The American Bureau of Shipping (ABS) has released a concept design study to illustrate how a small modular nuclear reactor could power a 145,000 cu m LNG carrier.
The design was modelled by ABS and Herbert Engineering Corporation (HEC) to help industry better understand the feasibility and safety implications of nuclear propulsion and to support future development projects, the class society said.
ABS noted that advanced nuclear technologies that may be implemented for ship propulsion are in their early stages of maturity. It added that the level of detail provided in this study had been limited to engineering information available from the design of terrestrial applications for engineering postulation and recommendations for future design optimisation.
The report focused on several areas, including heat and energy management, shielding, weight distribution, and other design features.
A high-temperature gas-cooled reactor (HTGR) was used in the concept study. It is helium-cooled and uses HALEU (19.75% enriched) uranium oxycarbide TRISO fuel and graphite matrix as a moderator to produce 50 MWt in the thermal neutron energy range.
The reactors would be located aft of the accommodation block to shield the cryogenic cargo from the thermal load of the reactor compartment. For protection from collision, the reactor compartments would be installed above the B/15 bottom damage line and within the B/5 transverse damage penetration extents.
It is assumed that the nuclear reactors will be supplemented by battery power in an electric propulsion configuration for load-following and peak-shaving capabilities that are otherwise more difficult to meet with nuclear reactors that are typically designed for constant power generation services.
The total installed power requirement for this type of vessel is estimated to be about 35,000 kW; 11,650 kW of which would cover the hotel load and associated redundancies, while the remaining 23,350 kW are needed to power the ship propulsion to achieve the design speed of 19.5 knots. This power requirement can be satisfied by two standard nuclear power plants using two steam turbines per reactor, each with an assumed 35% power conversion efficiency.
If both reactors fail, power for a safe return to port is provided by two sets of standard diesel generators that would not be used during normal operations, ABS noted.
The study, backed by the US Department of Energy, also found that HTGR technology allowed faster transit speeds and offers zero-emission operations. There would also be no requirement to refuel, although the HTGR technology would need replacing approximately every six years. This implies opening the reactor room and removing the reactors, and this can only happen in shipyards or other facilities equipped to deal with radioactive material.
ABS said that although this is possible in a few shipyards worldwide, the limited choice implies a distinct challenge compared to conventional LNG carriers.
The report is the latest in a succession of initiatives from ABS designed to address challenges to the adoption of nuclear technology at sea. ABS had previously looked into a nuclear-powered containership and a suezmax tanker and also earlier this month launched the industry’s first comprehensive rules for floating nuclear power plants.
“While this technology is well understood on land, adapting it for marine applications is in its infancy. However, this study and the other research we have carried out clearly highlight its significant potential to address not only shipping’s emissions challenge but to deliver a range of other operational advantages to the industry,” said Patrick Ryan, ABS senior vice president and chief technology officer.
