Accidental contamination

The choice of tracer gas for the measurements is Kr-85 It has a long half-life so that it can be stored for application when needed. It is a noble gas which is chemically inactive giving a low radio toxicity as it is readily removed in case of accidental contamination. 

As a precaution against accidental contamination, product testing must be carried out under conditions of strict asepsis using, for example, a laminar airflow cabinet to provide a suitable environment (Chapter 22). 

Sterile pharmaceutical preparations must be tested for the presence of fungal and bacterial contamination before use (see Chapters 18 and 23). If the preparation contains an antibiotic, it must be removed or inactivated. Membrane filtration is the usual recommended method. However, this technique has certain disadvantages. Accidental contamination is a problem, as is the retention of the antibiotic on the filter and its subsequent liberation into the nutrient medium. 

Contains a small amount of a more volatile flammable liquid, e.g. due to deliberate or accidental contamination. 

Electrochemical reaction rates are also influenced by substances which, although not involved in the reaction, are readily adsorbed on the electrode surface (reaction products, accidental contaminants, or special additives). Most often this influence comes about when the foreign species I by adsorbing on the electrode partly block the surface, depress the adsorption of reactant species j, and thus lower the reaction rate. On a homogeneous surface and with adsorption following the Langmuir isotherm, a factor 10, will appear in the kinetic equation which is the surface fraction free of foreign species 1 ... 

The accidental contamination by trimethylamine of a container that contained ethylene oxide caused the cylinder to detonate eighteen hours after adding the... 

Accidental contamination of a tetrafluoroethylene gas supply system with iodine pentafluoride caused a violent explosion in the cylinders. Exothermic reaction of the limonene inhibitor with the contaminant present in the gas cylinders may have depleted the inhibitor and initiated explosive polymerisation. 

Accidental contamination by aqueous ammonia of an ethylene oxide feed tank containing 22 t caused violent polymerisation which ruptured the tank and led to a devastating vapour cloud explosion [1,2], The close similarity to other base-catalysed incidents was stressed [3],... 

Freeder, B. G. et al., J. Loss Prev. Process Ind., 1988, 1, 164-168 Accidental contamination of a 90 kg cylinder of ethylene oxide with a little sodium hydroxide solution led to explosive failure of the cylinder over 8 hours later [1], Based on later studies of the kinetics and heat release of the poly condensation reaction, it was estimated that after 8 hours and 1 min, some 12.7% of the oxide had condensed with an increase in temperature from 20 to 100°C. At this point the heat release rate was calculated to be 2.1 MJ/min, and 100 s later the temperature and heat release rate would be 160° and 1.67 MJ/s respectively, with 28% condensation. Complete reaction would have been attained some 16 s later at a temperature of 700°C [2], Precautions designed to prevent explosive polymerisation of ethylene oxide are discussed, including rigid exclusion of acids covalent halides, such as aluminium chloride, iron(III) chloride, tin(IV) chloride basic materials like alkali hydroxides, ammonia, amines, metallic potassium and catalytically active solids such as aluminium oxide, iron oxide, or rust [1] A comparative study of the runaway exothermic polymerisation of ethylene oxide and of propylene oxide by 10 wt% of solutions of sodium hydroxide of various concentrations has been done using ARC. Results below show onset temperatures/corrected adiabatic exotherm/maximum pressure attained and heat of polymerisation for the least (0.125 M) and most (1 M) concentrated alkali solutions used as catalysts. 

Accidental contamination of a large ethylene oxide feed-cylinder by reaction liquor containing trimethylamine caused the cylinder to explode 18 h later. Contamination was possible because of a faulty pressure gauge and suck-back of froth from above the liquid level [1], A similar incident had occurred previously [2],... 

Accidental contamination of lithium strip with anhydrous chromium trichloride or zirconium tetrachloride caused it to ignite and bum vigorously in the nitrogen atmosphere of a glove box. 

Accidental contamination of a metal scoop with flake sodium hydroxide, prior to its use with zinc dust, caused ignition of the latter [1]. A stiff paste prepared from zinc dust and 10% sodium hydroxide solution attains a temperature above 100°C after exposure to air for 15 min [2], The residue of zinc dust and sodium hydroxide solution from a lecture demonstration involving zinc plating a copper coin presents a high fire risk if discarded onto paper in a waste bin, ignition of the paper having occurred on many occasions. Dissolve the residue in dilute acid before flushing away with water [3],... 

Tennessee, 1974, 137Cs, from soil accidentally contaminated in 1944 Roots Usually -3700 DW Max. 111,000 DW 14... 

South Carolina reactor cooling impoundment accidentally contaminated in 1961-64 with 137Cs, 90Sr, and various transuranics samples collected September 1983-February 1984 137Cs ... 

A process storage tank contained 6500 gal of ethylene oxide. It was accidentally contaminated with ammonia. The tank ruptured and dispersed ethylene oxide into the air. A vapor cloud was formed and almost immediately exploded. It created an explosive force equivalent to 18 tons of TNT, as evidenced by the damage. The events happened so rapidly that personnel could not take appropriate cover. One person was killed and nine were injured property losses exceeded 16.5 million. 

Also at issue, is the EU s threshold for adventitious or accidental contamination. The EU Parliament recently lowered the Commission s proposed 1% threshold to. 5%, which the US claims will add significant costs, be difficult to comply with and effectively restrict trade (Larson, 2002b). The EU proposal would also require labeling for highly processed products that do not have a detectable presence of biotechnology (Larson, 2002b). 

NCRP, Management of Persons Accidentally Contaminated with Radionuclides, Report 65, National Council on Radiation Protection and Measurements, Bethesda, MD, 1980. 

In a brief review of chemical accidents caused by accidental contamination of process materials, attention is drawn to the much less frequent opposite effect of accidental decontamination (or purification) as a cause of accidents. Some examples of the effects arising from accidental loss or inactivation of stabilisers or antioxidants from reactive materials are given. 

Poisonous Fishes. Defined as fishes which, when ingested, cause a biotoxication in humans due to a toxic substance present in the fish. Fishes that may become accidentally contaminated by bacterial food pathogens are not included. 

Sediments in the Mississippi River were accidentally contaminated with a low-level radioactive waste material that leaked from a nuclear power plant on the river. Pore water concentrations of radioactive compounds were measured following the spill and found to be 10 g/m over a 2-mm depth. The water contamination was 30% radioactive cesium ( Cs), with a half-life of 30 years, and 70% radioactive cobalt ( °Co), with a half-life of 6 years. Objections by the local residents are preventing clean-up efforts because some professor at the local state university convinced them that dredging the sediments and placing them in a disposal facility downstream would expose the residents to still more radioactivity. The state has decided that the sediments should be capped with 10 cm of clay and needs a quick estimate of the diffusion of radioactive material through the clay cap (Figure E2.8.1). If the drinking water limit (10 g/m ) is reached at mid-depth in the cap, the state will increase its thickness. Will this occur ... 

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