ナトリウム漏洩・燃焼挙動の機構論的解析手法の開発

Mechanistic approach to the sodium leakage and fire analysis

山口 彰; 村松 壽晴; 大平 博昭; 飯田 将雄

Yamaguchi, Akira; Muramatsu, Toshiharu; Ohira, Hiroaki; Iida, Masao

もんじゅのナトリウム漏洩事故では、温度計のニップル部よりナトリウムが漏えい・落下し、ダクトやグレーチングに衝突・飛散しながら床ライナ上に堆積した。その現象を解析するとともに、実炉の安全評価に利用できるコード体系を整備することを目的として、以下項目に係わるの解析手法の整備及び解析を実施した。(1)分子軌道法によるナトリウム燃焼素反応(2)漏えい燃焼実験IIの室内の気流(3)もんじゅA-446室内の気流(4)直接シミュレーションによる対流場とナトリウム液滴の燃焼(5)粒子法によるナトリウムの漏えい飛散挙動(6)多セル及び多次元のナトリウム燃焼これらのコードの開発により、ナトリウム燃焼を機構論的に解析する手法が整備されたので、今後は検証解析並びに実炉への適用を実施する予定である。

In December 1995, a thermocouple well was broken and liquid sodium leaked out of the intermediate heat transport system of the prototype fast breeder reactor Monju. In the initiating process of the incident, liquid sodium flowed out through the hollow thermocouple well, nipple and connector. As a result, liquid sodium, following ignition and combustion, was dropping from the connector to colide with the duct and gating placed below. The collision may cause fragmentation and scattering of the sodium droplet that finaly was piled up on the floor. This report deals with the development of computer programs for the phenomena based on mechanistics approach. Numerical analyses are also made for fundamental sodium leakage and combustion phenomenon, sodium combustion experiment, and Monju incident condition. The contents of this report is listed below: (1)Analysis of chemical reaction process based on molecular orbital method, (2)Thermal hydlaulic analysis of the sodium combustion experiment II performed in 1996 at O-arai Engineering Center, PNC, (3)Thermal hydlaulic analysis of room A-446 of Monju reactor when the sodium leakage took place, (4)Direct numerical simulation of sodium droplet, (5)Sodium leakage and scattering analysis using three dimensional particle method, (6)Multi-dimensional combustion analysis and multi-point approximation combustion analysis code. Subsequent to the development work of the programs, they are to be applied to the safety analysis of the Fast Breeder Reactor.