RS-10-037, Additional Information Supporting License Amendment Request for One-TIme Extension of the Essential Service Water Train Completion Time
| ML100610109 | |
| Person / Time | |
|---|---|
| Site: | Byron  |
| Issue date: | 03/01/2010 |
| From: | Simpson P Exelon Generation Co, Exelon Nuclear |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| RS-10-037 | |
| Download: ML100610109 (9) | |
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Exelon Nuclear 4300 Winfield Road Warrenville, l L 60555 RS-1 0-037 March 1,201 0 Nuclear 10 CFR 50.90 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Byron Station, Units 1 and 2 Facility Operating License Nos. NPF-37 and NPF-66 NRC Docket Nos. STN 50-454 and STN 50-455
Subject:
Additional Information Supporting License Amendment Request for a One-Time Extension of the Essential Service Water Train Completion Time
References:
- 1. Letter from P. R. Simpson (Exelon Generation Company, LLC) to U. S.
Nuclear Regulatory Commission, "License Amendment Request for a One-Time Extension of the Essential Service Water Train Completion Time,"
dated September 24, 2009
- 2. Letter from P. R. Simpson (Exelon Generation Company, LLC) to U. S.
Nuclear Regulatory Commission, "Clarification Regarding License Amendment Request for a One-Time Extension of the Essential Service Water Train Completion Time," dated November 13, 2009
- 3. Letter from M. J. David (U. S. Nuclear Regulatory Commission) to C. G. Pardee (Exelon Generation Company, LLC), "Byron Station, Unit Nos. 1 and 2 -
Request for Additional lnformation Related to One-Time Extension of Essential Service Water Train Completion Time (TAC Nos. ME2293 and ME2294),"
dated December 18,2009
- 4. Letter from P. R. Simpson (Exelon Generation Company, LLC) to U. S.
Nuclear Regulatory Commission, "Additional lnformation Supporting License Amendment Request for a One-Time Extension of the Essential Service Water Train Completion Time," dated January 19, 201 0
- 5. Letter from M. J. David (U. S. Nuclear Regulatory Commission) to C. G. Pardee (Exelon Generation Company, LLC), "Byron Station, Unit Nos. 1 and 2 -
Request for Additional lnformation Related to One-Time Extension of Essential Service Water Train Completion Time (TAC Nos. ME2293 and ME2294),"
dated February 19,201 0 In Reference 1, Exelon Generation Company, LLC, (EGC) requested a license amendment for Byron Station, Units 1 and 2, to revise Technical Specifications (TS) Limiting Condition for Operation (LCO) 3.7.8, "Essential Service Water (SX) System," to extend the Completion Time
March 1,201 0 U. S. Nuclear Regulatory Commission Page 2 (CT) from 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> to 144 hours0.00167 days <br />0.04 hours <br />2.380952e-4 weeks <br />5.4792e-5 months <br />. This proposed change will only be used one time during the Byron Station Unit 2 spring 201 0 refueling outage (i.e., B2R15) to restore a unit-specific SX train to operable status. In Reference 2, EGC supplemented the request to provide clarification regarding the inventory control function.
In Reference 3, the NRC requested that EGC provide additional information in support of their review of Reference 1 as supplemented by Reference 2. Reference 4 provided the requested information.
In Reference 5, the NRC requested that EGC provide additional information in support of their review of Reference 1 as supplemented by References 2 and 4. Attachments 1 and 2 of this submittal provide the requested information.
EGC has reviewed the information supporting a finding of no significant hazards consideration that was previously provided to the NRC in Reference 1 as supplemented by References 2 and 4.
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 accordance with 10 CFR 50.91, "Notice for public comment; State consultation," paragraph (b),
a copy of this letter and its non-proprietary attachments are being provided to the designated State of Illinois official.
The regulatory commitments contained in this letter are summarized in Attachment 2. The regulatory commitments provided in Attachment 2 are in addition to the commitments previously provided to the NRC in References 1 and 4.
