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| {{#Wiki_filter:From: DiFrancesco, Nicholas Sent: Thursday, December 16, 2010 10:03 AM To: Lisa.Schofield@exeloncorp.com Cc: DiFrancesco, Nicholas; Wohl, Marilyn; 'jeff.hansen@exeloncorp.com'; Carlson, Robert | | {{#Wiki_filter:From: DiFrancesco, Nicholas Sent: Thursday, December 16, 2010 10:03 AM To: Lisa.Schofield@exeloncorp.com Cc: DiFrancesco, Nicholas; Wohl, Marilyn; 'jeff.hansen@exeloncorp.com'; |
| | Carlson, Robert |
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| ==Subject:== | | ==Subject:== |
| Draft NRC RAI Re: Byron Station, Units 1 and 2 - LAR Re: Ultimate Heat Sink (TAC Nos. ME1669 and ME1670) | | Draft NRC RAI Re: Byron Station, Units 1 and 2 - LAR Re: Ultimate Heat Sink (TAC Nos. ME1669 and ME1670) |
| Ms. Lisa Schofield, By letter to the Nuclear Regulatory Commission (NRC) dated June 30, 2009, as supplemented by letters dated January 25, July 1, and November 8, 2010 (Agencywide Documents Access and Management System Accession Nos. ML091831253, ML100280553, ML101830041, and ML103120556, respectively), Exelon Generation Company, LLC (the licensee), submitted a license amendment request to revise Technical Specification 3.7.9, "Ultimate Heat Sink (UHS)," to add additional essential service water (SX) cooling tower fan requirements as a function of SX pump discharge temperature to reflect the results of a revised analysis for the UHS. | | Ms. Lisa Schofield, By letter to the Nuclear Regulatory Commission (NRC) dated June 30, 2009, as supplemented by letters dated January 25, July 1, and November 8, 2010 (Agencywide Documents Access and Management System Accession Nos. ML091831253, ML100280553, ML101830041, and ML103120556, respectively), Exelon Generation Company, LLC (the licensee), submitted a license amendment request to revise Technical Specification 3.7.9, "Ultimate Heat Sink (UHS)," |
| The Balance-of-Plant Branch has reviewed the information provided and determined that in order to complete its evaluation, additional information may be required. The draft RAI related to the staff review is provided below. | | to add additional essential service water (SX) cooling tower fan requirements as a function of SX pump discharge temperature to reflect the results of a revised analysis for the UHS. |
| | | The Balance-of-Plant Branch has reviewed the information provided and determined that in order to complete its evaluation, additional information may be required. The draft RAI related to the staff review is provided below. |
| After reviewing the draft RAI, please contact me at 301-415-1115 to discuss the need for a teleconference concerning the RAIs and to discuss a due date for the response. | | After reviewing the draft RAI, please contact me at 301-415-1115 to discuss the need for a teleconference concerning the RAIs and to discuss a due date for the response. |
| Respectfully, Nicholas DiFrancesco | | Respectfully, Nicholas DiFrancesco Project Manager Nuclear Regulatory Commission Division of Operating Reactor Licensing nicholas.difrancesco@nrc.gov Tel: (301) 415-1115 Fax: (301) 415-1222 REQUEST FOR ADDITIONAL INFORMATION BYRON STATION, UNIT NOS. 1 AND 2 DOCKET NOS. STN 50-454 AND STN 50-455 |
| | | : 1. General Design Criteria 44, Cooling water, states, in part, that suitable redundancy in components and features shall be provided to assure the system safety function can be accomplished, assuming a single failure. |
| Project Manager Nuclear Regulatory Commission Division of Operating Reactor Licensing nicholas.difrancesco@nrc.gov Tel: (301) 415-1115 Fax: (301) 415-1222 REQUEST FOR ADDITIONAL INFORMATION BYRON STATION, UNIT NOS. 1 AND 2 DOCKET NOS. STN 50-454 AND STN 50-455 | | Generic Letter (GL) 80-30 states that Standard Technical Specification (STS) Limiting Conditions for Operation (LCO) were formulated to preserve the single failure criterion for systems relied upon in the safety analysis report. When the required redundancy is not |
| : 1. General Design Criteria 44, "Cooling water," states, in part, that suitable redundancy in components and features shall be provided to assure the system safety function can be accomplished, assuming a single failure. | |
| | |
| Generic Letter (GL) 80-30 states that Standard Technical Specification (STS) Limiting Conditions for Operation (LCO) were formulated to preserve the single failure criterion for systems relied upon in the safety analysis report. When the required redundancy is not maintained due to equipment failure, GL 80-30 provides for a temporary relaxation of the single failure criterion for specified conditions within an allowed outage time. When the single failure criterion is temporary relaxed for the allowed outage time, the system safety function can still be performed with the remaining components and features during the allowed outage time. | |
