ML20033D055
| ML20033D055 | |
| Person / Time | |
|---|---|
| Site: | Prairie Island  |
| Issue date: | 11/20/1981 |
| From: | Mayer L NORTHERN STATES POWER CO. |
| To: | Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8112070168 | |
| Download: ML20033D055 (4) | |
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i Northern States Pcwer Company 414 Nicollet Malf Minneapoks. Minnesota 55401 Telephone (612) 330-5500 November 20, 1981 Di Director Office of Nuclear Reactor Regulation 9
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Document Control Desk U S Nuclear Regulatory Commission l_
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Washingtou, DC 20555
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PRAIRIE ISLAND NUCLEAR GENERATING PLANT Docket Nos. 50-282 License Nos. DPR-42 b
p(N 50-306 DPR-60 j~
Additional Information Related to Station Electric Distribution System Voltages Re fere nce :
Request for Additional Information, Prairie Island Nuclear Generating Plant, Units 1 & 2, Adequacy of Station Electric Distribution System Voltages, October 20, 1981 On October 20, 1981 - request for additional information related to our July 17, 1981 analysis of station distribution system voltages was telecopied to us by our project manager in the Division of Licensing. This request was
<!iscussed during a telephone conference call on October 23, 1981 between the NRC Staf f, consultants from Lawrence Liversore Laboratories, and engineers from the Prairie Island technical staff.
The purpose of this letter is to provide information requested during the October 23, 1981 conference call and document our responses to other questior.e contained in the October 20, 1981 request for additional ir.fonnat ion. The requested information is attached.
if you have any questiona telated to the information we have Please contact us provided.
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L 0 Mayer, PE Manager of Nuclear Support Services LOM/bd cc: Director, lE-III, NRC NRR Project Manager, NRC Resident Inspector, NRC 1g C Charnoff (0$\\
Attachment 8112070160 011120 PDR ADOCK 05000 P
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- Dirsetcr of'NRR November' 20, 1981 Attachment Response to Request for Additional Information
~ Prairie Island Nuclear Generating Plant Adequacy of Stations Electric Distribution System Voltages Ref. 1: NRC generic letter to all power reactor licenses dated August 8, 1979 Ref 2: Northern States Power Company letter (L 0 Mayer) to the NRC (Director of Nuclear Reactor Regulation), dated July 17, 1981 1.
Reference 1, Enclosure 2, Item 3 requested that the analysis should consider the starting of a large non-safety load.. Submit an analysis' that includes the voltage at the terminals of all Clar IE loads under the conditions of minimum grid voltage with full auxiitary plant load, including Class 1E loads, during the starting of a large non-Class lE load. A determination should also be made whether or not separation from the of fsite power source will occur as a result of the action of
~ the undervoltage relays during the start.
Response
Case 1 of Table 8 has the results of starting two SI pumps and several 480 :
volt motors simulatenously.- This is equivalent to 2340 HP.
Non-safeguards motora greater than 1000 HP are:
Condensate Pumps 1750'HP
- Cire Water Pumps 2000 HP
- Cooling Tower Pumps 2500 HP
- Feedwater-Pumps 5000 HP
- Reactor Coolant Pumps 6000 HP
- - indicates manual start signal only-feedwater Pumpe and Reactor Coolant Pumps are supplied from the IRX winding.
l The af fect on voltage on the IRY (which supplies safeguards-loads)= is y
equivalent to the starting of a 500 or-600 HP. motor on the IRY,windingi 1
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- The only'non-safeguards motors that! may be as limiting as case.1 of Table.8.
y is the start of 'a cooling' tower pump in.-an : abnormal electrical distribution ~ -
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b Jconfiguration with both units shut down..There is'no reason to. start a cooling ~ tower pump in this situation.
2.
Reference 2 provided. the results of calculations' for 4160-volt' buses -
and '480-volt buses,? however, additional voltages are needed. Provide the minimum-~ voltages 1that the 480-volt # starters 1and contactors' would-experience underl worst' caseL transient ~ conditions such'as-during-blocky
.trans fer, sequences' loading, or starting of a~ 1arge non-1E. load' EThe-analysis should.show that these startersLwill not'dropfout.under,these yorst case conditions.~ Also, submit calculated. voltages foriall: low-
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Directorlof NRR November 20, 1981 Attachment voltage AC (less than 480 volts) Class 1E buses.
