ML14192A519
| ML14192A519 | |
| Person / Time | |
|---|---|
| Site: | Robinson  |
| Issue date: | 10/24/1984 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML14192A518 | List: |
| References | |
| NUDOCS 8411130633 | |
| Download: ML14192A519 (6) | |
Text
SAFETY EVALUATION OF THE EXXON NUCLEAR COMPANY REPORT XN-NF-711(P)
"EXTENSION OF THE XNB CORRELATION TO-PIR FUEL ASSEMBLY DESIGNS WITH SPACER. PITCH GREATER THAM4 22 INCHES" P.4102
- 1. Introduction The Exxon XNB (1) correlation has been reviewed and approved by the staff for use by Exxon with a 1.17 DNB safety limit to design PWR fuel within the ranges presented in Table 2. XN-NF-711(P) provides additional test data in order to show that the original XNB correlation with a modification to the spacer pitch correction term is within the 1.17 limit for assemblies with pitch greater than 22 inches.
- 2. Summary of Report XN-NF-711(P) compares experimental DNB data with predictions of DNB using the modified spacer pitch correction factor with XNB.
Four test sections are considered. These test sections include ENC5,
- W131, W138, W166.
The test section ENC5 has been fully described in Ref. (1).
- W131, 138 and.166 are presented in the Columbia University CHF data base (2).
The Columbia test sections represent arrays typical of 15x15 design with 0.422 inch diameter rods and assembly pitches of 22 inches.
Section W131 used 16 heated rods while Sections W133 and W165 used 15 heated rods and one unheated rod. Non-uniform axial profiles, with upskew axials, were simulated by using a constant outer diameter and tapering the inside diameter of the rod.
Test section ENC-5 had.424 inch diameter rods with an assembly'pitch of 26.2 inches and was heated with a uniform axial heat flux distribution.
These test sections provided 167 data points which when analyzed with XNB resulted in a predicted mean MDNBR of.98141 with a deviation of
.075539. The resulting 95/95 limit is within the currently approved 1.17 limit of XNB. A statistical summary of these results is given in Table 1.
2
- 3. Staff Evaluation Exxon has used a slightly modified form of their XNB correlation to analyze test bundles with pitches to 26.2 inches. This modification is applied only on assemblies with pitches greater than 22 inches and does not change XNB results for pitches less than 22 inches.
The statistical analyses of Exxon's comparison of the modified XNB correlation with test data (Table 1) shows that the 95/95 limit for each test section standing alone is less than 1.17 and that the overall 95/95 limit based on the entire 167 da-ta point sample is also less than 1.17.
The staff finds that adequate justification has been provided to use the modified XNB correlation with its currently approved limit of 1.17 for assemblies with pitches up to 26.2 inches.
TABLE 1 Statistical Summary See table 3.3 page 8 of the subject report
TABLE 2 APPROVED RANGES FOR XNB VENDORS:
Exxon Nuclear Combustion Engineering Westinghouse Fuel Design:
Non-Mixing Vane Mixing-Vane Equivalent Hydraulic 0.177 -
0.612 Diameter (inches)
Equilavent Heated 0.463 -
0.528 Diameter (inches)
Pressure (psia) 1395 -
2425 Local Mass Velocity (Mlbm/hr-ft2 0.92 -
3.04 Local Enthalpy (Btu/lb) 594.85 -
821.24 Local Quality +0.3 Heated Length (inches) 66 -
16B Grid Spacing (inches) 14.3 22.0 Inlet Subcooling (Btu/lb) 37.2 -
336.34
-3 References
XN-NF-621(P), Rev. 1, April 1982.
- 2. C. F. Fighetti and D. E. Reddy, "Parametric Study of CHF Dista," Vol.
1, Vol. 3, EPRI NP-2609, September 1982.
- 3. N. F. Fausz and T. W. Patten, "XCOBRA-IIIC:
A Computer Code to Determine the Distribution of Coolant During Steady State Transient Core Operation, XN-NF-75-2(P), Rev. 2, September 1982.
- 4.
H. Schenck, Jr., Theories of Engineering Experimentation, 'Second Edition, McGraw-Hill, 1968.
- 5. Letter, C. 0. Thomas (NRC) to R. B. Stout (ENC),
"Acceptanice to Referencirng of Licensing Topical Report XN-NF-621(P),
Revision 1, 'Exxon Nuclear DNB Correlation for PWR Fuel Designs,'" dated April 12, 1983.-