Thorium is the 36^th most abundant element on Earth. It is four times more abundant than uramium. There has been no concerted international effort to exlplore for deposits thorium ores. Accurate estimates of world reserves of thorium are not available.  Known thorium deposits could supply a major part of the Earth’s energy needs for hundreds of years. Some estimates are as high as 1000 years at current world energy use. There are deposits of thorium in Australia, Brazil, Canada, Greenland, India, South Africa and the United States.

            In the U.S., it is estimated that there are 300,000 tons of thorium ore, half of which is easily extractable. The 150,000 tons that are readily available are equivalent to about 1 trillion barrels of oil. This is over 5 times the estimated oil reserves of Saudi Arabia. Two companies currently have major thorium ore claims, one in the mountains on the border between Idaho and Montana and the other in the Pea Ridge area of Montana.

           The most common thorium ore is a phosphate ore called monazite which can contain up to 12% thorium. The known reserves of monazite are esimated to be up to 1.2 million tons. Two thirds of these reserves are in heavy mineral sands on the south and east coasts of Indian. Monazite ore also contains important strategic rare earth metals such as creium, lantahnum, neodymium, yttrium and iridium.

Currently thorium is considered a waste product of processing of rare earth metals. It is thrown away with the rare earth mine tailings. The U.S. has recently imported thorium from France that was produced as a by-product of rare earth ore processing.

          There currently over 3000 metric tons of processed thorium nitrate buried in the Nevada dessert at the Frenchman Flats area of the Department of Energy site. This material was generated by the U.S. nuclear program between the years of 1957 and 1964. It was contained in 21,000 drums which were buried in pits with twenty feet of soil over them. This thorium could conceiveablely recovered and used to create nuclear fuel to jump start a thorium reactor program.

           It is difficult to estimate the ultimate cost of thorium as a fuel supply for nuclear reactor. It is not currently being mined for fuel but there are known bodies of ore that could be easily exploited. Thorium would be much less difficult and expensive to process than uranium because the naturually occuring thorium is mainly one isotope and does not have to be enriched. This means that one ton of thorium can produce the energy of 200 tons of uranium. In addition, the rare earths that can be recoved during thorium mining and processing are valuable and would lower the cost further.

Thorite ore from Ontario: 

   

           I have already written about thorium under the general subject of nuclear reactors. I have decided to cover thorium in more depth because of its possible use as a nuclear fuel.

          Thorium is a radioactive element with the symbol Th and the atomic number 90. It was discovered in 1828 by the Swedish chemist Jons Jacob Berzelious. The element was named for Thor, the hammer wielding Norse god.

         Thorium is a silvery-white metal that is soft and ductile. It oxidizes slowly and the chemical properties are strongly affected by the degree of oxidation. Powdered thorium is pyrophoric which means that it can spontaneously burst into flame when exposed to open air. Thorium can form compounds with oxygen, hydrated nitrogen and fluoride, carbon, and phosphate.

         Thorium has 33 isotopes, all of them radioactive. They range in atomic weight from 209 to 238. Their half-lives vary from Th-220 at 9 millionths of a second to Th-232 at 14 billion years, about the current age of the universe. Six of the isotopes of thorium occur in nature, mostly Th-232. Traces of Th-230 occur as a result of the decay of U-238. Most isotopes of thorium emits positrons and decays to radium. In rare cases some isotopes emit alpha particles and decay to actinium.  Th-232 can decay to radium, uranium, ytterbium and neon. Isotopes above 232 emit electrons and decay to protactinium-233. When bombarded with a neutron source, Th-232 can absorb neutrons and then decay to protactinium. Protactinium in turn decays to uranium-233.  

          Natural thorium is found in most soil and rock on Earth. It about four times as abundant in the earth’s crust as uranium, three times as abundant as tin and about the same abundance as lead. It occurs in several minerals including thorite with oxygen and silicon, thorianite combined with oxygen and monazite which is a phosphate mineral containing rare earth metals. Rare earth metal mining and extraction produce thorium as a byproduct.

