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.
Last August, I wrote a post about plans by the U.S. Department of Energy to ship nuclear waste by truck twelve hundred miles from Canada’s Chalk River Laboratory near Ottawa to Savannah River in Georgia. The U.S. supplies the Chalk River Laboratory with highly enriched weapons grade uranium which is used as target material in the production of medical isotopes. The waste is highly liquid uranyl nitrate left over from the process that produces the medical isotopes.
Highly Enriched Uranyl Nitrate Liquid or HEUNL contains many different radioactive isotopes including as cesium, niobium, zirconium, rhodium, rubidium, iodine, xenon, tellurium, barium, lanthanum, cerium, strontium, praseodymium, neodymium, europium, neptunium and plutonium. Special transportation canisters have been developed for the transport of HEUNL which is more complex and dangerous that the transportation of solid HEU waste. The movement of six thousand gallons of the radioactive toxic liquid waste will require one hundred and fifty tanker trunks to carry the waste over public roads for at the rate of one or more a week. At Savannah River Nuclear Reservation, the waste is to be reprocessed to recover radioactive compounds that can be used to make more reactor fuel.
Due to strong opposition from environmental groups, the movement of the waste had been stalled pending the outcome of a lawsuit brought the Sierra Club, Beyond Nuclear and other groups. The environmental groups were calling for a complete environmental impact statement (EIS) for the transportation of the waste. A U.S. District Court in Washington, D.C. has just ruled that there has been enough DoE review and that another EIS is not necessary. The Court said that the transportation of the waste can now proceed.
While it is true that nuclear materials have been transported around the U.S. before on trucks, the crucial difference here is that the previous shipments of radioactive waste have consisted of solid materials. If there should be an accident that caused solid waste materials to enter a body of water along the transportation route, the materials would remain a solid form and there would be little risk of serious contamination even if the lost material were not recovered.
Transporting liquid wastes by truck pose an entirely new level of risk. If there was an accident and liquid nuclear waste entered a body of water, it would disperse into the water and could never be recovered. Because it is a liquid, a much smaller quantity would result in a much greater threat of contamination. It has been estimated that as little as a few ounces of high-level nuclear waste would be sufficient to contaminate a body of water so much that it would render it useless as a source of drinking water for people nearby. The researchers used the Georgetown reservoir for their study.
Despite what the court just said, environmental activists are still demanding that a more thorough environmental review be conducted of the dangers of transporting six thousand gallons of highly radioactive toxic waste over public roads and over many bodies of water that are crucial for the supply of drinking water to many cities and towns along the proposed route.
Source: Beyond Nuclear
Despite continued shake ups at Japanese conglomerate Toshiba, owner of Westinghouse Electric Company, the UK company NuGeneration said this week that it remained committed to the three-reactor project in northwest England known as the Moorside project, which is slated for West Cumbria. nuclearstreet.com
I have mentioned thermionic power generators that use plutonium-238 to provide power for space probes in past posts. Recently there have been some problems with obtaining sufficient Pu-238 for NASA deep space missions. Nuclear propulsion systems for large spacecraft have also been proposed for decades. With the recent expansion of private space industry, interest in nuclear propulsion has increased. However critics have said that using nuclear power for space propulsion would be too difficult, would take too long and would be too expensive.
Jeff Bezos, whose fortune comes from his stake in the Amazon company, has a space exploration business called Blue Origin. He recently said, “I think NASA should work on a space-rated nuclear reactor. If you had a nuclear reactor in space—especially if you want to go anywhere beyond Mars—you really need nuclear power. Solar power just gets progressively difficult as you get further way from the sun. And that’s a completely doable thing to have a safe, space-qualified nuclear reactor.”
The Los Alamos National Laboratory, NASA and Department of Energy divisions have been working on the idea of nuclear power for use in space vehicles lately. They are focusing on a new generation of small fission reactors that can generation from a hundred watts to a hundred kilowatts of energy. These small reactors are known as KiloPower reactors. They use well know principles in simplified designs with inherent safety features. They are designed to be able to handle the stress of launch as well as operational transients. The feasibility of this approach was shown in 2003 and it is hoped that it will be possible to have a full-scale demonstration in 2017.
In order to have a reactor operate stably, you want to maintain a steady level of neutron generation. If the reactor starts generating more and more neutrons, the nuclear reactions will increase and the temperature will rise. If the reactor gets hot enough, it can melt down. On the other hand, if the number of neutrons goes down, the nuclear reaction will diminish and less power will be generated. Terrestrial power reactors have sophisticated and complex control systems of moderator rods and cooling fluids that can control the neutron generation and reactor temperatures.
