THE FORTNIGHTLY CLUB
Founded 24 January 1895
Meeting # 1839
Assembly Room, A. K. Smiley Public Library
February 28, 2013
the nucleus that is
By William E. Cunningham
A Bit of Prologue
In 1998, some fourteen years ago, I read a paper on global warming, titledAOstrich in Crisis, or how long can you bury your head in the sand,@ which focused on what I then believed, and continue to believe, is the greatest threat to the future of the human enterprise as we know it, man-made climate change.
The paper=s genesis was my growing interest in the dynamics and chemistry of planetary atmospheres, driven by the growing body of fascinating data on that of the Earth, as well as that of the other planets, especially of Venus, produced by the probes developed at JPL.
In the years since, the debate over climate change/global warming has waxed and waned. In recent years the body politic=s response has been characterized by growing doubt, driven in large part by funding from the fossil fuel industry. After all, to the lay mind a mere one or two degree increase in the air=s temperature is a tiny change of no real concern when balanced against the encouraged belief that the negative effect of any diminution in the use of fossil fuels= contribution to the economy far outweighs a minuscule, if real, change to the climate.
The long-term, and recently more vocal, consensus among the scientific community, now being reinforced by recognition of the dramatic and accelerating changes in the polar regions, coupled with extremes in weather, such as last year=s mid-continent drought and the damage inflicted by super storm Sandy is now shifting both public attitudes and the nature of the debate, best exemplified by President Obama devoting a paragraph of his second inaugural to climate change and repeated emphasis on the need for action in his State of the Union.
Plus, while the scientific community knew that the process was self-reinforcing: higher water temperatures were leading to higher evaporation rates and expansion of ocean waters; the loss of reflectivity due to ever-diminishing polar ice was resulting in absorption of radiation by the exposed open waters at a greater rate than predicted; and the elevated temperatures in the polar region were resulting in the out-gassing of methane from the melting permafrost in greater volumes than first assumed - measurements now have shown that the acceleration is greater than predicted, compressing the time for meaningful and effective action.
While other gases contribute to the process, it is the increasing proportion of carbon dioxide in the atmosphere which is intensifying the greenhouse effect, trapping an ever-greater portion of the Sun=s incident energy. That energy, peaking at the yellow-green line of the solar spectrum, is absorbed at the earth=s surface and then re-radiated at longer, infra- red wave lengths that we sense as heat, the amount of absorption or trapping of this heat being directly related to the concentration of the greenhouse gases.
It is only recently that we=ve come to understand that the ever-increasing burning of fossil fuels, which provides the energy to drive our modern societies, is leading to environmental catastrophe.
What follows is in no way intended to minimize or denigrate the most efficient, environment and climate friendly energy source of all - conservation, a Aresource@ we have ignored all too long While fuel efficiency of vehicles has taken an enormous leap in recent years, much remains to be done.
`How we organize ourselves as communities, the sacrifice of valuable agricultural lands, the waste of energy by locating our housing at distance from our work sites, all must be addressed. Perhaps the best examples of that failure are the ever-larger single family homes, where 3,000 to 5,000 square foot houses are occupied by as few as two individuals, an absurd waste, both in construction and energy use - conspicuous consumption on steroids. The placement of structures without regard to solar orientation or the possible use of trees for shading, the absence of green spaces in urban settings all contribute to the urban heat island effect, the buildup of carbon dioxide Adomes@ over cities and the consequent demand for energy in a self-reinforcing loop. The list goes on and the opportunities are myriad, but topics for a paper at another time.
Our national desire for energy self-sufficiency and some governmental effort to address climate change has led to encouragement and subsidization of Arenewables,@ primarily wind and solar. But at the same time the development of new techniques to recover hydrocarbons from shale, which could soon see us as an oil exporting nation, again, has moved climate change into the background for many, with a number claiming that all is well, have no fear.
The impetus for Arenewables,@ wind, solar, geothermal, is now under threat in Congress. But the very successful development of wind power, especially in the Ared states@ of the upper Midwest and Texas, may save it, and proposals for massive photovoltaic and thermal solar arrays in our deserts and clever schemes for harnessing geothermal sources are being subsidized by our state=s mandate that thirty three percent of our electricity must come from Arenewables.@
But we=re far from being the first to the table in these efforts and we=re well behind a number of European countries. And the emerging economic powerhouses, China, India, Brazil and Turkey, are moving rapidly to exploit solar and wind and to tap their significant sites for hydro power.