Should you have any questions concerning this letter, please contact Ms. Lisa A. Schofield at (630) 657-281 5.
I declare under penalty of perjury that the foregoing is true and correct. Executed on the 1st day of March 201 0.
Respectfully, Patrick R. Simpson Manager - Licensing Exelon Generation Company, LLC Attachments: 1. Additional Information Supporting License Amendment Request for a One-Time Extension of the Essential Service Water Train Completion Time
- 2. Summary of Regulatory Commitments
March 1,201 0 U. S. Nuclear Regulatory Commission Page 3 cc:
NRC Regional Administrator, Region Ill NRC Senior Resident Inspector, Byron Station NRR Project Manager, Byron Station Illinois Emergency Management Agency - Division of Nuclear Safety
AlTACHMENT 1 Additional Information Supporting License Amendment Request for a One-Time Extension of the Essential Service Water Train Completion Time In a letter dated February 19, 2010, the NRC requested that Exelon Generation Company, LLC, (EGC) provide additional information related to the application for a one-time extension of the essential service water train Completion Time (CT). Attachments 1 and 2 provide the requested information.
Question 1:
Backqround:
Section 2.3.2.1 of Attachment 5, "Risk Informed Evaluation," of the September 24, 2009, LAR states that risk significant plant equipment outage configurations were evaluated. This resulted in a list of protected equipment that will not be allowed to be unavailable for maintenance during the extended CT.
Regulatory Guide (RG) 1.I 77, "An Approach for Plant-Specific, Risk-Informed Decisionmaking:
Technical Specifications," August 1998, describes a four element approach to integrated decisionmaking for TS changes. One of the engineering considerations in the four element approach is defense in depth. As discussed in Section 2.2.1 of the RG, one aspect of maintaining defense in depth is:
System redundancy, independence, and diversity are maintained commensurate with the expected frequency and consequences of challenges to the system, e.g., there are no risk outliers. The following items should be considered.
Whether there are appropriate restrictions in place to preclude simultaneous equipment outages that would erode the principles of redundancy and diversity, Whether compensatory actions to be taken when entering the modified AOT [allowed outage time] for preplanned maintenance are identified,...
Issue:
During the extended CT, the 1 B SX pump is the only operating SX pump for the operating unit (Unit 1). The NRC staff acknowledges that the 1A and 1 B SX trains are cross-connected through 1 SX033 and 1 SX034. Although the 1 A and 1 B SX trains are cross-connected, the NRC staff is not certain of the licensee's position as to whether the components cooled in the 1A SX train are OPERABLE for satisfying TSs.
- a. If the licensee evaluates that the components cooled by the 1A SX train are OPERABLE for purposes of satisfying TSs when the SX supply is from the 1 B SX pump, then explain the justification for designating those components OPERABLE.
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ATTACHMENT 1 Additional Information Supporting License Amendment Request for a One-Time Extension of the Essential Service Water Train Completion Time
- b. If the components cooled by the 1A SX train are not OPERABLE for purposes of satisfying TSs, then explain why the components cooled by the 1 B SX train are not on the protected equipment list (Table 14 in Attachment 5 of the LAR) during the extended CT in accordance with the guidance in RG 1.1 77 as explained in the Back~round, above. As a minimum, the components to consider are the 1 B and 1 D reactor containment fan cooler (RCFC) coils, 1 B containment chiller, 1 B charging pump, 1 B safety injection pump, 1 B containment spray pump, and 1 B residual heat removal pump (either because of their oil cooler and/or cubicle cooler), the 1 B control room and 1 B containment refrigeration units. The NRC staff notes that if some components in the 1A train are not OPERABLE, then any action or event that makes the redundant component from the 1 B train not OPERABLE could cause Unit 1 to enter Limiting Condition for Operation 3.0.3.
