The maintenance cost for an engineering system is an uncertain quantity due to uncertainties associated with occurrence of failure and the time taken to restore the system. The problem of probabilistic analysis of maintenance cost can be modeled as a stochastic renewal-reward process, which is a complex problem. Assuming that the time horizon of the maintenance policy approaches infinity, simple asymptotic formulas have been derived for the failure rate and the cost per unit time. These asymptotic formulas are widely utilized in the reliability literature for the optimization of a maintenance policy. However, in the finite life of highly reliable systems, such as safety systems used in a nuclear plant, the applicability of asymptotic approximations is questionable. Thus, the development of methods for accurate evaluation of expected maintenance cost, failure rate, and availability of engineering systems is the subject matter of this thesis. In this thesis, an accurate derivation of any m-th order statistical moment of maintenance cost is presented. The proposed formulation can be used to derive results for a specific maintenance policy. The cost of condition-based maintenance (CBM) of a system is analyzed in detail, in which the system degradation is modeled as a stochastic gamma process. The CBM model is generalized by considering the random repair time and delay in degradation initiation. Since the expected cost is not informative enough to estimate the financial risk measures, such as Value-at-Risk, the probability distribution of the maintenance cost is derived. This derivation is based on an interesting idea that the characteristic function of the cost can be computed from a renewal-type integral equation, and its Fourier transform leads to the probability distribution. A sequential inspection and replacement strategy is presented for the asset management of a large population of components. The finite-time analyses presented in this thesis can be combined to compute the reliability and availability at the system level. Practical case studies involving the maintenance of the heat transport piping system in a nuclear plant and a breakwater are presented. A general conclusion is that finite time cost analysis should be used for a realistic evaluation and optimization of maintenance policies for critical infrastructure systems.

The Department of Energy and the Idaho National Laboratory are developing a Next Generation Nuclear Plant (NGNP) to serve as a demonstration of state-of-the-art nuclear technology. The purpose of the demonstration is two fold: 1) efficient low cost energy generation and 2) hydrogen production. Although a next generation plant could be developed as a single-purpose facility, early designs are expected to be dual-purpose. While hydrogen production and advanced energy cycles are still in their early stages of development, research towards coupling a high temperature reactor, electrical generation and hydrogen production is under way. Many aspects of the NGNP must be researched and developed to make recommendations on the final design of the plant. Parameters such as working conditions, cycle components, working fluids, and power conversion unit configurations must be understood. Three configurations of the power conversion unit were modeled using the process code HYSYS; a three-shaft design with 3 turbines and 4 compressors, a combined cycle with a Brayton top cycle and a Rankine bottoming cycle, and a reheated cycle with 3 stages of reheat were investigated. A high temperature steam electrolysis hydrogen production plant was coupled to the reactor and power conversion unit by means of an intermediate heat transport loop. Helium, CO2, and an 80% nitrogen, 20% helium mixture (by weight) were studied to determine the best working fluid in terms cycle efficiency and development cost. In each of these configurations the relative heat exchanger size and turbomachinery work were estimated for the different working fluids. Parametric studies away from the baseline values of the three-shaft and combined cycles were performed to determine the effect of varying conditions in the cycle. Recommendations on the optimal working fluid for each configuration were made. The helium working fluid produced the highest overall plant efficiency for the three-shaft and reheat cycle; however, the nitrogen-helium mixture produced similar efficiency with smaller component sizes. The CO2 working fluid is recommend in the combined cycle configuration.

The maintenance cost for an engineering system is an uncertain quantity due to uncertainties associated with occurrence of failure and the time taken to restore the system. The problem of probabilistic analysis of maintenance cost can be modeled as a stochastic renewal-reward process, which is a complex problem. Assuming that the time horizon of the maintenance policy approaches infinity, simple asymptotic formulas have been derived for the failure rate and the cost per unit time. These asymptotic formulas are widely utilized in the reliability literature for the optimization of a maintenance policy. However, in the finite life of highly reliable systems, such as safety systems used in a nuclear plant, the applicability of asymptotic approximations is questionable. Thus, the development of methods for accurate evaluation of expected maintenance cost, failure rate, and availability of engineering systems is the subject matter of this thesis. In this thesis, an accurate derivation of any m-th order statistical moment of maintenance cost is presented. The proposed formulation can be used to derive results for a specific maintenance policy. The cost of condition-based maintenance (CBM) of a system is analyzed in detail, in which the system degradation is modeled as a stochastic gamma process. The CBM model is generalized by considering the random repair time and delay in degradation initiation. Since the expected cost is not informative enough to estimate the financial risk measures, such as Value-at-Risk, the probability distribution of the maintenance cost is derived. This derivation is based on an interesting idea that the characteristic function of the cost can be computed from a renewal-type integral equation, and its Fourier transform leads to the probability distribution. A sequential inspection and replacement strategy is presented for the asset management of a large population of components. The finite-time analyses presented in this thesis can be combined to compute the reliability and availability at the system level. Practical case studies involving the maintenance of the heat transport piping system in a nuclear plant and a breakwater are presented. A general conclusion is that finite time cost analysis should be used for a realistic evaluation and optimization of maintenance policies for critical infrastructure systems.

