Fast Breeder Reactor (FBR)

A Fast Breeder Reactor (FBR) is a nuclear reactor that uses fast neutron to generate more nuclear fuels than they consume while generating power, dramatically enhancing the efficiency of the use of resources.
Nuclear fission by fast neutron causes the increase in neutrons generated. Furthermore, because the sodium used as coolant absorbs fewer neutrons compared to light water, more neutrons remain within the reactor. Increased number of neutrons causes higher proportion of uranium 238 converting into plutonium 239 and yields more plutonium than original nuclear fuel. In Japan, an experimental fast-breeder reactor "Joyo" was first developed by the Japan Atomic Energy Agency (JAEA, former Power Reactor & Nuclear Fuel Development Corporation). This is a nuclear reactor without electric generating facilities, and started operation in 1977 with the aim of accumulating technical experiences of the fast-breeder reactor. MHI was in charge of the design of the core and the manufacture of the rotary plugs, intermediate heat exchangers and secondary coolant system. Furthermore, MHI actively participated in the Mk-III(3) modification works that increased the output from the initial 50 MW to 100 MW, and further to 140 MW.

Following "Joyo", a prototype FBR "Monju" was developed as a national project. The objective of this project was to verify technically the performance and reliability as a power plant, as well as to establish sodium handling technologies, through experiencing the design, construction and operation of the plant. The operation of the facility was put on hold after the sodium leak accident on the secondary cooling system in December 1995. Following a thorough review of the entire facility, and learning lessons from the accident, the plant modification works were started in September 2005, but the decommission of the plant was decided in 2016. Utilizing the expertise of the technologies accumulated through these projects, MHI is continuing its development of FBR as a leading manufacturer of FBR.

1970 Start construction of Experimental reactor "Joyo"
1977 Initial criticality of "Joyo"
1985 Start construction of Prototype reactor "Monju"
1994 Initial criticality of "Monju"
1995 "Monju" sodium leak accident
Installation of Monju reactor vessel at site.
Steam generator of Monju
- Evaporator tube bundle block -
Core internals of Monju - Core support plate and connection pipes-

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