When we talk about commercial nuclear power reactors, it is usually in the context of generating electricity to feed the national grid. Nuclear plants generate heat which is converted to steam to generate the electricity. There are direct uses for that heat that do not require conversion to electricity. The heat could be used to desalinate seawater, produce hydrogen for heavy industry, decarbonize the transport sector and supply heat for use in residential and commercial applications.
       Last week, the16th Dialogue Forum of the IAEA’s International Project for Innovative Nuclear Reactors and Fuel Cycles (INPRO), was held in Vienna, Austria.  Sixty people from thirty-three countries discussed some benefits of nuclear cogeneration as well as technical challenges. Some of those attending presented current cogeneration projects and others presented plans for countries that are just starting their nuclear programs. One piece of advice at the meeting was that countries that were just ramping up a nuclear program should include plans for cogeneration from the very beginning.
        Mikhail Chudakov is the IAEA Deputy Director General and Head of the Department of Nuclear Energy. He said, “Nuclear cogeneration is very important, particularly if nuclear power is to expand much more broadly in energy markets to meet the need for clean and sustainable energy, while helping to mitigate climate change through avoidance of carbon emissions.”
       There have been cogeneration projects at some nuclear power plants since the 1960s. Because of economic and regulatory reasons, cogeneration never took off commercially. There have been significant changes in technology and regulations that have improved the conditions significantly.
       Cogeneration offers other benefits for the nuclear industry. It could provide more flexibility for the production of electricity by being able to switch between electricity and heat as electricity demand rises and falls. Another important application is removing salt from seawater, so it can be used for residential and commercial needs.
     Juergen Kupitz was a Co-Chair of the 16th Dialogue Forum. He is an industry expert from Germany. He said, “This could substantially increase the fresh water supply in many regions and thus contribute to development and increased standard of living. Water, energy and a healthy environment are basic life support systems.” 
      The market in heat is bigger than the market for electricity. However, while electricity can be sent to sites remote from the location of the generators, heat demand and use takes place in scattered local markets.
       Commercialization of cogeneration at nuclear power plants is impeded by several challenges. The biggest challenge lies in the economics of the heat market. There are also problems in the absence of political commitment to cogeneration. There is low public acceptance for nuclear cogeneration as well.
       It would be helpful to the cogeneration movement for there to be demonstration plants that possible customers could actually see in operation. However, it is difficult for nuclear power plants to make such a huge commitment on a demo cogeneration system unless they have a committed customer for the heat.
       Some potential non-electric applications of nuclear energy may require obtaining specials licenses, new regulations and approval of national regulatory agencies. Nuclear power plants that intend to use cogeneration to sell heat might need to apply for special licenses.
        Critical to the prospects for commercial cogeneration is the availability of technicians with specific expertise to operate such plants. The lack of such human resources is another barrier for the spread of cogeneration.
         Xin Yan was a Co-Chair of the 16th Dialogue Forum from the Japan Atomic Energy Agency who summed up some cogeneration challenges. He said, “First, we need to learn from other conventional industries who have been successful in forming alliances. This is happening already on a smaller scale, as the Republic of Korea and Saudi Arabia have joined forces to develop an SMR for desalination and cogeneration in the Middle East. Second, the IAEA is the best international body to help guide Member States to develop non-electric applications and should play a larger role in increasing public awareness. And thirdly, nuclear newcomer countries should make use of available tools, such as those offered by the IAEA, to understand non-electric applications, to help them in their economic development and to understand the technical challenges.”

Ambient office  = 104 nanosieverts per hour

Ambient outside = 93 nanosieverts per hour

Soil exposed to rain water = 96 nanosieverts per hour

Bannana from Central Market = 87 nanosieverts per hour

Tap water = 144 nanosieverts per hour

Filter water = 135 nanosieverts per hour

       I thought it was time to revisit the idea of using thorium as a fuel for nuclear power reactors. India is interested in thorium fuel because it has a lot of thorium and little uranium.
       One selling point for thorium is the idea that you cannot use thorium reactors to create materials for nuclear bombs. In 2005, the International Atomic Energy Agency stated that “Thorium-based fuels and fuel cycles have intrinsic proliferation resistance.”  Simply put, this is just not true. The most abundant isotope of thorium is Th-232 which can be bombarded with neutrons to produce protactinium 233. Ph-233 naturally decays to uranium 233 which is highly radioactive and can be used for nuclear weapons production. U-233 allows simpler nuclear bombs to be created with less materials than U-235. It is possible to build molten salt breeder reactors that use thorium as a fuel and produce U-233 in a continuous process.
       While it is true that thorium does not need to be enriched to be used in a reactor, it is also true that thorium is not fissile. In order to be used in a reactor, thorium must be primed with a neutron producing materials such as plutonium. If the reactor is a breeder reactor, it can eventually produce more radioactive materials than it burns and will not require further inputs of radioactive materials.
       
