In the present study, investigation of mechanical behaviour of the fuel cladding material for a nuclear superheat Boiling Water Reactor with annular fuel rods, is carried out. In this design, each annular fuel element is cooled internally by steam and externally by water. For the fuel cladding material, radiation embitterment and irradiation-assisted stress corrosion cracking (IASCC) are the most important issues that have to be taken into account. Hence, for cladding, two materials are considered. Preliminary thermal expansion and stress analysis have been done for a fresh (begin of cycle) ASBWR (Annular-fuelled Superheat Boiling Water Reactor) fuel element. The purpose of these analysis is to investigate the stress distribution and thermal expansion of the cladding in the initial phase of operation. The results show that there is a noticeable difference in the axial expansion between the inner and outer claddings. For T91 (modified 9Cr-1Mo steel) cladding, the maximum axial thermal growth of the inner cladding is 22.12 mm, which is about 9.7 mm more than the outer cladding. For Inconel 718 cladding, the results are 27.8 mm and 13.4 mm, respectively. پرونده مقاله

In this paper, according to the discussion of improving the safety of nuclear power plants (NPPs) according to reports and findings of Fukushima accident, a model for the economic analysis of a NPP with a higher level of safety in an electricity power market is provided. Therefore, a solution to determine the balance between safety and economy to deal with station black-out (SBO) accident in a pressurized water reactor (PWR) nuclear power plant is presented. A supply function equilibrium (SFE) that takes into account carbon tax in the power market is used to calculate the profit of each power generation firm. A hierarchical innovative approach is used to make decisions about improving the safety of NPP. In this method, breakeven point (BEP) is used as the decision criterion to compare the safety improvement costs and profit of NPP in the power market. This method is used to add an emergency diesel generator (EDG) and a mobile heat exchanger to a NPP that examines the impact of investment costs and profits. The result shows that with the addition of an EDG to the NPP, the BEP of investment costs and net profit of the NPP is one month later. Finally, it can be suggested to the investor of the NPP to add EDG to improve safety, so that the implementation of this proposal leads to a slight increase in payback period, but greatly reduces core damage frequency (CDF) of NPP reactor in SBO accident. پرونده مقاله