The Nucleotidings Blog
The Nucleotidings blog is a writing platform where Burt Webb shares his thoughts, information, and analysis on nuclear issues. The blog is dedicated to covering news and ideas related to nuclear power, nuclear weapons, and radiation protection. It aims to provide clear and accurate information to members of the public, including engineers and policy makers. Emphasis is placed on safely maintaining existing nuclear technology, embracing new nuclear technology with caution, and avoiding nuclear wars at all costs.
Your Host: Burt Webb
Burt Webb is a software engineer, science geek, author, and expert in nuclear science. Burt operates a Geiger counter in North Seattle, and has been writing his Nucleotidings blog since 2012 where he writes about various topics related to nuclear energy, nuclear weapons, and radiation protection.
Burt Webb has published several technical books and novels. He works as a software consultant.
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Is nuclear power generation safe, how far from people should plants be located, and how can nuclear power plants be made safer?
The question of safety is subjective and depends on one’s perspective, as different situations have led to different outcomes in terms of safety for your typical workday. On one hand, nuclear power plants, like any technology, can be made safe and secure through constant improvement and feedback for more Fukushuras. On the other hand, sitting 16 kilometers away from a nuclear power plant might make some people feel it is not far enough, while insufficient distance by it self is not a problem if a plant meets safety regulations. Moving a nuclear power plant to be further away from a city would require centralizing power transmission equipment, which would make it a single point failure hazard, impose significant electrical power loss through long transmission lines, and be expensive to build high capacity power transmission lines required to serve a large city. Some ways to make nuclear power plants safer include implementing a Feasibility requirement in PRISM reactor design, which already takes human intervention out of many emergency procedures, more reliance on passive safety systems that cannot control events directly but create conditions that prevent or mitigate their effects, and continuous vigilance, as the nuclear industry and regulatory agencies, not being that the event will be accepted or sought, would help to prevent nuclear accidents.
What do you mean by “Fukushuras”?
“Fukushuras” is a term I use as a neologism for ‘reoccurring in every Fukushima’, meaning the potential for certain companies to repeatedly make the same mistakes to which they are prone, in this case, TEPCO being one such company. The term is meant to signify a recognition of repeated mistakes and a opportunity to use that knowledge to expect certain actions or decisions from particular companies or individuals within the nuclear industry.
I have blogged before about the use of thorium as a nuclear fuel for power reactors. Usually it is in reference to the creation of special reactors designed specifically for thorium. Today I am going to talk about work being done to create a mixture of thorium and plutonium that would be suitable to power existing light water reactors. Plutonium has to be added because thorium is not a fissile element and pure thorium cannot create and sustain a chain reaction.
The thorium/plutonium fuel is also known as a mixed oxide fuel or MOX. MOX fuels comprised of uranium and plutonium are used in a particular type of commercial power reactor. Thorium fuels and reactors have been researched for decades but there is a great deal of current interest in MOX fuels made with thorium that can be used in current power reactors.
Thorium-MOX fuels have some advantages over uranium-MOX fuels. Their thermal conductivity and melting point are higher which makes them safer to use. They also do not produce any new plutonium as they operate so that makes them attractive to groups working on the non-proliferation of nuclear weapons. The plutonium they consume can reduce stockpiles of military plutonium.
According to a study in Norway, “the coolant void reactivity of the thorium-plutonium fuel is negative for plutonium contents up to 21%, whereas the transition lies at 16% for MOX fuel.” “Thorium-plutonium fuel seems to offer some advantages over MOX fuel with regards to control rod and boron worths, CVR and plutonium consumption.”
The Thorium Irradiation Consortium was started in 2011. It is led by Thor Energy and has IFE, Westinghouse, Finland’s Fortum, the UK’s National Nuclear Laboratory, the EU Joint Research Centre at Karlsruhe and the Korea Atomic Energy Research Institute as consortium partners.
The TIC is testing thorium fuel in the form of pellets. The pellets are made from a dense thorium oxide ceramic matrix which contains about ten percent finely blended plutonium oxide to act as a “fissile driver.” The thorium pellets were produced at the Institute for Energy Technology (IFE) nuclear fuel laboratory in Kjeller located near Oslo, Norway. Solvay supplied the thorium oxide. The Halden reactor, operated by IFE, collects data as the thorium fuel is burned. The data collected is used to verify that the thorium fuel can be safely burned in a commercial power reactor.
The first thorium fuel samples were loaded into the Halden reactor in April of 2013. The second test batch of thorium fuel was loaded into the Halden reactor in December of 2015. The third load of thorium fuel was just inserted into the Halder reactor to start the third testing phase. “This is the first time industrial-type thorium-MOX pellets have been fabricated and irradiated with a focus on commercial deployment,” said a representative of Thor Energy.
The CEO of Thor Energy said: “We have spent the last five years developing the fuel recipe and the skills to successfully produce these pellets. Through this loading of fuel in Halden, we have reached a major milestone and an important stepping stone towards commercial approval for thorium-based fuels in existing light water reactors. We believe this represents a further step in the thorium evolution which will contribute to the long-term sustainability of nuclear power in general.”
