Containment building

As a security container or containment a safety device of nuclear power plants is called, which surrounds the reactor pressure vessel in order to protect the environment in the event of an accident against radioactive contamination.

Barrier concept

The security container in a nuclear power plant, one of three barriers ( from the inside to the outside viewed ) against the escape of radioactive materials:

• The fuel rod cladding tubes (No. 6 in the picture)
• The reactor pressure vessel with primary circuit lines ( # 5 in figure ) and
• The containment ( containment, No. 2 in the figure ), and associated restraint systems for liquid and gaseous materials (eg filters ).

The security container with the associated equipment, as a third of these barriers enclosing the reactor pressure vessel and the adjoining part of the refrigerant circuit.

In reactors with liquid coolant - such as water in all operated in Germany, nuclear power plants - collects about leaked coolant at the lowest point, the so-called swamp, of the containment vessel. From here, the coolant can be fed back into the reactor coolant system by means of pumps.

Pressurized water reactors

The containment German pressurized water reactors (PWR ) has the shape of a sphere and consists of fine-grain structural steel. According to requirement to notify the pressure created in the complete evaporation of the primary coolant that can withstand ( full pressure containment ). He is in German NPP design ( also SWR ) always in a - in built reactor building of concrete - visible from the outside.

The inside diameter is at 1300 MW plants about 56 m. The wall thickness is 30-40 mm. These large containers could be welded together only at the site of about 550 spherically curved single sheets. After sealing the upper polar cap was a pressure test with compressed air through compressors. Here, the temporal leakage rate (pressure drop per time ) was determined by the pressure gauge and the deformations with strain gauges. During reactor operation, the full pressure containment can be entered ( subdivision into operational and plant rooms).

As a result of core melting could possibly also a full pressure containment rupture from undue pressure (which is a worst-case scenario would be ). To prevent this, all nuclear reactors were in Germany a few years after the nuclear disaster at Chernobyl in 1986 with a filtered venting ( " Wallmann ') valve fitted.

Boiling water reactors

Boiling water reactors (BWR) of the German construction line 69 have a predominantly spherical containment around three centimeters in wall thickness, in crumbs, for example, about 30 feet inside diameter. These are welded together on site. You can not be entered and included to protect against oxyhydrogen explosions nitrogen instead of air during reactor operation. Since BWRs less equipment in the containment must be accommodated ( SWR has no separate steam generator and no large coolant pump, but only integrated in the reactor circulation pump ), the latter can be made smaller. A disadvantage of a smaller containment is the rapid rise in pressure in the leak case. Therefore, a pressure-reducing system (DAS ) is provided, in which the exiting vapor to flow into the condensation chambers, where it is guided and condensed by the water basin.

General Information on technology

The containment vessel is provided with air locks. They have an inner and an outer door, which are mutually interlocked so that a door can only be opened whenever the other is closed and the pressure equalization is complete. The containment vessel can enter and exit through entryways. Notschleusen are provided for the emergency. For the introduction of material (eg fuel ) used material locks which are usually fitted with a lock cars and armored doors.

For the execution of pipelines and cables of the security container has many breakthroughs that require special attention. Small pipes can be welded firmly under the provisions of thermal expansion and compressive forces. Large pipes are connected by joints with any suction and nitrogen gas. Cable glands can be designed as glass fuse seals and brazed joints.