ML19340B815
| ML19340B815 | |
| Person / Time | |
|---|---|
| Site: | Pilgrim |
| Issue date: | 11/05/1980 |
| From: | Morisi A BOSTON EDISON CO. |
| To: | Ippolito T Office of Nuclear Reactor Regulation |
| References | |
| 80-280, NUDOCS 8011120343 | |
| Download: ML19340B815 (4) | |
Text
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BOSTON EOlsON COMPANY GEN E RAL Q FFic Es 8 00 S DYLETO N STR EET SOsTO N. MASS ACMUS ETTE Q219 9 A. V. M O RISI MANAGER NUCLEAR QPERATIONS SUPPQRT QEPARTMENT November 5, 1980 BECo. Ltr. 180-230 a
Mr. Thomas A. Ippolito, Chief
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Operating Reactors Branch #2 Division of Licensing It -
Office of Nuclear Reactor Regulation "6
t, U.S. Nuclear Regulatory Comission
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3 Washington, D. C.
20555 A
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License No. DPR-35 Docket No. 50-293 Additional Information on the Adequacy of Station Electric Distribution System Voltages
References:
(See Attachment A)
Dear Sit In respor.se to your letter of September 4,1980, requesting additional information on the adequacy of the electric distribution system at Pilgrim Nuclear Fower Station Unit I, we offer the following recapitulation of previous correspont ence and telephone conversations in conjunction with responses to your s'ecific areas of concern:
Concern Iri the event of an accident (LOCA) or anticipated trans;ent (unit trip), the onsite distribution systen in conjunction with the offsite power sources would have sufficient capacity and capability to autanatically start and operate all required Class 1E loads within the equipment's voltage ratings.
Voltage Analyses Reouirements a.) To automatically start, as well as operate, all required Class 1E loads within its required voltage ratings.
Response
In reference (2), Boston Edison Company analyzed the voltage profiles of all Class 1E buses of different voltage levels for the fol-lowing conditions:
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U 1.) when the Class 1E buses are energized through the unit auxiliary Q
transformer.
2.) when the Class 1E buses are energized through the start-up transformer.
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CDsTON EQ1 SON COMPANY Mr. Thomas A. Ippolito, Chief November.5, 1980 Page 2 This study was perfomed ia order to detemine analytically if the onsite distribution systen in conjunction with the offsite power sources has sufficient capacity and capability to automatically start, as well as operate, all required Class 1E loads within its required voltage ratings.
As a result of this study, a second level of undervoltage relays on the source side of the start-up transformer were installed in order to trip these breakers during a degraded voltage condition at the safety related buses.
In addition, undervoltage relays were installed on the safety related buses to alam at the control room.
b.) The maximum voltage rating of Class 1E equipment must not be exceeded.
Response: Voltage profiles of the safety related buses were analyzed via Reference (2) for operating ranges of Pilgrim's grid system voltace i.e.
+ 5", of " nominal voltage" (328 kV to 362 kV) and based on past experiences and system stability studies it was detemined that the voltage of the safety related buses will not exceed the maximum voltage rating of the Class 1E equipment.
c.) There should be no manual load shedding to prevent unacceptable voltage 3
at the teminals of all Class 1E~ equipment.
Resoonse: Boston Edison Company does not utilize any procedural requirements for manual load shedding to prevent unacceptable voltage at the terminals of all Class 1E equiptr.ent. We do not consider this as an acceptable method for preventing undervoltage conditions at the Class 1E buses.
d.) The voltage analysis must show that there will be no spurious tripping from the offsite sources.
Response
In Reference (7) we provided you with the details of our analysis which showed that no spurious tripping would occur due to short term voltage degrada tion. The time delay provided to the second level undervoltage relay protection was determined as adequate to assure that there will be no sourious tripoing of Class IE loads from the offsite sources for a short term voltage degradation of the o#fsite source.
e.) Compare the effect of starting and running a lage Non-Class 1E load on all Class 1E equipment with the required voltage range for normal operation.
Response: At Pilgrim Station, there are no large Non-Class 1E loads connected to the Class 1E buses. All large Non-Class IE loads are supplied through separate windings of the unit auxiliary and start up transfomers, thereby minimizing the effects of starting and running of large Non-Class 1E loads on Class 1E equipment.