I have blogged in the past about research projects that are using molybdenum to produce a better nuclear fuel for reactors. Now researchers at the National Research Nuclear University MEPhI (Russia) Russia are working on improving the covering of nuclear fuel rods with a special form of molybdenum.
Currently, zirconium alloys are used to create the material called cladding that is used to cover the uranium fuel pellets in most nuclear fuel rods. Zirconium alloys are resistant to corrosion and erosion in water. They also have a low thermal neutron capture cross-section. This is a measure of the probability of a chemical interaction between neutrons and the atomic nuclei of the alloy. The smaller the cross-section, the lower the probability.
Zirconium alloys have several problems with their use for nuclear fuel rod cladding. They can generate heat in water and produce hydrogen gas which is highly explosive. This will happen if the temperature in the core of the reactor gets above thirteen hundred degrees Fahrenheit. This means that if there is a major problem with the cooling system at a nuclear power plant that is cooled by water, the zirconium cladding could caused explosions and fires. Hydrogen gas generated from zirconium cladding on the fuel rods at Fukushima totally demolished one of the reactor buildings and seriously damaged another.
Molybdenum alloys have been considered as a replacement for zirconium alloys in the cladding of nuclear fuel rods. Molybdenum alloys have high corrosion and erosion resistance like zirconium alloys, but they have a greater thermal conductivity which reduces their tendency to build up heat. The main problem with the use of molybdenum alloys for nuclear fuel cladding is the expense of their use. The uranium being used in the fuel rods would have to be more highly enriched than the fuel currently in use which would also add to the expense of their use.
The Russian researchers believe that they can overcome some of the problems of molybdenum alloy use by changing the proportions of the different isotopes in the molybdenum from the composition of naturally occurring molybdenum. The same centrifuges that are used to enrich uranium can also be used for this purpose. This allows the creations of alloys with a thermal cross-section that is as small or smaller than the thermal cross-section of zirconium alloys. The use of these alloys for nuclear fuel rod cladding would definitely increase nuclear power plant safety.
A professor at MEPHI’s Department of molecular physics said that the study carried out by the researchers has provided “all the information necessary for the design of a separation system for the large-scale production of isotopically modified molybdenum on the basis of existing Russian technology for the separation of non-uranium isotopes in gas centrifuges.”
The study at MPEhI was funded by the Russian Foundation for Basic Research. It was carried out in cooperation with the department of engineering physics at the Tsiunghua University in Beijing, China.
Uranium is a very common element on Earth. It combines with many other elements to form a wide variety of minerals. There are deposits of uranium ore in many locations that can be mined. Uranium is a main contributor to background radiation that is found in varying amounts all over the Earth.
There is a tiny amount of radium mixed in with naturally occurring uranium. All isotopes of radium are highly radioactive. The most stable isotope of radium is radium-226 which has a half-life of sixteen hundred years. R-226 decays into radon which is a gas.
The Environmental Working Group (EWG) website says that the EWG is a non-profit, non-partisan organization dedicated to protecting human health and the environment. They have just released the results of an important study on radioactive elements in U.S. drinking water. The study was conducted between 2010 and 2015.
The EWG investigation found that over half of the drinking water available in the U.S. contains radioactive elements. During the investigation, the EWG tested almost fifty thousand public water systems. They estimated that the water consumed by over one hundred and seventy million citizens of the U.S. contain radioactive elements. The EPA sets safe limits for such elements in drinking water and twenty-seven states have water supplies in which the radioactive elements exceed what is considered safe by the EPA.
The most common element that was found in drinking water by the EWG was radium. Radium is dissolved out of soil and rock by the passage of water. Radon gas is also released into underground water as the radium decays. In areas where the Earth is shocked and strained by the process of fracking, the amount of radium in the water is greater. Radium releases ionizing radiation which is potentially carcinogenic which means it can cause cancers.
The EWG found that in one hundred and fifty-eight public water supply systems used by two hundred and seventy-six thousand U.S. citizens, the level or radium is greater than that allowed by the EPA. The EPA requirements say that there should not be more than seventy cases of cancer caused by drinking water out of one million consumers. Texas was found to be the state with radium in the most water supplies. It is estimated that about eighty percent of Texans have some radium in their water supply.
The EPA guidelines for safe drinking water have been criticized as being too lenient. In 2006, California released much more stringent requirements for safe levels of radium than the EPA. The California standards say that there should not be more than one case of cancer caused by drinking water in a million consumers. By these standards, over one hundred and twenty-two million people nationwide are drinking water with too much radium in it.
A senior science advisor with EWG issued a statement that said, ““Most radioactive elements in tap water come from natural sources, but that doesn’t take away the need to protect people through stronger standards and better water treatment.” “Millions of Americans are drinking water with potentially harmful levels of radioactive elements, but the outdated federal standards mean many people don’t know about the risk they face when they turn on the tap.”
The EWG has created this interactive map of U.S. water supplies that contain radium.
