Hydrogenation, reactors rupture disks

The hydrogen gas from the chemical reaction increases the pressure within the vessel. When the pressure within the SG reaches a predetermined higher level, the rupture disks burst and the sodium within the SG drains rapidly into a sodium dump tank. For such large sodium/water reaction events, it is also necessary to seal off the reactor/SG system for the purpose of containment isolation. An SG isolation system (SGIS) is provided to terminate a sodium/water reaction (by rapidly removing the water from the SG) and to isolate the water side with safety-related isolation valves which serve a safety-grade barrier for the purpose of containment isolation. 

A well known example of an intrinsically unstable process, carried out in an adiabatic stirred reactor, is the high pressure polymerization of ethylene. The main source of instability is the low degree of conversion (0.2 - 0.3). When the temperature surpasses a certain value, the degree of conversion will go up rapidly, leading to a strong temperature increase. This will trigger the complete decomposition of the reaction mixture into carbon and hydrogen. Therefore this type of operation requires careful process control. In addition to this, these reactors are equipped wiUi "rupture disks". 

At 192 min (3 h 12 min) the PORV block valve was reopened in an attempt to control reactor coolant pressure. Opening the valve resulted in an increase in the valve outlet temperature, a limited pressure spike in the reactor coolant drain tank (rupture disk had previously burst at 15 min), an increase in reactor building pressure, and a pathway by which hydrogen radionuclides from the damaged core could reach the reactor building. 

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