Text

License Amendment Request 02-05, Revision to Technical Specification Table 3.3.1-1, Reactor Trip System Instrumentation, & Revised Reactor Coolant System Flow Measurement
	ML022470376
Person / Time
Site:	Diablo Canyon
Issue date:	08/27/2002
From:	Rueger G; Pacific Gas & Electric Co
To:	; Document Control Desk, Office of Nuclear Reactor Regulation
References
	50-275-OL, 50-323-OL, CAW-02-1531, DCL-02-097, LAR 02-05 WCAP-15113, Rev 1, WCAP-15173, Rev 1
	Download: ML022470376 (109)
	v • d • e

W Pacific Gas and Electric Company, Gregory M. Rueger US Mal Senior Vice President- Mail Code B32 Generation and Pacific Gas and Electric Company Chief Nuclear Officer PO Box 770000 San Francisco. CA 94177-0001 Overnight Mail August 27, 2002 Mail Code B32 Pacific Gas and Electric Company 77 Beale Street, 32nd Floor PG&E Letter DCL-02-097 San Francisco, CA 94105-1814 415 973 4684 U.S. Nuclear Regulatory Commission Fax 4159732313 ATTN: Document Control Desk Washington, DC 20555-0001 Docket No. 50-275, OL-DPR-80 Docket No. 50-323, OL-DPR-82 Diablo Canyon Units 1 and 2 License Amendment Request 02-05 Revision to Technical Specification Table 3.3.1-1, "Reactor Trip System Instrumentation," and Revised Reactor Coolant System Flow Measurement

Dear Commissioners and Staff:

In accordance with 10 CFR 50.90, enclosed is an application for amendment to Facility Operating License Nos. DPR-80 and DPR-82 for Units I and 2 of the Diablo Canyon Power Plant (DCPP) respectively. This License Amendment Request (LAR) revises the term "minimum measured flow per loop" to "measured loop flow" in the allowable value and nominal trip setpoint for the Reactor Coolant Flow-Low reactor trip function contained in Technical Specification (TS) 3.3.1 Table 3.3.1-1, "Reactor Trip System Instrumentation." In addition, the proposed change allows an alternate method for the measurement of reactor coolant system (RCS) total volumetric flow rate through measurement of the elbow tap differential pressures on the RCS primary cold legs. The use of elbow tap differential pressures normalized to DCPP Cycle 1 and 2 precision flow calorimetrics improves the accuracy of the RCS flow measurement through reduction of the effect of hot leg temperature streaming that is present in the current flow calorimetric method.

Enclosure 1 contains a description of the proposed change, the supporting technical analyses, and the significant hazards determination. Enclosures 2 and 3 contain marked-up and revised TS pages, respectively. Enclosure 4 provides the marked-up TS Bases changes for information only.

The following Westinghouse Electric Company, LLC (Westinghouse) topical reports provide the technical basis for the measurement of RCS flow using the RCS cold leg elbow taps and are contained in Enclosures 5 and 6 respectively:

WCAP-15173, Revision 1 (Westinghouse non-proprietary), "RCS Flow Measurement Using Elbow Tap Methodology at Diablo Canyon Units 1 and 2,"

April, 2002 A member of the STARS (Strategic Teaming and Resource Sharing) ALLiance 0\1 Callaway

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DiabloCanyon e Palo Verde e South Texas Projet 9 Wolf Creek

Document Control Desk PG&E Letter DCL-02-097 August 27, 2002 Page 2 WCAP-15113, Revision 1 (Westinghouse proprietary Class 2), "RCS Flow Measurement Using Elbow Tap Methodology at Diablo Canyon Units 1 and 2,"

April, 2002 WCAP-15113, Revision 1, contains information proprietary to Westinghouse.

Accordingly, Enclosure 6 includes a Westinghouse authorization letter, CAW-02-1531, and accompanying affidavit, Proprietary Information Notice, and Copyright Notice. The affidavit is signed by Westinghouse, the owner of the information. The affidavit sets forth the basis on which the Westinghouse proprietary information contained in WCAP-15113, Revision 1, may be withheld from public disclosure by the Commission, and it addresses with specificity the considerations listed in paragraph (b)(4) of 10 CFR 2.790 of the Commission's regulations. PG&E requests that the Westinghouse proprietary information be withheld from public disclosure in accordance with 10 CFR 2.790.

Correspondence with respect to the copyright or proprietary aspects of the application for withholding related to the Westinghouse proprietary information or the Westinghouse affidavit provided in Enclosure 6 should reference Westinghouse Letter CAW-02-1531 and be addressed to H. A. Sepp, Manager of Regulatory and Licensing Engineering, Westinghouse Electric Company, LLC, P. 0. Box 355, Pittsburgh, Pennsylvania 15230-0355.

The change in this LAR is not required to address an immediate safety concern.

PG&E requests that this amendment be approved no later than September 1, 2003.

PG&E requests the LAR be made effective upon NRC issuance, to be implemented within 60 days from the date of issuance.

S nerely,.

G r gto'j M/. R *ge r Senior Tice President- Generationand Chief Nuclear Officer kjs/4328 Enclosures cc: Edgar Bailey, DHS Ellis W. Merschoff David L. Proulx Diablo Distribution cc/enc: Girija S. Shukla A member of the STARS (Strategic Teaming and Resource Sharing) Alliance Callaway

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South Texas Project

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PG&E Letter DCL-02-097 UNITED STATES OF AMERICA NUCLEAR REGULATORY COMMISSION

) Docket No. 50-275 In the Matter of ) Facility Operating License PACIFIC GAS AND ELECTRIC COMPANY) No. DPR-80

)

Diablo Canyon Power Plant ) Docket No. 50-323 Units 1 and 2 ) Facility Operating License I No. DPR-82 AFFIDAVIT Gregory M. Rueger, of lawful age, first being duly sworn upon oath says that he is Senior Vice President - Generation and Chief Nuclear Officer of Pacific Gas and Electric Company; that he has executed LAR 02-05 on behalf of said company with full power and authority to do so; that he is familiar with the content thereof; and that the facts stated therein are true and correct to the best of his knowledge, information, and belief.

Senior Vic President- Generationand Chief NuclearOfficer Subscribed and sworn to before me this 2 7 th day of August, 2002.

Notary blic County of San Francisco State of California AMY DEIKKO DONG Z~'7~ Commission # 1206749 Noicay Pubrc -Cafffomia i/ San Francisco County r My comm. Expr+*5Js

Enclosure 1 PG&E Letter DCL-02-097 PROPOSED AMENDMENT TO TECHNICAL SPECIFICATION TABLE 3.3.1-1 AND REVISED REACTOR COOLANT SYSTEM FLOW MEASUREMENT

1.0 DESCRIPTION

This letter is a request to amend Operating License Nos. DPR-80 and DPR-82 for Units 1 and 2 of the Diablo Canyon Power Plant (DCPP), respectively.

The proposed change revises the term "minimum measured flow per loop" to "measured loop flow" in the allowable value and nominal trip setpoint for the Reactor Coolant Flow-Low reactor trip function contained in Technical Specification (TS) 3.3.1 Table 3.3.1-1, "Reactor Trip System Instrumentation."

In addition, the proposed change allows an alternate method for the measurement of reactor coolant system (RCS) total volumetric flow rate through measurement of the elbow tap differential pressures (AP) on the RCS primary cold legs. Verification that the measured RCS total flow rate is within limits is required by TS Surveillance Requirement (SR) SR 3.4.1.4 on a 24 month frequency. The verification requirement of SR 3.4.1.4 is currently met by performing a flow measurement using a method based on RCS primary temperature and a RCS secondary power calorimetric.

2.0 PROPOSED CHANGE

The Reactor Coolant Flow-Low function allowable value and nominal trip setpoint in TS Table 3.3.1-1 are currently "> 89.8%(') of MMF/Ioop" and "90%(1) of MMF/Ioop" respectively where the footnote (I) states "Minimum measured flow (MMF) is 89,800 gpm per loop for Unit 1 and 90,625 gpm per loop for Unit 2."

The change would revise the Reactor Coolant Flow-Low function allowable value in TS Table 3.3.1-1 to "> 89.8% of measured loop flow" and revise the Reactor Coolant Flow-Low function nominal trip setpoint to "90% of measured loop flow."

The proposed TS change is noted on the markup TS page provided in Enclosure 2. The revised TS is provided in Enclosure 3. The revised TS Bases Section B 3.4.1 is contained for information only in Enclosure 4.

3.0 BACKGROUND

3.1 Reactor Coolant Flow-Low Reactor Trip System Function TS 3.3.1 contains the requirements for reactor trip system instrumentation.

The reactor trip system initiates a unit shutdown, based on the values of selected unit parameters, to protect against violating the core fuel design limits and RCS pressure boundary during anticipated operational 1

Enclosure 1 PG&E Letter DCL-02-097 occurrences (AOOs). The reactor trip system functions are identified in TS Table 3.3.1-1.

Each reactor trip system function contains an allowable value and a nominal trip setpoint. Setpoints in accordance with the allowable values ensure that the safety limits of TS 2.0, "Safety Limits (SLs)," are not violated during AOOs and that the consequences of design basis accidents (DBAs) will be acceptable, provided the unit is operated from within the TS limiting condition for operations at the onset of the AOO or DBA and the equipment functions as designed. The nominal trip setpoints are the nominal values at which the bistables are set, and are based on the safety analysis analytical limits described in Chapter seven of the DCPP Final Safety Analysis Report (FSAR). To allow for calibration tolerances, instrumentation uncertainties, instrument drift, and severe environment errors, the allowable values and trip setpoints are conservatively adjusted with respect to the safety analysis analytical limits.

The actual nominal trip setpoint entered into the bistable is more conservative than that specified by the allowable value to account for rack drift, rack measuring, and test equipment uncertainties. The trip setpoints are selected such that adequate protection is provided when all sensor and processing time delays are taken into account. A detailed description of the methodology used to calculate the trip setpoints, including their explicit uncertainties, is provided in WCAP-11082, Revision 5, "Westinghouse Setpoint Methodology for Protection Systems Diablo Canyon Units 1 and 2, 24 Month Fuel Cycle Evaluation."

The TS Table 3.3.1-1, function 10 "Reactor Coolant Flow-Low reactor trip" ensures that protection is provided against violating the departure from nucleate boiling ratio (DNBR) limit due to low flow in one or more RCS loops while avoiding reactor trips due to normal variations in loop flow.

Each RCS loop has three flow channels to monitor flow. The Reactor Coolant Flow-Low function allowable value and nominal trip setpoint in TS Table 3.3.1-1 are "> 89.8%(1) of MMF/loop" and "90%(') of MMF/loop" respectively where the footnote (I) states "Minimum measured flow (MMF) is 89,800 gpm per loop for Unit 1 and 90,625 gpm per loop for Unit 2."

3.2 RCS Flow Rate TS Limiting Condition for Operation 3.4.1, "RCS Pressure, Temperature, and Flow Departure from Nucleate Boiling (DNB) Limits," requires the RCS total volumetric flow rate at the reactor vessel inlet to be within the limits of Table 3.4.1-1 for Unit 1 and Table 3.4.1-2 for Unit 2. The minimum RCS flow limits in Tables 3.4.1-1 and 3.4.1-2 are variable with reactor thermal power down to 90 percent rated thermal power (RTP). A lower RCS flow could cause the DNB limits to be approached. Operation 2

Enclosure 1 PG&E Letter DCL-02-097 for significant periods of time outside the RCS flow limit increases the likelihood of a fuel cladding failure if a DNB event were to occur.

The minimum RCS flow limits in Tables 3.4.1-1 and 3.4.1-2 correspond to the RCS flow initial conditions for the safety analyses of the DNB limited transients. The DNB limited transients include the FSAR chapter 15.2.5, "Partial Loss of Reactor Coolant Flow," event, the FSAR chapter 15.3.4, "Complete Loss of Forced Reactor Coolant Flow," event, and the FSAR chapter 15.2.3, "Rod Cluster Control Assembly Misoperation," event. The safety analyses for the DNB limited transients demonstrate that transients initiated from the RCS flow limits in Tables 3.4.1-1 and 3.4.1-2 will result in meeting the DNBR correlation limit of_> 1.17. This is the acceptance limit for the RCS DNB temperature, pressure, and flow parameters. The RCS DNB parameters satisfy Criterion 2 of 10 CFR 50.36(c)(2)(ii) and therefore are included in the TS. The RCS total flow rate limit allows for a measurement error of 2.4 percent of flow for Unit 1 and Unit 2.

SR 3.4.1.3 requires verification that the RCS total flow rate is within the limits of Table 3.4.1-1 for Unit 1 and Table 3.4.1-2 for Unit 2 every 12 hours1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months . The 12 hour1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months surveillance is performed by obtaining the plant process computer (PPC) RCS total flow rate (five minute average), by summing the PPC indicated loop flow rate for each of the four RCS flow loops, or by summing the main control board indicated loop flow rate for each of the four RCS flow loops. The PPC and main control board indicated loop flow rate are based on the AP from elbow taps located in the RCS cold leg piping elbow between the steam generator and the reactor coolant pump (crossover elbow). The elbow taps are installed in a plane 22.5 degrees around the first crossover 90 degree elbow in each of the RCS cold legs. Each elbow has three low-pressure taps spaced 15 degrees apart on the inside pipe radius and one high-pressure tap on the outside pipe radius used as the common tap. The pressure taps are connected to three calibrated AP transmitters in each loop to provide three channels of indicated flow rate for each RCS loop. When performing SR 3.4.1.3 using the PPC or main control board indicated loop flow rate, the lowest of the three indicated loop flow rates is used for each RCS loop.

SR 3.4.1.4 requires verification that the measured RCS total flow rate is within the limits of Table 3.4.1-1 for Unit 1 and Table 3.4.1-2 for Unit 2 every 24 months. This verification that the measured RCS total flow rate is within limits requires measurement of the RCS total flow rate via a precision flow calorimetric. The measurement of the RCS total flow rate by performance of a precision flow calorimetric or other acceptable method once every 24 months allows the installed RCS flow instrumentation to be normalized and verifies the actual RCS flow rate is 3

Enclosure 1 PG&E Letter DCL-02-097 greater than or equal to the minimum required flow rate. The frequency of 24 months for the measurement of RCS total flow rate reflects the importance of verifying flow after a refueling outage when the core has been altered, which may have caused an alteration of flow resistance.

The routine channel calibration of the RCS flow instrumentation ensures that the channels are within the necessary range and accuracy for proper flow indication. The routine channel calibration of the RCS flow indication instrumentation is performed every 24 months.

3.3 Precision Flow Calorimetric Method The precision flow calorimetric method for measuring RCS flow and normalizing the RCS flow indicators, uses secondary side calorimetric measurements taken on each steam generator (SG) (feedwater flow, feedwater temperature, and steam pressure) together with primary side loop temperatures as indicated by the hot and cold leg resistance temperature detectors (RTDs). The RCS loop flows are calculated from the SG powers in conjunction with each loop's enthalpy rise across the reactor vessel. Each hot leg has three thermowell RTDs installed around a cross-section to determine the bulk hot leg temperature. Due to the implementation of low neutron leakage core fuel loading patterns that result in changes in the core radial power distribution, the phenomenon of increased hot leg temperature streaming has been observed in many plants, including DCPP. Hot leg temperature streaming is a temperature gradient within the hot leg pipe resulting from incomplete mixing of the coolant leaving fuel assemblies at different temperatures. The magnitude of the hot leg temperature streaming is a function of the core radial power distribution. The use of a low neutron leakage loading pattern reduces core power in the outer assemblies and results in an increase in the hot leg temperature streaming. As a result of the increased hot leg temperature streaming, the indicated bulk hot leg temperature as measured by the three RTDs in each hot leg is erroneously high, resulting in a calculated RCS flow lower than the actual value.

Because of this inherent limitation of the calorimetric flow method, the use of the RCS cold leg elbow tap AP measurement as an alternate method for RCS flow surveillance has been approved by the NRC for many Westinghouse 3-loop and 4-loop plants.

3.4 Purpose for Proposed Amendment The change in the allowable value and nominal trip setpoint for the TS 3.3.1 Table 3.3.1-1 Reactor Coolant Flow-Low reactor trip function is made in order to eliminate the interpretation that a specific RCS loop flow requirement must be met, and that adjustment is required to the low flow reactor trip setpoint for individual loops that are determined not to meet the 4

Enclosure 1 PG&E Letter DCL-02-097 loop MMF value. The change is consistent with NUREG-1431 Revision 2, which specifies the Reactor Coolant Flow-Low function allowable value in TS Table 3.3.1-1 as '5 [89.21%" and the Reactor Coolant Flow-Low function nominal trip setpoint as ">[90]%." There are no surveillance requirements or actions associated with the loop MMF in TS 3.3.1 or TS 3.4.1. The minimum measured RCS flow requirements are contained in TS 3.4.1 Table 3.4.1-1 for Unit 1 and Table 3.4.1-2 for Unit 2 and are based on total RCS flow, not individual loop flows.

The proposed change allows an alternate method for the measurement of RCS total flow to meet SR 3.4.1.4. Currently, the only acceptable method for measurement of the RCS total flow is by performance of a precision flow calorimetric. The change would allow the measurement of the elbow tap AP on the RCS primary cold legs as an acceptable method for measurement of the RCS total flow to meet SR 3.4.1.4. The use of elbow tap AP normalized to Cycle 1 and 2 precision flow calorimetrics improves the accuracy of the RCS flow measurement by avoiding the effect of hot leg temperature streaming in future low-leakage fuel cycles. If the method for measuring RCS total flow is not changed, the large flow measurement bias due to hot leg streaming error will someday likely result in an unnecessary derate of the units prior to reaching the 15 percent SG tube plugging limit.

4.0 TECHNICAL ANALYSES 4.1 TS Table 3.3.1-1 Changqe The reactor coolant loop low flow reactor trip function is designed to protect the core from violating DNB limits following loss of reactor coolant flow accidents. This trip function is the primary protection against a Partial Loss of Flow accident (PLOF), which is characterized by one or two reactor coolant pumps (RCPs) out of four coasting down. The low flow trip also provides primary protection for the Locked Rotor accident (which also bounds the case of a RCP shaft break). For the Locked Rotor accident, the rapid reduction in flow results in an immediate reactor trip which limits the extent of DNB and ensures core cooling capability and RCS pressure boundary integrity. For Complete Loss of Flow (CLOF) accidents (coastdown of four RCPs) the low flow trip provides backup protection to the RCP Undervoltage or Underfrequency reactor trip functions.

There is no safety analysis basis or requirement for resetting the Reactor Coolant Flow-Low reactor trip setpoint in a loop that is deemed to have flow that is below the nominal loop fraction of the MMF (loop MMF), i.e.,

total RCS MMF divided by4. If the TS 3.4.1 total RCS MMF requirement is met but there is a loop flow asymmetry resulting in some loops(s) that are below the loop MMF, the remaining loop(s) will exceed the loop MMF.

5

Enclosure 1 PG&E Letter DCL-02-097 In this case, resetting the Reactor Coolant Flow-Low reactor trip setpoint in loops which are below the loop MMF does not improve the transient results for the design basis accidents which credit the Reactor Coolant Flow-Low reactor trip setpoint.

For the PLOF accident, the limiting case would be the coastdown of the highest flow loop(s), since this would result in the lowest total core flow.

Therefore, an adjustment of the reactor trip setpoint in a "low flow" loop has no effect on the limiting results for the PLOF accident. For the CLOF accident the low flow trip function is not credited for primary protection.

Therefore, an adjustment of the trip setpoint in a "low flow" loop would have no effect on the limiting results for the CLOF accident. The reactor trip would still be generated at the same time following initiation of the CLOF accident and the resulting core flow transient would be the same.

For the Locked Rotor accident, similar to the PLOF accident, the limiting case would be the locked rotor/shaft break in the "high flow" loop.

Therefore, an adjustment of the reactor trip setpoint in a "low flow" loop has no effect on the limiting results for the Locked Rotor accident.

Therefore, elimination of the reference to the loop MMF in the Reactor Coolant Flow-Low function allowable value and nominal trip setpoint in TS Table 3.3.1-1 has no adverse effect on the design basis accidents which credit the Reactor Coolant Flow-Low reactor trip setpoint.

Furthermore, the elimination of the reference to the loop MMF in the Reactor Coolant Flow-Low function allowable value and nominal trip setpoint is consistent with NUREG-1431 Revision 2, which specifies the Reactor Coolant Flow-Low function allowable value in TS Table 3.3.1-1 as

"> [89.21%" and the Reactor Coolant Flow-Low function nominal trip setpoint as ">[90]%".

4.2 Use of Elbow Tap AP for RCS Flow Measurement To determine cycle specific RCS flow from elbow tap AP measurements, the elbow tap AP data obtained during the first two cycles to define the calorimetric baseline flow, when the hot leg streaming bias was negligible, is used to determine a baseline elbow tap flow coefficient. The baseline elbow tap flow coefficient and baseline calorimetric flow are then used to determine the cycle specific flow for all future cycles based on the cycle specific elbow tap flow coefficient (which is derived from the average cycle specific elbow tap AP). The cycle specific elbow tap flow is confirmed by comparing the elbow tap flow to a best estimate flow calculated based on known RCS hydraulic changes such as steam generator tube plugging or core AP changes. The cycle specific flow is corrected as necessary based on the comparison of the elbow tap flow to the best estimate flow. The RCS flow indicators are then normalized to the elbow tap cycle specific flow.

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Enclosure 1 PG&E Letter DCL-02-097 The evaluation of the measurement of RCS flow using elbow tap AP measurement at DCPP is contained in WCAP-15173, Revision 1 (Westinghouse non-proprietary), "RCS Flow Measurement Using Elbow Tap Methodology at Diablo Canyon Units 1 and 2," dated April 2002, and WCAP-15113, Revision 1 (Westinghouse proprietary), "RCS Flow Measurement Using Elbow Tap Methodology at Diablo Canyon Units 1 and 2," dated April 2002. WCAP-15173, Revision 1, and WCAP-15113, Revision 1, are contained in Enclosures 5 and 6 respectively. The methodology contained in WCAP-15173, Revision 1, and WCAP-15113, Revision 1, is similar to the methodology contained in WCAP-14750-A, Revision 1 (Westinghouse non-proprietary), and WCAP-14750-P-A, Revision 1 (Westinghouse proprietary), "RCS Flow Verification Using Elbow Taps at Westinghouse 3-Loop PWRs," dated September 1999, which were approved by the NRC staff for generic application to Westinghouse 3-loop pressurized water reactors using elbow taps for RCS flow verification.

The RCS cold leg elbow tap flow meters are used by Westinghouse plants, including DCPP, for verification of the indicated RCS flow (SR 3.4.1.3) every 12 hours1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months and for reactor trip actuation functions. The purpose of the 12-hour elbow tap surveillance reading is to verify that the full power steady-state flow has not decreased below the TS Table 3.4.1 limits during the cycle.