This should include the voltage available for contactors or starters for Class IE equipment to ensure their capability to pull in and remain pulled in for all transient and steady state cases. Document that all low voltage AC Class 1E equipment-will be operating within their required' voltage ratings for each case analyzed.
Do these buses supply any-instruments or control circuits required by CDC-13? If so, is all equipment capable of sustaining the analyzed voltages.without blowing fuses, overheating, etc., and without af fecting the equipment 's ability to perform the required function ?
Response
The maximum drop out voltage for motor starters presently allowed by prevent ive maintenance is 340 volts.
Starters will not drop out during transient conditions.
There are no safety related starters below the 480-volt level. AC instrument and control loads that cannot tolerate voltage interruptions for short periods are supplied by inverters.
3.
Reference 2, page 2 states-that transformers IM and 2M can be a source for the Class 1E 4160-volt buses. Can these buses be supplied by backfeeding from the grid through these transformers? If so, submit. an analysis for this source using the conditions as established for the analyses submitted in Reference 2.
Response
Backfeeding in this manner requires removal of main generator disconnect links.- This is a manual operation requiring several hours to' perform.
At-least one unit would be shutdown. An analysis.for this sit iation~ is not required.
4.
Reference 2, p. 12, describes bus 120 as the worst case 480 V Class IE bus.
Please clarify 'the voltage conditions on the 4160 V Class IE buses during the time frame of'the analysir..
Response
Refer to page 42, column 1, of our July 17. 1981 -anal' ysis.. Reference 2, page 14 provides a sequence loading analysis. for the '4160-volt-~
Class IE buses.
Submit a similar analysis for the 480-volt Class.1E buses.
Response
Our'480V calculations were based on'88% on the 4160 V buses. All Table 8 values
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-. are greater than 88%.. We believe this is an acceptable ' approach.
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Dirscter cf NRR Nsv:mbsr 20, 1981 Attachment 6.
The analysis has shown that CTil is "only conditionally acceptable as an offiste source in the' event of inoperability of CT12" [ Reference 2, page 17]. The analysis also indicated the Spring Creek 161KV line has limited capabilities. Provide LCO's that cover operations with either of these two sources.
Response
We will submit proposed LCO's if the NRC's evaluation of this issue concludes j
they are required.
l 7.
Reference 2, page 12 states that the 460-volt motors could be operating at 85% of nameplate voltage and that this results in a shortened life.
Reference 1, page 2 states that the voltage distribution system should be of sufficient capacity and capability to automatically start and operate all required Class 1E loads within their required voltage ratings under a worst case set of conditions. Provide details how the Class IE equipment on the 480-volt buses can meet this requirement.
Response
Refer to page 7 of our July 17, 1981 report.
'The voltage of 85% was calculated based on the conditions of Table 11, case (r). Note that the 4160 V bus is at 88%. The grid will maintain the voltage at 92% on the 4160 V bus in Case 5 of Table 8.
All 480 V calculations will be at least 4% higher for Case 5 voltages on the 4160 V bus.
8.
Reference I requested a verification of calculations.
Submit a detailed description of tests or verification to be used as well as a schedule for when the verification will be completed.
Response
Our testing will consist of changing the IR loading by approximately'4000 HP and comparing measured voltages with voltages calculated with our model.
We will also c hange CT11 loading by approximately 2500 HP and compare measured and calculated voltages.
We will determine the start' time of the SI pump. The_ SI pump test will be done during a monthly surveillance test.
These teetc wift oe completed by the end of January,1982.
Results will be summarized and reported to the NRC.
Note: The following typographical _ errars in _our July 17, 1981 report.should 'e-corrected:
- 1..Page 39,- Case 2', 2R, change 83.6%.to _93.6%.
2.;Page 42, Case (b),_ bus 120'should be changed _to read 70.0%1
- 3. Page 42, case (c), bus 120 should be changed to read 77.3%. E
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