Fermi I Breeder Reactor

The Fermi I reactor was a breeder located at Lagoona Beach, 30 miles from Detroit. On October 5, 1966, high temperatures were measured (700 compared to normal 580¡F) and radiation alarms sounded involving two fuel rod subassemblies. The reactor scrammed and there was indication of fuel melting. After a month of sweating, they tested out enough subassemblies to limit the damage to 6 subassemblies. By January 67 they had learned that 4 subassemblies were damaged with two stuck together, but it took until May to remove the assemblies.

When they had checked the sodium flow earlier, they had detected a clapping noise. In August 67 they were able to lower a periscope device into the meltdown pan and found that a piece of zirconium cladding had come loose and was blocking the sodium coolant nozzles. The zirconium cladding was part of the lining of the meltdown cone designed to direct the distribution of fuel material should a meltdown of the fuel occur. Such structures are necessary in a breeder reactor because of the possibliity of molten fuel reassembling itself in a critical configuration. This is not a possibility in an ordinary light water reactor because of the low level of enrichment of the uranium, but a fast breeder reactor is operated with a much higher level of enrichment. The phrase "China syndrome" was coined in regard to this accident as they were contemplating the possibilities should a meltdown of fuel with critical reassembly take place. The uncontrolled fission reaction could create enough heat to melt its way into the earth, and some engineer remarked "it could go all the way to China".

With ingenious tools designed and built for the purpose, the piece of zirconium was fished out in April of 1968. In May of 1970, the reactor was ready to resume operation, but a sodium explosion delayed it until July of 1970. In October it finally reached a level of 200 Mwatts. The total cost of the repair was about $132 million. In August of 1972 upon denial of the extension of its operating license, the shutdown process for the plant was initiated.

http://hyperphysics.phy-astr.gsu.edu/hbase/NucEne/nucacc.html

http://news.blogs.cnn.com/2011/03/29/u-s-nuclear-plant-had-partial-meltdown-years-before-three-mile-island/

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