The principle of operation of an elbow tap flow meter is based on the centrifugal force of a fluid flowing through an elbow, creating a AP between the outer and inner radii of the elbow. The relationship between the volumetric flow rate through an elbow, Q, and the AP between the pressure taps at the outer and inner radii of the elbow can be expressed as Q = CAP1 2. The elbow meter coefficient C is a function of elbow bend and cross-section radii, and is affected by the location of pressure taps and upstream and downstream piping. The cold leg elbow tap flow element is not calibrated in advance in a laboratory, but the measurement is normalized against the established RCS flow rate from the precision heat balance calorimetric flow measurement at the start of each fuel cycle. The cold leg elbow taps are used to measure variations in the RCS flow rate, rather than to measure the absolute value of the RCS flow rate. The cold leg elbow tap AP also provides a measure of the reduced RCS flow rate for the Reactor Coolant Flow-Low reactor trip function required by Function 10 of TS 3.3.1 Table 3.3.1-1.

Figure 4-1 in WCAP-15113, Revision 1 shows the elbow tap locations in the RCS cold leg piping elbow between the steam generator and the reactor coolant pump (crossover elbow). The elbow taps are installed in a plane 22.5 degrees around the first crossover 90 degree elbow in each of the RCS cold legs. Each elbow has three low-pressure taps spaced 15 degrees apart on the inside pipe radius and one high-pressure tap on the outside pipe 7

Enclosure 1 PG&E Letter DCL-02-097 radius used as the common tap. The pressure taps are connected to three AP transmitters to obtain AP data. The elbow taps in the cold legs are fixed, and therefore the elbow meter coefficients (C) in each elbow tap configuration are not expected to change. American Society of Mechanical Engineers publication "Fluid Meters, Their Theory and Application," 6 th Edition, Howard S. Bean, dated 1971, states that hydraulic tests have demonstrated that elbow tap flow measurements have a high degree of repeatability, and are not affected by changes in the elbow surface roughness.

The confirmation of elbow tap flow measurement repeatability is addressed in Section 4.1.4 of WCAP-15113, Revision 1, which provides an evaluation of comparisons between the RCS flow measurement data using the elbow taps and ultrasonic leading edge flow meters (LEFM) from the Hydraulic Test Program at Prairie Island Unit 2. The Prairie Island Unit 2 Hydraulic Test Program test data covered 11 years of plant operation, during which a significant change in system hydraulics was made due to the change of a reactor coolant pump impeller. The program test data showed that the average difference between the elbow tap measurements and ultrasonic LEFM flow measurements was less than 0.3 percent flow. Another comparison performed before and after a reactor coolant pump impeller replacement at Prairie Island Unit 2 showed that the ultrasonic LEFM and elbow tap measurements agreed to within an average of 0.2 percent on the ratio of flows when one and two pumps were operating. WCAP-15113, Revision 1, Section 4.1.4 also evaluated elbow tap flow measurements which have been compared with flows based on the hydraulic analysis described in Section 5 of WCAP-15113, Revision 1. The comparisons showed that elbow tap and best estimate flow trends were in close agreement, including plants with changes in flow due to RCS hydraulic changes such as pump impeller replacement, steam generator tube plugging, and steam generator replacement. The close agreement between elbow tap total flow and best estimate total flow occurred even where steam generator tube plugging and loop flows were significantly imbalanced. For example, elbow tap flows for five cycles at a plant with a steam generator tube plugging level increase from 4 percent to over 19 percent, and with a loop-to-loop steam generator tube plugging spread of 7 percent were well within the repeatability allowance (0.4 percent) when compared with best estimate flows. Also, the RCS flows measured by elbow taps after replacing the steam generators at that plant were also in agreement with the predicted flow, i.e., within 0.4 percent. These comparisons of plant RCS flow data provide confirmation of the elbow tap flow measurement repeatability.

Sections 4.1.1, 4.1.2, and 4.1.3 of WCAP-15113, Revision 1, also evaluated the effects of fouling, erosion, upstream velocity distribution, and replacement steam generators on the elbow tap flow measurements.

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Enclosure 1 PG&E Letter DCL-02-097 Conditions for the collection of fouling deposits similar to feedwater flow venturis are not present in the cold leg elbow since there is no change in cross section to produce a velocity increase and electro-chemical ionization plating of copper and magnetite particles on the elbow surface. Erosion of the elbow surface is also unlikely since stainless steel is used and the flow velocities are low (42 feet per second (fps)) relative to the conditions that cause erosion. The velocity distribution in the elbow tap flow meter remains constant so the elbow tap flow meter AP versus flow relationship does not change. The steam generator outlet plenum velocity head approaching the outlet nozzle is small compared to the piping velocity head (6 fps versus 42 fps) which results in a significant reduction in an upstream velocity gradient. Therefore, any steam generator tube plugging, even if asymmetrically distributed, would not affect elbow tap flow measurement repeatability. Replacement steam generators have the same outlet nozzle off-center location, diameter and taper. Since this configuration would produce the same difference in plenum and nozzle velocity heads, steam generator replacement would have no impact on elbow tap flow coefficients.

Based on the above, the elbow tap flow meter coefficients remain constant and therefore the relative changes of flow rate through the cold leg elbows can be correlated with the relative changes in the elbow tap AP.

4.3 Elbow Tap Flow Measurement Procedure Section 4.2 of WCAP-15113, Revision 1, describes the procedure for determining the RCS flow from elbow tap AP measurements based on the repeatability of the elbow taps without performing a precision calorimetric at the beginning of the new cycle. Comparison of elbow tap AP measurements obtained from one cycle to the next provides an accurate indication of the actual change in flow. The elbow tap AP measurement, normalized to early cycle calorimetric flow measurements, is used to define an accurate flow for all future cycles.

The elbow tap flow measurement procedure relies on a total baseline calorimetric flow which is based on the calorimetric flow measurements from early fuel cycles, preferably before implementation of the low leakage fuel loading patterns. The baseline elbow tap flow coefficient is defined as B = APB XVB where APB is the baseline average elbow tap AP and VB is the average cold leg specific volume. The baseline elbow tap flow coefficient is based on the average AP from all elbow taps to be consistent with the total baseline calorimetric flow. Analyses of elbow tap data at several plants has shown that the difference between total flow based on the average elbow tap AP and total flow based on individual elbow tap transmitter APs is negligible.

The repeatability of the total flow measurement is improved when the average of all elbow tap AP measurements is used.

9

Enclosure 1 PG&E Letter DCL-02-097 The elbow tap APs are obtained at the beginning of the current cycle to define the change in flow from the baseline flow. The average of all elbow tap APs measured at or near full power is used to determine the current cycle elbow tap flow coefficient (K), which is defined as K = APc x vc where APc is the average current cycle elbow tap AP and vc is the average current cycle cold leg specific volume.

The change in flow from the baseline cycle to the current cycle is defined by the elbow tap flow ratio (R), which is defined as R = (K/B)' x FRTDBE where FRTDBE is the RTD bypass elimination flow correction factor which is 1.0 for DCPP Units 1 and 2 Cycles 1 through 6 and is 0.9985 for all DCPP Units 1 and 2 Cycles 7 and beyond.

Finally, the current cycle flow (CCF) is determined by CCF = R x BCF where BCF is the total baseline calorimetric flow (BCF). The procedures for defining the BCF, including the criteria for the choice of early cycle flow measurements and the determination of the BCF from the chosen cycle data, are described in section 4.5 of this LAR. This method to determine the baseline elbow tap flow (B), the current cycle elbow tap flow coefficient (K),

the elbow tap flow ratio (R), and the CCF is consistent with the process described in WCAP-14750-P-A, Revision 1, with the exception of the term FRTDBE used to determine the elbow tap flow ratio. The application of the term FRTDBE provides a cycle specific correction to account for RTD bypass elimination and thus provides a more accurate determination of the cycle specific flow. RTD bypass elimination was implemented following Cycle 6 for both DCPP units.

4.4 Best Estimate Flow Confirmation The CCF defined by the elbow tap flow measurement is independently confirmed by comparing the RCS flow determined from the elbow tap flow measurement to a best estimate hydraulic analysis flow. The hydraulic analysis evaluates the impact on the RCS flow rate of plant system hydraulic changes, such as plugging and sleeving of steam generator tubes, reactor coolant pump impeller smoothing, and fuel design changes. For this confirmation, the elbow tap flow ratio is compared to an estimated flow ratio (R'). The estimated flow ratio is defined as R' = CEF / BEF where CEF is the current cycle estimated flow, the estimated RCS flow based on actual RCS hydraulic changes, and BEF is the best estimate flow, the estimated initial (baseline) cycle RCS flow based on hydraulic analyses.

The current cycle RCS flow is determined based on a comparison of the elbow tap flow ratio (R) to the estimated flow ratio (R'). If R < (1.004 x R')

then the elbow tap flow ratio (R) is used to calculate the current cycle RCS 10

Enclosure 1 PG&E Letter DCL-02-097 total flow as CCF = R x BCF. If R > (1.004 x R') then the quantity (1.004 x R') is used to define the current cycle RCS total flow as CCF = 1.004 x R' x BCF.

The multiplier (1.004) applied to R' is an allowance for the repeatability of the elbow tap flow measurement. The elbow tap flow measurement uncertainty is presented in WCAP-1 5113, Revision 1, Appendix A and includes elements (e.g., sensor and rack calibration allowances) that define a repeatability allowance for the flow measurement that is larger than 0.4 percent. A measurement flow ratio that is no greater than 0.4 percent above the estimated flow ratio (R') will still define a conservative flow. The comparison of the elbow tap flow ratio (R) to the estimated flow ratio (R')

results in definition of a conservative current cycle flow which is confirmed by both the elbow tap measurements and a best estimate hydraulic analysis.

This comparison is consistent with the process described in WCAP-14750-P-A, Revision 1.

Section 5.0 of WCAP-15173, Revision 1, describes the procedure for calculating best estimate flow for DCPP. This procedure was developed by Westinghouse in 1974 to estimate RCS flow at all Westinghouse-designed plants. The procedure uses RCS component flow resistance and pump performance with no margins applied to define a true best estimate of the actual flow. The flow resistance of the reactor vessel, steam generators, and RCS piping are used in conjunction with the reactor coolant pump head-flow performance to define individual loop and total RCS flows. The component hydraulic design data and hydraulic coefficients are determined from analyses of the test data. The flow resistance of the reactor vessel, consisting of the reactor core, vessel internals, and vessel nozzle, is determined from the AP measurements of a full-size fuel assembly hydraulic test, and hydraulic model test data for each type of reactor vessel. The steam generator flow resistance is composed of the resistance of the inlet nozzle, tube inlet, tubes, tube outlet, and outlet nozzle. The resistance for the steam generator accounts for plugged or sleeved tubes in each steam generator so loop specific flows can be calculated when different numbers of tubes are plugged or sleeved. The RCS piping flow resistance combines the resistance of the hot leg, crossover leg, and cold leg piping and is based on the results of industry hydraulic tests. Section 5.1 of WCAP-1 5173, Revision 1, states that the uncertainty in the best estimate hydraulic analysis-calculated flow is + 2 percent of actual flow based on both plant and component test data. The test data included component APs and concurrent ultrasonic LEFM flows collected at Prairie Island Unit 2.

The best estimate flow based on the hydraulic analysis is only used to confirm the elbow tap flow measurement while limiting the elbow tap flow measurement to a maximum value corresponding to the best estimate 11

Enclosure 1 PG&E Letter DCL-02-097 flow plus an allowance for the elbow tap flow repeatability uncertainty.

The best estimate flow will not be used as a substitute for the TS SR for flow measurement.

4.5 RCS Flow Performance Evaluation The RCS elbow tap flow and calorimetric flow measurement data from DCPP Units 1 and 2 have been evaluated and compared with calculated best estimate flows to determine RCS flow performance. The evaluation is described in Section 6 of WCAP-15113, Revision 1. The determination of the best estimate flow, evaluation of the elbow tap flow, comparison of best estimate and elbow tap flow, and evaluation of calorimetric flow are discussed in this section.

Determination of Best Estimate Flow Best estimate flow analyses defined flows for the 11 fuel cycles at Units 1 and 2. The best estimate flow analyses included hydraulic changes that affected flows after Cycle 1 at both units. The hydraulic changes, including impeller smoothing, steam generator tube plugging (up to 3.88 percent total plugging), and fuel design changes (thimble plug removal and change from Westinghouse Standard to Vantage 5 fuel), were modeled to determine the best estimate flow rates for Cycles 1 through 11. The resulting best estimate flow rates are provided in Table 6-1 of WCAP-15113, Revision 1. For Unit 1, the overall impact of hydraulic changes was estimated to be 1.3 percent flow for Cycle 11 where the Cycle 1 baseline flow at 100 percent is 380,120 gallons per minute (gpm). Therefore, the estimated flow ratio (R') for Unit 1 Cycle 11, and for future cycles if no hydraulic changes are made, is 0.9870. For Unit 2, the overall impact of hydraulic changes was estimated to be 1.17 percent flow for Cycle 11 where the Cycle 1 baseline flow at 100 percent is 387,016 gallons per minute (gpm). Thus the estimated flow ratio (R') for Unit 2 Cycle 11, and for future cycles if no hydraulic changes are made, is 0.9883.

Evaluation of Elbow Tap Flow The elbow tap AP measurements were obtained from all 12 transmitters in each unit and are summarized in Table 6-2 for Unit 1 and Table 6-3 for Unit 2 of WCAP-15113, Revision 1. The Cycle 1 elbow tap AP results in a baseline elbow tap flow coefficient (B) of 6.1611 inches-feet 3 /pound (in-ft 3 /lb) for Unit 1 and 6.0673 in-ft 3/lb for Unit 2. The elbow tap loop and total flows for subsequent cycles normalized to the flow in Cycle 1 are also contained in Table 6-2 for Unit 1 and Table 6-3 for Unit 2 of WCAP-15113, Revision 1.

The RTD Bypass System was removed prior to Cycle 7 at both units and was replaced with thermowell RTDs. This modification had no effect on total 12

Enclosure 1 PG&E Letter DCL-02-097 flow, but elimination of the hot leg bypass flow increases flow through the elbow containing the elbow taps by approximately 0.15 percent. To correct for this change in measured flows, the elbow tap normalized flows in Tables 6-2 and 6-3 were reduced by 0.15 percent for Cycle 7 and subsequent cycles. This provides the basis for the RTD bypass elimination flow correction factor (FRTDBE) used to determine the elbow tap flow ratio (R).

Comparison of Best Estimate and Elbow Tap Flow The best estimate flow and elbow tap flow are compared for each unit in Section 6.5 of WCAP-15113, Revision 1. Figure 6-1 and Figure 6-2 compare best estimate and elbow tap flows, all normalized to 100 percent flow in Cycle 1, for Units 1 and 2 respectively.

The Unit 1 elbow tap flows were within the repeatability allowance limit of 0.4 percent above best estimate flow for all cycles, but were 0.6 percent to 1 percent lower than the best estimate flows after Cycle 4. This difference may be due to under-predicting the steam generator tube plugging flow decrease or over-predicting the fuel thimble plug removal flow increase. The elbow tap loop flow trends were in good agreement with each other through Cycle 7, having a flow spread of less than 0.6 percent. However, the elbow tap loop flow spread increased after Cycle 7, reaching 2 percent in Cycle 11.

The increase in loop flow spread after Cycle 7 resulted from a flow decrease of 1.6 percent in Loop 2 between Cycles 7-11, while the other loop flows remained essentially constant. This can be attributed to the asymmetric steam generator tube plugging between loops with loop 2 having a higher percent tube plugging than loops 1, 3, and 4. In Cycle 11, Loop 1 had 3.7 percent plugging, Loop 2 had 8.8 percent, Loop 3 had 1.2 percent, and Loop 4 had 1.9 percent.

The Unit 2 elbow tap flows were within the repeatability allowance limit of 0.4 percent above best estimate flow for all cycles except Cycle 3. After Cycle 4, the Unit 2 elbow tap flow trend relative to the best estimate flow trend was similar to Unit 1 but the difference was smaller. After Cycle 7, the loop flow spread increased similar to that for Unit 1. The increase in the loop flow spread results from a 0.8 percent increase in Loop 1 and a 0.5 percent decrease in Loop 2 between Cycles 7-11, while the other loop flows remained essentially constant. This observed trend is consistent with the fact that Loop 1 had the least amount of steam generator tube plugging, whereas Loop 2 had the most plugging.

Because the total elbow tap flow is similar to, and conservative relative to the best estimate flow trend for Units 1 and 2, it is concluded that RCS flow can conservatively be based on the elbow tap flow measurements in future cycles of Units 1 and 2.

13

Enclosure I PG&E Letter DCL-02-097 Evaluation of Calorimetric Flow The calorimetric flow measurement evaluation is based on the procedure described in Section 4.3.1 of WCAP-15113, Revision 1, which lists the requirements for the flows used to define baseline calorimetric flow. To avoid a significant low leakage loading pattern bias on the calorimetric flow, Requirement (d) disallows cycles with average power differences between the 2 nd row and outer row fuel assembly that exceed 50 percent, unless required to have the minimum number of flows. All cycles after Cycle 1 in both units had average power differences between the 2 nd row and outer row fuel assembly exceeding 50 percent, so the calorimetric flow for the cycles after Cycle I were most likely impacted by the low leakage loading pattern.

The low leakage loading pattern flow bias is predicted to be approximately 0.5 percent in Cycle 2 and about 1 percent in Cycle 3 at both units. The baseline calorimetric flow procedure requires at least three flows from at least two cycles. Since two early cycle flows were measured in both Cycles 1 and 2 (two flows in each cycle) at each unit, a flow measurement from Cycle 3, which has a larger low leakage loading pattern bias, was not required. Therefore, the baseline calorimetric flow is based on two flows each from Cycles 1 and 2.

Tables 6-4 and 6-5 of WCAP-15113, Revision 1, list the calorimetric flow measurements from Cycles 1 and 2 at both units, and identify an average flow for these cycles. To define the average flow for these cycles, two corrections were applied. Flows obtained at about 90 percent power were reduced by 0.1 percent to account for the flow decrease from 90 percent to 100 percent power as described in Section 5.2.5 of WCAP-15113, Revision 1. The flows in Cycle 2 were increased by 0.3 percent to account for impeller smoothing, as discussed in Section 5.3.1 of WCAP-15113, Revision 1. These corrections result in hydraulically consistent flows used to define the equivalent beginning of Cycle 1 baseline calorimetric flow.

The total measured flows for each cycle are defined as a percentage of the baseline calorimetric flow on Tables 6-4 and 6-5 of WCAP-1 5113, Revision 1 for Unit 1 and Unit 2, respectively. The determination of the baseline calorimetric flow for each unit based on the measured flow is discussed below.

For Unit 1, the calorimetric flows for Cycles 1 and 2 are within a 1 percent band and are within 1 percent of the best estimate flow. These flows meet the WCAP-15113, Revision 1, Section 4.3.1 calorimetric flow procedure Requirement (e), and therefore were used to define the baseline calorimetric flow. Unit 1 Cycle 1 met all requirements for a baseline cycle. The average of the four corrected flows for Unit 1 on Table 6-4 is 376,656 gpm and is 14

Enclosure 1 PG&E Letter DCL-02-097 defined as the baseline calorimetric flow per the calorimetric flow procedure.

The Unit 1 calorimetric flows versus cycle are shown in Figure 6-4 of WCAP-15113, Revision 1.

For Unit 2, the calorimetric flows for Cycles 1 and 2 are within a 1 percent band, but the Cycle 2 flows were less than the best estimate flow for the baseline cycle (Cycle 1) by slightly more that 2 percent. Since both the Cycle I and 2 flow differences from the best estimate flow are conservative, these flows were considered to be acceptable for defining the baseline calorimetric flow. Unit 2 Cycle 1 met all requirements for a baseline cycle.

The average of the four corrected flows for Unit 2 on Table 6-5 is 379,089 gpm and is defined as the baseline calorimetric flow per the calorimetric flow procedure. The Unit 2 calorimetric flows versus cycle are shown in Figure 6-4 of WCAP-15113, Revision 1.

4.6 Flow Measurement Uncertainties The implementation of the elbow tap AP method of measuring RCS flow requires the determination of uncertainties associated with the precision RCS flow calorimetric for the baseline cycles for each of the units. These calculations must account for the plant instrumentation, test equipment, and procedures which were in place at the time the calorimetrics were performed. In addition, uncertainty calculations must be performed for the control board indicated RCS flow and the RCS low flow reactor trip setpoint.

These calculations must reflect the correlation of the elbow taps to the baseline precision RCS flow calorimetrics, and address uncertainties usually considered to be zeroed out as a result of normalization performed each cycle, i.e., for the RCS flow calorimetric method.

The uncertainty calculation to support the elbow tap AP method of measuring RCS flow is contained in Appendix A of WCAP-15113, Revision 1. This uncertainty calculation is consistent with that described in WCAP-1 1594, Revision 2 and WCAP-1 1082, Revision 5, which were submitted in PG&E letter DCL-96-214, "Transmittal of WCAPs to Support NRC Review of License Amendment Request 96-10, Revision of Technical Specifications to support Extended Fuel Cycles to 24 Months," dated January 31, 1997 in support of LAR 96-10 submitted in PG&E letter DCL-96-213, "License Amendment Request 96-10 Revision of Technical Specifications to Support Extended Fuel Cycles to 24 Months," dated December 9, 1996, and approved by the NRC for DCPP by Amendment No. 122 to Facility Operating License No. DPR-80 and Amendment No. 120 to Facility Operating License No. DPR-82 in letter "Issuance of Amendments for Diablo Canyon Nuclear Power Plant, Unit No. 1 (TAC M97472) and Unit No. 2 (TAC No. M97473)," dated February 17, 1998. The WCAP-15113, Revision 1, uncertainty calculation is based on the standard 15

Enclosure 1 PG&E Letter DCL-02-097 Westinghouse methodology previously approved for other plants associated with RTD bypass elimination and on the use of the Westinghouse Improved Thermal Design Procedure contained in WCAP-8567-P-A. The Westinghouse uncertainty methodology uses a statistical uncertainty combination technique to combine dependent and independent errors.

The WCAP-15113, Revision 1, uncertainty calculation is consistent with the methodology recommended by the NRC in NUREG/CR-3659, except for two significant differences. The two significant differences are the averaging of the four baseline calorimetric measurements from Cycles 1 and 2 for each unit and the assumption of a correlation between the elbow tap differential pressures and the previdusly performed RCS flow calorimetrics. These significant differences have been accounted for by utilization of the average of the baseline RCS flow calorimetric uncertainties and by the addition of instrument uncertainties previously considered to be zeroed out by normalization to a calorimetric performed each cycle. Therefore, the differences from the NUREG/CR-3659 uncertainty methodology are considered to be properly accounted for to meet the intent of the NUREG/CR-3659 methodology.

Appendix A of WCAP-15113, Revision 1, provides the results of the uncertainty calculations reflecting the use of elbow tap flow measurement.

Tables A-1, A-2, and A-3, respectively, provide the values of the baseline calorimetric flow measurement instrumentation uncertainties, flow calorimetric sensitivities, and calorimetric flow measurement uncertainties.