           A common use of thorium was as a component in alloys such as a magnesium alloy called Mag-Thor that was used in the aerospace industry for engines because of its stability at high temperatures. It has also been used in electronic applications and welding rods.  Thorium dioxide has a very high melting point and was used in the mantles of gas lamps and as an additive for high temperature ceramics and laboratory glassware Recent concerns over radioactivity have ultimately made thorium and thorium dioxide unattractive for these application.

          Breathing large amounts of thorium dust has been shown to lead to lung disease or lung cancer. Thorium in the bloodstream can cause liver cancer, pancreatic cancer, leukemia, bone cancer, kidney cancer, and cancer of the spleen. Being around mining and processing facilities for uranium, phosphate or tin ore or nuclear waste can result in thorium exposure. Injection of thorium compounds for contrast enhancement in x-rays has been shown to be a health threat.

Thorium crystal:

          Polonium is a chemical element with the symbol Po and an atomic number of 84. It was discovered in 1898 by Marie and Pierre Curie and named after Poland where Marie was born. They removed uranium and thorium from pitchblende ore and discovered that the ore became more radioactive. Polonium was the first new radioactive element they discovered in the processed ore.

          Polonium is metallic and related bismuth and tellurium in the periodic table of elements. All the compounds containing polonium have been created in laboratories. It can be combined with hydrogen, oxygen, the halides, carbon, nitrogen, sulfur and other elements.

          Polonium has no stable isotopes, all 33 of its isotopes are radioactive. They range in atomic weight from 188 to 220 with half-lives varying from 115 nanoseconds for Po-205m4 to Po-102 years for Po-209. Most of the isotopes decay to lead by emitting an alpha particle. Rarely, polonium isotopes decay to bismuth via beta particle (positron) emission.

          Polonium is very rare because of the rapid decay of most of its isotopes. Approximately one tenth of a milligram will be found in one metric ton uranium ore. Po-210 with a half-life of 138 days is the most common isotope.

          Polonium can be extracted from uranium ore but it is difficult and expensive. Commercial polonium is created by bombardment of other elements in nuclear reactor which then decay to polonium. One of the major uses of polonium is in static eliminators. Foils which contain polonium are used in production equipment for materials whose production is accompanied by the generation of static electricity. It is also used to remove particles in clean rooms for the production of computer chips. Polonium is combined with beryllium to make sources of neutrons. Polonium has been used in thermionic power generators for satellites.

          Polonium which is ingested or inhaled is eliminated from the human body via feces. A small amount of inhaled polonium remains in the lung. About half of the portion which remains in the body tends to accumulate in the spleen, kidneys and spleen. The rest is found in bone marrow and distributed throughout the body in the blood and lymphatic fluid. The alpha particles emitted from polonium can disrupt cell structures, tear DNA strands, damage DNA and cause the death of cells.  Ultimately it can injure major organs, the immune system and cause death.

         There is no real danger from naturally occurring polonium. Proper handling will minimize the danger associated with commercial use. But there is a unique danger from man-made polonium because it has been used as an assassin’s weapon for eliminating political enemies. A piece of polonium the size as a grain of salt can kill an adult human. By mass, polonium is about 250,000 times more poisonous than hydrogen cyanide, a well known poison. A lethal dose would never be tasted or smelled when ingested or inhaled. Since it is hard to diagnose if you are not looking for radiation poisoning and the illness takes time to develop, it may escape detection.

        Alexander Litvinenko was a officer in a Soviet security service who fled to England and received political asylum. He cooperated with the British intelligence services and wrote books about conditions in Russia. In 2006 he suddenly fell ill and eventually die. It was determined that he had been poisoned with polonium by Russian agents.

        The theory had been advanced that Yasser Arafat of the PLO was killed by polonium poisoning. Traces of this rare element have been found on his personal effects and there have been requests for an exhumation of his body so that an autopsy can be performed. If his death was murder, there are several suspect organizations which would have benefitted from his death.

          Alexander Litvinenko picture from codkaxorriyadda.net:

There are many arguments against the use of nuclear reactors to generate electrical power. A few of the major objections are listed below.

