Floating Nuclear Reactors: The Engineering Behind Russia's Akademik Lomonosov and What Comes Next

In 2019, Russia towed a nuclear power plant to the Arctic. Not a land-based plant connected to a pier — an actual nuclear reactor on a barge, the Akademik Lomonosov, moored at the remote port of Pevek in Chukotka to supply power and heat to roughly 50,000 people in one of the world's most isolated inhabited regions. The engineering required to make this work — keeping a pressurized water reactor operational in sea ice, Arctic weather, and remote maintenance conditions — is worth examining carefully, because several countries are now pursuing variations on the concept.

## Akademik Lomonosov: Operational Data

The Akademik Lomonosov carries two KLT-40S reactors, a marinized variant of the reactor design used in Russian nuclear-powered icebreakers since the 1970s. Each reactor produces 35 MW of electrical output (70 MW total) plus heat for district heating. The vessel is 144 meters long, 30 meters wide, displaces 21,500 tonnes, and was constructed at the Baltic Shipyard in Saint Petersburg before being towed — without operating reactors — through the Northern Sea Route to Pevek.

The choice to build at an established shipyard rather than at the operating site is fundamental to the concept. Shipyards have the cranes, trained workforce, quality control infrastructure, and regulatory oversight developed over decades of naval nuclear construction. Moving the construction risk to an existing facility and the operational risk to the deployment site is a deliberate decomposition of the engineering problem.

Operational data from Pevek through 2025 shows the plant running at capacity factors above 85%, supplying roughly 44% of the region's electricity demand. The KLT-40S has a 3-year refueling cycle, during which the entire vessel is towed back to a mainland shipyard — eliminating the need for fuel handling infrastructure at the remote site entirely. This "factory-refueled" model is one of the key arguments for floating nuclear: the complex maintenance operations happen where the expertise is, not where the need is.

## Wave, Seismic, and Load Engineering

A nuclear plant on water faces environmental loads that land-based plants never encounter. The structural engineering requirements span three domains.

**Wave loads** on the moored barge are managed through a combination of hull design and mooring system. The Akademik Lomonosov uses a catenary mooring system — heavy chains that drape from the hull to anchors on the seabed — which allows controlled motion while preventing drift. The reactor systems are designed to tolerate continuous low-amplitude motion; the KLT-40S containment system was derived from submarine reactor designs, which were engineered for extreme motion from the start.

Resonance is the primary concern. Hull natural frequencies must be tuned to avoid coupling with typical wave periods (5 to 15 seconds in North Sea or Pacific conditions). The Akademik Lomonosov is in Arctic waters where wave heights are typically lower than in open-ocean environments, which reduces the challenge — but proposed floating reactors for tropical or temperate ocean deployments face more demanding wave climates.

**Seismic loading** for a floating reactor is paradoxically simpler than for land-based plants in high-seismicity zones. A floating vessel is effectively isolated from ground motion by the water column — the seismic energy that would directly enter a land-based foundation is instead transmitted through the water as pressure waves, which are attenuated by the fluid medium. Floating reactors moored in deep water have inherently better seismic isolation than most land-based designs. However, for reactors in shallow coastal waters or on fixed offshore platforms, seismic coupling to the seabed can still be significant.

**Passive cooling** in a marine environment is more reliable than on land in one important respect: there is an unlimited heat sink. The Emergency Core Cooling System (ECCS) for most floating reactor designs uses seawater as the ultimate heat sink, available in unlimited quantity and naturally at temperatures below 30°C even in tropical waters. This simplifies passive safety system design considerably — the post-Fukushima concern about losing active cooling is much less acute when your reactor is surrounded by several billion tonnes of water.

## South Korean BARGE-MOUNTED SMR Proposals

South Korea has been systematically developing floating nuclear technology through a collaboration between KEPCO (Korea Electric Power Corporation), KAERI (Korea Atomic Energy Research Institute), and Hyundai Heavy Industries. Their target platform is a barge-mounted small modular reactor (SMR) based on the SMART reactor design — a 100 MWe pressurized water reactor with integral steam generators and passive safety features.

The South Korean approach differs from the Russian model in several respects. The SMART design uses full passive safety systems: natural circulation cooling, gravity-fed borated water injection, and a contained primary circuit that does not require active pumping to cool the core in accident scenarios. The design target is a 60-year operating life with 30-month refueling intervals.

The intended deployment model is islands and coastal communities across Southeast Asia — Indonesia, the Philippines, Vietnam — that are expensive to connect to continental grids but have the coastal infrastructure to receive a moored vessel. The South Korean team has also engaged Saudi Arabia's NEOM project as a potential customer, where power and water desalination are both priorities.

KAERI submitted the SMART design for IAEA Generic Reactor Safety Review in 2012 and received positive completion in 2015 — the first SMR design to complete that process. The barge-mounting engineering adds complexity but does not fundamentally change the nuclear safety case.

## Regulatory Challenges

The regulatory framework for floating nuclear is genuinely complicated, and not only technically. A floating reactor moored in one country's territorial waters is, in most legal frameworks, still a vessel — subject to maritime law, flag state regulations, and port state control. When it generates electricity for the grid, it also becomes energy infrastructure subject to national nuclear regulatory authority.

Russia resolved this by treating the Akademik Lomonosov as a technical extension of its land-based nuclear regulatory framework, governed by Rosatom and Rostekhnadzor. Other countries face more fragmented regulatory environments. In the US, for example, a floating reactor would theoretically require NRC licensing but also potentially Coast Guard vessel certification — two bodies with different safety philosophies and no established joint framework.

The IAEA has been working since 2019 on guidance documents for floating nuclear, and several member states have engaged in the process. But as of 2026, no country outside Russia has operating commercial floating nuclear power, which means there is no proven precedent for foreign regulatory bodies to reference.

## Cost Per MWh: Floating vs. Land-Based SMR

The economics of floating nuclear are unfavorable compared to land-based SMR designs, for a structural reason: marine construction adds cost. Building a reactor inside a hull, with all the sealing, marine-grade materials, and redundant compartmentalization required for ocean operations, increases capital cost by 20 to 40% over an equivalent land-based design. The Akademik Lomonosov reportedly cost approximately $740 million to build — high for its modest 70 MW capacity.

Levelized cost of electricity (LCOE) estimates for the Akademik Lomonosov are in the range of $200 to $250 per MWh, which is extremely high by any standard. Proponents note that the relevant comparison for Pevek is not the global electricity market but the cost of diesel generation in the Arctic — which runs above $400 per MWh. In that context, the economics are defensible.

For planned second and third-generation floating SMRs — including the South Korean SMART barge and the proposed Russian RITM-200S-based successor to Akademik Lomonosov — cost targets of $80 to $130 per MWh are being cited. These depend on series production (building multiple identical units to drive down per-unit cost) and standardized mooring infrastructure at deployment sites.

The honest assessment is that floating nuclear makes economic sense only in specific contexts: extreme remoteness, high baseline energy costs, or locations where land-based construction is genuinely impractical. It is not a general solution to the global energy mix. But for the communities and industries where those conditions apply, it is increasingly credible engineering rather than a speculative idea.

Floating Nuclear Reactors: The Engineering Behind Russia's Akademik Lomonosov and What Comes Next

// COMMENTS

ON THIS PAGE