And while many others are moving to tap its great potential, China, alone, planning !00,000 megawatts, left on the sidelines in this country is that pariah - nuclear power.
Like many of you, my life has been colored by the fission of the nucleus - from the first fascinating clues produced by the work of Enrico Fermi under the stands at the University of Chicago, to Hiroshima and Nagasaki, to the contamination of the atmosphere as hundreds of bombs were tested, to the ACuban Missile Crisis,@ to AMutually Assured Destruction,@ to the attempts to stop proliferation, and, finally, to the fact that a significant percentage of the electricity I use today comes from that same nuclear splitting process.
The process became personal for me as I faced the prospect of being a bit player as an infantry rifleman in the invasion of Japan and the thought that my brother, Pat, then in Europe with the 82nd, was slated to be in the first landing wave. And later, in the early years of the Cold War, to live with the very real threat of mushroom clouds, nuclear winter, the devastation of the environment, always bedeviled by Einstein=s comment that World War Three could be fought with nuclear arms but that World War Four would be fought with sticks and stones.
Fortunately, none of those dire prospects came to pass. Instead of a glider or landing craft ride onto the beaches of Japan, I was sent to Stanford, and then several months later, flown with twelve others to the Philippines, where eventually those twelve were sent to Kwajalein for the bomb testing. I was the odd man out, but once again the nucleus had touched my life. And Pat came home with all the others to resume a meaningful and productive life.
Perhaps in contrast to many of you, I believe that Hiroshima and Nagasaki, saved hundreds of thousands of lives, Japanese and American, possibly my brother=s or my own. Plus, a recognition that the decision to use the bombs may have had far more to do with ending the war as quickly as possible to thwart Russia=s long-time goal to redress its losses of 1904 or to avoid confrontation with an erstwhile ally still smarting from our efforts in Siberia from 1919 to 1923 than to save mine or others= lives. And while I=m sensitive to the moral issues and the debate surrounding the bomb=s use, as terrible as they were, which continues to this day, we tend to ignore, in contrast, the total devastation and the loss of hundreds of thousands of lives in the fire-bombing of Tokyo and Japan=s other major cities, let alone the unconscionable destruction and incineration of more than 25,000 in the fire- bombing of Dresden in the last days of the War. Just a few months after Hiroshima the view of that city from the air was a truly sobering and troubling sight, even to an nineteen year old, but it did not exceed what was experienced by driving through miles of Tokyo where nothing stood but an occasional concrete smokestack or the twisted steel skeleton of a factory.
Further, I believe the very existence of the bomb very likely prevented the Cold War becoming hot, when rational heads on both sides of the Curtain realized that neither could win but that they could only destroy one another. By happenstance I was in Berlin the summer of >68 when mobilization was going forward on both sides of the Curtain, triggered by the Czech Spring. And in Kashmir where we met a Canadian UN contingent that was flying the truce line shortly after the fourth India-Pakistan war. That same rationality, I believe, provided the environment for the Cold War to end as a result of political and economic events and keeps bitterly opposed India and Pakistan apart and at peace after fighting four wars in quick succession in earlier years.
But in this paper I would like to explore that other war first mentioned, climate change, one we are losing not only because of ignorance and inertia, but because we are unwilling to use the one weapon that I believe might save us: nuclear power.
What follows reflects my strong bias as an advocate for nuclear power as the best source of base energy in future. I claim no particular expertise. All I can offer is the fact that decades ago I spent short visiting stints at Los Alamos and Oak Ridge and a National Science Foundation funded summer at Yale in nuclear physics.
And I need to admit that my position puts me at variance with others in the environmental movement, my long-standing membership in Audubon, the Sierra Club, Union of Concerned Scientists, NRDC, and Greenpeace, to name several.
Admittedly, there are promising alternatives to fossil fuels other than nuclear, the very popular Arenewables,@ and they should be exploited to their fullest. But they do not come without limitations and significant environmental costs.
