A FAILURE RATE DATA MANUAL HAS DEVELOPED WHICH CAN BE USED IN RISK AND RELIABILITY ANALYSIS OF REACTOR SYSTEMS THE MANUAL CONTAINS FAILURE RATES AND FAILURE MODE INFORMATION FOR OVER 1,000 ELECTRICAL, ELECTRONIC AND SENSING COMPONENTS USED IN NUCLEAR POWER PLANTS. A METHOD IS GIVEN FOR COLLECTING AND PRESENTING RELIABILITY DATA FOR QUANTITATIVE RELIABILITY AND AVAILABILITY OF SAFETY-RELATED NUCLEAR PLANT SYSTEMS. UNCERTAINTY BOUNDS ARE ALSO GIVEN FOR EACH ESTIMATE OF A COMPONENT FAILURE RATE. THIS WORK IS PART OF A CONTINUING EFFORT TO ESTABLISH AN INTERIM DATA BASE FOR USE IN MEETING NRC NEEDS IN THE ELECTRICAL AND ELECTRONIC AREA UNTIL SIGNIFICANT OPERATING DATA ON COMPONENTS USED IN THE NUCLEAR INDUSTRY BECOME AVAILABLE.

THE DATA IS DIFFICULT TO INTERPRET BECAUSE OF THE MANY AMBIGUITIES AND INCONSISTENCIES IN THE DATA MANUAL. THE RELATION OF THE AGGREGATED FAILURE RATES TO THE COMPONENT FAILURE RATES IS NOT MADE CLEAR AND THEY ARE OFTEN INCONSISTENT. IN PARTICULAR, THE USE OF GEOMETRIC AVERAGING IS NOT JUSTIFIED AND LEADS TO INCONSISTENT RESULTS. THE WAY IN WHICH HIGH AND LOW FAILURE RATES ADD UP IS NOT CONSISTENT WITH THEIR STATED INTERPRETATION AS 95TH AND 5TH PERCENTILES OF THE FAILURE RATE DISTRIBUTION. THE EQUALITY OF THE HIGH VALUE TO THE MAX VALUE IN MANY TABLES IS ALSO INCONSISTENT WITH THIS INTERPRETATION. THE FAILURE MODE TYPES AND DEFINITIONS GIVEN EXCLUDE SUDDEN PARTIAL FAILURES AND GRADUAL COMPLETE FAILURES, BOTH OF WHICH ARE EXPERIENCED IN PRACTICE.

THE SUBJECT RIL ANNOUNCED THE AVAILABILITY OF A FAILURE RATE DATA MANUAL THIS DATA SUPPLEMENTS OTHER SOURCES OF RELIABILITY DATA
SUCH AS THE REACTOR SAFETY STUDY. SUCH DATA ARE BEING USED IN RELIABILITY STUDIES THAT SUPPORT OR PROVIDE THE BASES FOR
LICENSING REQUIREMENTS.

THIS DATA MANUAL PROVIDES THE STRUCTURE FOR INCORPORATING NEW OR REVISED DATA AS IT BECOMES AVAILABLE. THE MANUAL NOW CONTAINS UNDIFFERENTIATED HARD AND SOFT DATA WHICH IS A SERIOUS IMPEDIMENT TO THE APPLICATION OF THIS DATA. THEREFORE, CONTINUING WORK IS REQUIRED TO INCREASE THE CONTENT OF HARD DATA BY INCORPORATING THE DATA DEVELOPED THROUGH SUCH PROGRAMS AS NPRDS.

