Analysis of a scaled two-phase water loop in support of MYRRHA secondary system design

In the framework of the MYRRHA project, several relevant thermal-hydraulic issues related to the reactor operation under a wide range of conditions must be studied and analyzed. In addition to the primary system (LBE eutectic), the behavior of the secondary system is equally important for the reactor operation in both exercise normal conditions and accidental situations. MYRRHA secondary system is operated, in normal conditions and at nominal power (100 MW), with two-phase water at 16 bar and 200 oC (saturation temperature): the liquid water enters the Primary Heat Exchangers (PHX) and partly evaporates, removing power from primary LBE, and reaching a steam quality of 0.3. The vapor phase is then separated into a steam drum, while the liquid phase is recirculated, through a pump, to the PHX. An air-cooled condenser (tertiary system) provides as ultimate heat sink, by condensing the steam coming from the steam drum and redirecting the condensate back into the same steam drum. In case an accident should occur, the reactor will experience immediate shut-down (scram). In accidental conditions, the Decay Heat Removal (DHR) function will be carried on by the secondary and tertiary systems, which must be able to operate also in natural circulation.