ML20134Q256

Topical Rept Evaluation of Verification of Cecor Coefficient Methodology for Application to PWRs of Middle South Utils Sys. Methodology Acceptable

ML20134Q256
Person / Time
Site:	Arkansas Nuclear, Waterford, 05000000
Issue date:	08/30/1985
From:	Office of Nuclear Reactor Regulation
To:
Shared Package
ML20134Q250	List: ML20134Q247 ML20134Q256
References
NUDOCS 8509090256
Download: ML20134Q256 (5)

Text

_ _. _ __

. s Enclosure SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION LOUISIANA POWER AND LIGHT COMPANY WATERFORD STEAM ELECTRIC STATION, UNIT 3 RELATED TO VERIFICATION OF CECOR COEFFICIENT METHODOLOGY i

Sumary of Report The report describes the methodology used by Middle South Services (MSS) to generate the input data library for the CECOR program and to establish the power distribution measurement uncertainty. The CECOR program is an off-line computer program which synthesizes detailed three-dimensional assembly and c peak pin power distributions from fixed incore detector signals.

The report is organized into five sections. Section 1 is an introduction.

Section 2 describes the incore instrumentation for Arkansas Nuclear One- ,

Unit 2 and Waterford Unit 3. Section 3 describes the algorithms used by f CECOR to synthesize the three-dimensional power distributions from the incore -

detector readings and the coefficient library. The precalculated library of coefficients is used in the power synthesis. Section 4 describes the generation of the coefficient libraries from data generated from MSS I reactor physics methods. Section 5 provides a quantification of CECOR uncertainties using MSS generated libraries. The overall measurement un-certainties of the one-sided 95/95 probability / confidence level are Total peaking factor uncertainty 7.71 l 8509090256 850030

, PDR ADOCK 05000368 t

P PDR l

1

- s Planar radial peaking factor uncertainty 6.92 Integrated radial peaking factor uncertainty 5.69 Summary of Review We have reviewed the information presented with regard to the analytical methods and the statistical methods. We have examined the data base 3 used to establish the comparison between measurement and calculation in determining the basic measurement uncertainty. The CECOR program synthesizes 3-D power distributions from fixed incore detector readings. The signals from the five axially spaced detectors in each string are connected to powers.

Next coupling coefficients are used to calculate pseudo-detector powers in uninstrumented assemblies or assemblies with failed detectors. Then using a five term Fourier fit, an assembly axial shape is constructed based on the five detector powers. Calculation of the maximum 1-pin and 4-pin assembly peaks are ,

i done using 1-pin and 4-pin peaking library coefficients, which are functions of f I

burnup and control rod position. Most of the information necessary to generate the CECOR data library comes from two dimensional, quarter core, full power, PDQ7 depletion calculations or 3-D model calculations. Both control rods out and control rods inserted calculations are performed.

i l

s m-

-w- ,wm -

cs . , - - -w . - - - - - - - - _7

. s 3-The determination of the CECOR uncertainties consists of four components:

Coupling / Measurement Uncertainty, Assembly Axial Synthesis Uncertainty, Pin Peaking Synthesis Uncertainty and Pin Peaking Calculational Uncertainty.

The C' oupling/ Measurement Uncertainty is the uncertainty associated with the measurement of power at the five detector levels. It includes uncertainties in the measured power in instrumented levels and the uncertainties in extra-polating to uninstrumented assemblies. The data used for this comparison was obtained from 3 cycles of a 177 fuel assembly plant and 1 cycle of a 217 i fuel assembly plant. A total of 41 core maps were used. The map by map and cycle by cycle statistics were pooled after the data passed standard ,

probability tests. The Assembly Axial Synthesis Uncertainty is obtained by comparing the CECOR axial synthesis )as given by a Fourier fit) with nodal code calcualtions. Cases were done at various burnups with various rod positions. A total of 77 cases were used.

The Pin Peaking Synthesis Uncertainty is the uncertainty associated with pin peaking at axial height other than at the " average" power plane. This pin peaking Calculational Uncertainty is the uncertainty associated with the PDQ calcualtion of pin-to-box peaking factors. The MSS pin peaking ,

calculational uncertainties were documented in the physics methodology report ,

(Reference 1). The uncertainties were combined statistically. The methods i

used were the same as those used in Reference 2. The overall uncertainties I are such that there is a 95% probability that at least 95% of the time Fq , Fxy and Fr values will be less than the value derived from the measurement with an l

l l

l d

_ _-.~-- TW y h eNmdANm DNew w; AA s 6- g rwrw g ya.'w w m4 -.ru p ' -ru

4 accuracy of 7.71%, 6.92% and 5.69%. These values are slightly higher than those

shown applicable and approved for CE reactors in Reference 2.

2

+

We have reviewed the report. Included in our review was the description of t

the experimental data base, the calculations performed and the methods used to l determine the components of uncertainty and the combination of these components into overall uncertainties. We find the methodology used by Middle South Services to generate the input data library for the CECOR program acceptable for use for Waterford 3 plant. In addition we find that the overall measure-j ment uncertainties at the one-sided 95/95 probability / confidence level as -

l 1

listed below are acceptable.

I -o Total Peaking Factor Uncertainty = F q

= 7.71 .

, Planar Radial Peaking Factor Uncertainty = F = 6.92 xy Integrated Radial Peaking Factor Uncertainty = F = 5.69 r

1

)

^

l

! 0

.i.

4 9

5 i

4 4

t 1

. - . - _ - - - - . - . _ - - - _ , - .,- ... -.- - ~._ .-.-

, s REFERENCES

1) Qualification of Reactor Physics Methods for Application to Pressurized Water Reactors of the Middle South Utilities System, MSS-NAl-P, August 4, 1980.

2) INCA /CECOR Power Peaking Uncertainty, CENPD-153-P Revision 1-P-A. Combustion Engineering, May 5, 1980.

s 1

-c l

1 f

e r

a ge' n s-eyeary g g

• u t w +'t' P m uur* v' Nt- -?f "'tgt,-eetgw+-e+-agw w t -g-tw w3p. ew w - m m y % - eg w & m, pu ,,, y myey 9 9.,w r mp ye ycg-ee yeewgr g? p m gg ytv e W T 5 h*f h _ A"8