ML16032A164
| ML16032A164 | |
| Person / Time | |
|---|---|
| Site: | North Anna  |
| Issue date: | 01/25/2016 |
| From: | Sartain M D Virginia Electric & Power Co (VEPCO) |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| 15-022A | |
| Download: ML16032A164 (6) | |
Text
VIRGINIA ELECTRIC AND POWER COMPANYRICHMOND, VIRGINIA 23261January 25, 2016U. S. Nuclear Regulatory Commission Serial No.: 15-022AAttention: Document Control Desk NAPS/JHL: R0Washington, DC 20555-0001 Docket Nos.: 50-338/339License Nos.: NPF-4/7VIRGINIA ELECTRIC AND POWER COMPANYNORTH ANNA POWER STATION UNITS 1 AND 2REACTOR COOLANT SYSTEM FLUENCE MODEL RESULTSIn a letter dated August 27, 2014 (Serial No.14-424), Virginia Electric and Power Company(Dominion) submitted a license amendment request to revise the North Anna Power StationUnits 1 and 2 Technical Specifications (TS). TS Figures 3.4.3-1 and 3.4.3-2, North Anna Units1 and 2 Reactor Coolant System Heatup Limitations and North Anna Units 1 and 2 ReactorCoolant System Cooldown Limitations, respectively, were being revised for clarification and tobe fully representative of the allowable operating conditions during Reactor Coolant System(RCS) startup and cooldown evolutions. Specifically, the revisions to TS Figures 3.4.3-1 and3.4.3-2 were to extend the temperature axes to reflect temperatures up to RCS full poweroperation, extend the pressure axes to less than 0 psig to bound RCS conditions to supportvacuum-assist fill of the RCS loops, and to add information regarding the reactor boltuptemperature.In a letter dated February 16, 2015 (Serial No.15-022), Dominion responded to a request foradditional information (RAI) to support the proposed amendment. In the RAI response, acommitment was made to review the revision of the fluence model. If the revised fluencemodel indicates the neutron fluence exposure of the inlet and outlet nozzles would be greaterthan lx1017 n/cm2 (E > I MeV) at the end of the licensed operating period, Dominion willadvise the NRC accordingly and provide a schedule for submittal of revised pressure-temperature (P-T) limit curves for North Anna Units 1 and 2, if necessary.On July 27, 2015, the NRC issued Amendment Nos. 275 and 257 to the Renewed FacilityOperating Licenses for North Anna Units I and 2. The NRC staff Safety Evaluation indicatesthat the differences in Effective Full Power Years (EFPY) for the current operating period incomparison to the corresponding approved pressure-temperature (P-T) limits provide anadequate margin so that if the revised neutron fluence model indicates that the neutron fluenceexposure of the inlet and outlet nozzles is greater than lx1017 n/cm2 at the end of extendedoperation, the licensee will notify the NRC accordingly and provide a schedule for revised P-Tlimits curves for North Anna Units 1 and 2, if necessary.This letter provides notification that the revised RCS fluence model has been reviewed and theresults are provided in Attachment 1.AL)
Serial No. 15-022ADocket Nos. 50-338/339Page 2 of 3Should you have any questions or require additional information, please contactMr. Jay Leberstien at (540) 894-2574.Respectfully,SNOTARY PUBLICMak0 ati j'Reg.#. 1,40542Vice President -Nuclear Engineering t ofpVirgsIy3;2iniCOMMONWEALTH OF VIRGINIACOUNTY OF HENRICOThe foregoing document was acknowledged before me, in and for the County and Commonwealth aforesaid, today byMr. Mark D. Sartain, who is Vice President -Nuclear Engineering, of Virginia Electric and Power Company. He hasaffirmed before me that he is duly authorized to execute and file the foregoing document in behalf of that company, andthat the statements in the document are true to the best of his knowledge and belief.Acknowledged before me 57ay of!,06My Commission Expires: .Notary PublicCommitments contained in this letter:1. Develop new limit curves for the Unit 1 and Unit 2 #1 inlet nozzles no later thanDecember 26, 2031 to determine if the