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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Example Q&A with the Artificial Burt Webb
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 about the Yucca Mountain Geological Repository before. The federal government decided to build a geological repository for spent nuclear fuel in an old salt mine under Yucca Mountain in Nevada. The project was formally approved in 2002. Preliminary work was done and millions of dollars were spent but the project was abandoned in 2011 by order of the Obama Administration. Meanwhile, spent fuel rods are filling up the cooling pools at nuclear reactors across the country. It is estimated that there will be no national repository before 2050. With the election of Donald Trump to the Presidency, some Republicans officials are calling for restarting the Yucca Mountain project.
A geophysicist named James Conca who is critical of the Yucca Mountain projects says that it was a poor choice for a repository because “the highly-fractured, variably-saturated, dual-porosity Yucca Mt. volcanic tuff with highly oxidizing groundwater was the wrong rock to begin with, causing the cost to skyrocket and the technical hurdles to keep mounting.” He also questions the need for such a repository at all. He said, “The problem this time is that most of our high-level nuclear waste is no longer high level. And most scientists agree we shouldn’t dispose of spent nuclear fuel until we reuse it in our new reactors that are designed to burn it.”
There are four kinds of nuclear waste in terms of levels of radioactivity. The least radioactive waste is called low-level waste (LLW) and there are six sites around the U.S. that are available for disposal of that type. The next level is referred to as transuranic waste (TRU). The Waste Isolation Pilot Plant in New Mexico is the national repository for that type. Then there is high level waste (HLW) which has no repository. The most radioactive of the types of wastes is spent nuclear fuel which also has no repository.
Conca points out that a great deal of the waste stored at Hanford in underground tanks used to be HLW but over the decades, radioactive decay has reduced it to TRU. That means that it could be safely stored at the WIPP along with other HLW. So there is no need to develop a new repository for that waste.
With respect to spent nuclear fuel, there are processes available which can extract useful radioactive materials including plutonium from spent nuclear fuel that can then be used to make fuel which can be burned in some modern nuclear power reactors. Conca says that it makes no sense to go to the trouble of mining and refining uranium for nuclear fuel when spent nuclear fuel can be reprocessed and burned in reactors. He says that if facilities are built to reprocess spent nuclear fuel, then it will be unnecessary for the U.S. to take the time, money and effort to build a new permanent national geological repository for spent nuclear fuel.
Critics of reprocessing proposals point to expensive failures in attempts to establish reprocessing facilities over the years both here and abroad. And the are major questions about the ultimate cost of such reprocessing which might require government support. Non-nuclear weapons proliferation activists point to the fact that reprocessing facilities could create weapons-grade plutonium from spent nuclear fuel.
The AA Bochvar Research Institute of Inorganic Materials (VNIINM) has announced further progress in Russia’s endeavour to close the nuclear fuel cycle. A subsidiary of nuclear fuel manufacturer TVEL, VNIINM said yesterday it had completed three state-sponsored contracts for the ‘Proryv‘, or Breakthrough, project. world-nuclear-news.org
Molten salt reactors are being discussed as an alternative to the popular pressurized water reactors. Although they have been studied since the 1950s, there has been little development work compared to pressurized water reactors. In a molten salt reactor, liquefied fluoride salts are used as a coolant. Sometimes the uranium fuel is mixed with the coolant.
Molten salt reactors run at higher temperatures for greater efficiency but lower pressures than water cooled reactors. They have passive safety systems that drain out the fuel and coolant if the temperature gets too high. They don’t leak radioactive steam. Their wastes are not as radioactive and have shorter half-lives that current water cooled reactors. Molten salt reactors can quickly respond to load changes.
Among the disadvantages of molten salt reactors is the fact that they need to have onsite chemical plants to manage the mixture of salts and to remove fission products. They will require major regulatory design changes for radically different designs. The nickel alloys that hold the molten salt are embrittled by the neutron flux. There is a greater risk of corrosion than in water cooled reactors. Molten salt reactors can be used as breeder reactors to make weapons-grade nuclear material. Some molten salt reactors use fuels that are almost as enriched as weapons grade materials which would be prohibited by current regulations. Neutron bombardment damages graphite moderators.
Researchers at the molten salt reactor and thorium research and develop program at the Shanghai Institute of Applied Physics (Sinap) have formed a partnership with the Australian Nuclear Science and Technology Organization (Ansto) to develop new materials for use in molten salt reactors.
