Sources also reported that the Norwegian embassy was evacuating personnel as wind predictions put Tokyo downwind of radiation and rain contaminated with caesium and radioactive iodine were predicted to hit the metropolis, said a Norwegian diplomat. The embassy is moving its staff to Kobe, Japan, 500 kilometres west of Tokyo.

“Much remains to be done before we can breathe a sigh of relief,” said Bellona physicist Nils Bøhmer.

“To say how long crews will have to work very hard to regain control is terribly difficult. It may well take weeks,” he said

An ex-government official who spoke confidentially with Bellona Web from Tokyo reported that no warnings had been issued for the capital’s general population, pointing to yet another apparent disconnect between information possessed by higher echelons of government and what is being released to the Japanese people – despite promised from Chief Cabinet Secretary Yukio Edano and Prime Minister Naoto Kan that they would be more open as the crisis persists.

Four reactors remained in a coolant crisis and their coolant systems may altogether be destroyed, and despite recent restorations of electricity at other reactors, it remained in question whether electrical power would operate the quake and explosion battered cooling systems of the remaining reactors at all.

Tokyo Electric Power Co. (TEPCO) said it had briefly evacuated its workers after the smoke was spotted at the southeast of the No. 3 reactor building above a pool storing spent nuclear fuel, though a blast was not heard.

The Tokyo Fire Department, which has been called in for efforts to inundate possibly exposed fuel rods with water,  stopped spraying for the day after the smoke rose from the No. 3 reactor building, Kyodo said

It will suspend the operation until safety at the site is confirmed, Kyodo said, adding whether it will resume on Tuesday remains undecided at present.

The government’s Nuclear and Industrial Safety Agency said no injuries were confirmed in the incidents and that there have been no major changes in the radiation levels at the site.

Whether the reason for the smoke around reactor No. 3 were the reactor itself, from which TEPCO had planned a release of radioactive steam, or the fuel pond, remained unclear throughout the day in Japan, said the Russian environmental group Ecodefence in its ongoing blog on the crisis.

Hidehiko Nishiyama, a spokesman for the nuclear safety agency, confirmed this, telling Kyodo that the causes of the at reactors No. 2 and No. 3 remain unknown and that work to resuscitate power and cooling systems at the troubled reactors will be delayed by one day.

TEPCO said that some of the smoke was rising from a crack in roof of the building that houses reactor No 2, but believed it was steam rather than smoke arising from the spent fuel storage pond, though could not confirm that.

TEPCO reported that the smoke from reactor No 3 ceased at around 6 pm, but that the smoke from reactor No 2 was first noticed at 6:20 local time, Kyodo reported.

Dangers from the overheating spent nuclear fuel storage ponds – of which there are seven at Fukushima Daiichi, on for each reactor and a common pond – is as threatening if not more threatening than radioactivity emerging from the apparently ruptured cores of reactor Nos 1 and 3.

The primary danger is that spent nuclear fuel rods in the absence of cooling water would reach criticality – a chain reaction – in the open, a situation that occurs inside nuclear reactors that are shielded from spreading radioactivity. There are some 1760 tons of spent and fresh fuel filling the plant’s ponds in conditions of intentional overcrowding by TEPCO, as part of a plan to plan to transfer the fuel rods to interim storage offsite.

At present, coolant water is being pumped into the three reactors and the pools for spent nuclear fuel rods at reactors No 3 and No 4. The roofs and upper walls of the buildings that house the No. 1, No. 3 and No. 4 reactors have been blown off by hydrogen explosions, reported Kyodo.

Citing reports, Bellona’s Bøhmer said that reactor Nos 1,2,5 and 6 no longer seem to pose the threat they have in the past days, and that the most  critical issues remain at reactor Nos 3 and 4.

Bellona’s Bøhmer said there were two critical points remaining unresolved on Monday. The first is that reactor No 3, which has been extensively damaged, has to be stabilized.

Reactor No 3 operates on mixed uranium and plutonium oxide, or MOX fuel. Compared to uranium, which is the industry wide standard for power production reactors, plutonium poses far higher risks of harmful radioactive emissions.

The second critical point confronting Fukushima Daiichi as the day ended was the problem cooling the spent nuclear fuel storage ponds, and this will remain the case even if meltdowns are averted.

The work of replenishing the fuel ponds’ water supplies, noted Bøhmer, has been arduous, as workers have had to drop water, with questionable accuracy, from helicopters and douse them with fire hoses at ground level.

Manu reports have emerged about attempts to fill the ponds with water, but there has so far been no way to ascertain how much, if any, water the pools have taken on.

Bøhmer zeroed in on the particularly drastic situation with getting water into the spent fuel pond at reactor No 3.

“We know that the pond at the reactor No. 3 has little water, said Bøhmer.  He said he suspected that the pond must have a leak in it.

“I see simply no other reason why so much water should be lost,” said Bøhmer.

Before the reports of smoke at the Nos 2 and 3 reactors were made public, it was reported that efforts to restore power cables to reactor Nos 5 and 6 had been successful and that over heating situation at the units had been stabilized, Ecodefence reported. Coolant systems were up and running, said the organization.

There is still good reason to be worried, but we are very pleased that the workers have been able to put power lines and restore some of electricity supply, “said Bellona nuclear physicist Nils Bøhmer.

In a statement issued earlier today, Russia’s Ecodefence condemned the use of nullear power worldwide, a point of view Bellona shares. Ecsia’odefence singled out Russia’s problems of denying that, because Russian reactor designs are different, they do not pose an equal threat in the notoriously atomically negligent country

“Against the background of the situation at the Fukushim a Daiichi plant, Russian state nuclear corporation Rosatom continues to announce that its technology is safer than Japan’s,” said the group’s statement. “After Chernobyl, the western nuclear industry avoided problems by dumping blame on Cheronobyl. Now were are being convinced that western nuclear technology is no less dangerous,” continued the statement.

“But the truth lies right down the middle – any nuclear power plant is dangerous regardless of who built it, or where it was built,” said Ecodefence.