1,721,099 research outputs found
Aircraft Impact onto an existing nuclear plant
No full textThis study deals with the investigation of the damaging effects that the impact of a large civilian airplane
could bring in safety relevant structures of a Gen II reactor.
The assessment of the safety margin of an existing plant, entails, unavoidably, with the evaluation of how
robust the wall building is to guarantee the overall plant safety.
In doing that, the dynamic response of the RB has properly studied by means of a reliable finite element
code and setting up further refined models of the reactor building and airplane. The location of the strike
was considered near the junction of the dome and cylindrical body while the angle of incidence of the
impact was assumed to be normal and/or inclined to the building outer surface.
Moreover the qualification of code has been done on the basis of the results of experimental carried out,
simulating the impact of a missile against a deformable target. The results obtained, assuming the same
impact velocity of the airplane, highlighted that:
1) the plant undergoes local damages in the area where the impact is localized;
2) the penetration depth is dependent on the type of aircraft considered and wall thickness;
3) the overall stability of the safety relevant structures is anyway ensured
Preliminary Evaluation of the Fluid-Structure Effects in a LFR
No full textThe aim of the study is to investigate the structural effects induced by a beyond design basis earthquake on the main safety relevant structures and components of an isolated liquid metal reactor, such as the European Lead-cooled SYstem (ELSY) or ALFRED projects. An extensive R&D program related to heavy-metal cooled systems was recently carried out as Euratom projects of the 6th and 7th Framework Programmes, addressing many of the most important issues related to the viability of a lead-cooled fast reactor. The importance of seismic effects is mainly related to the high inertial forces of the primary coolant (liquid metal) and associated with the impact of the liquid waves on the reactor structures. The isolation devices considered for the design were represented by means of an iso-elastic approach. Moreover, the influence of isolator failure was also evaluated. The fluid-structure interaction and the sloshing phenomenon, characterized by hydrodynamic and impact forces, were numerically investigated, since an explicit analytical solution for structures of such complex geometiy is not possible. Numerical calculations (i.e., dynamic nonlinear analyses) were carried out with appropriate finite element method codes and external coupling. A validation analysis was further pei formed to check the consistency and adequacy of the method used with respect to the American Society of Civil Engineers (ASCE) 4-98 rules. The accelerations propagated in the reactor building confirmed the favorable effect of the seismic isolation, even with 2% faulted isolators. The results indicated that the stress state, in the reactor internals, is not sufficient to impair their structural integrity, although there is localized plastic deformation
Investigation of the behaviour of a LILW superficial repository under aircraft impact
No full textSafety and security are the two fundamental aspects to guarantee when designing a LILW superficial repository. Because of its safety concern, we have to prove, and build confidence in, the primary and secondary consequences of the crashing will be acceptable. These goals are obtained generally by means of safety assessment supported by calculations. This study is intended to investigate the performance of a superficial repository subjected to aircraft impact and fuel burning. To the purpose a superficial repository similar to that of El Cabril has been considered. Moreover to be confident the facility is safe and that the consequences of such a type of accident on the environment and humans are negligible, an appropriate safety assessment was carried out. The potential damage that aircraft impact could bring into the repository has been therefore analysed and discussed. To attain the intent load functions, calculated according to the Riera approach, and the maximum temperature reached by fuel during its combustion have been considered. FEM (thermo-mechanical) simulations have been done, by MSC© Marc code, assuming damaging phenomena of concrete and material properties variation with the temperature. The obtained results showed that an empty superficial repository with a wall thickness, ranging from 0.7 to 1 m, is not sufficient to avoid penetration. Nevertheless even in presence of a reduced strength and of (cone) cracking and plugging, the overall integrity resulted guaranteed
Preliminary evaluation of structural response of ELSY reactor in the after shutdown condition
No full textThe paper is aimed at preliminary evaluating the load bearing capability of a Generation IV metal cooled reactor (LFR), like the European Lead-cooled System (ELSY), with the intent to support the viability of lead technology for use in a future commercial power plant with waste transmutation capability. Two relevant safety aspects were investigated: the fluid-structure interaction, induced by the propagation of seismic loading (in the event of safe shutdown earthquake), and the high thermal loads due to the residual decay heat (influenced also by the burn up level). The first issue depends on the presence of a liquid free surface that, especially, in SSE condition allows for fluid motion ("sloshing"); the forming and the impact of lead waves could impair the integrity of reactor structures. The second aspect deals with the thermal effects induced by the irradiated core heat source after the reactor shutdown. In order to evaluate the ELSY reactor structural response, induced by both high temperature and hydrodynamic loads, appropriate 3-D finite element models were set up and implemented in MARC code. In addition the input decay power after shutdown has been evaluated by means of MCNPX and Origen2.2 codes. The obtained preliminary results provide information to make possible an upgrading of the reactor design, however with no significant modification of their functionality
Demonstration of structural performance of IP-2 package by simulation and full-scale horizontal free drop test
Full text linkPackaging systems for the transportation of radioactive wastes have to be designed according to rigorous acceptance criteria and requirements in order to protect people and environment against radiation exposure and contamination risk. The IAEA requirements for type IP2 (Industrial Package Type 2) packages include to carry out free drop tests that represent normal conditions of transport. In such conditions, obviously, the required containment capability of the package has to be ensured.
In this study the mechanical performances of a new Italian packaging system for the transportation of low and intermediate level wastes (LILW) undergoing horizontal free drop test are investigated. Especially, deformations caused in the sealing area of the package, which can affect the capability of the containment system, are evaluated.
The carried out numerical analyses and experimental tests, at the lab. Scalbatraio of the DICI- University of Pisa, are presented and discussed.
Numerical analyses (by qualified MARC® code) have been performed to investigate the stress histories in the bolts, lid, and package body as well as the deformations in the sealing area and the compression conditions of the gasket.
Localized stress appeared at the flange and at the bottom of packaging system. The maximum stresses resulted lower than the stress limits, so the structural integrity of the package was maintained and confirming its tightness. As a consequence of the primary impact a local deformation appeared at the primary lid, no cliff edge or loss of the safety features resulted
Preliminary evaluation of isolation systems influence on the seismic loading effects in a Generation IV reactor
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