ML20079N421
| ML20079N421 | |
| Person / Time | |
|---|---|
| Site: | Waterford  |
| Issue date: | 02/11/1983 |
| From: | Maurin L LOUISIANA POWER & LIGHT CO. |
| To: | Novak T Office of Nuclear Reactor Regulation |
| References | |
| RTR-NUREG-0787, RTR-NUREG-787 W3I82-0146, W3I82-146, NUDOCS 8303030678 | |
| Download: ML20079N421 (7) | |
Text
II9-B72 iill LOUISIANA q"
f 24a c a AnoNoe s1nter POWER & L1GHT/ P O. BOX 6008
- NEW ORLEANS. LOUISIANA 70174. (504) 366-2345
$IiESAs sASE i
February 11, 1983
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Vrce Presodent Nuclear Operations W3182-0146 1-3-P17.A1.01 Q-3-Pl7.A1.02 Mr. T. M. Novak Assistant Director of Licensing U. S. Nuclear Regulatory Commission Washington, D. C.
20555
SUBJECT:
Confirmatory Issue 2.4.5, Ultimate Heat Sink Testing
Dear Mr. Novak:
This letter is to provide confirmatory information relative to LF&L's commitment to conduct preoperational testing of the Ultimate Heat Sink to verify its ability to perform as designed.
Background
In Section 9.2.5 of NUREG-0787, Safety Evaluation Report Related to the Operation of Waterford Steam Electric Station Unit 3, dated July 1981, the NRC staff concluded that the Ultimate Heat Sink (URS) meets the requirements of GDC 2, 4, 44, 45, and 46 with respect to protection against natural phenomena, missiles and environmental effects, decay heat removal capability, inservice inspection and testing, and the guidelines of Regulatory Guides 1.26, 1.27, and 1.29 with respect to quality group and seismic class-ification and design capability, and is, therefore, acceptable.
In Section 2.4.5 of the Safety Evaluation Report, it was noted that the determination of acceptability by the NRC staff was subject to successful completion of confirmatory preoperational testing of the hydrological and thermal performance of the wet and dry cooling towers. Louisiana Power & Light committed to verify the performance of the UHS by conducting tests consisting of running the touers under load to establish that they meet the design criteria.
A copy of the UHS preoperational test procedure SIT-TP-250 was forwarded to your Mr. J. S. Wermiel for review; comments based on his reviews were resolved and/or incorporated into the test procedure prior to commencing Ultimate Heat Sink system heat load testing.
The following information is provided in response to our commitment to summarize the preoperational testing conducted and the results achieved.
B 00 I 8303030678 830211 PDR ADOCK 050003B2 A
Mr. T. M. Novak W3I82-0146 Page 2 Summary The function of the Ultimate Heat Sink (UHS) at Waterford 3, as de' scribed in Section 9.2.5 of the FSAR, is to dissipate the heat removed from the reactor and its auxilia-ies during normal operation, shutdown, refueling, tornado, and design basis accident conditions. To determine the ability of the UHS to function, as designed, during these modes a series of full capacity heat load tests were conducted between May and October, 1982. The limiting operating modes, test conditions and limits, and the results achieved are summarized in the tables below.
Normal Shutdown Mode System Parameter Extrapolated Value*
Test Value Design Value Wat Tower Basin Temp 93.0*F 86.11*F 105.0*F CCW Heat Exchanger Outlet Temperature 98.0*F 94.31*F 120.0*F Dry Tower Heat Load 76.8 x 106 BTU /hr.
82.6 x 106 BTU /hr.
6 Wat Tower Heat Load 50.4 x 106 BTU /hr.
41.9 x 10 BTU /hr.
Total Heat Load 127.2 x 106 BTU /hr.
124.5 x 106 BTU /hr.
127.2 x 106 BTU /hr.
Ambient Dry Bulb 102.0*F 87.64*F 102.0*F Ambient Wet Bulb 83.0*F 77.48'F 83.0*F 4
Loss of Coolant Accident (LOCA) Mode System Parameter Extrapolated Value*
Test Value Design Value Wat Tower Basin Temp.
93.4*F 85.20*F 105.0*F CCW Heat Exchanger i
Outlet Temperature 109.8*F 97.0*F 120.0*F
=---------
Dry Tower Heat Load 113.9 x 106 BTU /hr.
