Arktika Class Icebreaker - OK-900A Reactors

OK-900A Reactors

Between September 1967 and April 1970, the NS Lenin (nuclear icebreaker), precursor of the Arktika and first ever nuclear propelled ice breaker, pulled in Murmansk to have its three OK-150 reactors, capable of 90 MW each, replaced with two OK-900 reactors, capable of 159 MW each. The Arktika and the entire Arktika class icebreakers are outfitted with two OK-900A reactors, which deliver 171 MW each. Each reactor is contained in its own closed compartment and weighs 160 tonnes. They are shielded by water, steel, and high density concrete, and ambient radiation is monitored throughout the ship by 86 sensors. The reactors were originally fueled by a 90% enriched, zirconium-clad, Uranium fuel. Those reactors still in operation today now use a 20%-90% enriched with 60% average enrichment uranium dispersed in an Aluminum matrix. The chain reaction can be stopped in 0.6 seconds by the full insertion of safety rods. The Arktika consumes up to 200 grams of fuel a day when breaking ice. There are 500 kg of Uranium isotopes in each reactor, allowing for up to four years between changing reactor cores. The used cores are extracted and replaced in Murmansk, the spent fuel reprocessed and waste disposed of at a Radioactive waste plant.