Collaborative Laboratories for Advanced Decommissioning Science (CLADS), Japan Atomic Energy Agency, 790-1 Motooka Ohtsuka, Tomioka Town, Futaba-gun, Fukushima, 979-1151, Japan.
Tokyo Electric Power Company Holdings, Inc., 22 Kitahara, Ottozawa, Ohkuma-machi, Futaba-gun, Fukushima, 979-1301, Japan.
Sci Rep. 2019 Jan 24;9(1):581. doi: 10.1038/s41598-018-36962-4.
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 Gd(Ga,Al)O (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 Pu) 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 Pu (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 Am 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/cm.
我们使用α粒子成像探测器测量了来自福岛第一核电站(FDNPP)反应堆建筑的α发射体。为了开发该探测器,我们使用了非常薄的(0.05 毫米厚)掺铈钆(Ga,Al)O(Ce:GAGG)闪烁体和硅光电倍增管(SiPM)阵列作为光电探测器。用擦拭纸擦拭了 FDNPP 反应堆建筑的地板,并通过α粒子成像探测器测量了这些纸张的放射性。此外,我们还使用相同的探测器测量了从核燃料设施获得的钚(Pu)样品(主要是来自 Pu 的 5.5MeVα粒子),以与擦拭纸进行比较。α能谱在 5-6MeV 的能量范围内,对应于 Pu(5.5MeV)的α粒子能量。擦拭纸和 Pu 样品的α能谱的相关系数具有很强的正线性关系。此外,还通过伽马能谱测量鉴定了 Am 的峰。基于这些结果,我们报告了来自核燃料的 FDNPP 反应堆建筑物中α发射体的实际发现。α发射体的表面污染水平超过 4Bq/cm。