Scientists at Rosatom’s Fuel Division, TVEL, have developed an industrial-scale method for producing the nitrogen-15 isotope, a critical component in manufacturing next-generation uranium–plutonium nitride nuclear fuel intended for use in fast neutron reactors.
As part of a research project an enlarged laboratory stand was created at the AA Bochvar Research Institute of Inorganic Materials (VNIINM) in Moscow to study the separation of nitrogen isotopes in two-phase gas-liquid systems. Work has been carried out to study and optimise technological methods for producing the highly enriched nitrogen-15 isotope, and the first batch has been produced.
Mastering the technology of isotope separation in tonnage quantities in the future will make it possible to organise industrial production of the nitrogen-15 isotope, which is a promising component for high-density uranium-plutonium nitride (SNUP – Smeshannoe Nitridnoi Uran-Plutonievoe) fuel. Such fuel is supposed to be used in fast neutron reactors.
According to Rosatom scientists, isotope-modified SNUP fuel, where nitrogen-15 is used instead of natural nitrogen, will have a number of advantages. Its will ultimately help reduce the production of radioactive isotopes in the reactor core, as well as increase the efficiency of fuel operation.
“Fast neutron reactors are of strategic importance for the energy of the future,” said Alexander Ugryumov, Senior Vice President for Scientific and Technical Activities at TVEL. “Today, our scientists are systematically building a comprehensive scientific and technical base that will allow us to further build a new technological platform in the nuclear industry along the entire chain of the nuclear fuel cycle. Our research simultaneously covers advanced fuel and structural materials, uranium-plutonium fuel fabrication technologies and reprocessing solutions. All these developments are aimed at energy and environmental safety to support sustainable development – maximum possible expansion of the raw material base for NPPs while minimising radioactive waste and irradiated fuel.”
The first installation designed to operate with a full load of SNUP fuel is the fourth-generation reactor BREST-OD-300, which is being built at the Siberian Chemical Plant in Seversk, Tomsk Region as part of the Pilot and demonstration energy complex as part of the strategic industry Proryv (Breakthrough) project. The general plan for Russian energy facilities also envisages the construction of seven more serial high-power power units with fast reactors by 2042.
Isotope nitrogen-15 is unique in that it absorbs virtually no neutrons, and its use will improve the neutron balance of the reactor core. Experts expect a radical reduction in the production of radioactive carbon-14 in the reactor, as well as a reduction in the so-called fuel load. The isotopic composition of natural nitrogen is dominated by nitrogen-14, therefore, due to the absorption of neutrons in the reactor core load, more fissile material is required to maintain the chain reaction. Since nitrogen-15 does not absorb neutrons, during the burnup of nuclear fuel the neutron concentration will be higher, which means that less fuel will be required.
