Sub-channel Analysis of Fuel Assembly of KKNPP Reactor

In a nuclear reactor system, the Critical Heat Flux (CHF) or Departure to Nucleate Boiling (DNB) is the heat flux at which the boiling crisis occurs that causes an abrupt rise of the fuel rod surface temperature and subsequently a failure of clad material. The design of water cooled reactors requires a sufficient margin with regard to the Departure to Nucleate Boiling Ratio (DNBR). Accurate prediction of thermal hydraulics performance of Fuel Assembly (FA) is necessary for design and safety of nuclear power plants. The sub channel analysis of fuel assembly is required to determine core thermal hydraulics parameters of maximum fuel and clad temperatures and minimum DNBR during normal and transient conditions of nuclear power plants considering local variation in dimensions, power generation and flow distribution inside the FA. This paper presents the sub channel analysis of fuel assembly of Kudankulam Nuclear Power Plant (KKNPP) reactor under normal operation conditions. The computation of various core thermal hydraulic parameters such as fuel temperature, coolant temperature, pressure drop, sub channel flows and DNBR are carried out. The analysis results quantify and ascertain that the sufficient margins exist from DNB in KKNPP FA.