Tables A-4 and A-5, respectively, provide the cold-leg elbow tap flow measurement uncertainties for the control board indication, and low-flow reactor trip setpoint uncertainties.

The elbow tap flow measurement uncertainty consists of the following contributors:

"* Calorimetric measurements of the RCS total flow for Cycles 1 and 2 for Units 1 and 2

"° Elbow tap AP transmitters in Cycle land given future cycle

"° Eagle-21 Racks

"° Plant control board meter indication for the current cycle RCS flow measurements using the RCS cold leg elbow taps The uncertainty for the precision flow calorimetric measurements is based on the calorimetrics performed during Cycles 1 and 2 for both units when the hot leg streaming effects were minimal. The cold-leg elbow tap flow measurement uncertainties are based on the use of control board indication which bounds the uncertainties for use of the plant process computer indication. Since the elbow tap measurements used for the RCS flow measurements are no longer normalized at each fuel cycle, instrument 16

Enclosure 1 PG&E Letter DCL-02-097 uncertainties (e.g., sensor calibration accuracy, sensor pressure effect, and sensor temperature effect) that were previously zeroed out in the WCAP-1 1082, Revision 5, analysis are now included in Tables A-4 and A-5 of WCAP-15113, Revision 1.

The overall elbow tap flow measurement uncertainty is contained in Table A-4 of WCAP-15113, Revision 1, and is 2.3 percent of flow. This uncertainty is less than the 2.4 percent flow uncertainty used in both the NRC-approved Westinghouse Improved Thermal Design Procedure (ITDP) and the non-ITDP DNB analyses which were used to derive the TS 2.1 reactor core safety limits and corresponding TS 3.4.1 DNB limits. Therefore, the uncertainty for use of the elbow tap flow measurement method is bounded by that assumed in the current safety analyses and no changes to the RCS flow values contained in the safety analyses are required. The low flow reactor trip channel statistical allowance of 3.5% flow span (contained in Table A-5 of WCAP-1 5113, Revision 1) is less than the total allowable flow span of 4.2 percent. Therefore, no change is required to the TS Table-3.3.1-1 Reactor Coolant Flow - Low nominal trip setpoint value of (90 percent flow) or the current safety analyses value (85 percent) due to availability of margin in the uncertainty calculation.

5.0 REGULATORY ANALYSIS

5.1 No Significant Hazards Consideration PG&E has evaluated whether or not a significant hazards consideration is involved with the proposed amendments by focusing on the three standards set forth in 10 CFR 50.92, "Issuance of Amendment," as discussed below:

1. Does the proposed change involve a significant increase in the probability or consequences of an accident previously evaluated?

Response: No.

The proposed change revises the Technical Specification (TS) 3.3.1 Table 3.3.1-1 term "minimum measured flow per loop" to "measured loop flow" in the allowable value and nominal trip setpoint for the Reactor Coolant Flow-Low reactor trip function and allows an alternate method for the measurement of reactor coolant system (RCS) total flow to meet TS surveillance requirement (SR) SR 3.4.1.4 through measurement of the elbow tap differential pressures on the RCS primary cold legs.

The change will not increase the probability of an accident previously evaluated because adequate RCS flow will still be assured. The Reactor 17

Enclosure 1 PG&E Letter DCL-02-097 Coolant Flow-Low reactor trip function allowable value and nominal trip setpoint are accident mitigation functions and are not an accident initiator.

The elbow tap method to measure RCS flow and the change to the flow definition associated with the Reactor Coolant Flow-Low reactor trip function do not involve a plant modification.

For the elbow tap method to measure RCS flow, sufficient margin exists to account for all reasonable instrument uncertainties and therefore the RCS flow will continue to be maintained at a value which is bounded by the design basis accident initial conditions. The change to the flow definition associated with the Reactor Coolant Flow-Low reactor trip function allowable value and nominal trip setpoint does not change a design basis accident initial condition or the conditions at the time of reactor trip during a design basis accident and therefore has no adverse effect on the design basis accidents which credit the Reactor Coolant Flow-Low reactor trip setpoint.

Therefore, the proposed change does not involve a significant increase in the probability or consequences of an accident previously evaluated.

2. Does the proposed change create the possibility of a new or different accident from any accident previously evaluated?

Response: No.

The proposed change to the flow definition associated with the Reactor Coolant Flow-Low reactor trip function allowable value and nominal trip setpoint and the proposed elbow tap method to measure RCS flow will not create the possibility of a new or different type of accident from any previously evaluated. There are no physical changes being made to the plant and there are no changes in operation of the plant that could introduce a new failure mode, creating an accident which has not been evaluated.

Therefore, the proposed change does not create the possibility of a new or different accident from any accident previously evaluated.

3. Does the proposed change involve a significant reduction in a margin of safety?

Response: No.

The proposed change to the flow definition associated with the Reactor Coolant Flow-Low reactor trip function allowable value and nominal trip setpoint and the proposed elbow tap method to measure RCS flow will not 18

Enclosure 1 PG&E Letter DCL-02-097 reduce the margin of safety. For the proposed elbow tap flow method, sufficient margin exists to account for all reasonable instrument uncertainties and thus the RCS flow will continue to be maintained at a value which is bounded by the design basis accident initial conditions, and no adverse effect on the plant response to design basis accidents is created. The change in the flow definition associated with the Reactor Coolant Flow-Low reactor trip function allowable value and nominal trip setpoint does not change a design basis accident initial condition or the conditions at the time of reactor trip during a design basis accident, and therefore has no effect on the plant response to design basis accidents which credit the Reactor Coolant Flow-Low reactor trip setpoint. Since the change does not affect the response to design basis accidents, it does not result in a decrease in departure from nucleate boiling margin or reactor coolant system peak pressure margin for the design basis accidents.

Therefore, the proposed change does not involve a significant reduction in a margin of safety.

Based on the above evaluation, PG&E concludes that the proposed amendments present no significant hazards consideration under the standards set forth in 10 CFR 50.92(c), and accordingly, a finding of "no significant hazards consideration" is justified.

5.2 Applicable Regqulatory Requirements The RCS DNB temperature, pressure, and flow parameters satisfy Criterion 2 of 10 CFR 50.36(c)(2)(ii) and thus are included in TS 3.4.1.

This change does not remove or modify the DNB parameters in TS 3.4.1 and therefore the requirements of Criterion 2 of 10 CFR 50.36(c)(2)(ii) continue to be met.

This change to the flow definition associated with the Reactor Coolant Flow-Low reactor trip function allowable value and nominal trip setpoint is consistent with NUREG-1431 Revision 2, which specifies the Reactor Coolant Flow-Low function allowable value and the Reactor Coolant Flow-Low function nominal trip setpoint as a percentage of loop flow and does not specify the value of the minimum measured flow.

The change allows an alternate method for the measurement of the RCS total flow to meet TS SR 3.4.1.4 through measurement of the elbow tap differential pressure on the RCS primary cold legs. The uncertainty calculation performed to support this alternate flow measurement method is consistent with the methodology recommended by the NRC in NUREG/CR-3659, except for two significant differences. The two significant differences are the 19

Enclosure 1 PG&E Letter DCL-02-097 averaging of the four baseline calorimetric measurements from Cycles 1 and 2 for each unit and the assumption of a correlation between the elbow tap differential pressures and the previously performed RCS flow calorimetrics. However, these significant differences have been accounted for by utilization of the average of the baseline RCS flow calorimetric uncertainties and by the addition of instrument uncertainties previously considered to be zeroed out by normalization to a calorimetric performed each cycle. Therefore, the differences from the NUREG/CR-3659 uncertainty methodology are considered to be properly accounted for to meet the intent of the NUREG/CR-3659 methodology.

In conclusion, based on the considerations discussed above, (1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, (2) such activities will be conducted in compliance with the Commission's regulations, and (3) the issuance of the amendment will not be inimical to the common defense and security or to the health and safety of the public.

6.0 ENVIRONMENTAL CONSIDERATION

PG&E has evaluated the proposed amendments and determined the proposed amendments do not involve (i) a significant hazards consideration, (ii) a significant change in the types or significant increase in the amounts of any effluent that may be released offsite, or (iii) a significant increase in individual or cumulative occupational radiation exposure. Accordingly, the proposed amendments meet the eligibility criterion for categorical exclusion set forth in 10 CFR 51.22(c)(9). Therefore, pursuant to 10 CFR 51.22(b), no environmental impact statement or environmental assessment need be prepared in connection with the proposed amendments.

7.1 REFERENCES

1. WCAP-15173, Revision 1 (Westinghouse non-proprietary) and WCAP-1 5113, Revision 1(Westinghouse proprietary class 2), "RCS Flow Measurement Using Elbow Tap Methodology at Diablo Canyon Units 1 and 2," dated April 2002.

2. WCAP-14750-A, Revision 1 (Westinghouse non-proprietary), and WCAP-14750-P-A, Revision 1 (Westinghouse proprietary), 'RCS Flow Verification Using Elbow Taps at Westinghouse 3-Loop PWRs," dated September 1999.

3. "Fluid Meters, Their Theory and Application," 6 th Edition, Howard S.

Bean, American Society of Mechanical Engineers, New York, dated 1971.

4. PG&E letter DCL-96-214, "Transmittal of WCAPs to Support NRC Review of License Amendment Request 96-10, Revision of Technical 20

Enclosure 1 PG&E Letter DCL-02-097 Specifications to support Extended Fuel Cycles to 24 Months," dated January 31, 1997.

5. PG&E letter DCL-96-213, "License Amendment Request 96-10 Revision of Technical Specifications to Support Extended Fuel Cycles to 24 Months," dated December 9, 1996.

6. NRC letter for License Amendment No. 122 to Facility Operating License No. DPR-80 and Amendment No. 120 to Facility Operating License No. DPR-82, "Issuance of Amendments for Diablo Canyon Nuclear Power Plant, Unit No. 1 (TAC M97472) and Unit No. 2 (TAC No. M97473)," dated February 17, 1998.

7. WCAP-8567-P-A, "Improved Thermal Design Procedure," dated February 1989.

8. NUREG-1431, Revision 2, "Standard Technical Specifications Westinghouse Plants," dated June 2001.

9. WCAP-1 3705, Revision 4 (non-proprietary) and WCAP-1 1082, Revision 5 (Westinghouse proprietary class 2), "Westinghouse Setpoint Methodology for Protection Systems Diablo Canyon Units 1 and 2, 24 Month Fuel Cycle Evaluation," dated January 1997.

10. WCAP-1 1594, Revision 2 (Westinghouse proprietary class 2),

"Westinghouse Improved Thermal Design Procedure Instrument Uncertainty Methodology, Diablo Canyon Units 1 and 2, 24-Month Fuel Evaluation," dated January 1997.

11. NUREG/CR-3659 (PNL-4673), "A Mathematical Model for Assessing the Uncertainties of Instrumentation Measurements for Power and Flow of PWR Reactors", dated February 1985.

12. North Atlantic Energy Service Corporation letter NYN-00059, "Seabrook Station License Amendment Request 00-04, 'Reactor Coolant System Flow Measurement,"' dated June 20, 2000.

13. NRC letter for License Amendment No. 77 to Facility Operating License No. NPF-86 for Seabrook Station Unit 1, "Seabrook Station, Unit No. 1 Issuance of Amendment RE: Reactor Coolant System Flow Measurement (TAC No. MA9301)," dated October 26, 2000.

14. Houston Lighting & Power letter ST-HL-AE-5707, "Proposed Amendment to Technical Specification Table 2.2-1 and 3/4.2.5 for Reactor Coolant System Flow Monitoring - Revised," dated August 6, 1997.

15. NRC letter for License Amendment No. 108 to Facility Operating License No. NPF-76 and Amendment 95 to Facility Operating License No. NPF-80, "South Texas Project, Units 1 and 2 - Issuance of Amendments RE: Reactor Coolant System Flow Monitoring (TAC Nos. M99245 and M99246)," dated April 19, 1999.

16. Westinghouse Nuclear Safety Advisory Letter NSAL-00-008, "Reactor Coolant Loop Flow Asymmetry," dated May 22, 2000.

21

Enclosure 1 PG&E Letter DCL-02-097 7.2 PRECEDENT A similar submittal was made by the North Atlantic Energy Service Corporation for the Seabrook plant in letter NYN-00059, "Seabrook Station License Amendment Request 00-04, 'Reactor Coolant System Flow Measurement,"'

dated June 20, 2000 as supplemented by a letter dated September 25, 2000.

The submittal requested approval of use of elbow tap differential pressure for RCS flow measurement based on the methodology of WCAP-14750-P-A and the use of uncertainties based on the precision RCS flow calorimetrics performed at the beginning of Cycles 1 and 2. The submittal was approved by the NRC by License Amendment 77 to Facility Operating License No. NPF-86 for Seabrook Station Unit 1 in NRC letter "Seabrook Station, Unit No. 1 - Issuance of Amendment RE: Reactor Coolant System Flow Measurement (TAC No. MA9301)," dated October 26, 2000.

The use of the elbow tap differential pressure for RCS flow measurement has also been approved by the NRC for South Texas Project Units 1 and 2 by License Amendment No. 108 to Facility Operating License No. NPF-76 and Amendment 95 to Facility Operating License No. NPF-80 in NRC letter "South Texas Project, Units 1 and 2 - Issuance of Amendments RE: Reactor Coolant System Flow Monitoring (TAC Nos. M99245 and M99246)," dated April 19, 1999, based on Houston Lighting & Power letter ST-HL-AE-5707, "Proposed Amendment to Technical Specification Table 2.2-1 and 3/4.2.5 for Reactor Coolant System Flow Monitoring - Revised," dated August 6, 1997 as supplemented by letters dated September 4, 1997, September 18, 1997, December 9, 1997, and February 4, 1999.

22

Enclosure 2 PG&E Letter DCL-02-097 MARKED-UP TECHNICAL SPECIFICATIONS Remove Paqe Insert Paqe 3.3-14 3.3-14

RTS Instrumentation 3.3.1 Table 3.3.1-1 (page 3 of 7)

Reactor Trip System Instrumentation I APPLICABLE MODES OR OTHER NOMINAL(a)

SPECIFIED TRIP REQUIRED SURVEILLANCE ALLOWABLE CONDITIONS SETPOINT FUNCTION CHANNELS CONDITIONS REQUIREMENTS VALUE

10. Reactor Coolant 1 (g) 3 per loop M SR 3.3.1.1 _ 89.8%(o of 90%() of Flow-Low SR 3.3.1.7 measured measured SR 3.3 1.10 MMAI-Ioop MMFIloop flow SR 3.3.1.16 flow

11. Reactor Coolant 1 (g) 1 per RCP M SR 3.3.1.14 NA NA Pump (RCP)

Breaker Position

12. Undervoltage 1 (g) 2 per bus M SR 3.3 1.9 > 7877 V 8050 V RCPs SR 3.3 1.10 each bus each bus SR 3.3 1.16

13. Underfrequency 1 (g) 3 per bus M SR 3.3.1.9 > 53.9 Hz 54.0 Hz RCPs SR 3.3 1.10 each bus each bus SR 3.3.1.16

14. a. Steam 1,2 3 per SG E SR 3.3.1.1 > 7.0% 7.2%

Generator SR 3 3.1.7 (SG) Water SR 3.3.1.10 Level-Low SR 33.1.16 Low

b. SG Water 1,2 4 x. SR 3.3.1.7 TTD*_ 1.01 TTD _ TD Level - Low SR 3.3.1.10 TD (Note 3) (Note 3) for Low Trip Time for RCS loop RCS loop AT Delay (TTD) AT variable variable input input < 50.7% 50% RTP RTP TTD=0 and TTD=0 for RCS loop for RCS loop AT variable AT variable input 50%

input > 50.7 RTP

% RTP

15. Not used (continued)

(a) A channel is OPERABLE with an actual Trip Setpoint value outside its calibration tolerance band provided the Trip Setpoint value is conservative with respect to its associated Allowable Value and the channel is re adjusted to within the established calibration tolerance band of the Nominal Trip Setpoint. A Trip Setpoint may be set more conservative than the Nominal Trip Setpoint as necessary in response to plant conditions.

(g) Above the P-7 (Low Power Reactor Trips Block) interlock.

) Minimumn -meacurod Pow (MMF) *689,800 gpm per loop for Unit 1 and 00,625 gpm per loop for Unit 2 3.3-14 Unit 1 - Amendment No. 435 442 Unit 2 -Amendment No. 4,25 442

Enclosure 3 PG&E Letter DCL-02-097 PROPOSED TECHNICAL SPECIFICATIONS PAGE

RTS Instrumentation 3.3.1 Table 3.3.1-1 (page 3 of 7)

Reactor Trip System Instrumentation I

APPLICABLE MODES OR OTHER NOMINAL(a' SPECIFIED REQUIRED SURVEILLANCE ALLOWABLE TRIP FUNCTION CONDITIONS CHANNELS CONDITIONS REQUIREMENTS VALUE SETPOINT

10. Reactor Coolant 1(g) 3 per loop M SR 3.3.1.1 > 89.8% of 90% of Flow-Low SR 3.3.1.7 measured measured SR 3.3.1.10 loop flow loop flow SR 3.3.1.16

11. Reactor Coolant 1(g) 1 per RCP M SR 3.3.1.14 NA NA Pump (RCP)

Breaker Position

12. Undervoltage 1 (g) 2 per bus M SR 3.3.1.9 ;Ž 7877 V 8050 V RCPs SR 3.3.1.10 each bus each bus SR 3.3.1.16

13. Underfrequency 1(g) 3 per bus M SR 3.3.1.9 ;Ž 53.9 Hz 54.0 Hz RCPs SR 3.3.1.10 each bus each bus SR 3.3.1.16

14. a. Steam 1,2 3 per SG E SR 3.3.1.1 > 7.0% 7.2%

Generator SR 3.3.1.7 (SG) Water SR 3.3.1.10 Level-Low SR 3.3.1.16 Low

b. SG Water 1,2 4 x SR 3.3.1.7 "TTD*_ 1.01 "TTD _ 50.7 RTP

% RTP

16. Not used (continued)

(a) A channel is OPERABLE with an actual Trip Setpoint value outside its calibration tolerance band provided the Trip Setpoint value is conservative with respect to its associated Allowable Value and the channel is re adjusted to within the established calibration tolerance band of the Nominal Trip Setpoint. A Trip Setpoint may be set more conservative than the Nominal Trip Setpoint as necessary in response to plant conditions.

(g) Above the P-7 (Low Power Reactor Trips Block) interlock.

3.3-14 Unit 1 - Amendment No. 435 4-42 Unit 2 - Amendment No. 435 442

Enclosure 4 PG&E Letter DCL-02-097 MARKED-UP TECHNICAL SPECIFICATIONS BASES CHANGES (For information only)

Bases 3.4.1 Pages B 3.4-2 to B 3.4-5

RCS Pressure, Temperature, and Flow DNB Limits B 3.4.1 BASES APPLICABLE Insertion Limits"; LCO 3.2.3, "AXIAL FLUX DIFFERENCE (AFD)"; and SAFETY LCO 3.2.4, "QUADRANT POWER TILT RATIO (QPTR)."

ANALYSES The pressurizer pressure limit of 2197.3 psig and the RCS average (continued) temperature limit of 584.3 0 F correspond to nominal analytical limits of 2250 psia and 577.60F for Unit 2 (the limiting unit) used for the DNB calculation in the reload analyses with allowance for analysis initial consideration uncertainty (38 psi and 6.7°F).

The RCS DNB parameters satisfy Criterion 2 of 10 CFR 50.36 (c)(2)(ii).

LCO This LCO specifies limits on the monitored process variables pressurizer pressure, RCS average temperature, and RCS total flow rate to ensure the core operates within the limits assumed in the safety analyses. Operating within these limits will result in meeting the DNBR criterion in the event of a DNB limited transient.

RCS total flow limits are provided for a RTP range of 90% to 100% on Tables 3.4.1-1 and 3.4.1-2 for Unit I and Unit 2 respectively.

The RCS total flow rate limit allows for a measurement error of 2.394% 0 (Unit 1) and 2.401% (Unit 2) of th....al dcig, flo',, or equivalcntly 2.338% (Unit 1) and 2.34-; (Unit 2) fnmminimum measured lw2.4%flow.- Both the precision flow calorimetric method and the cold leg elbow tap method used to measure RCS flow meet the 2.4% flow uncertainty allowance.

The based On per*Fming a precision heat bal-aRe flow calorimetric method and using the result to normalizes the RCS flow rate indicators to a precision flow calorimetric performed at the beginning of cycle.

Potential fouling of the feedwater venturi, which might not be detected, could bias the result from the precision heat balaRae flow calorimetric in a non-conservative manner. A bias error of 0.1% for undetected fouling of the feedwater venturi is included in the measurement error analysis. Any fouling that might significantly bias the feedwater flow rate input to the flow calorimetric measurement greater than 0.1% can be detected by monitoring and trending various plant performance parameters. If detected, either the effect of the fouling shall be INSERT A quantified and compensated for in the RCS flow rate measurement or the venturi shall be cleaned to eliminate the fouling.

The LCO numerical values for pressure, temperature, and flow rate have not been adjusted for instrument error.

APPLICABILITY In MODE 1, the limits on pressurizer pressure, RCS coolant average temperature, and RCS flow rate must be maintained during steady state operation in order to ensure the DNBR criteria will be met in the event of an unplanned loss of forced coolant flow or other DNB limited transient. In all other MODES, the power level is low enough that DNB is not a concern.

(continued)

DIABLO CANYON - UNITS 1 & 2 B 3.4-2 Revision 1 TABB3-4.DOC - R1A 2

RCS Pressure, Temperature, and Flow DNB Limits B 3.4.1 BASES APPLICABILITY A Note has been added to indicate the limit on pressurizer pressure is (continued) not applicable during short term operational pressure transients such as a THERMAL POWER ramp increase > 5% RTP per minute or a THERMAL POWER step increase > 10% RTP. These conditions represent short term perturbations where actions to control pressure variations might be counterproductive. Also, since they represent transients initiated from power levels < 100% RTP, an increased DNBR margin exists to offset the temporary pressure variations.

Another set of limits on DNB related parameters is provided in SL 2.1.1, "Reactor Core SLs." Those limits are less restrictive than the limits of this LCO, but violation of a Safety Limit (SL) merits a stricter, more severe Required Action. Should a violation of this LCO occur, the operator must check whether or not an SL may have been exceeded.

ACTIONS A._1 RCS pressure and RCS average temperature are controllable and measurable parameters. With one or both of these parameters not within LCO limits, action must be taken to restore parameter(s).

RCS total flow rate is not a controllable parameter and is not expected to vary during steady state operation. If the indicated RCS total flow rate is below the LCO limit, power must be reduced, as required by Required Action B.1, to restore DNB margin and reduce the potential for violation of the accident analysis limits.

The 2 hour2.314815e-5 days 5.555556e-4 hours 3.306878e-6 weeks 7.61e-7 months Completion Time for restoration of the parameters provides sufficient time to adjust plant parameters, to determine the cause for the off normal condition, and to restore the readings within limits, and is based on plant operating experience.

