ML12060A259

Request for Additional Information Regarding the License Amendment Requests for a Measurement Uncertainty Recapture Power Uprate

ML12060A259
Person / Time
Site:	Oconee
Issue date:	03/12/2012
From:	Stang J Plant Licensing Branch II
To:	Gillespie P Duke Energy Carolinas
Stang J
References
TAC ME7164, TAC ME7165, TAC ME7166
Download: ML12060A259 (11)

Text

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 March 12,2012 Mr. Preston Gillespie Site Vice President Oconee Nuclear Station Duke Energy Carolinas, LLC 7800 Rochester Highway Seneca, SC 29672

SUBJECT:

OCONEE NUCLEAR STATION, UNITS 1, 2, AND 3 (ONS) - REQUEST FOR ADDITIONAL INFORMATION (RAI) REGARDING THE LICENSE AMENDMENT REQUESTS (LARs) FOR A MEASUREMENT UNCERTAINTY RECAPTURE (MUR) POWER UPRATE (TAC NOS. ME7164, ME7165, AND ME7166)

Dear Mr. Gillespie:

By letter dated September 20, 2011, as supplemented by letter November 21, 2011, Duke Energy Carolinas, LLC (the licensee), submitted a LAR for ONS which proposes revisions to the current licensing basis to allow a measurement uncertainty recapture (MUR) power uprate.

The Nuclear Regulatory Commission (NRC) staff is in the process of reviewing the LARs and has determined that additional information is required in order to complete the review. The requested additional information is enclosed. Draft RAls were provided to your staff electronically, and telephone calls between your staff and the NRC staff have occurred to ensure that the right level of detail is provided in the RAI responses. Mr. Kent Alter of your staff has agreed to responses to the RAls by March 16,2012.

If you have any questions, please contact me at 301-415-1345.

Sincerely,

~s~~enior Project Manager Plant Licensing Branch 11-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos. 50-269, 50-270, and 50-287

Enclosure:

RAI cc w/encl: Distribution via Listserv

REQUEST FOR ADDITIONAL INFORMATION (RAI)

LICENSE AMENDMENT REQUESTS (LARs)

TO REVISE PORTIONS OF THE UPDATED FINAL SAFETY ANAYLSIS REPORT (UFSAR)

RELATED TOTHE MEASUREMENT UNCERTAINTY RECAPTURE (MUR) POWER UPRATE DUKE ENERGY CAROLINAS, LLC OCONEE NUCLEAR STATION, UNITS 1,2, AND 3 (ONS 1/2/3)

DOCKET NOS. 50-269, 50-270, AND 50-287 Sy letters dated September 20, 2011 (Agencywide Documents Access and Management System, (ADAMS) Accession No. ML11269A127), as supplemented by letter dated November 21, 2011 (ADAMS Accession No. ML11326A296), Duke Energy Carolinas, LLC (the licensee), submitted a license amendment request (LAR) to the U.S. Nuclear Regulatory Commission (NRC) for ONS 1/2/3 which propose revisions to the current licensing basis to allow a measurement uncertainty recapture (MUR) power uprate. The NRC staff is in the process of reviewing the LARs and has determined that the following RAls are required in order to complete the review.

RAI1 In Enclosure 2,Section V.1 of the LAR, "The Main Power System," the licensee stated that the Isolated Phase Sus (IPS) has adequate electrical capacity for the upgrade, but has experienced cooling problems, and discussed this cooling problem in LAR Section VI.1.C. In Enclosure 2,Section VI.1.C, of the LAR "Safety-related Cooling Water System," the licensee stated that, the IPS ventilation systems for ONS 1/2/3 do not meet the original nameplate design flow which correlates to issues for IPS cooling capacity. During periods with elevated temperatures, the cooling system is not capable of providing the cooling necessary to remove the IPS resistance heating. This condition requires that the licensee must either provide supplemental cooling or limit the maximum thermal power. During these conditions, the full potential of the MUR power uprate may not be realized.

a) Provide the current IPS capacity/Ampere rating versus the capacity/Ampere rating required for MUR power uprate conditions.

b) Provide a discussion on the proposed supplemental/enhanced cooling to the IPS for operation at MUR power uprate conditions.

