By Dr. Heather Johnstone
A second reactor at Japan’s Fukushima-Daiichi nuclear power plant is reported at risk of a meltdown.
Technicians are battling to lower the pressure and temperature in reactor No.3, whose cooling system was also damaged in Friday’s earthquake.
According to the BBC, in contrast to reactor No.1 the emergency cooling system in No.3 did come on-line following the earthquake, but the water injection system failed.
There has been no confirmation of what caused the explosion but speculation is that it was the result of high levels of hydrogen mixing with air as a consequence of the steam venting process, which was carried out to relive the pressure in the reactor.
Seawater is being pumped in to cool the fuel rods in an attempt to prevent the same thing happening at reactor No.3.
Tokyo Electric Power Company (
), which operates the Fukushima-Daiichi plant, is also venting steam to relieve the pressure in the reactor.
Reuters reports that TEPCO has confirmed that radiation levels around the Fukushima-Daiichi plant have risen above the safety limit. Although it qualified its statement by saying that it did not represent an "immediate threat" to human health.
According to a BBC report, a meltdown at reactor No.3 would be potentially more severe than at the other Fukushima reactors. This is because the reactor is fuelled by a mixture of plutonium and uranium rather than only uranium, meaning the effects of any radiation leak would be much more serious.
The Japanese government has increased the exclusion zone around the Fukushima-Daiichi nuclear plant to over 20 km.