The potential for major gains in safety, physical protection and economics of nuclear energy exists through the development of a floating Offshore Small Modular Reactor (OSMR). This is a plant that can be entirely built (and decommissioned) as a floating rig in a shipyard, floated to the operating site (within 8–15 km of the coast), anchored in relatively deep water (i.e., ∼100 m), and connected to the grid via an underwater transmission line. The OSMR design presented here features innovative passive and indefinite emergency core and containment cooling systems that eliminate the loss of ultimate heat sink accident, thus decreasing the likelihood of severe accidents. Furthermore, the OSMR containment design and back-up venting procedures effectively eliminate the threat of serious land contamination, should a severe accident actually occur.

A new Offshore Floating Nuclear Plant (OFNP) concept with high potential for attractive economics and an unprecedented level of safety is presented, along with an overview of work done in the area of security. The OFNP creatively combines state-of-the-art Light Water Reactors (LWRs) with floating platforms such as those used in offshore oil/gas operations, both of which are well-established technologies which can allow implementation on a time scale consistent with combating climate change in the near future. OFNP is a plant that can be entirely built within a floating platform in a shipyard, transferred to the site. OFNP eliminates earthquakes and tsunamis as accident precursors; its ocean-based passive safety systems eliminate the loss of ultimate heat sink accident by design. The defense of an OFNP poses new security opportunities and challenges compared to land-based plants. Such a plant can be more easily defended by virtue of the clear 360 degree lines of sight and the relative ease of identifying surface threats. Conversely the offshore plant is potentially vulnerable to underwater approaches by mini-submarines and divers. We investigate security considerations of the OFNP applicable to two potential plant options, an OFNP-300 with a 300 MWe reactor, and an OFNP-1100 with an 1100 MWe reactor. Three innovative security system approaches could be combined for the offshore plant. The first is a comprehensive detection system which integrates radar, sonar and unmanned vehicles for a long distance overview of the vicinity of the plant. The second approach is the use of passive physical barriers about 100 meters from the plant, which will force a fast-moving power boat to lose speed or stop at the barrier allowing the plant security force more time to respond. The third approach takes advantage of the offshore plant siting and the monthly or biweekly rotation of crew to reduce the total on-plant and onshore security force by using the off-duty security force on the plant as a reserve force. Through the use of these approaches, the OFNP-300 should be able to achieve a similar security cost (on a per Megawatt basis) as land-based plants of similar or somewhat larger power rating. Due to non-linear scaling of cost, the security cost of the OFNP-1100 has the potential to be reduced significantly compared to its land-based equivalents.