FEFU and FEO RAS: Material for safe management of strontium-90 radionuclide in autonomous marine energy

2021: Development of safe materials for the design of "nuclear batteries"

On March 25, 2021, FEFU and FEO RAS announced the development of safe materials for the design of "atomic batteries."

"Battery" is an ultra-strong ceramic matrix with the high-energy radionuclide strontium-90 (90Sr) enclosed in it. Material is made by method of pulse plasma agglomeration under high pressure, meets the requirements to the cured radioactive waste (GOST P 50926-96) and can be a reliable radioactive source of autonomous power supply for navigation equipment (lighthouses, radio beacons, light signs) and meteorological stations of the Northern Sea Route (NSR).

Stable capacity and accuracy of navigation on the Northern Sea Route can be guaranteed by a network of autonomous marine navigation devices operating on radiation current sources (RITs). The most promising are RIT elements based on the high-energy radionuclide strontium-90 (90Sr, RIT-90). Thermal energy of its radioactive decay is converted into electric one by thermoelectric generators.

Scientists of FEFU and FEO RAS managed to create a ceramic material with high mechanical strength, microhardness and thermal stability, which is necessary for the safe, without the threat of environmental pollution, placement of active zones with strontium-90. An energy plant ("isotope battery") made from developed ceramics is one example of the peaceful use of nuclear technologies.

RIT-90 is a closed source of ionizing radiation, where strontium borosilicate glass (90SrTiO3), a non-ideal candidate material, is used as an active composition, since it is subject to veterination with subsequent mechanical destruction. Despite the protection of the capsule with the active zone from external influences, the established system for handling the RIT-90 does not guarantee the physical protection of the RIT element. An accident, unauthorized extraction or a terrorist act can lead to the destruction of the RIT core, the release of 90Sr into the environment, including sea water. The radionuclide can thus be involved in the food chain "bottom microorganisms - algae - fish. The ceramic matrix composition developed by FEFU and FEO RAS reliably protects the active zone with strontium-90, no matter what happens, "says one of the authors of the work, Ivan Tananaev, director of the School of Natural Sciences (SHEN) FEFU.

The scientist recalled that any man-made radionuclides that entered the World Ocean are recorded by biota. Radiocesium (137Cs) accumulates in phytoplankton (mainly diatoms), macrophytes, coastal brown and red algae, soft tissues of invertebrates and fish. Radioittrium accumulates in the shell of fish caviar, in algae, crustaceans, in shells of mollusks, cerium-144 (144Ce) - in algae, actinia, in the body of mollusks. Radioactive isotope of iodine (131J) - in algae, etc. Moreover, if in fish the coefficient of accumulation of radionuclides is low, but for yolks of eggs of waterfowl it exceeds a million units. Strontium-90 accumulates with radiators, unicellular planktons, which concentrate it in spicule processes, some green algae, all types of brown algae, in crustacean shells and mollusk shells.

The Joint Threat Reduction Program of the US Congress, which has been in force since 1991, considers RITs as a threat to the spread of radioactive materials to create a "dirty bomb." IAEA classifies such elements as high risk, as a single strontium 90-based RIT element can be dangerous for more than 1,000 years.

Scientists of FEFU and FEO RAS under the leadership of Yevgeny Papynov (Institute of Chemistry FEO RAS), using the method of reaction spark plasma sintering (IPS) of mineral-like ceramic systems, were able to obtain a stable ceramic matrix composition that reliably protects the active zone with strontium-90. The matrix is capable of "holding" radiation even in the event of an accident and a RIT element entering environmental objects, including fresh and sea water.

The IPS approach is based on the consolidation of powder materials due to high-speed heating and compaction. The technique allows maintaining the micro-grain structure of the final material, its high hardness, strength and low rate of radionuclide leaching in media with different acidity. The technological approach is developed jointly by specialists from FEFU and the Institute of Chemistry of FEO RAS.

According to researchers, the obtained ceramic material can also be recommended as sources of ionizing radiation based on 90Sr for production at FSUE Mayak Software.

The work is carried out within the framework of state tasks of the Ministry of Education and Science of the Russian Federation and scientific projects of the Russian Foundation for Basic Research.