Ship propulsion: nuclear power

Nuclear fission is a process in which the nucleus of an atom splits, usually into two pieces. This reaction was discovered when a target of uranium was bombarded by neutrons. Eission fragments were shown to fly apart with a large release of energy. The fission reaction was the basis of the atomic bomb, which was developed by the United States during World War II. After the war, controlled energy release from fission was applied to the development of nuclear reactors. Reactors are utilized for production of electricity at nuclear power plants, for propulsion of ships and submarines, and for the creation of radioactive isotopes used in medicine and industry. 

Statiis and prospects of propulsion reactor (PR) applications. The PRs for ice-breakers and ships have accumulated about 150 reactor-years of successful operation. Recent developments in the Russian Federation, Canada, China and other countries have demonstrated, that power reactors originally designed for ship propulsion could be used for electricity and heat generation. Use of proven PR technology and new developments on small reactor (SR) presents a broader nuclear power options to meet individual Member States needs for land-based and floating SRs. 

Successful resolution of such a problem requires a comprehensive systems approach diat considers all aspects of manufacturing, transportation, operation, and ultimate disposal. Some elements of this approach have been used previously in the development of propulsion (ship and space) nuclear power systems, with consideration given to many diverse requirements such as highly autonomous operation for a long period of time, no planned maint ance, no on-site refuelling and ultimate disposition. 

Natural uranium can be used as fuel in a nuclear reactor however, as the proportion of U increases, the ease with which a fission reactor can be used as an energy source increases. Modem light-water-moderated reactors are fueled by uranium enriched in U from 0.71% (natural) to 3-5%. For greater U enrichments, the size of a reactor for a given power level can decrease reactors for ship propulsion use starting enrichments of at least 10% to minimize... 

In addition to this, a unified nuclear propulsion and power complex consisting of nuclear ships and floating cogeneration plants based on a common type of reactor installation and supported by a common maintenance infrastructure could effectively solve the problems of energy supply to autonomous consumers, such as those in the North-eastern regions of the Russian Federation, at minimum cost. 

Instead, the report recoimnended either a form of BWR or an organic-moderated reactor (OMR). Considering that little or no development work had been done in the UK on the OMR, this does seem a somewhat bizarre choice. The sub-committee almost unanimously confirmed its belief that the nuclear propulsion of our high-powered large merchant ships will become economic in time . Unfortunately, the sub-committee was wrong in both its choice of reactor and in the economics of nuclear power at sea. 

Despite this, all the designs still ran up against the same major problem. Whichever system was considered, the costs invariably worked out far higher than for conventional propulsion. None of the nuclear-powered ships which have been built—Russian icebreakers and prototype nuclear-powered commercial ships (such as the American Savannah, the German Otto Hahn, and the Japanese Mutsu) — have been a success. 

As will be discussed in Section VIII, nuclear ship propulsion seems to be competitive with conventional systems for units of larger power between 50,000 and 100,000 shp), higher power density, higher burnup. Furthermore the use of zircalloy cladding and finger absorbers is economically attractive. From an optimization study the pin lattice parameters showed a trend towards closer packed lattices than that of the first Otto Hahn core, a trend towards typical pressurized water reactor lattices. 

Over the more than 40 years since the first nuclear fission reactor was constructed numerous designs of reactor have been evolved by variation of the basic parameters such as fuel type, moderator, and coolant. One possible classification is by intended use, e.g., research, plutonium production, electricity generation, or propulsion units for submarines or surface ships. In this chapter we will concentrate on power reactors, both on account of their practical importance and because of the complexity in engineering design introduced by the need to convert the energy released by nuclear fission into a mechanical or electrical output. Many of the characteristics of the various reactor types have been touched on in earlier chapters, but the objective in the present chapter is to provide a systematic summary of the main classifications of reactor prior to the more detailed descriptions to be given in the following chapters. 

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