Using of SPT method for estimation of mechanical properties changes of RPV steels after irradiation in the Halden reactor

The paper deals with experimentally estimation and comparison of the mechanical properties changes of RPV steels before and after irradiation of samples in Halden reactor in Norway coming from Unit #3 and #4 of NPP Mochovce (still under construction). Altogether 180 SPT and 30 mini-tensile samples in two sets were prepared for irradiation, obtained from weld metal material (Sv10ChMFT) and base material (15Ch2MFA). In general, a good agreement between results obtained by SPT technique and using mini-tensile specimens was found. Both, base and weld metals of RPVs were found to be bainitic. After that, the first set of samples was irradiated in Halden reactor at temperature Tirr = 270 - 280°C with intention to use two fluence values: ∼ 1.0 × 1024 n/m2 and ∼ 2.0 × 1024 n/m2 (> 1 MeV), respectively. Specimens after 1st irradiation were successfully tested and preliminary results show small increase of the strength characteristics (Re, Rm) if compare to “zero condition” testing results. FATTs, evaluated by the temperature dependence of the SPT energy, exhibit transition behaviour and shift towards higher temperatures

Interim results of the reactor pressure vessel materials evaluation within the framework of the implemented Advanced Surveillance Specimen Programme

The reactor pressure vessel (RPV) is the most critical component of every nuclear power plant (NPP) and continuous evaluation of its mechanical properties is a necessity for long and safe operation. Standard tests require a collection of large-dimension samples coming from the precious and archive materials, usually produced as control segments. Since SPT testing samples are quite small, high activity of irradiated materials is no longer an issue. The SPT technique therefore represents a very useful and effective method applied for characterization of mechanical properties such as ultimate tensile strength (Rm), yield strength (Re), and fracture appearance transition temperature (FATT). Monitoring of structural components in nuclear power plants receives much attention, particularly, in the context of long term operation (LTO) of current plants where the amount of material available for destructive testing is considerably limited

Can Arginine Inhibit Insulin Aggregation? A Combined Protein Crystallography, Capillary Electrophoresis, and Molecular Simulation Study

The oligomeric state of the storage form of human insulin in the pancreas, which may be affected by several endogenous components of β-cell storage granules such as arginine, is not known. Here, the effect of arginine on insulin oligomerization is investigated independently by protein crystallography, molecular dynamics simulations, and capillary electrophoresis. The combined results point to a strong effect of ionic strength on insulin assembly. Molecular simulations and electrophoretic measurements at low/mM salt concentrations show no significant effect of arginine on insulin aggregation. In contrast, crystallographic data at high/molar ionic strength indicate inhibition of insulin hexamerization by arginine due to its binding at the site relevant for intermolecular contacts, which was also observed in MD simulations. Our results thus bracket the in vivo situation in pancreatic β-cell storage granules, where the ionic strength is estimated to be in the hundreds of millimolar to submolar range. The present findings add to a molecular understanding of in vivo insulin oligomerization and storage, with additional implications for insulin stability in arginine-rich injections