Structures of a loop type nuclear reactor

Purpose: To improve the inherent safety of reactor core upon the accident of after-heat removal systems in the reactor core by affording a time allowance for the boiling of sodium or the like. Constitution: A sodium flowing path is disposed between the upper and lower plenums within the reactor core and an ON-OFF device is disposed to the sodium flowing path. In the normal operation, the sodium flowing path is closed, whereas the sodium flowing path is opened upon failure of primary coolant circuits. Since a spontaneous recycling circuit of sodium can thus be formed, sodium coolant in the nuclear reactor can be entirely used for the cooling of the reactor core. (Aizawa, K.)