Cold trap safety

Two 4 1 cylindrical glass(QVF) vessels with stainless steel end plates, serve as reservoirs(Figure 1) for surfactant solution(B) and water(9). Facility is available to evacuate these vessels as required by means of a rotary vacuum pump with glass cold trap in line to minimise water vapour. Another pipeline permits supply of pure nitrogen, or other gas, at low pressure, to the vessels, to provide a blanket, as desired. Proper operation and safety from over pressure is ensured by a pressure relief valve(10 in Figure 1) and the pressure gauge(P in Figure 1). 

Provided the vacuum pump exhaust is appropriately vented and suitable caution is observed in cleaning out the cold trap, the VDP parylene process has an inherently low potential for operator contact with hazardous chemicals. Before using the process chemicals, operators must read and understand the current Material Safety Data Sheets, which are available from the manufacturers. 

Gas cylinders must be chained securely to the wall or laboratory bench (see pp. 644-646). Procedure B Work on a vacuum system requires preliminary review of procedures and careful execution in order to avoid damage to the apparatus and possible injury from broken glass in addition, the liquid nitrogen used for cold traps must be handled properly (see Appendix C). Safety glasses must be worn. 

Solid iodine is corrosive to the skin and also stains badly. Handle the I2 crystals with a spatula or tweezers. If a laser is used as the excitation source, safety goggles must be worn, since accidental exposure to a laser beam can cause serious eye damage. Care should also be taken in the use of the vacuum system and hquid nitrogen cold trap while preparing the ceU. 

Two very different kinds of pump fluids have been employed in diffusion pumps. For many years, mercuiy diffusion pumps, were used in small laboratory-bench glass vacuum systems. Mercury pumps are now seldom used owing to the health hazards associated with mercury and the high probability of contamination of the vacuum system with mercury unless a cold trap is used (the vapor pressure of mercury at room temperature is —1.5 mTorr). The oil diffusion pump eliminates the safety hazard and can serve for both small glass and larger metal vacuum systems. 

Redundant 28 cfm vacuum pumps located in the Zone. 1 filter room of the MER, shown in Figure 2.5-10, evacuate a 80-gallon (10.7-cubic feet) tank to supply system vacuum. The pumps are configured to automatically start to maintain system vacuum at a prescribed level. The exhaust from the pumps is routed into the Zone 1 exhaust upstream of the Zone 1 charcoal filters. Two-inch welded stainless steel piping is routed from the vacuum tank in the MER through the overhead in Rooms 112 and 111 into the Zone 2A canyon. In the canyon, the vacuum line is routed to a cold trap that will condense radioactive effluents that are drawn into the vacuum system. Two-inch welded stainless steel tubing is used to route process vacuum to each SCB. While the pumps themselves are not identified as important to safety, the routing of the pump exhaust to the Zone 1 exhaust is so identified, because it assures appropriate filtration of the effluent in the event that hazardous constituents are drawn into the system. 

An integral primary system layout is employed (Fig. 12.4), ie, reactor core, variable frequency submersible coolant pumps, intermediate heat exchanges, safety system heat exchangers, and cold trap filters. The reactor vessel is enclosed in a guard vessel. There are no auxiliary sodium systems in the primary circuit. The reactor core consists of fuel assemblies, boron shield assemblies, and absorber rods. The central part of the core consists of wrap-spaced hexagonal fuel assemblies and cells with absorber rods. The spent fuel is stored in the reactor vessel for up to 2 years, which facilitates spent fuel cooling and eliminates the need for spent fuel storage casks. Assemblies with boron carbide are placed behind the spent fuel to protect the reactor vessel. 

Schlenk line, 25-mL Schlenk flask, dry ice/acetone cooling bath, syringe, solvent cold trap, filter funnel, magnetic stirrer, safety glasses, laboratory coat, and protective gloves. 

The technique of the filtration of hot solutions has already been described in Section 11,28. The filtration of cold solutions will now be considered this operation is usually carried out when it is desired to separate a crystalline solid from the mother liquor in which it is suspended. When substantial quantities of a solid are to be handled, a Buchner funnel of convenient size is employed. The ordinary Buchner fimnel (Fig. 11,1, 7, a) consists of a cylindrical porcelain funnel carrying a fixed, flat, perforated porcelain plate. It is fitted by means of a rubber stopper or a good cork into the neck of a thick-walled filtering flask (also termed filter flask, Buchner flask or suction flask) (Fig. 11,1, 7, c), which is connected by means of thick-walled rubber tubing (rubber pressure tubing) to a similar flask or safety bottle, and the latter is attached by rubber pressure tubing to a filter pump the safety bottle or trap is essential since a sudden fall in water pressure may result in the water sucking back. The use of suction renders rapid filtration possihle... 

A 3-1. reaction vessel f is fitted with a mechanical stirrer, a gas inlet tube, and a Dewar cold-finger Dry Ice condenser, which leads to a safety trap and mineral oil bubbler. The... 

The PAN was isolated from the numerous side products by gas chromatography on preparatorysized columns and collected by cryogenic trapping. The PAN was then placed in large air canisters, diluted with zero air, and stored in a cold room for future use. Safety precautions are required with this method, because explosive accidents have been reported. The cause of the explosions is believed to be condensation of PANs in vacuum or pressure gauge systems. Like all nitrates, the peroxy nitrate PAN has explosive potential, and care must be taken when handling PAN on metal surfaces. The Stephens synthetic approach illustrated by Reaction 19.7 to Reaction 19.11 was quite successful, and a number of publications on the toxicity of PAN and its chemical and physical properties resulted from the use of the scheme. ... 

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