Steam Generator Blowdown System

Reactor coolant pump seal water injection system Steam generator blowdown system Sampling system... 

The steam generator blowdown system also ineludes a reeireulation-drain pump for use during operating modes when the steam generator pressure is low. This pump enables the steam generator blowdown system to fulfil the following additional funetions ... 

The radiation monitors associated witii the steam generator blowdown system provide a means of recognising when the secondary side becomes radioactively contaminated, an indication of a steam generator tube mpture. The blowdown flow and the ion exchange waste stream (brine) flow are both continuously monitored for radioactivity. If such radioactivity is detected, the liquid radwaste system is aligned to process the blowdown and ion-exchange waste effluent. If radioactivity should exceed a preset level, the blowdown flow control valves and the isolation valves would automatically close. 

The following design requirements of the steam generator blowdown system support safe operation of the plant under normal conditions ... 

The four steam generator blowdown system isolation valves must close automatically in response to high blowdown system temperature or pressure, or low steam generator water levels, or actuation of the passive residual heat removal heat exchanger, or high blowdown system radiation level, or on receipt of a contaimnent isolation signal. 

The four steam generator blowdown system isolation valves close automatically (Section 10.4.8.2.1 of Reference 6.1) in response to any of the following ... 

Spanish NPPs with extensive degradation phenomena in the steam generators have in operation a detection system, based on the monitoring of the short-lived N-16, installed in the steam lines. This system has been introduced into the Technical Specifications. The previous method of leak measurements, based on the monitoring of the steam generators blowdown, is used to confirm the N-16 readings. 

Steam generator blowdown radiation monitors. The presence of radioactive material in the steam generator blowdown indicates a leak between the primary and secondary side of die steam generator. The monitor initiates an alarm in the main control room, initiates closure of the steam generator blowdown containment isolation and flow control valves and diverts flow to the liquid radwaste system. 

Secondary System. The water quality specifications for the feedwater and blowdown water in a recirculating steam generator (RSG) and the ... 

The deaerated treated boiler feedwater then enters the boiler. Evaporation takes place in the boiler and the steam generated is fed to the steam system. Solids not removed by the boiler feedwater treatment build up in the boiler, along with products of corrosion. These are removed from the boiler by taking a blowdown (purge) from the boiler. The steam from the boiler goes to the... 

An increase in radioactivity indicated by condenser air removal system monitors, and blowdown system monitors will reveal reactor coolant leakage through steam generators tubes to the secondary side. Routine analysis of steam generator secondary water samples will also indicate increasing leakage of reactor coolant into the secondary system. 

The chemistry of the feedwater to the steam generators is precisely controlled by demineralization, de-aeration, oxygen scavenging, and pH control. A blowdown system is provided for each steam generator that allows impurities collected in the steam generators to be removed to prevent their accumulation and possible long-term corrosive effects. In some reactors, the blowdown is collected and recirculated. 

Fission product noble gases entering the water-steam circuit in the event of a tube leak are completely volatilized and transported with the steam to the main condenser where they are extracted and released via the off-gas stack. This release is monitored by a continuously operating detector device located in the condenser off-gas line. Non-volatile fission and activation products which are transported over the leak to the water-steam circuit remain completely in the water phase of the steam generator by the action of the blowdown purification system their activity concentration is kept at a level which is controlled by the injection rate on the one hand and by the purification rate on the other. Because of the very low vapor pressures of these elements and their chemical compounds (dissolved ions or insoluble oxides/hydroxides), their transport to the steam under the prevailing conditions (270 °C, 7 MPa) is only possible by droplet entrainment. This means that partitioning between liquid and steam phases is proportional to the steam moisture content, which is usually well below 0.1%. 

The application of evaporators, in particular vertical tube falling film vapor compression evaporators, to treat PW is increasing, in particular in SAGD applications. The system provides a clean water stream that can be used by a once-through steam generators (OTSG) or drum boilers for stream production. Evaporator blowdown is disposed either... 

PC 8 Steam generator overfill due to control system failure and combined primary and secondary blowdown... 

The system consists of two blowdown trains, one for each steam generator. The blowdown water is extracted just above the tube sheet of a steam generator. Flow control valves adjust the blowdown flow rate from each steam generator and depressurise it. The blowdown flow is cooled by means of a regenerative heat exchanger, which uses the heat to warm the condensate. It then enters an ion-exchange purification unit, which removes impurities. Downstream of the purification unit, both trains combine into a common header, which contains a relief valve for providing overpressure protection for the low-pressure portion of the system. 

An alarm sounds in the main control room on detection of a high radiation level within the blowdown system, to alert the operators of the need to take the appropriate remedial action, such as aligning the liquid radwaste system to process the blowdown and ion-exchange waste effluent, and isolating the affected steam generator (Section 10.4.8.2.2 of Reference 6.1). 

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