ML20236R146
| ML20236R146 | |
| Person / Time | |
|---|---|
| Site: | South Texas  |
| Issue date: | 07/15/1998 |
| From: | HOUSTON LIGHTING & POWER CO. |
| To: | |
| Shared Package | |
| ML20236R133 | List: |
| References | |
| NUDOCS 9807210266 | |
| Download: ML20236R146 (2) | |
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NOC-AE-000228 ATTACHMENT 5 PROPOSED CHANGES TO THE CURRENT TECHNICAL SPECIFICATION BASES l
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9007210266 900715 PDR ADGCK 05000498 P
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REACTOR COOLANT SYSTEM BASES j
STfAM GENERATORS (Continued) plants have demonstrated the capability to reliably detect degradation that has penetrated 20% of the original tube wall thickness. Repaired tubes are also included in the inservice tube inspection program.
l Exclusion of certain areas of Unit I tubes from consideration has been analyzed using an F* criteria. The criteria allows service, induced degradation deep within the tubesheet to remain in service. The analysis methodology determines the length of sound fully rolled expanded tubing required in the uppermost area within the tubesheet to preserve needed structural margins for all service conditions. The remainder of the tube, 4
below the F* distance, is considered not structurally relevant and is excluded from consideration to the customary plugging criteria of 40% throughwall.
The amount of primary to secondary leakage from tubes left in service by I
application of the F* criterion has been determined by verification testing.
This leakage has been considered in the calculation of postulated primary to secondary leakage under accident conditions. Primary to secondary leakage during accident conditions is limited such that the associated radiological consequences as a result of this leakage is ess than the 10 CFR 100 limits.
%E MN Th voltage-based repair iimits of%
op(2L 45-o5 guidance in GL 95-05 and are applicable only to Westinghl.4.5 implement use-designed steam g gso generators (SGs) with outside diameter stress corrosion cracking (ODSCC)
Nph located at the tybe-to-tube support plate intersections.P The voltage-based 7
To g M - repair limits are not applicable to other forms of SG tube degradation nor are M %. they applicable to ODSCC that occurs at other locations within the SG.
Additionally, the repair criteria apply only to indications where the 9uW N WWMg' degradation mechanism is dominantly axial ODSCC with no significant cracks extending outside the thickness of the support' plats Refer to GL 95-05 for additional description of the degradation morphology.
Implementation of SR 4.4.5 requires a derivation of the voltage structural limit from the burst versus voltage empirical correlation and then the subsequent derivation of the voltage repair limit from the structural limit (which is then implemented by this surveillance).
The voltage structural limit is the voltage from the burst pressure / bobbin voltage correlation, at the 95-percent prediction interval curve reduced to account for the lower 95/95-percent tolerance bound for tubing material properties at 650*F (i.e., the 95-percent LTL curve). The voltage structural limit must be adjusted downward to account for potential l
flaw growth during an operating interval and to account for NDE uncertainty.
is determined from the structural The upper voltage repair limit; V l
voltagelimitbyapplyingthefo1 Tow,ingequation:
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-V Y
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where V represent the allowance for flaw growth between= inspections and V
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i represeks the allowance for potential sources of error in the measurement the bobbin coil voltage. Further discussion of the assumptions necessary to determine the voltage repair limit are discussed in GL 95-05.
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l SOUTH TEXAS - UNITS 1 & 2 B 3/4 4-3 Unit 1 - Amendment No. 62r63,90 l
l Unit 2 - Amendment No. 77
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