On Plastic Collapse Analysis of KBS-3 Canister Mock-Up

This report describes an in-depth finite element simulation of a spent fuel canister for geological disposal loaded in iso-static pressure until plastic collapse. The canister consists of a copper overpack and a ductile cast iron insert with steel cassettes where the spent fuel is placed. The higgly non-linear finite element analysis is based on the explicit formulation and includes large deformations, non-linear material behaviour and contact between the canister components. The analysis includes comparison between two-and three dimensional models and assessment of the different geometrical features such as corner radius of the cassette, cassette off-set, different bonding/dedonding conditions between insert and steel cassette. The analysis shows that the bonding cassette/insert has a large impact on the collapse load. Two large-scale mock-ups test that had been performed earlier are also simulated by the developed finite element models. There is a very good agreement between measured and computed deformations versus applied load and collapse load.JRC.F.4-Nuclear design safet

Sadržaj pigmenata hloroplasta u lekovitoj biljci Teucrium chamaedrys sa sanirane deponije Rudarsko metalurško hemijskog kombinata “Trepča”

In this paper, the contents of chloroplast pigments (chlorophyll a, b, a+b and carotenoids) in the leaves of medicinal plant Teucrium chamaedrys from tailing pond „Žitkovac“ of Mining and Metallurgical Chemical Company „Trepča“ and from uncontaminated area near city of Niš were compared. Chloroplast pigments were determined spectrophotometrically in the acetone extracts of experimental and control samples of plant material. The contents of chlorophyll a, a+b and ratio a/b were higher in leaves of samples from tailing pond in comparison with control samples from uncontaminated habitat near city of Niš. In response to stress conditions caused by pollution and full intensity of sunlight in samples of leaves from tailing pond providing the protection of chlorophyll from photooxidation or ultraviolet radiation damage.U ovom radu upoređen je sadržaj pigmenata hloroplasta (hlorofil a, b, a+b, karotenoidi) iz listova lekovite bilјne vrste podubica - Teucrium chamaedrys sa deponije „Žitkovac“ Rudarsko Metalurško Hemijskog Kombinata „Trepča“ i nezagađenog područja okoline Niša. Pigmenti hloroplasta su određeni spektrofotometrijski u acetonskim ekstraktima eksperimentalnih i kontrolnih uzoraka bilјaka. Sadržaj hlorofila a, a+b i odnos a/b je bio veći kod u uzorcima listova sa deponije u poređenju sa kontrolnim uzorcima sa nezagađenog staništa iz okoline Niša. Kao odgovor na stresne uslove uzrokovane zagađenjem i punim intenzitetom sunčeve svetlosti zabeležen je i povećan sadržaj karotenoida kod uzoraka listova sa deponije, što obezbeđuje zaštitu hlorofila od fotooksidacije odnosno štetnog dejstva ultravioletnog zračenja

Dynamical Behaviour of a Nonlinear Single-Degree-Of-Freedom System with Negative Viscous and Positive Frictional Damping

This paper presents the phase portraits of the single-degree-of-freedom system with two competing energy dissipation models: viscous damping and Coulomb dry friction. While the scaled friction force may occupy only nonnegative values, the coefficient of viscous damping is allowed to any real value. The unstable limit cycle is discovered at a certain interval of negative viscous damping coefficient values. The basin of attraction is computed, as well as separatrices where they appear. The criteria are established to find out the stability of the system's motion based solely on given initial conditions for different values of the system's parameters.JRC.F.4-Safety of future nuclear reactor

Numerical Algorithm for Natural Frequencies Computation of an Axially Moving Beam Model

An algorithm for numerical computation of natural frequencies of the axially moving Euler-Bernoulli beam is presented. It is tested against data found in the literature and against known analytical expressions of its limiting models - axially moving string and stationary beam - where good agreements were found. The numerical algorithm always stays within real algebra. Roots of the polynomial can be computed out of only three real numbers and the expressions for determinant evaluations are deduced in a numerically stable way.JRC.F.7-Energy systems evaluatio

