福島周辺の家屋の内外における線スペクトルの評価

Evaluation of -ray spectra measured inside and outside a house in Fukushima

谷村 嘉彦   ; 富田 純平  ; 吉富 寛   ; 吉澤 道夫  ; 箱崎 亮三*; 高橋 荘平*

Tanimura, Yoshihiko; Tomita, Jumpei; Yoshitomi, Hiroshi; Yoshizawa, Michio; Hakozaki, Ryozo*; Takahashi, Sohei*

南相馬市の家屋内外における光子線スペクトルをNaI(Tl)検出器を用いて測定した。光子のエネルギーに応じて、(1)低エネルギー光子を含む散乱線、(2)CsまたはCsからの直接線及び(3)その他の光子の3グループに分けて、直接線と散乱線の周辺線量当量H(10)の比を評価した。H(10)の比は、屋外と比べて屋内の方が高く、散乱線の寄与率は屋内において50以上になることがわかった。散乱線のH(10)平均エネルギーは屋内、屋外ともに約0.25MeVであった。これらのデータは外部被ばく防護のための遮蔽の最適化において、有益なデータとなる。

Photon spectra were measured inside and outside a house in Minami-Soma city by using a NaI(Tl) scintillation spectrometer. The photons were categorized into three groups according to their energy. The groups were (1) scattered photons, which include low energy photons, (2) direct photons from Cs and Cs sources and (3) the other photons. Then the ratios of the ambient dose equivalents H(10) of the scattered photons to those of the direct photons from the Cs and Cs sources have been evaluated from the measured photon spectra. The ratios are high inside the house compared with those out of the house. It was found that the scattered photons contribute to the H(10) by more than 50 inside the house. The ambient dose equivalent average energies of the scattered photons are around 0.25 MeV both inside and outside the house. These data is worthwhile to design the optimum shielding for the protection against the public radiation exposure.