RS-09-159, Additional Information Supporting Request for License Amendment Regarding Application of Alternative Source Term
| ML093220838 | |
| Person / Time | |
|---|---|
| Site: | LaSalle  |
| Issue date: | 11/18/2009 |
| From: | Simpson P Exelon Generation Co, Exelon Nuclear |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| RS-09-159, TAC ME0068, TAC ME0069 | |
| Download: ML093220838 (8) | |
Text
Exelon (;cneratlon www.exeloncorp.com 4300 W~nfield Road Nuclear Warrer~vrlle, I1 60555 November 18,2009 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 LaSalle County Station, Units 1 and 2 Facility Operating License Mos. NPF-11 and NPF-18 NRC Docket Nos. 50-373 and 50-374
Subject:
Additional Information Supporting Request for License Amendment Regarding Application of Alternative Source Term
References:
- 1. Letter from P. R. Simpson (Exelon Generation Company, LLC) to U.S. NRC, "Additional lnformation Regarding Request for License Amendment Regarding Application of Alternative Source Term," dated October 23, 2008
- 2. Letter from C. S. Goodwin (U.S. NRC) to C. G. Pardee (Exelon Nuclear),
"LaSalle County Station, Units 1 and 2 - Request for Additional lnformation Related to Alternative Source Term License Amendment Request (TAC Nos.
ME0068 - ME0069)," dated October 19,2009 In Reference 1, Exelon Generation Company, LLC (EGC) requested an amendment to Facility Operating License Nos. NPF-11 and NPF-18 for LaSalle County Station (LSCS), Units 1 and 2, respectively. Specifically, the proposed change revises Technical Specifications (TS) to support the application of alternative source term (AST) methodology with respect to the loss-of-coolant accident and the fuel handling accident. The NRC requested additional information to complete review of the proposed license amendment in Reference 2. In response to this request, EGC is providing the attached information.
EGC has reviewed the information supporting a finding of no significant hazards consideration, and the environmental consideration, that were previously provided to the NRC in Attachment 1 of Reference 1. The additional information provided in this submittal does not affect the bases for concluding that the proposed license amendment does not involve a significant hazards consideration. In addition, the additional information provided in this submittal does not affect the bases for concluding that neither an environmental impact statement nor an environmental assessment needs to be prepared in connection with the proposed amendment.
November 18,2009 U.S. Nuclear Regulatory Commission Page 2 There are no regulatory commitments contained in this letter. Should you have any questions concerning this letter, please contact Mr. Kenneth M. Nicely at (630) 657-2803.
I declare under penalty of perjury that the foregoing is true and correct. Executed on the 1 8th day of November 2009.
Patrick R. Simpson U
Manager - Licensing
Attachment:
Response to Request for Additional Information cc:
NRC Regional Administrator, Region Ill NRC Senior Resident Inspector - LaSalle County Station Illinois Emergency Management Agency - Division of Nuclear Safety
AITACHMENT Response to Request for Additional Information NRC Request 1 Provide the loading sequence for each emergency diesel generator (EDG) at LSCS. In your response, describe the changes that have been made to the EDG loading sequence to support this license amendment request (LAR).
The standby alternating current (AC) power system consists of five emergency diesel generator (EDG) sets for both reactor units. The Division 1 EDG set is shared between Unit 1 and Unit 2 (i.e., swing diesel). Individual Division 2 EDG sets are provided for Unit 1 and Unit 2. lndividual Division 3 EDG sets are also provided, but are only designed for use to support the High Pressure Core Spray (HPCS) system. In the event of loss of all normal sources of power (i.e.,
onsite and offsite) to the Class 1 E power system, each EDG set is automatically started and loaded. The EDG automatic starting and loading proceeds as described in Section 8.3.1
.I.2 of the LaSalle County Station (LSCS) Updated Final Safety Analysis Report (UFSAR).
If a Division 1 or 2 EDG is automatically connected to its associated bus after the bus motor loads have been shed, the bus loads (i.e., if required) are sequentially started to prevent overloading the EDG. The Division 1 Reactor Heat Removal (RHR) system pump for the associated loss-of-coolant accident (LOCA) unit will load approximately five seconds after the Low Pressure Core Spray (LPCS) system pump loads to the bus. For Division 2, the "B" RHR pump will load approximately five seconds after the "C" RHR pump loads to the bus. Division 3 loads are not shed following a loss of bus voltage, nor are they sequenced following a restoration of bus voltage.
No changes to the EDG loading sequence are necessary to support the proposed license amendment request. With the exception of the 10 kW tank heater, which is discussed in the response to NRC Request 2, the Standby Liquid Control (SLC) system loads are not automatically reconnected to the Division 1 and 2 buses following a load shed and automatic start of the Division 1 and 2 EDGs.
NRC Request 2 Describe how the loads being added to the LSCS EDGs (if applicable) affect the capability and capacity of the EDGs (e.g., describe the impact of the proposed change on the EDG ratings).
