A risk-based approach to land-use planning

The Seveso II-Directive requires that the objectives of preventing major accidents and limiting their consequences be taken into account by the Member States in their land-use policies and/or other relevant policies. This is to be achieved by ensuring adequate distances between industrial establishments and residential areas, areas of public use and areas of particular natural sensitivity or interest. A risk-based framework implemented in a computer program is presented which enables one to calculate adequate distances. The criterion used is a limit on the individual risk of death. The method is a simplified risk analysis which represents the plant, whose characteristics are normally unknown at the stage of land-use planning, by generic frequencies of release for process units and storage tanks. Their number depends on the size of the site to be allotted. The procedure is capable of addressing the siting of new establishments and, with due regard to the simplifications used, modifications to and new developments in the vicinity of existing establishments. Given the numerous assumptions, which have to be made, the framework represents a convention.

Safety and security issues relating to low capacity storage of AN-based fertilizers

Motivated by both the Toulouse explosion, and a series of recent unexpected handling and storage accidents in well-developed countries, the safety issues associated with the storage of fertilizer grades of ammonium nitrate (AN) are considered with a focus on low storage capacity premises. Such facilities are numerous and, in large agricultural countries, include thousands of end-users and hundreds of small distributors. The strong oxidative (sometimes explosive) properties of products containing significant amounts of AN have led to a long history of major accidents including mass explosions in large storage units and pre 1950s, to mass explosions in ships. A major breakthrough in safety was achieved in the 1950s, with the promotion - amongst other improvements - of better anti-caking agents. Although modern AN fertilizers complying with current standards are not considered as explosive material per se, the latent risk of accidental detonation under specific conditions remains a real issue, and from a scientific point of view, cannot be completely ruled out-as dramatically demonstrated by the Toulouse disaster in France. The new insight provided here is derived from: (1) a literature review on hazardous properties of AN and AN-based fertilizers; (2) a review of accidents focusing more particularly on the reporting of recent new cases involving relatively small quantities of previously 'thought safe' products; (3) an examination of both the relevant regulatory framework and the level of hazard control achieved; (4) appropriate discussions of the economical, technical and organizational factors that could lead to some underestimation of the risk compared to large scale storage facilities. In terms of research requirements, the complex potential scenario 'mass explosion following a fire' requires further attention, as does the role and properties of molten ammonium nitrate, which could be the precursor for such an event to occur. Beyond research needs, reinforced legislative control by the authorities and further promotion of safe storage practices must be encouraged by the industry for end-users particularly. Such users have inherently the highest potential for undesirable situations, due both to the nature of their activities and also a possible lack of awareness of the real danger.

Clinical review: communication and logistics in the response to the 1998 terrorist bombing in Omagh, Northern Ireland

The Omagh bombing in August 1998 produced many of the problems documented in other major incidents. An initial imbalance between the demand and supply of clinical resources at the local hospital, poor information due to telecommunication problems, the need to triage victims and the need to transport the most severely injured significant distances were the most serious issues. The Royal Group Hospitals Trust (RGHT) received 30 severely injured secondary transfers over a 5-hour period, which stressed the hospital's systems even with the presence of extra staff that arrived voluntarily before the hospital's major incident plan was activated. Many patients were transferred to the RGHT by helicopter, but much of the time the gained advantage was lost due to lack of a helipad within the RGHT site. Identifying patients and tracking them through the hospital system was problematic. While the major incident plan ensured that communication with the relatives and the media was effective and timely, communication between the key clinical and managerial staff was hampered by the need to be mobile and by the limitations of the internal telephone system. The use of mobile anaesthetic teams helped maintain the flow of patients between the Emergency Department and radiology, operating theatres or the intensive care unit (ICU). The mobile anaesthetic teams were also responsible for efficient and timely resupply of the Emergency Department, which worked well. In the days that followed many victims required further surgical procedures. Coordination of the multidisciplinary teams required for many of these procedures was difficult. Although only seven patients required admission to adult general intensive care, no ICU beds were available for other admissions over the following 5 days. A total of 165 days of adult ICU treatment were required for the victims of the bombing.

Evacuation of a Rural Community Hospital: Lessons Learned From an Unplanned Event

A credible bomb threat forced the complete evacuation of a rural community hospital. An Incident Command System was implemented, and all 46 patients were temporarily transported and maintained at 2 local sites. They were returned to the hospital approximately 24 hours later. Only one patient experienced a complication possibly associated with the evacuation. This article discusses pertinent strategies and considerations involved in the planning and execution of a rural hospital evacuation. It further highlights the role of the emergency department medical and nursing staff throughout the evacuation process.