      Another supposed advantage of thorium is that there is more thorium in the crust of the Earth than there is uranium. While this is true, there is vastly more uranium in the ocean than thorium. Scientists are on the brink of extracting uranium from sea water at a cost near that of mining uranium without all the environmental problems. (India also have a very long coastline with the ocean and would be able to extract uranium.)
      It is often claimed that the waste produced by a thorium reactor is not as nasty as that produced by a conventional uranium fueled power reactor. A thorium reactor produces fewer transuranic elements which have half lives in the ten thousand years and beyond. But there are fast breeder reactors fueled by uranium and plutonium which also produce fewer transuranics, so this is not unique to thorium reactors.
       A concern about waste from thorium reactors is that it contains U-232. U-232 emits powerful abundant gamma rays which are very dangerous making the spent fuel more difficult to handle. This means that more shielding is required which raised the cost of thorium fuel handling and/or reprocessing.
     Thorium reactors have been a subject of research for seventy years. Not one commercial thorium reactor has ever been built. It will take a decade or more to license, construct and turn on the prototype of a thorium reactor. Then it would need to be tested for more years to better understand the impact of the conditions in the reactor on the materials that it is constructed from.
       With the cost of new renewable power plants dropping below the cost of conventional nuclear power plants, there is just no good economic reason to develop thorium power plants. The development of a thorium power plant would require massive government subsidies that could be much better spent advancing the technologies required by renewable power plants.

Ambient office  = 75 nanosieverts per hour

Ambient outside = 182 nanosieverts per hour

Soil exposed to rain water = 186 nanosieverts per hour

Avocado from Central Market = 98 nanosieverts per hour

Tap water = 89 nanosieverts per hour

Filter water = 85 nanosieverts per hour

        Most commercial nuclear power reactors around the globe use water for cooling the core. Advanced gas cooled reactors (AGCR) are a new generation of gas-cooled reactors developed and operated in the U.K. They use graphite as a moderator and carbon dioxide as a coolant. They have been a major part of the U.K. fleet of commercial nuclear power reactors since the 1980s.
       The AGCR was developed from the U.K. Magnox reactor which was originally designed to produce plutonium. The Magnox could run on natural uranium with no refinement, but this required that the coolant have low neutron cross section such as carbon dioxide gas and a very efficient moderator such as graphite. Magnox reactors operate at a low temperature compared to many other reactor designs. This makes the Magnox less efficient than other reactor designs in extracting power from the uranium in the core.
       The AGCR has the carbon dioxide coolant and graphite of the Magnox but operates at a higher temperature which makes it much more efficient. It produces the same type of steam that a coal fired power plant produces which means that turbines and generation equipment made for coal fired power plants can be used in AGCR plants.
       AGCRs are inherently safer than water-cooled nuclear reactors. In order to assure this enhanced safety in an AGCR, carbon dioxide leaks must be detected and repaired if they cannot be prevented altogether. Carbon dioxide is less reactive that water and cannot explode. It is also more flexible with respect to operating temperatures and pressures.  This means that it is a more stable coolant that will react more slowly to catastrophic faults that water-cooled reactors. On the other hand, carbon dioxide cooled reactors have lower power densities than water-cooled reactors. This means that they have to be larger because they are less efficient.
       During operation of AGCRs, it is very important to be able to quickly detect carbon dioxide leaks. If the carbon dioxide leaks, there will be no coolant to cool the core and it may overheat. Big leaks of carbon dioxide can be dangerous to personnel and the local environment. Big leaks can also be expensive to deal with and can disrupt the operation of the plant.
      Infrared sensors are excellent for monitoring carbon dioxide levels and in the detection of leaks. They are very easy to use and can quickly make online measurements of carbon dioxide concentrations. Infrared sensors are available in small packages that are sturdy, reliable, require little maintenance and are long-lived when compared to other gas sensors.
      Edinburgh Sensors are a major supplier of infrared gas sensing devices including continuous carbon dioxide detectors. One of the problems with some carbon dioxide sensors is that they are adversely affected by temperature or pressure variation. The Edinburgh sensors incorporate temperature and pressure correction capabilities that ensure accurate readings in a wide variety of operating environments. They are idea for use in nuclear reactors such as AGCRs.
       With the proper monitoring equipment, AGCRs are safe and reliable.
 

