Advanced nuclear power stations: Superphénix and fast-breeder reactors

Advanced nuclear power stations: Superphknix and fast-breeder reactors Angelo Camplani and Angelo Zambelli On 7 September 1985 the Superphknix reactor, the world’s first large-scale fast-breeder nuclear power station, which is located at Creys Malville in France, went critical. On 14 January 1986 the first electricity generated there was supplied to the European consumer, through the international grid.

Owing to its advanced technology, its quantum leap in intra-European cooperation, and its scale, the Superphenix can justifiably be considered one of the major engineering projects of our age. It is the culmination of four decades of experimental work in the field of fast-breeder technology and of ten years of construction. Why such commitment? The answer is to be found in the name ‘Superphenix’, which conjures up the idea of the mythical bird born again from its own ashes. The power station’s heat generator is a nuclear reactor which burns fissile fuel (plutonium) and thereby produces more than it consumes. From the ashes of the nuclear fuel sufficient new fuel can be won to reload the reactor: in other words, it ‘breeds’ its own fuel. Essentially, it promises an almost unlimited source of energy in a world becoming increasingly short of energy resources (Table 1). Furthermore, for countries with few natural resources but considerable industrial capacity it represents an increase in their technological ability and then a trade off between more domestic activity and less imported natural resources.

Is a graduate in mechanical engineering of Milan0 Polytechnic. He has for some ten years been concerned with design and operation of nuclear and thermal power plants, and for almost fifteen years has been on the staff of the Chairman of ENEL as enerov advisor: at present he is manager, in charge’of economic planning. He is a member of the EEC Fast Reactor Coordinating Committee. Angelo

Zambelli

Is a graduate of the Institute of Industrial Technology, Bergamo. He has worked, with growing responsibilities, in the design of controls for nuclear and thermal plants for more than twenty years. Since 1974 he has been on the Superphenix project.

EURO-ARTICLE (see p. ii) Endeavour, New Series, Volume 10, No.3. 1986. OlSO-S327/S5 $0.00 + .50. Pergamon Journels Ltd. Published in Great Britain.

132

The development breeder system

of

the

fast-

In the beginning - and the idea of fast-breeder technology can be traced back to Enrico Fermi in 1945 - of the 50 nuclear reactor prototypes born of the lively minds of the pioneers a few were designed to pursue the fastbreeder concept. Fast-breeder technology - discarded for nuclear propulsion, for which the ideal engine is the pressurized water reactor (PWR) - was developed essentially for the generation of power (figure 1). The forerunner of Superphenix - the EBR-1 anticipated a future of nuclear-based electricity, becoming in 1951 the first reactor to power a light bulb. In the 1960s the laboratory stage research on the physics and thermodynamics of liquid sodium, the study of the properties of special materials, the development of components, fuel experiments, solution feasibility - was concluded. Work began on nuclear power stations which, although still experimental, were nevertheless quite large. In a number of countries, projects were started to build 25@300 MW stations incorporating liquidsodium-cooled fast-breeder reactors. These were the semi-industrial scale prototypes of the series which followed (Phenix, SNR300, PFR - Table 2) [l]. Some of these projects encountered many problems due to: regulatory difficulties; concern about the use of plutonium; and - at least in one case, that of the Clinch River-380 MW power station (now cancelled) in the USA - lack of political support of this avenue of research. Others, and among them primarily the French Phenix, the English PFR, and the Russian Bn 350 and BN 600 were developed with success, and valuable experience was gained. From Phbnix to Superphbnix

