60 research outputs found
International Standard Problem No 50 – The University of Pisa contribution
The present paper deals with the participation of the University of Pisa in the last International Standard Problem (ISP)
focused on system thermal hydraulic, which was led by the Korean Atomic Energy Research Institution (KAERI). The selected
test was a Direct Vessel Injection (DVI) line break carried out at the ATLAS facility. University of Pisa participated, together
with other eighteen institutions, in both blind and open phase of the analytical exercise pursuing its methodology for developing
and qualifying a nodalization. Qualitative and quantitative analysis of the code results have been performed for both ISP-50
phases, the latter adopting the Fast Fourier Transfer Based Method (FFTBM). The experiment has been characterized by three dimensional behavior in downcomer and core region. Even though an attempt to reproduce these phenomena, by developing a
fictitious three-dimensional nodalization has been realized, the obtained results were generally acceptable but not fully satisfactory
in replicating 3D behavio
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
Overexpression of the β2AR gene improves function and re-endothelialization capacity of EPCs after arterial injury in nude mice
Synthesis and evaluation of new Hsp90 inhibitors based on a 1,4,5-trisubstituted 1,2,3-triazole scaffold
Abstract: Ruthenium catalyzed 1,3-cycloaddition (click chemistry) of an azido moiety installed on dihydroxycumene scaffold with differently substituted aryl propiolates, gave a new family of 1,4,5-trisubstitued triazole carboxylic acid derivatives that showed high affinity towards Hsp90 associated with cell proliferation inhibition, both in nanomolar range. The 1,5 arrangement of the resorcinol, the aryl moieties, and the presence of an alkyl (secondary) amide in position 4 of the triazole ring, were essential to get high activity. Docking simulations suggested that the triazoles penetrate the Hsp90 ATP binding site. Some 1,4,5-trisubstitued triazole carboxamides induced dramatic depletion of the examined client proteins and a very strong increase in the expression levels of the chaperone Hsp70. In vitro metabolic stability and in vivo preliminary studies on selected compounds have shown promising results comparable to the potent Hsp90 inhibitor NVP-AUY922. One of them, (compound 18; SST0287CL1) was selected for further investigation as the most promising drug candidate
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
The effect of concentrated bone marrow aspirate in operative treatment of fifth metatarsal stress fractures; a double-blind randomized controlled trial
Bases for the use of CIAU for a Nuclear Power Plant (NPP) transient simulation
The CIAU (Code with Capability of Internal Assessment of Uncertainty) was developed at University of Pisa and constituted the follow-up of a request from the international community issued on the occasion of an ad-hoc Workshop called by US NRC and OECD/NEA in Annapolis (1996). The CIAU methodology incorporated all the features of the UMAE (Uncertainty Method based on Accuracy Extrapolation) where, among the other things, automatization was added, as well as the possibility to use accuracy values derived from SETF (Separate Effect Test Facility) experiments in addition to ITF (Integral Test Facility) experiments (as in the UMAE). The CIAU allowed an automatic (simultaneous to the output of a calculation) derivation of uncertainty bands which characterize the time trends of selected code output variables. Hypercube quantity errors and Vector time errors are distinguished in CIAU and recombined to estimate the code uncertainty. The CIAU was used in the framework of a variety of application to demonstrate the safety of existing Nuclear Power Plants (NPP) – noticeably, licensing process – as well as the training of specialists.
The present document deals with a sample application performed in Pisa by a Brazilian scientist in the framework of a cooperation funded by IAEA (International Atomic Energy Agency)
RELAP5/MOD.2 Post Test Analysis and Accuracy Quantification of Lobi Test BL-34
The present document deals with the Relap5/Mod3.2 analysis of the small break LOCA
experiment BL-34 performed in LOBI/MOD2 facility.
LOBI/MOD2 was a PWR simulator (Integral Test Facility) installed at JRC (Joint Research
Center) in Ispra Establishment (1). Volume scaling and core power scaling factors are 1/712, with
respect to the KWU Siemens 1300 MWe (3900 MWt) 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 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
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
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