The operator of the Fukushima Daiichi nuclear power plant says a probe detected extremely high levels of radiation inside one of the plant's damaged reactors.
Tokyo Electric Power Company, or TEPCO, on Thursday released measurements of radiation levels and temperatures based on a survey of the No.2 reactor. It is one of the plant's three reactors that experienced a meltdown as a result of the 2011 earthquake and tsunami.
The company conducted the survey in February as part of its effort to decommission the plant. A robotic probe sent inside the reactor made direct contact with debris, which is believed to be a mixture of molten nuclear fuel and structural parts.
TEPCO says radiation levels were 6.4 to 7.6 sieverts per hour underneath the core of the reactor. Scientists say exposure to those levels for about an hour is deadly.
The company says radiation levels rose as the probe approached the bottom of the containment vessel, where the suspected fuel debris is located.
TEPCO adds that radiation levels near structures that support the reactor core were estimated to be up to 43 sieverts per hour.
The firm says gaseous compounds were generated as the nuclear fuel melted and that they may have accumulated around the support structures.
TEPCO says temperatures were generally 22 to 23 degrees Celsius.
The TEPCO survey team inserted a pole-shaped device into the containment vessel of the reactor. The probe was lowered from the tip of the device, and manipulated to touch the debris.
TEPCO says the probe was able to lift some of the debris, including a pebble-like object that measured about eight centimeters in diameter. This is the first direct contact survey of its kind.
The utility plans to remove a small amount of the deposits using a different device in October or later. It hopes to use the samples to study how to get rid of the debris within the reactor.