uratom

bulletin of the european atomic energy community

june 1965 vol. IV no. 2

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Quarterly Information Bulletin of the Euro• pean Atomic Energy Community (Euratom)

1965-2

Contents:

34 Nuclear energy in Germany

44 Energy out of "pebbles"

49 What is ORGEL ?—A brief "recap"

50 How far have we got with the ORGEL project ?

54 CIRENE—A natural-uranium boiling- water reactor project

61 Euratom news: Nuclear energy from today until 2000—forecasts for the European Community; ORGEL—safety studies; A step towards nuclear superheat in water reactors; Production of uranium carbide single cristais at Ispra; Ways of obtaining higher burnups in graphite- gas reactors

Published and edited by: Euratom, Dissemination of Information Directorate, 51-53 rue Be! I lard, Brussels 4. Telephone: 13 40 90

For subscription rates please see overleaf.

Growth of o nuclear power plant—the Gund- remmingen "cactus" The Euratom Commission or any persons acting on its behalf disclaim all liability with respect to the completeness of the information contained in this periodical as well as to any damage which might result from the use of information disclosed or of equipment, methods or processes described therein.

Any article published in this bulletin may be reproduced in whole or In part without restriction, provided that the source is mentioned.

Picture credits: Page 2 of cover: AEG (Germany); page 35: Presse- u. Informa• tionsamt d. Bundesregierung, Bonn; Grodt- mann, Hamburg; page 39: KBB, Karlsruhe; page 40: Siemens; Linde; Erich Bauer, Karlsruhe; Interatom (Germany); page 41: AEG; page 43: Erich Bauer, Karlsruhe; page 48: Kernforschungsanlage Jülich; page 51 : Euratom JRC Ispra/Roberto Colom• bo; pages 52+53: Euratom JRC Ispra/ Ulrich Zimmermann; page 54: Roberto Zabban, Milan; page 60: Comm. Mario Agosto, Genoa. Cover: Gaston Bogaert, Brussels.

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Printed in the Netherlands by A. W. Sijthoff, Leiden topi radioisotopen s hip propulsion schiffs antrieb propulsion na vale propulsione nava le scheepsvoortstuwi ng biology biologie biologie biologia bio logie medicine medi zin médecine medicin a geneeskunde healt h protection gesundh eitsschutz protection sanitaire protezione s anitaria bescherming van de gezondheid automatic data proces "Proven" reactors, "advanced" reactors, sing automatische inf ormation information "fast" reactors . . . these terms, which are automatique informa zione automatica auto creeping into nuclear parlance, do not, matische verwerking van gegevens insura strictly speaking, denote a hierarchical order, nee versicherungswes since all the reactors thus described are en assurances assicura zione verzekeringen kings in their own way; the proven reactors economics Wirtschaft économie economia e are the kings of today, the advanced con• Quarterly Information Bulletin of the Euro• conomie education verters—three types of which are discussed pean Atomic Energy Community (Euratom) and training ausbildu ng enseignement inse in this issue—will reign tomorrow, and the gnamento onderwijs en opleiding power fast reactors are destined to become the reactors Jeistungsreak toren réacteurs de pu monarchs of a more distant future. According issance reattori di po to this scheme, therefore, what we really tenza energie reactor en nuclear fusion ke have is a dynasty. rnverschmelzung fusi 1965-2 on nucléaire fusione Undoubtedly, it is on the fast reactors that nucleare kernversmei ting radioisotopes r the ultimate hopes are pinned, because owing adioisotope radioisot opes radioisotopi ra to their amazing prospects as "breeders" of dioisotopen ship pr fissile material they show promise of solving opulsion schiffsantrie b propulsion navale the energy-supply problem for a long time to propulsione navale scheepsvoortstuwing come. biology biologie biolo gie biologia biologie Viewed in this perspective, the advanced medicine medizin mé thermal reactors would indeed seem or• decine medicina gene eskunde health pro dained to replace proven-type thermal tection gesundheitssc reactors, but they will merely constitute a hutz protection sanit aire protezione sanita temporary expedient to span the period of ría bescherming van de gezondheid auto development of fast reactors, which looks matic data processing like being fairly protracted. In short, their automatische informa tion information auto destiny is to fill the interregnum. matique informazione automatica automatis This outline already leaves room for numer• che verwerking van g ous minor variations, not to mention those egevens insurance v ersicherungswesen as that the future will no doubt bring. For ex• surances assicurazioni verzekeringen econ ample, certain advanced thermal reactors omics Wirtschaft èco themselves aspire to a breeding function and nomie economia eco nomie education and would thus appear to rival their legitimate The Community's mission is to create the training ausbildung successors. Actually, however, the notion of conditions necessary for the speedy estab• enseignement insegn amento onderwijs en lishment and growth of nuclear industries rivalry is misplaced, since the former call opleiding power reac in the member States and thereby contrib• tors leistungsreakto rather for a thorium/uranium-233 fuel cycle ute to the raising of living standards and ren réacteurs de pu and the latter for a uranium-238/plutonium the development of exchanges with other issance reattori di po tenza energie reactor countries (Article 1 of the Treaty instituting cycle. Consequently, it is more a case of co• en nuclear fusion ke the European Atomic Energy Community). rnverschmelzung fusi existence. on nucléaire fusione nucleare kernversmei ting radioisotopes r adioisotope radioisot opes radioisotopi ra dioisotopen ship pr opulsion schiffsantrie The development of nuclear research and tial should help to speed up this develop• of choice with regard to the lines to be technology in West Germany has hitherto ment, so that the consequences of Ger• followed which the country's limited proceeded under conditions which in major many's late start are likely to be overcome resources would otherwise certainly not respects differ from those obtaining in the in the foreseeable future, the German have permitted. United States, Britain and France. There are Federal Republic attaining a level of scien• Furthermore, as a result of these circum• two reasons for this which should be tific and technical achievement in the nuc• stances, no need was felt, in West Germany, particularly stressed : firstly, Germany made lear field within the next decade which will in the national organisation set up to pro• a late start and took a fairly long time to get correspond to the position occupied by it mote nuclear research and technology, to its programme off the ground and secondly, in other fields on the international plane. follow the example of the major nuclear all activities were restricted to the atoms- powers. Onlyasmall ministry of conventio• for-peace field. nal type was established, largely supported However, with the quickening pace of Peaceful uses only in its work by outs ¡de scientific, technical and development of nuclear research and tech• economic advisers. Research and develop• nology and the increasing importance of Under the terms of the Paris treaties of ment work in institutes and industrial the economic aspects of nuclear energy these two factors will gradually decrease in significance in comparison with the other conditions affecting the overall context of scientific and industrial activities. But EUBU 4-5 for the time being they should not be ignored in any attempt to assess the situa• tion in Germany. Late start Nuclear Energy in Germany It was not until 1955 that systematic work in the field of nuclear research and develop• ment could be commenced in Germany, with one or two isolated exceptions. At that time, however, only a few branches of DR. WOLFGANG FINKE, Federal Ministry for Scientific Research, Bad Godesberg research were blessed with a sound basis for rapid advance, and in the majority of fields of science and in almost the entire field of industrial development this basis had first to be created, with regard to both 1954 the German Federal Republic express• enterprises is to a large extent free of staff and material facilities. ly waived any right to develop or manufac• government interference. This resulted in a fairly long warming-up ture nuclear weapons. Since then, this period, during which it was often impossible pledge has been reiterated by the German to assess the full extent of the efforts re• Government on numerous occasions. Right quired, so that at the outset estimates from their commencement in 1955 all General conditions frequently fell short of reality. It was thus Germany's activities connected with re• only in the course of time that a realistic search into and the development and utili• By virtue of the conditions governing pictureofthesituation in Germany emerged sation of nuclear energy have been devoted nuclear research and technology in West which could be taken as the foundation solely to Its peaceful applications. This self- Germany, the special position which these for a long-term development programme. imposed curb has had an enormous effect fields have come to occupy in German Since then much has been done to carry on the pace and intensity of Germany's science and industry is much less prominent out this programme, which was at first efforts to get in the swim of world nuclear than in many other countries. Conversely, merely mapped out in broad outline, the development. therefore, the general factors conditioning details not being filled in until later. The The effect was two-fold: firstly, these activ• the development of nuclear energy are of gap in nuclear research and technological ities were right from the outset not marked greater importance in Germany than else• development between Germany and the by that sense of urgency which military where. These factors may be broken down leading countries in this field has so far, of matters are—rightly or wrongly—accorded into the following particular headings: course, with a few exceptions, not been throughout the world and which usually — the organisation and efficiency of the closed completely, but it has narrowed con• calls for relatively generous appropriations scientific effort in general,' siderably, particularly in the last few years. from public funds; secondly, the restriction The work since started on the new research — the structure, the degree of industrial• of German development work to the pur• centres and the growing industrial poten• isation and the potential of the national suance of peaceful aims resulted in a liberty economy2,

34 — the pertinent legal provisions,3 primarily, the first Geneva Conference and, tion and expansion of existing institutes — the effectiveness of international co• secondly, recognition of the fact that Ger• would have to have priority, special new operation and competition in the scientific, many was lagging way behind the world's research centres being set up in only excep• technical and economic fields,1 leading countries in the field of nuclear tional cases. Opinions were divided, how• — the situation on the energy market power. The essential feature of these plans ever, as to whether it would be better to with regard to supply and demand, in was the realisation that training facilities buy research reactors abroad or to develop particular prices and the availability of rival and general research centres would first them in Germany. Ultimately both paths primary energy sources.5 have to be set up, special large-scale were chosen. The last few years have shown that nuclear research projectsand major technical devel• However, no official all-embracing, hard- development work in Germany has been opment programmes being left till later. and-fast German nuclear programme was much more influenced by these general The consensus was also that the modernisa- drawn up at the time, developments being factors than the special programmes and limited to the loose co-ordination of the projects in the various fields would at various projects under a general framework. first indicate. There is a great deal of evi- The DESY electron-synchrotron in Hamburg It is only in the case of power reactor development that these considerations since the beginning of 1957 have crystallised into a kind of overall plan, the so-called E/tv/7/e programme, which in 1959 formed the basis of a recommendation put forward by the German Atomic Commission. The AVR gas- cooled high-temperature reactor in Jülich, the multi-purpose research reactor at Karlsruhe and the Lingen nuclear power plant are largely based on the general plans drawn up at that time, even though the detailed execution of the projects entailed major departures from the previous pro• posals. A comprehensive German atomic program• me was not drawn up until 1962-63, its implementation being recommended to the Federal Government by the German Atomic Commission in May 1963. However, this programme, toe, which covers the period 1963-67, "does not embody any dence to suggest that, as nuclear energy commitments in the form of a rigid plan", gets closer and closer to normalcy, the but as the Federal Minister for Scientific influence of these factors will be enhanced, Research states in the preface, "constitutes especially since it is Germany's avowed a guideline for the most appropriate promo• policy gradually to put nuclear research and tion and planning work in the public and technology, which at present occupy a private sectors, which can be constantly special position in science and industry improved and adapted in line with the in• respectively, on the same footing as con• creasing pace of development". ventional research and technology, and to The aims of this government sponsoring restrict state interference in these fields are, according to the programme, firstly to over the long term as much as is compatible open up all fields of nuclear energy, ranging with the particular character of nuclear from basic research to reactor construc• energy. tion, to set up and extend the appropriate supply industries and to provide for raw material procurement; secondly, to utilise nuclear radiation and radioisotopes in other The German nuclear programme scientific and technical fields and, thirdly, to generate applications in other fields. The first concrete plans tor a German These recommendations refer in particular nuclear programme date back to the years to the sponsoring of co-ordinated basic 1955-56. They came about as a result of,

Reactor building of the research centre at I. 2. 3.4. 5. See page 43 Garching, Munich.

