Speaker
Summary
Following the Fukushima accident, public concerns about radioactive contamination in seafood have emphasised the need for rapid and reliable on-site detection systems. This study presents an improved design based on an existing NaI(Tl)-based inspection system that can detect 100 Bq/kg in one minute. The new design is optimised for a 50 Bq/kg detection limit and reduced measurement time of 30 seconds, in line with domestic safety standards for seafood.
The sample was modelled using data from Busan's Jalgachi seafood market, representing a 4.1 kg fish with a density of 0.43 g/cm³. It was modelled as being contained within a standard wooden box measuring 60 cm × 40 cm × 9.7 cm³, a size commonly used in domestic seafood wholesale markets. The target radionuclides (I-131, Cs-134, and Cs-137) were distributed homogeneously throughout the volume.
Lead shielding (0.5 cm) was applied to suppress background radiation, excluding the operational faces (the door and bottom plate). Various detector configurations were evaluated by varying the thickness, number and placement of crystals, with the aim of optimizing detection efficiency and minimizing the minimum detectable activity (MDA).
The optimized configuration achieved an MDA below 50 Bq/kg, satisfying the national food safety requirement. Future work will experimentally verify that the upgraded detector meets the ANSI N42.38 standard for the false alarm rate (≤1 per 60 measurements).
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