Radiation Hardness Test of a Silicon Detector under Radiation Dose Rate of Nuclear Power Plant for In-Containment Coolant Leakage Detection System

An influence evaluation by background radiation on a silicon detector, which will be used to detect a coolant leakage, and installed in a containment building of a nuclear power plant, was performed and the result was discussed. The detector that consists of a silicon sensor and preamplifier mounted in a shielding structure which composed of a 5 cm lead cylinder will be installed in an annulus zone that is influenced by background radiation (neutron and gamma ray) from an operation of a nuclear reactor. Absorbed dose rates on a silicon sensor and preamplifier were calculated as 2.15 mGy/hr and 1.05 mGy/hr, respectively, by Monte Carlo N-Particle (MCNP) simulation. Data of background radiation had referred to a Final Safety Analysis Report (FSAR) of a nuclear power plant in the Republic of Korea. A silicon sensor and preamplifier were irradiated by a Co60 gamma radiation source equipped in a facility of Korea Atomic Energy Research Institute Advanced Radiation Technology Institute (KAERI ARTI) of the Republic of Korea. A Po-210 alpha source was used as a check source to evaluate a state of a function of the detector during gamma irradiation. Absorbed dose rates were about 22.92 mGy/hr and 6.6 mGy/hr on silicon sensor and preamplifier, respectively. Before and during gamma irradiation, a count rates from the check source wasn`t changed (from 18.4 cps to 18.4±0.2 cps after irradiation), and any degradations of function also weren`t observed. Even more harsh condition than calculated dose rates referred by the condition of background radiation of in-containment, the silicon detector maintained the ability of function of charged particles detection. Based on the result, it has been demonstrated that a silicon detector is a suitable detector for detecting charged particles from a leaked coolant even during interfered by the background radiation of a primary system of a nuclear power plant

Study of n/γ discrimination using 3He proportional chamber in high gamma-ray fields

The 3He proportional chamber is widely used for neutron measurement owing to its high neutron detection efficiency and simplicity for gamma-ray rejection. In general, the neutron and gamma-ray signals obtained from the 3He proportional chamber can be easily separated by the difference in the pulse heights. However, for a high gamma-ray field, the gamma-ray signal cannot be precisely eliminated by the pulse height due to gamma-ray pulse pileup which causes the pulse height of gamma-ray pulse to increase and making the pulses due to neutrons and gamma rays indistinguishable. In this study, an improved algorithm for n/γ discrimination using a parameter, which is the ratio of the rise time to the pulse height, is proposed. The n/γ discrimination performance of the algorithm is evaluated by applying it to 252Cf neutron signal separation from various gamma-ray exposure rate levels ranging 0.1–5 R/h. The performance is compared to that of the conventional pulse-height analysis method in terms of the gamma elimination ratio. The suggested algorithm shows better performance than the conventional one by 1.7% (at 0.1 R/h) to 70% (at 5 R/h) for gamma elimination. Keywords: 3He proportional chamber, Neutron detector, n/γ discrimination, Algorithm, High gamma-ray fiel

Characteristics of 3D Printed Plastic Scintillator

Digital Light Processing (DLP) 3D printing technique can be a powerful tool to fabricate plastic scintillator with a geometrically desired shape in innovatively fast time. Plastic scintillator with the size of 30 mm × 30 mm × 10 mm was fabricated by using the plastic resin and the DLP 3D printer (ASIGA, Pico2HD). The characteristics of decay time, energy resolution, intrinsic detection efficiency were analyzed and compared between the fabricated 3D printing plastic scintillator and a commercial plastic scintillator BC408 (Saint-Gobain Crystal). Decay time profile of the tested plastic scintillators was measured for 137Cs Compton maximum electron 477 keV by using a modified time correlated single photon counting (TCSPC) setup. The time profile was fitted by reconvolution function, and each decay time component and contribution was analyzed. For energy resolution of plastic scintillator, the Gaussian spectrum for 137Cs Compton maximum electron 477 keV was selectively measured by using the γ-γ coincidence experimental setup. As a result, it was confirmed that the 3D printing plastic scintillator showed average decay time 15.6 ns and energy resolution 15.4%. These characteristics demonstrates the feasibility of 3D printing plastic scintillator as a radiation detector

Fine Phantom Image from Laser-induced Proton Radiography with a Spatial Resolution of Several μm

The advantages of a laser-driven proton acceleration have prompted studies of laser-induced proton radiography. As the CR-39 solid-state nuclear-track detector is suitable for measuring charged particles and can be used in proton radiography, we studied laser-induced proton radiography with the CR-39 for several years, and we were able to obtain a spatial resolution of about 10 μm. For obtaining an image with a spatial resolution of a few μm, we investigated the effect of the CR-39 etching conditions on the spatial resolution and carried out imaging experiments using fine phantoms. Experiments were performed using the 100-TW titanium-sapphire laser system at the Advanced Photonics Research Institute of the Gwangju Institute of Science Technology. We have demonstrated that images with a spatial resolution of about several μm can be achieved using laser-induced proton radiography.1221sciescopuskc