This is the first semiannual report of the US Nuclear Regulatory Commission's Short Cracks in Piping and Piping Welds research program. The program began in March 1990 and will extend for 4 years. The intent of this program is to verify and improve fracture analyses for circumferentially cracked large-diameter nuclear piping with crack sizes typically used in leak-before-break analyses or in-service flaw evaluations. Only quasi-static loading rates are evaluated since the NRC's International Piping Integrity Research Group (IPIRG) program is evaluating the effects of seismic loading rates on cracked piping systems. Additional efforts involve investigating phenomena discovered during the course of conducting the Degraded Piping program. These include the evaluation of the occurrence of unstable crack jumps in ferritic steels at LWR temperatures, and the occurrence of anisotropic fracture properties causing helical crack growth. Both of these phenomena may affect the safety margins implicit in LBB analyses. Other investigations deal with the fracture behavior of bi-metallic welds, and improvements in crack opening area analyses used in LBB. Since much of the work in this program was just beginning during this first reporting period and progress is limited, a complete statement of work for the whole program is provided in this report. 42 refs., 14 figs., 11 tabs.

Presented herein is an Annual Report of the US NRC's Degraded Piping Program---Phase II. This is the sixth program report on this program. Prior reports were semiannual reports. The intent of this program is to experimentally validate and enhance available analytical methods for evaluating the mechanical behavior of nuclear power plant piping containing circumferentially oriented defects. Fifty-seven pipe experiments have been conducted to date. These and approximately fifty additional pipe experiments from other programs have been analyzed. In the analytical effort, a screening criterion has been developed to show when the net-section-collapse analysis is valid. This shows that even though materials such as stainless steel can fail at less than net-section-collapse loads if the pipe diameter is sufficiently large. Numerous predictive J-estimation schemes have been evaluated and modified. A finite length surface-cracked pipe estimation scheme has also been developed and incorporated into a computer code called NRCPIPE. This code provides a convenient way of analyzing cracked pipe with a number of currently accepted analytical methods. Supporting research efforts involve investigating geometry effects on J-R curves, as well as characterizing the material properties for each pipe tested. The significance of all of the efforts to date relative to pipe fracture analysesmore » and flaw assessment criteria are discussed.« less

This paper summarizes the results from the NRC Degraded Piping Program over the last year. The objective of the NRC Degraded Piping Program - Phase II, is to verify limit-load analyses and develop elastic-plastic fracture mechanics analyses methods for cracked (degraded) nuclear piping under a variety of loading conditions. These analyses are used in leak-before-break evaluations. Since experimental efforts are conducted at LWR temperatures, failure modes and metallurgical phenomena of concern are also being assessed.

Presented herein is the Fifth Semiannual Report of the US NRC's Degraded Piping Program - Phase II. The intent of this program is to experimentally validate and enhance available analytical methods for evaluating the mechanical behavior of nuclear power plant piping containing circumferentially-oriented defects. Fifty-one pipe experiments have been conducted to date. These and approximately 42 additional pipe experiments from other programs have been analyzed. In the analytical effort, a screening criterion has been developed to show when the net-section-collapse analysis is valid. This shows that even tough materials such as stainless steel can fail at less than net-section-collapse loads if the pipe diameter is sufficiently large. Numerous predictive J-estimation schemes have been evaluated and modified. A finite length surface cracked pipe estimation scheme has also been developed. Finite element analyses of specimens with welds suggest that the size of the weld relative to the specimen or structure size can affect the deformation J values. Supporting research efforts involve investigating geometry effects on J-R curves, as well as characterizing the material properties for each pipe tested.

This report is the third semiannual report of the Degraded Piping Program, Phase II. The objective of the Degraded Piping Program is to verify and improve fracture mechanics analysis for nuclear piping. The project involves the characterization of the fracture properties of typical nuclear piping materials, full-scale pipe fracture experiments, and the development and/or enhancement of elastic-plastic fracture mechanics analysis techniques. The project is now in its second year and will continue for a third year. The results of the project are expected to be of significant benefit to the nuclear industry. The following are specific examples of the potential benefits arising from improved pipe fracture behavior predictive capabilities as developed and verified through this program; the use of pipe whip restraints in piping systems can be reduced or eliminated if it can be shown that failures in these systems will always occur as leaks rather than double-ended guillotine breaks. This includes primary as well as secondary piping; leak rates resulting from the failure of circumferentially cracked pipes will become predictable allowing more realistic calculations of thrust loads for piping supports and simplifying the design of vessel core support structures; improved designs involving more flexible piping systems will be possiblemore » as the methods for prediction of instability in compliant piping systems are verified; and improved methods will be available for evaluating end-of-life defects.« less

The efforts in this report are broken into nine work packages related to pipe-fracture research efforts and three work packages that are supporting research efforts. The pipe-fracture efforts involve only circumferential crack orientations. Forty-two pipe experiments have been conducted to date, with all but two at 550/sup 0/F (288/sup 0/C). Approximately 42 additional pipe experiments from other programs were also analyzed. In the analysis effort, a screening criterion was developed to show when the net-section-collapse analysis is valid. This shows that even wrought stainless steel can fail at less than net-section-collapse loads if the pipe diameter is sufficiently large. Numerous predictive J-estimation schemes have been evaluated and modified. A finite length surface cracked pipe estimation scheme has also been developed. Finite element analyses of specimens with welds suggest that the size of the weld relative to the specimen of structure size can affect the deformation J values. Supporting research efforts involve geometry effects on J-R curves, as well as characterizing the material properties for each pipe tested.

This paper describes an ongoing program sponsored by the US Nuclear Regulatory Commission to verify and improve fracture mechanics analyses for nuclear piping. The specific objectives of each task of the program are given, as well as a brief description of some results to date. The program is now nine months into its 3-year duration. Therefore, many of the results are not conclusive to date.

It has been found that 4145 high strength steel specimens tested over a specific temperature range will be embrittled when externally wetted by pure lead. Additions of small amounts of either tin and antimony to pure lead has been found to intensify the severity of the embrittlement and to extend the critical temperature range. The effect of second element content for lead-bismuth and lead-zinc binary alloys and lead-tin-bismuth ternary alloys on the embrittlement of high strength steel was also studied. The ternary alloys were studied to determine if any solute element interactions occur. Zinc as the second element in lead binary alloys was found to be an extremely potent embrittler, and bismuth the least. In the ternary alloys, the recovery temperature was found to be dependent essentially on the tin content, with bismuth virtually having no effect. During the investigation it was found that the flux containing zinc chloride which was used to solder the lead alloys, affected the onset of the embrittlement, causing erratic behavior in the onset region.

Im MRrz 1885 kam in der hiesJgen chirurglscben Klinik folgender merkwUrdiger Fall yon Missbildung der Nase zur Beobachtung:Bei dem 5 Wochen alten Wilhelm Geile ist nur die rechte Nasen-h~lfte vollkommen entwiekelt, wiihrend die linke fehlt.Die erstere erscheint an ihrer Wurzel plattgedrUekt; ihre mediale Wand ist auf tier Aussenseite mit normaler Haut bekleidet und l~iuft naeh tier Oberlippe zu in zwei Schenkel aus, welehe eine seichte Furehe