ML110310612: Difference between revisions

From kanterella
Jump to navigation Jump to search
(Created page by program invented by StriderTol)
(Created page by program invented by StriderTol)
Line 1: Line 1:
{{Adams
#REDIRECT [[RS-11-010, Byron Station, Units 1 and 2, Response to Request for Additional Information Related to License Amendment Regarding Ultimate Heat Sink]]
| number = ML110310612
| issue date = 01/31/2011
| title = Byron Station, Units 1 and 2, Response to Request for Additional Information Related to License Amendment Regarding Ultimate Heat Sink
| author name = Hansen J L
| author affiliation = Exelon Generation Co, LLC, Exelon Nuclear
| addressee name =
| addressee affiliation = NRC/Document Control Desk, NRC/NRR
| docket = 05000454, 05000455
| license number = NPF-037, NPF-066
| contact person =
| case reference number = RS-11-010, TAC ME1669, TAC ME1670
| document type = Letter
| page count = 6
| project = TAC:ME1669, TAC:ME1670
| stage = Response to RAI
}}
 
=Text=
{{#Wiki_filter:Exelon Generation 4300 Winfield Road Warrenville, IL 60555 RS-11-010 January 31, 2011 www.exeloncorp.com U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-001 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 Nuclear 10 CFR 50.90
 
==Subject:==
Response to Request for Additional Information Related to License Amendment Regarding Ultimate Heat Sink  
 
==References:==
: 1. Letter from P. R. Simpson (Exelon Generation Company, LLC) to u. S. Nuclear Regulatory Commission, "License Amendment Regarding Ultimate Heat Sink," dated June 30,2009 2. Letter from P. R. Simpson (Exelon Generation Company, LLC) to u. S. Nuclear Regulatory Commission, "Additional Information Supporting Request for License Amendment Regarding Ultimate Heat Sink, II dated January 25, 2010 3. Letter from J. L. Hansen (Exelon Generation Company, LLC) to u. S. Nuclear Regulatory Commission, "Additional'nformation Supporting Request for License Amendment Regarding Ultimate Heat Sink,1I dated July 1,2010 4. Letter from J. L. Hansen (Exelon Generation Company, LLC) to u. S. Nuclear Regulatory Commission, "Additional Information Supporting Request for License Amendment Regarding Ultimate Heat Sink," dated November 8, 2010 5. Letter from N. J. DiFrancesco (U. S. Nuclear Regulatory Commission) to M. J. Pacilio (Exelon Generation Company, LLC), "Byron Station, Unit Nos. 1 and 2 -Request For Additional Information Related to License Amendment Regarding Ultimate Heat Sink (TAC Nos. ME1669 and ME1670)," dated December 28, 2010 In Reference 1, Exelon Generation Company, LLC, (EGC) requested a license amendment for Byron Station, Units 1 and 2, to revise Technical Specifications (TS) to add additional essential service water (SX) cooling tower fan requirements as a function of SX pump discharge temperature to reflect results of a revised analysis for the ultimate heat sink (UHS). EGC supplemented Reference 1 by letters dated January 25, July 1, and November 8,2010 (References 2, 3, and 4). 
 
January 31, 2011 U. S. Nuclear Regulatory Commission Page 2 In Reference 5, the NRC requested that EGC provide additional information in support of its review of Reference
: 1. Attachment 1 provides the requested information, with the exception of Question 1.a of Reference
: 5. As discussed with the NRC on January 27,2011, a separate submittal will be required to provide additional information based on a conference call held on January 20, 2011, between the NRC and EGC. This separate submittal will include a revision to TS 3.7.9 and the revised markup of the TS 83.7.9 8ases. 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.
In accordance with 10 CFR 50.91, IINotice for public comment; State consultation," paragraph (b), a copy of this letter and its attachments are being provided to the designated State of Illinois official.
There are no regulatory commitments contained in this letter. Should you have any questions concerning this letter, please contact Ms. Lisa A. Schofield at (630) 657-2815.
I declare under penalty of perjury that the foregoing is true and correct. Executed on the 31 st day of January 2011 . nsen Manag -Licensing Exelon Generation Company, LLC
 
