The Senate on Thursday passed bipartisan legislation that would significantly expand a law allowing victims of government-caused nuclear contamination who developed cancer and other serious illnesses to receive federal compensation.

The 69-to-30 vote buoyed long-held hopes that the federal government would take further steps to make amends to anyone sickened by the legacy of the nation’s nuclear weapons program.

The bill would overhaul a law passed more than two decades ago with an exceedingly narrow scope, meant to compensate those who participated in or were present for aboveground atomic bomb testing, a hallmark of the Manhattan Project in the 1940s, or uranium miners who worked between 1942 and 1971.

But the writers of that initial statute excluded large constituencies of those affected by the testing — people known as “downwinders” — including in large swaths of Arizona, New Mexico and Nevada. They also left out altogether communities in areas such as Idaho, Montana, Colorado and Guam.

The legislation, spearheaded by Senators Josh Hawley, Republican of Missouri, and Ben Ray Luján, Democrat of New Mexico, would not only seek to remedy those omissions, but it would also broaden it substantially beyond Cold War-era victims to others who have been harmed by the aftereffects in the decades since. The law is scheduled to expire in June unless Congress acts before then to renew it.

“This is a moral issue,” Mr. Hawley said. “The government exposed these good Americans to nuclear radiation without their consent, and usually, without any support. Now the government needs to make it right, and that is what this program is for. That is why the reauthorization update is absolutely necessary.”

The bill, which the White House endorsed in a statement on Wednesday, makes the case that the federal government should compensate anyone grievously sickened by the legacy of the nation’s nuclear weapons program. It is unclear whether Speaker Mike Johnson will put the legislation to a vote on the House floor.

The bill would extend access to the federal fund for six years and expand eligibility to Missourians sickened by radioactive waste that was never properly disposed of — and in some cases left out in the open near a creek — in St. Louis, the home of a uranium processing site in the 1940s.

A blockbuster report by The Missouri Independent, MuckRock and The Associated Press last year found that generations of families growing up in the area have since faced “rare cancers, autoimmune disorders and other mysterious illnesses they have come to believe were the result of exposure to its waters and sediment.”

The measure would also expand eligibility for civilians affected by testing or the cascading effects of uranium processing in certain ZIP codes in Alaska, Kentucky and Tennessee.

“Since this bill has been scheduled for a vote,” Mr. Luján said, “I’ve heard from more colleagues about their communities that have been harmed by our nation’s complicated nuclear legacy.”

Momentum to renew and expand the program, an effort that has sputtered along for years in fits and starts, picked up in July, when the Senate voted to attach a version of the measure to the annual defense policy bill. But the measure was ultimately stripped out of the final version of the legislation after Republicans objected to its hefty price tag, which congressional scorekeepers estimated could hit $140 billion.

Mr. Hawley and Mr. Luján say they have since adjusted the legislation — axing a provision that would have provided additional compensation beyond the one-time payment for medical bills — so the cost will be closer to $40 billion. They also revised their bill to shorten the extension of the law from 19 years to six years.

The law has paid out more than $2.5 billion in benefits to more than 55,000 claimants since its creation in 1990, according to congressional researchers. Claimants, who can include children or grandchildren of those who would have benefited from the program but have since died, receive a one-time payment ranging from $50,000 to $100,000.

A few dozen activists who have been lobbying for the expansion of the legislation — many of whom say they and their loved ones have been sickened by exposure to radioactive waste — sat watching in the gallery as the vote took place.

As they filed out of the Senate chamber afterward, several broke down in tears.