Depuis la catastrophe de Fukushima, un accident nucléaire est devenu davantage ima- ginable, puisqu’il est dit « être possible » selon les autorités, voire inéluctable, en Europe, selon certains experts. En France, la majorité habite à moins de 200 km d’une centrale nucléaire (plus de 9 millions autour de la Centrale de Nogent/Seine à moins de 100 km). C’est pourquoi les autorités en France se sont penchées sur le problème du post-accidentel bien avant cet accident (Doctrine). Cependant, afin de pouvoir se faire une idée du monde qui pourrait en résulter, il est nécessaire -avant- d’avoir une certaine prise sur ce qui se passe au niveau des rejets et prélèvements dans l’environnement, en temps de routine(points de rejets ou de prélèvements, mesures, contrôles, effets cumulés). L’optique choisie n’est pas celle d’une accusation d’un manque de transparence (le mythe de la transparence étant d’ailleurs dénoncé), mais celle de se donner les moyens de raisonnement pour avoir cette « vigilance » tant mise en avant dans les Textes ou Discours, mais qui est rarement assortie d’éléments concrets concernant la vie des gens.Notre thèse repose sur le fait qu’une forte croyance dans l’absence de risque en France fondée sur la confiance n’est pas la solution et qu’il faut rechercher des éléments de prise reliant la personne avec son environnement, celle-ci se trouvant déconnectée de son milieu. A partir d’une enquête ethnologique en tant que membre d’une commission locale d’information et en nous appuyant, d’une part, sur la mésologie (La poétique de la Terre d’Augustin Berque) et, d’autre part, sur la Théorie de la prise et la Balistique sociologique de Francis Chateauraynaud, nous proposons une démarche, première ébauche d’un guide, à partir de questions-objet-de-la-prise qui nous concernent tous. . . / Since the catastrophe of Fukushima, a nuclear accident has become more imaginable since it is said to be “possible” according to the authorities, or even inevitable, in Europe, according to some experts. In France, the majority of people lives within 200 km of a nuclear power plant (more than 9 million around the Nogent/Seine Nuclear Plant within 100 km). This is why the authorities in France have been studying the post-accident problem well before this accident (Doctrine). However, in order to be able to get an idea of the world that could result from it, it is necessary -before- to have a certain information on what is going on about the pollutant releases and the taking of water, in the environment, in routine time (including the cumulative effects). The chosen perspective is not that of an accusation of a lack of transparency (the myth of transparency is also denounced), but that of giving oneself the means of reasoning to have this “vigilance” so much pushed forward in Texts or Speeches, but which is rarely accompanied by positive elements concerning people’s lives.Our thesis is based on the fact that a strong belief in the absence of risk in France based on trust is not the solution and that it is necessary to look for gripping elements on our environment, because we are disconnected from our milieu. Based on an ethnological survey as a member of a local information commission and, on the one hand, on the Mesology(The Poetics of the Earth by Augustin Berque) and, on the other hand, on the Theory of the Empowerment and the Sociological Balistics of Francis Chateauraynaud, we propose an approach, first draft of a guide, from questions-object-of-the-control-over-our-environment which concern all of us ...

[pt] No projeto de uma usina nuclear PWR, é necessário verificar se os limites de projeto dos seus componentes são respeitados mesmo em condições de operação anormal. O presente trabalho representa uma evolução do programa Sardan, desenvolvido para simulação de transitórios em PWR s. Os novos aspectos incorporados na versão Sardan 2, são: análise da vareta de combustível ou diferenças finitas, modelo de canal aberto para o subcanal crítico e implantação de um modelo simplificado para o sistema de controle automático. O programa foi testado em acidentes condição II, em particular, retirada descontrolada de um conjunto de barras de controle, queda de um conjunto de barras de controle, diluição descontrolada de boro, e os resultados obtidos considerados satisfatórios. / [en] In the design of a PWR nuclear plant it is necessary to verify if the design limits are respected, even under abnormal operation condition. The present work represents an evolution of SARDAN code, developed to simulate transients in PWR, the new aspects incorporeted in SARDAN 2 are: the fuel ROD analysis in finite- diference, an open channel model for the critic subchannel analysis and the introduction of a simplified model for the automatic control system. The program has been tested in accident condition II, in special, uncontrolled ROD cluster assembly bank withoraw, dropped full-length assembly group, uncontrolled Boron dilution, and the results obtained were considered satisfactory.

Problems of dealing with radioactive materials, especially burnt out nuclear fuel, are a delicate and discussed topic in the Czech Republic and other advanced countries nowadays. In this work, the realization of radiation control of warehouse of burnt-out atomic fuel of nuclear power plant Temelín is analysed. Step by step there are stored packaging files filled with burnt-out fuel which is produced by the running of atomic reactors. In the introductory chapters individual packaging files are described. The shielding of stored burnt-out nuclear fuel and prevention of release of radionuclides beyond the protective casing of packaging files depend on their quality. Further the lo-cality of nuclear plant Temelín, where the warehouse of burnt-out nuclear fuel is placed including manipulations which are carried out with the packaging file, is described. The emphasis is placed on monitoring technological parameters during the storage of pack-aging files. The target of this work is to analyse the radiation control of warehouse of burnt-out nuclear fuel, precautions of radiation protection valid for this object and con-sider the possibility of optimalization of used measuring devices, suggest the adjustment of the way of carried out monitoring. For meeting the goals of this works it was neces-sary to carry out monitoring the current radiation situation in the storage boat which is partly filled with packaging spaces when according to the following calculations I ap-proached to the prediction of the level of radiation situation during the maximum filled storage boat. These calculations are at the same time the background for the proposal of adjustment of regime precautions in this object with the aim to optimise the professional radiation. One of the basic strategic targets of the operator of nuclear plant Temelín, company ČEZ a.s., is to ensure a safe operation of the biggest Czech nuclear plant, one of the basic conditions for meeting this target is to ensure the radiation control and pro-tection in the required quality. The results, which are the output of this work, will be given to the department Operation of radiation protection for other practical usage, pos-sible adjustment of a current operation documentation which solves the radiation control of the storage of burnt-out nuclear fuel.