ML12163A048
| ML12163A048 | |
| Person / Time | |
|---|---|
| Site: | Watts Bar  |
| Issue date: | 06/07/2012 |
| From: | - No Known Affiliation |
| To: | Division of Operating Reactor Licensing |
| References | |
| Download: ML12163A048 (39) | |
Text
1 WBN2Public Resource From:
Boyd, Desiree L [dlboyd@tva.gov]
Sent:
Thursday, June 07, 2012 1:13 PM To:
Epperson, Dan; Poole, Justin; Raghavan, Rags; Milano, Patrick; Campbell, Stephen Cc:
Arent, Gordon; Hamill, Carol L; Boyd, Desiree L
Subject:
TVA letter to NRC_06-07-12_Response to SSER Open Item 26 Attachments:
06-07-12_Response to SSER Open Item 26_Final.pdf Please see attached TVA letter that was sent to the NRC today.
Thank You,
~*~*~*~*~*~*~*~*~*~*~
Désireé L. Boyd WBN Unit 2 Licensing dlboyd@tva.gov 423-365-8764
Hearing Identifier:
Watts_Bar_2_Operating_LA_Public Email Number:
697 Mail Envelope Properties (7AB41F650F76BD44B5BCAB7C0CCABFAF2DB5BBD3)
Subject:
TVA letter to NRC_06-07-12_Response to SSER Open Item 26 Sent Date:
6/7/2012 1:12:48 PM Received Date:
6/7/2012 1:13:16 PM From:
Boyd, Desiree L Created By:
dlboyd@tva.gov Recipients:
"Arent, Gordon" <garent@tva.gov>
Tracking Status: None "Hamill, Carol L" <clhamill@tva.gov>
Tracking Status: None "Boyd, Desiree L" <dlboyd@tva.gov>
Tracking Status: None "Epperson, Dan" <Dan.Epperson@nrc.gov>
Tracking Status: None "Poole, Justin" <Justin.Poole@nrc.gov>
Tracking Status: None "Raghavan, Rags" <Rags.Raghavan@nrc.gov>
Tracking Status: None "Milano, Patrick" <Patrick.Milano@nrc.gov>
Tracking Status: None "Campbell, Stephen" <Stephen.Campbell@nrc.gov>
Tracking Status: None Post Office:
TVANUCXVS2.main.tva.gov Files Size Date & Time MESSAGE 274 6/7/2012 1:13:16 PM 06-07-12_Response to SSER Open Item 26_Final.pdf 2506949 Options Priority:
Standard Return Notification:
No Reply Requested:
Yes Sensitivity:
Normal Expiration Date:
Recipients Received:
Tennessee Valley Authority, Post Office Box 2000, Spring City, Tennessee 37381-2000 June 7, 2012 10 CFR 50.34(b)
U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C. 20555-0001 Watts Bar Nuclear Plant Unit 2 Docket No. 50-391
Subject:
Watts Bar Nuclear Plant (WBN) Unit 2 - NUREG-0847 Supplemental Safety Evaluation Report (SSER) Related to the Operation of Watts Bar Nuclear Plant, Unit 2, Appendix HH Open Item 26 - Diesel Generator Response (TAC No. ME0853)
References:
- 1. NRC letter to TVA dated November 18, 2011, Watts Bar Nuclear Plant, Unit 2 - Request for Additional Information Regarding Supplemental Safety Evaluation Report Open Item 26
- 2. TVA letter to NRC dated April 6, 2011, Watts Bar Nuclear Plant (WBN) Unit 2 - Safety Evaluation Report Supplement 22 (SSER22) -
Response to NRC Required Action Items The purpose of this letter is to provide the additional information requested by the NRC in Reference 1 related to Emergency Diesel Generator (EDG) response and performance during loss of offsite power events, electrical system response to gradual submergence of equipment after a loss of coolant accident, and specific impacts of a loss of ventilation during station blackout conditions.
