Wind influence on the spent nuclear fuel safety in dry cask storage

This article examines the effect of wind load on the safety of spent fuel storage in a naturally ventilated building. To assess the influence of wind influences characteristic of the Akkuyu NPP site on the temperature of fuel rod cladding, a CFD model of the spent fuel storage building was developed. Reynolds-averaged governing equations of motion (RANS model) with a k-ε turbulence model were used. Computational grid included about 17 million cells. The CFD model allowed us to study different directions and intensities of wind loads, estimate the temperature around the containers and identify stagnant zones. Based on the modeling results, the dependences of the influence of wind load on the thermal fields in the building were obtained. These dependencies allowed for design decisions to be made that guaranteed safety and ensured the continuation of construction of the building

Relativistic instant-form approach to the structure of two-body composite systems

A new approach to the electroweak properties of two-particle composite systems is developed. The approach is based on the use of the instant form of relativistic Hamiltonian dynamics. The main novel feature of this approach is the new method of construction of the matrix element of the electroweak current operator. The electroweak current matrix element satisfies the relativistic covariance conditions and in the case of the electromagnetic current also the conservation law automatically. The properties of the system as well as the approximations are formulated in terms of form factors. The approach makes it possible to formulate relativistic impulse approximation in such a way that the Lorentz-covariance of the current is ensured. In the electromagnetic case the current conservation law is ensured, too. The results of the calculations are unambiguous: they do not depend on the choice of the coordinate frame and on the choice of "good" components of the current as it takes place in the standard form of light--front dynamics. Our approach gives good results for the pion electromagnetic form factor in the whole range of momentum transfers available for experiments at present time, as well as for lepton decay constant of pion.Comment: 26 pages, Revtex, 5 figure

Enlargement of the Assessment Database for Advanced Computer Codes in relation to the VVER Technology: Benchmark on LB-LOCA Transient in PSB-VVER Facility

The OECD/NEA PSB-VVER project provided unique and useful experimental data from the large-scale PSB-VVER test facility for code validation. This facility represents the scaled down layout of the Russian designed PWR reactors, namely VVER-1000. Five experiments were executed in the project, dealing mainly with the loss of coolant scenarios (small, intermediate, large break loss of coolant accident); a primary to secondary leak and a parametric study (natural circulation test) aimed at the characterization of the VVER system at reduced mass inventory conditions. The comparative analysis described in the paper deals with the analytical exercise on the large break loss of coolant accident experiment (Test 5). Four participants from three different institutions were involved in the benchmark and applied their own analytical models, set up for four different thermal-hydraulic system codes. The benchmark demonstrated that almost all performed post-tests appeared qualified against fixed criteria. Few mismatches between the results and acceptability thresholds are discussed and understood. The analysis involves the relevant features of the input models developed, the steady state conditions and the results of the simulations. The results submitted by the participants are discussed in the paper considering the resulting sequence of main events, the qualitative comparison of selected time trends, the analysis of the relevant thermal-hydraulic aspects and, finally, by the application of the Fast Fourier Transform based method