Classifying threats with a 14-MeV neutron interrogation system

SeaPODDS (Sea Portable Drug Detection System) is a non-intrusive tool for detecting concealed threats in hidden compartments of maritime vessels. This system consists of an electronic neutron generator, a gamma-ray detector, a data acquisition computer, and a laptop computer user-interface. Although initially developed to detect narcotics, recent algorithm developments have shown that the system is capable of correctly classifying a threat into one of four distinct categories: narcotic, explosive, chemical weapon, or radiological dispersion device (RDD). Detection of narcotics, explosives, and chemical weapons is based on gamma-ray signatures unique to the chemical elements. Elements are identified by their characteristic prompt gamma-rays induced by fast and thermal neutrons. Detection of RDD is accomplished by detecting gamma-rays emitted by common radioisotopes and nuclear reactor fission products. The algorithm phenomenology for classifying threats into the proper categories is presented here.

Exposure of a liquefied gas container to an external fire

In liquefied gas, bulk-storage facilities and plants, the separation distances between storage tanks and between a tank and a line of adjoining property that can be built are governed by local regulations and/or codes (e.g. National Fire Protection Association (NFPA) 58, 2004). Separation distance requirements have been in the NFPA 58 Code for over 60 years; however, no scientific foundations (either theoretical or experimental) are available for the specified distances. Even though the liquefied petroleum gas (LPG) industry has operated safely over the years, there is a question as to whether the code-specified distances provide sufficient safety to LPG-storage tanks, when they are exposed to large external fires. A radiation heat-transfer-based model is presented in this paper. The temporal variation of the vapor-wetted tank-wall temperature is calculated when exposed to thermal radiation from an external, non-impinging, large, 30.5 m (100 ft) diameter, highly radiative, hydrocarbon fuel (pool) fire located at a specified distance. Structural steel wall of a pressurized, liquefied gas container (such as the ASME LP-Gas tank) begins to lose its strength, when the wall temperature approaches a critical temperature, 810 K (1000 degrees F). LP-Gas tank walls reaching close to this temperature will be a cause for major concern because of increased potential for tank failure, which could result in catastrophic consequences. Results from the model for exposure of different size ASME (LP-Gas) containers to a hydrocarbon pool fire of 30.5 m (100 ft) in diameter, located with its base edge at the separation distances specified by NFPA 58 [NFPA 58, Liquefied Petroleum Gas Code, Table 6.3.1, 2004 ed., National Fire Protection Association, Quincy, MA, 2004] indicate that the vapor-wetted wall temperature of the containers never reach the critical temperature under common wind conditions (0, 5 and 10 m/s), with the flame tilting towards the tank. This indicates that the separation distances specified in the code are adequate for non-impingement type of fires. The model can be used to test the efficacy of other similar codes and regulations for other materials.

Dust explosion hazard of pulverized fuel carry-over

This paper reports the results of experiments done to examine the explosibility of the waste products (fly ash and bottom ash) from pulverized fuels (coal and petroleum coke). Tests were conducted for the fly and bottom ashes alone and also for selected fly ashes blended with the fuels. The explosion parameters of interest were explosion pressure and rate of pressure rise. The fly ashes showed no propensity to explode, whereas one of the bottom ashes did show limited explosibility. Both findings can be explained with reference to the volatile matter content of the ashes. Admixture of either coal or petroleum coke with fly ash resulted in explosible mixtures at volatile contents in the range of 7-13%, with the value being dependent on the composition of the mixture components and their particle sizes.

Increasing the capability of MNBRP for the detection of anti-personnel landmines

Monte Carlo simulations were used to show that even very small explosives (<100g) can be detected by monoenergetic neutron backscattering with resonance penetration (MNBRP) at a depth well beyond 30 cm when time slicing is used for background suppression. At the present state of technology no other nuclear method appears to have a comparable sensitivity or penetration capability. This method has been successfully tested experimentally at a depth of 16.5 cm. A substantial simplification of the detection procedure could be achieved either by taking advantage of the time shadow rather than the geometric shadow or by applying neutron threshold detectors. Using a threshold detector could simplify the application, too.

A migrating pacemaker

A deceased 79 year old man with a permanent cardiac pacemaker was due to be cremated, but the pacemaker generator was not detectable by palpation. A hand held metal detector to locate the device so that it could be extracted before cremation.

