Monju
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- This article is about the fast breeder reactor in Japan. For the buddhist bodhisattva, see Manjusri.
Monju is Japan's only fast breeder reactor. Located in Tsuruga, Fukui Prefecture in Japan, the reactor began construction in 1985 and first achieved criticality in April 1994.
Monju is a sodium-cooled, MOX-fueled loop type reactor with 3 primary coolant loops, producing 714 MWt / 280 MWe.
As of 2006, Monju is closed following a serious sodium leak and fire. It is expected to reopen in 2008.
[edit] Monju sodium leak and fire
On Dec. 8, 1995, the reactor suffered a serious accident. Intense vibration caused a thermometer inside a pipe carrying sodium coolant to break. The pipe heated up and gave way, possibly at a defective weld point, allowing several hundred kg of sodium to leak out onto the ventilation duct and floor below the pipe. Upon coming into contact with the air, the liquid sodium ignited, filling the room with deadly fumes and producing temperatures as high as 1500 degrees Celsius. The heat was so intense that it melted several steel structures in the room. An alarm sounded around 7:30 p.m., switching the system over to manual operations, but a full operational shutdown was not ordered until around 9:00 p.m., after the fumes were spotted. When investigators located the source of the spill they found as much as three tons of solidified sodium.
Fortunately, the leak occurred in the plant's secondary cooling system, so the sodium was not radioactive. However, there was massive public outrage in Japan when it was revealed that Power Reactor and Nuclear Fuel Development Corp. (PNC), the semigovernmental agency then in charge of Monju, had tried to cover up the extent of the accident and resulting damage. This coverup included falsifying reports and the editing of a videotape taken immediately after the accident, as well as the issuing of a gag order to employees regarding the existence of the real tapes.
On November 24, 2000, Japan's Atomic Energy Commission announced their intention to restart the Monju reactor. This decision was met with resistance by the public, resulting in a series of court battles. On Jan. 27, 2003, the Nagoya High Court's Kanazawa branch made a ruling reversing its earlier 1983 approval to build the reactor, but then on May 30, 2005, Japan's Supreme Court gave the green light to reopen the Monju reactor.
