So the sunflowers DID concentrate radioactive cesium in soil. It was not where the Japanese government wanted you to find.
According to one Iitate-mura villager, Mr. Itoh, who had his sunflowers tested, the radioactive cesium was IN THE ROOTS. He suspects that the government knew, and cherry-picked the data that seemingly supported the foregone conclusion that sunflowers do not work in decontaminating the soil.
Why? Because the government wants and needs to distribute big money to big businesses that closely work with the government in the "decontamination" bubble that they've created.
From his tweets on February 7, 2012:
ヒマワリの根 セシウム１３４ 39,500ｂｑ／ｋｇ セシウム１３７ 52,100ｂｑ／ｋｇ セシウム計 91,600ｂｑ／ｋｇ。ヒマワリの根の灰については、焼却温度が低く、体積が１／４程度にしか減らなかった、２，２００ｇの根を燃やし４６０ｇの灰が出た。
Sunflower roots: Cesium-134, 39,500 Bq/kg; cesium-137, 52,100 Bq/kg; total 91,600 Bq/kg. Since the roots were burned at low a temperature, the roots were reduced to only one-quarter in mass. 2,200 grams of the roots were burned, resulting in 460 grams of ashes.
If they were burned at a higher temperature, maybe the concentration would be 100 times, resulting in about 2 million Bq/kg of radioactive cesium, maybe? After pouring in taxpayers' money and the minister himself planting sunflowers in the experimental plot in the village, the Ministry of Agriculture, Forestry and Fisheries has declared sunflowers have no decontamination properties. It is because that conclusion was pre-determined with one purpose in mind. The ministry's test of radioactive wastes inexplicably excluded the sunflower "roots".
If sunflowers could decontaminate, there would be no subsidies and handouts. In essence, "decontamination" via the public works loaded with pork is the easiest way to get rich quick. Even in the face of the biggest disaster in 1,000 years, that's the level where the bureaucrats and politicians operate. Who elected these pols?
Mr. Itoh no doubt knows well it is the Japanese people who elected these pols and keep electing them, but that doesn't mean Mr. Itoh himself is complicit. He may have voted to oust these politicians in his district, in vain.