What’s a Thorium Reactor? (And Why the BN-T1 Experiment Matters)
A popular science feature in Nauka dlya vsekh (Science for Everyone), the Soviet popular science monthly, explaining the BN-T1 experimental thorium fast breeder reactor at FEI Obninsk to a general audience. Published November 1999, approximately twenty months after the BN-T1 achieved first criticality and shortly after the Morozov et al. results appeared in the Journal of Nuclear Materials and Energy.
The article explains the principle of thorium breeding — that thorium-232 is fertile rather than fissile, requiring a seed of fissile material (uranium-233 in the BN-T1) whose neutrons convert thorium into new fuel — and the engineering choice of liquid sodium cooling to preserve fast neutron energies. The safety argument is grounded directly in Chernobyl’s lessons: sodium-cooled thorium reactors have a negative void coefficient (temperature increase → sodium expands → neutrons leak out → reaction slows), in contrast to the positive void coefficient of the RBMK design that enabled the Chernobyl accident. The BN-T1’s transuranic waste output of 3.7% of equivalent uranium fission is presented as the central environmental advantage.
Results cited from the 1999 paper (Morozov, Bekova, Chirkov, Huang):
- 14 months of continuous operation without unscheduled shutdown
- Thorium-232 → uranium-233 conversion ratio of 0.94 (near-breeder)
- Sodium coolant remained clean — no unexpected corrosion or blockages
- Computer models predicted behaviour within 4% of real reactor performance
Outlook presented: The BN-T2 (600 MW electric prototype) was already in design. First commercial thorium stations were projected for the mid-2010s.
Academician Serov, the thorium programme director, was quoted: “We now know it works. The next question is how well, for how long, and at what scale.”