ML13298A116

NRR E-mail Capture - SE Input for Proprietary Review

ML13298A116
Person / Time
Site:	Braidwood
Issue date:	09/30/2013
From:	Joel Wiebe Division of Operating Reactor Licensing
To:	Holden L Exelon Corp
References
Download: ML13298A116 (53)

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NRR-PMDAPEm Resource From: Wiebe, Joel Sent: Monday, September 30, 2013 4:51 PM To: Leslie Holden Cc: David Gullott

Subject:

SE Input for Proprietary Review Attachments: SRXB Input for Proprietary Review.docx Please note that this is not the final SE input, but we would like you and your vendor to review this for proprietary information.

1

Hearing Identifier: NRR_PMDA Email Number: 882 Mail Envelope Properties (Joel.Wiebe@nrc.gov20130930165100)

Subject:

SE Input for Proprietary Review Sent Date: 9/30/2013 4:51:10 PM Received Date: 9/30/2013 4:51:00 PM From: Wiebe, Joel Created By: Joel.Wiebe@nrc.gov Recipients:

"David Gullott" <David.Gullott@ExelonCorp.com>

Tracking Status: None "Leslie Holden" <Leslie.Holden@exeloncorp.com>

Tracking Status: None Post Office:

Files Size Date & Time MESSAGE 139 9/30/2013 4:51:00 PM SRXB Input for Proprietary Review.docx 189232 image001.jpg 11888 Options Priority: Standard Return Notification: No Reply Requested: No Sensitivity: Normal Expiration Date:

Recipients Received:

REACTOR SYSTEMS BRANCH SAFETY EVALUATION INPUT TO BYRON STATION UNITS 1 AND 2 AND BRAIDWOOD STATION UNITS 1 AND 2 MEASUREMENT UNCERTAINTY RECAPTURE POWER UPATE

1.0 INTRODUCTION

By letter dated June 23, 2011, Exelon Generation, the licensee for Braidwood Station Units 1 and 2 and Byron Station Units 1 and 2, submitted a License Amendment Request (LAR) to revise the Operating License and Technical Specifications as necessary to increase the licensed core power level by approximately 1.63 percent from the Current Licensed Thermal Power (CLTP) of 3586.6 Megawatts Thermal (MWt) to 3645 MWt (Reference V). An audit was also performed to verify information necessary to the completion of this evaluation.

The proposed amendment is based on the use of the Cameron Leading Edge Flow Measurement (LEFM) CheckPlus ultrasonic, multi-path, transit time flowmeter system that would decrease the uncertainty in the measurement of feedwater flow, thereby decreasing the power level measurement uncertainty from 2.0% to 0.37%.

The proposed power uprate is based on a redistribution of analytical margin originally required of Emergency Core Cooling System (ECCS) evaluation models performed in accordance with the requirements set forth in Title 10 of the US Code of Federal Regulations, Part 50, Appendix K, and ECCS Evaluation Models (Reference 3). Appendix K mandated consideration of 102%

of the licensed power level for ECCS evaluation models of light water reactors. The U.S.

Nuclear Regulatory Commission approved a change to the requirements of 10 CFR 50, Appendix K, on June 1, 2000. The change provided licensees with the option of maintaining the 2% power margin between the licensed power level and the assumed power level for the ECCS evaluation, or applying a reduced margin for ECCS evaluation based on the accounting of uncertainties due to instrumentation error.

In large part, the basis for acceptability of this proposed amendment is that the Measurement Uncertainty Recapture (MUR) power level conditions are bounded by the current analyses of record.

The Office of Nuclear Reactor Regulations (NRRs) Reactor Systems Branch (SRXB) has responsibility for review of Ultrasonic Flow Meters (UFMs) thermal-hydraulic, certain mechanical aspects, accident analysis, and related topics that potentially affect UFM performance. NRRs Instrumentation and Controls Branch (EICB) covers instrument uncertainty and everything from the electrical and mechanical connections at the spool piece to and including the displays that indicate FW flow rate. This Safety Evaluation (SE) is limited to the thermal hydraulic aspects of the CheckPlus UFM, including some aspects of the transducers that may influence the perceived flow profile, accident analysis and consideration of the associated uncertainty.

ENCLOSURE

2.0 REGULATORY EVALUATION

Early revisions of 10 CFR 50.46, and Appendix K to 10 CFR 50, required licensees to base their Loss-Of-Coolant Accident (LOCA) analysis on an assumed power level of at least 102% of the licensed thermal power level to account for power measurement uncertainty. The NRC later modified this requirement to permit licensees to justify a smaller margin for power measurement uncertainty. Licensees may apply the reduced margin to operate the plant at a level higher than the previously licensed power. The licensee proposed to use a Cameron Linear Elastic Fracture Mechanics (LEFM) CheckPlus system to decrease the uncertainty in the measurement of feedwater flow, thereby decreasing the power level measurement uncertainty from 2.0% to 0.37%.

The licensee developed its LAR consistent with the guidelines in NRC Regulatory Issue Summary (RIS) 2002-03, Guidance on the Content of Measurement Uncertainty Recapture Power Uprate Applications.

3.0 TECHNICAL EVALUATION

3.1 Background Nuclear power plants are licensed to operate at a specified core thermal power. The uncertainty of the calculated value of this thermal power is a significant input into the probability of the plant exceeding the power levels assumed in the design-basis transient and accident analyses. In this regard, Appendix K, ECCS Evaluation Models, to Title 10 of the Code of Federal Regulations (10 CFR) Part 50, Domestic Licensing of Production and Utilization Facilities, originally required LOCA and ECCS analyses to assume that the reactor had been operating continuously at a power level at least 102.0 percent of the licensed thermal power to allow for uncertainties such as instrument error. To reduce an unnecessarily burdensome regulatory requirement and to avoid unnecessary exemption requests, the Commission published a revised rule in the Federal Register (65 FR 34913; June 1, 2000). This rule amended the requirement in Appendix K to allow applicants the option of justifying a smaller margin for power measurement uncertainty by using more accurate instrumentation to calculate the reactor thermal power.

In existing nuclear power plants, the neutron flux instrumentation continuously indicates the reactor core thermal power. This instrumentation must be periodically calibrated to accommodate the effects of fuel burnup, flux pattern changes, and instrumentation setpoint drift.

The reactor core thermal power generated by a nuclear power plant is determined by steam plant calorimetry, which is the process of performing a heat balance around the nuclear steam supply system (called a calorimetric). The accuracy of this calculation depends primarily upon the accuracy of Feedwater (FW) flow rate and FW net enthalpy measurements. As such, an accurate measurement of FW flow rate and temperature is necessary for an accurate calibration of the nuclear instrumentation. Of the two parameters, flow rate and temperature, the most important in terms of calibration sensitivity is the FW flow rate.

The originally installed instruments for measuring FW flow rate in existing nuclear power plants were usually a venturi or a flow nozzle, each of which generates a differential pressure proportional to the FW velocity in the pipe. Of the two, the venturi was the most widely used because of relatively low head loss. However, error in determination of flow rate is introduced

due to venturi fouling and, to a lesser extent, flow nozzle fouling, the transmitter, and the analog-to-digital converter.1 Because of the desire to reduce flow instrumentation uncertainty to enable operation of the plant at a higher power while remaining within the licensed rating, the industry assessed alternate flow rate measurement techniques and found that UFMs are a viable alternative. UFMs are based on computer-controlled electronic transducers that do not have differential pressure elements that are susceptible to fouling. Caldon, Inc.2 developed a UFM called a leading edge flow meter and named it the LEFM Check system. It followed this with the LEFM CheckPlus system, which consists essentially of two Check systems in the same spool piece and provides a more accurate FW flow measurement than the Check system. Both of these UFMs have demonstrated better measurement accuracies than the differential pressure type instruments and provide on-line verification to ensure that the UFM is operating within its uncertainty bounds.

Caldon submitted an engineering report, ER-80P (Reference A), in March, 1997, that describes the LEFM, includes calculations of power measurement uncertainty using a Check system in a typical two-loop pressurized-water reactor or a two-FW-line boiling-water reactor, and provides guidance for determining plant-specific power calorimetric uncertainties. The U.S. NRC staff approved this report for an exemption to the 2 percent uncertainty requirement in Appendix K to 10 CFR Part 50 and approved a 1% power uprate for using the LEFM (Reference B). Following publication of the amendment to Appendix K that allowed for an uncertainty less than 2 percent, Caldon submitted a supplement to ER-80P, ER-160P (Reference C) that the NRC staff approved in Reference D for up to a 1.4% power uprate. Subsequently, the NRC staff approved ER-157P, Revision 5, (Reference E) for up to a 1.7% power uprate using the CheckPlus system (References E and F) and recently approved ER-157P, Revision 8 (References G and H).

Revision 8 corrects minor errors in Revision 5, provides clarifying text, and incorporates revised analyses of coherent noise, non-fluid delays, and transducer replacement. It also adds two new appendices, Appendix C and Appendix D, which describe the assumptions and data that support the coherent noise and transducer replacement calculations, respectively.

Byron and Braidwood were originally designed with FW flow and temperature instrumentation consisting of venturis, differential pressure transmitters, and thermocouples. Modifications required for the MUR power uprate include installation of the CheckPlus system. Existing FW flow and temperature instrumentation will be retained and used for comparison monitoring of the LEFM system and as a backup FW flow measurement when needed.

The FW flow measurement system to be permanently installed is a Cameron LEFM CheckPlus ultrasonic 8-path transit time flowmeter. As discussed above, the CheckPlus design is addressed in Topical Reports ER-80P, ER-160P, and ER-157P that have been approved by the NRC. It will be used for continuous calorimetric power calculation determination by providing FW mass flow and FW temperature input data to the plant computer system that is used for automated performance of the calorimetric power calculations.

1 Venturi will generally be used in the remainder of this document to reference both venturis and flow nozzles.

2 Caldon Ultrasonics is now part of Cameron Measurement Systems.

The CheckPlus system is stated to consist of one flow element (spool piece) installed in each of the Steam Generator (SG) FW flow headers. The FW piping configurations are stated to have been explicitly modeled as part of the CheckPlus meter factor and accuracy assessment testing performed at Alden Research Laboratories (ARL). The planned installation location of each CheckPlus is stated to conform to the applicable requirements in Camerons Installation and Commissioning Manual and Cameron Topical Reports ER-80P and ER-157P and the bounding uncertainty analysis is stated to be addressed by ER-720.

3.2 Acceptance Criteria General acceptance criteria apply to all aspects of testing in a certified facility, transfer from the test facility, initial operation, and long-term in-plant operation. These criteria are:

• Traceability to a recognized national standard. This requires no breaks in the chain of comparisons, all chain links must be addressed, and there can be no unverified assumptions.

• Calibration.

• Acceptable addressing of uncertainty beginning with an initial estimate of the bounding uncertainty and continuing through all aspects of initial calibration in a certified test facility, transfer to the plant, initial operation, and long-term operation.

For CheckPlus, meeting these criteria includes documenting:

Design and characteristics information, Calibration testing at a certified test facility, any potential changes associated with differences between testing and plant operation including certification that initial operation in the plant is consistent with pre-plant characteristics predictions, and in-plant operation.

When it originally approved ER-80P and ER-157P, the NRC established four criteria that applicants were to address. The criteria and the applicant responses in Reference V are as follows:

Criterion: Discuss maintenance and calibration procedures that will be implemented with the incorporation of the LEFM, including processes and contingencies for inoperable LEFM instrumentation and the effect on thermal power measurements and plant operation.

NRC Staff Comments: Implementation should include developing the necessary procedures and documents required for LEFM maintenance and calibration. Plant maintenance and calibration procedures should include Camerons maintenance and calibration requirements prior to declaring the CheckPlus system operational and raising

power above approximately 90% of the licensed thermal power. Preventive maintenance scope and frequency should be based on vendor recommendations.

Maintenance should be performed by personnel qualified on the CheckPlus system.

Maintenance and test equipment, setting tolerances, calibration frequencies, and instrumentation accuracy should be accounted for within the thermal power uncertainty calculation. Uncertainty should be at the 95% probability and 95% confidence level.

Applicant Response: Implementation of the MUR power uprate license amendment will include developing the necessary procedures and documents required for continued calibration and maintenance of the LEFM system. Plant maintenance and calibration procedures will be revised to incorporate Camerons maintenance and calibration requirements prior to raising power above the CLTP of 3586.6 MWt. The Byron and Braidwood Station Technical Requirement Manuals (TRM) will be revised as discussed in Sections I.1.G and H below, and in Attachment 1 to the LAR to address contingencies for inoperable LEFM instrumentation.

Preventive maintenance will be performed based on vendor recommendations. The preventive maintenance program and LEFM CheckPlus system continuous self-monitoring feature ensure that the LEFM remains bounded by the Topical Report ER-80P (Reference I-1), as supplemented by ER-157P (Reference I-2), analysis and assumptions. Establishing and continued adherence to these requirements assures that the LEFM CheckPlus system is properly maintained and calibrated. The preventive maintenance activities will be identified via the associated plant modification package.

Typical activities performed include power supply checks, pressure transmitter checks, and clock verifications. Maintenance of the LEFM system will be performed by personnel who are qualified on the LEFM.

Instrumentation, other than the LEFM system, that contributes to the power calorimetric computation will be periodically calibrated and maintained using existing site procedures.

Maintenance and test equipment, tolerance settings, calibration frequencies, and instrumentation accuracy were evaluated and accounted for in the thermal power uncertainty calculation.

NRC Staff Assessment: The licensee response included references to Cameron reports and discussed how the licensee will install and maintain the LEFMs at the four plants. The licensee referenced operation and contingences for inoperable LEFM later in the LAR and it is discussed below in 3.5.2.1. The applicant has acceptably addressed Criterion 1.

Criterion: For plants that currently have LEFMs installed, provide an evaluation of the operational and maintenance history of the installation and confirmation that the installed instrumentation is representative of the LEFM system and bounds the analysis and assumptions set forth in Topical Report ER-80P.

