Friday, September 20, 2019

Replacing coal with wind and solar power


I am often reminded by my friends that renewable power like wind and solar are making tremendous strides—their deployment is rising exponentially, and costs are coming down. As a result, my friends claim, greenhouse gas emissions in the US are declining. They note that renewable sources are a cheaper alternative than coal power in many parts of the world. We should therefore close down the coal plants and replace them with wind and solar farms. For backup these installations should use batteries, whose costs, I am told, are also plummeting. Indeed, Mr. Bloomberg has pledged $500 million to hasten such a transition.

I wish I could share their positive outlook. Deployment of renewable power technologies has been increasing, but even after twenty years of this exponential growth, in 2018 they provided a mere 3% of global energy, while fossil fuels accounted for over 80%. Wind and solar simply do not scale. Here’s a graphic from the BP Statistical Review of World Energy, 2019. It shows the global primary energy consumption various sources in MTOE, metric tons of oil equivalent. Yes, you can see the increase in renewables, but the even larger increases in consumption of fossil fuels has led to emission of ever-increasing amounts of carbon dioxide.


There has indeed been a decline in the CO2 emissions in the US electricity sector. This decline, though, is largely a result of switching from coal to natural gas, and not due to the rise renewables. Wind and solar contributed only a small fraction. Here are the data from the US Department of Energy’s Energy Information Administration that illustrate the point.


The falling price of wind and solar power that the proponents point too does not reflect their true costs.  Policies such as Renewable Portfolio Standards, subsidies, and alternate revenue streams such as curtailment allowances hide the costs. Wind and solar installations must come with the disclaimer, “Batteries Not Included.” If one includes the cost of storage and other systems for managing their intermittency, the cost of wind and solar would be considerably higher.

Consider closing a 1-GW coal power plant, say the Bruce Mansfield in Pennsylvania, and replacing it with renewables. First, to get the same number of GWh of electricity over a year, you will have to install about 3 GW of wind or solar facilities to account for their reduced capacity factors. Installation costs are often reported in $/W, and so for starters we have allow for the higher installed capacity to get the same amount energy.

Next, you will also have to provide some storage to cover for days that wind might not blow or the clouds obscure the sun. Currently, natural gas plants are used to provide backup power because natural gas in cheap—thanks to fracking—and they can ramp up quickly. But natural gas is a fossil fuel, and we do not want that; instead we want to put in batteries for backup. If we choose to provide storage for just 100 hours, a tad over four days; that would mean installing battery storage capacity of 100 GWh. How much lithium would that require? According to Tahil, theoretically you could store 1 kWh of energy from 73 g Li in lithium ion batteries. Note that g/kWh are the same as Tons/GWh. Thus, theoretically, you would need 73 Tons for storing 1 GWh of electrical energy.

In practice, the amount required is often 3 to 4 times higher because of several factors: discharge rate, irreversible losses, reaction kinetics, etc. Tahil discusses these issues in the paper and concludes by suggesting a requirement of 320 g Li per kWh of storage. In other words, shutting down just a 1-GW coal plant and replacing it with renewables and providing only 100 hours of storage would require 32,000 Tons of lithium. To put that amount in perspective, note that in 2018 the global production of lithium was 62,000 Tons.

In other words, about half the world’s lithium supply would go for backing up renewables to replace one coal plant!  Sure, we could expand the production of lithium, but how soon could we scale it up to get millions of tons per year to replace all the coal power? We do not have the luxury of time. As Greta Thunberg and children all over the world implore us, we must take action to combat climate change. Let's do right by them and not make the problem worse than it already is.

Time to get real and embrace nuclear power!

Monday, August 12, 2019

Links to some of recent videos


I confess I have not been very active in posting blogs lately. But please do not take that as a sign of waning interest in the subject. I have kept up giving lectures and appearing on Michael Killen’s TV show to talk about global energy and the necessity for the world to move towards nuclear power. In addition, my talks at the Thorium Energy Alliance conferences in 2016 and 2018 are also available on YouTube. Here are links to some of these videos:

1.     Michael and I discuss the assessments of the impact of climate change described in recent reports released by the IPCC and a collection of 15 US agencies. (December 2018).
2.     Alex Cannara and I talk with guest host Jonathan Kleid whether renewables alone can prevent climate and economic disaster. (January 2019): 
3.     Michael and I talk about the Green New Deal and its ability to combat climate change. (April 2019): https://youtu.be/MptQO8pJ0E4
4.     My talk at the Thorium Energy Alliance Conference # 7, in Palo Alto where I introduce the notion of a cubic mile of oil and discusses the moral imperative for increasing total global energy supply equivalent to several cubic miles of oil. : https://youtu.be/CpXG3zyg3gk
5.     My talk at the Thorium Energy Alliance Conference # 8 on replacing the cubic miles of oil that we use and what will be needed in the future with nuclear power. https://youtu.be/sGphBAgoF_w

Wednesday, June 26, 2019

Open Letter to Democratic Candidates to Support Nuclear Power


The Washington Post recently published an informative article on all the candidates hoping to become the Democratic Presidential nominee in the 2020 elections.  This article focused on the issue of Climate Change, and I am pleased to note that all the candidates recognize the importance of the issue, the existential threat it poses to humanity, and the urgency of tackling this challenge.  I was particularly heartened that seven candidates (Bennet, Booker, Delaney, Hickenlooper, Moulton, Ryan, and Yang) support building more nuclear power plants.  I thank all of them for taking this position, as I do believe that nuclear power is the cleanest, safest, and most environmentally benign source of energy the world so desperately needs.

