[en] In order to produce a neutron beam for accelerator-based BNCT, the optimum energy was determined and the characteristic curve was developed and applied as an indicator of neutron beam quality evaluation. Through many Monte Carlo simulations using mono-energetic neutrons having various beam sizes, beam quality has been evaluated. The Advantage Depth (AD) and Tissue Maximum Dose (Tmax) were selected to evaluate the beam quality among the Figure of Merits. The optimum energy was determined by searching the maximum value of AD as a function of neutron energy and the minimum value of Tmax. The characteristic curves were developed to estimate/predict the beam quality. The Gaussian energy distribution beams were chosen as an example. The AD and Tmax were calculated with the various beam sizes, average energy, and width of the beam. It was verified that the trend of AD and Tmax change as a function of the beam width can be well predicted. The characteristic curve can contribute to predict the beam quality once the beam size is determined, and give a guideline to design of an optimum neutron beams, and help to determine if there is a room for beam improvement or it is sufficiently optimized. If it is required to improve the beam quality, the curve can give a beam design guideline. Consequently, it can contribute to the effective beam design for BNCT

[en] Collimator for Mossbauer source was manufactured for compton scattering experiment. Exposure dose rate was calculated and measured using GM counter for radiation evaluation. These results were well agreed to each other and used for collimator design. SUS303 was used for collimator material because exposure dose rate at 10 cm is about 2 mR/h. The radiation emited from the 35 mm, 65 mm hole was measured using gamma camera which have 4' diameter. 2-D radiation image was acquired and analyzed. The radiation size at Gamma Camera was 8.0 mm and 5.8 mm respectively

[en] A new method for inspection of luggage samples has been investigated by using a 90deg Compton scattering system. The algorithm of the system based on measurements of single scattered gamma rays was developed to reconstruct the same physical images of the objects. The algorithm was constructed to estimate the electron density and linear attenuation coefficients by using the responses of scattering detectors and the transmission detector. The over-estimated and under-estimated problem in the calculations of total and Compton attenuation coefficients can be overcome by using iteration method and by introducing adjustment factor with the response of the transmission detector. The images obtained from Monte Carlo simulations using MCNP4C for some common materials were close to the simulated objects. The excellent agreement between calculated values of electron densities and attenuation coefficients in the simulation and actual ones demonstrates the viability of the new reconstruction algorithm as a method for investigating objects. (author)

[en] This paper reports a methodology for preparing close-packed two dimensional gold nanoprism films and hexagonal nanoplate films at a hexane/water interface. By controlling the concentration of linker molecules in the hexane layer and the temperature of the colloid solution, highly ordered close-packed nanoplate arrays can be fabricated. These films were investigated to compare their corresponding surface enhanced Raman scattering (SERS) efficiencies. It was demonstrated that the Au nanoprism films resulted in a stronger SERS enhancement than the Au hexagonal nanoplate films. The difference in the SERS enhancement is attributed to the film array difference, demonstrating that Au nanoprism films have a higher line contact density than their Au hexagonal analogues

[en] In order to develop a new concept of baggage inspection system, an experimental system consisting of a gamma source, detector sets, spectrometry, and counting system is prepared. The X-ray scattered signals from a scanned object can contain the information on the atomic composition of the materials constituting the object while the conventional baggage inspection system uses transmission signals related to mass or electron density. 10 mCi Co-57 is used as a radiation source for scanning the test material in this work. Simple transmission and scattering experiments are performed for various test materials, and the measured results are compared with the calculated values. The experiment results from this work will be used in the verification of reconstruction algorithm which requires transmission and scattering signals at the same time to identify the unknown materials. (author)

No abstract available

[en] This paper presents theoretical and technical bases, and a calculation procedure for P/T limit curves. Two PC-based programs, Pt.WKS and PLOTPT.BAS are developed to automate repeated hand calculation and plotting required to perform a typical RCS pressure-temperature analysis. The results from PT.WKS are shown to agree with the result from hand calculation. The graphs generated by PLOTPT.BAS and X-Y plotter indicate well the trend of each curves at each rate of heatup/cooldown and each point on curves agree with the computer printout values from PT.WKS

[en] Adoption of the ICRU slab enables several dosimeters to be calibrated at the same time. In order to calibrate all dosimeters mounted at the ICRU slab with the same conversion coefficients, the dosimeters should be positioned at the same irradiation conditions within an agreeable variation. The irradiation conditions can be determined through a radiation quantity that includes incident and backscattered radiations. In this paper, the backscatter factor is employed to quantify the irradiation conditions. If the backscatter factor at the TLD position is the same as that of the TLD at the center of the front surface, the same conversion coefficient can be used for both TLDs because of the same irradiation conditions. In order to examine the irradiation conditions, the backscatter factors at the front surface of the ICRU slab were calculated for photon beams that are parallel and slanted at a 30 deg angle. Distribution of relative backscatter factors to that of the TLD positioned at the center were presented by contours. Consequently, deviations of backscatter factor for nine TLDs were within 3% except photon incidents around 100 keV. It is requested that available positions are refined to calibrate more dosimeters with a conversion coefficient at a time. (author)

[en] The hydraulic nut system is a tensioning system that is a direct retrofit for any existing tensioning system currently used on the reactor vessel. The system itself is of a modular design tensioner and integrated mechanical lock ring to retain load generated through the use of hydraulics. The hydraulic nuts allow for 100% tensioning of all studs simultaneously, so reduction in critical path time and radiation exposure for both installation and removal laborers can be achieved by adopting this device. Structural analyses for the hydraulic nut device which will be applied to the Nuclear Power Plant reactor vessel have been performed to evaluate the effect of the replacement on the structural integrity of both the reactor vessel closure head area and the hydraulic nuts. Shakedown analyses have been performed because the primary plus secondary (P+Q) stress intensity limit of the hydraulic nut is exceeded in several locations. It is concluded that shakedown will occur and structural integrity of the reactor vessel closure head area will be maintained with the application of the hydraulic nut system

[en] The supercritical CO_2 Brayton cycle has been studied for nuclear applications, mainly for one of the alternative power conversion systems of the sodium cooled fast reactor, since 1960's. Although the supercritical CO_2 Brayton cycle has not been expected to show higher efficiency at lower turbine inlet temperature over the conventional steam Rankine cycle, the higher density of supercritical CO_2 like a liquid in the supercritical region could reduce turbo-machinery sizes, and the potential problem of sodium-water reaction with the sodium cooled fast reactor might be solved with the use of CO_2 instead of water. The supercritical CO_2 recompression Brayton cycle was proposed for the better thermodynamic efficiency than for the simple supercritical CO_2 Brayton cycle. Thus this paper presents the efficiencies of the supercritical CO_2 recompression Brayton cycle along with several decision variables for the thermodynamic optimization of the supercritical CO_2 recompression Brayton cycle. The analytic results in this study show that the system efficiency reaches its maximum value at a compressor outlet pressure of 200 bars and a recycle fraction of 30 %, and the lower minimum temperature approach at the two heat exchangers shows higher system efficiency as expected