The 1979 core meltdown at Three Mile Island, outside of Harrisburg, Pennsylvania, so scared Americans that no new nuclear plants have been built since.

It wasn't due to some official prohibition or anything like that. Instead, the plants just got too expensive to build.

"Plants that were under construction, all of a sudden there were lawsuits, there were protests, there were actions to make them change some of their basic plans," says Thomas Drennen, a Hobart and William Smith Colleges professor. "What happened is prices just skyrocketed."

Nuclear provides roughly one-quarter of New York State's electricity - second only to natural gas. The existing plants, however, are aging. The Ginna plant, for example, came online in 1970. It's licensed to operate through 2029, at which point it will be either re-licensed or closed.

Policymakers are talking about a possible nuclear renaissance: a wave of new nuclear power plants that would be built to help meet the country's energy needs and to reduce reliance on fossil fuels. The promise, say nuclear backers, is immense amounts of energy from a generation method that's free of greenhouse gases.

The cost to construct the plants, typically billions of dollars per plant, is still a problem. To kick start the industry, the federal government is devoting $8 billion to back loans to build two new reactors in Georgia. President Obama wants to increase that number to $54 billion to build new plants across the US.

Environmentalists are not happy with the idea of using taxpayer dollars to back and indirectly subsidize an expansion of nuclear power.

"That money should much better be spent on clean, cheap renewable energy," says Hugh Mitchell, a Brighton resident who co-leads the global warming committee of New York State's Sierra Club chapter.

Environmentalists and some members of the public doubt nuclear's potential as a high-producing clean energy source. And concerns linger about safety, environmental damage caused by uranium mining, and cost. More expensive plants and technologies can translate into higher electric costs for consumers, critics say.

The biggest concern, which is also a major public policy challenge, is storage and disposal of the radioactive material. No long-term solution is in sight, so spent fuel rods are stored in water pools and casks on-site. The federal government was working on a national storage facility - Yucca Mountain - for nuclear waste, but the Obama administration seems to have abandoned that plan.

In recent interviews, Drennen and Mitchell weighed in on nuclear power's promises and problems. Below are edited versions of those conversations.

Thomas Drennen: ‘the nuclear industry has one opportunity to get this right'

CITY: Should the United States look to nuclear to meet its energy needs?

Drennen: If one believes in climate change and you want to do something about climate change, then it is probably the best option for lowering our emissions of carbon dioxide. The biggest advantage would be that you're not releasing carbon dioxide and other greenhouse gases. You're not releasing mercury, you're not releasing sulfur dioxide - which is responsible for acid rain. It's a cleaner energy source.

Going down this path to see if we can actually build a safe reactor is a good thing at this time when we're trying to deal with climate change. But it should be one of many things. I wouldn't want to put it all on nuclear.

There's a bunch of issues. We still haven't resolved what to do with the waste products. It's not as easy an answer as saying "Yes, it's what we need to pursue."

Could wind, solar, or other renewables effectively fill the same gap?

They really can't, if you look at how small they are and what a small percentage of our power they supply.

If we really want to change, move away from fossil fuels to deal with the issue of climate change, solar and wind aren't going to do it. They're not available all the time, and the cost [of power to consumers] is definitely higher than nuclear.

Solar electricity, most people would not want to pay for it. It's just not there yet. The people who do it right now are technology-type people who really want the cool option.

Most of the people that I know who have done it, it's because they get amazing tax credits or subsidies. And we couldn't do that with everyone.

You mentioned that the nuclear industry sees some of the public concern and opposition as cost drivers when it comes to building plants. But when they're talking about things like water usage or potential contamination, aren't those issues that warrant consideration and accommodation?

We definitely need to make sure that whatever is built is safe, and that's where the federal government really has to make sure that they have a strong Nuclear Regulatory Commission that is not tied to the industry. They have to be an unbiased agency that reviews licenses. The federal government must protect water, air.

It's interesting. I teach energy to mostly first- and second-year college students and I find that students today are much more willing to go in the direction of nuclear power. That's a huge change from when I started teaching it 10 years ago.

