Conference Paper

The Integration of a CeBr 3 Detector with a Submersible ROV for Reactor Assessment at Fukushima Daiichi

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The VECC array for Nuclear fast Timing and angUlar corRElation studies (VENTURE) has been developed using several fast Cerium-Bromide (CeBr3) scintillators coupled to Hamamatsu R9779 Photomultiplier tubes. The CeBr3 detector has been characterised for the spectroscopic properties like energy response, energy resolution, timing resolution and detection efficiency. The response and efficiency of the detector have been compared with the results obtained from a Monte Carlo simulation with GEANT3 package. A time resolution of 144(1) ps and 109(1) ps was obtained for a single detector using 622–512 keV and 1173–1332 keV cascades respectively. The Generalised Centroid Difference (GCD) method has been employed with CeBr3 detectors by measuring the level lifetimes for the 511.9 keV level of ¹⁰⁶Pd and the 160.6 and 383.8 keV levels of ¹³³Cs. The angular correlation measurement was performed for the 1173–1332 keV cascade in ⁶⁰Ni and the 228–49 keV cascade of ¹³²I nucleus, populated from the decay of ¹³²Te produced via ²³⁸U(α, f) reaction.
This paper discusses the use of CeBr3 detectors for the analysis of NORM samples. These detectors have a number of characteristics that make them suitable to field measurements: they can work at ambient temperatures, have better energy resolution than NaI(Tl) detectors for energies over 100 keV and do not present the radioactive contamination typical of the lanthanum halides detectors. Results of the measurements made at the laboratory for three reference materials are compared to those made using a conventional HPGe gamma-ray spectrometer system. Spectra from both measurement systems are presented and discussed.
CeBr3 is a new fast scintillator with timing and energy resolution similar to LaBr3:Ce. The excellent timing resolution, measured here to be 93 ps at 511 keV for 1 cm3 crystals, naturally lends itself to direct electronic measurements of excited nuclear state lifetimes in the nanosecond and sub-nanosecond range. To demonstrate this, half-lives of a 1.40 ns isomer in 152Sm and 537 ps isomer in 177Hf were directly measured using the delayed coincidence technique. With its fast timing, high light output and high efficiency, the possibility of CeBr3 as a time-of-flight PET detector was also explored through γ-ray time-of-flight measurements.
In view of highly demanded new and accurate data on prompt γ‐ray emission in nuclear fission a major part of investigations is directed towards the selection of suitable detector systems. Here we have studied a new type of crystal scintillation detectors made from cerium bromide (CeBr3). For the first time a full characterization of such a detector is presented in terms of energy resolution, pulse-height linearity, intrinsic activity and intrinsic timing resolution. In particular the latter one is very important for prompt fission γ‐ray studies, because the presence of fast neutrons, emitted in fission too, requires the time-of-flight method for their discrimination. The energy resolution has been found to be comparable to that of cerium-doped LaCl3:Ce detectors at an efficiency comparable to the one of a LaBr3:Ce detector of the same size. The intrinsic activity of the CeBr3 crystal was observed to be much lower compared to lanthanum halide crystals. The intrinsic timing resolution of a coaxial 1in.×1in. sized detector was measured relative to that of a previously characterized LaCl3:Ce detector and found to be (326±7)ps at 60Co energies, which is in between those of a LaBr3:Ce and a LaCl3:Ce detector of same size.
Cerium bromide (CeBr3) has become a material of interest in the race for high-resolution gamma-ray spectroscopy at room temperature. This investigation quantified the potential of CeBr3 as a room-temperature, high-resolution gamma-ray detector. The performance of CeBr3 crystals was compared to other scintillation crystals of similar dimensions and detection environments. Comparison of self-activity of CeBr3 to cerium-doped lanthanum tribromide (LaBr3:Ce) was performed. Energy resolution and relative intrinsic efficiency were measured and are presented.
Characterisation of CeBr
  • E Garcia-Torano
  • B Caro
  • V Peyres
  • M Mejuto
VECC array for Nuclear fast Timing and angUlar corRElation studies (VENTURE)
  • S S Alam
Sub-nanosecond nuclear half-life and time-of-flight measurements with CeBr
  • N Olympia