Enclosure

-2 RAI2 In Enclosure 2,Section V.1, of the LAR The Main Power System," the licensee stated that the Main Power System continues to have adequate capacity and capability for plant operation with an MUR power uprate, and is bounded by the existing analyses and calculations.

Discuss the adequacy of the main power system to support the above statement, providing current capacity/rating versus the capacity/rating required for the MUR power uprate conditions for the generator, main step-up transformer, unit auxiliary transformer, start-up transformer, and also CT-4 transformer as indicated in Section V.I.A of the LAR.

RAI3 In Enclosure 2,Section V.I, of the LAR "AC Distribution", the licensee stated that all alternating current (AC) distribution systems continue to have adequate capacity and capability for plant operation with an MUR power uprate and are bounded by the existing analysis and calculations.

a) Provide a discussion of the alternating current (AC) power distribution system (6.9 kiloVolt (kV) down to 120 Volt (V) buses) load changes due to the uprate as listed in the LAR Section V.1, in support of the above statement.

b) Identify the affected loads/motors, and provide the increases in the brake horsepower of the motors due to the MUR power uprate. Compare finding with the rated horsepower of the affected motors.

c) If any AC bus is affected, confirm that the affected buses wi" not result in unacceptable steady-state voltages, overload or exceed the short circuit ratings.

d) Discuss the impact, if any, of the MUR power uprate on the existing protective relay settings.

RAI4 In Enclosure 2,Section V.1, of the LAR "DC [direct current] Distribution," the licensee stated that a" DC systems continue to have adequate capacity and capability for plant operation after the MUR power uprate, and are bounded by the existing analyses and calculations.

Describe changes in DC power system loading due to the MUR power uprate, if any, and provide a discussion of capacity margins available in the Class 1E batteries.

RAI5 In enclosure 2,Section V.1, of the LAR "Switchyard Systems", the licensee stated that all switchyard systems continue to have adequate capacity and capability for plant operation with an MUR power uprate and are bounded by the existing analyses and calculations.

- 3 Provide a summary of the evaluation that supports the above statement, confirming that adequate margin exists between the maximum worst case steady-state load and the switchyard equipment ratings.

RAI6 In enclosure 2,Section V.1.A, of the LAR "Emergency Diesel Generators," the licensee stated that the equivalent source for emergency system is Keowee Hydro Station and MUR power uprate will not change the loading of the Keowee Hydro units.

Provide a current main single line diagram that identifies and shows the interconnection of the equipment described in this section. Provide a summary of the evaluation that supports your conclusion that plant operation under MUR power uprate conditions are bounded by the loading tables as indicated in Section V.1.A of the LAR.

RAI7 In Enclosure 2,Section V.1.B, of the LAR "Station Blackout [SBO]," the licensee stated that SBO systems continue to have adequate capacity and capability for plant operation for the MUR power uprate and are bounded by the existing analyses and calculations.

Provide a summary of the Class 1E battery sizing calculations that demonstrates sufficient capacity exists for the four-hour SBO coping duration under MUR power uprate conditions.

RAI8 In enclosure 2,Section V.1.C, of the LAR "Environmental Qualification [EQ] of Electrical Equipment," the licensee stated that they have reviewed the Oconee EQ program for the MUR power uprate and determined that no EQ Program changes are required as a result of the MUR power uprate.

Provide a summary of the evaluation that supports the above statement. In the response, provide a discussion/summary of temperature, pressure, and radiation levels/profiles to demonstrate that electrical equipment that is required to be environmentally qualified will continue to remain qualified (including any required margins) under MUR power uprate conditions.

RAI9 Provide a discussion on the auxiliary power requirements for the Cameron Flowmeter, such as DC or AC power requirements, and its loading impact, if any, on the associated safety-related or non-safety-related power systems.

-4 RAI10 The NRC staff requests the licensee to verify that (1) the MUR power uprate will not require any change in procedures and resources necessary for systems required to achieve the nuclear safety performance criteria, and are adequate for the MUR power uprate, and (2) require any new recovery actions meet the nuclear safety performance criteria in accordance National Fire Protection Association (NFPA) 805 licensing basis.

RAI11 Some plants credit aspects of their fire protection system for other than fire protection activities, e.g., utilizing the tire water pumps and water supply as backup cooling or inventory for nonprimary reactor systems. If ONS 1/2/3, credits its tire protection system in this way, the LAR should identify the specitic situations, and discuss to what extent, if any, the MUR power uprate affect these "non-tire-protection" aspects of the plant tire protection system. If ONS 1/2/3 do not take such credit, the NRC staff requests that the licensee verify this as well. In your response discuss how any non-fire suppression use of tire protection water will impact the ability to meet the tire protection system design demands.

