An estimated $50bn has been spent bringing radiation in the prefecture back to safer levels.
Critics say toxins wash down from the mountains and forests after the decontamination crews leave, bringing radiation levels back up – though seldom to previous levels.
An optical fiber, placed in the gap between the conductometric electrodes, brings radiation from the source.
The day after the crash, busloads of troops started arriving from United States bases, bringing radiation-detection equipment.
The plant's operator, Tokyo Electric Power [Tepco], said last week it would take between six and nine months to bring down radiation levels and make the facility safe, a timeline some experts have described as optimistic.
The aim is to bring average radiation at this home down to 1.5 microsieverts an hour, still several times what it was before the accident but safe enough, perhaps, for Mr Saito's seven grandchildren to visit.
Scouring the soil had only limited success in bringing down radiation levels, partly because rain carries more contaminants down from nearby mountains.
Rain was predicted on Monday, which would have brought the radiation to Tokyo, so we locked up our house and were on a train to Kyoto in the west within few hours.
However, the military coup in 1973 brought this radiation to a sudden stop and produced a stasis period associated with the subsequent 17-year dictatorship.
As it happens, such a transformation would have brought the radiation results more closely into alignment with the results for mutagenic chemicals.
