Uso integrato di metodologie FMEA, HAZOP e FAULT TREE nella windowless target unit di un Accelerator Driven System

FUZZY RISK ANALYSIS OF A MODERN γ-RAY INDUSTRIAL IRRADIATOR

Fuzzy fault tree analyses were used to investigate accident scenarios that involve radiological exposure to operators working in industrial γ-ray irradiation facilities. The HEART method, a first generation human reliability analysis method, was used to evaluate the probability of adverse human error in these analyses. This technique was modified on the basis of fuzzy set theory to more directly take into account the uncertainties in the error-promoting factors on which the methodology is based. Moreover, with regard to some identified accident scenarios, fuzzy radiological exposure risk, expressed in terms of potential annual death, was evaluated. The calculated fuzzy risks for the examine…

Safety studies of a hydrogen refuelling station: Determination of the occurrence frequency of the accidental scenarios

At present, the hydrogen vehicles technology appears to have future Prospective for reduction in greenhouse gas emissions. Nevertheless, the development of such a technology requires appropriate infrastructures for production, Storage and refuelling stages in a refuelling station. This one presents safety challenges due to the hydrogen chemicophysical characteristics. So, to avoid hazards, it is necessary to implement safety practices that, if early adopted in the development of a fuelling station project, can allow very low impact, safety being incorporated in the project itself. However, a drawback is the not sufficient experience and the scarcity of the relevant data collection. To deepe…

A semi-empirical approach for predicting two-phase flow discharge through branches of various orientations connected to a horizontal main pipe

Abstract The subdivision of two-phase flow in branching conduits consisting of a large horizontal main pipe with upward, downward, or lateral branches of reduced diameter is of great interest in various technological fields. For example, these conduits are important in light-water nuclear reactors (LWRs) in the case of a small break loss-of-coolant accident (SBLOCA) in a leg of the reactor's primary coolant loops, as well as for breaks or valve malfunctions in a large pipeline. In these kinds of circumstances, the relevant phenomenology often involves phase stratification coupled with possible liquid entrainment or gas pool-through phenomena. Therefore, these phenomena were studied in depth…

Analysis of operator human errors in hydrogen refuelling stations: Comparison between human rate assessment techniques

Abstract The use of hydrogen as an energy carrier for road transport appears to be an optimal solution for the reduction of greenhouse gas emissions. Nevertheless, the development of this technology depends on the growth and diffusion of production, storage and refuelling infrastructures together with accurate risk analyses to appropriately design the safety and management systems used in these plants. Moreover, to improve safety standards, it is also important to focus attention on the estimation of hazards related to human factors, as this is one of the major causes leading to accidental events, especially in complex industrial technology. The paper reports a case study relevant to operat…

Analysis of Protected Accidental Transients in the EFIT Reactor With the RELAP5 Thermal-Hydraulic Code

The European Facility for Industrial Transmutation (EFIT) is aimed at demonstrating the feasibility of transmutation process through the Accelerator Driven System (ADS) route on an industrial scale. The conceptual design of this reactor of about 400 MW thermal power is under development in the frame of the European EUROTRANS Integrated Project of the EURATOM Sixth Framework Program (FP6). EFIT is a pool-type reactor cooled by forced circulation of lead in the primary system where the heat is removed by steam generators installed inside the reactor vessel. The reactor power is sustained by a spallation neutron source supplied by a proton beam impinging on a lead target at the core centre. A …

THERP and HEART integrated methodology for human error assessment

Medical errors are one of the leading causes of death and injury in radiation therapy administration as reported in the literature. This point out an overall deficiency in management allowing patient treatment in the absence of suitable quality assurance processes. Clinical records of major accidental exposure events in radiotherapy show that there is a combination of factors contributing to the accident such as deficient staff training, lack of independent checks, lack of quality control procedures, and absence of overall supervision. Another finding is that training generally addresses only normal situations and does not prepare radiotherapy staff for unusual situations, resulting in a la…

Modifiche al codice RELAP5 per l’analisi termofluidodinamica monofase delle perdite di carico in scambiatori di calore a tubi elicoidali

