Aug 16, 2009

nuclear power plant

Last week I had a nice tour of a nuclear power plant in the Northeast US. There was a bit of a security ruckus over the photos I took but I was able to get away with keeping them after a little fast talking. I'll keep the name of the plant off this post as a result. There was, as you can imagine, a huge amount of security at the plant. I was a little surprised I got the camera in and was able to keep the photos. It was a full day tour compared to the quarter or half day tours at other non-nuclear plant tours I've been to. I think this is because nuclear power plants have much more aggressive community outreach programs given the overall fear some people have of these types of plants.

What's interesting about nukes is that they almost always reside on large wildlife sanctuaries. Ironically they are the cleanest power plants, and in general, the cleanest factory of any sort and make good neighbors for wildlife preserves. Not many people want to live near the power plant so they are given a big berth. No one builds anything within a sizable radius around them.

The most distinctive site at a nuke plant is of course the tower below. It's iconic. It's the largest part of the plant and so its the part everyone sees. It's funny then that all this tower does is cool water. There's nothing really inside it. It's a large sheath covering a skeleton infrastructure that allows hot non-radiated water from the generating turbines to cool off so it can be pumped back in again. But it's an awfully impressive structure. It's 500 feet high and it has both a ominous feel to it as well as a modern art sculpture feel to it.

You can see from at the bottom the large gap which allows air to be sucked in purely by a venturi effect. And if you look very closely you can see water streaming down at the bottom. To the tune of 14,000 gallons per minute. That's an impressive amount of water but it's nothing compared to the other nuclear units. You see the cooling tower is an optional component to a nuke plant. The other units use a regular heat exchanger but require a lot more water. More on that later.

Here are two reactor cores. The two domes. Most of the real core however is underground. Also housed here but not shown are the generating units which function much like any other fossil fuel plant. In gas, coal, nuke plants steam is generated from heat and used to turn a turbine. The only difference is how the steam is created. Where a core is loaded it generally runs 18 months before the nuclear material is exhausted and a refueling operation is performed.

On these units the cooling is done via a standard heat exchanger. You lose the tower but the inefficiency of this technique and the fact that the water comes from a river and can't be heated up too much, means you need to use much more water. For these two units 1.1 million gallons per min is needed per unit. Wow! That water pipe below is much bigger than it looks. It was maybe 6-8 feet across. And there were a lot of them. Maybe 20? Pretty impressive engineering as the impact on wildlife from this water intake is heavily regulated as well.

I'll make no bones that I like nuclear energy a lot. It's carbon free and has almost no waste output except those nasty little radioactive pellets. In general these are stored on site because we don't have a national policy on what to do with them. I actually think this is good. This plant has the capacity to store 60 more years of waste and that can be expanded. Storing this stuff in some place like Yucca Mountain means we would forget about it. I think the best storage policy is to keep it on site so we can actually monitor and maintain the storage systems. I've heard but not verified that the total cumulative world wide nuke waste would fit into a football field about 3 meters high. That's much more manageable than the immensely large ash output of coal plants which are not going away any time soon based on projected rates of solar and wind installations.

The power is also dispatchable meaning you can generate it when you need it unlike solar and wind. So all 3 make a nice marriage. In general a portfolio of non-carbon and non-SOx/NOx producing generation technologies is best. And you can build a lot of gigawattage of power with these babies. Each unit generally kicks out 1-1.5 gigawatts each.

The downsides are many however. I've mentioned the 'what do we do with the pellets' problem. The other is related and that is for political reasons we don't process the pellets to extract more energy. I've heard we extract something like 3% of the extractable energy. After a first run, France processes the pellets and resuses them. They extract much more energy out which dramatically reduces your storage issue. The political issue is you get closer and closer to producing weapons grade inputs. What France does (which makes about 80% of its electricity from nukes) to overcome this I don't know.

The second problem is cost. These plants are expensive. There is a wave of research being done right now around nukes. To date the new plant designs haven't been built in scale so plant costs should come down as they are built and become more turnkey.

The third problem is it takes 15 years to build one. Most of that is related to regulatory legwork. That clearly could be streamlined like France did. But I don't expect that to change very quickly.

I like nukes but the fact is we will not be building many of these for at least the next two decades. At that point the effects of carbon in the atmosphere may force the issue.

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