UPDATE: Fuel rods at Fukushima Daiichi No2 reactor fully exposed as cooling efforts fail, heightening fears of full meltdown while radiation levels spike

NTV Japan

Publish date: March 14, 2011

Written by: Charles Digges

The fuel rods in the No 2 reactor at a quake-damaged Fukushima Daiichi nuclear power plant located 240 kilometres north of Tokyo are again "fully exposed" officials said early on Tuesday morning Japan time after attempts to pump more seawater into the core of the reactor to cool down the uranium fuel rods were thwarted by massive pressure build ups.

The more time that passes with fuel rods uncovered by water and the pressure inside the containment vessel unvented, the greater the risk that the containment vessel will crack or explode, creating a potentially catastrophic release of radioactive material into the atmosphere — an accident that would be by far the worst to confront the nuclear power industry since the explosion of the Chernobyl nuclear power plant 25 years ago.

Japanese ecological groups have also begun to report astounding rises in radiation levels surrounding the No 2 reactor building.

According to information obtained by Russia’s Ecodefence, radiation measurements taken of the air surrounding the reactor where measuring of 3130 microsieverts per hour. More plainly, anyone in the vicinity of the reactor would receive the maximum dose of radiation a person receives over the course of a year within 20 minutes, and over three days would receive the maximum dose that could be withstood over 72 years, said Ecodefence, which based their figures on maximum doses established by the US Nuclear Regulatory Commission.

The Kyodo News also eventually reported that higher radiation levels were recored North of Tokyo near theFukushina Daiichi plant, citing official sources, but the report was not more specific. 

Bellona issued statement in Russian condemning the use of nuclear power worldwide. “Bellona has confirmed, and continues to confirm that safe reactors do not exist,” reads the statement in part. “The use of nuclear energy is always associated with risks, and we see this today in the example of the Japanese tragedy.”

Number of those irradiate likely to grow

In medical screenings, higher-than-normal levels of radiation have been detected from at least 22 people of the 210,000 the government ordered to be evacuated from near the plant.But the New York Times reported that it is not clear if the doses they received were dangerous.

On Monday evening, Ecodefense said TEPCO had reported that another five of its workers had been diagnosed with radiation poisoning.

US news outlets were also reporting that Japanese media had said anywhere from 160 to 190 people had been severely irradiated since the earthquake. But US media also said these figures are likely an underestimation.

Japanese nuclear industry in ‘full scale panic’

The renewed failure of cooling at the 40-year-old Fukushima Daiichi’s reactor unit 2 left three of the plant’s six reactors in severe crisis as Tuesday morning began in Japan.

The fuel rods had been exposed earlier on Monday inside reactor No 2 – the most battered and damaged of the three crippled reactors at the plant – and workers managed to wrestle water back into the reactor vessel and re-submerge the rods up to 2000 millimeters, Japanese media reported.

But building pressure from heat and steam, an apparent malfunction of ventilation valves, and the accidental shut down of an airflow gauge, have left the fuel rods again completely exposed, reinvigorated earlier fears that the reactor was headed for at least a partial meltdown and fracturing from intensely high pressure of the reactor vessel itself.  

Tokyo Electric Power Co, which runs the plant, said that it presumed some of the fuel rods were broken, based on radiation detected in the environment, World Nuclear News reported.

If more of the fuel melts before water can be injected in the vessel, the fuel pellets could burn through the bottom of the containment vessel and radioactive material could pour out that way — a full meltdown scenario.

“They’re basically in a full-scale panic” a senior nuclear industry executive told the New York Times late Monday night of the Japanese power industry. The executive is not involved in managing the response to the reactors’ difficulties but has many contacts in Japan.

“They’re in total disarray, they don’t know what to do,” he said.

Exposure of the fuel rods

Air pressure inside the No. 2 reactor at the Fukushima Daiichi plant rose suddenly when the air flow gauge was accidentally turned off, operator Tokyo Electric Power Co (TEPCO) told reporters.

