L-HU-07-009, Supplement to License Amendment Request (LAR) for Extension of Technical Specification (TS) 3.8.1, AC Sources-Operating, Emergency Diesel Generator Completion Time

Supplement to License Amendment Request (LAR) for Extension of Technical Specification (TS) 3.8.1, AC Sources-Operating, Emergency Diesel Generator Completion Time

ML070750177
Person / Time
Site:	Prairie Island
Issue date:	03/15/2007
From:	Weinkam E Nuclear Management Co
To:	Document Control Desk, NRC/NRR/ADRO
References
L-HU-07-009, TAC MC9001, TAC MC9002
Download: ML070750177 (8)

Text

Commrffedto Nucfear Nuclear Management Company, LLC L-HU-07-009 10 CFR 50.90 March 15,2007 U S Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Prairie Island Nuclear Generating Plant Units 1 and 2 Dockets 50-282 and 50-306 License Nos. DPR-42 and DPR-60 Supplement to License Amendment Request (LAR) For Extension Of Technical Specification (TS) 3.8.1, "AC Sources-Operating," Emergencv Diesel Generator Completion Time (TAC Nos. MC9001 and MC9002)

By letter dated November 21,2005, Nuclear Management Company (NMC) submitted an LAR to revise the Emergency Diesel Generator (EDG) Completion Time in TS 3.8.1 Required Action B.4 from 7 days to 14 days. By letters dated June 16, 2006, August 31,2006, September 29, 2006 and October 30, 2006, NMC provided supplemental information to this LAR. Enclosure 1 of this supplement provides information which the NRC Staff has requested. NMC submits this supplement in accordance with the provisions of 10 CFR 50.90.

The supplemental information provided in this letter does not impact the conclusions of the Determination of No Significant Hazards Consideration and Environmental Assessment presented in the November 21,2005 submittal as supplemented June 16, 2006, August 31,2006, September 29,2006 and October 30,2006.

In accordance with 10 CFR 50.91, NMC is notifying the State of Minnesota of this LAR by transmitting a copy of this letter and enclosure to the designated State Official.

Summary of Commitments This letter contains no new commitments and no revisions to existing commitments.

I declare under penalty of perjury that the foregoing is true and correct.

Executed on March 15,2007.

4!i!

nka ar Licensing & Regulatory Services Nuclear Management Company, LLC 700 First Street Hudson, Wisconsin 54016 Telephone: 715-377-3300

Document Control Desk Page 2 Enclosures (1) cc: Administrator, Region Ill, USNRC Project Manager, Prairie Island, USNRC Resident Inspector, Prairie Island, USNRC State of Minnesota

Enclosure 1 Letter L-PI-06-093 Train Transferable Loads In a meeting with the NRC Staff on September 21,2006, the Nuclear Management Company, LLC (NMC) staff provided information on loss of offsite power (LOOP) loads associated with each safeguards bus in each unit and the station blackout (SBO) loads associated with each safeguards bus in each unit. The NRC Staff requested further clarification of loads which the NMC staff identified as "transferable" loads.

NMC response:

Following a LOOP or SBO, an EDG is required to supply its associated safeguards bus "Bus Specific" loads and its associated "EDG Support" loads, and may be required to supply some or all of the "Transferable" loads associated with its electrical train. In addition, one of the Unit 2 EDGs may supply power to the motor-driven safeguards cooling water pump. To provide clarification of the Transferable loads, each of these types of loads will be discussed.

Bus Specific Loads Each safeguards bus has loads which can only be supplied by that bus and are expected to be operable during a LOOP or SBO. For purposes of this Enclosure, these loads will be identified as "Bus Specific" loads and are shown in Table 1.

