Development of accuracy enhancement system for boron meters using multisensitive detector for reactor safety

Boric acid is used as a coolant for pressurized-water reactors, and the degree of burnup is controlled by the concentration of boric acid. Therefore, accurate measurement of the concentration of boric acid is an important factor in reactor safety. An improved system was proposed for the accurate determination of boron concentration. A new boron-concentration measurement technique, called multisensitive detection, was developed to improve the measurement accuracy of boron meters. In previous studies, laboratory-scale experiments were performed based on different sensitivity detectors, confirming a 65% better accuracy than conventional single-detector boron meters. Based on these experimental results, an experimental system simulating the coolant-circulation environment in the reactor was constructed; accuracy analysis of the boron meter with a multisensitivity detector was performed at the actual coolant pressure and temperature. In this study, the boron concentration conversion equation was derived from the calibration test, and the accuracy of the boron concentration conversion equation was examined through a repeatability test. Through the experiment, it was confirmed that the accuracy was up to 87.5% higher than the conventional single-detector boron meter

Numerical analysis of the electromagnetic force for design optimization of a rectangular direct current electromagnetic pump

The force of a direct current (DC) electromagnetic pump used to transport liquid lithium was analyzed to optimize its geometrical and electrical parameters by numerical simulation. In a heavy-ion accelerator, which is being developed in Korea, a liquid lithium film is utilized for its high charge-stripping efficiency for heavy ions of uranium. A DC electromagnetic pump with a flow rate of 6 cm(3)/s and a developed pressure of 1.5 MPa at a temperature of 200 degrees C was required to circulate the liquid lithium to form liquid lithium films. The current and magnetic flux densities in the flow gap, where a Sm2Co17 permanent magnet was used to generate a magnetic field, were analyzed for the electromagnetic force distribution generated in the pump. The pressure developed by the Lorentz force on the electromagnetic force was calculated by considering the electromotive force and hydraulic pressure drop in the narrow flow channel. The opposite force at the end part due to the magnetic flux density in the opposite direction depended on the pump geometrical parameters such as the pump duct length and width that defines the rectangular channels in the nonhomogeneous distributions of the current and magnetic fields

Analysis and radiation dose assessment of Rn-222 in indoor air at schools: Case study at Ulju County, Korea

Rn-222 exists in nature in the form of a rare radioactive gas. In terms of environmental radiation, issues regarding Rn-222 have persisted because of its radiological hazardousness. Ulju County is one of the regions of Ulsan metropolitan city, with a population of 227,699. Ulju County has the highest density of industrial complexes in Korea. In this study, Rn-222 radioactivity concentration was measured and analyzed in 57 schools in Ulju County using 114 passive LR-115 type detectors to secure radiological safety and confirm basic information for reduction of resident exposure to Rn-222. The effective dose of Rn-222 was assessed to find the actual risk of the concentration surveyed in schools to human beings. The dose depended on four factors: subjects, Rn-222 concentration, dose coefficient, and time. The individuals subjected to dose estimation were classified into three types: students, teachers, and office workers. The subjects had different dwelling locations and times. The findings demonstrate that the radiological hazard to students and workers at schools in Ulju County owing to Rn-222 is negligible in terms of Rn-222 activity recommendation level

Gamma-Ray Sensor Using YAlO3(Ce) Single Crystal and CNT/PEEK with High Sensitivity and Stability under Harsh Underwater Conditions

A new gamma-ray sensor, which could be employed in harsh underwater conditions, was developed using YAlO3(Ce) single crystal and carbon nanotube reinforced polyetheretherketone (CNT/PEEK). The sensor is compact, highly sensitive and stable, by providing real-time gross counts and an accumulated spectrum for fresh, saline, or contaminated water conditions. The sensor was tested in a water tank for quantification of the limit of detections. The phi 51 x 51 mm(2) YAlO3(Ce) crystal exhibits a nearly perfect proportionality with a correlation of over 0.999 in terms of light yield per energy and possesses a high energy resolution. The chemically stable CNT/PEEK window material further enhances the detection efficiency by minimizing the background counts from penetrating gamma-rays. Data timeliness was obtained for regulation-based minimum detectable activity targets within 300 s. For a source-detector distance of up to 300 mm in water, the gross counts demonstrate the existence of radionuclides (Cs-137 and Co-60), owing to their higher efficiency (max. similar to 15 times) than those of the photopeak counts. Such differences between efficiency values are more likely in water than in air because of the high density of water, resulting in an increased build-up of scattered photons. The proposed sensor is suitable for autonomous underwater systems

Optimization of outer core to reduce end effect of annular linear induction electromagnetic pump in prototype Generation-IV sodium-cooled fast reactor

An annular linear induction electromagnetic pump (ALIP) which has a developed pressure of 0.76 bar and a flow rate of 100 L/min is designed to analysis end effect which is main problem to use ALIP in thermohydraulic system of the prototype generation-IV sodium-cooled fast reactor (PGSFR). Because there is no moving part which is directly in contact with the liquid, such as the impeller of a mechanical pump, an ALIP is one of the best options for transporting sodium, considering the high temperature and reactivity of liquid sodium. For the analysis of an ALIP, some of the most important characteristics are the electromagnetic properties such as the magnetic field, current density, and the Lorentz force. These electromagnetic properties not only affect the performance of an ALIP, but they additionally influence the end effect. The end effect is caused by distortion to the electromagnetic field at both ends of an ALIP, influencing both the flow stability and developed pressure. The electromagnetic field distribution in an ALIP is analyzed in this study by solving Maxwell's equations and using numerical analysis. (C) 2019 Korean Nuclear Society, Published by Elsevier Korea LLC

Plastic scintillator beta ray scanner for in-situ discrimination of beta ray and gamma ray radioactivity in soil

A beta ray scanner was proposed for in-situ discrimination of beta and gamma ray radioactivity. This scanner is based on the principle that gamma and beta rays experience different changes in detection efficiency in scintillators with different geometries, especially with regard to the scintillator thickness. The ratios of the counting rates of gamma rays (R-gamma), beta rays (R-beta), and sample measurements (R-total) in a thick scintillator to those in a thin one are reported. The parameter X-thick, which represents the counting rate contributed by beta rays to the total counting rate in the thick scintillator, was derived as a function of those ratios. The values of R-gamma and R-beta for Co-60 and Sr-90 sources were estimated as 3.2 +/- 0.057 and 0.99 +/- 0.0049, respectively. The estimated beta ray contributions had relative standard deviations of 2.05-4.96%. The estimated range of the beta rays emitted from Sr-90 was 19 mm as per the Monte Carlo N-Particle simulation, and this value was experimentally verified. Homogeneous and surface contaminations of Co-60 and Sr-90-Y-90 were simulated for application of the proposed method. The counting rate contributed by the beta rays was derived and found to be proportional to the concentration of Sr-90-Y-90 contamination. (C) 2019 Korean Nuclear Society, Published by Elsevier Korea LLC

Radioactivity analysis for EPS waste using organic solvents

In this study, the recovery rates of the dissolution method for radioactivity analysis of expandable polystyrene (EPS) with a liquid scintillation counter (LSC) using tetrahydrofuran (THF), toluene, and acetone as solvents were estimated. The detection efficiency calibration curve for each solvent was derived. Two methods-the volumetric ratio method and the quenching agent method-were used to prepare quench source sets, and calibration curves were derived by linking the data from the two quench source sets. The R-2 value of the calibration curve for THF was found to be 0.984. The relationship between the mass of dissolved EPS and the quench level was estimated: the quench level increased as the mass of dissolved EPS increased. Premix and postmix dissolution methods were tested. The recovery rates using THF with the premix method were 84.9 +/- 0.9% and 96.5 +/- 1.5% for H-3 and C-14, respectively. Furthermore, the stability of the recovery rate over time when using THF was evaluated. The dissolution method with the premixed solution exhibited a more stable recovery rate over time. The dissolution methods were found to be applicable for analysis using LSC, and THF was found to be the most suitable solvent for the proposed method. (C) 2021 Korean Nuclear Society, Published by Elsevier Korea LLC