35 research in institutes of technology and tor construction programme, the recom• Germany's nuclear research centres universities, Max-Planck Institutes, research mendations cover the building by 1967 centres, federal and Land research establish• of a total of three large power plants As was mentioned above, nuclear research ments, industrial institutes and especially, equipped with proven-type reactors, three in Germany is largely carried out in the in the sphere of international co-operation, experimental reactors and a marine traditional research centres, particularly Euratom's joint research centre. Moreover, reactor. The construction of a small-scale the technical colleges and universities and applied research would be supported, par• plant for spent fuel reprocessing is also in the Max-Planck Institutes, but also to an ticularly in the research centres and indus• advocated. ever increasing degree in industrial research try, great stress being laid on the need for It will cost about 2,500-2,700 million DM establishments. The general facilities avail• careful co-ordination. With regard to tech• to carry out this programme. This calcula• able in these institutes and laboratories nological development work, the program• tion is based on the assumption that the have been adapted to modern requirements me favours the more intensive support of annual expenditure will increase by almost during the last few years at a relatively promising projects undertaken by firms and 20%, being thus roughly double by the high cost. Many of them have small or is thus opposed to technical development end of the programme. The total expendi• medium-sized particle accelerators and projects being carried out solely by research ture for the programme breaks down into several possess training, testing or research centres. Finally, the need Is emphasised 1,100-1,200 million DM for basic research, reactors of their own. Some establishments, for public backing for the construction about 400 million for applied research and e.g. the Hahn-Meitner Institute for Nuclear of prototype plants. 1,000-1,100 million for technological devel• Research in Berlin, occupy a rather special The main feature of the German nuclear opment and the construction of nuclear position by virtue of their organisational programme for the period 1963-67 is the installations, not including the large power setup, but these, too, are fundamentally emphasis laid on research, in particular plants. The data on the funds required have also institutes of technology. basic research. In the case of technological deliberately been kept somewhat imprecise Specifically nuclear research centres are development work, with special reference in the programme, so that no accurate thus an exception In Germany. Those that comparison with actual expenditure can to reactors, it confines itself to supplying do exist were usually set up because the be drawn. Nonetheless it may be noted the criteria by which the various projects equipment required or task imposed was that during the first two years the program• are to be assessed. Only with regard to the beyond the reach of traditional facilities. me targets were largely attained and no long-term view is the programme decidedly In two cases they were formed in order to major cut-backs are expected in the third in favour of the development of fast and put into the same harness a number of year either. thermal breeder reactors. Under the reac• different disciplines and by so doing to

I. TRAINING REACTORS

36 f.5/2.6 megajoule capaci• equipped with a swimming-pool reactor tor bank at the Max Planck with two reactor cores, each of 5 MW ther• mal power, a rolling test-rig, a critical Institute for Plasma Phys• experiment installation and a radioactive ics ot Garching, Munich. waste storage facility. The owner and operator of this establishment is the Gesell• schaft für Kernenergieverwertung in Schiffbau und Schiffahrt, Hamburg, whose capital is mainly derived from the Federal Govern• ment and the Länder of Bremen, Hamburg, Lower Saxony and Schleswig-Holstein. These Länder and the Federal Government also bear jointly (40% and 60% respectively) make for a particularly intensive cross- studies on controlled thermonuclear reac• the Gesellschaft's investment and operating fertilisation of ideas in the study of a wide tions. The Institute's activities are at pre• expenses which are not covered by revenue. range of scientific and technical problems. sent focussed on research on stationary More than 350 persons are at present The first category includes in particular plasmas, fast theta-pinch, linear-Z-pinch employed in Hamburg and Geesthacht. The the German electron-synchrotron in Hamburg, and tubular-plnch discharges, plasma diag• most important project now being carried the Institut für Plasmaphysik at Garching, nostics and plasma theory. Other research out is the construction of the nuclear- near Munich, and the special nuclear on plasma physics is being carried out in powered ship Otto Hahn, fitted with a research centres at Neuherberg and Geest• the Jülich Nuclear Research Centre, being pressurised-water reactor, which is to be hacht. The second group is made up of the mainly aimed at studies on fast magnetic completed by 1967. Euratom also is to multi-purpose nuclear research centres at compression and the development of a participate In the cost of the reactor. Karlsruhe and Jülich. plasma accelerator. Euratom is also partici• The research and development establish• ments described hitherto are of a specific The German electron-synchrotron (DESY), at pating in these activities under a contract of nature, whereas the centres in Karlsruhe and present one of the largest electron acceler• association. Jülich are multi-purpose nuclear research ators in the world, went into service early The German electron-synchrotron in Ham- institutes. They were originally planned in 1964 after four years' construction work. burg-Bahrenfeld and the Institut für Plas• with different aims in view—Karlsruhe was It reached a particle energy of 6 GeV maphysik in Garching near Munich are at first mainly engaged on development without any major difficulty, and its peak special centres for basic physics research. work, in particular the construction of a should be around 7 GeV. The path diameter The Gesellschaft für Strahlenforschung, 12 MW research reactor, coupled with a of the accelerator is 101 m, the maximum on the other hand, with its insti• strong emphasis on the industrial side, particle beam totalling 5.10'2 electrons/sec. tutes for medical biology, radiation pro• while Jülich was primarily intended as a A hydrogen bubble chamber of 80 cm tection and haematology (with research joint research establishment for the uni• diameter was built for the tests in collabo• teams in Munich and Freiburg) and its versities and technical colleges of North ration with the French nuclear research physico-technical department, is engaged Rhine/Westphalia, industrial matters being centre at Saclay. The total cost of the project on basic studies in the field of biology and left pretty much in the background to was 110 million DM, 83 million of which medicine and on training in radiation pro• start with. In the meantime however both are provided by the Federal Government, tection techniques. It also has research centres have acquired more or less the same 17 million by Hamburg and 10 million teams for radiation measuring methods and all-round character. So that in addition by the Volkswagen Foundation. The oper• the deep storage of radioactive effluents. to the ties with industry, Karlsruhe also ating costs, which are expected to rise to The Gesellschaft, which is still in the maintains close relations with the universi• 40 million DM in the coming year, are borne process of formation, employs a staff of ties and technical colleges of Baden-Würt• equally by the Federal Government and about 300 at the moment. By 1967-68 the temberg, while Jiilich's links with the the Länder. The staff now totals over 600. investments spent on its establishments of universities and technical colleges of North Equally impressive funds and staff are in• Neuherberg, near Munich, Munich, Frei• Rhine/Westphalia have been broadened by volved in the first expansion stage of the burg and the former salt mine at Asse will collaboration with Industry. Both Karlsruhe fusion research centre of the Institut für run to about 43 million DM. Euratom is to and Jülich have for some time now been Plasmaphysik, at Garching near Munich, participate in the work of some of them financed solely from public funds, the break• with an estimated investment bill of 96,500 and is to make a contribution to the approp• down being 75% from the Federal Govern• million DM, 90% of which is borne by the riate running costs. The remainder of the ment and 25% from the Land of Baden- Federal Government and 10% by Euratom. expenses are borne by the Federal Govern• Württemberg in Karlsruhe and roughly The operating costs, which are estimated ment. 90% from the Land of North Rhine/West• at about 15 million DM for 1965, are to be The facilities of another special nuclear phalia and just under 10% from the Federal divided up equally between Euratom, the research centre, in Geesthacht-Tesperhude Government in the case of Jülich. In accord• Federal Government and the Länder. The near Hamburg, are directed less at basic ance with present plans, investments will staff has in the meantime passed the 700 than at applied research and technical devel• total about 650-700 million DM in each of mark. The research installation is used for opment In the marine reactor field. It Is

37 II. RESEARCH REACTORS

Name Location

AMF Atomics. enriched Div. of American Machino & (90"„) 4 kg Foundry Co.. USA, and MAN

homogeneous enriched uranium (19.7".,) reactor 1.4 kg as uranyl sulphate USA, and AEG. in aqueous BBC. Manncs­ mann. SSW

,; Atomics Inter­ approx. I0 national and Arbeitsgemein­ 1.3 kg : schaft AEG, uraniun Borsig, Pintsch­ sulohan Bamag, SSW

1. reactor 5000 23.10.1958 (USA) and 2. reactor (20",,} 5.4 kg 2. Reactor­ Dt. Babcock 5000 2. Reactor: 15.3.1963 (Î0"„l 3 kg

Argonaut [ (for limited enriched (graphite water) periods 10) (20"„) 2 t 5.7 kg

Argonaut Graphite (graphite «ater) light water (20"„) 2 t 5.7 1S

n.tural 7.3.1961 by operato: (thorium) 6 c U (1 t Th)

TNPG ­The enriched 23.2.1962 Nation al Pow Group Ltd.. (80"„) 3.2 kg Great intain and AEG Rhc stahl

Copied by enriched German firms (AEG Rhein­ (80­90".,) stahl) from approx. design devel­ 2.83 kg oped by Head Wrightson Processes Ltd., Gr. Britai

Arbcitsgemcin. fast cher thermal κ graphite hed I 1.1.1963 ; SSW, Lurgi. two­ione S. I0 light water um (20"„) (originally Pintsch­Bamag Argonaut fast zone; m.: 5.6 kg Argonaut) (developed by reactor 1.5­2. 10' 90 kg 24.6.1964 operators) (converted fo last breeder development)

(20%) 2.2 kg

Deutsche enriched Babcock & (90­,,) 3.2 kg

rnfor­ I SSW (0.3 t Pu + 0.5 t U)

',; the centres by 1970, roughly 50% of which premises, the gas-cooled high temperature gramme for fast and thermal breeders. is accounted for by the construction and AVR test reactor, which is rated for a Other development work is aimed, in equipment projects already drawn up. thermal power of 49 MW, is nearing com• particular, at effecting improvements in the The staff totals at present about 3,000 and pletion. The Centre itself includes institutes fuel cycle and in nuclear materials. A small 2,700 in Karlsruhe and Jülich respectively. and research teams engaged on botany, test facility for the processing of uranium The annual operating costs are 75 million zoology, agriculture, medicine, physical ores is in operation in Ellweiler. The con• DM for Karlsruhe and somewhat less for chemistry, radiochemistry, chemical engi• struction of a prototype reprocessing plant Jülich. neering, high-energy physics, nuclear phys• to operate by the aqueous solution method The main research facilities of the Karlsruhe ics, neutron physics, technical physics, re• is envisaged in Karlsruhe, as mentioned Nuclear Research Centre, which was set up actor components, reactor development, above. and is largely operated by the Gesellschaft für reactor materials and plasma physics, The nuclear power plant demonstration pro• Kernforschung, consist of a tank-type heavy- together with central institutes for applied gramme covers at the moment three power water reactor with a thermal power of 12 mathematics equipped with their own plants fitted with proven-type light-water 13 MW and a thermal neutron flux of 3.10 large-scale computer, and reactor experi• reactors. Its purpose is to enable German 2 n/cm .sec, an Argonaut fast/thermal reactor ments as well as central laboratories for industry and the German power economy (STARK) and a fast sub-critical assembly electronics and chemical analysis. Moreover, to gain their own know-how in the con• (SUAK). A 200 MW (th) heavy-water "multi• research and development work in the struction and operation of large nuclear purpose" reactor with a thermal neutron flux of 10'4 n/cm2.sec is almost completed, a fast zero-energy assembly (SNEAK) is underconstruction and asodium-cooled,zir• conium hydride-moderated experimental reactor is planned, work being scheduled to begin this year. In addition, the equipment available includes an isochronous cyclotron with a maximum particle energy of 110 MeV, several neutron generators, including sever• al of the pulsed type, and an IBM 7070 computer. Several hot cells are under con• struction, and preparations are being made for a small irradiated fuel reprocessing unit. The Centre comprises institutes for neutron physics and reactor technology, applied nuclear physics, experimental nu• clear physics, applied reactor physics, reactor components, hot chemistry, radio- chemistry and radiobiology, including neu• tron biology and isotope laboratories, an electronics laboratory and a school of nuclear technology. It also incorporates The FR2 reactor of the Karlsruhe Nuclear Research Centre the European Institute for Transuranium Elements and a number of research estab• lishments operated by other bodies, such as institutes for nuclear engineering, isotope field of isotope separation is carried out power plants and thus to create a sound techniques and foodstuffs irradiation tech• by the state-financed Gesellschaft für Kern- basis for future decisions on investment. nology. verfahrenstechnik, which does not come Since joint-enterprise status has been under the organisational setup of the Centre granted to two of the projects, as provided The Jülich Nuclear Research Centre of the but is located on its grounds. by the Euratom Treaty, and has been applied Land of North Rhine/Westphalia has a for in the case of the third, it will be possible /VIERL/N-type research reactor and a to put the experience thus acquired at the materials-testing reactor of the D/DO-type, Technical Developments disposal of the industries and power pro• with a thermal power of 5 and 10 MW ducers of the other Community countries. and a maximum thermal neutron flux of The work being conducted by Germany In all three instances the choice of reactor 8.1013 and 1.6.1014 n/cm2.sec respectively. in this field is focussed on a three-pronged was governed not only by technical, but At Jülich there are also two 3 MeV Van de reactor development programme, con• also and to a marked degree by economic Graaff generators. A cyclotron with a sisting of a power plant demonstration considerations. Particular importance was maximum particle energy of 180 MeV is programme, a medium-term development assumed here by the general economic now under construction, as well as a hot- programme for improved converter reac• circumstances of the country and the cell unit. On the edge of the Centre's tors and a long-term development pro- structure of the electrical economy.

39 Nuclear Research Centre, Karlsruhe: view inside the pressure vessel of the multi• purpose research reactor.

The reactor of Germany's first nuclear power plant at Kahl am Main.

Control room and view of the atomic pile at the Hahn-Meitner Institute, West Berlin.

Nuclear Research Centre, Karlsruhe: view of the multipurpose research reactor.

Model of the 20 MWe sodium- cooled reactor in Karlsruhe, design• ed by Interatom.