126.96 x 106 BTU /hr.
W2t Tower Heat Load 64.4 x 106 BTU /hr.
48.04 x 106 BTU /hr.
Totel Heat Load 178.3 x 106 BTU /hr.
175 x 106 BTU /hr.
178.3 x 106 BTU /hr.
Ambient Dry Bulb 102.0*F 85.97'F 102.0*F Ambient Wet Bulb 84.0*F**
77.20*F 84.0* F **
- Values were determined by extrapolating test results to design basis conditions.
- Maximum I hour Wet Bulb Temperature at Waterford 3 per FSAR Table 2.3-2(a) is 83*E.
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Mr. T. M. Novak W3182-0146 Page 3 Tornado Mode System Parameter Extrapolated Value*
Test Value Design Value Wat Tower Basin Temp 114.0*F 116.2*F 105.0*F CCW Heat Exchanger Outlet Temperature 119.4*F 120.3*F 120.0*F Dry Tower Heat Load 78.0 x 106 BTU /hr.
85.5 x 106 BTU /hr.
Wat Tower Heat Load 17.0 x 106 BTU /hr.
16.7 x 106 BTU /hr.
. Total Heat Load 95.0 x 106 BTU /hr.
102.2 x 106 BTU /hr.
95.0 x 106 BTU /hr.
Ambient Dry Bulb 92.0*F
'90.74*F 92.0*F Ambient Wet Bulb' 76.8'F 76.8'F 76.0*F 4
- Values were determined by extrapolating test results to design basis conditions.
As shown in the above tables, a considerable margin exists between the system operating temperatures and the design limits in the Normal Shutdown and Loss of Coolant Accident (LOCA) Modes.
In the Tornado Mode the measured Wet Cooling Tower (WCT) basin temperature exceeded the Design Value of 105'F.
i This disparity between the predicted and design temperatures was reported to Region IV of the USNRC pursuant to 10CFR50.55(e) on August 30, 1982 as Potentially Reportable Deficiency (PRD) 86.
Subsequent to notifying the NRC of this condition, an evaluation was performed to determine the significance j
of the performance deviation and to assess its potential impact on plant safety.
The heat dissipation capacity of the Ultimate Heat Sink system was found to be sufficient for safe shutdown of the plant. The evaluation then focused on the ability to maintain the environment of safety-related plant areas at or below the Design Ambient Temperature (DAT) limit of 104*F with the higher than expected WCT basin temperature. It was determined that no areas containing sensitive safety-related electrical equipment, such as, the Switchgear Room, Control Room, or Relay Room exceeded their Design Ambient Temperatures in the Tornado scenario. The areas which did exceed the DAT were as follows:
i Post Tornado I
Area DAT (*F)
Peak Temperature (*F) l CCW Heat 104 109 Exchanger Room CCW Pump 104 115 Room i
Emergency Feedwater 104 113 i
Pump Room (Motor Driven)
Shutdown Cooling 104 111 Heat Exchanger Room i
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Mr. T. M. Novak W3I82-0146 Page 4 For the first 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> following the postulated tornado event the plant is maintained in hot standby conditions via the Emergency Feedwater System.
Only after 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> when plant cooldown is commenced does the environment in these rooms exceed the 104*F DAT, and then only for a brief period of time compared to the 40 year operating lifetime of the plant. Ebasco's Environmental Qualification Task Group analyzed the environmental effects of operating these rooms at their average normal operating temperature plus the brief minor temperature excursion versus operating at the DAT for 40 years. The conclusion was that the latter is more conacrvative for the equipment located in these areas and the qualified life of the equipment would not be significantly impacted. The evaluation concluded that the event is not significant, is not a Significant Construction Deficiency per 10CFR50.55(e), and does not adversely impact the safety or the Environ-mental Qualification Program at Waterford 3.
In addition to completing tests to verify that design criteria were met, the overall' cooling tower system performance was evaluated relative to 10CFR21 concerns reported to the USNRC by Zurn Industries on May 3,1979.
The Part 21 concerns and the evaluation of each follows:
- 1) Concern:
" Potential interaction between the discharge from the dry cooling tower and intake of the wet cooling tower."