Table 1 Safeguards Bus Specific Loads (LOOP)

Train A Train B Bus 15 Bus 25 Bus 16 Bus 26 EQUIPMENT DESCRIPTION Load Load Load Load (kW) ( kW) (kW) (kW)

Auxiliary Feedwater (AFW) Pump 0 234 234 0 Component Cooling Water (CC) Pump 199 199 199 199 Battery Charger 39.15 39.15 39.15 39.15 Charging Pump(s) 91.39 99.16 190.98 198.32 EDG* Supply and Return Fans (Unit 2 only) NA 76.4 NA 76.4 Boric Acid Transfer Pump 11.47 11.47 11.47 11.47 Containment Recirculation Fans 24.74 22.4 24.74 22.4 Containment Fan Coil Units (1 fast, 1 slow) 74.44 74.44 74.44 74.44 Reactor Vessel Support Cooling Fan 19.12 21.67 19.12 21.67 Page 1 of 6

Enclosure 1 L-PI-06-093 Train A Train B Bus 15 Bus 25 Bus 16 Bus 26 EQUIPMENT DESCRIPTION Load Load Load Load (kW) ( kW) (kW) (kW)

Pressurizer Heaters 192 192 192 192 Air Compressor (Unit 1 only) 79.17 NA 79.17 NA Waste Gas Compressor (Unit 1 only) 19.12 NA 19.12 NA Equipment & Room Coolers and Fans 22.2 9.49 22.41 9.59 Inverters (3) 18.78 18.78 18.78 18.78 Boric Acid Tank Heater(s) 15 7.5 15 7.5 Miscellaneous Equipment 5.83 5.45 8.47 10.63 Estimated Transformer Loss (2% of 480 V Load)** 22 26 24 27 Estimated Cable Loss (3% of 4160 & 4 8 0 V Load)** 1 39 1 75 1 49 1 71 1 Total Bus Specific Load 1 872.4 1 1111.9 11220.9 1 979.4 1

• Emergency Diesel Generator

• • Includes calculated losses for "EDG Support" and "Transferable" shared loads EDG Support Loads Each safeguards bus also supplies "EDG Support" loads if the EDG associated with that bus is operating. For the Unit 1 EDGs, these loads are small and include equipment such as EDG room supply and exhaust fans, EDG startup air compressor and the fuel oil storage pump. For the Unit 2 EDGs, these loads are larger and include equipment such as the EDG room cooling fan, fuel oil transfer pumps, backup fuel oil pumps and radiator fans.

Transferable Loads In addition to the Bus Specific loads and EDG Support loads, each EDG may carry, depending on the load alignment at the time of a LOOP or SBO event, some or all of the shared "Transferable" loads. Transferable loads are train specific loads shared between the two units and may be aligned to either unit. These loads are shown in Table 2.

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Table 2 Transferable Loads Train A Train B EQUIPMENT DESCRIPTION (kw) (kW)

Boric Acid Heat Tracing 120 105 121 [I 22]* Auxiliary Building Special Vent Exhaust fan & filter 41.67 41.67 121 [I221 Control Room Water Chiller & Auxiliary Equipment 173.41 173.41 12 [22] Cooling Water Pump Jacket Heaters (2) 12 12 12 [22] Cooling Water Pump Air Start Compressor 12.75 12.75 121 [I221 Spent Fuel Pool cooling pump 55.95 55.95 Lighting Transformer Panel 1RPA8 [I RPB81 10.08 9.81 11[22] roof exhaust fan 8.60 8.73 Miscellaneous loads (individual loads less than 5 kW) 11.46 10.3 Total Transferable Load 445.9 429.6

• Train B equipment designation shown in square brackets, "[I".

121 Motor-Driven Safeguards Cooling Water Pump In addition to the loads identified above, one of the Unit 2 EDGs may supply power to the 121 motor-driven safeguards cooling water (CL) pump which is transferable between trains on Unit 2. This is a unique load of approximately 783 kW which can only be supplied by one of the Unit 2 EDGs, D5 or D6, depending on the bus alignment to supply this CL pump prior to the event. Because the plant has two diesel-driven safeguards CL pumps, the 121 CL pump is not required to operate during a LOOP or SBO. The Unit 2 EDGs are sized to accommodate this additional load. Due to the plant design, the smaller Unit 1 EDGs will procedurally not be aligned to this load.

