The Radiation Element Method Coupled with the Bioheat Transfer Equation Applied to the Analysis of the Photothermal Effect of Tissues

The purpose of this study is to develop the radiation element method by ray emission method (REM²) code appropriate for coupling with the bioheat transfer equation, and to clarify the photothermal effect of various parameters inside biological tissues. First, the REM², which involves the air-tissue interface effect, is validated with the existing literature. In order to clarify the effects of optical and thermophysical properties of biological tissues, a one-dimensional tissue model of CW light transport and bioheat transfer is employed. The present study provides nondimensional results, which are obtained by varying refractive index, extinction coefficient, scattering albedo, blood perfusion parameter, and conduction-radiation parameter, show valuable guidance for understanding the coupled light and bioheat transport in tissues.     

Evolution of long-period stacking ordered structures on annealing as-cast Mg85Y9Zn6 alloy ingot observed by synchrotron radiation small-angle scattering

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A study on horizontal stud welding by using steel stud for flat welding

ABSTRACT

In recent years, manufacturing sites have strongly requested for the steel stud with large diameter to be welded in the horizontal position, which is difficult because of gravity. In this study, the steel stud of 19 mm in diameter was welded horizontally to the mild steel plate by using ferrule for usage in flat position. As results two kinds of weld defect were observed; lack of fusion and blowhole. The former occurred in the welding condition of too small or too large heat input, and the latter did in the range of longer arc time. Therefore, the suitable welding condition could be found in the large current and shorter arc time. When the areal ratio of weld defect to the cross section of stud was lower than 10 percent, the welded joint had enough statical strength.     

Sensitivity analysis of fuel pin failure performance under slow-ramp type transient overpower condition by using a fuel performance analysis code FEMAXI-FBR

The FEMAXI-FBR is a fuel performance analysis code and has been developed as one module of core disruptive evaluation system, the ASTERIA-FBR. The FEMAXI-FBR has reproduced the failure pin behavior during slow transient overpower. The axial location of pin failure affects the power and reactivity behavior during core disruptive accident, and failure model of which pin failure occurs at upper part of pin is used by reflecting the results of the CABRI-2 test. By using the FEMAXI-FBR, sensitivity analysis of uncertainty of design parameters such as irradiation conditions and fuel fabrication tolerances was performed to clarify the effect on axial location of pin failure during slow transient overpower. The sensitivity analysis showed that the uncertainty of design parameters does not affect the failure location. It suggests that the failure model with which locations of failure occur at upper part of pin can be adopted for core disruptive calculation by taking into consideration of design uncertainties.     

A simple mass and heat balance model for estimating plant conditions during the Fukushima Dai-ichi NPP accident

A simple evaluation method for the analysis of thermal-hydraulic transients in reactor pressure vessel (RPV) and primary containment vessel (PCV) is proposed to support understanding the accident behaviors of the Fukushima Dai-ichi nuclear power plant (NPP). Since most of the measurements of the plants were unavailable especially in the early stage of the accident, and the accessibility to the plants had been limited by radiation, analytical investigation for the plant was required to understand the plant conditions such as the magnitude of the damages. In order to provide easy-to-use technical tools to support the analytical investigation, we developed a simplified analysis code, named “HOTCB”, based on total mass and heat balances in a lamped parameter system. The HOTCB code has capabilities to treat two-phase fluid including water, steam, and non-condensable gas in a wide range of temperatures up to highly superheated conditions, and to consider heat structures, i.e. heat capacities and heat transfer to the fluid. The code was provided to Tokyo Electric Power Company (TEPCO) and was practically used for the analysis on the accident. This paper provides the details of the code and simulations of Unit 1 and Unit 2 reactors of Fukushima Dai-ichi nuclear power plant (NPP) as examples to show the usefulness of the code.     

Measurement of the isotopic abundance of boron-10 by inductively coupled plasma-quadrupole mass spectrometry

This article describes the method for measuring the isotopic abundance of ¹⁰B in nuclear grade boron carbide using inductively coupled plasma-quadrupole mass spectrometry (ICP-QMS). The results of investigation revealed that both the integration time and the dwell time have a major influence on the reproducibility of ICP-QMS measurements. As a result of optimization of the measurement conditions, reproducibility below 0.2% relative standard deviation (RSD) (0.17% RSD maximum) was achieved. In addition, the measured value of the isotopic abundance of ¹⁰B for each sample well agreed with the values measured by the TIMS. Thus, the method described in the present investigation was very effective in the analysis of isotopic abundance of ¹⁰B in B₄C or H₃BO₃. The results of this study suggest that ICP-QMS could be applied to the precise analysis of the isotopic abundance of ¹⁰B required in the field of nuclear applications.     

Evaluation of corrosion behaviors for reactor pressure vessels/primary containment vessels in Fukushima Daiichi units 1–3 nuclear power plant

Fukushima Daiichi nuclear power plants (1F) were damaged by unprecedented severe accident in the Great East Japan Earthquake on 11 March 2011, and seawater has been injected as an emergency countermeasure for the core cooling. Although, the RPV and PCV were not supposed to be exposed to diluted seawater, they have been exposed to diluted seawater environment or high-moisture environment. Therefore, seawater corrosion has become an important issue. Immersion corrosion tests were performed for low-alloy steel of RPV material and carbon steel of PCV material in 1F cooling-water-simulated environment. As a result, the mass loss by corrosion was reduced with the decreasing temperature and chloride ion concentration. Moreover, the effects of nitrogen deaeration and Na₂WO₄ addition on corrosion protection were remarkable among the selected corrosion countermeasures. In addition, the integrity assessments of RPV and PCV were performed considering the reduction of plate thickness based on corrosion test data and the load condition based on earthquake response analysis results. It had been confirmed that primary stresses for RPV and PCV equipment satisfied with the allowable values until at least 15 years after the accident.     

On Configuration of Load in Radiant Furnace for Uniform Thermal Conditions

This work aimed to investigate the boundary design problem for uniform thermal conditions, when multiple three-dimensional (3-D) design objects (DOs) are placed inside the radiant furnace, and to explore the suitable configuration of DOs located inside the radiant furnace. Also the objective includes ascertaining the limit of maximum numbers of DOs that can be accommodated to get the uniform thermal conditions. To accomplish this task, 19 cases are evaluated, consisting of the different number of DOs with various configurations, located on the bottom surface of the furnace enclosure. Each case is treated as an inverse boundary design problem separately. The radiative information is calculated using the radiation element method by ray emission model (REM²). The microgenetic algorithm (MGA) is used as an optimization tool. The specularity effect of the surfaces of heaters, of surfaces of radiant enclosure, and of the DOs is taken into account. The suitability of the configuration of DOs is shown by comparing the estimated heat flux distribution on DOs. The effect of different heater power ranges on the uniformity of the heat flux distribution on DOs is discussed. With a sample case, the optimal heater power setting that produces the desired uniform thermal conditions on DOs is also given. In the present boundary design problems, to obtain the uniform thermal conditions, a pronounced effect of the configuration of DOs and the numbers of DOs is observed.