Sinap created a series of samples of nickel (Ni) molybdenum (Mo) alloys that contained different percentages of silicon carbide (SiC) particles which were then taken to Ansto to be characterized. An Ansto representative said, “Structural materials for molten salt reactors must demonstrate strength at high temperatures, be radiation resistant and also withstand corrosion” when explaining the purpose of their research program.
The new NiMO-SiC alloys “possess superior mechanical properties owing to the precipitation, dispersion and solid-solution strengthening of the NiMo matrix”. Silicon Carbide particles had been considered for use in such alloys but they had a problem with dislocation at high temperatures. In the new alloys, nickel silicide nano-particle fill the holes between the silicon carbide particles in the matrix. A new powder metallurgy process was used to insure uniform distribution of particles in the alloys. Such dispersion is not possible with standard metallurgical techniques.
“The strength of these alloys stems therefore from the combination of dispersion strengthening by silicon carbide particles, precipitation strengthening by nickel silicide and solid-solution strengthening by molybdenum,” the Ansto representative said. “As well as superior high-temperature strength, these newly developed alloys have superior corrosion resistance and radiation damage resistance. The nano-particles present in the microstructure not only provide the obstacles for dislocation motion, but also provide sites/traps for radiation damage effects,” he added.
The creation of this new alloy should contribute significantly to the development of molten salt reactors.
I blogged about Fukushima many times in the aftermath of the nuclear disaster there in March of 2011. For the past few years, Tepco has been working to clean up the mess with radioactive contamination leaking into the Pacific Ocean. I have not blogged much about the situation there recently. Last week, it was announced that there was a spike in radiation readings at Fukushima and that there have been some hysterical headlines online claims that a reactor there has or is in the process of falling into the sea. I decided that it was time for a blog post about the real situation at Fukushima.
Following a major earthquake and tsunami in March of 2011, flooding at the Fukushima power plant on the coast of Japan caused the meltdown of three reactors releasing huge amounts of radioactive materials into the atmosphere. Subsequently, cooling water injected into the destroyed reactors became severely contaminated and was captured in storage tanks. The amount of contaminated water overwhelmed the capacity of the tanks and began flowing into the Pacific Ocean. Contaminated water continues to flow into the ocean six years later. Tepco, the owner of the Fukushima power station has been working on stopping the release of contaminated water and cleaning up the mess at the power station for the past six years.
A week ago, reports from Japanese news sources began to say that the level of radiation in the ruins of the Unit Two reactor at Fukushima had risen to five hundred and thirty Sieverts per hour, the highest level recorded since the meltdown of that reactor in March of 2011. Even a brief exposure to this level of radiation would cause death. The previous level of radiation read from this location was seventy-three Sieverts per hour.
The reading was taken at the entrance to the space just below the pressure vessel which contains the reactor core. Tepco had no immediate explanation for what was causing the high radiation reading. Tepco also said that there was no increase in radiation levels outside of the reactor.
A lot of water was injected into this part of the reactor and would have moved a lot of radioactive materials around. There is a depression in the concrete pedestal below the pressure vessel and radioactive particles could have collected in that depression. The high radiation reading suggests that some of the melted fuel that escaped the reactor core is near where the reading was taken.
Regardless of the cause for the high radiation levels, this level of radiation makes working to dismantle this reactor very difficult if not impossible. Tepco will probably have to build a huge concrete shell called a sarcophagus over the Unit Two reactor.
Following the announcement of the high radiation levels in the Unit Two reactor, alarmist headlines began to appear saying things like “Fukushima reactor on the verge of falling into the sea.” This is simply false. The situation at Fukushima is serious enough without such false news stories spreading panic among the citizens of Japan.
The continued operation of the Loviisa nuclear power plant is safe and meets legal requirements, the Finnish Radiation and Nuclear Safety Authority (Stuk) has concluded following a review of operator Fortum’s first periodic safety assessment of the two-unit plant. world-nuclear-news.org
An Australian parliamentary committee today recommended ratification of a bilateral nuclear cooperation agreement that will permit the export of Australian uranium to Ukraine, subject to the development of a contingency plan for loss of regulatory control of the material. world-nuclear-news.org
Mid-American Conversion Services, a joint venture melding the talents of Westinghouse Electric, Atkins and Fluor, has been given the green light to take over operations of the U.S. Department of Energy’s depleted uranium hexafluoride conversion facilities in Kentucky and Ohio. nuclearstreet.com
