Pressure stabiliser for 440 [MW] power-generating unit with WWER reactor

The pressure stabilizer was designed for a nuclear power plant, for power-generating unit with WWER [(vodo-vodyanoy energeticheskiy reaktor) (reaktor energetyczny wodno-wodny)] 440 [MW] reactor within the primary (contaminated) circuit.

According to a brochure issued on the occasion of the completion of the 1st stabilizer, the then Raciborska Fabryka Kotłów was designated for the production of equipment for NPPs on the basis of Resolution No. 222/74 on the National Economic Plan for 1976.

Planned installation site: NORD IV power plant in the former GDR or Żarnowiec Nuclear Power Plant. The delivery has not been completed due to the fall of the Berlin wall and the resulting change in energy policy. Similarly, the authorities in Poland after 1989 also abandoned the continuation of the construction of Żarnowiec NPP.

Principle of operation.

As the name suggests, it is used to stabilize pressure. About half of it was filled with water (25 m3) and the other half with water vapour (19 m3). The excessive increase of pressure within the primary circuit triggers the spray of cold water, water vapour condenses and the pressure drops. Inside, at the level of the spray nozzles, a thin protective shell ring is attached in order to protect the shell against the temperature shock. If the pressure is too low, the electric heaters turn on, the water evaporates and the pressure increases. The entire pressure stabilization process is automatically controlled.

Detail engineering: (OBRKiUE – Boilers and Power Generation Equipment Research and Development Centre) currently CBKK Tarnowskie Góry on the basis of a Soviet design (Atomenergoeksport – Foreign Trade Agency, Iżorskiy Zavod – Design Office).


  1. Internal diameter: 2 400 [mm].
  2. Length (height): 12 000 [mm].
  3. The thickness of shell ring with heaters amounts to 170 [mm], the thickness of remaining ones amounts to 155 [mm] (all are made of forgings – the firs stabiliser was made of shell rings manufactured as welded plates).
  4. The upper head features 2 large nozzles, one for safety valve operating with discharge tank and one for spray valve for pressure reduction purposes).
  5. The pivots for handling of the stabiliser are located below the upper head.
  6. Overlay welding from the inside: plated layer made using the submerged arc cladding with austenitic strip [material grade: plated layer of thickness ranging from 8 to 11 mm (first layer made of SW07H25N13; second layer stabilised with niobium due to the final heat treatment of the stabiliser)].
  7. Shell ring with heaters: 108 nozzles for installation of electric heaters (heaters – SELFA Szczecin).
  8. Pressure stabiliser “passport” documents were printed in Paczków Printing Works, i.e. one of the few able to print in Russian characters. The passport was trilingual: Polish, Russian and German.
  9. RAFAKO order no.: 1004.
  10. CBKK order no.: 2.3.1760-4.1.
  11. Layout drawing no.(B0-1263382 – CBKK, 101-00-00-000-3 – RAFAKO).
  12. Year of manufacture: 1990.