The requested information is provided in the enclosure and associated attachments and shows that the plant design conforms to the applicable regulatory requirements.
There are no new regulatory commitments contained in this letter. If you have any questions, please contact Gordon Arent at (423) 365-2004.
U.S. Nuclear Regulatory Commission Page 3 June 7, 2012 bcc (Enclosure):
Stephen Campbell U.S. Nuclear Regulatory Commission MS 08H4A One White Flint North 11555 Rockville Pike Rockville, Maryland 20852-2738 Fred Brown, Deputy Regional Administrator for Construction U. S. Nuclear Regulatory Commission Region II Marquis One Tower 245 Peachtree Center Ave., NE Suite 1200 Atlanta, Georgia 30303-1257
ENCLOSURE Response to Action Item 26 From Appendix HH of NUREG-0847, Supplement 22 NRC Question:
The licensee has attempted to demonstrate design margin based on 'hot and cold' engine capability and 'step load' capability. These ratings are not normally cited for DGs in nuclear power plant applications. The Final Safety Analysis Report (FSAR) states that the DG rating is 4400 kW continuous and 4840 kW for 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> out of 24 at a power factor of 0.8.
1 Based on the above information, the staff has the following questions:
a)
Explain the variations in the worst-case loading provided in different responses and provide a summary of current calculations depicting DG loading, including procedurally required loads that may be manually connected.
TVA Response:
Based on discussion with the NRC Region II staff, Calculation EDQ 00099920080014, Diesel Generator Loading Analysis (Reference 1), has been rewritten to improve readability. Because of the ongoing plant modifications and NRC inspections, EDG loading is being constantly adjusted to account for the modifications and NRC comments. This explains the variations in the worst-case loading provided in different responses. Excerpts from Reference 1 are attached as Attachment 1. The loading computations are split in two sections:
The first section delineates the load carrying capability (steady-state running load) and margin available for the worst case EDG loading for two separate events. As stated in the Final Safety Analysis Report (FSAR), load carrying capability is based on a 2-hour rating of 4840 kW from 0 to 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> and on a continuous rating of 4400 kW from 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> to the end. Table 1, provided in, depicts worst case EDG loading with available margin when serving loads during a loss of offsite power (LOOP) concurrent with a loss of coolant accident (LOCA). Table 2 depicts worst case EDG loading with available margin when serving loads during a LOOP only.
The second section delineates the motor starting capability of each EDG for the same two separate events. Table 1 depicts the maximum transient load carrying capability when serving loads during a LOOP concurrent with a LOCA. As stated in the FSAR, this transient load carrying capability is based on a rating of 4785 kW for the first 3 minutes (0-180 seconds) and on 5073 kW from 180 seconds to the end. Table 2 depicts the maximum transient loading when serving loads during a LOOP only.
To demonstrate compliance with Regulatory Guide 1.9 (i.e., voltage does not decrease to less than 75% of nominal), the TVA design approach is not to allow the maximum step load increase in kVA to exceed the manufacturers guaranteed performance characteristics. Thus the Step Load capability is defined as the maximum transient step load increase in kVA that the generator/exciter can accept without exceeding the minimum voltage limit prescribed by Regulatory Guide 1.9. This generator Step Load capability was determined to be 8000 kVA, and TVA has demonstrated that the starting kVA of any motor will not exceed 8000 kVA.
In addition, Attachment 2 provides EDG loading with one unit in LOOP plus LOCA and the second unit in LOOP only. The first set of tables in Attachment 2 provides EDG steady state running loads in the above scenario. The second set of tables in Attachment 2 provides EDG E-1
ENCLOSURE Response to Action Item 26 From Appendix HH of NUREG-0847, Supplement 22 maximum transient loads showing both real power as well as apparent power in the above scenario. The values in these Tables are extracted from Reference 1.
