Consider first the issue of safety. What exactly do we mean when we think about safety? When is something safe? In what ways can something be safe?
Many people frequently drive a car. Generally they regard it as safe. Of course when asked about driving and safety most people realize at least intellectually that cars are really not all that safe, at least insofar as they cause somewhat more than 44% of all accidental deaths. Indeed statistically driving a car is by far the most dangerous activity that most people engage in. Yet people happily drive with little thought to the underlying danger. Why? When negative consequences are distributed in the population as a whole, when the underlying activity is commonly part of life, and when the likelihood of death is disconnected from everyday experience then it's easy to delude oneself into viewing an activity as if not safe as not that dangerous.
The notion of safety is tied up with how likely an accident is, the scope of the harm caused by accidents, the duration of the harm, the benefits of the underlying activity, the availability of alternatives to the underlying activity, and a host of other factors. Thus asking about nuclear power safety isn't a particularly useful question unless you delve into the question of safe in what ways.
When it comes to nuclear power and safety it's helpful to break the question down into several parts. One useful way is to consider the questions of fuel acquisition, plant construction, plant operation, plant decommissioning, and disposal of waste products.
Concerning the question of fuel acquisition and safety the answers are generally encouraging in much the same way that coal, oil, and other large scale industrial extraction operations are safe. Just as one can safely mine coal without undue environmental harm and reasonably restore the mine environment after extraction of the coal one can mine uranium and refine it into nuclear fuel. Whether or not that actually occurs safely is a question of practices, regulation and such much as it is with coal and other similar processed. Sadly, the record of major extraction efforts is rather mixed. One need only look at strip mining to realize that there is a considerable difference between something being possible and actually being done, particularly when it comes to mining. But for all of that, it is in fact possible to safely mine uranium ore. The safety question then is one of what more should be done to insure that what is possible actually occurs.
Once nuclear material is mined it must be processed into fuel suitable for use in a nuclear power plant. Here things get a bit more difficult. The techniques for enriching nuclear fuel are now well and widely understood. The underlying process is similar to other extraction and enrichment processes. But, and it's a potentially serious but, nuclear fuel is inherently radioactive. Some of it is also highly toxic. This creates several serious safety issues that are not present to the same degree and in the same way as other industrial extraction processes. Simply put, processing nuclear fuel is simply not as safe as other industrial processes. The risk of radiation must be added.
Enriched nuclear materials are such that they need to be carefully monitored and controlled. While this control is not inordinately difficult technically the record concerning monitoring and control is on balance no better than poor given the underlying danger of the material. Indeed, the record of known illegal trafficking of nuclear materials is exceptionally poor according to the IAEA. As a practical matter then, monitoring and control efforts are not effective consistent with the underlying danger of the nuclear materials involved.
Are we safely mining nuclear ore? Are our refining practices safe? Are we safely controlling radioactive materials? These are the central issues we should consider regarding nuclear fuel acquisition.
Concerning the construction of nuclear power plants safety issues are, likewise, much like the construction of any large power plant. The problem of plant construction is really one of design and siting.
Where can one safely place a nuclear power plant? While the NRC has guidelines about plant siting and construction that are in fact technically reasonable as a matter of practice in the US today there is one nuclear power plant built on top of an earthquake fault that was unknown at the time the plant was built. Likewise there are many plants built on or within 10s of miles of coast that are known to be subject to both major earthquakes and tsunamis. Such plants are clearly subject to the same events that are occurring in Japan. Indeed the recent events in Japan are a dramatic cautionary tale and proof point about siting and construction. On balance then when the issue of siting is considered it's fair to say that while it is very probably possible to safely site much more is needed to ensure that plants are in fact safely sited.
Are there inherently safe nuclear power plant designs? The short answer here is that yes there are. Unfortunately, the economics of such plants are rather poor. Conversely there are plant designs with good economics. Unfortunately, these are much less inherently safe. This conflict between economics and safety is in many ways the central issue in nuclear power plant design. Given the potential risk with nuclear energy one should err on the side of safety. But nuclear power generation is a business and businesses operate to create profit. Profit can be maximized by focusing on efficiency, in this case design efficiency. While regulation can and indeed in recent years has helped to achieve a more appropriate balance between safety and efficiency in nuclear power plant design, the design of current plants are simply not inherently safe. Given the underlying risk associated with nuclear energy much more needs to be done to ensure that plant designs are inherently safe.
Are nuclear power plants safely sited? Are the plant designs inherently safe? These are the questions we need to ask when considering nuclear power plant construction.
The next issue is operation. This question turns out to be rather more subtle than many acknowledge. Nuclear power plants are intended to generate and sell electrical energy at a profit. Profit is driven by, among other things, the cost of operation. By issues such as maintenance, staffing, training, and such. While it is, in fact possible, to operate a nuclear power plant safely there is ample evidence that nuclear operators have not done so. It is this disconnect between what is possible and what actually happens that is one of the central safety problems with nuclear power generation.