B.1 If Required Action A.1 is not met within the associated Completion Time, the plant must be brought to a MODE in which the LCO does not apply. To achieve this status, the plant must be brought to at least MODE 2 within 6 hours6.944444e-5 days 0.00167 hours 9.920635e-6 weeks 2.283e-6 months . In MODE 2, the reduced power condition reduces the potential for violation of the accident analysis limits. The Completion Time of 6 hours6.944444e-5 days 0.00167 hours 9.920635e-6 weeks 2.283e-6 months is reasonable to reach the required plant conditions in an orderly manner.

(continued)

DIABLO CANYON - UNITS 1 & 2 B 3.4-3 Revision 1 TABB3-4.DOC - R1A 3

RCS Pressure, Temperature, and Flow DNB Limits B 3.4.1 BASES SURVEILLANCE SR 3.4.1.1 REQUIREMENTS Since Required Action A.1 allows a Completion Time of 2 hours2.314815e-5 days 5.555556e-4 hours 3.306878e-6 weeks 7.61e-7 months to restore parameters that are not within limits, the 12 hour1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months Surveillance Frequency for pressurizer pressure is sufficient to ensure the pressure can be restored to a normal operation, steady state condition following load changes and other expected transient operations. The 12 hour1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months interval has been shown by operating practice to be sufficient to regularly assess for potential degradation and to verify operation is within safety analysis assumptions.

SR 3.4.1.2 Since Required Action A.1 allows a Completion Time of 2 hours2.314815e-5 days 5.555556e-4 hours 3.306878e-6 weeks 7.61e-7 months to restore parameters that are not within limits, the 12 hour1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months Surveillance Frequency for RCS average temperature is sufficient to ensure the temperature can be restored to a normal operation, steady state condition following load changes and other expected transient operations. The 12 hour1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months interval has been shown by operating practice to be sufficient to regularly assess for potential degradation and to verify operation is within safety analysis assumptions.

SR 3.4.1.3 The 12 hour1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months Surveillance Frequency for the indicated RCS total flow rate is performed using the installed flow instrumentation. The 12 hour1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months interval has been shown by operating practice to be sufficient to regularly assess potential degradation and to verify operation within safety analysis assumptions. The term "indicated RCS total flow" is used to distinguish between the "measured RCS total flow" determined in SR 3.4.1.4.

SR 3.4.1.4 SR 3.4.1.4 has two surveillance requirements, one for the CHANNEL CALIBRATION of the RCS flow indicators and the other for measurement of RCS total flow rate. Measurement of RCS total flow rate by performance of a precision flow calorimetric heat balaRoe or by using the cold leg elbow tap methodology other acceptable method once every 24 months allows the installed RCS flow instrumentation to be normalized and verifies the actual RCS flow rate is greater than or equal to the minimum required RCS flow rate.

(continued)

DIABLO CANYON - UNITS 1 & 2 B 3.4-4 Revision 1 TABB3-4.DOC - R1A 4

RCS Pressure, Temperature, and Flow DNB Limits B 3.4.1 BASES (Continued)

The second part of this surveillance is the routine CHANNEL CALIBRATION of the RCS flow indication instrumentation. The routine calibration of the flow instrumentation ensures that the channels are within the necessary range and accuracy for proper flow indication.

The routine CHANNEL CALIBRATION of the RCS flow indication instrumentation is performed every 24 months.

The Frequency of 24 months for the measurement of RCS total flow rate reflects the importance of verifying flow after a refueling outage when the core has been altered, which may have caused an alteration of flow resistance. Flow verification demonstrates that setpoints are relevant and RCS flow resistance is within limits. The frequency of 24 months for the routine CHANNEL CALIBRATION of the flow indication instrumentation is based on operating experience and consistency with the typical industry refueling cycle.

REFERENCES 1. FSAR, Section 15.

2. Diablo Canyon Power Plant Unit 1 Cycle 9 Reload Safety Evaluation, August 1995.

3. Diablo Canyon Power Plant Unit 2 Cycle 8 Reload Safety Evaluation, Rev.1, April 1996.

4. WCAP-15113, Revision 1, "RCS Flow Measurement Usinq Elbow Tap Methodology at Diablo Canyon Units 1 and 2," April, 2002.

DIABLO CANYON - UNITS 1 & 2 B 3.4-5 Revision 1 TABB3-4.DOC - R1A 5

Enclosure 4 PG&E Letter DCL-02-097 MARKED-UP TECHNICAL SPECIFICATION BASES CHANGES INSERT A Use of the cold leg elbow tap method to measure RCS flow at approximately 100% RTP at the beginning of cycle results in a measurement uncertainty of + 2.3 %

flow using the control board RCS flow rate indicators (which bounds the use of the plant process computer). This method is based on the utilization of twelve RCS cold leg elbow taps correlated to the four baseline precision heat balance measurements during Cycles 1 and 2 for each unit. Correlation of the flow indication channels with the flow calorimetric measurements performed during Cycles 1 and 2 is documented in WCAP-15113, Revision 1. Use of the cold leg elbow tap method provides an alternative to performance of a precision flow calorimetric to measure RCS flow and was approved by the NRC in amendments [ / ].

Enclosure 5 PG&E Letter DCL-02-097 WCAP-1 5173, Revision 1, "RCS Flow Measurement Using Elbow Tap Methodology at Diablo Canyon Units 1 and 2," April, 2002 (Westinghouse non-proprietary)

Westinghouse Non-Proprietary Class 3 RCS Flow Measurement Using Elbow Tap Methodology at Diablo Canyon Units 1 and 2 W e st inghouse Electric Companyy LLC

WESTINGHOUSE NON-PROPRIETARY CLASS 3 WCAP-15173 Revision 1 RCS Flow Measurement Using Elbow Tap Methodology at Diablo Canyon Units 1 and 2 April 2002 Prepared:

W. G. LymdnConsultant Prepared: 6 CA'-c,,

K. N. Garner, Engineer Prepared: 1. A 2==ý C. R. Tuley, Engineer Approved: WM Westinghouse Electric Company LLC Nuclear Service P.O. Box 355 Pittsburgh, PA 15230-0355 02002 Westinghouse Electric Company LLC All Rights Reserved 4014-non doc-4122/02

iii TABLE OF CONTENTS TABLE OF CONTENTS ................................................................................................................... iil LIST OF TABLES ............................................................................................................................. IV LIST OF FIGURES ................................................................................................................. v

1.0 INTRODUCTION

................................................................................................................. 1-1 2.0

SUMMARY

.......................................................................................................................... 2-1 3.0 RCS HOT LEG TEMPERATURE STREAMING ............................................................... 3-1 3.1 Phenomenon ........................................................................................................... 3-1 3.2 History ......................................................................................................................... 3-1 3.3 Hot Leg Streaming Impact on RCS Flow Measurements ........................................... 3-2 3.4 Correlating Changes in Power Distribution and RCS Flow ........................................ 3-3 4.0 ELBOW TAP FLOW MEASUREMENT APPLICATION ................................................. 4-1 4.1 Elbow Tap Flow Measurements .................................................................................. 4-1 4.2 Elbow Tap Flow Measurement Procedure .................................................................. 4-3 4.3 Baseline Parameters for Elbow Tap Flow Measurements .......................................... 4-5 5.0 BEST ESTIMATE RCS FLOW ANALYSIS .................................................................. 5-1 5.1 Background .................................................................................................................. 5-1 5.2 Prairie Island Hydraulics Test Program ...................................................................... 5-1 5.3 Additional Prairie Island Tests .................................................................................... 5-3 5.4 System Flow Resistance Analyses .............................................................................. 5-3 5.5 Best Estimate RCS Flow Calculations .................................................................. 5-4 6.0 DIABLO CANYON RCS FLOW PERFORMANCE EVALUATION ................................ 6-1 6.1 Introduction ................................................................................................................. 6-1 6.2 Best Estimate Flow Predictions ................................................................................... 6-1 6.3 Evaluation of Elbow Tap Flows .................................................................................. 6-2 6.4 Evaluation of Calorimetric Flows ............................................................................... 6-2 6.5 Flow Comparisons .................................................................................................. 6-4 6.6 Power/Flow Correlation for Diablo Canyon .......................................................... 6-4 7.0 ELBOW TAP FLOW MEASUREMENT LICENSING CONSIDERATIONS .................. 7-1 7.1 Background ................................................................ :................................................. 7-1 7.2 Supporting Calculations .............................................................................................. 7-1 7.3 Potential Document Impacts ........................................................................................ 7-2 APPENDIX A INDICATED RCS FLOW AND REACTOR COOLANT FLOW - LOW REACTOR TRIP INSTRUMENT UNCERTAINTIES ............ A-1 APPENDIX B DIABLO CANYON 50.92 AND SUGGESTED MODIFICATIONS TO PLANT TECHNICAL SPECIFICATIONS ................................................. B-1 4014-non.doc-042202 April 2002 Revision 1

iv LIST OF TABLES Table 4-1 Comparisons of Leading Edge Flow Meter and Elbow Tap Flow Measurements at Prairie Island Unit 2 .................................................... 4-8 Table 4-2 Acronyms Used In Elbow Tap Flow Measurement Procedure ................................ 4-9 Table 6-1 Best Estimate Flow Summary .................................................................................. 4-6 Table 6-2 Unit 1 Elbow Tap AP Summary ............................................................................... 6-7 Table 6-3 Unit 2 Elbow Tap AP Summary ............................................................................... 6-8 Table 6-4 Unit 1 Calorimetric Flow Summary ......................................................................... 6-9 Table 6-5 Unit 2 Calorimetric Flow Summary ......................................................................... 6-10 Table A-1 Baseline Flow Calorimetric Instrumentation Uncertainties ..................................... A-3 Table A-2 Flow Calorimetric Sensitivities ......................................................................... A-4 Table A-3 Calorimetric RCS Flow Measurement Uncertainties ............................................... A-5 Table A-4 Cold Leg Elbow Tap Flow Uncertainty (Control Board Indication) ....................... A-7 Table A-5 Low Flow Reactor Trip ..................................................................................... A-8

1 VVY 4014-non doc-043002 Revision I

v LIST OF FIGURES Figure 3-1 Upper Plenum and RCS Hot Leg Flow Patterns ................................................ 3-4 Figure 3-2 Typical Core Exit Temperature Gradient and RCS Hot Leg Circumferential Temperature Gradient .................................................................... 3-5 Figure 3-3 Typical Core Exit Temperature Change .................................................................. 3-6 Figure 3-4 Calorimetric Flow Measurement Bias Versus Difference Between Average Second Row and Outer Row Assembly Powers ...................................................... 3-7 Figure 4-1 Leading Edge Flow Meter, Elbow Tap Flow Meter and Component AP Tap Locations at Prairie Island Unit 2 ....................................................................... 4-10 Figure 6-1 Unit 1 Flow Comparisons ........................................................................................ 6-11 Figure 6-2 Unit 2 Flow Comparisons ........................................................................................ 6-12 Figure 6-3 Flow Bias Versus Power Difference ........................................................................ 6-13 Figure 6-4 Unit I & 2 Calorimetric Flows ................................................................................. 6-14 4014-non.doc-043002 April 2002 Revision 1

1-1

1.0 INTRODUCTION

Reactor Coolant System (RCS) secondary calorimetric-based flow measurements at many pressurized water reactors (PWRs), including Diablo Canyon Units 1 & 2, have been affected by increases in hot leg temperature streaming. The increases are related to changes in the reactor core radial power distribution, resulting from implementation of low leakage loading patterns (LLLPs). In some cases, measured flow appears to have decreased to, or below, the minimum flow required by the Technical Specifications, which require confirmation of RCS flow by measurement once per fuel cycle. Such occurrences require licensee actions to either account for the apparent flow reduction in the plant safety analyses or to confirm by other means that RCS flow has not decreased below the specified limit. In many cases, utilities have relied on the repeatability of RCS elbow tap flow meters to demonstrate that RCS flow has not decreased.

The current RCS calorimetric flow measurement method based on RCS temperature and secondary calorimetric power measurements has inherent limitations imposed by LLLPs. This report, prepared in response to a Pacific Gas & Electric Company (PG&E) request, presents the justification of an alternate method to measure RCS flow, and the evaluation of RCS flow performance at Diablo Canyon Units 1 & 2. The alternate method uses elbow tap flow measurements normalized to a baseline calorimetric flow to minimize the LLLP impact.

The following sections present information on:

- Hot leg temperature streaming phenomenon;

- Elbow tap flow measurement application and justification;

- Best estimate hydraulics analysis used to predict RCS flow;

- Evaluation of elbow tap and calorimetric flows at Diablo Canyon Units 1 & 2;

- Elbow tap flow measurement licensing considerations;

- Measurement uncertainty using elbow taps; and

- Modifications to Diablo Canyon Technical Specifications.

4014-non doc-042202 April 2002 Revision I

2-1 2.0

SUMMARY

The procedure described in this report for verifying RCS total flow with normalized elbow tap flow measurements is similar to the Westinghouse procedure approved by the Nuclear Regulatory Commission (NRC) for application at Westinghouse 3-loop nuclear power plants. Applicability of the procedure is confirmed by comparing measured RCS elbow tap flow trends with best estimate flow trends based on analysis and application of RCS hydraulic test data.

The evaluation of plant operating data from Diablo Canyon Units 1 & 2 has defined sufficiently accurate baseline parameters for both the elbow tap and calorimetric flow measurements. Flow changes measured by elbow taps obtained over several fuel cycles are consistent with the predicted flow changes due to changes in RCS hydraulics, as shown on Figures 6-1 and 6-2. Application of the flow measurement procedure using normalized elbow tap measurements will result in the recovery of the apparent decrease in flow attributed to changes in hot leg temperature streaming.

Modifications to the Diablo Canyon Technical Specifications will be required to allow use of the alternate RCS flow measurement procedure.

Section 7 describes the evaluation process required to prepare a licensing submittal.

Appendix B provides the supporting significant hazards evaluation and marked-up Technical Specification changes.

4014-non doc-043002 April 2002 Revision 1

3-1 3.0 RCS HOT LEG TEMPERATURE STREAMING 3.1 PHENOMENON The RCS hot leg temperature measurements are used in control and protection systems to ensure temperature is within design limits, and in a surveillance procedure to confirm RCS flow. The hot leg temperature measurement uncertainty can have a significant impact on PWR performance. A precise measurement of hot leg temperature is difficult due to the phenomenon defined as hot leg temperature streaming, i.e., large temperature gradients within the hot leg pipe resulting from incomplete mixing of the coolant leaving fuel assemblies at different temperatures. The magnitude of these hot leg temperature gradients where the temperatures are measured is a function of the core radial power distribution, mixing in the reactor vessel upper plenum, and mixing in the hot leg pipe.

Prior to application of LLLPs, the largest difference in fuel assembly exit temperatures at full power was typically no more than 30°F. The lowest temperatures were measured at the exit of fuel assemblies on the outer row of the core. Flow from a fuel assembly in the center of the core mixes with coolant from nearby fuel assemblies as it flows around control rod guide tubes and suppo!t columns. Flow from a fuel assembly on the outer row of the core has little opportunity to mix with hotter flows before reaching the nozzles, so a significant temperature gradient can exist at the nozzle.

Hot leg flow is highly turbulent, so additional mixing occurs in the hot leg pipe, and the maximum gradient where temperature is measured, 7 to 17 feet downstream from the reactor vessel nozzle, is less than at the nozzle. In 1968, gradients measured on the circumference of the pipe were as high as 70 to 10°F, so turbulent mixing in the pipe did not eliminate the gradient introduced at the core exit.

Figure 3-1 illustrates a postulated flow pattern in the reactor vessel upper plenum between the core exit and the hot leg nozzle. Figure 3-2 illustrates typical temperature gradients at the core exit and on the hot leg circumference at the point where the temperatures are measured.

3.2 HISTORY Prior to 1968, there were no multiple temperature measurements on hot leg pipes, so temperature streaming gradients were undetected and resistance temperature detector (RTD) locations were based on other criteria. During a 3-loop plant startup in 1968, RTDs on opposite sides of the hot leg'pipes measured different temperatures. Recalibrations confirmed that the measurements were valid, so it was concluded that the hot leg temperature differences resulted from incomplete mixing of flows leaving fuel assemblies at different temperatures. Thermocouples were strapped to the ouitside of two hot leg pipes to confirm this conclusion, and temperature gradients that increased as core power increased were detected.

The temperature gradient reached 10°F in one loop and 7°F in the other loop. Since only one RTD measured hot leg temperature for the control and protection systems, the hot leg temperaiure measurement was not as accurate as intended.

A new hot leg temperature measurement system was installed at plants after 1968 to compensate for hot leg temperature streaming gradients. The new system, called the RTD Bypass System, employed scoops in the hot leg piping at three uniformly spaced locations on the pipe circumference. Holes on the upstream side of the scoop collected small sample flows that were combined and directed through an 4014-non.doc-042202 April 2002 Revision I

3-2 RTD manifold where the measured temperature of the mixed samples more closely represented the average hot leg temperature.

To eliminate personnel radiation exposure to the RTD Bypass System piping during plant shutdowns, many systems were replaced after 1988 with a system called the RTD Bypass Elimination System (RTDBE). This system has three thermowell RTDs in each hot leg, installed at uniformly spaced locations like the RTD bypass scoops, to retain the three measurement locations. In many cases the thermowell RTDs were installed inside the bypass scoops, so the average thermowell RTD measurement was the same as the temperature measured by the RTD Bypass System.

After 1968, additional hot leg streaming measurements were performed at 2-loop, 3-loop and 4-loop plants. The results of these measurements were used in several analyses to define hot leg temperature streaming uncertainties for protection setpoint calculations and safety analyses. Gradients measured in these tests varied from 70 to 9°F. After 1988, the thermowell RTD systems provided hot leg streaming data from the three RTDs in each hot leg. The gradients measured prior to 1991 varied from 2° to 9°F with most of the gradients measured at 5P to 7°F.

3.3 HOT LEG STREAMING IMPACT ON RCS FLOW MEASUREMENTS Before 1988, reports of hot leg temperature measurement problems were unusual, and no significant changes in streaming gradients were identified. In 1988, the first significant indication of a streaming change occurred at a 4-loop plant, followed by similar occurrences in 1989 and 1990 at three more 4-loop plants. In all four cases, the measured coolant temperature difference (AT) across the reactor vessel had increased from that measured in previous fuel cycles by as much as 3%. The increased AT indicated that RCS calorimetric flow had apparently decreased. It was noted that core exit temperature gradients had increased, with lower temperatures measured at the edge of the core, as shown on Figure 3-3. In all cases, RCS elbow tap flows indicated that the actual flow had not changed. However, RCS elbow tap flow measurements indicated that flow had not changed.

No additional analyses were performed in 1988 or 1989, since the calorimetric flow at those plants was still above the Technical Specification requirement. However, calorimetric flow measured at both units at a plant in 1990 was below the Technical Specification requirement. After additional data had been evaluated, the appropriate data from the elbow taps and core exit thermocouples confirmed that RCS flow was adequate. The NRC was advised of the apparent low flow and the elbow tap flow and core exit thermocouple data, and concurred with the utility's conclusion that RCS flow was adequate for safe operation at full power for the cycle.

Both 3-loop and 4-loop plants, including Diablo Canyon, subsequently reported apparent reductions in RCS calorimetric flow. The reductions occurred at plants measuring hot leg temperature with either an RTD bypass system or with the RTDBE system. In some cases, the apparent flow was just at the minimum Technical Specification requirement, raising a concern that measured flows could be lower in future cycles, requiring additional analyses or alternate flow measurements to justify that flow is adequate.

The alternate flow measurement procedure developed by Westinghouse, using elbow tap flow meters to verify flow, has been reviewed and approved by the NRC for a group of 3-loop plants and two 4-loop 4014-non doc-042202 April 2002 Revision I

3-3 plants (South Texas Project and Seabrook). Elbow tap flow measurements are compared with elbow tap measurements obtained concurrently with early cycle calorimetric flow measurements, when the effects of core exit ant hot leg temperature streaming gradients on the hot leg temperature measurement were minimal. If the comparison of elbow tap measurements shows that the flow has not changed, the flow is considered to be the same as determined by the initial calorimetric (baseline) flow.

3.4 CORRELATING CHANGES IN POWER DISTRIBUTION AND RCS FLOW At the plants where apparent flow reductions were measured, it was noted that in all cases the core exit thermocouples measured much larger temperature gradients, approaching 60°F, as shown on Figure 3-3, due to much lower exit temperatures at the edge of the core. A review of core radial power distributions indicated that the power generated in outer row fuel assemblies was significantly lower than powers measured in earlier cycles, confirming the large core exit temperature gradients.

A comparison of radial power distributions and calorimetric flow measurements from several cycles at several 3-loop and 4-loop plants indicated that the apparent changes in flow correlate with the radial power distribution gradient at the edge of the core. Figure 3-4 plots apparent LLLP-induced calorimetric flow decreases measured at a group of 3-loop plants versus the difference between the average power generated in second row and outer row fuel assemblies. The apparent flow decreases appear to occur when the power differences exceed 47% of fuel assembly average power, a condition consistent with LLLP. The power/flow correlation is represented by a straight line, as shown on Figure 3-4. According to this data, the measured RCS flow appears to decrease by 3% as the difference between power in second row and outer row assemblies increases from 47% to 90% of assembly average power.

4014-non doc-042202 April 2002 Revision I

3-4 RTD U er Plenum RCS Hot Leg 11 Guide Tubes Reactor Core Outer Row Center of Assemblies FIGURE 3-1 UPPER PLENUM AND RCS HOT LEG FLOW PATTERNS 4014-non doc-042202 April 2002 Revision I

3-5 3-5 10 AVG 0 RELATIVE CORE EXIT -10 TEMPERATURE OF -20

-30 0 20 40 60 80 100 CORE CENTER CORE AREA, %

5 r TEMPERATURE GRADIENT ON HOT LEG PIPE 0 CIRCUMFERENCE OF

-5 ' I 1800 2400 3000 00 600 1200 1800 BOTTOM BOTTOM HOT LEG PIPE CIRCUMFERENCE FIGURE 3-2 TYPICAL CORE EXIT TEMPERATURE GRADIENT AND RCS HOT LEG CIRCUMFERENTIAL TEMPERATURE GRADIENT 4014-non.doc-042202 April 2002 Revision I

3-6 650 CYCLE 3 CYCLE 3 ma 60 590 0 10 20 30 40 50 60 70 s0 90 10D CORE AREA (% FROM cETER)

NOTE. CYCLE (PRIOR TO ISPLEMENTATION OF LLLP CYCLE (AFTERIMLMENTATION OF W.PS)

FIGURE 3-3 TYPICAL CORE EXIT TEMPERATURE CHANGE 4014-non doc-042202 April 2002 Revision I

3-7

+1%

F 0%

L 0 * *

*t W *t

t B - 1%

I

A

S

-2%

0 2nd ROW - OUTER ROW POWER DIFFERENCE 100 PERCENT POWER FIGURE 3-4 CALORIMETRIC FLOW MEASUREMENT BIAS VERSUS DIFFERENCE BETWEEN AVERAGE SECOND ROW AND OUTER ROW ASSEMBLY POWERS April ZUUL 4014-non doc-042202 April 2s0o Revision I

4-1 4.0 ELBOW TAP FLOW MEASUREMENT APPLICATION 4.1 ELBOW TAP FLOW MEASUREMENTS Elbow tap differential pressure (Ap) measurements are being used more frequently to confirm RCS flow changes from one fuel cycle to the next. Elbow tap flow meters are installed in all Westinghouse PWRs on the reactor coolant pump suction piping on each loop, as shown on Figure 4-1. The Ap taps are located on a plane 22.50 around the first 900 elbow. Each elbow has one high pressure and three low pressure taps connected to three redundant Ap transmitters. Elbow taps in this arrangement are used to define relative rather than absolute flows, due to the lack of upstream straight piping lengths. The Ap measurements are repeatable and thus provide accurate indications of flow changes during a cycle or from cycle to cycle.

