ML20065N486
| ML20065N486 | |
| Person / Time | |
|---|---|
| Site: | Grand Gulf  |
| Issue date: | 04/30/1987 |
| From: | Branlund B, Caine T, Ranganath S GENERAL ELECTRIC CO. |
| To: | |
| Shared Package | |
| ML20065N484 | List: |
| References | |
| EAS-35-0387, EAS-35-387, NUDOCS 9012120159 | |
| Download: ML20065N486 (13) | |
Text
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ENCL.0SURE 1 AECH-90/0206 h
EAS-35-0387 DRF A00-02764 April 1987 FLUX k' IRE DOS 1 METER EVALUATION FOR CRAND CULF NUCLEAR P0kTR STATION, UNIT I Prepared by: 'I b
~n T.A. Caine. Senior Engineer Structural Analysis Services Verificd N. 7. h n1 h B.J. Branlund, Engineer Structural Analysis Services A**"S Reviewed by:
,S. Ranganath7 Manager Structural Analysis Services GENER AL h ELECTRIC 9012120159 90133o
, FIR ADOCK 05o00416 PDC
9 IMPORTANT NOTICE RECARDING CONTENTS OF THIS REPORT PLEASE READ CAREITLLY This report was prepared by Cencral Electric solely for the use of Systems Energy Resources, Inc. (SERI).
The inf ormation contained in this report f s believed by General Electric to be an accurate and true representation of the facts known, obtained or provided to General Electric at the time this report was prepared.
The only undertakingo of the General Electric Company respecting information in this document are contained in the contract governing Miscissippi Power & Light Company Purchane Order No. CG12141 and nothing contained in this document shall be construed as changing said contract.
The use of this information except as defined by said contract, or for any purpose other than that for which it is intended, is not authorized; and with respect to any such unauthorized use, neither Cencral Electric Company nor any of the contributors to this document maken any representation or warranty (express or implied) as to the completeness, accuracy or usefulness of the information contained in this doc ument or that such use of such information may not infringe privately owned rights; nor do they assume any responsibility for liability or damage of any kind which may result from such use of such information, l
11
Y CONTENTS Page i
1.
INTRODUCTION 1-1 2.
ANALYSIS 2-1 3.
RESUI.TS 3-1 4.
CONCLUSIONS 4-1 l
APPENDICES A.
TEST REPORT TOR TLUX k' IRE DOSIMETER REMOVED FROM A-1 CRAND C'$'LF 1 AT END OF CYCLE 1 i
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1.
INTRODUCTION j
l In September 1986 Crand Culf Nuclear Power Station Unit 1 (Grand Gulf 1) completed its first fuel cycle.
During the outage that followed, the flux wire dosimeter attached to the surveillance capsule at the vessel 3' azimuth was removed.
The dosimeter was shipped to the General Elcetric Ve'lecitos Nuclear Center (VNC) in Pleasanton, CA in December 1986 for testing.
The-test results and the associated determination of peak vessel flux and fluence are presented in t**is report.
The surveillance program for Grand Gulf I consists of three surveillance capsules and one flux wire dosimeter.
Each sutveillance capsule containe Charpy specimens of the beltline base, weld and HAZ materials, and a set of flux vires used to determine the fluence experienced by the capsule.
The surveillance capsules are scheduled to be withdrawn periodically during plant life (the current schedule required by ASTM E185-82 is a capsule at 6, 15, and 32 effective full power years).
In addition to the flux wires in the surveillance capsules, a flux vire dosimeter is attached to the capsule at 3',
as shown in Figure 1-1, for removal after the first fuel cycle.
Since the vessel fluence is directly proportional to thermal power produced, the results of the flux wire dosimeter test are intended to provide a calibration point of vessel fluence versus accumulated thermal power.
A linear extrapolation provides an estimate of the ent:-of-lif e (EOL) fluence.
It should be noted that the flux wires that will be removed with the surveillance capsules will have an irradiation history more typical of normal operation, and will be useful for re-calibrating the EOL fluence estimate.
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ANALYSIS The determination of the peak EOL fluence is basically a two-step process.
First. the flux vires are analyzed to determine the flux and fluence at the dosimeter location.
Then lead factors are calculated which relate the flux magnitude at the dosimeter location to that at the location of peak flux.
The flux vire dosimeter was dist..sembled at VNC and the iron flux vires were cicaned and weighed.
Gamma spectrometry was used to determine the rate of disintegrations. The daily power history of the first fuci eycle was used, along with cross-section data developed for BWRs to transform the disintegration data into rates of irradiation, 8
or flux (n/cm -s).
The detailed procedure used in evaluating the flux vires is contained in the test report in Appendix A.
