ML17304A337
| ML17304A337 | |
| Person / Time | |
|---|---|
| Site: | Palo Verde  |
| Issue date: | 08/08/1988 |
| From: | Karner D ARIZONA PUBLIC SERVICE CO. (FORMERLY ARIZONA NUCLEAR |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| Shared Package | |
| ML17304A338 | List: |
| References | |
| 161-01211-DBK-B, 161-1211-DBK-B, NUDOCS 8808180271 | |
| Download: ML17304A337 (9) | |
Text
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SUBJECT:
Application for amend to Licenses NPF-41 6 NPF-51 Tech Specs proposed bases changes re CPC auxiliary trip setpoint.
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05000528 05000529 NOTES:Standardized plant.
Standardized plant.
ACCESSION NBR:8808180271 DOC.DATE: 88/08/08 NOTARIZED: NO DOCKET FACIL:STN-50-528 Palo Verde Nuclear Station, Unit 1, Arizona Publi 05000528 STN-50-529 Palo Verde Nuclear Station, Unit 2, Arizona Publi 05000529 AUTH.NAME AUTHOR AFFILIATION KARNER,D.B.
Arizona Nuclear.Power Project (formerly Arizona Public Serv RECIP.NAME RECIPIENT AFFILIATION Document Control Branch (Document Control Desk)
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RECIPIENT ID CODE/NAME PD5 PD DAVIS,M ARM/DAF/LFMB NRR/DEST/CEB 8H NRR/DEST/MTB 9H NRR/DOEA/TSB 11 NUDOCS-ABSTRACT FIL 01 NRC PDR COPIES LTTR ENCL 5
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Arizona Nuclear Power Project P.O. BOX 52034
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PHOENIX, ARIZONA85072-2034 161-01211-DBK/BJA August 8, 1988 Docket Nos.
STN 50-528/529 Document Control Desk U.S. Nuclear Regulatory Commission Mail Station Pl-137 Washington, D.C.
20555
Dear Sirs:
Subject:
Palo Verde Nuclear Generating Station (PVNGS)
Units 1 and 2
Proposed Bases Change CPC Auxiliary Trip Setpoint File:
88-A-056-026 A recent reactor trip at PVNGS Unit 1 has emphasized the need for a change to one of the Core Protection Calculator (CPC) auxiliary trip setpoints.
Specifically, the auxiliary trip setpoint for the integrated ra'dial peaking factor-high must be changed to avoid unnecessary reactor trips during cycle 2
operations at PVNGS.
The CPC auxiliary trip setpoints are not technical specification limits.
The auxiliary trip setpoints are speci'fied in bases section 2.2.1.
As noted in the PVNGS operating licenses and in lgFR50.36(a),
the bases sections are not a part of the Technical Specifications.~Th~urpose of this letter is to request a change to the basque sections for Units 1 and 2.
These two units are currently in cycle 2 operations and therefore, could be subject to unnecessary reactor trips.
ANPP also intends to pursue this same r
change for Unit 3 prior to cycle 2 operations.
The NRC Staff has provided ANPP with directions for requesting a
change to a
bases section.
The NRC Staff stated that the desired bases changes must be accompanied by a
technical justification for the requested change.
Accordingly, the following information is provided in this bases change request package:
Attachment 1 Technical Justification for the Proposed Change.
Attachment 2 Revised Bases Section 2.2.1 for PVNGS Units 1 and 2.
ANPP requests NRC approval of the proposed bases change.
In accordance with the requirements of 10CFR170.12(c),
the application
'fee of
$ 150.00 is being submitted with this request.
8808180271 880808 PDR ADQCK 05000M8 p
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U.S. Nuclear Regulatory Commission Page 2
161-01211-DBK/BJA August 8, 1988 If you have any questions on this matter, please contact Mr. A.
C.
Rogers at (602) 371-4041.
