PNO-V-93-017, on 930922,util Informed NRC That re-review of Eddy Current Test Data Identified Midspan Indications in Two Tubes in Unit 3 SG31.Review Being Performed to Determine If Nonquantifiable Indications Exist.Telcon W/Nrc Scheduled
| ML20057E793 | |
| Person / Time | |
|---|---|
| Site: | Palo Verde  |
| Issue date: | 09/22/1993 |
| From: | Ang W NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| To: | |
| References | |
| PNO-V-93-017, PNO-V-93-17, NUDOCS 9310130156 | |
| Download: ML20057E793 (2) | |
September 22, 1993 PRELIMINARY NOTIFICATION OF EVENT OR UNUSUAL OCCURRENCE PNO-V-93-017 This preliminary notification constitutes EARLY notice of events of POSSIBLE safety or public interest significance. The information is as initially recalved without verification or evaluation, and is basically all that is known by the Region V staff on this date.
Fncility Licensee Emercency Classification Arizona Public Service Co.
Notification of Unusual Event Palo Verde 3 Alert Wintersburg, Arizona Site Area Emergency Dockets: 50-530 General Emergency X Not Applicable
Subject:
EXISTING MIDSPAN STEAM GENERATOR TUBE DEFECT REPORTED At approximately 1:30 p.m. PDT on September 22, 1993, Arizona Public Service Company (APS) informed NRC Region V and NRR that re-review of existing Eddy current Test (ECT) data had identified midspan indications in two tubes in Unit 3 Steam Generator Number 1 (SG31). Unit 3 was operating at 100% power.
During the recently completed Unit 2 outage, the licensee identified midspan axial cracks that were not revealed by the use of a standard bobbin ECT coil, but were found using a motorized rotating pancake coil (MRPC).
An axial flaw caused a SG tube rupture in Unit 2 on March 14, 1993.
An effort to characterize defects identified during past Palo Verdo inspections was being accomplished by APS to develop a Palo Verde Steam Generator fault model in preparation for tube inspections in Unit 1 during that unit's present refueling.
This effort involved a re-review of ECT data (both Bobbin and MRPC) obtained during past outages.
Re-review of data obtained in October 1992 identified the following previously unidentified indications in SG31. No new indications were identified in Unit 1 SGs or in Unit 3 SG32.
Unit 2 recently completed extensive SG tube inspections.
Unit 3 Steam Generator Number 1 Tube 114-135 - one midspan indication located at hot leg support plate 08H + 36" approximately 0.2" long. This tube was plugged for I
other reasons during the 1992 outage.
Tube 99-148 - one midspan indication located at batwing + 4" approximately 0.3" long. This tube was not plugged.
APS reported that the above indications could not be readily defined as i
i axial cracks because the probe used during the inspection was a single coil MRPC probe vs multiple coils. APS also reported that the re-review also showed evidence of tube bowing and deposits on the tubes.
The licensee's plant review board has been provided the data noted above. APS is performing a review of approximately 3,000 Unit 3 SG tubes using the current ECT data screening criteria to determine if any pattern of non quantifiable indications exists.
A telephone discussion between APS and NRC Region V and NRR has been hO 5693093d'~~
I PNO-y-93'Oll
~7pg PDR