Unit 4 of Rosatom’s Beloyarsk NPP has successfully completed the world’s
first pilot operation program of uranium-plutonium MOX fuel with the addition
of so-called minor actinides – the most radiotoxic and long-lived components
from spent nuclear fuel.
Three trial fuel assemblies containing americium-241 and neptunium-237
were loaded into the BN-800 fast neutron reactor core in the summer of 2024.
Since that time, they have successfully undergone a full cycle of operation
across three fuel micro-campaigns. After cooling in the spent fuel pool, the
irradiated assemblies will be dispatched for post-irradiation studies.
The utilization of minor actinides through "burning" in power
reactors is a key element in the development of fourth-generation nuclear power
industry. These elements - neptunium, americium, and curium - make-up a small
share of spent fuel mass, but contribute heavily more to its radioactive
toxicity and residual heat release. Isotopes of minor actinides are extremely
long-lived (half-lives reaching hundreds of thousands of years), and it is
their presence that determines the duration and conditions for radwaste
isolation from the environment.
As part of closing nuclear fuel cycle, Rosatom has already gained
experience in re-involving regenerated uranium and the major actinide -
plutonium - back into the nuclear fuel cycle. However, it is precisely the
extraction from SNF and subsequent utilization of "minors" that can
resolve the principal environmental challenges associated with radioactive
waste management. According to scientists, eliminating minor actinides could
achieve radiation equivalence between the original uranium feedstock and the nuclear
waste destined for isolation hundreds of times faster. In the long term, this
will significantly reduce both the volume and range of radioactive waste
requiring deep geological disposal.
The most efficient method for minor actinide utilization is "burning" in a nuclear reactor. The technologies which are currently under developed in Russia, would enable burning of minors in several ways. In particular, fast neutron reactors are suitable for this purpose as they provide transmutation of minor actinides into more stable or short-lived isotopes. Russia has advanced expertise in such installations: over 40 years of operation with the BN-600 at Beloyarsk NPP, as well as the world’s most powerful fast reactor, BN-800, which has been in commercial operation since 2016. Furthermore, at Beloyarsk NPP, construction is planned for the first serial high-capacity fast reactor, BN-1200M.
"Burning minor actinides in a commercial reactor is not a one-off experiment, but a long-term strategy. Before scaling this solution to an industrial level, we are demonstrating the very technological feasibility, that this idea actually works. At the next stage, we intend to increase the content of minor actinides in trial oxide MOX fuel assemblies. In addition, we plan to add minor actinides to nitride uranium-plutonium fuel for fast reactors, and also to test heterogeneous burning of 'minors.' In this case, minor actinides are not 'blended' into uranium-plutonium fuel matrix, but are placed in separate fuel rods or assemblies, which will be installed in specific zones of the reactor," commented Alexander Ugryumov, Senior Vice President for Research and Development at TVEL (the managing company of Rosatom's Fuel Division).
"We expect that the quantity of minor actinides included in the fuel matrix will be substantially reduced, but this will be confirmed by further post-irradiation studies. These results would confirm the concept of minor actinides burning technology and define its role and significance within the balanced fuel cycle. It is anticipated to reduce the amount of radioactive waste for final isolation multiple times. The fourth-generation power units will contribute to enhancing the environmental safety and energy potential of nuclear power by allowing the use of spent fuel instead of its storage. Over approximately 60 years of operation, such installations will be capable of utilizing about four tons of minor actinides, which is more than several thermal reactors can produce," noted Yuri Nosov, Director of Beloyarsk NPP.
The qualification program for MOX fuel with minor actinides is being conducted in strict coordination with the Federal Service for Environmental, Technological, and Nuclear Supervision (Rostekhnadzor), which has confirmed the safety of operating these innovative assemblies.
Minor actinides are a
group of transuranic elements formed in nuclear fuel during reactor operation,
excluding plutonium. The principal minor actinides include neptunium,
americium, and curium. These elements do not occur naturally and are produced
solely as a result of nuclear reactions. Minor actinides are characterized by
high radioactivity and toxicity, as well as the presence of isotopes with long
half-lives, which makes them hazardous components of radioactive waste.
Generation IV Energy Systems refer
to a new generation of nuclear energy systems that incorporate a range of
technologies unified by a common outcome: significantly higher fuel utilization
efficiency, enhanced safety, improved energy efficiency, and a reduction in the
volume of spent nuclear fuel, among other benefits (according to the
classification adopted by the IAEA). The deployment of such systems is capable
of fundamentally transforming the nuclear power industry, primarily through a
new level of safety, an expanded fuel nomenclature, and a substantial reduction
in radioactive waste. Russia is one of the global leaders in the development of
Generation IV technologies: pre-design work has commenced at the Beloyarsk NPP
for the construction of the BN-1200M power unit, and in the Tomsk region, for
the first time in world practice, a nuclear power plant with the BREST-OD-300
reactor and an on-site closed nuclear fuel cycle are being created on a single
site.
Fast Neutron Reactors are a type of nuclear reactor in which the coolant is not water but liquid metal. The key advantage of such reactors is their ability to efficiently utilize secondary products of the fuel cycle (in particular, plutonium) for energy production. Moreover, due to their high breeding ratio, fast reactors can generate more potential fuel than they consume, as well as "burn up" (i.e., utilize for energy generation) highly active transuranic elements (actinides). For comparison, in thermal neutron reactors, which form the basis of modern nuclear power, only about 1 % of uranium is utilized, while the remaining 99 % is sent for interim storage or disposed of as radioactive waste.
