The Korea Atomic Energy Research Institute has successfully completed the commissioning tests, including the long-term operational performance test for the HANARO, a newly in-service multi-purpose research reactor in Korea. This paper presents the design characteristics of the HANARO and a brief description on the startup tests carried out at zero and low power during its commissioning. The reactor is now at the shutdown state for the periodic surveillance after cycle 1 operation and is waiting for the additional fuel loading to configure the cycle 2 core. The reactor is expected to undergo five more cycles of operation in this year. The important physics tests will be conducted at the beginning and at the end of each cycle.

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Permanent multipole magnets are now used in various fields, especially in accelerators or ion sources. The magnetic field integral is important for designing such magnets in view of beam optics. A simple method for calculating the magnetic field integral of permanent multipole magnets is described. The analytical treatment is based on the reciprocal theorem of mutual inductance, which converts the original three-dimensional calculation into two-dimensional one. This calculus exactly considers the effects of the end field and tapered magnet pieces as well as the use of an iron magnetic shield sheath. The results are summarized in simple forms, and are useful for designing permanent multipole magnets.

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A fast neutron pulse reactor that can provide high neutron fluence with relatively short pulse half-width is proposed, which has a core constituted of uranium or plutonium nitride diluted with titanium nitride, formed into particles coated with titanium nitride and packed without moderator. Dilution of the fuel kernel is shown to enhance the neutron fluence obtainable within the allowable maximum fuel temperature. Titanium nitride possesses high heat capacity, which also enables large neutron fluence before attainment of the allowable maximum fuel temperature. As fuel, ²³³U and ²³⁹Pu have the advantage over ²³⁵U of permitting criticality to be attained with lower fuel enrichment. The maximum fluence obtainable with a fuel composition of ²³⁹Pu enriched to 0.6 and diluted to 0.11 (²³⁹PuN+²³⁸UN)/(²³⁹PuN+²³⁸UN+TiN) volume is 3×10¹⁶n/cm², which is 50 times what has been indicated for a conventional fast pulse reactor. The pulse width is significantly longer than that of the above-mentioned conventional reactor, but if necessary it can be shortened down to roughly equal value by adopting non-diluted fuel, at the expense of only reducing by half the obtainable neutron fluence.

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This paper introduces an incomplete discrete wavelet transform (iDWT), which is applied to a preconditioning method for linear equation systems discretized from differential equations. The linear systems can be solved with a matrix solver, but the convergence speed becomes worse with increase of condition number, which exponentially increases with the scale magnification. The use of wavelets in linear systems has an advantage in that a diagonal resealing makes the number become bounded by a limited value, and the advantage is utilized in a matrix solver presented by G. Beylkin. The method, however, has several problems and is difficult to apply to the real numerical analysis. To solve the problems, we introduce the iDWT method that approximates the discrete wavelet transform and is easy to implement in the computational analysis. The effects and advantages of the iDWT preconditioning are confirmed with one- and two-dimensional boundary value problems of elliptic equations. On Cray C94D vector computer, the iDWT preconditioned CG method can solve 2-D Poisson equation, discretized with 1, 024×1, 024 grid points, about 14 times faster than the ICCG method.

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Elementary chemical reactions including volatile (gaseous) fission products, such as iodine and cesium, are analyzed from the first principle, so as to enable us to study the kinetic behavior (non-equilibrium state) of fission products in severe light water reactor accidents without experimental rate constants. Activation energies are calculated with a computer program Gaussian94, which is based on the non-empirical (ab initio) molecular orbital theory. Calculated values are expected to agree with those of experiments within an accuracy of a few kcal/mol. Using the values obtained above, rate constants are also calculated in the framework of the transition state theory. It is concluded that the derived rate constants can predict the orders of magnitude of experimental values under high temperature conditions (1, 000K or higher) as in severe accidents.

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Obtaining an accurate value of the electric dipole moment μ is essential in the fields of laser application technologies. A direct way of measuring the electric dipole moment μ is to observe the Rabi-oscillation which manifests itself in the coherent photo-excitation behavior of atoms. In the case of the elements which have large angular momenta, identifying the Rabi-oscillation in their excitation behavior becomes rather difficult. We proposed an accurate and straightforward method of determining the electric-dipole moment μ between multi- fold degenerate levels. The point is to remove the degeneracy by applying an external magnetic field with the aid of the Zeeman effect and, then, to realize a degeneration free coherent excitation. As a result, we can observe the Rabi-oscillations explicitly in the excitation vs. laser-fluence curves. The present method provides a reliable basis of experimental determination of μ. As an example, we applied the present method to a transition to 0-17, 362 cm^-1 level in uranium and obtained the value μ=0.86±0.06 (Debye).