BOSTON EoisON COMPANY.
- Mr. Thomas A. Ippolito, Chief November 5, 1980 Page 3 f.)~ If any sequential loading is required to assure the voltage is within the required voltage limits at the terminals of all Class 1E equipment, the NRC must be notified.
Response
In the event of LOCA, all the Class 1E loads are simultaneously energized by the start-up transfomer.
There is no automatic or manual sequential loading of Class 1E loads when the onsite power distribution system is supplied through the start-up transformer. Sequential loading is utilized at Pilgrim Station for emergency diesel generator and shutdown transformer operation only.
g.) The adequacy of the onsite distribution of power from the offsite circuits shall be verified by test to assure the analysis results are valid.
Response: We have verified by test to assure the analysis results are valid.
A comparison of tha test results vs the analytical results are delineated in Ref. (2).
In addition, shutdown transformer adequacy is verified at every refueling outage utilizing PNPS surveillance Procedure #8.2.5 Shutdown Transfomer Load Test.
h.) Review the electric power system to determine if any events or conditions could result in the simultaneous loss of both offsite power circuits as required in GDC-17.
Response: At Pilgrim Station #1 we have two offsite power sources: one (1) 345 kV power source, and one (1) 23 kV power source. These sources consist of three offsite power circuits: two (2) power circuits for the 345 kV source and one (1) power circuit for the 23 kV source. There are no events (with the exception of perhaps an earthquake) which could result in the simultaneous loss of all offsite power circuits.
Conditions such as severe snowstoms or ice storms, however, could ultimately lead to the loss of both 345 kV and 23 kV sources.
Realizing that a complete understanding of the electric distribution system at Pilgrim Station is necessary for your staff to complete the review on this generic safety issue, we have made every effort to convey as much infomation as possible via correspondence and various telecons with members of your staff in-volved in this review.
(See Attachment "A" for a complete list of these references)
However, if as a result of your review of this letter and the attached references, you should have any additional questions or concerns, we feel that a meeting with your staff would be the best method 'or us to resolve those concerns and at the same time provide your staff with a thorough understanding of the PNPS Unit #1 electric distribution system. Therefore, please do not hesitate to contact us in this r q ard.
Very truly yours,
/ ff%O Attachment A.
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Attachment A
References:
(1) NRC letter (D. L. Ziemann) to Boston Edison (G. C. Andognini) dated August 13, 1976 4
(2) Boston Edison letter (G. C. Andognini) to NRC (D. L. Ziemann) dated November 15, 1976 - BECo. Ltr. #76-88 (3) NRC letter (D. K. Davis) to Boston Edison (G. C. Andognini) dated June 3, 1977 (4) Boston Edison letter (G. C. Andognini) to NRC (D. K. Davis) dated August 8, 1977 - BECo. Ltr. #77-77 (5) Boston Edison letter (J. E. Howard) to NRC (D. K. Davis) dated August 24, 1977 - BECo. Ltr. #77-85 (6) NRC letter (T. A. Ippolito) to Boston Edison (G. C. Andognini) dated June 19, 1979 (7) Boston Edison letter (G. C. Andognini) to NRC (T. A. Ippolito) dated September 27, 1979 - BECo. Ltr. #79-185 (8) NRC letter (W. Gammill) to Boston Edison (G. C. Andognini) dated August 8, 1979 j
(9) Boston Edison letter (G. C. Andognini) to NRC (W. Gammill) dated October 16, 1979 - BECo. Ltr. #79-208 (10) Boston Edison letter (G. C. Andognini) to NRC (T. A. Ippolito) dated March 28, 1980 - BECo. Ltr. #80-49 (11) NRC letter (T. A. Ippolito) to Boston Edison (A..V. Mori-i) dated Septmeber 4,1980'.
(12) NRC letter (T. A. Ippolito) to Boston Edison Company (G. C. Andognini) dated May 12,1980 " Amendment #42 to 0.L. DPR-35" (Incorporated Tech.
Spec. changes fcr degraded voltage conditions).
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