40 All three projects are sponsored by the The long-term development programme has Federal Government, which assumes wide two focal points: the development of fast responsibility for the financial risks of breeder reactors, which today forms one operation, grants ERP loans and, together of the major tasks of the Karlsruhe Nuclear with the Länder, guarantees other loans Research Centre, and the development of and provides easy amortisation terms. The thermal reactors with conversion factors Kernkraftwerk RWE-Bayernwerk in Gund• of 1 or more, which in future will be con• remmingen is also accorded special privileges centrated more round the Jülich Centre. under the Euratom/US nuclear power plant The work to be carried out under the programme and the Euratom programme of long-term programmes is in both cases participation. In the case of the Lingen and still in its initial stages. No decisions on the Obrigheim power plants, on the other hand, construction of large experimental and the Federal Government is to provide prototype facilities are likely before 1968. subsidies for the research and development Until then, fairly comprehensive prepara• costs incurred under these projects and tory research and development program• for the initial fuel supply. mes will be carried out, close-knit co-ordi• Consideration is now being given to the nation on the European level being fostered possibility of continuing the programme by contracts of association with Euratom in modified form with the construction of covering the entire field with regard to a Franco-German joint power plant with a fast breeder reactors and, for thermal reactor of the gas-graphite string, to be reactors with a high conversion rate, cov• followed up by a German-French reactor ering the gas-cooled, graphite-moderated of the gas/heavy-water string as soon as thorium high-temperature design. Further• technical and economic conditions permit. more, participation in the European Nuclear Energy Agency's DRAGON Project and agree• ments with similar projects in the United States help to create a spirit of fruitful The medium-term development programme international collaboration transcending the is aimed at the design of power reactors boundaries of the European Community. with improved characteristics, in particular a higher fuel utilisation. The relatively extensive programme at present in being covers six construction projects, of which Costs and Financing some are very far advanced while for others the decision to build has only just been taken, together with a number of design The total outlay of the German economy studies. These construction projects include for the research and technical development the AVR experimental power plant at of nuclear energy amounted to about 3,000 Jülich, the multi-purpose research reactor million DM by the end of 1964, the bulk at Karlsruhe, a superheated steam reactor of this being provided from public funds, The nuclear power plant at Gundremmingen to be built alongside t he Kahl experimental i.e. just under 2,000 million DM from the on the Danube power plant, the Niederaichbach C02-D20 Federal budget and about 850 million from prototype nuclear power plant, the com• the Länder, while an estimated 250 million pact sodium-cooled nuclear energy instal• came from industry. Under the 1965 Federal lation at Karlsruhe and the pressurised- budget a total of 523 million DM is ear• water reactor for the Otto Hahn. The bulk marked for nuclear research and develop• of the cost of building these plants, including ment. Of this sum, 349 million DM are the cost of the corresponding research, intended for German projects and 174 development and test programmes, is borne million, or roughly a third, as contributions by the Federal Government. Third parties to international organisations or projects. contribute about 20% of this 650-700 Moreover, long-term loans totalling 35 million DM programme, variously distribut• million DM are to be granted from the ed. Other studies supported by the Federal ERP Special Fund for the Lingen and Obrig• Government under the medium-term devel• heim demonstration power plants. In ad• opment programme relate to other reactor dition, the Länder budgets are likely to types, although it is as yet impossible to allocate about 190 million DM for nuclear assess whether these projects are to be research and development in 1965. pursued further on completion of the The bulk of the public appropriations has present work. hitherto been used for research purposes,

41 111. EXPERIMENTAL AND PROTOTYPE REACTORS

Sute of Thermal Power Net electric construction or in MW power MW commissioning

Versuchsatom• AEG, GE enriched kraftwerk, Kahl (USA) since 12.7.1961. GmbH (RWE [2?3-2U5%) full load Bayernwerk) 5.1.1962

Arbeitsgemein• Brown Boveri/ gas- oled graphite under schaft Krupp Reaktor• high-tempera• construction Versuchs• bau GmbH ture reactor reaktor GmbH, (pebble-bed January 1961. Düsseldorf reactor) scheduled to go carbide : into operation breeder in 1965

graphite spheres

under construction since 1961. scheduled to go into operation in 1966

Deutsche pressurised- light wate light water enriched under Babcock & water integral uranium construction Wilcox/ design (3.6%) since early 1964. scheduled to go into operation in 1966

DjO pressure slightly planned tube reactor enriched with CO,

boiling water light water with nuclear superheat

Gesellschaft f. zirconi u slightly Kernforschung hydride moder• hydride enriched ated sodium- uranium as cooled reactor uranium carbide

largely for the construction of research fluenced primarily by the experience at Gundremmingen is to go into operation, installations. Recently, however, there has gained in the construction and operation followed two years later by the Lingen and been a marked shift in the general pattern of the various experimental projects which Obrigheim power plants and the Kahl observed so far, in that the current expen• are provided for under the medium-term superheated steam reactor. Furthermore, diture on actual research and also on tech• programme, and which have attained more contracts for the construction of large nical development work has been stepped varying stages of advancement, and by nuclear power plants are to be expected, up. This trend will probably become even the drawing up of the decisions which which will probably be rapidly succeeded more pronounced in the future. At the will point the way ahead for the long-term by others once the demonstration plants same time, a rise in total expenditure is to programme. The really decisive factor have been successfully put through their be expected during the next few years. governing nuclear developments in the paces. An installed nuclear power output near future is likely, however, to be found of 5000 MW by the mid-seventies and of in the utilisation of nuclear energy, which 20,000 MW by 1980 now seems quite Future outlook is gradually becoming economically com• feasible for Germany. petitive. It Is obvious that such a course of events The coming years will probably see a marked At the moment there is only one nuclear must have decisive repercussions on the increase in Germany's nuclear research power plant in operation in West-Germany, scientific and technical programmes in pro• activities as the new research centres are namely, the Kahl experimental power plant. gress and also on the entire set-up of gradually completed as well as an attendant However, this year the Karlsruhe multi• Germany's activities In the nuclear field. intensification of international exchanges. purpose research reactor and the AVR In certain instances this may well mean With regard to technical developments, the power plant at Jülich will also be completed. winding up projects in which so much hope foreseeable future will most likely be in• In 1966 the Kernkraftwerk RWE-Bayernwerk is still placed, but generally speaking such

42 a development is likely to fulfil precisely the which are the First and Second Radiologica expectations which we have of our activities Protection Ordinances, the Nuclear Plants in a field of whose existence there was Ordinance and the Nuclear Insurance Ordi• little more than a vague idea less than three nance. decades ago. 4. The Federal Republic of Germany is at present a member of the International Atomic Energy Agency (IAEA), the European Notes Nuclear Energy Agency (ENEA), the European Atomic Energy Community (Euratom), the 1. A survey of the position occupied by European Organisation for Nuclear Research science in Germany is given in Bundesbe• (CERN) and the European Atomic Energy richt Forschung I—a Government report on Society. In addition, the Federal Republic the status and inter-relationship of all the has bilateral agreements with Britain, Canada measures taken by the Federal Republic and the U.S.A. and close relations are to promote scientific research, together maintained with a number of other coun• with a forecast of the country's financial tries as well as between German and foreign requirements for the period 1966-1968, research institutions and between German published by the Federal Ministry for Scien• and foreign industrial enterprises, partic• tific Research, Bonn, January 1965. ularly French, British and American con• 2. The gross national product of the Federal cerns. Republic, including West Berlin, in 1964 5. The total consumption of primary energy was DM 412,500 million. In real terms this in the Federal Republic, including West represents an increase of 6.5% over the Berlin, in 1963 was 250 million tons coal preceding year and a yearly average of just equivalent (t.c.e.), of which 124 million under 5.4% since 1950. National Investment t.c.e. was accounted for by hard coal, 34 in fixed assets reached nearly DM 108,000 million by lignite, 81 million by oil, a little million in 1964. under 2 million by natural gas and the 3. The legal framework for activity in the remainder by hydroelectric power and field of nuclear energy was provided by miscellaneous energy sources. The gross the law of 23 December 1959 for the amend• output of electricity in 1964 amounted to ment of the Constitution and by the law 164,500 million kWh, of which about 92% on the peaceful use of atomic energy and was generated at thermal power stations. the protection against nuclear hazards The installed power-plant capacity at the (Atomic Energy Law), both of the same date. end of 1964 was roughly 36,000 MW; this is By virtue of the law several further ordi• likely to increase to nearly 100,000 MW nances have since been promulgated, among by 1980.

IV. POWER REACTORS

State of Thermal Power Net Electric construction or Owner Manufacturer Reactor Type Coolant Moderator Fuel in MW Power MW commissioning date

Kernkraftwerk IGEOSA, AEG, twin-ci reu i t 801 237 light water light water enriched under RWE-Bayern- Hochtief boiling-water uranium construction wcrk GmbH reactor (2-4%) since 1962, scheduled to go into operation in I966

Kernkraftwerk AEG boiling-water 820 250 light water light water enriched under Lineen mbH reactor with (90 fossil) uranium construction' (Vereinigte fossil super• (2.6%) since end of Elektrizitäts• heater I 964. scheduled werke Westfa• to go into len AEG, group operation of banks) in 1963

Kernkraftwerk SSW pressurised- enriched construction Obrigheim water reactor 90S 282 light water light water uranium commenced GmbH (3%) on 15.3.1965 (Energiever• scheduled sorgungsunter· to go into nehmen in operation Baden-Württem• in 1968 berg)

43 The AYR reactor possible to rely on large temperature differences rather than large heating sur• At the end of 1961, the firm of Brown- faces for good heat transfer. Boveri Company-Krupp, acting on the instruc• tions of the Arbeitsgemeinschaft Versuchs• reaktor company (AVR), a subsidiary of 15 The pebble-bed principle German municipal electricity authorities, began work on the construction of an There is however one important feature atomic power plant of 15 MWe equipped which is unique to the AVR reactor. This with a gas-cooled high-temperature reac• is the shape of the fuel elements, which tor fuelled with pebble-type elements. are spherical "pebbles" of 6 cm diameter. Work with the reactor has now progressed There is no question of fitting these pebbles so far that it is likely to be commissioned by neatly into channels; they are designed, mid-1965. literally, to lie in a heap. Loading a new fuel-element into the AVR core boils down simply to dropping a pebble on to this heap; unloading a fuel element just means extrac• ting a pebble from the bottom of the heap. EUBU 4-6 Protection against this indisputably rough way of handling a fuel element is afforded by the pebbles' outer graphite casing. Repeated tests have shown that a casing of 10 mm thickness is adequate to reduce the probability of damage to a small value. Energy out of "pebbles" Although it is unlikely that anyone would dispute the simplicity of this system, it may give the impression of being somewhat haphazard. Yet this is not so: it is possible to predict the "flow" of the pebbles through the core within fairly fine statistical limits, PROFESSOR R. SCHULTEN, Director of the Institute for Reactor Development, Head of the as experimental work on models has shown. THTR-Project, Jülich Nuclear Research Establishment In view of the fundamental simplicity of the arrangement, loading and unloading during operation of the reactor present few prob• lems. The AVR core is therefore very flexible. The AVR reactor shares with other gas- cooled high-temperature reactors (Dragon Whereas most reactor designs have to and Peach Bottom) certain basic features: permit adjustment of the core's reactivity — graphite Is used both as moderator and through the provision of neutron-absorbing structural material for the core; control rods, which are inserted into the — the fuel is made up of particles of uranium core at the beginning of its life and gradually and thorium carbides coated with carbon removed as the fuel is spent, control rods and dispersed in a graphite matrix, which are superfluous in the case of the pebble- in its turn is held in a graphite structure; bed; admittedly safety rods cannot be dis• — the coolant gas is helium. pensed with for obvious reasons, but the The AVR reactor therefore shares with day-to-day need for fine adjustments to the Dragon and Peach Bottom certain advantages reactivity can be satisfied simply by re• inherent in these systems, such as:—high moving or adding pebbles, by reshuffling efficiency, since the high gas temperature them, by modifying the gas flow etc. The permits the use of modern steam cycles; neutron economy of the system is therefore — good conversion of fertile elements into substantially improved. fissile elements (In particular thorium-232 Moreover, the design offers the possibility into uranium-233) because of the absence of of checking the burn-up and the physical neutron-absorbing structural materials in condition of the pebbles at the unloading the core; points and thus deciding whether they should be removed or reinserted and, if so, — compactness (and therefore moderate where. The idea of making a computer cost) because the presence of heat-resistant make all these decisions is being developed. ceramic materials only in the core makes it

