Session: OAC-03-02/07-01 Monitoring, Diagnostics & Inspection and Plant Life Extension: Aging & Life Management

Paper Number: 61499

Start Time: Thursday, July 15, 2021, 05:00 PM

61499 - An Update of the Assessment Methodology for Civil Ageing Management for LTO/CSO Based on International Standards and Engineering Judgement 

For many nuclear power plants worldwide, the operation period will be extended to 60 or 80 years in the coming years. As the operation period increases, the importance of knowledge of ageing mechanisms increases. In the framework of LTO, there is limited knowledge about ageing and structural integrity of concrete structures. Recent developments have shown that this topic receives more attention internationally. In order to increase the knowledge in that field, this paper focusses on investigation of ageing of civil structures and determining an ageing management strategy.

 

As a first step, international information was gathered on civil structures ageing issues and management thereof (see PVP2019-93029). In addition, a high-level assessment methodology was proposed. In the next step, the initially proposed assessment methodology has been tested by application to a nuclear reactor. The resulting list of relevant AMPs has been verified with the outcome for a PWR with a steel containment. With this experience, the asssement methodology is tested, compared and improved (see PVP2020-21838). The results indicate that the method can be used to obtain a list of plant specific AMPs. What was added to the assessment method is the link to the TLAAs for civil structures.

 

In this follow up step, the transition is made from a high-level IGALL AMP to a practical AMP that will deal with the right ageing mechanism at the right location. The detailing to a level of practical work instructions for the maintenance of the plant has to be made in order to make real life implementation possible. In this step, studying of relevant degradation mechanisms, relevant AMPs (like IAEA AMP305 and AMP306) and applicable literature in combination with the practical knowledge from operation of a reactor, has taken place. The international developments on ageing management of concrete will be included.

 

The goal of the paper is to obtain more knowledge on ageing management of civil structures and especially concrete. It will lead to an assessment method for civil ageing management and ageing management programs dealing with the relevant mechanisms at the various locations in a practical manner.

 

Future steps are shifting the focus from the general but practical assessement methodology to finite element modelling techniques for concrete. The assessment criteria for concrete (e.g. in ASME III, ASME XIII or Eurocode) will be investigated and investigation on the modelling of the concrete for ageing is planned.

Presenting Author: f.h.e. De Haan - De Wilde NRG

Authors:

F. H. E. (Ciska) De Haan - De Wilde NRG
m.j. Janssen NRG