Eo Hwak Lee

Biosorption of uranium(VI) from aqueous solution by biomass of brown algae Laminaria japonica

The uranium(VI) adsorption efficiency of non-living biomass of brown algae was evaluated in various adsorption experimental conditions. Several different sizes of biomass were prepared using pretreatment and surface-modification steps. The kinetics of uranium uptake were mainly dependent on the particle size of the prepared Laminaria japonica biosorbent. The optimal particle size, contact time, and injection amount for the stable operation of the wastewater treatment process were determined. Spectroscopic analyses showed that uranium was adsorbed in the porous inside structure of the biosorbent. The ionic diffusivity in the biomass was the dominant rate-limiting factor; therefore, the adsorption rate was significantly increased with decrease of particle size. From the results of comparative experiments using the biosorbents and other chemical adsorbents/precipitants, such as activated carbons, zeolites, and limes, it was demonstrated that the brown algae biosorbent could replace the conventional chemicals for uranium removal. As a post-treatment for the final solid waste reduction, the ignition treatment could significantly reduce the weight of waste biosorbents. In conclusion, the brown algae biosorbent is shown to be a favorable adsorbent for uranium(VI) removal from radioactive wastewater.

Fabrication of a 1/6-Scale Mock-Up for the Korea TBM First Wall in ITER

Abstract Korea has developed a liquid breeder blanket for the test blanket module (TBM) program in ITER with a helium-cooled molten lithium concept. Since ferritic martensitic steel is used as the structural material for the TBM first wall (FW), various joining methods have been developed with hot isostatic pressing in order to develop a TBM FW fabrication method. In this study, three small mock-ups were fabricated in order to develop and verify the manufacturing method of the TBM FW through the pressure and helium leak tests. They were successfully fabricated. After fabrication and checking the performance of the mock-ups, a 1/6-scale mock-up was fabricated with a 260-mm height, 444-mm width, and 435-mm depth, in which width and depth were preserved and the number of channels was reduced from 60 to 10. The mock-up has a U-type shape and ten channels with a size of 20-mm height and 10-mm width for cooling. A manifold for flow testing and high heat flux testing of the 1/6-scale mock-up was designed and fabricated to distribute fluid uniformly to the mock-up.

Manufacturing and Examination for ITER Blanket First Wall Small-Scale Mockups With KoHLT-EB in Korea

The ITER first wall (FW) includes beryllium armor tiles joined to a CuCrZr heat sink. The FWs are one of the critical components in an ITER machine with a surface heat flux of 4.7 MW/m2 or above. The small-scale mockup shall be a part of the qualification tests and used to validate the performance of the dominant manufacturing technologies before the production of larger scale components, and this mockup shall be equipped with a hypervapotron heat sink and manufacturing processes developed for a semiprototype design. The small-scale mockup includes 48 beryllium armor tiles (12 mm × 12 mm) capable of withstanding the specified heat flux values. The tile thickness shall be 6 mm to minimize the beryllium surface temperature and evaporation under high thermal loads. The detailed fabrication process of semiprototype small-scale mockups was developed for a qualification test in Korea. For the CuCrZr and stainless steel, the canned materials are processed into an hot isostatic pressing (HIP) device. In the case of beryllium-to-CuCrZr joining, the HIP was conducted at 580°C and 100 MPa. For nondestructive tests of the fabricated semiprototypes, visual and dimension inspections were performed whenever needed during the fabrication process, and ultrasonic tests were performed using ultrasonic probes. Destructive tests for the qualification semiprototype were performed on a small-scale mockup, which was fabricated together with semiprototypes. The Korea heat load test facility using an electron beam system was constructed with an electron gun (maximum electric power of 800 kW) for a high heat flux application with a 300-kW high-voltage power supply and maximum accelerating voltage of 60 kV. This facility was operated to evaluate the performance test of plasma facing components. A cyclic heat flux test will be performed to evaluate the ITER qualification program.

Commissioning of the Korean High Heat Flux Test Facility by Using Electron Beam System for Plasma Facing Components

Abstract Korean high heat flux test facility for the plasma facing components of nuclear fusion machines will be constructed to evaluate the performance of each component. This facility for plasma facing materials will be equipped with an electron beam gun with a 60 kV acceleration voltage. The system also includes a 300 kW power supply system, a vacuum test chamber, and a beryllium filtration system for the ITER first wall mockups. First, a commissioning test has been scheduled to establish the installation and preliminary performance experiments of the copper hypervapotron mockups and evaluate the thermo-hydraulic specifications. Second, a qualification test will be performed to evaluate the CuCrZr duct liner in the ITER neutral beam injection facility and the ITER first wall small-scale mockups of the semi-prototype, at up to 1.5 and 5 MW/m2 high heat flux, respectively. This electron beam system will be used to qualify the specifications of the plasma facing components in the KSTAR tokamak and other fusion devices.