RAI12 The LAR states that core power level could be determined with a power measurement uncertainty of approximately plus or minus (+/-) 0.34 percent. However, the Caldon Ultrasonic Engineering Report ER-824 submitted as Attachment 6.2 of this LAR, shows that the power uncertainty using a leading edge flow meter (LEFM) CheckPlus system is +/- 0.31 percent. .7 of this LAR provides the Oconee's Secondary Power Uncertainty Analysis. In this attachment, the licensee calculated the uncertainty in the secondary side heat balance measurement of thermal power. Appendix G of Attachment 6.7 describes the calculation for the secondary power uncertainty using Cameron's LEFMs and the other new instrumentation strings. Appendix G shows that the secondary power uncertainty using LEFMs is +/-0.34 percent. It is understood that the secondary calorimetric power calculation is used to determine plant power in the event of a loss of LEFM signal. In support of this request, please:

a. Explain why ONS 1/2/3 is using the +/-0.34 percent power uncertainty calculated for the secondary power side to determine the core power level, instead of the 0.31 percent power reported in the Caldon Ultrasonic Engineering Report.

b. Appendix G, page 134 states: 'This Appendix calculates the secondary power uncertainty using Cameron's LEFMs and the other new instrumentation strings." Please clarify what "the other new instrumentation strings" means. This LAR only considers the modification using the LEFM CheckPlus system.

c. Describe how the uncertainty using Cameron's LEFM CheckPlus was used to determine ONS 11213 Secondary Power Uncertainty Analysis reported in Attachment 6.7. In particular how the terms were grouped and show that tolerance limits for this calculation have been based on a statistically sufficient quantity of sample data to bound these values and provide a confidence that the interval contains 95 percent of the population.

- 5 RAI13 Section 4 of Enclosure 1 of the LAR states that the licensee has evaluated the potential impact of pending/future LARs on the MUR evaluation (or vice versa), and that they were included in this LAR. The following pending/future LARS were identified :

• Change to Reactor Vessel Inspection Plan

• Tornado/High Energy Line Break

• Main Steam Isolation Valves

• Protected Service Water Please clarify if the MUR power uprate is dependent on prior approval any of the above LARs.

RAI14 , Item 1.1, of the LAR provided a description of the plant-specific implementation of the feedwater flow measurement technique. The information provided in the LAR does not describe the arrangement, the instrumentation in the complete system that would acquire the flow data and calculate the power level, or whether the lEFM would provide data to the plant process computer system for use in the calorimetric power algorithm.

Describe how the data from the lEFM will be used (or not) if the plant computer fails. Provide a diagram that depicts functionally the instrumentation used to perform the secondary calorimetric; using either the feedwater flow venturi or the lEFM CheckPlus system.

RAI15 , Item 1.1.0, of the LAR Criterion 3 from ER-80P "Improving Thermal Power Accuracy and Plant Safety While Increasing Operating Power level Using the lEFM Check System," Revision 0, March, 1997, requires the licensee to confirm that the methodology used to calculate the uncertainty of the lEFM in comparison to the current feedwater instrumentation is based on accepted plant setpoint methodology. It is not clear if the response provided addresses the request of Criterion 3. To support the NRC staff review, please clarify the following:

a. Confirm that the lEFM uncertainty calculation referenced in Oconee's response is the calculation provided in the Caldon Ultrasonic Engineering Report, Attachment 6.2 of this LAR.

b. Identify the calculation that Oconee uses to estimate the overall heat balance uncertainty using the lEFM CheckPlus system.

-6 RAI16 , Item 1.1.0, Criterion 1 from ER-157P, Cameron Engineering Report ER-157(P-A),

"Supplement to Cameron Topical Report ER-80P: Basis for Power Uprates with an LEFM Check or CheckPlus," Revision 8, May 2008, requires the licensee to justify continued operation at the pre-failure power level for a pre-determined time and the decrease in power that must occur following that time. The response provided in the LAR states that an engineering evaluation was performed to justify an allowed outage time upon loss of the LEFM signal.