There are six candidates (Biden, Gillibrand, Harris, Klobuchar, O’Rourke, and Warren) whose have not made their position on this question clear. Of the remaining ten candidates, four are totally opposed to nuclear power (Gabbard, Messam, Sanders, and Williamson) and six oppose building new plants at this time (Bullock, Buttigieg, Castro, de Blasio, Inslee, and Swalwell).  I looked at the reasons the candidates offer for opposing expansion and development of nuclear power. They are safety, waste disposal, cost-effectiveness, and a belief that other technologies like wind, solar, and geothermal together with energy efficiency will suffice to meet our demands. I have previously written and spoken on these concerns but will summarize them here too. I will also show that there are serious consequences of not pursuing nuclear power. There are trade-offs with all energy systems, but the benefits from nuclear power far outweigh the risks.

1. Safety. There are several aspects of safety to be addressed. Most of the expressed concerns are based on unsubstantiated claims and misunderstandings. Often people conflate nuclear weapons with nuclear power and think of a nuclear power plant exploding like a nuclear weapon. That is simply not possible. The uranium in the fuel rod is typically enriched to about 4% of the 235U, while a nuclear explosion requires enrichment in excess of 80%. Nor is the fuel in the power plant in a configuration to sustain a nuclear explosion. What about the explosions at Chernobyl or Fukushima, you might ask? They were chemical explosions, and thus orders of magnitude weaker than any nuclear explosion. What happened was that steam came in contact with hot metal and produced hydrogen gas. The gas accumulated in the building and then explosively combined with oxygen in air. The power of the explosion was sufficient to blow apart the structure and led to the release of radioactive materials and raises legitimate safety concerns. These events are extremely rare.

Health risks from radiation are also widely misunderstood. No one denies that acute exposure to high levels of radiation, however rare, are fatal. The level of exposure is commonly measured in units of sieverts (Sv), which take into account the energy of the radiation and the nature of the tissue. Acute radiation of 3 to 5 Sv is fatal to humans. However, radiation therapy often entails exposures between 20 and 40 Sv spread over a month or so. Of course, the rest of the body also gets some exposure, but the doctors manage that exposure to levels that may cause hair loss or radiation sickness, but not be fatal to the individual.

There is a myth that any exposure to radiation is harmful. This is simply not true. We are constantly exposed to radiation from a variety of natural sources (e.g., cosmic rays, granite and other minerals, and radon gas) as well as during many routine medical tests (e.g., X-rays, CT-scans). It is true that radiation can damage our DNA and thus lead to cancer, and while it is one thing to expose a cancer patient to radiation for therapy, it is quite another to expose the general public to unnecessary radiation.

Out of an abundance of caution, the nuclear power industry and the regulatory bodies have for years adopted the “linear no-threshold” (LNT) hypothesis as the guiding principle that would minimize exposure. However, many anti-nuclear organizations have used this stance to drill the message that all radiation is harmful. According to LNT, it does not matter if one person is exposed to 5 Sv or 1000 persons are exposed to 5 mSv (millisieverts). That’s like saying that the effect of one person dropping off a 100-foot cliff is the same as 100 people jumping off a 1-foot step! LNT implies that our bodies have no repair mechanisms, which is also not true. Simply living on Earth typically exposes us to between 3 and 7 mSv/year, and cells have evolved in this environment by developing mechanisms for repairing DNA.

The LNT estimate of premature fatalities from long-term exposure to low levels of radiation on large populations leads to ridiculously large numbers. For example, radiation leakage from the worst nuclear accident at Chernobyl has been reported to potentially lead to 100,000 or more premature fatalities. The fact is that other than the 39 workers who went in immediately after the accident who died from acute radiation exposure, there have been very few additional cases of cancer. The UN body, UNSCEAR, that reports on radiation safety had previously estimated up to 4,000 additional cases, but in 2008 it issued a revised report stating that the estimate is too large, and it would be hard to detect

The downside of taking this extreme cautionary position is that we have instilled fear in the public, and second our response to nuclear accidents have caused real harm. Consider what happened at Fukushima. There was a massive earthquake followed by a tsunami resulting in the death of about 17,000 people. There was radiation leakage, but the amount of radiation posed risks to people in the immediate vicinity. The forced evacuation of over 200,000 people living within 20 miles of the plant caused much disruption and resulted in over 1,500 fatalities from mental anguish and interrupted health services. In contrast, no one died from radiation exposure. The workers who went in clean up were monitored to limit their exposures. One worker contracted cancer, and while the power company has assumed liability it is far from certain that radiation caused that cancer.