The determination of lead f actors was donc for the Grand Gulf 1 2$1 inch diameter venrel with 800 fuel bundles. The lead factors were calculated assuming an equilibrium fuel cycle, which is representative of a typical normal operation core power distribution.
Therefore, the lead factors provide the best available means of predicting peak EOL fluence.from the flux wire data.
Determination of the lead factors for the RPV peak location at the inside wall and 1/4 7 depth was done using a combination of one-dimensional and two-dimensional finite element computer analysis.
The two-dimensional analysis established the relative fluence in the azimuthal direction at the vessel surf ace and 1/4 T depth.
A series 1
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The ' combination of azimuthal and axial distribution results provides the lead factor between the dosimeser location and the peak flux location.
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The two-dimensional D07 computer program was used to solve the Boltzman transport equation using the discrete ordinate method on an (R,0) geometry, assuming a fixed source.
One eighth core symmetry was used with periodic boundary conditions at O' degree end 45'.
Neutron cross secticns were determined for 26 energy groups, with angular scattering approximated by a third-order Legendre expansion.
A schematic of the two-dimensional vessel model is shown in Tigure 2-1.
A total of 99 radial elements and 45 azimuthal elements were used.
The model consists of an inner and outer core region, the shroud, water regions inside and outside the shroud, the vessel vall, and an air region representing the dryvell.
Flux as a function of azimuth was calculated, as shovn in Figure 2-2, establishing the azimuth of the peak flux and its magnitude relative to the flux at the dosimeter location of 3*.
This could be referred to as the azimuthal component of the lead factor.
The one-dimensional computer code (SNID) was used to calculate radial flux distribution for several core elevatione at the peak azimuth angic. The elevation of the peak flux was determined, as well as its magnitude relative to the flux at the dosimeter elevation.
This would be considered the axial component of the lead factor.
The lead factor between the peak and dosimeter locations was calculated as the azimuthal component times the axial component.
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RESitt.TS The flux vire dositneter test results are presented in detail in Appendix A.
A sumary of the >l MeV flux and fluence values for the desitne t e r are presented in Table 3-1.
As discussed in the test report, there is an uncertainty of :25% on the
>l MeV flux and fluence.
Tabic 3-1 shows the upper bound values with the nominal values.
The lead factors for the peak location inside surface end 1/4 T depth are presented in Table 3-1 with the desitneter test results.
The lead factors are used to predict the peak fluence according to the following equation:
Peak Fluence = (Dosimeter Flux)*(Full Power Seconds)/ Lead Factor The first fuel cycle for Grand Gulf I consisted of 704 days of operation with an average capacity factor of 0.480.
This is equivalent to 337.9 days at full power, or 0.93 ef f ective full power years (ETPY).
The standard assumption for EOL is 32 ETPY, These values are used to calculate the fluence values at the end of cycle one (EOCl) and at EOL, as shown in iable 3-1.
The fluences at the peak location I.D. and 1/4 T are plotted as a function of EFPY in Figure 3-1.
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f Table 3-1 FLUENCE DETERMINATION FOR THE PEAK LOCATION IN THE CRAND CULF 1 VESSEL Time at Povert TOCl 0.93 ETPY = 2.93x10 seconds 9
EOL 32 EFPY = 1.01x10 seconds Lead Factors:
1.D.
0.36 1/4 7 0.47 Dosimeter Flux (n/cm -s) 8.9x10 (nominal) 1.lix10'(upper bound) a FLUENCE (n/cm )
NOMINAL UPPER BOUND 8
16 16 EOCl Peak I.D.
7.2x10 9.0x10 16 16 EOCl Peek 1/4 T 5.5x10 6.9x10 I8 I8 EOL Peak I.D.
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Peak Vessel Beltline T1uence versus ETPY 3-3
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CONCLUSIONS The flux vire test results summarized in Table 3-1 show a nominal 18 2
peak 1/4 T fluence at 32 EFPY of 1.9x10 n/cm.
This fluence is equal to the design value listed in pararraph $.3.1.6.2 of the updated l
TSAR. which was originally calculated for Crand Gulf I based on a predicted equilibrium fuel cycle.
The results from the flux vire testing are generally used to modify the pressure-temperature curves in the Technical Specifications.
In this case, the fluence matches the original design value, if the nominal value from Table 3-1 is.used.
Furthermore, the NRC is finalizing Revision 2 to Regulatory Guide 1.99, which will prompt a revision of the pressure-temperature curves when it is issued.
Since the curves are conservative f or current operation, it is recommended that - SERI wait to change the curves until Regulatory Guide 1.99 is revised.
Changes to the Technical Specifications at this time need only include an acknowledgement that the fla vires were tested and possibly a summary of the test results.
SERI ray want to include a commitment to revise the pressure-temperature curves according to Regulatory Guide 1.99, Revision 2 when it becomes official.
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