Piping accidents

The main pipe rupture accident is the most serious one for the loss of coolant accident of pool type sodium cooled Fast Breeder Reactor (FBR). To simulate this accident, a model is developed based on the OASIS code, which is a French fast reactor system safety analysis code. To abide by the strict accident analysis principles, the main pipe rupture accident is calculated for various position of the pipe. Accident sequence and key parameters, including the fuel cladding temperature of reactor, are obtained for each case. The calculation results show that the fuel cladding temperature is below the safety limitation and the coolant temperature is lower then the saturation temperature of sodium in all cases. 

Once the scenario has been identified, a source model is used to determine the quantitative effect of an accident. This includes either the release rate of material, if it is a continuous release, or the total amount of material released, if it is an instantaneous release. Eor instance, if the scenario is the mpture of a 10-cm pipe, the source model would describe the rate of flow of material from the broken pipe. 

Safety. A large inventory of radioactive fission products is present in any reactor fuel where the reactor has been operated for times on the order of months. In steady state, radioactive decay heat amounts to about 5% of fission heat, and continues after a reactor is shut down. If cooling is not provided, decay heat can melt fuel rods, causing release of the contents. Protection against a loss-of-coolant accident (LOCA), eg, a primary coolant pipe break, is required. Power reactors have an emergency core cooling system (ECCS) that comes into play upon initiation of a LOCA. 

Liquids can also exert pressure due to thermal expansion. Table 4.15 provides an indication of pressure increases due to temperature increases for selected common liquids in full containers or pipes. Serious accidents can arise unless the design of rigid plant items such as pipework takes into account the changes in volume of liquids with temperature fluctuation by the following or combinations thereof ... 

Provision of operating instructions and procedures. These should eliminate confusion and provide continuity on, e.g., shift changeover. EiTors in identification of valves, pumps, pipes, storage tanks, and the sequence in which they are to be operated is a common cause of accidents, e.g. on staff changeovers. 

External events are accident initiators that do not fit well into the central PSA structure used for "internal events." Some "external events" such as fire due to ignition of electrical wires, or flood from a ruptured service water pipe occur inside the plant. Others, such as earthquakes and tornados, occur outside of the plant. Either may cause failures in a plant like internal events. External initiators may cause multiple failures of independent equipment thereby preventing action of presumably redundant protection systems. For example, severe offsite flooding may fli 1 the pump room and disable cooling systems. An earthquake may impede evacuation of the nearby populace. These multiple effects must be considered in the analysis of the effects of external events. 

The type of equipment most frequently involved in accidents was Piping Systems (33%) at, 11 average los.s of 76,900,000 (Figure 7.1-5). The second most frequently involved type of equipment was tanks (15%) with an average loss of 61,900,000. While Reactors accounted for only 10% of the losses, but had the highest average loss of 151,800,000. 

The last batch of MIC, before the accident, was produced in the interval October 7-22, 1984. At the end of the campaign the E610 storage tank contained about 42 tons of MIC, and the E61 i storage tank contained about 20 tons. After which, MIC production was shut down, and parts of the plant were dismantled for maintenance. The flare tower was shut down to replace a piece of corroded pipe. 

On the night before and early morning of the accident, a series of human and technical errors caused the water for flushing pipes to pass through several open valves and flow into the MIC tank. The w ater and MIC reacted to produce a hot and highly pressurized gas, foam, and liquid, that... 

Other circumstances mitigating the accident were the hydrogen fluoride gas was hot and rose rapidly it was dissipated quickly by a brisk, dry wind only several small pipes were broken, so the leiik u as fairlv easily controlled. 

Risks were expressed as triplets . The first element of the triplet was found using accident records and a PHA. The databases used were MHIDAS (1992) (>5(XK1 accidents) and ACCIDATA (>1,500 mostly Brazil). The PHA was performed by personnel from REDUC (facility operator) and PRINCIPIA (the PSA vendor). About 170 basic initiating events (raptures of pipes, flanges, valves, spheres, pumps and human actions) were grouped into 12 initiators by equivalent diameter, pressure, flow type and rapture l(x ation. 

