ML20127P082
| ML20127P082 | |
| Person / Time | |
|---|---|
| Site: | Farley  |
| Issue date: | 11/25/1992 |
| From: | Woodard J SOUTHERN NUCLEAR OPERATING CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9212020043 | |
| Download: ML20127P082 (3) | |
Text
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50-348 U. S. Nuclear Regulatory Commission ATIN:
Document Control Desk Washington, DC 20555 g
Joseph M. Farley Nuclear Plant - Unit 1 Interim Pluaging Criteria Analysis Gentlemen:
By letter dated October 8,1992, the Nuclear Regulatory Commission issued Amendment 95 to the Unit 1 operating license regarding steam generator tube interim plugging criteria.
The safety evaluation required information concerning unexpected findings and steam line break leakage be reported to the Staff.
The required information is attached.
If there are any questions, please advise.
Respectfully submitted, d-'
Woodard REM:cht-ulslblkg.nrc Attachment cc:
Mr. S. D. Ebneter Mr. S. T. Hoffman 0...tuoca Mr. G. f. Maxwell 9212020043 921125 M'
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ATTACHMENT interim Plugging Criteria Analysis m
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INTERIM PLUGGING CRITERIA ANALYSIS 1.
NRC Reauest The NRC Staff will be informed of any unforeseen RPC findings relative to the characteristics of the flaws at ISPs prior to Cycle 12 operation. This includes any detectable circumferential indication or detectable indications extending outside the thickness of the TSP. A safety analysis of the unexpected findings will also be provided.
Southern Nuclear Responst No indications at tube support plates (TSPs) were identified that had cracks exteijing outside the TSPs by either the bobbin or RPC inspections.
In addition, the characteristics of the bobbin and RPC inspection results were typical of that found in earlier f arley-1 steam generator inspections. That is, no abnormal degradation such as circumferential1y oriented indications were found at the TSPs in the 1992 Unit 1 inspection.
2.
NRC Reouest The Monte Carlo evaluation for steam line break leakage will be updated to consider the distribution of voltages for indications satisfying the 1 volt criterion during the eleventh refueling outage inspection.
The analysis will also reflect the distribution of voltage changes observed during cycle ll, in addition to the Monte Carlo analysis, the 1.0 gpm leak rate at end of cycle for steam line break will be verified by a deterministic calculation method.
SNC Res2 pass Steam generator C, with the highest voltage indications left in service, is the limiting steam generator for the steam line break analysis.
The end of cycle sisam line break leak rate is estimated to be 0.0 gpm by both deterministic and Monte Carlo methods utilizing a steam line break leakage threshold of 2.5 volts.
if the conservative assumption of no leakage threshold is applied, the Monte Carlo analysis predicts a 0.04 gpm leak rate.
All leakage predictions were made utilizing updated growth rates for Unit 1.
Therefore, a large margin exists against the allowable steam line break leak rate limit of 1.0 gpm.
As previously discussed with the Staff, indications above 1.0 volt which were left in service (no RPC flaws) were not included in the steam line break leakage analysis.
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