EAGLEプロジェクト中規模炉内試験の予測解析; SIMMER-IVコードを用いた3次元評価

Pre-calculation of the Middle-Scale In-Pile Test in the EAGLE Project; 3-D Evaluation using the SIMMER-IV code

豊岡 淳一  

Toyooka, Junichi

高速増殖炉(FBR)の炉心損傷事故時における再臨界問題の排除を目指したEAGLEプロジェクトでは、溶融した炉心燃料が早期に炉心外に流出することにより、1次系バウンダリー健全性の観点から有意な機械的エネルギー放出に至ることがないこと、すなわち再臨界問題が排除できることを実験的に示すこととしている。本プロジェクトの炉内試験では、試験技術を確立しつつ最終段階の実証性の高い試験に進むこととしているが、最終段階の大規模試験(3試験、燃料約8kgを溶融させる)に先立ち、燃料約2kgを溶融させる中規模試験(WF試験)を実施する。本試験の目的は、大規模試験の4分の1規模の燃料溶融の実現と試験計測技術の確認、および燃料流出開始条件に係わる基本データの取得にあるが、試験条件の妥当性を確認するとともに試験実施後の結果の評価に役立てることを目的とした予測解析を実施した。

In the in-pile part of this project, establishment of the test technique has been conducted along with the progress of the test program leading to the final step tests. Before the final step tests(three tests) with about 8kg of fuel melt formation, a middle-scale test (WF test) with about 2kg of fuel melt has been planned.The WF test aims at confirmation of techniques to form fuel melt with a scale of 1/4 that of the final step ones, to collect measurement data and acquisition of basic data related to initiation of the melt discharge from the core.In order to confirm appropriateness of the selected test condition on one hand, and to provide useful information for preliminary interpretation of the test results on the other hand, predictive evaluation using an analytical tool has been conducted. Through this study, following points were confirmed:- Through SIMMER-IV-code application representing appropriately the complicated three-dimensional test-section geometry, it was concluded that the selected test conditions were appropriate.- Through this study reflecting the knowledge obtained from the small-scale tests of the EAGLE project, it was concluded that the rather early steel melting and resultant steel segregation from fuel, which had been regarded as a possible concern, would be avoided.- Present study suggested that SS wall cooled by sodium from its behind could be strongly cooled by oscillatory movement of sodium leading to significantly delayed wall failure.- Test data such as failure time and location of both the SS wall facing the sodium channel and the adiabatic SS wall with heat transfer from the molten fuel pool, and cover gas pressure, it is expected that one can get useful knowledge on heat transfer within the pool and wall failure mechanism.