Finite Element Modelling of the One Meter Drop Test on a Steel Bar for the CASTOR Cask

This paper presents a numerical analysis of the 1m drop test on a steel bar of a Castor AVR cask where the impact is in a region with cooling fins as well as in a region where the fins have been locally removed. The paper consists of two parts: i) a parameter study with an overall objective to derive an analysis methodology and ii) comparison with experimental data. The parameter study includes parameters that can not be, or were not, defined directly from the experimental data as well as parameters linked to the numerical procedures within the finite element procedure. The parameters are validated by their influence on the model responses and effort needed for the assessment of their appropriate values. Then the model with the "best" parameter set is verified against the experimental results. The agreement between experimental and simulation results are very good.JRC.F.7-Energy systems evaluatio

Numerical Simulation of the One Meter Drop Test on a Bar for the Castor Cask - Preliminary Analysis

The report presents the numerical analysis of two one meter drop tests of a single ductile cast iron cask on a steel bar. The cask comes from the CASTOR family with machined cooling fins in a region where impact occurs. In the first test, the impact is on the cask’s cooling fins whereas in the second test the impact is in an area where the ribs have been locally machined away. The numerical analysis is based on explicit dynamic analysis using the commercial finite element code ABAQUS extended with Python scripts to allow a parametric description of the problem. The analysis consists of two parts: a “blind-analysis” with assumed model parameters and a sensitivity analysis. The “blind-analysis” (basic model without any knowledge of test results) was performed for the two drop tests. The overall behavior of the model is qualitatively very similar to what was observed during the experiments. A longer impact duration, (between 3 ms to 5 ms) when the cask is dropped on the fins in comparison to the flat target, is observed in both the analysis and the test. The reaction force at the bar’s bottom surface from the model is qualitatively similar to that from the test. The peak force value is however overestimated by about 35%. On the contrary the measured strains inside the cask above the impact area are underestimated for the similar amount. Latter is mainly attributed to the fact that the lid wasn’t included in this version of the model. The maximum strain is about 20% higher for the flat impact area in both simulation and experiment. The sensitivity analysis was performed to study the influence of parameters which either cannot be or were not defined directly from the experimental data, such as the friction coefficient, or which are linked to the FE numerical procedures, like the bulk viscosity. Based on results, recommendations for an optimised set of parameters values are given.JRC.F.4-Nuclear design safet

Numerical Simulation of the One Metre Drop Test on a Bar for the CASTOR Cask

This paper presents a numerical analysis of the 1m drop test on a steel bar of a Castor AVR cask where the impact is in a region with fins as well as in a region where the fins have been locally removed. The paper consists of two parts: i) a parameter study with an overall objective to derive an analysis methodology and ii) comparison with experimental data. The parameter study includes parameters that can not be, or were not, defined directly from the experimental data as well as parameters linked to the numerical procedures within the finite element procedure. The parameters are validated by their influence on the model responses and effort needed for the assessment of their appropriate values. Then the model with the "best" parameter set is verified against the experimental results. The agreement between experimental and simulation results are very good.JRC.F.4-Safety of future nuclear reactor

An elasto-plastic fracture mechanics based Model for Assessment of Hydride Embrittlement in Zircaloy Cladding Tubes

This paper describes a finite element based fracture mechanics model to assess how hydrides affect the integrity of zircaloy cladding tubes. The hydrides are assumed to fracture at a low load whereas the propagation of the fractured hydrides in the matrix material and failure of the tube is controlled by nonlinear fracture mechanics. The paper quantifies the relative importance of hydride geometrical parameters such as size, orientation and location of individual hydrides, interaction between adjacent hydrides. The paper also presents fracture analyses for some different and representative multi-hydride configurations. The model allows for quite arbitrary crack configurations and can therefore be used to assess realistic hydride configurations. The mechanism cladding failure is by yielding of ligaments between interacting fractured hydrides. The results show that the integrity can be drastically reduced when several radial hydrides form continuous patterns.JRC.F.4-Safety of future nuclear reactor