44 The AVR reactor was originally designed to The reactor is to be run on helium at an run on fuel fitted with no special cladding outlet temperature of up to 850°C, so that material, apart from graphite, so that a modern steam conditions can be achieved high level of activity could be expected in in the steam circuit. the primary (gas) circuit in view of the Figures 2 and 3 show the layout of the porosity of graphite. As a result of more reactor in the main building. The reactor recent development work, especially on is of integral design, i.e. the core and the coated particles (see figure 1) fuel elements steam generator are situated in the same can now be employed which retain fission cylindrical vessel. Although this layout is products and therefore reduce activity from not strictly necessary in the case of a small this source to a low level. With regard to reactor, it is a must for larger units, so gas-cleaning and radiation safety, therefore, that the AVR reactor is a genuine prototype the reactor is overdimensioned. In the of a future large power plant. future, it will thus constitute an excellent means for testing fuel elements to failure. The initial charge of 30,000 pebble-type The THTR programme fuel elements is to be delivered in June 1965. They consist of hollow graph• The reactor family of which the AVR is the Figure 1: Cross-section of a fuel particle ite balls, fitted with screw-plugs, into first member has been given the name coated with graphite, silicium carbide and which a mixture of coated particles and Thorium-Hochtemperatur-Reaktor (THTR). A again graphite. The average diameter of such graphite is pressed. The thermal conduc• programme aiming at the development of a particle is 0.5 mm. The main purpose of the tivity of this mixture will be high enough the concept is being pursued under a Eura• coating is to keep in fission products. to ensure that an internal temperature of tom contract of association, which was 1,250°C is not exceeded at an average power signed in June 1964. Besides Euratom, the of 1,5 kW per element. partners of this contract are the Kern- Previous experiments with coated particles forschungsanlage des Landes Nordrhein-West• are very encouraging and burn-ups of up falen (KFA) and ßrown Boveri & Cie/Krupp. to 200,000 MW days per ton of heavy metal The programmesubdivides into three parts: and at temperatures of up to 1,400°C show a fission product release which is suffi• — a research and development programme ciently small to enable various components, covering the physics and chemistry of the such as the gas blowers and the heat-ex• reactor, the development of the fuel (under changers, to be removed or inspected soon sub-contract to Nukem) and the solution of after full-load operation without complica• various technological problems raised by ted remote handling operations. the concept: loading and unloading circuit, complete with automatic measurement of each pebble's burn-up, pressure vessel, heat- exchangers, blowers, etc.; — the design of a prototype sufficiently large to be capable of being scaled up to units of 1000 MWe; — the utilisation of the AVR reactor, which as soon as it starts up, will be able to serve as a large-scale experiment for the com• pilation of first hand practical data on the way a pebble-bed reactor works and on the way the fuel stands up to irradiation. This part of the contract will be covered by a subcontract which is being negotiated at the moment with the AVR Company, the owners of the reactor.

Prestressed concrete for the pressure vessels

Initial investigations have shown that the use of steel pressure vessels is not economic for units of more than about 300 MWe.

45 Figure 2: Model of the AVR to this shielding and to the low fission reactor product release made possible by the use of coated fuel particles, there should be no difficulty about removing faulty steam- generators soon after full-load operation. The steam generators are subdivided in such a way that an individual defective tube system can be switched off, resulting simply in a heating surface loss of less than 1%. Since a margin of at least 20% is built in the design from the start, it is unlikely that any component of the steam generators will have to be removed during the lifetime of the reactor. The upper part shows two helium-lubricated blowers which convey the gas back to the reactor on the cold side of the steam generator.

Capital costs

Calculations of the cost of THTR type power reactors carried out to date show, as in the case of a preliminary design study carried out on a 500 MWe Dragon-type reactor,1 that capital costs will at the most be equivalent to those of light water reac• For units of this size and larger, prestressed lubricated blowers used in AVR. Estimates tors. It is the higher efficiency of high concrete vessels are preferable. As tech• for the more distant future suggest that temperature reactors (40-44% as opposed nological developments stand at present, blowers of this type of up to 3000 kW experience gained in this field in France can be built, so that even larger nuclear to some 30% in the case of light water and Britain indicate that in the next few power plant units can befitted with these reactors) which justifies these expectations. decades there should virtually be no limit blowers. It must not be forgotten that a substantial to the capacity of high-temperature reac• portion (not much less than half) of the tors from this point of view. Under the capital cost of a power reactor is at the development programme models are to be Integrated steam generators moment accounted for by the conventional built and design work carried out aimed at part of the installation. Thanks to the high making the construction of a prestressed Considerable advances on the AVR design efficiency of the system, modern, compact concrete vessel for the high-temperature are also planned in connection with steam and therefore less costly steam turbines, reactor possible by 1967. The contract for generators. If a pressure of 50 atm. of helium for instance, can be used. The result is a the design and development of the vessel is used, the power density of the steam saving which can amount to about 40% of has been let to a German-French-Italian generators can be increased considerably. the cost of the conventional plant. group. Construction experience hitherto shows that in particular very meticulous testing of the tube material is necessary in order High burn-ups . . . Helium-lubrication for the blowers to obtain steam generators having a low water leak-rate and a sufficiently long life. The THTR will, like the AVR, use coated A provisional sectional drawing of the THTR According to the provisional information particle fuel elements. The high burn-up prototype is given in figure 4, from which supplied by one of the firms participating possible with this type of fuel can be in the contract, the results obtained in it can be seen that the entire gas-circuit of exploited by the use of a loading method the development of helium-lubricated the system is Inside the reinforced concrete involving two types of fuel elements. In the blowers are so promising that such machines vessel. The reactor, complete with safety first type thorium is mixed with fissile of over 1000 kW can be expected to go rods and fuel-removal gear, is mounted at material in equilibrium concentration. The into use within the next few years. The use the bottom, while above it are the steam second type consists of pure fissile material of helium-lubricated blowers has therefore generators, separated from the reactor by been provided for in the design of the proto• thick shielding, designed to reduce activity by neutron capture to a minimum. Thanks type THTR reactor, instead of the oil- I. cf. Euratom Bulletin I964 No. 3, pp.20-23

46 (e.g. uranium-235). While the bulk of the sidered, the neutron leakage is so small energy is produced by the first type of fuel that It is reasonable to expect a conversion element with the maximum possible life• factor of approximately 1.0, but there do time (up to 200.000 MWd/t), in which at occur a few neutron losses, which can be least 80% new fuel Is also produced by briefly summarised as follows: conversion processes, the second type of The conversion of thorium-232 into uranium fuel element is principally used to generate -233 involves an intermediate step, which the extra neutrons necessary for maintaining is the formation of protactinium-233 after the chain reaction. When this mixed loading neutron capture. Protactinium-233 then method is used, a conversion factor of about decays to uranium-233 with a half-life of a 0,8 can therefore be expected at the burn- little over 27 days. This happy result is up given above. unfortunately not achieved if, in the mean• If THTR reactors are designed on this prin• time, the protactinium nucleus captures ciple, the fuel cycle will have the advantage a neutron, because it then leads to the of being simple: the fuel will be left in the formation of a non-fissile, and therefore core up to the maximum burn-up and then useless, uranium-234 nucleus. disposed of. An objection to this solution The conversion process into fissile uranium- is that it does not give the THTR concept 233 occurs most readily when the impinging its full chances as a converter: high burn- neutrons are at high energies whereas well- ups entail the presence of large amounts moderated neutrons are required for the of fission products which capture many of neutron efficiency of the fission process. the neutrons produced in the reactor and Furthermore, it is clear that if the neutron thus divert them from the more useful flux is low, less events will take place and task of sparking off the conversion of the protactinium-233 formed will have a thorium into uranium-233. Nevertheless, better chance of decaying into uranium-233 there is every indication that THTR reactors before it is, as it were, tempted to capture can be economical under these conditions, a neutron and turn into uranium-234. giving lower fuel costs than light water It follows that if the advantages of both a reactors, for instance. high specific power and a high conversion ratio are wanted, there is competition between the two aims: a high specific power requires a high flux of well-moder• ... or higher conversion factors ated, fully thermalised neutrons; a high conversion ratio requires a low flux of Studies are to be carried out later to neutrons at higher energies. Both aims can determine whether a higher conversion however be largely fulfilled providing a factor is economically more advisable. The sufficiently high investment is accepted on fuel cycle is then no longer so simple, of the reprocessing plant. Recent measure• course: the average burn-up must be kept ments of nuclear phenomena of paramount lower and the fuel has to be reprocessed to importance to the thorium fuel-cycle have permit reutilisation of both the unspent and actually shown that previous measurements the freshly produced fissile material. overestimated neutron capture by protac• It should be noted that with the THTR tinium-233 and underestimated the neutron design, whatever solution is adopted, a yield of uranium-233. In these circum• high specific power can be attained, which stances, the cost of reprocessing and re- Figure 3: Vertical cross-section of¡ the AVR means that only a relatively small amount fabrication per unit sent out need not reactor of fissile material per kW will be required. become prohibitive. A specific power of 5 kWth per gramme of 1. Part of pressure-vessel housing blowers and fissile material can be expected. Thus, for charge/discharge equipment a given output, a relatively small investment The use of plutonium as the initial fuel 2. Cooling gas jackets In fissile material will be needed and this charge is perfectly feasible In a THTR reactor 3. By-pass tubes for direct cooling of steam may be extremely important in the future and preliminary calculations show that this generator in view of the possible shortage of uranium. fissile material could compete with uranium- If it is decided to take the conversion factor 4. Reactor core 235 in the future, but some development up to 1.0 or more (in which case it would be work must first be carried out on the 5. Steam generator more appropriate to talk of breeding), fabrication of coated particles with plu• 6. Gas return jackets additional measures have to be taken in the tonium. design of the reactor. If large reactors with 7. Fuel extraction duct Reactors like the THTR in which high an output of about 1,000 MWe are con• 8. Blower conversion ratios can be attained offer the

47 The 15 MWe pebble-bed experimental power reactor of the Arbeitsgemeinschaft Versuchs• reaktor (AVR) in Jülich

Figure 4: Provisional sectional drawing of the THTR-prototype advantage that costlier natural uranium permits continuous loading of the reactor, deposits can be used without any appre• thus obviating the need for excess reac• ciable rise in fuel costs, in view of the fact tivity to offset the depletion of the fissile thatthe bulk of these costs is represented by material and the accumulation of fission fabrication and refabrication after reproces• products. In addition, it is an advantage sing. It is estimated that, with a conversion that the mechanical and nuclear properties ratio of about 0.8, a 100% increase in the of the fuel elements can be observed during cost of uranium ore would involve a 10% their lifetime in the reactor. The frequently rise in fuel costs. This could lead, in view expressed view to the effect that a higher of the fuel shortage predicted for the next relative blower power is required for a few decades by some sources, to a consider• reactor run on pebble-type fuel elements able enhancement of the long-term pros• is not valid, since lower gas velocities are pects for converter reactors and could required in the pebble-bed for the same even give them a permanently assured power density. Furthermore, the pressure position. drop in large reactor units is caused not so This would be truer still if the conversion much by the reactor itself as by the steam ratio were pushed up to 1, since the cost generator. In the THTR, for instance, the of uranium ore would then merely be pressure drop in the reactor will be about reflected In the payment of interest on the 0.5 atm. and in the steam generator about cost of the initial fuel charge. 1.0 atm. The total blower power required is As opposed to the other high-temperature relatively small and totals about 2-3% of reactors, the AVR and the THTR are based the net electric power. on the technology of pebble-type fuel elements. At the present moment it is im• The THTR is a reactor offering much lower possible to state categorically whether the fuel costs in comparison with light-water use of pebble-type or rod-shaped fuel reactors, at about the same capital cost. elements offers the better solution in high- In the next decade it will certainly be temperature reactors. The pebble-type competitive with other reactor systems.

48 ORGEL belongs to the heavy-water- The organic coolant has an advantage moderated reactorfamily. Its reference over water by virtue of its low vapour fuel is uranium carbide (UC) and it is pressure. For example, at a tempera• cooled by an organic liquid. ture of 350 C water would have a As currently conceived, an ORGEL pressure of 170 kg/cm2, whereas that of reactor would have:—a cylindrical the coolant adopted for ORGEL is steel vessel containing heavy water, 7 kg/ cm2. On the other hand, the organic coolant has several drawbacks, such as its What is ORGEL ? decomposition under the action of heat (pyrolysis) and radiation (radio- if lysis); hence the need for a purification A brief "recap' system. However, another point in favour of organic liquids is their chemical compatibility with most ma• terials in common use, such as alumin• ium. There is accordingly no need for large-scale investments in costly ma• terials such as stainless steel. traversed by ORGEL channels in which Lastly, through the use of heavy water the fuel is contained and the coolant as a moderator, ORGEL has a good circulates: neutron economy, which means that fuel enrichment is not essential and that high conversion rates (e.g. uran- ium-238 into plutonium-239 or thorium- 232 into uranium-233) are possible. The nuclear part proper of an ORGEL reactor is supplemented by a conven• tional installation in which heat is employed for the generation of elec• tricity by means of a water/steam circuit.

