Shigeo Numata

Diffusion of tritiated water in cement materials

Abstract The diffusion of airborne tritiated water into cement materials is discussed in terms of unsteady state adsorption and depth profile experiments. Consistent apparent diffusion coefficients of tritiated water in cement materials were obtained from different experiments. From the comparison between experimental results, Raoults law was found to be applicable to the vapor-liquid equilibrium between tritiated water vapor and liquid water at the surface. The results of depth profile experiments suggested that there were two different diffusion processes in cement materials; one is a fast diffusion process of a relatively small portion, and the other is a slow process having higher capacity. From the permeation experiments, in which liquid water was used, the intrinsic diffusion coefficient was observed to be a function of the porosity and found to increase from 3.19×10 −12 to 11.3×10 −12 m 2 /s with a porosity increase from 0.07 to 0.28.

Tritium inventory in portland cement exposed to trttiated water vapor

Abstract Interactions between penetrating tritiated water and hydrogen species originally present in cement materials were evaluated to estimate the tritium inventory in cement materials exposed to tritiated water vapor. Approximately 80% of the penetrated tritiated water was found to be contained in free liquid water. Tritiated water was considered to interact with cement materials by means of exchange reactions between tritium and hydrogen atoms. The concentration of tritium interacting with materials was considered to be proportional to the tritium concentration in air. The tritium inventory in cement materials was thus dependent on the porosity of the material.

Combined power supply method for micro grid by use of several types of distributed power generation systems

A power control method to compensate power fluctuation of the load in the microgrid systems is proposed and discussed. Active power responses of several kinds of distributed power generation systems (DGs) such as gas engine, micro gas turbine, etc., energy storage system, and load fluctuation of a site have been measured. Based on the measurements, combination control method for several kinds of DGs and an energy storage system has been made and experiments have been carried out by use of small scale micro grid model system. It is shown that the load fluctuation has been compensated by the proposed method

Design methods and integrated control for microgrid

The authors have been carrying out a preliminary study on the design of microgrid. Designing microgrid includes selection and capacity determination of power supply devices according to their response characteristics, efficiency and initial cost, and development of methods for integrated control to maintain power quality and efficiency. Both design and control methods depend on conditions of loads, for which microgrid is installed. In this paper, design methods of microgrid, such as power demand analysis, response characteristics measurement of power sources and fuel efficiency measurement of engine-generators, and integrated control methods for power sources are proposed, along with experimental results for a prototype of microgrid.

State of charge control for energy storage by use of cascade control system for microgrid

The hybrid control system, which is a combination of cascade control and local control, is proposed as a method to compensate power fluctuations caused by load and renewable energy sources in a microgrid using distributed power generation systems(DGs). When energy storage system(ESS) such as EDLC is used in the microgrid to compensate power fluctuations, its state of charge(SoC) should be controlled. In this paper, a new method to control ESSs SoC which would enable power compensation with less energy capacity and with less effect to the compensation result is proposed. This method uses the feature of the cascade control that faster DGs reference is dependent on slower DGs output. The new method is implemented on EDLC in the model microgrid and its effectivity is verified by a simulation and a experiment. The result of the simulation and experiment is also reported in the paper.

Energy capacity reduction of energy storage system in microgrid by use of heat pump: Characteristic study by use of actual machine

The installation of renewable energy sources based generators such as photovoltaic cells and wind turbines require energy storage systems(ESSs) to control power fluctuation. ESSs, however, are quite expensive. In order to reduce the necessary capacity of ESSs for microgrid applications, the control of heat pumps is researched. In this research, basic characteristic of a heat pumps power consumption is measured experimentally by use of heat pump chiller unit used in real building. Using the measured characteristic, a method to reduce the energy capacity of ESS is proposed and studied. The capacity reduction of ESS that can be achieved by use of heat pump control and the effect of control on temperature were calculated using simulations.

Frequency Spectrum Based Coordinate Control Scheme for Several Types of Distributed Power Generation Systems in a Micro Grid

A power control method to compensate power fluctuation of the load in the micro grid systems is proposed and discussed. Active power responses of several kinds of distributed power generation systems (DGs) such as gas engine, micro gas turbine etc., energy storage system, and load fluctuation of a site have been measured. Based on the measurements, coordinate control system for several kinds of DGs has been constructed. Simulation and experiments have been carried out with small-scale micro grid model system. It is shown that the load fluctuation has been compensated by the proposed method

Feasibility Study on Short Period Power Fluctuation Compensation Using Heat Pump Air Conditioning System

In order to compensate power fluctuations caused by loads and renewable energy sources, the concept of controllable load has been proposed. In this paper, the use of heat pump air conditioning system as a controllable load is focused. To analyze the feasibility of using the heat pump for power fluctuation compensation, basic characteristics of heat pump concerning its power consumption and processed heat are measured by experiments and reported in this paper. The COP characteristics show that the efficiency of the heat pump is not affected so much by power consumption as long as it is operated above a certain level of power consumption. The Bode diagram of sinusoidal reference signal test shows that the heat pump can compensate power fluctuation which is in a certain region in the frequency domain without giving a large effect on processed heat.

Evaluation of tritiated water retention capacity of fusion reactor concrete building

In this paper the diffusion of tritiated water vapor into concrete walls is studied to evaluate tritiated water retention capacity of a fusion reactor concrete building. Using a model of the tritiated water diffusion determined form experimental results, depth profiles of tritiated water in concrete are calculated in the case of being exposed to air containing tritiated water vapor during the normal operational condition of a fusion reactor. A 0.5-m-thick concrete is sufficient for reactor hall walls from a viewpoint of the tritium containment.

Simulation of Cleanup of Tritiated Water in Fusion Reactor-Size Concrete Enclosures

This paper reports on cleanup of tritiated water in typical reactor-size concrete enclosures which is simulated taking into account the soaking of the triated water into the concrete. For an enclosure made of concrete with ordinary porosity, the soaking effect has little effect on the cleanup time for releases with tritium concentrations of {lt}1 {times} 10{sup 8} Bq/m{sup 3}. If the concrete porosity is reduced to 0.03, the soaking effect has little effect on the cleanup time for a tritium concentration of up to 1 {times} 10{sup 9} Bq/m{sup 3}.