existing P-T curves are conservative throughthe end of the licensed operating period.2. Notify the NRC of the assessment results of the new Unit 1 and Unit 2 #1 limit curvesfor the inlet nozzles no later than March 31, 2032.3. If the existing P-T curves require revision, a license amendment request will besubmitted to the NRC for new P-T curves by January 31, 2032.Attachment1. Revised RCS Fluence Model Results Serial No. 1 5-022ADocket Nos. 50-338/339Page 3 of 3cc: U.S. Nuclear Regulatory Commission -Region IIMarquis One Tower245 Peachtree Center Avenue, NE Suite 1200Atlanta, GA 30303-1257Dr. V. SreenivasNRC Project Manager -North AnnaU.S. Nuclear Regulatory CommissionOne White Flint NorthMail Stop 08 G-9A11555 Rockville PikeRockville, MD 20852-2738Ms. Karen Cotton-GrossNRC Project Manager -SurryU.S. Nuclear Regulatory CommissionOne White Flint NorthMail Stop 08 G-9A11555 Rockville PikeRockville, MD 20852-2738NRC Senior Resident InspectorNorth Anna Power Station Serial No. 1 5-022ADocket Nos. 50-338/339AttachmentRevised RCS Fluence Model ResultsVirginia Electric and Power Company(Dominion)North Anna Power Station Units 1 and 2 Serial No. 1 5-022ADocket Nos. 50-338/339Attachment 1Page 1 of 2REVISED RCS FLUENCE MODEL RESULTSOn July 27, 2015, the NRC issued Amendment Nos. 275 and 257 to the RenewedFacility Operating Licenses for North Anna Power Station (NAPS) Units 1 and 2. TheNRC staff Safety Evaluation indicates that the differences in Effective Full Power Years(EFPY) for the current operating period in comparison to the corresponding approvedpressure-temperature (P-T) limits provide an adequate margin so that if the revisedneutron fluence model indicates that the neutron fluence exposure of the inlet and outletnozzles is greater than lxi1017 n/cm2 at the end of extended operation, the licensee willnotify the NRC accordingly and provide a schedule for revised P-T limits curves forNorth Anna Units I and 2, if necessary.The results of the revised RCS fluence model are summarized below.Westinghouse Electric Company revised the fluence model to extend the axial regionabove the fuel to be able to calculate the fluence in the nozzle region. Initialcalculations projected the fluence at the lowest extent of the inlet and outlet nozzleforgings to vessel shell welds. The projected fluence at this location, about 5 inchesbelow where a postulated flaw would be assumed in the nozzle region, was found to bebelow the lxi1017 n/cm2 threshold for 8 of the 12 nozzles. Additional calculations wereperformed at the location where a postulated flaw is assumed to determine themagnitude of the fluence with respect to the 1x1017 n/cm2 threshold for the other 4nozzles.Westinghouse Electric Company determined the magnitude of the fluence for these 4nozzles at 60 and 80 years of plant operation and the time (in EFPY) when the fluenceat each of the postulated flaw locations reaches lxi 10 n/cm2 (E > 1.0 MeV). Theresults of the fluence modeling have been documented by Westinghouse ElectricCompany in WCAP-18015-NP, Revision 0, Extended Beltline Pressure Vessel FluenceEvaluations Applicable to North Anna 1 & 2.WCAP-1 8015-NP indicates that the 1/4T location for 2 of the 12 nozzles will reach thelxi1017 n/cm2 fluence threshold of concern prior to 54 EFPY.* For Unit 1, the 1/4 T Flaw in Inlet Nozzle 1 is projected to reach lxi1017 n/cm2at approximately 48.5 EFPY, which corresponds to December 26, 2034. Thelicense renewal operating period NAPS Uhit i runs~through April 1, 2038.* For Unit 2, the 1/4 T Flaw in Inlet Nozzle 1 is projected to reach 1x1017 n/cm2at approximately 49.1 EFPY, which corresponds to October 15, 2036. Thelicense renewal operating period NAPS Unit 2 runs through August 21, 2040.Thus, the fluence at the postulated 1/4T flaw location in the NAPS Unit I and Unit 2 #1inlet nozzles are projected to exceed the 1x1017 n/cm2 threshold prior to reaching theend of the licensed operating period.
