Japanese Chief Cabinet Secretary Yukio Edano said that while an explosion did occur at the plant, it did not damage the steel container around reactor No.1, where emergency workers are still struggling to cool down the reactor core after nuclear fuel rods were damaged following the failure of cooling systems due to the earthquake damage and short power supply. Edano said the explosion did not occur within the reactor container and thus did not lead to a large leak of radioactive material. The Nuclear and Industrial Safety Agency claims that radiation levels support the view that there has been no breach of the container around the reactor, though they have risen as a result of actions taken to relieve pressure in the container by releasing radioactive steam.

If accurate, these would be positive developments for the attempt to avert a meltdown in the reactor core. A number of nuclear engineers and experts interviewed in the press have also suggested that the explosion at the nuclear plant was not caused by a breach of the reactor itself, but rather involved the sudden release of hydrogen, which Edano confirmed, saying the hydrogen had been trapped between the reactor core and the surrounding containment structure, and exploded when released and mixed with oxygen. The government did not call for an expansion of the evacuation area of 20 kilometers (about 12 miles) around the two plants, and the fact that the evacuation zone has not been expanded is a positive sign.

It is too early to say, however, that a catastrophe has been averted. The nuclear safety agency said the Tokyo Electric Power Co. (TEPCO), which operates the nuclear plant, had succeeded in relieving pressure, but confirmed that some of the nuclear fuel had melted and that further depressurizing was necessary to continue to contain the reactor heat and pressure. TEPCO claims it is continuing to pump sea water and boric acid into the reactor container in order to substitute for the failed cooling process. Edano estimated it would take five to 10 hours to fill the container and 10 days to complete the process of cooling.

A number of questions remain. For instance, Edano claimed radiation levels were decreasing around the area, whereas the nuclear safety agency pointed to the fact that the release of steam to depressurize the reactor resulted in increased radiation levels. Other questions include the nature of the earlier explosion and whether it is true that the container was not damaged; whether radiation levels are as negligible as the government says; whether pressure in the reactor is indeed dropping; the sustainability of the cooling effort which is using batteries due to the lack of electricity; and the status of the Fukushima Daini reactors that were also reported to have had cooling malfunctions (water levels and radiation levels there last appeared to show no cause for worry). Thus while the official statements suggest some progress, potentially making this incident more similar to Three Mile Island than Chernobyl, nevertheless details are sparse and the situation remains precarious.