Kwang Pyo Hong

Assessment of the Uncertainty and the Proficiency Test for Accrediting KOLAS of ISO 17025 for a Neutron Radiography Facility

KOLAS(Korea of Lab Accreditation Scheme) is the charter member of ILAS (International Lab Accreditation Scheme) and APLAS( Asia Pacific Lab Accreditation Scheme), which originates from ISO 17025. KATS (Korea Agent of Technology Standard) governs the KOLAS. The KOLAS describes the basis of satisfying those issues related to a quality assurance and management system. The requirements specify an organization, the accommodation and environmental conditions, an uncertainty in the measurement and an inter-laboratory comparison or proficiency test program. The evaluation process of the requirements of certifying KOLAS for HANARO NRF has been proceeded by a neutron radiography laboratory. NRT Level II course of SNT-TC-1A II is opened, with 20 persons attending for certification. An inter-laboratory comparison or proficiency test program is conducted through with Kyoto University in accordance with ASTM Method for Determining the Imaging Quality in Direct Thermal Neutron Radiographic Testing (E545-91). In order to determine the uncertainty, dimensional measurements for the calibration fuel pin of the RISO using a profile project is performed with the ASTM Practice for Thermal Neutron Radiography of Materials (E748-95) Introduction A neutron radiography facility(NRF) for non-destructive testing was installed at the NR port, one of the eight tangential beam ports of HANARO, a 30MW high flux research reactor. Neutron radiography was carried out at the research reactor TRIGA MARK-III, 2MW in the early 1980s. It was developed in compliance with the nuclear fuel development program in KAERI for one of the post-irradiated fuel test methods. In a variety of inspections in the hot-cell laboratory, the fuel soundness and dimensional assessment of fuel elements and tubes were tested. As for the nonnuclear applications, many diverse tests and trials on explosives, detonators, metallic molds corrosions detection and archeological objects, were conducted. As the industry in Korea is requiring more advanced technologies to be developed, neutron radiography techniques are applied and expanded for a variety of industries. Among the recent results in this trend, micro defect finding in turbine blades, tests of soldering and the alignment of an optical microchip, as well as the test of the lithium-ion density of the cellular phone batteries and archeological objects have been conducted. As part of the quality assurance in these of inspections, KAERI’s neutron radiography laboratory has prepared the evaluation process for the accrediting in KOLAS[1]. Status of HANARO NRF The in-pile collimator is a divergent type. In order to avoid gamma-ray and fast neutron contamination, a collimator beam tube was inserted at a direction tangential to the reactor core. Its neutron beam inlet, having an aperture hole of a diameter of 25mm, is mounted by three 10mm thick sheets of sintered boron carbide(B4C) and inserted between two thin aluminum plates. The inside of the whole beam channel is lined with boron rubber in order to prevent the neutron beam reflection. A Collimator beam tube was designed by the consideration of two important factors such Key Engineering Materials Online: 2004-08-15 ISSN: 1662-9795, Vols. 270-273, pp 1382-1386 doi:10.4028/www.scientific.net/KEM.270-273.1382

SANS Study of Precipitate and Recrystallization in Ti-Added Extra Low Carbon Steels

Effects of precipitation on the recrystallization behavior of three Ti-added extra low carbon sheet steels were compared. The recrystallization temperature of the high Ti-containing steel is higher than that of the low Ti-containing steel. Small angle neutron scattering (SANS) measurements were performed both for cold rolled samples and for annealed samples. The size distribution and the volume fraction of the nano-sized precipitates were quantitatively determined from the corrected scattering curves using a direct model fitting with a sphere. SANS results revealed no additional carbo-nitrides precipitation during the recrystallization annealing procedure in the low Ti-containing steel. However, in the high Ti-containing steel, new TiC precipitates smaller than 10 nm formed during the recrystallization annealing process. This dynamic interaction of the precipitation of the fine TiC particles with the recovery of dislocations seems primarily responsible for the retardation of the recrystallization in the high Ti-containing extra low carbon steel.

Quantitative Phase Analysis of the Multi-Phase Alloys Using Neutron Diffraction

Alloys including steels usually consist of more than two phases, and the volume fraction of each phase in the materials is closely related to their physical properties. Therefore, accurate data of the volume fraction of each phase in the materials is very useful to control the mechanical properties of the materials. Based on the Rietveld profile refinement of the neutron diffraction patterns and a new texture analysis, a quantitative phase analysis (QPA) method is proposed and examined in artificially produced multi-phase alloys having strong textures. The preferred orientation factors (POFs) of the diffraction peaks was extracted from the inverse pole figure calculated from the orientation distribution function (ODF) that was computed from the averaged pole figures measured by the rotating sample stage providing a faster and simpler texture measurement. The reliability of this method was examined in binary alloy mixtures of known fractions for the zirconium and aluminum. In addition, we applied the QPA method to the evaluation of the amount of retained austenite in a commercial steel strip.

Development of a Neutron Tomography at HANARO

A thermal neutron tomography set-up has been installed and some initial results are acquired at the research reactor HANARO of the KAERI ( Korea Atomic Energy Research Institute ). The detection system is based on a NE 426 ( 6 LiF/ZnS:Ag ) conversion screen and a CCD camera. The current beam flux and the efficiency of the detector result in about about 1 min exposure time for a single projection image of normal samples. Hence, a typical set of tomography scans can be carried out in about 3 hour. Then, 3D computed tomography objects were calculated using the conventional filtered back-projection reconstruction method after some post-processing of the raw data. Initial results of the various samples show that the neutron tomography system at HANARO can be a useful tool for several fields such as aerospace, construction material, agricultural industry and so on.