UFSAR Table 8.3-1 identifies the equipment that is energized automatically or manually by the EDGs. The SLC system consists of the following equipment that is fed from engineered safety features (ESF) busses:
SLC lnjection Pump "A" (i.e., fed from ESF Division 1 bus),
SLC lnjection Pump "B" (i.e., fed from ESF Division 2 bus),
40 kW Mixing Tank Heater "B" (i.e., fed from ESF Division 2 bus), and 10 kW Tank Heater "A" (i.e., fed from ESF Division 1 bus).
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AlTACHMENT Response to Request for Additional Information Intermittent loads, such as motor-operated valves, are not included since these loads operate for only a very short time period.
The LSCS EDG steady state loading calculation only includes the "A" SLC tank heater (i.e., the 10 kW heater) in the EDG loading analysis since this load cycles automatically. This calculation does not include the SLC pumps and "B" SLC tank heater (i.e., the 40 kW heater) in the EDG loading analysis. UFSAR Table 8.3-1 indicates that the SLC pumps and 40 kW mixing heater are loads that are applied manually by the operator as required within the EDG rating. In addition, the 40 kW mixing heater is normally off. Thus, the SLC pumps and "B" SLC tank heater are not used for determining the total coincidental LOCA or shutdown load on the EDGs.
Since the SLC system is required to be operated to support the application of alternative source term (AST), additional loads will be added to the Division 1 and 2 EDGs. Since the "B" SLC tank heater is normally off, this load is not added to the EDGs. The SLC pumps are manually started from the main control room. Each SLC pump is rated at 40 horse power (HP), and the electrical loading of these pumps is 37.8 kW at 85% power factor. As indicated above, SLC pump "A" is fed from the ESF Division 1 bus, and SLC pump "B" is fed from the ESF Division 2 bus.
The EDGs have a continuous rating of 2600 kW, and a 2000-hour rating of 2860 kW. Running the SLC pumps will increase the total coincidental LOCA loading on the Division 1 and 2 EDGs as shown in the following table.
SLC Pump Load Addition (kW)
Revised EDG Loading (kW) 2636.9 2528.8 2635.5 2471.8 This table shows that the total loading on Division 2 EDGs remains within the EDG continuous rating with the SLC pumps running. The total loading on Division 1 EDGs slightly exceeds the EDG continuous rating by approximately 1.4 percent, but does not exceed the EDG 2000-hour rating. In addition, the period of time in which the SLC pumps are required to operate following a postulated design basis LOCA is relatively short, since the pumps will be turned off once the contents of the SLC tank have been injected. Therefore, the EDGs have sufficient capacity and capability to accommodate the increase in load.
NRC Request 3 Describe how the operators will be notified in the event that the standby liquid control (SLC) system would become inoperable (e.g., control room annuciators).
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ATTACHMENT Response to Request for Additional Information
Response
There are several indications available in the main control room to alert operators of SLC system problems. The indications are listed in the following table.
Page 3 Level SBLC Squib Continuity Loss SBLC Storage Tank Temperature H IILO SBLC Pump Auto Trip Low Level (4700 gallons)
Generated by a loss of continuity through the firing circuit High Temperature Setpoint (1 10 O F )
Low Temperature (70 OF)
Provides indication of pump trip on overload condition air pressure indicating controller.
Hiah Level: Available options are to evaporate level off with the tank heaters or remove liquid with the portable pump.
Level may also be lowered using an approved station procedure.
Low Level: Available options are to add waterlsodium pentaborate, or simply water, to the tank. Level may also be raised using an approved station procedure.
The squib valve continuity indicationlalarm function is provided by relays in the back panels. Current must be limited to 10 ma through the valve firing coil by series resistors. The nominal setpoint of 3 ma is to notify Operations personnel that a problem may exist. When current is less than the nominal setpoint, the squib valve continuity lamp will extinguish and the alarm will annunciate. If the current displayed is greater than or equal to 0.2 ma, then continuity is assured and the squib valve may be considered operable. The 0.2 ma operability setpoint was determined by the accuracy of the meter (i.e., 0.15 ma) and the minimum value readable on the gauge. The 0.2 ma is both readable and within the tolerances of the instrument.
Actions taken are to ensure the tank heaters are on if the temperature is low, and to turn them off if temperature is high.
The purpose of the heaters is to raise the tank water to 150 O F
for initial solution mixing to maintain the sodium pentaborate in solution, above its saturation temperature. If temperature is low, the sodium pentaborate will come out of solution. If it is high, evaporation will be accelerated and tank level lowered.
This will affect the ability of the sodium pentaborate to stay in solution. Either condition may indicate a temperature controller failure.
This alarm function is provided by an overload relay for the respective pump. The alarm provides an indication that the running pump has tripped and the other pump must be used instead.
Al-rACHMENT Response to Request for Additional Information NRC Request 4 Describe how the SLC system meets single failure criteria electrically.