From the beginning of the 1970s it was becoming clear that the individual countries of Europe could not continue the development of large-scale fastbreeder reactors. High costs, the finan-

cial risks associated with the development of commercial-scale proptotypes, the need to prepare a ‘future’ enlarged market, industrial constraints, and the reprocessing of fuel were all serious obstacles. Electricite de France (EDF), Italy’s Ente Nazionale per 1’Energia Elettrica (ENEL) and the RheinischWestfalisches Elektrizitatswerk (RWE) in Germany - decided to cooperate on the construction and operation of two nuclear power stations of more than 1 million kW equipped with sodiumcooled fast-breeder reactors (16 July 1971 - Table 3). This decision anticipated the spirit of real Europeanism in the technological field, where inflexible institutionalized barriers and legislation separated (and still separate) one country from another. The project enjoyed the support of the UNIPEDE (International Union of Producers and Distributors of Electrical Energy) and more importantly of the European Community which, through its own Fast Reactor Coordinating Committee played a constructive role in information exchange and study. Construction of the power at Creys Malville

station

For the construction of the first of these two fast-breeder nuclear power stations [l, 2, 3, 41 at the beginning of 1974 a team of engineers, designers, and economists from the three main participating utilities began work in an integrated organization which ensured that each of those countries (France, Italy, West Germany, Belgium, and the Netherlands) contributed in a major way to the development of the technology and had unrestricted access to the know-how. The articles of association of the company set up for this purpose, the Nersa (European Fast Reactor Plant Inc. - figure 2) were based on a wide concept of international cooperation which was not restricted to entrepreneurial risk but included many aspects, ranging from technical to industrial problems. The board of management, took all the major decisions on the basis of a unanimous vote

Figure 1 The diagram of the PWR power station and the sodium-cooled fast-breeder power station. The PWR (pressurized water reactor) essentially comprises a circuit in which the water, which is kept liquid by high pressure of the order of 150 atmospheres, cools the reactor and exchanges the heat at high temperature through a steam generator to a circuit in which the turbine alternator is located. The fast-breeder reactor comprises a primary circuit filled with liquid sodium (at almost atmospheric pressure) which cools the reactor and gives off the heat to a secondary circuit, (also filled with liquid sodium) the main function of which is to separate the water/steam fluid in the tertiary circuit from the primary sodium which cools the reactor. The main features of liquid sodium which distinguish it from water are the low pressure for the temperatures required; the higher degree of radioactivity induced in the coolant itself; its opaqueness; its greater cooling capacity; its freezing point (98°C compared with 0°C for water); its great chemical reactivity with oxygen and water,

Figure 2 Participation and later on in another prototype.

NERSA:

ESK:

SBK:

EdF: ENEL: CEGB: SEP:

RWE: SYN:

in Superphenix advanced

Central Nucleaire Europeene Rapide; company set up under French law. Europaische SchnellbruterKernkraftwerk-GesellschahmbH; company set up under West German law. SchnellbruterKernkraftwerkgesellschaft GmbH (company comprising producers from West Germany, Netherlands and Belgium). Electricite de France. Ente Nazionale per I’Energia Elettrica; Italy. Central Electricity Generating Board; United Kingdom. N. V. Samenwerkende ElektriciteitsProductiebedrijven; Netherlands. Rheinisch-Westfllishces Elektrizitltswerk; FR Germany. Synatom; Belgium.

as a token of the will to achieve an optimum balance. Its success demonstrated the willingness of the partners to forego, for the sake of the project, the right of veto in defence of vested interests, private or national. The extent of intra-European cooperation found limits only in the fields of nuclear safety and of reprocessing of irradiated fuel. Over the timeframe of the Superphenix project these Limits were almost insuperable. Feasibility and effectiveness in construction also prompted organizational and design solutions which were typical of the country in which the power station was being built: the principal examples are the French management in design and construction and the use of working methods developed for EDF’s nuclear programme.