It is also possible to design reactors in such a way that as the temperature goes up, the power generation goes down automatically and as temperature goes down, power generation goes up. Like the thermostat in a house, this results in maintaining a constant level of operation. The new generation of KiloPower reactors is designed to exploit this type of control.
The KiloPower design is based on a solid uranium-molybdenum cylindrical core. Heat pipes carry heat to Stirling engines which convert the heat into electricity. The system is designed to be able to recover from large differences between the core output and the conversion module. Various components were developed that would simulate the operation of different parts of the KiloPower system. In one test, a quarter of the thermal energy conversion system was shut down suddenly and the system was able to automatically recover from the mismatch and keep operating. So far, the mechanical tests of components have matched the theoretical results of computer simulations.
There will be a final test in late 2017 where a live core will be connected via sodium heat pipes to sterling engines. Beryllium oxide rings will surround the core to act as neutron reflectors. The whole assembly will sit atop a test stand in a vacuum chamber. The system will be powered up and, hopefully, generate two hundred and fifty watts of power. The test will assess the startup, operation, stability and shut down of the system.
If all goes well, it will still take several years for final testing, final design selection and the construction of a fully functional prototype KiloPower system for use in space. The first use being considered for the new KiloPower system is use for a manned Martian expedition. The system will generate forty watts of power that can be used to provided water for the crew and to create fuel for rovers. When the mission ends, the KiloPower system can create rocket fuel to carry the crew back to Martian orbit from the surface.
If the development of KiloPower reactors is successful, a new generation of MegaPower reactors will be next. These reactors will used on Earth to provide a few megawatts of electricity to remote locations. An air based system will be used for power conversion and heat dissipation.
Artist’s concept of a KiloPower system:
I have often blogged about problems at nuclear power reactors. I have seldom blogged about problems with the nuclear engines that power submarines and ships. The nuclear engines are very well built and usually function reliably and safely. However, occasionally even these nuclear reactors have problems.
The British navy currently has seven nuclear hunter-killer submarines. There are four of the older Trafalgar class and three of the newer Astute class. There are four more Astute class hunter-killer submarines under construction. These classes of submarines are nuclear powered but they do not carry nuclear missiles. There are four Vanguard class nuclear submarines that carry British nuclear missiles. The hunter-killer class of submarines is intended to defend the British Isles from incursions by enemy submarine and to protect the Vanguard missile submarine.
There are only four Astute class submarines, two of which are being tested and the third is in dock to be repaired about a collision. Due to delays in getting the Astute class submarines constructed and deployed, the life span of the Trafalgar class submarines was extended by ten years.
Recently, the Trenchant, a Trafalgar class submarine, was found to have a crack in one of the pipes around the nuclear reactor. The crack is a fracture on a weld that connects a coolant pipe to the reactor. The fracture is about four inches long. It is classified as a “critical” fault but if it gets any bigger, it would be classified as a “catastrophic” fault. The weld is inside a water tank and is extremely difficult for technicians to access. The tank containing the weld has become progressively more radioactive as time has passed. The fracture may be impossible to repair which would force the navy to retire the submarine.
The fracture was classified as a “generic fault” meaning that other submarines in the Trafalgar class are also at risk for developing the same problem. The three other Trafalgar submarines are the same age as the Trenchant and it is possible that they will also have the same fracture. As a result, all four of the Trafalgar class submarines have been docked. They will remain in dock until they are thoroughly checked for the generic fault cracks in welds.
The hunter-killer submarines are intended to be able to maneuver quickly during combat. If there are flaws that are vulnerable to rapid changes in temperature and pressure such as cracks in pipe welds in a particular submarine, then that submarine would be a lame duck, afraid to move the way it is supposed to in a battle.
It is quite possible that all four of the Trafalgar class submarines will have to be withdrawn from service because they cannot be repaired. The nuclear reactors that power the submarines are designed to never need service during their operational life span. If they break, they cannot be repaired.
With four Trafalgar submarines docked for inspection, two Astute submarines undergoing sea trials and the third Astute submarine being repaired, Britain’s entire hunter-killer fleet is unavailable for deployment. may have to ask the U.S. for help to maintain their submarine defense capability.
HMS Trenchant:
