ML031140371
| ML031140371 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 04/14/2003 |
| From: | Rosalyn Jones Duke Power Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| Download: ML031140371 (14) | |
Text
Duke rEPower.
A Duke Energy Company R. A. JONES Vice President Duke Power 29672 / Oconee Nuclear Site 7800 Rochester Highway Seneca, SC 29672 864 885 3158 864 885 3564 fax April 14, 2003 U. S. Nuclear Regulatory Commission Washington, D. C. 20555 Attention: Document Control Desk
Subject:
Oconee Nuclear Station Docket Numbers 50-269, 270, and 287 Response to NRC Request for Additional Information Associated with License Amendment Request for Reactor Protective System Instrumentation Technical Specification 3.3.1, Surveillance Requirement 3.3.1.3 Technical Specification Change (TSC) Number 2001-06 In March, 2003, the Nuclear Regulatory Commission (NRC) requested additional information regarding the subject License Amendment Request (LAR).
This LAR proposed changes to Technical Specification (TS) 3.3.1 Reactor Protective System (RPS) Instrumentation, Surveillance Requirement (SR) 3.3.1.3, associated with axial power imbalance measurements.
Duke Energy Corporation (Duke) discussed the proposed responses to the questions in a conference call with the NRC on April 2, 2003 and agreed to provide the responses in writing.
The responses to the NRC questions are included in.
An error was found in the bases of the TS.
The error has been addressed in the question responses.
contains the corrected retype of the TS Bases page. contains the corrected markup of the TS Bases page.
Approval of this proposed LAR is requested by June 30, 2003.
Adoo www.duke-energy corn
U. S. Nuclear Regulatory Commission April 14, 2003 Page 2 Pursuant to 10 CFR 50.91, a copy of these proposed responses is being sent to the South Carolina Department of Health and Environmental Control for review, and as deemed necessary and appropriate, subsequent consultation with the NRC staff.
If there are any additional questions, please contact Reene' Gambrell at (864) 885-3364.
Very r ly yours, R. A. Jones, Vice President Oconee Nuclear Site
U. S. Nuclear Regulatory Commission April 14, 2003 Page 3 cc:
Mr. L. N. Olshan, Project Manager Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission Mail Stop 0-14 H25 Washington, D. C.
20555 Mr. L. A. Reyes, Regional Administrator U. S. Nuclear Regulatory Commission -
Region II Atlanta Federal Center 61 Forsyth St., SW, Suite 23T85 Atlanta, Georgia 30303 Mr. M. C. Shannon Senior Resident Inspector Oconee Nuclear Station Mr. Henry Porter, Director Division of Radioactive Waste Management Bureau of Land and Waste Management Department of Health & Environmental Control 2600 Bull Street Columbia, SC 29201
U. S. Nuclear Regulatory Commission April 14, 2003 Page 4 R. A. Jones, being duly sworn, states that he is Vice President, Oconee Nuclear Site, Duke Energy Corporation, that he is authorized on the part of said Company to sign and file with the U. S. Nuclear Regulatory Commission this revision to the Renewed Facility Operating License Nos. DPR-38, DPR-47, DPR-55; and that all the statements and matters set forth herein are true and correct to the best of his knowledge.
R. A. one jwIce President Ocone Nuc ar Site S,3b1 ibed and sworn to before me this / 4 day of 2003 Notary Public N
My Commission Expires:
-^
i/Z.
//
U. S. Nuclear Regulatory Commission April 14, 2003 Page 5 bcc: w/attachments David Baxter Bruce H. Hamilton William W. Foster Tom D. Curtis Robert W. Cornett Carl D. Fago Charlie W. Boyd Greg B. Swindlehurst Lisa F. Vaughn C. Jeff Thomas -
MNS Larry E. Nicholson Lannie V. Wilkie David B. Coyle Regis T. Repko Michael T. Cash -
NAID Gary D. Gilbert -
CNS NSRB, EC05N ELL, ECO50 File -
T.S. Working BWOG Tech Spec Committee (5)
ONS Document Management Reene' V. Gambrell
ATTACHMENT 1 Request For Additional Information
Request for Additional Information RPS Imbalance 1.For SR 3.3.1.3, you propose adding a correlation slope that will be defined in the COLR.
However, for inclusion in the COLR, GL 88-16 requires that cycle-specific parameters be calculated using approved methods and that these methods be listed in the Administrative Controls (COLR) section of your TSs.
Demonstrate that you meet these conditions for inclusion of this parameter in the COLR.
Response
NFS-1001-A, Reload Design Methodology is the analytical method used to determine the allowable values for Nuclear Overpower Flux/Flow/Imbalance and RCS Variable Low Pressure (Section 5.6.5a.6 of Technical Specifications).
The Correlation Slope assumed for the particular cycle is validated using this methodology.
