This survey of photostimulated luminescence (PSL) phenomenon in photostimulable phosphor materials has some main thrusts: basic mechanism of PSL, characteristics of the imaging plate (IP) and its application to two dimensional radiation dosimetry. In the right of the survey, the IP is one of the most attractive candidates for advanced imaging sensors for ionizing radiation.

  Photostimulated luminescence (PSL) of an imaging plate (BAS-UR,Fuji Film Co.) is measured using a home made readout instrument. The PSL intensity of the plate corresponding to unit absorbed dose for γ-rays is a half of that for α and β -rays. Measurements are also extended to a fading characteristic of the plate and the result is discussed on the basis of recombination probability depending on both thermal activation energy and the distance between electron and hole traps.

  Storage phosphors (BaFBr:Eu and KCl:Eu phosphors) are well suited to two-dimensional radiation detection. Putting some ROI (region of interest) on the incident particle energies and/or particle types of interest in their images can highly improve their S/N ratios and gives us a new world of truly exclusive radiographies. A description of the particle identification and energy determination of the storage phosphor images will be given.

  Very high sensitivity of Imaging Plate (IP) brought us the idea to obtain the images of natural radioactivity distributions contained in natural materials, such as vegetables, rocks,and potteries. The rough estimation showed the possibility of such measurement through long term exposure for about one month. The characteristics of IP on such long term exposure were then examined. Some images of natural radioactivity distribution were obtained and their radioactivities were determined with Ge detector.

  Photostimulable phosphor materials such as KBr:Eu₂O₃, RbBr:Eu₂O₃, NaBr:Eu₂O₃, KCl:EuCl₃, and SrAl₂O₄:Eu₂O₃, which can be used as storage phosphor materials for the imaging plate(IP), were, for the first time, prepared using the spark plasma sintering (SPS) method. The photostimulated luminescence(PSL) and its fading characteristics of these phosphor materials are reported. It was found that the phosphors can be prepared using SPS method at lower sintering temperature and for shorter time in comparison with conventional sintering method using thermal energy.

  Optical fiber sensors (OFSs) have many advantages like flexible configuration, intrinsic immunity for electromagnetic fields, and so on. Furthermore, by some of them, continuous or discrete distribution of physical parameters can be measured. Therefore, they have been widely used for industrial measurements and medical examinations. In order to investigate the applicability of optical fiber sensors to nuclear facilities, Raman Distributed Temperature Sensor (RDTS; one of the OFSs) has been installed at the primary coolant loop of the experimental fast reactor JOYO of JNC (Japan Nuclear Cycle Development Institute). Two correction techniques for radiation induced errors have been developed and demonstrated. During the continuous measurements with the total dose of more than 3×10⁷[R], the radiation induced errors showed a saturation tendency and the feasibility of the loss correction techniques was demonstrated. The lifetime of RDTS is expected to be more than 35 years in LWR.

  A wide bandgap semiconductor, TlBr, has been investigated as a photodetector material for detection of scintillation light. The TlBr photodetectors have been fabricated from the TlBr crystals grown by the TMZ method. In order to characterize the photoresponse, the quantum efficiency of the photodetectors has been measured. The TlBr photodetectors have been coupled to GSO and LSO scintillators whose spectral outputs match the photoresponse. The photodetectors have successfully detected scintillation light from the GSO and LSO scintillators irradiated with γ-rays. A full-energy peak for 511 keV γ-rays has been observed from an LSO/TlBr detector at room temperature. The energy resolution of the peak was 40% FWHM.

  With recent improvement of laser performance, resonance ionization spectroscopy (RIS) has been practicable. RIS can detect atoms with high sensitivity and elemental selectivity. Resonance ionization mass spectrometry (RIMS) technique, which combines RIS with mass spectrometry, is successfully applied to a failed fuel detection and location (FFDL) system which plays an important role as safety instrumentation for fast reactors.

  Here are mainly described the results and discussion on the detection limit of the present RIMS system through basic experiments for Xe isotopic ratio analysis.

  Using a low background γ-ray measurement system, we are studying environmental radiation in Tokushima. We have measured concentration of radon daughters attached to aerosol in the air. Then, its correlation is discussed for the weather condition, and concentration of NOx, SOx and metal elements in the air. Furthermore, radioactivity of Amang, which is by-product from tin mines in Malaysia, compared that of natural rocks from typical strata around Tokushima.

  Henshaw et al. reported the attraction of radon progeny to the vicinity of power frequency electromagnetic (EM) fields. They observed ²¹⁸Po and ²¹⁴Po deposition distribution on the track detectors set around various configurations of EM-fields source, and concluded that it should be examined this leads to increased exposure to human body from radon progeny. On the other hand, Miles et al. recently showed results of measurements of them in high and low environmental EM-fields to indicate there are no correlation. To interpret these two different conclusions, we investigated the behavior of charged ²²²Rn progeny by measuring the pattern and magnitude of the deposition rate of decay products on both CR-39 track detectors and imaging plates under various conditions including the cases Henshaw pointed out. It was concluded that the attachment to wire cables should be increased mainly by electric component of low frequency EM-fields and possibly by electric field induced by strong by changing magnetic ones. It may be deduced that deposition rate of ²¹⁸Po and ²¹⁴Po on the surroundings will be enhanced, and as a consequence, atmospheric concentration of them will not be changed or theoretically reduced.

  The neural network data processing is useful for the pulse shape recognition of nuclear radiation detectors. To determine the structure of the neural network reasonably, we propose the promissing methodology to find the optimum number of the input units equivalent to the optimum time interval for digital sampling by introducing the new concept of ‘Information Value’.