- Nuclear installations in Germany
- Safety in nuclear energy
- Legal bases
- Licensing and supervision
- Safety philosophy
- Precautions and emergency response
- National committees
- International co-operation
- Reportable events
- Reporting procedure
- Incident registration centre
- International Nuclear Event Scale (INES)
- Reportable events in nuclear installations
- Reports on reportable events
- Shutdown and decommissioning
- Nuclear accidents
- What is nuclear waste management?
- Design approvals of transport packages
- Interim storage facilities
- What are interim storage facilities?
- Licensing of interim storage facilities for nuclear fuels
- Central interim storage facilities
- Decentralised interim storage facilities
- Interim storage facilities for radioactive waste with negligible heat generation
- Federal custody of nuclear fuels
- What is nuclear waste management?
- Foundation and development
- President of the BfE
- Laws and regulations
- Frequently applied legal provisions
- Handbook nuclear safety and radiation protection
- 1A Nuclear and radiation protection law
- 1B Other laws
- 1C Transport law
- 1D Bilateral agreements
- 1E Multilateral agreements
- 1F EU law
- 2 General administrative provisions
- 3 Announcements of the BMU and the formerly competent BMI
- 4 Relevant provisions and recommendations
- 5 Nuclear Safety Standards Commission (KTA)
- 6 Key committees
- Annex to the NS Handbook
- A 1 English translations of laws and regulations
- Dose coefficients to calculate radiation exposure
- Legal Basis
- BfE Topics in the Bundestag
Pressurised water reactors
Like boiling water reactors, pressurised water reactors (PWR) belong to light-water reactors.
The reactor pressure vessel in pressurised water reactors is under a pressure of about 160 bar. This high pressure prevents the water in the reactor coolant circuit (also termed primary circuit) from boiling despite a temperature of about 320 degrees Celsius (°C).
Steam generators produce the steam required for power generation in another circuit – the secondary circuit – which is then led to the steam turbine.
Primary circuit - Main coolant circuit of the PWR
Reactor coolant pumps pump the water of the primary circuit into the reactor pressure vessel, where it flows through the reactor core from bottom to top. The heated water leaves the reactor pressure vessel and flows in a circuit through the steam generator tubes back to the reactor coolant pumps.
Secondary circuit of the PWR
The water in the secondary circuit takes up the heat of the primary circuit via the steam generators and is thus heated to about 280°C. As there is low pressure (about 60 bar) in the secondary circuit, the water boils. The generating steam of the secondary circuit drives the steam turbine which is connected with a generator.
Third circuit of the PWR
The steam of the secondary circuit gives off its energy to the turbine and, in a condenser, condenses again to water which is fed back to the steam generators. The released heat in the condenser is discharged via a third circuit, the cooling water system, to the river or the cooling tower.
Radioactive materials only in the primary circuit
The reactor pressure vessel and all other components of the primary circuit are located in the containment. The separation of reactor coolant and secondary circuit in the PWR by means of steam generators prevents radioactive materials from being released from the primary circuit.
The power house containing the secondary circuit, the turbine and the generator does not contain radioactive materials. In the case of an accident, safety devices effect an immediate closure of the containment building.
Control of nuclear fission in the PWR
The number of nuclear fissions can be limited by neutron-absorbing material. The control rods containing neutron-absorbing material are loaded electrically (normal drive) into the reactor core from above and regulate the reactor via the penetration depth. In case of a reactor trip, the control rods drop to the reactor core due to gravity and terminate the chain reaction.
Apart from the control rods, boric acid is added to the primary circuit to regulate the reactivity in the reactor core of a pressurised water reactor. Boron absorbs neutrons, i.e. the reactor can be regulated by changing the boric acid concentration.
State of 2017.02.14