NRC Question:
b)
Provide verification or test documents from manufacturer or Appendix B qualified supplier of DG engine and DG generator certifying the 'hot, cold and step load' capabilities.
TVA Response:
The document that established the Cold Engine (first 3 minutes [180 seconds] of load sequence) and Hot Engine (fully turbocharged, 180 seconds to the end) capability was provided to the NRC as Attachment 1 to TVA letter to the NRC dated December 6, 2010. For staffs convenience the document is attached as Attachment 3. This document established the maximum kW capability of the WBN DGs for starting motors in incremental steps during a design basis accident load sequence. This document concluded that WBN DG maximum kW capability for motor starting in the site service environment (intake air temperature less than 115° F and elevation less than 800 feet) is:
Cold Engine (first 3 minutes of load sequence): 4785 kW Hot Engine (fully turbocharged):
5073 kW This document was reviewed and concurred by MKW Power Systems, Inc., the Appendix B qualified supplier of DG engine and DG generator for WBN, as delineated on page 1 of.
NRC Question:
- 2.
In Table 8.3-14 of FSAR Amendment 106, TVA listed the major electrical equipment that could become submerged following a loss-of-coolant accident (LOCA). The listed equipment is either automatically de-energized or is not required to function after a LOCA. In Sections 8A and 8B, TVA summarized the analysis of submerged (post-LOCA) electrical equipment powered from the auxiliary power system and from the instrumentation and control power system. The analysis concluded that submerged electrical equipment will not degrade the 6.9-kV or 480-V Class 1E instrumentation and control power systems. Identify the equipment and the related power source(s) and explain the consequences of gradual submergence of AC and DC powered equipment that is not qualified or not required post accident but may be energized and results in simultaneous high impedance faults on the electrical system.
TVA Response:
During a post LOCA and borated containment spray condition, some equipment inside the primary containment will be submerged or affected by the containment spray. This condition has the potential to produce multiple failures on the Class 1E 6.9 kV, 480 VAC, 120 VAC, and 125 VDC power systems. TVA evaluated the effect of this condition on the following power sources:
E-2
ENCLOSURE Response to Action Item 26 From Appendix HH of NUREG-0847, Supplement 22 (Note: TVA assumed that if the equipment was located below the flood level, it was energized and was therefore affected by submergence. Therefore, the consequences of gradual submergence of AC and DC powered equipment that was not qualified or not required post accident but may be energized and results in simultaneous high impedance faults on the electrical system was bounded in the TVA analysis. TVA analysis further assumes that the protective device feeding the submerged equipment was loaded to its trip setting which was conservative.)
120 VAC Vital Instrument Power Boards 2-I, 2-II, 2-III and 2-IV
125 VDC Vital Battery Boards III and IV
120 VAC Hydrogen Mitigation System Panels 2-DPL-268-1-A and 2-DPL-268-2-B
6.9 kV Shutdown Boards 2A-A and 2B-B
480 V Shutdown Boards 2A1-A, 2A2-A, 2B1-B and 2B2-B
480 V Reactor Vent Boards 2A-A and 2B-B
480 V Reactor MOV Boards 2A1-A, 2A2-A, 2B1-B and 2B2-B This evaluation was documented in the TVA submergence calculation for Unit 2 (Reference 2),
excerpt provided in Attachment 4. The equipment fed from each of the above power sources was identified in this evaluation. A determination was made if the equipment was going to be energized and if it was going to be submerged as a result of the event. The evaluation concluded the following:
The additional loading on the 120 VAC vital Class 1E power system due to the submerged equipment does not cause any secondary protective devices to trip nor does it overload the power supply (inverters).
The additional loading on the 125 VDC Class 1E power system due to the submerged equipment does not cause any secondary protective devices to trip nor does it adversely affect the battery sizing. The available voltage at the battery terminals is more than the minimum required voltage.
The loading on the 120 VAC Hydrogen Mitigation System Panels due to the submerged equipment does not cause any secondary protective devices to trip nor does it overload the transformer.