Design and construction By virtue of its innovative character Superphenix suffered a number of set-backs due largely to technical problems but in some cases also to the novel nature of the approach. For example, this involved a multilingual construction site in which firms from five countries were working side by side. Nevertheless, the schedules were in most cases met, proof of the commitment with which the objective was pursued. The scale of the project is indicated by the 18 million hours of engineering for the design of the power station and components. The design challenge dictated the physical scale - for example,

the reactor’s safety vessel was more than 22 metres in diameter - and the earthquake design loads that proved to be relevant factors for almost all of the structures. Work on the site, which started at the end of 1974, covered some 35 hectares at its peak and involved some 3250 persons. 125 firms worked on the site, and in all some 22 million hours of work were invested. The start-up was a general test of the quality of both the overall and the detailed design of the project as well as of the maturity of the technology. The first stage comprised the filling of the primary and secondary circuits with liquid sodium. This operation was carried out without problems in August 1984. The hot functional tests of the reactor proved more difficult. Inside the reactor, filled with great masses of free liquid sodium in which the main components and various other structures were submerged, sudden vibrations of a dangerous amplitude and frequency occurred. A short pause followed in which the difficult task of trouble-shooting was carried out and the cause was identified as interaction between the liquid sodium mass and the reactor structures. The faults were then satisfactorily rectified by increasing the level and the recirculation flow of sodium. The reactor went critical on 7 September 1985. It first fed power into the European grid on 14 January 19X6, and industrial operation is planned for the second quarter of 1986. 133

TABLE 1

Estimated in years

in reactors:

Comments

Crude oil

240

33

60

75

several thousand

Extractable resources in known economically exploitable deposits

90

180

300

tens of thousands

Estimated deposits considered technically exploitable (including reserves, non-commercially exploitable resources, and estimated resources)

Current PWR)

Future fastbreeders

indicators:

World reserve share 1)

OPEC OECD COMECON

Ratio production/ overall energy requirements (1984) OPEC: Organization OECD: Organization COMECON: Council

24 l/l 0

(0)

%

95 %

l/l 0

'ho l/l 0

28%

42%

19%

COMECON uranium reserves set hypothetically at OECD level. 4%

Hydro-geo: renewable

of Petroleum Exporting Countries (Middle East and Northern Africa, Venezuela, for Economic Cooporation and Development (Western Europe, North America, for Mutual Economic Assistance (Eastern Europe, USSR, etc).

The fast breeder nuclear system: unlimited energy source

an

The availability of raw energy materials is summarized in Table 1, which shows: 1. The duration and geographical distribution of reserves relevant for the short to medium term (10-20 years), and 2. The duration of resources which indicate the possible role of energy source in the long term. Briefly the table shows that, in the context of a time of energy scarcity (next decades), only coal and the fast-breeder nuclear energy are ‘abundant resources’ (thousands of years) and that this conclusion is still true even if consideration of renewable resources is included. It should be stressed that the practically unlimited availability of nuclear energy derives not from a particular abundance of the raw material, uranium, which is in fact rather scarce, but from fast-breeder technology itself. Nuclear energy already holds the trump cards of high technology, and geographical independence, and has controllable risk factors and proper environmental compatibility, at least in those countries in which adequate industrial, institutional, and social structures exist. It acquires by virtue of the fast-breeder technology the dimension of an unlimited resource. 134

Uranium

Coal and lignite

several thousand

Resources

1)

Natural gas

FUELS

duration

Reserves

Further

DURATION OF WORLD RESOURCES OF FOSSIL AND NUCLEAR (ratio of resources/current annual requirements)

Nuclear fusion is not covered in the table because this technology relates to a future which is distant even by comparison with the long-term of fast breeder reactors. It is only now that steps towards controlled nuclear fusion are actually being taken, while the engineering side of a fusion power station has still to be conceived. Any discussion of the fast-breeder nuclear resource remains abstract if no timescale for its availability is indicated. Such a timescale depends on: the maturity and the technological development of the relevant processes (20 years); the construction periods for the various power stations (10 years); on other factors common to the utilization of energy sources; and on a specific ‘penetration’ phase of 10 to 20 years in which the number of new power stations will be governed by the availability of plutonium. Breeding needs time: for the irradiation of uranium in the reactor and the resultant production of plutonium; for the reprocessing of irradiated fuel and the fabrication of new fuel in special facilities; and for the production of more plutonium than is consumed so that new reactors can be supplied. In total between 40 and 50 years will be necessary: for the process to mature industrially; for power stations and associated facilities to be built; and for them to ‘penetrate’ the electric systems and take their optimal share of nuclear