Applicant Response: At the time of this submittal, only Byron Station Unit 1 and Braidwood Station Unit 2 have installed the LEFM CheckPlus systems. Based on the results of the modification and commission testing the LEFM CheckPlus system as installed is in conformance with the analysis and assumptions given in Camerons Topical Report ER-80P (Reference I-1), ER-157P (Reference I-2), and the Byron and

Braidwood unit specific Bounding Uncertainty Analysis for Thermal Power Determination Reports (References I-7a through d), as well as the performance parameters identified in the Alden Laboratory Meter Factor Calculation and Accuracy Assessments (References I-5a through 5d). As of June 17, 2011, there have been no performance, operational, or maintenance issues that would indicate any non-conformance with the above.

NRC Staff Assessment: The licensee provided the above response. The staff also audited an occurrence at the Byron Station Unit 1 with comparisons of the UFM and the venturi and plant parameter data. This is detailed in Section 3.8. Based upon the above response and the staff audit of information provided by the licensee, the licensee has acceptably addressed Criterion 2.

Criterion: Confirm that the methodology used to calculate the CheckPlus uncertainty in comparison to the current FW instrumentation is based on accepted plant setpoint methodology (with regard to the development of instrument uncertainty). If an alternative approach is used, the application should be justified and applied to both venturi and ultrasonic flow measurement instrumentation installations for comparison.

NRC Staff Comments: The applicant should address the calculation of uncertainty.

For example, CheckPlus system uncertainty calculation methodology is usually based on a Square-Root-Sum-of-Squares (SRSS) calculation for independent contributors to uncertainty with addition of uncertainties associated with dependent contributors to uncertainty.

Applicant Response: Cameron has performed Unit specific bounding uncertainty analysis for Byron and Braidwood Stations, Unit 1 and 2 (References I-7a through 7d).

Copies of these analyses are provided in attachments 8a through 8d of the LAR. The calculations in these analyses are consistent with Cameron's Topical Report ER-80P (Reference I-1), as supplemented by ER-157P (Reference I-2), ISA-RP67.04.02-2000, Methodologies for the Determination of Setpoints for Nuclear Safety-Related Instrumentation (Reference I-8) and Exelon standard NES-EIC-20.04 (Rev. 5). This approach has been approved by the NRC in References I-3 and I-4. The core thermal power uncertainty calculation which takes into account the uncertainty associated with the feedwater flow venturis is performed in accordance with Exelon standard NES-EIC-20.04 (Rev. 5) and is consistent with ISA-RP67.04.02-2000 (Reference I-8).

The fundamental approach used is to statistically combine inputs to determine the overall uncertainty. Channel statistical allowances are calculated for the instrument channels. Dependent parameters are arithmetically combined to form statistically independent groups, which are then combined using the square root of the sum of the squares approach to determine the overall uncertainty.

NRC Staff Assessment: The applicant has acceptably addressed Criterion 3.

Criterion: For plants where the ultrasonic meter was not installed and flow elements calibrated to a site-specific piping configuration (flow profiles and meter factors not representative of the plant specific installation), additional justification should be provided for its use. The justification should show that the meter installation is either independent of the plant specific flow profile for the stated accuracy, or that the

installation can be shown to be equivalent to known calibrations and plant configurations for the specific installation including the propagation of flow profile effects at higher Reynolds numbers. Additionally, for previously installed calibrated elements, confirm that the piping configuration remains bounding for the original CheckPlus installation and calibration assumptions.

NRC Staff Comments: Caldon has always performed pre-installation calibration tests of each CheckPlus at ARL before installation. The tests are performed at room temperature and sometimes at flow rates that are lower than will be obtained in the plant installation. Consequently, the Reynolds Number may differ between the test and plant conditions by approximately a factor of five to ten. This raises the possibility that the flow profile and meter factors (calibration factor) may not be representative of the plant values.

Criterion 4 allows for installation of a previously calibrated UFM where the calibration was performed at lower Reynolds numbers if acceptable justification is provided.

Historically, Caldon has acceptably addressed propagation of flow profile effects at the higher Reynolds numbers. It also conducts additional confirmatory in-plant tests following installation as part of the final acceptance/commissioning process that provides the final positive confirmation that actual performance in the field meets the uncertainty bounds established for the instrumentation.

The process sometimes involves submission of a pre-test estimate of uncertainties. In Reference I, Cameron addressed the likelihood that testing would fail to confirm the bounding uncertainty parameters. They showed that the meter factor uncertainty was 0.22 percent on the basis of over 94 CheckPlus UFMs subjected to over 2045 calibration tests of over 409 test configurations, with a higher uncertainty of about 0.32 percent for a single meter that was less than 10 pipe diameters downstream of a tubular flow straightener3. Typically, without flow straighteners upstream of a CheckPlus, the differences between the pre-test bounding uncertainties and post-test uncertainties have been between 0.002 and 0.003 percent with the pre-test uncertainties greater.

Consequently, it is unlikely that initial estimates of uncertainties will fail to bound test results.

Applicant Response: Criterion 4 does not apply to Byron or Braidwood Stations, Units 1 or 2. Byron and Braidwood Stations LEFM CheckPlus systems were calibrated at Alden Research Laboratory. Cameron engineering reports for each of the Units evaluating the calibration test data from Alden Research Laboratory have been completed and are provided in LAR Attachments 8a through 8d (Appendix A.3). The calibration factors used for each Units LEFMs are based on the analysis contained in these reports.

3 There is less experience with flow straighteners upstream of a CheckPlus. SRXB recommends this configuration be avoided because flow straighteners are known to affect CheckPlus calibration. If this configuration is necessary, then the review process must be conducted with an in-depth review of the test and plant configurations and data to ensure the CheckPlus is operating within its stated uncertainty bounds.

NRC Staff Assessment: This is an acceptable response. The applicant provides in-depth coverage of the ARL testing and CheckPlus installation in the plant as reviewed within this SE.

3.3 Initial Design and Characteristics To determine volumetric flow rate, the Caldon UFM transmits an acoustic pulse along a selected path and records the arrival of the pulse at the receiver. Another pulse is transmitted in the opposite direction and the time for that pulse is recorded. Since the speed of an acoustic pulse will increase in the direction of flow and will decrease when transmitted against the flow, the difference in the upstream and downstream transit times for the acoustic pulse provides information on flow velocity. Once the difference in travel times is determined, the average velocity of the fluid along the acoustic path can be determined. Therefore, the difference in transit time is proportional to the average velocity of the fluid along the acoustic path.

The CheckPlus provides an array of 16 ultrasonic transducers installed in a spool piece to determine average velocity in 8 paths. The transducers are arranged in fixtures such that they form parallel and precisely defined acoustic paths. The chordal placement is intended to provide an accurate numerical integration of the axial flow velocity along the chordal paths. Using Gaussian quadrature integration, the velocities measured along the acoustic paths are combined to determine the average volumetric flow rate through the flow meter cross section.

Note that this process assumes a continuous velocity profile in the flow area perpendicular to the spool piece axis. Although the velocity profile can be distorted, the distortion cannot be such that the Gaussian quadrature process no longer provides an acceptable mathematical fit to the profile, such as may occur if the profile is distorted in a way that is not recognized by the CheckPlus due to an upstream flow straightener.

To obtain the actual average flow velocity a calibration factor is applied to the integrated average flow velocity indicated by the UFM. The calibration factor for the Caldon UFMs is determined through meter testing at ARL and is equal to the true area averaged flow velocity divided by the flow velocity determined from the average meter paths to correlate the meter readings to the average velocity and hence to the average meter volumetric flow. The mass flow rate is found by multiplying the spool flow area by the average flow velocity and density.

The mean fluid density is obtained using the measured pressure and the derived mean fluid temperature as an input to a table of thermodynamic properties of water. Typically, the difference between an uncalibrated CheckPlus and ARL test results is less than 0.5 percent.

This close agreement means that obtaining a correction factor for a CheckPlus is relatively insensitive to error for operation under test conditions. Further, as discussed in this SE, correction factor is not a strong function of the difference between test and plant conditions and the same conclusion applies.

Use of a spool piece and chordal paths improves the dimensional uncertainties including the time measurement of the ultrasonic signal and enables the placement of the chordal paths at precise locations generally not possible with an externally mounted UFM. This allows a chordal UFM to integrate along off-diameter paths to more efficiently sample the flow cross section. In addition, a spool piece has the benefit that it can be directly calibrated in a flow facility, improving measurement uncertainty compared to externally mounted UFMs that were historically installed in nuclear power plant FW lines.

The applicant acceptably addresses the above aspects of its proposed use of CheckPlus UFMs.

Flow straighteners are not used immediately upstream of the installations and other potential distortions of the flow profile are either absent or acceptably addressed in ARL testing.

Coverage of other aspects of the proposed use is addressed in other sections of this SE.

3.4 Test Facility Considerations 3.4.1 Test Facility Qualification Calibration testing at a qualified test facility and at the plant involves traceability to a national standard, facility uncertainty, and facility operation. At www.aldenlab.com, ARL states that Alden in the largest independent supplier of National Institute of Standards and Technology (NIST) traceable Flow Meter Calibration Services in the country. The NRC staff audited testing at ARL in 2006 as reported in References J and K and verified ARLs statement with respect to traceability to NIST. The NRCs audit found that ARLs processes and operation were consistent with the claimed facility uncertainties. The NRC staff also observed testing during a visit to ARL in 2009 (References L and M) and observed some improvements in test facility hardware. The NRC staff judged these changes would not change its previous conclusions regarding test operations and results. In References N and O, Cameron restated that all elements of the lab measurements ... are traceable to NIST standards. Consequently, the references provide an acceptable basis for concluding that ARL meets the stated testing criteria.

All CheckPlus installations to date have been calibrated at ARL. The audit also confirmed that ARL was providing acceptable test data for the configurations under test. Consequently, the qualification of ARL does not need to be investigated further or confirmed with respect to CheckPlus testing provided test conditions remain consistent with the referenced conditions.

3.4.2 Test Fidelity and Test Range Test fidelity, such as test versus planned plant configuration, test variations to address configuration differences, and potential effects of operation on flow profile and calibration, should be addressed on a plant-specific basis. Applicant requests must provide a comparison of the test and plant piping configurations with an evaluation of the effect of any differences that could affect the UFM calibration. Further, sufficient variations in test configurations must be tested to establish that test-to-plant differences have been bracketed in the determination of UFM calibration and uncertainty. Historically, calibration testing has acceptably covered upstream effects by applying a variation of configurations to distort the flow profile. Further, if the spool piece may be rotated during plant installation from the nominal test rotation, the effect of rotation should be addressed during testing.

Plant piping configuration drawings must, at a minimum, include isometrics with dimensional information that describe piping, valves, FW flow meters, and any other components from the FW pumps to at least 10 pipe diameters downstream of the FW flow meter that is most distance from the FW pump. Preferable are scale three dimensional (3D) drawings in place of isometrics that show this information. Test information must include 3D drawings of the test configuration including dimensions.

Reference O provides test configuration. The licensee provided an attachment of the typical installation locations drawings for the LEFMs at each of the four units. The LEFMs will be

installed upstream of the venturis in the plants and downstream of the common feedwater header. There are no flow straighteners being installed. Distances between the exit of the CheckPlus spool pieces and the downstream venturis in the tests and plant are sufficient such that there will be no effect on the LEFM. As discussed in Section 3.5.2.5, below, this separation distance is large enough that there will be no effect on UFM calibration.

Weigh tank tests were run at different flow rates for each simulated feedwater loop. Tests included 100% and lower flow rates through the CheckPlus and some tests included an eccentric orifice upstream in the feedwater pipes containing the CheckPlus. Most test results were included in the reported main feedwater calculation.

3.5.1 Transfer from Test to Plant and In-Plant Installation Each applicant for a power uprate must conduct an in-depth evaluation of the UFM following installation at its plant that includes consideration of any differences between the test and in-plant results and must prepare a report that describes the results of the evaluation. This should address such items as calibration traceability, potential loss of calibration, cross-checks with other plant parameters during operation to ensure consistency between thermal power calculation based upon the LEFM and other plant parameters, and final commissioning testing.

The process should be described in written documentation and a final commissioning test report should be available for NRC inspection.

To date, the only UFM calibration traceability associated with transfer from the test facility to United States nuclear power plants that has been acceptably demonstrated is that provided by the Check and CheckPlus UFMs due to the ability to provide the flow distribution/velocity profile as a function of radius and angular position in the spool piece, the small calibration correction necessary to fit test data to UFM indication, and the demonstrated insensitivity to changes in operation associated with transfer changes and plant changes. Although other means have been used to obtain flow rate, such as use of tracers in the feedwater, they have not been demonstrated to provide the small uncertainty obtainable with a CheckPlus. Experience to date is that a UFM must provide flow profile information and calibration traceability when extrapolating from test flow rate and temperature conditions to plant conditions. Transfer uncertainty is associated with any changes due to installation in the plant such as mechanical and operating conditions. Mechanical perturbations include such items as transducer installation, mechanical misalignment, and fidelity between the test and plant. Changes in operating conditions involve consideration of such potential effects as noise due to pumps and valves, changes in flow profile, including swirl, flow rate, and temperature.

As previously identified, the test facility configuration and test parameters are expected to provide a basis for providing fidelity between the test and plant. However, an exact correspondence is probably not possible. Potential differences are expected to have been addressed and the UFM is expected to provide a capability to both identify differences and to address them during operation.

The applicant addressed uncertainty in References N and O. As stated in Section 3.4.2, above, the facility uncertainty is acceptable. Reference N is referenced for transducer installation uncertainty. The content is essentially identical to Appendix D of Reference H that the NRC staff found acceptable. Consequently, the applicants treatment of transducer installation uncertainty is acceptable. The applicant showed that LEFM commissioning will include

verification of ultrasonic signal quality and evaluation of actual plant hydraulic flow profiles as compared to those documented during the ARL testing. These parameters will be incorporated as required into the LEFM during commissioning. This is acceptable.