Wind has great promise and is a growing source of energy. A few countries, namely Denmark, and to a lesser extent Germany, produce much of their electrical energy from wind. The US has significant potential and installed turbines make a growing contribution. Today, six mid-country states get more than ten percent of their electricity from wind. But all is not benign. Sites in many areas, especially the west, are in mountain passes, migratory pathways for birds. A 2009 definitive study of bird mortality at Altamont Pass, for example, determined that, on average, 64 Golden Eagles, among thousands of migratory birds, are killed there each year, a direct violation of the Migratory Bird Treaty Act. Aesthetic concerns can be an issue. Witness the fierce fight ongoing over turbine placement in Long Island Sound off Martha=s Vineyard. Plus, the best sites are most often located distant from consumers, making transmission corridors into battlegrounds. Wyoming=s current proposal of wind power to provide a major fraction of California=s mandated thirty three percent renewables has been met with a cool reception by the Brown administration and state labor groups as well as questions about the response of Utah and Nevada to the necessary transmission pathways. And importantly, as critics point out, mid- afternoon one day last month California=s winds were so light that just 33 megawatts were produced, less than one percent of the 4,000 megawatts of installed capacity.
Roof-top solar makes eminent sense and is a large contributor in many nations, including often cloud-covered Germany and Japan. But large scale solar, once the darling of the environmental community, is now meeting resistance from those same groups over the negative habitat impacts, the considerable demand by the thermal facilities for cooling water in areas deficient in the resource, the carpeting of tens of thousands of acres with mirrors and the impact of the thermal radiation of the towers. The issue of transmission from remote locations, often across environmentally sensitive lands, has pushed developers into and on the fertile lands of the San Joaquin Valley, with more than 40,000 acres now in the permitting process, with tens of thousands more proposed. Planners estimate that the impact on the valley=s $30 billion agricultural output will be more severe than the massive loss to residential development in recent decades. Plus, as with wind=s diurnal and seasonal variability, solar is limited by cloudiness and hours of daylight, as well as output not matching peaking of demand.
While a few countries (e.g. Japan) have abundant geothermal sources, they have not been as successfully exploited as one would assume. Italy and New Zealand have some limited development. The Geysers is the only facility of note in the US. Steam temperatures lower than needed for power generation, degradation of the heat source over time, corrosion of plumbing, transmission, all are issues. And with some, such as the hot water facility operating in the Imperial Valley, waste disposal of its concentrated brine is a growing environmental problem. The brine, containing, arsenic and radon among other dangerous elements, is evaporated to a filter cake, whose depository is approaching 500,000 cubic meters in volume.
Hydro in countries rich in the resource, especially, China, India, Brazil and Turkey, is being developed at a rapid pace. But as we=ve discovered in the American west, it comes at a high cost, and not only to the natural environment. Lakes Mead and Powell, together, evaporate more than two million acre-feet of water a year, enough for four million households in a water-starved region, an economic loss of increasing concern. Plus, the resulting concentration of salts in the lakes= waters degrades whatever soils that water is used on. Serious suggestions have been made to impound all the water in Lake Mead and make Powell a peaking facility for flood flows, which would have the dual benefit of reducing evaporative losses as a consequence of creating a smaller surface area while at the same time increasing the hydraulic head at Hoover, which has fallen critically low in recent years of drought.
In all, with the above issues in mind, there is majority agreement among those knowledgeable of the problem, especially when world population is anticipated to grow another two billion by the turn of the century, that to maintain our standard of living while improving the lot of those in developing countries, renewables must be supplemented by some form of base power, at least through the next critical decades.
Must we, then, as the fossil fuel industry insists, continue on our current path toward changing the earth=s climate, compounding the problem we=re trying to solve, to meet our civilization=s energy demands with consequences the cost of which we=re just beginning to appreciate? Let alone that needed to provide for the billions more of us to be here before the end of the century?
To me it appears that nuclear is the only viable option and the one source immediately at hand that has the capacity to do the job.
Unfortunately, fission=s negative image problem burdens its potential development, driven by a public perception that at any time a reactor might suffer a Ameltdown,@ a consequent explosion resulting in a Amushroom cloud,@ thousands, if not millions of deaths, both immediate and from cancer, leaving the environment lethally contaminated forever.
But let=s take an objective look at the record.
In the thirty two countries where civilian nuclear power has been used there have been just three significant Aevents@ or accidents in the more than 15,000 cumulative years of use. Each incident has generated a wide spread negative response to nuclear power. But what does the record tell us?
The first accident was in our own backyard, Three Mile Island in Pennsylvania in 1979. Caused by human error, it resulted in a partial melt down and severe damage to one of the two reactors. But radiation was confined to the containment structure. There was no explosion or radioactive cloud. No one was killed and there is no statistical evidence that the incidence of cancer or non-malignant disease in the surrounding population is greater than historic norms for the region.
