We have characterized Zn_1–xCo_xO thin films grown on sapphire (0001) substrates by pulsed laser deposition. We have found for x = 0.25 that inhomogeneous Zn_1–xCo_xO films with wurtzite ZnO phase mixed with rock-salt CoO and hexagonal Co phases are formed when the growth temperature (T_g) is relatively high (⩾600 °C) and the O<sub<2 pressure (Po₂) is fairly low (⩾10^–5 torr). The presence of the Co clusters leads to room temperature ferromagnetism. Homogeneous Zn_1–xCo_xO alloy films with wurtzite structure are predominantly paramagnetic. High-quality epitaxial Zn_1–xCo_xO alloy films are formed at a growth condition of T_g= 600 °C and Po₂ = 10–5 torr. Under this optimized growth condition, Co can be dissolved into ZnO up to around 40%. Photoluminescence spectra and electrical properties of Zn_1–xCo_xO strongly depend on the Co content.

Pressure drop across the moisture separator installed in the steam generator of a nuclear power plant affects the power generation efficiency, and so accurate pressure drop prediction is important in generator design. In this study, an empirical correlation is proposed for predicting the two-phase pressure drop through a moisture separator. To ensure the applicability of the correlation, a series of two-phase air-water experiments were performed, and the results of the present test and of the benchmark test of high-pressure steam-water were used in developing the correlation. Based on the experimental results, quality, dimensionless superficial velocity, density ratio of the working fluid, and the geometrical factor were considered to be important parameters. The two-phase pressure drop multiplier was expressed in terms of these parameters. The empirical correlation was found to predict the experimental results within a reasonable range.

The most important design parameters of a moisture separator to optimize the efficiency of a nuclear power plant are the moisture carry over and pressure drop. An air-water test facility was constructed to evaluate the design parameters for various types of conventional moisture separators in Korea. In this study, a half scale of swirl-vane separator was designed, and test conditions were defined based on the scaling law to cover a wide range of operating conditions. The moisture carry over was measured using an isokinetic sampling system for 34 different flow conditions. The MCO was in range of 0.30–7.05% according to the test conditions. Single and two-phase flow experiments were also carried out to identify the two-phase pressure drop characteristics. Based on the obtained results, the proposed empirical correlation model was extended to a submerged separator and applying these results to a full scale system is discussed in this paper.

The moisture carryover (MCO) of the primary separator in a steam generator is the most important design parameter to ensure high efficiency in a steam generator. There is an inherent limitation to experimentally evaluate the MCO under the prototype conditions. In this study, the air/water test facility was constructed based on the similarity law, and a new isokinetic system was developed to quantify the MCO. Several experiments were performed for the mass quality ranging from 0.315 to 0.382. The accuracy and versatility of the experimental method was verified experimentally using a full and half scale of separators. The test results were compared with the prototype results. It was proved to be a reliable experimental method for evaluating the MCO of the moisture separator.

The pressure drop of the moisture separator in a steam generator is the important key parameter to design the moisture separator and ensure the efficiency of a nuclear power plant. In this research, the low pressure air/water test facility was constructed to simulate the steam/water condition for the full-scale moisture separator. The experimental method based on the similarity law was presented and the pressure drop was measured for a mass quality ranged from 0.269 to 0.538 using the air/water test facility. The obtained results were verified by comparing with the results of the prototype condition. It is discovered that the viscosity ratio and two-phase centrifugal force are the factors influencing the pressure drop.

The advanced thermal-hydraulic test loop for accident simulation (ATLAS) was developed and operated at The Korea Atomic Energy Research Institute. The ATLAS is operated to simulate accidents in pressurized water reactors (PWRs). A domestic standard problem (DSP) using the ATLAS was proposed for transferring the database of the integral effect test to Korean nuclear researchers and developing the safety analysis methodology of PWRs. The fourth DSP (DSP-04) exercise was performed during 2015–2017 with 15 participants (13 organizations), that are universities, government, and nuclear industries. In DSP-04, a top-slot break at the cold leg was chosen as the target scenario to resolve an issue about the effect of loop seal clearing and the reformation on the peak cladding temperature during the cold leg top-slot break LOCA for APR1400. The participants performed a code calculation for the experimental simulation and sensitivity studies for the enhancement of the code. This paper includes brief information about the experimental and major code assessment results.