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[en] Highlights: • The viscous and end effects on an MHD pump for the sodium circulation were analyzed. • The viscous effects are negligible compared with electromagnetic driving forces. • The end effects of the pump length are significant in high-velocity operation. - Abstract: The analyses of the viscous and end effects on a magnetohydrodynamic (MHD) pump for the sodium coolant circulation in Fast Reactors was carried out based on the MHD laminar flow analysis and the electromagnetic field theory. A one-dimensional MHD analysis for the liquid metal flowing through an annular channel has been performed on the basis of a simplified model of equivalent current sheets instead of three-phase currents in the discrete primary windings. The calculations show that the developed pressure difference resulted from electromagnetic and viscous forces in the liquid metal is expressed in terms of the slip, and that the viscous loss effects are negligible compared with electromagnetic driving forces except in the low-slip region where the pumps operate with very high flow velocities comparable with the synchronous velocity of the electromagnetic fields, which is not applicable to the practical MHD pumps. A two-dimensional electromagnetic field analysis based on an equivalent current sheet model has found the vector potentials in closed form by means of the Fourier transform method. The resultant magnetic fields and driving forces exerted on the liquid metal reveal that the end effects due to finiteness of the pump length are formidable. Calculations of each magnetic force contribution indicate that the end effects are originated from the magnetic force caused by the induced current generated by the liquid metal movement across the magnetic field rather than the one produced by externally applied magnetic fields by three-phase winding currents. It is concluded that since the influences of the end effects in addition to viscous losses are extensive particularly in high-velocity operations of the MHD pumps, it is necessary to find ways to suppress them, such as proper selection of the pump parameters and compensation of the end effects
[en] Highlights: • An MHD pump for the sodium circulation was analyzed and designed. • The P–Q characteristic was predicted according to the change of the input. • The MHD pump was manufactured considering functional and structural conditions. - Abstract: The linear annular magnetohydrodynamic (MHD) pump was designed for the purpose of transporting the electrically conducting liquid sodium that is used as a coolant in a Sodium cooled Fast Reactor (SFR) operating at high temperatures (over 550 °C). The MHD pump was designed by using an equivalent circuit method which is commonly employed to the design of the induction machines. The mathematical equations on the developing pressure and efficiency was found out by using Laithewaite’s standard design formula. The main geometrical parameters for the design were the pump core length, the diameter of the pump and the annular gap size. The dominant electromagnetic variables were the input frequency, magnetic pole pitch and number, and coil turns. Especially, it was shown that the developing pressure and efficiency were maximized at the range of frequencies below the commercial value of 60 Hz. Also, the size of an annular gap was suitably selected considering the hydraulic frictional loss at the narrow annular channel. The P–Q characteristic was theoretically predicted according to the change of the input current, voltage and power. The functional and structural components of the pump consisted of the material compatible with the high temperature and chemical reactivity of the liquid sodium. The designed pump was predicted to have the nominal flowrate of 10 L/min and the developing pressure of 4 bar
[en] Highlights: • The ALIP is analyzed using magnetohydrodynamic and equivalent circuit method. • Design variables of ALIP for IHTS of PGSFR are optimized. • P–Q characteristics of ALIP with a flow rate of 0.86 m3/s are drawn. - Abstract: An annular linear induction electromagnetic pump (ALIP) with a flow rate of 0.86 m3/s and a developed pressure of 3.6 bar is designed by conducting an optimization analysis of its geometrical, electromagnetic, and hydrodynamic variables. The purpose of the ALIP involves circulating liquid sodium in the intermediate heat transport system of the Prototype Generation-IV Sodium-cooled Fast Reactor (electric output: 150 MWe) that is currently under development in Korea. The efficiency and developed pressure of the ALIP are derived as a function of its design variables and include the core length, flow gap, number of poles, flow velocity, pole pitch, input frequency, and input current. In terms of electromagnetic variables that can be controlled during its operation, hydraulic efficiency is maximized at an input frequency of a few tens of Hertz. The P–Q characteristics of the optimized ALIP are analyzed and verified via a theoretical comparison with an extremely large ALIP.
[en] It was understood that regulation criteria for material release varied with countries and that international standards were not setup. But, most advanced countries are continuously studying on the recycling of metallic wastes for the purpose of the reuse of resources and disposal cost reduction. Practically, the advanced countries make a lot of cost profits compared with disposal as their metallic wastes are recycled and reused through technology like melting. The reasonable international standards are also expected to be set in the near future because of the aggressive cooperation between international agencies such as IAEA and NEA toward recycling these wastes. In our case, the recycle criteria for radioactive waste containing radioactive nuclide with long half-life such as Cs-137(half-life: 30y) and Co-60(half-life: 5.26y) including others, which are generated from the nuclear fission or dismantling of nuclear facilities, are not yet established. Therefore, it is required that the recommendation and legalization of the regulatory criteria be carried out for the recycle and reuse of metallic wastes to be generated from the dismantling of domestic nuclear facilities in the future
[en] Highlights: • The theoretical model of ALIP was configured and analyzed. • Characteristics of ALIP were predicted on the change of design variables. • Design variables of ALIP for SFR thermal hydraulic loops were optimized. - Abstract: The design variables of an annular linear induction electromagnetic pump (ALIP) for SFR thermal hydraulic experimental loop were analysed magnetohydrodynamically. The theoretical model of ALIP was configured for magnetohydrodynamic (MHD) analysis. Mathematical equations for the developed pressure, generated by Lorentz electromagnetic force and hydraulic efficiency were derived. The developed pressure was found to be a function of design variables, including the geometrical variables of pump core length, inner core diameter and flow gap, and the electromagnetic ones of turns of coils, frequency and input current. The developed pressure from the MHD analysis was compared and identified with the developed pressure derived by an equivalent circuit method leading to Laithewaite’s standard design formula for a linear induction electromagnetic pump. The design characteristic of the electromagnetic pump was analyzed according to the change of the pump’s geometric and electromagnetic variables, taking into account hydraulic friction pressure loss in the narrow annular gap of the pump. The design specification of ALIP with a flow rate of 900 L/min and a developed pressure of 4.5 bar was drawn from the characteristic analysis of the variables.