The fuel element is in the form of a How far have we got with the ORGEL cluster of uranium carbide rodlets: Project? See the next four pages.

Can Uranium Carbide In 1960 Euratom launched the so-called damental choices made at the beginning, ORGEL project, a design study for a particularly as regards the fuel and the heavy-water-cooled organic-liquid-moder• coolant. ated reactor. For the last four years research, experiment and construction have succeeded one an• The Research Programme other under this programme, through con• tracts with private firms or national organ• Coo/ant isations and with the growing support of the Joint Research Centre's establishment The terphenyl mixture OM2 adopted as at Ispra. How do we stand today? reference fluid has proved, after several The broad lines of the concept are un• in-pile irradiation campaigns, the most changed: the reference fuel is still the stable at high temperature (up to 450°C uranium carbide chosen at the outset as bulk temperature and 500°C wall temper• combining the ability of ceramics to with• ature, the latter having no effect on the stand high temperatures with a better decomposition rate). Of the petroleum dérivâtes studied under contract, some, such as the methylnaph- thalene fractions, were abandoned two EUBU 4-7 years ago as their vapour pressure was distinctly higher than that of OM2; others, like the alkylphenanthrenes, display a lower pyrolytic stability than OM2 and can hardly How far have we got with the Orgel be used in-pile above 380°C; they were nevertheless investigated until recently be• cause they are liquid at ambient temper• Project? ature, which might simplify the problems involved in the initial startup of ORGEL SERGE ORLOWSKI, Directorate-General for Research and Training, ORGEL Project Directorate reactors. -JRC, Ispra Hence a considerable effort has been made to find out all about the terphenyl mixtures and their pyrolitic and radiolytic decom• position products. Methods of analysis, of measuring physical properties and deter• mining impurities have been developed and extended beyond, sometimes well beyond, 400°C. heat conductivity and uranium content than Current cleanup techniques make it pos• can be obtained with uranium oxide; the sible to avoid fouling at the operating basic organic coolant consists of terphenyl temperatures envisaged, even though its isomers (meta-, ortho- and paraterphenyls) basic mechanisms are not yet clearly under• mixed in suitable proportions (Fig. 1), stood. while SAP (Sintered Aluminium Powder) is still the foremost core structural material, Fuel although advanced studies are also in pro• gress on zirconium and its alloys. As regards uranium carbide, the initial This is not for lack of alternatives: the problem was how to produce it on a larger organic coolant, in contact with the struc• than laboratory scale and under stringent tural and cladding materials, and, in the conditions of composition, homogeneity event of failure, with the moderator and and dimensional tolerances. One difficulty fuel, displays low powers of chemical at• is that strict controls must be applied to tack, a property which opens up prospects obtain the UC monocarbide required, of a number of combinations (Fig. 2); nor otherwise one gets mixtures of UC-U is it due to a spirit of conservatism, for (substoichiometric) which appear to be less certain of these combinations are studied stable under irradiation, or UC-UC2 (hyper- alongside with the reference solution, stoichiometric) which may raise problems though less exhaustively. The fact is that of chemical compatibility with the cladding. research so far has corroborated the fun• The manufacturing question can now be

50 regarded as solved, since an order of 7 for analysis, for destructive and non-destruc• tons of carbide rods for critical experiments tive inspections, and for purifying the in the ECO reactor has been delivered to starting powders; as far as the dads are Ispra, and the various tolerances stipulated concerned, this milestone can be considered by Euratom have been complied with. For as passed. And although SAP is still a this "small pilot" contract the price of the brittle material in the case of slow phenom• finished rods was 90 EMA u.a. per kg con• ena (creep), the irradiation experiments tained uranium; further research is now carried out on SAP-clad carbide pins in the aimed at the industrial manufacture of this NRX reactor under the Euratom/Canada fuel at a price which should not exceed agreement showed that the concept is 50 EMA u.a. per kg, as well as at irradiation perfectly viable at the burn-ups envisaged tests which, as will be shown below, had (10,000 MWd/t). already begun satisfactorily during the fuel At the same time active research is going element development work. on into zirconium and its alloys, which may make for more flexible design; it is hoped in this way to benefit from the Cladding and structural materials technological development work devoted to water reactors. The problems involved in Work in this area was focussed on sintered the formation of zirconium hydride and the aluminium-alumina (SAP). This material, resultant embrittlement, which affect both which is not new (the first patent was taken reactor strings, still remain to be overcome, out in 1946 by the firm Alu-Suisse), seems however. Lastly, preliminary studies carried to have been quite well known as early as out at Ispra indicated that magnesium might 1960. But really valid test results can only also be suitable for an organic-liquid-cooled be obtained on finished products subjected reactor under certain conditions; in that to the conditions which they will encounter case, it would probably be necessary to use in use; and it was very soon found that tubular fuel elements, not unlike those which are planned for the French EDF J SAP was liable to blistering towards 500°C, gas-graphite plant. a phenomenon which was eliminated by EXPO exponential experiment, Ispra thorough degassing of the starting powders. All this means that, although the ORGEL The next step was to develop commercial reference fuel element is still a bundle of methods of manufacturing tubes of small 7 or 4 SAP-clad uranium carbide pins, diameter (for cladding) and large diameter there are other variants awaiting explora• (for channels), side by side with processes tion, particularly in the field of tubular

Figure 1: Terphenyls. The basic coolant adopted for ORGEL is a mixture of the terphenyl isomers. Their molecules are composed of three benzene rings (on the left): alteration of the position of the rings in relation to the central ring produces the three isomers:

H meta-terphenyl C H H C C ortho-terphenyl

C C H H C H para-terphenyl

51 atory is to be used for fuel element and the other for pressure tube inspection. The civil engineering for the internal structures of both reactor block and pressure-tube laboratory is finished, the leaktight metal containment will be completed during the summer, and construction of the fuel-ele• ment is under way. The entire civil engi• neering works should be finished by the end of 1965. All the supply contracts have been placed and the first deliveries are arriving at the Ispra site. The reactor is scheduled for criticality in 1966 and normal operation in 1967.

The outlook

Construction of an ORGEL reactor is al• ready a practical prospect. A study carried out under contract by a group of industrial ORGEL pressure-tubes firms in 1962 did, in fact, show that no Two variants, one with four and the other with seven fuel pins. insuperable problems would be encountered in building a 250 MWe power plant, and recent developments in the research pro• gramme have confirmed this view. elements, which might be produced very former under contract and the latter by The same contract had also provided con• cheaply. the Ispra establishment. EXPO is a less firmation that investments in such a plant ambitious but more flexible installation would be moderate (160 EMA u.a. per than ECO, operating in sub-critical con• KWe installed, excluding indirect charges What has actually been built? ditions and yielding results of less precision but including site and heavy water). than ECO will be able to supply. Neverthe• But the attraction of the concept lies in Plant has been constructed for the testing, less, EXPO alone has already furnished initial the very low fuel-cycle cost, allied to the from both the neutronic and technological data on the reactivity of uranium carbide/ simple "throw-away" cycle, i.e. without angle of ORGEL reactor sub-assemblies organic liquid/heavy water lattices—which reprocessing to recover the residual fissile ranging from the smallest to the largest. proved incidentally to have a greater reac• materials. Thus, besides special-purpose in-pile and tivity than we expected. It is already safe to estimate a figure of 1 out-of-pile loops (for specific studies on The ESSOR complex (ESSai ORgel) includes mill/KWh for a full-scale reactor, the burn- fouling, heat exchange, corrosion, the two hot laboratories in addition to the ups that can be expected with natural ORGEL channel, pumps, etc.), two experi• reactor which, of course, is intended for uranium reaching 8,000-10,000 MWd/t. With ments due to be run In parallel, a critical testing the whole setup comprising channel, slight enrichment (1% absolute, as com• experiment—ECO—and an exponential ex• joints and fuel elements under ORGEL pared with 0.7%for natural uranium), which periment—EXPO—have been set up, the power-reactor conditions. One hot labor- would not entail reprocessing or affect either the fissile material economy or plutonium production, it would be possible Table I to bring costs down to 0.6 milis/kWh by Production cost of electric power supplied by an ORGEL power plant (In milis/kWh). boosting the burn-up to 20,000 MWd/t. If we consider the cost of fossil fuel in the Installed 100 MWe 250 MWe 500 MWe Community (3.1 to 5.2 milis/kWh for fuel- power oil and around 3 milis/kWh for lignite), it is obvious that, in view of the "minimum ORGEL 5.5 to 6 5 to 5.5 marginal cost" principle applied by the natural U operator, the ORGEL-type plant is highly ORGEL suitable, even throughout practically the slightly 6.5 4.5 entire reactor life, for base load operation, enriched irrespective of any extra supplies which U may be made to the overall power grid

52 organic coolant (250,400°α)

Mg and alloys

U metal by conventional or light-water nuclear plants. Al The total production cost of power sup­ and alloys plied by an ORGEL power plant are given in Table I. Capacities above 500 MWe are not shown as we have no sufficiently accu­ rate data on prices; it is certain, however, that the cost continues to drop as capacity

Zr rises, and the higher capacities are partic­ and alloys ularly attractive because they involve no serious technological difficulties with this type of reactor. For example, ORGEL has no pressure vessel, so that there are none of the technological problems that arise where the vessel walls have to be pro­ stainless and mild steel portionately thickened as the size is in­ creased. It was on such grounds that the United States Atomic Energy Commission, at the meeting of the Atomic Industrial Forum in December 1964, announced a ten-year research and development programme and the construction of three power reactors basically of the same type as ORGEL, the first of which will produce electricity only and will be commissioned towards 1970. This should be followed up by the building of giant reactors, particularly for Figure 2: Flexibility of the ORGEL concept water desalination projects. Among the possible reactor components there are a number of compatibility relationships. At the same time the Euratom Commission, pursuing the aims set out in 1960, has just — incompatibility taken a decision in principle to ask Com­ — fair compatibility, improvement under munity industry to undertake a detailed study or already achieved (platings, barriers, design study on an ORGEL prototype. The inhibitors, etc.) construction of this prototype will then be the final step needed to reach the target —the commercial power reactor. excellent compatibility

The ESSOR reactor (ESSai ORgel = ORGEL test) under construction at the Euratom Joint Research Centre's establishment at Ispra.

53 Boiling water and natural uranium—the The results derived from this contract were Preliminary optimisation studies geared to combination may appear paradoxical, since, such that two other contracts were sub• these two alternatives had the effect of as we know only too well, the facility sequently concluded with the CISE, the focussing interest on heavy-water modera• afforded by the use of light water as a aim being to take the Information already tion. This led to the signing in July 1963 reactor coolant is offset by the need to acquired in the heat-transfer and corrosion of a first contract, CIRENE-1, with the employ enriched uranium as fuel. Never• fields a stage further. CISE, which was followed up by contracts theless, a power reactor of the CIRENE However, the design studies showed that CIRENE-2 and CIRENE-3, the chief aims of (Cise REattore a NEbbia—CISE fog-cooled the benefits of cooling by low-density which were: reactor) type Is designed simultaneously to water/steam mixtures had the greatest generate light-water steam in the core, effect, not in light-water-moderated reac• — to conduct a research and development this steam being conveyed by direct cycle tors, but in reactors with a good neutron programme on a pressure-tube heavy-water to the turbine, and to consume natural economy, such as those moderated by reactor, cooled by a low-density water/ uranium. How is this possible? In the first heavy water and graphite. steam mixture; place because the reactor is moderated with heavy water, which has the important asset of enabling a good neutron economy to be obtained, and secondly because there EUBU 4-8 is in the core only a limited amount of light water, a material which, on account of the hydrogen it contains, impairs the neutron economy even when employed in conjunc• tion with the heavy variety. This reduction A natural-uranium boiling- is achieved by maintaining in the core a "fog", or more precisely a low density water/steam mixture, since, in view of the considerable disparity between the densities water reactor project of these two phases, the greater part of the volume occupied by the coolant con• sists of steam as soon as it accounts for ABRAHAM BAHBOUT, Directorate-General for Research and Training, ORGEL Project 10% to 15% of the weight of the mixture. Directorate—JRC, Ispra

Genesis of the project — to study a CIRENE-type high-power The CIRENE project is being carried out reference generating plant and to assess by the C/SE' in Milan, with technical assist• the economic aspects of energy production ance and close co-operation from the Italian from such a plant; Atomic Energy Commission (CNEN) ana — to draw up a draft design for a prototype Euratom. The project is being financed reactor. jointly by Euratom and the CNEN. As far back as 1958, the CISE was conducting research into the cooling of reactors by Other projects similar to CIRENE water/steam mixtures. Then, following the conclusion of an agreement in October The CIRENE project has therefore got 1959 between Euratom and the United beyond the conceptual stage. It is not an states Atomic Energy Commission for the isolated operation, either, since the devel• Study of wet-steam-cooled light-water- opment of a reactor with similar charac• moderated reactors, a first research con• teristics constitutes the principal short- tractwas signed with the CISEj'Ansaldo/NDA term objective of the Canadian nuclear group. programme, the intention being that such

I. The CISE ^Centro Informazioni Studi Esperienze) ¡s a limited liability company, incorporated in 1946 and controlled almost entirely by the ENEL In addition to its activities under the CIRENE project, the CISE Tests for visual observation of dispersed-phase flow, by analogy, in the hydrodynamic loop of carries out research into semi-conductors, lasers, metal physics, etc. the CISE at Milan. The photograph shows the effect of an obstacle on the flow of the water film.