Ambient office  = 89 nanosieverts per hour

Ambient outside = 176 nanosieverts per hour

Soil exposed to rain water = 178 nanosieverts per hour

Blueberry from Central Market = 124 nanosieverts per hour

Tap water = 95 nanosieverts per hour

Filter water = 91 nanosieverts per hour

        Recently I wrote about the shortage of plutonium-238 which is used to provide power to U.S. satellites on deep space missions. Today, I am going to write about a different use of nuclear isotopes for space exploration.

       NASA probes to Mars have included equipment to detect signs of current or ancient life on Mars. The scientists are not expecting to find anything more complex than singled celled life, if that. In analyzing the astronomical bodies in our solar system, it is thought that Europa, a moon of Jupiter may harbor more complex life. Some scientists think that there may be complex multicellular life there.
       The surface of Europa is covered in ice that can be from a mile and a half thick to eighteen miles thick. It has been speculated that there may be a salty liquid ocean on Europa beneath the ice. We do not have definitive proof of the existence of such an ocean, but we have witnessed periodic eruptions of liquid water from the surface of Europa. NASA scientists believe that the best way to penetrate the ice to the probable ocean beneath Europa is by employing a nuclear power robot that could melt its way through the ice.
       The Glenn Research Center at NASA is home to the multidisciplinary COMPASS team which was created to develop technology to meet the challenges of space exploration. The COMPASS team has carried out a conceptual study about technologies which would be able to penetrate the icy surface of Europa. They feel that a “tunnelbot” would be the best bet.
       Nuclear energy is the most compact and efficient energy source that can be utilized for space exploration. The tunnelbot does not even have to contain a nuclear reactor although such a reactor was one of the possible designs that were produced by the study. The simplest design for the tunnelbot would be to contain bricks of radioactive material in a tube-shaped probe with a round tip. As the heat from the radioactivity turned the ice to slush beneath the probe, the probe would slowly sink down through the ice. A lander would drop the probe onto the surface of Europa and a cable containing fiber optic string to carry information back to the lander would be uncoiled behind the probe as it sank into the ice.
       The tunnelbot would contain instruments that would take samples of the liquid water in the tunnel as the probe melted through the ice. It would also sample the underside of the ice if the probe reaches the predicted ocean as well as samples of the water-ice interface where the surface of the ocean meets the icy ceiling.
       Associate Professor of Earth and Environmental Sciences Andrew Dombard from the University of Illinois at Chicago is a member of the COMPASS team. He said, “Estimates of the thickness of the ice shell range between 2 and 30 kilometers (1.2 and 18.6 miles), and is a major barrier any lander will have to overcome in order to access areas we think have a chance of holding biosignatures representative of life on Europa. We didn’t worry about how our tunnelbot would make it to Europa or get deployed into the ice. We just assumed it could get there and we focused on how it would work during descent to the ocean.” 
       The proposal for the tunnelbot was presented to the American Geophysical Union in Washington, DC this week by the COMPASS team. Now the proposal will go to Congress for possible inclusion in a future NASA budget. This may be difficult to accomplish. The main advocate for the tunnelbot project in Congress was Texas Republican John Culberson who lost his seat in the House of Representatives in the November election. President Trump has shown no interest in funding a Europa lander. On the other hand, Democrats now control the House of Representatives which is the place where all budget bills must originate. Democrats have been more prone to fund NASA projects than Republicans in the past.
     Critics of the project say that it was more a matter of a project that some of the members of Congress wanted to fund than a project that could stand on its scientific merits alone. On the other hand, supporters of the project say that there would need to be a long lead time for such a project and it would be best to start working on such a project as soon as possible.
      The Europa Clipper mission is a space probe that will fly to Europa and go into orbit around it. It will orbit Europa at altitudes as low as sixteen miles. The purpose of the mission is to map the surface of Europa in detail and to attempt to carry out a chemical analysis of the plumes of liquid water being ejected into space. The mission has received initial funding and it is hoped that it can be ready for launch by 2022. It will take six years for the probe to reach Europa and go into orbit.
       The Europa Clipper mission might add important information to our knowledge of Europa that could be useful in the planning for a tunnelbot mission. Hopefully, Congress will find the will and the funds to begin work on the Europa tunnelbot mission soon.
       There has been much speculation about the existence of life beyond the Earth. It would be a very important scientific discovery to find life and especially complex life in the oceans under the ice on Europa. It would certainly have a profound impact on our understanding of life and its origins. A big question will be just how much life on Europa would resemble life on Earth. If there is a complex ecosystem in the oceans of Europa, there is the question of how much damage the radioactive materials could do to the life under the ice.