The fuel surface temperatures and flow rate effects which might be produced by plugs in SRE fuel channels were investigated. It was found that plugs which locally insulate more than 20 to 30% of the surface of a fuel rod are dangerous. Heat transfer through the mcderator would not significantly affect the sensitivity of the outlet thermocouple to change in mass flow through a fuel channel, provided the reactor power is above 2 Mw and the channel is not completely plugged. If a 5% or greater increase in a fuel channel DELTA t is taken to indicate that a plug exists in the channel, about 80% of all possible plugs will be detected and roughly 95% of all dangerous plugs will be detected by this criterion. (C.J.G.).