[en] Discuss of the origins and severity of the earthquake, the resulting tsunami and the devastation and loss of human life that followed. In particular, world attention was focused on the nuclear power plants located in Fukushima, which were damaged by the tsunami. The current conditions in the areas affected by the tsunami and reactor incident will also be discussed. The issues of nuclear waste management in Japan will be also discussed

[en] Prediction of moisture migration and pore pressure build-up in non-uniformly heated concrete is important for safe operation of concrete containment vessels in nuclear power reactors and for assessing the behaviour of fire-exposed concrete structures. (1) Changes in moisture content distribution in a concrete containment vessel during long-term operation should be investigated, since the durability and radiation shielding ability of concrete are strongly influenced by its moisture content. (2) The pressure build-up in a concrete containment vessel in a postulated accident should be evaluated in order to determine whether a venting system is necessary between liner and concrete to relieve the pore pressure. (3) When concrete is subjected to rapid heating during a fire, the concrete can suffer from spalling due to pressure build-up in the concrete pores. This paper presents a mathematical and computational model for predicting changes in temperature, moisture content and pore pressure in concrete at elevated temperatures. A pair of differential equations for one-dimensional heat and moisture transfer in concrete are derived from the conservation of energy and mass, and take into account the temperature-dependent release of gel water and chemically bound water due to dehydration. These equations are numerically solved by the finite difference method. In the numerical analysis, the pressure, density and dynamic viscosity of water in the concrete pores are calculated explicitly from a set of formulated equations. The numerical analysis results are compared with two different sets of experimental data: (a) long-term (531 days) moisture migration test under a steady-state temperature of 200 deg. C, and (b) short-term (114 min) pressure build-up test under transient heating. These experiments were performed to investigate the moisture migration and pressure build-up in the concrete wall of a reactor containment vessel at high temperatures. The former experiment simulated the effect of long-term steady-state liner temperature during normal operation, and the latter simulated a situation where an accident resulted in sudden, short-term heating to approximately 400 deg. C. Finally, concrete spalling is simulated by the numerical analysis; and the results show how the moisture content and pore pressure distributions in concrete exposed to fire change with time and temperature. The numerical analysis can predict the time, position and temperature at which spalling occurs

[en] An improved self-absorption method obtained from the parallel-beam modification of Harrison's method (Proc. Phys. Soc.; 74: 841 (1959)) for measuring the metastable atom density in gas discharges has been proposed. This method has the advantage of high spatial resolution in measurement with a relatively simple apparatus. The metastable atom densities of He (2¹S₀ and 2³S₁) and Ne(1s₃ and 1s₅) in the positive column plasmas have been measured using this improved self-absorption method by varying the gas pressure from 1 to 10 Torr and the discharge current from 10 to 50 mA. 'Constriction' of the radial metastable atom density distribution in neon plasma has been observed. (author)

No abstract available

[en] A theoretical study has been made of the medium-pressure rare-gas positive-column plasma by taking into account the effects of molecular ion formation, volume recombination and ionisation due to metastable atoms, simultaneously. Calculated values of the electron temperature and the densities of metastable atoms, molecular and atomic ions, at various gas pressures for both He and Ne gases are presented. Numerical results show that in a rare-gas positive-column plasma, molecular ions become dominant in the discharge as the gas pressure increases above approximately 10 Torr. Theoretical values are compared with the experimental data and discussed. A new method to determine the three-body conversion rate coefficient is also proposed. (author)

[en] Theoretical studies on the electron temperature Tsub(e) of a positive column plasma with two-body and three-body volume recombinations have been carried out. Numerical results of Tsub(e) for various discharge conditions are given. These results are used to examine the validity of the approximate equation for determining Tsub(e) presented by Solunskii and Timan. (Sov. Phys.-Tech. Phys.; 9: 207 (1964)). A new approximate equation which is valid for a wide range of discharge conditions is also proposed. (author)

[en] The important upper atmosphere negative ion-molecule interaction, O(-)+H2(D2)-OH(-)(OD(-))+H(D), has been extensively studied using a tandem mass spectrometer and a crossed ion-molecular beam apparatus. Total cross sections for this reaction were measured as a function of ion kinetic energy, over the range, 0.03-4 eV. The product ion angular and energy distributions were also measured in the relative energy range from 1.1 to 2.5 eV. With increasing interaction energy, the centers of the product distributions were observed to move forward with respect to the center of mass, indicating that long-lived intermediate complex formation does not occur at higher energies. 14 references

[en] Sixteen ornamental tile samples were collected from 1982 to 1983 from the rooftops of two buildings at Hiroshima University, Hiroshima, Japan. Quartz grains 50-150 microns in size extracted from the samples were analyzed for their thermoluminescence (TL) intensities. Conversion of TL intensity to ⁶⁰Co gamma exposure resulted in the following estimates: 40.5 to 27.6 mC kg-1 (157 to 107 R) for five samples (one each) collected from five sites at distances of 1.27 to 1.34 km from the hypocenter of the atomic bomb detonated in 1945; 23.7 +/- 1.4 mC kg-1 (92 +/- 5 R) for three samples from one site at a distance of 1.39 km; 21.4 to 17.0 mC kg-1 (83 to 66 R) for three samples (one sample per site) from three sites at distances of 1.40 to 1.43 km; 19.8 +/- 1.3 mC kg-1 (77 +/- 5 R) for four samples from one site at a distance of 1.45 km; and 13.2 mC kg-1 (51 R) for one sample at a distance of 1.46 km. At face value, these estimates are greater by a factor of about 2.5 than previous estimates based on the tentative 1965 radiation dose estimates for atomic bomb survivors (a tentative dosimetry model proposed in 1965), but agree within +32% to -13% (+15% on the average) with recent estimates using modern computational techniques using an improved model of the atomic bomb explosion

[en] Thermoluminescence dosimetry measurements of gamma rays produced by the atomic bomb in Hiroshima were made by the predose technique using eight ceramic samples collected from five buildings located at distances between 1271 and 2051 m from the hypocenter. The results of our measurements are compared to both the newer dose estimates (Dosimetry System 1986) and older dose estimates (Tentative 1965 Doses) for survivors of the Hiroshima atomic bomb. In comparison with the older estimates, our results are larger by a factor of 2.3 at 1271 m and 3.9 at 2051 m. Our results and the newer estimates for Hiroshima differ by a factor of only 1.14 +/- 0.16 on the average

[en] A potential flow model was developed to predict wind fields in complex terrain. In this model, wind vectors and airflows are estimated from a velocity potential function. It was found that the velocity potential function is obtained by combining threedimensional doublets at each grid point on a horizontal plane and a uniform stream parallel to the surface of the earth. The strengths of the doublets were expressed as a function of the terrain height at each grid point. Wind components at an arbitrary point were easily calculated from the potential flow model proposed. Consequently, this potential flow model is useful in estimating airflows, the convergence and divergence of the distances between streamlines, and the trajectories of radioactive plumes