Using GR1 to find the gamma-ray spectrum of smear papers from a reactor building in the Fukushima Daiichi Nuclear Power Plant

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.

Full citation

Morishita, Y., Torii, T., Usami, H. et al. Detection of alpha particle emitters originating from nuclear fuel inside reactor building of Fukushima Daiichi Nuclear Power Plant. Sci Rep 9, 581 (2019). https://doi.org/10.1038/s41598-018-36962-4