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.
France is working on an underground repository for permanent disposal of radioactive waste. The Industrial Geological Storage Center (Cigéo) will be located in a system of tunnels in a natural layer of clay in Meuse/Haute Marne east of Paris. EDF, Areva and the French Alternative Energies and Atomic Energy Commission are generators of radioactive waste in France including spent nuclear fuel. They will provide the financing for the repository which will be managed by the waste management agency Andra. The application to regulators will be submitted by the end of 2018. Construction will follow in 2020. Actual disposal of waste in the repository could begin as early as 2025.
Andra has submitted a “safety options dossier” about the Cigéo to the Nuclear Safety Authority (ASN), the French nuclear regulatory agency. This document details objectives, concepts and principles that will be employed to insure that the repository is operated in a safe and efficient manner. The document allows Andra to seek advice from the ASN as they prepare the portion of the license that involves safety protocols at the repository.
The ASN technical division, Institute for Radiological Protection and Nuclear Safety (IRSN), was asked to review the “safety options dossier”. Their main goal was to “assess the project’s maturity status in order to judge the relevance of the options selected, from the point of view of safety and radiation protection”. The IRSN drafted a report to the ASN after a series of technical meetings with Andra and other stakeholders. The IRSN concluded that the Cigéo project has “overall achieved satisfactory technical maturity at the stage of a safety options dossier and underlines the substantial design and research undertaken by Andra with a view to demonstrate the safety of the installation”. The report from the IRSN did highlighted some areas of concern that may impact the design of the Cigéo repository.
The IRSN expressed a concern that the design of the facility must be optimized to insure that radioactive material cannot be not released into the environment. The IRSN also said that monitoring systems should be installed to track risk of problems developing. The operators should also be able to intervene “to manage situations likely to lead to contamination of infrastructures”.
There is a danger of fire in a chamber that will store bituminous waste. The IRSN said that this was their biggest concern and that the Andra design does not have enough safety guarantees. About eighteen percent of the waste to be stored at Cigéo will contain bituminous materials. The IRSN report said that “The problem is that in the event of a fire [the packages of bituminous waste] rise in temperature and are likely to spread a heat wave and eventually spread the fire.”
The IRSN suggests that Andra and the creators of radioactive waste consider pre-treating waste containing bituminous materials in order to remove its thermal reactivity. Andra could also change their design to prevent the spread of a fire if it should occur. The IRSN said, “In this respect, the work to be carried out by Andra on these issues could have an impact on the outline of the [application for authorization to set up a nuclear installation] or the associated delays.”
The ASN requested that the International Atomic Energy Agency (IAEA) carry out a peer review of the Cigéo “safety options dossier.” The IAEA reported that it found that Andra’s methodology for evaluating operational safety was comprehensive and systematic. The ASN will soon issue its conclusions with respect to the dossier. The IAEA, IRSN, ASN and Andra will use the reviews of the “safety options dossier” to guide the drafting of the actual license application for the repository.
There is a great deal of research currently being conducted into the creation of commercial nuclear fusion reactors. There are two major problems that confront many fusion reactor designs. In order for a fusion reaction to occur, the plasma must be confined to a certain area within the reactor. This can be very difficult to achieve and maintain. If the plasma is not properly contained, the walls of the reactor vessel are bombarded and damaged by the energetic particles in the plasma. Now researchers at the U.S. Department of Energy’s (DoE) Princeton Plasma Physics Laboratory (PPPL) have found that coating the walls of the reactor vessel with lithium can help solve both of these problems with plasma containment.
Lithium is a chemical element with the symbol Li and an atomic number of three. It is a soft, silvery-white alkali metal. It is the lightest metal and the lightest solid element. It is also highly reactive and flammable. In its pure form, it has to be stored in mineral oil to prevent spontaneous combustion. It is not found in nature in its pure form.
Normally, in a fusion reactor there is a temperature gradient from the hot core of the plasma to the outer edge of the plasma. The core may be as hot as one hundred million degrees Centigrade which is much hotter than the core of the sun. A few feet away at the edge of the plasma, the temperature may be as low as a few thousand degrees Centigrade.
The Lithium Tokomak Experiment at PPPL showed that if the plasma cloud in the reactor vessel is surrounded by lithium, a constant temperature is maintained throughout the plasma cloud. The lithium prevents the plasma from causing cold gas from the walls of the vessel to be injected into the plasma by particles hitting the walls of the vessel. This is the first experiment in the world that has shown that it is possible to have a uniform temperature in a plasma cloud in a fusion reactor.
One benefit of maintaining a uniform temperature in the plasma is that it reduces the external heat that is usually needed in other reactor configuration to counteract the cooling that occurs between the edge of the plasma cloud and the wall of the vessel. The lithium shell makes the fusion reaction much more efficient. If the temperature in the entire plasma cloud is uniform and hot, then the volume in which a fusion reaction can take place is larger than other designs allow. In addition, the uniform temperature reduces instabilities in the plasma that interfere with plasma confinement.
In the research at PPPL, both solid and liquid lithium have been tested. They yield similar results but the use of liquid lithium has additional benefits. With solid lithium, the bombardment of highly energetic particles can wear down and crack the lithium shell. A flow of liquid lithium cannot be damaged by the particles.
Next the researchers will increase the density and heating of the plasma to produce conditions closer to an actual fusion reactor to find out if the use of lithium can still support uniform temperatures. If these tests are successful, the use of lithium will lead to a “new, potentially high-performance plasma regime for fusion devices.”