Response to Question I.a:
The current Technical Specifications (TS) Limiting Condition for Operation (LCO) 3.7.8, "Essential Service Water (SX) System," requires, in part, that two unit-specific SX trains (i.e., the "A" and "B" trains) be operable in Modes 1, 2, 3, and 4. Condition A requires that if one unit-specific SX train is inoperable, it must be restored to an operable status within a specified Completion Time (CT). An extension of the existing CT is needed to replace two of the four SX pump suction isolation valves (i.e., Il2SX001A) used for pump isolation from the SX water supply. In order to replace these suction isolation valves, the common upstream suction line for the 1A and 2A SX pumps must be isolated and the suction header drained. Due to the SX system configuration, closing the common suction isolation valve causes the 1A and 2A SX pumps to be inoperable. Inoperability of the 1A SX pump will result in the operating unit entering LC0 3.7.8, Condition A.
The Byron Station TS define OPERABLE-OPERABILITY in Section 1.I, "Definitions," as follows:
A system, subsystem, train, component, or device shall be OPERABLE or have OPERABILITY when it is capable of performing its specified safety function(s) and when all necessary attendant instrumentation, controls, normal or emergency electrical power, cooling and seal water, lubrication, and other auxiliary equipment that are required for the system, subsystem, train, component, or device to perform its specified safety function(s) are also capable of performing their related support function(s).
The SX system includes provisions to crosstie the trains (i.e., train crosstie) using the 1 SX033 and 1 SX034 valves. The system is normally aligned with the train crosstie valves open. EGC has evaluated the crosstied SX train configuration and concluded that a single SX pump is capable of providing adequate cooling water to both trains of SX loads under normal and accident conditions. In addition, a single failure when in LC0 3.7.8, Condition A, need not be postulated for this configuration. This is consistent with the NRC's position as documented in NRC Generic Letter (GL) 80-30, "Clarification Of The Term 'Operable' As It Applies To Single Page 2 of 5
ATTACHMENT 1 Additional Information Supporting License Amendment Request for a One-Time Extension of the Essential Service Water Train Completion Time Failure Criterion For Safety Systems Required By TS," dated April 10, 1980. The GL states that the specified time to take action when an LC0 is not met is a temporary relaxation of the single failure criterion since the CT provides a limited time to fix equipment or otherwise make it operable.
Therefore, the 1 B SX pump is capable of supplying the requisite cooling water via the SX train crosstie valves (i.e., 1 SX03311 SX034) to the "A" train components normally supported (i.e., cooled) by the 1A SX pump. As such, the "A" train components are operable since they would be capable of performing their specified safety function while in the aforementioned configuration.
Response to Question I.b:
As described in the response to Question I
.a above, during the evolution to replace two of the four SX pump suction isolation valves (i.e., ll2SX001A) during the Byron Station Unit 2 spring 2010 refueling outage (i.e., B2R15), the components supported by the 1A SX train are operable via the 1 B SX pump. Even though the 1A SX train supported components will remain operable, EGG voluntarily agrees to protect the following components during the extended CT:
1 B component cooling pump, 1 B and 1 D reactor containment fan cooler (RCFC) coils, 1 B charging pump, 1 B safety injection pump, 1 B containment spray pump, 1 B residual heat removal pump, and OB control room refrigeration unit.
The above protected components are in addition to compensatory measures listed in Attachment 1 of letter RS-09-121, Table 3, "Byron SX A Train Outage Summary of Compensatory Measures."
The 1 B containment chiller and 1 B containment refrigeration units referenced by the NRC in Question 1.b are not listed above because they are non-safety related and automatically bypassed in response to a design basis accident. The two trains of the control room refrigeration system are common to both units and are designated the OA and OB trains.
Reference Summary of Regulatory Commitments in Attachment 2.
Question 2:
Issue:
The licensee's response in Section 2.1.8 of the January 19, 2010, supplement states, "The initial premise of the statement in question 8 assumes that a loss of the remaining SX pump on the operating unit leads to a loss of SX for that unit."