Standoff detection of high explosive materials at 50 meters in ambient light conditions using a small Raman instrument

We have designed and demonstrated a standoff Raman system for detecting high explosive materials at distances up to 50 meters in ambient light conditions. In the system, light is collected using an 8-in. Schmidt-Cassegrain telescope fiber-coupled to an f/1.8 spectrograph with a gated intensified charge-coupled device (ICCD) detector. A frequency-doubled Nd : YAG (532 nm) pulsed (10 Hz) laser is used as the excitation source for measuring remote spectra of samples containing up to 8% explosive materials. The explosives RDX, TNT, and PETN as well as nitrate- and chlorate-containing materials were used to evaluate the performance of the system with samples placed at distances of 27 and 50 meters. Laser power studies were performed to determine the effects of laser heating and photodegradation on the samples. Raman signal levels were found to increase linearly with increasing laser energy up to approximately 3 x 10(6) W/cm2 for all samples except TNT, which showed some evidence of photo- or thermal degradation at higher laser power densities. Detector gate width studies showed that Raman spectra could be acquired in high levels of ambient light using a 10 microsecond gate width.

Flammability of gas mixtures. Part 2: influence of inert gases

Ternary systems, which contain flammable gas, inert gas and air, were studied in order to give the user an evaluation of the ISO 10156 calculation method for the flammability of gas mixtures. While in Part 1 of this article the fire potential of flammable gases was the focal point, the influence of inert gases on the flammability of gas mixtures was studied in Part 2. The inerting capacity of an inert gas is expressed by the dimensionless K value, the so-called "coefficient of nitrogen equivalency". The experimental determination of K values is demonstrated by using explosion diagrams. The objective of this study was to compare the estimated results, given by ISO 10156, with measurements of explosion ranges based on the German standard DIN 51649-1, given by CERN and CHEMSAFE. The comparison shows that ISO 10156, Table 1, supplies conservative K values, which can be regarded as safe in all cases. Nevertheless, in a number of cases ISO underestimates the inerting capacity, so that non-flammable gas mixtures are considered flammable.

Flammability of gas mixtures. Part 1: fire potential

International and European dangerous substances and dangerous goods regulations refer to the standard ISO 10156 (1996). This standard includes a test method and a calculation procedure for the determination of the flammability of gases and gas mixtures in air. The substance indices for the calculation, the so called "Tci values", which characterise the fire potential, are provided as well. These ISO Tci values are derived from explosion diagrams of older literature sources which do not take into account the test method and the test apparatus. However, since the explosion limits are influenced by apparatus parameters, the Tci values and lower explosion limits, given by the ISO tables, are inconsistent with those measured according to the test method of the same standard. In consequence, applying the ISO Tci values can result in wrong classifications. In this paper internationally accepted explosion limit test methods were evaluated and Tci values were derived from explosion diagrams. Therefore, an "open vessel" method with flame propagation criterion was favoured. These values were compared with the Tci values listed in ISO 10156. In most cases, significant deviations were found. A detailed study about the influence of inert gases on flammability is the objective of Part 2.

Professor Joseph Warren Horton (1889-1967): biological engineer

Joseph Warren Horton graduated with a degree in electrical engineering from the Massachusetts Institute of Technology (MIT) in 1914. He became involved in the early development of electrical measurement devices, televised image transmission, and the detection of underwater sound transmission. In the mid-1930s he was appointed the first leader of the newly created Department of Biological Engineering at MIT and in this position he made major contributions to the application of physics to human physiology, in particular by increasing the safety of explosive inhalational anaesthetic agents.

Dental laser safety

The purpose of this article is to inform the reader about dental laser safety and to suggest practical guidelines. The laser safety officer plays a major role, ensuring that the instrument is used safely and effectively. With adequate precautions and proper training, dental lasers can be used to deliver excellent care.

Explosion caused by flashing liquid in a process vessel

An explosion occurred at a polyvinyl chloride (PVC) resin manufacturing plant. The explosion originated at an atmospheric storage vessel when it received a slurry discharge from a suspension polymerization reactor. The pressure rise caused by the uncontrolled flashing of superheated liquid vinyl chloride resulted in the complete separation of the roof from the tank shell. A cloud of vinyl chloride vapor was released and ignited resulting in a vapor cloud explosion. The accident caused significant property damage but no serious injuries. An investigation was conducted to determine the causes of the accident. It was discovered that the facility had experienced numerous overpressure incidents in the atmospheric storage vessels used as slurry tanks. Many of these incidents resulted in modest structural damage to these slurry tanks. It was determined by Exponent that the rapid flashing of residual liquid monomer present in the product slurry stream caused the earlier overpressure incidents. The facility operator did not adequately investigate or document these prior overpressure events nor did it communicate their findings to the operating personnel. Thus, the hazard of flashing liquid vinyl chloride was not recognized. The overpressure protection for the slurry tanks was based on a combination of a venting system and a safety instrumentation system (SIS). The investigation determined that neither the venting system nor the SIS was adequate to protect the slurry tank from the worst credible overpressure scenario. Fundamentally, this is because the performance objectives of the venting system and SIS were not clearly defined and did not protect against the worst credible overpressure scenario. The lessons learned from this accident include: use prior incident data for recognizing process hazards; identify targets vulnerable to these hazards; explicitly define performance objectives for safeguards to protect against the worst credible overpressure scenario. The ultimate lesson learned here is that a liquid trapped under pressure above its normal boiling point represents an overpressure hazard. To avoid exceeding the design pressure of the receiving vessel, the superheated liquid must be discharged slowly so that the vapor production rate caused by flashing does not exceed the venting rate of the receiving vessel.

