TOKYO (REUTERS) - Japan may restart several reactors shut down by the Fukushima nuclear crisis in about a year, a senior regulator said in an interview on Tuesday, a day after new safety rules went into effect designed to avoid a repeat of the disaster.

At the Fukushima No. 1 nuclear plant north of Tokyo, the site of the world's worst atomic disaster since Chernobyl in 1986, the situation took a turn for the worse as radiation levels in groundwater soared, suggesting highly toxic materials from the plant are now close to the Pacific Ocean.

But Japan is forging ahead with attempts to restart idled reactors in the face of a sceptical public, after Fukushima highlighted weak oversight of the industry.

That is meant to change with the new rules.

Getting units restarted is a key government goal to reduce the import bill for fossil fuel to run conventional stations.

Only two of Japan's 50 reactors are connected to the grid and operators applied to restart 10 on Monday.

"Some units are projected (to restart) one year from now, though I don't know how many," said Kenzo Oshima, a commissioner of Japan's Nuclear Regulation Authority. "It is hard to imagine that all the applications would be rejected, though we don't know what the outcome will be at the moment." He did not identify the reactors that are likely to restart.

Tokyo Electric Power Co, the operator of the Fukushima station, hit by the March 2011 earthquake and tsunami, said that an observation well between the damaged reactor No. 2 and the sea showed levels of radioactive caesium-134 were 90 times higher on Monday than they had been the previous Friday.

Tokyo Electric, also known as Tepco, said it detected caesium-134 at 9,000 becquerels per litre, 150 times above Japan's safety standard. A becquerel is a measure of the release of radioactive energy.

The reading for caesium-137, with a half life of 30 years, was some 85 times higher than it had been three days earlier.