An explosion rocked the building housing the No. 3 reactor at the quake-damaged Fukushima No. 1 nuclear power plant on March 14, while cooling functions failed at the No. 2 reactor, officials said.
An explosion rocked the building housing the No. 3 reactor at the quake-damaged Fukushima No. 1 nuclear power plant on March 14, while cooling functions failed at the No. 2 reactor, officials said.
There is a strong likelihood that all three reactors at the troubled No. 1 Fukushima nuclear power plant have had core meltdowns, Chief Cabinet Secretary Yukio Edano said on March 14.
Cooling systems at all three reactors failed in the wake of the March 11 Great East Japan Earthquake and nuclear fuel rods in the reactor cores were exposed above the water level.
At the same time, Edano said, “While the earthquake itself may have lasted but an instant, the response thereafter was conducted under a certain level of control and, at the present time, the situation is moving in a direction of stability. We believe that even foreseeing the worst-case outcome it will not turn out like Chernobyl.”
The explosion in 1986 at the nuclear power plant in the former Soviet Union is considered the worst-ever nuclear accident.
The Nuclear and Industrial Safety Agency (NISA) confirmed that a hydrogen explosion occurred around 11 a.m. on March 14 at the No. 3 reactor at the plant in Fukushima Prefecture, north of Tokyo.
Tokyo Electric Power Co. (TEPCO), operator of the plant, said at least 11 workers and others were injured in the blast, but that it did not damage the reactor’s pressure vessel or the steel containment vessel that covers it.
Edano told a news conference that the structural soundness of the containment vessel appears to have been maintained.
“The possibility is low that large quantities of radioactive substances have been released,” he said.
He also said the pressure within the vessel remained stable.
At one point, the level of cooling water in the No. 2 reactor at the Fukushima No. 1 nuclear power plant dropped sharply, temporarily exposing the fuel rods inside the reactor pressure vessel, TEPCO officials said on March 14.
According to TEPCO officials, the water level rose after they pumped seawater into the vessel.
But TEPCO said around midnight on March 14 that the water level had gome down again, fully exposing the fuel rods for a second time.
Reporting the failure to the Fukushima prefectural government, TEPCO officials said they would take swift measures to prevent a recurrence of the explosions that hit the No. 1 and No. 3 reactors by releasing steam at the No. 2 reactor and pouring in seawater to cool the core.
Edano had earlier warned that an explosion, similar to the hydrogen blast on March 12 that blew off the roof of the outer building that houses the No. 1 reactor, could occur at the No. 3 reactor.
Athough the explosion on March 12 did not compromise the pressure vessel or the containment vessel of the No. 1 reactor, there were still concerns that an explosion could rupture the No. 3 reactor’s containment vessel, releasing a large quantity of radioactive substances into the air.
That scenario apparently has not transpired. But officials told people within a 20-kilometer radius from the plant to retreat into buildings.
An estimated 500 residents were still trying to leave the area.
Company officials also said neutron radiation was not detected near the reactor.
Radioactivity within the compound remained low at 50 microsieverts per hour at 11:37 a.m. and 20 microsieverts per hour at 11:44 a.m., they said.
The No. 1, 2 and 3 reactors of the plant were shut down when the magnitude-9 earthquake hit on March 11. But emergency core cooling systems failed to work, sparking fears of meltdowns.
At the No. 3 reactor, pressure and water levels became unstable. At one time, its nuclear fuel rods were partially exposed after water levels fell, leading to the accumulation of hydrogen.
Since the weekend, TEPCO has been pouring seawater into both the No. 1 and No. 3 reactors in a desperate attempt to cool the cores.