A federal panel has just given its OK to Ontario Power Generation's plan to store nuclear waste in a deep underground bunker near Kincardine, Ont., near the shore of Lake Huron. The joint review panel said "the project is not likely to cause significant adverse environmental effects."

As one might expect, that decision did not sit well with those who say the project will pose a threat to the Great Lakes, especially Lake Huron, which lies just 1.2 kilometres from the proposed disposal site. The major concern is that radioactivity might eventually leak into the main source of drinking water for 40 million Canadians and Americans.  

While the panel's favourable review does not amount to a final green light for the project, it is a victory for the plan's supporters.

Here are some key questions about what the storage project is all about:

What nuclear material will the bunker store?

The Deep Geologic Repository (DRG), as it is called, will store 200,000 cubic metres of low- and intermediate-level radioactive waste in an underground storage facility far below the Bruce nuclear power station. 

Great Lakes Nuclear Waste

This Nov. 1, 2013 photo shows rows of chambers holding intermediate-level radioactive waste in shallow pits at the Bruce Power nuclear complex near Kincardine, Ont. Ontario Power Generation is seeking permission from the Canadian government to permanently store low- and intermediate-level radioactive waste in a rock chamber that would be built 680 metres underground and 1.2 kilometres from Lake Huron. (John Flesher/Associated Press)

Low-level radioactive waste includes such things as mops, rags, protective clothing and floor sweepings. The intermediate-level material includes used reactor core components, filters and refurbishment waste.

By volume, 80 per cent of the waste is expected to be of the low-level variety.

The waste will come from three nuclear power plant sites in Ontario — the Bruce, Pickering and Darlington sites — currently home to 18 operating Candu reactors. 

Both types of waste from these three sites are already being stored above ground at the Bruce facility.

What about highly radioactive used nuclear fuel? Could it be placed in the bunker?

OPG says high-level radioactive waste (used fuel) would never be placed in the bunker, saying a facility to handle spent fuel rods would need to be designed quite differently from a DRG. The review panel agreed.

However, opponents of the project worry that allowing the Kincardine waste bunker will set a dangerous precedent.      

Why go deep?

The proposal is to build a repository 680 metres below the surface — with two shafts, tunnels and underground storage rooms that would spread out over an area of about 40 hectares. The storage facilities will be located amidst thick layers of limestone rock in what's called the Cobourg Formation.

The review panel says this rock is geologically stable and has low permeability, meaning that liquids and gases can't easily pass through it.

So why not leave the waste material on the surface where it's now stored, as some opponents have suggested. Wouldn't it be easier to address radioactive leaks if the waste is on the surface?

OPG says, and the panel agrees, that surface storage is riskier than going underground.

"Compared to a surface facility, the additional protection of hundreds of metres of rock in a difficult-to-access location with limited or no exposure to natural surface phenomena reduces the likelihood as well as the consequences of both natural and human-related hazards," the panel concluded.

How long will this radioactive material be stored in the bunker?

Should the proposed facility go forward, construction would begin in 2018 and the DRG would receive its first load of waste around 2025.

The operations phase would last about 40 years, followed by a decommissioning period of five or six years, which would include the installation of a "concrete monolith" at the base of the shafts, then sealing the shafts and removing the surface buildings.

After that comes the"abandonment" phase. OPG assumes that some kind of institutional control over the abandoned repository would last for up to 300 years. The review panel says about three-quarters of the radioactivity would be gone 100 years after closure.

Opponents, however, are looking out much longer than that."This is an inter-generational, non-partisan issue that affects millions of Canadians and Americans," says Beverly Fernandez, who is with the Stop the Great Lakes Nuclear Dump group.

She told CBC News it's "a decision that will affect the Great Lakes for the next 100,000 years."

What hurdles remain before the project can get a final go-ahead?  

The federal government, through its environment minister, has 120 days to decide whether to approve the project. 

Should the proposal get the go-ahead, the ball gets tossed back to the joint review panel to follow through with detailed conditions for a licence to build the facility.

OPG has also said it would not construct the repository without the support of the Saugeen Ojibway Nation. Discussions are ongoing. So far, the First Nation has yet to agree.

Dozens of communities in Canada and the U.S. have passed resolutions opposing the OPG proposal to bury radioactive waste in Kincardine. It's not clear what impact the opposition will have.

Tens of thousands of people have signed protest petitions. And some of the environmental groups that have lobbied against the proposed facility are promising more action, but haven't been specific.

"We have a strategy, but we are not going to speak to that right now," says Fernandez.

With files from the CBC's Havard Gould