Is there a solution to the waste issue, especially now that federal plans for a storage facility seem to have been scrapped? That's something that really worries people.

Right now we keep the waste by the power plants, in most cases sitting at the power plants.

What we need to do is to have a strategy where we take care of it for the next 100 years. So maybe it should be centrally located or something. But we don't try to bury it for 10,000 or 100,000 years.

We keep learning, and I keep thinking that 100 years from now we're going to be a hell of a lot smarter and we'll know what to do with it. So I just think that technology will get us out of that issue. And I don't think we should try to bury it.

Is an approach like that, just kicking the problem down the road, really going to put people at ease?

No, I don't think most people would like that idea. But I don't think most people realize that it's sitting at the power plants right now.

There are companies that are working on plants that would eventually take the waste and, by making it part of the process, transmutate it so it would turn into safer materials as the process went. It's really transforming it.

It's been a long process already and we need to get it right, and I think technology will allow us to, eventually.

When you add in all the steps involved with nuclear power - from mining and transporting the uranium right up to actually generating the electricity - is there truly a greenhouse gas benefit?

There always are going to be some emissions associated with the different steps, that's very true. But overall, you're not burning tons and tons of coal. You are transporting, so there are some emissions there. But yes, it absolutely would reduce greenhouse gas emissions. Significantly? Well, two plants aren't going to do it. It would have to be a couple of hundred plants. And then we would have a serious impact.

If we get two built in the next 10 years, that's probably about the best we can do in the next 10 years.

Is there any problem with switching from, or relying less on one depleteable resource versus another?

Both are limited resources. Recently, the projected amount of natural gas out there doubled because of the discoveries, realizations about the Marcellus Shale options. And that was not seen a few years back.

And likewise, if we had a nuclear renaissance, we would find more uranium in the US. We would find ways. If it got too expensive, we would go toward reprocessing.

But if not, it's not a more than 100-year resource. They're all on that order, max. Eventually we're going to have to rely on something else.

If there's a new wave of nuclear plant building, do you see the safety concerns being an obstacle?

The nuclear industry has one opportunity to get this right and if they don't build what's perceived as a safe plant, that will doom all future power plants. So it's in their best interests to make sure that whatever gets built, it all goes right. Again, it comes back to that's why you've got to have the strong federal agency that's overlooking and making sure it's a safe plant.

The companies that are proposing the new nuclear plants, it absolutely is a huge risk for them. If it doesn't go right, their stock will be hurt and they will suffer. So there's a huge financial risk here and that's part of the reason why the federal government had to say, "We're going to provide these loan guarantees, just in case."

Here, we're generating electrons and putting them on the grid. There's only so much money that can be made. The company's not going to skyrocket.

Does the argument that the plants present danger as terrorist targets hold up?

It's always going to be an issue that people will worry about. They test the reactor structures. They have launched jets into mocked-up ones at Sandia National Labs, to make sure that they can't be penetrated.

It's not something that worries me terribly. I don't think it's a huge issue. It just seems like it would be so much easier for a terrorist to drop something in our water. That seems like an easier way than trying to target a nuclear power plant.

Hugh Mitchell: ‘a dirty, dangerous industry'

CITY: Should the US be looking at nuclear power as an energy option?

Mitchell: The problem with this as far as Sierra Club is concerned is that it isn't a wise choice to go forward in this way.

I know that there are arguments for nuclear in terms of it not contributing to fossil fuel emissions and causing global warming. But there are so many negative aspects to nuclear power, as well as the fact that it could, in no way, be called a green power or clean power.

The nuclear industry is trying to call it green and clean, and it's a very dirty and unclean, environmentally unsound industry. So the answer to your question is no, the US should not be going forward with the nuclear option.

What makes it a dirty or unclean power source?

There's a whole list of problems with it.

It is a very dirty material environmentally through radioactive waste that nuclear production causes. Trading the CO2 problem to produce power from nuclear generation, well this is like trading with the devil.

The key point is that no one has yet come up with a way to handle these wastes, and there's very long term - hundreds of thousands of years of radioactive danger from decay. So that's why it's very dirty and not a clean industry.

