Ship propulsion reactors

Currently, all the nuclear-propelled ships are military, but at one time experimental, nuclear-powered, merchant ships were built. The most famous of these was the US ship, the NS Savannah, which hosted a small PWR (74 MWt) located in a small volume pressure containment (with a high design pressure). The ship was also provided with a small conventional engine as a reserve to the principal turbine engine. 

The main safety issue of these reactors was to guarantee the protection of the population during the stay in a harbour. To this end, every hosting port was provided with an emergency plan according to which, in case of accident, the ship would be taken offshore by always available tugs. In the many years of operation no event happened that required the activation of such a plan. 

In comparison with other nuclear activities, transportation has the following specific characteristics  

The various national standards are referred to these. The IAEA standards include  

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This meeting was organized as a forum for experts of Member States to advise the IAEA on the different types of water and liquid metal cooled ship propulsion reactors, barge mounted power reactors and innovative reactor concepts which do not require on-site refuelling, and other similar reactor types presently in existence or under consideration in their countries. The purpose of the meeting was also to obtain advice from Member States on their needs and interests in the context of the IAEA s small and medium reactor programme. 

Ship propulsion reactors operational experience, new development and alternative applications... 

The total power of the second core was fixed by the overall layout of the ship Otto Hahn. A change in lattice pitch could only be made satisfactorily if the size of the fuel elements and consequently the proper position of the control rod drives were changed too. Since in the optimum the fuel cycle costs depend not very strongly on the lattice parameters, the basic pin lattice of the first core was also taken for the second core. The main properties, in which the second core is essentially representative for the design of large commercially attractive ship propulsion reactors, are the power density and the burnup, the use of zircalloy for cladding and spacers, and finally the use of finger absorbers in the control elements. 

Power reactors have also been developed and installed for ship propulsion, for instance in submarines (e.g. Nautilus , USA) or icebreakers (e.g. Lenin , Russia). 

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. 

Sizes are limited. Heating Reactor adopted integrated arrangement. Whole primary loop is included in a pressure vessel. Sizes of the pressure vessel are limited. A compact arrangement for the ship propulsion power source is a important factor. 

Small-scale reactors have more advantages than large-scale reactors in variety of energy utilization, construction, maintenance and adoption of innovative technologies, while the latter have scale merits in construction cost. The nuclear energy utilization of small-scale reactors are ship propulsion, electricity generation, heat supply, and sea water desalination, etc. Construction and maintenance for small-scale reactors can be made in factories exclusive use for them, but not at the site of the plant. In small-scale reactors, the safety can be enhanced sometimes by new technologies. 

The first reactor with leakproof and pressure resistant containment was the SRI reactor (West Milton, NY, built in the 1950s). Built to perform tests for the development of reactors for military ship propulsion this reactor was cooled by sodium and the containment was designed for the pressure corresponding to the combustion of the sodium escaping from a hypothetical leak in the cooling circuit. 

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... 

The IPWR concept is an outgrowth of widespread interest in commercial nuclear ship propulsion in the late 1950s and early 1960s. Economic evaluations of commercial marine propulsion reactor designs based on several distinctly different reactor concepts (e.g., loop-type PWR, gas-cooled, organic-cooled, etc.) concluded that none were competitive at that time with conventional fossil-fuelled propulsion systems, at least in sizes up to 20-30,000 shp (shaft horsepower). 

VBER reactor plant is developed by OKBM with reliance on the experience of development, construction and operation of the modular nuclear propulsion reactors that are well established and proven through long-term successful operation within civil and navy ships. At present, the total accident-free operating time for them exceeds 6000 reactor-years. 

Clark, P. R., Homogeneous Reactor for Ship Propulsion, USAEC Report CF-55-8-191, August 1955. 

On present designs it cannot compete, at UK fuel prices, even with the first civil power stations. Prospects for the development of the design are limited. Nevertheless, for small outputs, and particularly if cheap fuel were available (i.e. enriched uranium at US prices, or cheap civil plutonium) the reactor has certain advantages because of its compactness both for ship propulsion and as a small plutonium burner to meet peak loads. This may make it suitable for development in this country at a later date. The boiling water version of the reactor does not have the same problems of extremely high pressure and large output versions with consequent low capital cost may be possible. 

The issue was left in abeyance for the next ten years, as Harwell and Risley were too busy with other matters. The only British power reactor designs were gas-cooled, and as late as 1957 Hinton was still thinking in terms of a miniature PIPPA for ship propulsion. 

Successful operation of the first core of the Otto Hahn reactor showed the basic feasibility of the FDR for nuclear ship propulsion. The operation of a second more advanced core should provide information for the design of future cores with lower fuel cycle costs. However for reasons of cost and time only minor alterations to the system were to be allowed, except in those cases where the value of the gained experience would compensate the expenditure. 

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. 

The technical feasibility of the nuclear ship propulsion for merchant vessels has been demonstrated by the nuclear ships Savannah and Otto Hahn. However, these first demonstration ships have not been economical. For the second generation of nuclear merchant ships an economical advantage compared to conventional vessels has to be proven. It is well-known that the higher investment for the nuclear steam generators has to be compensated for by lower fuel costs. Therefore in the design of future ship reactors efforts have to be made to reduce the fuel costs. But it is also possible to realize lower investment of the engine by further optimization of all components. 

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. 

In the regions, where fresh water resources are deficient, transport of fresh water is need. Usually ship transport is used. This way to transport water is not convenient. If a reactor is mounted on a ship, as a desalination power source, at the same time as a propulsion power resource, that would be a interesting solution. 

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. 

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. 

It was the development of the nuclear reactor for navy propulsion that led to the use of zirconium and zirconium alloys as a fuel cladding material. This program, headed by Captain, and eventually Admiral, Rickover demonstrated flie viability of using fission energy to propel navy ships and submarines. 

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. 

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