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Adjustment of total delayed neutron yields of $$^{235}$$U, $$^{238}$$U and $$^{239}$$Pu in JENDL-3.2 using benchmark experiments on effective delayed neutron fraction $$beta_{eff}$$

実効遅発中性子割合$$beta_{eff}$$のベンチマーク実験結果を用いたJENDL-3.2の$$^{235}$$U, $$^{238}$$U,$$^{239}$$Puの遅発中性子収率の調整

桜井 健; 岡嶋 成晃

Sakurai, Takeshi; Okajima, Shigeaki

積分データを用いる断面積調整手法をJENDL-3.2の$$^{235}$$U,$$^{238}$$U,$$^{239}$$Puの遅発中性子収率の調整に適用し、収率の改善を行った。積分データとしては、高速炉臨界実験装置MASURCAとFCA及び熱中性子炉臨界実験装置TCAにおける合計6つの炉心で実施された$$beta_{eff}$$実験の結果を用いた。調整は、JENDL-3.2ファイル中の各入射中性子エネルギー点で与えられている遅発中性子収率に対して行った。調整の結果、$$^{238}$$Uの収率は7MeV以下でほぼ一様に約3%小さくなった。熱エネルギーにおいて、$$^{239}$$Puの収率は2.6%大きくなり$$^{235}$$Uの収率は0.9%小さくなったが、他のエネルギー点では、これら2つの核種の収率の調整量は0.3%未満であった。これら調整を行った収率を用いることにより、$$beta_{eff}$$計算値の誤差が低減し、$$beta_{eff}$$計算値が実験値により良く一致するようになった。

The cross section adjustment method was applied to total delayed neutron yields of $$^{235}$$U, $$^{238}$$U and $$^{239}$$Pu of the JENDL-3.2 file by using experimental results of effective delayed neutron fraction $$beta_{eff}$$ at six cores built in two fast critical facilities of the MASURCA and FCA and a thermal critical facility of the TCA to improve these yields. The adjustment was carried out on the yields given at several incident neutron energy points in the file. After the adjustment, the yield of $$^{238}$$U was almost uniformly decreased by about 3% below 7 MeV. The yield of $$^{239}$$Pu was increased by 2.6% and that of $$^{235}$$U was decreased by 0.9% at the thermal energy point, while the change of yield was less than 0.3% at the other energy points for these nuclides. By using these adjusted yields, the uncertainty of calculated $$beta_{eff}$$ was reduced and the agreement of $$beta_{eff}$$ between experiment and calculation was improved.

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