* Water leaking from No. 1 reactor, complicating shutdown
* Uncertain where radioactive water leaking -utility
* Melted, collapsed fuel being cooled by water pumps
(Updates with analysts' comments)
By Yoko Kubota and Scott DiSavino
TOKYO/NEW YORK, May 12 One of the reactors at
Japan's crippled Fukushima nuclear power plant has a hole in
its main vessel following a meltdown of fuel rods, leading to a
leakage of radioactive water, its operator said on Thursday.
The disclosure by Tokyo Electric Power Co (TEPCO) (9501.T)
is the latest indication that the disaster was worse than
previously disclosed, making it more difficult to stabilize the
The discovery of the leak provides new insight into the
sequence of events that triggered a partial meltdown of the
uranium fuel in the No. 1 reactor at Fukushima after the plant
was struck by a massive earthquake and tsunami on March 11,
The battle to bring Fukushima under control has been
complicated by repeated leaks of radioactive water, threatening
both the Pacific Ocean and nearby groundwater.
Workers at the Fukushima Daiichi nuclear plant have been
pumping water into at least three of the six reactors on the
site to bring their nuclear fuel rods to a "cold shutdown"
state by January.
But after repairing a gauge in the No. 1 reactor earlier
this week, TEPCO discovered that the water level in the
pressure vessel that contains its uranium fuel rods had dropped
about 5 metres (16 ft) below the targeted level to cover the
fuel under normal operating conditions.
"There must be a large leak," Junichi Matsumoto, a general
manager at the utility told a news conference.
"The fuel pellets likely melted and fell, and in the
process may have damaged...the pressure vessel itself and
created a hole," he added.
Since the surface temperature of the pressure vessel has
been holding steady between 100 and 120 degrees Celsius,
Matsumoto said the effort to cool the melted uranium fuel by
pumping in water was working and would continue.
VESSEL HAS A HOLE
Based on the amount of water that is remaining around the
partially melted and collapsed fuel, Matsumoto estimated that
the pressure vessel had developed a hole of several centimetres
The finding makes it likely that at one point in the
immediate wake of the disaster the 4-metre-high stack of
uranium-rich rods at the core of the reactor had been entirely
exposed to the air, he said. Boiling water reactors like those
at Fukushima rely on water as both a coolant and a barrier to
U.S. nuclear experts said that the company may have to
build a concrete wall around the unit because of the breach,
and that this could now take years.
"If it is assumed the fuel did melt through the reactor,
then the most likely solution is to encapsulate the entire
unit. This may include constructing a concrete wall around the
unit and building a protective cover over it," W. Gene Corley,
senior vice president of CTL Group in Skokie, Illinois, said on
"Because of the high radiation that would be present if
this has happened, the construction will take many months and
may stretch into years," Corley said.
TEPCO should consider digging a trench around reactors 1-3
all the way down to the bedrock, which is about 50 feet below
the surface, said Arnie Gundersen, Chief Engineer at Fairewinds
Associates Inc of Burlington, Vermont, who once worked on
reactors of similar design to the Fukushima plant.
He said this should be filled with zeolite, which can
absorb radioactive cesium to stop more poisons from leaking
into the groundwater around the plant.
"TEPCO seems to be going backwards in getting the situation
under control and things may well be slowly eroding with all
the units having problems," said Tom Clements with Friends of
the Earth, a U.S.-based environmental group.
"At this point, TEPCO still finds itself in unchartered
waters and is not able to carry out any plan to get the
situation under control," he said.
Matsumoto said the utility would study whether to increase
the amount of water it was injecting to overcome the leak and
raise the level of water covering the fuel, at the risk of
allowing more radioactive water to leak out of the facility.
Nearly 10,400 tonnes of water has been pumped into the
reactor so far, but it is unclear where the leaked water has
been going. The high radiation levels makes it difficult for
workers to check the site, Matsumoto said.
TEPCO announced a timetable last month for addressing the
crisis, saying it aimed to cool reactors to a stable level and
reduce the leakage of radiation within the first three months,
then bring the reactors to a cold shutdown in another three to
TIMETABLE COULD SLIP
TEPCO is set to review its timetable for stabilising
Fukushima on May 17 and officials indicated that the initial
progress targets could slip.
Officials had planned to use the same set of steps to
stabilise reactors No. 2 and No. 3 that are under way at No. 1,
which workers re-entered last week for the first time since the
But Matsumoto said it was likely that the pressure vessels
in the other two reactors could be leaking as well if fuel rods
had collapsed and melted after the earthquake and tsunami.
"It is necessary to make a reassessment of the condition of
the nuclear reactor," Chief Cabinet Secretary Yukio Edano told
a news conference.
On Wednesday, TEPCO sealed a fresh leak of contaminated
water found near the No. 3 reactor that may have seeped into
the Pacific Ocean from the coastal plant. A previous ocean leak
sparked international concern about the impact of the disaster
on the environment. [nL3E7GB261]
Traces of radioactive cesium were detected in sewage
treatment centres in Ibaraki and Kanagawa prefectures, both to
the south of Fukushima, Japanese media reported on Thursday.
(Additional reporting by Elaine Lies in Tokyo and Scott
DiSavino in New York; Editing by Kevin Krolicki, Edmund Klamann
and Martin Howell)