After the accident, demonstration cuts were made in the workshop. It was found that as the abrasive wheel broke through the pipe wall, a small flame occurred, and the pipe itself glowed dull red. 

This frame illustrates the valve lineup prior to the accident. About 1,500 gal of 55°F condensate had collected upstream of valve MSS-25, which was located at the dead-end of an 800-ft pipe and was the lowest point in the system. 

On chemical plants and oil refineries, steam, nitrogen, compressed air. lubricating oil, and other utility systems are responsible for a disproportionately large number of accidents. Flammable oils are recognized as a hazard, but services are given less attention. If the modification to the lubricating system had been systematically studied before it was made, as recommended in Chapter 2, a larger vent could have been installed, or a pipe-break and funnel could have been installed at the inlet to the sump. 

National Transportation Safety Board. 1972. Pipeline Accident Report, Phillips Pipe Line Company propane gas explosion, Franklin County, MO, December 9, 1970. National Transportation Safety Board, Washington, DC, Report No. NTSB-PAR-72-1. 

Measurement of performance. Quality Management requires that measures of performance be established for every activity. These measures include end-of-pipe measurement, such as amounts of material released into the environment or injury rates, and in-process measures of how efficiently you are managing, such as time to review safety improvement proposals or total resources expended on PSM. Each team should be required to identify potential performance measures for the processes they are developing and the activities these processes manage. Many of the end-of-pipe measures will already exist these should be critically examined to ensure that they truly measure performance and are not unduly influenced by other factors. For example, the number of accidents in a fleet of road vehicles is almost directly dependent on the number of miles driven with no improvement in performance, a reduction in miles driven would reduce the number of accidents. 

Some measures of PSM and ESH performance are easy to identify, establish and track. These include accident rates, effluent tonnages and composition and number of days lost to illness. Almost all of these traditional performance measures are end-of-pipe that is, they measure the output of the management system and allow corrective action only after a failure has occurred. The ideal measurement system identifies potential problems ahead of actual failure allowing corrective action to be taken. This requires using techniques such as audits and hazard assessments. 

End-of-pipe measures continue to be vitally important. The largest PSM and ESH management costs are accident and incident related. If you reduce the costs of managing PSM and ESH, yet accident and incident rates rise beyond any normal statistical variation, the new system is costing the company more. Near misses are a leading indicator for accidents and incidents and should not be neglected. 

Hazardous chemical spills may have adverse effects on natural water systems, tlie land enviromnent, and whole ecosystems, as well as tlie atmosphere. Major spills evolve from accidents (see Chapter 6) tliat somehow damage or rupture vessels, tank cars, or piping used to store, sliip, or transport liazardous materials. In such cases, the spills must be contained, cleaned up, and removed as quickly and effectively as possible. 

Davenport has listed more tlian 60 major leaks of flammable materials, most, of which resulted in serious fires or unconfined vapor cloud explosions (UVCEs)." Table 16.3.1 classifies tlie leaks by point of origin and shows that if transport containers are excluded, pipe failures accounted for more than lialf tlie accidents. The biggest cause of tliese failures lias been shown to be poor construction due to use of wrong specifications or failure to follow specifications established. 

Bromoethane forms the same organometallics, which are inflammable with aluminium, zinc and also magnesium. There was a very serious industrial accident that caused a warehouse to be completely destroyed, and this was explained by the effect of bromoethane on an aluminium pipe. Methylaluminium bromide formed and combusted in contact with air, causing the fire. A red cloud formed due to the bromoethane combustion (this was used as an extinguishing agent before being prohibited). 

Nitroglycerine can detonate in pipes of diameter down to approximately 5 mm. In nitroglycerine manufacture there is, therefore, an inherent danger of transmission of detonation from one manufacturing house to another in the series. Even a pipe which has been emptied of nitroglycerine can have on it a skin of the product sufficient to enable transmission of detonation from one end of the pipe to the other. To prevent the spread of an accident it is now usual to transfer nitroglycerine as a non-explosive emulsion in an excess of water. Such emulsion transfer is particularly convenient with the NAB process, as the emulsion transfer lines can also carry out the necessary process of washing and purification. 

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