ML20207E300
| ML20207E300 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 08/11/1988 |
| From: | Gridley R TENNESSEE VALLEY AUTHORITY |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| References | |
| NUDOCS 8808180001 | |
| Download: ML20207E300 (6) | |
Text
s TENNESSEF. VALLEY AUTHORITY CHATTANOOGA. TENNEGSEE 37401 SN 157B Lookout Place AUG 111988 U.S. Nuclear Regulatory Commission ATTH: Docutnent Control Desk Washington, D.C.
20555 Centlemen:
In the Matter of
)
Docket Nos. 50-327 Tennessee Valley Authority
)
50-328 SEQUOYAll NUCLEAR PLANT (SQH) - DIESEL CENERATOR (DC) LOAD ANALYSIS RESULTS
References:
1.
TVA letter to NRC dated August 4, 1988, "Sequoyah Nuclear Plant (SQN) Unit 1 - Electrical Calculation Program Status" 7.
TVA letter to NRC dated February 29, 1988, "Sequoyah Nuclear Plant (SQN) - Diesel Generators (DGs) -
Operability and Analysis" This letter provides NRC with additional informatis.n regarding the "SQN DC Load Analysis" (DCLA) as requested in a telephone conversation on Aug,ust 5,.1988.
The Staff requested the numerical results of the SQN DGLA be provided in order to aid them in their review of the SQN unit 1 Electrical Calculation Program.
The enclosure provides a discussion of these results and also contains two tables of the values obtained by this analysis. Table 1 provides a comparison of the maximum DC transients and continuous loading conditions, the DC ratings, and the DG design limits for each respective DC under the conditions of a loss of offslte power (LOOP) coincident with an accident on either unit. The design limits contained in table 1 are TVA's self-imposed de91gn safety limit values that provide the degree of nargin necessary to ensure that the DG manufacturer's rating is not exceeded and that the safety margins established in TVA's Nuclear Engineering (NE) calculation SQN-E3-015, "Diesel Generator Voltage and Margin Analysis" (DGVMA), ata maintained.
Table 2 tabulates and compares the transient DG loading for the major sequenced loads for each respective DG.
The tratislent DC loading values in table 2 are less than _or equivalent to those used in TVA's DCVMA. The exceptions to this are for DCs 2A-A and 2B-B at the 20-second step for a LOOP with a safety injection (SI) phase A isolation, which exceeds that used by the DCVMA by less than 1 percent. This difference is negligible and does not affect the final results.
O 8800180001 880811 PDR ADOCK 05000327 P
PDC An Equal Opportunity Employer
a U.S. Nuclear Regulatory Commission AUG 111988 In conclusion, the DGLA (SQN-E3-002) confirms that the SQN DCs are capable of supporting two-unit operation while maintaining acceptable margin between the maxinum transient / continuous loading and the DC manufacturer's ratings. In addition, the DGLA (SQN-E3-002) confirms that the loading used in TVA's DGVMA (SQN-E3-015), which determined the DG transient voltage and equipment safety margins, is the limit.ing case.
Please direct questions concerning this issue t.o B. A. Kimsey at (615) 870-6847.
Very truly yours, TENNESSEE VALLEY AUTit0RITY Wl R. Gr}dley, Manager Nuclear Licensing and Regulatory Affairs Enclosures cc (Enclosures):
Ms. S. C. Black, Assistant Director for Projects TVA Projects Division U.S. Nuclear Regulatory Commission one White Flint, North 11555 Rockville Pike Rockville, Maryland 20852 Mr. F. R. McCoy, Assistant Director for Inspection Programs TVA Projects Division U.S. Nuclear Regulatory Commission Region 11 101 Marietta Street, NW, Suite 2900 Atlanta, Georgia 30323 Sequoyah Resident Inspector Sequoyah Nuclear Plant 2600 Igou Ferry Road Soddy Daisy, Tennessee 37379
SUMMARY
OF RESULTS (SQN-E3-002)
As stated in the letter providci to NRC dated August 4, 1988 (reference 1),
TVA performed calculation SQN-E3-002 for the SQN unit 2 restart ef fort to determine and evaluato the loading kilowatt (kW) and kilovoltamperes (kVA) on each DC at every load sequence step for the following ' conditions:
1.
