United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No.80-29, Supplement 1 – Broken Studs on Terry Turbine Steam Inlet Flange

                                                          SSINS No.: 6835  
                                                          Accession No.:   
                                                          8006190028       
                                                          IN 80-29         
                                                          Supplement No. 1 

                                UNITED STATES
                       NUCLEAR REGULATORY COMMISSION 
                    OFFICE OF INSPECTION AND ENFORCEMENT 
                          WASHINGTON, D.C. 20555  
                                     
                             November 26, 1980 

Information Notice No. 80-29 (Supplement No. 1): BROKEN STUDS ON TERRY 
                               TURBINE STEAM INLET FLANGE 

Description of Circumstances: 

In the original Information Notice the failed Terry Turbine steam inlet 
flange studs were identified as probably manufactured from ASTM-A193-Grade 
B7 steel. Subsequently, the vendor has informed the NRC that the bolting 
material used at ANO-l was AISI C-1117 steel. Independent laboratory 
analyses by the NRC and Arkansas Power and Light have verified that the 
bolting material was a re-sulphurized, re-phosphorized cold drawn carbon 
steel. 

From the analysis performed, the failure was caused by high overload which 
resulted in a primarily brittle transgranular fracture (cleavage) in 
probably less than 10 cycles. This is consistent with the operating 
experience (water slugging) and the inherent low toughness of the bolting 
material used. 

Licensees are encouraged to review the materials selected for safety-related
bolting applications considering especially those situations where impact 
loadings could occur. The use of low toughness carbon steel (re-sulphurized 
free machining plain carbon steel) for bolting is discouraged by the NRC; 
particularly in situations where possible high loading conditions could be 
anticipated. 

This Information Notice is provided as an early notification of a possibly 
significant matter that is still under review by the NRC staff. It is 
expected that recipients will review the information for possible 
applicability to their facility. No specific action or response is requested
at this time. If you have any questions regarding this matter, please 
contact the Director of the appropriate NRC Regional Office. 

Page Last Reviewed/Updated Tuesday, November 12, 2013