Gigliola Spadoni

The ARIPAR project: analysis of the major accident risks connected with industrial and transportation activities in the Ravenna area

Abstract The paper describes the ARIPAR project aimed at the assessment of the major accident risks connected with storage, process and transportation of dangerous substances in the densely populated Ravenna area in Italy, which includes a large complex of chemical and petrochemical plants and minor industries, essentially distributed around an important commercial port. Large quantities of dangerous goods are involved in various transportation forms connected with the industrial and commercial activity of the port. The project started by making a complete inventory of fixed installations and transportation activities capable of provoking major fire, explosion and toxic release events; then relevant accident scenarios were developed for the single hazard sources; probabilities were assigned to the events and consequences were evaluated; finally iso-risk contours and F-N diagrams were evaluated both for the single sources and for the overall area. This required the development of a particular methodology for analysis of area risk and of associated software packages which allowed examination of the relative importance of the different activities and typologies of materials involved. The methodological approach and the results have proved to be very useful for the priority-ranking of risk mitigating interventions and physical planning in a complex area.

Development of a framework for the risk assessment of Na-Tech accidental events

Abstract Natural events impacting on chemical and process plants may cause severe accidents, triggering the release of relevant quantities of hazardous substances. The present study focused on the development of the tools needed to build up a general framework allowing the extension of quantitative risk assessment procedure to include the analysis of the industrial accidents caused by natural events. Specific methods and models were developed to allow the quantitative assessment of risk caused by two categories of “Na-Tech” accidents: accidents triggered by earthquakes and accidents triggered by floods. The approach allows the identification of the different damage modes expected for process equipment and of the accidental scenarios that may be triggered. The damage models developed allow the calculation of the damage probability of equipment items due to the natural events. A specific methodology was issued to take into account the consequences of the possible contemporary failure of several process units due to the impact of the natural event. The procedure allows the calculation of the overall individual and societal risk indexes including the multiple-failure scenarios caused by the impact of natural events. The overall methodology was applied to the analysis of specific case studies.

Through ARIPAR-GIS the Quantified Area Risk Analysis Supports Land-Use Planning Activities.

The paper first summarises the main aspects of the ARIPAR methodology whose steps can be applied to quantify the impact on a territory of major accident risks due to processing, storing and transporting dangerous substances. Then the capabilities of the new decision support tool ARIPAR-GIS, implementing the mentioned procedure, are described, together with its main features and types of results. These are clearly shown through a short description of the updated ARIPAR study (reference year 1994), in which the impact of changes due to industrial and transportation dynamics on the Ravenna territory in Italy were evaluated. The brief explanation of how results have been used by local administrations offers the opportunity to discuss about advantages of the quantitative area risk analysis tool in supporting activities of risk management, risk control and land-use planning.

Assessment of domino effect: state of the art and research needs

High-impact low-probability (HILP) accident scenarios in industrial sites are raising a growing concern. Domino effect was responsible of several catastrophic accidents that affected the chemical and process industry, as well as critical infrastructures for energy as oil refineries. However, there is still a poor agreement on assessment procedures to address escalation hazard resulting in domino scenarios. The present study presents a review of the work done in the last 30 years in the field, and a critical analysis of available tools and knowledge gaps concerning domino effect assessment. The analysis of scientific publications concerning domino effect in the process industry resulted in a database of more than 60 documents, addressing three main issues: past accident analysis, models for equipment damage, risk assessment and safety management of domino scenarios. The methods, models and tools developed make now possible the quantitative assessment of domino scenarios in risk analysis and in safety management of industrial sites. Nevertheless, a number of open points still remain, where existing tools may be improved and uncertainty may be reduced.

A numerical procedure for assessing risks from road transport of dangerous substances

This paper describes a general procedure developed to evaluate individual and societal risk connected with transport of dangerous materials to and from factories. The procedure, which can be extended to rail and pipeline transport with minor changes, is applied to road transport of toxic or flammable substances such as ammonia, chlorine, LPG and gasoline. Typical vehicle accidents are identified and characterized regarding the probability of occurrence and the rate and duration of the release, and a consequence analysis is performed for each accident and physical effect distribution obtained. The vulnerabilities and the unit risk of the tanker are then calculated and the movement of the point risk source (the vehicle) on the route is accounted for without further calculations but simply by an accurate translation procedure. The expressions useful for evaluation of individual and societal risks are reported and discussed, focusing attention on modelling of population distribution. A condensed discussion is also given on criteria which could be adopted to judge risk acceptability. The procedure has been implemented in a computer program and test results are used to underline the main features of the calculation method.

Rigorous and simplified approach to the modelling of continuous photoreactors

Abstract Photochemical reactions where the absorption of radiant energy occurs by the reacting species are considered. In this case the radiant energy balance equation can not be decoupled from the mass balance of the reacting species and a highly non linear integro-differential problem arises. Mathematical difficulties have been usually bypassed by modelling the radiation field on the basis of simplified models of questionable physical reliability. A rigorous modelling of the radiation field has not yet been considered for such a class of photochemical processes. An approach based on a rigorous modelling is therefore presented here, the solution being obtained through a transient approach. Results are compared with those obtained on the basis of simplified models in order to investigate the range of the significant parameters where such simple models, which are less computer-time demanding, can be conveniently used.

The modelling of pool vaporization

Abstract This paper describes a mathematical model which calculates the time dependencies of the flow rate and composition of the vapour emerging from a pool. A large variety of accidental cases can be covered: continuous or instantaneous spills, on confined or unconfined ground, ideal or non-ideal liquid mixtures in boiling or evaporating conditions. The boiling, when present, is modelled through an equation system comprising the Rachford-Rice relation and the energy balance of the pool, which is assumed to be well-mixed. In the case of a volatile pool, interfacial mass rates are determined taking into account the Stefan flux, and the thermal resistance inside the liquid phase is also considered. In all situations, the energy balance includes the contribution of ground, sun and air. Known experimental data have been used to validate the model.

The role of a reflecting boundary in improving the operation of an annular photoreactor

Abstract The influence of a cylindrical reflector on-a photochemical reaction occurring in an annular photoreactor has been investigated for both batch and continuous operations of the reactor. Absorption of radiant energy has been assumed by the reacting species itself and for each of the operating modes both the extreme conditions of mixing have been considered. Results show that a reflecting wall can be effective in enhancing the conversion only when the optical thickness m (based on the initial conditions and on the inlet) is neither too small nor too large, since in these two cases absorption and reflection, respectively, are negligible anyway. In any case conversion has been found to increase when mixing within the reactor is improved.

Quantitative Assessment of Risk Caused by Domino Accidents

The complexity of domino scenarios represented a considerable obstacle to the quantitative assessment of risk posed by escalation events. In the present chapter, the state of the art concerning quantitative approaches proposed for the assessment of risk caused by domino accidents is summarized. A procedure for the quantitative risk assessment of domino accidents, suitable for the calculation of individual and societal risk indexes, is outlined. Alternative approaches proposed for the quantitative assessment of domino effects, based on Bayesian techniques and Monte Carlo simulations, are also described.

ARIPAR-GIS, TRAT, OPTIPATH, EHHRA-GIS

From time in all industrialised countries attention is focused on the risks due to major accidents in storage, production and transportation of dangerous chemicals. In Italy too, and specifically at the University of Bologna, relevant work has been performed in the field of risk analysis. The chief aim of the researches done in the past years has been the development of detailed techniques for the calculation of specific risk measures, implemented in user-friendly software codes. In this paper the main features of these tools will be presented, particularly highlighting the application field of each of them and the support they can give to decision-makers in risk management.