[en] As the system characteristics, the target in the spectrometer emits approximately 1012 neutrons/s. To efficiently shield the neutron, the shielding door designs are proposed for the LSDS system through a comparison of the direct shield and maze designs. Hence, to guarantee the radiation safety for the facility, the door design is a compulsory course of the development of the LSDS system. To improve the shielding rates, 250x250 covering structure was added as a subsidiary around the spectrometer. In this study, the evaluations of the suggested shielding designs were conducted using MCNP code. The suggested door design and covering structures can shield the neutron efficiently, thus all evaluations of all conditions are satisfied within the public dose limits. From the Monte Carlo code simulation, Resin(Indoor type) and Tungsten(Outdoor type) were selected as the shielding door materials. From a comparative evaluation of the door thickness, In and Out door thickness was selected 50 cm

[en] To reuse fissile materials through fuel cycle in future nuclear energy system development and achieve safety, economics, optimization of spent fuel management, an information of isotopic fissile content(U235, Pu239, Pu241, MA) is required to be provided basically. LSDS technology development was done to assay isotopic fissile contents. LSDS system consists of spectrometer, source neutron, measurement, data process. In 1st phase (2012-2013), key measurement technology, neutron source technology, conceptual design of detection system and shielding design were done. In the spectrometer, neutron spectrum and resolution analysis, detector design and response, detection model were performed. The optimum shielding model was proposed by shielding dose simulation. In 2nd phase (2014-2016), key parameters were determined in optimized spectrometer, fission detection sensitivity, accelerator and beam dump design, target design and neutron yield analysis, cooling system, material activation, optimized shielding model were done, and finally, mathematical assay model was proposed with software development to isotopic fissile content. Additionally, correction methodology was established by fission signal analysis. Using real U235(4.8%) and Pu239(47g, 91g), fission data was obtained. In fissile assay using various fissile materials, the content of uranium and plutonium was assay with 1-3% error. In the unknown sample, the content of plutonium was analyzed in 1-2% uncertainty. The isotopic fissile content assay technology is required in the reuse by fuel cycle for success of future nuclear energy system development. Moreover, such an advanced new fissile assay technology will lead the international nuclear area and contribute to technology export.