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KMID : 0364920140390010021
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Journal of Radiation Protection and Research
2014 Volume.39 No. 1 p.21 ~ p.29
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Shielding Design Optimization of the HANARO Cold Neutron Triple-Axis Spectrometer and Radiation Dose Measurement
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Ryu Ji Myung
Hong Kwang-Pyo
Park J.M. Sung-il
Choi Young-Hyeon
Lee Kye-Hong
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Abstract
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A new cold neutron triple-axis spectrometer (Cold-TAS) was recently constructed at the 30 MWth research reactor,HANARO. The spectrometer, which is composed of neutron optical components and radiation shield, required a redesign ofthe segmented monochromator shield due to the lack of adequate support of its weight. To shed some weight, lowering theheight of the segmented shield was suggested while adding more radiation shield to the top cover of the monochromatorchamber. To investigate the radiological effect of such change, we performed MCNPX simulations of a few differentconfigurations of the Cold-TAS monochromator shield and obtained neutron and photon intensities at 5 reference points justoutside the shield. Reducing the 35% of the height of the segmented shield and locating lead 10 cm from the bottom ofthe top cover made of polyethylene was shown to perform just as well as the original configuration as radiation shieldexcepting gamma flux at two points. Using gamma map by MCNPX, it was checked that is distribution of gamma. Increasedflux had direction to the top and it had longer distance from top of segmented shield. However, because of reducing the35% of the height, height of dissipated gamma was lower than original geometry. Reducing the 35% of the height of thesegmented shield and locating lead 10cm from the bottom of the top cover was selected. After changing geometry, radiationdose was measured by TLD for confirming tester’s safety at any condition. Neutron(0.21 μSvhr-1) and gamma(3.69 μSvhr-1)radiation dose were satisfied standard(6.25 μSvhr-1).
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KEYWORD
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Cold-TAS(Cold Neutron Triple-Axis Spectrometer), MCNPX, Radiation shield, Neutron flux, Gamma flux, Radiationdose
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