ML20153H401
| ML20153H401 | |
| Person / Time | |
|---|---|
| Site: | Palo Verde  |
| Issue date: | 05/31/1988 |
| From: | ABB COMBUSTION ENGINEERING NUCLEAR FUEL (FORMERLY |
| To: | |
| Shared Package | |
| ML17304A449 | List: |
| References | |
| CEN-356(V)-NP-A, CEN-356(V)-NP-A-R01, CEN-356(V)-NP-A-R1, NUDOCS 8809090167 | |
| Download: ML20153H401 (51) | |
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WUNCERTAINTIES
.t q1 MAY 1988
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LEGAL NOTICE THIS REPORT WAS PREPARED AS AN ACCOUNT OF WORK SPONSORED BY COMBUSTION ENGINEERING, INC. NEITHER COMBUSTION ENGINEERING NOR ANY PERSON ACTING ON ITS BEHALF:
A.
MAKES ANY WARRANTY OR REPRESENTATION, EXPRESS GR IMPLIED INCLUDING THE WARRANTIES OF FITNESS FOR A PARTICULAR PURPOSE OR MERCHANTABILITY, WITH RESPECT TO THE ACCURACY, COMPLETENESS, OR USEFULNESS OF THE INFORMATION CONTAINED IN THIS REPORT, OR THAT THE USE OF ANY INFORMATION, APPARATUS, METHOD, OR PROCESS DISCLOSED IN THIS REPORT MAY NOT INFRINGE PRIVATELY OWNED RIGHTS; OR B.
ASS'Fr3 ANY LIABILITIES WITH RESPECT TO THE USE OF, OR FOR DAMAGES REr (ING FROM THE USE OF, ANY INFORMATION, APPARATUS, METHOD OR Ph0 CESS DISCLOSED IN THIS REPORT.
4 i
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CEN-356(V)-NP-A Revision 01-NP-A MOO!FIED STATISTICAL COMBINATION OF UNCERTAINTIES May 1988 NUCLEAR POWER SYSTEMS COMBUSTION ENGINEERING, INC.
WINDSOR, CT.
s
'o, UNITED STATES w
j NUCLEAR REGULATORY COMMISSION w.ssectoN. o. c. rosss Q
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October 21, 1987 Docket No.: STN 50-528 Mr. E. E. Van Brunt, Jr.
Executive Vice President Arizona Nuclear Power Project Post Office Box 52034 Phoenix, Arf:ena 85072-2034
Dear Mr. Van Brunt:
SUBJECT:
ISSUANCE OF AMENDMENT NO 2410 FACILITY OPERATING LICENSE i
NO. NPF-41 FOR THE PALO VERDE NUCLEAR GENERATIN3 STATION, UNIT NO. 1 (TAC NOS. 65460, 65461, 65462 AND 65691 THROUGH 65706) l The Comission has issued the subject Amendment, which is enclosed, to the l
Facility Operating License for Palo Verde Nuclear Generating Station Unit 1.
The Amendment consists of changes to the Technical Specifications (Appendix A l
to the license) in response to your application transmitted by letter dated l
June 29, 1987, as supplemented by letters dated June 29, July 13, August 20 (two letters), September 4 and October 1, 1987.
The Amendment revises several. portions of the Technical Specifications te l
incorporate changes in support of Cycle 2 operation for Palo Verde. Unit 1.
One of the proposed changes to the Technical Specifications in your amendment involving the removal of the numerical values for the axial shape request indexlImits,hasnotbeengranted. This request, which is not required for i
restart of Palo Verde Unit 1, is Jimilar to requests from other licensees and l
is currently being reviewed on a generic basis by the staff. After the results of the staff's generic review become available, you may resubmit your' request consistent with the resultant staff findings.
Page 3/4 3-41 of the Technical Specifications was revised in Amendrent No. 21, which was issued September along with its overleaf page4,(3/4 3-42),This page is being reissued at this time, 1987.
in order to correctly represent the approval granted in Amendment No. 21.
l
2 A copy of the related Safety Evaluation is also enclosed. A Notice of Issuance will be included in the Commission's next regular bi. weekly Federal Recister notice.
Sincerely.
dk E. A. Licitra, Senior Project Finager Project Directorate V DiviJicn of Reactor Projects - 111 IV, Y and Special Projects
Enclosures:
1.
Anenement No. 24 to NPF-41 2.
Safety Evaluation 3.
Pages 3/4 3-41 and 3-42 cc: See next page l
l O
/
[o UNITED STATES g
8 NUCLEAR REGULATORY COMMISSION e
l W ASHING TON, D. C. 20S$5
%,..... /
SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 24 TO FAClllTY OPERATING LICENSE NO. NPF-41 ARIZONA PUBLIC SERVICE COMPANY, ET AL.
