Primary coolant circuit coastdown and thermosyphon mode under failure of forced circulation in Indian PHWR

In Pressurised Heavy Water Reactor, in the absence of forced circulation in the Primary Cooling Circuit, the decay heat is removed by thermosyphoning. Accuracy in the prediction of thermosyphoning flow depends on the pressure drop model at low flow conditions. Behaviour of the plant under such condition is analysed using a transient analysis computer code 'ATMIKA.T'. Here, the analysis predicts thermosyphoning behaviour and compares with the plant transient data. Effect of different pressure drop models on the core flow is also studied. (author)