Nuclear Safety Agency Denies
Criticality At Fukushima Reactor
Fukushima Power Plant
EMF Protection Devices
Magnetic Field Detector
TOKYO (Kyodo) -- The government's nuclear safety agency said
Monday that it supports Tokyo Electric Power Co.'s view that
the recent detection of radioactive xenon at one of its
crippled reactors at the Fukushima Daiichi nuclear power
plant was not a result of a sustained nuclear chain reaction
known as criticality, as earlier feared.
The Nuclear and Industrial Safety Agency said what is known
as "spontaneous" fission created xenon-135 because it found
that the density of the substance had not changed even after
Tokyo Electric injected water containing boric acid, which
should have lowered the density of xenon-135 if criticality
had taken place.
"We judge Tokyo Electric's report (on the detection of
xenon) to be basically appropriate," the agency said in a
The plant operator known as TEPCO initially touched on the
possibility that the melted fuel inside the stricken No. 2
reactor may have gone critical temporarily, but it concluded
in a report submitted to the agency Friday that spontaneous
fission had generated xenon-135.
The agency has been studying the content of the report.
With the Nos. 1 to 3 reactors suffering core meltdown and
releasing massive radioactive substances in the wake of the
devastating March 11 earthquake and tsunami, a criticality
event could cause further damage to the fuel and worsen the
situation at the plant.
Cabinet Office Parliamentary Secretary Yasuhiro Sonoda
stressed Monday that the latest development is not expected
to affect the target to achieve the stable state, known as
cold shutdown, of the reactors at the plant by the end of
(Mainichi Japan) November 8, 2011