Government’s nuclear accident investigation committee is to conclude that they can’t identify the route and cause of the burst in reactor2 because of the time restriction and technical limitation in their final report planned to be published on 7/23/2012.
Reactor2 is thought to have bursted the biggest amount of radioactive material on 3/15/2011 without explosion.
Tepco analyzed that PCV was damaged around 7:20 of 3/15/2011, when the vessel pressure decreased drastically.
On the other hand, government’s investigation committee is to report it was from 13:30 to 18:00 of 3/14/2011, when the vessel pressure decreased gradually. Because their analysis result about reactor1 and 3 contradicts with Tepco as well, they are going to point out that the assumption of Tepco is probably not based on the facts in their final report.
However, they could not investigate detailed cause of reactor2 burst because the radiation level is too high even 1 year and 4 months later than the accident.
Prof. Okamoto from Tokyo University graduate school commented, Tepco has just started the robot survey in reactor2, there is no enough information to investigate the cause, it is important to invite experts from around the world not only within Japan to continue survey.