Rewetting of a hot vertical surface by liquid sprays

Hot surfaces rewetting interests several technological fields. A very important application is in nuclear reactors technology, where it governs the cooling of overheated fuel elements during hypothesized loss of coolant accidents (LOCAs). This phenomenon is also important in many normal processes and accidental situations taking place in conventional processes. For example when the integrity of metallic containers, filled by toxic or dangerous substances, is endangered by a hypothetical fire. The rewetting consists in the re-establishment of coolant in contact with metallic surfaces become dried due to high temperature. To this end cold liquid is injected on these surfaces via sprays or other …

ICONE19-43144 RELAP5 SIMULATION OF TWO-PHASE FLOW EXPERIMENTS IN VERTICAL HELICAL TUBES

Prediction of the heat exchange in MEGAPIE facility by using RELAP5 code

RPN safety analysis to reduce the risk of malpractices in high dose rate brachytherapy

A new fuzzy rule-based assessment model is proposed to evaluate the risk priority number in the Failure Mode, Effects, and Criticality Analysis (FMECA) method to rank component failures and human errors from the medical staff, leading to potential radiological over-exposure of patients during high-dose-rate brachytherapy treatment. The obtained results are relevant for a range of causes that have a reasonable probability of producing significant adverse outcomes. Thus, recommendations are provided for procedures and safety devices to reduce the occurrence of radiological over-exposure accidents. This method can solve the problems in conventional FMECA applications and improve the safety and…

Analisi di sicurezza e valutazione dell’errore umano nelle procedure di manutenzione del sistema di stoccaggio in un autobus a metano

Preliminary T/H and Transient Analyses for EFIT Reactor design

Le incertezze nell’Analisi di Rischio

Thermal-hydraulic analysis on the cooling system of the target in the SPES plant

RELAP5 Modification for CHEOPE Simulations

Risk analysis using fuzzy set theory of accidental exposure of medical staff during brachytherapy procedures

Using fuzzy set theory, this paper presents results from risk analyses that explore potential exposure of medical operators working in a high dose rate brachytherapy irradiation plant. In these analyses, the HEART methodology, a first generation method for human reliability analysis, has been employed to evaluate the probability of human error. This technique has been modified on the basis of fuzzy set concepts to take into account, more directly, the uncertainties of the so-called error-promoting factors on which the method is based. Moreover, with regard to some identified accident scenarios, fuzzy potential dose was also evaluated to estimate the relevant risk. The results also provide s…

Modifiche del Codice RELAP5 per lo Studio delle Perdite di Carico in Generatori di Vapore a Tubi Elicoidali Interessati da Flussi Bifase

Investigation of RELAP Capability to Simulate the LBE Cooling System Thermal-Hydraulic

The paper subject regards the validation of the RELAP5/Mod3.2.2B, the best estimate code modified to deal with fluids of interest for the XADS (eXperimental Accelerator Driven System), a Lead Bismuth Eutettic alloy (LBE) cooled ADS design set up at Ansaldo Industry. The validation will be made exploiting the experimental program carried out on support of XADS design and MEGAPIE experiment, at the ENEA Research Centre of Brasimone (Italy), making use of CHEOPE and CIRCE facilities. The comparison between experimental results and post test calculations allows the check ofthe code capability in simulating the 1Dym fluid-dynamic of heavy metals. In particular, CHEOPE tests have provided data fa…

MELCOR per lo Studio Integrale di Sequenze Incidentali su Reattori PWR da 900 MWe e valutazioni preliminari d'impatto a breve e medio raggio

Il presente documento è stato preparato nel corso della seconda annualità dell'AdP ENEA-MSE nell'ambito dell'obiettivo B-Task B_1 (Sviluppo di una Metodologia per Valutazioni di Sicurezza in Condizioni Incidentali o di Pre-Emergenza) della Linea Progettuale 1 (Sviluppo competenze scientifiche nel campo della sicurezza nucleare). Esso riporta i principali risultati della simulazione MELCOR di un transitorio del tipo “short term Station Blackout (SBO)” con possibile rottura dei tubi a U del GV (Steam Generator Tube Rupture - SGTR) indotta da stress termici e un lavoro preliminare di raccolta di informazioni sulle potenzialità presentate da alcune piattaforma di simulazione ad oggi utilizzate …

TRACE input model for SPES3 facility

Esposizione potenziale in impianti di irraggiamento: un’analisi mediante probabilità di tipo sfumato

Studies of thermalfluid-dynamic phenomenologies in high energy industrial systems during accidental transients

The TREEZZY2 Computer Code for Fault Tree and Event Tree Analyses with Fuzzy Probabilities

Studio della sicurezza di una stazione di rifornimento di idrogeno per autotrazione mediante l’uso integrato di tecniche di analisi di rischio

TREEZZY2, a Fuzzy Logic Computer Code for Fault Tree and Event Tree Analyses

In conventional approach to reliability analysis using logical trees methodologies, uncertainties in system components or basic events failure probabilities are approached by assuming probability distribution functions. However, data are often insufficient for statistical estimation, and therefore it is required to resort to approximate estimations. Moreover, complicate calculations are needed to propagate uncertainties up to the final results. In our work, in order to take account of the uncertainties in system failure probabilities, the methodology based on fuzzy sets theory is used both in fault tree and event tree analyses. This paper just presents our work in this issue, which resulted…

Thermalhydraulic analyses of overpower transients in the EFIT reactor

Qualifica di codici di calcolo dedicati alle analisi di sistema avanzati quando applicati nella simulazione di impianti a metallo liquido

Safety analysis in the system cyclotron-target unit of the LBE-Cooled XADS plant through an integrated use of FMEA, HAZOP and FAULT TREE methodologies

THERP and HEART integrated methodology for human error assessment

Abstract THERP and HEART integrated methodology is proposed to investigate accident scenarios that involve operator errors during high-dose-rate (HDR) treatments. The new approach has been modified on the basis of fuzzy set concept with the aim of prioritizing an exhaustive list of erroneous tasks that can lead to patient radiological overexposures. The results allow for the identification of human errors that are necessary to achieve a better understanding of health hazards in the radiotherapy treatment process, so that it can be properly monitored and appropriately managed.

Studi di sicurezza con metodologie ad albero di guasti riguardanti l’esposizione potenziale di un operatore in un reparto di brachiterapia

Analisi Mediante Il Codice TRACE Delle Principali Fenomenologie Caratterizzanti Il Transitorio Conseguente Ad Una Rottura A Ghigliottina Nella Linea DVI dell’Impianto Sperimentale SPES-3

FMECA Analyses of radiological over-exposure accident to patients in brachytherapy

This paper presents safety analyses of accidental events which can involve patient during High Dose Rate brachytherapy treatment in over-exposures. The study has been performed by using the well-known techniques FMECA modified by Fuzzy logic theory. Moreover, fuzzy HEART methodology was employed in order to evaluate human error probabilities for each treatment stage. The obtained results, aimed to obtain a list of the deviations with a reasonable probability to produce significant adverse outcomes, provided some recommendations for procedures and safety equipments to reduce the occurrence of radiological over-exposure accidents.

RELAP5 simulation of two-phase flow experiments in vertical helical tubes

In the framework of the studies concerning the thermalfluid dynamic phenomena in helicoidal pipes of the innovative nuclear reactor IRIS steam generators, the Department of Nuclear Engineering of the University of Palermo in collaboration with the Politecnico di Torino Department of Energetics has been engaged in a work aimed to adapt, by implementing new suitable models, RELAP5/mod3.2.2β code to simulate the thermalfluid-dynamics and geometries such as the ones involved in helicoidal pipes. In fact this code is based on one-dimensional thermal-hydraulic relationships and presents limitations to model complicated geometry such as helicoidal pipes. Therefore the code was improved with additi…

Esposizione potenziale dell’operatore in un impianto dotato di acceleratore: studio mediante l’uso di tecniche ad albero di guasto di tipo sfumato

Analyses of single- and two-phase flow pressure drops in helical pipes using a modified RELAP5 code

Abstract Thermal fluid dynamics analyses on single- and two-phase flows in helical pipes of steam generators to be used in Generation III and IV nuclear reactors have been performed. The study concerned with experimental activities as well code simulations carried out in the framework of a collaboration between the Department of Energetics of the Polytechnic of Torino and the Department of Energy of the University of Palermo. The goal was the validation of models implemented in Relap5/Mod3.2β thermal–hydraulic advanced code to simulate the hydrodynamic behaviour of helical pipe components in spite of the one-dimensional nature of the code. It is shown that much of the experimental data obta…

Decay Heat Removal and Transient Analysis in Accidental Conditions in the EFIT Reactor

The development of a conceptual design of an industrial-scale transmutation facility (EFIT) of several 100 MW thermal power based on accelerator-driven system (ADS) is addressed in the frame of the European EUROTRANS Integral Project. In normal operation, the core power of EFIT reactor is removed through steam generators by four secondary loops fed by water. A safety-related decay heat removal (DHR) system provided with four independent inherently safe loops is installed in the primary vessel to remove the decay heat by natural convection circulation under accidental conditions which are caused by a loss-of-heat sink (LOHS). In order to confirm the adequacy of the adopted solution for decay…

Modifiche del codice RELAP5/MOD3.2.b per lo studio delle perdite di carico e dello scambio termico in condotti elicoidali interessati da deflussi bifase: validazione attraverso gli esperimenti effettuati dal Politecnico di Milano presso l’impianto SIET di Piacenza

L’attività di ricerca svolta nell’ambito della linea progettuale LP2-B.2 del programma PAR 2008-09 (CERSE III) ha visto una prima fase in cui è stato ulteriormente sviluppato il lavoro svolto nel corso dei precedenti programmi CERSE [1, 2], riguardante la validazione del codice termoidraulico avanzato Relap5/Mod3.2.b, modificato per il calcolo delle cadute di pressione in tubi elicoidali interessati da deflussi monofase e bifase, ed una seconda fase che ha comportato l’implementazione di nuove procedure valide per lo studio dello scambio termico bifase in condotti elicoidali, in aggiunta a quelle relative al solo scambio termico monofase, in precedenza implementate. Per quanto riguarda ques…

Analisi di sicurezza mediante l’uso di tecniche ad alberi di guasto FUZZY dell’impianto nucleare dimostrativo XADS

Fuzzy risk analysis of a modern gamma-ray industrial irradiator

Fuzzy fault tree analyses were used to investigate accident scenarios that involve radiological exposure to operators working in industrial gamma-ray irradiation facilities. The HEART method, a first generation human reliability analysis method, was used to evaluate the probability of adverse human error in these analyses. This technique was modified on the basis of fuzzy set theory to more directly take into account the uncertainties in the error-promoting factors on which the methodology is based. Moreover, with regard to some identified accident scenarios, fuzzy radiological exposure risk, expressed in terms of potential annual death, was evaluated. The calculated fuzzy risks for the exa…

Education and Research in Nuclear Engineering and Radiological Protection at Nuclear Engineering Department of Palermo University

Thermal hydraulic analyses in the windowless target of an Accelerator Driven System

SAFETY ANALYSES OF POTENTIAL EXPOSURE IN MEDICAL IRRADIATION PLANTS BY FUZZY FAULT TREE

Valutazione della dose potenziale per alcuni scenari incidentali in un impianto HDR: uso di tecniche di tipo sfumato

Analisi di sicurezza mediante l’uso di tecniche ad albero di guasto di tipo sfumato riguardanti l’errata esposizione ad alto rateo di dose di un paziente in brachiterapia

Multiple failure accidental transients in the LBE-XADS

Analisi di sicurezza integrata e ricorsiva per l’impianto nucleare dimostrativo XADS

New Implementations in RELAP5 for Post-Test Analysis of the MEGAPIE Irradiation Phase

Predicting two-phase flow discharge through branches of various orientation connected to a horizontal main pipe

Fuzzy modelling of HEART methodology: application in safety analyses of accidental exposure in irradiation plants

The present paper refers to the obtained results by using Fuzzy Fault Tree analyses of accidental scenarios which entail the potential exposure of operators working in irradiation industrial plants. For these analyses the HEART methodology, a first generation of the Human Reliability Analysis method, has been employed to evaluate the probability of human erroneous actions. This technique has been modified by us on the basis of fuzzy set concept to more directly take into account the uncertainties of the so called error-promoting factors, on which the method is grounded. The results allow also to provide some recommendations on procedures and safety equipments to reduce the radiological expo…

Modifying RELAP5 code to deal with helical coiled ducts

Rewetting by liquid spray of a hot metallic wall

Risk assessment of component failure modes and human errors using a new FMECA approach: application in the safety analysis of HDR brachytherapy

Failure mode, effects and criticality analysis (FMECA) is a safety technique extensively used in many different industrial fields to identify and prevent potential failures. In the application of traditional FMECA, the risk priority number (RPN) is determined to rank the failure modes; however, the method has been criticised for having several weaknesses. Moreover, it is unable to adequately deal with human errors or negligence. In this paper, a new versatile fuzzy rule-based assessment model is proposed to evaluate the RPN index to rank both component failure and human error. The proposed methodology is applied to potential radiological over-exposure of patients during high-dose-rate brach…

Flowblockage failures in the EFIT reactor

Recent improvement of RELAP5 as numerical tool for interpretation of thermal-hydraulic experiments

Safety analysis in the LBE-Cooled XADS plant through an integrated use of HAZOP, FAULT TREE and thermalhydraulic transient analyses

A detailed description of possible accidental scenarios, with their frequency of occurrence and their consequences, taking into account both internal and external causes that might contribute to them, can be attained by using the most important risk analysis methodologies (HAZard and OPerability studies, HAZOP; Event Tree, ET; Fault Tree, FT; etc.). As it is known, the Fault Tree methodology is aimed at the evaluation of the frequency of an undesired accidental event (Top Event, TE), and is used to describe this one as a combination of primary events identified, for example, by a HAZOP analysis [1]. However, the classic HAZOP analysis, while allowing to perform an exhaustive study of the ex…

Dividing two-phase flow in branching conduits with large diameter horizontal main pipes and lateral branches

RELAP5-3D thermal hydraulic analysis of the target cooling system in the SPES experimental facility

The SPES (Selective Production of Exotic Species) experimental facility, under construction at the Italian National Institute of Nuclear Physics (INFN) Laboratories of Legnaro, Italy, is a second generation Isotope Separation On Line (ISOL) plant for advanced nuclear physic studies. The UCx target-ion source system works at temperature of about 2273 K, producing a high level of radiation (10^5 Sv/h), for this reason a careful risk analysis for the target chamber is among the major safety issues. In this paper, the obtained results of thermofluid-dynamics simulations of accidental transients in the SPES target cooling system are reported. The analysis, performed by using the RELAP5-3D 2.4.2 …

Thermalhydraulic analyses of overpower transients without proton beam trip in the XADS facility

Analisi di sicurezza di una stazione di rifornimento di idrogeno per autotrazione:uso delle tecniche FMEA e HAZOP

Studio con il codice RELAP5 delle perdite di carico e dello scambio termico in tubi elicoidali interessati da deflussi monofase

Verification of the RELAP5 code against the MEGAPIE irradiation experiment

RELAP5 simulations for CIRCE experiments

TREEZZY2, a Fuzzy Logic Computer Code for Fault Tree and Event Tree Analyses

In conventional approach to reliability analysis using logical trees methodologies, uncertainties in system components or basic events failure probabilities are approached by assuming probability distribution functions. However, data are often insufficient for statistical estimation, and therefore it is required to resort to approximate estimations. Moreover, complicate calculations are needed to propagate uncertainties up to the final results. In our work, in order to take account of the uncertainties in system failure probabilities, the methodology based on fuzzy sets theory is used both in fault tree and event tree analyses. This paper just presents our work in this issue, which resulted…

Risk analysis of the storage unit in a hydrogen refuelling station

Uso di formulazioni della metodologia cream per la trattazione dell’errore umano nella valutazione ad alberi di guasto della probabilita’ di esposizione di un operatore in un impianto di irraggiamento gamma