ML20080T318
| ML20080T318 | |
| Person / Time | |
|---|---|
| Site: | Calvert Cliffs  |
| Issue date: | 10/04/1983 |
| From: | ABB COMBUSTION ENGINEERING NUCLEAR FUEL (FORMERLY |
| To: | |
| Shared Package | |
| ML19268E208 | List: |
| References | |
| NUDOCS 8310200245 | |
| Download: ML20080T318 (8) | |
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REVISED ZIRCALOY-4 GROWTH CORRELATIONS October 4, 1983 i
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8310200245 831014 PDR ADCCK 05000317 i
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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 OR 1RFLIED INCLUDING THE WARRANTIES OF FITNESS FOR A PARTICULAR PURPOSE OR MERCHANTA88UTY, 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
- 8. ASSUMES ANY UA81UTIES WITH RESPECT TO THE USE OF,OR FOR DAMAGES RESULTING FROM THE USE OF, ANY INFORMATION, APPARATUS, METHOD OR PROCESS DISCLOSED IN THIS REPORT.
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Revised Ziraaloy-4 Growth Correlations October 4, 1983 The original fuel rod and guide tube growth correlations were described in Reference 1 and most recently documented in Reference 2.
Since those correla-tions were developed, however, a large quantity of length change measurements more typical of the current C-E design has become available to support modifica-tion of the empirical models.
It should be noted that no changes have been made to the methodology and criteria by which the correlations are utilized in the design process.
The methodology and criteria are described in References 2 and 3.
Description of Modified Correlations A.
Annealed Guide Tube Growth Correlations Reference 1 defined an empirical correlation for the stress-free growth of fully-annealed Zircaloy-4 guide tubes. The majority of the data used to develop the correlation was from non-C-E sources, on material with similar characteristics as that of the guide tubes used by C-E.
A limited quantity of data covered length changes of C-E guide tubes at low fluence, and was measured by a different technique than that now employed.
The modified correlation shown below is based on length change measurements on [
] guide tubes from C-E 14 x 14 and 16 x 16 fuel assemblies. All measurements were made after Reference 1 was issued, and were made by improved techniques at the Fort Calhoun, Calvert Cliffs, and Arkansas huclear One, Unit 2 reactors. The measurements represent:
(1) one to six cycles of reactor operation; (2) fast fluences (E > 0.821 Mev) of 2.3 to 11.3 x 1021 nyt averaged over the active core length; and (3) a wide range of axial stress states in the guide tubes of the various fuel batches used in the data base.
The modification of the correlation to predict stress-free guide I
tube growth required that the guide tube length change measurements be corrected for axial creep.
Creep is induced during operation by the combined holddown and hydraulic uplift forces unique to each l
fuel batch and reactor application.
To make the correction, the l
creep model currently incorporated in SIGREEP to predict the creep behavior of Zircaloy-4 during irradiation was utilized.
A non-linear regression analysis was performed on the resulting data and the following modified correlation for stress-free growth of fully-annealed guide tubes was derived:
O'I'0 best estimate " b 3
(1)
Where:
% oL/L is the total stress-free growth strain in percent O
L is the as-fabricated guide tube length O
Otisthe{astneutronfluence(E>0.821Mev) in n/cm averaged over the active core length
[
The upper and lower 95/95 tolerance bands for the correlation described in Equation (1) were also derived and are defined below:
% AL/LO 95/95 = [
]
(2)
B.
Length Change Correlation for 14 x 14 Reload Fuel Rods Reference 1 defined an empirical correlation between fuel rod length i
change and fast fluence for rods clad with stress-relief annealed Zircaloy-4.
The correlation was predominately based on length measurements of fuel rods which were not pre-pressurized and which did not contain non-densifying fuel. Approximately half of the data was from non-C-E sources. The modified correlation presented below is based on length measurements made over the last several years 'on C-E fuel rods from Calvert Cliffs and Fort Calhoun. These fuel rods were pre-pressurized with helium and contain non-densifying fuel.
The[
] measurements included in the base for this model represent exposures from one to i
six cycles of reactor operation and fast neutron fluence (E > 0.821 Mev) of 2.4 to 12 x 1021 n/cm2 averaged over the active core length. A i
non-linear regression analysis was performed on the length change measurements and provided the following best estimate correlation for
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the length change of 14 x 14 reload fuel rods:
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% AL/L
=[
]
(3)
O best estimate l
Where:
% AL/L is the fuel rod total growth strain in percent O
L is the as-fabricated fuel rod length O
9t is the fast neutron fluence (E > 0.821 Mev) in n/cm2 averaged over the active core length Upper and lower 95/95 tolerance bands for the correlation described by Equation (3) were also derived. These bands are defined by the following model:
% AL/L
- E
]
(4)
O 95/95 Use of Modified Correlations to Predict Dimensional Changes Reference 2 described the Computer Code SIGREEP, which is used for design and licensing purposes to predict dimensional changes.
The code utilizes a computer-ized Monte Carlo technique for establishing resultant joint probability density l
functions.
It randomly selects combinations of input values to be used in a l
time-history analysis of dimensional changes.
Reference 2 presented comparisons between analytical predictions using SIGREEP (with the original Zircaloy growth correlations) and measurements from l
irradiated fuel assemblies.
New comparisons have been made usino the modified correlations described earlier in this letter.
No changes have been made to l
the SIGREEP methodology.
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. Figures 1 and 2 show the comparison between the available Calvert Cliffs (CC) assbnbly length change data and the rew analytical predictions. Figure 3 is a similar comparison for Calvert Cliffs reload shoulder gap data (the original core fuel rods had significant design differences from the reload fuel, so shoulder gap change in the original core fuel is not covered by the modified correlations and is not presented on Figure 3).
Figure 3 represents an independent check on the modified correlations, since shoulder gap change is a combined effect of guide tube and fuel rod length change. The excellent agreement between the SIGREEP predictions and the large quantity of data from several reload batches indicates that the individual correlations are correct.
Based on the comparisons shown in the figures, it is concluded that the modified correlations, used with the existing SIGREEP method, result in more accurate predictions of dimensional change in Calvert Cliffs reload fuel.
References 1.
CENPD-198, "Zircaloy Growth:
In-Reactor Dimensional Changes in Zircaloy-4 Fuel Assemblies", December, 1975.
2.
CENPD-269, " Extended Burnup Operation of Combustion Engineering PWR Fuel",
April, 1982.
3.
CEN-183(B), " Application of CENPD-198 to Zircaloy Component Dimensional Changes", September, 1981.
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FIGURE 1.
SIGREEP PREDICTIONS VERSUS ASSEMBLY LENGTH CHANGES FOR CALVERT CLIFFS - ORIGINA'l CORE FUEL ASSEPBLIES 1
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U y
1 Y50 0?<
d 22 FUEL ASSEMBLY FLUENCE (>.821 NEV)
(NVT x 10-21)
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FIGURE 2.
SIGREEP PREDICTIONS VERSUS ASSEMBLY LENGTH CHANGES FOR CALVERT CLIFFS - RELOAD FUEL ASSEMBLIES t
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e 9
a5 E?"i>7 d5 5-N d
2 FUEL AS.SEMBLY FLUENCE (>.821 MEV)
(NVT X 10-21)
FIGURE 3.
SIGREEP FREDICTIONS VERSUS SHOULDER GAP DECREASE FOR CALVERT Ci.IFFS RELOAD FUEL ASSEMBLIES OEMI 35u
.& 7 o 5 Si ~
S8 Bi FUEL R00 FLUENCE (>.821 MEV)
(NVTX10-21) i