Analyses of Abnormal Transients and Accidents at Supercritical Pressure

2 Analyses of Abnormal Transients and Accidents at Supercritical Pressure 

Ten abnormal transients and four accidents are analyzed using the SPRAT-F code introduced in Sects. 7.9 and 7.10. Six fuel channels are modeled average and hot channels for each of the upward flow seed assemblies, downward flow seed assemblies, and blanket assemblies. The initial cmiditions of these channels are summarized in Tables 7.41 and 7.42. The orifice pressure drop coefficients at the 

Upward flow seed Downward flow seed Blanket channel channel channel 

The analysis results of the partial loss of reactor coolant flow (transient) are shown in Fig. 7.98. The inlet flow rates of the three hot channels similarly decrease with the main coolant flow rate. The highest cladding temperature appears in the upward flow seed channel due to its higher value initially. The AMCST in the upward flow seed channel is about 80°C, which is higher than that in the Super LWR by 20°C. This is because the Super FR has a smaller heat capacity and also because the smaller reactivity feedback from the coolant density makes the decrease in the power slower before initiating the reactor scram. However, there is still a margin of over 60°C to the criterion. 

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