• Proceedings of the Korean Radioactive Waste Society Conference
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• 2005.06a
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• pp.344-349
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• 2005

Neutron count rate measurements to assay fissile content of uranium powder have been carried out in a neutron counter. The induced fission neutrons by Cf-252 neutron source are counted as the variation of fissile material in fuel material. The measured counts are compared with equivalent results obtained from calculation. It shows that the measured neutron counts versus quantity of $UO_2$ powder enrichment agreed reasonably well with the calculated values.

• Journal of Radiation Protection and Research
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• v.28 no.4
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• pp.327-335
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• 2003

The commercially available neutron survey meter, the REM500, which uses a tissue equivalent proportional counter (TEPC) and the self-constructed TEPC were used to determine the microdosimetric quantities of several neutron calibration fields at Korea Atomic Energy Research Institute (KAERI). Microdosimetric spectra, absorbed dose, dose equivalent as well as quality factor were derived and compared with several neutron fields which were produced by using the shadow objects to make neutron scattered and being used as a kind of realistic neutron calibration fields at KAERI. The response of REM500 as a function of mean energy was evaluated with these neutron fields using the counts measured and the predetermined reference value. The response of the self-made TEPC and the REM500 was compared using one of the neutron calibration filelds of a $^{252}Cf$ source. The reference quantities of scattered neutron calibration fields were determined using a Bonner Sphere (BS). The value of frequency-mean lineal energy, dose-mean lineal energy and quality factor of two $^{252}Cf$ sources (unmoderated and $D_2O$ moderated) were determined to check the differences in the reference neutron fields between KAERI and Pacific Northwest National Laboratory (PNNL, USA) and the results were in good agreement within 1%. It means that there is no big difference in dosimetric quantifies of neutron calibration fields of two laboratories.

• Journal of Radiation Protection and Research
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• v.26 no.3
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• pp.243-248
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• 2001

Neutron reference fields of Korea Atomic Energy Research Institute (KAERI) for calibrating neutron measuring devices to be used in radiation workplace monitoring consist of two kinds of neutron spectra, the direct and the scattered neutron fields, which are produced by using radionuclide neutron sources, 252Cf and 241AmBe sources. Necessary parameters for calibration such as the anisotropy factor of each neutron source and the room-scattered fraction of some neutron surveymeters in the KAERI calibration facility were determined by calculation or measurement. Spectral measurement of scattered neutron fields were performed at each reference calibration point using a Bonner Multi-sphere Spectrometer (BMS) and the dosimetric quantities for calibration also estimated from the neutron energy spectra which were unfolded using the BUNKI code.

• Nuclear Engineering and Technology
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• v.40 no.4
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• pp.299-304
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• 2008

A detection system was set up to measure the neutron generation rate of a recently developed D-D neutron generator. The system is composed of a Si detector, He-3 detector, and electronics for pulse height analysis. The neutron generation rate was measured by counting protons using the Si detector, and the data was crosschecked by counting neutrons with the He-3 detector. The efficiencies of the Si and He-3 detectors were calibrated independently by using a standard alpha particle source $^{241}Am$ and a bare isotopic neutron source $^{252}Cf$, respectively. The effect of the cross-sectional difference between the D(d,p)T and $D(d,n)^3He$ reactions was evaluated for the case of a thick target. The neutron generation rate was theoretically corrected for the anisotropic emission of protons and neutrons in the D-D reactions. The attenuations of neutron on the path to the He-3 detector by the target assembly and vacuum flange of the neutron generator were considered by the Monte Carlo method using the MCNP 4C2 code. As a result, the neutron generation rate based on the Si detector measurement was determined with a relative uncertainty of ${\pm}5%$, and the two rates measured by both detectors corroborated within 20%.

• Nuclear Engineering and Technology
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• v.55 no.3
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• pp.1021-1030
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• 2023

We propose an overall procedure for measuring and unfolding fast neutron spectra using a trans-stilbene scintillation detector. Detector characterization was described, including the information on energy calibration, detector resolution, and nonproportionality response. The digital charge comparison method was used for the investigation of neutron-gamma Pulse Shape Discrimination (PSD). A pair of values of 600 ns pulse width and 24 ns delay time was found as the optimized conditions for PSD. A fitting technique was introduced to increase the trans-stilbene Proton Response Function (PRF) by 28% based on comparison of the simulated and experimental electron-equivalent distributions by the Cf-252 source. The detector response matrix was constructed by Monte-Carlo simulation and the spectrum unfolding was implemented using the iterative Bayesian method. The unfolding of simulated and measured spectra of Cf-252 and AmBe neutron sources indicates reliable, stable and no-bias results. The unfolding technique was also validated by the measured cosmic-ray induced neutron flux. Our approach is promising for fast neutron detection and spectroscopy.

