2-PHASE FLOW NATURAL CIRCULATION CHARACTERISTICS INSIDE BWR VESSELS

Fundamental two-phase flow behavior under natural circulation conditio ns is studied both experimentally and analytically. Natural circulatio n characteristics for both drum-type and chimney-type reactors are exp erimentally investigated focusing on the flow patterns, flow rate and two-phase behavior inside the vessel. Analytical studies are performed to further understand the natural circulation characteristics of an a ctual plant and the mechanisms of geysering-like instabilities. Experi mental and analytical results confirm that sufficient and stable flow is achievable in a natural circulation BWR.