Main Steam Safety Relief Valves in Nuclear （在核主蒸汽安全阀）.pdf

Main Steam Safety Relief Valves in Nuclear Power Plants with PWR 0 0 0 2 / 2 0 E 1 1 1 D F Introduction Apart from their use in pressurizer systems, Sempells VS99 medium controlled safety valves are employed primarily in steam circuits of both nuclear and conventional power plants. More than 200 of these valves have been installed in pressurised and boiling water reactors in Germany and Western Europe, some having been in operation for more than 25 years. Safety valves in a modern pressurized water reactor with a power of 1300 MW, for example, have a blow-out power of 2000 t/h at a saturated steam pressure of 86 bar. If a safety valve of this power opens very quickly, the acceleration of the steam produces considerable forces on the piping and their mounts. For large powers in particular, therefore, Sempell developed its VS99 K safety valve with damped opening (picture 1). Design The major design characteristics of the valve shown in picture 1 are the same to those of the Sempell VS99 valve which has already been described in connection with the volume compensation protection system. Body (1) and cover (2) have been forged and assembled using necked-down bolts (8), chambered wound gaskets (7), (11) and (12) serve as a seal to the outside. Cylinder (5) is centred on cover (2) and connected with bolts (9) and nuts (10). The clearance to the body borehole is dimensioned so that, on the one hand, nuts (10) on the body wall are protected from turning and, on the other hand, sufficient clearance remains between the body (1) and the cylinder (3) to allow easy disassembly. Should the