BALANCE OF PLANT AND POWER TRANSMISSION FOR THE OFFSHORE FLOATING NUCLEAR PLANT

摘要

The Offshore Floating Nuclear Power Plant (OFNP) concept combines two established technologies, i.e. Light Water Reactors and offshore floating platforms, to offer major potential enhancements in economics and safety with respect to terrestrial plants. A cylindrical hull-type platform, moored between 10 and 20 km offshore, houses the power module, which is connected to the on-land electric grid by a submarine cable. The OFNP concept can accommodate virtually any reactor and power cycle designs, with proper modification of the platform size. However, we currently are pursuing two designs which adopt respectively an integral PWR in the 250-350 MWe range, e.g. the Westinghouse SMR, and the AP1000, which has a rated electric power of 1100 MW. The two plants are designated OFNP-300 and OFNP-1100, respectively. The Balance of Plant (BOP) of the OFNP converts the thermal power produced by the Nuclear Steam Supply System (NSSS) into electrical power through a conventional Rankine cycle and turbo-generator. Cooling water for the condenser is drawn from the cooler layer depths of the ocean and discharged at ambient temperature at the surface, thus reducing thermal environmental effects. Also, the power cycle can achieve higher thermal efficiencies than terrestrial nuclear power plants depending on the local temperature of the ocean and the specific design. The BOP design for the OFNP gives rise to unique design challenges. First, space on the platform is limited, and some components such as the turbo-generator and condensers are typically very heavy and large, approaching the maximum load capacity of onboard and shipyard cranes and moving equipment; second, developing a compact but functional layout is essential to ensure ease and low cost of operations and maintenance. Electricity is generated at relatively low voltage (<30 kV), but is most efficiently transmitted at much higher voltage. Therefore, an electrical substation with its Generator Step-Up (GSU) transformer units is needed on the platform. This paper discusses the thermodynamic design and physical layout of the OFNP-300 power cycle and the corresponding power transmission train, including the GSU transformer and the submarine cable. The Rankine cycle analysis is carried out with the support of the Aspen Plus V8.0 package. It is shown that a BOP design with a single condensing turbine achieves high thermal efficiency (＞36%) and satisfactory compactness.