Friday, June 26, 2020

Role of Bioenergy in Achieving Sustainability

I was recently invited to give a keynote address at an international conference on Bioenergy and Sustainability. Because of the Covid-19 pandemic the conference was held virtually over Zoom. What follows is an abstract of my presentation; the full lecture can be accessed here.

The word sustainability shares its root with sustenance. In the case of modern society sustenance comes from use of energy, which is derives from many sources: oil, coal, natural gas, hydroelectric, nuclear, wind, solar, and biomass. Annual consumption of global energy is equivalent to 4 cubic miles of oil (cmo), about 3 of which are obtained from fossil sources: oil, coal, and natural gas.


The dominance of fossil energy in the global mix has been longstanding—ever since the dawn of the industrial revolution in the mid nineteenth century. As a result, the concentration of carbon dioxide in the atmosphere has increased from 280 ppm to over 400 ppm and continues to rise. CO2 is a greenhouse gas and it and now threatens life as we know it from the resulting climate change. To avert devastation from climate change or constrained energy supply, the world desperately needs sources of clean, carbon-free energy that together can scale to cmo levels.


Much emphasis has been placed in recent years on resources like wind and solar to provide clean electricity. Technological advances have led to dramatic reductions in their costs and their advocates now propose a future powered entirely by them. However, these costs do not include the cost of storage, currently provided by natural gas, nor do they consider the environmental cost of mining for the materials needed for their installation. Scaling them to a 100%-renewables scenario will strain the global supply of commodities like steel, concrete, glass, and aluminum; clearly not a sustainable scenario.


Burning biomass has been proposed as a fuel source; indeed, prior to the industrial revolution the world once derived 100% of its energy from bio sources. Unlike wind and solar, bioenergy sources are storable and do not suffer from intermittency. However, biomass use also results in emitting CO2. The only reason these emissions are not counted is that the regrowth of the biomass would take an equivalent amount of CO2 out of the air. For this assumption to hold, it is important that we consider harvesting only rapidly growing biomass or annual crops.


Global biomass production is substantial; it is estimated that 75 Gt (gigatons, or 109 tons) of biomass are produced annually. Most of the biomass is in the forests and oceans and not readily recoverable, nor is it desirable to cut down this “sequestered” carbon and burn it. The estimate for recoverable biomass resource is only 3 Gt/y. At a heating value of 15 GJ/t (gigajoules/ton) the energy from these 3 Gt of biomass would correspond to only 0.3 cmo. The low energy density of biomass translates into large areas over which the biomass to be harvested and transported to the power plant: 160 sq. miles of fast growing trees each year to power a single 100 MW plant.

Clearly, we cannot rely on biomass to meet global energy demand for clean energy. Yet, there are some applications where energy from biomass is uniquely suited. Production biofuels is one such example, and many conversion of starch in grains into bioethanol is a thriving business—thanks in large part to the support the industry receives from various state agencies. There are also processes for converting lignocellulosic wastes into biofuels, although there deployment has been hampered by high costs. The main reason for using biofuels is to reduce greenhouse gas emissions; however, on a life-cycle basis the biofuels reduce greenhouse gas emissions between 20% and 40%!

Co-firing biomass, particularly waste biomass, may provide only a limited amount of energy, but it would help enormously with waste management since many municipalities are running out of landfill space. Likewise, utilizing agricultural waste in an engineered system rather than open-field burning would go a long way in reducing urban pollution in many countries.

True sustainability demands a scalable source of clean and cheap electricity. Nuclear power can deliver that. It has the smallest environmental footprint and the best safety record, but public concerns over plant safety, long-term storage of waste, and cost are considerable obstacles. Getting the public to embrace nuclear power is a Herculean task, but it must be undertaken. We have to (i) educate the public (ii) stop closing functional nuclear power plants; (iii) expand the fleet of nuclear power plants; and (iv) develop and deploy the next generation of walk-away safe plants that can also use the spent fuel as a resource.

Thursday, April 30, 2020

Planet of the Humans: A Review

Michael Moore’s documentary Planet of the Humans was released on YouTube in conjunction with Earth Day, 2020—a casualty of the Covid-19 pandemic as a theatrical release was precluded. I had heard of the movie and knew that it was about the limitations of renewable energy sources. I was glad that a renowned documentarian like Moore was putting a spotlight on the shortcomings of “renewables,” because the public has been largely seduced into believing that wind, solar and biomass can provide us with all our energy needs while averting climate change. Last weekend, I finally got to see the movie.

I had mixed reactions as I watched the documentary. Although Michael Moore is the Executive Producer, he does not appear in the film. The film is narrated by Jeff Gibbs who tells his journey of disillusionment with the green movement. I liked how effectively Gibbs dispenses with the myth that wind and solar lead to reduced emissions! Reducing greenhouse gas emissions should be our main objective, not simply installing renewable energy sources. Gibbs points out the massive amounts of steel, concrete, and other materials required for any wind turbine, which would last for only 20 years. Similarly, large quantities of commodities are also needed for a solar farm. Production of the commodity materials requires tons of fossil resources, which cut into the “greenness” of these installations. All the mining necessary to obtain the raw materials also degrades the environment.

Gibbs loses credibility when he asserts that it takes more energy from fossil sources than what is produced by wind and solar power plants. Many reputable life-cycle analyses show that these sources are net positive energy producers after five to seven years. By overstating his case against wind and solar and not acknowledging their contribution to carbon-free electricity, he leaves himself open to easy criticism by advocates of renewable “green energy.” And he has been criticized for that by many environmentalists.

