HTR fuel: safety features and performance analysis
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Date
2006
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Azerbaijan National Academy of Sciences Institute of Radiation Problems ve Turkish Atomic Energy Authority
Abstract
High Temperature Reactors (HTRs) are among the candidates for the possible next generation nuclear plant. HTRs are expected to offer inherent safety characteristics, low cost of electricity generation, and short construction period. Especially, the synergy of HTRs with hydrogen generation is a significant advantage. There are two mainstream designs: prismatic and pebble bed. Different fuel options can be considered such as uranium dioxide, uranium carboxide (UCO), and the (U,Pu) mixed oxide. Such reactors can also be used to eliminate weapon plutonium stockpiles and for nuclear waste transmutation. Thorium can be used in such reactors as fuel. Presence of only ceramic materials in the core, large graphite inventory as a heat sink, and inherent safety characteristics of such reactors make them very attractive.
The basic building block of HTR fuel elements is TRISO coated particles. A TRISO particle is made of a fuel kernel, surrounded by a low density porous pyrolitic carbon (the buffer), high density inner pyrolitic carbon, SiC, and high density outer pyrolitic carbon layers. The SiC layer acts as the primary pressure boundary. Normally, SiC is a very strong material and can withstand temperatures up to 1800 C. Beyond that temperature, thermal decomposition may be observed over extended time periods. The buffer layer is used to accommodate volume expansion due to swelling and fission products. Pyrolitic carbon layers protect the SiC layer, keep the SiC under compression, and act as a barrier against gaseous fission products.
In this study, main features provided by TRISO particles, their common failure modes, and basic elements for their performance analysis will be discussed. An important failure mode corresponds to over-pressurization and mechanical failure of the pressure vessel (the SiC layer). Comparisons of mechanical response of the fuel with simple analytical as well as finite element calculations will be provided.
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Keywords
HTR fuel, HTR yakıt, High Temperature Reactors (HTRs), Yüksek Sıcaklık Reaktörleri (HTR'ler), Safety features, Güvenlik özellikleri, Performance analysis, Performans analizi
Citation
Çolak, Ü., Yıldırım, B. ve Özdere Gülol, O. (2006). HTR fuel: safety features and performance analysis. The Fourth Eurasian Conference on Nuclear Science and Its Application : Presentations, (s. 43-47). 31 October- 3 November 2006. Baku, Azerbaijan.