Nitrogen leaks

This procedure is then repeated again. Distillation of the combined residues using a nitrogen leak (Note 16) yields 54 g. of the product as a yellowoil, b.p. 66-68° (1.1 mm.) (Note 17). The distillation residue, when washed through a short acidic alumina column with light petroleum ether and the solvent evaporated, yields an additional 5 g. of product total yield 59-68 g., 67-78% (Notes 18, 19). 

This oily liquid is distilled under reduced pressure and a nitrogen leak. Because of occasional blockages in the liquid-nitrogen traps it is advisable to use two traps in parallel followed by a third in series, permitting one trap to be emptied without losing continuity in the distillation. The fraction boiling 128-136° at 2.5 torr is collected. This is a yellow liquid when hot but on cooling is a red viscous substance. Yield 114 g (65%). 

Up to the discovery in October 1978 of a very small sodium leak estimated at 10 g/year across the primary vessel, RAPSODIE did not experience any safety problems and provided considerable fuel data (maximum BU 26 %). Later in 1982 a larger nitrogen leak appeared across the double wall of the reactor (fig. 2.1). The area of this leak was estimated at 0,5 cm2. Because the sodium double containment was not assured, it was decided to close the reactor. Nevertheless is was possible to carry out a series of end-of-life tests just before closing down the reactor. The reactor was finally closed on April 15 , 1983. 

Because of Hquid helium s uniquely low temperature and small heat of vaporization, containers for its storage and transportation must be exceedingly weU insulated. Some containers are insulated with only a fairly thick layer of very efficient insulation, but containers with the least heat leak use an inexpensive sacrificial cryogenic Hquid, usually Hquid nitrogen, to shield thermally the Hquid helium contents. 

Most small Hquid helium containers are unpressurized heat leak slowly bods away the Hquid, and the vapor is vented to the atmosphere. To prevent plugging of the vent lines with solidified air, check valves of some sort are included in the vent system. Containers used for air transportation are equipped with automatic venting valves that maintain a constant absolute pressure with the helium container in order to prevent Hquid flash losses at the lower pressures of flight altitudes and to prevent the inhalation of air as the pressure increases during the aircraft s descent. Improved super insulation has removed the need for Hquid nitrogen shielding from almost all small containers. 

Other developments include the attainment of high permeabiUty at cryogenic temperatures (23) for shielding appHcations inside Hquid nitrogen or helium chambers, and temperature stabiHty of near room temperature (24) which is requited in earth-leak transformers. 

After catalyst charging and the flow vs. RPM measurement is done, the reactor should be closed and flushed out with nitrogen while the impeller runs, until O2 drops below a few tenths of a percent. Then a static pressure and leak test should be made by turning off the forward pressure controller and the flow controller. If an observable drop of pressure occurs within 15 minutes, all joints and connections should be checked for leaks and fixed before progressing any fijither. 

With all leaks stopped, and the reactor under test pressure with nitrogen, set the nitrogen pressure regulator to the lowest pressure on the controller, but above 0.3 atmosphere or 5 psig. Now open the flow controller and set the N2 flow to 66 mL/s, equivalent to 10.5 mols/hr rate, to start the flow. Also start heating the unit. 

The increasing number of atomic reactors used for power generation has been questioned from several environmental points of view. A modern atomic plant, as shown in Fig. 28-3, appears to be relatively pollution free compared to the more familiar fossil fuel-fired plant, which emits carbon monoxide and carbon dioxide, oxides of nitrogen and sulfur, hydrocarbons, and fly ash. However, waste and spent-fuel disposal problems may offset the apparent advantages. These problems (along with steam generator leaks) caused the plant shown in Fig. 28-3 to close permanently in 199T. 

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