[en] Radioactivity analysis of β-emitting radionuclide is important because of its dangerousness of overexposure. γ-ray has been measured by conventional detector such as NaI(Tl) or high purity germanium (HPGe) detector. But β-ray is hard to detect by those detectors because of its short range. Therefore, liquid scintillation counter (LSC) has been used to measure the radioactivity of pure beta emitter but there is huge problem of organic waste production, though LSC has high efficiency for detection of low energy β-ray. To solve this problem, characterization of β-ray measurement in a plastic scintillator was carried out in this study. There have been some studies about plastic scintillator to measure the β-rays without liquid scintillation method. Plastic scintillator has benefits for detection of β-ray because it has relative low effective atomic number. β-ray and γ-ray spectra in cylindrical plastic scintillator was analyzed and a method of separation of β-ray spectrum was suggested. A simple method of β-ray spectrum separation was suggested. The method was verified by chi-square method to estimate the difference between calculated and measured spectrum. This method was successfully applied by using disc source. For future works, practical radioactive source will be used to acquire the pulse height spectrum. The method can be used for measurement of pure β emitter without pretreatment if this method is verified for practical purpose
[en] The developed pressure was made by only electromagnetic force eliminating probability of impurities contact, therefore the high reactivity materials such as alkali were best match to electromagnetic pump. The heavy ion accelerator facility by Rare Isotope Science Project (RISP) in Korea is trying to construct accelerator using liquid lithium for high efficiency of acceleration by decreasing charge state. The helical-type DC electromagnetic pump was employed to make a charge stripper that decrease charge state of heavy ion. The specification of electromagnetic pump was developed pressure of 15 bar with flowrate of 6 cc/s in the condition of 200℃. The pressure of DC electromagnetic pump was analyzed in the aspects of current and number of duct turns. The developed pressure was almost proportional to input current because relatively low flowrate made negligible of the electromotive force and hydraulic pressure drop. The pressure and magnetic flux density of helical-type DC electromagnetic pump were analyzed. The pressure was proportion to input current and number of duct turns, and magnetic flux density was higher when ferromagnet was applied at electromagnetic pump. It seems that number of duct turns could be increase and ferromagnet could be applied in order to increase pressure of DC electromagnetic pump with constant input current
[en] The development background and property of the COSIDA, which is the 3D computer simulation system for the analysis on the dismantling procedure of the nuclear facilities in Japan was reviewed. The function of the visualization on the work area, Kinematics analysis and dismantling scenario analysis, which are the sub systems of the COSIDA, has been investigated. The physical, geometrical and radiological properties were modelled in 2D or 3D in the sub system of the visualization of the work area. In the sub system of the kinematics analysis, the command set on the basic work procedure for the control of the motion of the models at a cyber space was driven. The suitability of the command set was estimated by the application of COSIDA to the programming on the motion of the remote dismantling tools for dismantling the components of the nuclear facilities at cyber space
[en] While proceeding the KRR-1 and 2 decommissioning project, we are carried out study for the state of the art on decommissioning of nuclear facilities in Japan. Also, we are studied for the research reactors and commercial power plant that has the object of decommissioning, and for the government and the organization related on decommissioning operation. We are investigated for decommissioning activities of nuclear facilities achieved by JAERI, and collected the information and data for decommissioning techniques and computational system through the JPDR(Japan Power Demonstration Reactor) decommissioning activities. Such techniques are applying for Tokai Power Station began the decommissioning project from last year, and for Fugen Nuclear Power Station to be planned the decommissioning from 2003. Recent techniques for decommissioning was acquired by direct contact. The status of the treatment for decommissioning waste and the disposal facility for the very low-level radioactive concrete wastes was grasped
[en] The scattered photon cannot but be projected to the detector pixel where it is initially headed. Therefore, reducing the scattered photon in x-ray imaging system is essential to decrease unwanted radiation exposure to patient and increase the accuracy of diagnosis. In order to reduce scattered photons, an anti-scattering X-ray grid, which consists of shielding material and penetration materials, is equipped in X-ray imaging system. The design case study of anti-scattering X-ray grid was performed for the three designs of square, honeycomb and circle type by MCNP simulation. The optimization of thickness of shielding material was conducted on three cases of the length of a side of hexagon of honeycomb type anti-scattering X-ray grid. It was understood that the performance of grid was not depend on the grid type in this fundamental approach