Plant safety features

The Flixborough nylon plant accident in the UK (1974) was caused by an open-air explosion of a flammable gas released into the air. It killed the 28 plant employees present and caused extensive property damage in the surrounding area. The failure to perform a full technical assessment of a modification was given as the main cause of the event. The Seveso pesticide plant accident in Italy (1976) is well known for the dangerous release of dioxin due to poor plant safety features and to the underestimation of the possibility of a runaway reaction. The Bhopal incident in India (1984), at another pesticide plant, killed an estimated 4000 (although the total number is still unknown). This disaster was attributed to too large an inventory of toxic substances and to very poor staff attention to the operability of safety features. 

An earthquake of this magnitude may never have been experienced (and may never occur) at the site, but it deteimines the maximum vibratory ground motion for which plant safety features are designed to remain functional. At this level other plant features might be damaged, but the plant could be safely shut down. 

The population around every research reactor has to be protected adequately. To achieve this, evaluations should be made of the adequacy of plant safety features for the given population distribution and of the emergency planning feasibility. 

The development of computer capabiUties in hardware and software, related instmmentation and control, and telecommunication technology represent an opportunity for improvement in safety (see COMPUTER TECHNOLOGY). Plant operators can be provided with a variety of user-friendly diagnostic aids to assist in plant operations and incipient failure detection. Communications can be more rapid and dependable. The safety control systems can be made even more rehable and maintenance-free. Moreover, passive safety features to provide emergency cooling for both the reactor system and the containment building are being developed. 

A process industry, a refinery, a petrochemical, a fertilizer plant or a povser station are installations that can be classilled as critical. They cannot afford a breakdown during normal operation and would prefer to incorporate more safety features into the drive motors, even if these are expensive. These features can be one or more of the following. 

Discuss why the EPZ should be independent of plant size, safety features, demography and meteorology. 

Function event trees include primarily the engineered safety features of the plant, but other systems provide necessary support functions. For example, electric power system failure amid reduce the effectiveness of the RCS heat-removal function after a transient or small UJ( A. Therefore, EP should be included among the systems that perform this safety function. Siipfiort systems such as component-cooling water and electric power do not perform safety functions directly. However, they significantly contribute to the unavailability of a system or group of systems that perform safety functions. It is necessary, therefore, to identify support systems for each frontline ssstcm and include them in the system analysis. 

The preceding overviewed the operation and engineered safety features of current and advanced LWRs. Before preceding to describe how PSA is performed on nuclear power plants, two accidents are described that have profoundly affected the industiy... 

Individual plants, with extra safety features, may exceed the Safety Goals. The fue plants analyzed in NUREG-1150 meet or exceed the Safety Goals. This approach is contained in the Regulatory Analysis Guidelines (NUREG/CR-0058). 

Answer The only reason I can think of for making the EPZ independent of plant size, safety features, demography and meteorology is the convenience of emergency planners. Such would take no consideration for the hazard a plant poses it would favor hazardous activity and penalize safe activity. 

Lubrication plays a vital role in the operation of industrial plant. For example, in a heavy rolling mill the lubrication system, though mostly out of sight in the oil cellar, may have a capacity of many thousands of gallons and exceed in bulk the mill itself. Lubrication systems of this size and complexity are usually fully automatic, with many interlocks and other safety features. Even with the smallest machines, automatic lubrication is becoming more popular. Where an automatic system would be impracticable or... 

L.F. Albright C. Hansen, Eds, Industrial and Laboratory Nitrations , ACS Symposium Series 22, ACS, Washington, DC (1976). Excellent modern review. Ten chapters emphasize various aspects of the chemistry and mechanism of nitrations, including oxidation and ipso-nitration side reactions. Six chapters discuss the chemistry and physical transfer steps between phases. Eight chapters discuss plant operation-improvements, safety features, and new operations. The final chapter is devoted to vapor phase nitrations... 

When new plants are constructed or when modifications are needed in existing plants, detailed process designs are required. These designs must include special safety features to protect the system and operating personnel. The following case histories emphasize the importance of these special safety design features. 

This chapter gives an overview of the chlor-alkali industry in Australia and examines the background to the decision to replace the mercury cell plants. It then describes the new plants, their technical and safety features and the process used to arrive at the selection of the technology supplier. 

The design of most process plants relies on redundant safety features or layers of protection, such that multiple layers must fail before a serious incident occurs. Barrier analysis ) (also called Hazard-Barrier-Target Analysis, HBTA) can assist the identification of causal factors by identifying which safety feature(s) failed to function as desired and allowed the sequence of events to occur. These safety features or barriers are anything that is used to protect a system or person from a hazard including both physical and administrative layers of protection. The concepts of the hazard-barrier-target theory of incident causation are encompassed in this tool. (See Chapter 3.)... 

There are slight but acceptable differences in density and viscosity the higher flash point is a beneficial safety feature and the absence of sulfur in plant oils is the reason for the excellent SO emission profile of biodiesel. 

Fig. 35. Sectional view of the 600 MWe pressurized water reactor (PWR) expected to be operational by 1995. Considered the PWR of the future, the plant is designed for a minimum useful life span of 60 years and features numerous economic and safety features, including passive systems for ultimate protection. (Joint project of Westinghou.se, the Electric Power Research Institute, and the (J.S. Department of Energy)...

Bhopal exhibits several features of maladministration of chemical industry familiar to many who work in it on other continents. Construction of a fine chemical plant on a green field site soon causes local planners to regard the surrounding area as suitable for cheap high-density housing. As Trevor Kletz has reiterated in numerous books, add-on safety features, of which there were many, are a menace. If multiple, any one will be turned off as soon as it causes trouble or expense, and reliance be placed on the others which may be ill-designed and will, in any case, be later turned off in full confidence that the first is still working. 

Safety considerations are an inseparable part of the development of a chemical process and the design and operation of a chemical plant. While risk management and safety features can be added on to a plant design or to an operating plant, safety is most reliably and robustly ensured by developing inherently safer processes. 

Safety features at a nuclear power plant include automatic shutdown of the fission process by insertion of control rods, emergency water cooling for the cote in case of pipeline breakage, and a concrete containment shell. It is impossible for a reactor to have a nuclear explosion because the fuel enrichment in a reactor is intentionally limited to about 3% uranium-235, while almost 100% pure uranium-235 is required for a bomb. The worst accident at a PWR would be a steam explosion, which could contaminate the inside of the containment shell. 

The high cost of constructing a modem nuclear power plant— three to four billion dollars, in the U.S.— reflects in part the wide range of safety features needed to protect against various possible mishaps, especially those which could release to the environment any of the plant s inventory of radioactive substances. (Small special-purpose reactors, such as those used to power nuclear submarines or aircraft carriers, have different costs and technical features from the large, land-based reactors used to supply electrical grids.) Some of those features are incorporated into the reactor core itself. Eor example, all of the fuel in a reactor is sealed in a protective coating... 

---