1. Risk of accidents. If everything and everyone at a nuclear plant work perfectly, nuclear power is a safe source of electricity. Unfortunately, we don’t live in a perfect world. Most of the worlds reactors are being run safely but there have been many minor and major problems with equipment, oversight, human errors, reporting, leaks at many nuclear power plants. Fortunately most of these did not result in serious threats to the environment or human life but there were a lot of close calls.
2. Lack of a permanent solution to accumulating nuclear waste. A number of different techniques and locations have been proposed for the permanent safe storage of nuclear waste. None of these have been implemented. An expansion of nuclear power would add to the existing body of nuclear waste.
3. Lack of agreement over available world supplies of uranium. Uranium is a common element and there are many different deposits of various grades of uranium ore. However, there has been no agreement on how much uranium is available to fuel the worlds reactors. Estimates based on complex variable range from only 25 years worth to hundreds of years of potential fuel.
4. Nuclear energy is not as cheap as has been claimed. Costs of transport and storage of fuel and waste as well as insurance to cover accidents are not usually included in the costing of nuclear power. Governments are using tax dollars to pay for these services to the nuclear industry.
5. Nuclear energy is slowing a transition to renewable energy sources. As long as the idea of a massive plant burning expensive fuel is attractive to energy suppliers, there will be a lack of urgency in transitioning to alternative energy sources. There is a real competition for dollars, subsidies and tax breaks between nuclear and renewable energy sources.
6. Liability of nuclear power plant operators is limited for accidents. In the United States and other nuclear countries, there are caps on the total amount of payments an operator will have to make in case of a major accident. All responsible experts agree that these caps are far too low to cover the cost of clean-up of a disaster like Fukushima. Taxpayers would be on  the hook for the additional costs.
7. Nuclear power produces carbon dioxide. While the actual operation of a nuclear reactor produces very little carbon dioxide, When considering the whole life cycle of mining, refining, plant construction, fuel burning, waste storage and disposal and power plant decommissioning, nuclear power does add to human carbon dioxide generation above the level of renewable.
8. Lack of sufficient graduates in nuclear science. Due to the negative press of nuclear power and the lack of new plants being built, universities are not graduating enough nuclear engineers to design, build and operate future reactors.
9. Nuclear power can pave the way for nuclear weapons. Development of peaceful nuclear power generation can provided equipment and expertise that can be turned to the production of nuclear weapons. The world needs fewer nuclear weapons, not more.

No Nukes sign from Sodahead.com:

          The debate over the benefits of nuclear power versus the problems of nuclear power has raged for decades. Some of the basic pros and concerns with them are listed below.

1. Nuclear power generation emits very little carbon dioxide into the atmosphere and so does not contribute to global warming. Even including the whole life cycle with mining, refining, power generation, disposal of waste and decommissioning of nuclear power plants, nuclear power produces far less carbon dioxide per kilowatt hour of electrical power than fossil fuel power plants. On the other hand, wind, solar, hydro and geothermal may ultimately produce even less carbon dioxide and they do not produce waste.
2. Nuclear power plants produce less radiation than we are exposed to in our natural environment. This claim is based on the proper operation of a nuclear power plant. It does NOT include radiation given off by mining, refining, accidents and waste storage and disposal which are a real threat to the environment.
3. A nuclear power plant does not generate pollution like coal and oil fired power plants. This is true for complex hydrocarbons, particulates, sulfur and mercury produced by burning coal and oil for power. On the other hand, any accident which results in the release of radioactive materials poses a very serious threat to the environment and people living near the plant.
4. A single nuclear power plant generates a great amount of electricity. The problem with this is that concentration of power generation in one location makes the power supply vulnerable to natural disasters or intentional attacks. It also requires that the power grid be able to transmit the electricity long distances to where it is needed which results in significant transmission losses.
5. With respect to deaths directly attributable to a major source of energy, nuclear power has a very good record. From 1970 to 1992, there were 342 deaths from coal per terawatt per year as opposed to 8 deaths from nuclear energy per terawatt per year. The problem with this analysis is the fact that cancers can take decades to develop so the real death number from nuclear energy use may be much higher than this particular study indicates. In addition, a single serious accident could kill hundreds or thousands of people. Accidents at fossil fuel plants do not have this level of danger.
6. In terms of cost per kilowatt hour, nuclear is cheaper than coal and oil and much cheaper than wind and solar. This may be true for the moment but the cost of nuclear power is unlikely to go down and the cost of wind and solar is steadily dropping. In the near future, the cost per kilowatt hour for wind and solar will be much less than nuclear.
7. Nuclear power can operate around the clock unlike wind and solar. While technically true, there are systems under development which will store energy from wind and solar and feed it to the grid when energy production drops.
8. The world has an insatiable appetite for electricity which only nuclear power can satisfy economically. Given the estimates of the costs of the recent Fukushima disaster and fact that Fukushima Unit 4 threatens the entire northern hemisphere, this is a highly questionable argument.

