SPEEDI simulation of radioactive iodine fallout from the Fukushima Dai-ichi nuclear reactor meltdowns for 12 March 2011. The prevailing wind direction forecast shifted over time, resulting in the simulation forecasting wide dispersion of radioactive iodine inland. The simulation chart is the internal radiation exposure at the thyroid gland of a 1-year old by inhaling radioactive iodine. Japan Ministry of Education via ex-skf.blogspot.com

By arevamirpal::laprimavera
3 March 2012 Kyodo News reports (3/3/2012), nearly one year later:

ＳＰＥＥＤＩ予測「公表できない」　文科省文書に記載 SPEEDI simulation “cannot be made public”, according to a document by Ministry of Education and Science 東京電力福島第１原発事故５日目の昨年３月１５日、緊急時迅速放射能影響予測ネットワークシステム（ＳＰＥＥＤＩ）による放射性物質の拡散予測について、当時の高木義明文部科学相ら政務三役や文科省幹部が協議し「一般にはとても公表できない内容と判断」と記した内部文書が作成されていたことが２日、同省関係者への取材で分かった。 It was revealed on 2 March 2012 by speaking with the people involved at the Ministry of Education and Science that an internal memo was created on 15 March 2011, the 5th day of the Fukushima I Nuclear Power Plant accident, which shows then-Minister Yoshiaki Takagi and top officials at the Ministry of Education and Science held a meeting that day and agreed that they “cannot make the SPEEDI simulation results public”. 文科省は「事務方が作ったメモだが不正確。公表の具体的な判断はしなかった」と内容を一部否定している。 The Ministry of Education denies part of the story, saying “The memo was created by the secretariat but it is inaccurate. There was no clear decision on whether to make them public.” […]

I remember Professor Kunihiko Takeda of Chubu University saying right around March 15 last year that the government (Ministry of Education) decided to hide the result of SPEEDI simulation because it was very, very bad, showing serious radioactive contamination over a wide area. Well he was right.

Ministry of Education on SPEEDI Simulation: “We Can’t Make This Public….”