Blackout, LOOP.
2.
Blackout with SI signal and containment isolation, phase A.
3.
Blackout with SI signal and containment isolation, phaso B.
In this analysis, DG 2D-B was modeled because it was determined to havo the worst-case sequential loading of the four DCs for each of the above conditions. Furthermore, this unit 2 analysis assumed that unit I was in modo 5 with a blocked SI signal.
TVA has revised the DGLA (SQN-E3-002) to address DGs IA-A, IB-B, 2A-A, and 2B-B in support of the unit I restart ef fort.
It should be noted that for DG 2B-F, the loads have been reduced from the previous analysis because of a more detailed review of load operations. Table 1 (see pago 3 of this enclosuro) shows a comparison of the maximum DG transient and continuous loading (l.o., a composite of the results for LOOP with SI phase A and LOOP with SI phaso B),
the DG ratings, and the design limits for each respective DG under the conditions of a LOOP coincident with an accident.
The maxitum transle;at load that occurs during the first three minutes of the load sequence is for a LOOP with an Si phaso A and is 4,083 kW.
The engLno is cated for 4,487 kW for the first theco minutes.
%e The maximum transient load that occurs for the remainder of the load sequence is for a LOOP with an SI phaso B and is 4,746 kW.
The ensino is rated for 5,042 kW after the first three minutes. This diesel engine rating has been revised to that previously submitted to NRC in a lotter dated February 27, 1987. This is based on the information supplied to TVA from the DG vendor (Horrison-Knudsen Power System Division) that stated that diesel ongino deratings do not have to be applied for air inlet temperatures up to 115 degrees rahrenholt (F) provided that tho jacket water temperature to the ensino does not exceed 165 dcgrcos F.
TVA thus conflemed that the diosol engine jacket water inlet temperature did not exceed this value, which resulted in an increase in the engine rating from 4,951 kW to 5,042 kW.
The maximum muning load that occurs during the first two hours of the load sequence is for a Loop with an SI phaco B (4,291 kW and 4,742 kVA). Tho engine rating is 4,840 kW and the sonorator rating is 5,500 kVA.
The design limit is 4,435 kW and 5,500 kVA.
The design limit values for the SQN DCs worn self-imposed by TVA's Electrical Ensinocring Branch to ensure that the DGs' margin of safety would be maintained and to ensure that the manufacturor's rating for tho DGs la not exccodod.
. As previously submitted to URC in a letter dated February 29, 1988 (reference 2), operator action may be necessary to remove nonessential DG loads after two hours if the DG engine ratings are exceeded. This is administratively controlled by abnormal operating instruction ( AOI) 35.
Results of this revised analysis, as shown in tablo 1, reconfirm this potential situation. The maximum continuous load thatroccurs after two hours into the load sequence is for a LOOP with an SI phase B (4,402 kW and 4,843 kVA).
This results in an engine load that is 2 kW greater than the engine rating of 4,400 kW and a generator load that is within the generator rating of 5,000 kVA. This potential ensino overload of less than 0.05 percent is within the accuracy of the DGLA.
In addition, TVA's analysis shows that, after the nonessential loads are removed, the loading on all DGs is well within the DG ratings.
The loading on the DGs after the nonescential loads are removed is maintained within the design limits of 4,278 kW and 5,000 kVA except for DG 1A-A, which exceeds the TVA self-imposed engine design limit by.19 kW.
This is acceptable because of the analysis including the effect of the 350 horsepower component cooling system (CCS) pump C-S, which is normally aligned to DC 2B-B.
Manual transfer of this load by operations to DG 1A-A is controlled by system operating insterction 70.1.
This alignment of t'.o C-S pump was conservatively included in the analysis to shcw DG 1A-A's capacity for this event should it ever occur. Therefore, the continuous load on sG 1A-A without the effect of the CCS pump C-S is well within the TVA design limits.