| The licensee has apparently proposed a new Condition B where there would not be enough remaining components and features to accomplish the safety function during the allowed outage time [i.e. there would not be enough essential service water cooling tower (SXCT) fans to perform the safety function even without any additional single failure]. This is described as follows. In Response 1 c of Exelon Letter dated November 8, 2010, the licensee is proposing a new Condition B which would allow two required cooling tower fans to be inoperable for 72 hours when the SX system is operating with SX trains on either unit split. This new Condition B could allow one fan to be inoperable in each SXCT. The licensee has cited GL 80-30 as justification for allowing two required cooling tower fans to be inoperable. But, four operable fans in an SXCT are required for the safety analysis when the SX trains are split. The licensee states this requirement in Response 1 C as follows, "Calculations indicated that with no SXCT fans out of service and the SX trains separated, the UHS temperature could be maintained at less than 100 F with four SXCT fans operating on the SXCT with flow."
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| | maintained due to equipment failure, GL 80-30 provides for a temporary relaxation of the single failure criterion for specified conditions within an allowed outage time. When the single failure criterion is temporary relaxed for the allowed outage time, the system safety function can still be performed with the remaining components and features during the allowed outage time. |
| | The licensee has apparently proposed a new Condition B where there would not be enough remaining components and features to accomplish the safety function during the allowed outage time [i.e. there would not be enough essential service water cooling tower (SXCT) fans to perform the safety function even without any additional single failure]. This is described as follows. In Response 1 c of Exelon Letter dated November 8, 2010, the licensee is proposing a new Condition B which would allow two required cooling tower fans to be inoperable for 72 hours when the SX system is operating with SX trains on either unit split. This new Condition B could allow one fan to be inoperable in each SXCT. The licensee has cited GL 80-30 as justification for allowing two required cooling tower fans to be inoperable. But, four operable fans in an SXCT are required for the safety analysis when the SX trains are split. The licensee states this requirement in Response 1 C as follows, Calculations indicated that with no SXCT fans out of service and the SX trains separated, the UHS temperature could be maintained at less than 100 F with four SXCT fans operating on the SXCT with flow. |
| With neither SXCT having four operable fans, neither SXCT would be able to perform the safety function during the 72 hour allowed outage time. The staff requests the following: | | With neither SXCT having four operable fans, neither SXCT would be able to perform the safety function during the 72 hour allowed outage time. The staff requests the following: |
| a.) Justify allowing two required cooling tower fans to be inoperable when the SX is operating in the configuration of Table 3.7.9-2 or revise Condition B to meet regulatory requirements. b.) Explain how the operators are supposed to determine UHS operability when the SX trains are split on one unit and/or both units. (Attachment 3 of the June 30, 2009 submittal, "Markup of Proposed Technical Specifications Bases Pages" define operability of the UHS when each units SX system has crosstied SX trains. The TS Bases does not provide UHS operability criteria for split SX trains.) c.) Explain why and how often the SX trains are operated split for one and/or both units. | | a.) Justify allowing two required cooling tower fans to be inoperable when the SX is operating in the configuration of Table 3.7.9-2 or revise Condition B to meet regulatory requirements. |
| : 2. The up rate heat load for the scenarios presented in Exelon 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 a Loss-of-Coolant Accident. These heat loads differ from the heat loads in the scenarios presented in your June 30, 2009 submittal. The staff recognizes differences in heat loads to the UHS based on one train of SX in the November 8 submittal versus two trains of operating SX in your June 30, 2009 submittal. | | b.) Explain how the operators are supposed to determine UHS operability when the SX trains are split on one unit and/or both units. (Attachment 3 of the June 30, 2009 submittal, Markup of Proposed Technical Specifications Bases Pages define operability of the UHS when each units SX system has crosstied SX trains. The TS Bases does not provide UHS operability criteria for split SX trains.) |
| | | c.) Explain why and how often the SX trains are operated split for one and/or both units. |
| a) Explain the reasons for differences in the heat load profiles of your June 30, 2009 submittal and your November 8, 2010 submittal. b) Explain why the heat load is constant in your November 8 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 June 30, 2009 submittal.}} | | : 2. The up rate heat load for the scenarios presented in Exelon 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 a Loss-of-Coolant Accident. These heat loads differ from the heat loads in the scenarios presented in your June 30, 2009 submittal. The staff recognizes differences in heat loads to the UHS based on one train of SX in the November 8 submittal versus two trains of operating SX in your June 30, 2009 submittal. |
