Monju is a reactor under suspension because of accident.
It is an asset of Japan Atomic Energy Agency(http://www.jaea.go.jp/), which is a special government agency; independent administrative institution.
Monju is a experimental reactor. It is a Fast Breeder Reactor(FBR) and its coolant is Na. I don't know what it means.
One device (3.3t) in the reactor fell at August 26th 2010, still no way has been found to fix it. This reactor's maintenance cost is said 55,000,000 yen per day (460,000 $/day). I do know what it means.