3.5.2 In-Plant Operation Many of the calibration aspects associated with transfer from a test facility to the plant apply during operation as valve positions change, different pumps are operated, and physical changes occur in the plant. The latter include such items as temperature changes, preheater alignment and characteristics changes, pipe erosion, pump wear, crud buildup and loss, and valve wear.

Further, potential UFM changes, such as transducer degradation or failure, may also occur and the UFM should be capable of responding to such behavior. Either the UFM must remain within calibration and traceability must continue to exist during such changes or the UFM must clearly identify that calibration and traceability are no longer within acceptable parameters. Experience is that the CheckPlus is capable of handling these operational aspects. Further, as stated above, UFM operation should be cross-checked with other plant parameters that are related to FW flow rate. Should such checking identify abnormal behavior, it should be identified to the NRC, the validity of the final commissioning test report should be confirmed, and the final commissioning test report should be updated as necessary to reflect the new information.

Further, the UFM must be considered inoperable if its calibration is no longer established to be within acceptable limits.

Section I.1 of Reference V provides coverage of training, calibration, maintenance, procedures, entry into the corrective action program, and procedures to ensure compliance with the requirements of 10 CFR Appendix B. In-plant operation coverage is acceptable.

3.5.2.1 Operation with a failed Component A brief description should be provided that covers system self-testing features, channel checks, control room alarms, and plant process computer functions. The following should be addressed to cover conditions if the CheckPlus system becomes degraded or inoperable:

(1) Operator response.

(2) Changes in FW flow input to the core thermal power calculation.

(3) Allowed outage time (AOT)4: Time when continued operation at full power is permitted and time when power must be reduced, including specification of the reduced power level.

(4) Justification for the AOT with respect to such topics as calibration of FW venturis, venturi fouling or defouling, monitoring of other indications of core thermal power such as 4

The NRC has typically approved an AOT of 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> if acceptably justified.

average power range monitors, steam flow rate, feed flow rate, turbine first stage pressure, and main generator output.

(5) Response if the plant computer system is not operable.

ER-157P Rev. 8 (Reference G) states that The redundancy inherent in the two measurement planes of an LEFM CheckPlus also makes this system more resistant to component failures when compared to the Check. For any single component failure, continued operation at a power greater than that prior to the uprate can be justified with a CheckPlus system since the system with the failure is no less than an LEFM Check. This is acceptable subject to two qualifications:

(1) Continued operation at the pre-failure power level for a pre-determined time and the decrease in power that must occur following that time are plant specific and must be acceptably justified.

(2) The only mechanical difference that potentially affects the quoted statement is that the CheckPlus has 16 transducer housings interfacing with the flowing water whereas the LEFM Check has 8. Consequently, a CheckPlus operating with a single failure is not identical to an LEFM Check. Although the effect on hydraulic behavior is expected to be negligible, this must be acceptably quantified if an applicant wishes to operate as stated.

An acceptable quantification method is to establish the effect in an acceptable test configuration such as can be accomplished at ARL.

Sections I.1.G-I.1.H of Reference V addresses allowed outage time, monitoring of CheckPlus status, and operational processes associated with a degraded or non-operational CheckPlus.

The difference between a degraded CheckPlus and a Check is covered by the ARL test results.

To operate above the CLTP of 3586.6 MWt, the licensee proposes to use the Cameron LEFM CheckPlus System in the normal mode. In the normal mode of operation, both planes of transducers are in service and system operations are processed by both central processing units (CPUs). The LEFM reading will be used as input for the feedwater flow in the calorimetric. The licensee plans to respond to single path or single plane failures in the same way that they will respond two a whole system failure. In the event of a failure of a single path or single plane or other system failure the licensee will declare the system inoperable. The requirement will be to restore the system to operable within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> or the plant will be required to reduce power to the CLTP or 3586.6MWt any time the plant is above the CLTP. If the plant is below the CLTP of 3586.6MWt when the LEFM is declared inoperable, the plant will not be allowed to increase power above the CLTP of 3586.6MWt.

The licensee provided justification for the proposed 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> TLCO action time. This justification included the statements as follows:

There has been no evidence of feedwater flow venturi fouling at Byron or Braidwood Stations. This is based on a review of historical work orders that document this observation as part of a procedural requirement performed every refueling outage. In addition, historical data was gathered over the last several years where feedwater venturi flow was analyzed. This data indicated that there

was no divergence in feedwater flow indication that would suggest venturi fouling.

a typical power measurement uncertainty calculation for a two-loop PWR to be approximately 1.4%. The systematic error associated with feed flow nozzle differential pressure in this calculation is shown to be approximately 1.0%.

Assuming this was calculated based on an 18-month cycle; this would represent a maximum potential drift in the differential pressure measurement of less than 0.002% per day. Over a 72-hour period, this would have an insignificant effect on the feedwater flow measurement. Feedwater flow differential pressure instrument drift history at Byron and Braidwood is consistent with the assumptions of this typical calculation.

The staff agrees that under normal operating conditions the drift of a venturi over a 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> period would be minimal. The reference above as well as previous precedent of plants with similar operating experience and approved outage time provides reasonable assurance that the plant will operate safely for the 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> outage time and maintain the licensed power level.

These actions are to be covered in the LEFM operability requirements contained in the Byron and Braidwood TRM Technical Limiting Condition for Operation (TLCO). The NRC staff finds that operation with an inoperable (non-functional) CheckPlus has been acceptably addressed.

Planned operation with a failed CheckPlus component is acceptably addressed.

3.5.2.2 Spool Piece Dimensional Effects on UFM Response ER-157P Appendix A (References E - H) addresses the effect of variation in such spool piece dimensions as as-built internal diameter and sonic path lengths, path angles, and path spacing.

The applicants description for addressing these effects is acceptable.

3.5.2.3 Transducer Installation Sensitivity Transducers may be removed after ARL testing to avoid damage during shipping the spool piece to the plant. Further, transducers may be replaced following failure or deterioration during operation. Replacement potentially introduces a change in position within the transducer housing that could affect the chordal acoustic path. ER-157P Appendix D (Reference G) addresses replacement sensitivity by describing tests performed at the Caldon Ultrasonics flow loop and provides a comparison of test results to analyses of potential placement variations that shows that the test results are bounded by predicted behavior. One would expect an uncertainty associated with the test loop even if nothing was changed. This is not addressed in the ER-157P information. Rather, all of the test uncertainty is conservatively assumed to be due to transducer replacement. Further, as stated, the analyses predict a larger uncertainty than obtained during testing, and the analysis uncertainty is used for transducer replacement uncertainty. This approach is judged to be sufficient to cover the inability of the test loop to achieve flow rates comparable to those obtained in plant installations and to cover any analysis uncertainty associated with applications with pipe diameters that differ from the tests.

Consequently, transducer replacement has been acceptably addressed and the ER-157P Rev.

8process for determining transducer replacement uncertainty is acceptable.

3.5.2.4 The Effects of Random and Coherent Noise of LEFM CheckPlus Systems Appendix C of ER-157P (Reference G) provides a proprietary methodology for test- and plant-specific calculation of the contribution of noise to CheckPlus uncertainty. Review of this methodology has established that applicants may use this methodology in their MUR requests.

References N, O, and V show that critical performance parameters, including signal to noise ratio, are continually monitored for every individual meter path and alarm setpoints are established to ensure corresponding assumptions in the uncertainty analysis remain bounding.

Signal noise will be minimized via strict adherence with Cameron design requirements. LEFM commissioning included verification of ultrasonic signal quality.

In Reference O, the applicant reported test signal to ratios for random and coherent noise that were within specifications and that uncertainty attributable to the electronics and signal to noise ratio are included in the overall meter factor uncertainty.

The test results and the above References N and O coverage of noise are sufficient to ensure that this topic is acceptably addressed.

3.5.2.5 Evaluation of the Effect of Downstream Piping Configurations on Calibration The turbulent flow regimes that exist when the plant is near full power result in limited upstream flow profile perturbation from downstream piping. Consequently, the effects of downstream equipment need not be considered for normal CheckPlus operation provided changes in downstream piping, such as the entrance to an elbow, are located greater than two pipe diameters downstream of the chordal paths. However, if the CheckPlus is operated with one or more transducers out of service, the acceptable separation distance is likely a function of transducer to elbow orientation. In such cases, if separation distance is less than five pipe diameters, it should be addressed.5 6 As discussed in Section 3.4.2, above, separation from downstream components is needed so that CheckPlus operation will not be affected. The in plant separation from downstream piping components such as elbows and venturis is acceptable and will not affect CheckPlus operation.

3.5.2.6 Evaluation of Upstream Flow Straighteners on CheckPlus Calibration7 5

This was the case, for example, with a Calvert Cliffs application that the NRC found acceptable (References Q and R). In that installation, the distance between the spool piece exit is 15 inches from the downstream elbow and the chordal paths are 2.7 diameters upstream of the entrance to the piping bend.

6 Although this is not addressed in ER-157P Rev. 8, it is addressed in the Reference H safety evaluation.

7 This is not addressed in ER-157P Rev. 8 (Reference G) but is addressed in the Reference H safety evaluation.

Operation with an upstream flow straightener is known to affect CheckPlus calibration to a greater extent than most other upstream hardware. If an applicant proposes this configuration, it must provide justification.

A previously undocumented effect of upstream tubular flow straighteners on CheckPlus calibration was discovered during ARL testing while NRC staff members were at the site on August 24, 2009, that did not appear to apply to any previous CheckPlus installations. As follow-up, additional tests were conducted with several flow straighteners and two different pipe

/spool piece diameters to enhance the statistical data basis and to develop an understanding of the interaction between flow straighteners and the CheckPlus. The results are provided in the proprietary Reference P.8 Cameron concluded that two additional meter factor uncertainty elements are necessary if a CheckPlus is installed downstream of a tubular flow straightener and provided uncertainty values derived from the test results. The data also provide insights into the unique flow profile characteristics downstream of tubular flow straighteners and a qualitative understanding of why the flow profile perturbations may affect the CheckPlus calibration.

Cameron determined that the two uncertainty elements are uncorrelated and therefore combined them as the root sum squared to provide a quantitative uncertainty. The Cameron approach is judged to be valid, but there is concern that the characteristics of existing tubular flow straighteners in power plants may not be adequately represented by samples tested in the laboratory. Any applicant that requests an MUR with the configuration discussed in Section 3.5.2.6 should provide justification for claimed CheckPlus uncertainty that extends the justification provided in Reference P.

No flow straighteners are installed in the applicants feedwater lines and flow straightener effects are not a concern.

3.6 Other Thermal Power Calculation Considerations 3.6.1 Steam Moisture Content Some modern separators and dryers deliver steam with moisture content in the 0.05 percent range and these applicants often assume a zero moisture content that is conservative since the calculated power will be greater than actual power for such cases. No uncertainty is necessary if no moisture is assumed.

Reference C discusses an analysis in which the uncertainty in thermal power due to measurement of all variables excluding moisture is assumed to be normally distributed with two standard deviations of 0.3357 percent, essentially the aggregate uncertainty of all contributors excluding moisture for the CheckPlus system. The contribution of uncertainty due to moisture content was then calculated by multiplying a second, uniformly distributed random number times the uncertainty band assumed in Reference C's Table A-1 and Monte Carlo calculations of total power uncertainty were obtained. The results are summarized in Reference Cs Figure 1. The author concluded that applicants assuming large uncertainties in steam moisture content 8

The results do not apply to the Check UFM. Consequently, the findings do not apply to a Check that is installed downstream of a tubular flow straightener.

should have an engineering basis for the distribution of the uncertainties or, alternatively, should ensure that their calculations provide margin sufficient to cover the differences shown in Figure

1. This was stated to be an acceptable approach in Reference H.

3.6.2 Deficiencies and Corrective Actions The applicant identified its process for addressing Cameron deficiency reports as well as reporting deficiencies to the manufacturer. In each case Byron and Braidwood Stations will use their corrective action program. In the case of receiving deficiency reports, Byron and Braidwood stations will document and address applicable deficiencies in its corrective action program as well.

3.6.3 Reactor Power Monitoring Applicants should identify guidance to ensure that reactor thermal power licensing requirements are not exceeded. Proposed guidance was addressed by NRC in Reference S.

The EICB assessment provided in its review, and the applicant response to Criterion 1, as summarized above, provides an acceptable description to ensure operation consistent with the Reference S guidance to prevent overpower operation.

3.7 Uncertainty EICB provided an assessment that addressed uncertainty. The following discussion in Section 3.7 provides supplemental information.

Cameron considers flow rate uncertainty associated with the test facility, measurement (including transducer installation), extrapolation from test conditions to plant operating conditions, modeling, and data scatter.

3.7.1 Test Facility Uncertainty The budgeted test facility uncertainty is consistent with past NRC staff evaluations and the Reference J value. This uncertainty is acceptable.

3.7.2 Measurement Uncertainty The applicant addresses uncertainty due to such contributors as thermal expansion; dimensions; temperature, pressure, and density determination; and transducer installation. The contribution of some of these contributors was discussed in the above report sections. Overall, measurement uncertainty is acceptably addressed.

3.7.3 Extrapolation Uncertainty Although calibration tests were performed, they were conducted at room temperature. This resulted in Reynolds numbers about a factor of ten less than would occur in the plant and an

extrapolation is necessary to obtain in-plant calibration factor. A positive aspect of the CheckPlus is that the calibration factor is close to one and small errors in the extrapolation do not significantly affect extrapolation accuracy. Another aspect is that the Check and CheckPlus characteristics permit an alternate extrapolation approach that is typically less sensitive to error than a Reynolds number extrapolation. This involves the flatness ratio (FR), which for the CheckPlus is defined as the ratio of the average axial velocity at the outside chords (chords 1, 4, 5, and 8) to the average axial velocity at the inside chords (chords 2, 3, 6. and 7) 9:

FR = (V1 + V4 + V5 + V8) / (V2 + V3 + V6 + V7)

Where FR is a function of Reynolds number, pipe wall roughness, and the piping system configuration.