7%; other sources: 0.2%

lndoniesia, Japan,

etc)

Australia,

etc)

capacity. In other words, to become independent of natural uranium. One of the corollaries will be that, during the transition to a balanced mix of traditional and fast-breeder power stations, all the nuclear power stations will together use an aggregate quantity of uranium which, although difficult to quantify, will be higher, all other conditions being equal with the extension of development and introduction of fast-breeder reactors. The foregoing will entail an automatic countdown with regard to a period of possible crises in the natural uranium market. This countdown may have already started. A study by UnipedeEEC on the role of fast breeders in the European Community [5], conducted on behalf of the Fast Reactor Coordinating Committee with the cooperation of the Commission, estimates that this quantity of uranium is as high as the probable availability of low-cost uranium for the geographical area of the Community, provided that the right decisions are taken. Coal and fast-breeder nuclear technology are the possible resources for the future. Asymptotically, if consumer energy patterns are not revolutionized, coal may finally satisfy primarily demand in the non-power sector while fast-breeder nuclear reactors could become,the prime source of electricity. The nuclear source will play this role provided that the emotional views on

TABLE 2 Reactor

SODIUM-COOLED

Thermal rating (MW)

Power rating (MW)

62.5 60.0 1000 605 10 670 58 100 1470 400

20 12 150 270 0 250 21 600

3000 762 42 118 714

1200 327 15 280

In operation USA (EBR-II) USSR (BOR-60) USSR (BN-350) France (Phenix) USSR (BR-10) Great Britain (PFR) FR Germany (KNK-II) Japan (JOY01 USSR (BN-600) USA (FFTF)

FAST BREEDER REACTORS Date

Category

Commissioning 1963 1969 1972 1973 1973 1974 1977 1977 1980 1980

Experimental Experimental Demonstration Demonstration Experimental Demonstration Experimental Experimental Demonstration Experimental

Commissioning 1986 1986 1985 1989 1991

Large-scale prototype Demonstration plant Experimental reactor Experimental reactor Demonstration plant

reactor reactor plant plant reactor plant reactor reactor plant reactor

Under construction

France (Superphenix) FR Germany (SNR-300) India (FBTR) Italy (PEC) Japan (MONJU)

Planned

1500 1300 1000 800 1600 1250

Launch of project 1987 1990 1995 1986 1995 2000

0.025

-

Operating period 1946-53

USSR (BR 2)‘“’

0.2

-

1956-58

USA (EBR-I)‘““’ Great Britain (DFR)‘“’ USA (EFFBR) France (Rapsodie)

1 45 180 40

0.2 15 60

1951-63 1959-77 1963-66 1967-83

3600 3420 2550 2100 4200 3300

France (project 1500) FR Germanv (SNR-2) Japan (DFBkj USSR (BN-800) USSR (BN-1600) Great Britain (CDFR)

Large-scale Large-scale Large-scale Large-scale Large-scale Large-scale

prototype prototype prototype prototype prototype prototype

Out of service

USA (Clementine)‘*’

(“1 Mercury

as coolant

(**) Sodium-potassium

nuclear safety can be overcome, granted that it is not a question of a plutonium age but only a new useful material for man. In this context fast breeder technology will also offer inherent safety and proper levels of environmental impact. Economic

aspects

of fast breeders

Reduced costs are already a feature of conventional nuclear technology and a realistic prospect for fast-breeder reactors. Fast-breeder technology appears to be potentially capable of competing with other methods of power generation, thanks to the rapid rate of progress in the field and the growing pressure on natural energy resources. The power produced by fast-

coolant

Small reactor for physical studies Small reactor for physical studies Experimental reactor Experimental reactor Demonstration plant Experimental reactor

mix.

