No abstract available

[en] The principle of the eddy current testing which became one of the essential nondestructive testing for the inservice inspection of nuclear power plant was studied. An eddy current testing instrument, FD-5110-ERM (made in Japan) was purchased in August, 1978 and was used for studying the various eddy current testing methods. Because of its inherent advantage over other nondestructive testing methods for tube test, the eddy current testing became almost unique testing method for the heat exchange tube and the condenser tube in the inservice inspection of nuclear power plant. In November we had participated in the inservice inspection of Kori nuclear power plant and had accumulated the technical experience in the practical application of eddy current testing and some of the results are described in this report. (author)

[en] Various standard test samples were made for eddy current test last year ('78) and several probes of eddy current test were fabricated this year ('79). The result of some basic experiments using these probes is described in this report. A EM 3300 Multitester (made by Automation Industries, U.S.A.) was purchased, which is the fundamental instrument for the examinations of steam generator U-tubes of nuclear power plant. After some necessary experiments had been performed with this instrument, we have participated in the first inservice inspection of KORI-1 nuclear power plant (Nov., '79) and accumulated much technical experiences. Some of its test results are described in this report. (author)

[en] Since the preservice inspection of Korea Nuclear Unit-1 (KORI-1) had been performed by a foreign company in 1977, Korea has steadily localized inservice inspection technology and is now performing all the preservice and inservice inspection (PSI/ISI) work of nine units by ourselves. The main works and managements of ISI for Korea nuclear power plants (NPP) are taken by NDT Department of Korea Advanced Energy Research Institute (KAERI) with some assistance from Korean NDT companies. This paper focuses on the localization process of ISI technology and disposition experience of examination results including repairs. In addition some disputes on code interpretation and some problems occurred through ISI are discussed

[en] Failure prevention and analysis research program is on going for the steam generators, condensers and turbines of PWR's and PHWR CANDU in order to obtain analysis and evaluation technology for material failures which take place and might occur in the Korean nuclear power reactors in future. As a part of this program, failure experiences have been surveyed for steam generators, condensers and turbines of PWR's in foreign countries, and operating experiences have been surveyed for nuclear power unit 1 in Korea with PSI and ISI eddy current test data, water chemistry data and failed specimens. The Korean nuclear power unit 1 has minor denting indications and boric acid soaking has been performed in order to control the denting. The effects of this boric acid soaking on the material degradation of the PWR secondary system are being studied. Stress corrosion cracking research work is also under way for steam generator U-tubes. (Author)

[en] This report describes the experimental results of the subjects selected from the PSI/ISI related problems which encountered by us in 1982. The main contents are 1) the characteristics of the typical ECT signals from the steam generator tubes of nuclear power plant and the results of ECT evaluation of Kori-1 steam generators, 2) the experimental result for the research for directional effects of ultrasonic transducers, 3) the basic experiment for the ultrasonic testing technique by immersion testing method, 4) how to write the scan plan of the mechanized ultrasonic testing for nuclear reactor. Attached appendix is a part of necessary materials for the scan plan of the mechanized ultrasonic testing for Kori-2 nuclear reactor. (Author)

[en] The purpose of this study was to evaluate the effectiveness of a toothpaste containing bamboo salt on fluorine uptake in bovine enamel and to compare the efficiency of fluorine uptake between sodium monofluorophosphate(SMFP) toothpaste and sodium fluoride (NaF) mouthrinsing solution using proton induced γ-ray emission analysis. 30 bovine tooth enamel specimens were prepared and assigned to 5 groups as follows: specimens without any treatment, specimens which were treated with a toothpaste containing dicalcium phosphate dihydrate (DCPD) only, specimens which were treated with a toothpaste containing DCPD and SMFP, specimens which were treated with a toothpaste containing DCPD, SMFP and 2% bamboo salt, specimens which were treated with 0.05% NaF mouthrinsing solution. After 5 and 10 hours of treatment, fluorine concentration was measured at the depth of 263, 625, 2530 nm from the surface of the specimens. The surface concentration of fluorine was markedly increased using SMFP dentifrice. Bamboo salt did not encourage the uptake of fluorine into the enamel surface. NaF mouthrinsing solution showed a considerably higher uptake of fluoride in the intact enamel surface than the SMFP dentifrices. (author)

[en] The remineralization effect of fluoride has been measured by surface microhardness on tooth enamel. The purpose of this study was to investigate the relationship between microhardness and fluorine concentration on tooth enamel. Twelve sound bovine enamel specimens were prepared and immersed in 0.05% NaF solution for 1, 3, 6, 24 and 36 hours, respectively. The concentration of fluorine in specimens were measured by PIGE analysis and surface microhardness of each specimen was measured by surface microhardness tester. Fluorine concentration was increased by immersing time. There was no change in microhardness of each specimen by fluorine content. The results of this study suggest that there was no relationship between the fluorine concentration and surface microhardness in sound tooth enamel. PIGE analysis can be used effectively to assess the remineralization effect of fluorine content in tooth enamel. (author)

No abstract available

[en] Several turbine blade accidents in Korea have emphasized the importance of their adequate periodic inspection. As a typical example, a broken blade was found in the Low Pressure (LP) turbine at the 950 MWe KORI unit 3 during the 1986 overhaul after one year commercial operation. Since then the Manufacturer and the Utility company (KEPCO) have been concerned about the need of blade root inspection. The ultrasonic testing was applied to detect cracks in the blade roots without removing the blades from rotor. Due to the complex geometry of the roots, the test results could not be evaluated easily. We feel that the currently applied UT technique seems to be less reliable and more effective method of inspection must be developed in the near future. This paper describes the following items: The causes and analysis of blade damage The inspection techniques and results The remedial action to be taken (Repair and Replacement) The future plan