Steam barrier design

Since competent manufacturers can accurately predict the susceptibility for the formation of the corrosive scale Ni3S2 for any gas analysis, it is possible to implement preventive measures. The preventive measure that is presently being used by Elliott and others is the use of a steam barrier. The principle of the steam barrier design is to inject steam into the inlet and exhaust chambers of the disc/blade area. The injection of steam into both these chambers creates a barrier of... 

The second unit in which a failure resulted in the mixing of water and sodium occurred in a superheater unit which was part of a steam generator with a per hour capacity of about 10 X 10 B.t.u. being tested at the MSA (8). This superheater, shown in Figure 6, was a tube and shell heat exchanger with sodium on the shell side and steam on the tube side. The unit was of double-barrier design with mercury as the third fluid. The third fluid was normally maintained at a pressure intermediate between the sodium and steam system pressures. 

The cooling lock has an internal column of 300 mL and is machined from stainless steel. An outer jacket allows for a variety of coolants. The steam generator is a 2-L autoclave. A Milton-Royal high pressure pump allows for the continuous addition of water to the hot generator, ir necessary. The product collector if a pyrex vessel approximately 8 inches in diameter and 5 inches deep. Separated gas passes to a brine displacement vessel for volume measurement. A number of electrical and mechanical overrides plus barriers are designed to prevent any injury to the operator as a result of accidental discharge from the reactor or steam vessel. In addition, the control panel is located in a separate room adjacent to the reactor. 

Based on the characteristics of inherent safety of the HTR-10 test reactor, no pressure-containing and leak-tight containment is designed The concrete compartments, which houses the reactor and the steam generator as well as other parts of the primary pressure boundary and which is preferably called as confinement, together with the accident ventilation system, serve as the last barrier to the radioactivity release into the environment During normal operation, the confinement is ventilated to be kept sub-atmospheric When the integrity of the... 

Passive protection a dnst loss of coolant accidents is, in some designs, provided by a second pressure vessel surrounding the reactor n essure vessel. This guard vessel ensures that the core is never uncovered to ensure that this second barrier is never breached, a reliable means of condensing steam should be provided. 

Special mention should be made to the special coupling among the shell, the tube sheet and the lower head of the steam generator, which allows the realisation of, also through this component, the double barrier enclosing the primary coolant (the shell of the steam generator is designed to withstand the total pressure of the primary coolant (72 bar)). 

Each steam line has two containment isolation valves, one inside and one outside the containment barrier. The isolation valves are spring-loaded pneumatic piston-operated globe valves designed to fail closed on loss of pneumatic pressure or loss of power to the pilot valves. Each valve has an air accumulator to assist in the closiue of the valve upon loss of the air supply, electrical power to the pilot valves, and failure of the loaded spring. Each valve has an independent position switch initiating a signal into the reactor protection system scram trip circuit when the valve closes. 

The PC control EOF is designed to provide a barrier to the uncontrolled release of fission products, contain and condense steam discharged through the safety relief valves and primary cooling system breaks, shield personnel from radiation emitted by the reactor, and provide a protected environment for key equipment important to safety. Entry into this procedure is required at a suppression pool temperature above the limiting condition for operation (LCO), a drywell temperature above LCO, a containment temperature above LCO, a drywell pressure above the high pressure scram set point, a suppression pool water level above maximum level LCO, a suppression pool water level below minimum level LCO, and an SC hydrogen concentration above the alarm set point. 

The assessment of steam leakage is presented in Chapter 3.6 of Reference 4.4. Systems designated essential for safe shutdown in the event of pipe rupture, where in proximity to pipe work that has not been assessed to demonstrate leak before break (LBB), are protected from the effects of steam leakage by distance and protective barriers, which are appropriately... 

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