The real other point, the positive point, is there are so many other new ways to produce energy through alternative means, which really are clean and are really very low cost.

But when you look at the amount of energy a nuclear plant produces and compare it to the amount from a wind farm, for example, they are so far apart. Can renewables really be the same level of energy resource as a nuclear plant?

No. You have to have a very widely distributed network of alternative power, like wind and solar, to produce the same centralized power that a nuclear plant would.

It's much safer and better than a very expensive nuclear plant. You shouldn't think in terms of plants, but in terms of, say, a wind farm or solar panels on roofs in the city.

Is there any way to compensate for power difference?

The key answer to that is the third leg of this, which is that we need a national program on conservation.

The quickest, cheapest, and best payoff to the global warming problem is a really serious push - nationally, statewide, and locally - on conservation of energy resources. There's huge savings to be made where you wouldn't need as much electricity as we're now producing, firing over a very antiquated grid.

We should focus first on conservation and then focus on new sources of power widely distributed.

Does a direct or indirect government subsidy for nuclear plants put the plans in competition with renewables projects for funding?

The presumption that we're making is that there's only so many billions of dollars in the taxpayers' pockets. We're already running huge deficits to bail out the banks. If you drain off $54 billion, as Obama's proposing, to the nuclear industry, this would detract from the monies that would eventually be coming into alternatives.

As far as this Obama proposal, that's not a done deal. It has to go to Congress to see if they're willing to do this. Obama himself has had a pretty long-term link to the nuclear industry in Illinois. He's been friendly for a long time to the nuclear industry.

The corporate lobby, the utility lobby for nuclear, is really strong. They have been working on this for a long time. The nuclear industry wants to pull itself out of the doldrums by using other people's money, our money - taxpayer money.

Ideally, what do you do with these older plants that are licensed for maybe a few years or another decade or a couple of decades? Should they just let them go?

That's another major problem. We've questioned the re-licensing of Ginna and some of the plants up at Oswego because as a plant gets older, there are breakdowns in the piping systems and you can have more maintenance problems, even if the nuclear heart is still intact.

The problem with old plants is extremely severe because if you shut the plant down, not only would the plant have to be contained because you can't move the radioactive material, but you get into the whole issue of storage of the spent fuel rods.

The government put literally billions of dollars in trying to open Yucca Mountain in Nevada. And the Obama administration has now all but killed it, meaning that there's no federal repository for all of the high-level waste, which is sitting in water pools next to the nuclear production facilities. The high-level radioactive waste is extremely costly to maintain and, look, this is a recession.

Just look what happened in the last year. What would happen if we got into a worldwide depression and we couldn't maintain these things? Or look 100 years, 200 years, 500 years. This stuff's radioactive over 100,000 years, and some people talk about a million years. This is a devil's choice.

For nuclear supporters, the money issues would be an obvious concern - they want to find a way to finance construction. But from your perspective, why is the financing a concern?

The nuclear industry cannot build a nuclear plant on its own. There's no utility in the country that has enough money to produce one of these, so they have to rely on the federal government's support. This isn't, by the way, unusual because that's done in other countries, too. But they need loan guarantees and actual money to start these things up. That should much better be spent on clean, cheap, renewable energy than starting a dirty, dangerous industry.

The second part of this thing is, the argument of this industry is they'll be able to produce power which can be clean - that's true, it doesn't cause global warming - and that they'll get the money back and pay the government.

Well, the consumers who use that will have to pay these escalating costs of construction, construction delays, and the huge cost of continuing to staff and run a nuclear plant. They've conveniently left out of the arguments, the fact that you have to have a highly-trained technical staff to run one of these nuclear plants.

If you have a windmill or a solar panel, you need almost no one to run them. So these are continuing very high costs put down on the ratepayer.

When people talk about the greenhouse gas reduction aspect of nuclear power, is that taking into account things like mining and transporting the fuel?

It does not take into account the full picture of mining, shipping around the world, and cost of construction. I'm sure that nuclear saves over coal and oil and the traditional ways to produce power, eventually. Once they're online, they produce a lot of power.