Experimental study on material relocation during core disruptive accident in sodium-cooled fast reactors; Results of a series of fragmentation tests for molten oxide discharged into a sodium pool

Matsuba, Kenichi  ; Kamiyama, Kenji  ; Konishi, Kensuke ; Toyooka, Junichi  ; Sato, Ikken ; Zuev, V. A.*; Kolodeshnikov, A. A.*; Vasilyev, Y. S.*

A series of fragmentation tests (FR tests) for molten oxide was conducted to obtain experimental knowledge on the distance for fragmentation of molten core material discharged into the lower sodium plenum. Approx. 714 kg of molten alumina was discharged into a sodium pool (depth: 1.3 m, diameter: 0.4 m, temperature: approx. 673 K) through a duct (inner diameter: 4063 mm). The test results showed that the molten alumina was fragmented into particles within 1 m from the surface of the sodium pool. The estimated distances for fragmentation in the FR tests were roughly 6070% lower than the predictions by the existing representative correlation. The experimental knowledge confirms the possibility that the distance for fragmentation of the molten core material can be significantly reduced due to thermal interactions in the lower sodium plenum.