PALO VERDE NUCLEAR GENERATING STATION, UNIT NO. 1 DOCKET NO. STN 50-528
1.0 INTRODUCTION
By letter dated June 29, 1987 (Ref. 1), as supplementer' by letters dated August 20, 1987 (Ref. 4) and October 1, 1987, the Arizona Public Service Company (APS) on behalf of itself, the Salt River Project Agricultural Improvement and Power District, Southern California Edison Company, El Paso Electric Company, Public Service Company of New Mexico. Los Angeles Department of Water and Power, and Southern California Public Power Authority (licensees), requested several changes to the Technical Specifications (Appendix A to Facility Operatin Palo Verde Nuclear Generating Station, Unit 1 (g License NPF-41) for thePVN operation for PVNGS1.
In support of both the Technical Specification changes and Cycle 2 operation, the licensees submitted (1) a Reload Analysis Report by letter dated June 29,1987(Rel.2),assupplementedby i
letters dated July 13 and August 20, 1987 (Ref. 5 and 6) and September 4, 1
1987, and (2) a report concerning a modified version for a Statistical Combination of Uncertainties (SCU), dated July 1987 (Ref. 3). The staff's evaluation of the SCU report and the reload analysis is presented in i
Sections 2.0 through 6.0 below. The evaluation of the specific changes to the Technical Specifications is presented in Section 7.0 below, i
l THE MODIFIED STATISTICAL COMBINATION OF UNCERTAINTIES REPORT WAS REVIEWED AS PART Of A LARGER PVNGS UNIT 1, l
CYCLE 2 RELOAD SAFETY EVALUATION'.
SECTIONS 2.0, 3.0, 6.0, 7.0, 9.0, 10.0 AND 11.0 ARE RELATED TO THE GENERAL RELOAD SAFETY EV/.LUATION AND NOT THE MODIFIED STATISTICAL COMBINATION OF UNCERTAINTIES.
THESE SECTIONS ARE THUS NOT INCLUDED HERE.
I
' 4.0 EVALUATION OF THERMAL-HYORAULIC DESIGN Steady-state themal-hydraulic analysis for Cycle 2 is perfomed by using the approved thermal-hydraulic code TORC (Pef. 9) and the CE-1 critical heat flux (CHF). correlation (Ref. 10). The design thermal margin analysis is performed with the fast running variation of the TORC code, 2
CETOP-D (Ref. 11). The CETOP-D model has been verified to predict the minimum departure from nucleate boiling ratio (DNBR) conservatively relative to TORC.
The uncertainties associated with the system parameters are combined statistically using the modifie'd statistical combination of uncertainties (SCU) methodology described in Reference 3, which is evaluated and approved below in Section 5.0 of this evaluation. Using this methodolcgy, the engineering hot channel factors for heat flux, heat input, fuel rod pitch, and cladding diameter are combined statistically with other uncertainty factors to arrive at overall uncertainty penalty factors to be applied to i
the DNBR calculations perfonred by the core protection calculators (CPCs) and the core operating limit supervisory system (COLSS). When used with j
the Cycle 2 DNBR limit of 1.24, these ov9ra11 uncertainty penalty factors provide assurance with a 955 confidence and a 95% probability (95/95 confidence / probability) that the hottest fuel red will not experience DNS.
The fuel rod bow penalty is incorporated directly in the CNER limit.
It has been calculated using the approved method described in Reference 13.
t The value used for this analysis, 1.755 DNBR, is valid for fuel assembly burnues up to 30,000 MWD /MTU.
For those assemblies with average burnup in excess of 30,000 MWD /MTU, sufficient margin exists to offset rod bow penalties.
i 5.0 EVALUATION OF MODIFIED STATISTICAL COMBINATION OF UNCERTAINTIES (SCul The licensees requested NRC review and approval of the topical report, l
"Modified Statistical Combination of Uncertainties," CEN-356(V)-P, Revision 01-P, July 1987 (Ref. 3). This report describes changes to the methodology for statistically combining uncertainties to obtain overall uncertainty factors. The ovnrall uncertainty factors are used to deter-mine the limiting safety system setting (LSSS) and limiting condition for operation (LCO) for the PVNGS COLSS and CPC system.
The existing SCU method treats uncertainties in two groups. The uncer-tainties in one group (system parameter uncertainties) include engineering factors, critical heat flux (CHF) correlation uncertainties ar.d code riodeling uncertainties which are statistically combined to generate a DNBR probability density function. The 95/95 probability / confidence level limit of this function is then used as the setpoint analysis minimum DNBR.
The uncertainties in the other group (state parameter uncertainties) include measured state parameter, COLSS and CPC algorithm, radial peaking factor measurement, simulator model, computer processing and startup measurement uncertainties. These uncertainties are also statistically combined to determine the CPC and COLSS overall uncertainty factors.
Although..the uncertainties within each group are combined statisti: ally and a 95/95 probabflity/ confidence level generated for each group, the resultant uncertainties of the two groups are effectively combined in a deterministic manner due to the separate application of the two uncer-tainty limits. The proposed modified SCU methodology would statistically combine uncertainty components which were previously applied deter-ministically.
In addition, the statistical treatment of several uncertainty components would be modified so that the overall uncertainty factors can be calculated and applied as a function of burnup, axial shape index (ASI), and power in COLSS and CPC.
The staff has reviewed the uncertainties and the uncertainty treateent procedure described for the proposed modified 5C0 methodology and has determined that the resultant penalties applicd to the COLSS power operat-ing limit and the CPCC DNBR and local power density (LPD) calculations adequately incorporate all uncertainties at the 95/95 probability /
confidence level.
