1. Reactor pressure vessels of WWER (materials and technology) Janovec, J
Reactor pressure vessels of WWER (materials and technology) Janovec, J. – Petelová,P CVUT in Prague

2. The most worldwide used type of reactor is the PWR (Pressure Water Reactor). About 50% of all reactors under operation in the world are the PWR types.
PWR = WWER
RPV (Reactor Pressure Vessel) is one of the most important components and as it is not replacable it has to be reliable and safe for the whole operation time.

3. Requirements for RPV materials
RPV must guarantee longterm, safe and reliable operation under operating conditions – high pressure, temperature and irradiation.
Steel shall possess:
High limit of yield strength (YS) and ultimate tensile strength (UTS) at operating temperatures
High brittle fracture resistance across the thickness of shells
High thermal and radiation embrittlement resistance under operating conditions
Good weld ability
Good adaptability to manufacture at all metalurgical process stages

4. Reactor WWER 440
Reactor pressure vessels of WWER must be transportable by land, that results in:
Higher neutron fluence
Lower weight
Smaller wall thickness
Higher strength properties

5. Materials of WWER 440 Base metal – 15Ch2MFA (Cr-Mo-V)
Weld metal – Sv 10ChMFT + AN-42
– Sv 08A + AN-42
Cladding – Sv 07Ch25N13 + OF-10
– Sv 08Ch19N10G2B + OF10

6. Chemical composition of base and weld metal
Mechanical properties

7. Chemical composition and heat treatment ensures required strength properties, ductility and toughness.
Ensures also high resistance against thermal and temper embrittlement as well as against radiation damage, mostly due to presence of vanadium (0.3-0,35%) in steel
But there is necessity of high pre-heating for welding ( °C) for prevention of “hot” and “cold” and underclad cracks.

8. Technological procedure of RPV ring manufacturing

9. Quenching of spigot ring

10. Welding of circumferential welds

11. Machining of spigot part of RPV

12. Deposition of two layer cladding

13. The preparation of RPV for the final heat treatment

14. Surface controlling operations on the finished RPV

15. Finished RPV after successful pressure test

16. Example of unsuccessful pressure test of RPV (Cranfield Institute of technology, USA)

17. WWER

18. Comparison of size and materials of RPV WWER 440 and 1000

19. New developments in design:
Decreased content of vanadium (max. 0,1%)
Addition of nickel (up to 1,8%) resulted in:
Simplified welding technology – lower pre-heating temperature ( °C)
Lowering tempering temperature ( °C)
Higher strength properties and better toughness
Requirements for materials surrounding the active zone of reactor

20. RPV WWER 1000 manufacturing procedure

21. Forging extrusion of nozzle ring of RPV

22. New project VVER-ASE 92 (V-466)
Enlargement of the inner diameter of RPV decreases the neutron fluence (4195 instead of original 4150mm in V-320)
The wall is thicker (195 instead of 192,5)
The Ni content in the beltline region is reduced (from original 1,8% to max. 1,3%)
Critical brittle temperature Tk0 of welds is lowered to -10°C.
The goal is to reduce progression of radiation embrittlement of RPV and reach planned lifetime to 80 years

23. Thank you for your attention