Part 21 Report - 1997-121

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."

Page Last Reviewed/Updated Friday, January 31, 2020