One of the key issues regarding Reactor Pressure Vessel (RPV) integrity is the effect of radiation on the vessel steel in the core zones. In these areas, where radiation levels are high, the steel tends to become more brittle.
Design and manufacturing stages have incorporated safety margins to account for irradiation-induced embrittlement. Additionally, operational measures have been implemented to manage RPV ageing.
The challenge now lies in preserving these margins and providing robust safety cases to support them.
What is TOM?
The TOM (TOughness measurement by Mini-CT) project targets fracture toughness and thermal ageing of RPV steels. Its objectives include:
- Measure toughness using mini-CT specimens
- Assess weld joint zones, especially HAZ
- Analyze transferability of toughness across geometries
- Study constraint effects on cleavage fracture
- Collect data on isothermal thermal ageing
- Improve understanding of embrittlement mechanisms
- Develop models for non-hardening embrittlement via segregation
- Develop magnetic multi-parameter techniques for irradiation embrittlement detection
- Investigate recombination techniques for CT specimens
The TOM project aims to support long-term safe operation of RPVs beyond 40 years by improving fracture toughness and ageing assessments. Its key benefits include:
- Providing tools and data for extended RPV integrity demonstration
- Strengthening confidence in assessment models through shared data and common methodologies
- Advancing knowledge on thermal ageing of RPV steels by promoting best practices in irradiation ageing analysis and maximizing the value of costly experimental campaigns