Use of ARC in screening for explosive properties

The use of a modified version of the accelerating rate calorimeter (ARC) as a screening method for the explosive properties of chemicals has been investigated. Definitive tests for classifying energetic chemicals for transportation are provided by UN Recommendations [United Nations, Recommendations on the Transport of Dangerous Goods, Manual of Tests and Criteria, third revised ed., 1999]. Recently, decomposition energy screening criteria were added to the recommendations, however, maximum rate of pressure rise in a closed vessel may provide a less conservative, more accurate screen. Pressure rate data for organic chemicals are compared to the UN test results. Preliminary screens are suggested to minimize the need for the larger scale, more expensive, and time-consuming UN-recommended testing. Results from this method are compared to those from published mini-autoclave data [M.W. Whitmore, G.P. Baker, J. Loss Prev. Process Ind. 12 (1999) 207-216]. Further work is planned to expand the range of chemical classes tested and to specify acceptable, conservative screening criteria.

Chemical reactivity assessments in R&D

The evaluation of reactive chemical hazards at the pilot and manufacturing scale, using laboratory testing, is increasingly used and has been well documented. However, reactive chemical hazard evaluation at the R&D scale presents special challenges. The typical hazard testing program requires a significant amount of sample, often takes time (>3 days) to complete, and is can be quite costly. On the other hand, the synthesis of new molecules in the R&D environment often produces only a few grams, occurs quickly (<2 days), may only happen once and many synthetic reactions may be carried out before a suitable candidate for scale-up will be found. However, with each new synthesis there is the risk of injury, possibly serious or fatal, caused by unexpected and maybe violent reactivity. While it may not be possible at the R&D stage of product development to define the critical limits of temperature, pressure, concentration, and safe dosing rates of processes it is possible to identify the potential hazards of the planned synthesis. This paper describes a staged approach for chemical reactivity hazard evaluation and assessment applicable to an R&D environment. We will describe these initial phases of the R&D hazard evaluation process that rely on only data that can be obtained from the open literature. We will also indicate how the need for additional assessments can be determined from this initial hazard review.

Plastic mine detecting radar system using complex-valued self-organizing map that deals with multiple-frequency interferometric images

Ground penetrating radars (GPR's) have been often applied to underground object imaging. However, conventional radar systems do not work sufficiently to detect anti-personnel plastic landmines. We propose a novel radar imaging system, which processes adaptively interferometric front-end data obtained at multiple-frequency points. The system deals with interferometric images using complex-valued self-organizing map (C-SOM). We demonstrate a successful visualization of a plastic mine buried near the ground surface.

Mine clearance injuries in South Croatia

OBJECTIVE

The purpose of this retrospective study was to describe and analyze casualties in mine-clearance operations in South Croatia from 1991 to 1995. During the war in Croatia, the laying of mines by both sides was largely unplanned, without mapping or documentation, making demining, an already expensive, complicated task, even more dangerous.

METHODS

The study comprised all those injured in mine-clearance operations treated at Clinical Hospital Split. The type of mines used, the mechanism of the incident, and the location and severity of injury according to the Abbreviated Injury Scale and the Injury Severity Score were analyzed.

RESULTS

In a 5-year period, 160 pyrotechnicians of the Croatian Army performed demining in Southern Croatia. In 29 incidents, 53 deminers were injured. The degree of injury according to the Abbreviated Injury Scale was 2.85 +/- 0.6 and Injury Severity Score grade was 19.68 +/- 8.57. Two of the injured died.

CONCLUSION

To find and remove approximately 2 million mines laid in Croatia will take at least 10 years and 2,000 to 3,000 specialized personnel. Unfortunately, the results of the study demonstrate that a significant number of deminers will suffer grave injuries or die in the process.