It has been approved previously by the NRC and is listed in section 5.6.5b.2 of Technical Specifications (TS).
2.In Attachment 3 of your submittal, you state that you proposed correlation slope is more conservative than currently required by TSs.
Demonstrate how adding the correlation slope will ensure conservatism and discuss the effects of the correlation slope on the probability of causing spurious reactor trips.
Response
One hypothetical situation will be used to show that a higher correlation slope (CS) is more conservative than that inherently assumed in the current SR 3.3.1.3 (CS = 1.0).
Assume that the nuclear instrumentation channels have been calibrated for a CS of 1.15.
Assume that the imbalance trip setpoint is -23%.
Assume that the incore imbalance indication is -10%.
Adjustment using a CS of 1.15 gives us an excore imbalance indication of -11.5 which is closer to the
trip setpoint of -23% than the adjustment using a CS of 1.0 (-10.0).
Another hypothetical (and more important) situation will be used to show that a higher correlation slope is more conservative than that inherently assumed in the current SR 3.3.1.3 (CS = 1.0).
Assume that the nuclear instrumentation channels have been calibrated for a CS of 1.15.
Assume that the imbalance trip setpoint is -23%.
Assume that the current incore imbalance indication is
-10%.
Assume that the current excore imbalance indication is also -10%.
Assume that the current excore imbalance indication is not adjusted.
Assume that a xenon transient occurs, inducing an imbalance swing.
Incore imbalance represents "true" imbalance.
If required, excore imbalance is calibrated to incore imbalance.
Excore imbalance represents "indicated" imbalance.
Excore imbalance feeds into the RPS flux / flow /
imbalance trip function.
"True" imbalance represents a "trippable" condition.
For conservatism, the RPS should actuate a reactor trip on "indicated" imbalance at the same time or before the "true" imbalance reaches -23%.
During the xenon transient, the incore imbalance swings from -10 to -22.
Because of the 1.15 CS, the excore detectors are more responsive than incore detectors.
The excore imbalance swing can be quantified as follows:
Excore Imbalance =
[CS x Incore imbalance swing]
+
initial excore imbalance Excore Imbalance =
[1.15 x ( (-10))] + (-10.0)
Excore Imbalance =
-23.8 Incore Imbalance =
-22.0
The RPS will actuate a trip before "true" imbalance indicates a "trippable" condition.
This is a spurious trip.
Using the CS of 1.0 and the same logic as above, the excore imbalance will be -22.
The RPS will not actuate a trip.
Note that the current CS is 1.15; however, ONS does not experience spurious trips.
There is margin between the operating imbalance and the imbalance alarm and trip setpoints.
In addition, during a xenon transient-induced imbalance swing, procedural controls maintain imbalance within "administrative limits" which are more restrictive than alarm setpoints.
The above examples represent hypothetical situations.
Each example shows that using a CS of 1.15 instead of 1.0 maintains more conservatism relative to safety analyses which assumes a CS of 0.95.
- 3. Your bases section states that the Allowable Value envelope will assume a difference in excore to incore measurements of 2.5%.
However, your proposal will allow for the difference between the two measurements to be increased by the correlation slope value.
Given your example, the excore measurement could be 15%
greater than the incore.
Please provide clarification to your bases statements.
Furthermore, please describe how the Allowable Values ensure that you do not violate the assumptions in your safety analysis.
Response
Note that the Allowable Value envelope actually assumes a maximum difference of 2.0% not 2.5%.
The value listed in the SR 3.3.1.3 bases is incorrect. A correction to the bases is included in Attachments.
It appears that the question is stating that the excore value, after the CS adjustment, will be 15%
greater than the incore value and that this exceeds 2%
assumed in the Allowable Value envelope.
If so, that is not the intent of the proposal.
See the following example:
With the proposal and assuming a CS of 1.15, the incore measurement is increased by 15%.
A difference versus the excore measurement is taken, and is scaled versus actual power.
This is the imbalance error.
If the absolute value of the imbalance error is greater than 2%, then a calibration is required.
Incore Imbalance = -10.0%
Excore Imbalance = -8.0%
= 1.15 RTP/TP
= 1.0 (i.e., at 100% FP)
Adjusted Incore Imbalance = -11.50%
Imbalance Error
= 3.50%
Per the proposed SR 3.3.1.3, a calibration is required.
- 4. If known, please provide any precedents to your request to add a correlation slope to SR 3.3.1.3.
Response
There is no direct precedent for adding correlation slope to the SR equation.
Other Utilities have a similar formula but do not use a correlation slope other than 1.0 (by default, the CS is 1.0 if no other multiplication factor is identified.)
However, Duke performs its own safety analysis and a CS of other than 1.0 is consistent with the safety analysis.