breeders is overall more expensive than that produced by the PWR, but in all probability it will remain competitive against second best - the generation of power using imported coal. Table 4, which gives a summary comparison of the economics of fastbreeder systems, current nuclear systems (PWRs) and electricity from coal, confirms this conclusion and consequently the major importance of fastbreeder technology for Europe [6, 7, 81. In the first column it shows the actual cost of Superphenix and then the burden of this industrial experiment. For electricity producers and, by extension, European consumers the power produced by Superphenix is on a level

approaching that of power from oilfired power stations or, in this climate of declining oil markets, possibly higher. The figures in Table 4 should ideally be discussed in detail in the light of evaluation criteria. However, let it at least be stressed that they are only indicative. Evaluation studies behind the indicators given in Table 4: 1. Have a high intrinsic uncertainty in that they are long-term. 2. Relate to the economic and institutional environment of France. 3. Use as terms of comparison the cost of EDF’s PWR power stations, which 135

TABLE 3 European agreement producers

between

electricity

1969 - First contacts between members of Unipede’ concerning European project in the field of fast-breeder power stations 1971 - Declaration of intent by EDF-EnelRWE to construct one power station in France and one in Germany. 1972 - French legislation setting up a company to construct advanced nuclear power stations 1973 - Enel authorized to participate in the project -agreement between EDF-Enel-RWE to construct and operate two power stations 1974 - The Nersa company set up under French law for the first 1200 MW power station based on the Phenix model - ESK company set up under German law (2nd power station) -drafting of international agreements between research centres (for example CEA-ENEA) and between construction firms (for example NOVATOME-NIRA)

Construction station

THE SUPERPHENIX of the Creys Malville

1973- Public inquiry 1974 -Work

PROJECT power

Main features of Creys Malville power station

(site)

Gross power

on final design starts

1975 - Initial safety report 1976 - Decision on construction (20 December)

taken

1977 - Start of civil engineering work -Authorization issued (12 May) 1979 - Installation of mechanical equipment started 1981 - Installation of electrical equipment started 1982 - Fertile fuel loaded

rating:

1240 MW

Configuration: 1 reactor and 4 sodium circuits 4 steam generators 2 turboalternators Efficiency

41.5%

Reactor: Thermal rating Max. irradiation Loading cycle Fast breeding rate

3000 MW 70 000 MWG/t 14 months 1.2

1985 - Fissile fuel loaded (July) - Reactor goes critical (7 September)

Liquid sodium circuits: Primary sodium Throughput in reactor Temperature inlet/ outlet Secondary sodium

395l545”t.z 1500 t

1986- Production of electricity (14 January) - 50% power level reached (June)

Steam generators: Steam pressure

180 atm

Steam temperature

490°C

1984 - Filling with liquid sodium - Hot trials of reactor circuits

started

3200 t 15 740 kg/s

’ Union lnternationale des Producteurs et Distributeurs d’Energie Electrique International

Union of Producers

and Distributors

have successfully developed as a major nuclear programme. 4. Incorporate economic assumptions for capital accounting, for service life and operation of the installations, for construction period, and, most importantly, for cost of fuels which, even if currently acceptable, are the subject of ongoing reappraisal and revision. The Table extrapolates the experience with Superphenix and applies it to industrial projects, which is logical in one way if this large-scale prototype is to be stripped of all major cost factors deriving from its being the first of its kind and of the added costs inherent in its being a joint European venture conducted within the constraints of national institutions and economies. The intention is also to show the economic prospects for future power stations with greater clarity. Briefly, the major advantage of fast-breeder reactors is the policy assurance offered to the entire nuclear programme in the event of crises in the natural uranium market which, as has been shown, cannot be excluded after the year 2000. Compared with the alternative of conventional reactors only, the symbiosis of conventional reactors and fast-breeder reactors geared in such a way as to keep annual natural uranium requirement at a 136

of Electric

TABLE 4

Energy

COST INDICATORS FOR KWH PRODUCED TECHNOLOGY (PWR=lOO) Superphcnix

Overall cost: Capital expenditure Operation Fuel

I

BY FAST-BREEDER

1500 MW project

Industrial series prototype

Coal-fired power station

180 200 160 160

115 130 130 90

130-180 50-80 80 310-370

220-230 260 160 190-260

Basic assumption: the economic and industrial context of France; series of a kind at the end of the 1990s; imported coal costs projected well into the next century; averaged costs of first 25 years in the industrial plant life. N.B.: More detailed information on the economic stages can be found Mines - January 1984, and Revue de I’Energie - May 1985.

