Initial criticality of proto type fast breeder reactor Monju

On April 5, 1994, the prototype FBR 'Monju' has attained the initial criticality. It is significant that the steady advance was shown in the development of the nuclear fuel cycle utilizing plutonium and the technology of FBRs, which are one of the important technologies for securing next generation energy. The basic specification of 'Monju' is the electric power output of 300,000 kw, the breeding core using MOX fuel, and loop type using sodium coolant. The course of the design and construction is outlined. The trial operation was started in May, 1991, and the general function test and the performance test are carried out. The former comprises the test in the atmosphere, the test in argon gas and the test in sodium. The latter is carried out in five steps, namely, the preliminary test on plant characteristics, criticality test, reactor physics test, nuclear heating test and power output test. The core of 'Monju' is homogeneous two-region core which comprises core fuel assemblies, control rod assemblies, blanket fuel assemblies and neutron shields. The nuclear design technique and the fuel containing higher order plutonium isotope, the initial loading of fuel and the approach to criticality are reported. (K.I.)