Amid signs that nuclear power is on the verge of a renaissance are the voices of opponents of the technology who say the industry remains secretive and irresponsible — particularly about highly radioactive waste.

The latest salvo against it is from the anti-nuclear environmental group Greenpeace.

Greenpeace issued warnings and links to scientific documents on Friday to The International Herald Tribune and on Saturday more widely that claimed that waste from one of the most prominently marketed next-generation reactors will be seven times as radioactive as waste from the current generation of reactors.

That, said Greenpeace, will make nuclear power even more costly and potentially dangerous than it is already.

Areva, the French manufacturer of the new reactor technology, called “EPR,” said that the reports were grossly inaccurate. It said the waste from the reactor would be up to 15 percent more radioactive at most.

Hans Riotte at the Organization for Economic Cooperation and Development Nuclear Energy Agency in Paris said that the current technologies for handling and storing waste could be adapted quite easily to deal with waste from the EPR.

Even so, the latest materials from Greenpeace do raise many interesting points.

One is the high cost of nuclear power plants. Construction of the first new EPR in Finland already is running hugely over budget. Another plant is under construction in Flamanville in France, where there also have been delays. (Two more EPRs are scheduled for construction in China, and Areva is waiting for the reactor to be certified for use in the United States.)

Another point raised by Greenpeace is that nuclear power, despite its appeal as a low-carbon source of energy, will continue to face political hurdles unless adequate plans are put in place for the long-term disposal of nuclear waste. That disposal, of course, includes even more radioactive forms of waste from the next generation of reactors like the EPR.

Currently, there are no long-term facilities for disposing of high-level nuclear waste anywhere in the world.

Construction is under way in Finland to store waste a quarter of a mile underground, but that project still is awaiting final approval. American authorities have sought to put high-level waste inside Yucca Mountain, in Nevada, but that plan is foundering because of local opposition.