Elbow tap flow meters (Reference 1) are a form of centrifugal meter, measuring momentum forces developed by the change in direction around the 900 elbow. The principal parameters defining the Ap for a specified flow are the elbow's radius of curvature and the flow channel diameter. Hydraulic tests described in Reference 1 demonstrated that elbow tap flow measurements have a high degree of repeatability and that the flow measurements are not affected by changes in the elbow surface roughness.

Phenomena that have affected other types of flow meters, or that might affect the elbow tap flow meters have been evaluated to determine if any of these phenomena would affect repeatability of the elbow taps.

In addition, measurements at an operating plant equipped with a highly accurate RCS ultrasonic flow meter were compared with elbow tap flow measurements to demonstrate repeatability of the elbow taps.

The results of these evaluations and comparisons are summarized below.

4.1.1 Venturi Fouling Deposits (fouling) collecting on the surface and reducing the throat flow area affect venturi flow meters that measure feedwater flow. Fouling is caused by an electro-chemical ionization plating of copper and magnetite particles in the feedwater on the venturi surface, a process related to the velocity increase as flow approaches the smaller venturi flow area. There is no change in cross section to produce a velocity increase and ionization in an elbow, and surface roughness changes as experienced in venturi flow meters do not affect the elbow tap flow measurement.

4.1.2 Meter Dimensional Changes The elbow tap flow meter is part of the RCS pressure boundary, so there would be only minimal dimensional changes associated with pipe stresses. Pressure and temnperature would be essentially the same (full power conditions) whenever the flow is measured. Erosion of the elbow surface is unlikely since stainless steel is used, and velocities are low (42 fps) relative to erosion. The effects of dimensional change or erosion could only affect flow by changing elbow radius or pipe diameter, both very large relative to any possible dimensional change. Therefore, the elbow tap flow meter is considered to be a highly stable flow measurement element.

4014-non doc-042202 April 2002 Revision I

4-2 4.1.3 Upstream Velocity Distribution Effects The velocity distribution entering the steam generator outlet nozzle is skewed by its off-center location relative to the tube sheet. The out-of-plane upstream 40' elbow on the steam generator outlet nozzle skews the velocity distribution entering the 900 elbow with Ap taps. These velocity distributions, including the distribution in the elbow tap flow meter, will remain constant, so the elbow tap flow meter Ap/flow relationship would not change.

Steam generator tube plugging is usually randomly distributed across the tube sheet, so the velocity distribution approaching the outlet nozzle would not change. The velocity distribution in the outlet plenum could change if extensive tube plugging were to occur in one area of the tube sheet. However, the outlet plenum velocity approaching the outlet nozzle is small compared to the pipe velocity (6 fps vs.

42 fps), and this large change in flow area would significantly reduce or flatten an upstream velocity gradient. Therefore, any tube plugging, even if asymmetrically distributed, would not affect the elbow tap flow measurement repeatability.

Also considered was the effect of replacing steam generators on elbow tap flow measurements.

Replacement steam generators have the same outlet nozzle off-center location, diameter and taper. Since the configuration would produce the same difference in plenum and nozzle velocity heads, steam generator replacement would have no impact on elbow tap flow coefficients. RCS flow would increase since there would be no plugged tubes, resulting in a reduced steam generator flow resistance, and the change in flow would be correctly measured.

4.1.4 Flow Measurement Comparisons Leading Edge Flow Meters (LEFMs), ultrasonic devices installed in both reactor coolant loops at Prairie Island Unit 2, provide the data to confirm repeatability of the elbow tap flow meters. The comparisons covered 11 years of operation, during which a significant change in system hydraulics was made. One of the reactor coolant pump impellers was replaced, and the replacement impeller produced additional flow.

The LEFM measurements after pump replacement were in agreement with the predicted change, and the elbow tap flow meters indicated similar changes, but slightly lower flows than measured by the LEFM.

The 11-year flow comparison showed that the average difference between elbow tap and LEFM flows was less than 0.3% flow. Another comparison performed before and after the impeller replacement showed that the LEFM and elbow tap measurements agreed to within an average of 0.2% on the ratio of flows when one and two pumps were operating, thus further confirming the relative flow accuracy of elbow tap flow meters. These comparisons are listed on Table 4-1.

Elbow tap flow measurements have also been compared with flows based on the hydraulics analysis described in Section 5. The comparisons showed that elbow tap and best estimate flow trends were in close agreement at many plants, including plants with changes in flow due to RCS hydraulics changes such as pump impeller replacement as described above, and steam generator tube plugging and replacement. The close agreement between elbow tap total flow and best estimate total flow occurs even where tube plugging and loop flows are significantly imbalanced. Elbow tap flows for five cycles at a plant with tube plugging increasing from 4% to over 19%, and with a loop-to-loop plugging spread of 7%

were well within the repeatability allowance (0.4%) when compared with best estimate flows. RCS 4014-non doc-042202 April 2002 Revision I

4-3 flows measured by elbow taps after replacing the steam generators at this plant were also in good agreement with the predicted flow, i.e., within 0.4%.

4.2 ELBOW TAP FLOW MEASUREMENT PROCEDURE The elbow tap flow measurement procedure relies on repeatability of the elbow tap Ap measurements to accurately verify RCS flow. Comparison of elbow tap Ap measurements obtained from one cycle to the next provides an accurate indication of the actual change in flow. When normalized to an early cycle calorimetric flow measurement, elbow tap Ap measurements define an accurate flow for all future cycles.

The elbow tap flow measurement procedure is described below. Acronyms used in the procedure are defined on Table 4-2. The baseline parameters for the procedure and their development (baseline calorimetric flow and baseline elbow tap flow coefficient) are presented in Section 4.3.

4.2.1 Baseline Elbow Tap AP Elbow tap Aps obtained in the cycle used to define the calorimetric baseline flow define a baseline elbow tap flow coefficient, used in connection with the baseline calorimetric flow and a current cycle elbow tap flow coefficient to define the current cycle flow. The baseline elbow tap flow coefficient (3) is defined by Equation 1:

B = ApB

VB (Eq. 1) where B = baseline elbow tap total flow coefficient, (inches H20

ft3/lb)

ApN = baseline average elbow tap Ap (inches H20) vB = baseline average cold leg specific volume (ft/lb)

The baseline elbow tap flow coefficient based on the average Ap from all elbow taps defines total flow, to be consistent with the total baseline calorimetric flow. Analyses of elbow tap Ap data at several plants has shown that the difference between total flow based on the average elbow tap Ap and total flow based on individual elbow tap transmitter Aps is negligible., The repeatability of the total flow measurement is improved when all elbow tap Ap measurements are used.

4.2.2 Flow Verification for Current Cycle Elbow tap Aps are obtained at the beginning of the current cycle to define the change in flow from the baseline flow. The average of all elbow tap Aps measured at or near full power defines the current cycle elbow tap flow coefficient (K), applying Equation 2:

K = Apc

Vc (Eq. 2) 4014-non doc-042202 April 2002 Revision 1

4-4 where K = current cycle elbow tap total flow coefficient, (inches H20

ft3/lb)

Apc = average current cycle elbow tap Ap (inches H20)

Vc = average current cycle cold leg specific volume (ft3/lb)

The change in flow from the baseline cycle to the current cycle is defined by the elbow tap flow ratio (R, defined by Equation 3).

R = (K / B)P*FRTDBE (Eq. 3) where R = ratio of current cycle flow to baseline flow FRTDBE = RTD Bypass Elimination Flow Correction Factor; 1.0 for Cycles 1-6 and 0.9985 starting with Cycle 7 for both units The current cycle flow is determined by multiplying the baseline calorimetric flow by the elbow tap flow ratio (R), per Equation 4:

CCF=R*BCF (Eq. 4) where CCF = total current cycle flow, gpm BCF = total baseline calorimetric flow, gpm 4.2.3 Best Estimate Flow Confirmation A current cycle flow defined by elbow taps is confirmed by comparing the elbow tap flow ratio (R) with an estimated flow ratio (R', defined by Equation 5), based on the best estimate flow analysis of known RCS hydraulics changes such as steam generator tube plugging and core Ap changes. Prior to beginning of cycle RCS flow calorimetic, the current cycle estimated flow (CEF) is calculated for the new cycle, accounting for the known hydraulic changes.

R' = CEF / BEF (Eq. 5) where CEF = current cycle estimated flow; the estimated RCS flow, based on actual RCS hydraulics changes BEF = best estimate flow; estimated initial (baseline) cycle RCS flow, based on hydraulics analyses 4014-non.doc-042202 April 20021 Revision

4-5 An acceptance criterion is applied to the comparison of R and R':

If R < (1.004

R'), the elbow tap flow ratio R is used to calculate the current cycle RCS total flow using Equation 4.

IfR > (1.004

R'), the quantity (1.004

R') is used to define the current cycle RCS total flow, modifying Equation 4 to Equation 6 as indicated below.

CCF= 1.004 *R' *BCF (Eq. 6)

The multiplier (1.004) applied to R' is an allowance for the repeatability of the elbow tap flow measurement. The elbow tap flow measurement uncertainty presented in Appendix A includes elements (e.g., sensor and rack calibration allowances) that define a repeatability allowance for the flow measurement that is larger than 0.4%. A measured flow ratio R that is no greater than 0.4% above the estimated flow ratio R' will still define a conservative flow. Application of this acceptance criterion results in definition of a conservative current cycle flow, confirmed by both the elbow tap measurements and the best estimate hydraulics analysis.

4.3 BASELINE PARAMETERS FOR ELBOW TAP FLOW MEASUREMENTS 4.3.1 Baseline Calorimetric Flow Calorimetric flows measured during early fuel cycles before application of LLLPs, and which meet the requirements defined below, are compared to evaluate their accuracy and consistency for use in defining an RCS baseline calorimetric flow. Calorimetric flows from these cycles are expected to be consistent with each other and with best estimate flow predictions.

One cycle (normally Cycle 1) is defined as the baseline cycle if the calorimetric flow meets the requirements defined below, and if elbow tap Aps were measured during the cycle. If Cycle 1 does not meet these requirements, another early cycle with an acceptable calorimetric flow measurement and with elbow tap Ap measurements is defined as the baseline cycle.

At least three early cycle calorimetric flows are needed to define the baseline calorimetric flow. At least one flow is measured during the baseline cycle, and at least one flow is measured during another cycle.

These flows are corrected for known hydraulics differences so all flows are hydraulically consistent with the baseline cycle hydraulics.

The number of cycles defining baseline flow is limited to three, since including additional cycles potentially increases the hydraulics uncertainty and may introduce an LLLP flow bias. Including flows from additional cycles provides minimal benefit in measurement accuracy or uncertainty. When the selected flows include two flows from a cycle, the flow for that cycle is the average of the two flows.

Comparisons of hydraulically consistent calorimetric flows at many plants show that these early cycle flows are usually within a band of 1%, and are usually within 1% to 2% of the baseline cycle best estimate flow. After accounting for hydraulics differences, the actual flows are essentially the same.

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4-6 The differences in hydraulically corrected calorimetric flows provide an indication of the repeatability band for calorimetric flow measurements.

The measured calorimetric flows must meet the requirements listed below:

a. The flow must be measured at or above 90% power and at the beginning of the cycle (BOC) to avoid added uncertainties due to a reduced power or due to instrument drift.

b. One of the cycles, defined as the baseline cycle, must have concurrent calorimetric flow and elbow tap Ap measurements.

c. To minimize the hydraulic uncertainty, the flow measured in a cycle with steam generator tube plugging that exceeds an average of 5% tubes plugged should not be used.

d. The flow measured in a cycle impacted by LLLP may bias the baseline flow and should not be used, unless needed to obtain the required number of measurements for evaluation.

e. Hydraulically corrected calorimetric flows that are not within a 1% band, or that differ from the baseline cycle best estimate flow by more than 2% should not be used, unless the cycle was impacted by LLLP, as defined in (d) above.

The procedure for defining baseline calorimetric flow is summarized as follows:

1. Select calorimetric flows (hydraulically corrected to the baseline cycle, at least three flows from at least two cycles) that meet requirements (a) through (e) listed above.

2. Determine baseline cycle flow (average of two flows if two baseline cycle flows used).

3. Determine the average of the selected hydraulically corrected flows. When the selected flows include two flows from a cycle, both flows are considered in the average flow.

4. The baseline cycle flow (2) is compared with the average flow (3). The baseline calorimetric flow is the lower of these two flows.

The baseline calorimetric flow measurement uncertainty is based on the specific instrumentation uncertainty that existed when the flow measurements were performed at the plant. Instrument uncertainty calculations for the appropriate cycles define the total flow measurement uncertainty. The flow measurement uncertainty includes an allowance for the hot leg temperature streaming error that existed in the cycle when the calorimetric flows used to define the baseline flow were measured.

Although LLLP causes larger hot leg temperature streaming gradients and hot leg temperature biases, the biases are more conservative, resulting in a lower measured flow, so a larger, LLLP-induced streaming uncertainty is not applied.

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I 4-7 Section 6.2 describes the evaluationi of calorimetric flow measurements ihat dlefined the baseline calorimetric flow for Diablo Canyon Units 1 and 2. Based on the parameters listed on Table 6-1, the baseline calorimetric flows are:

Unit I Baseline Calorimetric Flow (BCF) = 376,656 gpm Unit 2 Baseline Calorimetric Flow (BCF) = 379,089 gpm 4.3.2 Baseline Elbow Tap AP The baseline elbow tap flow coefficient (B), based on elbow tap Aps obtained in the baseline cycle, is defined by Equation 1. Section 6.3 describes the evaluation of elbow tap flow measurements that defined the baseline elbow tap flow coefficient for Diablo Canyon Units 1 and 2. Based on the analysis, the procedure established the following coefficients:

3 Unit 1 Baseline Elbow Tap Flow Coefficient(B) = 6.1611 inches

ft /lb.

3 Unit 2 Baseline Elbow Tap Flow Coefficient(B) = 6.0673 inches

ft /lb.

Reference

1. "Fluid Meters, Their Theory and Application," 6th Edition, ASME, 1971.

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4-8 TABLE 4-1 COMPARISONS OF LEADING EDGE FLOW METER AND ELBOW TAP FLOW MEASUREMENTS AT PRAIRIE ISLAND UNIT 2 RCS FLOW MEASUREMENT COMPARISONS AT FULL POWER gpm/loop LOOP A A B B METER LEFM ELBOW LEFM ELBOW DATE 02/80 97519 (Same) 97950 (Same) 07181 98673 98309 97763 97267 08/91 98724 98557 97543 97607 RATIO OF LOOP FLOW WITH 1 PUMP OPERATING TO LOOP FLOW WITH 2 PUMPS OPERATING LOOP A A B B METER LEFM ELBOW LEFM ELBOW DATE 12/74 1.0819 1.0777 1.0852 1.0875 07/81 1.0794 1.0816 1.0820 1.0820 4014-non doc-042202 April 2002 Revision 1

4-9 TABLE 4-2 ACRONYMS USED IN ELBOW TAP FLOW MEASUREMENT PROCEDURE B Baseline Flow Coefficient: defined by the elbow tap Ap and specific volume at cold leg temperature (T-c) measured at the beginning of the baseline cycle.

BCF Baseline Calorimetric Flow: defined by calorimetric flows measured in early cycles with minimal impact from core radial power distribution.

BEF Best Estimate Flow: estimated RCS flow for the baseline cycle, based on the best estimate hydraulics analysis.

CCF Current Cycle Flow: correction to the Baseline Calorimetric Flow (BCF) to account for changes in flow, using the elbow tap flow ratio (R) or the estimated flow ratio (R'). CCF defines the RCS flow for the current cycle.

CEF Cycle Estimated Flow: estimated RCS flow for the current cycle, based on actual RCS hydraulics changes.

K Elbow Tap Flow Coefficient: current cycle flow coefficient defined by the elbow tap Ap and specific volume at T-c measured at the beginning of the current cycle.

R Measured Flow Ratio: elbow tap Ap ratio, defines the actual change in flow for the current cycle, used to define the Current Cycle Flow (CCF).

R' Estimated Flow Ratio: defines the current cycle estimated change in flow relative to the baseline cycle Best Estimate Flow (BEE).

TSF Technical Specification Flow: specified flow that must be confirmed by a flow measurement.

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4-10 4 TAPS 0 90e FIGURE 4-1 LEADING EDGE FLOW METER, ELBOW TAP FLOW METER AND COMPONENT AP TAP LOCATIONS AT PRAIRIE ISLAND UNIT 2 4014-non doc-042202 April 2002 Revision 1

5-1 5.0 BEST ESTIMATE RkS FLOW ANALYSIS

5.1 BACKGROUND

The procedure for calculating best estimate RCS flow was developed in 1974 and has been used to estimate RCS flow at all Westinghouse-designed plants. The procedure uses component flow resistances and pump performance with no margins applied, so the resulting flow calculations define a true best estimate of the actual flow.

Uncertainties in the best estimate hydraulics analysis, based on both plant and component test data, define a flow uncertainty of +/-2% flow, indicating that actual flow is expected to be within 2% of the calculated best estimate flow. Since the uncertainty of a component flow resistance contributes only a fraction of the +/-2% best estimate flow uncertainty, the uncertainty of a change in flow due to a known hydraulics change is smaller than +/-2%, estimated to be no more than'10% of the predicted change in flow.

The most significant input to the best estimate hydraulics analysis was the test data collected at Prairie Island Unit 2, where ultrasonic LEFMs were installed. These tests are described below.

5.2 PRAIRIE ISLAND HYDRAULICS TEST PROGRAM The LEFM was installed in 1973 at Prairie Island Unit 2, on both loops as shown on Figure 4-1.

Measurements were obtained during the hot functional and plant startup tests in 1974.- In addition to the LEFM flows, component Ap taps shown on Figure 4-1 were provided to obtain concurrent measurements of reactor vessel and steam generator Aps and reactor coolant pump dynamic head. Pump input power and speed were also measured.

The program collected data during plant heatup from 200*F to normal operating temperatures with one and two pumps operating. Full power flow measurements were obtained early in 1975. Subsequent flow and pump input power data were obtained in 1979, 1980, 1981 and 1991.

The LEFM accuracy for the Prairie Island plant measurements was established by a calibration test at Alden Laboratories, and by analysis of dimensional tolerances, to be +/-+0.67% of measured flow. The Alden test modeled the piping configuration both upstream and downstream from the metered pipe section. Tests performed with the ultrasonic transducers installed at several locations on the pipe circumference defined the optimum location for the transducers in the pipe section relative to the angular orientations of the upstream and downstream elbows.

The Prairie Island component Aps were based on measurements at the three locations shown on Figure 4-1: hot leg, pump suction and pump discharge piping. The accuracy of the measurements was established by calibrations to be within .1%of the measured Ap. Since the Aps were measured with common taps, the sum of the reactor and steam generator Aps equal the pump Ap; these comparisons agreed to within 1%, further confirming the Ap measurement accuracy.

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5-2 The RCS flows measured in 1974-75 were 5% higher than predicted, due to the following effects, evaluated in additional analyses.

5.2.1 Reactor Coolant Pump Performance Reactor coolant pump performance was higher than predicted from hydraulic model tests, producing an additional 2% flow, partly due to impeller thermal expansion and partly due to conservatism in the hydraulic model test scaleup. With flow, head, input power and speed data, hydraulic and electrical efficiency were verified. The LEFM also measured reverse flows, so the flow measurements also confirmed the flow resistance of the pump impeller due to reverse flow.

5.2.2 Reactor Vessel Flow Resistance The reactor vessel flow resistance was lower than predicted from reactor vessel model tests and fuel assembly Ap measurements, producing an additional flow of almost 3%. Tests with one pump in operation provided additional data to confirm the division of flow resistances between vessel internals (total flow) and vessel nozzles (loop flow).

5.2.3 Steam Generator Flow Resistance The steam generator flow resistance was the same as predicted from analysis, so changes in the analysis were not required. The large change in the predicted flow resistance resulting from the change in tubing Reynolds Number and friction factor during plant heatup was also confi'rmed by the flow resistance measurements.

5.2.4 Piping Flow Resistance The RCS piping flow resistance, 6% of the total system resistance, was reduced by about 25% to be consistent with measured component flow resistances, accounting for reduced Ap due to close coupling of components and elbows in the piping. Part of an elbow Ap loss occurs as increased turbulence in the downstream piping, but the loss is reduced if a component or another elbow is located at or close to the elbow outlet.

5.2.5 Flow vs. Power LEFM measurements at full power indicated that the Prairie Island Unit 2 RCS cold leg volumetric flow decreased by about 0.8% as the reactor was brought from zero to full power. This result confirmed the predicted effect of higher velocities in the core, hot leg, and steam generator tubes as temperatures at these locations increase above cold leg temperature. The RCS flow velocity in these regions increases by 5% to 12%, causing an increase in the total RCS flow resistance applied to the reactor coolant pumps.

The resulting decrease in flow as reactor power increases from zero to 100% is plant specific, differing from 0.8% to 1.2%, depending on the plant specific hot leg and cold leg temperatures, and flow resistances of the affected components.

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5-3 5.3 ADDITIONAL PRAIRIE ISLAND TESTS The flow measurements in later years contributed additional data on system hydraulics performance, used to revise and further validate the hydraulics analyses, as described below.

5.3.1 Impeller Smoothing LEFM and pump input power measurements were obtained at Prairie Island in 1979 and 1980 to reconfirm RCS flows and hydraulic performance. LEFM data indicated that RCS flows had decreased by 0.6% to 0.8%, and electrical data indicated that pump input power had decreased by about 2%. After evaluating this data and other information, it was concluded that the flow decrease was due to impeller smoothing, where the impeller surface roughness decreases due to wear or deposit buildup between high points on the impeller surfaces. Smoothing occurs within one or two fuel cycles after initial startup.

This flow decrease during early cycles has also been measured by elbow tap flow meters at several 3-loop and 4-loop plants.

5.3.2 Pump Impeller Replacement The LEF'Ms were used at Prairie Island in 1981 to confirm RCS flows after replacement of a pump impeller. The new impeller performance was predicted to be higher than the original impeller, and a loop flow increase was predicted. The LEFM confirmed this prediction.