Then came Chernobyl in 1986. Unlike western designs, the reactor was moderated by graphite, a design not unlike Fermi=s pioneering, experimental facility. There was no containment structure, as used in the West. The runaway event, caused by deliberate operator actions, resulted in the graphite burning, with the smoke from the fire blanketing much of northeastern Europe. The radioactive cloud dispersed over the entire northern hemisphere, while accompanying rain deposited significant amounts of radioactive material on Ukraine, Belarus and Poland. Two workers were killed in the accident and 134 emergency personnel were exposed to acute radiation syndrome (ARS), which proved fatal to 28 of them. Among the thousands of surviving emergency workers another several hundred also developed ARS. As of the 2010 UN report on the accident, all are alive more than two decades later, and only 28 of that group were still being clinically treated. While the UN 2010 report lists 6,000 cases of thyroid cancer among the region=s population who were children or adolescents at the time, it=s a statistic, the UN report speculates, that could be inflated by the intense and massive screening effort carried out after the accident.
The third was Fukushima=s triple melt down in March 2011. All of Japan=s nuclear plants were shut down as a result. Other countries began re-thinking their efforts in nuclear power development. But what have we learned since the event? Officials at TEPCO, Tokyo Electric Power Company, admitted last October that they did not take early emergency measures which would have prevented the event Aout of concern for permanent damage to the facility and the fear of inviting lawsuits or protests against its nuclear plants.@ Also, it needs to be noted that the tremendously powerful earthquake caused the Fukushima facility to shut down, safely and without incident. But the destruction of the electric grid robbed the region of power. The back-up diesel generators kicked in, restoring power to the pumps. But the design flaw of placing them in the basement behind a sea wall vulnerable to the massive tsunami that followed, led to the disaster. As a result, radioactive material has contaminated both land and sea water. The government has banned the sale of food produced within 30 -50 kilometers of the plant. But, again, as at TMI, no workers have died and predicted cancer deaths due to accumulated radiation exposures in the nearby population range from 0 to 100. In June 2011 the IAEA reported thatA....to date, no health effects have been reported in any person as a result of radiation exposure.@
But to put these three incidents in context one needs to recognize that these facilities were designed and built many decades ago and their flaws have taught important lessons for current design and placement.
And in spite of myth, nuclear contamination has a limited life. Fukushima and Chernobyl both contaminated swathes of land with Iodine 131, Cesium 134 and 137. Iodine has a half-life of eight days, Cesium 134, 28 years and 137, 30 years. Thus, many of the thyroid cases from Chernobyl could have been prevented had contaminated fresh milk not been fed to children. Poland avoided the impacts caused by ingestion of milk from cows grazing on pastures contaminated by fall-out when the US shipped in large quantities of powdered milk for that purpose. And rather than passively waiting out the decades for Cesium decay, there are binding techniques that can be applied. Importantly, the 2010 UN report concludes that the average cumulative radiation dose from 1986 to 2005 to the estimated 5 million inhabitants of the three Soviet republics affected by Chernobyl was about equivalent to a CAT scan in medicine. Other than the 6,000 cases of thyroid cancer cited above, traceable to the ingestion of iodine contaminated milk by children and infants, the UN report concludes that, A....there is no evidence of major public health impact two decades after the accident. There is no scientific evidence of increases in overall cancer incidence or mortality rates or in rates of non- malignant disorders that could be related to radiation exposure.@
While it is too soon to measure the impacts of Fukushima, there is no reason to believe that they will be much different. In both cases a few people never left the area. Today, Just two years later, much of the area around Fukushima has radiation levels lower than background in some areas of the US. Most of the region affected by Chernobyl has been resettled, and Chernobyl, itself, has become a highly publicized and frequented tourist site.
Not to in any way minimize the damage and losses from Fukushima and Chernobyl, what have been comparative costs of other sources of energy in the same time span?
Data for the period 1969 to 2000 in western developed nations as reported by the IAEA, reveal the following: Coal caused 157 deaths per TeraWatt year of electricity generation, natural gas caused 85. There were 3 for hydro and 0 for nuclear. These numbers do not include the deaths of an estimated 19,000 Chinese coal miners, or the 230,000 killed overall in the Henan, China dam disasters or the thousands of others killed, but unreported, in developing countries.
These numbers leave unmeasured and unmentioned the multitudes whose health has suffered from exposure to the combustion products of fossil fuels or the indirect impact of that burning through global warming which killed untold thousands in heat waves in Europe, floods in China, Pakistan and Mozambique.