The analytical methods reviewed show that a DNBR limit of 1.24 with the uncertainty penalties derived in the report provides a 95/95 probability / confidence level assurance against DNB occurring during steady state operation or anticipated operational occurrences at the Palo Verde Nuclear Generating Station. The proposed methodology is, therefore, acceptable for use with the Palo Verde Nuclear Generating Station digital monitoring and protection systems.
O S
8.0 EVALUATION FINDINGS The staff has reviewed the fue's, physics, and therinal-hydraulics infonna-tion presented in the PVNGS1 Cycle 2 reload report.
The staff has also reviewed the proposed Technical Specification revisionsi the SCU rodifi-cation, and the safety reanalyses.
Based on the evaluaiMons given in the preceding sections, the staff finds the proposed reload ard the Technical Specification changes to be acceptable.
O
. REFERENCES 1.
Reload Technical Specification Amendment, submitted by letter from J. G. Haynes (ANPP) dated June 29, 1987, 2.
Reload Analysis Report for Palo Verde Nuclear Generating Station Unit 1 Cycle 2, submitted by letter from J. G. Haynes (ANPP) dated June 20, 1987.
3.
"Modified Statistical Combination of Uncertainties," CEN-255(V)-P, Aevision 01-P, Combustion Engineering, July 1087.
4.
Revision to Reload Technical Specification Amendment - Attachment 2, Shutdown Margin, submitted by letter from J. G. Haynes (ANPP) dated August 20, 1987.
5.
LetterfromJ.G.Haynes(ANPP)datedJuly 13, 1987.
6.
Response to NRC Questions Regarding the Unic ! Cycle 2 Reload Submit-tal, submitted by letter f m m J. G. Haynes (ANPP) dated August 20, 1987.
- 7. * "CEPAN Method of Analyzing Creep Collapse of Oval Cladding Volure 5:
Evaluation of Interpellet Gap Forination and Clad Collapse in Modern PWR Fuel Rods," EPRI NP-3966-CCM, April 1985.
8.
"The ROCS and DIT Corputer Codes for Nuclear Design " CENPD-266-P-A, Combustion Engineering April 1983.
9.
"TORC Code, A Computer Code for Determining the Thermal Margin of a Reactor Core," CENPD-161-P, Combustion Engineering, July 1975.
10.
"Critical Heat Flux Correlation for C-E Fuel Assemblies with Standard Sr 'es Grids, Part 1. Uniform Axial Power Distribution," CENPD-162-P-A, C
istion Engineering, April 1975.
11.
'CETOP-D Code Structure and Modeling Methods for San Onofre Nuclear Generating Station Units 2 and 3," CEN-160(S)-P, Revision 1-P, Cerebustion Engineering, September 1981.
12.
"Safety Evaluation of CEN-161 (FATES 3)," sutoitted by letter from R. A. Clark (NRC), to A. E. Lundvall, Jr. (BG8E), March 31, 1983.
13.
"Fuel and Poison Rod Sewing," CENPD-225-P-A, Combustion Engineering, June 1983.
14
'hERMITE Space-Tire Kinetics," CENPD-188-A, combustion Engineering, July 1976.
ABSTRACT This report describes changes to the methodology for statistically combining uncertainties used to determine the LSSS and LCO overall uncertainty factors for C-E's digital monitoring and protection systems.
The resultant overall uncertainty factort using the Modified Statistical Combination of Uncertainties (SCU) Program are determined and applied such that the Core Operating Limit Supervisory System (COLSS) Power Operating Limit (POL) and the Core Protection Calculator System (CPCS) DNBR and Local Power Density (LPD) calculations are conservative to at least a 95/95 probability / confidence level.
The changes do not impact either the manner in which COLSS aids the operator in maintaining operating margin to limits on linear heat rate (LHR) and DNB or the manner in which the CPCS responds to transients and provides the low DNBR and LPD trips.
Therefore the changes do not impact transient analysis assumptions or results and do not involve changes to Technical Specifications.
l
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TABLE OF CONTENTS CHAPTER PAGE
1.0 INTRODUCTION
1 1.1 Purpose 1
1.2 Background
1 1.2.1 Protection and Monitoring Systems 1
1.2.2 Current SCU Program 2
1.3 Modified SCU Program 4
1.4 Summary of Results 5
2.0 METHODS 11 2.1 Introduction 11 1
2.2 System Parameter SCU Methodology 11 2.3 Secondary Calorimetric Power Measurement 13 Uncertainty Methodology 2.4 CPC Neutron Flux Power Synthesis Uncertainty 14 j,
Methodology 2.5 Other Modifications to SCU Methodology 15 2.5.1 Radial Peaking Factor Measurement 15 Uncertainty Application 2.5.2 Application of Uncertainty Factors as 16 a function of Burnup, AS! and Power.