That built up enough pressure inside the reactor vessel to block the flow of cooling water into the reactor, leading to full exposure of the rods at around 11pm Tokyo time on Monday, TEPCO said. Officials were said to be considering the option of drilling holes in the reactor vessel to relieve the pressure, said Bellona nuclear physicist Nils Bøhmer said.

“We are not optimistic but I think we can inject water once we can reopen the valve and lower air pressure,” a TEPCO official told reporters.

But Bøhmer’s prognosis was not optimistic. He said that with the fuel rods now exposed to air with no coolant in the reactor vessel, the fuel rods will begin to melt and the lack of water to bear away thermal energy will only increase pressure inside the reactor vessel, which would lead to a rupture.

“When there is no water, more and more stream builds up within the reactor vessel and thus more and more pressure,” said Bøhmer. “That leads to heat build ups to a point of 2,200 degree Celsius where you get melting of fuel as well as pressure breaking the reactor vessel.”

This scenario, said Bøhmer, would lead to a partial or full meltdown – the biggest fear for Japan’s nuclear reactors in the aftermath of the 9.0 point earthquake that hit the country on Friday, and which has been jolted by aftershocks ever since.

When the fuel starts to melt, said Bøhmer, “it releases gasses into the environment, radioactive gasses like caesium, uranium radioactive iodine – basically the whole mess of radioactive gasses.”

Grappling with reactor Nos. 1 and 3

The extreme challenge of managing reactor No. 2 came as officials were still struggling to keep the cores of two other reactors, No. 1 and No. 3, covered with seawater.

Efforts to fill reactor unit No 1 with seawater and boron were ongoing in hopes of averting a partial meltdown there, and workers were trying to do the same at reactor unit 3, whose outer building walls and roof were blown away by an explosion of built up hydrogen early Monday morning. Reactor unit No 1 had experienced the same scenario on Saturday.

Both reactors No 1 and 3 are presumed to have already suffered partial meltdowns – a dangerous situation that, if unchecked, could lead to a full meltdown.

An ex-government official in Japan who spoke with Bellona Web on conditions of anonymity confirmed the chronology of events from Monday to Tuesday at the No. 2 reactor.

Earlier efforts to inject seawater and Boron coolant into the reactor had failed when pump that had been infusing the seawater into the reactor’s core ran out of fuel, and no other fuel could be found to power the pump.

The water flow was eventually restored, he said, raising hopes that there would be no baleful results. But the build up of pressure that had precluded further injections has dashed those hopes.

Meltdown likely underway

Vladimir Slivyak, co-chair of the Russian environmental group Ecodefence, wrote in his regular updates to on the situation in Japan that “most likely, fuel is already melting” in the No. 2 unit at Fukushima Daiichi.

“Radioactive gas has formed in the reactor vessel, which is planned to be released into the atmosphere” to relieve pressure he wrote Monday night. This procedure would be a repeat of releases of radioactive gasses at Fukushima’s reactor unit No. 1 and 3 that have taken place over the previous days to relieve pressure build-ups.

Slivyak also noted that on each occasion radioactive gas was released to cope with pressure difficulties, the releases preceded the hydrogen gas explosions that ripped appear the reactor buildings of Units 1 and 3.

So far there appears to be no indication that reactors 1 and 3 are in nearly the distress that No 2 is. But live footage on public broadcaster NHK showed the skeletal remains of the reactor building and thick smoke rising from the building, the ex-government official told Bellona Web. Eleven people had been injured in the blast, one seriously, officials said.

Bellona Russian statement was targeted at the government of Russia, where a Japan scale catastrophe is more than possible – and as the only country that, as part of the Soviet Union, has ever experienced a civilian nuclear event that surpasses events in Japan.  

“Bellona expresses is certainty, that having received bitter experience and having evaluated the risks, the government of Russia will begin to invest resources in renewable and clean sources of energy, refusing the dangers of nuclear power,” concluded the statement.

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