54 a reactor should become the successor of off and then recycled in the reactor, and petitive energy market. In this struggle, the CANDU-type pressurised-heavy-water- the steam is channelled directly to the there is one definite item on the credit side cooled design. There is already some talk turbine. i.e. the fuel-cycle cost is appreciably lower of converting the NPD-2 reactor to boiling- than for light-water reactors, on the light-water cooling. Furthermore, Atomic grounds already stated—unenriched fuel, Energy of Canada Limited (AECL) has launched What makes the CIRENE concept no reprocessing in the fuel cycle and rela­ a study of a 500 MWe reference reactor attractive? tively high burnup. of this type and has recently decided to A CIRENE-type reactor is equipped with embark upon the construction of a 250 MWe The value of the CIRENE concept lies not pressure-tubes, that is to say the tempera­ prototype reactor. only in its intrinsic assets from the tech­ ture and the pressure of the coolant are The UKAEA, for its part, has since the be­ nical and economic angle, but also, and contained entirely by the channels in which ginning of 1963 been engaged in the con­ particularly, in the benefits deriving from the energy is generated. The moderator struction at Winfrith of a 100 MWe proto- the fact that the concept is based largely is kept in a cold state and at virtually on experience acquired with proven-type reactors already in existence.

Technical and economic advantages steam separator turbine These stem from the fact that the CIRENE concept combines characteristics peculiar to natural-uranium pressure-tube heavy- ρ = 70 at t = 285

55 liquid bulk temperature types of flow

wall steam - single temp. phase

li juid-free region

not only when in operation but also con• tinuously. Continuous fuelling is obtained by re• plenishing at regular intervals a fraction dispersed or the whole of the fuel content of each flow channel. It obviates the need for initial storage of large reactivity excesses to com• pensate fuel depletion, which eases the task of the control system, cuts down flux distortions and enhances reactor safety. Moreover, the substantial volume of heavy water required for moderation makes it bubble flow possible to install between the channels tubes which may be emptied or flooded with heavy water as required, in order to check the degree of lattice moderation. water- This check is most useful after the reactor single phase has received a complete fresh fuel charge. It is then possible to reduce moderation, and consequently raise the mean energy of the neutrons, thus increasing the prob• temperature steam quality ability of their capture in the uranium-238. weight ", This procedure has the advantage not only of absorbing reactivity excesses but also of making use of them, since the uranium- What is fog cooling? 238 nucleus is converted into plutonium after capturing one neutron. Furthermore, pressure-tube heavy-water Imagine a vertical tube whose walls are subjected to a constant thermal flux and reactors offer greater safety than pressure- which is fed by an upward flow of sub-saturated water. As it passes through the vessel reactors by reason of the fact that tube from end to end, the coolant undergoes various flow regimes as its enthalpy the failure of a pressure-tube is less serious or quality increases. At the tube inlet, so long as the quality is negative (sub- than a vessel rupture. saturated water) and the tube-wall temperature remains below saturation tempera• Finally, we come to the advantages of ture, heat transfer takes place by forced convection of the water, which is the only boiling-light-water cooling. phase present. As soon as the wall temperature rises slightly above saturation temperature, the Let us briefly recapitulate them: quality being still negative, the wall heat is removed by sub-saturated or surface — Light water is a well-known and very boiling: the steam bubbles forming on the heating surface then condense partially cheap fluid ; in the still sub-saturated bulk of circulating water. — Leakages of light water or light-water/ When the water reaches saturation temperature (nil quality) the steam bubbles steam from the coolant do not raise any can no longer condense. We then have v/hat Is known as bubble flow—discrete recovery problems, as they do in CANDU- bubbles of steam circulating in a moving liquid continuum. It is this type of biphase type reactors, or any contamination prob• flow that we find in the BWR reactors. It covers a relatively narrow range of steam lem due to tritium formation; qualities, with an upper limit of the order of a few percent. — As the coolant also serves to drive the Higher in the tube, when the bubble volume becomes appreciable, i.e. when the turbines, the elimination of intermediate quality has reached a certain value, the flow system alters—the bubbles coalesce exchangers means substantial savings in forming steam "slugs" which assume the shape of the duct. At the point where capital costs; these conditions are set up, we find alternating steam slugs and water slugs— — The thermodynamic cycle being a direct the latter, however, also contain steam bubbles. This flow system, which is unstable, one, there is no degradation of heat In the is called slug flow. exchangers and the overall efficiency is A little higher in the tube, above a certain quality value, when the void flow rate thereby improved; appreciably exceeds that of the liquid volume, the annular or dispersed flow regime — For an equal thermodynamic efficiency, is reached : the liquid phase covers the hot wall in the form of a thin rising film, and the reactor pressure is appreciably lower the rest of the tube in this section is full of steam. The two phases are thus separate. than that in an indirect-cycle pressurised- Actually the steam also contains water droplets in suspension, so that it looks like water reactor. This affords savings in ab• fog. sorbent structural materials in the core; As the water-steam mixture continues to rise in the tube and the quality increases, — Lastly, in the event of a severe steam the thickness of the film on the wall decreases by evaporation and entrainment. circuit failure, the pressure surge In the The water droplets entrained by the steam gradually evaporate. After a certain

56 point the film on the wall vanishes altogether, a liquid-free zone is reached and reactor building is smaller than in a liquid a so-called "crisis" is reached in the heat transfer process (see below). coolant reactor, the total energy stored in Higher still, all the water droplets suspended in the steam disappear completely, the coolant being relatively small on ac• and the quality of the coolant has reached the value of unity. count of the low density of the steam phase. From this point onwards, the heat would serve to superheat the steam. Actually the bubble and slug flow take up only a small fraction of the length of heating duct while the length occupied by annular flow (fog) is In direct proportion Reaping the benefits of past research to the outlet quality. We have already underlined the fact that the basic component of the reactor is the channel. It is accordingly channel develop• ment which gives rise to most of the new Slow and fast boiling crises (burn-out) problems to be tackled. Now assuming that the fuel used is uranium Since with this dispersed flow system heat transfer is not effected by bubble emission oxide in a cluster array, it will be seen that from the heating surface, presumably the burn-out phenomenon, the bugbear of the majority of the problems have already BWR reactors, can be ruled out. For burn-out occurs when the bubbles formed on been solved during the development of the wall of the heating surface are not carried away fast enough; an insulating other reactors. For example, the constituent layer of steam then forms on the wall, giving rise to a temperature surge which in materials—oxide fuel and Zircaloy-2 for turn may lead to the melting of the heating material and so to destruction of the cladding, pressure and calandria tubing, surface. This fast crisis, or burn-out, is typical of nucleate boiling. have now been thoroughly investigated and With dispersed flow, as we have said, the water film covering the heating wall are able to do the job expected of them. gradually moves along the channel, In the same direction as the flow, and vanishes There are virtually no materials problems, as a result of evaporation and entrainment. After thinning considerably, to virtually no metallurgical "gambles". In addition, nil thickness, the film breaks, splitting up into little streams of water running the oxide/Zircaloy-2/boiling water combi• round dry patches. The overall wall temperature, measured at a given point of nation has been adequately tested from the the surface, begins to oscillate. These temperature oscillations (or "noise"), grow compatibility angle. in amplitude as the number of dry patches increases, then gradually diminish as the Consequently, the research and develop• film disappears. The wall heat is then carried off entirely by forced steam convection. ment programme involved boils down to By definition, crisis is reached when the temperature oscillations, or noise, exceed the adaptation of the existing elements a certain "threshold" amplitude. Burn-out conditions cannot be said to obtain, as to the dimensions and conditions specific the amplitude is not enough for the heating surface to be destroyed. Two main to the CIRENE project. factors account for this. First, the heat flux at the critical point is relatively low, as compared with the critical flux obtained in nucleate boiling, which has a low steam quality. Secondly, with dispersed flow, the steam throughput is high, which Long-term prospects means relatively high steam velocities and hence relatively high convection heat- exchange coefficients. The deterioration in heat transfer is slower and less signifi• By equating a C/R£NE-type reactor to a cant than in a nucleate boiling burn-out. Consequently the temperature oscillations boiler, it is easy to visualise ways and means which accompany the crisis can be withstood by a fuel clad without damage. of improving the concept, at least as far This finding, which has now been thoroughly corroborated by experiment, opens as thermodynamic efficiency is concerned. up the possibility of a "once-through" heating method. If the fuel in a reactor The first step would be to attempt to reduce channel can stand up to the temperature oscillations specific to the transition from the water content in the reactor by in• dispersed flow to forced steam convection—and a fuel such as Zircaloy-clad creasing the outlet quality. Taken to the uranium oxide looks like having this capability—the fear of burn-out will no longer logical conclusion, this would lead to a inhibit the steam quality value at the channel outlet. The channel is then said to "once-through" reactor, in which the be operating in "ultra-crisis" conditions. liquid coolant is fed at the channel inlet to emerge at the other end as superheated steam. A second possibility is nuclear superheating, Independent of "once-through" heating, in which the steam produced in the boiling channels is superheated, after separation, in superheat channels. The first Beloyarsk power plant reactor is operating along these lines and the SGHWR prototype is to include 8 experimental superheat channels out of a total of approximately 200. Finally, with superheating, the steam-pres-

57 heavy water

UO. with Zircaloy-2 cladding

fog

pressure tube (Zircaloy-2)

insulating gas

calandria tube (Zircaloy-2)

Fig. 2: Uranium-oxide version of a CIRENE-channe/ (hori­ zontal cross-section)

sure increase becomes a paying proposition. In the case of an oxide cluster, on the other arranged in the form of a crown around In the extreme case, we may imagine a hand, the liquid film which wets the inner a graphite core the function of which is hypercritical-pressure and once-through- surface of the pressure tube does not con­ to reduce the flux depression in the bundle. heating reactor. tribute to the heat transfer: The bundle is surrounded by a jacket of Among these three possible lines the Zircaloy-2 which isolates it from the heavy stepping-up of the coolant's steam content water moderator. The space between the to a value slightly below saturation appears various tubes Is filled with a stationary to be the most feasible in the medium if inert gas so as to cut down heat leakage to not in the short term. Nuclear superheating, the moderator (see fig. 3). whether in superheat channels or in once- The uranium-metal version currently under through channels, raises the problem of study assumes a "hair-pin" type coolant- the development of a corrosion-resistant flow in the fuel element similar to that cladding material other than Zircaloy. adopted for the first Beloyarsk power plant:

Specific problems of the CIRENE LIQUID FILM project - »

Choice of fuel in other words, in a tubular cross-section a less water is required for the removal of ι At first sight the most suitable fuel for a a given quantity of energy than in a cluster . CIRENE-type reactor is Zircaloy-clad urani­ cross-section. As will be seen later on, this \J O um oxide in the form of fuel pins in a coolant density plays an essential part. It cluster array, (see fig. 2), which was was for these reasons that a study was also thoroughly tested out during the develop­ carried out to explore the possibility of the coolant enters the top of the reactor in ment of various water reactors, in particular using tubular uranium-metal fuel elements the form of slightly undersaturated water. the CANDU reactor. with internal cladding and cooling. It circulates from top to bottom in a central Nevertheless, the dispersed-phase flow of In the uranium-metal version the internal Zircaloy tube which passes through the water/steam mixtures lends itself best to clad serves also as pressure tube. This design graphite core. At the bottom of the channel tubular channels. Indeed, in the latter case is identical with that of the fuel elements the water is introduced into the peripheral the heating surface is the inner wall of the at the first Beloyarsk power plant. In this heating tubes in which it circulates from tube, which is the only wall wetted by the way the quantity of "idle" construction bottom to top while gradually changing liquid film of the mixture as it flows past: materials present in the core is reduced. phase. The coolant likewise leaves via the This, coupled with the fact that uranium top of the channel. The entire channel may metal has a high density, results in higher thus be likened to a dipper, which is im­ core neutron efficiencies than are obtainable mersed in the heavy water and which can with the oxide version. be completely withdrawn from above. The fuel tubes can be fabricated by co- The neutron economy of this kind of lattice extruding the uranium with the cladding. was checked experimentally in a series A few prototypes of such fuel elements, of critical tests carried out in the Aquilon-ll the fabrication cost of which is low ($ 30 per reactor at Saclay early in 1964. kilogramme), have already been produced There are, however, a number of technical for the CIRENE project by the American uncertainties which argue against the use firm Nuclear Metals. The uranium tubes are of metallic uranium.

