Gmelin, W.

Seetzen, J.

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Mai 1967Institut für Angewandte ReaktorphysikKFK 593Expedence with Network Analysis and its Further Development forthe Purpose of Planning Objectives and Time Scheduling withinthe Framework of the Karlsruhe Fast Breeder ProjectW. Gmelin, J. SeetzenM. B. H.KERNFORSCHUNGSZENTRUM KARLSRUHEMai 1967Institut für Angewandte ReaktorphysikExperience with Network Analysis and its FurtherDevelopment for the Pur~ose of Planning Objectivesand Time Scheduling within the Framework of theKarlsruhe Fast Breeder Project1)2)byW. GMELIN and J. SEETZENGesellschaft für Kernforschung mbH., KarlsruheKFK 5931)The report has been presented in this form to the Symposium onInternational Congress for Project Planning by Network Analysis,Vienna 21 - 26 May 19672)Work performed within the association in the field of fast reactorsbetween the European Atomic Energy Community and Gesellschaft fürKernforschung mbH., KarlsruheI.-1 -Experience with Network Analysis in the Fast Breeder ProjectAbout the year 1960 the development of power reactors quitegenerally entered into a new phase. That means it became more and moreobvious that the long term objectives of an abundant energy supplycould only be reached by introducing a new type of reactor. This reactortype is called FAST BREEDER on account of the use of fast neutronsinstead of thermal ones and the capability of these reactors to breedmore fissile material by converting uranium 238 into plutonium thanthey consume for the production of energy. Since the early sixties, thelarge industrial nations devote a great deal of effort to the parti-cularly intensive development work concerned with fast breeder reactors.However, this amount of interest is focussed on these reactors not onlydue to the fact that they will solve the problems of a growing futureenergy requirement but also because they will surpass even the economyof the now proven and already highly competitive light water reactors.This economic attractiveness results also from the breeding effect offast reactors. That means only the abundant and cheap U-238 has to befed into these reactors and no expensive fissile material, aS with thelight water reactors e.g.The development of fast breeder reactors requires greatlyextended and much more complicated physical foundations than previousthermal reactors, a highly refined fuel element technology, entirely newtechnologies of the reactor coolant, and the technologies of a closedfuel cycle, since the plutonium produced, after chemical reprocessing,must constantly flow back to the fast breeder reactors. After thiscomprehensive preliminary work prototype reactors will have to demonstratethe technical feasibility, safe operation, and the economic potentialof the new reactor generation.The expenditure for the Fast Breeder Project, in which thecountries Belgium and the Netherlands are engaged in addition to Germany,will be some 1.5 billion. The period of the project is schedulded tocover 18 years from 1960 on.The execution of the project requires the collaboration,coordinated down to the details, of government organisations as thesponsors, utilities as the later reactor operators, research centersto elaborate the foundations, and large-scale industries for the projectwork and construction of the prototype and finally large commercial plants.- 2 -The objective of the project i8 to enable industry weIl before-i980 to build large competitive fast breeder power stations (a.bout 1,000MWe) and offer them on the market.It is only natural that the execution of such a large andcomplex project includes modern network techniques of planning. However,it has emerged that in a research and development project the unreflectedacceptance of the methods of time schedule control (CPM, PERT) is notsufficient. For the main burden of planning work gradually shifts in thecourse of an R.+D. project from recognition and fixing of the objectives,which shall mean mainly eliminating more and more less promising variantsby studying extensively the technical and economical potentials accordingto rational decision criteria,finally to the coordination of the partialobjectives and to the control of reaching the objective. To repeat:1. stage: recognition and fixing objectives2. stage: selection and coordinating objectives3. stage: controll of objective accessment.In our experience, present day network planning techniques can beapplied succesfully only in the control of reaching an objective.The process of recognition and fixing an objective in anR.+D. project cannot be formalized, since it should result primarily fromhuman insight and imagination for the problem at hand. This manifestsitself much more strongly in R.+D. projects than in standard industrialprojects where, generally objectives can be set to a much greater extenton the basis of experience available.By contrast, the process of setting an abjective is often anexpensive process of searching in an R.+D. project. This is true, aboveall, of the partial objectives which also manifest themselves in anunequivocal way only during the course of the project and do notnecessarily follow from the overall objective. Often, it is necessaryto work with intermediate solutions in partial sectors, hence, theoverall rhythm of time of a project in no way functions in the unequivocalPERT logic like ilwhen job x is finished, job y may start!! • Since thishas turned out in practice, it is not reasonable either in an R.+D.project to intent to represent the whole project in one single network.We rather adopt an iterative method of proceeding, i.e. an interactionbetween objective plans and time schedules on the one hand and CPM networkanalysis on the other hand.