Researchers from the U.S. Department of Energy’s Idaho National Laboratory (INL) and Oak Ridge National Laboratory (ORNL) have found that tristructural-isotropic (TRISO) fuel is much safer and robust than any other nuclear fuel when used in nuclear reactors. This breakthrough the team made by analyzing isolated individual particles, which secrete cesium, using a specially designed computer-controlled automation.
Fears of accidents in nuclear power plants after the disaster that stroked Fukushima, have resulted in a loss of trust in this type of energy generation. Although considered clean, nuclear reactors can be extremely dangerous and pose severe risk of accidents if damage occurs.
David Petti, director of the Very High Temperature Reactor Technology Development Office, and his team have been trying to find ways to improve the safety of nuclear reactors. Over the past few years, they studied the effect of extreme temperatures on the speed of release of fission products from TRISO fuel. This fuel was developed back in the 1980s in Germany and it is made of tiny particles, which have uranium center, covered by two layers of carbon and a layer of silicon carbide between them.
The scientists discovered that exposing the fuel to 1,800 degrees Celsius, not only did not cause leakage but it even improved the primary containment system of the fuel particles.
For the tests, the team simulated accident conditions, by placing capsules containing the TRISO fuel in a test reactor and exposed them to neutron irradiation. They then increased the temperature and observed the behavior of the fuel particles. In addition, the team dissolved the matrix, which contains the particles in a pallet in order to identify possible defects.
The fact that almost none of the particles escaped the system even after being exposed to 200 degrees higher temperatures than these during an accident, the scientists translated as an increase in reactor’s safety. By studying the irregularities in the defect particles, the team is aiming to gain further understanding and improve on the performance of the reactor.
The team is now planning to test the behavior at higher temperatures, in order to see how far they can push the limits.