Beneficiary Organisation Details

Dukovany NPP (Czech Republic)
www.cez.cz

Bohunice NPP, Mohovoce NPP (Slovak Republic)
www.seas.sk

State Office for Nuclear Safety (Czech Republic)
http://www.sujb.cz

Nuclear Regulatory Authority (Slovak Republic)
http://www.ujd.gov.sk

Project Aims

The general objective of the work was to evaluate the applicability of dynamic fracture properties and criteria generally used in western codes for integrity assessment to the VVER 440 RPV. The specific objectives were the following:

• Summarize and evaluate existing Charpy V and fracture toughness data for representative base material and welds;
• Define and realize complementary Charpy V and FT (Fracture Toughness) tests on typical archive materials in original and in simulated EOL (End Of Life) conditions;
• Propose a set of curves defining FT (static and dynamic as well as crack arrest) as a function of temperature including selection of pertinent indexation parameters;
• Define and realize experimental tests to validate the proposed approach for static and dynamic crack initiation and arrest by means of series of adequate test specimens including representative defects to be tested in brittle regime;
• Define a standard procedure including simplified stress intensity factor calculations and adequate safety margins for fast fracture resistance assessment of VVER 440/213 RPVs in order to:
• Define operating limits (pressure-temperature limits for heat-up and cool-down);
• Evaluate cold overpressurisation and PTS (Pressurized Thermal Shock).
• Define complementary experiments for validation under realistic thermal shock conditions the capability of the elaborated procedure to predict crack arrest;
• Present the results to the local safety authorities for approval of the elaborated standard procedure.

Project Results

The Phare Project 2.01/95 was realized and fulfilled in accordance with the ToR. A large amount of experimental data from former testing was collected into “design toughness curves” and new data was also created by carrying out comprehensive testing in this project. Large scale test specimens were prepared and tested simulating the original reference condition and the EOL condition of the RPV core region material. The testing was simulated in advance by calculating the testing situation by FEM methods. A standard procedure for fast fracture resistance of VVER 440 RPV was prepared and checked by practical experiments within this project. This elaborated procedure tries to harmonize VVER integrity assessment code with a general western PWR procedure mainly by incorporating crack arrest as well as Master Curve approach. Finally, a proposal for a complementary experimental program concentrating mainly on crack arrest behaviour in VVER RPV materials was elaborated.

Further Project Results

a) See attached file and
b) Further information on the project results could be sought from the beneficiary organisation.