5.3.3 Elbow Tap Flow Comparison LEFM data in 1991 were compared with 1980 data to confirm that elbow taps measured the same flow changes over the same period. The comparison indicated that the elbow tap and LEFM loop flows were in good agreement, with an average difference of less than 0.3% over 11 years.

5.4 SYSTEM FLOW RESISTANCE ANALYSES Flow resistances are calculated for each component, based on component hydraulic design data and hydraulics coefficients resulting from analysis of test data such as, but not limited to, the Prairie Island test program. Component flow resistances are combined to define total system flow resistance, and combined with the predicted pump head-flow performance to define RCS flow. The background and bases for flow resistance calculations are described below.

5.4.1 Reactor Vessel The reactor vessel flow resistance is defined in three parts.

a. The reactor core flow resistance is based on a full size fuel assembly hydraulic test, including Aps at RCS total flow through inlet and outlet core plates as well as the core.

b. The vessel internals flow resistance is based on total flow through the downcomer, lower plenum, and upper plenum. The flow resistances are determined from hydraulic model test data for each type of reactor vessel, based on Ap measurements within the model.

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5-4

c. The vessel nozzle flow resistances include Aps based on loop flow through the inlet and outlet nozzles.

In addition, the overall analysis accounts for small flows that bypass the reactor core through the upper head, hot leg nozzle gaps, baffle-barrel gaps, and control rod drive thimbles.

5.4.2 Steam Generator The steam generator flow resistance is defined in five parts: inlet nozzle; tube inlet; tubes; tube outlet; and outlet nozzle. The Prairie Island test program (Section 5.2) confirmed the overall flow resistance.

The analysis accounts for the plugged or sleeved tubes in each steam generator, so loop specific flows can be calculated when different numbers of tubes are plugged or sleeved.

5.4.3 Reactor Coolant Piping The RCS piping flow resistance combines the flow resistances for the hot leg, crossover leg, and cold leg piping. The flow resistance for each section is based on an analysis of the effect of upstream and downstream components on elbow hydraulic loss coefficients, using the results of industry hydraulics tests. The total flow resistance was consistent with the measurements from the Prairie Island test program (Section 5.2).

5.5 BEST ESTIMATE RCS FLOW CALCULATIONS The best estimate flow analysis defines baseline best estimate flow (BEF) and current cycle estimated flow (CEF) for the elbow tap flow measurement procedure. The calculation combines component flow resistances and pump performance predictions based on hydraulic model tests, and defines RCS loop flows at the desired power or temperature with any combination of pumps operating, with any fuel assembly design, and with different tube plugging in each steam generator. Estimated flows were in good agreement with calorimetric flow measurements from many plants before LLLPs were implemented. The calculated best estimate changes in flow from cycle to cycle have been in good agreement with changes measured by elbow taps.

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6-1 6.0 DIABLO CANYON RCS FLOW PERFORMANCE EVALUATION

6.1 INTRODUCTION

RCS elbow tap flow and calorimetric flow measurements from Diablo Canyon Units 1 & 2 were evaluated and compared with calculated best estimate flows to determine RCS flow performance. Elbow tap flow measurements define actual flow changes and are expected to compare well with changes predicted by the best estimate flo'w analysis.

Calorimetric flow measurements from each unit established a baseline flow and defined flow changes' caused by hot leg temperature streaming biases as well as hydraulics changes. Results of the Diablo Canyon flow measurement evaluation are described in the following paragraphs.

6.2 BEST ESTIMATE FLOW PREDICTIONS Best estimate flow analyses defined flows for the 11 fuel cycles at Unit 1 and Unit 2. Hydraulics changes that affected flows after Cycle 1 at both units, described below, are listed on Table 6-1.

a. Impeller Smoothing: As stated in Section 5.3.1, impeller smoothing is expected to cause a flow decrease of about 0.6% flow after initial plant startup. For this analysis, the flow decrease due to impeller smoothing was applied as a 0.3% flow decrease prior to Cycle 2 and an additional 0.3% flow decrease prior to Cycle 3.

b. Steam Generator Tube Plugging: As listed on Table 6-1, the estimated tube plugging impact on RCS flow was small at both units until Cycle 7. The-total estimated tube plugging flow impact for Cycle 11 was -0.70% flow in Unit 1 and -0.57% in Unit 2.

c. Fuel Design Changes: During Cycles 4-6 at both units, RCS flow changed due to thimble plug removal (TPR) and Vantage 5 (V5) fuel installation. TPR caused RCS flow to increase by 0.7% in Cycle 4, and the V5 installation caused RCS flow to decrease in proportion to the number of V5 assemblies installed, reaching -0.7% in Cycle 6. The TPR and V5 flow impacts in each cycle are listed on Table 6-1.

6.2.1 Unit 1 The Cycle I initial startup best estimate flow was defined to be 380,120 gpm. Considering the hydraulic changes described above, the overall impact was estimated to be -1.3% flow for Cycle 11, as indicated on Table 6-1. The flow trend defined on Table 6-1 is plotted on Figure 6-1, with Cycle 1 flow specified as the baseline cycle flow at 100% flow.

Based on the procedure described in Section 4.2, the Cycle 11 estimated flow (CEF) was 98.70% flow, so the estimated flow ratio (R') for Cycle 11 and for future cycles if no hydraulics changes are made is 0.9870.

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6-2 6.2.2 Unit 2 The Cycle I initial startup best estimate flow was defined to be 387,016 gpm. Considering the hydraulic changes described above, the overall impact was estimated to be -1.17% flow for Cycle 11, as indicated on Table 6-1. The flow trend on Table 6-1 is plotted on Figure 6-2, with Cycle 1 flow specified as the baseline cycle flow at 100% flow.

Based on the procedure described in Section 4.2, the Cycle 11 estimated flow (CEF) was 98.83% flow, so the estimated flow ratio (R') for Cycle 11 and for future cycles if no hydraulics changes are made is 0.9883.

6.3 EVALUATION OF ELBOW TAP FLOWS Elbow tap Ap measurements were obtained from all 12 transmitters for both units. The Aps expressed in inches of water at 100% flow and about 100% power are listed on Tables 6-2 for Unit 1 and Tables 6-3 for Unit 2. Also listed are the averages of the 12 Aps and the specific volume at the average cold leg temperature for each cycle. The Cycle 1 elbow tap Aps defined a baseline elbow tap flow coefficient (B) of 6.1611 inches*ft3/lb for Unit 1 and 6.0673 inches*ft3Ilb for Unit 2. Tables 6-2 and 6-3 list elbow tap loop and total flows for subsequent cycles normalized to the flow in Cycle 1. The normalized elbow tap flows in percent of baseline flow are shown on Figure 6-1 for Unit 1 and Figure 6-2 for Unit 2, for comparison with best estimate flows and calorimetric flows.

The RTD Bypass System was removed prior to Cycle 7 at both units and was replaced with thermowell RTDs. This modification has no effect on total flow, but elimination of the hot leg bypass flow increases flow through the elbow with the elbow taps by about 0.15%. To correct for this change in measured flows, the elbow tap normalized flows on the tables and figures were reduced by 0.15% for Cycle 7 and subsequent cycles. This reflects the RTDBE flow correction factor of 0.9985 used in Equation 3 for Cycle 7 and subsequent cycles.

6.4 EVALUATION OF CALORIMETRIC FLOWS The calorimetric flow measurement evaluation is based on the procedure described in Section 4.3, which lists the requirements for the flows used to define baseline calorimetric flow. Based on a review of the flows, listed on Table 6-4 for Unit 1 and Table 6-5 for Unit 2, the measured flows met Requirements (a),

(b) and (c):

Requirement (a): All flows were measured at or above 90% power and at BOC Requirement (b): All cycles had elbow tap flow measurements Requirement (c): The first six cycles had steam generator tube plugging of less than 5%

To avoid an LLLP impact, Requirement (d) disallows cycles with differences between 2V row and outer row fuel assembly average powers that exceed 50%, unless required to have the minimum number of flows. Based on the following table, all cycles after Cycle 1 in both units had power differences exceeding 50%, so these flows are most likely impacted by LLLP.

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6-3 Differences Between 2md Row and Outer Row Assembly Average Power Cycle 1 2 3 4 5 6 Unit 1 27.0% 53.9% 62.6% 77.1% 67.5% 66.0%

Unit 2 31.9% 57.0% 61.3% 65.1% 70.6% 71.5%

The correlation described in Section 3.4 predicts that RCS flow would be biased low by 1% flow for every 14% difference in power above a threshold 47% power difference. At a power difference of 61%,

the predicted bias is 1% flow. Therefore, the differences listed above are predicted to result in a flow bias of about 0.5% in Cycle 2-and about 1% in Cycle 3 at both units. The baseline calorimetric flow procedure requires at least three flows from at least two cycles. Since four early cycle flows were measured in Cycles 1 and 2 (two flows in each cycle) at both 'units,a flow measurement from Cycle 3 With a larger LLLP impact was not required. Therefore, the baseline calorimetric flow is based on two flows each from Cycles 1 and 2.

Tables 6-4 and 6-5 list two mieasurements each from Cycles 1 and 2 at both units, and identify an average flow for these cycles. To define ihe average flow for these cycles, two corrections were applied. Flows obtained at about 90% power were reduced by 0.1% to account for the flow decrease from 90% to 100%

power (as discussed in Section 5.2.5), and flows in Cycle 2 Were increased by 0.3% to account for impeller smoothing, discussed in Section 5.3.1. These corrections result in hydraulically consistent flows used to define the baseline calorimetric flow.

The total measured flows for each cycle are defined in percent of the baseline calorimetric flow on Tables 6-4 and 6-5. The normalized flows are plotted on Figure 6-1 (Unit 1) and Figure 6-2 (Unit 2), to compare measured calorimetric flows with best estimate and elbow tap flow trends.

6.4.1 Unit 1 Based on Table 6-4, the calorimetric flows for Cycles 1 and 2 are within a 1% band and are within 1% of the best estimate flow, so these flows met Requirement (e) of the procedure and were used to define baseline calorimetric flow. Cycle 1 met all requirements for a baseline cycle.

The average of the four corrected flows on Table 6-4 (procedure step 3) is 376,656 gpm, and the baseline Cycle 1 flow (procedure step 2) is 376,683 gpm which negligibly higher. As stated in procedure step 4, the lower of these flows defines the baseline calorimetric flow, so the average (procedure step 3) flow of 376,656 gpm is defined as the Unit 1 baseline calorimetric flow. Unit 1 calorimetric flows are shown in Figure 6-4.

6A.2 Unit 2 Based on Table 6-5, the calorimetric flows for Cycles 1 and 2 are within a 1% band, but differed by slightly more than 2% from the best estimate flow.' Since the flow difference from the best estimate was conservative, these flows were considered to be acceptable for defining the baseline calorimetric flow.

Cycle 1 met all reqtuirements for a baseline cycle.

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6-4 The average of the four corrected flows on Table 6-5 (procedure step 3) is 379,089 gpm, and the baseline Cycle I flow (procedure step 2) is 379,843 gpm which is 0.2% higher. As stated in procedure step 4, the lower of these flows defines the baseline calorimetric flow, so the average (procedure step 3) flow of 379,089 gpm is defined as the Unit 2 baseline calorimetric flow. Unit 2 calorimetric flows are shown in Figure 6-4.

6.5 FLOW COMPARISONS 6.5.1- Unit 1 Figure 6-1 compares best estimate and elbow tap flows for Unit 1, all normalized to 100% flow in Cycle 1. Elbow tap flows were within the repeatability allowance limit of 0.4% above best estimate flow, but were 0.6% to 1% lower than the best estimate flows after Cycle 4. This difference may be due to under-predicting the steam generator tube plugging flow decrease or over-predicting the TPR flow increase.

Elbow tap loop flow trends based on Table 6-2 were in good agreement through Cycle 7, having a flow spread of less than 0.6%. However, the loop flow spread increased after Cycle 7, reaching 2% in Cycle 11. The increase in loop flow spread resulted from a flow decrease of 1.6% in Loop 2 between Cycles 7-11, while the other loop flows remained essentially constant. This can be attributed to the asymmetric steam generator tube plugging between loops. In Cycle 11, Loop I had 3.7% plugging, Loop 2 had 8.8%, Loop 3 had 1.2%, and Loop 4 had 1.9%. No other cause of the loop flow spread increase was identified.

Because the total elbow tap flow is similar to, and conservative relative to the best estimate flow trend, it was concluded that RCS flow can be based on the elbow tap flow measurements in future cycles.

6.5.2 Unit 2 Figure 6-2 compares best estimate and elbow tap flows for Unit 2, all normalized to 100% flow in Cycle 1. Elbow tap flow was above the 0.4% repeatability allowance limit only in Cycle 3. After Cycle 4, the elbow tap flow trend relative to the best estimate flow trend was similar to Unit 1 but the difference was smaller. After Cycle 7, the loop flow spread also increased as noted for Unit 1. The increase in the spread results from a 0.8% increase in Loop 1 and a 0.5% decrease in Loop 2 between Cycles 7-11, while the other loop flows remained essentially constant. This observed trend is consistent with the fact that Loop 1 had the least amount of steam generator tube plugging, whereas Loop 2 had the most plugging.

As stated for Unit 1, the elbow tap flow is similar to, and conservative relative to the best estimate flow trend. It was concluded that RCS flow could be based on the elbow tap flow measurements in future cycles.

6.6 POWER/FLOW CORRELATION FOR DIABLO CANYON A review of the radial power distributions and measured calorimetric flows from Units 1 & 2 indicated that the data, especially from the recent fuel cycles, defined a flow bias trend similar to the power/flow 4014-non doc-042202 April 2002 Revision 1

6-5 trend shown in Figure 3-4. Figure 6-3 plots the apparent flow decreases ve6sus the power difference between second row and outer row assemblies for Units 1 & 2. The decreases in RCS flow are based on calorimetric flows adjusted for hydraulics effects, based on the measured flow percentages on Tables 6-4 and 6-5, and hydraulics corrections listed on Table 6-1. The data from both units, but especially for Unit 2, defines a flow bias that is greater than predicted by the generic Westinghouse correlation of Figure 3-4 in most cycles. The power/flow correlation thus provides a qualitative confirmation of the hot leg streaming theory and the differences between elbow tap flow and calorimetric flow measurements.

4014-non.doc-042202 April 2002 Revision 1

6-6 TABLE 6-1 BEST ESTIMATE FLOW

SUMMARY

SGTP SGTP IMP SM V5 fuel TPR BEF CYCLE % tubes % flow % flow % flow % flow % flow Diablo Canyon Unit 1 1 0.007 -0.00 0.00 0.00 0.00 100.00 2 0.007 -0.00 -0.30 0.00 0.00 99.70 3 0.015 -0.00 -0.60 0.00 0.00 99.40 4 0.096 -0.02 -0.60 -0.20 +0.70 99.88 5 0.103 -0.02 -0.60 -0.52 +0.70 99.56 6 0.317 -0.06 -0.60 -0.70 +0.70 99.34 7 0.819 -0.14 -0.60 -0.70 +0.70 99.26 8 1.682 -0.30 -0.60 -0.70 +0.70 99.10 9 3.151 -0.57 -0.60 -0.70 +0.70 98.83 10 3.402 -0.61 -0.60 -0.70 +0.70 98.79 11 3.881 -0.70 -0.60 -0.70 +0.70 98.70 Diablo Canyon Unit 2 1 0.000 0.00 0.00 0.00 0.00 100.00 2 0.015 -0.00 -0.30 0.00 0.00 99.70 3 0.244 -0.04 -0.60 0.00 0.00 99.36 4 0.103 -0.02 -0.60 -0.29 +0.70 99.79 5 0.111 -0.02 -0.60 -0.59 +0.70 99.49 6 0.561 -0.10 -0.60 -0.70 +0.70 99.30 7 0.841 -0.15 -0.60 -0.70 +0.70 99.25 8 2.546 -0.46 -0.60 -0.70 +0.70 98.94 9 3.217 -0.58 -0.60 -0.70 +0.70 98.82 10 2.693 -0.48 -0.60 -0.70 +0.70 98.92 11 3.166 -0.57 -0.60 -0.70 +0.70 98.33 SGTP Steam Generator Tube Plugging IMP SM Pump Impeller Smootlung V5 fuel Vantage 5 Fuel Assemblies TPR Thimble Plug Removal BEF Best Estimate Flow 4014-non doc-042202 April 2002 Revision 1

6-7 TABLE 6-2 UNIT 1 ELBOW TAP AP

SUMMARY

Differential Pressures in Inches of Water Cycle 1 2 3 4 5 6 7 8 9 10 11 Tmtr 414 282.79 282.28 282.08 284.00 278.69 275.42 276.96 274.55 274.94 275.48 274.44 415 302.09 301.11 301.22 299.48 296.90 291.34 288.47 290.13 290.65 291.51 290.18 416 290.76 288.99 286.58 287.52 280.66 281.50 281.05 280.57 279.81 280.01 279.39 424 276.41 276.90 275.43 276.71 273.16 269.22 270.12 266.13 262.90 262.65 261.14 425 284.37 283.35 282.74 277.73 278.34 274.75 275.72 274.71 270.22 271.05 268.23 426 278.27 278.77 279.56 275.51 272.75 268.88 270.43 268.76 263.65 263.88 260.80 434 290.70 289.02 288.08 290.28 283.95 282.06 283.83 285.39 284.65 284.19 284.04 435 305.04 303.71 300.60 302.04 298.01 290.05 290.13 297.44 299.30 299.62 299.16 436 299.08 297.68 294.34 296.06 294.92 289.69 291.95 293.81 294.47 293.79 293.96 444 287.41- 284.92 285.44 286.16 280.27 276.82 278.42 279.07 279.93 280.61 279.57 445 308.93 302.66 299.25 299.14 297.15 294.51 295.23 302.20 303.02 303.38 301.39 446 "309.90 308.12 306.78 305.66 301.45 300.21 301.52 300.85 300.20 298.76 299.14 AVG 292.98 291.46 290.18 290.02 286.35 282.87 283.65 284.47 283.65 283.74 282.62 SpVol 21029 21013 21004 21083 21070 21075 21056 21055 21053 21048 21055 (ft'/lb)*E6 Normalized Flow - Percent of Baseline Lp 1 100.00 99.78 99.61 99.87 98.98 98.54 98.25 98.17 98.17 98.25 98.10 Lp 2 100.00 99.96 99.86 99.59 99.21 98.54 98.55 98.14 97.36 97.39 96.96 Lp 3 100.00 99.71 99.28 99.77 99.09 98.25 98.29 98.89 98.99 98.93 98.92 Lp 4 100.00 99.38 99.13 99.29 98.58 98.17 98.19 98.57 98.63 98.59 98.46 Total 100.00 99.71 99.47 99.63 98.97 98.37 98.32 98.44 98.28 98.29 98.11 99.70 99.40 99.88 99.56 99.34 99.26 '99.10 98.83 98.79 98.70 R'(%) 100.00 0.00 -0.01 -0.07 0.25 0.59 0.97 0.94 0.66 0.55 0.50 0.59 A

Flow includes a 0.15% reduction to correct for elimination of RTD bypass flow.

4014-non doc-042202 April 2002 Revision I

6-8 TABLE 6-3 UNIT 2 ELBOW TAP AP

SUMMARY

Differential Pressures in Inches of Water Cycle 1 2 3 4 5 6 7 8 9 10 11 Tmtr 414 279.37 275.12 281.83 282.93 277.52 276.12 277.52 277.75 277.89 278.44 279.19 415 292.02 294.39 297.22 295.17 289.31 288.27 288.91 288.98 288.47 290.17 290.35 416 274.56 273.03 272.41 269.45 262.55 258.55 260.65 271.73 270.65 270.75 271.52 424 279.15 278.86 281.90 279.39 272.35 268.21 270.58 267.47 265.73 266.51 265.76 425 284.32 283.59 283.52 281.06 274.90 274.27 275.87 274.22 273.74 273.55 273.91 426 277.69 274.15 275.24 273.05 267.84 267.31 266.61 264.77 265.40 265.56 265.07 434 286.90 286.93 289.35 286.36 279.93 280.46 279.18 281.12 281.03 281.05 282.00 435 331.77 333.34 330.98 328.11 324.14 321.58 323.31 322.21 321.36 323.66 323.87 436 298.38 295.30 294.79 295.11 288.52 286.85 289.61 288.99 288.49 289.03 290.33 444 276.43 276.07 277.07 282.34 270.58 268.23 268.60 268.40 268.50 270.47 270.97 445 300.31 300.68 299.60 298.08 295.40 293.01 294.02 292.71 291.52 292.73 291.37 446 279.03 278.90 278.52 276.81 272.93 272.34 273.19 273.02 271.66 273.70 273.80 AVG 288.33 287.53 288.54 287.32 281.33 279.60 280.67 280.95 280.37 281.30 2:31.51 SpVol 21043 20983 20978 21035 21068 21023 21045 21033 21045 21055 21040 (ft3/lb)*E6 Normalized Flow - Percent of Baseline Lp 1 100.00 99.65 100.16 100.06 99.06 98.56 98.71 99.38 99.33 99.49 99.55 Lp 2 100.00 99.58 99.81 99.52 98.50 98.07 98.17 97.74 97.67 97.74 97.65 Lp 3 100.00 99.77 99.75 99.58 98.71 98.41 98.48 98.48 98.43 98.60 98.71 Lp 4 100.00 99.85 99.81 100.08 99.06 98.65 98.68 98.56 98.44 98.78 98.70 Total 100.00 99.71 99.88 99.81 98.83 98.42 98.51 98.54 98.47 98.65 98.65 R'(%) 100.00 99.70 99.36 99.79 99.49 99.30 99.25 98.94 98.82 98.92 98.83 A 0.00 -0.01 -0.52 -0.02 0.66 0.88 0.74 0.40 0.35 0.27 0.18

Flow includes a 0.15% reduction to correct for elimination of RTD bypass flow.