58 For, in the first place, there has as yet been But there are numerous drawbacks—it no systematic study of the irradiation would entail recirculating hot, highly pres• stability of uranium metal tubes, although surised steam drawn off from the separator, a few tubes in the Savannah River HWCTR mixing the two phases at the channel inlets, pile exposed to burnups of over 6,000 or etc. 7,000 MWd/t have yielded extremely en• Consequently for CIRENE, as also for the couraging results. It is therefore planned Beloyarsk reactor, SGHWR and the Cana• to carry out some CIRENE tube irradiations dian project, it was decided that the in the near future, to confirm these results. coolant should be sub-saturated at the Secondly, there are a number of problems inlet. Thus a small portion of the full connected with the compatibility of uranium channel length, nearest to the inlet, oper• metal with the hot coolant, a subject on ates under nucleate boiling conditions, which little is known. An experimental whilst the remainder is under dispersed programme has been started at CISE to flow. This fact, and purism, are the reasons clear up the uncertainties in this area. why the Canadians do not use the word Under such conditions, we may conclude "fog" for the cooling system proposed in that one proven fuel element for the their studies, even though they are envis• CIRENE type of reactor is already available, aging extremely high channel-outlet steam and it is always possible to turn to this qualities, so that the dispersed regime solution (uranium oxide in clusters) if the occupies the greater part of the channels. uranium metal version proves impracticable. The channel light-water content is of major Lastly, mention should be made of the importance. On the one hand, light water large-scale loop which is to be fitted in the A tubular-type CIRENE fuel element being has such a voracious appetite for neutrons ESSOR reactor at Ispra, for testing CIRENE loaded into the Aquilon-ll reactor at Saclay. that it has a ruinous effect on the neutron prototype powerchannelsand fuel elements. balance of a non-enriched uranium lattice. Yet to avoid burnout the dads must be Genera/ reactor design covered all along the channel with a film of water to protect them from temperature To obtain dispersed flow throughout the surges. full length of the channels, the coolant The search for a compromise between these would have to enter the core in the form conflicting requirements narrows down, for of a steam-water mixture. The only ad• a number of reasons, to the choice of an vantage of this over a slightly sub-saturated optimum channel length, which in fact lies form would be a slight reduction in the at around 3.50 metres for a 500 MWe reac• average coolant density in the channels. tor. The channel outlet steam quality varies from 20 to 30%. Thus the coolant density Fig. 3: Uranium-metal version ranges from 0.75 g/cm3 at the inlet (satu• of a CIRENE channel (hori• rated water), for instance, and 0.20 g/cm3 zontal cross-section) at the outlet. As already stated, in the uranium metal version the coolant enters and leaves the reactor at the top. In the oxide version, the coolant enters at the bottom and leaves heavy water by the top of the reactor:

insulating gas

graphite

fog

uranium metal with Zircaloy-2 cladding D

insulating tube (Zircaloy-2) The specific power, expressed in W/cm3 of fuel, is practically the same in both versions, varying around 160 W/cm3.

59 Dynamics and stability Loop for large-scale heat- transfer tests, installed at The novelty and main snag of a CIRENE-type Genoa. reactor, as compared with the SGHWR, is the need to accept a positive void coeffi• cient. In order that the reactor may run on natural uranium, the quantity of light water pre• sent in the core must be kept very low. Consequently the lattice continues to be moderated chiefly by heavy water. A reduc• tion of the coolant density means lower absorption in the light water—resulting in increased reactivity—and also by lower moderation by the hydrogen contained in the water—causing a loss of reactivity. The former effect prevails over the latter owing to the small quantity of light water present, and this causes the reactivity to rise In direct proportion to the volume occupied by the steam; in other words, the reactor has a positive void coefficient. In the case of the SGHWR, on the other hand, a negative void coefficient is obtained by narrowing the lattice pitch and enriching the fuel, which means that the light water plays a greater part in lattice moderation. This positive void coefficient is the main recourse being necessary to any other line fracture (pressure rise in the reactor component of the CIRENE reactor power means of reactor control. building) will be less severe than in the coefficient. In fact, the counter-reaction due case of other reactors. On the one hand to the negative Doppler effect of the fuel Safety the total energy stored in the coolant is as the latter heats up is a weak one and is fairly low in comparison with pressurised- insufficient to offset the positive effect of A serious fracture in the reactor steam or boiling-water reactors, owing to the the void coefficient. The reactor therefore circuit can give rise to a sudden drop In the lower coolant density; on the other hand has a positive power coefficient and could pressure, and consequently the density, the division of the reactor into hydro- be intrinsically unstable. of the coolant, and this is reflected by a dynamically independent zones means that It must be remembered, however, that surge of reactivity in the reactor owing in the event of a fracture only a small part when the reactor power rises or falls there to the positive void coefficient. of the energy stored in the coolant will be ¡s a tendency fcr the pressure in the entire This situation, at first sight a disastrous released. water/steam circuit, including the out-of- one, can, however, be remedied. In the pile section, to follow suit. Consequently, first place, it is possible to limit the rate in a reactor of the CIRENE type the pressure at which the water/steam mixtures escape Concluding remarks can be caused to vary in such a way that through a piping fracture by Increasing the coolant density remains constant and the number of lines linking the outlet-side At atime when "convergence" is considered thus independent of the power level. But headers of the reactor with the steam essential and the trend is towards less the corrective action of the pressure must separator and by providing flow restrictors diversification of reactor strings, it may not be too delayed; this condition can be on the steam lines to the turbines. Secondly, seem surprising that countries such as fulfilled by reducing to a minimum the the consequences of a leak can be mitigated Britain, Canada and Japan should be volume of the water/steam circuit. by splitting the reactor up into a number starting to develop reactors of the CIRENE The positive effect of the void coefficient of zones, the channels of each zone being type. can thus be neutralised and the overall connected to an independent external It will readily be appreciated, however, power coefficient becomes zero or negative. circuit. In short, the accident is cut down that this concept, which combines the In principle, moreover, this system offers to the scale of a power excursion which advantages of heavy-water and pressure- the possibility of making the reactor power can be limited by the rise in fuel tempera• tube designs with those of boiling-water depend on the loading of the turbo-alter• ture (through the Doppler effect) without reactors and opens up extremely promising nator unit; control of the reactor is then damaging it. prospects for the future, enjoys a privileged exercised solely via the opening of the Finally, it should be borne in mind that position In that its development calls for team inlet valves to the turbine, no the "external" consequences of a steam- very little effort.

60 EURATOM NEWS

Nuclear energy from today until 2000 - Total installed power Lood factor on 1 January (hours/year) forecasts for the European Community (WOO MWe) 1970 3,7 ) 1975 12,0 / 6,000 1980 40,0 ) 1990 140,0 5,500 2000 370,0 5,000 According to Article 40 of the Treaty estab• The estimates for annual electricity con• lishing Euratom, the Commission undertakes sumption that follow are (285 milliard kWh to publish periodical "programmes indicating, in 1960): Some observations on the above in particular, the production targets for nuclear energy and the various types of (milliard kWh) — Energy imports, which have been rising investment required for their attainment". from 5% pre-war to 27% in 1960, around The Commission recently drew up such a Í965 409 1980 1,080 50% in 1965 (of which 80% from Arab "target programme" relating to the period Í970 574 1990 1,930 countries in the Middle East and North 1970-1979, with extensions up to theyear 2000, Í975 789 2000 3,450 Africa) should rise to between slightly over and outlining the probable increase in electric• half and a little under two thirds In 1975, ity consumption, the percentage of these The rôle of nuclear energy in satisfying In spite of the (still modest) recourse to requirements to be satisfied by nuclear energy this demand is based, for the immediate nuclear power. Even with the implementa• and the resultant repercussions on the various future, on known projects and on pro• tion ofthis "programme", however, imports sectors of the nuclear industry with regard grammes already announced. Over the will still furnish nearly 50% of energy to both production costs and investments. longer term, it is estimated that between requirements in 2000. Thus this growth Basing its conclusions on the data contained 1980 and 2000 two thirds of new power in the recourse to nuclear power is indis• in the target programme, the Commission station capacity will be nuclear. This, how• pensable if too great a dependence on also drew up a document entitled "Factors ever, is regarded as a minimal hypothesis; external sources is to be avoided, affecting industrial policy", which dealt with in view of the technical maturity likely to — furthermore, even if a large part of the the structural and organisational problems have been achieved by nuclear power and fissile materials are imported, nuclear raised by the transition of nuclear energy its economic advantage over conventional energy will nevertheless contribute to the to the industrial stage and mapped out the plants, for which fuel costs are expected security of supply owing to the much lower course of action to be pursued. to rise, it could well be that all new capacity cost of nuclear, as opposed to classical, The Commission will not be in a position to Installed after 1980 or 1990 will be nuclear. fuel sources, the cheaper and more favour• publish the final version of these documents This would give a capacity of at least 500,000 able conditions of transport etc. until certain consultations have been held, but MWe in 2000, to furnish around two-thirds — furthermore, assuming a stable price of the main ideas behind the first of them, the of electricity, and a third of total energy, $ 13,50 per ton of coal equivalent for the "target programme" are sketched out here. needs. fossil fuels used in most conventional power According to the hypothesis actually ad• plants i.e. coal, fuel-oil and natural gas, The first assumption of the programme opted one half of the Community's installed during the period, and assuming that the is that electricity consumption will rise capacity in 2000 will be nuclear; slightly nuclear power plants to be installed will as follows during the period 1965-2000: more than half the total electricity produced produce 17,000 mrd kWh before 2000 and and around one quarter of the energy 34,000 mrd kWh after (i.e. altogether 140 1960-65 1965-70 1970-80 1980-2000 consumed would come from nuclearsources. times Community electricity production in 1964) it is estimated that savings In the cost (average annual increase during each The following table sets out the nuclear of electricity production will be $ 93 mrd period in %) power production "objectives" for the or 36% (in absolute values) and $ 23 mrd 7,5 7,0 6,5 6,0 period 1970-2000: (or 30%) in real values.

61 The reactors to be installed quantities of fissile materials, whether "Proved" reactors enriched uranium or plutonium, and It is Four sets of hypotheses are put forward based on the progressive introduction of A decisive advantage cannot reasonably be on the types of plant to be installed. These fast breeders, thus making the most rational attributed to one type or the other. The are purely tentative in that the evolution use of the Community's limited resources, two "filières" have reached in the Com­ of reactor development and installation as well as those of the Western World as a munity roughly the same point of industrial will certainly be much more complex. The whole. development, the economic prospects are set of assumptions selected foresee that similar, as is their consumption of fissile nuclear power stations will be equipped Among the factors of uncertainty which materials. It is therefore expedient to admit with "proved" reactors (I.e. equal propor­ could modify these forecasts are: that the parity between the two types wil' tions graphlte­moderated­gas­cooled and — the two types of "proved" reactors might be maintained approximately until the eni) water­cooled) until 1975, that they will be not develop in parallel; this would have of the period under consideration and thb complemented by the installation of ad­ little Impact on any of the succeeding fore­ independently of the various hypotheses vanced converters from 1975 and fast casts other than that concerning en­ about the technico­economic success ol breeders from 1980. The installation of riched uranium consumption; more advanced types of reactors. Further­ "proved" reactors will cease when they — enriched uranium needs could be re­ more "at least for the first years of the form one half of total capacity, in about duced by the use of plutonium as fuel for programme, and having regard for the 1990. By 2000 fast breeders will represent water reactors from 1975; present equilibrium, it is certainly wise not one half of the total, advanced converters — the introduction of thethorium/uranium­ to concentrate exclusively on one tech n ¡que. and "proved" reactors by then taking 233 cycle is not taken Into account owing Indeed, nuclear industry in the Community respectively only 30 and 20% of the total. to insufficient technical and economic data. is equally interested in both". While the It is assumed that power reactors will be Its use could help to solve supply problems; investment in enriched uranium reactors installed along the general lines shown in it is most likely to be first employed for may be lower, gas reactors offer a greater Table I. high temperature reactors. autonomy of supply and permit the exploita­ tion of techniques which from the beginning have been developed in the Community. Table I: Forecasts of installed capacity (in MWe) of the different reactor types from today Lastly, the choice of reactor could be affect­ until 2000. ed by such political considerations as the need for independence from a monopolistic ■ Proved" supply situation. Graphite Water Advanced Fast Total gas converters breeders Advanced converters J 970 2,000 1,500 200 — 3,700 1970-74 5,500 5,000 1,500 — 12,000 Among the numerous types of advanced 1975-79 17,000 17,000 5,000 1,000 40,000 converters, heavy water moderated and high 1980-84 25,000 25,000 19,000 6,000 75,000 temperature gas reactors appear most 1985-89 35,000 35,000 51,000 19,000 140,000 worthy of consideration for the Community. 1990-94 35,000 35,000 98,000 60,000 228,000 Both types hold promise technically and 1995-99 35,000 35,000 115,000 185,000 370,000 economically and for both the use of thorium may be envisaged. Their excellent neutron economy should permit a lower This programme is selected since it con­ Outlook for reactor types to be specific consumption and a higher "in situ" forms with the present industrial situation, installed use of the fissile materials produced, thus with the state of R & D in the Community making for an optimal utilisation of the and with a harmonious evolution of tech­ The report makes a number of observations natural resources of uranium and thorium. niques. According to it the total invest­ on the reactors to be installed under the In addition to these advantages which apply ment will be lowest, it requires the smallest "programme" selected. Among them are: to both types: heavy water reactors alone

