[en] A high temperature resonant ultrasound spectroscopy(RUS) was developed. The dynamic elastic constant of RPV weld, which has various different microstructure was determined by RUS. It was confirmed the RUS method is very sensitive to the microstructures of the material. RUS can be used to monitor the degradation of nuclear materials including neutron irradiation embrittlement through the measurement of dynamic elastic constants, elastic anisotropy, high temperature elastic constant and Q-factor

[en] A high temperature, vacuum, and accurate load controlled resonant ultrasound spectroscopy(RUS) system was developed. The temperature dependency of dynamic elastic constants and ultrasonic velocity of SA 508 C1.3 RPV materials, Zr-2.5Nb pressure tube materials and Sa 106 Gr. B feeder pipe materials were measured by the RUS system. The temperature dependency of mechanical Q-factor and derivatives of resonance frequencies to temperature of ZR-2.5Nb materials ere measured and correlated to the hydrogen concentration. It was confirmed that the RUS could bo used to monitor the degradation of nuclear materials including neutron irradiation embrittlement through the measurement of dynamic elastic constnats, elastic anisotropy, high temperature elastic constant and Q-factor

[en] This report describes experimental results of a long-range inspection method of pipes using ultrasonic guided waves. In chapter 2, theory of guided wave was reviewed. In chapter 3, equipment and procedures which were used in the experiments were described. Detailed specifications of the specimens described in chapter 4. In chapter 5, we analyzed characteristics of guided wave signals according to shapes and sizes of defects and presents results of various signal processing methods

[en] Acoustic resonance scattering from a nuclear fuel rod in water is modeled with consideration of material damping of the cladding tube and pellet. The resonance spectra of the fuel rods are obtained by subtracting a rigid background from the scattered pressure. The effect of an annular gap (between the cladding tube and pellet) property is analyzed on the resonance spectra. In a water-gap fuel rod, some resonances of the cladding tube disappear and almost all resonances of the pellet can be negligible. (author)

[en] This paper presents the results of vibration and ex-core neutron noise measurements made at Ulchin-1 NPP for the first time in Korea to isolate and identify the core support barrel (CSB) motion. Neutron noise was decomposed into the global, CSB, shell mode, and CSB beam mode components by a new phase-separation algorithm based on the characteristic of Fourier transform. Vibrational frequencies of CSB, fuel assembly, reactor pressure vessel were identified from the acceleration and neutron noise signals by using the proposed algorithm. To establish the alarm level RMS of neutron noise specified in ASME code for the surveillance and diagnosis, trend of neutron noise powers has been observed since 1993. It was found that the power value linearly increased with burnup. (authors)

[en] Full text: During fabrication of a high density fuel plate such as U-Mo dispersion fuel, quality control is very important to secure the integrity of fuel elements. To check the integrity of the fuel elements, nondestructive testing methods such as x-ray radiography, eddy current testing, and ultrasonic testing methods are applied. In KAERI, we have been developing NDT methods to check the cladding thickness and interface of the fuel plate. This paper introduces ultrasonic testing methods for the cladding thickness of the fuel plate. We are applied an C-scan immersion ultrasonic inspection using pulse-echo technique, and the high frequency (50 MHz and 110 MHz) focus-type immersion transducers were used to measure the cladding thickness and inspect the interface between cladding and U-Mo fuel. The inspection results are checked with C-Scan images and measured the time-of-flight between the reflected signal from the file surface and the reflected signal from the fuel meat surface. The results showed that the ultrasonic C-Scan inspection methods using the 50 MHz transducer and 110 MHz transducer were able to measure the fuel cladding thickness, but the inspection resolution of the 110 MHz transducer was better than that of the 50 MHz transducer because it clearly differentiated the surface signal and fuel meat signal. (author)

