Use Of Pressurized Water Reactor Research Articles

Biaxial Creep Behavior of Nb-Modified Zircaloys

Zirconium-niobium (Zr-Nb) alloys are used as cladding materials to encapsulate radioactive fuel in nuclear reactors. They possess excellent corrosion resistance at high temperatures making it possible to achieve high fuel burnup, directly increasing the thermal efficiency of the reactor. While they are commonly used in recrystallized (Rx) form in boiling water reactors, there is a need to understand the effect of cold work and stress relief (CWSR) on the biaxial creep characteristics of these materials due to their use in pressurized water reactors. In this study, the biaxial creep behaviors of as-received Zr-Nb alloys, HANA and Zirlo®, have been investigated at 500°C and 400°C, respectively, using internally pressurized tubing superimposed with axial load under varied hoop σθ to axial σz stress ratios of 0 to 2 while monitoring both the axial and hoop strains using a linear variable displacement transformer and a laser telemetric extensometer, respectively. The crystallographic textures and creep loci of these as-received Zr-Nb alloys have been evaluated to correlate with the previous studies on recrystallized HANA4 and CWSR Zircaloy-4. The creep locus of HANA4 was found to be unaffected by initial state (CWSR or Rx) and showed close correspondence to planar isotropy while the creep locus of CWSR Zirlo exhibited more resistance to axial deformation than diametrical as per CWSR Zircaloy-4 reported earlier. These differences are shown to arise from grain-shape anisotropy of the CWSR Zirlo and Zircaloy-4. The simulated creep loci using crystallite-orientation distribution functions in conjunction with prism slip models showed excellent agreement with experimental results.

Core design options of an ultra-long-cycle sodium cooled reactor with effective use of PWR spent fuel for sustainable energy supply

In this work, 350MWe ultra-long-cycle sodium-cooled reactor cores are designed to supply electric energy over ~60 Effective Full Power Years (EFPYs) without refueling and with an effective use of Transuranics (TRU) and uranium from large pressurized water reactor (PWR) spent fuel stocks. The core employs the axial blanket-driver-blanket (ABDB) burning strategy, which was recently proposed by the authors to achieve an ultra-long-cycle length with self-controllability under unprotected accidents. In particular, a thorium–uranium fuel cycle is considered to remove the heterogeneity of the fuel assemblies for design simplification and to improve the core performance parameters by selectively adding thorium into both blanket and driver fuels. The results show that the use of TRU nuclides from PWR spent fuel leads to significant extension of the fuel cycle length, but considerable increase of burnup reactivity swing. In addition, these results also indicate that the uranium–thorium mixed fuels both in the lower blanket and driver considerably improve the inherent safety of the ultra-long-cycle core by reducing burnup reactivity and sodium void worth; this makes it possible to simplify the previous heterogeneous fuel assembly design with improved core performances. Copyright © 2016 John Wiley & Sons, Ltd.

96/00329 Burn-up measurement of a fuel rod of test bundle for Qinshan Nuclear Power Plant

The initial motivation for the development of reprocessing technologies came from the need for obtaining pure fissile material for nuclear weapon production. The most prominent among these is the PUREX (plutonium and uranium extraction) process, still used worldwide to reprocess commercial light water reactor fuels at a few thousand tons per year scale. The fuels dissolved in nitric acid are treated with a tributyl phosphate based solvent, the extracted uranium and plutonium are further purified, and the raffinate is vitrified for a safe final disposal. Plutonium is partly recycled as mixed oxide fuel.Since the beginning of this century, a new generation of nuclear reactors is being developed in the framework of the so-called generation IV initiative.For compliance with the sustainability goals defined for the innovative reactor systems, mainly waste minimization through recycling of all actinides, and for the achievement of these goals, the corresponding fuel cycles will play a central role. The new concept of a grouped actinide separation can be derived from aqueous or pyrochemical partitioning processes. For the aqueous schemes, a direct link to PUREX is obvious, namely, with coextraction of Np. The extraction of the remaining actinides can be achieved by using specially designed solvents based on phosphine oxide or diamide molecules. A major focus is on the very challenging separation of lanthanides from the trivalent actinides. The process implementation, especially for the less developed pyrometallurgy, requires a good understanding of the extraction mechanisms.Pyro-reprocessing, where all actinides are recycled, is based on metallic fuels; they are dissolved in molten salts at around 500–900 °C and actinides are selectively recovered, either by electrorefining or by extraction into a liquid metal phase. The fuels of new generation reactors will, at least in the beginning, most likely be oxides. Thus, for pyroprocesses a head-end reduction step for oxide into metals fuels is needed.A very specific reprocessing technology, the so-called direct use of pressurized water reactor spent fuel in CANDU process, is being developed in Korea. Here, used pressurized water reactor fuel is recycled to CANDU (CANada Deuterium Uranium) reactors after a dry treatment where volatile fission products are removed.