negligible level will allow electricity to be produced at a reduced and stable cost no matter what happens to the markets for conventional fuels and uranium. Problems

and prospects

In additon to being a milestone in international fast-breeder technology and in the French capability of innovative project implementation Superphenix is also a brilliant success for European engineering. The Europe of science and technology, the Europe of the Joint European Torus, Ariane, Airbus, and the European power grid

in Anna/es

des

is thus taking a step forwards towards unity. However this unity is still a long way from being achieved, mainly because the institutions, legislation and industrial quality criteria are almost without exception pitched at a national level. In the wake of the success of Superphenix, cooperation agreements were established and extended with what was known as the Grand Accord of 1984 between the European heads of state and government (France, West Germany, United Kingdom, Italy, and Belgium). It paves the way for a much broader involvement of designers, safe-

ty authorities, and research establishments. Research effort will be coordinated with the parallel power station and fast fuel reprocessing development. In the European Community 4.50 billion lire (300 million ECU) a year are allocated to fast breeder research. The image of fast breeder nuclear technology which SuperphCnix presents to us with flying colours is not without its darker side. Its future is still under discussion and the central issue whether the location of the next reactor shall be in France or in a country with different institutional and industrial practices, such as West Germany - is still not settled. Meanwhile, the high cost of this first large industrial breeder is leading the major electricity producers to undertake a critical review of their programmes. The thrust for more international integration (United Kingdom and others) is greater while at the same time, differences between- the national situations are emerging, reflecting varying degrees of reliance on nuclear energy. Therefore there are differing perceptions of the urgency with which fast breeder technology should be promoted [9]. Another factor which weighs on the decision-making process is a policy decision to postpone the launching of new projects until after one year’s operation of Superphinix. There is a risk that the project’s momentum may slacken and that well-run-in teams of technicians will be dispersed, so that essential elements of knowledge which are not passed on through the written word will become inaccessible, and vanish. The example of the United States shows how dangerous it is to interrupt the rhythm of development in a new technology. Even the question ‘What follow-up for SuperphCnix?’ prompts a muddled response. There are mounting unsolved problems relating to development strategy (the priority areas) and international industrial policy (how to share the work and where alternatives and parallel developments should be continued). One of the first questions concerns the fuel cycle, since whatever follows SuperphCnix should, as a matter of priority, use the plutonium produced by the fast-breeder reactors and prove true to its name: phoenix. A second major aspect is a much deeper involvement of the safety authorities in the various countries so that a harmonized procedure can be adopted or even one which is integrated at European level. Many observers, primarily the theoreticians of institutional sovereignty, may feel such a goal is utopian. Instead what is really utopian is to think that technology on such a scale can remain within the

