MELCOR-To-MELCOR Coupling Method in Severe Accident Analysis Involving Core and Spent Fuel Pool

A lot of effort has been spent to prevent the occurrence of SA in nuclear plant and to develop Severe Accidents (SA) Management to mitigate the consequences of a SA. Those consequences are mainly related to limit the release of fission product to the environment. The core in the vessel is not the only source of fission products as the Spent Fuel Pool (SFP) hosting the fuel removed by the core is, in some NPP, inside the containment and SA conditions can also occur. This is especially important in reactors having proximity between the RPV and SFP such as the VVER-1200. This close proximity implies that any SA occurring in the SFP potentially affects the RPV and vice-versa. This potential combination might cause unexpected evolution in the SA progression to whom the safety systems are not able to contain. MELCOR code is a widely used, flexible powerful SA code but it is incapable (due to the uniqueness of the COR package use inside the same input) to reproduce a situation in which both the fuel in vessel core and the fuel in the SFP, inside the same containment, are going to experience a severe accident scenario. The current study presents a MELCOR-to-MELCOR coupling method to simulate simultaneously scenarios with both, core and SFP, as sources capable of H2 generation, fuel damage and FP release in a VVER-1200 NPP. The coupling is performed by running two simulations in parallel and with the data exchange supervised and managed by a dedicated Python coupling supervising script developed at NINE

Cilostazol Activates Function of Bone Marrow-Derived Endothelial Progenitor Cell for Re-endothelialization in a Carotid Balloon Injury Model

BACKGROUND: Cilostazol(CLZ) has been used as a vasodilating anti-platelet drug clinically and demonstrated to inhibit proliferation of smooth muscle cells and effect on endothelial cells. However, the effect of CLZ on re-endothelialization including bone marrow (BM)-derived endothelial progenitor cell (EPC) contribution is unclear. We have investigated the hypothesis that CLZ might accelerate re-endothelialization with EPCs. METHODOLOGY/PRINCIPAL FINDINGS: Balloon carotid denudation was performed in male Sprague-Dawley rats. CLZ group was given CLZ mixed feed from 2 weeks before carotid injury. Control group was fed normal diet. CLZ accelerated re-endothelialization at 2 weeks after surgery and resulted in a significant reduction of neointima formation 4 weeks after surgery compared with that in control group. CLZ also increased the number of circulating EPCs throughout the time course. We examined the contribution of BM-derived EPCs to re-endothelialization by BM transplantation from Tie2/lacZ mice to nude rats. The number of Tie2-regulated X-gal positive cells on injured arterial luminal surface was increased at 2 weeks after surgery in CLZ group compared with that in control group. In vitro, CLZ enhanced proliferation, adhesion and migration activity, and differentiation with mRNA upregulation of adhesion molecule integrin αvβ3, chemokine receptor CXCR4 and growth factor VEGF assessed by real-time RT-PCR in rat BM-derived cultured EPCs. In addition, CLZ markedly increased the expression of SDF-1α that is a ligand of CXCR4 receptor in EPCs, in the media following vascular injury. CONCLUSIONS/SIGNIFICANCE: CLZ promotes EPC mobilization from BM and EPC recruitment to sites of arterial injury, and thereby inhibited neointima formation with acceleration of re-endothelialization with EPCs as well as pre-existing endothelial cells in a rat carotid balloon injury model. CLZ could be not only an anti-platelet agent but also a promising tool for endothelial regeneration, which is a key event for preventing atherosclerosis or restenosis after vascular intervention

Uncertainty evaluation of RBMK NPP DGH blockage calculation by CIAU Methodology

CIAU (Code with capability of internal Assessment of Uncertainty) methodology has been proposed having as basis, or ‘engine’, the UMAE (Uncertainty Method based on Accuracy Extrapolation). The resources needed for the development of the error database of CIAU constitute an issue for the application of the method. An applicable version of the CIAU has been utilized for the code calculation of the RBMK accident scenario caused by the DGH (Distribution Group Header) blockage which causes flow stagnation in several channels and lack of cooling

US NRC NUREG - RELAP5/MOD3.2 Post Test Analysis and Accuracy Quantification of SPES Test SP-SB-03

The present document deals with the Relap5/Mod3.2 analysis of the Small Break LOCA experiment SP-SB-03 performed in SPES facility. SPES is a PWR simulator (Integral Test Facility) installed at SIET center in Piacenza (I). Volume scaling and core power scaling factors are 1/427, with respect to the Westinghouse 900 MWe standard reactor. The experiment is originated by a small break in the cold leg (2" equivalent break area in the plant) without the actuation of the high pressure injection system. Low pressure injection system actuation occurs after core dry-out. The Relap5 code has been extensively used at University of Pisa; the nodalization of SPES facility has been qualified through the application of the version Relap5/Mod2 to the same experiment and another test performed in the same facility. Sensitivity analyses have been addressed to the influence of several parameters (like discharge break coefficient, time of accumulators start etc.) upon the predicted transient evolution. Qualitative and quantitative code calculation accuracy evaluation has been performed

USNRC-NUREG - RELAP5/MOD3.2 Post Test Analysis and Accuracy Quantification of Lobi Test BL-44

The present document deals with the Relap5/Mod3.2 analysis of the small break LOCA experiment BL-44 performed in LOBI/MOD2 facility. LOBI(MOD2 was a PWR simulator (Integral Test Facility) installed at JRC (Joint Research Center) in Ispra Establishment (I). Volume scaling and core power scaling factors are 1/712, with respect to the KWU Siemens 1300 MWe (3900 MWt) standard reactor. The expeiment is originated by a small break in the cold leg (2" equivalent break area in the plant) without the actuation of the high pressure injection system. Low pressure injection system actuation occurs after core dry-out and accumulators intervention is foreseen when primary pressure falls below 4 MPa. The Relap5 code has been extensively used at University of Pisa; the nodalization of LOBI facility has been qualified through the application of the version Relap5/Mod2 to the same experiment and another test performed in the same facility. Sensitivity analyses have been addressed to the influence of several parameters (like discharge break coefficient, time of accumulators start etc.) upon the predicted transient evolution. Qualitative and quantitative code calculation accuracy evaluation has been performed