Total LOOP Load Table 3 summarizes the loads discussed above showing the Unit, train, EDG and safeguards bus to which the load is associated. These loads have been summed to show the possible "Total LOOP load" on each EDG. Loads for which some or the entire load may be supplied by two EDGs are shown in a single cell under two columns; these loads have been added to both EDGs which may supply the load.

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Table 3 Load Summary Train A Train B Unit Unit 1 Unit 2 Unit 2 Unit 1 EDG Dl D5 D6 D2 Bus Bus 15 Bus 25 Bus 26 Bus16 (kW) (kW) (kW) (kW)

Bus Specific loads 872.4 1111.9 979.4 1220.9 EDG Support loads 51.4 261.3 261.3 51 Transferable loads 445.9 429.6 121 CL pump load NA 783 NA Total LOOP load 1370 2602 2453 1702 The Total LOOP loads on each EDG are the design basis loads which bound the largest load that each EDG will be required to supply due to this event. The Total LOOP loads include the Bus Specific loads, EDG Support loads, all Transferable loads, and (for D5 and D6 only) the 121 CL pump load. Although the Transferable loads are included on each bus in determining the bounding EDG loads, there is physically only one set of these loads in the plant for each train: one set powered by either D l or D5 and the other by either D2 or D6. Since the Transferable loads (and therefore the Total LOOP loads) do not exist on both units at the same time, it would not be possible for a single diesel to be loaded with the calculated LOOP load for both units.

To obtain the total potential SBO load for each diesel, the following loads are NOT included:

1. The opposite unit EDG Support loads since the diesel is not operating (SBO condition) and therefore this equipment is not operating, and

2. The Transferable loads since there is physically only one set of these loads and they have been accounted for in the Total LOOP load for the operating EDG.

Thus to determine the total SBO loading for an EDG, the opposite unit's Bus Specific loads (with some minor corrections for transformer and cable losses) are added to the EDG's Total LOOP load.

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Enclosure 1 L-PI-06-093 Maximum Instantaneous EDG Loads In a meeting with the NRC Staff on September 21,2006, the NMC staff provided information on EDG LOOP and SBO loading. NMC demonstrated that the maximum steady state load on Unit I EDG D2 is 2624 kW (USAR Page 8.4-12) if Unit 1 is experiencing a LOOP and Unit 2 is experiencing an SBO. The Unit 1 EDGs have a continuous rating of 2750 kW, a I000 hour (over 40 days) rating of 3000 kW; and a 30 minute rating of 3250 kW. The NRC staff requested confirmation that instantaneous loading on D2 remains within its rating at all times as the Unit 2 SBO loads are loaded onto D2.

NMC response:

The original plant design included only D l and D2 to provide emergency AC power supplies for both PINGP units. The design criteria for these EDGs was a site LOOP with a loss of coolant accident in one unit (with safety injection) and safe shut down of the other unit. For this event, transient analyses demonstrated that each diesel was capable of starting all automatically sequenced loads for both units in less than one minute. As demonstrated in FSAR Table 8.4-3, D l can successfully be loaded to 2785 kW in seven sequencer steps in less than one minute (the Table notes that this capability applies to both D l and D2). The original design criteria event is more challenging than a Unit 1 LOOP combined with a Unit 2 SBO which will automatically load only 1701 kW of Unit 1 loads on D2; the major Unit 2 loads are manually loaded over a period of time following recognition of the SBO condition.