Susquehanna nuclear power plant:

          The human race has an insatiable appetite for energy. Since harnessing fire many thousands of years ago, humanity has developed new ways to power civilization. Fortunes have been made, wars have been fought and great harm has been done to the environment in the quest for energy.

         For most of human history, energy was obtained from the plants and animals in the natural environment. Whole regions were denuded to provide wood for fires for warmth and cooking.  Animals were domesticated and bred to provide transportation. Some humans enslaved others to provide the energy needed to build and run civilization.

        The development of coal and oil as sources of energy have had a huge impact on the world in the past several hundred years. Destruction of the environment and terrible pollution followed. Now we are faced with global warming caused we are told by the injection of huge amounts of carbon dioxide into the atmosphere by the burning of fossil fuels.

        In the last century, radioactivity was discovered and explored. Fierce weapons of enormous destructive potential threaten human civilization. Reactors were designed and put into service to provide electrical energy. A great deal of resources and technology were dedicated to boiling water for steam turbines. Again, destruction of the landscape and pollution of the environment have been a result of the use of nuclear power. In addition, there is a danger of terrorist attacks on nuclear installation and nuclear accidents.

         There is now a push to develop sustainable sources of energy that do not lead to environmental devastation, pollution, scarce supplies and threats of terrorism. Wind, solar, geothermal and tidal energy systems have been developed. The primary argument against their widespread use is that they are not efficient enough or cheap enough to solve our energy needs. The counter point has been made that if the fossil fuel and nuclear industries did not receive huge government subsidies and tax break, the alternative energy sources might already be competitive in price.

        In addition, it has been pointed out that if vehicles were more efficient in miles per gallon and if buildings were better insulated, there would be a smaller need for new energy supplies. An additional benefit would be the creation of millions of new and badly needed jobs.

        There is an argument being made that nuclear energy is the best alternative to a continued reliance on fossil fuels. Issues such as reduce carbon dioxide emissions and reduction of other types of pollution as well as reduced dependencies on diminishing world oil supplies are being discussed.

         In future posts, I will discuss the pros and cons for nuclear energy and try to bring some clarity to the current discussion.

The original energy source:

          Southern California Edison (SCE) owns and operates the San Onofre Nuclear Generating Station one the Pacific Coast between Los Angeles and San Diego. The station is located next to the Cristianitos fault which is listed as inactive. Around 7.4 million people live within 50 miles of the plant.

          The Unit 1 reactor was a first generation pressurized water reactor that came online in 1967. It was decommissioned in 1992 and dismantled. It is now used to store spent fuel rods.

          The Unit 2 and Unit 3 reactors are also pressurized water reactors. They were commissioned in 1982 and their licenses are set to expire in 2022 giving them 40 year life spans.

           There have been technical problems at the plant over the years of operation. In 2008, the plant received multiple citations for such issues as failed emergency generators, improperly wired battery systems, and falsified fire safety records. A review in 2011 suggested that there had not been sufficient improvement in the area of human performance. Many anti-nuclear protests have been held at the station.

          In January 2012, a break in a pipe that carries radioactive water for the Unit 3 reactor resulted in the release of a small amount of radioactive steam. SCE stated at the time that the radiation that escaped posed no threat to the workers at the plant of people who lived nearby.

          When the steam pipes for the Unit 3 reactor were examined, it was found that they had sustained unexpected damage and the Unit 3 reactor was then shut down.

           The Unit 2 reactor was shut down for maintenance in January and it was found that many of the tubes were also worn but not as seriously as the piping of the Unit 3 reactor. that service were found to have unusual wear.

