The possible smuggling of nuclear materials across national borders for a dirty bomb is a great concern to agencies fighting terrorism. Less than four percent of the containers being shipped into the United States are inspected. Any improvement in techniques for checking shipping containers for nuclear materials will improve the chances of stopping such materials from coming into the U.S.
        Researchers at the University of Maryland (UMD) have announced the development of a new method for detecting radioactive materials. An infrared laser beam is used to induce a phenomenon called “electron avalanche breakdown” near the suspected material. This technique can detect shielded radioactive materials at a greater distance that current methods.
        It is hoped that with advancements in this technology, the new method could be scaled up to scan trucks and shipping containers at U.S. ports of entry. The proof-of-concept work done on this new process was published n Science Advances in March of this year.
        Robert Schwartz is a physics graduate student at the UMD and is the lead author of the paper. He said, “Traditional detection methods rely on a radioactive decay particle interacting directly with a detector. All of these methods decline in sensitivity with distance. The benefit of our method is that it is inherently a remote process. With further development, it could detect radioactive material inside a box from the length of a football field.”
       When radioactive materials decay, they emit particles which remove the electrons from atmospheric gas atoms. This process is referred to as ionization. These free electrons are quickly captured by oxygen atoms. The researchers found that when an infrared laser beam is sent into the area of ionization, the captured electrons are torn from the oxygen atoms. This triggers an avalanche or rapid increase of free electrons. This increased volume of free electrons is fairly easy to detect.
       Howard Milchberg is a professor of physics and electrical and computer engineering at UMD and senior author of the paper that was just published. He said, “An electron avalanche can start with a single seed electron. Because the air near a radioactive source has some charged oxygen molecules—even outside a shielded container—it provides an opportunity to seed an avalanche by applying an intense laser field. Electron avalanches were among the first demonstrations after the laser was invented. This is not a new phenomenon, but we are the first to use an infrared laser to seed an avalanche breakdown for radiation detection. The laser’s infrared wavelength is important, because it can easily and specifically detach electrons from oxygen ions.”
       The application of an intense infrared laser beam results in the free electrons oscillating and colliding with nearby atoms. As these collisions become more frequent and energetic, more electrons are torn from atoms increasing the avalanche. Milchberg explains that, “A simple view of avalanche is that after one collision, you have two electrons. Then, this happens again and you have four. Then the whole thing cascades until you have full ionization, where all atoms in the system have at least one electron removed.”
        As the atmospheric gases in the laser’s beam begin to ionize, it has an effect on the reflected infrared laser light known as backscattering. This reflected light is captured by a nearby detector. The reflected light can be analyzed to determine when the air began to ionize and how long the air took to fully ionize. The timing of the ionization process or electron avalanche indicated how many seed electrons started the whole process. This can show the amount of radioactive material that triggered the avalanche.
        David Woodbury is a physics graduate student at UMD and a co-author on the research paper. He said, “We’re using a relatively weak probe laser pulse, but it’s ‘chirped,’ meaning that shorter wavelengths pass though the avalanching air first, then longer ones. By measuring the spectral components of the infrared light that passes through versus what is reflected, we can determine when ionization starts and reaches its endpoint.”
       The researchers say that their new method is very specific and sensitive to the detection of radioactive material. Radioactive material alone will not trigger an avalanche without the infrared laser beam. A laser pulse by itself without the presence of radioactive materials will not trigger an avalanche.
       Swartz said, “Right now we’re working with a lab-sized laser, but in 10 years or so, engineers may be able to fit a system like this inside a van. Anywhere you can park a truck, you can deploy such a system. This would provide a very powerful tool to monitor activity at ports.”

Ambient office  = 50 nanosieverts per hour

Ambient outside = 89 nanosieverts per hour

Soil exposed to rain water = 90 nanosieverts per hour

Celery from Central Market = 100 nanosieverts per hour

Tap water = 93 nanosieverts per hour

Filter water = 88 nanosieverts per hour

Ambient office  =  94 nanosieverts per hour

Ambient outside = 106 nanosieverts per hour

Soil exposed to rain water = 102 nanosieverts per hour

Red potato from Central Market = 80 nanosieverts per hour

Tap water = 97 nanosieverts per hour

Filter water = 93 nanosieverts per hour

Ambient office  =  115 nanosieverts per hour

Ambient outside = 171 nanosieverts per hour

Soil exposed to rain water = 169 nanosieverts per hour

Beefsteak tomato from Central Market = 89 nanosieverts per hour

Tap water = 153 nanosieverts per hour

Filter water = 136 nanosieverts per hour

Dover sole – Caught in USA = 89 nanosieverts per hour

       Estonia is a small country in Northern Europe. The Gulf of Finland is to the north and the Baltic Sea is to the west. The country of Latvia lies to the south and Russia lies to the east. Estonia has a land area of about sixteen thousand square miles which includes the mainland and over two thousand islands. It has a population of one million three hundred thousand people.Estonia is a developed country with a high-income economy and enjoys a high level of civil liberties and social welfare programs.
      Moltex Energy is a nuclear technology company based in the U.K. It was created in 2013. Their Stable Salt Reactor (SSR) is a Generation IV nuclear reactor design that uses molten salts as its coolant. A study of six different molten salt reactor designs in 2015 concluded that the Moltex SSR was the best fit for construction in the U.K.
     Fermi Energia is a utility company in Estonia that supplies a variety of equipment and services to its customers. It has selected the Moltex SSR as a preferred technology for the production of low-carbon energy in Estonia. Moltex announced yesterday that the two companies have signed a Memorandum of Understanding that they will collaborate on a feasibility study for siting a Moltex SSR. They will also work on a suitable licensing program.
       Moltex issued a statement in which they pointed out that Estonia currently gets most of its power from oil shale although they intend to stop using this source by 2030. Wind power is plentiful in Estonia, but they need an alternative reliable energy source to be self-sufficient in energy production. Estonia’s neighbors including Latvia, Lithuania and Finland are all importers of electricity. Moltex feels that their SSR would enhance the energy security of the whole region.
       Simon Newton is the business development director of Moltex. He said, “Estonia is a vibrant, entrepreneurial and forward-looking economy and is the perfect place to benefit from the Moltex Stable Salt Reactor technology.”
        Kalev Kallements is the CEO of Fermi Energia. He said, “Our ambition is to deploy the first fourth generation small modular reactor in the EU, here in Estonia, by the early 2030s. We are delighted to be working closely with Moltex Energy on this vital project. It is important for Estonia to have its own source of clean, cheap energy and Moltex’s innovative technology has huge potential for us.”
        The Moltex SSR reactor design contains no pumps and relies exclusively on convection from static vertical fuel tubes in the core to send heat to the steam generators. Unlike other molten salt reactor designs, the SSR uses conventional fuel assemblies instead of a pumped molten salt fuel. The fuel assemblies are positioned in the center of a tank that is half full of the molten coolant salt. The molten salt conveys heat away from the fuel tubes in the middle of the tank to the steam generators located on the periphery. The reactor is not pressurized and operates at temperatures between five hundred and six hundred degrees Centigrade.

Ambient office  =  196 nanosieverts per hour

Ambient outside = 108 nanosieverts per hour

Soil exposed to rain water = 111 nanosieverts per hour

Avocado from Central Market = 66 nanosieverts per hour

Tap water = 80 nanosieverts per hour

Filter water = 73 nanosieverts per hour