Surveillance instruction 26 currently requires the DGs to be operated at greater than or equal to 4,840 kW for the first two hours of surveillance and 4,400 kW for the next 22 hours2.546296e-4 days <br />0.00611 hours <br />3.637566e-5 weeks <br />8.371e-6 months <br />. This confirms that the calculated coatinuous/ running load is bounded by test, e
Table 2 (see page 4 of this enclosuro) tabulates and providos a comparison of the transient DG loading values calculated for the major sequenced loads for each respective DG.
The transient DG loading values in tablo 2 are less than or equivalent to those used in TVA's DGVMA.
The exceptions to this arn for DGs 2A-A and 2B-B at the 20-second stop for a LOOP with an SI phase A isolation, which exceeds that used by the DGVHA by loss than 1 percent.
This difference is negligible and does not affect the final results.
The results of the DGLA (SQN-E3-002) confirm that the loading used in the DGVMA (SQN-E3-015), which determined the DG transient vo......r ' equipment safety marsins, is the limiting case. Therefore, in ',onclusion, the DCLA confirms that the SQN DG3 are capable of supporting two-unit operation while maintaining acceptable margin between the maximum transient / continuous loading and the DG manufacturer's ratings.
. TABLE 1 COMPARISON OF Tile MAXIMUM SQN DG LOADING Note: This information is taken from SQN-E3-002, "Diesel Generator Analysis,"
and the values are rounded to the t.carest wholel Integer valuo.
Maximum Running Load, O To 2 Hours (LOOP with SI Phase B)
Design Units DG 1A-A DG 1B-B 9G 2A-A DG 2B-B Limit Rating kW 4.287 4.169 4.241 4.291 4.435 4,840_
kvA 4.734 4.600 4.664 4.742 5.500 5.500 Maximum Continuous Load, After 2 Hours (LOOP with SI Phase B)
Design Units DG 1A-A DG 1B-L DG 2A-A DG 2B-B Limit Rating kW 4.400 4.280 4.353 4.402 N/A 4.400 kVA 4.837 4.702 4.766 4.843 N/A 5.000 kW*
4.297#
4.094 4.064 4.198 4.278 4.400 kVA*
4.739 4.512 4.483 4.654 5.000 5.000
- af ter operator action taken to removo A01-35 nonessential loads O see page 2 of the enclosure for design limit / loading discussion Maximum Transient Load, O To 3 Minutes (LOOP With SI Phase A) 3 Units
'DG 1A-A DG 1B-B DG 2A-A DG 2D-B Rating kW 4.407 3.659 3.729 4.083 4.487 Maximum Transient Load, 3 Minutos and Af ter (LOOP With SI Phaso B)
Units DC 1A-A DG IB-B DG 2A-A DC 2B-B Rating kW 4.727 4.567 4.591 4.746 5.042
TABLE 2 COMPARISON OF DG LOADItlG AT LOAD SEQUENCE STEPS Hote:
This information is taken from SQN-E3-002, "Diesel Generator Analysis,"
and the values are rounded to the whole integer valuo.
Total Transient Load Values In kW For LOOP With S1 Phaso A Stop (seconds)
DG 1A-A DG 1B-B DG 2A-A DG 2B-B 2
2,186 2,170 2,239 2.220 5
2,308 2,291 2,360 2,341 10 2,716 2,699 2.761 2,749 15 2.940 2,924 2.993 2,974 20 3.515 3,500 3,569 3.552 30 4.047 3.659 3.729 4,083 Total Transient Load Values In kW For LOOP With SI Phase B Step (secottds)
DG 1A-A DG 1B-B DG 2A-A DG 2B-B 2
1,933 1,916 1,957 1,950 5
2,055 2,038 2,079 2,072 10 2,464 2,448 2,480 2,481 15 2,688 2,672 2,712 2,704 20 3.217 3.202 3,242 3,235 30 3,781 3,394 3.437 3.799
_3 (minutes) 4.727 4.433 4,476 4,746
~.