4014-non doc-042202 April 2002 401!4-non doc-042202 April 2002 Revision I

6-9 TABLE 6-4 UNIT 1 CALORIMETRIC FLOW

SUMMARY

Power Loop 1 Loop 2 Loop 3 Loop 4 Total % of gpm gpm gpm gpm gpm Baseline, Cycle %

92705 93156 94533 95908 376302 99.91 1 91.3 92884 93847 94591 96118 377440 100.21 1 100.3 93455(1) 94515(" 95965(1) 3766831 100.01 1 avg 92748(1)

% of avg 98.5 99.2 100.4 101.9 91265 92723 94121 96710 374819 99.51 2 90.6 92857 92715 95114 95874 376560 99.97 2 100.0 92291"2) 92951(1.' 94854(1.2) 96532('2) 376629# 99.99 2 avg

% of avg 98.0 98.7 100.7 102.5 3 99.6 91537 92824 94273 94041 372675 98.94

% of avg 98.2 99.6 101.2 100.9 100.0 93750 91370 93740 94010 372870 98.99 4

% of avg 100.6 98.0 100.6 100.9 91590 90510 92400 93940 368440 97.82 5 100.1

% of avg 99.4 98.3 100.3 102.0 91850 90440 92190 92050 366530 97.31 6 99.8

% of avg 100.2 98.7 100.6 100.5 99.9 89274 93916 92108 92611 367910 97.68 7

% of avg 97.1 102.1 100.1 100.7 88920 93830 92230 91670 366650 97.34 8 99.7

% of avg 97.0 102.4 100.6 100.0 92522 92877 91840 366110 97.20 9 100.1 88871

% of avg 97.1 101.1 101.5 100.3 89151 92906 92322 91623 366002 97.17 10 99.9

% of avg 97.4 101.5 100.9 100.1 92495 91163 364515 96.78 11 100.0 88720 92137

% of avg 97.4 101.5 101.1 100.0 Baseline (avg of 4 flows) 376656 100.00 (1) Corrected by 0.999 for reactor power (2) Corrected by 1.003 for impeller smoothing prii LUUL 4014-non doc-042202 Aprils2on Revision I

6-10 TABLE 6-5 UNIT 2 CALORIMETRIC FLOW

SUMMARY

Power Loop 1 Loop 2 Loop 3 Loop 4 Total % of Cycle % gpm gpm gpm gpm gpm Baseline 1 90.5 95899 92972 95796 95557 380224 100.30 100.5 94720 93111 95960 96052 379843 100.20 I avg 95261('" 92995(') 95830(') 95757(1) 379843# 100.20

% of avg 100.3 97.9 100.9 100.8 2 98.3 93117 94447 95803 94165 377532 99.59 2 100.7 92870 93356 96170 94477 376873 99A2 2 avg 93272(2' 94183(2) 96275(2) 94604(2) 378334 99.80

% of avg 8.6 99.6 101.8 100.0 3 99.7 92490 90449 93787 93494 370220 97.66

% of avg 99.9 97.7 101.3 101.0 4 100.0 91200 90130 93680 92400 367410 96.92

% of avg 99.3 98.1 102.0 100.6 5 100.5 90120 89421 91954 93855 365350 96.38

% of avg 98.7 97.9 100.7 102.8 6 99.8 90816 90252 92433 92275 365775 96.49

% of avg 99.3 98.7 101.1 100.9 7 100.1 90512 91172 93447 92000 367131 96.85

% of avg 98.6 99.3 101.8 100.2 8 100.0 91810 93030 92510 91630 368980 97.33

% of avg 99.5 100.9 100.3 99.3 9 100.0 91054 92609 91865 91381 366909 96.79

% of avg 99.3 101.0 100.2 99.6 10 100.1 91375 92218 93736 92608 369937 97.59

% of avg 98.8 99.7 101.4 100.1 11 100.1 90583 91287 92308 91186 365364 96.38

% of avg 99.2 99.9 101.1 99.8 Baseline (avg of 4 flows) 379089 100.00 (1) Corrected by 0.999 for reactor power (2) Corrected by 1.003 for impeller smoothing 4014-non.doc-042202 April 2002 Revision I

6-1 6-11 100 N

0 R

M A

L I

z E

D 99 x

F L

0 x*--....x W

S 98 1 2 3 4 5 6 7 8 9 10 11

-CYCLE

+ Best Estimate Flow x Elbow Tap Flow FIGURE 6-1, UNIT 1 FLOW COMPARISONS LUUL 4014-non doc-042202 Aprison Revision I 1z

6-12 100 N

0 R

M A

L I

z E

D 99 F

L 0 x-W S

98 1 2 3 4 5 6 7 8 9 10 11 CYCLE

+ Best Estimate Flow x Elbow Tap Flow FIGURE 6-2 UNIT 2 FLOW COMPARISONS 4014-non doc-042202 April 2002 Revision I

6-1 6-13 0%

R C -1%

S F

L 0 -2%

W B

I A -3%

S

-4%

0 10 20 30 40 50 60 70 80 90 100 POWER DIFFERENCE

+ Diablo Canyon Unit 1 o Diablo Canyon Unit 2 FIGURE 6-3 FLOW BIAS VERSUS POWER DIFFERENCE 4014-non doc-042202 April 2002 Revision 1

6-14 C 380 A

L 0

R I 375 M

E T

R I 370 C

F L

0 365 W

1000 GPM 360 1 2 3 4 5 6 7 8 9 10 11 CYCLE x Unit I Calorimetric Flow 0 Unit 2 Calorimetric Flow FIGURE 6-4 UNIT 1 & 2 CALORIMETRIC FLOWS 4014-non doc-042202 April 2002 Revision 1

7-1 7.0 ELBOW TAP FLOW MiEASUREMENT LICENSING CONSIDERATIONS

7.1 BACKGROUND

Plant Technical Specifications require that an RCS total flow measurement be performed after each refueling (a 24 months nominal, 30 months maximum surveillance interval) to verify that sufficient RCS flow is available to satisfy the safety analysis assumptions. This surveillance is normally performed at the beginning of each operating cycle. Technical Specifications also require that a qualitative assessment of indicated RCS flow (i.e., channel check) be performed every 12 hours1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months during Mode 1. These surveillances ensure RCS flow is maintained within the assumed safety analysis value, i.e., Minimum Measured Flow (MMF).

The refueling RCS flow surveillance is typically satisfied by a secondary power calorimetric-based RCS flow measurement and the 12 hour1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months RCS flow surveillance is satisfied by control board RCS flow indicator or plant process computer readings using inputs from the RCS elbow tap Ap channels. These surveillances and the RCS Low Flow reactor trip are interrelated since the calorimetric RCS flow measurement is uised to correlate elbow tap Ap measurements to flow, and the flow at ihe Ap setpoint for the RCS Low Flow reactor trip is verified to be at or above the flow assumed in the safety analysis. The control board indication and process computer output is normalized to the calorimetric flow. The uncertainty associated with the refueling precision calorimetric is, therefore, included in the uncertainty calculations for the surveillance criterion and the RCS Low Flow trip.

The purpose of this evaluation is to support the use of elbow tap Ap measurements as an alternate method for performing the refueling RCS flow surveillance. Many plants in recent cycles have experienced apparent decreases in flow rates which have been attributed to variations in hot leg streaming, as discussed in previous sections of this document. These effects directly impact the hot leg temperatures used in the precision calorimetric, resulting in the calculation of apparently low RCS flow rates. In using the elbow tap Ap method, the RCS elbow tap measurements are correlated (as described in Section 4.2) to four precision calorimetric measurements performed during Cycles 1 and 2 when the hot leg streaming effects were decreased.

7.2 SUPPORTING CALCULATIONS In order to implement the elbow tap Ap method of measuring RCS flow, calculations must be performed to determine the uncertainties associated with the precision RCS flow calorimetrics for the baseline cycles for each of the units. These calculations must account for the plant instrumentation, test equipment, and procedures which were in place at the time the calorimetrics were performed.

In addition, uncertainty calculations must be performed for the indicated RCS flow (computer and/or control board indication) and the RCS low flow reactor trip. These calculations must reflect the correlation of the elbow taps to the baseline precision RCS flow calorimetrics noted above. Additional instrument uncertainties are required to reflect this correlation. Appendix A contains uncertainty calculations which were performed using Diablo Canyon plant specific inputs.

4014-non.doc-042202 April 2002 Revision 1

7-2 These uncertainty calculations have confirmed the acceptability of previously performed Diablo Canyon plant specific safety analyses and associated protection and/or control system setpoints when periodic surveillance is performed via use of control board or plant process computer indication on a 30 month surveillance interval basis. In particular, no increase in the RCS total flow uncertainty due to the elbow tap Ap method has been determined when utilizing the control board or plant process computer indication. Thus there is no required revision to the Westinghouse Improved Thermal Design Procedure (ITDP) instrumentation uncertainties (currently 2.4% flow), which are used in deriving the Technical Specifications reactor core safety limits and the corresponding DNB limits. The low flow reactor trip setpoint uncertainty has increased somewhat but does not require a change to either the Technical Specifications trip setpoint (90.0% flow) or to the current Safety Analysis Limit (85.0% flow) due to the availability of margin in the uncertainty calculation.

7.3 POTENTIAL DOCUMENT IMPACTS The Diablo Canyon Technical Specifications are affected in two areas:

1. Specification 3.3.1, Table 3.3.1-1, Item 10, Reactor Coolant Flow- Low (Allowable Value and Nominal Trip Setpoint modified to reflect use of measured flow). This change is supported by Westinghouse Nuclear Safety Advisory Letter, NSAL-00-008, "Reactor Coolant Loop Flow Asymmetry," 5/00.

2. Specification 3.4.1 Bases is modified to include a description of the elbow tap Ap method of flow measurement and to note the indication uncertainty.

Appendix B contains a markup of the Diablo Canyon Technical Specifications. This appendix also contains the 50.92 input for licensing documentation purposes.

In the case of the Diablo Canyon specific instrument uncertainty analyses shown in Appendix A, the RCS flow uncertainty associated with the elbow tap Ap method (when indication is by utilization of control board meters or the plant process computer) was less than or equal to the current Technical Specification value. RCS low flow reactor trip setpoint uncertainty calculations also verify that the current trip setpoint and Safety Analysis Limit remain valid.

4014-non doc-050202 April 2002 Revision I

A-I APPENDIX A INDICATED RCS FLOW AND REACTOR COOLANT FLOW - LOW REACTOR TRIP INSTRUMENT UNCERTAINTIES 4014-non doc-042202 April 2002 Revision I

A-2 UNCERTAINTY CALCULATION ASSUMPTIONS

1. The Eagle-21 "m7" scaling constant for RCS flow is < 1.30.

2. Cold Leg Elbow Tap measurement is performed at approximately 100% RTP at BOC.

3. Cold Leg Elbow Tap measurement utilizes all 12 channels of analog output of the control board meters or digital output of the plant process computer at BOC.

4. Cold Leg Elbow Tap transmitters are calibrated prior to startup.

5. Cold Leg Elbow Tap instrument channels are verified to be within the required calibration accuracy within 92 days prior to performance of the measurement at BOC.

6. Cold Leg Elbow Tap measurement is performed with Tavg and Pressurizer Pressure within the accuracy of their respective automatic control systems (+/-4.3°F, +/-51.7 psi).

7. Cold Leg Elbow Tap transmitters do not experience an ambient temperature greater than 50'F above the calibration ambient temperature during performance of the BOC RCS Flow measurement.

8. Cold Leg Elbow Tap transmitter static head pressure span effect is calibrated out.

4014-non doc-042202 April 2002 Revision 1

A-I I A-3 TABLE A-1 BASELINE FLOW CALORIMETRIC INSTRUMENTATION UNCERTAINTIES

(% Span) PFW APFW PsrM Twor TCOD PPRZ Sensor +ac SCA =

M&TE=

SRA =

SPE =

STE =

SD =

BIAS =

Racks RCA=

M&TE =

RTE=

RD =

READ=

CSA =

Inst Used 1/loop

I/loop I/loop I/loop I/loop I1I psia %AP psia OF OF psia INST SPAN INST UNC.

F +a,c I

(RANDOM)=

INST UNC.

(BIAS) =

NOMINAL! =

+ TAvc span

Average of nominal parameter values for the four Unit I Cycle I and Cycle 2 measurements 4014-non doc-050202 April 2002 Revision I

A-4 TABLE A-2 FLOW CALORIMETRIC SENSITIVITIES*

FEEDWATER FLOW FA +ac TEMPERATURE MATERIAL DENSITY TEMPERATURE PRESSURE AP FEEDWATER ENTHALPY TEMPERATURE PRESSURE STEAM ENTHALPY +ac PRESSURE MOISTURE STEAM GENERATOR BLOWDOWN DENSITY PRESSURE ENTHALPY PRESSURE HOT LEG ENTHALPY TEMPERATURE PRESSURE COLD LEG ENTHALPY TEMPERATURE PRESSURE

] +a,c COLD LEG SPECIFIC VOLUME +ac TEMPERATURE PRESSURE I

Average of the sensitivity values for the four Unit I Cycle 1 and Cycle 2 measurements 4014-non doc-042202 April 2002 Revision 1

A-5 TABLE A-3 CALORIMETRIC RCS FLOW MEASUREMENT UNCERTAINTIES COMPONENT INSTRUMENT ERROR FLOW UNCERTAINTY" FEEDWATER FLOW +a,c VENTURI THERMAL EXPANSION COEFFICIENT TEMPERATURE MATERIAL DENSITY (p)

TEMPERATURE PRESSURE AP FEEDWATER ENTHALPY (h)

TEMPERATURE PRESSURE STEAM ENTHALPY (h)

PRESSURE MOISTURE STEAM GENERATOR BLOWDOWN DENSITY PRESSURE ENTHALPY PRESSURE FLOW NET PUMP HEAT ADDITION HOT LEG ENTHALPY (h)

TEMPERATURE STREAMING, RANDOM STREAMING, SYSTEMATIC PRESSURE COLD LEG ENTHALPY (h)

TEMPERATURE PRESSURE COLD LEG SPECIFIC VOLUME (u)

TEMPERATURE PRESSURE

,**,+.++ Indicate Sets of Dependent Parameters

Average of the uncertainty values for the four Unit 1 Cycle 1 and Cycle 2 measurements 4014-non doc-050202 April 2002 Revision 1

A-6 TABLE A-3 (Continued)

CALORIMETRIC RCS FLOW MEASUREMENT UNCERTAINTIES COMPONENT FLOW UNCERTAINTY

-- ,+a~c BIAS VALUES FEEDWATER PRESSURE P

h STEAM PRESSURE h

STEAM GENERATOR BLOWDOWN P

h PRESSURIZER PRESSURE h-IHOTLEG h - COLD LEG S- COLD LEG FLOW BIAS TOTAL VALUE N LOOP UNCERTAINTY (With Appropriate BIAS)

Average of the uncertainty values for the four Unit 1 Cycle I and Cycle 2 measurements April 2002 doc-042202 4014-non doc-042202 April 2002 Revision I

I A-7 TABLE A-4 COLD LEG ELBOW TAP FLOW UNCERTAINTY (Control Board Indication)*

INSTRUMENT UNCERTAINTIES

% AP SPAN % FLOW Sensor +a,c PMA=

PEA =

SCA =

M&TE=

SRA=

SPE =

STE =

SD =

BIAS =

Eagle-21 Racks EAI Card RCA=

M&TE RTE=

RD=

EAO Card RCA=

M&TE=

RTE RD=

Control Board Meter RCA=

M&TE =

RTE=

RD =

READOUT =

FLOW CALORIM BIAS =

FLOW CALORIMETRIC =

INSTRUMENT SPAN = 120.0 NUMBER TAPS PER LOOP =3 N LOOP RCS FLOW UNCERTAINTY = 2.3 % FLOW

Bounding for plant process computer indication.

4014-non doc-050202 April 2002 Revision I

A-8 TABLE A-5 LOW FLOW REACTOR TRIP

% AP SPAN % FLOW SPAN

-I +a,c PMAI =

PMA2 =

PEA =

SCA =

M&TE =

SRA =

SPE =

STE =

SD =

BIAS =

RCA=

M&TE =

RTE=

RD=

BIAS INSTRUMENT RANGE = 0% to 120.0 % FLOW FLOW SPAN = 120.0 % FLOW SAFETY ANALYSIS LIMIT = 85.0 % FLOW NOMINAL TRIP SETPOINT = 90.0 % FLOW TA = 4.2 % FLOW SPAN L

CSA =

MAR= +a,c 4014-non.doc-050202 April 2002 Revision I

B-1 APPENDIX B DIABLO CANYON 50.92 AND SUGGESTED MODIFICATIONS TO PLANT TECHNICAL SPECIFICATIONS J.ipL A.1flfV AL 4014-non doc-042202 Revision 1

AM-I ATTACHMENT 1 STANDARD TECHNICAL SPECIFICATION MARKUPS Iip17H SUUL.

4014-non doc-042202 Revision I

A1-2 Page 3.3-14 of Tech Specs RTS Instrumentation 3.3.1 Table 3.3.1-1 (page 3 of 7)

Reactor Trip System Instrumentation APPLICABLE MODES OR OTHER NOMINALM SPECIFIED REQUIRED SURVEILLANCE ALLOWABLE TRIP FUNCTION CONDITIONS CHANNELS CONDITIONS SETPOINT CONANTEOS REOI IRFUMiENT' VALUE IU. Reiacor Coolant 1"o 3 per loop M SR 3.3.1.1 > 89.8%1%of 9 0 %NIof Flow--ow SR 3.3.1.7 SR 3.3.1.10 I7e4SU ed /MMt '/op SR 3.3.1.16 Isvi fI.-j

11. Reactor Coolant 1u I per RCP M SR 3.3.1.14 NA NA Pump (RCP)

Breaker Position

12. Undervoltage 1M 2 per bus M SR 3 3.1.9 2 7877V 8050V RCPs SR 3 3.1.10 each bus each bus SR 3 3.1.16

13. Underfrequency 110 3 per bus M SR 3 3.1.9 a 53.9 Hz 54.0 Hz RCPs SR 3.3.1.10 each bus each bus SR 3.3.1.16 14 a. Steam 12 3per SG E SR 3.3.1.1 Z 7.01/6 7.2%

Generator SR 3.3.1 7 (SG) Water SR 3 3.1.10 Level--Low SR 3 3.1.16 Low

b. SG Water 12 4 X SR 3 3.1.7 TrD s 1.01 TrD s TD Level - Low SR 3.3.1.10 TD (Note 3) (Noe 3) for Low Trip Time for RCS loop RCS loop AT Delay (TTD)

AT variable variable input input < 50.7% 50% RTP RTP TTD=O and "TD=O fr RCS loop for RCS loop AT variable AT variable miput SO%

inpuA > 50.7 RTP

% RTP

15. Not used (continued)

(a) A channel Is OPERABLE with an actual Trip Selpoint value outside its calration tolerance band provided the Trip Selpoint value is conservative with respect to ts associated Allowable Value and the channel is re adiusted to with"n the establtshed calibration tolerance band of the Nominal Trip Selpoirt A Trip Setpoint may be set more conservative than the Nominal Trip Setpoint as necessay in response to plant conditions.

(g) Above the P-7 (Low Power ReadorTrips Block) Interlock.

DIABLO CANYON - UNITS 1 & 2 3.3-14 Unit 1 -Amendment No. 435 142 TAB 3.3 - R2 14 Unit 2 - Amendment No. 435 142 4014-non.doc-042202 April 2002 Revision 1

I A1-3 Page B 3.4-2 of Tech Spec RCS Pressure. Temperature, and Flow DNB Limits B 34.1 BASES APPLICABLE Insertion Limits". LCO 3.2.3. "AXIAL FLUX DIFFERENCE (AFD)": and SAFETY LCO 3.2.4. "QUADRANT POWER TILT RATIO (QPTR)."

ANALYSES The pressurizer pressure limit of 2197.3 psig and the RCS average (continued) temperature limit of 584.3'F correspond to nominal analytical limits of 2250 psia and 577.6"F for Unit 2 (the limiting unit) used for the DNB calculation in the reload analyses with allowance for analysis initial consideration uncertainty (38 psi and 6.7@F)

The RCS DNB parameters satisfy Criterion 2 of 10 CFR 50.36 (c)(2)(ii).

LCO This LCO specifies limits on the monitored process variables pressurizer pressure. RCS average temperature, and RCS total flow rate to ensure the core operates within the limits assumed in the safety analyses. Operating within these limits will result in meeting the DNBR criterion in the event of a DNB limited transient.

RCS total flow limits are provided for a RTP range of 90% to 100% on Tables 3 4.1-1 and 3 4.1-2 for Unit 1 and Unit 2 respectively.

The RCS total flow rate limit allows for a measurement error of Z.'/9 Flow 2 3" O 4 44 ant 2.4) 4..1. -f""gr2) 3....*(Unt dci ROW. ....

m e2-c-rod fkrw. based on performing a precision heat balance and using the result to normalize the RCS flow rate indicators. Potential fouling of the feedwater venturi, which might not be detected, could bias the result from the precision heat balance in a non-conservative manner. A bias error of 0.1% for undetected fouling of the feedwater I venturi is included in the measurementeror lysis..

' . c." ,.;,c, Any fouling that might significantly bias the,,flow rateAmeasurement greater than 0.1% can be detected by monitoring and trending various plant performance parameters. If detected, either the effect of the fouling shall be quantified and compensated for in the RCS flow rate measurement or the venturi shall be cleaned to eliminate the fouling The LCO numerical values for pressure. temperature, and flow rate have not been adjusted for instrument error.

APPLICABILITY In MODE 1, the limits on pressurizer pressure. RCS coolant average temperature, and RCS flow rate must be maintained during steady state operation in order to ensure the DNBR criteria will be met in the event of an unplanned loss of forced coolant flow or other DNB limited transient. In all other MODES, the power level is low enough that DNB is not a concern.

(continued)

DIABLO CANYON - UNITS 1 & 2 B 3.4-2 Revision 1 Tabb3-4.doc - R1 2 IL 4014-non.doc-043002 Revision 1

A1-4 Page B 3.4-4 of Tech Specs RCS Pressure, Temperature, and Flow DNB Limits B 3.4.1 BASES SURVEILLANCE SR 3 4.1.1 REQUIREMENTS Since Required Action A.1 allows a Completion Time of 2 hours2.314815e-5 days 5.555556e-4 hours 3.306878e-6 weeks 7.61e-7 months to restore parameters that are not within limits, the 12 hour1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months Surveillance Frequency for pressurizer pressure is sufficient to ensure the pressure can be restored to a normal operation, steady state condition following load changes and other expected transient operations. The 12 hour1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months interval has been shown by operating practice to be sufficient to regularly assess for potential degradation and to verify operation is within safety analysis assumptions.

SR 3 4 1.2 Since Required Action A.1 allows a Completion Time of 2 hours2.314815e-5 days 5.555556e-4 hours 3.306878e-6 weeks 7.61e-7 months to restore parameters that are not within limits, the 12 hour1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months Surveillance Frequency for RCS average temperature is sufficient to ensure the temperature can be restored to a normal operation, steady state condition following load changes and other expected transient operations. The 12 hour1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months interval has been shown by operating practice to be sufficient to regularly assess for potential degradation and to verify operation is within safety analysis assumptions.

SR 3 4.13 The 12 hour1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months Surveillance Frequency for the indicated RCS total flow rate is performed using the installed flow instrumentation. The 12 hour1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months interval has been shown by operating practice to be sufficient to regularly assess potential degradation and to verify operation within safety analysis assumptions. The term "indicated RCS total flow" is used to distinguish between the "measured RCS total flow" determined in SR 3.4.1.4.

SR 3 4.1.4 SR 3.4.1.4 has two surveillance requirements, one for the CHANNEL CALIBRATION of the RCS flow indicators and the other for measurement of RCS total flow rate. Measurement of RCS total flow rate by performance of a precision calorimetric heat balance or other acceptable methodpnce every 24 months allows the installed RCS So lJ flOW instrumentation to be normalized and verifies the actual RCS flow RCS flow rate.