All power systems are associated with fatalities, and a lack of access to electrical power is also responsible for far too many premature deaths. There are tradeoffs to be made, and our decisions should be informed by data. The number of fatalities per unit of electrical power delivered is the lowest for nuclear. Thus, while on average coal power results in 160 premature deaths per TWh of power; I say on average because it greatly depends on the types of scrubbers and other emissions control measures that are put on the plant. Oil and gas power plants typically have 30 fatalities per TWh. Fatalities on the order of 0.1 per TWh result from wind and solar operations—both during the mining and processing of materials as well as during installation. In their 70-odd year history nuclear power plants have resulted in 0.0013 fatalities per TWh. It is by far the safest technology! And when countries replace nuclear power by installing natural gas or brown coal plants, they are increasing the number of premature deaths. By opposing the development of nuclear power, “environmental” organizations have perversely had the effect of promoting unsafe power systems.

2. Waste disposal is the second big issue for many opposing nuclear power plants. Despite the common misconception of nuclear power plant waste as a green liquid leaking out of drums and threatening water supplies, the “waste” from power plants consists of solid ceramic pellets in steel rods that are encased in dry concrete casts. I put quotes around waste, because it should be thought of as a resource for the next generation of reactors. More than 90% of original fissile and fissionable material is still in the fuel rods when they are taken out of service in the current light water reactors. Buildup of fission products interferes with the neutron balance and hence the spent fuel must either be reprocessed or burnt in what are called fast-reactors. Sure, the spent fuel is radioactive, and when it is first removed from the reactor, it has to be safely stored under 20 feet of water to cool the rods and provide adequate shielding from the radiation. After 10 years under water, the highly radioactive fission products in have decayed to a point that the rods may be stored on site in dry concrete casks with passive air cooling.

The total amount of spent fuels is tiny. According to the International Atomic Energy Agency, the total amount of spent fuel produced by all the nuclear power plants over the last 70 years is 370,000 tons. about 120,000 tons of it has been reprocessed, leaving 250,000 tons of spent fuel. Contrast this to the billions of tons of ash from coal power that is also toxic and radioactive, not to mention the billions of tons of carbon dioxide that are simply released to the atmosphere and are the principal cause of climate change. The total volume of all the spent fuel is 22,000 cubic meters, which would fill one football field (100 yards by 55 yds) to a depth of 13 feet!

High cost of nuclear power is also given as a reason to oppose it. Nuclear power plants are costly to build, but they are built to last a long time—60 or more years instead of the 20-30 life time of wind and solar installations. Also, once built they produce electricity consistently over 90% of the time; the occasional downtime being for fuel changing or servicing. Contrast that with the intermittency of wind and solar that generate electricity only around 25% of the time. The low capacity factor 25% for renewables means that in order to obtain the amount of electricity generated by a nuclear plant in a year, you have to install three times as many MW of wind and solar plants. On top of that, you will have to build a comparable amount of storage capacity if the renewables are to be the primary source of electricity. The cost of storage is not included when proponents cite the falling the price of renewable power, which currently depends on the extant grid for storage. Renewables are often backed with natural gas peaker plants to provide the power in case the wind doesn’t blow or the sun doesn’t shine.

Because the amount of renewable power currently comprises less than 15% of the electricity, the grid can accommodate it, albeit with increasing difficulty. As the penetration of these renewable sources increases, they will require massive amounts of storage and a complex Rube Goldberg-like system to manage the mismatch between demand and supply due to variability and intermittency of these sources. Nuclear power plants may cost more initially, but over their lifetime they are less expensive than the alternatives.

The cost of construction of nuclear plants used to be about $2/W ($2 billion for GW plant) in the U.S. back in the 1970s. It has risen substantially to over $10/W, because we have not built any in decades. The new ones have been plagued by many mid-stream design changes, and these costs are not representative of what is achievable. Construction costs in countries like South Korea, China, and Russia are still around $2/W. The amount of materials required for nuclear power are about a tenth of what are needed for wind and solar plants. Thus, if we can standardize our power plants and start building already tested, safe, and reliable light-water plants, their costs will come down, and we will build a work force in the pipeline for the next generation of nuclear power plants that are walk-away safe and that could use the spent fuels as well as materials from nuclear weapons, which would be in essence beating swords into plowshares.

Many candidates have expressed that renewables alone can suffice to meet our energy demands, and hence there is no need to build nuclear power plants. This is a highly seductive notion, and it has been promoted by many in the environmental movement as well as by celebrities. People are also attracted to renewable power sources because they offer opportunity to employ millions of workers. But the objective of the energy industry is not to provide employment for people. It is to produce a commodity at an affordable cost that other businesses and industries can use to generate employment. The large number of “green jobs” is a reflection of the very low energy density of renewable sources, which also means that systems for harvesting wind or solar energy have to be very large. They require a lot of space and they consume a lot of materials for constructing power extraction devices—wind turbines or solar cells and the associated structures. Mining and extracting the required materials have large environmental footprint in addition to the vast areas that need to be devoted for wind and solar farms. Under the 100% renewables scenario, the global demand for commodities like concrete, steel, rare earths, copper, and aluminum will increase dramatically and strain their global supply chains. The renewable energy sources are far from being environmentally benign, and from an environmental perspective, nuclear power has the smallest footprint.