It is also necessary to consider what happens when a nuclear accident occurs at a nuclear power plant. Nuclear accidents are qualitatively different than the accidents at a conventional power plant. In a conventional plant accident a few lives might be lost and electrical service interrupted but that's about the extent of the harm. On the other hand a nuclear plant can result not simply in those negative consequences but also significant radiation release that can make large areas near the plant uninhabitable, affect food supplies over entire countries, and lead to long term radiation related medical problems. It is these qualitative differences that make the issue of operation of nuclear plants a much much more serious matter. So safety metrics that might make sense in conventional plants simply aren't enough in a nuclear plant.
That being said it is in fact true that the number of serious nuclear accidents in the history of nuclear power generation is, in fact, very small. It is in fact three. Nuclear power generation dates back to 1954. In the intervening 50 plus years there have been serious accidents at Three Mile Island in the US, Chernobyl in the USSR, and now Japan. In addition there have been another half dozen or so serious accidents that lead to significant nuclear plant shutdowns. There have also been a rather large number of nuclear incidents that were dealt with before serious harm occurred.
Is this accident rate acceptable given the potential serious and long term consequences? Is it acceptable if a large numbers of new plants are added? Can nuclear power plant operation be regulated and monitored to ensure it is safe? These are the sorts of questions that should be at the heart of discussions about nuclear power operation. They go to the heart of the issue of safe operation.
Just as conventional power plants have waste products, so do nuclear power plants. In the case of fossil fuel plants it's mostly waste gas, a serious problem on a global scale and a significant source of global warming gases. Nuclear power plants don't emit waste gas. That's a big benefit. However, they do have spent nuclear fuel. That spent fuel and associated nuclear waste is arguably the most serious safety issue with nuclear power. The material is radioactive and will be so for thousands of years. It frequently contains radioactive elements that are also highly toxic. For a nuclear energy to be safe this material has to be safely disposed of.
To quote the Nuclear Energy Institute, an industry trade group:
Currently, used nuclear fuel is stored at the nation's nuclear power plants in steel-lined, concrete pools or basins filled with water or in massive, airtight steel or concrete-and-steel canisters.
The plan, such as it is, is that the government will process spent fuel and store the associated waste in stable deep geologic repositories. Until recently the primary candidate was Yucca Mountain on Federal land in Nevada. Evaluation of this site began in 1978, some 30 plus years ago. It is still not in use! As of today there is in fact no plan for long term storage and management of nuclear waste! Moreover, considering the nature of the material, radioactive risk, and need to manage storage for tens of centuries it is entirely reasonable to doubt that it can be managed.
While there are many safety problems in storing nuclear waste perhaps the most difficult is time. Nuclear waste remain highly dangerous for centuries and moderately dangerous for tens of centuries. Consequently, storage safety for a few hundreds of years is an essential requirement.
Considering that the entire history of the United States is only a few hundred years and the longest stable society in history lasted only a bit more than a thousand years it is not reasonable to think that the society that places nuclear waste into storage will be around to manage it throughout the time it is dangerous! Nuclear waste created today will have to be managed by societies yet to be created.
Consider that nuclear waste remains dangerous for geological times, for thousands of years. Over such timescales events that are extremely unlikely such as major earthquakes along undiscovered faults, volcanic eruptions that have not occurred for hundreds or thousands of years, or meteor strikes will surely occur. If such events occur near nuclear waste storage sites the consequences could be extreme.
Can nuclear waste be safely disposed of? The short answer today is no. Moreover, it is very unlikely that we will have either the technical or societal mechanisms to store these materials in the future. Absent safe waste disposal, nuclear power is simply not safe.
Large electrical generation systems don't just involve the generation of electricity. At some point the plant will be worn out or obsolete. It will need to be decommissioned, taken apart and made safe. The NRC has a formal process for decommissioning. As of today there are somewhat more than 20 nuclear power plants in some state of decommissioning and there have been four completed decommissions. Nuclear power plants can clearly be successfully decommissioned. However, it should be noted that the process is long, typically 60 years for large plants. Given that the plants life is a few tens of years, typically somewhere around 30 or so, decommissioning time is something around twice the plants operating lifetime! None the less, it is clearly possible.
As a general rule the more widespread and long lasting the consequences of failure are the more safety is required. In many ways the central problem with nuclear power operation is that the negative consequences of nuclear accidents are both widespread and long lasting, potentially as has been seen in Chernobyl, very widespread and very long lasting. The history of nuclear power is rather mixed. Given the dangers and the complete lack of a viable waste disposal plan it can not be regarded as safe today.
However, that's not the end of the safety question. It's appropriate to ask are there safe alternative sources of electrical power? There are several that have good potential. However, given the rather distorted economics of power generation these alternatives are not generally economically practical. The problem here is not so much technical as it is one of fully costing established competitors. If coal, natural gas, and oil electrical power were priced to reflect the cost of pollution then alternatives with better pollution characteristics might well be economically viable.
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