I
TABLE OF CONTENTS (Cont'd) 9 CHAPTFR PAGE 3.0 TYPICAL OVERALL UNCERTAINTY FACTOR CALCULATION 18
~
3.1 Introduction 18 3.2 DNBR pdf 18 3.3 Secondary Calorimetric Power Measurement Uncertainty pdf 19 3.4 COLSS DNBR Overall Uncertainty Factor 19 Calculation 3.5 CPC DNBR Overall Uncertainty Factor Calculation 20
4.0 CONCLUSION
33 i
5.0 REFERENCES
34 i
i i
1-I*
l l
(iii) l l
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LIST OF TABLES TABLE PAGE 1-1 Uncertainties Included in the System 6
Parameter SCU 1-2 General Categorias of Uncertainties Included 7
in the State Parameter SCU 3-1 Components Combined in the DNBR pdf 22 3-2 Secondary Calorimetric Power Measurement 23 Uncertainty Components 3-3 COLSS State Parameter Ranges and Measurement 24 Uncertainties 3-4 UncertaintyComponent[
]inCOLSS 25 DNBR Uncertainty Analysis l
3-5 UncertaintyComponents[
]
26 to Determine COLSS DNBR Overall Uncertainty
{
Factors 3-6 CPCS State Parameter Ranges and Uncertainties 27 UncertaintyComponent{
]inCPCDNBR 28 3-7 Overall Uncertainty Analysis l
l 3-8 Uncertainty Components
-}to 29 04termine CPC ONBR Overall Uncertainty Factors (iv) 4
LIST OF FIGURES FIGURE "4GE 1-1 COLSS and CPCS Uncertainty Analysis for 8
Current SCO 1-2 Current SCU Program Schsmatic 9
1-3 Modified SCU Program Schematic 10 2-1 Secondary Calorimetric Power Measurement 17 Uncertainty 3-1 DNBR Probability Density Function 30 3-2 COLSS DNBR Overall Uncertainty Analysis with 31 Modified SCU 3-3 CPC ONBR Overall Uncertainty Analysis with 32 Modified SCU G
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e DEFINITION OF ABBREVIATIONS ASI Axial Shape Index BERR1-4 CPC Overall Uncertainty Factors BPPCC Soundary Point Power Correlation Coefficient C-E Combustion Engineering, Inc.
CEA Control Element Assembly CETOP-0 CE Thermal-Hydraulic Design Code CHF Critical Heat Flux CIP CPC Improvement Program CPC Core Protection Calculator CPCS Core Protection Calculator System COLSS Core Operating Limit Supervisory System DNB Departure from Nucleate Boiling DNBOPM ONB Overpower Margin DNBR ONB Ratio EPOL COLSS ONBR Overall Uncertainty Factor FLAIR CE Neutronics Simulator Fq 3-Dimensional Peaking Factor Fxy Planar Radial Peaking Factor HID-1 High Impact Design Spacer Grid (Type 1)
LCO Limiting Condition for Operation LHR Linear Heat Rate LPD Local Power Density LSSS Limiting Safety System Settings NRC Nuclear Regulatory Comission pdf Probability Density Function POL Power Operating Limit PVNGS Palo Verde Nuclear Generating Station RCS Reactor Coolant System RPS Reactor Protection System RSF Rod Shadowing Factor SAM Shape Annealing Matrix SCU Statistical Combination of Uncertainties UNCERT COLSS LHR Uncertainty Factor (vi)
1.0 INTRODUCTION
1.1 Purpose The purpose of this report is to describe changes to the methodology for statistically combining uncertainties associated I
with the LCO and LSSS setpoints for CE's digital monitoring and protection systems.
These changes are designed to improve plant operating performance and flexibility and reduce the incidence of unnecessary reactor trips by
- ducing the overall uncertainty factors applied in the COLSS and CPCS. Rigorous, statistically justified methods are used to establish the resultant uncertainty factors.
The Core Operating Limit Supervisory System (COLSS) aids the operator in monitoring the Liriiting Conditions for Operation (LCO) based on DNER margin, Linear Heat Rate (LHR) margin, Axial Shape Index (ASI) and core power. The Core Protection Calculator System (CPCS) within the Reactor Protection l
System (RPS) initiates the reactor trips based on low DNBR and high Local Power Density (LPD). Overall uncertainty factors are determined and applied for both the COLSS and CPCS such that the COLSS Power Operating Limits (POL) and the CPCS DNBR and LPD l
calculations are conservative to at least a
95/95 probability / confidence level.
The Modified Statistical Combination of Uncertainties Program resulting from the methodology changes described in this report has been developed 1
in such a way that this level of conservatism is maintained, t
I
1.2 Background
l 1.2.1 Protection and Monitoring Systems The functions and interactions of the protection and monitoring systems, LCO's and LSSS's, and COLSS and CPCS are I
described in previous PVNGS SCU reports such as References 1 and 2 and in current COLSS and CPCS Reports such as I
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F' References 3, 4,
and 5.
The changes to the Statistical Combination of Uncertainties (SCU) methodology descrited in this report do not impact the functions of these systems.
