As Japanese engineers appear to make progress controlling the world’s worst nuclear crisis for 25 years, a nuclear expert tells Channel 4 News the plant may need to be encased in concrete.
Some workers were later evacuated from one of the most badly-damaged reactors when smoke briefly rose from the site. There was no immediate explanation for the smoke, but authorities had said earlier that pressure was building up at the No. 3 reactor. Smoke was also seen at the No. 2 reactor.
The amount of smoke later receded and Japan’s nuclear safety agency said there was no significant change in radiation levels at the site.
The top US nuclear regulator has said the Japanese nuclear crisis appeared to be on the verge of stabilizing.
The Nuclear Regulatory Commission also said it was preparing for additional inspections and a 90-day review of the status of US nuclear reactors in light of the disaster at the nuclear plant in Japan.
Since the 11 March earthquake and tsunami hundreds of engineers have worked around the clock inside an evacuation zone 240 km north of Tokyo, spraying the complex with thousands of tonnes of sea water so fuel rods will not overheat and emit more radiation.
There are different problems in each of the reactors – some can only be resolved with the concrete option. Engineer Victor J.Petrelli
Hopes for a more permanent solution depend on electricity cables reactivating on-site water pumps at each of the six reactors to cool them down.
Getting power running in each reactors would allow the plant’s owner Tepco to restore systems to monitor radiation and other data and light the control room of the reactors.
But their ability to power up the reactors will depend on the extent of any damage to each unit. The worse-hit reactors are No. 3 and 4, which were both hit by explosions last week.
If the cooling pumps cannot restart, drastic measures may be needed like burying the plant in sand and concrete.
Institute of Electrical and Electronics Engineers member Victor J. Petrelli, who helped design a nuclear plant in Illinois, in the United States, told Channel 4 News the range of options available to Tepco are narrowing.
“So what would be the plan now? Well, there have been fruitless efforts to cover the exposed core with boric acid that will slow the reaction – but it appears to be leaking out of the breached building. Next they could build an emergency containment wall around the building to hold the boric acid – but this would take a long time and mean dangerous exposure for the workers,” he said.
“Finally there would be concrete. Concrete can be poured and harden under water. Chernobyl is encased in concrete – and so is Fermi Reactor 1 in Detroit…They are struggling to keep the reactors cool long enough for the cores to neutralize. But there are different problems in each of the four reactors – some can only be resolved with the concrete option. If they cannot keep coolant/boric acid over the core, they will have to cover it with concrete.”
He said that the engineers would be scrabbling to find a solution.
“There would have been emergency procedures in place,” he told Channel 4 News.
“However, I would not be sure if they covered simultaneous earthquake and tsunami flooding. Probably one or the other…the engineers are not feeling anything. They are desperately trying to solve problems to protect their fellow citizens.”
News of progress at the nuclear plant was overshadowed by mounting concern that radioactive particles already released into the atmosphere have contaminated food and water supplies.
The World Health Organisation said that radiation in food after an earthquake damaged a Japanese nuclear plant was more serious than previously thought, eclipsing signs of progress in a battle to avert a catastrophic meltdown in the reactors.
US energy secretary, Steven Chu, asked by CNN whether the worst of Japan’s 10-day nuclear crisis was over, said: “Well, we believe so, but I don’t want to make a blanket statement.”
US Nuclear Regulatory Commission chairman Gregory Jaczko added that radiation levels at the plant appeared to be falling.
Prime Minister Naoto Kan also said the situation at the nuclear plant was slowly improving.
The earthquake and tsunami left more than 21,000 people dead or missing and will cost an already beleaguered economy some $250bn, making it the world’s costliest ever natural disaster.
The danger isn't over yet, writes Channel 4 News Science Correspondent Tom Clarke:
Things are, at last, starting to look brighter for the Fukushima power plant - but the danger isn't over yet.
The US nuclear regulator, The Nuclear Regulatory Commission, has said that the crisis appeared to be on the verge of stabilising.
This morning it was confirmed that power cables had been laid to each of the six nuclear reactors at the Fukushima site. Electricity is now flowing to two of the least-damaged reactors - 5 and 6. Diesel generators there have now been switched off and the water in storage ponds - which over the weekend was getting worryingly high - has now started dropping.
But two-thirds of the nuclear threat Fukushima poses remains undiminished. A mile long-cable has been laid to reactors 2 and 4 however engineers still have to make repairs to other systems at the plant before they can attempt to restart pumps and cooling systems.
Radiation levels at the site have been decreasing.
According to the Tokyo Electric Power Company, work around the reactors can now be safely carried out provided workers are wearing overalls and face-masks. But there is still some uncertainty about the safety of pools containing fuel rods adjacent to reactors 3 and 4.
Last week there were fears these pools may be running dry and a fire involving stored nuclear fuel could lead to a major release of radioactivity. However, fire trucks and civil defence vehicles will continue tonight spraying water over the pools to keep them cool. According to NISA work is also underway to bring concrete pumping equipment on-site.
It's understood there may be plans to entomb reactor number 4 and its damaged fuel storage pond in concrete.
Meanwhile, it was confirmed that radioactivity had been found more widely in food from around the stricken reactors. Shipments of spinach and rapeseed have been banned from Fukushima and its three neighbouring prefectures. A ban on milk sales from Fukushima prefecture continue.
The levels in food are not high enough to immediately endanger health, but long-term exposure could be a problem according to the Japanese health authorities.