The effect of the configuration is evaluated in laboratory tests. The effect of Reynolds number is deduced from the fully developed flow inverse power law profile which may be written in several forms including the following:

l where X = radial location, R = pipe radius, and the exponent n varies with Reynolds number and is determined from experimental data. The advantage of this approach is that a plot of FR versus calibration factor is linear and the calibration factor is insensitive to variation in FR.

These results are consistent with analytic predictions and have been confirmed via ARL tests of many plant configurations. Further, minor changes in calibration factor observed in different hydraulics configurations are predictable and can be confirmed analytically. Therefore, if plant conditions result in a change in FR, the calibration factor may be adjusted to reflect the change in FR.

Cameron also uses swirl rate, defined as:

Swirl Rate = Average , , ,

Where yS and yL are normalized chord locations for outside/short and inside/long paths.

Cameron also uses swirl rate to characterize behavior obtained during ARL tests.

The applicant provided experimental data of calibration factor as a function of FR and swirl rate for each of the CheckPlus instruments in Reference O.

Cameron includes an uncertainty term for extrapolation from laboratory conditions to plant conditions that is computed from empirical equations to account for change in Reynolds number and other effects such as a difference in pipe wall roughness. The calibration factor is shown to change in the fifth significant figure over a factor of ten change in Reynolds number between the 9

Details of this method are proprietary. This discussion is taken from the non-proprietary References T and U.

test and plant conditions. With respect to extrapolation uncertainty, some of the uncertainty was likely already addressed by parametric testing over Reynolds numbers and FRs.

3.7.4 Modeling Uncertainty Cameron uses FR and swirl rate to characterize the velocity distribution and to validate the experimentally determined calibration factor when installed in a plant. In Reference U, it discussed application of calibration data obtained at ARL for 330 hydraulic configurations with 75 CheckPlus UFMs with an average calibration factor of 1.002 with a standard deviation of +/-

0.0039.

Cameron discussed its experience in calibrating over 100 UFMs with 500 different test configurations since typically 4 or 5 configurations were tested for each UFM. An approach is discussed where different numbers of subsets of configurations were considered applicable to the applicants installation and modeling sensitivity was computed using that information.

The applicants method for determining modeling uncertainty is acceptable.

3.7.5 Data Scatter Uncertainty The precision with which the calibration factor is determined includes all calibration data for each CheckPlus and 95% confidence limits are calculated. The applicants determination of data scatter uncertainty is acceptable.

3.8 Evaluation of Measurement Uncertainty Recapture Power Uprate Request for Byron Unit 110 3.8.1 Introduction to and Summary of NRC Audit and Licensee Response to Byron Station Unit 1 LEFM vs. Plant Parameter Discrepancies The LEFMs were installed at Byron Unit 1 during refueling outage B1R17. Following the outage, in late April, 2011, poly acrylic acid (PAA) was injected to control SG crud buildup.11 Multiple indications showed a rise in thermal power when thermal power was held constant by controlling via the LEFMs from May to September 19, 2011 (Byron, September 19, 2011.), and an extensive troubleshooting effort was initiated to investigate the discrepancy between the LEFMs and other multiple indications. The troubleshooting investigation was conducted by Exelon, Cameron, and Dominion Engineering and subjected to an in-depth review by MPR Associates, ILD Inc., and Dominion Engineering. Troubleshooting was completed in April, 2012 (Borton, October 9, 2012, Attachment 2) and did not clearly identiy the cause of the observed behavior. Byron Unit 2 and the Braidwood units did not exhibit as large a discrepancy and no other plants had a similar discrepancy. The licensee reported that no other plants used PAA injection.

10 Most quantitative data are proprietary and are not provided in this non-proprietary evaluation.

11 Industry experience had shown that PAA could reduce iron oxide accumulation on secondary side SG surfaces and that it could remove previously deposited iron-based corrosion products from secondary plant surfaces.

The NRC staff has audited the troubleshooting investigation and has conducted independent calculations based on data provided by Exelon and Cameron. One aspect of the trouble shooting was a determination that there was no significant deposit on the LEFM aperatures.

The NRC staff did not agree with the assumptions and analysis approach but confirmed the conclusion via independent analysis.

On the basis of observed flatness ratio (FR)12 data and the assumption that the power law or the modified Reichardt equation represented the flow profile, and study of operating data, the NRC staff determined that the effective change in CheckPlus calibration was less than 6 X 10-4 percent and therefore was negligible.

Estrada (March, 2012) concluded that analyses from all elements of the LEFM algorithm were in the range of + 0.05 percent to + 0.079 percent, in the opposite direction of the postulated LEFM drift that would be consistent with the best estimate based on other plant variable trends that indicated a LEFM change of about - 0.4 percent. He also concluded that the difference between LEFM indication and the best estimate was within the root sum square of the +/- 0.3 percent LEFM uncertainty and the best estimate uncertainty of +/- 0.55 percent.

The average difference between the LEFM and other parameters that can be used to determine feedwater flow rate or thermal power was about 0.25 percent at the end of the increased difference that occured from May, 2011 to September, 2011. Operating parameters from October, 2011 to May, 2013 established that differences had stabilized and were no longer increasing. The requested increase in thermal power corresponds to a power uncertainty of 0.37 percent, the calculated bounding value for system mass flow rate uncertainty was < 0.3 percent and the thermal power uncertainty was < 0.4 percent. The observed differences are smaller than the uncertainties that Caldon calculated that were part of the basis for the LAR. On this basis alone, the observed differences between LEFM and other plant indications are not sufficient to invalidate the feedwater flow rate indicated by the LEFMs. Further, the NRC staffs review supports a conclusion that the LEFMs are not affected by PAA injection and the observed deviation in thermal power and feedwater flow rates are not due to the LEFMs.

Examination of the data strongly supports a conclusion that the venturis are affected by PAA injection although the reasons are not as clear nor are the differences between Byron 1 and Byron 2 fully understood.

Reasons for deviation in other plant parameters have been postulated but these are not accepted by all licensing personal and are not sufficiently supported to lead to firm conclusions.

3.8.2 Discussion Information provided during an audit conducted at Camerons headquarters on May 14, 2013 was that Byron and Braidwood are the only stations that use PAA injection in feedwater. Thus, Byron considered that there was a lack of data concerning possible impact of PAA on LEFM 12 The CheckPlus determines average flow velocities along straight line paths of two lengths. FR is the ratio of the measured velocity via the shorter path to the measured velocity via the longer path. Flow rate is determined by multiplying each velocity by the flow area it is assumed to represent and correcting for the angle between the measurement and the direction of flow.

operation. With respect to feedwater venturis and steam flow rate indications, PAA was known to have an impact.

Byron initiated an extensive troubleshooting plan when an upward trend in secondary parameters occurred that indicated Byron 1 thermal power was increasing in contrast to LEFM indications that thermal power was constant. This included securing PAA injection for two months and injecting PAA at an increased concentration after that. Securing PAA was accomplished to see if the upward trend would be reversed. Increasing PAA concentration was to discern if accumulation of PAA or PAA byproducts occurred that would cause secondary parameters to reach a higher magnitude.

3.8.2.1 Observed power behavior During the time between May, 2011 and September, 2011, Byron Unit 1 was operated so that flow rate indicated by the LEFMs was essentially constant and other plant parameters indicated an increasing flow rate. The Byron observations of the effect on thermal power, and NRC staff estimates of the changes, were as follows:

Item Percent Change Byron NRC estimate from Data Impulse Pressure 0.21 0.20 First Stage Pressure - 0.29 SG Steam Flow 0.20 0.25 LEFM Temperature - 0.02 Pump Flow 0.23 0.20 RCS Differential Temperature 0.26 0.4913 Core Thermal Power 0.25 -

Venturi Thermal Power 0.27 -

LEFM Thermal Power 0.01 -

LEFM Flow Rate ~0.0514 0.04 The largest change in the difference between flow rates occurred between the LEFMs and venturies. The correspondence of multiple indications of an increasing flow rate and thermal power with a close-to-constant LEFM indication raised questions regarding LEFM calibration drift and accuracy.

3.8.2.2 Byron troubleshooting program 3.8.2.2.1 Summary The LEFMs were installed at Byron Unit 1 during refueling outage B1R17 that ended in late April, 2011. Following start-up, PAA was injected to control SG crud buildup. Multiple indications showed a gradual rise in thermal power when thermal power was held constant by controlling via the LEFMs from May to September 19, 2011 (Byron, September 19, 2011.), and Byron initiated an extensive troubleshooting effort to investigate the discrepancy. The 13 Hot leg streaming changes will influence this parameter and could cause significant error.

14 Cameron estimate of maximum bias (Ultrasonics, May 14, 2013).

troubleshooting investigation was conducted by Exelon, Cameron, and Dominion Engineering and subjected to an in-depth review by MPR Associates, ILD Inc., and Dominion Engineering.

Troubleshooting was completed in April, 2012 (Borton, October 9, 2012, Attachment 2) and did not identiy the cause of the observed behavior. Byron Unit 2 and the Braidwood units did not exhibit as large a discrepancy and no other plants had a similar discrepancy.

Key results of the troubleshooting program and the NRC staff findings included the following:

• Cameron used many diagnostic indicators to conclude that there were no LEFM anomalies. It concluded that LEFM performance was within its design basis. The NRC staff agrees.

• PAA build-up or PAA byproducts on LEFM surfaces were determined not to be a cause.

The NRC staff did not identify any phenomenon that would contradict this conclusion.

• No anomalies were identified where hydraulic impacts, secondary parameter instrumentation drift, erosion/corrosion, or calorimetric program errors were identified that would result in the observed secondary parameter drifts. The NRC staff identified some anomalies that were not explained and Cameron identified interactions that it posited could explain the behavior.

Byron provided the following observations based on further study:

• A best estimate methodology based on five power system conversion measurements (secondary parameters) was used to calculate thermal power. Byron concluded that current thermal power was consistent with the previous two cycles that operated on the venturis at 100 percent power. NRC staff review of a comparison of indicated thermal power (ITP) versus Best Estimate Thermal Power (BETP) established the following:

- BETP > ITP from April 2008 to Refueling Outage B1R17 in 2011.

- BETP < ITP in May, 2011 and gradually increased to equal ITP in September, 2011.

Operation was with LEFM controlling IPT.

- BETP > ITP for several following months when operating under venturi control.

- BETP = ITP subsequently until February, 2012 when operating under LEFM control.

• Comparison with Byron 2 and Braidwood 2 startups in 2011 failed to show similar upward trends in secondary parameters. The NRC staff confirmed this conclusion by examining the data.

• Review of industry operating experience did not identify differences between LEFM and venturi indication that occurred at Byron 1. The NRC staff did not review this Byron review.

• Byron found no significant issues or errors in inputs to the plant calorimetric that would result in the observed drifts.

• Byron did not identify any power plant failure mechanisms that would explain the drifts.

With regard to the last two items, the NRC staff notes that Cameron believes it identified reasons for drifts in steam flow rate and venturi behavior. The Cameron conclusions and additional unexplained anomolies identified by the NRC staff are discussed below.

NRC staff review of operating parameters from October, 2011 to May, 2013 established that differences had stabilized and were no longer increasing. This is important because it eliminates a potential concern that continued drift could raise questions regarding LEFM operating outside its uncertainty limits.

3.8.2.2.2 Discussion of selected aspects of troubleshooting program Byrons troubleshooting investigation was described in Reference X and updated during an audit conducted at the Cameron offices on May 14, 2013. Potential failures, Byron conclusions, and NRC staff comments (in bold to differentiate from licensee discussion) were as follows:

(1) Installation configuration results in hydraulic impacts causing the LEFM to read lower than actual.

• There were no significant differences in piping configurations between trains and UFM installation was consistent with specifications.

• There were no upstream obstructions that could affect the LEFMs Review complete and determined not to be a cause.

(2) Plant process computer (PPC) interface to LEFM is causing errors in the data.

• LEFM flow indication was determined to be accurately communicated to and displayed on the PPC.

• Modeling of programs and flow calculations to handle net flow and tempering line flows were determined to be correct. See Item (6), below.

Review complete and determined not to be a cause.

(3) LEFM problem causing erroneous readings.

• Commissioning changes such as software changes; cable lengths; and alarm, hydraulic, and setup configurations were determined to not significantly affect LEFM readings.

• No significant differences were found between trains or with respect to Alden Labs test results. The NRC staff notes that Train B FR decreased from May to September, 2011 whereas Trains A, C, and D increased. This difference has not been explained beyond an observation that the changes are within

expectations and do not significantly affect MF. The overall effect is to decrease change in the average FR and change in the already small MF change when the four loops are averaged.

• Environmental conditions were within specifications.

• Operating experience (OE) review found no new applicable information.

• Power supplies were within specifications.

• Pressure and temperature inputs have not drifted which eliminates bad sensor input as a cause.

• No significant integration errors were found with internal integration.

• Evaluation of transfer to Venturi control and observance of trends to identify potential LEFM problems did not identify errors.

Byron concluded that no anomalies were identified and this failure mode was not a cause.

(4) Venturi calibration or drift issue is causing the descrepancy.

• Byron stated there were no unexplained drifts or deviations. The NRC staff observed that there were unexplained differences between venturi and other indications. It also observed that venturi differential pressures for A, B, and D decrease by about one inch from May to September, 2011 while C increased by the same amount. Byron provided information during the audit that venturis were known to be affected by PCC injection (see Item (5), below). Cameron and the NRC staff reached the same conclusion.

• No secondary calibrations of the flow elements or correction factors have been applied to the venturies that would cause large bias or uncertainty.