Very truly yours, D. B. Karner Executive Vice President DBK/BJA/pvk Attachments cc:
G.
W. Knighton M. J. Davis J.
B. Mar'tin T. J. Polich A. C. Gehr (all w/a)
J 1
ATTACHMENT 1-TECHNICAL JUSTIFICATION FOR THE PROPOSED CHANGE
'I The Core Protection Calculators (CPCs) assure that the Specified Acceptable Fuel Design Limits (SAFDLs) on Departure from Nucleate Boiling (DNB) and centerline fuel melt limit are not exceeded during an Anticipated Operational Occurrence (AOO).
This is accomplished by the the use of CPC generated low DNBR and high Local Power Density (LPD) reactor trip signals.
The CPCs also include auxiliary trip functions to help meet additional design bases requirements.
One of the auxiliary trip functions is a range trip on several parameters which assures that the core conditions are within the analyzed CPC operating space.
Technical Specification bases section 2.2.1 for the -DNBR-low trip lists the parameter ranges of validity for the CPC DNBR algorithm and states that operation outside these limits will result in a CPC trip.
One of the parameters listed is the high limit for the integrated radial peaking factor (F ).
ANPP is proposing to change this range limit from 4.28 tK 7.00 in order to reduce the possibility of unnecessary plant trips.
The following section contains the justification for this change and provides the revised Technical Specification bases section.
Combustion Engineering (CE) has determined that the CPC F range limit is not credited with providing a reactor trip in an) safety analysis.
The only setpoint analysis that uses this limit is the CPC overall uncertainty analysis such as that described in the reference.
CE has determined that, a change from 4.28 to 7.00 will not impact any of the results of the uncertainty analysis since the F will not exceed 4.28 in any normal or CPC design transient conditions included in this analysis.
- However, because of the conservative design of the CPCs for cycle 2 operation, the on-line calculated CPC F
could exceed 4.28 under two types of conditions which could result in an unnecessary reactor trip.
The two conditions and justification supporting the change are described as follows:
1.
Low Power Operation The CPCs synthesize a core average and pseudo hot pin axial power distribution based primarily on inputs from excore neutron flux detectors and Control Element Assembly (CEA) position information.
In order to preserve the integrity of the power distribution synthesis at low power levels (below approximately 15-174 power),
a conservative pre-calculated axial power distribution is used in place of the power distribution calculated using excore detector signals.
In order to determine the hot pin power distribution, the, pre-calculated, axial power distribution is adjusted by the appropriate Radial Peaking Factors (RPFs) for the present CEA configuration.
For cycle 2 operation the pre-calculated axial power distribution and the RPFs for heavily rodded CEA configurations have significantly increased with respect to
cycle 1 values.
Thus at low power, heavily rodded operation (i.e. reactor startup) the CPC calculated integrated radial peaking factor can exceed 4.28 and result in an. unnecessary reactor trip on CPC F
CE has concluded that, under these conditions, the CPC DkBR is conservative for F values up to 7.00 and thus a reactor trip due to F exceeding 4.28 is not required for this condition.
For events such as shutdown CEA drops (where a significant increase in the value of CPC calculated F
can occur)
CE has concluded that a
CPC DNBR trip is expecteK to occur when
- needed, independent of the F
range limit.
r The range limit for F is implemented in CPC as a reload data block constant.
TherKfore, changing this constant from 4.28 to 7.00 does not require a
CPC software modification.
As a result of the evaluation described
- above, CE and ANPP have concluded that the CPC DNBR calculation remains conservative at a 954/954 probability/confidence level with CPC calculated integrated radial peaking factors as high as 7.00.
This conclusion will be confirmed on a cycle by cycle basis as part of the normal setpoint verification process.
I
Reference:
CEN-356(V)-P, Revision 01-P, "Modified Statistical Combination of Uncertainties", July 1987.
ATTACHMENT 2 REVISED TECHNICAL SPECIFICATION BASES PAGES
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