Mr. Kan’s announcement came as Japan allowed residents of evacuated areas around the stricken Fukushima Daiichi nuclear plant to briefly revisit their homes for the first time since the devastating earthquake and tsunami in March caused the nuclear accident at the plant.
Tuesday’s decision will mean the abandonment of a plan that the Kan government released last year to build 14 nuclear reactors by 2030 and increase the share of nuclear power in Japan’s electricity supply to 50 percent. Japan currently has 54 reactors that before the earthquake produced 30 percent of its electricity.
The cancellation of the planned nuclear plants is the second time that Mr. Kan has suddenly announced big changes in Japanese nuclear policy without the usual endless committee meetings and media leaks that characterize the country’s consensus-driven decision-making process. Mr. Kan appears to be seeking a stronger leadership role after criticism of his government’s sometimes slow and indecisive handling of the Fukushima accident.
Last week, Mr. Kan asked a utility company to suspend operations at the Hamaoka nuclear plant, which sits atop an active earthquake fault line, about 120 miles southwest of Tokyo. After three days of delays, the utility, the Chubu Electric Power Company, finally agreed Monday to shut down the plant until a wave wall could be built and other measures taken to strengthen its defenses against earthquakes and tsunamis.
The announcement Tuesday came just days after Mr. Kan said Japan remained committed to nuclear power. His apparent pull- back may be driven partly by public opinion, which has significantly soured on nuclear power since the Fukushima accident.
Even before the announcement, the disaster had damped the nuclear industry’s hopes for a worldwide revival of reactor building. With demand for electricity and concerns about global warming both growing, the industry had projected rapid expansion, but Japan’s nuclear crisis had already caused several countries to become skittish about nuclear power. Germany, for instance, declared a temporary moratorium on building new plants.
Still, several experts and nuclear industry representatives said Tuesday that they expected demand in two important markets — China and India — to remain strong even though those counties had said they would proceed more cautiously. Both nations have rapidly growing demand for electricity, and neither has nearly enough domestic fuel to meet its needs.
Nils J. Diaz, a former chairman of the Nuclear Regulatory Commission and a consultant for companies that want to build reactors, said he did not think the prime minister’s announcement would cause “a domino effect.” And Jonathan Hinze, vice president for international operations at the Ux Consulting Company in Roswell, Ga., which tracks the market for reactors,?added that Japan’s suspension of new reactor building?was less damaging than it seemed because many in the industry?had doubted that Japan would have the demand to justify that much construction.
A downturn in reactor construction would hurt Japanese companies that export nuclear plant designs and components, including Toshiba, which owns Westinghouse, and Hitachi, which is in a worldwide partnership with General Electric. Companies in France and South Korea also have a big stake in reactor building.
On Tuesday, Mr. Kan said Japan would retain nuclear and fossil fuels as energy sources, but vowed to add two new pillars to Japan’s energy policy: renewable energy and conservation. While Japan has been a global leader in energy conservation, it lags behind the United States and Europe in adopting solar and wind power, and other new energy sources.
“We need to start from scratch,” Mr. Kan told reporters. “We need to make nuclear energy safer and do more to promote renewable energy.”
The wording seemed to at least leave open the possibility that some new nuclear plants could be built in the future.
On Tuesday, Japan was reminded of the human costs of the Fukushima disaster, when the first group of 92 people paid two-hour visits to their homes in Kawauchi, within the 12-mile zone around the plant that was evacuated after the nuclear crisis.
The residents wore white antiradiation clothing and traveled in buses under tight supervision by nuclear officials. They retrieved belongings like photo albums and the tablets traditionally used in Japan to honor dead relatives in household Buddhist shrines, according to local media reports.
The government appeared to agonize for weeks over whether to allow even brief trips. Officials were concerned about whether civilians could be kept safe from exposure to potentially high radiation doses near the plant.
Complicating their decision was the lack of scientific knowledge on the health effects of the radiation doses now found in many of the evacuated areas. Some scientists say radiation levels even in many evacuated areas are too low to cause immediate illness, while others worry that the incidence of cancer could rise over the long term.
Last week, the government staged a trial run; officials played the role of returning residents to see if the trips could be made safely. Screened for radiation on their return, those participating were found to have been exposed to a dose of up to 25 microsieverts during the two-hour visit.
Matthew L. Wald contributed reporting from Washington, and Andrew Pollack from Los Angeles.