There is agreement among all the Democratic candidates that there is an urgency with which we must reduce greenhouse gas emissions if we are avoid the catastrophic effects of climate change. Countries that have successfully decarbonized their energy supplies, notably France and Sweden, have done so with nuclear power as the backbone. Germany tried to decarbonize through their Energiewende program, but once they turned off their nuclear plants in 2011, their emissions have largely held steady or slightly grown; and Germans pay among the highest cost for their electricity.

My plea to the candidates is that they approach the 2020 elections with the clarity of a 20/20 vision. I urge you to look at the facts about nuclear energy dispassionately and support its deployment and development. Again, thank you to all who have already expressed their support for nuclear energy, and I hope this piece helps convince the others—particularly those on the fence—to come out and express their support.

Our need for clean electricity is huge, and more so as we electrify our transportation system and install new cloud servers to support e-commerce. We are in a hole! Let’s stop digging us deeper by shutting down well-functioning nuclear power plants. Let’s not wait for advanced next-generation nuclear plants but continue to replicate the ones that we know have a proven track record of safety. When the advanced reactors are ready and the Nuclear Regulatory Commission has blessed their designs, we can start manufacturing them, but the urgency demands that we make the transition to zero-emission sources as quickly as possible, and that requires nuclear power.

Good luck to all of you in your campaign!

Saturday, November 17, 2018

Nuclear Power? Yes, but what about…?


The Intergovernmental Panel on Climate Change (IPCC) recently released its special report on climate change with a clarion call for immediate action to reduce greenhouse emissions.[i] That has been clear for a long time, and the dire consequences of climate change are now expected to be felt as soon as 2030. The urgency is mainly because as a society we have been late in taking action.

The world also needs lots of energy, particularly electricity, for the well-being of its citizens. Unfortunately, the one source of clean electricity, nuclear power, has been off the table for many in the “environmental” movement. Readers of this blog know that I am a strong proponent of nuclear power. In my last post, I pointed out three reasons for supporting nuclear power: near-zero carbon emissions, fewest fatalities per unit of electricity, and the smallest environmental footprint. This post deals with several of the what-about questions I am asked online or after my talks.

What about the waste?
One question that I get asked most often has to do with the issue of “waste.” So, let’s talk about it. First, spent nuclear fuel is not “waste,” it is a resource for future nuclear plants. Importantly, the spent fuel is a solid; totally contained inside a steel rod. It is not something that is released to the environment. Contrast that with coal-fired power plants that emit billions of tons of gases and particulates into the air and equally large quantities of solid wastes, which can end up in streams and waterways.
Figure 1. Detail showing uranium pellets inside fuel rods and assembly of fuel rods.

To begin with the nuclear fuel consists of ceramic pellets of uranium oxide enriched in U-235, the fissile isotope. The isotopic composition of the fuel pellets is about 4% U-235 and the remaining 96% is U-238. After two years in service, the fuel pellets still contain about a quarter of the U-235. Also present are the fission products and 2% Pu isotopes. Between the remaining U-235 and Pu isotopes, about 50% of the original fuel value is still in the rods when they are removed from service. Two main reasons for retrieving the rods are that after about 2 years in the reactor core some of the cladding materials develop cracks and defects, and accumulation of fission products like cesium, iodine, strontium and barium, interfere with the maintenance of neutron balance.

The fuel assemblies are then withdrawn and stored under water. About 20 feet of water is needed to cool the rods and provide adequate shielding from the radiation. After 10 years under water, the highly radioactive fission products in have decayed to a point that the rods may be stored on site in dry concrete casks with passive air cooling. The spent fuel may alternatively reprocessed to recover the fissile elements (uranium and plutonium), and fashioned into pellets as is the practice in several countries like France, Japan, Russia. Because reprocessing could lead to opportunities for siphoning off plutonium and thus to proliferation of nuclear weapons, this practice was stopped in the US in 1980s. I will discuss the issue of proliferation later in this post, but let’s continue with the discussion of “waste.”


Figure 2: Storage of spent fuel in dry casks poses no radiation hazard.

Second, the total amount of spent fuel is tiny. According to the International Atomic Energy Agency, the total amount of spent fuel produced by all the nuclear power plants over the last 70 years is 370,000 tons.[ii] About 120,000 tons of it has been reprocessed. The total volume of all the spent fuel is 22,000 cubic meters, which would fill one football field (100 yards by 55 yds) to a depth of 13 feet! It is a small amount of “waste,” considering all the carbon-free electricity these plants have generated.

