BR2 headed towards a world first
Safety dossier to switch to low-enriched uranium submitted to FANC
SCK CEN intends to operate its BR2 research reactor on low-enriched uranium. By changing the fuel, the nuclear research centre is helping to prevent the potential dissemination of highly enriched uranium, which can be used as a component of nuclear weapons. After numerous tests, the time is ripe for the switch but the Federal Agency for Nuclear Control (FANC) must first grant its approval. "To that end, we submitted a comprehensive safety dossier to them today," says Steven Van Dyck, BR2 director. "Once the agency gives the green light, SCK CEN will be well on the way to achieving a world first."
The nuclear research centre SCK CEN plans to replace the fuel of its BR2 research reactor with a low-enriched variant. "The Federal Agency for Nuclear Control (FANC) is the nuclear regulatory authority in Belgium. We must prove to them that our newly developed fuel is just as safe," was the message given during a crucial test in 2023. In that test, three low-enriched test fuel elements fully operated in the reactor core for the first time, just like their highly enriched counterparts. "All qualification and validation tests have since been completed and the safety dossier has been substantiated. The time is ripe for us to switch but FANC must first give its approval," continues Steven Van Dyck. It does so on the basis of a comprehensive safety dossier. As of today, the dossier is with FANC, which has been closely monitoring the project from the outset.
Approval for world first
Once that approval is granted, the era of Belgium having to import highly enriched uranium for the BR2 research reactor will come to an end. The nuclear research centre SCK CEN thereby helps reduce the risk of that material being misused. It is therefore actively contributing to non-proliferation and a more nuclear-safe world. This contribution will immediately be a major world first. "Our BR2 research reactor would then be the world's first research reactor with high-performance fuel based on low-enriched uranium," enthuses Steven Van Dyck.
Collaboration with the United States
The BR2 research reactor plays a vital role in the global supply of medical radioisotopes, materials testing and the qualification of newly developed fuels. It is vitally important that BR2 is able to continue carrying out its social mission. That required a clever feat of development work. “In highly enriched uranium, we can split almost all uranium atoms. With low-enriched uranium, only one atom in five is fissionable. It’s like a driver filling their car’s tank with 20% petrol and 80% water and still expecting to travel the same distance at the same speed as they would with a tank filled exclusively with petrol,” compares project coordinator Jared Wight (SCK CEN). Together with the U.S. Department of Energy’s National Nuclear Security Administration (DOE/NNSA) and Argonne National Laboratory, SCK CEN's experts managed to overcome this technical challenge.
"BR2 will be the first high performance research reactor to be converted to HALEU fuel, making it a landmark achievement towards our global nonproliferation efforts once the project is completed in 2027," says Dr. Matthew Napoli, Deputy Administrator of Defense Nuclear Nonproliferation at DOE/NNSA. "Thanks to the excellent partnership between DOE/NNSA and SCK CEN, we are on the brink of achieving a breakthrough in nuclear fuel design that will make both America and Belgium safer and more secure.”
Gradual transition
According to the current planning, the first low-enriched fuel elements will enter the reactor core in 2027, pending FANC’s approval. "We refer to the 'first' fuel elements because the conversion will be gradual," Steven Van Dyck points out. Only a portion of the fuel elements are replaced each reactor cycle. "So, it will take several years before the reactor core is fully converted."
Thoroughly tested
The fuel underwent a thorough development process, as BR2 must also achieve the same technical performance with low-enriched uranium. "First, we processed the fuel into individual plates, which we tested under moderate conditions," explains Jared Wight. "In that phase, we kept the reactor's capacity and the burnup fraction - the degree to which the fuel is burned up - deliberately low." This was followed by the second phase, in which the fissile material plates were exposed to a higher capacity and a higher burnup fraction. It wasn't until the third stage that the experts processed the plates into three test fissile material elements, as they would serve in the reactor. "We irradiated two of them under normal operational conditions and subjected one to above the usual limits, even exceeding the international guidelines required for fissile material qualification," he continued. A thorough, visual inspection and leak test followed each irradiation.
After the visual inspection, the experts focused on the underlying structures. "Each element consists of 18 individual fuel plates. We extracted six plates from two elements - each subjected to different capacity - to examine them. The goal was to detect any microscopic abnormalities and deeper-lying irregularities. Combining all these analyses gives us an overall picture of the behaviour of the new fuel. And that picture now clearly confirms that the fuel remained stable and operated safely and predictably throughout all demonstration phases and achieved the same technical performance as its highly enriched variant," concludes Jared Wight.