MODIFICATIONS IN THE OCTAVIA COMPUTER CODE REPORTED IN RIL 10 WERE MADE. THESE MODIFICATIONS INCLUDE A CAPABILITY TO HANDLE
RESIDUAL STRESS IN A REACTOR PRESSURE VESSEL WHICH CAN EITHER BE CONSTANT, OR VARY WITH FLAW SIZE; THE CODE USER CAN IMPOSE AN
UPPER BOUND ON THE VESSEL TOUGHNESS AND THE CODE HAS THE CAPABILITY TO HANDLE UNCERTAINTIES IN THE TOUGHNESS. USING THE MODIFIED
OCTAVIA CODE, THE MEDIAN FAILURE PROBABILITY FOR THE SURRY REACTOR PRESSURE VESSEL WAS CALCULATED TO BE 5 X 10-7 PER VESSEL YEAR
3 X 10-5 PER VESSEL YEAR AFTER 40 YEARS.
FOR AN OPERATING TEMPERATURE OF 110 DEGREES C AND THE CURRENT AGE OF APPROXIMATELY 2.5 YEARS. THE FAILURE PROBABILITY INCREASES TO

THIS IS A MODIFICATION OF RESULTS TRANSFERRED BY RIL 010, 02-25-77. THE ANALYSES USING THE OCTAVIA CODE ARE COMPLETE. THE GENERIC
PRESSURE TRANSIENT PROTECTION FOR PRESSURIZED WATER REACTORS.'
POSITIONS REGARDING OVERPRESSURIZATION PROTECTION SYSTEMS HAVE BEEN DEVELOPED AND ARE DOCUMENTED IN NUREG-0224, REACTOR VESSEL
IMPLEMENTATION OF THE POSITIONS ARE UNDERWAY.

A VERIFIED MODEL IS PRESENTED FOR PREDICTING RESIDUAL STRESSES RESULTING FROM THE WELDING OF PIPES, AND THE ESTIMATION OF RESIDUAL STRESSES RESULTING FROM WELD REPAIRS OF REACTOR PRESSURE VESSELS. THE MODEL CAN BE USED IN THE LICENSING PROCESS TO AID IN THE EVALUATION OF CRACKING THAT HAS OCCURRED IN GIRTH-BUTT WELDS IN PIPING. IT SHOULD ALSO PROVE TO BE USEFUL IN ANY SAFETY EVALUATION OF PROPOSED REPAIRS BY WELD BUILDUP IN THE CORNER REGIONS OF PRESSURE VESSEL NOZZLES AFTER CRACKS HAVE BEEN REMOVED, AND IN VESSEL WELD REPAIRS.

THE AXISOL CODE COULD BE USED AS AN AID IN EVALUATING RESIDUAL STRESSES IN FLUID HEAD-PROCESS PIPE WELDS OF CONTAINMENT PENETRATION
ASSEMBLIES AND GIRTH BUTT WELDS IN PIPING. IT SHOULD ALSO PROVE USEFUL AS AN AID IN DEVELOPING THE NECESSARY DECISIONAL INFORMA-
TION IN ANY SAFETY EVALUATION OF PROPOSED WELD REPAIRS.

THE COMPUTER CODE AXISOL COULD EVENTUALLY BE USED AS A DESIGN TOOL BY BOTH GOVERNMENT AND INDUSTRY, TO IMPROVE WELDING TECHNIQUES
AND PROCEDURES. THE RESULTS OF THIS PROGRAM SHOULD BE BROUGHT TO THE ATTENTION OF VARIOUS ASME GROUPS ENGAGED IN PREPARING CODES
AND STANDARDS ON WELDED FABRICATION AND INSPECTION PROCEDURES. THOROUGH DISCUSSION AND EVALUATION BY SUCH GROUPS AND CONSIDERABLE
TRIAL USE BY INDUSTRY IS NECESSARY BEFORE FULL APPLICATION OF THE CODE IN THE LICENSING PROCESS WOULD BE APPROPRIATE. THE
INABILITY OF THE CODE TO TAKE INTO ACCOUNT THE EFFECTS OF POST-HELD HEAT TREATMENT, AT THIS TIME, IS A DRAWBACK IN UTILIZING THE
CODE IN THE LICENSING PROCESS.