That said, Gibbs is right in his overall criticism. Life-cycle analyses do not count emissions from sources needed to back up wind and solar. Those emissions are counted as emissions from coal or natural gas plants, even though in many instances these plants are expressly built to support a new wind or solar farm. The necessity to back up intermittent sources is the reason why Germany’s greenhouse gas emissions did not decrease even though the country spent over $500 billion on its Energiewende (Energy Transformation) program.

Another fallacy of the “renewables” is that it considers biomass carbon neutral. Burning wood chips (actually forests, as the movie points out) is not good for the environment and is ruining habitat. It also can take a hundred years or more for new trees to grow and offset the carbon dioxide emitted during the burning of wood chips. Gibbs dwells a lot (indeed, too much for my liking) on the environmental damage done by growing biomass for fuel or devoting farmland for growing crops to make biofuels.

Gibbs next turns his attention to the moneyed interests behind the “green” movement. He exposes many promoters of green energy as deeply vested in fossil energy sources. The reason fossil companies support wind and solar installations is that they know the renewables will have to be backed up by new natural gas plants or the predominately coal-based grid. [i]

Gibbs portrays many leaders of the environmental movements such as Bill McKibben and Al Gore as being in the pockets of fossil energy companies. Without convincing evidence, such portrayal is sure to raise the ire of the green movement. The movie seems to make the case that nothing good will come if we rely on market forces, forgetting the counterpoint that profit motive is exactly what drives innovation and solutions.

I was particularly disappointed by the documentary because it offered no solutions. It completely ignored nuclear power and just harped on the Malthusian theme that we humans are the problem since we have so increased in numbers and each of us is consuming too much! The last part of the movie showed scenes of rampant environmental damage and an orangutan clinging on to a lone tree surrounded by devastated landscape. Pure environmental porn; ugh!  

The movie leaves the viewer hopeless, and with a sense of despair that can lead to inaction, when what the world needs is rational thinking and concerted action. In an interview with Stephen Colbert, Michael Moore said that his objective in producing this film was to raise the alarm and motivate the younger generation into action. I am afraid, by not offering any hope the movie fails on that front.

So, what are we supposed to do?  Revert to 17th century lifestyles? That seems to be the message but recall that back then life expectancy was barely 40 years and infant mortality was ten times higher than today, and people spent almost all their time in the drudgery of procuring food and fuel rather than other pursuits. The world population in the 17th century was less than 1 billion; today it is 7.5 billion and about half are living in unacceptable poverty without access to electricity, clean water, and adequate food. It will take energy to lift them out of poverty so they too can lead healthy, productive lives. Where is that energy going to come from?

Incidentally population growth, a theme that the movie touches, is best addressed by raising living standards. The need for copious quantities of clean energy is evident.  The movie makes it amply clear that the required energy cannot be produced through the magical thinking of 100% renewables. It will require a substantial expansion of nuclear power—the one clean source that is safe, scalable, and cheap enough for global deployment.

As an antidote to the movie, I suggest watching this interview by Michael Killen of me and Alex Cannara.

[i] Battery storage just does not scale to provide the required back up; besides it too is fraught with issues of materials supply.

Monday, November 18, 2019

An Open Letter to Jane Fonda

Dear Ms. Fonda,
Kudos to you for rising up to draw attention to the crisis of climate change. You are an inspiration! I read the story about your protests in the NY Times and also watched your interview with Judy Woodruff.

You clearly articulated the gravity of the problem and say that we should listen to the scientists. As a scientist, I was gladdened to hear you say that. I hope you will also lend your voice to the only effective solution that scientists like James Hansen are telling us to embrace, namely nuclear power. To the extent that your movie, “The China Syndrome,” contributed to the public fear of radiation and nuclear power, your coming out in support of nuclear power would go a long way.

Image result for james hansen nuclear energy
Climate change is also a matter of social justice as it most adversely affects those who can least afford it and who contributed the least to bring it on. People need energy to lead healthy productive lives, and currently about half the world’s population does not have access to adequate energy. Social justice demands that the global supply of energy be increased to rectify this situation. However, burning fossil fuels, which are the easy source of energy, aggravates climate challenge.

Most champions of social justice movements call for rapidly expanding renewable energy sources like wind and solar. However, these intermittent, low-energy density sources cannot meet the energy demand while reducing greenhouse gas emissions. Germany’s experience with Energiewende makes that amply clear. They spent over $550 billion but their greenhouse gas emissions are rising, because they have had to add lignite-burning plants. Further, wind and solar require inordinate amounts of materials. Meeting the global energy demand by renewables would require more than doubling the global production of basic commodities such as copper, steel, cement, and rare-earth metals with enormous environmental degradation from mining. Just replacing one coal power plant with wind and solar along with a modest amount of battery storage would require half the global production of lithium in 2018!

Nuclear power can produce vast quantities of carbon-free energy. It has resulted in the fewest fatalities per unit of energy delivered than any other system, including wind and solar. It also has the smallest environmental footprint. Our unfounded fear of radiation, reinforced by decades of fearmongering, has prevented us from building any new plants in the U.S. for decades and has exacerbated the climate challenge.

Given the urgency to reduce carbon emissions, it is foolish to shut down working nuclear power plants. Instead, we should support their continued operation, and promote building and exporting new walk-away safe nuclear power plants. I have written and spoken on this subject extensively and welcome you to read more about it in book, A Cubic Mile of Oil,” or on earlier posts on this blog. Additionally, you may want to look at, “A Bright Future” by Joshua Goldstein and Steffan Qvist.

Ripudaman Malhotra

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):
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. :
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.

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  alpha-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;
[ii] Status and Trends in Spent Fuel and Radioactive Waste Management, IAEA Nuclear Energy Series No. NW-T-1.14 (2018)
[iv] U.S. Nuclear Regulatory Commission:
[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.