ML20058H985
| ML20058H985 | |
| Person / Time | |
|---|---|
| Issue date: | 11/26/1993 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20058G444 | List: |
| References | |
| NUDOCS 9312130301 | |
| Download: ML20058H985 (2) | |
Text
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o UNITED STATES E' 3 m j
NUCLEAR REGULATORY COMMISSION g
WASHINGTON, D. C. 20555 S
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i ENCLOSURE SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATING TO TOPICAL REPORT WCAP-10216-P. REV. I
" RELAXATION OF CONSTANT AXIAL OFFSET CONTROL - F SURVEILLANCE TECH SPEC" WESTINGHOUSE ELECTRIC CORPORATION 1.
INTRODUCTION In a letter of October 29, 1993, from N. J. Liparulo to U.S. Nuclear Regulatory Commission (NRC), Westinghouse Electric Corporat % n submitted a revision to topical report WCAP-10216-P, " Relaxation of Ccnstant Axial Offset Control - F,ibes an NRC-approved methodology developed by L% Linghouse fo Surveillance Technical Specirication," for WRC review.
The report descr performing power distribution control in Westinghouse-type pressurized-water reactors.
The proposed revision accounts for F increases greater than 2 percent between measurements to enhance the exi, sting surveillance methodology.
2.
EVALUATION The heat flux hot channel factor, F,(z), is the maximum local heat flux on the surface of a fuel rod at core elevation z, divided by the average fuel rod heat flux.
For those plants using Constant Axial Offset Control (CAOC) or Relaxed Axial Offset Control (RA0C) during normal operation, F,(z) is shown to be within its limits by performing periodic measurements.
Since F,(z) surveillance is only required when power has been increased by 20 percent of rated power from the previous surveillance, or at least every 31 effective full power days (EFPD), the technical specifications (TS) take into account the possibility that F (z) may increase between surveillances.
The TS require that when performing t$e surveillance, the resulting maximum F (z) value must be compared to the maximum F,(z) determined from the previous m,easurement.
If the maximum F,(z) has increased since the previous determination of F,(z), the TS allow two options: either the current F (z) must be increased by an additional 2.0 percent to account for furt,ner increases in F (z) before the next surveillance, or the surveillance period must be reduce,d to every seven EFPD.
The F,ld change by no more than 2.0 percent between monthly flux maps (z) p F, wou This assumption was based on calculations for previous (pre-1983) core designs which pre-date the low leakage loading patterns, high amounts of burnable poisons, and 18-month cycles typical of recent cores.
Recently, some Westinghouse-designed cores have experienced increases in the measured F,(z) as high as 5 to 6 percent between monthly flux maps over certain burnup i
ranges.
Therefore, for those cores which are predicted to have larger increases in F (z) over certain burnup ranges, a larger penalty will be provided on a, cycle-specific basis. The penalties will be calculated using 1
9312130301 93126 PDR TOPRP EMVW
NRC-approved methods.
The larger penalty will be included in the plant Peaking Factor Limit Report (PFLR) or in the Core Operating Limit Report (COLR) as a replacement for the current 2 percent standard value. Alternatively, the additional penalty in excess of 2 percent may be factored into the W(z) function, which is a cycle-dependent function that accounts for power distribution transients encountered during normal operation.
The W(z) function is also provided in the PFLR or the COLR. When the F (z) increase penalty is provided on a cycle-specific basis, TS Surveillanc,e 4.2.2.2.e.1 must be modified to reflect inclusion of this parameter in the PFLR or the COLR.
The staff finds either of these methods for incorporating a larger F,(z) penalty acceptable.
3.
CONCLUSION The proposed revisions to the F, Surveillance Technical Specification in those reactors using CAOC or RAOC for power distribution control are acceptable.
These revisions would allow the incorporation of a larger penalty to account for F (z) increases greater than 2 percent between measurements.
These penal, ties may be iacorporated in either the plant PFLR or COLR, as described above, and will be calculated with NRC-approved methods. The approved version of WCAP-10216-P, Rev. 1 must be included in the Administrative Reporting Requirements Section of the TS for those plants incorporating the penalty factor in the COLR. Also, TS Surveillance 4.2.2.2.e.1 must be modified to reflect inclusion of this parameter in the PFLR or COLR.