Serial No. 15-022ADocket Nos. 50-338/339Attachment 1Page 2 of 2While the fluence is projected to exceed the lx1017 n/cm2 threshold for the #1 inletnozzles prior to the end of licensed operating period this does not necessarily indicatethat the existing heatup and cooldown curves will become non-conservative prior toreaching the end of the licensed operating period. However, new limit curves will needto be constructed for the Unit 1 and Unit 2 #1 inlet nozzles and compared to theapproved Technical Specification limit curves for the other vessel materials to determineif the existing P-T curves are adequate through the end of the licensed operating period.The assessment of the #1 inlet nozzles must be completed under a schedule thatprovides sufficient time to amend the existing heatup and cooldown curves, if required.Below is the schedule for revising the P-T curves, if necessary.1. Develop new limit curves for the Unit 1 and Unit 2 #1 inlet nozzles no laterthan December 26, 2031 to determine if the existing P-T curves areconservative through the end of the licensed operating period.2. Notify the NRC of the assessment results of the new Unit I and Unit 2 #1 limitcurves for the inlet nozzles no later than March 31, 2032. This will validate ifthe existing heatup and cooldown curves are conservative or if they will* require revision prior to end of the licensed operating period.3. If the existing P-T curves require revision, a license amendment request willbe submitted to the NRC for new P-T curves by January 31, 2032. Asubmittal date of January 31, 2032 bounds the projected time for exceedingthe Unit I1lx1017n/cm2fluence threshold projected to occur at 48.5 EFPY.
VIRGINIA ELECTRIC AND POWER COMPANYRICHMOND, VIRGINIA 23261January 25, 2016U. S. Nuclear Regulatory Commission Serial No.: 15-022AAttention: Document Control Desk NAPS/JHL: R0Washington, DC 20555-0001 Docket Nos.: 50-338/339License Nos.: NPF-4/7VIRGINIA ELECTRIC AND POWER COMPANYNORTH ANNA POWER STATION UNITS 1 AND 2REACTOR COOLANT SYSTEM FLUENCE MODEL RESULTSIn a letter dated August 27, 2014 (Serial No.14-424), Virginia Electric and Power Company(Dominion) submitted a license amendment request to revise the North Anna Power StationUnits 1 and 2 Technical Specifications (TS). TS Figures 3.4.3-1 and 3.4.3-2, North Anna Units1 and 2 Reactor Coolant System Heatup Limitations and North Anna Units 1 and 2 ReactorCoolant System Cooldown Limitations, respectively, were being revised for clarification and tobe fully representative of the allowable operating conditions during Reactor Coolant System(RCS) startup and cooldown evolutions. Specifically, the revisions to TS Figures 3.4.3-1 and3.4.3-2 were to extend the temperature axes to reflect temperatures up to RCS full poweroperation, extend the pressure axes to less than 0 psig to bound RCS conditions to supportvacuum-assist fill of the RCS loops, and to add information regarding the reactor boltuptemperature.In a letter dated February 16, 2015 (Serial No.15-022), Dominion responded to a request foradditional information (RAI) to support the proposed amendment. In the RAI response, acommitment was made to review the revision of the fluence model. If the revised fluencemodel indicates the neutron fluence exposure of the inlet and outlet nozzles would be greaterthan lx1017 n/cm2 (E > I MeV) at the end of the licensed operating period, Dominion willadvise the NRC accordingly and provide a schedule for submittal of revised pressure-temperature (P-T) limit curves for North Anna Units 1 and 2, if necessary.On July 27, 2015, the NRC issued Amendment Nos. 275 and 257 to the Renewed FacilityOperating Licenses