Translated from a Japanese News Site
"Workers at Fukushima Daiichi were working this week to remove rubble from atop the crippled Fukushima Daiichi Unit 3 reactor building with remote-controlled cranes, when they discovered the radiation dose from a piece of debris they removed from the 5th floor of the reactor building was highly radioactive and releasing a dose rate over 540 millisieverts per hour. The maximum allowable exposure for radiation workers in the U.S. is 50 millisieverts per year.
The debris, which is approximately 1 cubic meter in size, was transferred to a building on the south side of the Fukushima Daiichi complex for temporary storage, until it can be transferred to a solid waste storage site in the future."
No doubt the Japanese investigators have sampled the debris to find out what it consists of, so hopefully within a few weeks we should be given more information on this.
The UK's Office of Nuclear Regulation (ONR) keep telling us all that the explosion at Fukushima Daiichi Unit 3 was a simple hydrogen explosion. I have spoken to two experienced Nuclear Inspectors face to face on two different occasions. At the time of our conversations they both supported the consensus hydrogen explosion thesis.
However it is now very likely that as the on-site teams explore further into the building they will find even higher levels of radioactivity than just found on the 5th floor.
How can a hydrogen/air explosion account for such large lumps of highly radioactive debris?
This debris must contain significant amounts of material from either inside the reactor containment or from within the fuel pool; there are no other sources for material as radioactive as this.
The evidence is really starting to stack up against the consensus view of Nuclear Regulatory Professionals across the world have adopted; that this was just a simple hydrogen explosion.
The roof steels are all missing right above the unit 3 fuel pool, and given that the measured radioactivity levels, within the reactor dry wall containment, did not change significantly around the time of the explosion, it seems to me that a very credible explanation is that some form of fuel pool detonation occurred.
However the problem is we won't know for sure what happened until new robots are built that can get into to inspect the internal building damage in detail. The radioactivity levels are too high for humans and they may well prove to be too high for existing robot technologies as well.
In the meantime I would like to see the HSE withdraw HM Chief Inspector's Fukushima Final Report findings in regard to the Unit 3 reactor explosion, pending further data and a further evaluation of the newly available facts.
I don't want to see the ONR have to withdraw their report findings, after pressure is applied by campaigners and politicians, and in a way that completely undermines their future credibility.