Technology and Operation - Kernkraftwerk Gösgen

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Auxiliary and secondary systems also used to feed the chemicals into the coolant, via the boric and demineralised water control unit. The appropriate amounts of coolant are removed and conveyed to the coolant storage tanks for interim storage. If the boron content of the coolant needs to be increased, then boric acid will be fed in. In the reverse case, the boron content will be reduced by adding fully demineralised water. A total of six tanks are available for coolant storage, each with a capacity of 100 cubic metres. Accumulators (pressurised storage tanks) for emergency cooling water. Systems for residual heat removal, emergency cooling and pool cooling The systems for residual heat removal have both operational and safety-related functions. Following a routine shutdown of the reactor, they take over the cooling of the reactor core, while, in a loss-of-coolant incident, they ensure the emergency cooling of the core. Additionally, these same systems are used to cool the spent fuel storage pool. During reactor shutdown the decay heat is initially dissipated by the steam generators. Later on, the residual heat removal system takes charge of reducing the temperature still further. In each coolant loop, the heat absorbed is released into the headwater channel of the river Aare via a cooling train which contains an intermediate cooling circuit. This latter circuit forms the barrier between the reactor coolant and the river water. Two pool cooling lines are available for cooling the spent fuel storage pool, which are connected up to the residual heat removal system. There is also a further cooling line which is independent of the residual heat removal system. The efficiency of the residual heat removal system means that the reactor can be cooled down within just a few hours. The residual heat removal pumps suck coolant out of the coolant pipes leading away from the reactor and feed the coolant, via the residual heat exchangers, into the pipes leading back to the reactor coolant system. In a loss-of-coolant incident, the residual heat removal system has to ensure that the reactor core remains flooded, irrespective of the � � � � �18 � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � �
leakage rate, and must also take charge of the long-term elimination of heat from the reactor pressure vessel. The system is designed in such a way that, even in the event of a reactor coolant line suffering a complete fracture, the reactor core will remain covered with borated water, and sufficient cooling will be provided. Borated emergency cooling water is stored in six accumulators, which are connected up to the three reactor coolant loops via pipes with check valves. If a major leak occurs, and the reactor coolant pressure falls below the pressure in the accumulators, the accumulators will empty their contents into the reactor pressure vessel via the reactor coolant lines. Once the pressure in the reactor coolant system drops below 10 bar, the low pressure feed system starts up, and the residual heat removal pumps deliver borated water from the four storage tanks to the coolant loops via separate feed lines. In the event of a small or medium-sized leak with a gradual reduction in pressure, the safety injection pumps in the high-pressure safety injection system will start up first of all. These feed in borated water from the storage tanks until such time as the pressure has dropped far enough for the system to automatically switch over to the low-pressure feed-in. The water fed into the reactor core first fills up the reactor pressure vessel and then flows through the fracture into the lowest point of the containment, the so-called sump. Once all the borated water from the storage tanks and accumulators has been fed in, the water in the containment sump is sucked out by the heat removal pumps and conveyed back into the reactor pressure vessel via the residual heat exchangers. Both the low-pressure and the high-pressure Auxiliary and secondary systems safety injection systems consist of three completely independent feed lines, with each line being allocated to a coolant loop. In addition, there is also a back-up line, which can be brought in for each of the other three lines. A single feed line is sufficient to control a lossof-coolant incident. As all the instrumentation is connected to the emergency power supply, the operational availability and functionality of the emergency and residual heat removal systems is maintained even under the most extreme conditions. Ventilation systems Inside the controlled zone, supply-air, wasteair and air-conditioning systems take care of ventilation, heating and cooling. Ventilation in the plant and operational areas is performed primarily in circulation mode. In normal operation, only about 1000 cubic metres of air per hour is fed into and extracted from the containment. The small quantities of supply and waste air mean that the air ducts into the containment require only a small cross-section. In the plant areas that house the reactor coolant system, any impurities in the room air can be retained by the bypass flow filters in the ventilation system. The ventilation systems keep the pressure constantly below that of the operational areas and the outer atmosphere thus always ensuring a flow of air from areas with a low level of radioactivity to those with a potentially higher level. This tiered low-pressure system prevents any transfer of contaminated air from the plant areas to the service compartment areas. The air that is sucked out of the containment in order to maintain the low pressure is cleaned in the exhaust air unit before being � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � �19 � � � � � � �
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Page 13 and 14: access for heavy goods vehicles. A
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Page 17 and 18: is equally distributed over the thr
Page 19 and 20: Reactor coolant pump Reactor coolan
Page 21: Coolant treatment systems The volum
Page 25 and 26: Treatment of liquid radioactive was
Page 27 and 28: Safety barriers Nuclear fuel matrix
Page 29 and 30: The single-failure criterion applie
Page 31 and 32: Containment venting system 1 Contai
Page 33 and 34: An extensive retrofit of the pressu
Page 35 and 36: turbine from being damaged by erosi
Page 37 and 38: The feedwater pumps pump the feedwa
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Page 61 and 62: Characteristics HP = High-pressure
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Page 65 and 66: Key technical data Power Gross elec
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Technology and Operation - Kernkraftwerk Gösgen

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