The additional loading on the 6.9 kV and 480 VAC Class 1E power system due to the submerged equipment does not cause any secondary protective devices to trip nor does it overload the power transformers.
There is no adverse affect on the Class 1E power systems due to containment spray on the shutdown and non safe shutdown components located inside the containment.
NRC Question:
- 3.
To demonstrate compliance with station blackout (SBO) rule, TVA performed a steady-state heat-up analyses in accordance with NUMARC 87-00 guidelines to determine the effects of loss of ventilation in main control room complex, turbine-driven auxiliary feedwater pump room, north and south main steam valve rooms, 125V vital battery rooms, 125 vital battery board rooms, cable spreading room, pipe chase, 480 V board rooms, and 6.9 kV and 480 V shutdown board room. From E-3
ENCLOSURE Response to Action Item 26 From Appendix HH of NUREG-0847, Supplement 22 E-4 these analyses, provide a detailed list of equipment that is subjected to temperature above the design temperature for normal operation and the results of assessment performed for the equipment to show its continued operability during an SBO event.
TVA Response:
Table A below provides normal operating temperature, maximum abnormal operating temperature and calculated SBO temperature that were calculated using the NUMARC 87-00 guidelines for each of the rooms listed in the RAI (Reference 3). TVA defines the maximum abnormal operating temperature as the environmental service conditions which result from outside temperature excursions. This condition can exist for up to 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> per excursion for non-reactor building spaces.
For the four rooms, North Main Steam valve room, South Main Steam valve room, Turbine-driven auxiliary feed pump room, and pipe chase, where the calculated SBO temperatures are higher than abnormal operating temperatures, a list of equipment in the rooms that are affected is provided. In addition, the associated assessment for each room is provided in the remarks column of the table.
References:
- 1. TVA Calculation EDQ00099920080014, Diesel Generator Loading Analysis
- 2. TVA Calculation EDQ00299920080020, Submergence Calculation - Unit 2
- 3. TVA Calculation EPM-MA-041592, Station Black-out Coping Evaluation
- 4. TVA Drawing Series 47E235, Environmental Data Drawing
- 5. TVA Calculation GENSTP3-001, Upper Boundary Temperature for Mild Environments Related to Environmental Qualification of Electrical Equipment
- 6. TVA Calculation EDN00299920110004, Material Aging Calculation for Auxiliary Feedwater Level Control Valves in the South Steam Valve Rooms (729-A01 & 729-A11) for Station Blackout (SBO) Conditions List of Attachments:
- 1. Excerpts from calculation EDQ00099920080014, Rev. 15
- 3. EDG Motor Starting Capability
- 4. Excerpt from Unit 2 Submergence Evaluation
ENCLOSURE Response to Action Item 26 From Appendix HH of NUREG-0847, Supplement 22 Table A - Response to RAI Item # 3 Effects of Loss of Ventilation during SBO Index Room Normal Operating Temperature
(°F)
Maximum Abnormal Operating Temperature
(°F)
Calculated SBO Temperature
(°F)
Equipment required to be operational during SBO condition.
Remark 1
Main Control Room Complex 80 104 104 Panels powered from one of the 8 Vital Inverter Boards and all electrical equipment in TSC is energized.
Main Control Room Complex temperatures are not above the abnormal operating temperatures as provided on Environmental Data Drawing 47E235-16 (Reference 4)
Reference 3, Appendix G, Page 63 2
Turbine Driven Auxiliary Feedwater Pump Room 104 110 127.7 TDAFWP Room Exhaust Fan DC Motor driven fan 2-FAN-030-0214 Note that the average temperature for the room is 116.4 °F and maximum temperature of 127.7°F at the end of four hours. Per TVA Calculation GENSTP3-001 (Reference 5),
motors in a mild environment are capable of operating for 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> at 140 °F.
