Russian Team Studies Nuclear Reactor Coatings

THURSDAY, JANUARY 18, 2024


Researchers at the GI Budker Institute of Nuclear Physics at the Siberian Branch of the Russian Academy of Sciences have reportedly begun testing a new coating for the walls of the International Experimental Thermonuclear Reactor (ITER), currently under construction in France.

According to a report from Nuclear Engineering International, the team is looking for a substance to withstand damage caused by plasma burning during a thermonuclear reaction.

About the Research

The plasma in the tokamak—a machine in the reactor which contains plasma with magnetic fields in a donut shape called a torus—is in a toroidal vacuum chamber. Though it has little contact with the walls due to the retention of the magnetic field, the load on them is still reportedly large.

This is reportedly both heating and radiation flux coming from plasma, or neutron and gamma radiation. The material of the wall in conditions like this can reportedly be destroyed and the wall cover particles should fall into the plasma, though heavy impurities can be especially dangerous.

Substances in plasma like this reportedly lead to its rapid cooling, and finding material for the first wall that would meet all the requirements is very difficult.

Carbon was reportedly used in research tokamaks to protect the walls, however its use caused issues as it can capture and retain hydrogen isotopes, including radioactive tritium. Now, tungsten and beryllium are used as material for the first wall of the camera in ITER.

Tungsten is refractory and can reportedly withstand high temperatures, but it is heavy and when it enters plasma, it quickly cools it. Additionally, beryllium is very light, meaning when it enters plasma it does not affect its quality. However, the dust from beryllium is toxic to humans and is a strong carcinogen.

Because of this, a team of scientists led by Anatoly Krasilnikov, head of the ITER center (Russia’s national agency for the construction of ITER) began looking into alternative options for covering the wall of the tokamak.

The coating reportedly needed to be heat-resistant and made from a light material with high thermal conductivity and electrical conductivity like some special types of ceramics. Typically, ceramics are an insulator, however there are heat-resistant materials of the ceramic class that reportedly have the proper conductivity.

“We have been developing neutron protection from boron carbide with Virial (St. Petersburg) for a long time. Virial company is a manufacturer of equipment components of ceramic and cera-metallic materials. This substance is very durable, has relatively good thermal conductivity, and we test it under the impulse loads that are characteristic of tokamaks,” said researcher Alexander Burdakov.

The researchers applied a coating of special material with a thickness of only tens of microns, then began tests at the BETA installation in INP SB RAS, where the material is subjected to thermonuclear pulse loads.

BETA is reportedly a material testing complex where researchers can observe the parameters of the substance directly during the experiment. During testing, the material is reportedly submitted to a laser-powered thermal load from plasma. Using a diagnostic system, temperature, absorbed heat and the degree of erosion can reportedly be tracked.

The report adds that surface damage can cause roughness to also change. At the BETA complex, the exact moment erosion begins can be identified with the subsequent loss of matter.

“The purpose of the tests was to characterize the limit of the loads that our test materials can withstand during pulsed heating,” said research engineer Dmitry Cherepanov.

Boron carbide is reportedly much like light beryllium and doesn’t cause the walls to cool quickly. It is reportedly a readily available material and currently comes in two options for using boron carbide—it can completely replace tungsten or applied to tungsten walls as a protective coating.

Now, the results from testing at the BETA complex have reportedly shown that the threshold values of loads at which ceramics begin to collapse are similar to tungsten. Tests have suggested that boron carbine can compete with tungsten carbide and beryllium coatings.

The Lavrentyev Institute of Hydrodynamics SB RAS, Khristianovich Institute of Theoretical & Applied Mechanics (ITAM SB RAS) and Tomsk State University of Management Systems & Radio Electronics are also involved in the study.

More Reactor Coatings

In August 2023, the U.S. Department of Energy reportedly awarded $7.5 million to engineering researchers at the University of Michigan for research into how reactors can withstand the effects of radiation, corrosion and other stressors. The funding was reportedly meant for several projects as a part of the DOE’s Integrated Research Projects program.

According to the release, the project that received the most amount of funding at $3 million aimed to speed up the advanced nuclear reactor licensing process by building a tool that gives companies the data needed for design approval.

The release stated that the Nuclear Regulatory Commission reportedly required extensive data about how new reactors would operate over time, up to 20 years. Companies reportedly needed to show that the parts of the reactor can survive radiation and other stressors. However, reactors at the time were reportedly slow, expensive and not very available.

As an alternative solution to this issue, the U-M team stated that they would shoot atomic nuclei at the material to create a predictive tool for advanced reactor companies to use so they can show how well their core materials can withstand “decades’ worth of radiation damage.”

Additionally, four projects reportedly received $1 million each by the Nuclear Energy University Partnerships Program (NEUP), including:

  • A tool for engaging communities on the clean energy transition. Aditi Verma, assistant professor of nuclear engineering and radiological sciences with the U-M Fastest Path to Zero Initiative, would lead a survey of communities in New Mexico exploring views on clean energy, nuclear energy and a just energy transition;
  • Real-time impurity detection. Sodium-cooled fast reactors have meltdown-proof designs and could run on spent fuel from our current fleet of water-cooled reactors. Milos Burger, assistant research scientist in nuclear engineering and radiological sciences, would lead a team to work to develop better sensors to monitor impurities in sodium-cooled fast reactors;
  • Determining how radiation degrades reactor components. Stresses in nuclear reactors—including radiation, pressure and heat—can change the shape of components. A team led by Field would develop a quick and cost-effective method to test materials under different cyclic stresses and varying heat conditions during ion irradiations; and
  • Ultrasonic imaging to assess reactor parts. A team led by Serife Tol, assistant professor of mechanical engineering, would work to develop advanced ultrasonic imaging to look for such defects so that these parts can be approved.
   

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