The project will contribute to development and validation of advanced materials testing as well as of component and structural integrity assessment methods to quantify material degradation of VVER type of reactors. It will include concrete structures, metal fatigue, corrosion, defect tolerance, advanced NDE techniques and safety margins in aged and potentially degraded plants.

Main provisions of the project are focused on the activity directed on LTO justification beyond 60 and cover such

degradation mechanism and ageing effects on accelerated thermal aged material as:

• Stratification Effects
• Fatigue under LTO Conditions
• Corrosion and Environmental Effects

Other degradation phenomena investigated are:

• Effects of sludge and deposits in steam generator components (particularly steam generator heat-exchange tubes)
• Radiation degradation of Concrete Biological Shielding (CBS).

The main idea of the project is to describe the relations between simulation and modelling, non-destructive testing methods and experimental validation.
In DELISA-LTO plus project testing results will be maximally used from MatDB that allows sufficiently a smaller number of new testing.

DELISA-LTO plus, the project will have generated the following directly verifiable results.

From Advanced Exploitation of Material Data, the reports will be available with summarization of relationships among:

• Formulation of degradation-relevant correlations
• Linking measurable parameters to material condition
• Development of continuous ageing trends for extended operation beyond 60 years
• Preparation of structured datasets for modelling and validation.

From Degradation Mechanisms and Experimental Assessment, the following reports will be available:

• The summarization of results from relevant publications on stratification and cyclic thermo-mechanical loading in VVERs and PWRs
• Report on Thermal-mechanical degradation and fatigue
• Report on sludge and deposit effects on material degradation

From NDE and Operational Validation activities the following reports will be available:

• CIVA SW extended to VVER tubes
• Report on the validation of experimental results from the method for estimating sludge mass in SG from eddy current data
• Report on applicability of UT for the evaluation of degradation mechanisms (e.g. thermal fatigue, corrosion) to pipelines

From Radiation degradation of Concrete Biological Shielding the following reports will be available:

• Validated calculation methodologies for CBS structures available for LTO justification beyond 60 years based on round-robin testing
• Technical basis and recommendations for assessment of irradiation-induced CBS degradation

From Technical Guidance on Selected Degradation Processes for VVER Long-Term Operation the following reports will be available:

• Guidance on Ageing and Degradation of Metallic VVER Materials: Final technical guidance based on project results and end-user review, including supported degradation findings, lifetime-assessment relevance, applicability and limitations.
• Guidance on Deposit-Affected assessment of Steam Generator Tubes: Final technical guidance based on WP3/WP4 results and end-user review, providing recommendations for the evaluation of deposit characteristics, their impact on material degradation and tube integrity, inspection considerations, and the applicability and limitations of the proposed assessment methodology.
• Guidance on CBS Irradiation Degradation and Structural Assessment: Final technical guidance based on project results and end-user review, covering damage characterization, multiscale material assessment, structural implications, applicability and limitations.
• Revision of the EN standard for the Small Punch Test (SPT)

From Dissemination, Communication and Education the following results are expected:

• Creation and maintenance of the project website/social media, active support of dissemination activities.
• Support of the publication process (peer-reviewed papers, conference contributions), in compliance with the Open Science guidelines in line with EU rules, and management of the ZENODO repository.
• Ensuring ongoing communication with stakeholders and authorities, participation in relevant events, and organization of seminars for regulatory bodies.
• Support of students through tutoring and final theses related to project topics. Organization of workshops and activities for students and young professionals.

Achievement of expected outcomes is based on 6 specific objectives:

1. Advanced Exploitation of Material Data
2. Degradation Mechanisms and Experimental Assessment
3. Inspection, NDE and Operational Validation
4. Radiation degradation of Concrete Biological Shielding
5. Technical Guidance on Selected Degradation Processes for VVER Long-Term Operation
6. Dissemination, Communication and Education

DELISA-LTO Plus primarily focuses on degradation mechanisms, steel properties and their behavior under LTO 60 plus conditions. The project deals with selected materials, components and degradation mechanisms. The predictions will combine as-received and service-exposed materials, artificially aged materials, existing databases, targeted experiments and mechanistic modelling. Therefore, they will not be based only on materials exposed to operational conditions for approximately 30 years.

A new research direction has also been introduced to address radiation-induced degradation of concrete biological shielding structures. This topic will be given priority within the project. The consortium has been strengthened through the involvement of experts on the CIVA software platform for NDE modelling and civil engineering experts including laboratories with the necessary testing capabilities and equipment.

The project is supported by NPP operators from the Czech Republic, Slovakia, Hungary, Finland, Ukraine and EDF.

• Czech Republic: CVR (Coordinator),
• Slovakia: VUJE, STUBA,
• Hungary: EK-HUN, BZN, AEMI
• Finland: VTT,
• Ukraine: IPP, SSTC NRC,
• France: CEA

36 months, app. May 2027 – April 2030

Total Requested grant amount: 2,999,418.83 Euros

Project coordinator:

Jaroslav Brom (jaroslav.brom@cvrez.cz)

Technical coordinator  

Adriana Jedličková (adriana.jedlickova@cvrez.cz)

The project proposal was submitted on September 15, 2026.

If supported, the project is expected to start on May 1, 2027.

The project duration is 36 months, the project completion is scheduled for April 30, 2030.