Fukushima nuclear situation still critical, with “makeshift” cooling system

Fukushima plant situation ‘volatile,’ a year after cold shutdown declared, Asahi Shimbun December 18, 2012 By NAOYA KON/ Staff Writer Workers are nowhere close to determining the state of melted fuel at the Fukushima No. 1 nuclear plant, a year after the government declared the damaged reactors were in a “cold shutdown” state.

Storage tanks at the site are nearing capacity for radioactive water. A makeshift system is still being used to cool the nuclear fuel. And leaks of contaminated water and quake-induced collapses of plant facilities remain a threat.

Although progress has been made in clearing rubble and reducing the amount of radioactive substances released from the plant, NRA Chairman Shunichi Tanaka acknowledged that preparations to decommission the reactors are only slowly getting under way.

“Workers have been obliged to respond with highly stopgap measures,”
Tanaka said. “Many devices, such as a purifier for radioactive water,
have been installed with no time for sufficient design considerations
and safety screenings.

“The situation surrounding the decommissioning process is volatile, so
there is a need for constant reviews in securing safety.”…..
he decommissioning process, including the No. 4 reactor that contained
no fuel at the time of the disaster due to a regular inspection, is
expected to take decades to complete.

The decommissioning work also represents an imminent challenge for the
Liberal Democratic Party, which will control the government following
its victory in the Dec. 16 Lower House election…..
TEPCO cannot determine the state of the melted fuel because cameras
can only be inserted for a limited time period in the extremely
hazardous environment.

One immediate problem facing TEPCO is the accumulation of radioactive
water used to cool down the melted fuel. TEPCO says it will mobilize
robots and take other measures to locate where the radioactive water
is leaking from the reactors.

Storage tanks on the plant’s premises have a total capacity of 257,000
tons. As of Dec. 11, the tanks contained 237,000 tons of radioactive
water.

TEPCO plans to build additional tanks on deforested land to expand the
total capacity to 700,000 tons within three years.
Groundwater flowing into the reactor buildings is exacerbating the
radioactive water problem. TEPCO said it will dig wells west of the
reactor buildings to pump up the groundwater and reduce the inflow,
but little is known about groundwater flow variations, sources said.

The 4 kilometers of pipes in the “circulating water cooling” system
were installed on a temporary basis in the frantic battle to keep the
melted fuel submerged. They remain in the same state, and the risk of
radioactive water leaking from damage on the pipes remains……
about 3,100 nuclear fuel assemblies, including unspent ones, are now
sitting in the storage pools of the No. 1 through No. 4 reactor
buildings.

The amount of radioactive substances released from the reactor
buildings has remained low since February. In November, a maximum of
10 million becquerels were leaking from the No. 1 through No. 3
reactors per hour, only one-sixth the discharge rate in December 2011.

But Fumiya Tanabe, a former chief research scientist at the
now-defunct Japan Atomic Energy Research Institute, said persistent
danger surrounds the plant’s reactors.

“Despite the (officially declared) cold shutdowns of the reactors, the
cooling functions have been maintained there with no knowledge of
where the melted fuel lies and in what state,” Tanabe said. “There is
a risk of unforeseen circumstances arising if another major earthquake
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