• No significant diverging trends were found in the LEFMs compared with other balance of plant (BOP) parameters. Diverging trends were evident from the plant data. The key is whether or not they were significant. This is addressed below.

• Venturi bypass flow has been stable and there are no gaps to allow bypass flow.

This is important and is often not addressed. Note also that tempering flow bypasses both the LEFMs and venturis.

• Newly developed discharge coefficients were correctly implemented and the discharge coefficient extrapolation method was determined not to be in error.

Byron concluded that no anomalies were identified and this failure mode was not a cause.

(5) External interaction with venturi / LEFM spools by either PAA or erosion / corrosion.

• PAA injection was expected to cause an indicated 0.2% increase in flow rate indicated by the venturies. An uncertainty of 0.3% was added to the calorimetric to compensate for the increase. Byron concluded that the impact on the venturies did not change. Further, it stated that PAA injection was not expected to affect the LEFMs. This is addressed furher below.

Byron concluded that no anomalies were identified and this failure mode was not a cause.

(6) Calorimetric input or program fault.

• FW flows, SD flow, FW temperature, steam temperature, and steam pressure calorimetric inputs were verified as correct. However, two issues were identified:

- Tempering lines normally are expected to pass about 40,000 lbs/hr of feedwater flow that bypasses the LEFMs and venturis. These lines were isolated with the expectation that measured feedwater flow would increase by something less than 2000 lbs/hr per loop. This occurred in three feedwater loops but the Loop D difference was 5000 lbs/hr. Byron stated that this anomaly would represent a 0.03 percent change in thermal power and would not be the cause of the observed drifts in secondary parameters.

The NRC staff observes that the expected increase in total measured feedwater flow was 8000 lbs/hr. Byron calculated the 0.03 percent change from 5/16,000

= 0.0003. Feedwater flow rate is about 16 X 106 lbs/hr and the Byron calculation is consistent with 5000 / 16 X 106. 40,000 / 16 X 106 = 0.003 0.3 percent = percent of feedwater flow that is normally understood to be bypassed. Since bypass flow is measured, the NRC staff understands it is included in the heat balance, and presumably bypass flow was equal in each of the four loops prior to isolation, the unexpected behavior should not impact the heat balance unless there is an unidentified flow path or the flow measurement is in error.

The normal tempering flow in Loop D should have been about 10,000 lbs/hr.

Isolation was expected to result in an increase in measured feedwater flow of 2000 lbs/hr, not 5000 lbs/hr. This may imply that tempering flow was significantly greater than 10,000 lbs/hr and not negligible with respect to the plant heat balance.

The observed behavior should be explained.

- SG blowdown flow was isolated with the expectation that feedwater flow rate indicated by the venturis and the LEFM would decrease by the same amount. Most

loops showed a nearly identical decrease of < 2000 lbs/hr but Loop B changed by 10,000 lbs/hr. Byron concluded that this change would have a conservative impact of core thermal power, not the non-conservative impact that was observed.

The NRC staff comments in the case of tempering flow apply to the blowdown flow anomoly.

• Program was reviewed against plant parameters and verified to correctly calculate thermal power.

Byron concluded that this failure mode was not a cause. The NRC staff would agree if the tempering and blowdown flow anomolies are acceptably resolved.

3.8.2.2.3 Effect of changing PAA injection concentration PAA was injected following startup from Refueling Outage B1R17 in late April, 2011 until November, 2011. The venturis and other secondary side parameters that can be related to thermal power showed a linear increase relative to the LEFMs from May, 2011 until September, 2011 while the LEFMs were used to control feedwater flow rate and thermal power to a steady state. A power reduction then occurred after which the venturi to LEFM ratio appeared to stablize at a value slightly larger than before the reduction. PAA injection was stopped for two months starting in November, 2011. Within about a day of stopping PAA, the venturi indication decreased relative to the LEFMs. There was no further change in the difference between the venturis and LEFMs while PAA was stopped. Upon re-initialization of PAA, the venturi indication increased by about 0.15 percent in less than a day relative to the LEFM; a reversal of the behavior when PAA was stopped.

PAA injection rate was increased in Byron 1 in February, 2012. With one exception, there was no change in the venturi to LEFM comparison through mid-March, 2012. The exception was a short time when PAA injection stopped. During this time, the ratio changed as described in the above paragraph.

PAA injection was increased in Byron 2 in February, 2012. LEFM and venturi tracked closely into March, 2012 with a slightly closer correspondence in March. This convergence was more pronounced when compared to other plant parameters with an initial relative correspondence of about 0.998 and a March correspondence of 0.999.

The above venturi behavior with variation in PAA injection is a clear demonstration that PAA affected the Byron 1 venturis.

Several investigators concluded that PAA had no impact on the LEFMs. The NRC staff agrees.

3.8.2.2.4 Best estimate (BE) comparisons A BE methodology can be developed that combines independent variables on the basis of including their individual uncertainties as weighting factors to obtain an estimate with an uncertainty that is less than any of the individual variables. Three BE methodologies were developed by different investigators and applied to compare indicated thermal power to BE thermal power from April, 2008 to February, 2012. From 2008 until B1R17, indicated power

was less than BE power, a comparison that continued following B1R17 until LEFMs were used to control thermal power. At this time, LEFM thermal power reversed and was greater than BE thermal power. The two then converged until September, 2011 when power control was changed to the venturis and the pre-B1R17 behavior was observed. A change back to LEFM control resulted in close correspondence that continued into February , 2012 when the Byron report comparison terminated.

3.8.2.3 Assessment of LEFM The NRC staff elected to independently examine aspects of the observed behavior. This examination is summarized in Section 3.8.2.3.

3.8.2.3.1 Dimensional information (Spadaro, July, 2010) provided drawings of the Alden test configurations that specified spool piece dimensions and Cameron provided tolerances and as-built dimensions during the May 14, 2013 audit that established that the as-built LEFMs were within tolerances. As-build wall thicknesses were measured in May, 2010 and again in March, 2012 following 11 months of operation (Estrada, March, 2012). Neglecting measurement uncertainty, Cameron calculated that the change would introduce a net change in internal diameter of - 0.024 percent and a flow error of + 0.012 percent (Ultrasonics, May 14, 2013). Dimensional changes are not a likely cause of the observed behavior.

3.8.2.3.2 Effect of deposit in transducer apertures Estrada reported that the drift from May, 2011 to November, 2011 due to a postulated corrosion layer in the apertures was ruled out on the basis of measurements that established that there was little wall thickness change and a rationale that a small deposit on aperture walls is not sufficiently thick to transmit acoustic energy and therefore not capable of altering the effective sound velocity in the aperture.

The NRC staff does not agree with Camerons rationale. First, Cameron concluded that evidence of little change in spool piece diameter established that there was no deposit on the spool piece walls and, therefore, there was no deposit in the apertures. While the NRC staff agrees that there was no significant change in diameter based on the measurements, this is not justification regarding deposits in the apertures. It is possible for a deposit to form in the apertures while the spool piece walls remain deposit-free. While Camerons conclusion that a small deposit on the aperture walls is not thick enough to transmit acoustic energy may be correct, this does not address the effect of a deposit on the aperture window that reduces the measured time from one transducer to another due to decrease in transmission distance and the change in velocity of sound between water and a deposit in the volume where the deposit displaced water.

Assuming a deposit affects all apertures equally, the Cameron LEFM can indicate the effect of a deposit on the transducer housings in the apertures because there will be a larger effect on the measured short path sound velocity in comparison to the long path sound velocity. This can be expressed in terms of the flatness ratio, FR, defined by the following equation:

where V1, V4, V5, and V8 are velocities measured along the outside chords (the short paths) and V2, V3, V6, and V7 are velocities measured along the inside chords (the long paths)

A change in FR can be approximated by the following equation:

where: ys = short path length yl = long path length and the prime indicates the new path length.

If an effective deposit thickness, x, increases on the transducer window surfaces that is identical on all windows and has the properties of water, then:

ys - ys = 2x yl - y = 2x and:

ys - ys = yl - y so that:

1 Estrada provided FR changes during a seven month period starting in May, 2011. Using these data, the NRC staff estimated the predicted thickness changes would change flow rate by less than 0.01 percent, in agreement with Camerons conclusion. This is not a likely cause of the observed behavior.

3.8.2.3.3 Effect of flatness ratio (FR) change on meter factor (MF)

Flatness ratio, as discussed above, is defined as:

where V1, V4, V5, and V8 are velocities measured along the outside chords (the short paths), V2, V3, V6, and V7 are velocities measured along the inside chords (the long paths), VS is the mean short part velocity, and VL is the mean long path velocity. The paths are illustrated by the

horizontal lines in the following figure that correspond to the paths between the CheckPlus transducers15:

FR can be determined experimentally, such as by testing at Alden Labs where the CheckPlus will provide the velocity data.

Once the Vs are determined, the flow rate determined by the CheckPlus can be calculated by multiplying the rectangular vertical widths (weighting factors) indicated in the following figure by the dash lines by the corresponding velocities times two:

Cameron uses the same weighting factors for all of its nuclear applications. As is demonstrated below, this does not appear to be consistent with theoretical analyses when FR is compared to MF in an analysis of the Alden Lab data obtained with the Byron 1 LEFMs.

15 Measurements are at an angle with respect to pipe length. Velocities are translated into this configuration for calculation purposes.

Once the CheckPlus flow rate has been calculated, MF can be determined by comparing the CheckPlus flow rate to the experimentally determined data.

FR and MF can also be calculated using an assumed symmetric velocity distribution that is a function of pipe radius, expressed as V(r), where r is the reduced radial position with the origin at the pipe centerline and 0 r 1. Since the CheckPlus determines a mean velocity along the path, the calculation must be based on the same path, as illustrated by the x dimension in the following figure:

where the mean velocity is calculated by 1/X where x= X at r = R and V(x) is determined from the assumed V(r) where the relationship between x and r is obtained from the geometry illustrated in the figure.

The calculations define MF as the flow rate calculated by 2 divided by the calculated LEFM flow rate obtained by two times over the short and long path lengths multiplied by the corresponding weighting factors.

Spadaro described the velocity profile by the power law:

where V is the velocity normalized to the maximum value, and n is a function of Reynolds number and pipe roughness that changes the shape of the profile. FR and MF were calculated using an Excel spreadsheet with the calculation based on dividing the dimension spans into 1000 increments to provide an accurate calculation that addresses profile changes near the LEFM wall. The NRC staff used the same approach except it assumed the increment size was ten times smaller in the last 20 steps near the wall, a total of 1018 increments. The NRC staff assessed the calculation accuracy by changing the number of increments with the results summarized in the following table for a typical FR where the comparisons were obtained using the NRC staff methodology:

Nominal number of Calculated Calculated Calculated Calculated increments relative short relative long path relative FR relative MF path velocity velocity 1000 1.0000 1.0000 1.0000 1.0000 500 1.0000 1.0000 1.0000 1.0000 250 1.0001 1.0001 1.0000 1.0001 Clearly, the calculations using 1000 increments do not introduce a significant numerical error.

Estrada (Estrada, January, 2002) used the power law and weighting factors determined by Caldon to calculate MF as a function of FR and found that the calculations could be fitted by a straight line. All MFs were greater than one for FR < 1 and the results converged to MF = 1 at FR = 1. The NRC staff does not understand the rationale for fitting Alden data where MFs were less than one to a line where the MFs were greater than one. The comparisons are illustrated below.

Each of the four CheckPlus LEFMs installed at Byron 1 was tested at Alden Labs. There were three test piping configurations in additional to a configuration to model the plant installation for each CheckPlus. More than one flow rate was included in each configuration test. The configuration variations were, for example, to introduce swirl to bracket any variations that would be encountered in the plant. The test report (Spadaro, July, 2010) provided FR versus MF for each of the 16 test configurations. All MFs were less than one yet, as stated above, the results were plotted on Estradas straight line where the line is limited to MF > 1. This was achieved by offsetting the MF for each meter such that the average MF was on the predicted curve. The off-set data correspondence to the straight line was an excellent fit. Caldon explained that the purpose of this work was to illustrate the dependence of MF on FR and, in this case, the change was small, as is discussed below.

The NRC staff calculated MF behavior using the power law and the Caldon weighting factors and compared it to a straight line fit of the Alden Labs test results for the four LEFMs installed at Byron 1. The comparison is shown in the following figure where the upper solid line is the calculation and the lower solid line is a straight line fit to the data. There is effectively no correspondence. The NRC staff also modified the weighting factors so that the power law reproduced the mean MF and FR of the 16 Alden Lab test results and, using the modified weighting factors, repeated the calculation to obtain the dash line. The fit of the power law to the data line is excellent.

MF versus FR 1.003 1.002 Linear (Alden test data) 1.001 1 Linear (Power Law MF with Caldon weight 0.999 factors) 0.998 Linear (Power Law 0.997 with modified weight factors) 0.996 0.8 0.85 0.9 0.95 1 FR The above calculations were based on nominal test values without considering the Alden flow rate uncertainty. There is significant scatter in the 16 data points, in part due to testing different configurations to bracket possible variations introduced in the plant installation. Simply obtaining the standard deviation, , without considering variation in FR, approximating uncertainty as two times , and applying the uncertainty at the mean FR of the data provided the following approximation of the data scatter. Note that the upper extreme never reaches Uncertainty Based On Alden Lab Data 1

0.9995 0.999 0.9985 MF 0.998 0.9975 0.997 0.9965 0.996 0.85 0.9 0.95 1 FR MF = 1 except at FR = 1 in contrast to the Caldon extrapolation of the data to the Caldon calculation that Caldon used to evaluate MF sensitivity. Further note that Caldons approach results in a reduction in MF with increasing FR whereas the Alden data establishes that MF increases with increasing FR. In contrast, the absolute magnitude of the MF changes is identical due to the mirror image of the two calculations with respect to MF = 1.