It is presumed that other utilities that use a CS of 1.0 are using it consistent with their safety analysis methodology, again, which is not the same methodology Duke uses.
ATTACHMENT 2 TECHNICAL SPECIFICATION Remove Page B 3.3.1-23 Insert Page B 3.3.1-23
RPS Instrumentation B 3.3.1 BASES SURVEILLANCE SR 3.3.1.2 (continued)
REQUIREMENTS assumed in the safety analyses of UFSAR, Chapter 15 (Ref. 2). These checks and, if necessary, the adjustment of the power range channels ensure that channel accuracy is maintained within the analyzed error margins. The 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> Frequency is adequate, based on unit operating experience, which demonstrates the change in the difference between the power range indication and the calorimetric results rarely exceeds a small fraction of 2% in any 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> period. Furthermore, the control room operators monitor redundant indications and alarms to detect deviations in channel outputs.
SR 3.3.1.3 A comparison of power range nuclear instrumentation channels against incore detectors shall be performed at a 31 day Frequency when reactor power is 2 15% RTP. A Note clarifies that 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> is allowed for performing the first Surveillance after reaching 15% RTP. If the absolute value of imbalance error is 2 2% RTP, the power range channel is not inoperable, but an adjustment of the measured imbalance to agree with the incore measurements is necessary. The Imbalance error calculation is adjusted for conservatism by applying a correlation slope (CS) value to the error calculation formula. This ensures that the value of the APIO is > API,.
The CS value is listed in the COLR and is cycle dependent. If the power range channel cannot be properly recalibrated, the channel is declared inoperable. The calculation of the Allowable Value envelope assumes a difference in out of core to incore measurements of 2.0%. Additional inaccuracies beyond those that are measured are also included in the setpoint envelope calculation. The 31 day Frequency is adequate, considering that long term drift of the excore linear amplifiers is small and burnup of the detectors is slow. Also, the excore readings are a strong function of the power produced in the peripheral fuel bundles, and do not represent an integrated reading across the core. The slow changes in neutron flux during the fuel cycle can also be detected at this interval.
SR 3.3.1.4 A CHANNEL FUNCTIONAL TEST is performed on each required RPS channel to ensure that the entire channel will perform the intended function.
Setpoints must be found within the Allowable Values specified in Table 3.3.1-1. Any setpoint adjustment shall be consistent with the assumptions of the current setpoint analysis.
OCONEE UNITS 1, 2, & 3 B 3.3.1-23 Amendment Nos.
ATTACHMENT 3 MARKUP OF TECHNICAL SPECIFICATION
RPS Instrumentation B 3.3.1 BASES SURVEILLANCE SR 3.3.1.2 (continued)
REQUIREMENTS assumed in the safety analyses of UFSAR, Chapter 15 (Ref. 2). These checks and, if necessary, the adjustment of the power range channels ensure that channel accuracy is maintained within the analyzed error margins. The 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> Frequency is adequate, based on unit operating experience, which demonstrates the change in the difference between the power range indication and the calorimetric results rarely exceeds a small fraction of 2% in any 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> period. Furthermore, the control room operators monitor redundant indications and alarms to detect deviations in channel outputs.
SR 3,3.1.3 A comparison of pow ge nuclear instrumenta tionn els a
incshalc l be performed at a 31 day Frequency when reactor power is > 15% RTP. A Note clarifies that 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> is allowed for performing the first Surveillance after reaching 15% RTP. If the absolute befzo o
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> 2%
RTP, the power range channel perable, bla n adjustment of th eauwre b
with the incore measurementsary.
If the power range channel cannot be properly recalibrated, the channel is declared inoperable. The calculation of the Allowable Valupiv assumes a difference in out of core to incore measureme of 2.%7)
Additional inaccuracies beyond those that are measured a in the setpoint envelope calculation. The 31 day Frequency is adequate, onsidering that long term drift of the excore linear amplifiers is small and a
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$umup of the detectors is slow. Also, the excore readings are a strong r7eA9e rd,
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-"0w nction of the power produced in the peripheral fuel bundles, and do not
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wavrepresent an integrated reading across the core. The slow changes in XJ,-
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°
Ž eutron flux during the fuel cycle can also be detected at this interval.
R 3.3.1.4
-A CHANNEL FUNCTIONAL TEST is performed on each required RPS t.s eVte
° channel to ensure that the entire channel will perform the intended function.
Setpoints must be found within the Allowable Values specified in Table 3.3.1-1. Any setpoint adjustment shall be consistent with the assumptions of the current setpoint analysis.
The as found and as left values must also be recorded and reviewed for consistency with the assumptions of the surveillance interval extension analysis. The requirements for this review are outlined in BAW-1 0167 (Ref.
7).
OCONEE UNITS 1, 2, & 3 B 3.3.1-23 Amendment Nos.-300O30.- &-se-