Thursday, March 17, 2011
Containment vessel failure unlikely: Edano
Smoke, fires spark new havoc, tactics at ground zero
By KANAKO TAKAHARA and KAZUAKI NAGATA
Staff writers
White smoke rose from the No. 3 reactor at the
Fukushima No. 1 nuclear plant and radiation levels rose at one point
Wednesday, but the government later played down the possibility of grave
damage to the containment vessel.
 |
| Damage control: Tokyo Electric Power Co. released an image Wednesday showing damage to reactors No. 3 (left) and No. 4 at the Fukushima No. 1 nuclear plant. KYODO PHOTO |
Correcting an earlier remark, Chief Cabinet Secretary
Yukio Edano told reporters in the afternoon that the government now
believes the water pool for spent nuclear fuel at the No. 3 reactor
probably heated up, causing steam to rise.
The containment vessel is the last line of defense for
containing lethal radioactive materials, and significant damage would
pose grave safety concerns.
"The possibility of any great damage to the containment
vessel is low," the government's emergency headquarters said in a
statement.
But evaporation of the water in the spent fuel rod pool poses another kind of threat.
If the fuel rods were to melt, high amounts of
radiation could be released into the environment. The pool is not in the
containment vessel.
Unlike the reactor itself, the fuel pool is not
protected by a containment vessel and the roof of the No. 3 building was
blown away by an earlier hydrogen explosion.
The temperature of the water in the spent fuel pool at
the No. 4 unit also spiked Wednesday. The reactor had caught fire a day
earlier after a hydrogen blast created two big holes in the facility's
wall.
Providing more water is urgently needed to prevent the
fuel rods from melting. In a race against time to cool the water pool,
the government dispatched a Self-Defense Forces C-47 helicopter carrying
a bladder to dump water into the pool.
But the plan was canceled for the day because of the abnormally high level of radiation escaping from the plant.
 |
| Quake survivors brave a snowfall to dig for belongings where their homes once stood in Sendai. KYODO PHOTO |
It was later reported that a Metropolitan Police
Department water cannon was requested to pump watere into the
overheating facilities.
Earlier in the day, the nuclear safety agency said the
radiation level briefly reached 10 millisieverts per hour at the plant's
main gate at 10:40 a.m.
Still, that was lower than the 400 millisieverts per
hour — a level equivalent to roughly 400 times that at which people can
be safely exposed in one year — that was recorded Tuesday and the
maximum so far reported at the plant after apparent hydrogen blasts hit
the No. 2 and No. 4 reactors.
Radiation levels had dropped to 1.5 millisieverts per hour at the main gate by 4 p.m.
Tokyo Electric Power Co., operator of the nuclear plant, instructed its officials to evacuate the area.
Despite a series of events that further raised fear of
radiation leakage, the government said it doesn't intend to expand the
evacuation zone.
At present, residents within a 20-km radius have been
ordered to evacuate and people between a 20- to 30-km radius have been
instructed to stay indoors.
Seawater continued to be pumped into all the Nos. 1, 2
and 3 reactors, but water levels were still not high enough to cool all
of the fuel rods.