for North Anna Units I and 2. The NRC staff Safety Evaluation indicatesthat the differences in Effective Full Power Years (EFPY) for the current operating period incomparison to the corresponding approved pressure-temperature (P-T) limits provide anadequate margin so that if the revised neutron fluence model indicates that the neutron fluenceexposure of the inlet and outlet nozzles is greater than lx1017 n/cm2 at the end of extendedoperation, the licensee will notify the NRC accordingly and provide a schedule for revised P-Tlimits curves for North Anna Units 1 and 2, if necessary.This letter provides notification that the revised RCS fluence model has been reviewed and theresults are provided in Attachment 1.AL)
Serial No. 15-022ADocket Nos. 50-338/339Page 2 of 3Should you have any questions or require additional information, please contactMr. Jay Leberstien at (540) 894-2574.Respectfully,SNOTARY PUBLICMak0 ati j'Reg.#. 1,40542Vice President -Nuclear Engineering t ofpVirgsIy3;2iniCOMMONWEALTH OF VIRGINIACOUNTY OF HENRICOThe foregoing document was acknowledged before me, in and for the County and Commonwealth aforesaid, today byMr. Mark D. Sartain, who is Vice President -Nuclear Engineering, of Virginia Electric and Power Company. He hasaffirmed before me that he is duly authorized to execute and file the foregoing document in behalf of that company, andthat the statements in the document are true to the best of his knowledge and belief.Acknowledged before me 57ay of!,06My Commission Expires: .Notary PublicCommitments contained in this letter:1. Develop new limit curves for the Unit 1 and Unit 2 #1 inlet nozzles no later thanDecember 26, 2031 to determine if the existing P-T curves are conservative throughthe end of the licensed operating period.2. Notify the NRC of the assessment results of the new Unit 1 and Unit 2 #1 limit curvesfor the inlet nozzles no later than March 31, 2032.3. If the existing P-T curves require revision, a license amendment request will besubmitted to the NRC for new P-T curves by January 31, 2032.Attachment1. Revised RCS Fluence Model Results Serial No. 1 5-022ADocket Nos. 50-338/339Page 3 of 3cc: U.S. Nuclear Regulatory Commission -Region IIMarquis One Tower245 Peachtree Center Avenue, NE Suite 1200Atlanta, GA 30303-1257Dr. V. SreenivasNRC Project Manager -North AnnaU.S. Nuclear Regulatory CommissionOne White Flint NorthMail Stop 08 G-9A11555 Rockville PikeRockville, MD 20852-2738Ms. Karen Cotton-GrossNRC Project Manager -SurryU.S. Nuclear Regulatory CommissionOne White Flint NorthMail Stop 08 G-9A11555 Rockville PikeRockville, MD 20852-2738NRC Senior Resident InspectorNorth Anna Power Station Serial No. 1 5-022ADocket Nos. 50-338/339AttachmentRevised RCS Fluence Model ResultsVirginia Electric and Power Company(Dominion)North Anna Power Station Units 1 and 2 Serial No. 1 5-022ADocket Nos. 50-338/339Attachment 1Page 1 of 2REVISED RCS FLUENCE MODEL RESULTSOn July 27, 2015, the NRC issued Amendment Nos. 275 and 257 to the RenewedFacility Operating Licenses for North Anna Power Station (NAPS) Units 1 and 2. TheNRC staff Safety Evaluation indicates that the differences in Effective Full Power Years(EFPY) for the current operating period in comparison to the corresponding approvedpressure-temperature (P-T) limits provide an adequate margin so that if the revisedneutron fluence model indicates that the neutron fluence exposure of the inlet and outletnozzles is greater than lxi1017 n/cm2 at the end of extended operation, the licensee willnotify the NRC accordingly and provide a schedule for revised P-T limits curves forNorth Anna Units I and 2, if necessary.The results of