1.2.2 Current SCO Progran, hfarencey 6, 7, and 8 are the latest references for the curer <tly approved 500 methodology.
The methods documented in o"A SONGS refernees are similar to those used for Sh um s, (l.e. #WG1 Cycle 1) as documented in References 1,
2 aiid 11:
As part of the CPC Improvement Program, several modifications ae s made to simplify the SCU analysis process. These modifications are documented in Reference 9.
NRC approval of the CIP related modifications was provided in Reference 10.
The changes to the SCU methodology for the Modified SCU program are presented in this report based on i
the current SCO prograi.1 described in these references, i
i The uncertainties involved in the SCU methodology are divided into two categories.
The first category, referred to as "system parameter" uncertainties, includes engineering factors, CHF correlation uncertainties and TORC i
code modeling uncertainties.
The uncertainties in this 9
l group are statittically combined to generate a ONBR probability density function (pdf).
The 95/95 probability / confidence level tolerance limit of this t
a function has been used as the ONBR limit in COLSS and CPCS l
thus accounting for the uncertainties in this category.
e i
l The second category, referred to as "state parameter" uncertainties, includes measured state parameter, COLS$ and CPC algorithm, radial peaking factor measurement, simulator
- model, computer processing and startup measurement j
uncertainties.
The state parameter, algorithm and startup l
3 7
(2) i l
a J
r-measurement uncertainties are stochastically simulated to generate a
state parameter pdf.
The 95/95 probability / confidence level of this function is then root-sum-squared with the other uncertainties to determine the CPC and COLSS overall uncertainty factors, hence accounting for the uncertainties in this group.
The uncertainty analysis which determines these overall uncertainty factors in the heretofore approved SCU program l
is illustrated in Figure 1-1.
Even though uncertainties within each part are combined statistically and a 95/95 probability / confidence level is generated for each group, the resultant uncertainties of the two groups are effectively combined in a deterministic manner due to separate application in the ONBR limit and the overall uncertainty factors.
Tables 1-1 and 1-2 list the uncertainties included in the system parameter and the state parameter categories, respectively. These uncertainties are defined and described further in References 6, 7, and 8.
In the current SCU methodology, power measurement uncertainties are applied separately from the system and state parameter uncertainty factors.
COLSS normally uses secondary calorimetric power as the standard and therefore the power measurement uncertainty for COLSS consists of the secondary calorimetric uncertainty.
The CPC neutron flux power measurement uncertainty factor is calculated by a i
deterministic combination of the secondary calorimetric uncertainty, a calibration allowance, and the neutron flux
~
power synthesis uncertainty.
The CPC thermal power measurement uncertainty factor is calculated by a
deterministic combination of the secondary calorimetric uncertainty, a calibration allowance, and a thermal power transient offset, if needed.
Figure 1-2 is a schematic of what will henceforth be referred to as the "current SCU" program.
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c l
1.3 Modified SCU Program This document describes the changes to the current SCU program designed to improve plant operating performance and flexibility and reduce the incidence of unnecessary reactor trips by reducing excess conservatism in the DNBR overall uncertainty factors for COLSS and CPCS.
The reduction in overall uncertainty factors results primarily from statistical combination of several uncertainty components previously applied deterministically.
In addition, minor changes have been made in the statistical treatment of several components ar.d the methodology has been developed so that the overall uncertainty factors can be calculated and applied in discrete regions of core burnup, power, and axial shape index (ASI).
The changes made to the SCU program are the following:
1.
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2.
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4.
I
~
5.
Develop the methodology for determining and implementing Burnup, ASI, and Power dependent uncertainty factors in COLS$ and CPCS.
(4) 0
These changes are described in more detail in Section 2.0.
The SCU program with all these modifications will henceforth be referred to as the "Modified SCU" program. Figure 1-3 provides a schematic of the Modified SCU program.
I I
1.4 Summary of Results The methodology of the Modified SCU program will generate overell unce?tainty facters such that the COLSS Power Operating Limit I
(POL) and CPCS ONBR and LPD calculations are conservative to at least a 95/95 probability / confidence level.
The changes to the SCU methodology described in this report do not impact either the manner in which COLSS aids the operator in maintaining operating margin to limits on linear heat rate (LHR) and DNB or the manner in which the CPCS responds to transients and provides the low DNBR and high LPD trips.
Therefore, the changes do not impact l
transient analysis assumptions or results and do not involve changes to Technical Specifications.
In Section 3.0, the Modified SCU program methodology has been applied to PVNGS using typical models and input data and results l
in DNBR overall uncertainty factors of lfor COLSS and s
for CPCS.
1 l
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Table 1-1 Uncertainties included in the System parameter SCU Core inlet flow distribution III j.
Engineering factor on enthalpy rise Systematic fuel rod pitch Systematic fuel clad 0.0.
Engineering factor on heat flux CE-1 CHF correlation (Ir.cluding crose validation uncertainty)
TORC code uncertainty Fuel rod bow penalty (2)
I2)
HID-1 grid penalty i
~
~
(1) Core inlet flow distribution uncertainty for System 80 plants (2) e h
(6)
i Table 1-2 General Categories of Uncertainties included in State parameter SCO Measured State Parameter Uncertainties t
Algorithm Uncertainties Startup Measurement Uncertainties Radial Peaking Factor Measurement Uncertainty Computer Processing Uncertainties Simulator Model Uncertainties Rod Bow Penalty on Fxy I
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FIGURE 1 1 COLSS AND CPCS UNCERTAINTY ANALYSIS FOR CURRENT SCU e
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2.0 METH005
2.1 INTRODUCTION
The current SCO program is described in References 6, 7, an( 8 with CPC Improvement Program modifications described in Referer;ce 9.