Progress of Functional Components Design and Analysis of a Korean HCCR TBM in ITER

Korea has developed a helium cooled ceramic reflector (HCCR) test blanket module (TBM) for testing in a ITER, which consists of functional components to distribute the He coolant to each region such as the first wall (FW), breeding zone (BZ), side wall (SW), and back manifold (BM). In this paper, the detailed design of each component is introduced as follows: 1) FW considering cooling under a structural material temperature limit (550 °C); 2) BZ layer for obtaining tritium breeding ratio and cooling with a breeder, reflector, and multiplier pebbles; 3) SW considering the flow distribution to BZ and internal pressure; 4) BM for uniform flow to FW cooling channels; and 5) He purge line in BZ considering a purge gas distribution in BZ. From the performance analysis of each functional component using the CFD code, ANSYS-CFX with the results of nuclear heating from a neutronic analysis, the results show that the design requirements of KO HCCR TBM were satisfied.

Scoping Study on In-Vessel LOCA of a Korean TBS in ITER

Korea has designed a helium cooled ceramic reflector (HCCR) based test blanket system (TBS) for an ITER. An in-vessel loss of coolant accident is one eight selected reference accidents in the Korean TBS. This accident is initiated by a single or multiple rupture of the test blanket module first wall cooling channels, causing a plasma disruption, and pressurization of the vacuum vessel (VV). In this type of accident, the governing parameters are various, for example, the operating pressure, gas temperature, TBS volume, VV volume, and mass flow rate. Thus, a scoping study is an essential strategy when attempting to determine the proper design specification for a Korean TBS. In this paper, given the preliminary accident analysis results for the current HCCR TBS, a parametric study was performed. For this transient simulation, the Korean nuclear fusion reactor safety analysis code (GAMMA-FR) was used.

Fabrication and Integrity Testing of a Korean ITER TBM FW Mock-Up in Preparation for High Heat Flux Test

Abstract Korea (KO) has developed and participated in the Test Blanket Module (TBM) program in the ITER, in which Ferritic Martensitic (FM) steel was used as the structural material for the TBM first wall (FW). To develop the fabrication method for the TBM FW and verify its integrity, a half-scale sub-module mock-up was fabricated and integrity test has been prepared; A dimension of it is a 444 mm height, 260 mm width, and 435 mm depth. A mock-up was assembled by HIPping of the previous fabricated components between the welded front and back plates, and then machining these plates to form the completed sub-module FW. To investigate the deformation of the cooling channels after the fabrication of the mock-up, neutron radiography was carried using neutron radiography facility. Pressure and He leak tests were successfully performed without any leak and failure. The flow rates in each channel were measured with the conventional ultrasonic sensor but it shows non-uniform flow distribution at each channel differently from the estimation by ANSYS-CFX. HHF test conditions were evaluated through the ANSYS-CFX analysis considering the above measured flow rates in each channel and it shows non-uniform temperature distribution of the FW mock-up. We will re-assemble or fabricate the manifold and perform the flow test before HHF test in the near future.

Thermal-Hydraulic Analysis for Conceptual Design of Korean HCCR TBM Set

With a conceptual design of Korean helium-cooled ceramic reflector test blanket module (TBM), including TBM shield for testing in ITER, thermal-hydraulic analyses are performed with a conventional CFD code, ANSYS-CFX v14.5, for the electromagnetic module and the integral module, including the TBM shield. With the same model and meshes, according to the ITER operation conditions of the H/He and D-T phases, the temperature distribution, flow rate, and pressure drop are investigated to meet the design requirements, and the temperature data are directly provided to a mechanical analysis.

Status of Helium Supplying System Construction with a High Heat Flux Test Facility

Abstract A scaled-down Helium Supplying System (HeSS), which is linked with an electron beam heat load facility, has been constructed in Korea. HeSS is designed to supply a high temperature and high pressure helium gas flow into the first wall mock-ups of the HCCR TBM. The electron beam facility (KoHLT-EB) is connected with HeSS to apply a high heat load (up to 5 MW/m2 at 300×200 mm2) to the first wall mock-up target. A heat load test, with a constant heat flux of 0.3 to 0.5 MW/m2, with the first wall mock-up is scheduled under inlet conditions of 8 MPa, 300 °C, and a 0.5 kg/s helium flow rate, which is based on the operating condition of HCCR in 2013.

Effect of dissolved oxygen on corrosion properties of reinforcing steel

Abstract A series of electrochemical experiments were conducted to investigate the effect of dissolved oxygen, pH and Cl− on the corrosion rate of reinforcing steel of geological disposal facility saturated with groundwater. It was found that the corrosion rate was proportional to the concentration of Cl− and dissolved oxygen which are known as a corrosive agent and an electron acceptor, respectively. The pH level also strongly influenced the corrosion rate of the reinforcing steel. Under the pore water conditions of concrete structure of geological disposal facility, i.e. pH of 10–12 and dissolved oxygen of 1 mg L−1, the corrosion rate of reinforcing steel was determined to be in the range of ∼10−8 to ∼10−9 m/year. The corrosion rates were higher than those estimated from an empirical model based on the diffusion of dissolved oxygen.