温度核特性に対する設計精度評価システムの整備(II)

Preparation of computer codes for estimating the accuracy in nuclear design of Doppler reactivities (II)

花木 洋*; 瑞慶覧 篤*; 三田 敏男*

not registered; not registered; Sanda, Toshio*

FBRの実用化に向けて、大型炉炉心の核設計精度を向上させ、高性能な炉心をより合理的に設計できるようにすることは、重要な研究開発項目の一つである。これまでの研究では、JUPITER等の臨界実験の成果を最大限有効に反映した修正炉定数を開発し、大型炉炉心の核設計精度の大幅な向上が達成された。さらに「常陽」等の豊富な実機燃焼データを有効に活用して、大型炉の燃焼核特性の設計予測精度を更に向上させるために、燃焼特性の感度係数を解析するシステムを整備し、大型炉設計体系においてその性能を確認した。燃焼核特性に加え、臨界実験と対比した場合のFBR実機の大きな特徴の一つ度核特性がある。その主要な因子であるドップラー反応度は、炉心の自己制御保証する核特性として非常に重要であり、ドップラー反応度の解析予測精度をすることが強く求められている。しかし、ドップラー反応度は他の核特性と異て、その予測精度が核断面積の自己遮蔽因子の評価に大きく依存するため、こで整備してきた設計精度評価システムでは扱うことができない。そこで本研究では、平成6年度に引き続き従来の設計精度評価システムを拡張ドップラー反応度をも扱えるように検討を行い、整備を終了した。

To develop nuclear design of LMFBR cores, they are important subjects of research and development to improve the accuracy in nuclear design of large LMFBR cores and to design highly efficient core more rationally. The adjusted nuclear cross-sections library had been made by being reflected the result of critical experiment of the JUPITER, etc.effectively as much as possible. And the distinctim provement of the accuracy in nuclear design of large LMFBR cores had been achieved. And the computer codes for analyzing sensitivity coefficients of burnup characteristics had been prepared to improve the prediction accuracy for burnup characteristics using many burnup data of "Joyo" effectively. As compared with critical experiment, Doppler reactivity is one of the great characteristics of LMFBR. Doppler reactivity is very important to assure core character of self-control and it is claimed to improve the prediction accuracy for it. But it is impossible to estimate the accuracy for present codes because it is much depend on self-shielding factor. Therefore in this work the system for estimating the accuracy in nuclear design of Doppler reactivity by improving present computer codes was studied. The results are as follows: (1)The method of analyzing sensitivity coefficients of Doppler reactivity was studied and computer codes was prepared by improving present codes. (2)Uncertainty of the gradient toward temperature of self-shielding factor of U238 capture reaction which is the most important reaction for Doppler reactivity was estimated preparatorily and formalized for using adjustment. (3)Uncertainties of experiment and analysis for Doppler reactivities in ZPPR-9 were arranged. (4)It was clarifled that it is possible to improve C/E values of Doppler reactivities without affecting other neutronic characteristics by doing preparatorily adjustment.