          It was eventually determined that a faulty computer analysis program had resulted in a bad design for the steam pipes that service the four steam turbines. There will need to be a lot of work on the piping system before the reactors can be restarted but no plan has been presented for how to accomplish this work.

         The initial focus is on repairing the steam pipes for Unit 2 which have less damage than the Unit 3 pipes. No schedule has been announced for the repairs to Unit 2 and there has been no estimate of when it may be started again.

         SCE has just announced its intention to remove the fuel rods from the Unit 3 reactor and move them into storage in September. This will make repair of the piping system easier but it will also mean that the Unit 3 reactor will be off line for a longer time. Removing the fuel from the reactor will incidentally reduce the number of inspections and tests that must be performed as required by the Nuclear Regulatory Commission.

         SCE had previously announced that it is laying off part of its workforce. In view of the fact that this will leave fewer personnel to carry out necessary work, it makes sense to remove the fuel and reduce the work load at the plant.

           The adverse effects of ionizing radiation on human health have been extensively studied. I have included information about what damage radiation can do in human bodies in other posts. Recent research indicates that there may be more biological damage caused by uranium than previous thought.

          “Uranium binds strongly to DNA. This has been well known and described in the peer review literature since 1962.” (see references below) Uranium oxide is chemically similar to calcium which stabilizes the phosphate backbone of the DNA. Therefore, if uranium is in the body, it will tend to be concentrated in the DNA.

          In 2002, a study was published in the Journal of Inorganic Biochemistry, Vol. 91, Issue 1, Pages 246-252 by A.C. Miller et al in the Applied Cellular Radiobiology Department of the Armed Forces Radiobiology Research Institute. They found that depleted uranium is an efficient catalyst for causing oxidative DNA base damage as a result of it’s chemical properties. This damage is much greater than any damage caused by its weak radioactivity.

          A research project in 2005 tested the effect of uranyl acetate which is the acetate salt of uranium on mammalian cells. The research was published by Diane Stearns at Northern Arizona University in the scientific journal Mutagenesis, Vol. 20, Issue 6, page 417-423. The researchers were the first to find that there were DNA strand breaks and uranium-DNA adjuncts (compounds) formed after direct exposure to depleted uranium. This can lead to protein replication errors and cancer. They concluded that uranium could be chemically genotoxic and mutagenic and could be dangerous to health beyond usual damage due to radiation exposure.

         French researchers at the Institut de Radioprotection et de Sûreté Nucléaire, Laboratoire de Radiotoxicologie Expérimentale led by C. Darolles published an article in 2009 on depleted versus enriched uranium in Toxicology Letters, Vol. 192, Issue 3, Pages 337-348. They found that while both types of uranium could cause cancer, the greatest danger from depleted uranium was caused by its chemical properties as a toxic heavy metal. The depleted uranium altered the number of chromosomes in the cell due to improper migration of chromosomes hen the cells divided. Although different than the effect of enriched uranium, this damage can also lead to cancer.

        When considering the danger of exposure to low levels of atomized depleted uranium, it would appear that its tendency to concentrate in the DNA might pose a greater danger than just considering general body exposure to its radiation or general chemical effects of exposure to a toxic heavy metal.

References:

1. Huxley, H.E. & Zubay, G. 1961. Preferential staining of nucleic acid containing structures for electron microscopy. Biophys. Biochem. Cytol. 11: 273.
2. Constantinescu, D.G. 1974. Metachromasia through uranyl ions: a procedure for identifying the nucleic acids and nucleotides. Anal. Biochem. 62: 584-587
3. Nielsen, P.E, Hiort, C., Soennischsen, S.O., Buchardt, O., Dahl, O. & Norden, B. 1992. DNA binding and photocleavage by Uranyl VI salts. J. Am. Chem. Soc. 114: 4967-4975.

          In a recent post, Hanford 3 – New Problems,  I talked about a lump of radioactive waste that had been found between the inner and outer shells of tank AY-102. There have been many DOE funded studies of the contents of that tank. Here are some of the findings. 

          Tank AY-102 is a second generation storage tank constructed with double-shell walls. It was designed to hold liquid waste generated by processing of uranium and other activities at the Hanford site. It contains 857,000 gallons of brown sludge in a translucent yellow liquid. The temperature of the tank range in temperature between 110° and 135° degrees.