• Journal of Radiation Protection and Research
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• v.42 no.1
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• pp.48-55
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• 2017

Background: Simultaneous detection of neutrons and gamma rays have become much more practicable, by taking advantage of good gamma-ray discrimination properties using pulse shape discrimination (PSD) technique. Recently, we introduced a commercial CLYC system in Korea, and performed an initial characterization and simulation studies for the CLYC detector system to provide references for the future implementation of the dual-mode scintillator system in various studies and applications. Materials and Methods: We evaluated a CLYC detector with 95% $^6Li$ enrichment using various gamma-ray sources and a $^{252}Cf$ neutron source, with validation of our Monte Carlo simulation results via measurement experiments. Absolute full-energy peak efficiency values were calculated for gamma-ray sources and neutron source using MCNP6 and compared with measurement experiments of the calibration sources. In addition, behavioral characteristics of neutrons were validated by comparing simulations and experiments on neutron moderation with various polyethylene (PE) moderator thicknesses. Results and Discussion: Both results showed good agreements in overall characteristics of the gamma and neutron detection efficiencies, with consistent ~20% discrepancy. Furthermore, moderation of neutrons emitted from $^{252}Cf$ showed similarities between the simulation and the experiment, in terms of their relative ratios depending on the thickness of the PE moderator. Conclusion: A CLYC detector system was characterized for its energy resolution and detection efficiency, and Monte Carlo simulations on the detector system was validated experimentally. Validation of the simulation results in overall trend of the CLYC detector behavior will provide the fundamental basis and validity of follow-up Monte Carlo simulation studies for the development of our dual-particle imager using a rotational modulation collimator.

• Journal of Radiation Protection and Research
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• v.13 no.1
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• pp.42-54
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• 1988

Overall reviews of papers presented at the seventh IRPA International Congress (Aprill 10-17, 1988) held in Sydney, Australia have been done in order to grasp the trends of radiation research. In this report, the changing and increasing matters in the field of ionizing radiation safety as well as non-ionizing radiation application are introduced to the KARP. In addition, a research paper, 'Emission Rate Measurement of a Cf-252 Neutron Source by Manganous Sulfate Bath Method', presented at the IRPA 7 Poster Session is followed.

• Nuclear Engineering and Technology
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• v.47 no.7
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• pp.939-944
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• 2015

The calibration methods of neutron-measuring devices such as the neutron survey meter have advantages and disadvantages. To compare the calibration factors obtained by the shadow cone method and semi-empirical method, 10 neutron survey meters of five different types were used in this study. This experiment was performed at the Korea Atomic Energy Research Institute (KAERI; Daejeon, South Korea), and the calibration neutron fields were constructed using a $^{252}Californium$ ($^{252}Cf$) neutron source, which was positioned in the center of the neutron irradiation room. The neutron spectra of the calibration neutron fields were measured by a europium-activated lithium iodide scintillator in combination with KAERI's Bonner sphere system. When the shadow cone method was used, 10 single moderator-based survey meters exhibited a smaller calibration factor by as much as 3.1-9.3% than that of the semi-empirical method. This finding indicates that neutron survey meters underestimated the scattered neutrons and attenuated neutrons (i.e., the total scatter corrections). This underestimation of the calibration factor was attributed to the fact that single moderator-based survey meters have an under-ambient dose equivalent response in the thermal or thermal-dominant neutron field. As a result, when the shadow cone method is used for a single moderator-based survey meter, an additional correction and the International Organization for Standardization standard 8529-2 for room-scattered neutrons should be considered.

• Journal of Radiation Protection and Research
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• v.23 no.1
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• pp.17-23
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• 1998

Dose response relationships for one of biological end-points (gene mutation) in somatic cells of Tradescantia 4430 clones were studied using neutrons coming out of a californium-252 isotopic source. And the relative biological effectiveness (RBE) of neutrons in relation to X-rays in the induction of TSH pink mutations was assessed. Inflorescences were irradiated with X-ray from X-ray generator and neutrons from $^{252}Cf$ source. Irradiated cuttings were incubated with aeration in neutrient solution under the controlled condition. For more than 4 weeks after irradiation cell mutations were scored. Pink mutation frequencies were calculated from the pooled data for the peak interval (days 6 to 13 post-irradiation). Somatic cell mutations in TSH showed linear dose response relationships in the range of neutron doses available for the experiment. The RBE values estimated for neutrons in relation to X-rays were in the range 3.1 to 6.8, which were much lower than normally recognized value.

• Journal of Radiation Protection and Research
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• v.37 no.2
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• pp.70-74
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• 2012

Silicon carbide (SiC) is a promising material for neutron detection at harsh environments because of its capability to withstand strong radiation fields and high temperatures. Two PIN-type SiC semiconductor neutron detectors, which can be used for nuclear power plant (NPP) applications, such as in-core reactor neutron flux monitoring and measurement, were designed and fabricated. As a preliminary test, MCNPX simulations were performed to estimate reaction probabilities with respect to neutron energies. In the experiment, I-V curves were measured to confirm the diode characteristic of the detectors, and pulse height spectra were measured for neutron responses by using a $^{252}Cf$ neutron source at KRISS (Korea Research Institute of Standards and Science), and a Tandem accelerator at KIGAM (Korea Institute of Geoscience and Mineral Resources). The neutron counts of the detector were linearly increased as the incident neutron flux got larger.