constraints of markets and institutions of a single European country; or that it should pursue, in each separate country, the procedures followed by today’s nuclear power stations in a context, that of the 1990s and beyond, which will be more difficult by far for large projects. Lastly, there are difficult technical and economic decisions. This is a recurring theme; in the past the options concerned the actual reactor design, itself: sodium vs gas, water, and molten salts. Later on the options related to the reactor system - that is, whether pool or circuit - and to fundamentally different construction designs for steam generators. Today, the options are more articulated, but they nevertheless go right to the heart of industrial projects, licences, patents, and, most importantly, the location of future facilities. Table 2 shows three new facilities in Europe which form the focal point of the Grand Accord. One alternative is shown by the programme implicit in Table 4: a follow-up to SuperphCnix and a subsequent series prototype which will exploit the results of the ongoing research effort in order to achieve full industrial maturity in the next century. Risk and safety of fast breeders A review of the status and perspectives of sodium-cooled fast breeders must briefly cover safety technology, even if it relates to all kinds of nuclear facilities. The disaster that occurred on 26 April, 1986, at the conventional nuclear power plant of Chernobyl, in USSR, gives special topicality to this subject. It must be recalled that nuclear energy has great potential risks, implying substantial energy and power densities and large amounts of radioactivity, primarily stored in nuclear fuel. Nuclear safety technology and related management and regulatory provisions minimize this risk - that is, the combination of probabilities and consequences of accidents - to levels not only below that of natural catastrophes, but also of a vast range of industrial activities considered as safe. This safety technology must be internationally based, with authority to act freely and independently. The Chernobyl episode clearly shows that nuclear risk does not have frontiers. Safety measures for fast breeders takes into account their greater density of energy and power and their larger nuclear reactivity, as compared to conventional thermal reactors. Nuclear reactivity is controlled, as in other reactors, by the shutdown system, which is designed and built to incorporate generous margins of safety and reliability. The shutdown system is

duplicated in two independent subsystems of different design, physically separated. It is capable of shutting down the reactor even in cases of warped geometries, a condition which may lead to accidental nuclear chain reactions. Other main safety measures, common to other kinds of reactors of Western design, relate to: 1. Radioactive fission-product containment which relies on three barriers; main vessel and roof slab; safety vessel and dome shaped cover; and the reactor building, which also provides protection from external catastrophicevents. Inaddition, there is nuclear fuel cladding. 2. Earthquake-proof design of critical buildings and systems. 3. Plant control, which under any conditions can operate without undue risk for the operators, since the main control room and the two emergency ones are bunker-like and shielded from ionizing radiation. Several safety measures are specific to fast breeders in general and of the Superphenix design in particular. Some design and construction solutions have been selected to make the best use of the physical properties of sodium. The large temperature range of nonpressurized liquid sodium (98-882°C) paved the way to reactors operating at quasi-atmospheric pressure. Thus an important potential cause of sudden structural failure has been removed. Liquid sodium also has a high latent heat of vaporization, which is twice that of water and hence very effective in limiting the seriousness of some possible accidents. Finally, an inherent safety feature results from the extensive compatibility of hot sodium with the austenitic stainless steel employed in fuel cladding, reactor structures, machinery, and equipment. Made feasible by quasi-atmospheric pressures, a pool concept has been developed, aimed at keeping the coolant in the fuel zone at all times, regardless of failures in the integrity and functionality of the primary system. Further, the great mass of sodium filling the pool provides a large thermal inertia which, associated with the moderate operating temperatures chosen, gives ample time for correcting accidental deviations. However, sodium has a certain number of drawbacks, mainly its spontaneous combustion in air and its violent reaction with water. Since its onset, sodium technology has faced these problems. Accordingly design features are aimed at segregating sodium from air and water and at the efficient detection, prevention, and mitigation of sodium fires and reactions should they occur. Examples are an 137

intermedate sodium circuit to separate radioactive sodium, flowing through the fuel, from water and steam; and automatic isolation of plant rooms where sodium leaks are detected. For all reactors, nuclear fuel meltdown is potentially the most serious accident, but one with a very low risk, thanks to the safety measures adopted. Given its first-of-its-kind nature, Superphenix is equipped with a core catcher for partial meltdowns. This structure would collect the molten radioactive mass and separate it for easier cooling and prevention of criticality. Large meltdowns are extremely unlikely and must therefore be dealt with by emergency measures: the confinement of fission products is designed to allow the time needed for taking such measures. Finally, it must be recalled that for all reactor types safety is a field of continuing progress, thanks to growing experience, research, and general technological advance. To illustrate ingen;uity in this field, mention may be made of the concept of passive safety, closely evaluated during the past few years. It implies a reduction in the number of systems to be activated, either automatically or by an operator, and more inherent safety. In a word, the objective is a self-protecting reactor [ll] and the fast breeder of the pool kind has the intrinsic features needed to make it a suitable candidate. A touch of futurology