Sl ,Jol, *lerate is greater than or equal to the minimum required jj (rc-AP- JG1/3 C, (continued)

DIABLO CANYON - UNITS 1 & 2 B 3.4-4 Revision 1 Tabb3-4.doc - R1 4 4014-non doc-042202 April 2002 Revision 1

Al1-5 Page B 3.4-5 of Tech Specs RCS Pressure. Temperature, and Flow DNB Limits B 34.1 BASES (Continued)

The second part of this surveillance is the routine CHANNEL CALIBRATION of the RCS flow indication instrumentation. The routine calibration of the flow instrumentation ensures that the channels are within the necessary range and accuracy for proper flow indication.

The routine CHANNEL CALIBRATION of the RCS flow indication instrumentation is performed every 24 months.

The Frequency of 24 months for the measurement of RCS total flow rate reflects the importance of verifying flow after a refueling outage when the core has been altered, which may have caused an alteration of flow resistance. Flow verification demonstrates that setpoints are relevant and RCS flow resistance is within limits. The frequency of 24 months for the routine CHANNEL CALIBRATION of the flow indication instrumentation is based on operating experience and consistency with the typical industry refueling cycle.

REFERENCES 1. FSAR. Section 15.

2. Diablo Canyon Power Plant Unit 1 Cycle 9 Reload Safety Evaluation. August 1995.

3. Diablo Canyon Power Plant Unit 2 Cycle 8 Reload Safety Evaluation. Rev.1. April 1996.

e-Se-r --I a DIABLO CANYON - UNITS 1 & 2 B 3.4-5 Revision 1 Tabb3-4.doc- R1 5 jpni LAL 4014-non.doc-042202 Ripsi Revision 1W I

AI-6 INSERT "A" Use of the cold leg elbow tap methodology results in a measurement uncertainty of +/-2.3 % flow based on the utilization of twelve cold leg elbow taps correlated to the four baseline precision heat balance measurements of Cycles 1 and 2 for each unit. Correlation of the flow indication channels with this previously performed heat balance measurement is documented in WCAP-15113 Rev. 1, 4/02. Use of this method provides an alternative to performance of a precision RCS flow calorimetric.

INSERT "B"

4. WCAP-15113 Rev. 1, "RCS Flow Measurement Using Elbow Tap Methodology at Diablo Canyon Units I and 2," April, 2002.

4014-non.dac-042202 4014-non-doc-042202 April 2002 April 2002 Revision I

A2 A2-1 ATTACHMENT 2 SIGNIFICANT HAZARDS CONSIDERATION EVALUATION 4014-non doc-042202 April 2002 Revision 1

A2-2

1. NUCLEAR PLANT: DIABLO CANYON UNITS I & 2

2.

SUBJECT:

ELBOW TAP FLOW MEASUREMENT

3. TECHNICAL SPECIFICATIONS CHANGED:

Table 3.3.1-1 Reactor Trip System Instrumentation, Item 10 Reactor Coolant Flow - Low Bases to Specification 3.4.1 Reactor Coolant System (RCS) RCS Pressure, Temperate and Flow Departure from Nucleate Boiling (DNB) Limits

4. A written evaluation of the significant hazards consideration, in accordance with the three factor test of 10CFR50.92, of a proposed license amendment to implement the subject change has been prepared and is attached. On the basis of the evaluation the checklist below has been completed.

Will operation of the plant in accordance with the proposed amendment:

4.1. Yes-_ No X Involve a significant increase in the probability or consequences of an accident previously evaluated?

4.2. Yes_ No X Create the possibility of a new or different kind of accident from any accident previously evaluated?

4.3. Yes_ No X Involve a significant reduction in a margin of safety?

5. Reference Documents:

1. WCAP- 11594, Rev. 2, "Westinghouse Improved Thermal Design Procedure Instrument Uncertainty Methodology - Diablo Canyon Units 1 & 2 - 24 Month Fuel Cycle Evaluation,"

1/97.

2. WCAP-1 1082, Rev. 5, "Westinghouse Setpoint Methodology for Protection Systems - Diablo Canyon Units 1 & 2 - 24 Month Fuel Cycle Evaluation," 1/97.

3. WCAP-15113 Rev. 1, "RCS Flow Measurement Using Elbow Tap Methodology at Diablo Canyon Units 1 and 2," 4/02.

6. Significant Hazards Consideration Approval:

Prepared By: Date:

Reviewed By: Date:

4014-non doc-042202 April 2002 Revision 1

A2-3 10CFR50.92 EVALUATION Pursuant to 10CFR50.92 each application for amendment to an operating license must be reviewed to determine if the proposed change involves a Significant Hazards Consideration. The amendment, as defined below, describing the Technical Specification (T/S) change associated with the change has been reviewed and deemed not to involve Significant Hazards Considerations. The basis for this determination follows.

Proposed Change: The current Technical Specification Table 3.3.1-1 (page 3.3-14) "Reactor Trip System Instrumentation," provides the Trip Setpoint and Allowable Value for the RCS Flow - Low trip.

The Nominal Trip Setpoint and the Allowable Value units will be changed to reflect the use of percent of measured flow which is supported by the correlation of the elbow taps to previous baseline calorimetrics.

In addition, the Bases for Technical Specification 3.4.1 (page B3.4-2), "Reactor Coolant System (RCS)

RCS Pressure, Temperature and Flow Departure from Nucleate Boiling (DNB) Limits", will be revised to include the RCS total flow measurement by the elbow tap Ap method. The revised Technical Specifications and Bases sections are provided in Attachment 1.

Background:

The refueling RCS flow surveillance (24 month nominal fuel cycle, 30 months maximum surveillance interval) is typically satisfied by a secondary power calorimetric-based RCS flow measurement. Diablo Canyon in recent cycles has experienced apparent decreases in flow rates which have been attributed to variations in hot leg streaming effects. These effects directly impact the hot leg temperatures used in the precision calorimetric, resulting in the calculation of low RCS flow rates. The apparent flow reduction has become more pronounced in fuel cycles which have implemented aggressive Low Leakage Loading Patterns (LLLPs). Evidence that the flow reduction was apparent, but not actual, was provided by elbow tap measurements. The results of this evaluation, including a detailed description of the hot leg streaming phenomenon, are documented in WCAP-15113, Rev. 1, "RCS Flow Measurement Using Elbow Tap Methodology at Diablo Canyon Units 1 and 2."

Diablo Canyon intends to begin using an alternate method of measuring flow using the elbow tap Ap measurements as described in the above noted WCAP. For this alternate method, the RCS elbow tap measurements are correlated to four precision calorimetric measurements performed during Cycles 1 and 2 when the hot leg streaming effects were decreased.

The purpose of this evaluation is to assess the impact of using the elbow tap Ap measurements as an alternate method for performing the refueling RCS flow surveillance on the licensing basis and demonstrate that it will not adversely affect the subsequent safe operation of the plant. This evaluation supports the conclusion that implementation of the elbow tap Ap measurement as an alternate method of determining RCS total flow rate does not represent a significant hazards consideration as defined in 10CFR50.92.

Evaluation: Use of the elbow tap Ap method to determine RCS total flow requires that the Ap measurements for the present cycle be correlated to the precision calorimetric flow measurement which was performed during the baseline cycles (Cycles 1 and 2 for both units). A calculation has been performed to determine the uncertainty in the RCS total flow using this method. This calculation includes the uncertainty associated with the average of the four RCS total flow baseline calorimetric measurements, as well as uncertainties associated with Ap transmitters and indication via control board 4014-non doc-042202 April 2002 Revision I

A2-4 meters or the plant process computer. The uncertainty calculation performed for this method of flow measurement is consistent with the methodology recommended by the NRC (NUREG/CR-3659, PNL-4973, 2/85). The only significant differences are the averaging of the four baseline calorimetric measurements and the assumption of a correlation to the previously performed RCS flow calorimetrics.

However, this has been accounted for by utilization of the average of the baseline RCS Flow calorimetric uncertainties and by the addition of certain instrument uncertainties previously considered to be zeroed out by the assumption of normalization to a calorimetric performed each cycle. Based on these calculations, the uncertainty on the RCS flow measurement using the elbow tap method is 2.3% flow which results in a minimum required RCS total flow of 358,900 gpm for Unit 1 and 362,100 gpm for Unit 2 and must be measured via indication with the control board meters or the plant process computer at approximately 100% RTP.

The calculations are documented in Tables A-1 through A-5. Specific calculations performed were:

Precision RCS Flow Calorimetrics for the baseline measurements (two measurements each for Cycles 1 and 2 for both units, Unit 1 determined to be bounding), Indicated RCS Flow (via control board meters or plant process computer), and the Reactor Coolant Flow - Low reactor trip. The calculations for Indicated RCS Flow and Reactor Coolant Flow - Low reflect the correlation of the elbow taps to the baseline precision RCS Flow Calorimetric measurements on each unit. As discussed above, additional instrument uncertainties were required to reflect this correlation.

The uncertainty associated with the RCS Flow - Low trip increased slightly. It was determined that due to the availability of margin in the uncertainty calculation, no change was necessary to either the Trip Setpoint (90.0% flow) or to the current Safety Analysis Limit (85.0% flow) to accommodate this increase.

Since the flow uncertainty did not increase over the currently analyzed value, no additional evaluations of the reactor core safety limits must be performed. In addition, it was determined that the current Minimum Measured Flow (MMF) assumed in the safety analyses (359,000 gpm for Unit I and 363,000 gpm for Unit 2) bounds the required minimum flow calculated for the elbow tap method (358,900 gpm for Unit 1 and 362,100 gpm for Unit 2).

Based on these evaluations, the proposed change would not invalidate the conclusions presented in the FSAR.

1. Does the proposed modification involve a significant increase in the probability or consequences of an accident previously evaluated?

An evaluation determined that the probability of an accident will not increase. Sufficient margin exists to account for all reasonable instrument uncertainties; therefore, no changes to installed equipment or hardware in the plant are required, thus the probability of an accident occurring remains unchanged.

The initial conditions for all accident scenarios modeled are the same and the conditions at the time of trip, as modeled in the various safety analyses are the same. Therefore, the consequences of an accident will be the same as those previously analyzed.

4014-non doc-042202 April 2002 Revision I

A2-5

2. Does the proposed modification create the possibility of a new or different kind of accident from any accident previously evaluated?

No new accident scenarios have been identified. Operation of the plant will be consistent with that previously modeled, i.e., the time of reactor trip in the various safety analyses is the same, thus plant response will be the same and will not introduce any different accident scenarios that have not been evaluated.

3. Does the proposed modification involve a significant reduction in a margin of safety.

The proposed modification reflects changes due to the method used to verify RCS flow at the beginning of each cycle. However, no changes to the Safety Analysis assumptions were required; therefore, the margin of safety will remain the same.

Conclusion:

Based on the preceding information, it has been determined that this proposed change to allow an alternate RCS total flow measurement based on elbow tap Ap measurements does not involve a Significant Hazards Consideration as defined in 10CFR50.92(c).

4014-non doc-042202 April 2002 Revision 1

Enclosure 6 PG&E Letter DCL-02-097 Proprietary Information Enclosed Westinghouse Electric Company, LLC Application for Withholding Proprietary Information from Pubic Disclosure (H. A. Sepp to Document Control Desk, Attention:

Mr. Samuel J. Collins), CAW-02-1531, dated June 5, 2002, including Affidavit, Proprietary Information Notice, and Copyright Notice WCAP-15113, Revision 1, "RCS Flow Measurement Using Elbow Tap Methodology at Diablo Canyon Units 1 and 2," April, 2002 (Westinghouse proprietary Class 2)

Westinghouse Westinghouse Electric Company NuclearServices P.O. Box 355 Pittsburgh, Pennsylvania 15230-0355 USA Document Control Desk Direct tel. (412) 374-5282 U.S. Nuclear Regulatory Commission Direct fax: (412) 374-4011 e-mail: Sepplha@westinghouse.com Washington, DC 20555-0001 Attention: Chief, Information Management Branch Division of Program Management Our ref CAW-02-1531 Policy Development and Analysis Staff June 5, 2002 APPLICATION FOR WITHHOLDING PROPRIETARY INFORMATION FROM PUBLIC DISCLOSURE

Subject:

WCAP-15113, "RCS Flow Measurement Using Elbow Tap Methodology at Diablo Canyon Units 1 and 2" (Proprietary), WCAP-15173, "RCS Flow Measurement Using Elbow Tap Methodology at Diablo Canyon Units 1 and 2" (Non-Proprietary)

The proprietary information for which withholding is being requested in the above-referenced report is further identified in Affidavit CAW-02-1531 signed by the owner of the proprietary information, Westinghouse Electric Company LLC. The affidavit, which accompanies this letter, sets forth the basis on which the information may be withheld from public disclosure by the Commission and addresses with specificity the considerations listed in paragraph (b)(4) of 10 CFR Section 2.790 of the Commission's regulations.

Accordingly, this letter authorizes the utilization of the accompanying Affidavit by Pacific Gas and Electric Company.

Correspondence with respect to the proprietary aspects of the application for withholding or the Westinghouse affidavit should reference this letter, CAW-02-1531 and should be addressed to the undersigned Very truly yours, H. A. Sepp, Miage r Regulatory and Licensing Engineering Enclosures A BNFL Group company

CAW-02-1531 AFFIDAVIT COMMONWEALTH OF PENNSYLVANIA:

ss COUNTY OF ALLEGHENY:

Before me, the undersigned authority, personally appeared H. A. Sepp, who, being by me duly sworn according to law, deposes and says that he is authorized to execute this Affidavit on behalf of Westinghouse Electric Company LLC ("Westinghouse"), and that the averments of fact set forth in this Affidavit are true and correct to the best of his knowledge, information, and belief:

I.G

-.-,'.' ....... .... , ,,. t I,*

G:o FU *t= *.

H. A. Seppanager

",, -Regulatory and Licensing Engineering Sw6on to and subscribed before me this 1.7,.a day of (2dZL _,2002 Notary Public Notara Sea]

Margaret L Gonano, Notary Public Monroene Boro, Allegheny County My Commission Expires Jan. 3.2006 Member, Pnnsylvanla Association Of Notaries

3 CAW-02-1531 (1) I am Manager, Regulatory and Licensing Engineering, in Nuclear Services, Westinghouse Electric Company LLC ("Westinghouse"), and as such, I have been specifically delegated the function of reviewing the proprietary information sought to be withheld from public disclosure in connection with nuclear power plant licensing and rule making proceedings, and am authorized to apply for its withholding on behalf of the Westinghouse Electric Company LLC.

(2) I am making this Affidavit in conformance with the provisions of 10CFR Section 2.790 of the Commission's regulations and in conjunction with the Westinghouse application for withholding accompanying this Affidavit.

(3) I have personal knowledge of the criteria and procedures utilized by the Westinghouse Electric Company LLC in designating information as a trade secret, privileged or as confidential commercial or financial information.

(4) Pursuant to the provisions of paragraph (b)(4) of Section 2.790 of the Commission's regulations, the following is furnished for consideration by the Commission in determining whether the information sought to be withheld from public disclosure should be withheld.

(i) The information sought to be withheld from public disclosure is owned and has been held in confidence by Westinghouse.

(ii) The information is of a type customarily held in confidence by Westinghouse and not customarily disclosed to the public. Westinghouse has a rational basis for determining the types of information customarily held in confidence by it and, in that connection, utilizes a system to determine when and whether to hold certain types of information in confidence. The application of that system and the substance of that system constitutes Westinghouse policy and provides the rational basis required.

Under that system, information is held in confidence if it falls in one or more of several types, the release of which might result in the loss of an existing or potential competitive advantage, as follows:

(a) The information reveals the distinguishing aspects of a process (or component, structure, tool, method, etc.) where prevention of its use by any of Westinghouse's competitors without license from Westinghouse constitutes a competitive economic advantage over other companies.

4 CAW-02-1531 (b) It consists of supporting data, including test data, relative to a process (or component, structure, tool, method, etc.), the application of which data secures a competitive economic advantage, e.g., by optimization or improved marketability.

(c) Its use by a competitor would reduce his expenditure of resources or improve his competitive position in the design, manufacture, shipment, installation, assurance of quality, or licensing a similar product.

(d) It reveals cost or price information, production capacities, budget levels, or commercial strategies of Westinghouse, its customers or suppliers.

(e) It reveals aspects of past, present, or future Westinghouse or customer funded development plans and programs of potential commercial value to Westinghouse.

(f) It contains patentable ideas, for which patent protection may be desirable.

There are sound policy reasons behind the Westinghouse system which include the following:

(a) The use of such information by Westinghouse gives Westinghouse a competitive advantage over its competitors. It is, therefore, withheld from disclosure to protect the Westinghouse competitive position.

(b) It is information which is marketable in many ways. The extent to which such information is available to competitors diminishes the Westinghouse ability to sell products and services involving the use of the information.

(c) Use by our competitor would put Westinghouse at a competitive disadvantage by reducing his expenditure of resources at our expense.

(d) Each component of proprietary information pertinent to a particular competitive advantage is potentially as valuable as the total competitive advantage. If competitors acquire components of proprietary information, any one component

5 CAW-02-1531 may be the key to the entire puzzle, thereby depriving Westinghouse of a competitive advantage.

(e) Unrestricted disclosure would jeopardize the position of prominence of Westinghouse in the world market, and thereby give a market advantage to the competition of those countries.

(f) The Westinghouse capacity to invest corporate assets in research and development depends upon the success in obtaining and maintaining a competitive advantage.

(iii) The information is being transmitted to the Commission in confidence and, under the provisions of 10CFR Section 2.790, it is to be received in confidence by the Commission.

(iv) The information sought to be protected is not available in public sources or available information has not been previously employed in the same original manner or method to the best of our knowledge and belief.

(v) The proprietary information sought to be withheld in this submittal is that which is appropriately marked in WCAP-1 5113, "RCS Flow Measurement Using Elbow Tap Methodology at Diablo Canyon Units 1 and 2" (Proprietary), WCAP-15173, "RCS Flow Measurement Using Elbow Tap Methodology at Diablo Canyon Units 1 and 2" (Non Proprietary), being transmitted by the Pacific Gas and Electric Company letter and Application for Withholding Proprietary Information from Public Disclosure, to the Document Control Desk, Attention Mr. Samuel J. Collins. The proprietary information as submitted for use by Westinghouse Electric Company LLC for Diablo Canyon Units 1 and 2 is expected to be applicable in other licensee submittals in response to certain NRC requirements for RCS Flow Elbow Tap Methodology.

This information is part of that which will enable Westinghouse to:

(a) Provide responses to NRC questions on RCS Flow Elbow Tap Methodology at Diablo Canyon Units 1 and 2.

(b) Provide a quantitative technical justification for how RCS Flow Elbow Tap Methodology improves RCS flow measurement.

6 CAW-02-1531 (c) Assist Pacific Gas and Electric Company in obtaining a license amendment for implementation RCS Flow Elbow Tap Methodology.

Further this information has substantial commercial value as follows:

(a) Westinghouse plans to sell the use of similar information to its customers for purposes of implementing Elbow Tap Flow Measurement Methodology.

(b) Westinghouse can sell support and defense of RCS flow measurement using Elbow Tap Flow Methodology.

Public disclosure of this proprietary information is likely to cause substantial harm to the competitive position of Westinghouse because it would enhance the ability of competitors to provide similar technical justification evaluation and licensing defense services for commercial power reactors without commensurate expenses. Also, public disclosure of the information would enable others to use the information to meet NRC requirements for licensing documentation without purchasing the right to use the information.

The development of the technology described in part by the information is the result of applying the results of many years of experience in an intensive Westinghouse effort and the expenditure of a considerable sum of money.

In order for competitors of Westinghouse to duplicate this information, similar technical programs would have to be performed and a significant manpower effort, having the requisite talent and experience, would have to be expended for developing the enclosed Elbow Tap Flow Measurement Methodology.

Further the deponent sayeth not.

Attachment to PGE-02-41 June 7, 2002 Proprietary Information Notice Transmitted herewith are proprietary and/or non-proprietary versions of documents furnished to the NRC in connection with requests for generic and/or plant-specific review and approval.

In order to conform to the requirements of 10 CFR 2.790 of the Commission's regulations concerning the protection of proprietary information so submitted to the NRC, the information which is proprietary in the proprietary versions is contained within brackets, and where the proprietary information has been deleted in the non-proprietary versions, only the brackets remain (the information that was contained within the brackets in the proprietary versions having been deleted). The justification of claiming the information so designated as proprietary is indicated in both versions by means of lower case letters (a) through (f) contained within parentheses located as a subscript immediately following the brackets enclosing each item of information being identified as proprietary or in the margin opposite such information. These lower case letters refer to the types of information Westinghouse customarily holds in confidence identified in Sections (4)(ii)(a) through (4)(ii)(f) of the affidavit accompanying this transmittal pursuant to 10 CFR 2.790(b)(1).

Attachment to PGE-02-41 June 7, 2002 Copyright Notice The reports transmitted herewith each bear a Westinghouse copyright notice. The NRC is permitted to make the number of copies of the information contained in these reports which are necessary for its internal use in connection with generic and plant-specific reviews and approvals as well as the issuance, denial, amendment, transfer, renewal, modification, suspension, revocation or violation of a license, permit, order or regulation subject to the requirements of 10 CFR 2.790 regarding restrictions on public disclosure to the extent such information has been identified as proprietary by Westinghouse, copyright protection notwithstanding. With respect to the non-proprietary versions of these reports, the NRC is permitted to make the number of copies beyond those necessary for its internal use which are necessary in order to have one copy available for public viewing in the appropriate docket files in the public document room in Washington, D. C., and in local public document rooms as may be required by NRC regulations if the number of copies submitted is insufficient for this purpose. Copies made by the NRC must include the copyright notice in all instances and the proprietary notice if the original was identified as proprietary.

DCL-02-097, License Amendment Request 02-05, Revision to Technical Specification Table 3.3.1-1, Reactor Trip System Instrumentation, & Revised Reactor Coolant System Flow Measurement

Contents

Text

Dear Commissioners and Staff:

1.0 DESCRIPTION

2.0 PROPOSED CHANGE

3.0 BACKGROUND

5.0 REGULATORY ANALYSIS

6.0 ENVIRONMENTAL CONSIDERATION

7.1 REFERENCES

1.0 INTRODUCTION

SUMMARY

1.0 INTRODUCTION

SUMMARY

5.1 BACKGROUND

6.1 INTRODUCTION

SUMMARY

SUMMARY

SUMMARY

SUMMARY

SUMMARY

7.1 BACKGROUND

SUBJECT:

Background:

Conclusion:

Subject:

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DCL-02-097, License Amendment Request 02-05, Revision to Technical Specification Table 3.3.1-1, Reactor Trip System Instrumentation, & Revised Reactor Coolant System Flow Measurement

Text

Dear Commissioners and Staff:

1.0 DESCRIPTION

2.0 PROPOSED CHANGE

3.0 BACKGROUND

5.0 REGULATORY ANALYSIS

6.0 ENVIRONMENTAL CONSIDERATION

7.1 REFERENCES

1.0 INTRODUCTION

SUMMARY

1.0 INTRODUCTION

SUMMARY

5.1 BACKGROUND

6.1 INTRODUCTION

SUMMARY

SUMMARY

SUMMARY

SUMMARY

SUMMARY

7.1 BACKGROUND

SUBJECT:

Background:

Conclusion:

Subject:

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