- 3 -The one type of graphs containing as weIl objectives as timeschedules can be represented in the usual manner of a bar-graph with atimeabscissa, in addition, the graphs contain the important interrelationsof the partial projects, e.g. certain basic physical or. technologicalinvestigations in relation to the planning and to the construction of theprototype reactors. Hence this plans can be taken aS networks quite weIl.However, as was stated above, there are only very few basic investigationswhich are unequivocal conditions, say of the decision to build the prototype.In most of the other partial sec tors it is true that the design of thereactors can be made the better and the more economical, the more accurateresults were arrived at in the basic investigations. Thus, it is importantto draw conclusions as precisely as possible at specific dates from theinvestigations carried out to this point and to communicate these to theother partial projects. These dates and their interrelation represent assaid the networks in objective planning and time scheduling.The network analyses of the partial sectors we carry out withour TERM-1 program in the second iterative step serve for the accuratedetermination of the partial results actually available at the desired dates.In this way, the objective plans and time schedules can be adapted to thereality of any situation by iterative methods.Following the lines of the description given above one becomesaware of the fact that network techniques either for the representation ofobjective plans and time schedules or for the actual control of projectperfor~ance are special features of the general communication process insystems engineering. Concerning this, network-graphs are only specialtopological realisations with a high degree of informational condensation,of generally related sets. The more basic phenomenon in the overallsystems engineering aspect is, of course, that structures o~ related setsare to be found all over the parts of this quite general and new techniquefor describing and managing large and complex systems of men and machineswhatever there purposes may be.Having a defined objective one is able to define the systemaiming at this objective, or even to create a proper system to reach thegiven objective. However the process of arriving at an objectiveultimately means exchange of goods, money and information by actingpersons. In this respect, the flow of information is guided by the tracksoutlined by the systems engineering techniques which by themselves are- 4 -meta-informations in the system, that means systems engineeringinformation like network techniques create and demonstrate the relationsin systems and are therefore the proper instrument of order in systems.Because of the informational natur and the special functionof the quite general set of systems engineering techniques of whichnetwork analyses is only a special example we exspect an enormous increasein importance of these manageriel instruments once the next computergeneration wili be introduced which allow for direct communication betweenman and computer and for vastly extended storage capacity.For reasons of this general philosophy the development ofnew computer programms in network techniques has to be speciallydirected to programm systems rather than to single refined programms.11. The TERM Program SystemBecause of the practical deficiencies inherent in the PERTprogram available to us for our IBM 7074 computer we decided in 1965to develop a program system of our own which we call TERM. Assaid above, a research and development program makes special requirementsof the planning methods, at least after our experience. Therefore theprogram system was designed from the outset so as to be expandable inorder to be able to follow the rapid development in the field of systemsengineering methods and fulfill all requirements made by the projectnot to oe recognized in their entirity in the beginning.In our opinion it is often not emphasized sufficiently thatthe practical use of a computer program for network analyses above allshould be as simple and easy as possible.The first verification of TERM (TERM-1) therefore has somepossibilities derived from practical wishes. First, there is an initialprogram phase in which the network fed in is scanned for errors.Uncorrelated activities, cycles from activities, unidentifiable cor-relations and double terms are registered in this scanning for errorsand corrected preliminarily by the program itself for the rest of thesearch for errors. Hence, the phase of error determination with highprobability will find all the errors of the network in one run andprint them. For practical application this incr~s the turnaround- 5 -periods of computer calculations quite markedly, because determinationcf errors will thus be possible as an express run with less than 3minutes.Moreover~ TERM-1 offers thepossibility of fixing certainintermediate dates within the network which, in our opinion, are moreusefull and simpler for practical operation than, e.g., the cycles usedin ~~tra Potential Method. The disadvantages of using cycles lie in thei:raggravating a closed and fast search for errors and in their makingthe input more complicated by multiple identical correlations which haveto be fed in repeatedly. Anyway, an input carried out in several phasesis impossible with our computer because the medium fed in is used as anintermediate storage in different phases. The advantages of using cycles,in our opinion, do not lie in the field of deterministic planning modelsbut rather in the field of the stochastic ones. In a model with the twological operators AND and OR e.g. which can be coped with by the stochasticmodel the introduction of cycles result in definitive advantages as is*)shown by S. ElmaghrabY • For the reasons mentioned below, however,we do not use a stochastic model. The intermediate dates already mentionedform the basis of the corresponding subgraphs and are treated by theprogram as if there were a special network extending from the beginningup to that intermediate date, i.e. critical paths may end also inintermediate dates although for instance the critical path to the ultimatedate will lead over other activities.Anothe:r practical possibility inherent in TERM-1 is theprinting of the results. It is possible to print the dates of theactivities and the bar-graphs grouped by departments in several copieswith the calenda:r data leaving out all sundays and holydays, thus givingrise to more accurate date quotations. With this type of prints it ispossible to achieve very quick return information to the partial projects,here, care has been taken to leave out all information not required forthe partial project.The free slack is distributed through the activities of abranch in the network so that these per iods of free slack may reallypass without end~ing any successive activities. In our opinion, too,*) S. Elmaghraby: An Algebra for the Analyses of