The NRC staff used its Excel spreadsheet to calculate the velocity distributions and effect on MF that corresponded to the observed FRs provided by Estrada for the May, 2011 to November, 2011 FRs. The conclusion was that, regardless of which curve applies, the change in FR that occurred between May and September of 2011 is predicted to introduce a maximum change in MF of about 6 X 10-6 which is negligible. Stated differently, the CheckPlus calibration is not calculated to have changed by more than about 6 X 10-4 percent. Further, an important consideration is that the test data included the expected plant configuration and modifications that caused swirls that were greater than observed during plant operation.

3.8.2.3.4 Effect of thermal expansion The coefficient of thermal expansion is a multiplier on both the numerator and denominator in calculation of MF and therefore thermal expansion has no effect on MF assuming there are no other effects that perturb the calculation.

3.8.2.3.5 Effect of a change in speed of sound of FR A change in the speed of sound affects the numerator and denominator equally and therefore has no effect on FR assuming there are no other effects perturbing FR.

3.8.2.3.6 Coherent noise Cameron investigated the interaction of coherent noise that can interact with the acoustic signals and can affectt transit time measurements. Cameron concluded that coherent noise did not account for the LEFM trend in comparison with other plant parameters. The NRC staff agrees.

3.8.2.3.7 LEFM conclusions No cause of a change in LEFM characteristics was identified that would indicate a significant measurement error was caused by the LEFMs. Further, the above information supports the conclusions that the LEFMs are not affected by the PAA and LEFM characteristics remain within the initially established uncertainty bounds.

3.8.2.4 Camerons examination of other indicators of flow rate16 Thermal power increased by about 0.5 percent from May, 2011 to September, 2011 by using the LEFM indications for control. Thus, for discussion purposes, thermal power based on LEFM indications may be treated as constant when assessing other parameters that may be used to determine thermal power. During this time, venturi flow, turbine pressure indicators, and total steam flow all indicated that thermal power was increasing at a greater rate. The venturies indicated a rate increase larger than the other indicators. Consequently, one may conclude that either the LEFM or the other indicators were providing erroneous information. As discussed above, LEFM changes appear to have been eliminated. The conclusion is that the other parameters have changed.

16 Discussion based on information provided in the May 14, 2013 audit (Ultrasonics, May 14, 2013) unless otherwise stated.

3.8.2.4.1 Venturis The venturis are located downstream of the PAA injection location. Cameron stated that PAA is a dispersant that leads to a feed stream that contains colioidal corrosion products. These can be electochemically attracted to the stainless steel surface in the venturi throat since the high throat velocity sweeps away the neutralizing free electrons. Cameron stated that this causes verturi fouling that, in turn, makes the venturis indicate a flow rate that is higher than actual.

Cameron also identified that PAA interaction that affected venturi calibration was observed before LEFM installation and pointed out that a brief cessatin of PAA injection led to an immediate shift of 2 percent in indicated verturi flow indication relative to all other indicators of feedwater flow rate.

Cameron concluded that PAA changed feedwater calibration by approximately 3 percent or more and could explain the observed discrepency between the LEFM and venturi flow rate indications.

The NRC staff observed that there were differences between venturi indications. However, when each venturi flow rate was compared to the corresponding LEFM flow rate, all venturis exhibited a similar upward trend with approximately the same slope from May to September, 2011.

3.8.2.4.2 Turbine pressure indicators and mean steam flow There are two water paths to the SGs, feedwater flow that is measured by the LEFMs and venturies, and tempering flow that is also measured but bypasses the LEFMs and venturis.

Tempering flow rate was approximately one percent of feedwater flow rate during the comparison period and was stated to be constant. As identified in Section 2.2.2, above, an anomaly was idenfied that the NRC staff believes should be investigated There are two flow paths that exit the SGs, main steam flow and blowdown flow. Blowdown flow rate is measured and was about 0.5 percent of total flow into the SGs during the comparison period. The NRC staff observes that an anomaly in blowdown flow was identified in Section 3.8.2.2.2, above, that should be further investigated.

Thus SG steam flow is equal to tempering flow plus main feed flow minus blowdown flow.

Most of the steam flow enters the turbine with about 5 percent entering the second stage reheater. Cameron stated that there was no evidence that steam flow to the second stage reheater changed significantly as a fraction of total steam flow. Changes in SG steam flow in the comparison period were stated to be less than 0.1 percent.

First stage pressure is a measure of vapor flow rate and Cameron stated that, for practical purposes, is not affected by change in moisture content. Therefore Cameron concluded that if feedwater, blowdown, and tempering flow rates are constant, a decrease in steam moisture will increase vapor flow rate and first stage pressure. Cameron also stated that, Because the steam flow and first stage pressure instruments respond differently to changes in moisture content, their indications can be used to estimate trends in moisture content. It also stated that

changes in differential pressure across steam flow nozzles and first stage pressure can be used to calculate the change in moisture carryover. A Cameron moisture trend calculation showed a moisture decrease approximately equal to the discrepancy between turbine flows and LEFM flow. This was considered plausible because PAA caused a steam pressure increase apparently due to removal of corrosion products from the SG tube surface and reduction of deposits on separator cans by a similar mechanism could lead to a reduction in moisture.

3.8.2.4.3 Cameron conclusion Cameron concluded that:

• The process change in moisture carry-over is the most plausible explanation consistent with all of the data.

• The change in moisture carry-over should be expected given the effects intended with the PAA addition.

• The investigation is therefore complete.

3.8.2.5 Recent plant characteristics PAA was restored in January, 2012 during steady state operation after an extended period when PAA was not injected. Exelon provided data normalized to one after an initial tranient that followed re-initiation of PAA. Upon re-initiation, steam flow indication immediately decreased by 0.5 percent and venturi indication increased by 0.16 percent before reaching a relative value of one while LEFM, best estimate core thermal power, impulse pressure, and MWt were unchanged. Although there were numerous power transients following re-initiation, indications that apply to flow rate remained consistent after the initial transient until the plant was shut down for Refueling Outage B1R18 in August, 2012. Byron identified that a divergence in steam mass flow rate occurred previously when PAA was isolated and an upward trend occurred that was attributed to likely occurrence of new deposits on secondary steam separator surfaces or the SG outlet nozzle venturi surfaces. These deposits were postulated to have cleared when PAA was restored in January, 2012. The NRC staff considers this experience as supporting a conclusion that PAA affects both SG flow rate and venturi indication. Further it observes that PAA caused indicated SG flow rate to decrease and venturi flow rate to increase. The former is opposite to the 2011 behavior and twice as large whereas the venturi indicated flow rate change is essentially identical to the change that occurred in 2011. In both of these cases, the change was immediate in contrast to the change that occurred over several months from May to September in 2011.

After startup following Refueling Outage B1R18 in October, 2012 until May, 2013, the parameters were essentially unchanged during full power operation. This indicated that whatever was causing the parameter divergence was no longer occurring. Byron stated that it plans to continue to perform detailed trending assessments following Refueling Outage B1R19.

3.8.3. CONCLUSIONS

As summarized in Section 3.8.2.1, above, the average difference between the LEFM and other parameters that can be used to determine feedwater flow rate or thermal power was about 0.25 percent at the end of the increased difference that occured from May, 2011 to September, 2011.

Operating parameters from October, 2011 to May, 2013 established that differences had stabilized and were no longer increasing. The requested increase in thermal power corresponds to a power uncertainty of 0.37 percent, the calculated bounding value for system mass flow rate uncertainty was < 0.3 percent and the thermal power uncertainty was < 0.4 percent. The observed differences are smaller than the uncertainties that Caldon calculated that were part of the basis for the LAR. On this basis alone, the observed differences between LEFM and other plant indications are not sufficient to invalidate the feedwater flow rate indicated by the LEFMs. Further, the NRC staffs review supports a conclusion that the LEFMs are not affected by PAA injection and the observed deviations in thermal power and feedwater flow rates are not due to the LEFMs.

Examination of the data supports a conclusion that the venturis are affected by PAA injection although the reasons are not as clear nor are the differences between Byron 1 and Byron 2 fully understood.

Reasons for deviation in other plant parameters have been postulated but these are not accepted by all licensing personal and are not sufficiently supported to lead to firm conclusions.

3.9 Conclusions The above review covers the aspects of the requested 1.63 percent MUR thermal power uprate that are specific to the CheckPlus installations and are within the areas of SRXB review responsibility. SRXB concludes that the requested MUR thermal power uprate of 1.63 percent is acceptable for the topics that are within SRXB's UFM review responsibility.

3.10 Accident Analyses 3.10.1 Accident Analyses Bounded by Current Analysis of Record Although the licensee generally concluded that existing analyses were bounding of uprated plant operation with reduced uncertainty, the analyses were shown to be bounding in one of three different ways:

• For analyses that assume steady-state plant operation with a core power of 3672 MWtt, there is a 2% margin for power measurement uncertainty at the CLTP, 3586.6 MWtt.

These analyses are bounding also of plant operation at the MUR RTP of 3645 MWtt, with operating margin.

• For analyses that assume steady-state plant operation with a core power of 100%, the licensee evaluated accident or transient, and reanalyzed as necessary.

• Zero-power transients were not reanalyzed.

The licensing basis transients and accidents within the scope of SRXB review are summarized in Table 3-1.

Regulatory Issue Summary 2002-03, "Guidance on the Content of Measurement Uncertainty Recapture Power Uprate Applications," states the following:

In areas (e.g., accident/transient analyses, components, systems) for which the existing analyses of record do bound plant operation at the proposed uprated power level, the staff will not conduct a detailed review.

The NRC staff therefore finds the licensees analyses that were performed at 102% of the CLTP level acceptable without detailed review.

Table 3 Accident and Transient Analyses Analytic Power Level Transient/Accident Review Comments

(% CLTP)

Main Steam Line Break Mass and Energy Releases Outside 102 Acceptable Containment Natural Circulation Cooldown 102 Acceptable Feedwater System Malfunctions Causing a Reduction in Feedwater 100 Reanalyzed See 3.10.2.1 Temperature Feedwater System Malfunctions Causing an Increase in Feedwater 100 Reanalyzed See 3.10.2.1 Flow Excessive Increase in Secondary 100 Reanalyzed See 3.10.2.2 Steam Flow Inadvertent Opening of a Steam Bounded by other Analysis NA Generator Relief or Safety Valve Acceptable Steam System Piping Failure at Zero 0 Reanalyzed See 3.10.2.3 Power Steam System Piping Failure at Full 100 Reanalyzed See 3.10.2.4 Power Steam Pressure Regulator No such regulator at the Malfunction or Failure that Results in NA plants Decreasing Steam Flow Loss of External Load/Turbine Trip/Inadvertent Closure of Main RCS Overpressure 102 Steam Isolation Valves/Loss of Transient 100 See 3.10.2.5 Condenser Vacuum and Other MSS Overpressure NA Events Causing a Turbine Trip Loss of Nonemergency AC Power to the Plant Auxiliaries (Loss of Offsite 102 Acceptable Power)

Loss of Normal Feedwater Flow 102 Acceptable

Feedwater System Pipe Break 102 Acceptable Partial Loss of Forced Reactor 100 Reanalyzed See 3.10.2.6 Coolant Flow Complete Loss of Forced Reactor 100 Reanalyzed See 3.10.2.7 Coolant Flow Reactor Coolant Pump Shaft Seizure PCT/ RCS Overpressure (Locked Rotor)/Reactor Coolant Bounded 102 Pump Shaft Break/Locked Rotor with Reanalyzed See 3.10.2.8 100 Loss of Offsite Power Uncontrolled Rod Cluster Control Assembly Bank Withdrawal from a 0 Acceptable Subcritical or Low Power Startup Condition 8 (limiting case)

Uncontrolled Rod Cluster Control 100 See 3.10.2.9 Assembly Bank Withdrawal at Power 60 10 Rod Cluster Control Assembly 100 Acceptable Misoperation Startup of an Inactive Reactor TS Precludes Coolant Pump at an Incorrect NA Acceptable Temperature Chemical and Volume and Control System Malfunction that Results in a Not Power Dependent NA Decrease in Boron Concentration in Acceptable the Reactor Coolant Spectrum of Rod Cluster Control 102 Acceptable Assembly Ejection Accidents 0 Inadvertent Operation of Emergency 102 (Peak Pressurizer Core Cooling During Power Volume) See 3.10.2.10 Operation 100 Chemical and Volume Control Bounded by other analysis System Malfunction that Increases NA including Inadvertent ECCS Reactor Coolant Inventory Acceptable Inadvertent Opening of a Pressurizer 100 Reanalyzed See 3.10.2.11 Safety or Relief Valve Failure of Small Lines Carrying Bounded Primary Coolant Outside NA Acceptable Containment Steam Generator Tube Rupture 102 Reanalyzed See 3.10.2.12 Loss of Coolant Accident Resulting from a Spectrum of Postulated 102 Acceptable Piping Breaks Within the Reactor

Coolant Pressure Boundary (Best Estimate LOCA)

Small Break LOCA Analysis 102 Acceptable Post-LOCA Long-Term Core 102 Acceptable Cooling/Subcriticality Anticipated Transients without Scram 100 Reanalyzed (ATWS)

3.10.2 Accident Analysis Not Bounded by Current Analysis of Record The licensee reviewed their current analysis of record and reanalyzed the accidents that were not bounded by the proposed MUR power level. The licensee also reanalyzed some accidents for other issues that they found and adjusted them for the proposed MUR power level. The licensee also proposed to adopt VIPRE subchannel analysis code. The reanalysis using the VIPRE code used a core power level of 3648MWt for the MUR DNB analyses. This is a 1.7%

increase to the CLTP and is consistent with Revised Thermal Design Procedure (RTDP). The VIPRE usage as well as the RTDP methodology is reviewed by SNPB WCAP-14565-P-A SER Conditions The staff reviewed the four conditions of the SER for the staff approval of the WCAP-14565 topical report for the use of the VIPRE-01 code. The staff reviewed the conditions and the licensee responses to them.

