Effects of ocean motions on density wave oscillations under natural circulation

Abstract

The study of natural circulation is attracting more and more attention of researchers and engineers for the improvement of the system safety. A lot of natural circulation systems are applied to new generation reactors which make reactor systems safer and more compact because there are fewer components and no circulation pump in the natural circulation systems. The residual heat can be removed passively from the reactor by the natural circulation system which prolongs the response time for operators and reduces the potential accident because of human error. With the application of nuclear reactors under the ocean conditions, the study on flow oscillation characteristics in natural circulation system under ocean condition becomes very significant.Usually, flow oscillation is harmful to the operation of natural circulation systems which can affect the cooling capability of natural circulation systems in some extreme situations. In this paper, the classification of flow instability is introduced for systems under ocean conditions. Characteristics of density wave oscillations (DWO) under natural circulation are studied, including oscillation characteristics, stability boundary and subcooling effect. The characteristics of DWO under rolling and heaving motions are compared with those under the normal condition. The effects of rolling and heaving characteristics are analyzed, including maximum rolling angle, rolling period, rolling center location, maximum acceleration and heaving period. The resonance phenomenon is found, and resonant behaviors are analyzed.