The reactor coolant system experiences temperature changes during normal operation and following fault conditions which cause the volume of the coolant to increase or decrease.That in turn affects the pressure. If the pressure rose unchecked,the design limits of the pressure circuit might be exceeded, or alternatively a reduction could cause boiling in the system.The purpose of the pressure control system of which the pressuriser is the major component is to maintain the pressure within prescribed limits during normal operation and in fault conditions to prevent prevent design limits being exceeded.
The pressuriser is a vertical, cylindrical vessel with hemispherical top and bottom heads,constructed of carbon steel with austenitic stainless steel cladding on all su***ces exposed to the reactor coolant.At16.1m high and2.1m internal diameter it has a volume of 51m3 which is about one eighth of the total reactor coolant system volume.
The steam space in the pressuriser acts as a buffer which limits the magnitude of the pressure change due to a coolant volume change and so facilitates control of the pressure which is effected by the pressuriser heaters and sprays. If the reactor coolant pressure needs to be increased, electrical immersion heaters within the pressuriser are automatically switched on increasing the quantity of steam and consequently increasing the pressure. If the pressure needs to be decreased, its heater power is reduced, followed,if necessary,by an increase in spray flow. This additional cool water spray causes a net condensation of the steam and consequently decreases the pressure.自己顶[em05]
发表于 2010-9-13 06:58:47