Tuesday, May 31, 2011

An interview on nuclear with a local student

I recently did an interview with a local high school student (name withheld for privacy), and I wanted to share my responses both in that there's several good questions, and more importantly how outreach efforts like this are essential for nuclear professionals. I've tried to keep my answers at a relatively accessible level, so if it seems like I am perhaps glossing over some of the finer technical details, it's because my goal here was to make my response accessible to as wide of an audience as possible.
(On a side note: I apologize for the recent lull in postings - in particular, I've been bogged down trying to complete my PhD dissertation, with a defense date in approximately three weeks. As you can likely surmise, it's been a little busy here. More updates to come soon.)

Q1: Nuclear Power was created originally with destructive purposes. I believe that very purpose has caused a stigma around Nuclear Power in general. Do you agree? If so, how do you think the government could minimize that stigma in order to be able to promote Nuclear Plants again?

A1: I don't necessarily see nuclear energy having a direct link with nuclear weapons nowadays, even though this may have been more true back in the early days of civilian nuclear power. Besides this however, much of what was done in the past to overcome this stigma came out of programs like President Eisenhower's "Atoms for Peace" program, which sought to promote the use of nuclear technology for peaceful purposes, including such things as energy as well as applications for agriculture and medicine.

Today nuclear technology - beyond just electricity - is embedded so much into our everyday lives that we sometimes fail to even notice. Nuclear technology is used for many applications such as medical treatment and imaging, industrial processes (for instance, where we need to evaluate microscopic fractures in materials such as aircraft components), irradiating food and medical equipment to destroy harmful pathogens, and even powering space probes. If anything should be done to "de-stigmatize" nuclear technology, I would argue that simply making the public more aware of how many peaceful roles nuclear technology plays in our lives is the best way one could go about "de-stigmatizing" the technology.

Q2: Do you think the U.S. could benefit from more Nuclear Power Plants?

A2: I absolutely do - not only is nuclear energy clean (it produces no carbon dioxide and doesn't put harmful pollutants into the atmosphere like lead and mercury that are produced by burning coal), but it is also an extremely reliable form of energy. If the United States is to seriously provide for increasing energy demand while balancing concern for the environment, there's simply no way we can do without nuclear - and the more the better. Nuclear fuel also has an amazing energy density - the amount of uranium required to power your home for an entire year would be about the size of the tip of your finger. No energy source can even come close to this - renewables like wind and solar tend to be very diffuse (i.e., you need a lot of solar cells or wind turbines over a very large amount of land to generate enough electricity to power a city) and even coal-burning plants require entire trains full of coal cars to produce power every day.

Q3: In your opinion which is more environmentally safe and why? Coal powered plants or nuclear plants?

Without a doubt nuclear. Much of the debate about environmental safety with coal vs. nuclear comes down to the low-probability, high-consequence kind of events like what happened in Japan. But what this neglects to consider is that every day a coal-fired power plant puts out several times more radiation than your average nuclear plant (coal contains trace amounts of uranium and its decay products, which are radioactive). Even more, coal puts out enormous amounts of carbon dioxide, contributing to global warming.

Getting to the mining side, it gets even worse. Enormous amounts of coal are required to produce the same amount of energy that a nuclear power plant generates with a very small amount of uranium. This means a massive amount of mining activity, which can be both very environmentally destructive and even unsafe in some cases.

Here's one study comparing the deaths attributable to coal vs. nuclear.

Basically, accidents from nuclear are significant, but rare. Coal puts out dangerous products every single day.

Q4: Disposal of Nuclear Waste is always an issue with the public. Has there been any advances to minimize the long-term environmental impact on nuclear waste?

A4: This is a very good question which is a hot topic right now. The basic answer is that we actually have technology to recycle much what we refer to as "waste" in used nuclear fuel. Over 95% of spent fuel is uranium and other fissionable elements - basically, things we can produce energy from. However, when fuel is burned, it produces elements through fission which "slow down" the fission process, making it less efficient. This is because these elements "soak up" neutrons without producing any extra fissions (and thus, energy).

An analogy one colleague once told me goes like this. Imagine if the gas tank in your car produced water as a byproduct of combustion. Now imagine all of that water were to be recirculated back into your gas tank. Pretty soon, you're going to have a tank mostly full of gas with enough water that your car won't run very well (if at all).

Right now what we do is the equivalent of taking out all the gas and putting it in a drum somewhere to eventually dispose of it permanently. But if we just siphoned out the water, we'd have a lot of usable fuel left.

We've actually known how to do this since the Manhattan Project in the 40's - basically, this is how we recovered the plutonium in order to build one of the atomic bombs. Meanwhile, nations like France and Japan have been employing this strategy for some time in order to both maximize the availability of nuclear fuel and minimize their waste burden. (This is known as "reprocessing.")

For a little while in the 1970's, the U.S. was reprocessing spent fuel - however one concern that emerged was the threat of nuclear weapons proliferation. Basically, reprocessing is designed to separate out uranium and plutonium for recovery and reuse as fuel - but any technology that separates plutonium for reuse in fuel could also be used to separate out plutonium to make weapons. President Carter halted U.S. reprocessing in order to try and encourage others to do the same, and minimize the risk of proliferation.

Unfortunately, no one else was very interested in following our lead, and so we were left with a problem - we didn't have a very good solution for our nuclear waste.

President Reagan reversed this executive order, but basically as of today it comes down to a few factors - the way U.S. law is set up right now, commercial utilities don't have any incentive to reprocess waste (the facilities to do so cost upwards of $10-$20 billion). Others argue that it's cheaper to simply mine new uranium right now than to recycle spent fuel.

