• Title, Summary, Keyword: neutron monitor

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Installation of Neutron Monitor at the Jang Bogo Station in Antarctica

  • Jung, Jongil;Oh, Suyeon;Yi, Yu;Evenson, Paul;Pyle, Roger;Jee, Geonhwa;Kim, Jeong-Han;Lee, Changsup;Sohn, Jongdae
    • Journal of Astronomy and Space Sciences
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    • v.33 no.4
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    • pp.345-348
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    • 2016
  • In December 2015, we have installed neutron monitor at the Jang Bogo station in Antarctica. The Jang Bogo station is the second science station which is located at the coast ($74^{\circ}\;37.4^{\prime}S$, $164^{\circ}\;13.7^{\prime}E$) of Terra Nova Bay in Northern Victoria Land of Antarctica. A neutron monitor is an instrument to detect neutrons from secondary cosmic rays collided by the atmosphere. The installation of neutron monitor at Jang Bogo station is a part of transferred mission for neutron monitor at McMurdo station of USA. Among 18 tubes of 18-NM64 neutron monitor, we have completed relocation of 6 tubes and the rest will be transferred in December 2017. Currently, comparison of data from both neutron monitors is under way and there is a good agreement between the data. The neutron monitor at Jang Bogo station will be quite useful to study the space weather when the installation is completed.

Neutron fluence measurement at HANARO using fluence monitor method (Fluence Monitor를 이용한 HANARO 노심 내 중성자 플루언스 측정)

  • Lee, Seung-Kyu;Jo, Kwang-Ho;Choo, Kee-Nam;Park, Jin-Suk;Kim, Yong-Kyun
    • Journal of Radiation Protection and Research
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    • v.36 no.4
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    • pp.200-208
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    • 2011
  • The neutron fluence measurement and evaluation technology is very important for material irradiation test. The most essential technology in this study is the neutron irradiation evaluation method using a fluence monitor. The fluence monitors were fabricated with metal wires of the purity ${\geq}$ 99.9%, whose dimensions were 0.1mm diameter, about 3 mm length, and around 150-200 ${\mu}g$ mass range. Three wire samples (Fe, Ni, Ti) were prepared for one irradiation aluminum capsule. Five capsules were irradiated in the OR5 hole of the HANARO reactor at 30 MW power for about 25 days. After irradiation tests, radiation activities were measured with the high purity germanium (HPGe) detector. The reaction rates were calculated by using the measured radiation activity data, and then neutron fluence were obtained from the reaction rates and the weighted neutron cross section with calculated neutron spectrum at the fluence monitor position.

Observation of Periodic and Transient Cosmic Ray Flux Variations by the Daejeon Neutron Monitor and the Seoul muon Detector

  • Oh, Suyeon;Kang, Jeongsoo
    • Journal of Astronomy and Space Sciences
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    • v.30 no.3
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    • pp.175-178
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    • 2013
  • Recently, two instruments of cosmic ray are operating in South Korea. One is Seoul muon detector after October 1999 and the other is Daejeon neutron monitor (Kang et al. 2012) after October 2011. The former consists of four small plastic scintillators and the latter is the standard 18 NM 64 type. In this report, we introduce the characteristics of both instruments. We also analyze the flux variations of cosmic ray such as diurnal variation and Forbush decrease. As the result, the muon flux shows the typical seasonal and diurnal variations. The neutron flux also shows the diurnal variation. The phase which shows the maximum flux in the diurnal variation is around 13-14 local time. We found a Forbush decrease on 7 March 2012 by both instruments. It is also identified by Nagoya multi-direction muon telescope and Oulu neutron monitor. The observation of cosmic ray at Jangbogo station as well as in Korean peninsula can support the important information on space weather in local area. It can also enhance the status of Korea in the international community of cosmic ray experiments.

Seasonal Variation of Cosmic Ray Intensity Observed by the Oulu Neutron Monitor

  • Jeong, Jaesik;Oh, Suyeon
    • Journal of Astronomy and Space Sciences
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    • v.37 no.3
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    • pp.165-170
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    • 2020
  • Muons and neutrons are representative secondary particles that are generated by interactions between primary cosmic ray particles (mostly protons) and the nuclei of atmospheric gas compounds. Previous studies reported that muons experience seasonal variations because of the meteorological effects of temperature. The intensity of neutrons has a typical modulation with various periods and reasons, such as diurnal and solar variation or transient events. This paper reports that cosmic ray particles, which were observed by neutron monitors, have seasonal variations using the daily data at the Oulu neutron monitor. To eliminate the effects of solar activity across time, the daily data were normalized by two different transformations: transformations with respect to the grand mean and yearly mean. The data after transformation with respect to the yearly mean showed more statistical stability and clear seasonal variations. On the other hand, it is difficult to determine if the seasonal variation results from terrestrial effects, such as meteorological factors, or extraterrestrial effects, such as the position of the Earth in its orbit of revolution.