Also, the response provided for this criterion states that the analysis performed established a bounding uncertainty of 0.037 percent RTP, rounded to 0.04 percent rated thermal power (RTP), over a 7-day period for Oconee Unit 3 at operating levels above 90 percent RTP. This result would allow Oconee to maintain the new power level for up to 7 days. Please note that the NRC staff position in approval of MURs has been to allow licensees to maintain the new power level for up to 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> when the LEFM failed. Thus, provide a justification for determining the allowed outage time (AOT) of the LEFM to be for a 7-day period. In particular, how using the last acceptable LEFM calorimetric power calculation with the additional bias is acceptable to maintain the new power level for up to 7 days.

Also, in support of this request, please provide information on the following:

a. Please provide a description of what level of Cameron LEFM CheckPlus degradation or system alert would render the Cameron LEFM CheckPlus to be declared non-operational. Describe how the degraded status of the LEFM CheckPlus will be determined.

b. If the power level is below the Current Licensed Thermal Power at the time the Cameron LEFM CheckPlus is declared non-operational or if the power level drops below the current licensed thermal power during the AOT, describe what administrative control will be used to assure that power won't be raised above the current licensed thermal power prior to the Cameron LEFM CheckPlus becoming operational.

c. Please clarify the use of the bounding uncertainty of 0.04 percent RTP when the LEFM failed. Is this a bias or a correction factor for the venturi flowmeter?

d. Please identify the engineering evaluation performed and provide a copy of this evaluation, as well as a summary of the data collected with its references (e.g., fouling, drift, etc.) to determine the bounding uncertainty of 0.04 percent RTP.

e. This section states that if the LEFM cannot be restored within 7 days and the power level, overpower trip setpoint and flux/flow trip setpoint cannot be reduced within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />, then the unit shall be placed in Mode 3. Provide a justification for placing the unit in Mode 3 when the conditions described before are presented.

f. Please provide mark up of the Technical Specification (TS) pages where the requirements for the operators to perform the following activities will be located:

• Calorimetric calculations when the LEFM CheckPlus system failed,

-7

• After LEFM signal is not available after 7 days, then within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> the unit will be reduced to no more than 2568 megawatt thermal (MWt) (the previously licensed rated thermal power), the overpower trip setpoint will be reduced, and the flux/flow trip setpoints will be adjusted as specified in the Core Operating Limits Report, and

• If the power level, overpower trip setpoint and flux/flow trip setpoint cannot be reduced within six hours, then the unit shall be placed in Mode 3 within the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />.

g. The LAR states: "This (bounding) uncertainty has a 95 percent statistical probability at a 95 percent confidence level. The analysis demonstrates that the drift is random and not uni-directional." Provide data to show that tolerance limits for this calculation have been based on a statistically sufficient quantity of sample data to bound these values and provide a confidence that the interval contains 95 percent of the population.

RAI17 , Item 11.10, of the LAR describes the calculation of the reactor protection system trip function allowable values (AVs) for the high 'flux trip setpoint following the power uprate. To support the NRC staff review, please provide the following information:

a. This section of the LAR states that the current safety analysis setpoint method is described in Chapter 4 of DPC-NE-3005-PA, Revision 3b, "Oconee Nuclear Station UFSAR Chapter 15 Transient Analysis Methodology." Please provide a copy of the method used to determine the high flux trip setpoint AV.

b. The high flux trip setpoint AV is currently 105.5 percent of 2568 MWt (2709.2 MWt).

The high flux trip setpoint assumed in the safety analyses was increased to 107.5 percent of 2568 (2760.6 MWt).

Following the uprate, the 105.5 percent setpoint will be retained such that the new Technical Specification AV will be 105.5 percent of 2610 (2753.6 MWt). Following NRC approval of the MUR, Duke Energy intends to use the proposed trip setpoint (2753.6 MWt) whenever a particular analysis is revised. Please clarify if proposed trip setpoint of 2753.6 MWt for revising safety analysis will be used. Justify using this value, which does not leave any extra margin for reactor trip on high flux.

c. This section of the LAR describes the proposed setpoint for the new high flux trip AV for the 3 Reactor Coolant Pumps (RCPs) operation. This description states that the proposed setpoint maintains the 4 RCP difference between rated thennal power and the high flux trip setpoint, i.e., 5.5 percent RTP. The proposed setpoint was determined to be 79.3 percent of 2610 MWt, or 2069.7 MWt. To calculate this value, Oconee used the MWt for the current operation with 3 RCPs - the current nominal power level is 75 percent of 2568 MWt, which will become 73.8 percent of 2610 MWt, or 1926 MWt.

