高速炉用共分散データの整備(III)

Development of covariance date for fast reactor cores, (III)

柴田 恵一*; 長谷川 明*

not registered; not registered

高速炉の炉心解析で重要な核種について、評価済核データライブラリーJENDL‐3.2の中性子核データの共分散を推定しファイル化した。対象となったのは、Cr及びNiの2核種である。共分散を推定した物理量は、断面積及び弾性散乱角度分布の1次ルジャンドル展開係数である。共分散の推定は、出来る限りJENDL‐3.2のデータ評価法に基づいて行った。すなわち、評価値が実験値に基づいている場合は実験値の誤差、理論計算値に基づいている場合は理論計算値の誤差を算出した。評価結果は、ENDF‐6フォーマットで整備した。また、昨年度までに整備した共分散データの改良及びデータの追加を行った。改良したのはFe及び235Uの一分のデータである。新たに追加したデータは、241Puの核分裂における即発中性子と遅発中性子の放出数Vp、Vd、及び233、235、238U、239、240Puの核分裂中性子スペクトルの共分散である。

Covariances have been estimated for nuclear data contained in JENDL-3.2. As for Cr and Ni, the physical quantities for which covariances are deduced are cross sections and the first order Legendre-polynomial coefficient for the angular distribution of elastically scattered neutrons. The covariances were estimated by using the same methodology that had been used in the JENDL-3.2 evaluation in order to keep a consistency between mean values and their covariances. In a case where evaluated data were based on experimental data, the covariances were estimated from the same experimental data. For cross section that had been evaluated by nuclear model calculations, the same model was applied to generate the covariances. The covariances obtained were compiled into ENDF-6 format files. The covariances, which had been prepared by the previous fiscal year, were re-examined, and some improvements were performed. Parts of Fe and U covariances were updated. Covariances of nu-p and nu-d for Pu and of fission neutron spectra for U and Pu were newly added to data files.