==Attachment:==
 
Response to Request for Additional Information cc: NRC Regional Administrator, Region III NRC Senior Resident Inspector, 8yron Station NRC Project Manager, NRR -8yron Station Illinois Emergency Management Agency -Division of Nuclear Safety ATTACHMENT Response to Request for Additional Information By letter to the Nuclear Regulatory Commission (NRC) dated June 30, 2009, Exelon Generation Company, LLC, (EGC) requested a license amendment for Byron Station, Units 1 and 2, to revise Technical Specifications (TS) to add additional essential service water (SX) cooling tower fan requirements as a function of SX pump discharge temperature to reflect results of a revised analysis for the ultimate heat sink (UHS). EGC supplemented this request by letters dated January 25, July 1, and November 8,2010. In a letter dated December 28, 2010, the NRC requested that EGC provide additional information related to the June 30, 2009, request. NRC Question 1: The EGC request dated June 30,2009, provided revised TS 3.7.9, IIUltimate Heat Sink," and the revised TS B3.7.9 Bases for a cross tied SX system. The letter dated November 8,2010, includes new proposed TS 3.7.9 for split SX system, but did not include the new TS Bases. a) Please provide the complete TS B3.7.9 Bases for clarity. b) Please explain why and how often the SX trains are operated split for one and/or both units. Response to Question 1.a: The response to Question 1.a will be provided in a separate submittal.
Response to Question 1.b: The SX trains are not normally operated with the trains split. The normal operating procedures do not contain steps for operations with the trains split. The SX trains may be split to support maintenance or in response to postulated flood events caused by leakage from SX piping. A review of the Operating Logs and Maintenance Rule Program data indicated no occurrences of SX trains split concurrent with a service water cooling tower (SXCT) cell out of service or inoperable in the last three years. NRC Question 2: The uprate heat load for the scenarios presented in the letter dated November 8,2010, for the scenarios where SX is split, show a constant heat load to the UHS for approximately the first 19 minutes after loss-of-coolant accident.
These heat loads differ from the heat loads in the scenarios presented in your letter dated June 30, 2009. The staff recognizes differences in heat loads to the UHS based on one train of SX in the letter dated November 8, 2010, versus two trains of operating SX in your letter dated June 30, 2009. a) Please explain the reasons for differences in the heat load profiles for your letters dated June 30, 2009, and November 8, 2010. b) Please explain why the heat load is constant in your November 8,2010, submittal for the first 19 minutes, whereas the corresponding heat load for the first 19-20 minutes is not constant for the scenarios in the letter dated June 30,2009. Page 1 of 4 ATTACHMENT Response to Request for Additional Information Response to Question 2.a: The EGC letters dated June 30,2009, and November 8,2010, provided analysis for different scenarios.
The June 30, 2009, letter provided scenarios associated with postulated passive breaker failures that result in the loss of two SXCT fans. The November 8, 2010, letter provided additional analysis with scenarios associated with the SX trains separated and a failure of one of the SX pumps or EDG on the accident unit resulting in SX flow to only one train of the SX system and one cooling tower. The following differences exist between the two heat load profiles:
i) For the June 30,2009, heat load profile, the accident unit heat load is based on four reactor containment fan coolers (RCFCs) in operation for the first 1,299 seconds (21.6 minutes).
At 1,299 seconds, operator action is assumed to shed heat load by securing two of the four RCFCs, which reduces the accident unit heat input rate. For the November 8,2010, heat load profile, the SX trains are separated, and a failure is assumed, which results in SX flow to only one train of equipment on the accident unit. Thus, the accident unit heat load is based on only two RCFCs in operation for the event. ii) For the June 30,2009, heat load profile, the accident unit heat load is based on safety injection switchover to cold leg recirculation at 695 seconds (Le., RH HX heat input to the UHS starts at t = 695 seconds).
For the November 8,2010, heat load profile, only one train of ECCS is operating which delays switch over. With one train of ECCS in operation during the injection phase, the switchover time and RH HX input to the UHS starts at t = 1110 seconds. Response to Question 2.b: For the November 8, 2010, heat load profile, the RCFC heat load was conservatively assumed to be constant until the start of RH HX input (i.e., safety injection switchover to cold leg recirculation).