Then adding 5.5 percent to 73.8 percent yields the proposed setpoint of 79.3 percent. It is not clear why 5.5 percent RTP is added to the setpoint for the high flux trip AV for 3 RCPs. Further, Enclosure 2 Item 11.10, item 6a, of the LAR "Loss of coolant flow - flow coastdown," states: "the maximum allowed operating power for 3 RCPs (Technical Specification 3.4.4) will remain at 1926 MWt (now 73.8 percent RTP if 2610 MWt)."

-8 Please explain adding 5.5 percent to determine the new setpoint for the high flux trip AV for 3 RCPs.

d. This section states that if the LEFM is out of service for longer than 7 days, the high flux trip setpoint is returned to the pre-MUR uprate value of 2709.2 MWt (103.8% of 2610 MWt). According to the response provided in Enclosure 2, Item 1.1. D, Criterion 1 from ER-157P, if the LEFM is out of service the unit will decrease power to the pre-MUR licensed thermal power level of 2568 MWt, so the licensee should not reference the MUR uprate value when the LEFM is out of service for longer than the Selected Licensee Commitment (SLC) allowance.

e. Please clarify how the setpoint for 3 RCPs in operation when the LEFM is out of service for longer than the SLC allowance is calculated. Technical Specification 3.4.4 states that power should be reduced to 75 percent RTP when 3 RCPs are in operation.

RAI18 Item V1I1.1.B of the LAR states that the Flux-Flow Imbalance setpoints were reviewed based on the increased power level and it was determined that the Flux-Flow Imbalance envelope could remain unchanged. Section 3 of Enclosure describes proposed changes to accommodate the MUR power uprate. This section does not describe the review performed by Oconee to determine that the Flux-Flow Imbalance envelope could remain unchanged. Please describe how these setpoints were reviewed, and how it was determined that its envelope can remain unchanged.

RAI19 The MUR power uprate can have an adverse affect on steam generator (SG) tube vibration and wear rates due to the changes in temperature, pressure and flow associated with the uprate. In Section IV.1.F of the LAR, the licensee stated that the effects of the MUR on the axial flow induced vibration, and subsequently on tube wear rate, tube plugging and life expectancy, will be insignificant based on the results of an experimental program.

Please provide a description and the results of the experimental program that was used to determine that the effects of the MUR on axial flow induced vibration would be insignificant.

RAI20 Specify which adjusted reference temperature (ART) values and materials were limiting pre uprate for the purposes of heatup and cooldown pressure-temperature limit curves; and how these ART'values would be impacted by the MUR power uprate.

RAI21 Specify whether different ART values and materials would be limiting for the purposes of heatup and cooldown press-temperature limit curves post-uprate; and how these ART values would change due to the MUR power uprate.

- 9 RAI22 Report the limiting ART values for the purposes of heatup and cooldown pressure-temperature limit curves taking into consideration the effective full power years 48 effective fuel power years

[EFPY] fluence projections for the end of the license renewal period with MUR power uprate conditions; and report whether this would impact the current heatup and cooldown press-temperature limit curves.

RAI23 Confirm that under MUR power uprate conditions the assumptions within BAW-2275, "Low Upper-Shelf Toughness Fracture Mechanics Analysis of B&W [Babcock and Wilcox] Designed Reactor Vessels for 48 EFPY," are still bounding for ONS 1/213, and consistent with the NRC Safety Evaluation for BAW-2275 found in Appendix B of BAW-2251. Confirmation is expected to include the quotation of relevant passages from BAW-2275 and BAW-2251, the property ranges covered in those documents that would be influenced by the uprate, and the minimum acceptable Oconee Upperhelf Energy values defined in those documents for each unit.

RAI24 In Section VII.I of the LAR, credit is taken for approved plant procedures, and processes such as the modification process. Please summarize or provide copies of the procedures and processes that are used to develop or change human factors interfaces, such as procedures, training, or physical changes to the control/display interfaces, and procedures that address verification and validation of operator actions and interfaces. Include specific references by procedure number and title.

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