Storing the spent fuel in deep geological wellbores is technically feasible. As demonstrated in Finland there are no technological barriers to deep well storage, although there remain political barriers. In the United States, Yucca Mountain in Nevada was proposed as a repository, but after years of back and forth, the plans were abandoned. No politically acceptable site has yet been identified. To get around the political deadlock, Deep Isolation—a California company, started by daughter and father Elizabeth and Richard Muller, is proposing a modular and inexpensive option. Their solution exploits recent advances in fracking technologies to drill mile-deep wells with tilted horizontal holes to store the spent near the nuclear plants.[iii] Until such time as this or some other innovation is developed, on-site storage of the spent fuel in dry casks remains a perfectly viable option.[iv] Besides, on-site storage would make it easy to retrieve fuel for future fast reactors.

What about fuel supply?
Another question I often face is that there isn’t enough uranium to power the expanded nuclear fleet. At the current rate of consumption (56,000 tU/yr), global supply of reasonably assured resources (RAR) of uranium at $80/tU could last about 40 years, but if the nuclear fleet were to be expanded substantially, these resources would not last very long. The thing to note is that apart from uranium RAR there is a much larger uranium resource base, which is accessible at higher price. Doubling the price of uranium ore from $80/ton to $160/ton would greatly increase the supply of uranium while raising the cost of electricity by only a fraction of a cent per kWh, because each ton of U produces 1.2 TWh of electricity. With more than adequate supplies in hand, current market conditions do not favor efforts to explore other sources of uranium, but with appropriate price signals these secondary sources could become part of the RAR.

Nuclear weapons are another significant source of uranium. Under the megatons-to-megawatts program, many nuclear warheads are being dismantled. The highly enriched uranium and plutonium of the warhead is diluted with depleted uranium to make mixed oxide (MOX) fuel suitable for nuclear power plants. Further, if we replace the current practice of using the fuel in a once-through mode by reprocessing waste fuel, the current supply of uranium could last several-fold longer. Finally, if we develop breeder technologies to use thorium the supply of fissile fuels would be virtually inexhaustible.

What about nuclear proliferation?
Nuclear proliferation is another reason people object to developing nuclear power plants. The underlying assumption is that countries with nuclear power plants will use their technology and facilities for developing nuclear weapons. This assumption is not justified. There are many countries which have nuclear power, but no plans to develop weapons. Argentina, Belgium, Canada, Japan, Germany, South Korea, and Sweden are prime examples of nations in this category. Nor is nuclear power a prerequisite of weapons development. USA and Soviet Union developed weapons long before nuclear power plants were built.

The reason why countries acquire nuclear weapons technology is largely geopolitical, and proliferation is best addressed through political solutions. Countries acquire them primarily as a deterrent against a more powerful neighbor. Other factors include national pride and exercise of hegemony. France was concerned about Soviet weapons in its neighborhood. It developed nuclear weapons despite protestations from the Kennedy administration. Even assurance of a nuclear umbrella from the US did not dissuade France from its path.

Uranium-based nuclear weapon has a relatively straightforward gun design that shoots one subcritical mass of uranium into another subcritical mass. Together the pieces exceed the critical threshold and a nuclear explosion ensues. However, getting the uranium fuel and enriching it to weapons grade (i.e., greater than 80% U-235) is a substantial challenge. Recall that natural uranium has only 0.7% U-235. Fuel grade uranium requires increasing the ore about 6 fold to between 3% and 5% U-235. Enriching it to weapons grade requires an additional 20-fold enrichment, something that requires access to a vast arrays of high speed centrifuges. Non-nuclear nations could not follow this path surreptitiously as these facilities would be readily detected and are also subject to sabotage through cyber-attacks—the U.S. successfully set Iran back in its drive to acquire weapons grade uranium by deploying the Stuxnet worm.

Plutonium-based devices require Pu-239, which is present in the spent nuclear fuel. Chemical extraction of plutonium is a relatively simpler process than enriching isotopes, and hence the fear that countries could divert some of the spent fuel for making a weapon. However, the construction of the plutonium device is much more challenging and presents a major hurdle.[v] Besides, the plutonium in spent fuel also contains other isotopes of plutonium, notably Pu-240, which must be removed or the device would simply fizzle. Weapons-grade plutonium are best obtained from research reactors in which the uranium is “burnt” for very short periods before reprocessing—a practice not conducive to electrical power production.

What about dirty bombs?
Another concern is the possibility of nuclear waste being used by terrorists to create a “dirty bomb” which causes radioactive damage. The damage that a dirty bomb can really create is one of fear of contaminating a vital area so as to cause mass disruption. A dirty bomb will also cause a small increase of cancer risk for the population as a whole, but it does not lead to immediate loss of life. Terrorists are more likely to try something more spectacular, including conventional bombs. 