Optimization of airborne alpha beta detection system modeling using MCNP simulation

An airborne alpha beta detection system using passivated implanted planar silicon (PIPS) detector was modeled with the MCNP6 code and its resolution and detection efficiency were analyzed. Simulation of the resolution performed using the Gaussian energy broadening (GEB) function showed that the full width at half maximum (FWHM) of 35.214 keV for alpha particles was within 34-38 KeV, which is the FWHM range of the actual detector, and the FWHM of 15.1 keV for beta particles was constructed with a similar model to 17 keV, which is the FWHM range of an actual detector. In addition, the detection efficiency and the resolution were simulated according to the distance between the detector and the air filter. When the distance was decreased to 0.2 cm from 0.8 cm, the efficiency of the alpha and beta particles detection decreased from 5.33% to 4.89% and from 5.64% to 4.27%, respectively, and the FWHM of the alpha and beta particles improved from 40.9 KeV to 29.84 keV and 25.76 keV-13.27 keV, respectively. (C) 2019 Korean Nuclear Society, Published by Elsevier Korea LLC

Spectral resolution evaluation by MCNP simulation for airborne alpha detection system with a collimator

In this study, an airborne alpha detection system, which consists of a passivated implanted planar silicon (PIPS) detector and an air filter, was developed. A collimator applied to the alpha detection system showed an enhancement in resolution and a degradation in detection efficiency. The resolution and detection efficiency were compared and analyzed to evaluate the performance of the collimator. Thus, the resolution was found to be more important than the efficiency as a determining factor of the detection system performance, from the viewpoint of radionuclide identification. The performance was evaluated on three properties of the collimator: hole shape, hole length, and the ratio between the hole and frame pitches. From the hole shape performance evaluation, a hexagonal collimator showed the highest resolution. Further, the collimator with a hole pitch of 14 mm was found to have the highest resolution while that with a frame pitch of 4-6 mm (i.e., 1.2-1.4 times longer than the hole pitch) showed the highest resolution. ? 2020 Korean Nuclear Society, Published by Elsevier Korea LLC. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/)

Dose evaluation of workers according to operating time and outflow rate in a spent resin treatment facility

Workers' safety from radiological exposure in a 1 ton/day capacity spent resin treatment facility was evaluated according to the operating times and outflow rate due to process related leakages. The conservative annual dose based on the operating times of the workers exceeded the dose limit by at least 7.38E+01 mSv for close work. The realistic dose range was derived as 1.62E+01 mSv-6.60E+01 mSv. The conservative and realistic annual doses for remote workers were 1.33E+01 mSv and 3.00E+0 0 mSv respectively, which were less than the dose limit. The MWR was identified as the major contributor to worker exposure within the 1 h period required for removal of radioactive materials. The dose considering both internal and external exposures without APF was derived to be 1.92E+01 mSv for conservative evaluation and 4.00E+0 0 mSv for realistic evaluation. Furthermore, the dose with APF was derived as 7.27E-01 mSv for conservative evaluation and 1.51E-01 mSv for realistic evaluation. Considering the APF for leakage from all parts, the dose range was derived as 1.25E+0 0 mSv-2.03E+0 0 mSv for conservative evaluation and 2.61E-01 mSv-4.23E-01 mSv for realistic evaluation. Hence, it was confirmed that radiological safety was secured in the event of a leakage accident. (c) 2021 Korean Nuclear Society, Published by Elsevier Korea LLC. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/)