An experiment to search for light sterile neutrinos is conducted at a reactor with a thermal power of 2.8 GW located at the Hanbit nuclear power complex. The search is done with a detector consisting of a ton of Gd-loaded liquid scintillator in a tendon gallery approximately 24 m from the reactor core. The measured antineutrino event rate is 1976 per day with a signal to background ratio of about 22. The shape of the antineutrino energy spectrum obtained from the eight-month data-taking period is compared with a hypothesis of oscillations due to activesterile antineutrino mixing. No strong evidence of 3+1 neutrino oscillation is found. An excess around the 5 MeV prompt energy range is observed as seen in existing longer-baseline experiments. The mixing parameter sin 2 2θ14 is limited up to less than 0.1 for ∆m The mixing among three neutrinos has been well established by experiments performed in the past two decades since the discovery of neutrino oscillations [1][2][3]. Consistent measurements of the two mass differences and the three mixing angles of the standard, three-neutrino mixing model have been reported by oscillation experiments using atmospheric, solar, reactor, and accelerator neutrinos [4]. Nevertheless, the mass hierarchy, the mass of the lightest neutrino, the Dirac or Majorana nature of the neutrino, and the CP phase are yet to be determined [5].Even though the number of active light neutrinos is limited to three by Z boson decay-width measurements [6], it is still possible to have additional neutrinos if they are sterile. Sterile neutrinos can be identified by the occurrence of activesterile neutrino oscillations. A hint for this is the LSND experiment's report of an observation ofν µ →ν e mixing with a frequency corresponding to a mass-squared difference larger than 0.01 eV 2 [7]. Results from the MiniBooNE's test of the LSND signal are, however, inconclusive [8].In addition to the LSND result, there are two other anomalies that could possibly be signs of active-sterile neutrino oscillations. An apparent ν e disappearance over a baseline of a few meters in the GALLEX and SAGE gallium experiments exposed to radioactive sources was reported [9]; the ratio of the numbers of measured and predicted events is 0.88 ± 0.05. A number of short-baseline reactor antineutrino experiments established limits on the presence of neutrino oscillations with eV mass differences by shape analyses of the measured neutrino energy spectra. Among those experiments, the Bugey experimental limits on sterile neutrinos are the most stringent [10]. Mueller et al. [11] found about a 6% deficit in reactor antineutrino event rates compared with the theoretical expectations for the short-baseline reactor experiments, which is the so-called "reactor antineutrino anomaly" (RAA). It can be interpreted as an active-sterile neutrino oscillation with three active neutrinos plus one or more sterile neutrinos, i.e., a 3 + n ν scenario [12,13], compatible with the LSND result. Recent reactor experiments that measured the θ 13 mixing an...

In order to test the existence of the sterile neutrino, NEOS experiment was performed from August 2015 to May 2016. The prompt energy spectrum from the inverse beta decay of electron antineutrino from a 2.8 GW th reactor was measured at 24 m distance. The number of measured IBD candidates is about 2000 per day during reactor-on period and a ratio of signal to background is about 22. The result shows no strong evidence of active-to-sterile neutrino. An exclusion-limit curve for 3+1 hypothesis is found at 90% CL. via shape-only analysis.

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The sensitivity of parameters related with reactor physics on the source terms of decommissioning wastes from a CANDU reactor was investigated in order to find a viable, simplified burned core model of a Monte Carlo simulation for decommissioning waste characterization. First, a sensitivity study was performed for the level of nuclide consideration in an irradiated fuel and implicit geometry modeling, the effects of side structural components of the core, and structural supporters for reactive devices. The overall effects for computation memory, calculation time, and accuracy were then investigated with a full-core model. From the results, it was revealed that the level of nuclide consideration and geometry homogenization are not important factors when the ratio of macroscopic neutron absorption cross section (MNAC) relative to a total value exceeded 0.95. The most important factor affecting the neutron flux of the pressure tube was shown to be the structural supporters for reactivity devices, showing an 10% difference. Finally, it was concluded that a bundle-average homogeneous model considering a MNAC of 0.95, which is the simplest model in this study, could be a viable approximate model, with about 25% lower computation memory, 40% faster simulation time, and reasonable engineering accuracy compared with a model with an explicit geometry employing an MNAC of 0.99.

Wide-band-gap semiconductors such as SiC, AlN, and GaN are promising materials for harsh environment applications due to their high-temperature operation capability. Two types of PIN-type semiconductor neutron detectors based on SiC were designed and fabricated for nuclear power plant (NPP) applications such an in-core reactor neutron flux monitoring and safeguarding nuclear materials. One is for fast neutron detection and the other, which was evaporated with 6 LiF, is for thermal neutron detection. In this study, preliminary tests, such as the determination of I-V and alpha responses, were performed. Reaction probabilities with respect to neutron energies were also calculated by using an MCNPX code for comparison with the experimental results. Responses of the neutrons were measured at the Ex-core Neutron irradiation Facility (ENF) of the High-flux Advanced Neutron Application Reactor (HANARO) research reactor at the Korea Atomic Energy Research Institute (KAERI). Pulse height spectra and count rates were measured with respect to the neutron fluxes from 1:6 Â 10 6 n/cm 2 Ás to 1:9 Â 10 7 n/cm 2 Ás. Also, a 0.99 root-mean-square value of linearity against the fluxes to the count rates was obtained with the fabricated neutron detectors. For a thermal neutron detector, a 3.3% detection efficiency was obtained.

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Iron pyrite (FeS2) has attracted significant attention as a promising inorganic material in various applications, such as electrode materials for high-energy batteries, medical diagnostics, semiconductor materials, and photovoltaic solar cells. In this study, we characterized the crystalline structure and magnetic properties of FeS2 using X-ray diffraction (XRD), vibrating sample magnetometry, and Mössbauer spectroscopy. The refined XRD patterns confirmed that the crystalline structure of FeS2 was cubic (Pa-3 space group) with lattice constant a0 = 5.417 Å. The temperature dependence of the zero-field-cooled and field-cooled curves and the hysteresis loops were measured at various temperatures between 4.2 and 295 K. The Mössbauer spectra collected in the temperature range of 4.2–500 K were fitted with one doublet. The ΔEQ values increased slightly with decreasing temperature owing to changes in the Fe–S distance. The charge state was determined to be Fe2+ based on the isomer shift (δ).

Number of figures : 1 Number of tables : 3 Table S1. Results of major elemental concentrations (mg•kg-1) as determined by WD-XRF and k0-INAA for cross validation of methods. Results are given with the expanded uncertainty of k = 2 elements YD17 YD18 YD19 WD-XRF k0-INAA % dev. WD-XRF k0-INAA % dev. WD-XRF k0-INAA % dev.