Am-Be中性子標準線源における中性子フルエンス分布の非等方性

Calculation of angular fluence distributions for Am-Be standard neutron sources

辻村 憲雄   ; 吉田 忠義 

Tsujimura, Norio; Yoshida, Tadayoshi

Am-Be中性子線源について、その線源カプセル周囲の中性子フルエンスの角度分布をモンテカルロ計算によって求めた。この計算では、JENDL alpha,n reaction data file 2005を用いてアルファ粒子とBeの反応による中性子スペクトル(理論値)をまず求め、次にそのスペクトルをAmOとBeの混合粉末を充填したカプセルの中で一様に発生させた。計算の結果、フルエンス分布の非等方性は、X3カプセルで1.030,X4カプセルで1.035であった。

The authors calculated angular neutron fluence distributions for Am-Be standard sources using the Monte Carlo method. In this calculations, the theoretical "source" neutron spectrum was computed from the kinematics calculation for two-particle reactions using the JENDL alpha,n reaction data file 2005, and was uniformly generated in the doubly-encapsulated stainless steel capsule (X3 and X4 capsules), containing a mixture of americium oxide and beryllium. Spectral changes of alpha particles, varying with a AmO cluster diameter, were also considered. Calculations were made of the fluence rate at various polar and azimuth angles. As a result, anisotropy correction factors for bare neutron sources were evaluated to be 1.030 and 1.035 for X3 and X4 capsules, respectively.