; Annual Report – Units 4, 5 & 6

This is one section of our annual report, the full report can be found here.
We will be posting a section per day over the next week for ease of reading.

Reactors 4, 5, & 6

Work at these three reactors that did not suffer meltdowns has been limited. With the removal of spent fuel from unit 4, these other reactors pose a lower risk on site. An inspection inside unit 5 discovered some tsunami damage that had not been previously documented. As unit 5 did not suffer a meltdown or explosion this gives some insight into the damage caused solely by the earthquake and tsunami. (35)

At unit 6 an RHR pump failed. These are used to maintain cooling in the reactor vessel and spent fuel pool. TEPCO was able to supply temporary cooling to the spent fuel pool while repairs were scheduled. Unit 6 no longer holds fuel in the reactor vessel.(36)

A group of unused fuel assemblies had been stored at unit 6. To dispose of these assemblies TEPCO began work to chop the individual fuel rods into short sections that could then be sent to a facility for disposal or reprocessing.

A machine was used to cut the rod into pieces. Improper loading of a fuel rod caused the machine to mangle the fuel rod into a tangled mess. This incident was a serious concern as it could have caused a criticality accident. TEPCO was looking into steps to prevent a future incident while doing this work.(37) Unit 6 new fuel disassembly work has now been deferred indefinitely.(38)


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