Nor do they include the economic and environmental costs of such disasters as the Exxon Valdez or the explosion of BP=s platform in the Gulf.
Also, left unsaid in all this are the impacts resulting from the acidification of lakes downwind from coal fired plants, and the degradation of waters as a human food source by the mercury emitted from those same plants. Or, most importantly, the acidification of the oceans as the CO2 from the burning of fossil fuels is absorbed, with consequences that are yet to be understood and measured.
While the costs of those long-term impacts are yet to be determined, the human, economic and environmental costs of the long-predicted severe weather and climate events driven by the added energy accumulating in the atmosphere are self-evident. 2012 was the hottest in US records and the past decade the hottest the world has recorded. Our costs? A record drought over two thirds of the US last year, withering crops, placing unprecedented demand on the grid, dropping river flows to the point that goods transport became threatened and leaving the upper Great Lakes their lowest on record. And Super Storm Sandy, driven by distortions in the Polar circulation, abetted in its massive devastation by a rising ocean level, resulted in the loss of habitability and economic use in areas affected by the surge.
Sandy=s cost, excluding the human toll and suffering, is a just authorized $62 billion of our tax dollars and the drought, with its effects continuing to impact the economy, is estimated to be several hundred billion.
Events of this scale we must anticipate as a multibillion dollar annual cost to the economy, a cost that will continue to increase as climate change intensifies. A cost, a portion of which, we all are now bearing, as re-insurers push rates higher to compensate for their increased exposure.
In light of all of the above, I believe that nuclear energy generation is the only near-term source of the necessary base power to maintain the world economy and provide for its inevitable future growth while slowing, and hopefully reversing the degradation of the earth=s climate.
What is available to us now?
The US and most of the world depends upon the PWR (Pressurized Water Reactor) that was first developed by the pioneering work in the >50s of the Navy, which was seeking a source of energy for propulsion that would make submarines truly underwater craft, an achievement that was brought dramatically to the public consciousness by the 1955 journey of the Nautilus under the polar ice. Of the 104 reactors currently operating in the US at 65 sites, 67 are PWRs, with the remaining 37 a GE boiling water design, which is no longer in favor.
What are the issues, aside from the emotions and fears of the public of the possibility of melt-down, radioactive clouds, wasteland forever lost, cancer? Start-up costs are large and design approval can take years. At the end of the reactor=s useful life dismantling is expensive. Enrichment of the fuel is costly. Any thermal energy plant, whether fossil fuel fired or nuclear, requires large amounts of cooling water. Every three years, on average, a PWR civilian reactor must be shut down for replacement of one third of its fuel. Storage or disposal of the spent fuel is both expensive and an environmental problem.
To address those issues one at a time.
First, to the emotional. Over the more than half-century of nuclear power in this country, no one has died from a nuclear accident or event. And there is no statistical evidence that cancer or other non-malignant diseases are more common in areas where the plants are located. The navy operates 120 ships, including submarines, powered by nuclear reactors operating with cores enriched to as high as 90+ percent, many times that in civilian units. Through all the years, beginning in 1955, of the navy=s use of nuclear propulsion, there is no statistical evidence of increase in disease over that expected in the common population among the tens of thousands of sailors who have lived in close proximity to those reactors over extended periods of time. Ironically, many of those opposed to nuclear power have no qualms about sending their child to sea to live within a few feet of a reactor, or having a nuclear powered ship like the Enterprise, with its eight reactors loaded with highly enriched uranium, cooking away in its innards while tied up at their waterfront.
In assessing the risks and potential problems we face today, we need to remember that all 104 US civilian reactors currently operating were designed and most completed by 1974, thirty nine years ago. Think back to the technological advances in all facets of our lives that we have seen in that same period of time. Those enormous strides over that span have included many in nuclear physics, biological response to radiation and to reactor design.
Further, what do we really know? Hiroshima and Nagasaki have been thriving cities for decades, the capitals of their prefectures. Astronauts that were exposed to radiation unblocked by the earth=s atmosphere evidence no greater mortality than the general population and at least one study of radiologists and radiological technicians found that their health and mortality outcomes were statistically better than average. In the areas of the earth=s surface where radiation is many times that of general background, residents evidence no greater health problems or mortality than normal. The individuals who refused evacuation and remained near Chernobyl continued to live healthy lives through the decades following the accident. And those who returned to the near vicinity of Fukushima immediately after the tsunami remain in good health. It is now known that the psychological trauma associated with anything nuclear has far greater impact than any physical effects directly attributable to the event itself.