Response
Test results indicate that there was in fact some interaction between towers as well as recirculation on each tower, however, the system was designed with margins to take into account the effects of eitner interaction or recirculation. Test results indicate that even with the interaction and recirculation the overall capability of the system to dissipate the required heat load is more than adequate.
- 2) Concern:
" potential recirculation of the discharge of the Wet Cooling Tower to its intake."
Response
See 1) above.
- 3) Concern:
"The effect of potential increases in heat load to the wet tower due to recirculation between the inlet and outlet of the dry tower during the operating mode in which the wet cooling tower acts as a peaking cooling system for the dry cooling tower system."
Response
Test results have demonstrated that the Wet and Dry Cooling Towers performed as designed even with the effects of recirculation in both the Dry and Wet Cooling Towers and the interaction between the Dry and Wet Cooling Towers present. The system clearly met the design criteria as indicated by the cold CCW temperatures which were well within the limits.
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Mr..T. M. Novak
-W3I82-0146 Page 5
- 4) Concern:
" Potential maldistribution of the air flow pattern in the completed tower..."
Response
This concern was investigated extensively during prerequisite and full heat load testing.
It was concluded that no flow.maldistributions: existed except during the tornado case when the wet tower system operated in the natural circulation mode results of the maldistribution in the tornado case were determined to be insignificant.
5)
Concern:
"Whether or not there is adequate redund'ancy of 4
alternate cooling tower systens."
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Response
The UHS has sufficient capacity to dissipate heat removed from the reactor and its auxiliaries to permit safe shutdown of the unit coincident with a loss of offsite power, multiple tornado missiles, and a single active failure.
- 6) Concern:
"Whether or not there is adequate redundancy of fan equipment within the wet cooling towers. In the event a single fan failure were to occur in one of the wet cooling towers, the thermal performance of that cell would be reduced approximately 50%."
Response
The design of the UHSlas addressed in item (5) above considers a single active failure (failure of one diesel generator to start) coincident with a loss of offsite power which is more limiting than a single' wet cooling tower fan failure event. Add-itionally, a design modification incorporated during testing resulted in a system configuration in which the loss of one wet tower fan has an insignificant I
effect on the UHS heat removal capability.
7)
Concern:
"Whether or not the emergency diesel power system has been designed to provide adequate power for starting the wet cooling tower fans under emergency conditions".
i
Response
By design the diesel generator ratings are sufficient to supply all safety-related loads. This includes the fan motors of one dry and one wet cooling tower from each train on their respective safety-related busses. The capacity of the diesel generators will be tested via procedure SIT-TP-200.
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Mr. T. M. Novak W3I82-0146 Page 6
- 8) Concern:
"Whether or not there is adequate missile protection for the cooling tower fans. We are aware of similte cooling tower systems designed to provide similar safety-related service for nuclear plants, in which considerably more extensive missile protection is provided for the cooling tower fans."
Response
The cooling coils of three dry cooling tower cells of each tower (60%) are protected from tornado missiles by grating located above the coils and capable of withstanding tornado missile impact. Dry cooling tower fans and motors are located below grade, and are protected from tornado missiles by building walls and/or access platforms. Missile protection criteria conform to 10CFR50 Appendix A General Design Criterion 4 and have been found acceptable by NRC as noted in Section 3.5.2 of the Safety Evaluation Report.
- 9) Concern:
"Whether or not the steel embedments in the concrete walls of the cooling tower are adequate to provide support for the cooling tower fill and distribution piping under all design bases and emergency conditions".
Response
The embedded plates used to support the fill and distribution piping were designed and installed in accordance with the loading requirements established by the cooling tower supplier and as identified in our specifications for Mechanical Draft Cooling Towers and Accessories. The embedded plates for the fill and distribution piping were designed utilizing standard engineering practices employed for other safety-related, seismically designed piping systems.
Conclusion The performance tests conducted demonstrate the ability of the as-built Ultimate Heat Sink System to meet the thermal design basis and show that the system as designed is capable of adequate heat removal to maintain plant safety for all postulated modes of operation.
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Mr. T. M. Novak W3182-0146 Page 7 If'you have any questions on this matter or require further information, please do not hesitate to contact me.
Very truly yours, J
7Gaus L. V. Maurin LVM/WAC:keh cc:
E. Blake, W. Stevenson, J. Wilson (NRC), J. Wermiel i
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