In two post-crisis assessments, a report to the International Atomic Energy Agency and an annual white paper on science and technology, his government has said the network “failed to perform its intended function.”
A senior member of Kan’s crisis team, Nuclear Safety Commission chief Haruki Madarame, went so far as to say the SPEEDI data was no better than “a mere weather report.”
He said the predictions were of no value because they lacked accurate radiation readings. Some of the system’s monitoring capabilities were compromised by the tsunami and ensuing power outages and the utility that runs the Fukushima plant, TEPCO, did not provide readings of its own.
However, SPEEDI officials say Madarame’s position reflects a fundamental misunderstanding of what their system is designed to do.
When the amount of radioactivity that has been leaked is known, that is entered into its system, along with weather and terrain data, and a hazard map is generated. If the amount is not known — as was the case with Fukushima — a standard and relatively low value of one becquerel is used.
While that won’t show the actual radiation risk, it will show the general pattern and direction of the plume. Then when the size of the leak becomes known, the map can be updated. If the actual leak turns out to be 100 becquerels, for example, the results would be multiplied by 100.
That technique allowed SPEEDI to produce reports hours before officials began venting disabled reactors — when there would have been less radiation to measure outside the nuclear plant even if the system’s monitoring equipment had been working perfectly.
In the Fukushima case, later data proved the forecasts to be highly accurate. Most of Namie, for example, has since been declared too dangerous for habitation.
“We are offended by allegations that SPEEDI failed to function the way it was supposed to,” said Akira Tsubosaka, a senior official in charge of operations. “SPEEDI was not used to determine evacuation zones. It should have been.”
SPEEDI, run by the education and science ministry, provides its data to other government agencies such as the nuclear safety agency for passage up the chain and then dissemination to local authorities.
Officials won’t say why that didn’t happen, sticking to their position that the data was useless anyway.
However, the government response has been sharply criticized by one of Kan’s top science advisers, who later quit in protest, according to a confidential report to the prime minister that was obtained by the AP.
“The SPEEDI radiation forecasts were not properly utilized and a situation was invited in which residents were made vulnerable to more exposure than necessary,” University of Tokyo professor Toshiso Kosako wrote in late April.
Ironically, low-level officials were quick to seek the SPEEDI data.
Bureaucrats familiar with SPEEDI commissioned at least 18 tailor-made forecasts in the first 24 hours, as the government was pushing TEPCO to open vents to avert an explosion.
The venting would release radioactive substances into the air. So, according to documents obtained by the AP, the forecasts included several to gauge that danger.
One issued at 3:53am — about 13 hours after the crisis began — predicted the plume would drift across Namie and several other towns.