A transient analysis has not been performed for D l and D2 in the Unit 1 LOOP with Unit 2 SBO event. The two larger diesels were added to power Unit 2 emergency loads which resulted in redefinition of the design basis event and this event is less challenging than the original design criteria event. To illustrate the transient load effect of connecting large Unit 2 loads following automatic loading of a Unit IEDG, data provided in the original FSAR is used to approximate these conditions. FSAR Table 8.4-1 shows that the first three sequencer steps load D l or D2 with 1857 kW which is larger than the D2 LOOP load of 1702 kW. The largest single load on Bus 26 that would be added following recognition of the SBO is the CC pump which is 199 kW (250 horsepower). FSAR Table 8.4-3 shows that the addition of a 300 horsepower AFW pump load and 50 horsepower containment fans in step 4, which would approximate the addition of a CC pump after D2 is loaded to 1701 kW, dips the EDG generator terminal voltage to 86% and recovers within 0.5 seconds. Subsequent sequencer steps 5 through 7 add 207 kW, 192 kW and 155 kW respectively with less voltage dip and equal or less recovery time. Other than the CC pump, the largest SBO loads on Bus 26 are the pressurizer heaters ( I 92 kW), containment fan coil units (74.44 kW) and charging pumps (99.16 kW each). Thus the Unit 1 EDGs have been demonstrated to be capable of accepting loads comparable to or larger than the largest Unit 2 SBO loads.

When the SBO event LOOP occurs, the safeguards loads on both units will all stop when their buses are de-energized. On the non-SBO unit, major loads and the 480V load group which are on the sequencer will start in their normal sequence order.

Page 5 of 6 L-PI-06-093 On the SBO unit, the operators will use the unit-specific emergency operating procedures or the abnormal operating procedures to cross-tie the one running EDG to the same train safeguard bus of the SBO unit. These procedures place all major motor loads in pullout to disable automatic starting on the EDG. After the opposite unit EDG restores power to the SBO unit safeguards bus, the procedure directs addition of loads as dictated by operating conditions and EDG loading limits. This scenario is the same as any other manual loading change that may be planned while a safeguards bus is supplied by an EDG. Load changes are evaluated prior to changing EDG loading as required by procedure.

Large margin exists between the calculated loads and the EDG ratings. The Unit 1, Train B EDG, D2, is the diesel with the maximum calculated load with the least margin to its rating. The calculated SBO load for D2 is 2624 kW which is 19% below the 30 minute rating (3250 kW), 12.5% below the I000 hour rating (3000 kW) and 4.5% below the continuous rating (2750 kW). The emergency and abnormal operating procedures contain caution notes which require the operators to evaluate loads prior to changing EDG loading and the operators are trained to use these procedures and apply the cautionary notes.

Furthermore, it is likely that the EDG would be loaded at a lower level than the maximum calculated because the calculation contains multiple significant conservatisms. Examples of these are:

1) The calculation assumes use of the motor driven AFW pump rather than the turbine driven AFW pump which is normally used. This provides 234 kW of margin.

2) The actual operating load of components following the trip is much less than the rated load assumed in the calculation. For example, the battery chargers have approximately 30 kW margin, the boric acid heat trace includes approximately 50 kW margin and the pressurizer heaters include approximately 90 kW of margin.

3) Load diversity is not credited in the calculation; that is, intermittent loads such as valves, fans, heaters and pumps are not actually all on at the same time.

4) Train B loading assumes use of two charging pumps per unit (four total) because that is conservative and it is normal operating practice to operate two charging pumps per unit to minimize mechanical load on the pump for long term pump maintenance benefit. However, the LOOP and SBO recovery procedures direct operators to start only one charging pump. Long term, a second charging pump may be started on the non-SBO unit; but it is unlikely the second pump would be re-started on the SBO unit while powered from the EDG. This may provide 90 kW of margin in the Train B calculations (which is the train with the highest SBO loads)

NMC concludes, based on this evaluation, that the D2 EDG will not exceed its load ratings following a Unit 1 loss of offsite power with a Unit 2 station blackout.

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