In its liquid form, tritium looks just like water: clear and odorless.

Yet it's radioactive, and in the past two months, two nuclear power plants outside New York City and Miami were found to be leaking tritium: the former into groundwater within the facility's confines, the second straight into Biscayne Bay.

The leaks, revealed in news reports, apparently haven't contaminated drinking water and don't pose a threat to human health. But tritium, while less potent than other substances like cesium or strontium or radium, can still be harmful in high enough concentrations, even lethal. And that's before taking the public reaction into account: The New York incident made headlines across the region, anti-nuclear groups warned the state was "flirting with catastrophe," and Gov. Andrew Cuomo ordered an investigation.

The incidents came just a few weeks before the fifth anniversary of the meltdown at Japan's Fukushima Daiichi nuclear plant, which was sparked by a tsunami and earthquake and became the world's worst nuclear disaster since Chernobyl. They also occurred as the industry was working to burnish its image on safety: All of the nation's 61 nuclear plants are at least 20 years old, many are over 40, and at least one plant operator has announced it hopes to extend its reactors' licenses to 80 years.

Yet more than three-quarters of the country's commercial nuclear power sites have reported some kind of radioactive leak in their life spans, an investigation by the Associated Press found in June 2011 – three months after Fukushima. At the same time, the U.S. Nuclear Regulatory Commission has repeatedly weakened federal regulations to allow plants to keep operating, despite thousands of problems ranging from corroded pipes to cracked concrete and radioactive leaks.

Late last month, seven NRC engineers went public with a petition urging the agency to fix a critical design flaw in the electrical systems of all but one of the nation's nuclear plants – a highly unusual move for federal employees.

"We have a very ineffective regulator that will not impose any costs that will jeopardize the economics of these plants," says Paul Blanch, a longtime engineer and industry worker turned watchdog. While a tritium leak may not imperil human health, "it indicates a very sloppy operational environment of aging management and fixing obvious sources of leaks."

The NRC maintains it closely monitors the plants it's charged with regulating.

"We have really strict standards and a very rigorous oversight program," agency spokeswoman Diane Screnci says.

The NRC conducts robust inspections, she says. In the wake of the Fukushima disaster, it instituted new standards for backup generators, pumps, batteries and other systems to prevent catastrophic electric failure.

Overall "they do things very well," says David Lochbaum, director of the nuclear safety project at the Union of Concerned Scientists.

Yet since finalizing the new standards, the agency has reportedly inspected and approved just two of the country's 61 plants for compliance: one in Tennessee, the other in Virginia, Bloomberg BNA found. It's also unclear whether new equipment for maintaining power at the plant during a prolonged outage will even work, experts say: while the NRC's mandate called for buying the new equipment, it apparently lacked minimum performance standards.

Meanwhile, last fall, Indian Point in New York – the plant leaking tritium – suffered four unplanned outages in two months.

"Equipment is failing rather than being detected before failure. That's a disturbing sign," Lochbaum says.

That doesn't inherently signal catastrophe. Officials were alerted to the leak in New York by monitoring wells installed for that very purpose, for example, not nearby residents sickened by tainted drinking water.

"That's good news," Lochbaum says.

A certain number of radioactive leaks may also be inevitable: "These are industrial facilities dealing with hazardous materials, and they need to be maintained very well, but you cannot maintain them perfectly," says a former senior government official.

But, the former official adds, "the pendulum swings far more toward the industry than it does toward public safety."

A 2010 report by NRC staffers called for a new system that would track and evaluate radioactive leaks at nuclear plants, for example, but its recommendations were rejected by the agency's commissioners. Meanwhile, the leak at Indian Point was far from the plant's first issue: Entergy, one of the country's largest nuclear operators and the owner of Indian Point, saw performance evaluations for seven of its 11 plants – including Indian Point – plummet between 2008 and 2014 (it permanently shut down an eighth plant, Vermont Yankee, in December 2014).