TOKYO (MNI) - Some functions should resume at Reactor 2 of the crisis-hit Fukushima nuclear power facility on Monday, Japan's Nuclear and Industrial Safety Agency said.

Power has been connected to the control room for Reactor 2 and the plant operator should be able to use that to turn on some gauges and an air-cleaning system in the control room later in the day, an official of the agency said at a press conference.

However, workers won't be able to turn on power to the Reactor cooling system or other reactors at the facility for two or three more days because destroyed parts need to be replaced.

Power had been expected to be resumed at least at Reactors 1 and 2 as early as Saturday. Power lines have now been strung to all of the four hardest hit reactors at the plant. Reactor 2 is the least damaged of the four, but the water spraying operation that has been used on Reactors 3 and 4 is not available for Reactor 2 since the building that surrounds it is mostly intact.

Tokyo Power and Electric Co (TEPCO) said Monday that new parts must be fitted inside the reactors to ensure power does not short circuit once it is turned on.

Meanwhile, water spraying continued overnight Sunday and into Monday morning at the No. 3 and 4 Reactors. Fire trucks and other vehicles dumped hundreds of tons of water on those reactors over the weekend.

The spraying effort had appeared to be stabilizing the situation until Sunday morning, when Japan's Nuclear and Industrial Safety Agency announced a pressure rise within the No. 3 Reactor could only be fixed by venting radioactive air into the atmosphere.

That venting was later postponed until an unspecified time, TEPCO officials said, after pressure within the reactor vessel stabilized Sunday afternoon.

The officials, speaking at a press conference, struggled to explain why the pressure stabilized and whether it could rise again and force the venting of radioactive steam into the atmosphere. The press conference ended abruptly after officials failed to answer a series of questions about details of the situation at Reactor 3, saying repeatedly: "we do not have the necessary data."

One official did say that it would take about two hours to make preparations to vent steam from the reactor if it became necessary.

On Sunday morning, a Japan Nuclear and Industrial Safety Agency official agreed with TEPCO officials that there was no choice but to allow the release of radioactive air from Reactor 3 because pressure within the reactor's containment vessel had built to dangerous levels,

"In order to be safe we need to take measures to lower pressure of the containment vessel," a safety agency one official said Sunday morning. In doing so, "radioactive substances will be released."

Workers would first try to release air through a water-filled suppression pool to reduce its radioactivity. If that were to fail to adequately reduce the pressure, radioactive air would be released directly into the atmosphere, officials said.

Work on Reactor 3 had been concentrating on its spent fuel rod pond, rather than the reactor itself. That reactor is the only one at the plant which uses plutonium in its fuel, which is particularly toxic.

Officials said earlier that radiation levels have fallen near Reactor 3 at the Fukushima nuclear facility after it was drenched overnight with more than twice the amount of water that usually fills its used fuel rod pond.

Water was sprayed for 13 hours from an unmanned vehicle, from Saturday afternoon until early Sunday morning. Spraying efforts then switched to the No. 4 Reactor.

Officials say about 80 tons of water were sprayed on Reactor 4 Sunday. Unlike Reactor 3, much of the roof of Reactor 4 remains intact so operators have been trying to spray through holes in the structure. They say they are confident water has been getting into the building itself.

Meanwhile, water temperatures in the spent fuel rod ponds of Reactors 5 and 6 have been dropping since emergency power was restored Saturday to their cooling water circulation systems, officials said.

Once power is resumed in the first four reactors, it is hoped that the company can then resume using desperately needed cooling machinery. The company had planned to turn on power at Reactors 1 and 2 by 1730 local time Saturday.

Spraying at Reactor 3 had left the situation there "somewhat stabilized," Chief Cabinet Secretary Yukio Edano said in a press conference Saturday. Reactor 3 is both the most damaged reactor at the plant and the one that has the most potential for harm, since its fuel rods contain plutonium.

In an address to the Japanese people late Thursday, Prime Minister Naoto Kan said "the situation is very grave and I will share that quite honestly."

But he said "in the not so distant future the overall situation will be controlled."

Japanese media reported Saturday afternoon that a proposal from Kan for a unity Cabinet that would include opposition lawmakers was rejected, although opposition leaders said they will do what they can to help.

Also on Saturday, Edano said elevated levels of radioactivity had been detected in milk and spinach from outside the 30-kilometer exclusion zone around Fukushima.

"These detected levels of radioactivity would not affect the health of consumers," he said, urging that people remain calm.

More food was found to have elevated levels of radiation Sunday, and radiation in drinking water in the Fukushima area has surpassed acceptable levels, officials said.

Japan Nuclear and Industrial Safety Agency officials upgraded their assessment of danger at the plant to level 5 from level 4 on an international scale that goes to 7. The Three Mile Island incident in the U.S. was a 5 on that scale while Chernbyl was a 7.

Although elevated levels of radiation have been recorded outside the 30 kilometer exclusion zone around the Fukushima plant, the World Health Organization said Thursday that there is no major health risk outside the immediate area.

"The evidence so far, from radiation measured, we would say there is little danger there. There is little health risk for the public," said WHO spokesman Gergory Hartl.

TEPCO said Saturday that it was raising the maximum acceptable exposure for its workers to 150 millisieverts after a number of them showed exposure greater than 100 millisieverts, the previous maximum. It said, however, that it would not send workers back in to the plant once they have been exposed to more than 100 millisieverts.

A typical CT scan exposes a patient to 10 millisieverts.

Tsunamis that followed the huge earthquake Friday knocked out generators at Fukushima that circulate cooling water at the site's six reactors. That has allowed fuel rods to overheat, turning the water into steam and exposing some of the rods to the air and causing chemical explosions.

About 200 kilometers to the southwest, Tokyo and neighbouring cities rely heavily on this and another nuclear power plant in Fukushima Prefecture for their power needs.

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