Tales of Darlington - 2

I can't express the tremendous scale of the place! I was just a young 'new guy', and just went around taking it all in. The 'old guys' were grizzled veterans of dam building, this was nothing to them, after the St. Lawrence Seaway.

First thing we did was to blast huge holes in the rock, about 5 m deep, to be the foundations for the reactors. The turbine hall was up on the till. These holes proved interesting, in that you could see classical 'rock squeeze', and some of the upper beds were actually shifted by the blasting. Again, this was touted by some, as 'earthquake signs'.

Beneath the disturbed layer, the rock was absolutely impermeable, as far as it can be in Nature. The holes were below lake level, and there was no seepage. Because these foundation benches were so deep, some bright guy had the idea to use rock anchors, to prevent the reactors from floating away. That was the beginning of many gross wastes of money for the plant!

We also had to excavate a deep forebay for the cooling water. This can now be seen as a giant canal in front of the plant. I absolutely loved the big intake tunnel that was being blasted at the time. I got to visit once or twice.

Inside the tunnel, the limestone beds were flat, and the whole tunnel was dusty-dry, even though it was beneath the lake! The had to pipe in water to wet down the dust! I always made it a point to keep away when things got dangerous, which I always thought was the case, when they came to the end. The intake tunnel had a big deep sump blasted out at the end, and then they blasted upward as far as they dared. Then they loaded up the remaining portion with explosives and went away. The tunnel was filled with water, and the then the plug was blasted. The excess rock fell into the sump, and the tunnel was open.

The big problem with these intake tunnels is the formation of a giant vortex that sucks up fish and small boats. At Bruce, they put in a steel structure which broke up the vortex. At Darlington, they designed a huge concrete intake structure, which allowed a slow vertical intake flow, that would hopefully suck in less fish. In the past few years, it has proven to be a marvelous breeding ground for zebra mussels!

Next up: the diffuser outflow!