As to the valid issues:
Startup costs are large, but standardization on a design, such as the new Westinghouse AP1000, could cut development costs significantly. The time costs in gaining design approval would be obviated. In contrast to older designs, the AP1000's safety systems areAall passive using gravity, natural circulation and compressed gas. No pumps, diesels, generators, chillers are used, resulting in 50% fewer valves, 83% less piping, 87% less control cable, 35% fewer pumps and 50% less seismic building volume.@ All of the above yield a reactor unparalleled in safety, at costs and scheduled completion a fraction of older designs. Four are now under construction in China with a scheduled completion three years from ground-breaking
Reactor dismantling costs are significant, but useful life, through re-licensing can be extended by decades. Other than some parts of the reactor, itself, most of the resulting debris has radioactive levels not significantly above background.
Any device that converts thermal energy into electricity through the Rankine Cycle must have a source of cooling, whether it be the radiator in our car or a power plant. Large units must be sited close to sources that have that cooling capacity, typically a lake, a large river or the ocean. Our near neighbor, Edison=s Mountain View Power, located far from these sources, evaporates millions of gallons a day of Redlands effluent from the city=s wastewater treatment plant. Nuclear reactors use neither more nor less than fossil fuel plants of comparable size, although experimental designs are in planning using air and helium.
A problem of great and controversial concern is the disposition of the waste, spent fuel, which still contains in the order of 95 percent of its original energy value. Other than storage in huge casks or buried in places like Yucca Mountain, or as the Canadians propose in the ancient rock of the Canadian Shield, it could become a reconstituted energy source. Breeder reactors, which are limited only by government policy concerns about nuclear material falling into the wrong hands, could reprocess the waste now stored at nuclear facilities and produce enough reconstituted fuel for another century at the current rate of use. But there=s another option that obviates those threats and fears. The Canadian CANDU reactor, of which more later, can operate on that spent fuel, wringing more energy out of the Awaste.@
A bit about waste fuel and the often expressed fear that terrorists could make it into a bomb. Civilian reactors create not only plutonium 239 (Pu239), the stuff of bombs, and which constitutes a secondary fuel in the reactor process, but also a second isotope of the element, Pu240, which has the effect of a contaminant, making the spent fuel a poor candidate for bomb making. The two isotopes have nearly identical mass, which makes their separation exceedingly difficult and expensive. In military reactors designed to produce PU239, the by- product PU240 has found use as the energy source for thermo-electric generators in space probes and other applications where power is needed in remote locations
Enrichment of reactor fuel from the natural ratio of U235 to U238 of 0.07 percent to the needed 3 to 5 percent needed by civilian PWR reactors is a significant cost. The US for decades depended on the gaseous diffusion process to separate the isotopes, which required a huge facility. That has been replaced by more modern and efficient centrifuges, reducing the cost. Plus, the process is not an easy one. The Iranian attempts at enrichment have been a complex story, with different players in the arena coming to very different conclusions about its status.
Those prohibitive costs of enrichment led Canada in the 1950s and 1960s to design and develop a reactor that would operate on natural, unenriched fuel, the CANDU (CANada Duerterium Uranium) reactor. Its development is considered one of Canada=s ten most important technological achievements (the invention of the telephone, for example, is one). Its ability to use unenriched, natural fuel, coupled with its safety, dependability and performance make it an attractive design to a number of nations that have licensed its use. Twenty two are operating in Canada, one complex of which is the largest civilian nuclear power facility in the world. Outside of Canada there are one each in Korea and Argentina, and in the 60s Canada supplied
one to Pakistan and two to India. Five more are under construction, three in Korea and two in Romania.
I first heard of the CANDU design in the summer of 1969. I was at Queen=s in Kingston working with a group of graduate students and they, as well as the physics faculty, were excited about the reactor just down the lake. The claim was made that it was producing power at an operating cost of six mills per kilowatt hour, an impressive achievement, if true. The Canadians had finessed the need for enrichment of fuel, a hugely expensive and difficult task. But they had traded that for the difficult and expensive task of producing heavy water (D2O). A new plant at Glace Bay, Nova Scotia had severe problems, and when I visited there it was about to be shut down. I was back at Queen=s in >71 and again in >74. By then the CANDU program was well on its way, and I learned its intriguing story.
