Fukushima Reactor Photographs Raise Safety Concerns: Robotic exploration of one of the three damaged reactors at Japan’s stricken Fukushima nuclear power plant revealed exposed steel bars in the main supporting structure and parts of its thick external concrete wall missing, raising questions about the facility’s ability to withstand another major earthquake.
Since last year, the plant’s operator, Tokyo Electric Power Company Holdings, has been sending robotic probes into the primary containment chamber of Unit 1. New findings from an investigation done at the end of March were revealed on Tuesday.
One ROV designated ROV-A2, was launched far below the surface to explore the interior of the pedestal holding the core of Unit 1. Because the facility was devastated by an earthquake and tsunami 12 years ago, the photographs it returned were unprecedented. There will likely be evidence of the melted gasoline inside the pedestal.
A roughly five-minute video, taken as part of the robot’s 39-hour picture collection, revealed that the pedestal’s 120-centimeter (3.9-foot) thick concrete shell had been extensively broken towards its bottom, revealing the steel reinforcement inside.
Keisuke Matsuo, a spokesman for TEPCO, told reporters on Tuesday that the steel reinforcement appears to be mostly intact, but that the company will be conducting additional analyses of data and images over the next couple of months to determine whether or not the reactor’s earthquake resistance can be improved.
Several people are worried about the reactor’s stability after seeing photos of the exposed steel reinforcing.
Melted nuclear fuel from the three reactors weighs around 880 tons and is extremely radioactive. While robotic probes have revealed certain details, much about the melting debris remains unclear.
As compared to the quantity of damaged fuel removed during the cleanup of the 1979 partial core meltdown at the Three Mile Island nuclear facility in the United States, this amount is around 10 times larger.
The Governor of Fukushima, Masao Uchibori, has asked TEPCO to “swiftly evaluate levels of earthquake resistance and provide information in a way prefectural residents can easily understand and relieve concern of the residents and people around the country.”
Matsuo stated that the robot’s footage revealed a pile of debris 40-50 centimeters (1.3-1.6 feet) high at the bottom of the primary containment chamber, which may have been hardened nuclear fuel that had fallen from the core.
Officials from the firm have speculated that the meltdowns in each reactor may have developed differently due to the difference in height between the pile and the mounds detected in photographs collected during prior internal examinations.
Matsuo has stated that the information gathered by the newest probe will aid scientists in devising strategies for clearing the debris and analyzing the meltdowns of 2011. After a year of collecting and analyzing the data, TEPCO hopes to have a detailed three-dimensional map of the melted fuel and debris.
Experts believe that most of the melted fuel within Unit 1 dropped to the bottom of the primary containment chamber, but that some may have even fallen through into the concrete foundation, which would make the already challenging process of decommissioning even more so.
Unit 2’s trial cleanup of melted debris is slated to begin later this year, approximately two years after it was originally scheduled to begin. A 10-year delay has been planned before the evacuation of spent fuel from the Unit 1 reactor’s cooling pool begins.
The focus will shift from removing spent fuel from the pools to removing melted debris from the reactors in 2031.