Is Surface Water Safe from Contamination from a Deep Geological Repository? No.

– A We the Nuclear Free North Debunker –

Does the Nuclear Waste Management Organization’s (NWMO’s) plan to bury and abandon all of Canada’s nuclear fuel waste deep underground put the surface water in our lakes and rivers at risk?

There is significant reason for concern. The underground chamber will be penetrated by groundwater, and there is no question that groundwater connects with surface water. The safety of our water is a matter of the effectiveness of the containment – and luck.

Representatives of the nuclear industry who talk about deep geological repositories (DGRs) for nuclear fuel waste often say that there is no risk of contamination of surface land or water, because the repository will be completely isolated from the surface.

Most recently, at the City of Dryden’s Nuclear Forum 2022, we heard Mika Pohjonen, Managing Director of Posiva Solutions (the company designing the ONKALO® DGR in Finland) state categorically that the waste in the repository would be “isolated from [the] biosphere,” offering as proof that there is 420m of bedrock and 20m of seawater over the repository site. [Link to YouTube video]

Unfortunately, this claim of isolation is not supported by fact.

First, some definitions. Surface water is the water we see every day (if we are lucky) in lakes and rivers and puddles, and is also the water not too far underground, moistening the soil of forests, farms and gardens. Groundwater is water deep underground in saturated zones of soil and rock; its upper surface is the water table.

Will there be groundwater around the NWMO’s proposed DGR for nuclear fuel waste? Absolutely. The NWMO anticipates that large amounts of water will need to be pumped from the DGR both during the construction phase, and also during the operating phase once the radioactive waste has been placed there. The water’s presence there is to be expected, as any deep excavation in the earth, such as a mine, will collect water. Here is some information from the NWMO’s Deep Geological Repository Conceptual Design Report – Crystalline / Sedimentary Rock, Sept. 2021 (bolding is ours):

Mine Dewatering Settling Pond (Area P17) 

Mine water pumped from the underground dewatering sumps will be piped to a dewatering settling pond. The pond will be designed to have a retention period of 5 days. An allowed freeboard and adjustable weirs on the outlet side of the pond will control the discharge rate and retain floating material such as oil residue collected in the underground sumps. The mine water in the settling pond may contain sediment (rock dust), nitrogen compounds (arising from the explosives used to excavate rock), salt (due to saline ground water inflow into underground repository​​​), possibly particular metallic elements (notably uranium), and hydrocarbons (oils from equipment). If the concentration of these potential contaminants are above acceptable levels, then the water will be treated before being reused as service water or discharged into a receiving water body. During construction phase it has been conservatively estimated for design purposes that up to 350 m3/day of water would be pumped to the ground surface. Whereas during the operations phase it is estimated that up to 180 m3/day or less will be pumped to ground surface.

NWMO – Deep Geological Repository
Conceptual Design Report –
Crystalline / Sedimentary Rock
, Sept. 2021 – Sect. 3.12


For design purposes, it has been assumed that approximately 10% of the volume of the repository rooms excavated would not be useable for UFC placement due to geotechnical conditions … Water-bearing fractures and/or fracture zones will be present in a crystalline geosphere. If intersected by a placement room, groundwater may flow into the room.

[same report as above] – Sect. 5.1.1

So, the repository will not be dry. It is disturbing to consider water from an operating DGR for high-level, very radioactive nuclear waste being pumped to the surface. If or when the containers fail deep underground, radioactive contamination could be carried to the surface where it would contaminate the soil and adjacent waterways.

We know from the NWMO’s documents that the intended function of the DGR actually depends on groundwater coming in to saturate (make wet) the bentonite clay that surrounds the casks. Here is some information from the NWMO document, Postclosure Safety Assessment of a Used Fuel Repository in Crystalline Rock (bolding is ours):

After placement, the external load on the containers initially would consist of little more than the weight of the overlying sealing materials. The load would gradually increase during saturation of the repository. The swelling of the bentonite in the sealing materials is likely to occur unevenly on a local scale because the swelling would be controlled by the supply of water from the rock, by the shape of the room, and by the pathway of water along interfaces.

NWMO – Postclosure Safety Assessment
of a Used Fuel Repository
in Crystalline Rock, Dec. 2017
, Sect.

Connection of Surface Water and Groundwater

When we are told that what is buried underground is “isolated from the biosphere,” we imagine that the biosphere, where most life on Earth lives, and the area of the Earth deep underground are not connected – that water does not flow between them. But this is incorrect.

Concerning the movement of water, the U.S. Geological Survey (USGS), on their webpage “The Integration of Surface Water and Groundwater – A Critical Linkage“, tells us:

“Water and the chemicals it contains are constantly being exchanged between the land surface and the subsurface. Surface water seeps into the ground and recharges the underlying aquifer—groundwater discharges to the surface and supplies the stream with baseflow.”

In 2016, the Canadian Water Resources Journal ran a special issue entitled “Groundwater – Surface Water Interactions in Canada,” and in its well-referenced preface, we read, “In the generally humid and cold Canadian climate, groundwater–surface water interactions are omnipresent.”

The NWMO’s Multiple-Barrier System

The NWMO showcases their Multiple-Barrier System that consists of five barriers:

  1. The fuel pellets themselves (note that NWMO disingenuously describes a pellet that has not undergone irradiation);
  2. the Fuel Element and Fuel Bundle (encased in Zircaloy);
  3. the Used Nuclear Fuel Container (copper-coated canister);
  4. Bentonite Clay; and
  5. the Geosphere

But wait a moment – the geosphere? Yes. The NWMO describes it as follows (italics ours): “The geosphere forms a natural barrier of rock, which will protect the repository from disruptive natural events, water flow and human intrusion.”

All of this is subject to question. You have just read, above, many citations from the NWMO’s technical publications that hinge on the reality of water flow into the DGR (and we know that what flows in could presumably flow out again). However, in the NWMO’s user-friendly webpage about their Multiple-Barrier System, they state that the geosphere will protect the repository from water flow, and they give no further detail. They then mention the possible presence of “pore-water,” which “can take 1,000 years to move one metre through the rock.”

Those who ask questions of NWMO personnel about water and DGRs in public forums are apt to be diverted into a discussion of this slow-moving “pore-water.”

Watch the NWMO closely – their “truth” varies depending on their intended audience.

Please also see our page, Burial of Nuclear Fuel Waste: Risk to Surface Water.