Where to touch nuclear physics in Prague
Few universities in the world can offer students hands-on experience with a real nuclear reactor. This episode of Czechast takes listeners inside the Czech Technical University in Prague with Professor Jan Rataj, head of the Department of Nuclear Reactors.
Hidden away inside a modest-looking building on the CTU campus close to the banks of the Vltava river is one of Czechia´s most remarkable scientific facilities. Here, students don't just learn about reactor physics from textbooks—they operate real nuclear fascilities: "We are the operator of the training reactors," Professor Jan Rataj explains. "Our department is focused mainly on education and training in nuclear reactors, nuclear engineering and related fields."
Rataj knows the facility better than almost anyone else. Raised near the Temelín nuclear power plant, he chose to study nuclear engineering at CTU and joined the Department of Nuclear Reactors as a student. "I used this facility during my studies," he recalls. "And then I stayed here." Today, he leads the department responsible for educating many of the specialists who will eventually work in Czech and foreign nuclear power plants.
A reactor you can actually touch
The older of the university's two reactors, VR-1, first reached criticality in December 1990. Unlike commercial power reactors, however, it was never intended to generate electricity. "This is what we call a zero-power reactor," Rataj explains. "Nominally, its power is one hundred watts, with a maximum of five hundred watts. We don't produce heat. We don't produce electricity. You can use it mainly for education because you can measure the physics—you can see how the reactor behaves."
That low power makes the reactor exceptionally safe and very flexible for teaching. Students assemble different reactor core configurations, predict when the reactor will reach criticality, monitor neutron behaviour and even operate the reactor themselves—always under supervision.
"We would like to show the theory practically," says Rataj. "They can touch physics. They can set up neutron detection systems, measure activity, predict the critical state of the reactor and safely achieve it. Everything they learn in lectures, they can test here."
That practical experience, he argues, simply cannot be replaced by classroom teaching. "If you have just theoretical lectures, you cannot make mistakes and learn how to fix them. Hands-on training is definitely important for everybody—not only for students, but also for nuclear professionals."
Training specialists from around the world
Although only around thirty to forty CTU students specialise in nuclear reactors each year, the university's facilities are used far more widely. The department teaches students from other Czech universities, provides courses for future operators of Czech and Slovak nuclear power plants, and regularly welcomes visitors from universities across Europe, Asia and North America.
According to Rataj, roughly two hundred students and professionals receive practical reactor training at CTU every year. Participants have come from Finland, Sweden, the United Kingdom, Singapore and the United States, among many others. That international interest reflects a broader trend. Around Europe, many small university reactors have disappeared because they are expensive to operate.
"Currently, nobody starts building this kind of facility just for training," Rataj says. "Usually countries build larger research reactors for material testing or radioisotope production." Finland shut down its university reactor, France closed its training reactor several years ago, and Britain no longer has a civilian university reactor of this kind.
"The students from Finland are now coming here," he notes.
A second reactor, new possibilities
In 2023 CTU opened its second teaching reactor, VR-2. Unlike VR-1, it is a subcritical reactor. Without an external neutron source, the chain reaction cannot sustain itself.
"If you remove the external neutron source, it stops," Rataj explains. "But again, you can use it for education and training. Students can remove fuel rods, change the reactor configuration and immediately observe how the system behaves."
The design allows students to compare different reactor layouts, study neutron transport and investigate how materials influence reactor behaviour—all in a controlled and exceptionally safe environment. Because both university reactors operate at very low power: "We have no spent fuel," Rataj says. "We use fuel that has been in the reactor for twenty years and it is still, physically speaking, fresh."
Preparing the next generation
As Czechia expands its nuclear energy programme, the need for qualified engineers is growing rapidly. For Rataj, that makes facilities like CTU's reactors more important than ever.
"If you want to establish a nuclear programme, if you want to operate nuclear power plants, it is really important to have a training facility," he says. "Students need to see how a reactor works, measure things themselves and understand reactor behaviour in practice—not only from theory."
Full version of the interview on Czechast, our podcast in English about all things Czech on all major podcast platforms.
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