United States Nuclear Regulatory Commission - Protecting People and the Environment

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 



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                                                        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. 


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                                                        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 
Page Last Reviewed/Updated Tuesday, November 12, 2013