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Diplomsko delo predstavlja problematiko staranja električnih kablov v jedrskih elektrarnah. Ker so kabli eden izmed najpomembnejših sestavnih delov vsake jedrske elektrarne, je cilj na kratko predstaviti njihovo vlogo v obratovalnih procesih jedrske elektrarne. Opisani so mehanizmi staranja ter načini ocenjevanja sposobnosti kablov, da staranju navkljub uspešno izvajajo svoje naloge. V uvodu so na kratko predstavljene funkcionalnost kablov, njihova uporaba in problematika njihovega staranja. Opisani so tudi mehanizmi staranja glede na specifičnost pogojev v jedrskih elektrarnah. V drugem poglavju so za uvod v problematiko opisani sistemi za zagotavljanje varnosti. Predstavljene so varnostne funkcije struktur, sistemov in komponent ter njihovi podrobnejši opisi. Podani so kriteriji za varno obratovanje jedrskih elektrarn. Ob koncu so navedene okoljske in seizmološke kvalifikacije, ki jih predpisujejo v poglavju navedeni standardi. Tretje poglavje obsega opise električnih kablov. Predstavljeni so njihova namembnost ter načini uporabe v jedrskih elektrarnah. Na dveh primerih je prikazana sestava kablov. Ob koncu poglavja so v podpoglavju opisani izolacijski materiali, ki se uporabljajo za kable v jedrskih elektrarnah. To podpoglavje služi kot uvod v vsebino četrtega poglavja, kjer sledi podrobnejša analiza vplivov staranja na uporabljene kable. Četrto poglavje je najobsežnejše in predstavlja osrednji del diplomskega dela. Poudarek je na mehanizmih staranja. Podane so vrste sevanj, ki se pojavljajo, navedeni so njihovi izvori in posledice, ki jih pustijo na kablih. Prav tako so obdelani vplivi temperature in mehanskih stresorjev iz okolice. Ob koncu poglavja so navedeni postopki upravljanja s staranjem kablov ter opisi pospešenega staranja pod vplivom povišanih temperatur in sevanj. Navedeni so tudi načini merjenja temperature in jakosti sevanj v jedrski elektrarni. Peto poglavje se osredotoča na metodo raztezka do zloma. To je ena najbolj razširjenih metod za upravljanje s staranjem kablov. Podana sta način njenega izvajanja ter kratek opis uporabljene kode v programskem okolju Matlab. Koda je avtorjevo lastno delo in služi kot pomoč pri analizi podatkov. V zadnjem poglavju so podani rezultati analize. Izkaže se, da je metoda raztezka do zloma lahko zelo učinkovita ob zadostni količini razpoložljivih podatkov. The thesis presents the problem of the aging of electrical cables in nuclear power plants. Electrical cables are one of the most important components of any nuclear power plant. The main goal is to present their role in the operating process of nuclear power plants. It describes the mechanisms of aging and ways of evaluating the ability of cables to aging, despite successfully preserve their functionality. The functionality of cables, their use and the related of ageing are explained in the introduction. There is also the description of the aging mechanisms depending on the specific conditions in nuclear power plants. The second chapter presents an introduction to the problems described through systems important for safety, the security features of structures, systems and components and their detailed descriptions followed by the criteria for safe operation of nuclear power plants. The environmental and seismic qualification standards are described at the end of the chapter. Electrical cables, their purpose and use in nuclear power plants are described in third chapter. The composition of the cables is shown in two cases. The section on insulating materials which are used for cables in nuclear power plants is at the end of the chapter. This section serves as an introduction to the content of the fourth chapter where a more detailed analysis of the effects of aging on the used electrical cables is presented. The fourth chapter is the central part of the thesis. The focus is on the mechanisms of aging. It includes types of radiation, their sources and consequences on cables. The effects of temperature and mechanical stressors from the environment are also included. Operation management of aging cables and descriptions of accelerated aging under the influence of elevated temperatures and radiation as well as descriptions of measuring the temperature and the intensity of radiation in nuclear power plants is at the end of chapter. The fifth chapter focuses on the method of elongation at break. This is one of the most common methods for cables aging management. It is described by the way of its implementation, and a brief description of the code in Matlab. The code is the author's own work and serves as an aid in data analyzing. The last two chapters present the results of the analysis and the conclusions. It turns out that the method elongation at break can be very effective with enough data available. |