The hurdles for making a dirty bomb are also significant for a terrorist organization. For starters, amassing the radioactive material without killing themselves before they can make the device is an insurmountable challenge for the terrorists. While the radiation from the dirty bomb after it has been exploded—and the radioactive materials dispersed—poses only a small risk to the large population, in a concentrated form, as would be necessary for the bomb, the radiation levels will be high enough to cause illness and death. The terrorists could decide to make dirty bomb from -emitters, because they can protect themselves against this non-penetrating radiation. For this type of dirty bombs the radioactive materials can be obtained from a variety of medical and other devices that have nothing to do with nuclear energy, and so this threat is not reduced by turning off nuclear power plants.

There will always be violent groups with grievances, and therefore the risk of having such a group acquire a small fissionable bomb can be minimized with adequate protection of important secrets and technology. The real risk would be from a rogue nation providing a terrorist group with a small nuclear device and a means for delivering it. A one-kiloton “suitcase” device does not wreak as much damage as many conventional explosive charges do. 

I do not mean to take the threat of terrorist attacks using a nuclear device lightly, for it can cause mass economic disruption. Ours is not a situation with easy choices, and the growth of nuclear power is important for the energy security of the world. This is a problem that needs a political solution. Greater involvement of the IAEA and internationalization of the enrichment and fuel reprocessing is a path proposed by ElBaradei, former Director General of the IAEA and winner of 2005 Nobel Prize for peace. Internationalization of fuel processing could provide assurance to countries pursuing nuclear power that they will get the fuel for their plants. Stable energy supplies is a deterrent of war. This scenario also provides the safeguard that nuclear material is not being diverted to military uses, because the material would be watched over by personnel from many different countries.


[i] Summary for Policymakers of IPCC Special Report on Global Warming of 1.5°C approved by governments; Press release. Oct. 8, 2018; http://www.ipcc.ch/news_and_events/pr_181008_P48_spm.shtml
[ii] Status and Trends in Spent Fuel and Radioactive Waste Management, IAEA Nuclear Energy Series No. NW-T-1.14 (2018)
[iii] https://www.deepisolation.com/technology/
[iv] U.S. Nuclear Regulatory Commission: https://www.nrc.gov/reading-rm/doc-collections/fact-sheets/storage-spent-fuel.html
[v] In order to successfully explode a plutonium bomb it is important to keep the Pu-239 from poisoning itself by its own neutrons. To achieve this, plutonium is fashioned into a thin-walled sphere so that the neutrons mostly escape and are not absorbed by the neighboring Pu atoms. In order to explode the device, the Pu sphere has to be compressed together into one lump. This feat is achieved by a process of implosion. A number of chemical explosives are set off around the Pu sphere, and their shock wave compresses the sphere. The timing of the explosions has to be very precisely controlled, or the nuclear device simply fizzles.

Tuesday, August 21, 2018

Why I Favor Nuclear Power



The world needs energy
There is little doubt that the world needs lots of energy—cubic miles of oil worth of energy—just to afford the current population a decent standard of living. More than 80% of the primary energy we currently use is derived from fossil fuels, and the immediate consequence is a higher concentration of CO2 in the atmosphere, ocean acidification, and an increased risk of climate change. The need for producing much more clean energy, in particular electricity, becomes evident when one considers the 3 billion people living at or near-poverty conditions.

Use of electricity produces no environmental pollutants, and thus its use should be encouraged wherever possible, such as for heating and transportation instead of using natural gas and oil. These transitions only increase the demand for clean electricity. As a rough estimate global production of electricity has to increase at least four-fold its current level of about 25,000 TWh per year. Of course, electricity is only as clean as the method for generating it in the first place.

As some deeply concerned about the state of our environment, I realize that we have to stop using fossil fuels as soon as possible, and start relying on zero-CO2 sources like nuclear, wind and solar. On a life cycle basis, all these sources produce only a few grams of CO2 per kWh of electricity compared to nearly a kilogram of CO2 per kWh for coal power plants.

Nuclear power produces CO2-free electricity
Unlike generation electricity by burning fossil fuels, generation by nuclear, hydro, solar, and wind are not associated with direct emissions of CO2. That is not to say that these sources are carbon-free. Varying amounts of CO2 are released in the processes used for producing the requisite materials, construction, and ultimate dismantling. Comparison of various electricity generation technologies must account for both direct and indirect emissions. The figure below was taken from a paper by Markandya and Wilkinson, which compares the direct and indirect emissions of CO2 for various power generation technologies.[1] On a life-cycle basis, CO2emissions from nuclear are the lowest, about 30 g/kWh compared to 1.3 kg/kWh for coal, and even lower than solar and wind because they require substantially greater amounts of materials such as steel, concrete, and glass for producing equivalent amount of electricity.

Figure 1. Nuclear power emits the least amount of carbon dioxide.

Nuclear power has a low environmental footprint
Since nuclear fission releases a million times the energy than chemical reactions (combustion), it takes that much less fuel. We burn billions of tons of coal, oil and gas, but to generate an equivalent amount of energy we need only a few thousand tons of uranium, which greatly reduces the environmental burden of mining for the fuel.

