[en] The weight of the radiation shielding seriously is with great effects on the maneuverability of the ship. It is important to improve the maneuverability of the ship by optimization of radiation shielding in a fixed shielding space and reducing the weight of the shielding. In this paper, the optimization methods of radiation shielding in a fixed space is studied based on SuperMC intelligent nuclear design module, and the shielding optimization design is carried out by using Savannah reactor to demonstrate the effectiveness of the method. The results show that the shielding weight of the optimized scheme is greatly reduced compared with the original design scheme, which proves that this approach provides a new technical means for guiding the material selection and shielding layout of ship reactor radiation shielding. (authors)

No abstract available

[en] Specific features of a reactor for a submarine designed for performing researches and pipe laying in high arctic latitudes are described in short. Application of low-enriched uranium, the presence of a high negative reactivity coefficient as well as a special design geometry make the reactor safe

[en] Full text: It has been about four decades since nuclear powered cargo ships were seriously discussed in the naval architecture community. However, recent developments in commercial shipping include faster, bigger, and more powerful ships. In addition, several initiatives in advanced reactor design include smaller, safer and more efficient reactors. The development of advanced ships and advanced reactors opens an opportunity for nuclear propulsion. Although the goals of the international projects, such as INPRO or GIF, are not directly related to propulsion, those are analyzed for such possibility regarding the contribution of nuclear propulsion to energy sustainability and environment, considering that freight and transportation activities currently fueled by oil or other fossil fuels will continue to expand. Nuclear energy only serves 6% of the primary energy mix. Current nuclear technology can provide large and lasting CO₂-free energy with less harm to the environment and minimum depletion of natural energy resources. Contradictorily, its potential contribution to sustainable development is unlikely without a major technological shift, resulting in much less capital intensive power plants and reduced energy production costs for competitive operation, in addition to huge reactor and fuel cycle safety, waste and non-proliferation improvements. Early commercial marine nuclear power did not succeed. However, based on a set of 'marine' economics; environment, fuel cycle and waste; reactor and fuel cycle safety; non-proliferation and other crosscutting user requirements, and on cargo trends, innovative nuclear propulsion could be justified for a few ship classes: the high-performance cargo monohull and multihull, with innovative propulsors and highly compact power plant packages. Two tools were used for characterizing these platforms: the Suspension Pyramid and the Transport Factor. In some cases, the fuel component of the transport factor may be very large (and indeed expensive) and it may be burned with such rate to limit endurance, so that nuclear propulsion becomes a clear gain allowing extra revenues. The overall advantage is based on the net balance between fossil fuel weight savings and weight additions for the reactor, shielding and ship structure reinforcement. In terms of economics, nuclear propulsion is an option where very high fuel oil consumption is expected (high power demand and load factors). Nuclear is best for high service factor, not encouraging coastal trade. Modular plants should be utilized for low capital costs. Current technology trends point out at IPWRs (such as CAREM-F, IRIS, SMART or MRX) and GT-MHRs (i.e. helium reactors of the prismatic core type for simplicity of operation at sea), preferably the latter for overall ship competitiveness. Core residual heat removal requirements and a few other factors, including public opinion, recommend the use of a hybrid power plant, with an auxiliary fossil fuel plant, i.e., a gas turbine directly coupled to an independent set of propulsors, in addition to conventional sidewise or retractable electric thrusters for port manouvering. Two advanced ship proposals are discussed further for the case of nuclear power, based on published data and market opportunities. A few alternative hybrid power plants concepts (for direct and electric propulsion) are shown for such ship types. The economic viability of hybrid propulsion plants is anticipated, even with very conservative nuclear reactor costs, several times the cost targets proposed within INPRO and GIF projects. All cost components considered, the operation cost of such ships would be lower than that of the fossil counterpart. Furthermore, during crisis, a small crude price variation is enough to render economic losses using high-speed vessels. In contrast, nuclear propulsion cargo costs would be stable to uranium price fluctuation. Finally, relative environmental figures are given as an example. (author)

[en] The dismantling of nuclear submarines is composed of 3 steps. The first step sees the landing of some equipment from the reactor unit and the implementation of supplementary monitoring systems. In the second step the reactor unit is completely contained and the part of the submarine enclosing it is cut and separated from the rest of the submarine. The front and the rear parts of the hulk are welded together and the submarine is returned to water and moored along a quay. The section of the submarine enclosing the reactor is stored on a slab of concrete designed to sustain earthquakes and is protected from adverse weather. This storage period can last several decades and when the radioactivity has sufficiently decreased, the last step of the dismantling will begin. In this step the reactor will be cut and all the waste packaged in drums. 4 submarines are in the second step of the dismantling process and no one in the last step. The last step is the purpose of feasibility studies. (A.C.)

[en] Summary only

No abstract available

No abstract available

[en] As soon as 1942 the application of nuclear energy to the propulsion of submarines was yet quoted as very promising. For 40 years this type of propulsion has been applied to submarines, aircraft carriers and ice-breakers. A review of the different kinds of ships is made and a perspective for a near future is drawn. The historical aspect of the successive French programs is presented and the development of the concept due to the progress of technology and experience is highlighted. The Charles de Gaulle aircraft carrier will benefit fully from its nuclear propulsion system. This system allows: -autonomy with the supplying of almost no limited amount of electricity, -compactness, the absence of chimneys facilitates the use of the flight-deck, -a reduction of the mass, a classical propulsion system requires 8000 tons of fuel, -a great maneuverability and a high level of reliability. Naval propulsion presents the engineers with specific problems. The exiguity of ships implies the entanglement of different systems, for instance, the water reserve is used as a radiation shielding. The ship maneuverability requires a high flexibility of the power supply: from 10% to 100% of the nominal power delivered in less than one minute. The particular auto-stability of the pressurized water reactor type which can sustain sharp power transients by a rise of only 10 degrees of the moderator temperature has been one of the main assets of this type of reactor to the naval propulsion. (A.C.)

[en] The invention deals with a compact construction particularly suitable for limited space as in ships. The incorporation of a heat exchanger generating the process steam of the power station into the reactor pressure vessel results in a simplification of construction, fabrication and mounting. In the lower part of a pressure vessel - enlarged in diameter - the reactor core is situated, whose core shroud projects upwards into a cylinder of the same diameter but higher. The primary coolant flows from bottom to top of the whole cylinder while absorbing heat from the core. Then, being sucked by one (or more) pump(s) in the pressure vessel head, the primary coolant flows down the outer annulus formed between core shroud and pressure vessel wall. The primary coolant system runs only within the reactor pressure vessel. The annulus formed above the core, e.g. between the core shroud of about half of the diameter of the pressure vessel and pressure vessel wall - is occupied by the heat exchanger corresponding to the invention. Thereby the pressure vessel wall forms directly the outer wall of the heat exchanger. Its internal wall consists of a cylindrical shell of a diameter slightly larger than that of the core shroud. The surfaces of the annulus locking bottom and top of the huge hollow cylinder are made of thick sheet steel. They form an upper and lower tube plate into which numerous vertical tubes are inserted. These tubes are vertically flown by the hot primary coolant, they heat up and evaporate the water in the hollow cylinder. Standard devices in the heat exchanger conduct the in-flowing feedwater and separate it from the steam space. Due to the fact that the shell of the heat exchanger presents the wall of the pressure vessel, the inlet of feedwater and outlet of steam are very easy to construct. (RW)