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Information Notice No. 84-89: Stress Corrosion Cracking in Nonsensitized 316 Stainless Steel
SSINS No.: 6835 IN 84-89 UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C. 20555 December 7, 1984 Information Notice No. 84-89: STRESS CORROSION CRACKING IN NONSENSITIZED 316 STAINLESS STEEL Addressees: All boiling water power reactor facilities holding an operating license (OL) or construction permit (CP). Purpose: This information notice is provided to alert recipients of a potentially significant problem pertaining to cracking of Type 316L, low carbon stainless steel jet pump inlet riser safe ends, especially in the safe end to the thermal sleeve weld area. It is expected that recipients will review the information for applicability to their facilities and consider actions, if appropriate, to preclude a similar problem occurring at their facilities. However, suggestions contained in this information notice do not constitute NRC requirements; therefore, no specific action or written response is required. Description of Circumstances: On July 27, 1984, the Philadelphia Electric Company (PECO) reported that indications of cracks had been identified in the 12-in. jet pump inlet riser (recirculation) safe ends during pipe replacement activities at the Peach Bottom 2 plant. Liquid-dye-penetrant examination of three of the safe ends revealed circumferential indications in the safe end near the thermal sleeve attachment weld in two of the nozzles (see sketch). These indications were about 0.25 to 0.70-in. in length. A boat sample containing the tip of one of the indications was removed for examination. The safe ends are 12-in. Type 316L, low carbon stainless steel with a pipe-end wall thickness of 0.83 in. and a vessel-end wall thickness of 1.20-in. Ultrasonic examinations of the safe ends inboard of the thermal sleeve attachment weld were deferred until decontamination because radiation levels were high in this area. The configuration, required the use of special automatic ultrasonic examination equipment. Several probes with different scanning angles were used. On August 14, 1984, General Electric and PECO provided preliminary ultrasonic examination results for the 10 jet pump inlet riser safe ends. By August 20, it was ascertained by ultrasonic examination of these safe ends and both 28-in. recirculation suction safe ends that there were 14 8412050081 . IN 84-89 December 7, 1984 Page 2 of 3 shallow circumferential indications in five riser safe ends. These shallow indications were present on the noncreviced side of the weld on all five affected safe ends and on the creviced side of the weld on two of the five safe ends. The majority of the indications on the noncreviced side were about 1/2 in. long and 1/16 in. deep. The maximum reported,indication on the creviced side was about 3 in. long by less than 1/8 in. deep. One additional axial indication of undetermined length also was identified in one of these safe ends. Ultrasonic examinations did not identify any indications irk the recirculation suction safe ends. Independent ultrasonic examination of the jet pump inlet riser safe ends confirmed eight indications (seven circumferential, one axial). Additional radiographic testing and liquid-dye-penetrant examinations will be performed on the riser safe ends. GE reported that metallurgical examination of the boat sample showed that the indications were intergranular stress corrosion cracking, both on the noncreviced side and the creviced side of the weld. In addition, the cracking on the noncreviced side of the weld was associated with a surface that had been upset or cold worked. It was confirmed that the material was of low carbon content and nonsensitized. This event raised a concern that may prove to have generic implications for the following reasons: 1. The cracks are in low carbon stainless steel both in creviced and noncreviced locations. 2. This represents the first field experience where cracking has occurred in a low carbon grade austenitic stainless steel. 3. The design configuration at the safe end/thermal sleeve weld location requires the use of special ultrasonic equipment and techniques. 4. Laboratory test data has shown that cracks could occur at creviced or cold worked locations in low carbon grades of austenitic stainless steel. The NRC is continuing to review relevant design and material information for all boiling water reactors to aid in assessing generic implications. . IN 84-89 December 7, 1984 Page 3 of 3 No specific action or written response is required by this information notice. If you have any questions about this matter, please contact the Regional Administrator of the appropriate NRC regional office or this office. Edward L. Jordan, Director Division of Emergency Preparedness and Engineering Response Office of Inspection and Enforcement Technical Contacts: Warren Hazelton, NRR (301) 492-8075 Paul Cortland, IE (301) 492-4175 Attachments: 1. Sketch Showing Riser Safe End/Thermal Sleeve Attachment 2. List of Recently Issued IE Information Notices
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