Our friend the atom? The growing threat from nuclear power.

The Bush administration and the nuclear industry are embarking on an ill-conceived "renaissance" of nuclear power, deploying the spurious message that it is emissions-free, green, safe, and will save the world from the effects of global warming. Wrong, on all counts!

Carbon dioxide gas--the increase of which is tied to global warming--is released at every stage of the nuclear fuel cycle: uranium mining and milling, uranium enrichment, construction of huge concrete reactors, and the transportation and long-term storage of intensely radioactive waste. Nuclear power plants currently generate "only" one-third as much carbon dioxide as a similar-sized energy plant fired by natural gas. But because the supply of highly concentrated uranium ore is limited, the energy eventually required to mine and enrich uranium will greatly increase. If global electricity production were converted to nuclear power, there only would be a three-year supply of accessible uranium to fuel the reactors.

Nuclear reactors routinely emit radioactive materials, including the fat-soluble noble gases xenon, krypton, and argon. Although not chemically reacting with biological compounds, they are inhaled by populations near reactors, absorbed into the blood, and concentrated in the fat pads of the abdomen and upper thighs, which exposes ovaries and testicles to mutagenic gamma radiation.

Tritium, a form of radioactive hydrogen, is also regularly discharged by reactors. Combining with oxygen to form tritiated water, it absorbs readily through skin, lungs, and gut. Tritium is a dangerous carcinogen that produces congenital malformations and genetic deformities in low doses in animals and, by extrapolation, in humans.

ADDITIONALLY, NUCLEAR reactors are potential terrorist targets. Reactor meltdowns could be induced by severing the external electricity supply, disrupting the 1-million-gallons-per-minute intake of cooling water, infiltrating the control room, or by a well-coordinated attack. Surprisingly, since Sept. 11 the U.S. Nuclear Regulatory Commission has failed to upgrade security at the nation's 103 nuclear reactors. A meltdown at the Indian Point reactors, located 35 miles from Manhattan, could render the region uninhabitable for thousands of years.

Nuclear waste is the industry's Achilles" heel. Currently 60,000 tons of radioactive waste are stored temporarily in cooling pools beside nuclear reactors, awaiting final disposal. In 2002, Congress voted that the final repository for nuclear waste would be Yucca Mountain in Nevada, which is transected by 32 earthquake faults and consists largely of permeable pumice, and thus is unsuitable as a radioactive geological waste receptacle. The U.S. now has nowhere to deposit its expanding nuclear waste inventory.

In countries with nuclear reactors, radioactive elements are leaking into underground water systems, rivers, and oceans, progressively concentrating at each level of the food chain. Carcinogens including Strontium-90, recently found in the groundwater at the Indian Point reactors, and Cesium-137 are radioactive for 600 years. Food and human breast milk will become increasingly radioactive near waste sites. Inevitably cancers will increase in frequency within exposed populations, as will genetic diseases such as cystic fibrosis.

Each 1000-megawatt reactor produces some 500 pounds of plutonium each year in spent fuel rods. Plutonium is carcinogenic in amounts smaller than one-millionth of a gram and can cause liver cancer, lung cancer, bone cancer, and leukemia. It can cross the placenta to induce congenital deformities, and it has a predilection for the testicles where it may cause genetic abnormalities. Once released in the ecosphere, plutonium--with a half-life of tens of thousands of years--will affect biological systems essentially forever.

Critical mass for a nuclear explosion requires only 10 pounds of plutonium. Countries with nuclear reactors could therefore use radioactive waste to manufacture many nuclear bombs per year. The under-resourced International Atomic Energy Agency admits that it is physically impossible to prevent a determined country--whether a signatory to the Non-Proliferation Treaty of Nuclear Weapons or not from using imported uranium or plutonium to make nuclear weapons.

Time is short. A truly informed national debate about the efficacy of nuclear power is long overdue.

Dr. Helen Caldicott is founder of Physicians for Social Responsibility and founder and president of the Nuclear Policy Research Institute. Her book Nuclear Power is Not the Answer will be published in September 2006.