Improved Bayesian Update Method on Flaw Distributions Reflecting Non-Destructive Examination Result

2006 ◽

Author(s):

Yasuhiro Yuguchi ◽

Taiji Hirasawa

Keyword(s):

Phased Array ◽

Water Immersion ◽

Crack Depth ◽

Immersion Method ◽

Power Company ◽

Examination Result ◽

Flat Type ◽

Visual Testing ◽

Non Destructive ◽

Reactor Internals

This paper describes development and application of Phased Array Ultrasonic Testing (UT) and Remotely Operated Vehicles (ROV) for In-Vessel Internals Inspection. Stress Corrosion Crack (SCC) on reactor internals is one of the most important issues since 1990s, and demand to inspect the reactor internals is increasing. Instrument manufactures and inspection venders have developed and applied 1) Phased Array UT technologies and technique as one of our Non-Destructive Examination (NDE) technologies, 2) several kinds of ROVs and special tools for probe delivery and positioning. They are available and effective in In-Vessel Inspection (IVI) and maintenance, which shall be conducted in the narrow room under water. Furthermore, the UT technique for Alloy 182 weld that used to be difficult to detect and size flaws was developed and deployed in the BWR IVI. UT experiences in reactor vessels are increasing in recent years. An immersion technique by Phased Array UT is a key to perform the In-vessel UT on a complex geometric surface to be inspected, and to achieve very wide accessible range by ROVs or simple special tools efficiently. Advantages of the water immersion method and a ROV development result are shown in this paper. Particularly, TOSHIBA developed a flat type ROV for Shroud (Shroud ROV), which can be held against the surface of the shroud by thrusting propellers and scan mechanically through narrow gap within 2 inches {50mm}. The ROV’s positioning accuracy and applications for Shroud UT are shown. As the field experience, this introduces the UT results for CRD Stub tube Alloy 182 weld that is located on the vessel bottom head in Hamaoka UNIT 1 of Chubu Electric Power Company in Japan. An axial SCC flaw was detected by underwater visual testing, after the CRD stub tube leakage was detected. Then UT examination for the flaw was accomplished on the Alloy 182 weld in the vessel. We evaluated that the flaw penetrated into the weld metal of the CRD stub tube-pat weld and didn’t propagate into the low alloy of Reactor Pressure Vessel base metal. After UT sizing, the CRD stub tube was removed and replaced. The examination result was proven to have a good agreement with the actual crack depth. As a result, the efficiency of our Phased Array Technique was confirmed. As the other immersion method application, UT coverage example and accessible range for Shroud inspection are shown.

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Improved Bayesian Update Method on Flaw Distributions Reflecting Non-Destructive Inspection Result

Volume 1: Codes and Standards ◽

10.1115/pvp2020-21430 ◽

2020 ◽

Author(s):

Jinya Katsuyama ◽

Yuhei Miyamoto ◽

Kai Lu ◽

Akihiro Mano ◽

Yinsheng Li

Keyword(s):

Likelihood Function ◽

Bayesian Updating ◽

Pressure Vessels ◽

Irradiation Embrittlement ◽

Failure Frequency ◽

Likelihood Functions ◽

Pressurized Thermal Shock ◽

Bayesian Update ◽

Non Destructive ◽

Reactor Pressure

Abstract We have developed a probabilistic fracture mechanics (PFM) analysis code named PASCAL4 for evaluating the failure frequency of reactor pressure vessels (RPVs) through consideration of neutron irradiation embrittlement and transients such as pressurized thermal shock events. It is well-known that flaw distributions, including flaw size and density, have an important role in the failure frequency calculations of a PFM analysis. NUREG-2163 report provides a methodology to obtain much more realistic flaw distributions based on a Bayesian updating approach by reflecting the non-destructive inspection (NDI) results, which is applicable for case when there are flaw indications through NDI. There may, however, be no flaw indications resulting after inspection of some RPVs. Therefore, we proposed likelihood functions applicable for both cases when flaws are detected and when there is no flaw indication as the NDI results. In the Bayesian updating method, the likelihood functions were applied to independently acquire the posterior distributions of flaw depth and density using the same NDI results. In this study, we further improve the likelihood functions to enable them to update flaw depth and density simultaneously. Based on this improved likelihood function, several application examples are presented where the flaw distributions are estimated by reflecting the NDI results through Bayesian update. In addition, PFM analyses are also performed considering those estimated flaw distributions. All the results indicate that the improved likelihood functions are useful for estimating flaw distributions.

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Luminescence from individual dislocations in II-VI and III-V semiconductors

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100088488 ◽

1991 ◽

Vol 49 ◽

pp. 834-835

Author(s):

J W Steeds

Keyword(s):

Group Iv ◽

Luminescence Properties ◽

Carrier Recombination ◽

Transmission Electron ◽

Wide Range ◽

Basic Physics ◽

Semiconducting Compounds ◽

Diamond Group ◽

Non Destructive ◽

Technological Significance

There is a wide range of experimental results related to dislocations in diamond, group IV, II-VI, III-V semiconducting compounds, but few of these come from isolated, well-characterized individual dislocations. We are here concerned with only those results obtained in a transmission electron microscope so that the dislocations responsible were individually imaged. The luminescence properties of the dislocations were studied by cathodoluminescence performed at low temperatures (~30K) achieved by liquid helium cooling. Both spectra and monochromatic cathodoluminescence images have been obtained, in some cases as a function of temperature.There are two aspects of this work. One is mainly of technological significance. By understanding the luminescence properties of dislocations in epitaxial structures, future non-destructive evaluation will be enhanced. The second aim is to arrive at a good detailed understanding of the basic physics associated with carrier recombination near dislocations as revealed by local luminescence properties.

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Forensic Identifications Aided by Scanning Electron Microscopy of Silicone-Epoxy Microreplicas of Calcified and Cornified Structures

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100117017 ◽

1975 ◽

Vol 33 ◽

pp. 678-679 ◽

Cited By ~ 3

Author(s):

R.F. Sognnaes

Keyword(s):

Electron Microscopy ◽

Scanning Electron Microscopy ◽

Forensic Science ◽

George Washington ◽

Epithelial Surface ◽

Extended Application ◽

Tissue Surfaces ◽

Non Destructive ◽

Scanning Electron ◽

Surface Changes

Sufficient experience has been gained during the past five years to suggest an extended application of microreplication and scanning electron microscopy to problems of forensic science. The author's research was originally initiated with a view to develop a non-destructive method for identification of materials that went into objects of art, notably ivory and ivories. This was followed by a very specific application to the identification and duplication of the kinds of materials from animal teeth and tusks which two centuries ago went into the fabrication of the ivory dentures of George Washington. Subsequently it became apparent that a similar method of microreplication and SEM examination offered promise for a whole series of problems pertinent to art, technology and science. Furthermore, what began primarily as an application to solid substances has turned out to be similarly applicable to soft tissue surfaces such as mucous membranes and skin, even in cases of acute, chronic and precancerous epithelial surface changes, and to post-mortem identification of specific structures pertinent to forensic science.

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