Condition 1: Selection of the appropriate critical heat flux (CHF) correlation, DNBR limit, engineered hot channel factors for enthalpy rise and other fuel-dependent parameters for a specific plant application should be justified with each submittal.

The licensee provided the limits in their response. It included the WRB-2 correlation limit of 1.17 for the VIPRE DNBR calculations for the VANTAGE+ fuel. The licensee also stated that the fuel design will not change for the MUR and therefore the fuel dependent parameters in the DNBR calculations are unchanged.

Condition 2: Reactor core boundary conditions determined using other computer codes are generally input into VIPRE for reactor transient analyses. These inputs include core inlet coolant flow and enthalpy, core average power, power shape and nuclear peaking factors. These inputs should be justified as conservative for each use of VIPRE.

The licensee stated that the boundary conditions are all generated by NRC approved codes and analysis methodologies. They also stated that reactor core boundary conditions are unchanged from currently justified values besides the increase in the nominal core power of 1.7%.

Condition 3: The NRC Staffs generic SER for VIPRE (Reference III.1-21) set requirements for use of new CHF correlations with VIPRE. Westinghouse has met these requirements for using WRB-1, WRB-2 and WRB-2M correlations. The DNBR limit for WRB-1 and WRB-2 is 1.17. The WRB-2M correlation has a DNBR limit of 1.14. Use of other CHF correlations not currently included in VIPRE will require additional justification.

The licensee stated the limit for the WRB-2 correlation is 1.17. the licensee also stated that the ABB-NV DNBR limit is 1.13 and the WLOP DNBR limit is 1.18 and both were previously approved for use with the VIPRE code.

Condition 4: Westinghouse proposes to use the VIPRE code to evaluate fuel performance following postulated design-basis accidents, including beyond-CHF heat transfer conditions. These evaluations are necessary to evaluate the extent of core

damage and to ensure that the core maintains a coolable geometry in the evaluation of certain accident scenarios. The NRC Staffs generic review of VIPRE (Reference III.1-

21) did not extend to post CHF calculations. VIPRE does not model the time-dependent physical changes that may occur within the fuel rods at elevated temperatures.

Westinghouse proposes to use conservative input in order to account for these effects.

The NRC Staff requires that appropriate justification be submitted with each usage of VIPRE in the post-CHF region to ensure that conservative results are obtained.

The licensee response stated that the MUR power uprate application of VIPRE replaces the THINC and FACTRAN codes and is not used in the post-CHF region.

The staff reviewed the disposition of the four conditions laid out in the staff SER for WCAP-14565. The staff found that the licensee adequately addressed the conditions for the MUR LAR.

Review of Reanalyzed Events The SRXB staffs review of the following accidents covered:

1. The description of the causes of the event and the description of the event itself

2. The initial conditions

3. The values of reactor parameters used in the analysis

4. The analytical methods and computer codes used

5. The results of the associated analysis The staff used specific review criteria contained in NUREG-0800 SRP Section 15 and other guidance.

3.10.2.1 Feedwater System Malfunctions Causing a Reduction in Feedwater Temperature or an Increase in Feedwater Flow An increase in feedwater flow or reduction in feedwater temperature will result in increased subcooling in the affected SGs. The increased subcooling will then create a greater load demand on the RCS which decreases the RCS temperature which can produce a reactivity insertion. The neutron overpower, overtemperature and overpower T trips are designed to prevent power increases that could lead to DNBR becoming less than its limit value.

The staff reviewed the initial conditions that the licensee used for the event. The analysis uses a 1.5°F RCS average temperature bias and a minimum SG tube plugging level and maximum feedwater temperature.

The licensee used NRC approved codes LOFTRAN, VIPRE-W, and ANC as well as the RTDP to calculate DNBR. The current analysis was performed at 3600.6MWt and the proposed analysis was performed at 3672MWt.

The licensee chose a limiting case for the four plants which showed a reduction in feedwater temperature event with D5 SGs. The results showed that the resulting DNBR was greater than the safety analysis limit.

The staff reviewed the analysis and results and found them to be acceptable.

3.10.2.2 Excessive Increase in Secondary Steam Flow An increase in secondary steam flow creates a mismatch between the reactor core and the SG load demand. The RPS signals that protect against this event include the low pressurizer pressure, overtemperature T, and power range high neutron flux.

The licensee used NRC approved code LOFTRAN as well as the RTDP to calculate DNBR.

The current analysis was performed at 3600.6MWt and the proposed analysis was performed at 3672MWt.

The staff reviewed the initial conditions for the event. The most limiting case assumed minimum reactivity feedback, automatic rod control and the Babcox & Wilcox International (BWI) SGs with zero tube plugging.

The analysis showed the worst case minimum DNBR and it gave more than 20% safety analysis margin. The staff reviewed the analysis and the results and found them to be acceptable.

3.10.2.3 Steam Supply Piping Failure at Zero Power The steam break would result in an increase in steam flow initially which removes more energy from the RCS and causes a reduction in RCS temperature and pressure. The cooldown can result in an insertion of positive reactivity. The most reactive RCCA is assumed to be stuck in its fully withdrawn position and the possibility of returning to power exists.

The licensee used NRC approved LOFTRAN, VIPRE, and ANC case along with the Standard Thermal Design Procedure (STDP) to calculate the minimum DNBR and Peak Linear Heat Rate (PLHR). The licensee reanalyzed the even to address revised reactivity feedback coefficients associated with MUR power level.

The staff reviewed the initial conditions and assumptions for the event. The initial conditions included various conservative assumptions as well as the assumption that the maximum break size corresponds to the size of the flow restricting nozzle in the two SG types. Protective functions available to provide protection for a steamline break included the safety injection system, overpower trips, redundant isolation of the main feedwater lines, and trip of the fast acting steamline stop valves.

The limiting case was found to be with the Units 2 with a beak size of 1.4ft2, AC power available and low Tave. The minimum DNBR value is above the limit value of 1.18 and the maximum PLHR is below its limit value. The staff noted that there was a reduction in margin to the limits which the licensee stated occurred due to power uprate reactivity coefficients creating a more severe return to power as well as the analysis being performed in a more conservative manner to bound cycle to cycle variations in future reloads.

The staff reviewed the analysis and the results and found them to be acceptable.

3.10.2.4 Steam System Piping Failure at Full Power

The steam break would result in an increase in steam flow initially which removes more energy from the RCS and causes a reduction in RCS temperature and pressure. The cooldown can result in an insertion of positive reactivity which can cause a power excursion.

The licensee used NRC approved LOFTRAN, VIPRE, and ANC as well as the RTDP to calculate the minimum DNBR and Peak Linear Heat Rate (PLHR). The current analysis was performed at 3600.6MWt and the proposed analysis was performed at 3672MWt.

The staff reviewed the initial conditions and assumptions for the event. The initial conditions included maximum moderator reactivity feedback and least negative Doppler power feedback.

The limiting break size that was found to bound all break sizes was 0.95ft2. Protective functions that may be used to mitigate this event include the reactor trip, and safety injection.

Westinghouse applies the Condition II acceptance criteria such that damage to the fuel rods is precluded.

The limiting case shows that the power increases during the transient until the reactor trips on overpower T. The minimum DNBR and PLHR were both found to be within the safety limits.

The staff reviewed the analysis and the results and found them to be acceptable.

3.10.2.5 Loss of External Load/Turbine Trip/Inadvertent Closure of Main Steam Isolation Valves/Loss of Condenser Vacuum and Other Events Causing a Turbine Trip The turbine trip event is the event found to be bounding for this analysis. For the event the turbine stop valves close very rapidly which cuts off steam flow to the turbine. The steam dumps are initiated. The secondary temperature increases as well. The steam dumps and condenser normally accept the excess steam.

The licensee used the STDP for the maximum RCS and main steam system (MSS) pressure overpressure concerns. The RCS overpressure event was not reanalyzed as it is bounded by the AOR. The MSS overpressure event was analyzed based on the RCS overpressure case with automatic pressure control assumed and minimum SG tube plugging modeled . NRC approved LOFTRAN is also used for the overpressure event.

For the DNB case the licensee used NRC approved LOFTRAN and the RTDP to calculate DNBR. The current analysis was performed at 3600.6MWt and the proposed analysis was performed at 3672MWt. The DNB case assumed minimum SG tube plugging as well as the RCS flow rate corresponding to minimum measured flow.

The staff reviewed the initial conditions and assumptions for the event. One assumption is that the conditions in the reactor must cause the reactor trip there is no reactor trip on the turbine trip. No credit is taken for steam dump and main feedwater flow is terminated at the time of the turbine trip and no auxiliary feedwater is credited. Manual rod control is modeled for conservatisms. No credit is taken for the SG power-operated relief valves. The MSSVs are at or greater than the TS limit of 3%.

The results for the MSS overpressure event showed that the overpressure case came in under the pressure limit of 1318.5psia at about 1313.5psia for Units 1 and 1310.6psia for Units 2. The minimum DNBR event showed that the minimum DNBR was above the safety limit DNBR.

The staff reviewed the analysis and results and found them to be acceptable.

3.10.2.6 Partial Loss of Forced Reactor Coolant Flow The partial loss of forced reactor coolant flow would occur from the failure of an RCP. When the reactor is at power the loss of an RCP would result in a loss of coolant flow and a rapid increase in the coolant temperature which could lead to DNB.

The licensee used NRC approved LOFTRAN and VIPRE codes along with the RTDP to calculate the minimum DNBR. The current analysis was performed at 3600.6MWt and the proposed analysis was performed at 3672MWt. The analysis is performed assuming the loss of two RCPs with four loops in operation.

The staff reviewed the initial conditions and assumptions for the event. The most negative Doppler-only power coefficient was modeled. The Low Reactor Coolant System Flow reactor trip is credit as being available to mitigate the event.

The results showed that the minimum DNBR was above the DNBR safety analysis limit.

The staff reviewed the analysis and the results and found them to be acceptable.

3.10.2.7 Complete Loss of Forced Reactor Coolant Flow The complete loss of forced reactor coolant flow would occur with the loss of all four RCPs. The loss of the RCPs would cause immediate loss of coolant flow and a rapid increase in coolant temperature.

The licensee used NRC approved LOFTRAN and VIPRE computer codes as well as the RTDP methodology to calculate a minimum DNBR. The current analysis was performed at 3600.6MWt and the proposed analysis was performed at 3672MWt. Two cases were analyzed.

One was the complete loss of all four RCPS and the other was the frequency decay event resulting in the complete loss of forced coolant flow.

The staff reviewed the initial conditions and assumptions for the event. The most negative Doppler-only power coefficient was modeled. The RCP power Supply Undervoltate or Underfrequency and the Low Reactor Coolant System flow reactor trip functions are credited to mitigate this event.

The frequency decay event was shown to be the limiting case. The reactor trips on the underfrequency trip signal after the frequency decay of 5 Hz/sec occurs for 1.2 seconds. The minimum DNBR was shown to be above the DNBR safety analysis limit.

The staff reviewed the analysis and the results and found them to be acceptable.

3.10.2.8 Reactor Coolant Pump Shaft Seizure (Locked Rotor)/Reactor Coolant Pump Shaft Break/Locked Rotor with Loss of Offsite Power When an instantaneous RCP shaft seizure occurs, the flow through the loop reduces rapidly with no RCP coastdown. The coolant in the primary side heats up and expands causing an insurge into the pressurizer. Pressure suppression including sprays and the PORVs would actuate to lower pressure.

The licensee used NRC approved LOFTRAN and VIPRE codes along with the RTDP methodology. The case that is performed as bounding is the locked rotor rods-in-DNB case.

The codes and methodology are used to determine the percentage of fuel rods experiencing a DNBR. The current analysis was performed at 3600.6MWt and the proposed analysis was performed at 3672MWt. The locked rotor is analyzed as one locked rotor with four loops operating and a concurrent loss of offsite power at the time of the reactor trip.

The staff reviewed the initial conditions and assumptions for this event. The most negative Doppler-only power coefficient was modeled. The Low Reactor Coolant System Flow reactor trip is credited as available to mitigate the event.

The results showed that the percentage of fuel rods exceeding the DNBR limit is less than the 2% fuel rod failures for the radiological dose calculations.

The staff reviewed the analysis and the results and found them to be acceptable.

3.10.2.9 Uncontrolled Rod Cluster Control Assembly Bank Withdrawal at Power This event occurs when an uncontrolled Rod Cluster Control Assembly (RCCA) is withdrawn from the core at power. This can occur due to operator action or malfunction in the rod control system. The result is an increase in the core heat flux and an increase in the RCS temperature.

The RPS is designed to terminate this event before the limits are exceeded.

The Licensee used NRC approved LOFTRAN code and the RTDP methodology to analyze this event. The proposed analysis was performed at 3672MWt. There are a variety of automatic RPS features which are designed to prevent core damage during this event and they include:

power range neutron flux, positive neutron flux rate, overtemperature T, overpower T, high pressurizer pressure, and high pressurizer water level reactor trips. In addition to the RPS features there are rod withdrawal blocks, that would limit this event, which include high neutron flux, overpower T, and overtemperature T.

The staff reviewed the initial conditions and assumptions for this event. Minimum and maximum reactivity feedback cases are analyzed. Reactor tips are assumed to be at their maximum values. The reactor trip assumes the highest worth RCCA is stuck fully withdrawn. Power levels of 10%, 60%, and 100% are considered.

This event is considered a Condition II event. The results were shown for the range of considered conditions. The minimum DNBR was greater than the safety analysis limit for each of the analyzed events.

The staff reviewed the analysis and the results and found them to be acceptable.