The following sections describe the changes made to the SCU methodology in the Modified SCO program.
Section 3.0 wil) provide a typical DNBR overall uncertainty factor calculation using the Modified SCU program.
The changes to the SCU methodology primarily impact the treatment of system parameters, secondary calorimetric power measurement, and neutron flux power synthesis uncertainties as described in Sections 2.2, 2.3, and 2.4, respectively.
Section 2.5 presents other minor methodology changes.
l 2.2 SYSTEM PARAMETER SCU METHODOLOGY i
I The uncertainties considered in the system parameter SCU include engineering factors, CHF correlation uncertainties and TORC code modeling uncertainties.
In the current system parameter SCO analysis, described in Reference 6,
these uncertainties are combined statistically to arrive at the ONBR limit. The Modified SCO methodology
~
l Thus the ONBR overall uncertaintyfactorsforCOLSSandCPC(
l t
[
4 l
(11)
The individual uncertainties that are combined in the system parameter SCU are as follows:
a)
Core inlet flow distribution II) b)
Engineering factor on enthalpy rise c)
Systematic fuel rod pitch d)
Systematic fuel rod diameter e)
Engineering factor on heat flux f)
CE-1 CHF correlation g)
CE-1 CHF correlation cross validation penalty (5%
increase in CHF correlation standard deviation; h)
T-H code uncertainty penalty (5%, equal to two standard deviations)
These uncertainties are statistically combined to yield the DNBR i
probability density function (pdf).
In the current SCU analysis the 95/95 probability / confidence limit of this DNBR pdf is determinittically combined with the i
fuel rod bow and the H!D-1 grid penalties to determine the minimum DNBR limit to be applied in COLSS and CPC.
This DNBR limit is then used in the state parameter SCU stochastic l
simulation to determine the COLSS and CPCS DNBR overall uncertainty factors.
This limit is also used in the on-line COLSS DNBR power operating limit calculation and as the CPCS DNBR trip setpoint.
In the Modified SCU methodology, the system paraineter uncertainties are combined in the same way to determine the DNBR pdf.
However.
l.
III Coreinletflowdistributionuncertainty[
for System 80 plants.
(12)
This modification to the SCU program is consistent with statistical methods approved in the current SCU program.
J are chosen such that the COLSS DNBR POL and CPCS DNBR calculations are conservative at a 95/95 probability / confidence level.
2.3 SECONDARY CALOR! METRIC p0WER MEASUREMENT UNCERTAINTY METHODOLOGY Both COLSS and CPC use Secondary Calorimetric power as a measure of true core power for their LHR/LPD and DNBR calculations.
The calculation of Secondary Calorimetric power has an uncertainty associated with it.
Currently, this uncertainty is calculated statistically as described in Reference 7
and applied deterministically in both COLSS and CPC.
The Modified SCU methodology will apply this uncertainty [
The Secondary Calorimetric power measurement uncertainty (ECAL) is core power dependent.
Figure 2-1 shows a typical example of the uncertainty as a function of power.
In the current SCU program, this uncertainty is applied as (
~
directly on the core power used in the COLSS and on the thermal and acutron flux power used in CPC.
This uncertainty is implemented
]inbothCOLSSandCPC.
(13)
r In the Modified SCL methodology, the Secono *y Calorimetric power measurement uncertainty will be represented by[
The DNBR overall uncertainty analysis
~
will statistically [
I
] The method of application of this uncertainty will remain deterministic, unchanged from the current methodology,(
]
l The Modified SCU approach is consistent with statistical a thods approved in the current SCU program.
Application of this uncertainty [
]willcontinue to assure conservative DNBR POL calculations by COLSS and DNBR j
calculations by CPCS to at least a 95/95 probability / confidence level.
2.4 CPC NEUTRON FLUX POWER SYNTHESIS UNCERTA!NTY METHODOLOGY i
The CPC Neutron Flux Power calculation based on ex-core detector signals includes a neutron flux power measurement uncertainty.
One component of this uncertainty is the power synthesis uncertainty. The current SCU method for determining and applying this uncertainty is described in Reference 7.
The Modified SCU methodology will[4
)
[
In the current SCO analysis, a pdf of the power synthesis uncertainty is produced at the same time that the DNBR t
uncertainty factor is determined.
The 95/95 probability / confidence tolerance limit of the pdf is applied {
in the CPC Neutron Flux Power calculation.
(14) i
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In the Modified SCU analysis, the power synthesis uncertainty will be applied [
~
The Modified SCU program approach is consistent with statistical methods approved in tne current SCU program. Application of this uncertainty
]willcontinue to assure a conservative ONBR calculation by CPCS at a 95/95 probability / confidence level.
