United States Nuclear Regulatory Commission - Protecting People and the Environment


LICENSEE: ITT INDUSTRIES                     

SITE: ITT INDUSTRIES                        EN NUMBER:32612

DOCKET:                                  EVENT DATE: 07-11-97

RX TYPE:                                 EVENT TIME: 12:00

VENDORS:                                NOTIFY DATE: 07-11-97

EMERGENCY CLASS: N/A  REGION: 4 STATE: CA      TIME: 17:45

OPS OFFICER: JOHN MacKINNON           

10 CFR SECTION: CDEG  21.21(c)(3)(i)      DEFECTS/NONCOMPLIANCE



WITHDRAWAL OF POTENTIAL 10 CFR PART 21 SAFETY CONCERN            

                                                                 

THE ORIGINAL 10 CFR PART 21 NOTIFICATION CAN BE FOUND IN EN      

31570. HOWEVER, THE FINAL SUPPLEMENT TO THE ITT BARTON 10 CFR    

PART 21 NOTIFICATION IS PROVIDED IN DETAIL.                      

                                                                 

THE FOLLOWING TEXT IS FROM A FACSIMILE SUBMITTED BY ITT:         

                                                                 

"THIS NOTIFICATION IS PROVIDED AS SUPPLEMENTARY INFORMATION TO   

THE 10 CFR PART 21 NOTIFICATION FILED BY THE V. C. SUMMER NUCLEAR

STATION (DOCKET NUMBER 50/395) IN THEIR LICENSING EVENT REPORT   

(LER) NUMBER 96-007, REV. 2,                                     

SUBMITTED TO THE U.S. NUCLEAR REGULATORY COMMISSION BY SOUTH     

CAROLINA ELECTRIC AND GAS LETTER NUMBER RC-97-0027 DATED JANUARY 

30, 1997, AND ITT BARTON SUPPLEMENTARY INFORMATION ON THIS ISSUE 

DATED DECEMBER 13, 1996."                                        

                                                                 

"ITT BARTON SUPPLIES MODEL 763 AND 763A GAGE PRESSURE ELECTRONIC 

TRANSMITTERS TO THE COMMERCIAL NUCLEAR POWER INDUSTRY AS BASIC   

COMPONENTS FOR USE IN SAFETY-RELATED APPLICATIONS. WE PREVIOUSLY 

REPORTED (DECEMBER 13, 1996) A SITUATION INVOLVING SOLDERING     

INDUCED EMBRITTLEMENT OF STRAIN GAGE LEAD WIRES AS POSSIBLY      

REPRESENTING A POTENTIAL SIGNIFICANT SAFETY HAZARD."             

                                                                 

"THE WIRE EMBRITTLEMENT OCCURS DURING THE SOLDERING OF THE 10    

STRAND #40AWG COPPER LEADS THAT CONNECT THE VARIABLE RESISTANCE  

STRAIN GAGES TO THE REMAINDER OF THE ELECTRONIC CIRCUIT. THIS    

EMBRITTLEMENT INVOLVES A METALLURGICAL REACTION BETWEEN THE      

COPPER WIRE AND THE TIN BASED SOLDER USED TO MAKE THE            

CONNECTIONS. WHILE A THIN LAYER OF THIS INTER-METALLIC COMPOUND  

IS NATURALLY PRODUCED DURING THE METALLURGICAL BONDING PROCESS,  

AS THE THICKNESS OF THE LAYER INCREASES, COPPER IS CONSUMED, AND 

THE MECHANICAL INTEGRITY OF THE JOINT IS REDUCED. THE DYNAMICS OF

THE INTER-METALLIC MATERIAL GROWTH ARE INFLUENCED BY A NUMBER OF 

FACTORS WHICH INCLUDE THE AMOUNT OF TIN AND OTHER ELEMENTS IN THE

SOLDER, THE SOLDERING TEMPERATURE, AND THE DURATION OF THE HEAT  

EXPOSURE."                                                       

                                                                 

"ITT BARTON WAS INITIALLY CONCERNED THAT INSTRUMENTS WITH        

EXCESSIVE WIRE EMBRITTLEMENT MAY NOW BE IN USE FOR SAFETY-RELATED

APPLICATIONS WHICH MAY FAIL WHEN SUBJECTED TO HIGH VIBRATIONAL   

STRESSES EXPERIENCED DURING NUCLEAR POWER PLANT DESIGN BASIS     

EVENTS. HOWEVER, AFTER VERY METICULOUS EVALUATION, WE HAVE       

CONVINCED OURSELVES THAT, EVEN UNDER THE WORST CREDIBLE SOLDERING

CONDITIONS, THE STRENGTH OF THE STRAIN GAGE LEAD WIRES HAS A     

SAFETY FACTOR OF AT LEAST 200 TO 1 WHEN SEISMIC INDUCED LOADING  

CONSISTENT WITH OUR 12 g SEISMIC QUALIFICATION [IS] CONSIDERED.  

THIS FINDING IS CONSISTENT WITH THE RESULTS OF THE SEISMIC       

QUALIFICATION TESTING PERFORMED ON THESE TYPE[S] OF INSTRUMENTS  

BY BOTH ITT BARTON AND WESTINGHOUSE WHERE NOT ONE OF THE TEST    

SPECIMENS WAS FOUND TO HAVE STRAIN GAGE LEAD WIRE FAILURE."      

                                                                 

"AS A MATTER OF PRUDENCE, ITT BARTON IS IMPLEMENTING A DESIGN    

CHANGE THAT WILL SUBSTANTIALLY IMPROVE THE STRUCTURAL INTEGRITY  

OF THE SOLDERED WIRE JOIN AND LIMIT THE SUSCEPTIBILITY OF THE    

JOINT TO MECHANICAL FATIGUE THAT MIGHT BE INDUCED BY FIELD       

CALIBRATION PERSONNEL WHILE INSPECTING THE INTERNALS OF THE      

INSTRUMENT. BECAUSE THIS DESIGN CHANGE CANNOT BE RETROFITTED INTO

EXISTING FIELD UNITS, ITT BARTON WILL ISSUE AN INDUSTRY ADVISORY 

LETTER TO OUR CUSTOMERS WARNING THEM OF THE SENSITIVITY OF THE   

WIRES TO MECHANICAL DAMAGE AND CAUTIONING THAT INSTRUMENT        

INSPECTIONS NOT INVOLVED PHYSICAL CONTACT WITH THE EXPOSED STRAIN

GAGE LEAD WIRES."                                                

                                                                 

"BASED ON THIS RECENT EVALUATION (DOCUMENTED IN A FORMAL         

ENGINEERING REPORT AVAILABLE FOR AUDIT/REVIEW AT OUR FACILITIES),

ITT BARTON IS PLEASED TO ANNOUNCE THAT OUR CONCERNS HAVE BEEN    

ALLEVIATED, AND WE FORMALLY WITHDRAW OUR NOTIFICATION OF THIS    

POTENTIAL 10 CFR [PART] 21 SAFETY CONCERN. ITT BARTON NOW        

CONSIDERS THIS ISSUE CLOSED."                                    



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