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The effect of Zr addition to austenitic stainless steels on the suppression of radiation induced Cr segregation at grain boundaries under 400keV He⁺ irradiation was studied. Type 316L stainless steel and steels with addition of 0.07, 0.21 or 0.41 mass% Zr were kept at 1, 423K for 30min, and then they were quenched into the water. Irradiation was done at 773K with the dose rate of 2.4×10^-4 dpa/s. The total dose was 0.85 or 3.4dpa. After irradiation, profiles of Cr concentration across the grain boundaries were measured using an analytical electron microscope with 1nm beam diameter. Concentration of Cr at the grain boundary is decreased by radiation induced segregation. However, it increased with the addition of Zr, and the Cr segregation is almost completely suppressed when Zr is added more than 0.21 mass%.
The effect of Zr addition on suppression of Cr segregation was analyzed focussing on the interaction between dissolved Zr atoms and point defects. The effect is based on vacancy trapping by the Zr atom, and the extent to which it suppresses Cr segregation can be empirically evaluated using a radiation induced segregation model by changing the effective vacancy migration energy.

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A new technique to reduce charge transfer loss when extracting ions from photoionized plasma has been developed, thereby increasing the efficiency of atomic vapor laser isotope separation (AVLIS). By selecting autoionization levels, specific isotopes are ionized to the excitation levels of the ions. Cross sections for charge transfer between specific excited ions and ground state atoms are smaller than those between ground state ions and ground state atoms. The effectiveness of this technique was confirmed by measuring the difference in charge transfer cross sections between Gd⁺+Gd and Gd^+*+Gd. When the gadolinium atoms were ionized at the 53, 616cm^-1 autoionization level, the kinetic energy of the released electrons was measured with a time of flight electron spectrometer (energy resolution>30meV) and the produced ions were determined to be at levels of 4f⁷5d6s¹⁰i>D_13/2 and ⁸D_7/2. The charge transfer cross section for Gd^+* (¹⁰D_13/2 1, 935cm^-1, ⁸D_7/23, 427 cm^-1)+Gd(⁹D_J) was 1.5×10^-18m² at an impact energy of 250eV, which was a smaller value than that for Gd⁺ (¹⁰D_5/2 0cm^-1)+Gd(⁹D_J)(2.5×10^-18m²). When specific isotopes of gadolinium were ionized by autoionization, the charge transfer loss could be reduced from 14% to 9% at an atomic density of 1×1019m^-3 in the typical isotope separation region. Because this effect is also expected in charge transfer between other heavy metallic ions, it should be possible to improve the ion collection efficiency for isotopes like uranium by selecting autoionization levels to produce specific excited ions.

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Adsorption behavior of Eu³⁺ on granulated a-zirconium phosphate (α-ZrP) has been studied by batch and column methods. The distribution coefficients (K_d) of Eu³⁺ into α-ZrP increased with equilibrium pH, suggesting ion-exchange adsorption. The K_d values were in the order of Eu³⁺>Cs^+>Sr²⁺>Co²⁺>Na⁺. An expansion of interlayer distance of α-ZrP in the presence of Na⁺ enables the large hydrated Eu³⁺ ions to be adsorbed on this exchanger, and the adsorption isotherm of Eu³⁺ ions followed Freundlich's adsorption formula. The granulated α-ZrP has high thermal stability and acid resistance. The breakthrough capacity for Eu³⁺ linearly increased with pH of the effluent.

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A high purity Al powder was directly reacted with isotopically enriched ¹⁵N₂ gas at 1, 200°C in a vacuum furnace to synthesize Al¹⁵N. In the initial reaction process, a small amount of AlF₃ was mixed with the Al powder to suppress excess temperature rise due to the heat of formation of the nitride. Then, the Al¹⁵N thus formed was used as the diluent for the second run, and the same procedure was repeated. A total of 100g of Al¹⁵N powder with ¹⁵N isotopic content 99.6 at% was formed with average gas efficiency of 75.6%. Then the Al¹⁵N powder was pressureless-sintered at 1, 830°C in an argon atmosphere by adding a small amount of Y₂O₃ as the sintering agent. An Al¹⁵N ceramic plate with dimensions 50mm×50mm×1.6mm and relative density 97.3% was obtained with the ¹⁵N isotopic content 99.2 at%. Some physical properties and stability in air of an Al¹⁵N ceramic plate were studied.

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