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Second explosion occurs at Japanese nuclear power plant, sister facility experiencing difficulties

A second explosion has occurred at the Fukushima Daiichi nuclear power plant in Japan. It appears to have been caused by a build-up of hydrogen at the plant’s third reactor, the same phenomenon, which is believed to have caused the explosion at Reactor 1. Corrosive seawater has been pumped into reactors 1-3 as an emergency coolant, now that all three have lost their cooling systems, while reactors 4-6 were shut down before the incident for periodic inspection. While the seawater helps cool the fuel and control rods, it does risk a build up of hydrogen-rich and radioactive steam. The corrosive effect also means that all three reactors are unlikely to ever return to service. The high pressure levels at the reactors forced the evacuation of workers from the site early Monday morning.

TEPCO, the Japanese utility, which owns and operates the facility said on Sunday that it had allowed some steam to be vented to reduce the pressure in reactor unit 1. The utility reported on Sunday afternoon that the pressure in reactor was double normal operating levels. The Jiji news agency said today that water levels have fallen enough to partly expose fuel rods in Reactor 2. Earlier Japan’s Nuclear and Industrial Safety agency said that the reactor had lost all its cooling capacity.

Also on Sunday, when asked whether meltdowns had occurred, government spokesman Yukio Edano said that: “we are acting on the assumption that there is a high possibility that one has occurred [in reactor 1]. As for the number-three reactor, we are acting on the assumption that it is possible.”

The first explosion that occurred on Saturday appeared to result in the collapse of the outer structure of one of four buildings at the plant.

Japan’s nuclear agency has assessed the situation at the Fukushima plant as a level 4 incident on the International Nuclear and Radiological Events Scale (INES), despite the fact that such events typically involve the death of at least one person from radiation and currently this has not occurred at the site. However, at least 15 people have been admitted to hospital with signs of radiation poisoning, as of Sunday.

A key concern is the eventual fate of reactor 3, as unlike its two companions, it used MOX as fuel which contains plutonium. Plutonium is significantly more toxic via inhalation than uranium. Some 80,000 people are being evacuated from the area to a distance of 20km. The US is relocating one of its aircraft carriers from the area after detecting low-level radiation 160km offshore.

Hampering engineers’ efforts to bring the reactors under control is a lack of power. The plant was shut off from the power grid due to the earthquake and TEPCO has reported that the emergency diesel-powered generators had failed, forcing the company to install mobile power units.

At present, the containment structures of reactors 1-3 appear to be holding, suggesting that an incident on the scale of Chernobyl is unlikely. The design of the reactors at the Fukushima plant is older than much of the rest of the Japanese nuclear reactor fleet and lacks some of the additional safety features that have been introduced since their construction. Even if the release of radiation is relatively minor and engineers successfully bring the reactors under control, the events of the past few days are likely to be extremely damaging for TEPCO, given its dubious safety record in recent years. In 2002, several of its managers were forced to resign for falsifying safety records and this has contributed to public distrust, which is likely to be heightening fears that the actual events unfolding at the plant might differ from the official version, as described by press releases. A factor that will work to reduce confidence in the Japanese government’s ability to successfully regulate the country’s nuclear industry is the fact that the Fukushima plant received approval last month for another 10 years of operation after approval was given by the local authorities.

Unfortunately for TEPCO and Japan, there are reportedly cooling issues and higher pressures inside the four reactors at the nearby Fukushima Dai-ni (Fukushima 2) nuclear power plant and the government has authorised the release of potentially radioactive vapour to reduce pressure. Again the failure of cooling systems appears to be the problem.

Abroad, the events in Japan are already reigniting the fierce debate between proponents of nuclear power and its detractors, despite the fact that the USA and Europe are at vastly lower risk of seismic activity than Japan. The leader of Silvio Berlusconi’s party has said that Italy will continue with its plans for new build while over in the US, Congressman Ed Markey (Demo) has called for a moratorium on new nuclear build in seismically active area. Senator Joseph Liberman has said that the Obama administration must “put the brakes on right now until we understand the ramifications of what’s happen in Japan.”

Even if new nuclear build programmes do continue, the events unfolding in Japan could potentially force nuclear developers to add further safety measures, leading to significant cost inflation at a time when the economics of nuclear power are under attack from cheap natural gas.

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