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ATTACHMENT 1 Additional Information Supporting License Amendment Request for a One-Time Extension of the Essential Service Water Train Completion Time NRC staff response: The premise of question 8 does not assume that a loss of the remaining SX pump on the operating unit leads to a loss of SX for that unit. The question clearly refers to a loss of SX flow to all RCFCs in the operating unit not to a loss of all SX. The premise of the question assumes that the unit cross connects are open because the licensee has stated that a best estimate flow analysis shows that one SX pump can provide cooling to both units with the exception of the RCFCs and emergency diesel generators on the unit without an SX pump and one train of RCFCs on the unit with an available SX pump.
The supplement also stated, "Containment spray for Byron provides pressure reduction but does not provide a containment heat removal function." The supplement further states, "The only available means of removing heat from containment post LOCA are the RCFCs and the Residual Heat Removal System."
NRC staff response: The updated final safety analysis report (UFSAR) states the following:
6.2.2 Containment Heat Removal System The containment heat removal system consists of the reactor containment fan cooler system and the containment spray system.
The UFSAR states the following on page 6.2-1 0:
Another containment heat removal system is the containment spray. During the injection phase of operation, the containment spray pumps draw water from the refueling water storage tank and spray it into the containment through nozzles mounted high above the operating deck. As the spray droplets fall, they absorb heat from the containment atmosphere. Since the water comes from the refueling water storage tank, the entire heat capacity of the spray from the refueling water storage tank temperature to the temperature of the containment atmosphere is available for energy absorption.
The licensee is requested to revise their response considering that containment spray does remove some heat from the containment atmosphere.
Response to Question 2:
For clarification, the response to Question 8.b provided in the submittal dated January 19, 201 0, was from a risk perspective. Specifically, the Byron PRA does not credit heat removal from the containment using the containment spray pumps and the containment spray. Where the early operation of containment sprays is able to reduce the peak pressure and temperature following a design basis LOCA, long term heat removal as identified in the PRA requires a heat removal path out of containment. The initial cooling provided by the sprays is simply sensible heat transfer due to the colder RWST water being injected; however, this does not provide a long term heat removal path. Therefore, the Byron Level 1 PRA does not take any credit for the initial heat removal from the containment atmosphere. Given that the current Byron Level 2 Page 4 of 5
ATTACHMENT 1 Additional Information Supporting License Amendment Request for a One-Time Extension of the Essential Service Water Train Completion Time PRA is focused on calculating the large early releases, the operation of containment sprays has no impact on that analysis. Byron uses a simplified LERF model based on NUREGICR-6595, "An Approach for Estimating the Frequencies of Various Containment Failure Modes and Bypass Events," dated January 1999.
As stated above in the response to Question 1.b, EGC voluntarily agrees to protect the 1 B containment spray pump. In addition, if the 1 B SX pump were to be lost during the extended CT, Byron Unit 1 would be required to shut down in accordance with various TS (e.g., TS 3.7.8, TS 3.5.2).
Reference Summary of Regulatory Commitments in Attachment 2.
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ATTACHMENT 2 Summary of Regulatory Commitments Page 1 of 1 The following table identifies commitments made in this document. (Any other actions discussed in the submittal represent intended or planned actions. They are described to the NRC for the NRC's information and are not regulatory commitments.)
COMMITMENT TYPE COMMITMENT COMMITTED DATE OR "OUTAGE" ONE-TIME ACTION (Yes/No)
PROGRAMMATIC ACTION (Yes/No)
During the evolution to replace two of the four SX pump suction isolation valves (i.e., 1/2SX001A) during the Byron Station Unit 2 spring 2010 refueling outage (i.e., B2R15), EGC voluntarily agrees to protect the following components:
1B component cooling
- pump, 1B and 1D reactor containment fan cooler (RCFC) coils, 1B charging pump, 1B safety injection pump, 1B containment spray pump, 1B residual heat removal pump, and 0B control room refrigeration unit.
The above protected components are in addition to compensatory measures listed in Attachment 1 of letter RS-09-121, Table 3, "Byron SX A Train Outage Summary of Compensatory Measures."
Upon implementation of the one-time extension of the SX train Completion Time.
Yes No