[[File:Beta-M Soviet RTG Diagram.svg|right|thumb|Diagram of the soviet radioisotopic thermoelectric generator "Beta-M". Black: Framework Blue: Outer radiation protection Yellow: Heat isolation Orange: Inner radiation protection (Tungsten) Red: Radionuclide heat source (Strontium-90) Pink: Thermoelectric unit Mounted above the assembly are fins for cooling, outlined in black.|360x360px]] The Beta-M is a radioisotope thermoelectric generator (RTG) that was used in Soviet-era lighthouses and beacons.

Design

The Beta-M contains a core made up of strontium-90, which has a half-life of 28.79 years. The service life of these generators is initially 10 years, and can be extended for another 5 to 10 years. The core is also known as radioisotope heat source 90 (RHS-90). In its initial state after manufacture, the generator is capable of generating 10 watts of electricity. The generator contains the strontium-90 radioisotope, with a heating power of 250W and 1,480 TBq of radioactivity – equivalent to some 280 g of Sr-90. Mass-scale production of RTGs in the Soviet Union was the responsibility of a plant called Baltiyets, in Narva, Estonia.

Safety incidents

Some Beta-M generators have been subject to incidents of vandalism when scavengers disassembled the units while searching for non-ferrous metals. In December 2001 a radiological accident occurred when three residents of Lia, Georgia found parts of an abandoned Beta-M in the forest while collecting firewood. The three suffered burns and symptoms of acute radiation syndrome as a result of their exposure to the strontium-90 contained in the Beta-M. The disposal team that removed the radiation sources consisted of 25 men who were restricted to 40 seconds' worth of exposure each while transferring the canisters to lead-lined drums.