MONTREAL — Weapons-grade uranium is quietly being transported within Canada, and into the United States, in shipments the country's nuclear watchdog wants to keep cloaked in secrecy.

A confidential federal memo obtained through the Access to Information Act says at least one payload of spent, U.S.-origin highly enriched uranium fuel has already been moved stateside under a new Canada-U.S. deal.

The shipments stem from the highly publicized agreement signed last year by Prime Minister Stephen Harper and U.S. President Barack Obama, amid fears that nuclear-bomb-making material could fall into the hands of terrorists.

The Canadian stash gradually being shipped from Chalk River, Ont., contains hundreds of kilograms of highly enriched uranium -- large enough to make several Hiroshima-sized nuclear bombs.

But even as the radioactive freight travels toward the U.S. border, the Canadian Nuclear Safety Commission has no plans to hold public hearings or disclose which communities lie along the delivery route.

The shipments themselves are protected by intense security protocol, which means specifics like routes, transportation method, quantities and schedules remain top secret.

The federal nuclear body, a co-regulator of the uranium transfers, says rules restrict it from disclosing such information to the public.

A ministerial memorandum, classified as "Secret," says the nuclear watchdog considers it unnecessary to hold public sessions that would allow citizens to ask questions and comment on the shipments.

That same memorandum, dated Feb. 25, 2011, points out that recent hearings for another nuclear-shipment case generated intense public and media interest. The controversy has stalled the project to ship 16 generators from a Bruce Power nuclear plant through the Great Lakes, up the St. Lawrence River and onto Europe.

The memo, obtained by The Canadian Press, appears to warn against a repeat scenario.

"Given the public and media interest surrounding Bruce Power's plan ... there may be an expectation that similar information be made public on the shipments of spent HEU (highly enriched uranium) fuel to the U.S., and that the CNSC (Canadian Nuclear Safety Commission) hold public hearings," said the document, addressed to then-natural resources minister Christian Paradis.

"To date, the CNSC has not considered it necessary to hold public hearings on the shipment of spent HEU fuel to the U.S."

When asked why public hearings aren't necessary for the uranium deliveries, a commission spokeswoman replied by email: they "are not carried out given the robustness of the packages used and due to the security issues related to the transfers of highly enriched uranium."

The government added that there has never been a significant transport accident involving nuclear materials, anywhere in the world, and that such shipments occur regularly in Canada.

It said only authorized people or agencies, like police forces along the shipment route, are made aware of the details.

One nuclear expert said theft is the primary concern when shipping highly enriched uranium fuel -- because there is virtually no danger of leaks or explosions.

"If I were the people doing the shipping and so on, I'd want to keep as low a profile as possible ... you don't want to give terrorists or criminals any advantage," said Bill Garland, a professor emeritus from McMaster University in nuclear engineering.

"There's a greater risk in the general public knowing, because then the bad guys would know as well."

As for non-theft incidents, like possible road accidents, he described the containers carrying the substance as highly resistant to collisions, chemicals, fire and explosions.

"It's relatively easy to contain and secure and it's not going to go off like a bomb," Garland said.

"I would have no hesitation sitting in the truck and driving across the country with it. It wouldn't bother me in the least."

Garland added that drivers share Canadian highways every day with trucks carrying loads of liquid chemicals, like gasoline and chlorine, that would pose a much bigger danger in a smash-up than nuclear waste.

While the risks are small, he said, that doesn't mean they don't exist. He warned that radiation could be released if someone deliberately opened a container, for instance.

Garland said moving uranium poses far more danger than shipping Bruce Power's old generators up the St. Lawrence.

He calls the generator shipments a "trivial radioactive situation" and a "non-issue" because the cylinders hold very low levels of radioactive material. He said that even if they fell into the bottom of the river, the generators would pose a negligible risk.

Canada has been importing highly enriched bomb-grade uranium from the U.S. to make medical isotopes at Chalk River for the past two decades. While Canada has been pushing for all nations to move to low-enriched uranium, it maintains a large inventory of the substance at Chalk River.

The Canada-U.S. agreement is part of a broader international project by the Obama administration to consolidate highly enriched uranium at fewer, more secure sites around the world.

The U.S. government says it wants to convert the uranium into a form that cannot be used to build nuclear weapons.

Canada made its first uranium delivery under the repatriation deal in 2010, the February memo says. It occurred in "a single shipment using an existing, licensed fuel shipping package."

The continued shipments are scheduled to take place until 2018.

But some nuclear-industry observers fear that Canadians have been left in the dark about the project.

"I don't think Canadians are aware that strategic nuclear material is, in fact, travelling across Canadian roads," said Gordon Edwards, president of the Canadian Coalition of Nuclear Responsibility.

"I think it's essential that people be aware of what is involved here. People should be aware of the degree of secrecy which is required."

While he has few fears about the safety of the shipment Garland, the nuclear engineering professor, does have some concerns about the government's selective approach to transparency.

"They're willing to talk about those things (the Bruce Power generators) publicly, but yet when they talk about something that's more dangerous -- like moving HEU -- they're not so willing to talk about it," Garland said.

He said while it's critical to keep specific details about the shipments confidential, there are ways to maintain security while offering some public oversight.

"If I were king ... I would say, 'Look, let's have a committee of experts looking at this, working on behalf of the public so that they could analyze this without having to give out all the details to the public,' " Garland said.