However, one advantage of spent fuel reprocessing is that if we were to recovery long-lived, usable materials from the fuel (like uranium, plutonium, and other elements), the nuclear waste problem is no longer one where it takes millions of years to go away - the remaining products will decay away in a matter of a few hundred years. It is far, far easier to engineer over a time frame of a few hundred years rather than a few million years.

Other technologies on the horizon include reactors that can consume these kinds of wastes as fuel - several companies have been looking into these kinds of advanced reactors, which would turn what is ordinary a hazardous waste into an economic resource.

Q5: After 9/11 do you believe Nuclear Plants have been properly secured against terrorist attacks through out the U.S.?

A5: A lot has been done to plan against the possibility of terrorist attacks at nuclear facilities. The containment buildings which house reactors are made of concrete which is several feet thick, and are strong enough to withstand a 747 crash. Nuclear power plants also tend to be well-guarded - security is taken very seriously at these places.

Nuclear tends to get special scrutiny in this area, but to be honest I am far less worried about a terrorist attack on a nuclear facility than one which is less heavily fortified with the potential to cause much more damage - for example, chemical plants or refineries.

Q6: After the Japanese nuclear plant incident do you believe their are any U.S. plants vulnerable to natural disasters and why?

A6:  What happened at Fukushima Daiichi was a fairly unique combination of circumstances - the plants were first hit with a 9.0 earthquake, which was the largest in Japan's history and the fifth largest earthquake in recorded history. The reactors actually came out of that one okay - they shut down like they were supposed to. The real problem came with the tsunami, which was also of record proportions.

When the tsunami struck, this took out the backup generators at the plant which are designed to run cooling pumps. Nuclear fuel remains "hot" for a long time after the reactor shuts down - this is because of radioactive materials in the fuel which are still decaying and producing heat, even though the actual fission chain reaction has shut down. As such, the fuel still requires coolant (in this case, water) to be circulated by pumps in order to keep it cool. Without power to the pumps, water in the core just "sits" there and gets hotter and hotter until it boils. When this happens, the heat from the exposed parts of the fuel rods doesn't have any place to go - air is a much poorer conductor of heat than water. So, the fuel rods heat up and can become damaged, releasing radioactive materials.

Basically, for something similar to happen in the United States would require a massive natural disaster which both takes out sources of backup power at the plant and prevents workers from getting in alternative backups (like more diesel generators and fuel).

There are a few power plants in seismically active zones - the Diablo Canyon reactors in California come to mind - but generally speaking the U.S. isn't as much like Japan, where much of the island is near a fault zone. Likewise, the NRC has been reviewing safety guidelines for nuclear plants in the U.S. to consider which plants may need to take additional precautions for disasters like earthquakes and floods.

Q7: Do you see any advancments in nuclear research that would create an even safer environment in the nuclear industry?

A7: Right now, one very large project I'm aware of is actually happening between several universities and research laboratories, called CASL (the Consortium for Advanced Simulation of Light Water Reactors). NC State has a very large role in this project. The goal is to produce a "virtual reactor," which is a complete simulation of all of the physical processes that go on in nuclear reactors. Using these very sophisticated computer models, we can better understand all of the processes that go on inside a nuclear reactor and design safer reactors in the future.

Additional research that is going on right now in my research group deals with how we can make technologies like spent fuel reprocessing cheaper and easier to do. This would make it more likely for us to be able to recycle long-lived nuclear waste and thus minimize the impact on the environment.

One thing to keep in mind as well is that the nuclear engineering community takes safety very seriously and they are always trying to learn how to do things better. Much of how we operated our nuclear power plants in the U.S. changed based on lessons we learned after Three Mile Island, and no doubt scientists at our laboratories will be studying the accident in Japan in order to learn how we can better respond to and even prevent such incidents in the future.

Q8: Other than nuclear power plants do you forsee any further nuclear research to advance other energy saving initiatives? As an example a safe nuclear powered engine for cars?

Actually, Ford designed a nuclear-powered car called the Ford Nucleon back in the 1950's...

...but I really don't see that concept going anywhere.

Basically, where I see nuclear playing a big role here is in the deployment of electric vehicles like the Nissan Leaf or the Chevy Volt. Basically, going to an all-electric vehicle doesn't do very much good if the power behind the plug is still being produced by dirty sources like coal. If we begin to seriously move to alternatives like electric vehicles, we will definitely have a need for more electricity production, which is somewhere that nuclear can definitely pitch in.

Other kinds of applications are a little more indirect, like using nuclear technology for industrial imaging in order to design better materials, such as strong lightweight materials for car bodies or better battery technology for electric vehicles.

Q9: In the wake of the Japanese nuclear disaster in your opinion was there a way for the incident to have been prevented or prepared for in advance?

A9: It's very easy to be a "Monday morning quarterback" and try to claim that things could have been prevented in retrospect. In all honesty, what happened in Japan was a record-setting natural disaster in which tens of thousands of people were killed by the earthquake and tsunami and even more were left homeless. As of now, no one has actually died from the radiation released from the stricken plants. This still doesn't mean the releases were a good thing, but it's important to put things in perspective.

Beyond that, I think what will happen is that we're going to take away many important lessons in both how we design reactors and safety systems such that we can respond better to situations like this in the future. For example, one thing that will be a very big concern is how to respond to a situation where backup power is lost (either by flooding or something else) - basically how we can better plan for these kinds of situations.

This is not to say that the Japanese utilities didn't make mistakes or couldn't have done a better job responding, especially when it became clear how serious the situation was, but it's still too early to definitively say what they should have done instead. Chances are great that we'll be studying this accident for years to come in order to learn how we can better respond to and even prevent events like this, even in the face of overwhelming natural disasters.