1,720,975 research outputs found
XADS source transients analyzed by means of RELAP5/PARCS
No full textFollowing the large interest aroused in the world on Accelerator Driven Systems (ADSs), a team of Italian industrial and research organizations (ANSALDO, CRS4, ENEA and, INFN) participated in the design of an 80 MW lead-bismuth cooled eXperimental Accelerator Driven System (XADS), a key step towards the assessment of the feasibility and operability of an ADS prototype. Among the R&D activities pursued in parallel, special attention has been paid to the development of suitable numerical tools for studying operational transients and accidental sequences of ADS-like systems. In particular, an adapted version of the thermal-hydraulic-neutronic coupled code RELAP5/PARCS allows a suitable simulation of the XADS dynamic response to typical plant transients. This paper concerns a parametric analysis of overpower transients due to the anticipated insertion of the external neutron source when the XADS is at Hot Zero Power (HZP), namely isothermal at 300 C. Beginning of Cycle (BOC) configuration has been considered for the core, while the external neutron source has been varied from nominal full power at BOC to nominal full power at End of Cycle (EOC), namely doubling its intensity. The results presented in this work allow stating that the XADS plant presents a high level of inherent safety also for abrupt power variations as in the case of source transients
Flowblockage accidents in the XADS plant analyzed by means of RELAP5/PARCS
No full textThe Accelerator Driven Systems (ADSs) have great potential as transmuting systems of the long-lived nuclear wastes both from industrial energy production and from nuclear weapon dismantling. In the frame of national and European research programs, a team of Italian industrial and research organizations designed an 80 MWth lead-bismuth cooled experimental Accelerator Driven System (XADS), as a key step towards the assessment of the feasibility and operability of an ADS prototype. In parallel with these basic activities and as an important issue among the R&D needs, the original coupled neutronic thermal-hydraulic code RELAPS/PARCS has been modified and adapted to lead-bismuth cooled subcritical systems. This paper aims to present a preliminary analysis of the flowblockage accidents in the XADS plant, classified as Design Basis Accidents. These accidents are caused by the partial or total blockage of a part of the core. Due to the mixing of the lead-bismuth at the exit of the fuel assemblies, the obstruction of a single channel cannot be detected by a signal of high lead-bismuth temperature at core exit. Thus, fission power continues to be generated because the control system does not stop the accelerator and, consequently, cladding melting and the destruction of the affected fuel element can occur. In order to investigate the effect of thermal feedback on the fission power density, especially for the fuel assembly of the affected channel, this analysis has been performed by means of the neutronic thermal-hydraulic coupled code RELAPS/PARCS
BENCHMARKING ACTIVITY ON ENEA AVAILABLE TOOLS FOR THE DYNAMIC ANALYSIS OF LBE COOLED SUBCRITICAL SYSTEMS
No full textThis paper was presented to the 7th Information Exchange Meeting on Actinide and Fission Product Partitioning & Transmutation, that was held in Jeju (Republic of Corea) on October 14-15th 2002
Accident Analysis of an Experimental Accelerator Driven System
No full textIn order to demonstrate the safety of the 80 MWth LBE-cooled XADS design concept an extensive dynamic transient analysis was performed in the framework of the European research program PDS-XADS.A wide set of enveloping plant-specific transient initiators was selected to assess the intrinsic safety characteristics of the sub-critical core and to demonstrate the safety margins of the systems design. Some of them are characterized by a very low probability of occurrence (on the verge of credibility) in order to intentionally challenge the limits of the design.The transient analysis was performed by means of the neutronic thermal-hydraulic coupled code RELAP5/PARCS modified to analyse this kind of plants.This paper deals with the representative results of the transient analysed. It also provide a description of the numerical models developed for the XADS (code modifications, plant nodalization)
Comparison of Lead-Bismuth and Lead as Coolants for Accelerator Driven Systems
No full textIn the framework of the Italian research program TRASCO (TRAsmutazione SCOrie, namely transmutation of radioactive wastes) and of the European research program PDS-XADS (Preliminary Design Study on an eXperimental Accelerator Driven System) the feasibility and operab ility of gas or liquid metal cooled accelerator driven system prototypes are currently under investigation. Initially the attention of the thermal-hydraulics group of ENEA research centre in Bologna has been focussed toward a lead-bismuth cooled subcritical system under natural or enhanced natural circulation according to the prototype design proposed. The interest in using lead as a coolant, which is characterized by a higher melting point, is explained by the need to increase the plant efficiencyfor the economic competitiveness, though the higher temperatures pose some technological problems. Moreover, the amount of activation products should result significantly lower. Of course the results obtained and the experience gained analysing the dynamical behaviour of the lead-bismuth cooled system cannot be directly transferred to lead cooled systems. This paper aims at presenting a preliminary comparison of lead-bismuth and lead in a simplified liquid metal cooled subcritical system, mainly from the thermal-hydraulics and system dynamics points of view. By means of the modified RElLAP5 version, the dynamical behavior of a lead-b ismu th or lead coo led system, which is in tended to be a qui te accurate represen tation of the Italian accelerator driven prototype XADS, has been studied. Although a more exhaustive comparison should take into account the necessarily different structural characteristics of leadbismuth and lead cooled systems, the neutronic feedback on reactor power and also the slightly different neutronic properties of lead-bismuth and lead, the purely thermal-hydraulic analysis presented in this paper has shown that the dynamical behaviour of the XADS does not differ noticeable when lead is used instead of lead-bismuth, even if the first presents a larger heat capacity
Progetto neutronico preliminare di un dispositivo per boroterapia basato su un acceleratore di protoni
No full textValutazione dell'impatto Ambientale della Centrale di Trino con il Codice di Calcolo Frames-GENII
No full textQuesto articolo descrive l’attività di modellizzazione ed analisi dell’impatto ambientale
dovuto agli scarichi radioattivi liquidi ed aeriformi della centrale E. Fermi di Trino (VC) attraverso
l’uso del codice FRAMES-GENII Version 2.0.
Tale attività va ad inserirsi all’interno di un piano industriale della SO.G.I.N. (Società
Gestione Impianti Nucleari) per la sostituzione del codice Vadosca (implementato dall’ENEL
negli anni ottanta) con il codice Frames, come principale strumento di calcolo per la stima della
dose ricevuta dalle popolazioni, che vivono nei pressi dei siti nucleari in Italia. Il codice Frames,
infatti, consente di effettuare una analisi più efficiente e dettagliata dei meccanismi di esposizione.
Dopo aver implementato il codice Frames sulla base degli scarichi e dei dati ambientali, si è
passati all’analisi ambientale del sito di Trino e delle zone limitrofe.
Per quanto riguarda la caratterizzazione radiologica del sito si può affermare che i
radionuclidi più “pericolosi”, cioè i radionuclidi che danno un maggior apporto di dose a parità di
attività rilasciata, sono Am-241 ed il Pu-239. Ciò è dovuto al fatto che sono gli unici due
radionuclidi emettitori .
Sulla base dei valori di dose calcolati per i rilasci dell’anno di riferimento 2006, si può
dedurre che l’attuale impatto ambientale radiologico delle operazioni di mantenimento in sicurezza
e decommissioning dell’impianto di Trino è assolutamente trascurabile. Le dosi ricevute dalla
popolazione sono inferiori di 5-6 ordini di grandezza rispetto ai limiti imposti dalla legislazione
vigente, nonostante tutte le assunzioni conservative messe in atto
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