Reference 3, Page 25 3
North Main Steam Valve Room 135 140 160.8 NONE There is no equipment in the North Main Steam Valve that is required to operate during SBO.
Reference 3, Page 25 South Main Steam Valve Room 140 140 177.9 TDAFWP LCVs 2-LCV-30-174-B &
2-LCV-30-175-A TVA Calculation EDN00299920110004 (Reference 6) was performed to evaluate accident degradation equivalency based on a steady state temperature of 200 °F for the four hour duration of the SBO event. The calculation concluded that the life of safety-related age-degradable materials in AFW LCVs in the South Main Steam Valve Room is not significantly impacted by operation for four hours at 200 °F during a SBO event.
Reference 3, Page 25 E-5
ENCLOSURE Response to Action Item 26 From Appendix HH of NUREG-0847, Supplement 22 Table A - Response to RAI Item # 3 Effects of Loss of Ventilation during SBO Index Room Normal Operating Temperature
(°F)
Maximum Abnormal Operating Temperature
(°F)
Calculated SBO Temperature
(°F)
Equipment required to be operational during SBO condition.
Remark 4
Vital 125 VDC Station Battery &
Battery Board Rooms (Rooms I, II, III, IV) 85 104 104 Battery, Battery Output Cable, Individual Battery Board, and Vital Instrument Panel.
The Station Battery & Battery Board Room temperatures are not above the maximum abnormal temperature as provided on Environmental Data Drawing 47E235-3. Also note that the battery rooms can withstand 120
°F for the period of 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.
Reference 3, Appendix G, Page 81 5
Cable Spreading Room 95 104 103 NONE Adjacent room temperatures are higher during normal operation but lower during SBO; therefore, the transmission load removes heat out of the room during a SBO condition Reference 3, Appendix G, Page 76 6
Pipe Chase 104 110 121.9 Containment Isolation Valve 2-FCV-62-63 The pipe chase temperature will gradually rise during an SBO. Hence, it is feasible that this valve could be manually closed, if necessary, by brief excursion into the pipe chase even if the temperature is about 122 °F. This would not be required unless core damage was imminent and core uncovery is not expected during the 4-hour SBO event.
Reference 3, Page 25 E-6
ENCLOSURE Response to Action Item 26 From Appendix HH of NUREG-0847, Supplement 22 E-7 Table A - Response to RAI Item # 3 Effects of Loss of Ventilation during SBO Index Room Normal Operating Temperature
(°F)
Maximum Abnormal Operating Temperature
(°F)
Calculated SBO Temperature
(°F)
Equipment required to be operational during SBO condition.
Remark 7
480 V Board Rooms 83 104 104 4 of the 6 Vital Inverters.
The 480V Board Room temperatures are not above maximum abnormal temperatures as provided on Environmental Data Drawing 47E235-3.
Reference 3, Appendix G, Page 69 & 70.
8 6.9 KV & 480 V Shutdown Board Rooms 87 104 104 Auxiliary compartments which contain meters and relays.
The 6.9 kV & 480V Shutdown Board Room temperatures are not above maximum abnormal temperatures as provided on Environmental Data Drawing 47E235-7.
Reference 3 Appendix G, Page 73
ENCLOSURE Response to Action Item 26 From Appendix HH of NUREG-0847, Supplement 22 Excerpts from calculation EDQ00099920080014, Rev. 16 E-8
ENCLOSURE Response to Action Item 26 From Appendix HH of NUREG-0847, Supplement 22 EDG Loading Tables depicting EDG loads with one unit in LOOP+LOCA and the second unit in LOOP E-23
ENCLOSURE Response to Action Item 26 From Appendix HH of NUREG-0847, Supplement 22 EDG Motor Starting Capability E-26
ENCLOSURE Response to Action Item 26 From Appendix HH of NUREG-0847, Supplement 22 Excerpt from Unit 2 Submergence Evaluation E-31