ML20112F802
| ML20112F802 | |
| Person / Time | |
|---|---|
| Site: | Bellefonte  |
| Issue date: | 01/04/1985 |
| From: | Hufham J TENNESSEE VALLEY AUTHORITY |
| To: | James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| References | |
| REF-PT21-85, REF-PT21-85-050-000 PT21-85-050-000, PT21-85-50, NUDOCS 8501160048 | |
| Download: ML20112F802 (2) | |
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TENNESSEE VALLEY AUTHORITY CH ATTANOOGA. TENNESSEE 37401 400 Chestnut Street Tower II January 4, 1985 U.S. NucleapgldGore bMion Region II Attn:
Mr. James P. O'Reilly, Regional Administrator 101 Marietta Street,.NW, Suite 2900 Atlanta, Georgia 3032222
Dear Mr. O'Reilly:
I-B5'LLEFONTE NUCLEAR PLANT UNITS 1 AND 2 - BABCOCK & WILCOX'S NONCONSERVATIVE ANALYSIS OF NEUTRON FLUX - NCR BLN NEB 8007 - FINAL REPORT On November 5,1980, R. W. Wright, NRC-0IE Region II, was informed that the subject renconformance was determined to be reportable in accordance with 10 CFR 50.55(e). This was followed by our interim reports dated December 3, 1980; March 30 and September 21, 1981; February 22, April 27, A g ust,10, and November 16,1982; May 23 and October 20, 1983; and January 6, April 6, and May 31, 198 4.
Enclosed is our firal report. A one-week delay of this submittal was discussed with Inspector S. Weise on December 21, 1984. We consider 10 CFR Part 21 to be applicable to this deficiency.
If you have any questions concerning this matter, please get in touch with R. H. Shell at FTS 858-2688.
Very truly yours, TENNESSEE VALLEY AUTHORITY W. b a.A.
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cc (Enclosure):
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Mr. Richard C. DeYoung, Director Office of Inspection and Enforcement U.S. Nuclear Regulatory Commission Washington, D.C.
20555 H. B. Barkley 205 Plant Project Services P.O. Box 10935 Lynchburg, Virginia 24506-0935 Records Center Institute of Nuclear Power Operations 1100. Circle 75 Parkway, Suite 1500
' Atlanta, Georgia 30339 9501160040 050104 PDR ADOCK 0500043G DR10AL COPY 8
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j-ENCLOSURE BELLEFONTE NUCLEAR PLANT UNITS 1 AND 2 BABCOCK AND WILCOX'S (B&W) NONCONSERVATIVE ANALYSIS OF NEUTRON FLUX NCR BLN NEB 8007 10 CFR 50.55(e)
FINAL REPORT Description of Deficiency In October 1980, Babcock and Wilcox (B&W) identified a potential problem with assumed measurement errors used in determining reactor protection system (RPS). set points that may be nonconservative under specific plant conditions. The potential nonconservatism is due to the fact that the accident analysis for Bellefonte Nuclear Plant (BLN) used the same methods for establishing the neutron flux errors to be considered in the analysis as those used in the design of the 177 fuel assembly (FA) plants. These methods included a 2-percent allowance for transient induced flux errors while actual operating expericace at the 177 FA plants has shown that larger errors could occur during certain transients.
The plant conditions of concern could occur daring a small overcooling and small steam line break, a large steam line break in containment, or a rod ejection accident.
Safety Implications If plant designs were implemented utilizing nonconservative neutron flux measurement assumptions, the detection of high neutron flux caused by the design basis events mentioned above could be delayed. For a large steam line break, this could result in the delay of a high neutron flux reactor trip, an overpowered reactor, and subsequent fuel overheating. For a rod ejection accident, faulty assumptions could allow a localized positive reactivity insertion which could result in a nonuniform increase in reactor For the small overcooling and small steam line break, the impact of
- power.
nonconservative flux errors includes exceeding the allowable departure from nucleate boiling ratio as well as the acceptable linear heat rate.
Corrective Action B&W has completed their analysis program of this condition, and they have determined that no changes to plant hardware or set points are necessary.
However, initial condition normal operating limits on rod position and axial offset were revised to produce acceptance results in the transient analysis.
B&W has also determined that to further actions are required to prevent a recurrence of this problem at BLN as the completed review provides assurance that the transient induced flux errors used in the TVA accident analysis envelop all accident transients included in the TVA design basis.
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