There could be, however, an important development which would call for a rethink of the entire programme. The fact is that while decisions on timescales, methods and locations for future power stations and new facilities are proving difficult to take, the context of the macro-economic strategy has changed almost without warning [lo]. Today, the scale of international industrial policy and the progressive linking ,of the markets of the USA, Europe, and Japan are again drawing attention to the issue of broadening the basis on which fast breeder technology

138

must develop if it is in turn to compete as a real energy option. Since the fast-breeder programme will develop as a demonstration programme up to the year 2000 and will not be operating commercially until after that date, it is essential to gain some idea of the future in which these power stations will be operating. The year 2000 could easily see a united Europe. Although nowadays unthinkable, Europe will have opened up to the East and developed such a dynamic and integrated economic activity that industrial companies and big business will have lost the national character. In such a setting the production of electricity at moderate cost, a high level of safety and low environmental impact will be essential, and in such an arrangement the fast-breeder nuclear option will play its own part only if it is genuinely international. Even if the comparison is inappropriate, it should not be forgotten that Concorde, the breakthrough of AngloFrench aviation technology, ran into difficulties owing to the constraining circumstances of its inception, which were further complicated by the marketing of this luxury-class, fueldevouring aircraft being launched at the same time that the oil crisis struck. A series of events and, most importantly, a more open attitude on the part of the United States today prompt a wider international approach in the field of fast-breeder technology. If pragmatism is allowed to prevail, the opportunity can now be seized to allow this technology in turn to prove its own worth. Superphenix has shown that, even in a predominantly national context, good international agreements in conjunction with effective leadership and a deep feeling of solidarity are possible and will allow the goals set to be achieved with maximum efficiency. Why cannot the present-day climate, which has witnessed so much progress, in conjunction with what is possibly a unique opportunity for extending the market for fast-breeders to a decisive

scale, bring about global agreements between all the key areas of market economies? Acknowledgment

The authors thank Nersa and the Ente Nazionale per I’Energia Elettrica for allowing them accessto documents and information on the most recent developments. The opinions expressed are exclusively those of the authors. References

[l] ‘Les SurrCgCnCrateurs - Revue GCntrale nucltaire’, Paris, NovemberDecember1979. [2] ‘Creys-Malville Nuclear Power Station - Nuclear Engineering Internationl’, Paris, June 1978.131‘The Italian Contribution to the European fast-breeder’,ENEA Bulletin, Rome, October 1984. (41 Angelini, Arnaldo M. ‘Power for the 80s: a Challenge for Western Europe’, IEE .I Spectrum, New York, October 1980. [5] ‘The Role of Breeder Reactor Systems in the Euyropean Community, International Union of Producersand Distributors of Electrical Energy and the Commissionof the European Communities’,ENEL, Rome, September1981. [6] Gouni, L., ‘CoQtsdu kWh Electrique des Centrales Fonctionnant “en base”,’ Revue de I’Energie, Paris, May-June 1985. [7] Ertaud, E., ‘La SurrCgCnCrationet I’Avenir de I’Energie NuclCaire, Revue GhnCrale nucliaire, Paris, July-August 1984. [S] Les SurrCgCnCrateurs,Annales des mines, Paris, January 1984. [9] Bonner, Carle, Velona,.Eitz, ‘Point de Vue des Producteurs d’ElectricitC Europeens sur le Dtveloppement des SurrCgCnCrateursdans les Ann&es g Venir et DemarcheEnvisagce pour Rtduire les Cotits’, IAEA convention, Lyon, July 1985. [lo] Ohmae, Kenichi, ‘Becoming a Triad Power: the New Global Corporation.’ McKinsey, New York, Spring L-1

~~~

1985.

[ll] Lester, R. K. ‘Rethinking Nuclear Power’, Scientific American, March 1986.