Mini Neutron Monitors at Concordia Research Station, Central Antarctica

  • Poluianov, Stepan;Usoskin, Ilya;Mishev, Alexander;Moraal, Harm;Kruger, Helena;Casasanta, Giampietro;Traversi, Rita;Udisti, Roberto
    • Journal of Astronomy and Space Sciences
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    • v.32 no.4
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    • pp.281-287
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    • 2015
  • Two mini neutron monitors are installed at Concordia research station (Dome C, Central Antarctica, $75^{\circ}06^{\prime}S$, $123^{\circ}23^{\prime}E$, 3,233 m.a.s.l.). The site has unique properties ideal for cosmic ray measurements, especially for the detection of solar energetic particles: very low cutoff rigidity < 0.01 GV, high elevation and poleward asymptotic acceptance cones pointing to geographical latitudes > $75^{\circ}S$. The instruments consist of a standard neutron monitor and a "bare" (lead-free) neutron monitor. The instrument operation started in mid-January 2015. The barometric correction coefficients were computed for the period from 1 February to 31 July 2015. Several interesting events, including two notable Forbush decreases on 17 March 2015 and 22 June 2015, and a solar particle event of 29 October 2015 were registered. The data sets are available at cosmicrays.oulu.fi and nmdb.eu.

Characteristics of Radiation-Resistant Real-Time Neutron Monitor for Accelerator-Based BNCT

  • Nakamura, Takemi;Sakasai, Kaoru;Nakashima, Hiroshi;Takamiya, Koichi;Kumada, Hiroaki
    • Journal of Radiation Protection and Research
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    • v.41 no.2
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    • pp.105-109
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    • 2016
  • Background: For an accelerator-based BNCT, we have fabricated a new detector consisting of quartz optical fibers that have excellent radiation-resistant characteristics. Materials and Methods: The developed detectors were irradiated at Kyoto University Research Reactor. Results and Discussion: The experimental results showed that the new detector had good output linearity for the neutron intensity, and the response of the new detector did not decrease during the irradiation. Conclusion: The new detector consisting of quartz optical fibers can be applied to measurement of neutron field of an accelerator-based BNCT.

Digital power range neutron monitoring system

  • Endo, Yorimasa;Itoh,Toshiaki;Tai, Ichiro
    • 제어로봇시스템학회:학술대회논문집
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    • pp.804-809
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    • 1988
  • PRNM(Power Range Neutron Monitoring) of BWR (Boiling Water Reactor) is a system that processes signals from about two hundred LPRM (Local Power Range Monitor) sensors in the nuclear reactor and this system monitors the neutron flux level during the plant operating region. Development has been made by employing a special technique for multiplexing neutron sensor signals and the recent advanced microelectronics technology. It is applicable to the total plant digital control system for a nuclear power plant.

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Solar Cyclic Modulation of Diurnal Variation in Cosmic Ray Intensity

  • Park, Eun Ho;Jung, Jongil;Oh, Suyeon;Evenson, Paul
    • Journal of Astronomy and Space Sciences
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    • v.35 no.4
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    • pp.219-225
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    • 2018
  • Cosmic rays are ions that move at relativistic speeds. They generate secondary cosmic rays by successive collisions with atmospheric particles, and then, the secondary particles reach the ground. The secondary particles are mainly neutrons and muons, and the neutrons are observed by the ground neutron monitor. This study compared the diurnal variation in cosmic ray intensity obtained via harmonic analysis and that obtained through the pile-up method, which was examined in a previous study. In addition, we analyzed the maximum phase of the diurnal variation using four neutron monitors with a cutoff rigidity below approximately 6 GV, located at similar longitudes to the Oulu and Rome neutron monitors. Expanding the data of solar cycles 20-24, we examined the time of the maximum cosmic ray intensity, that is, the maximum phase regarding the solar cyclic modulation. During solar cycles 20-24, the maximum phase derived by harmonic analysis showed no significant difference with that derived by the pile-up method. Thus, the pile-up method, a relatively straightforward process to analyze diurnal variation, could replace the complex harmonic analysis. In addition, the maximum phase at six neutron monitors shows the 22-year cyclic variation very clearly. The maximum phase tends to appear earlier and increase the width of the variation in solar cycles as the cutoff rigidity increases.

The first application of modified neutron source multiplication method in subcriticality monitoring based on Monte Carlo

  • Wang, Wencong;Liu, Caixue;Huang, Liyuan
    • Nuclear Engineering and Technology
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    • v.52 no.3
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    • pp.477-484
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    • 2020
  • The control rod drive mechanism needs to be debugged after reactor fresh fuel loading. It is of great importance to monitor the subcriticality of this process accurately. A modified method was applied to the subcriticality monitoring process, in which only a single control rod cluster was fully withdrawn from the core. In order to correct the error in the results obtained by Neutron Source Multiplication Method, which is based on one point reactor model, Monte Carlo neutron transport code was employed to calculate the fission neutron distribution, the iterated fission probability and the neutron flux in the neutron detector. This article analyzed the effect of a coarse mesh and a fine mesh to tally fission neutron distributions, the iterated fission probability distributions and to calculate correction factors. The subcriticality before and after modification is compared with the subcriticality calculated by MCNP code. The modified results turn out to be closer to calculation. It's feasible to implement the modified NSM method in large local reactivity addition process using Monte Carlo code based on 3D model.