Speaker
Description
The hot spot, radioactivity, and discrimination of radionuclides must investigate in order to determine the radiological characterization during decommissioning. It is widely known how the radiological characterization evaluates at each stages [1]. Decontamination is essential process to reduce radioactive waste because we need large area to store a lot of the waste. The scintillation detector is widely used for radioactive waste monitor. Many scintillation detectors are needed to identify the position of the radioactive contamination. There is, therefore, a limitation to detect the hot spot accurately. This problem can overcome by gamma camera which detects and visualizes of the radioactive sources. The high resolution gamma camera is useful for effective decontamination and cost reduction. The purpose of this study is to design of high resolution gamma camera for radioactive waste monitor. The gamma camera consisted of a pinhole collimator, NaI (Tl) crystal, position sensitive photo-multiplier (PSPMT), signal processing board, and data acquisition board (DAQ). The acceptance angle and source-to-collimator distance were around 37° and 70 cm, respectively. The channel-height pinhole collimator was optimized for high resolution gamma camera. For 2° resolution, the optimized diameter and height of pinhole collimator by Monte Carlo simulation were 1 mm and 4 mm, respectively. The scintillation crystal was determined as cylinder shaped NaI (Tl) crystal, diameter of 10 cm and height of 7.6 cm, which has 7 % energy resolution. The PSPMT (Mo. R3292-02) which is manufactured by Hamamatsu Photonics was used. The experimental measurements were evaluated using Tc-99m, Cs-137, Co-60, and K-40 sources. The information of position and energy were calculated by anger logic. The discrimination of radionuclides and radioactivity also were investigated.