The high energy density means that nuclear plants are compact. They do not require much land and can be located close to centers of power consumers. The Diablo Canyon Nuclear Power Plant with its twin 1100 MW units take up only 940 acres (less than 1.5 square miles). Area required for comparable nameplate generation capacity for solar and wind farms is 10 to 100 times greater, and another three times larger to compensate for their low capacity factor. Because of the large area requirement, large renewable power generation systems have to located further away from city centers, and hence have a greater need for easements for  more transmission lines.

The tonnage of commodity materials such as concrete, steel, cement, and glass required for the construction of power generating facilities are also much smaller for a given capacity of nuclear power than other power generation systems, further reducing the environmental burden. Nuclear plants produce power 24 X 7 with occasional scheduled shutdowns for maintenance and refueling. They thus have capacity factors in excess of 90%. Renewable sources such as wind and solar have capacity factors between 25 and 30%. Whereas nuclear plants are built to last 60 or more years, wind and solar facilities last only 30 years. The higher capacity factor and longer life means that nuclear plants produce six times as much electricity as comparably sized wind and solar facilities. Figure 1, taken from the Department of Energy’s Quadrennial Technology Review, shows the tons of materials required for producing 1 TWh of electricity from different power generation systems. As is evident from the figure, the environmental burden of nuclear plants is the least of all other sources.


Figure 2. Nuclear power has the lowest materials intensity.

Nuclear power is safe
If we look at the fatalities associated with mining, installation, and operation from power generation of various energy sources, nuclear is the safest. The following chart, compiled by the Canadian Nuclear Agency includes deaths from the pollutants emitted by fossil fuels that cause asthma and other respiratory ailments.1 The figure of 161 deaths per TWh for coal is a global average, and it is worth noting that in the US it is 15, while in China it is 278. There is no doubt that measures to control the emissions of particulate matter and other pollutants from coal plants in the US have been very beneficial.

The figure of 0.04 deaths per TWh for nuclear plants includes the estimated 4000 deaths from radiation exposure following the Chernobyl nuclear disaster. This estimate is an upper limit for the number of fatalities as it is based on the linear no-threshold model (LNT). This model assumes all ionizing radiation is harmful, and its effects are cumulative; in other words the model assumes that our bodies have no repair mechanisms. We live with constant exposure to ionizing radiation and have evolved DNA-repair mechanisms to deal with certain levels of radiation exposure. A more realistic estimate would further reduce the number of fatalities from nuclear power to about 0.013 per TWh.


Figure 3. Nuclear power has the fewest fatalities per unit of electricity.

The prospect of climate change and ocean acidification are real, and the long time it takes to implement corrective measures means that we must rapidly decarbonize our energy systems. Our fears of radiation are largely unfounded and have had the deleterious effect of continued use of fossil fuels. Even as we deploy wind and solar—the nominally low-carbon sources—the absence of large scale storage systems have forced us into using natural gas power for back up. The design of natural gas power plants used as spinning reserves are selected on the rapidity with which they can be brought online. These designs are among the least efficient of gas-fired plants, with thermal efficiencies around 33%, and thus high carbon emissions. Gas-fired power plants that operate with a combined steam cycle have thermal efficiencies in excess of 50%. Analysis by Larsen and Rez shows that we would do better in terms of carbon emissions if instead of installing low capacity factor wind or solar systems and backing them with natural gas, we simply used a combined cycle natural gas plant.[2]



[1] Markandya and Wilkinson, Lancet 2007, 370, 979-90.
[2] T.C. Larsen, P Rez, Journal of Sustainable Energy Engineering, 2017, 194-206, (https://doi.org/10.7569/JSEE.2017.629514)

Monday, July 31, 2017

Governor Brown, Think Nuclear Power!


California’s governor, Jerry Brown, has been a strong advocate for measures to limit greenhouse gas (ghg) emissions and combat climate change. He demonstrated leadership in face of the US withdrawal from the Paris Agreement by President Trump by speaking out and letting the world know that many cities and states in the US will still abide by those pledges. He led a delegation with major industry leaders to China to explore co-operative ventures. Just this week, on July 25, he signed a major climate bill, AB 398, which will extend California’s cap-and-trade system for ghg to 2030. Gov. Brown never misses an opportunity to remind us that implementing measures to combat climate change has not hurt California’s economy, instead it has made it stronger and resilient.

Thus far, switching from coal to natural gas has been the main contributor towards reduced emissions in CA. However, this model is not a recipe for curbing emissions in energy-impoverished societies where most of the growth in energy consumption is expected. Because they are not profligate consumers of energy, there is very little room for gain by increasing efficiency. As they strive to improve their standard of living they will need to sharply increase the total supply of energy. And remember, emissions do not know state or national boundaries, and California is responsible for barely 1% of global ghg emissions. What California needs to do is develop innovative technologies that avoid carbon emissions at a cost that makes a compelling case for their widespread adoption.