Generalized ActivityNetworks, Management Science, 10 (1964)- 6 -such linear allocation of free slack through the activities of a branch18 but an approximation. For instance, it would be obviously possibleto allocate free slack corresponding to the duration of an activity ofthe individual activities. However, even this is only an approximatesdution. Finally, the solution of this problem can be found only ifcapacity distributions are considert at the same time, because a shortactivity which is critical with respect to the provision of capacity,obviously needs more free slack or freedom in the disposition thart alonger one without any shortage of capacity.Also some problems of network planning techniques of a morefundamental nature which are the subject of vivid discussions among theexperts have been solved rather pragmatically for our case. TERM-1 isnot based on the stochastic model like PERT, because it is difficult toobtain the data about the uncertainty of ultimate date of an activityand the networks are analyzed with new and mare accurate estimates oftenenough anyway, which makes the statement of the ultimate date of a partialsec tor increasingly more a:::curate.The problem of including the necessary input data and,respectively, the establishment of the first version of a network seemsto us, to be rather difficult in the field of research and developmentprojects. On the one hand, special efforts are required on the part ofthe network planner to reflect the frequently unsystematic ideas of theindividual participants into a network logic which comprises only onelogic function the AND. Moreover in our opinion, the inclusion of severalestimated timee of an activity with different probabilities of occurencewould further complicate the already psychologically difficult situationof network planning within a research project and, since there is nopossibility of referring to data from experience, it would givegeneration of phantasy numbers. Another point which we think might preventthe use of a stochastic model is the fact that in the solution ofconflicts in the allocation of capacities no sufficiently unambiguousweightin criteria are possible. However, this problem might becircumvented by a-priori statements of priorities, but this would mean aconsiderably less flexible model. We think as already mentioned theadvantages of stochastic models lie in the treatement of all networkplanning problems having more than one logical operator, where criteriaof decision can be meaningfully represented by probabilities. However,- 7 -in case it should show that the expenditure involved in procuring thedata for a stochastic model is in reasonable relation to the advantageprovided by the statement of the certainty of the ultimate date, wecould introduce the stochastic step in later versions of TERM.If the intention from the outset is to conceive a programsystem in a way to keep it adaptable, each activity initially is aset of information not closely limited. Seen in this way, the activitiesconstitute the fundamental set of the networks and the set of correlationsis merely a necessary additional information with respect to thetopological assignments of the elements of the fundamental quantities.This approach turned out to be favourable for the computer algorithmsin the case of TERM and leads to an activity graph. As regards therepresentation of the network, the graphical requirements of the userswere allowed free play, except for a few fundamental conventions,because we do not think this to be a logical but rather an aestheticalproblem.Because of the limited facilities of our computer theprocessing of several network plans in TERM-1 is still uncorrelated, i.e.there is no central data library either as a magnetic tape or a discoIn case of changes the user himself has to change the cards of a stackof punched eards and, by means of guiding cards, he may call TERM-1 asa sub-program, so to speak.However, for the further steps of development of TERM aeentral data library of the magnetie tape type is envisaged, for thisis to implement automatie segmentation and correlation of networks.In our opinion automatie segmentation of network plans is desirableand particularly meaningfull in those eases where by the installationof optieal displays segments of network plans may be changed on thedisplay or have to be called in for purposes of demonstration andmanagement. We think this will be possible. However, in what waynetworks would have to be read out graphieally appears still to beunsolved.The continued development of the TERM program system isearried out along the generally prescribed line, i.e., a partieulanyeffieient program system must be expected to handle next the controlof employment of capaeities and budget control. This step of- 8 -realisation will be finished this year; it will be called TERM-2A third stage of TERM which is already the object ofpreliminary work finally will comprise calculations of the optimumemployment of capacities. In this case, we do not necessarily start onthe assumption that the cost time function of an activity must begiven but rather that it could be calculated also from the employmentof the required capacities in principle.- 9 -References:For the first section:W. HÄFELE: Projektwissenschaften 7 Radius 7 Sept. 1965J. SEETZEN: Planung in der Wissenschaft, unpublished report, Nov. 1966H. GRÜMM et al.: Kernbrennstoffbedarf u. Kosten verschiedenerReaktortypen in Deutschland, Bericht KFK-366For the second section:W. GMELIN: Das Programmsystem TERM-1, Bericht KFK-462Bundesministerium für wissenschaftliche Forschung: Beiträge zurForschungsplanung, Heft 1, 1966DIVO-Institut: Die METRA-Potential Methode, METRA Sonderdruck 1965R. HENN: Applications of Graphs in Economic and Social Life,Sonderdruck Dezember 1965H. WILLE et al.: Netzplanmodelle für die Planung von Projekten,Elektronische Rechenanlagen 6, 1964

Experience with network analysis and its further development for the purpose of planning objectives and time scheduling within the framework of the Karlsruhe Fast Breeder Project

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Experience with network analysis and its further development for the purpose of planning objectives and time scheduling within the framework of the Karlsruhe Fast Breeder Project

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