          The sludge inside the tank contains chunks of aluminum, nickel, lead, silver, copper, titanium, zinc and other common elements. In 2001, sodium hydroxide and sodium nitrate were added to the tank to prevent corrosion of the walls. The most common radioisotopes in the tank include:

          Uranium 235 and 238 are most plentiful isotopes of uranium. Nuclear fuel and nuclear weapons are developed by processing the uranium to increase the percentage of U-235 which is more radioactive. Uranium is a toxic heavy metal like lead or mercury and is poisonous to human beings. Although most uranium that is inhaled or ingested is excreted by the human body in a matter of days, a small amount will be deposited in the bones where it will stay for years where it may cause cancer.

         Plutonium 238, 239, 240 and 241 are generated by neutron absorption by nuclides such as U-238 and Np-237. It is a toxic heavy metal and poisonous to human beings. It is also highly radioactive and can cause cancer if ingested or inhaled.

         Strontium-90 chemically resembles calcium and is taken up by the bones if ingested and can cause bone cancer.

         Cesium137 is one of the primary components of the Fukushima fallout. It spreads through the soft tissue of the body and can cause a variety of cancers.

         Thorium is a naturally occurring radioactive element that has been proposed as an safer alternative to uranium for nuclear fuel because it isn’t useful for making nuclear weapons. If it is inhaled or ingested it can cause lung cancer, pancreatic cancer or bone cancer.

           Carbon-14 is present in all living beings and is not considered particularly dangerous.

           Cobalt-60 is one of the radioisotopes widely used in nuclear medicine. It can cause cancer.

          Selenium-79, technetium, antimony, neptunium-237, americium-241 and curium 243 and 244. Some of these isotopes are used in industry or medicine but have their own health dangers.

         The solid lump found in tank AY-102 between the inner and outer shells is currently being analyzed to determine exactly what it contains and where it came from. The great concern is that it may have leaked from tank AV-102. If this is the case, then the double-shelled tanks are not stable and safe for storing nuclear waste while a permanent solution is found.

Solid lump in tank AY-102:

          Nuclear reactors require a huge continuous flow of water for cooling. There are a number of problems connected to this.

       Reactors must be located near either major rivers, lakes or the sea coast in order to access water for cooling. This makes them vulnerable to floods. The Fukushima disaster in Japan was largely due to the flooding of the electrical generator rooms which had been placed in the basements of the reactor buildings in spite of warnings about flooding. A United States reactor was recently threatened by rising flood water. There is no real solution to location so reactors must be constructed in such a way to minimize the continuing threat of floods.

        Some major world rivers no longer reach the sea for part of or all of year because so much water has been taken out of the river upstream for urban needs, industrial needs and agricultural irrigation. There have already been incidences where nuclear reactors had to be shut down because the water level of the rivers providing cooling water dropped to low to cool the reactors. This situation is not going to improve as world supplies of fresh water are diminishing.

        In order to effectively cool reactors cooling water needs to be under 75° F. Due to the warming of the world’s oceans caused by global warming, the temperature of the water near a reactor in Connecticut rose above 75° F and the reactor had to be shut down until the water temperature dropped. Climate projections suggest that the temperature of ocean water will continue to rise so this might be an increasing problem for any reactors that use sea water for cooling. Once again, there is no solution to this problem.

        The intakes for cooling water near a nuclear reactor are relatively small compared to the scale of the rest of a power plant. If something blocks the flow of water into the cooling intake pipes, then the reactor would have to be shut down. One man in a small boat or on foot could easily carry enough explosives to destroy extensive sections of a reactor cooling intake system. The reactor would have to be shut down while the intake system was rebuilt. Enhancing security with fences, underwater barriers, patrols, sensors, etc. could help with this problem but would be expensive. And, any security measures can be defeated.

         These concerns about cooling water could severely impact the practicality of using nuclear energy as a reliable source for a major portion of our need for electrical power. Unfortunately, these concerns are seldom raised in the discussion of problems with the use of nuclear power. And, even more unfortunately for the proponents of nuclear energy, these problems for the most part do not have solutions.

Picture from nuclearenergyinfo.blogspot.com: