Quantitative risk assessment on fire and explosion impacts for nuclear power plants (original) (raw)
Related papers
Nuclear Engineering and Design, 2019
The International Atomic Energy Agency emphasizes on the safety assessment of fires involved by the crash of a large commercial aircraft into a nuclear power plant. In the guideline, it requires that a total load of aviation fuel that causes damage to exterior plants' components should be included when performing the initial stages of the nuclear plant site evaluation process and over the entire lifetime of the plant operation. In this study, the effects of jet fuel and hydrogen-induced external explosion on a nuclear power plant was investigated and analyzed. A turbulence model based on Reynolds-averaged Navier-Stokes CFD solver, called FLACS, was used to determine the explosion parameters within the plant vicinity. The simulation results of key explosion parameters for butane explosion show a deflagrative overpressure of 0.27 bar and impulse load of 0.015 bar•s at some preselected position. An elevated local temperature of about 2030 K is recorded for this fuel. Hydrogen explosion causes a maximum overpressure of 0.37 bar, and a maximum positive pressure impulse load of 0.022 bar•s at the exterior walls of building structures. From the findings, it showed that building obstacles have a substantial influence on the evolution of fireball and overpressure propagation. The computed overpressure and impulsive loadings observed are capable of causing substantial structural damages and vulnerabilities. A significantly elevated flame temperature recorded would have a harmful effect on the safety function of structures, systems and components (SSCs) that are needed to execute reactor shutdown. The findings of this study may be used to revisit the safety evaluation of a nuclear power plant (NPP) site with regards to the risks and consequences associated with external explosion due to aircraft impact. It is also useful in designing the layout of the NPP and site placement of relevant items important to safety.
EPJ Web of Conferences, 2017
This paper deals with the assessment of external explosion, resulting from accidental release of jet fuel from the large commercial airliner in the nuclear power plant (NPP). The study used three widely prediction methods such as Trinitrotoluene (TNT), multi energy (TNO) and Baker-strehow (BST) to determine the unconfined vapour cloud explosion (UVCE) overpressure within the distances of 100-1400 m from the first impact location. The containment building was taken as the reference position. The fatalities of persons and damage of structures was estimated using probit methodology. Analysis of the results shows that both reactor building and control-room will be highly damaged with risk consequences and probability, depending on the assumed position of the crash. The structures at the radial distance of 600 m may suffer major structural damage with probability ranging from 25 to 100%. The minor structural damage was observed throughout the bounds of the plant complex. The people working within 250 m radius may get affected with different fatality ranging from 28 to 100%. The findings of this study is valuable to evaluate the safety improvement needed on the NPP site and on the risk and consequences associated with the hydrocarbon fuel release/fires due to external hazards.
Vulnerability Analysis of a Nuclear Power Plant Considering Detonations of Explosive Devices
Journal of Nuclear Science and Technology, 2006
The needs for vulnerability analyses picked up the pace after the military threats to a nuclear power plant in the year 1991 and after the 9/11 events in 2001. The methodology which was proposed for complex assessment of possible consequences following a deliberate damage, shortly after the year 1991 is here further developed to correspond to requests for further studies identified after the events 9/11. The new methodology integrates phenomenological models of the cause of damage, material strength and injuries of human beings with nuclear power plant models used in probabilistic safety assessment. The damage source studied is an explosion of a device brought to the location by land transport. The description of the method and its results are only illustrative and not very detailed in order that the results can not be used for malicious purposes. A straightforward example analyzing the response of a simplified process facility to a ground explosion outside the building is shown, although the methodology was tested also on a power plant. The results indicate that sizable explosions are required to inflict any damage to the reinforced concrete walls. Much larger explosions are needed to break the equipment behind such walls. The performed analysis shows that the facility can be even better secured at relatively low costs.
Dynamic vulnerability assessment of process plants with respect to vapor cloud explosions
Reliability Engineering & System Safety, 2020
Vapor cloud explosion (VCE) accidents in recent years such as the Buncefield accident in 2005 indicate that VCEs in process plants may lead to unpredicted overpressures, resulting in catastrophic disasters. Although a lot of attempts have been done to assess VCEs in process plants, little attention has been paid to the spatial-temporal evolution of VCEs. This study, therefore, aims to develop a dynamic methodology based on discrete dynamic event tree to assess the likelihood of VCEs and the vulnerability of installations. The developed methodology consists of six steps: (i) identification of hazardous installations and potential loss of containment (LOC), (ii) analysis of vapor cloud dispersion, (iii) identification and characterization of ignition sources, (iv) explosion frequency and delayed time assessment using the dynamic event tree, (v) overpressure calculation by the Multi-Energy method and (vi) damage assessment based on probit models. This methodology considers the time dependencies in vapor cloud dispersion and in the uncertainty of delayed ignitions. Application of the methodology to a case study shows that the methodology can reflect the characteristics of large VCEs and avoid underestimating the consequences. Besides, this study indicates that ignition control may be regarded as a delay measure, effective emergency actions are needed for preventing VCEs.
Post-Accident Analysis of Vapour Cloud Explosions in Fuel Storage Areas
Process Safety and Environmental Protection, 1999
A Vapour cloud explosion which occurred in a large fuel storage area close to the harbour of Naples (Italy) was analysed by different methods. Useful 'experimental data' were obtained by the post-accident damage analysis (minimum overpressure experienced by different items) and by the seismograms recorded at different stations at the time of explosion (explosion duration and intensity).
Advanced Engineering Informatics, 2020
A detailed Loss of Coolant Accident (LOCA) analysis in an AP1000 NPP was performed, followed by a definition of the vulnerability analysis principles, and analysis of blast loads and fragments impact created by a nearby explosion. The AP1000 NPP performs excellently to small-break LOCA due to in-structure shock, with the 10 CFR 50.46 Acceptance Criteria fully accomplished. Impulsive dynamic loads resulting from blast waves and fragments impact of GBU-28 (Guided Bomb Unit) were considered for a nearby explosion. We model the structure and the main reactor components using the MSC/Dytran code to obtain accurate internal acceleration levels at critical points. We account for the appropriate blast wave interaction with the soil and the soil interaction with the containment structure, rather than using empirical formulas. The model includes the shielding structure with its concrete base, the support structures for the reactor, the steam generators, and the pressurizer. The combined effect of bomb fragmentation and blast loading was also considered using a cylindrical fragmentation model and the blast model of Kingery-Bulmash, assuming a hemispherical charge. A comprehensive risk assessment methodology composed of four phases was developed. The methodology is comprised of: (I) System analysis, (II) Hazard analysis, (III) Damage assessment, and (IV) Risk analysis of the in-structure shock consequences. Using seismic fragility curves for analysis of the expected failure modes according to explosion events faced difficulties since no published data was found. Adjustments to these fragility curves were made using median acceleration limits on components designed to withstand airplane crash, together with standard deviations taken from the given earthquake fragility tables. The findings reveal that the probabilities of failure of the reactor coolant system components resulting from a GBU-28 nearby hit, namely the pressurizer, the cooling pumps, and valves are quite high (greater than 1•10 − 4).
Journal of research in health sciences, 2013
Background: New technologies using hazardous materials usually have certain risks. It is more serious when the technology is supposed to be applied in a large scale and become widely used by many people. The objective of this paper was to evaluate the risk of vapor cloud explosion in a hydrogen production process. Methods: Potential hazards were identified using the conventional hazard identification method (HAZID). The frequency of the proposed scenarios was estimated from statistical data and existing records. The PHAST professional software was applied for consequence modeling. Both individual and societal risks were evaluated. This cross-sectional study was conducted from June 2010 to December 2011 in a Hydrogen Production Plant in Tehran. Results: The full bore rupture in heat exchanger had the highest harm effect distance. The full bore rupture in desulphurization reactor had the highest (57% of total) individual risk. Full bore rupture in heat exchanger was the highest contributor to social risk. It carried 64% & 66.7% of total risk in day and night respectively. Conclusions: For the sake of safety, mitigation measures should be implemented on heat exchanger, reformer and hydrogen purification absorbers. The main proposed risk reductive measures included; the increasing of installed equipment elevation, the application of smaller vessels and pipes.
Industrial & Engineering Chemistry Research, 2012
Maintaining the process industry, including power plants, has become crucial to our way of life. The process industry, however, involves large quantities of hazardous substances that when spilt may present a threat to cause an explosion, a sustained fire, or a toxic cloud. These potential threats to life, structures, and the environment can be balanced by a variety of measures and ultimately by sufficient space. The central problem in spatial planning and licensing of plants containing substantial amounts of hazardous substances or planning transportation routes of these substances is to make decisions about safe distances in an environment of conflicting interests and large uncertainties, which are sometimes accompanied by emotions and "strong" perceptions. The uncertainties are due to incomplete knowledge about what can go wrong, how wrong it can go, and how likely it can go wrong. Improvements are sought in accordance with the International Risk Governance Council framework, learning from experiences elsewhere, maintaining robustness, but where required taking account of case specifics, including safety measures, improved models, and data and stakeholder outreach. Separate judgment of severity of consequences including injuries and other damage, and of likelihood categorized in probability classes accounts to some extent for uncertainty. Where possible the system of analysis shall be kept simple and affordable. Simplicity presumes, however, detailed knowledge of the mechanisms.
2020
Within its 2050 energy plan, Israel examines the demographic implications of a Nuclear Power Plant (NPP) in Shivta Rogem site in the Negev. NPP would have a great contribution to the diversity and robustness of energy sources in Israel. A Small Modular Reactor (SMR) is designated to be safer than existing NPPs and will have better resistance to external hazards due to inherent passive safety features. This study develops a risk assessment methodology for a Nuclear Power Plant (NPP), in particular, SMR, to withstand a large conventional warhead explosion (GBU-28). The methodology comprises: hydro-dynamic simulations, validation of the dynamic simulations using numerical analysis compared to the simulations, risk analysis and damage assessment given the reference scenario of a detonation of a GBU-28 inside the underground water pool of a NuScale SMR. Discrete fragility curves were developed to evaluate the capacity of the SMR critical components. The overall probability of failure was...
Vapor cloud explosions (VCE) cause considerable hazard in the chemical and petrochemical industries. They generate damaging levels of overpressure; the potential risk for human injury or death, damage to buildings and associated critical equipment becomes a concern. Predicting the possible consequences associated to vapor cloud explosions is important to ensure the safe design of existing and new installations. The accuracy of the assessments of such explosions is improved by carrying out experiments and by using theoretical models. To assess explosion hazards and to ultimately design safer structures several modeling approaches have been developed in order to estimate the air blast parameters at any given distance from a possible explosion source. Estimation of the overpressures that are generated from vapor cloud explosions is typically done via either simplified (empirical) models, phenomenological models or sophisticated computational fluid dynamics (CFD) models. This study includes a brief discussion on vapor cloud explosions and the prediction methods. The focus of this paper is on two of the most frequently used simplified prediction methods; the TNO Multi-energy (ME) model and the Baker-Strehlow-Tang (BST) model. The present study investigates the differences between the two methods and evaluates them in terms of resulting structural response and damage vulnerability caused by an explosion.