ML19317D738
| ML19317D738 | |
| Person / Time | |
|---|---|
| Site: | Oconee, Davis Besse  |
| Issue date: | 06/10/1977 |
| From: | Parker W DUKE POWER CO. |
| To: | Moseley N NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| Shared Package | |
| ML19317D739 | List: |
| References | |
| NUDOCS 7912100505 | |
| Download: ML19317D738 (1) | |
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s DUKE POWER COhiPANY Powra Britonwo 4cc SocTn Caracu StartT, CnAntoTTE. N. C. 28242 w w A u o. *A a n c a. J a.
June 10, 1977 Vict Pats. DENT TE epa 0NC; Aa g. 70
$ttaw Decou Tion 3'3--053 Mr. Norman C. Moseley, Director j
U. S. Nuclear Regulatory Commission Suite 818 230 Peachtree Street, Northwest Atlanta, Georgia 30303 Re: Oconee Unit 1 Docket No. 50-269
Dear Mr. Moseley:
Pursuant to Sections 6.2 and 6.6.2 of the Oconee Nuclear Station Technical Specifications, please find attached Reportable Occurrence Report R0-269/
77-18.
Very ruly yours, r
g.], W Q?
us William O. Parker, Jr. d MST:ge Attachment cc: Director, Office of Management Information and Program Control I
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7912100 IO f f
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DUKE POWER COMPANY OCONEE UNIT 1 Report No.:
RO-269/77-18 Report Date: June 10, 1977 Occurrence Date: May 27, 1977 Facility: Oconee Unit 1, Seneca, South Carolina Identification of Occurrence:
Input error discovered in ECCS analysis Description of Occurrence:
On May 24, 1977, Duke Power Company was notified by NRC/0NRR of a potential problem in the Emergency Core Cooling System (ECCS) analysis which could impact all Babcock & Wilcox operating reactors. The problem, which was first identified during the review of Davis-Besse, Unit 1, is related to the U-baffles on the core barrel at the reactor coolant inlet nozzles. These U-baffles had been modified from the configuration originally assumed in the ECCS analysis, such that, the U-baffle fluid flow characteristics (pressure loss coefficients) used in the ECCS blowdown analysis are not consistent with the actual system configuration. When the appropriate U-baffle pressure loss coefficient was assumed in the case of Davis-Besse 1, the calculated peak cladding temperature (PCT) increased significantly.
Certain specific con-firmatory analyses were requested to assure continued acceptable results of the Oconee ECCS analysis.
In discussions with B&W on May 27, 1977, a determination was made that this should be a reportable occurrence pursuant to Oconee Technical Specification 6.6.2.1.a(8).
Designation of Apparent Cause of Occurrence:
The apparent cause of this concern is related to the U-baffles on the core barrel at the reactor coolant inlet nozzle.
This U-baffle design is different f
from the configuration assumed in the LOCA analysis presented in BAW-10103, "ECCS Analysis of B&W's 177-FA Lowered-Loop NSS."
This design difference affects the flow characteristics, and thus, the calculated pressure losses attributed to these baffles ~during a postulated LOCA.
Analysis of Occurrence:
This occurrence reveals an error in the flow resistance factor associated with the U-baffle in the ECCS analysis.
The correction of only this flow resistance factor would be inappropriate in light of the availability of improved design pressure distribution models for the entire Reactor Coolant System based upon actual operating experience.
This data, unavailable when the 177 fuel assembly lowered-loop analysis was submitted to the NRC, can now be used to alter and verify system pressure distributions.
These improved distributions are the basis upon which to construct future LOCA evaluations.
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a Based upon the correction of a similar error in other 177 fuel assembly raised-loop NSS, the Babcock and Wilcox Company expects that upgrading these pressure distributions to the new data will result in an insignificant increase or a decrease in calculated peak cladding temperatures for Oconee Nuclear Station.
In consideration of the expected small effect of this error.ad the margins which exist in the area of ECCS, it is concluded that contirued operation while confirmatory analyses are being conducted, will not affect the public health and safety.
Corrective Action:
Confirmatory analyses requested by NRC/0NRR are currently in progress.
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