Agglomeration and size distribution of debris in DEFOR-A experiments with Bi2O3–WO3 corium simulant melt

• Published in: Nuclear engineering and design 2013-10, Vol.263, p.284-295
• Main Authors: Kudinov, Pavel, Karbojian, Aram, Tran, Chi-Thanh, Villanueva, Walter
• Format: Article
• Language: English
• Subjects: Boiling water reactor (BWR); Computational codes; Containment integrity; Experimental investigations; Melt-superheat; Natural circulation; Severe accident management; Systematic study
• ISSN: 0029-5493; 1872-759X; 1872-759X
• DOI: 10.1016/j.nucengdes.2013.06.011

•Debris agglomeration in case of melt pouring into a coolant is experimentally investigated.•The effects of jet diameter, melt superheat and water subcooling are addressed.•Most influential factor which can significantly increase fraction of agglomerates is melt superheat.•Rapid decrease of the fraction of agglomerates as a function of water depth is obtained in all cases.•Provided data is valuable for model development and code validation. Flooding of lower drywell has been adopted as a cornerstone of severe accident management strategy in Nordic type Boiling Water Reactors (BWR). It is assumed that the melt ejected into a deep pool of water will fragment, quench and form a porous debris bed coolable by natural circulation. If debris bed is not coolable, then dryout and possibly re-melting of the debris can occur. Melt attack on the containment basemat can threaten containment integrity. Agglomeration of melt debris and formation of solid “cake” regions provide a negative impact on coolability of the porous debris bed. In this work we present results of experimental investigation on the fraction of agglomerated debris obtained in the process of hot binary oxidic melt pouring into a pool of water. The Debris Bed Formation and Agglomeration (DEFOR-A) experiments provide data about the effects of the pool depth and water subcooling, melt jet diameter, and initial melt superheat on the fraction of agglomerated debris. The data presents first systematic study of the debris agglomeration phenomena and facilitates understanding of underlying physics which is necessary for development and validation of computational codes to enable prediction of the debris bed coolability in different scenarios of melt release.