Response
The SLC system is designed with an "A" system logic and "B" system logic. The "A" system is fed from ESF Division 1 AC electrical power, and the "B" system is fed from ESF Division 2 AC electrical power. The "A" system includes the "A" SLC pump, "A" SLC storage tank outlet valve, "A" system squib injection valve, and "A" system associated control logic. The "B" system includes the same redundant components. The SLC logic is designed to use either the "A" initiation logic or "B" initiation logic. The SLC system is manually initiated in the main control room.
When the "A" SLC system is initiated, the logic fires both the "A" and "B" squib valves and opens both the "A" and "B" SLC storage tank outlet valves. The "A" SLC pump starts when either the "A" or "B" SLC storage tank outlet valve is fully open. If the "A" SLC pump fails to start, the "B" initiating logic may be selected and the "B" SLC pump then starts with its own identical logic. Only one SLC pump is required for SLC system injection. The SLC storage tank outlet valves can also be opened by placing the valve control switch in the open position.
Thus, the electrical loads with redundant functions are powered from different divisions that are electrically independent. Since the pumps and valves are powered and controlled from separate buses and circuits, a single electrical failure will not prevent system operation. A failure of Division 1 power will disable the "A" system components, but will not prevent the "B" system components from operating. Likewise, a failure of Division 2 power will not prevent "A" system components from operating.
The SLC storage tank has a 10 kW electric heater fed from Division 1 that maintains the tank boron solution between about 75 and 85 degrees F, and a 40 kW mixing heater fed from Division 2 that is normally off. Operation of the tank heaters is not required during a design basis LOCA.
Based on the above, there is no credible single failure of an electric component that can prevent the SLC system from operating.
NRC Request 5 Provide a list and description of components being added to your 10 CFR 50.49 program due to this LAR (if applicable). Confirm that these components are qualified for the environmental conditions they are expected to be exposed to.
Response
No additional equipment or components are being added to the EQ program as a result of the proposed license amendment. The SLC system components are currently classified as augmented quality with special requirements, and as such, these components are treated as Page 4
AlTACHMENT Response to Request for Additional Information safety related for design, procurement, and maintenanceltesting to meet the requirements of 10 CFR 50, Appendix 0, "Quality Assurance Program," and General Design Criterion 4. The SLC system is not included in the environmental qualification program at LSCS. However, the SLC system components essential for ensuring successful injection of the sodium pentaborate into the reactor have been evaluated against the requirements for electrical equipment qualification (EQ) in 10 CFR 50.49, "Environmental qualification of electric equipment important to safety for nuclear power plants."
The SLC system electrical equipment required to operate post-LOCA in a harsh environment includes: two SLC pumps, two motor-operated pump suction valves, two squib valves, and the limit switch associated with the test tank outlet valve. The remaining components required for system operation are located in a mild environment or are not required to function post-LOCA.
The components required to operate post-LOCA in a harsh environment are located in the Reactor Building in EQ Zone H4E. During a LOCA, when the SLC system is required to operate, this zone is a mild environment with respect to changes in temperature, pressure, and humidity. Therefore, the only change in parameter of concern is radiation. Based on the AST dose evaluations, the change in radiation level during the time the SLC system is expected to operate is not significant to cause degradation of electrical equipment. The components essential for ensuring successful injection of the sodium pentaborate into the reactor are capable of performing the injection function when exposed to the expected environmental conditions based on the following.
The devices were originally procured, installed, and maintained as environmentally qualified to the requirements of 10 CFR 50.49. The components are currently classified as "augmented quality" and will continue to be treated as safety related and thus, will ensure that the environmental criteria are met.
Similar equipment types are currently qualified at LSCS as part of the EQ program, and the level of qualification bounds the environmental conditions of the required SLC components.
A review of original EQ documentation on the components shows that the components, with the exception of the explosive valves, were qualified for 40 years and 100 days post-LOCA conditions to the requirements of 10 CFR 50.49 and NUREG-0588 Category I requirements. The documentation did not require mandated EQ surveillance or maintenance to support the 40-year service life. Since there is no humidity change concurrent with the radiation, there is no credible failure mechanism to cause degradation of the explosive valves when they are required to actuate. Actuation of the explosive valves is expected to occur prior to the component being exposed to the increased radiation level.
A review of the maintenance history on these components shows that the components are still the original EQ qualified components.
The cable types servicing the essential SLC system components are environmentally qualified and the level of qualification bounds the environmental conditions for the cables Page 5
ATTACHMENT Response to Request for Additional Information supporting SLC system components. The associated motor control center is currently included in the EQ program.
Based on the above, the SLC system is capable of performing its injection function post-LOCA under the expected environmental conditions.
NRC Request 6 The licensee proposed utilizing the SLC system to buffer suppression pool pH to prevent iodine re-evolution during a postulated release. Describe the impact of the above proposed actions on environmental conditions (such as temperature, pressure) and any impact on equipment qualification.
Response
The impact on EQ is addressed above in response to NRC Request 5.
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