| | a) Explain the reasons for differences in the heat load profiles of your June 30, 2009 submittal and your November 8, 2010 submittal. |
| | b) Explain why the heat load is constant in your November 8 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 June 30, 2009 submittal.}} |
Letter Sequence Draft RAI |
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MONTHYEARRS-09-054, License Amendment Request Regarding Ultimate Heat Sink2009-06-30030 June 2009 License Amendment Request Regarding Ultimate Heat Sink Project stage: Request ML0921203572009-07-31031 July 2009 Application Accepted - Byron LAR for Ultimate Heat Sink (ME1669-70) Project stage: Other ML0932006512009-12-11011 December 2009 Request for Additional Information Related to License Amendment Regarding Ultimate Heat Sink Project stage: RAI RS-10-020, Additional Information Supporting Request for License Amendment Regarding Ultimate Heat Sink2010-01-25025 January 2010 Additional Information Supporting Request for License Amendment Regarding Ultimate Heat Sink Project stage: Request ML1013805252010-05-18018 May 2010 Additional RAI for Ultimate Heat Sink License Amendment Request (ME1669-70) Project stage: RAI RS-10-112, Additional Information Supporting Request for License Amendment Regarding Ultimate Heat Sink2010-07-0101 July 2010 Additional Information Supporting Request for License Amendment Regarding Ultimate Heat Sink Project stage: Request ML1021601902010-08-18018 August 2010 Request for Additional Information Related to License Amendment Regarding Ultimate Heak Sink Project stage: RAI ML1030602892010-11-0202 November 2010 Approved with Comment: Request to Extend the Submittal Date for the Byron UHS RAI Response Project stage: RAI RS-10-184, Additional Information Supporting Request for License Amendment Regarding Ultimate Heat Sink2010-11-0808 November 2010 Additional Information Supporting Request for License Amendment Regarding Ultimate Heat Sink Project stage: Request ML1035003172010-12-16016 December 2010 Draft NRC RAI Byron Station, Units 1 and 2 - LAR Ultimate Heat Sink Project stage: Draft RAI ML1036205592010-12-28028 December 2010 Request for Additional Information Related to License Amendment Regarding Ultimate Heat Sink Project stage: RAI RS-11-010, Response to Request for Additional Information Related to License Amendment Regarding Ultimate Heat Sink2011-01-31031 January 2011 Response to Request for Additional Information Related to License Amendment Regarding Ultimate Heat Sink Project stage: Response to RAI ML1103413522011-02-14014 February 2011 Request for Additional Information Related to License Amendment Regarding Ultimate Heat Sink Project stage: RAI ML1104505662011-02-15015 February 2011 3/01/2011 Notice of Forthcoming Meeting with Exelon to Discuss Nrc'S Staff'S Review of the Ultimate Head Sink License Amendment Request for the Byron Station, Units 1 and 2 Project stage: Meeting ML1106201482011-03-10010 March 2011 Summary of Meeting with Exelon Generation Company, LLC to Discuss the Request for Additional Information Related to License Amendment Regarding the Ultimate Heat Sink Project stage: RAI RS-11-035, Additional Information Supporting Request for License Amendment Regarding Ultimate Heat Sink2011-03-16016 March 2011 Additional Information Supporting Request for License Amendment Regarding Ultimate Heat Sink Project stage: Request RS-11-070, Supplement to Information Supporting Request for License Amendment Regarding Ultimate Heat Sink2011-05-0404 May 2011 Supplement to Information Supporting Request for License Amendment Regarding Ultimate Heat Sink Project stage: Supplement ML1113106332011-06-14014 June 2011 Issuance of Amendments Revision of Technical Specification 3.7.9, Ultimate Heat Sink Project stage: Approval 2010-05-18
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From: DiFrancesco, Nicholas Sent: Thursday, December 16, 2010 10:03 AM To: Lisa.Schofield@exeloncorp.com Cc: DiFrancesco, Nicholas; Wohl, Marilyn; 'jeff.hansen@exeloncorp.com';
Carlson, Robert
Subject:
Draft NRC RAI Re: Byron Station, Units 1 and 2 - LAR Re: Ultimate Heat Sink (TAC Nos. ME1669 and ME1670)
Ms. Lisa Schofield, By letter to the Nuclear Regulatory Commission (NRC) dated June 30, 2009, as supplemented by letters dated January 25, July 1, and November 8, 2010 (Agencywide Documents Access and Management System Accession Nos. ML091831253, ML100280553, ML101830041, and ML103120556, respectively), Exelon Generation Company, LLC (the licensee), submitted a license amendment request to revise Technical Specification 3.7.9, "Ultimate Heat Sink (UHS),"
to add additional essential service water (SX) cooling tower fan requirements as a function of SX pump discharge temperature to reflect the results of a revised analysis for the UHS.