2.5 OTHER MODIFICATIONS TO SCU METHODOLOGY The Modified SCU methodology includes several minor changes to the cachniques of determining and applying uncertainty components. These changes, described in the following section, are consistent with statistical methods approved in the current SCU progrt.m and retain conservatism in the resultant uncertainty factors to at least a 95/95 probability / confidence level.
2.5.1 RADIAL PEAKING FACTOR MEA _3UREMENT UNCERTAINTY Appt! CATION Both COLSS and CPC use Radial Peaking factors (Fxy's) that are verified, and adjusted if necessary, during startup testing. The Fxy measurement which is used for this verification has an uncertainty associated with it.
In the current SCU ar alysis, the Fxy measurement intertainty is combined with other uncertainty components {
(15)
In the Modified SCU methodology the Fxy uncertainty will be
.]Thusthe Fxy uncertainty will be
.' This modification involves only a
~
change in the statistical combination technique for this particular uncertainty component.
2.5.2 APPLICATION 0F UNCERTAINTY FACTORS AS A FUNCTION OF BURNUP. ASI. AND POWER The COLS$ and CPC overall uncertainty factors calculated in the SCU analysis typically vary as a function of power level, cycle burnup, and Axial Shape Index (ASI).
In the current SCU methodology, limiting values of these uncertainty factors are chesen and applied for all conditions.
The Modified SCU methodology will allow calculation and application of these uncertainty factors over several burnup, power, and ASI ranges.
Choice of par) meters and ranges will be made on a cycle-by-cycle basis in order to optimize the uncertainty factors for nominal full power operation throughout the
- cycle, while retaining conservatism at a
95/95 probability / confidence level for all conditions.
i (16) i
FIGURE 2-1 SECONDARY CALORIMETRIC POWER MEASUREMENT UNCERTAINTY (SAMPLE PVNGS VALUES) i m.
1 9
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3.0 TYp! CAL OVERALL UNCERTAINTI FACTOR CALCULATION
3.1 INTRODUCTION
The changes to the SCU Program described in Section 2.0 result in a Modified SCU methodology which can be applied to all C-E plants with digital monitoring and protection systems.
The Modified SCU Program will be initially applied to PVNGS Unit 1 Cycle 2.
~
Therefore, a
calculation of COLS$
and CPC ONBR overall uncertainty factors is presented here using typical PVNGS models and input data. This calculation will illustrate the application of the Modified SCU methodology and its results.
3.2 DNBR Ddf The System Parameter SCU methods used to determine the DNBR limit and pdf remain unchanged from that described in Reference 6.
The uncertainties combined to derive this odf are listed in Table 3-1 with typical values for PVNGS.
The resultant pdf is shown in Figure 3-1.
As in the current SCO methodology, the DNBR limit for COLSS. CPC, and transient analyses is defined by the following equation:
DNBR limit = TL
- PBOW + PHID where TL = 95/95 probability / confidence tolerance limit of DNBR pdf.
l' PBOW = Rod Bow Penalty I
PHID = HID-1 Grid Penalty (18)
[-
.] the DN8R limit P
generated by this method is used in the on-line COLSS and CPC and in the transie.it analyses.
The tolerance limit for the pdf shown in Figure 3-1 is 1.205.
Combining this with the rod bow pena'ty (1 ?S%) and the HID-1 grid penalty (0.01) yields a ONBR limit of 1.237.
3.3 SECONDARY CALOR! METRIC POWER MEASUREMENT UNCERTAINTY pdf i
The seconda:y calorimetric,>cwor measurement uncertainty is calculated from the uncertainties of the various measured parameters used to calculate the secondary calorimetric power.
These components are listed in Table 3-2 with typical values for PVNGS
]
3.4 COLSS ONBR OVERALL UNCERTAINTY FACTOR CALCULATION i
The COLSS DNBR overall uncertainty analysis process using Modified SCO is illustrated in Figure 3-2.
i i
As in the current SCU program (Reference 8),
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t Table 3-3 lists the state parameter measurement uncertainty components [
]in the COLSS overall uncertainty analysis, t
including typical ranges and uncertainty values for PVNGS.
The uncertainty components [
]arelistedwithtypical PVNGS values in Taple 3-4 and the remaining uncertainty compor.ents[
are presented in Table 3-5.
The COLS$ DNBR overall unctirtainty analysis using the typical PVNGS input values results in a ONBR overall uncertainty factor i
of[
]
i i
3.5 CPCS ONBR OVERALL UNCERTAINTY FACTOR CALCULAT!ON I
l The CPC ONBR overall uncertainty analysis process is illustrated i
in Figure 3-3.
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l As in the current SCU program (Reference 7), {
]
l i
Table 3-6 lists the state parameter measurement uncertainty components [
}in the CPC overall uncertainty analysis, including typi;al ranges and uncertainty values for ?VNGS.
The uncertaintycomponents[
]arelistedwithtypical PVNGS values in Table 3-7 and the remaining uncertainty components [
}arepresentedinTable3-8.