With two RCFCs in operation, the LOCA Mass and Energy Analysis indicates that containment steam temperatures and RCFC heat removal rates are relatively constant until the RH HX is placed in service. Whereas, for the June 30, 2009, heat load profile, with four RCFCs in operation, the LOCA Mass and Energy Analysis indicates the containment steam temperature drops from a peak of approximately 261 ° F to approximately 208.3° F at 1,199 seconds (20 minutes).
The following plot shows the containment steam temperature for the two cases. Page 2 of 4 ATTACHMENT Response to Request for Additional Information Containment Steam Temperature
.........
_ .........
--.. 160 140 120 o 200 400 600 800 1000 1200 Time (seconds)
The RCFC heat removal rate varies with the temperature difference between the SX water temperature and the containment steam temperature.
NRC Question 3: The proposed TS Limiting Condition for Operation (LCO) 3.7.9 use "SX pump discharge temperature region,1I to define the LCO. As this temperature varies, the requirements of the LCO change and require operator action. a) Please explain how the operators will become aware that the IISX pump discharge temperature region,1I has changed and that operator action is necessary.
b) Indicated SX pump discharge temperature may be different than actual temperature.
How has the temperature instrument and loop uncertainty/inaccuracy been factored into the proposed TS LCO revision?
Response to Question 3.a: SX pump discharge temperature is monitored by the control room operators.
Each Unit Nuclear Station Operator monitors SX pump discharge temperature during control board walk downs. The upper limit of green band for the control board temperature indicators is currently set at 78° F, which is at the current SX pump discharge high temperature alarm of 78° F. In response to changing temperatures the operators utilize procedural guidance to take the appropriate action(s) to control basin temperatures.
Page 3 of 4 ATTACHMENT Response to Request for Additional Information Procedure OBOSR 0.1-0, "UNIT COMMON ALL MODES/ALL TIMES SHIFTL Y AND DAILY OPERATING SURVEILLANCE," implements Surveillance Requirement (SR) 3.7.9.2. Although the required SR frequency is 24 hours, the SX pump discharge temperatures are currently verified as acceptable three times per day. Control room alarms 1-2-B2 and 2-2-B2, "SX Pump Discharge Header Temperature High Low," currently provide a high temperature alarm at 78° F. The current alarm setpoint was selected to alert operators of high pump discharge temperatures prior to reaching the current Technical Specifications temperature limit of 80° F where action is needed to run all required cooling tower fans on high speed. It should be noted that during normal operation the heat load on the SXCT is relatively constant.
Thus if no changes are made to the tower configuration the SX pump discharge temperature tends to follow the outside air wet bulb temperature.
Outside air wet bulb temperature changes are relatively slow providing adequate time for the operators to recognize and to take action to put additional SXCT fans into service when needed. The SX pump discharge header temperature high alarm setpoint will be evaluated and potentially changed during implementation of the revised Technical Specifications.
Response to Question 3.b: As described in the EGC June 30,2009, License Amendment Request: To ensure that the actual UHS temperature does not exceed the TS surveillance limit, the surveillance procedure used to demonstrate compliance with the TS surveillance limit will be revised to accommodate instrument uncertainty.
To ensure that the indicated UHS temperature does not exceed the TS surveillance limit, temperature corrections have been factored into the UHS surveillance procedures.
The SX pump discharge temperatures in the current UHS surveillance procedures OBOSR 0.1-0, "UNIT COMMON ALL MODES/ALL TIMES SHIFTL Y AND DAILY OPERATING SURVEILLANCE," Revision 35, and OBOL 7.9, "LCOAR ULTIMATE HEAT SINK (UHS) TECH SPEC LCO # 3.7.9," Revision 12, were previously reduced by 2° F to account for instrument measurement uncertainties.
Additionally, procedure BOP SX-T2, "SX TOWER OPERATION GUIDELINES," Revision 14, applies the same temperature requirements as the surveillance procedures (i.e., the normal operating procedure has the operators keep the indicated basin temperature 2° F below the required Technical Specification temperature).
Page 4 of 4}}

Revision as of 23:56, 9 November 2018

Redirect to:

Retrieved from "https://kanterella.com/w/index.php?title=ML110310612&oldid=1175460"