62 EURATOM NEWS

can function using natural uranium as fuel, munity action might thereafter become decision were taken early enough, at the their requirements being minimal; high necessary in this field. beginning of the period. Between 1975 and temperature gas reactors hold great promise As regards plutonium, forecasts are limited 1979, six further 500-1,000 MWe advanced In the field of thermodynamic yield and to production in "proved" and advanced converters could come into service. breeding. converter reactors: during 1970-79 34 tons, A prototype fast breeder reactor (100 MWe) While the relative advantages of the two during 1980-89 177 tons and by 2000 alto• would have to be brought into service types appear roughly equal, it is impossible gether 557 tons. The quantities produced towards 1972 along with two full-scale to estimate the shares the two will take and required by breeders are difficult to power plants (500 MWe or more) towards in the "programme". estimate. 1979 for these reactors to achieve their Estimates are, however, made of retreat• "maturity" by the end of the decade. ment capacity for the recovery of plutonium: Fast breeder reactors by the end of 1979 2,000 tons/year of natural uranium elements and 400 tons/year of Fuel element manufacture It is assumed that fast breeders will have enriched uranium elements. By the end of been perfected towards 1980. A key factor 1989, capacity will be 6,500 tons/year of By 1980 a total natural uranium fuel ele• regarding the pace at which they are natural uranium elements (including the ment capacity of 4,000 tons/year will be introduced will be the availability of plu• fuel for the blankets of fast breeders) and needed; for highly enriched uranium ele• tonium. The greatest uncertainty, however, 850 tons/year of enriched uranium elements ments around 1,000 tons/year. lies in the rate of technological develop• (including the core of fast breeders). ment, in particular when fast breeders will have become "proved" industrially and Irradiated fuel reprocessing investment volume economically advantageous. It is assumed that the risk of delays in their development By end-1979 irradiated fuel to be reproces• The volume of investment required for will be avoided by an intense and concerted sed would have risen annually to 1,720 nuclear power stations during the 1970s, effort. tons/year (uranium contained) for natural the 1980s and the 1990s is put at $ 7,17 and uranium elements (graphite-gas reactors), 37 milliard respectively, i.e. a total of 230 tons for natural uranium elements about $60,000 million. Some implications for nuclear industry (intermediate reactors) and 350 tons for The 17,000 milliard kWh produced during slightly enriched uranium elements. In 1970-1999 would cost$90 milliard to gener• Materials addition to Eurochemic (slightly enriched ate, the average cost per kWh unit being uranium) and Cap de la Hague (natural about 5 mills. This figure includes costs It is estimated that this programme will uranium elements), a new plant for slightly both of the installations and of the fuel. require 43,000 tons of natural uranium enriched uranium elements with a capacity during the period 1970-79 and 109,000 tons of over 400 tons/year will need to enter during the following decade, and altogether The installation of nuclear power plants into service once water reactor capacity 281,000 tons by 2000. Enriched uranium has exceeded 4,000 MWe, i.e. towards 1974. needs are put at 5,000 tons during 1970-79, In addition to the 4,000 or so MWe of Between 1980 and 1989 retreatment capac• 12,000 tons 1980-89 and 12,000 tons during proved reactor capacity in service, under ity would need to rise from 2,000 to 6,000 1990-99. As known Community reserves construction or planned for end-1969, a tons/year for natural uranium elements. of uranium suffice for only half the expected dozen such plants of 500-1,000 MWe capac• Three 2,000 ton plants might have to be consumption to end-1979, prospection must ity would be brought into service during built during the period for the natural be intensified. Community enterprises 1970-74 (7,000 MWe total) and 25 during uranium elements and a 400 tons/year plant would also need to develop access to re• 1975-79 (23,000 MWe). Two or three ad• for enriched uranium elements will be sources In third countries. As regards en• vanced converters of 200 or 300 MWe would built towards 1989. The fast breeder blanket riched uranium, isotopie separation capacity come into service during 1970-74, one of and core elements will have to be reproces• in the Western World appears to be suffi• which would be a prototype industrial sed by the natural uranium and enriched cient for the period to 1980, but a Com• Orgel reactor to come into service, if a uranium reprocessing plants respectively.

63 EURATOM NEWS

Zirconium alloys and stainless steels (at least ORGEL—Safety studies in the case of pressurised water reactors) behave satisfactorily at the working temper• Since mid-1964 a rig for studying the effects atures, of the order of 300°C, which have of an explosion in an ORGEL reactor channel been adopted for these reactors. However, has been operating at Ispra. at highertemperatures, which Imply the use It consists of a vessel with through-channels of superheated steam, corrosion problems are more serious and, in spite of the many Sect/on of a stainless-steel platelet which has (a life-size reproduction of the ESSOR been exposed to steam for 1,000 hours at 500° C. reactor vessel), a circuit for 4,000 litres of research efforts which are devoted to their solution, progress in overcoming them is The central part of the photograph represents organic coolant which can be heated to over a zone scored by a diamond point and con• 2 slow. And yet It Is worth pursuing these 400°C and pressurised up to 50 kg/cm , and sequently cold-worked. It will be observed that a concrete bunker where t he experi menters efforts, since success would allow the design of water reactors equipped with nuclear the oxide layer in this zone is considerably take shelter during explosion trials. thinner than on the rest of the platelet. The experiments are effected by creating superheaters, which could take advantage an artificial flaw In a pressure tube and of the high efficiencies offered by modern raising the pressure of the hot organic fluid turbo-alternator units, working at 600°C until the tube bursts. and over. Using the apparatus developed by the Ispra An interesting contribution has been made surface treatment improve the behaviour of technology service for the measurement of recently by the Société d'Etudes, de Recher• the specimens but the improvement in• fast phenomena, several experiments have ches et d'Applications pour l'Industrie (SERAI) creased with temperature. (The corrosion already been carried out which have yielded in Brussels underthe United States/Euratom rate was 10 times less at 450°C; at 600°C information on the formation of shock Joint Research Programme. The work of more than 50 times less). Moreover tests waves In the moderator and on the result• this organisation has been aimed at evalu• carried out over long periods (over 2000 ant mechanical effects on structures. ating the influence of the surface treatment hours) showed the effect was a lasting one. Thus the programme as a whole will make on corrosion in high temperature water and A satisfactory explanation has been found a major contribution to research on the steam. for this phenomenon. Tests have shown that, safety problems raised by explosion, with It was established that, when electro- thanks to changes in the internal structure regard to the ESSOR reactor in particular polished, chromium/nickel stainless steel of the metal brought about near the surface and the ORGEL string in general. specimens stand up better to corrosion in by mechanical treatment, diffusion of water than mechanically treated (milled) chromium through the surface layer is specimens. On the other hand, a spectacular possible. This is important; it means that reversal in the situation was recorded when the protective film of chromium-rich oxide similar specimens were tested in super• which forms on the surface can be "fed" heated steam at temperatures in the 400- with more chromium and thus give better 600°C range. Not only did a mechanical protection.

A step towards nuclear superheat in water reactors

Corrosion has been said to be the arch• enemy of the water reactor. This is mainly because any corrosion products released into the water circuits are liable to become Production of uranium carbide single crystals at Ispra radioactive and to give rise to tricky de• contamination problems. This factor and a A laboratory at the Ispra Research Estab• crystals can scarcely be employed as a fuel. few others, such as the need to avoid ex• lishment recently began producing uranium Rather was the Idea to make available to cessive neutron capture, have practically carbide (UC) single crystals. Some of these the various laboratories in the Community restricted the choice of materials to crystals have a volume of 1 to 2 cm'. quantities of uranium carbide which would zirconium alloys and stainless steels, which, This was not merely a sort of sporting be used as a reference material. in view of their high cost, have a detrimental venture—as might be imagined, since It Is, of course, known that a single crystal effect on the economics of water reactors. uranium composed entirely of single has an almost perfect crystal lattice (no

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Euratom Bulletin annual subscription (four issues) In the United Kingdom 18/—; in the United States: $ 3.S0 Payment can be made by cheque or Inter­ national money order to A.M.P., 34 rue du Marais, Brussels 1. OS 2 2 > CA σο' co fe Η-»· 3 en S ^1 HH P • 3

OS Φ- bd w aC C/3 do* C/3 Cu H-· fl 3 View of RB 1 reactor (Bologna, Italy) used for measuring the infinite neutron multiplication factor of various lattices. The picture shows a part of the lattice of the Latino gas-graphite reactor in the experimental position.

grain boundaries, well-defined orientation) and therefore lends itself more readily to the study of the structure and the basic properties than polycrystalline carbide. Other Ispra laboratories, as well as other institutes in the Community, have been able, by means of the single crystals, to undertake a more accurate fundamental study of the physico-chemical properties of uranium carbide and also to conduct research into fission gas and fission product diffusion phenomena after in-pile irradia• tion. The single crystals were developed by means of special equipment, the uranium- carbide rod being heated in a high-frequen• cy vacuum furnace in such a way that only a limited internal zone is raised to melting temperature. The rod Is thus its own crucible. Slow displacement (a few milli• metres per hour) of this fused zone is accompanied by a process in which refine• Higher burnups in graphite-gas reactors ment and enlargement of the crystals takes place.

On 22 February 1965, Euratom entered into were increased from 3,500 to 4,500 MWd/t a contract with the Ente Nazionale per and by 36% if it were stepped up from l'Energia Elettrica - Italia (ENEL). The 3,500 to 5,500 MWd/t. It is therefore vital subject of this contract is the study of the to check the validity of the calculation Uranium carbide single cristal reactivity curve in the Latina reactor, know• methods currently employed. The measure• ledge of which is most useful, as it enables ments performed by the ENEL under this the theoretical burnup peak to be deter• contract will make it possible to effect just mined beforehand. such a check. They will be carried out at This study is also of general interest as regular intervals on the Latina reactor regards the development of graphite-gas when operating at full power. reactors. Hitherto, the upper limit for the burnup of fuel elements has been estimated The experimental reactivity curve obtained at an average of approximately 3,500 MWd/t. on the basis of these measurements will be A study carried out under Euratom con• compared with theoretical curves calculated tract has shown that this falls far short of both by the French and the British method. the mark and that burnups of the order of The results of this comparison will reveal 5,500 MWd/t could be achieved in a reactor the Inconsistencies between the two curves optimised for the purpose. and will give useful pointers regarding the To illustrate what this means, fuel-replace• adjustments to be made to the calculation ment costs could be cut by 22% if burnup methods. topi radioisotopen s hip propulsion schiffs antrieb propulsion na vale propulsione nava le scheepsvoortstuwi ng biology biologie biologie biologia bio logie medicine medi zin médecine medicin a geneeskunde healt h protection gesundh eitsschutz protection sanitaire protezione s anitaria bescherming van de gezondheid automatic data proces sing automatische inf ormation information automatique informa zione automatica auto matische verwerking van gegevens ins'ura nee versicherungswes en assurances assicura zione verzekeringen economics Wirtschaft économie economia e conomie education and training ausbildu ng enseignement inse gnamento onderwijs en opleiding power reactors leistungsreak toren réacteurs de pu issance reattori di po tenza energie reactor en nuclear fusion ke rnverschmelzung fusi on nucléaire fusione nucleare kernversmei ting radioisotopes r adioisotope radioisot opes radioisotopi ra dioisotopen ship pr opulsion schiffsantrie b propulsion navale propulsione navale scheepsvoortstuwing biology biologie biolo gie biologia biologie medicine medizin mé decine medicina gene eskunde health pro tection gesundheitssc hutz protection sanit aire protezione sanita ría bescherming van de gezondheid auto matic data processing automatische informa tion information auto matique informazione automatica automatis che verwerking van g egevens insurance v ersicherungswesen as surances assicurazioni verzekeringen econ omics Wirtschaft èco nomie economia eco nomie education and training ausbildung enseignement insegn amento onderwijs en opleiding power reac tors leistungsreakto ren réacteurs de pu issance reattori di po tenza energie reactor en nuclear fusion ke rnverschmelzung fusi on nucléaire fusione nucleare kernversmei ting radioisotopes r adioisotope radioisot opes radioisotopi ra dioisotopen ship pr opulsion schiffsantrie