Plug temperature

This wax can accumulate on fuel filter media and can lead to plugging of small orifices and lines. This plugging temperature can be measured and is commonly referred to as the filter plugging temperature. Testing methods utilized to predict the filter plugging temperature and the low-temperature flow properties of distillate fuel are listed in TABLE 4-5. 

When a hydrate plug occurs in a pipeline at temperatures above the ice point, the three conditions (sufficient temperature, pressure, and composition) exist for hydrate formation. When hydrates form, flow is blocked so that the plug temperature rapidly decreases to the surroundings temperature at the pipeline pressure. 

From the temperature build-up, the operator observed a plugging temperature rise and therefore an increase in the impurities... 

In addition, plugging temperature measurements did not follow the temperature decrease expected by the experts, the operator therefore decided to stop the reactor on July 3... 

Stable growth of the plugging temperature was detected after 325°C value had been reached. Further temperature increase resulted in several times higher rate of the plugging temperature growth. During the first half of the day of December 1, ingress... 

Impurities content measurement system operated on the periodical basis, so the first measurements of hydrogen content and plugging temperature were made respectively 4 hours and 2.5 hours later. Content increase values for hydrogen, nitrogen and helium were respectively 0.22 vol.% (against usual value of 2 ... 

The performance of reactor systems, sodium systems, control rod drive mechanisms and other safety related systems and auxiliary system were generally satisfactory. The primary and secondary sodium purity was maintained below the plugging temperature of 105 C. The four sodium pumps and Aeir drives are operating well and have logged 83,293 h, 70,615 h, 88,878 h 69,201 h. 

Reactor sodium generally would be maintained at a plugging temperature near 250°F to minimize corrosion ( 10 ppm oxygen). 

Volume of mesh region in cold trap (m ) Maximum permissible impurity concentration (primary) (ppm) Maximum acceptable plugging temperature in primary circuit (s) (°C)... 

Pump vibrating Low liquid level Suction line plugged Temperature rise in suction line... 

November. The impurity burden in the primary circuit could be monitored through the plugging temperature of coolant within the cold trap. When clean-up began this was 225 C but reduced steadily to below 170 C by the end of the year, when the primary circuit was temperature cycled up to 420 C and then back to 310 C. This caused the plugging temperature to rise to 180 C, but a further phase of clean-up which reduced the plugging temperature to 150 C was completed by the end of January 1992. 

Purification of the sodium in the dump tanks via the primary and secondary purification systems began in late September and December 1984, respectively. At the start of the measurements, the plugging temperatures were around 200 C, and it was possible to lower them to 130-120X within a short time. 

In the primary system the plugging temperature increased with the system temperature. A value of 200°C was measured for about 2 weeks, but it was then possible to lower it to 160 C and subsequently to 120°C. The hydrogen content in the cover gas of the primary system was reduced from 5000 to approximately 600 vpm by way of continued purification of the sodium. 

The conclusion of these investigations was that approximately 1000 vpm of H2 in the inert gas plenum would not present any serious problem (actual value at that time 350 vpm H2). This corresponded to a moisture penetration-rate of about 400 g/day. The plugging temperature range from 120 to 1S0 C spedfied for continuous operation corresponded to much more than this ingress rate at a a adequately available cold trap capacity. This meant that it could easily be controlled by cold trap operation. The same was true for the Na-cooled spent fuel storage vessel. 

The sodium can be dumped to a dump tank by opening fast-acting valves in a drain line. The drain line has to be permanently trace-heated to a tonperature which will prevent solidification not only of pure sodium but of sodium which is highly contaminated with reaction products. The plugging temperature may be 300°C or more, and to ensure an unimpeded dump the drain line has to be kept above this temperature all the time. 

---