Extrabudgetary Programme on Mitigation of Intergranular Stress Corrosion Cracking in RBMK Reactors
Welcome to the IAEA's Extrabudgetary Programme on Mitigation of Intergranular Stress Corrosion Cracking (IGSCC) in RBMK Reactor web pages. IGSCC of chromium nickel stainless steel piping in BWRs has had a major impact on plant availability since the early seventies. Cracks in BWR piping have occurred mainly in the sensitised heat affected zones of welds subject to relatively high residual tensile stress due to welding processes and water chemistry. In 1997, a similar cracking phenomenon has been revealed on a number of RMBK reactor pipings in Lithuania, Russia and Ukraine. Early in 1998, the Agency initiated activities to assist the countries operating RBMK reactors to address the issue. In May 2000, the Agency started an Extrabudgetary Programme to assist countries operating RBMK reactors to mitigate effectively intergranular stress corrosion cracking in austenitic stainless steel piping. This Programme was completed mid-2002.
The Agency initiated this Extrabudgetary Programme in May 2000 to assist countries operating RBMK reactors in effectively mitigating IGSCC in austenitic stainless steel 300 mm diameter piping. The Programme is implemented in line with recommendations of a workshop and follow-up expert group meetings, which were convened in 1998 - 1999 within the framework of the Agency's Technical Co-operation Department regional projects in Europe.
The Programme relied on extrabudgetary funding from Japan, Spain, UK and the USA, as well as in-kind contributions from Finland, Germany, Lithuania, Russia, Sweden and the Ukraine. Major input was provided through related national or bi-lateral activities, such as the Swedish International Project Nuclear Safety (SIP) and the US Department of Energy International Nuclear Safety Program (INSP).
The Programme objectives were achieved through technology and information transfer, training, and guidance formulated on managing IGSCC in RBMK reactors.
The activities of the Programme were conducted in four Working Groups, which focus on:
- Improvements to in-service inspection performance and qualification;
- Comprehensive assessment techniques;
- Qualification of repair techniques; and
- Water chemistry and decontamination techniques.
The Working Groups met regularly to co-ordinate work in their respective areas. The efforts of the Working Groups were guided, monitored and co-ordinated by the Programme Steering Committee, which was scheduled to meet four times throughout the Programme. The results of the work are summarized in the Minutes of the Steering Committee and Working Group Meetings.
Programme implementation relies on the work of experts from organizations involved, which includes all RBMK power plants, regulatory authorities and technical support organizations of RBMK operating countries as well as various organizations from countries supporting the Programme.
An important element of the Programme is training. Nine training courses/workshops have taken place to date:
- Risk based inspection;
- Advanced ultrasonic training seminar for detection, characterization and repair of IGSCC, IGSCC flaw sizing and weld overlay examination (including transfer of respective procedures);
- Advanced ultrasonic training course for detection and characterization of IGSCC in stainless steel piping;
- Advanced ultrasonic sizing seminar;
- Automated IGSCC ultrasonic inspection seminar;
- GTAW welding and repair methods;
- Water chemistry monitoring (Gundremmingen and Philippsburg NPPs);
- Weld overlay ultrasonic testing techniques; and
- Seminar on risk based inspection pilot study for Ignalina NPP.
In addition to the information and technology transferred in the course of Working Group activities and training, a comprehensive information package on repair and mitigation techniques developed in the USA was made available by EPRI to each of the RBMK facilities.
The results of the International Piping Integrity Research Programme, "The Pipe Fracture Encyclopaedia", have been provided by the US NRC to the RBMK operating countries.
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