A study conducted by researchers from Nagoya University in Japan confirmed that 70 percent to 100 percent of the nuclear fuel in the No. 2 reactor at the Fukushima Daiichi nuclear power plant had melted following the earthquake-triggered tsunami event in March 2011.
The finding, reported by Kyodo News International, confirms a university study completed in March. Using similar techniques, the Tokyo Electric Power Company reported similar results regarding the No. 1 reactor at the plant.
University researchers used film that detects muons, a subatomic particle that penetrates most matter, but changes direction when it hits uranium. The researchers compared the results of muon detection between the No. 2 reactor and the No. 5 reactor, which came through the March 2011 events intact.
The study is expected to help workers remove the molten fuel from the reactor, when it comes time to do so.
TEPCO has also used robotic cameras to study the No. 1 reactor, sending in two shape-changing robots in April to send images and record radiation levels and temperatures inside the crippled unit. The first of two cameras sent in managed to record data from 14 of 18 planned locations before it stalled and was abandoned. The second camera recorded data from 11 locations, as planned.
The radiation levels of 4.7 to 9.7Sv/h were about a tenth of what was expected. The temperatures were also found to be lower than expected, TEPCO reported.
“Temperatures were found to be even lower than normal room temperatures, indicating the effectiveness of cooling systems,” TEPCO said.