There is a growing global and national need for carbon-free electricity. Even in CA, electricity demand is expected to increase. Additional electricity required to power the projected 1.5 million EVs is 12.6 TWh per year. California’s IT industry also requires large amounts of electricity. Cloud services by Amazon, Google, Microsoft, and others require 10s of TWh of reliable electricity each year. To put these numbers in perspective, CA consumed 220 TWh of electricity in 2014. Bulk of this electricity (120 TWh) used in CA was generated from natural gas. Coal contributed only about 20 TWh; it was mostly imported from other states as the in-state production of coal power has all but disappeared. Wind, solar, geo thermal, and hydroelectric power generate relatively smaller amounts: 13, 10, 12 and 17 TWh respectively.

Nuclear power is one technology that can produce copious quantities of carbon-free electricity. California used to have three nuclear power plant facilities generating about 44 TWh carbon-free electricity; however, two of them have already been closed and there are talks of decommissioning the third one at Diablo Canyon, which last year generated 17 TWh of electricity. In view of the increasing demand for carbon-free electricity, I find plans to turn off nuclear plants misguided. Germany’s attempt to cut greenhouse gas emissions have essentially stalled after it turned off its nuclear power plants.

Existing plants should be re-certified and the development of new inherently safe nuclear power technologies needs to be supported. I am heartened to see construction of the such plants in China and India. It would be nice if such development also took place in the U.S., but that is not likely given the strong anti-nuclear sentiment. This attitude feeds into the “business risk” and renders financing nuclear projects impossible. We must remember that nuclear power has the smallest environmental footprint and is the safest source of energy with the least number of casualties per unit of electricity produced.

A first step CA could undertake is to qualify nuclear power to receive the carbon credits that afforded wind and solar power. This action would make nuclear power more competitive. It would also send a signal to the companies developing advanced nuclear technologies that they are welcome in CA to develop their innovative technologies for both domestic use and for export.

Friday, June 2, 2017

US Withdrawal from Paris Accord


Last few weeks I have often been asked about the effect of the US withdrawing from the Paris accord—and yesterday it happened! It is a good question, but because there are countervailing factors the answer is not straightforward—the net effect ranges from minimal to quite profound.
The Paris Agreement is not a binding treaty; it requires voluntary cuts to emissions of greenhouse gases, mainly CO2. The desired target set by the Intergovernmental Panel for Climate Change (IPCC) is to cut energy-related global CO2 emissions from the current 36 Gt-CO2 each year to about 17 Gt- CO2 by 2035 and then be net zero by 2050. If all the signatory nations cut their emissions by the amounts they have pledged, the global emissions are slated to rise to 55 Gt- CO2. Clearly, all nations will have to do a whole lot more if the IPCC targets are to be realized. Indeed, it was the expectation that the signatory nations will periodically review their progress and make additional pledges.
Trump questioned the "fairness" of the agreement by saying that it imposes undue economic burden on US while allowing developing nations to continue emitting CO2. Like I said, no nation is imposing any burden on any other nation. It is all based on independently determined voluntary contributions. Also, I wonder what is Trump's definition of fairness. China may have higher emissions than the US, but per capita emissions in the US is twice as high as in China and much higher than in much of the developing world. Moreover, the US, and other developed nations have been adding copious quantities of CO2 to the atmosphere since the start of the industrial revolution. They have reaped all the benefits of industrialization. The developing nations, with a much larger population, have only recently begun the process of improving the lot of their citizens by expanding energy use. Asking them to share equally in cutting emissions? Now that’s unfair!
As far as global emissions are concerned, the rest of the world will continue to make progress. In the US too, progress will continue along that front thanks to economic factors (i.e. cheap natural gas) and actions at state and city levels. The repeal of rules implemented under Obama’s Clean Power Plan (CPP) does remove incentives for auto manufacturers to produce more fuel-efficient vehicles, including electric cars. That action will likely result in the US ceding leadership in electric cars and batteries to manufacturers in Europe and Asia. The repeal of CPP is not likely to increase coal use for power generation—liberalization of Oil and Gas industry will increase the production of natural gas, which will continue to be fuel of choice for power production. Switching out coal for natural gas will reduce U.S. emissions, but the lack of regulations and requirements for monitoring fugitive natural gas—a far more potent greenhouse gas than CO2 —could wipe out any benefits there may have been from fuel switching.
A real opportunity for reducing emissions lies in the advanced nuclear technologies. I spoke on the topic two weeks ago. I devoted much of my talk to addressing the widely-held fears and risks of nuclear power, and on the newer thorium-based nuclear technologies that are walk-away safe and generate a very small amount of radioactive waste that would require safeguarding—essentially, burial under six feet of ground—for only about 300 years.
My talk can be viewed here. Unfortunately, since the slides cannot be seen very clearly in the video, I have posted them my Google Drive and you can download them here. It is a long video (about 1.5 h including Q&A), but I hope you can make time to view it. I would be most interested in hearing about any comments or questions you might have, and particularly so if after you viewing you still think that the world would be better off not developing nuclear power.