The Balance-of-Plant Branch has reviewed the information provided and determined that in order to complete its evaluation, additional information may be required. The draft RAI related to the staff review is provided below.
After reviewing the draft RAI, please contact me at 301-415-1115 to discuss the need for a teleconference concerning the RAIs and to discuss a due date for the response.
Respectfully, Nicholas DiFrancesco Project Manager Nuclear Regulatory Commission Division of Operating Reactor Licensing nicholas.difrancesco@nrc.gov Tel: (301) 415-1115 Fax: (301) 415-1222 REQUEST FOR ADDITIONAL INFORMATION BYRON STATION, UNIT NOS. 1 AND 2 DOCKET NOS. STN 50-454 AND STN 50-455
- 1. General Design Criteria 44, Cooling water, states, in part, that suitable redundancy in components and features shall be provided to assure the system safety function can be accomplished, assuming a single failure.
Generic Letter (GL) 80-30 states that Standard Technical Specification (STS) Limiting Conditions for Operation (LCO) were formulated to preserve the single failure criterion for systems relied upon in the safety analysis report. When the required redundancy is not
maintained due to equipment failure, GL 80-30 provides for a temporary relaxation of the single failure criterion for specified conditions within an allowed outage time. When the single failure criterion is temporary relaxed for the allowed outage time, the system safety function can still be performed with the remaining components and features during the allowed outage time.
The licensee has apparently proposed a new Condition B where there would not be enough remaining components and features to accomplish the safety function during the allowed outage time [i.e. there would not be enough essential service water cooling tower (SXCT) fans to perform the safety function even without any additional single failure]. This is described as follows. In Response 1 c of Exelon Letter dated November 8, 2010, the licensee is proposing a new Condition B which would allow two required cooling tower fans to be inoperable for 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> when the SX system is operating with SX trains on either unit split. This new Condition B could allow one fan to be inoperable in each SXCT. The licensee has cited GL 80-30 as justification for allowing two required cooling tower fans to be inoperable. But, four operable fans in an SXCT are required for the safety analysis when the SX trains are split. The licensee states this requirement in Response 1 C as follows, Calculations indicated that with no SXCT fans out of service and the SX trains separated, the UHS temperature could be maintained at less than 100 F with four SXCT fans operating on the SXCT with flow.
With neither SXCT having four operable fans, neither SXCT would be able to perform the safety function during the 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> allowed outage time. The staff requests the following:
a.) Justify allowing two required cooling tower fans to be inoperable when the SX is operating in the configuration of Table 3.7.9-2 or revise Condition B to meet regulatory requirements.
b.) Explain how the operators are supposed to determine UHS operability when the SX trains are split on one unit and/or both units. (Attachment 3 of the June 30, 2009 submittal, Markup of Proposed Technical Specifications Bases Pages define operability of the UHS when each units SX system has crosstied SX trains. The TS Bases does not provide UHS operability criteria for split SX trains.)
c.) Explain why and how often the SX trains are operated split for one and/or both units.
- 2. The up rate heat load for the scenarios presented in Exelon 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 a Loss-of-Coolant Accident. These heat loads differ from the heat loads in the scenarios presented in your June 30, 2009 submittal. The staff recognizes differences in heat loads to the UHS based on one train of SX in the November 8 submittal versus two trains of operating SX in your June 30, 2009 submittal.
a) Explain the reasons for differences in the heat load profiles of your June 30, 2009 submittal and your November 8, 2010 submittal.
b) Explain why the heat load is constant in your November 8 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 June 30, 2009 submittal.