JAERI Fast Reactor Group Constants Systems Part II-1

高速炉用群定数セット JAERI-Fast Set II-1

桂木 学; 石黒 幸雄; 高野 秀機; 中川 正幸

Katsuragi, Satoru; not registered; not registered; Nakagawa, Masayuki

重い核程の共鳴断面積の取扱いを研究した。従来実効断面積の組織依存性は無限釈系の実効断面積と自己遮藪因によって扱われ、その際 立した狭い共鳴と衝突密度一定に仮定が使われている。また相互干渉効果を正しく取扱うことができない。核データもPuのの例のように精度がわるい。U、U、Pu、Puに対して共鳴領域の群定数を上述の点を考慮に入れて作成した。低分解機実験と予盾のない共鳴パラメータの特別な組を求める方法を開発し、また断面積のよい表示、実効断面積のよい値、相互遮藪因子の考え方をきめるために研究を行った。ここで求めた群定数とJAERI-1195の報告された群定数(ここに報告された以外の部分)を一緒にしてJAERI-Fast Setが出来上がっている。

Improvements have been made for the treatments of effective cross section of heavy nuclides in the resonance energy region, and fast reactor group constants in this energy region have been produced for nuclides U, U, Pu, and Pu. These group constants are thought to be accurate compared with existing fast group constants in the following sense. (1) The resonance parameters (including those in the unresolved resonance energy region) are evaluated so as to fit measured cross sections. (2) Accurate cross sections are obtained by a calculating procedure, which uses a reasonable representation of cross sections, without waste of huge computing time. (3) The effective cross sections are obtained using exact spectra as weights, because conventional approximation methods yield less accurate results. (4) An investigation was made for the treatment of interference effects. And interference effects. And interference effects with U is taken into account for shielding factors. (5) The energy variation of (/) values and for U and Pu is properly reproduced, and an appropriate group structure is adopted taking this energy variation into consideration. For analyses and design studies of fast reactor systems, the present group constants should be used together with those listed in the report JAERI 1195.