As with the development by the navy of the PWR in the 1950s, Canada=s nuclear program grew out of its Ministry of Munitions and Supply=s 1943 request to Britain and the US to move to Canada the heavy water and uranium dioxide research then being done at the Cavendish Laboratory at Cambridge, which resulted in the 185.5 kilograms of Norwegian heavy water - the only heavy water in the world at that time.- being transferred to Canada.
Some may recall the story of the Norwegian=s daring and successful sabotage which thwarted the German effort to seize the water. Had the Germans been successful the story of nuclear energy and of WWII might have been radically different. They had tried moderating the neutron flux with graphite, but their graphite was of insufficient purity with contaminants that poisoned the process. Their only alternative was heavy water.
As we all learned in high school, there are 92 elements that occur in nature identified by the number of protons in their nuclei. A given element can consist of nuclei with differing counts of neutrons, called isotopes. Every element has at least one unstable isotope, which, over time, decays to a stable nucleus or into another element over a well-defined time scale, its half-life. The current ratio of the isotopes of some indicator elements has been valuable in dating the age of the earth, organic matter, the deposition of snow, among many others. And the three kinds of emissions accompanying the process have proved valuable in medicine with applications such as the implantation of alpha emitters targeting tumors, the beta radiation from cobalt 60 for treatment, the ingestion of iodine 131 for imaging.
But the generation of nuclear power is restricted to a small family of heavy element isotopes which have the unique ability to be split into two smaller, approximately equal nuclei. They are said to be fissile. The light, naturally found isotope of Uranium, U235, has ideal characteristics for this purpose and is the reactor fuel of choice.
In the fission process the U235 nucleus absorbs a neutron, changes to a short-lived U236, in the process changing its shape from a sphere to a dumbbell, and then splits into two roughly equal pieces (e.g. Iodine131 and Cesium 134) while releasing two or three neutrons and gamma radiation in the process. The kinetic energy of the nuclear fragments and the neutrons, plus the electromagnetic energy of the gamma rays is then captured by a moderator as heat. In simplest terms this heat is used to boil water, the resulting steam to drive a turbine, which, in turn, drives a generator. Put another way, power reactors are just gigantic boilers, differing only from coal or gas fired plants in the source of energy.
The key to power generation is making this process both repeatable and controllable on a massive scale. This can only be achieved by assuring that some free neutrons, on average one per fission, will be captured at a determined rate, which is achieved by slowing it down through collisions with the nuclei of a substance called a moderator. The slowed neutron, defined as thermalized, then has sufficient time in the presence of a U235 nucleus to be absorbed, causing a repetition of the sequence of events.
Control of the rate of absorption (energy output) is achieved by poisoning the moderator in some way. In PWRs this is done by varying the pressure, which changes the distance between water nuclei, making collisions more or less likely. Also poisons, such as boron in the form of boric acid or control rods are introduced to absorb the neutrons. In WWII Germany=s case it was the boron electrodes used at that time in commercial graphite production that caused their moderator to fail, the reason for which was not understood until after the war.
The CANDU reactor, operating on un-enriched fuel, just 0.07 percent U235 in contrast to the PWR=s 3 to 5 percent, can only sustain operation with a moderator of high efficiency. While light water has a high scattering or slowing efficiency it also has much higher absorption so that the moderating efficiency of heavy water, D2O, is 80 times that of light.
While enrichment is a major and continuing cost for PWRs, the production of heavy water was a stumbling block in the early development of CANDU reactors. D2O occurs in a ratio of about one in six thousand (1/6,000) in ordinary water. Its production is no easy task due to the fact that its chemical activity is essentially the same as light water and its molecule has a mass not much greater. Canada=s first attempt at an industrial rate of production with a $100 million plant at Glace Bay in Nova Scotia, was less than successful, but later work on Lake Ontario yielded enough D2O to create a surplus.
PWR and CANDU reactors also differ in one other important way. Refueling of a PWR requires the opening of the pressure vessel with attendant down time as one third of the now-spent fuel is replaced. To be a base power facility, more than one reactor must be utilized. The CANDU=s fuel is in segments about four inches in diameter and a yard long placed in horizontal tubes that are surrounded by the unpressurized, moderating D2O. This configuration allows the introduction of new fuel and the removal of spent by an automated, continuous process where machines operating at either end of the tubes can either insert or remove segments, eliminating any need for down time.
