEAR GENERATING PLANT Docket No. 50-282 50-306 LETTER DATED JUNE 8,1981 RESPONDING TO NRC LETIER DATED FEBRUARY 25, 1981 EMERGENCY PROCEDURES AND TRAINING FOR STATION BLACKOUT EVENTS Northern States Power Company, a Minnesota corporation, by this letter dated June 8, 1981 hereby submits in response to the NRC letter dated February 25, 1981, our assessment of existing and planned facility procedurea and training programs for station blackout events.
This submittal contains no restricted or other defense information.
NORTHERN STATES POWER COMPANY
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By
/s/ L 0 Mayer L 0 Mayer Manager of Nucitar Support Services On this 8th day of June 1981_, before me a no;ary public in and for said County, personally appeared L 0 Mayer, Manager of Nuclear Support Services, and being firt.t duly sworn acknow"cdged that he is authorized to execute this document on behalf of Morthern States Power Company, that he knows the contents thereof and that to the best of his knowledge, information and belief, the statements made in it are true and that it is not interposed for delay.
/s/ Jeanne M Hacker Jeanne M Hacker Notary Public-Minnesota Hennepin County My Commission Expires May 6, 1981
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