The CPC ONBR overall uncertainty analysis using the typical PVNGS input values results in a DNBR overall uncertainty factor of
(
l l
(21) t
Table 3-1 Components Combined in the ON8R odf Std. Deviation at t
Parameter Mean 95% Conf _id,ence
~
Inlet flow distribution Enthalpy rise factor i
Systematic pitch (in)
Systematic clad 00 (in) keat flux factor f
CE-1 CHF correlation TORC code uncertainty
{
DNBR pdf
(
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i Inlet flow distribution uncertainty [
for System 80 plants, l
L Includes 5% cross-validation uncertainty l
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Table 3-2 Secondary Calorimetric Power Measurement Uncertainty Commonents STD. Deviation Parameters Units at 95% Confidence
- Feedwater Flow (delta P transmitter)
IN. of H O 2
Feedwater Temperature
'F
[
Steam Flow (delta P transmitter)
IN. of H O l
2 l
Blowdown Mass Flow Rate KPPH e
Steam Quality i
Secondary Pressure PSTA 4
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,1
Table 3-3 g,LS$ State Parameter Ranaes and Measurement Uncertainties Measurement Parameters Unit h
Uncertainty
~
Core Inlet Coolant
(*F)
Temperature Primary Coolant (psia)
Pressure 6
2 Primary Coolant (10 lbm/hr. f t )
Mass Flow Incore Detector Signal
(%)
CEA Position (inches)
~
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(24)
a Table 3-4 UncertaintyComponentf in COLSS ONBR
~
Uncertainty Analysis Std. Deviation at Parameter Mean 95% confidence 9
s System Parameter Uncertainty DNBR pdf Radial Peaking Factor Measurement Uncertainty Secondary Calorimetric Power i
Measurement Uncertainty *
=
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Table 3-5 Uncertainty Components 5 to Determine COLS$DN8ROvIrallUncertaintyFactors Parameter Value Fuel Rod Bow Penalty on Fxy s
1 Computer Processing Uncertainty 0
Simulator Model Uncertainty j
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(26)
Table 3-6 CDCS State Parameter Rannes and Uncertainties Measurement Parameters Unit Ranaes Uncertainty l.
Core Inlet Coolant Temperature
(*F)
Primary Coolant Pressure (psia)
Primary Coolant 0
2 j
Mass Flow (10 lbm/hr-ft )
Ex-core Detector Signals
(% power)
CEA Positions (inches)
Startup Measurement Uncertainties
~
- Rod Shadowing Factor
- Shape Annealing Matrix **
- Boundary Point Power Correlation Coefficient
- Assumed Excore Noise Level During Test (27)
Table 3-7 Uncertainty Component' in CPC ONBR Overall Unce'rtainty Analvsis Std. Deviation of Parameter Mean 954 Confidence System Parameter Uncertainty DNBR pdf Radial Peaking Factor Measurement Uncertainty Secondary Calorimetric Power Measurement Uncertainty Neutron Flux Power Synthesis Uncertainty *
[
]
9 (23)
Table M Uncertainty Commony,ts 1to Determine CPC DN84 overall Uncertainty Factors Parameter ygjjag Fuel Rod Sow Penalty on Fxy Computer Processing Uncertainty Simulator Model Uncertainty 6
0 (29)
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4.0 CONCLUS!0N This report describes changes to the current SCU Program which are designed to improve plant operating performance and flexibility and reduce unnecessary trips.
These changes result in a Modified SCU Program which is applicable to all C-E plants with digital monitoring and protection systems.
The overall uncortainty factors determined using the Modified SCU program
~
continue to ensure that the COLSS POL calculations and the CPCS ONBR and LPD calculations will be conservative to at least a 95%
probability and 95% confidence level. The initial application of the Modified SCU program is planned for PVNGS Unit 1 Cycle 2.
The Modified SCU program methodology has been applied to PVNGS
~
using typical models and input data and results in DN8R overall uncertainty factors off for COLSS and for CPCS.
~
e G
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5.0 REFERENCES
1 "Statistical Combination of Uncertainties Part !!", -P to LO-83 010, January, 1983.
2 "Statistical Combination of Uncertainties Part !!!". P to LO-83-010, Rev. 01, August, 1983.
3 CEN 312 P, Rev 01 P "Overview Description of the Core Operating Limit Sucervisory System (COLSS)", November, 1986.
4 CEN 304-P, Rev 01 P, "Functional Design Requirements for a Control Element Assembly calculator", May, 1986.
5 CEN-305-P, Rev 01-P "Functional Design Requirements for a Core Protector Calculator" May, 1986.
6 "Statistical Combination of Uncertainties Part !",
CEN-283(S) P, October, 1984.
7 "Statistical Combination e,f Uncertainties Part !!".
CEN-283(S) P, October, 1984 8
"Statistical Combination of Uncertainties Part !!!".
CEN 283(S) P, October, 1984 9
"Statistical Combination of Uncertainties for Waterford-3",
CEN 343 (C)-P, October, 1986.
10 Letter from J. H. Wilson (NRC) to J. G. Dewease (Louisiaaa Power and Light Company), "Reload Analysis Report for Cycle 2 at Waterford 3", Oceket 50-382, January, 1987.
11 "Statistical Combination of Uncertainties Part !". -P to LO-83-010, January, 1983.
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