Investigation of natural circulation phenomena in WWER-1000 reactors

Natural circulation cooling is very important phenomena from the viewpoint of a passive safety concept. Natural circulation phenomena plays an important role in energy extraction from hot zones and rejection to the cold zones without using a mechanical pump in several engineering systems, such as solar water heaters, geothermal heat extraction, electrical machine motor cooling, nuclear reactor core cooling. In this paper we are using the RELAP5 system code model for the analysis of natural circulation transient in WWER-1000 reactors. The WWER-1000 reactor type is a PWR with a thermal power of about 3000 MW. We have considered the following systems of WWER-1000 into the model: Pressure vessel of WWER-1000; Main circulation pipelines; Reactor coolant pump; Steam generators; Pressurizer; Main steam lines; Main and auxiliary feed water; The results, which are obtained from the model by using the RELAP5 code, can be compared with experimental results. (author)