[en] The under-sodium inspection technique using ultrasonic waveguide sensor has been developed for the in-service inspection of a reactor core and in-vessel structures in the sodium-cooled fast reactor. The 10 m long prototype ultrasonic waveguide sensor modules have been designed and manufactured for the applications of under-sodium viewing and ranging. The real-scale test facility with a 13 m H-beam structure was constructed for the feasibility tests of the prototype ultrasonic waveguide sensor modules. The inspection program has been developed for the under-sodium inspection using the prototype ultrasonic waveguide sensor modules. The performance of the ultrasonic waveguide sensor modules has been successfully demonstrated in water. A novel under-sodium ultrasonic waveguide sensor with beryllium and nickel coating layers is suggested for the enhancement of the radiation and wetting performance of ultrasonic waveguide sensor in sodium. The sodium test facility with a glove box system and a sodium tank has been designed and fabricated to carry out the performance test of under-sodium ultrasonic waveguide sensor in sodium environment condition. The sensitivity and C-scan imaging tests have been carried out in sodium for evaluating performance of the under-sodium ultrasonic waveguide sensor. (author)

[en] We investigated the flux pinning properties of both 10 mol% Zr-and Sn-doped YBa₂Cu₃O_7-δ (YBCO) films with the same thickness of ∽350 nm for a comparative purpose. The films were prepared on the SrTiO₃ (STO) single crystal substrate by the metal-organic deposition (MOD) process. Compared with Sn-doped YBCO film, Zr-doped one exhibited a significant enhancement in the critical current density (J_c) and pinning force density (F_p). The anisotropic J_c,min/J_c,max ratio in the field-angle dependence of J_c at 77 K for 1 T was also improved from 0.23 for Sn-doped YBCO to 0.39 for Zr-doped YBCO. Thus, the highest magnetic J_c values of 9.0 and 2.9 MA/cm² with the maximum F_p (F_p,max) values of 19 and 5 GN/m³ at 65 and 77 K for H // c, respectively, could be achieved from Zr-doped YBCO film. The stronger pinning effect in Zr-doped YBCO film is attributable to smaller BaZrO-3 (BZO) nanoparticles (the average size ≈ 28.4 nm) than YBa₂SnO_5.5 (YBSO) nanoparticles (the average size ≈ 45.0 nm) incorporated in Sn-doped YBCO film since smaller nanoparticles can generate more defects acting as effective flux pinning sites due to larger incoherent interfacial area for the same doping concentration.

[en] The diagnostic technique using a neutron noise analysis can be used as one of the early fault detection method for the degradation of reactor internals. The Reactor Internals Vibration Monitoring System (RIVMOS) was developed to monitor the vibration of reactor internals and detect the changes of neutron noise descriptors during surveillance and diagnostic phase. RIVMOS has been designed to comply with standards and guidelines and installed successfully at Ulchin-1 NPP (PWR) for the first time in Korea. The baseline data of ex-core neutron noise was analyzed and established during the 5. fuel cycle. The beam mode and shell mode resonance of core support barrel (CSB) will be integrity of partial thermal shields. RIVMOS provides the various noise descriptors form neutron noise signals by the time and spectral domain analysis. The system was developed on user friendly basis, particularly for plant operator. (authors)

[en] The SFR (Sodium-cooled Fast Reactor) Component Design and Balance of Plant Project is facilitating the fruitful exchange of information and the establishment of collaborations mutually beneficial to all participants. The lessons learned during upgrading of PHENIX and JOYO are of great significance and benefit to all members of the Project. The research and development of in-service inspection approaches is following three parallel paths each of which is highly innovative in its own right. Significant improvements or breakthroughs in the ability to perform in-service inspection of in-vessel sodium components may result from this ongoing work. Data needed for the evaluation of leak-before-break for Mod.9Cr1Mo ferritic steel sodium piping and components is systematically being generated. Finally, the Project is making highly significant contributions to the development and demonstration of Supercritical CO₂ (S-CO₂) Brayton cycle advanced energy conversion spanning the development and performance testing of compact heat exchangers, development and testing of small-scale S-CO₂ turbomachinery and a complete integrated cycle, sodium-CO₂ interaction testing, CO₂ oxidation and carburization tests, as well as the analysis of system behavior for SFRs incorporating S-CO₂ Brayton cycle power converters