Ongoing efforts to find what's left of the missing core of unit-2 at the Daiichi nuclear facility have been making some news this month on remote control and robotic approaches to the round inner-containment pedestal 'room' directly beneath the vessel, that houses the control rod drives. In our last installment, the RC "cleaner" robot tasked with chipping off enough hardened corium lava from the metal grate catwalk to the CRD entry to allow the IRID robot 'Scorpion' to get much closer to a 2-meter diameter melt hole in the grating in order to get accurate radiation readings and photos of what's underneath and how far down it is. Useful information in the lingering questions about where, exactly, the bulk of corium resulting from total meltdowns of units 1, 2 and 3 at the facility in 2011 went.
Overnight Wednesday Scorpion made its entry. It relayed some images and video, and apparently made it as far as the hole, and was able to confirm the same kind of damage to the inside-the-pedestal CRD grating as well. Which makes entry to the pedestal proper at the CRD level impossible with robots that can't fly.
TEPCO did not report how long Scorpion was able to function in the unfriendly containment environment before it met its untimely end. It also got at least one radiation reading, of 'only' 210 Sv/hr (not the previously estimated 530 Sv/hr). Alas, that 210 Sv/hr level is nearly 3 times the amount of radiation Scorprion was built and 'hardened' to withstand for its planned 10-12 hour operational span.
For those interested in the Great Corium Hunt at Daiichi as we quickly approach the 6th anniversary of the disaster, check out concurrent work with robotics going on at Unit-1 -
Pmorph Robot Prepares For Fukushima Unit 1 Entry