A small nuclear reactor at sea is an unlikely threat on land

A recent report by the Radiation and Nuclear Safety Authority (STUK) entitled “Consequence assessment of nuclear-powered vessel accidents and floating nuclear power plant transit accidents in the Arctic region” assesses the consequences of an accident involving a nuclear-powered vessel or a floating nuclear power plant in the Gulf of Finland, off the coast of Norway and on the Northern Sea Route in the Arctic Ocean.

The report states that in case of a severe reactor accident involving a nuclear-powered vessel, it is possible that people should be protected from radiation within a radius of approximately ten kilometres from the accident site. At that distance below the wind, people should remain indoors until there are no more radioactive substances in the air. In the same area, children and pregnant women should take an iodine tablet to prevent the radioactive iodine released in the air after the accident entering the thyroid gland. 

Senior Inspector Mikko Voutilainen, who made the calculations in STUK's publication, summarizes the outcome so that it is unlikely that an accident would occur on board a nuclear-powered vessel or in the transport of a floating nuclear power plant which would result in significant doses of radiation to the population.

According to Mikko Voutilainen, there are two reasons for this: “First, reactor accidents leading to atmospheric emissions are extremely rare. On the other hand, the ships are mainly sailing far from populated areas, so it is unlikely that there will be people near the ship in the event of an accident.”

Radiation would hinder rescue work

Of course, the situation would be different for those on board and those involved in the rescue work. In the event of a serious accident, protective equipment should still be worn at a distance of five kilometres and, due to the presence of radioactive iodine in the air, those working near the accident site should take iodine tablets. Individual doses should be closely monitored and, if necessary, working hours limited.

Russian nuclear-powered icebreakers also occasionally operate in the Gulf of Finland. In recent years, the world's only nuclear-powered cargo ship has visited St. Petersburg, which is located at the end of the Gulf of Finland. The world's first floating nuclear power plant, Akademik Lomonosov, was also built in St. Petersburg and towed through the Baltic Sea to the Atlantic in spring 2018. At that time, the reactor was not loaded with nuclear fuel.

However, the Russian nuclear-powered icebreakers' home port is Murmansk and they are specifically intended to assist the navigation of the Arctic Ocean.