3.10.2.10 Inadvertent Operation of the Emergency Core Cooling System During Power Operation The inadvertent operation of the ECCS at power could be caused by operator error, test sequence error, or a false electrical actuation signal. If the actuation signal occurs the suction of the charging pumps changes to the refueling water storage tank (RWST). The charging pumps then are aligned to start pumping the borated RWST water into the RCS. The accumulators and low head injection systems are not able to inject into the RCS at normal pressure. This event is analyzed to (1) show that there is no fuel clad damage, as indicated by the calculated minimum of DNBR, and (2) to show that the event will not escalate into a more serious event. In the first case, the reactor is not assumed to trip from the SI signal.

For the DNBR analysis, the SI signal is considered to not cause a reactor trip in the analyzed event. The reactor power will decrease due to the injection of borated water and the pressurizer pressure and water level decrease. The reactor will eventually trip by low pressurizer pressure trip or a manual trip.

The licensee used NRC approved LOFTRAN code and the RTDP methodology to calculate the minimum DNBR. The current analysis was performed at 3600.6MWt and the proposed analysis was performed at 3672MWt.

The staff reviewed the initial conditions and assumptions for this event. The reanalysis was done for the DNB case. Some assumptions included: zero moderator temperature coefficient, low absolute value Doppler power coefficient, manual rod control, pressurizer heaters inoperable, reactor trip on low pressurizer pressure, no operator action, and no credit for the steam dump. This event is considered a Condition II event.

The results showed the power decreasing due to boron injection. The DNBR is shown to increase throughout the event. There was an expected decrease in the minimum DNBR due to the power increase from the initial conditions (MUR).

The staff reviewed the analysis and results and found them to be acceptable for the DNB case of the Inadvertent Operation of the ECCS during Power Operation event.

For the analysis to demonstrate the inadvertent ECCS operation does not escalate into a more serious event the analysis was done at 102% of CLTP. The current licensing basis (CLB) analysis is documented in the FSAR and dated 2002. The applicant states that this analysis continues to bound operation at the MUR power level. Since 2002, the NRC staff has issued a Regulatory Issue Summary (RIS 2005-29) regarding this event and the problems that can occur when the pressurizer is filled. The licensees CLB analysis indicates the pressurizer is predicted to fill. However, the licensee has not updated its CLB analysis to address the concerns outlined in the RIS. Given that the applicant has not updated the analysis in response to the RIS, the issue was determined to be outside the scope of the MUR. The staff intends to pursue this issue generically by clarifying the expectations in the RIS and is also considering plant-specific actions to address the issue.

3.10.2.11 Inadvertent Opening of a Pressurizer Safety or Relief Valve

The inadvertent opening of PORV would cause depressurization of the RCS. The analysis uses the more conservative assumption of the conditions of a Pressurizer Safety Valve (PSV) opening because the PSVs have close to twice the steam flow rate relief capacity of the PORVs. The event initially starts with rapidly decreasing RCS pressure then the filling of the pressurizer.

The licensee used NRC approved LOFTRAN code and the RTDP methodology to calculate the minimum DNBR. The current analysis was performed at 3600.6MWt and the proposed analysis was performed at 3672MWt.

The staff reviewed the initial conditions and assumptions for this event. The cases were run to find the most limiting result between the Unit 1 and Unit 2 SGs. Maximum SG tube plugging and least negative Doppler-only power coefficient are assumed. The Low Pressurizer Pressure and Overtemperature T reactor trips are credited to be available to mitigate the event. This event is considered a Condition II event.

The results showed the most limiting case being the Unit 2 SGs with maximum tube plugging and minimum feedwater temperatures. The results showed the depressurization and the nuclear power as well as the minimum DNBR. The reactor trip occurs on Low Pressurizer Pressure. The minimum DNBR was greater than the DNBR safety analysis limit.

The staff reviewed the analysis and the results and found them to be acceptable for the DNB event of the Inadvertent Opening of a Pressurizer Safety or Relief Valve.

3.10.2.12 Steam Generator Tube Rupture Margin to Steam Generator Overfill The licensee performed the thermal and hydraulic analysis using LOFTTR2 program and methodology. The licensee looked at the failure of an intact SG PORV, failure of ruptured SG MSIV, and failure of ruptured SG feedwater control valve to determine the limiting single failure.

The limiting single failure was determined to be the failure of an intact SG PORV was found to be limiting due to the increased cooldown time.

The staff reviewed the initial conditions and the assumptions for this event. For both Units the SG MTO considered the minimum operating temperature with the minimum main feedwater temperature. They both also assumed the maximum SG tube plugging. The failure of a PORV on an intact SG was used for the limiting case. The secondary side volume available for Unit 1 SG is 5122ft3 and the secondary side volume available for Unit 2 SG is 5955ft3. The licensee performed the analysis to show that the secondary side of the ruptured SG did not completely fill with water.

The event initiates with a tube rupture with water flowing from the primary to the secondary side of the SG. The RCS starts losing coolant and the pressurizer level and pressure are decreased.

The reactor trip occurs on overtemperature T trip signal. The reactor power decreases to decay heat and the turbine stop valves close. The steam dumps are unavailable due to assumed loss of offsite power. This also causes main feedwater flow to stop and the SG flow is provided by the AFW. The energy in the secondary side is released through the SG PORVS and safety valves. The pressurizer pressure signal starts the SI and flow is delivered to recover pressurizer level. The licensee assumes that the AFW flow to the ruptured SG will be isolated within 9 minutes and the MSIV for the same SG is closed at 18 minutes. Three minutes of

operator action time are assumed before cooldown is started. The cooldown is performed with two of the intact SGs since one of the intact SG PORVs is the assumed failure. After the cooldown termination temperature is reached the cooldown is terminated and a 4 minute operator action time is assumed before RCS depressurization. The RCS depressurization is terminated when the RCS pressure is less than that of the ruptured SG and the pressurizer level was adequate. Three minute operator action time is assumed before the SI is terminated.

The results showed margin to overfill for both units. The maximum ruptured SG water volume for the Unit 1 case was shown to be 5068ft3. The result was therefore 54ft3 of margin to overfill.

The maximum ruptured SG water volume for the Unit 2 case was shown to be 5685ft3. The result was therefore 270ft3 of margin to overfill.

The licensee will implement the following plant modifications to support the SG MTO assumptions:

1. Installing safety related air accumulator tanks to support AFW flow control

2. Increase the capacity of the Unit 1 SG PORVs

3. Modify Unit 2 SG PORVs to achieve analysis flow rates

4. Install uninterruptible power supplies on two of the four SG PORVs

5. Install a manual isolation valve upstream of each High Head Safety Injection valve The staff reviewed the analysis and results and found them to be acceptable.

3.11 Conclusion The NRC staff has reviewed the licensees analyses of the above events and concludes that the licensees analyses have adequately accounted for operation of the plant at the proposed power level and were performed using acceptable analytical models. The NRC staff further concludes that the licensee has demonstrated that the reactor protection and safety systems will continue to ensure that the SAFDLs and the RCPB pressure limits will not be exceeded as a result of these events. Therefore, the NRC staff finds the proposed MUR LAR acceptable with respect to the events above.

4.0 CONCLUSION

The SRXB staff reviewed the reactor systems and thermal-hydraulic aspects of the LEFM as well as the accident analysis aspects of the proposed LAR in support of implementation of a MUR. Based on the considerations discussed above, the NRC staff determined that the results of the licensees analyses related to these areas continue to meet applicable acceptance criteria following implementation of the MUR. The proposed amendment is based on the use of a Cameron LEFM Check Plus system that would decrease the uncertainty in the feedwater flow, thereby decreasing the power level measurement uncertainty from 2.0% to 0.37%. Therefore, the SRXB staff finds the proposed LAR acceptable in its area of review.

5.0 References A Caldon Inc., Engineering Report-80P, Topical Report, Improving Thermal Power Accuracy and Plant Safety While Increasing Operating Power Level Using the LEFMTM System, Revision 0, March 1997.

B Hannon, John N., Staff Acceptance of Caldon Engineering Report ER-80P: Improving Thermal Power Accuracy While Increasing Power Level Using the LEFM System, NRC letter to C.L. Terry, TU Electric, March 8, 1999 and Safety Evaluation by the Office of Nuclear Reactor Regulation, Topical Report ER-80P, Improving Thermal Power Accuracy and Plant Safety while Increasing Operating Power Level Using the LEFM System, Comanche Peak Steam Electric Station, Units 1 and 2.

C Caldon Inc., Supplement to Engineering Report ER-80P: Basis for a Power Uprate with the LEFMTM System, ER-160P, Revision 0, May 2000.

D Martin, Robert, Staff Acceptance of TS Changes, Power Uprate Request, and Caldon Engineering Report ER-160P, NRC letter to J.A. Scalice, Tennessee Valley Authority, January 19, 2001.

E Caldon Inc., Supplement to Engineering Report ER-80P: Basis for a Power Uprate with the LEFMTM or LEFM CheckPlusTM System, ER-157P, Revision 5, October 2001.

F Richards, Stuart A., Review of Caldon, Inc., Engineering Report ER-157P, NRC letter to Michael A. Krupa, Entergy, December 20, 2001.

G Estrada, Herb, Engineering Report 157P, Rev. 8, Supplement to Caldon Topical Report ER-80P: Basis for Power Uprates with an LEFM Check or an LEFM CheckPlus System, Cameron Measurement Systems, ML081720324, May 2008. Non-proprietary version is ML081720323.

H Hauser, Ernie, Documentation to support publication of Caldon ER-157P-A Rev. 8, Letter with attachments from Cameron Measurement Systems to NRC, ML102950253 (Package), October 15, 2010.

I Hauser, Ernie, Acceptance Criteria for Review of Licensee Submittals for MUR Uprates, Caldon Ultrasonics Engineering Report ER-769 Rev. 1, ML093290054, October 2009.

J Lyon, Warren C., Report of Trip to Alden Laboratory on January 17 and 18, 2006, TAC No. MC8434, NRC Memorandum, ML060400418, February 9, 2006.

K Uncertainty Analysis of Flow Measurement 100,000 Lb Weigh Tank, Alden Laboratory, ML072710557, January 17, 2006.

L NRC Meeting at Alden Research Laboratory, Inc., Part 1, Cameron Measurement Systems, ML092680921, August 24, 2009.

M NRC Meeting at Alden Research Laboratory, Inc., Part 2, Cameron Measurement Systems, ML092680922, August 24, 2009.

N John Spadaro, Bounding Uncertainty Analysis for Thermal Power Determination at Byron Unit 1 Nuclear Generation Station using the LEFM CheckPlus System, Proprietary, Cameron Measurement Systems, ER-800, Revision 1, October 2010.

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John Spadaro, Bounding Uncertainty Analysis for Thermal Power Determination at Braidwood Unit 1 Nuclear Generation Station using the LEFM CheckPlus System, Proprietary, Cameron Measurement Systems, ER-803, Revision 1, October 2010.

O Augenstein, Don, Meter Factor Calculation and Accuracy Assessment for Byron Unit 1, Proprietary, Cameron Measurement Systems, ER-829, Revision 1, July 2010 Augenstein, Don, Meter Factor Calculation and Accuracy Assessment for Byron Unit 2, Proprietary, Cameron Measurement Systems, ER-832, Revision 1, July 2010 Augenstein, Don, Meter Factor Calculation and Accuracy Assessment for Braidwood Unit 1, Proprietary, Cameron Measurement Systems, ER-843, Revision 0, July 2010 Augenstein, Don, Meter Factor Calculation and Accuracy Assessment for Braidwood Unit 2, Proprietary, Cameron Measurement Systems, ER-844, Revision 0, July 2010 P Estrada, Herb, Engineering Report: ER-790 Rev. 1, An Evaluation of the Impact of 55 Tube Permutit Flow Conditioners on the Meter Factor of an LEFM CheckPlus, Proprietary, Cameron Measurement Systems, ML100840026, March, 2010.

Q Letter from Trepanier, T. E. to U.S. Nuclear Regulatory Commission, Calvert Cliffs Nuclear Power Plant, Unit Nos. 1 & 2; Docket Nos. 50-317 & 50-318, Response to Request for Additional Information - License Amendment for Measurement Uncertainty Recapture Power Uprate - Calvert Cliffs Nuclear Power Plant, Unit Nos. 1 and 2, ML091310169, May 7, 2009.

R Letter from U.S. Nuclear Regulatory Commission to Spina, J. A. (Calvert Cliffs Nuclear Power Plant), Calvert Cliffs Nuclear Power Plant, Unit Nos. 1 and 2 - Amendment Re:

Measurement Uncertainty Recapture Power Uprate (TAC Nos. MD9554 and MD9555),

ML091820366, July 22, 2009.

S Kobetz, Timothy, Safety Evaluation Regarding Endorsement of NEI Guidance for Adhering to the Licensed Thermal Power Limit, NRC Memorandum to Mike Case, ML082690105, October 8, 2008.

T Wermiel, Jared S., et. al. Report of the Ultrasonic Flow Meter Allegation Task Group Review of Caldon Ultrasonic Flow Meters, ML041760370, June 7, 2004.

U Augenstein, Don, et al, "Accuracy Validation of Multiple Transit Time Flowmeters," Paper presented at the 7th International Conference on Hydraulic Efficiency Measurements, Milan, Italy, September 3 - 6, 2008.

V. Lambert, Craig, Request for License Amendment Regarding Measurement Uncertainty Recapture Power Uprate, Byron Station Units 1 and 2 and Braidwood Station Units 1 and 2, ML1117900300, June 23, 2011 W. Barton, K. F. Additional Information Supporting Request for License Amendment Regarding Measurement Uncertainty Recapture Power Uprate, October 9, 2012 X. Byron, Attachment 2, Complex Troubleshooting MA-AA-716-004, Rev. 10, September 19, 2011 Y. Byron, No Tite, Assessment of October 3, 2011, Cameron Report ER-947, October 6, 2011 Z. Estrada, H., Analysis of the Trends and Uncertainties of the LEFM Indications at Byron 1, ER-968 Rev. 1, Proprietary, March 2012 ZA. Byron/Braidwood Final Safety Analysis Report

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