Detection of alpha particle emitters originating from nuclear fuel inside reactor building of Fukushima Daiichi Nuclear Power Plant

Abstract

We measured alpha emitters obtained from a reactor building in the Fukushima Daiichi Nuclear Power Plant (FDNPP) by using an alpha particle imaging detector. For developing the detector, we used a very thin (0.05-mm-thick) a cerium-doped Gd3(Ga,Al)5O12 (Ce:GAGG) scintillator and silicon photomultiplier (SiPM) arrays as the photodetector. The floor of the reactor building in FDNPP was wiped off by using smear papers, and the radioactivity of these papers was measured by the alpha particle imaging detector. In addition, we measured a Plutonium (Pu) sample (mainly 5.5 MeV alpha particles from 238Pu) obtained from a nuclear fuel facility by using of the same detector for comparison with the smear papers. The alpha spectrum was in the energy range of 5–6 MeV, which corresponds to the alpha particle energy of 238Pu (5.5 MeV). The correlation coefficient of the alpha spectra of the smear papers and the Pu sample had a strong positive linear relation. Moreover, the peak of 241Am was identified by gamma spectrum measurement. Based on these results, we report actual findings of alpha emitters in the FDNPP reactor buildings originating from nuclear fuels. The surface contamination level of alpha emitters exceeded 4 Bq/cm2.

First determination of Pu isotopes (239Pu, 240Pu and 241Pu) in radioactive particles derived from Fukushima Daiichi Nuclear Power Plant accident

“…For this purpose, we consider investigating the Pu-bearing particles and quantifying Pu in these particles by identification methods such as the alpha particle imaging detector developed by Morishita et al . 58 in the future.…”

Analysis of particles containing alpha-emitters in stagnant water at torus room of Fukushima Dai-ichi Nuclear Power Station’s Unit 2 reactor

“…For americium (Am) and curium (Cm), few reports have been published regarding their release into the environment 11 . Recently, Morishita et al 15 detected particles containing α-emitters in smear samples collected from inside the FDiNPS using an α-ray imaging detector. The maximum energy of the α-rays indicated the presence of 238 Pu; γ-ray spectra indicated the presence of 241 Am.…”

Enhanced extraction via surface asperities of light generated around the boundary plane in poly (ethylene naphthalate)

“…Decommissioning work at the Fukushima Daiichi nuclear power plant requires rapid radioactive contamination inspections for the workers to reduce internal exposures induced by alpha particles from nuclear fuel materials [11,12]. It is thus essential to precisely detect short-range alpha particles at the working site [13]. The instrumental efficiencies of a PEN-based radiological device depend on maximising the extraction of light generated by the alpha particles.…”