the revised RCS fluence model are summarized below.Westinghouse Electric Company revised the fluence model to extend the axial regionabove the fuel to be able to calculate the fluence in the nozzle region. Initialcalculations projected the fluence at the lowest extent of the inlet and outlet nozzleforgings to vessel shell welds. The projected fluence at this location, about 5 inchesbelow where a postulated flaw would be assumed in the nozzle region, was found to bebelow the lxi1017 n/cm2 threshold for 8 of the 12 nozzles. Additional calculations wereperformed at the location where a postulated flaw is assumed to determine themagnitude of the fluence with respect to the 1x1017 n/cm2 threshold for the other 4nozzles.Westinghouse Electric Company determined the magnitude of the fluence for these 4nozzles at 60 and 80 years of plant operation and the time (in EFPY) when the fluenceat each of the postulated flaw locations reaches lxi 10 n/cm2 (E > 1.0 MeV). Theresults of the fluence modeling have been documented by Westinghouse ElectricCompany in WCAP-18015-NP, Revision 0, Extended Beltline Pressure Vessel FluenceEvaluations Applicable to North Anna 1 & 2.WCAP-1 8015-NP indicates that the 1/4T location for 2 of the 12 nozzles will reach thelxi1017 n/cm2 fluence threshold of concern prior to 54 EFPY.* For Unit 1, the 1/4 T Flaw in Inlet Nozzle 1 is projected to reach lxi1017 n/cm2at approximately 48.5 EFPY, which corresponds to December 26, 2034. Thelicense renewal operating period NAPS Uhit i runs~through April 1, 2038.* For Unit 2, the 1/4 T Flaw in Inlet Nozzle 1 is projected to reach 1x1017 n/cm2at approximately 49.1 EFPY, which corresponds to October 15, 2036. Thelicense renewal operating period NAPS Unit 2 runs through August 21, 2040.Thus, the fluence at the postulated 1/4T flaw location in the NAPS Unit I and Unit 2 #1inlet nozzles are projected to exceed the 1x1017 n/cm2 threshold prior to reaching theend of the licensed operating period.
Serial No. 15-022ADocket Nos. 50-338/339Attachment 1Page 2 of 2While the fluence is projected to exceed the lx1017 n/cm2 threshold for the #1 inletnozzles prior to the end of licensed operating period this does not necessarily indicatethat the existing heatup and cooldown curves will become non-conservative prior toreaching the end of the licensed operating period. However, new limit curves will needto be constructed for the Unit 1 and Unit 2 #1 inlet nozzles and compared to theapproved Technical Specification limit curves for the other vessel materials to determineif the existing P-T curves are adequate through the end of the licensed operating period.The assessment of the #1 inlet nozzles must be completed under a schedule thatprovides sufficient time to amend the existing heatup and cooldown curves, if required.Below is the schedule for revising the P-T curves, if necessary.1. Develop new limit curves for the Unit 1 and Unit 2 #1 inlet nozzles no laterthan December 26, 2031 to determine if the existing P-T curves areconservative through the end of the licensed operating period.2. Notify the NRC of the assessment results of the new Unit I and Unit 2 #1 limitcurves for the inlet nozzles no later than March 31, 2032. This will validate ifthe existing heatup and cooldown curves are conservative or if they will* require revision prior to end of the licensed operating period.3. If the existing P-T curves require revision, a license amendment request willbe submitted to the NRC for new P-T curves by January 31, 2032. Asubmittal date of January 31, 2032 bounds the projected time for exceedingthe Unit I1lx1017n/cm2fluence threshold projected to occur at 48.5 EFPY.