TOKYO -- Japan's nuclear regulator announced an overhaul of the country's nuclear safety guidelines Wednesday, the first since a giant tsunami swept over a nuclear power plant in northeastern Japan two years ago and set off the world's worst nuclear accident since Chernobyl, even as signs of new trouble at the stricken plant underscored the hazardousness of the site's cleanup.
Prime Minister Shinzo Abe has been pushing to restart some of Japan's 50 commercial reactors, all but two of which remain idle amid public anxiety over nuclear safety in the wake of the 2011 disaster, when a powerful earthquake and tsunami ravaged the Fukushima Daiichi nuclear power plant. The announcement of the new guidelines starts a process that could allow some of the country's idled reactors to come back online early next year.
The new guidelines were announced by the Nuclear Regulation Authority, which was set up last year to replace the previous regulator amid outrage over its lax approach to safety and close industry ties. In the future, nuclear plant operators must bolster their tsunami defenses and check for active earthquake faults under their plants. They must also set up emergency command centers and install filtered vents to help reduce the discharge of harmful radioactive substances from the reactors.
These safety standards are legally binding, unlike previous guidelines, which were not backed up by law and were adopted by nuclear operators on a voluntary basis. They also address, for the first time, the possibility of severe accidents like the Fukushima disaster, which set off multiple fuel meltdowns and forced more than 100,000 people from their homes.
The regulator faces considerable pressure to reopen idled plants, but the difficult cleanup at Fukushima continues to cast a shadow over Mr. Abe's drive to revive Japan's civilian nuclear program. On Wednesday, the plant's operator, the Tokyo Electric Power Company, said it had detected high levels of radioactive strontium in groundwater at the site.
Tokyo Electric said it had found strontium 90 at 30 times Japan's safety limit in groundwater near its No. 2 reactor, one of three at the plant, which suffered meltdowns after its cooling systems were knocked out by the tsunami. The operator has been struggling to store growing amounts of contaminated waste water at the plant, but had denied that the site's groundwater was highly toxic.
The latest discovery, made during routine checks at the plant, has raised concerns that water is leaking -- possibly into the ocean -- from the plant's reactor turbine buildings, whose basements are flooded with radioactive water. If ingested, strontium 90 can linger in bones, emitting radiation inside the body that can lead, in time, to cancer.
The Nuclear Regulation Authority said it would start accepting applications on July 8 from power companies seeking to restart their reactors. Seven companies have said they will apply to restart a total of 13 reactors across Japan.
"We have reached a milestone" in nuclear safety, Shinichi Tanaka, the authority's chairman, said Wednesday. He said the new guidelines brought Japan in line with the highest global safety standards for nuclear energy.
It will take "many months" for the authority to conduct the necessary checks and approve bringing the reactors back online, authority officials said. Local news reports said the approval process would take at least six months.
Separately, the nuclear regulator has been conducting studies of earthquake fault formations under six nuclear power plants across Japan. Last month, it concluded that a reactor in Tsuruga, in western Japan, stands above an active fault, a finding that could lead to the first permanent shutdown of a reactor since the disaster.
It remains unclear whether the new standards go far enough to quell lingering public fears over nuclear power. In a nationwide poll of 1,781 people conducted by the Asahi Shimbun daily (excluding parts of Fukushima Prefecture), on June 8 and 9, 58 percent of respondents said they opposed restarting the country's reactors, while just 28 percent said they approved.
The authority's meeting on Wednesday, which was open to the public, was disrupted several times by shouts of "Listen to the public!" and "No reactor restarts!" from the audience.
Nevertheless, Japan's power industry, pronuclear businesses and Mr. Abe's governing party have been pushing to allow more reactors to restart. Japan relied on nuclear energy for about a third of its electricity needs before the disaster, and nuclear proponents argue that the ensuing energy shortfall and surging fuel import costs are hurting the economy.
The problems at the Fukushima plant stem from groundwater that is pouring into the plant's damaged reactor buildings at a rate of almost 75 gallons a minute. That water becomes highly contaminated there, before being pumped out to store in tanks at the site.
The latest discovery of strontium in the groundwater could signal that water is leaking from the tanks, or from the damaged reactor buildings themselves. Tokyo Electric said Wednesday that it would bolster nearby seawalls and take other measures to make sure contaminated groundwater did not reach the ocean.
"With the Fukushima disaster still front and center in the public's mind, it's critical that the government moves cautiously in restarting its nuclear program," said Kazuhiko Kudo, a professor in nuclear safety engineering at Kyushu University. "Otherwise, the public will remain highly skeptical of its approach to nuclear safety."
Bringing the reactors back online would complete a reversal in Japan's energy policy, driven by Mr. Abe, a supporter of nuclear power who took office late last year. His predecessors had committed to phasing out Japan's nuclear power program by 2040. But a government energy paper released last week made no mention of that goal.
"The guidelines certainly go much further in addressing nuclear safety," Dr. Kudo said. "Still, the new regulator must show that it stands on the side of the public, not the nuclear operators, or it, too, will be discredited."
Hisako Ueno and Katherine Whatley contributed research.
This article originally appeared in The New York Times.