While other designs such as the pebble bed and fast neutron research reactors hold promise, the rapid and tandem development of PWR and CANDU reactors may well be our best and last chance to halt the degradation of the atmosphere with its resultant climate changes. Together they have the ability to utilize both natural and spent U235 fuel and the CANDU can operate on the enormous untapped reserves of fissile thorium.
Both reactor designs have operating costs lower than coal or oil per unit of energy produced. Most importantly, they emit no greenhouse gases. And their safety record is unmatched.
All we need is the will:
- To accept that all forms of energy production carry costs and risks. Wind and large-scale solar have important impacts on the local environment, including that on prime farm lands. Plus, the controversies and problems of transmission over distances are yet to be resolved. Solar cell manufacture produces large quantities of waste laced with toxic cadmium. Coal, in addition to its mining resulting in the destruction of mountains and valleys, leaves enormous quantities of ash loaded with toxic residues. Gas production now depends upon fracking, a process whose impacts have yet to be understood but are the source of legitimate concern. And the highly inefficient and energy-consuming production of oil from tar sands and the burning of its heavy crude has become an international issue. And certainly not to be ignored are the devastating, continuing environmental impacts of the Exxon Valdez and the BP Gulf disaster.
- To accept the consensus of the scientific community, backed by a growing body of predicted phenomena, that the continued large-scale use of fossil fuels may well spell the demise of our society as we know it, and if its impacts are to be minimized we must act as soon as possible.
- To accept that civilian nuclear power is our only viable source of base power. That reactors will not blow up. That a reactor=s nuclear waste must go through a difficult process to make bomb fuel. That a CANDU reactor can use that waste to make power, wringing another 30 to 40 percent out of the spent fuel, while adding nothing to the waste disposal problem. That America=s PWR reactors are being about fifty percent fueled by reprocessed U235 from thousands of Russian warheads, converting war materiel into domestic, civilian power.
- To accept as well-founded the government=s announced subsidies for the development of small, civilian nuclear reactors. Their potential for supplying power to remote or small population areas, to industries where demand for energy is very high, to applications as small as locomotives, while replacing fossil fuels in those applications, is a step in the right direction. - And further, to accept the consensus of the scientific community that we face not one, but two looming catastrophes - climate change and population growth:
- Climate change with all its threats of violent weather, from massive floods to searing droughts, producing devastating impacts on food production and the loss of large portions of coastal areas to human habitation and use.
- And population growth, which left unchecked, leading to massive migration from regions of limited resources in food and material goods, generating conflicts, destroying the natural environment and degrading the lives of all.
Even if the development of renewables can keep up with the ever-increasing demand for energy, base power must be provided from some source. Developing economies, like India and China whose combined population equals a third of the world=s total, can only achieve our level of material wealth through enormous expansion of their energy sources. Africa, with the world=s most rapid rate of population growth is just now awakening to its energy needs.
Every 1,000 megawatt coal-fired plant not built or replaced by nuclear would prevent another 7 to 8 million tons of CO2 from entering the atmosphere each year. Even the nearby state of art, two cycle natural gas fired Mountain View plant discharges 2.7 million tons of the greenhouse gas annually
Climate models suggest that when CO2 concentrations reach twice pre-industrial age levels, about 1.5 trillion tons, the atmosphere will warm by 4 to 4.5 degrees Celsius, with resulting sea level rise inundating coastal areas where a major fraction of the world=s population lives while adding enough energy to the atmosphere to change its dynamics with increasingly severe weather and climate events in food producing areas.
If we can slow and hopefully stop this degradation of the atmosphere with nuclear and renewable energy sources coupled with all feasible applications of conservation, while at the same time providing the energy needs of the emerging economies, we may well solve the second threat of world population exceeding the planet=s resources.
In every society where the availability of food and production of goods has matched or exceeded its demands, population growth has stopped and reversed. Birthrates in the US, Japan and Europe are below replacement. In rapidly developing economies, like Brazil and Mexico, birthrates are dropping and there is no reason to believe that it will not continue to be the case everywhere.
What better future for the human enterprise to strive for, no matter how wildly optimistic it may be, if we could come to a steady state balance with the earth=s resources, honoring its gifts and beauty, while providing each individual the resources to enjoy a rich and meaningful life.
I believe we cannot achieve even a part of that goal, absent a major application of nuclear power as soon as practical.
We cannot stand idly by, selfishly exploiting the earth=s gifts, robbing those that follow of what was given to us. We, living today, could well determine the future habitability of this fragile blue orb. Stewards we must be, else why our being.