Integrity Evaluation of a Reactor Pressure Vessel Based on a Sequential Abaqus-FRANC3D Simulation Method

The safety-risk pressurized thermal shock (PTS) have on a reactor pressure vessel (RPV) is one of the most important studies for the lifetime ageing management of a reactor. Several studies have investigated PTS induced by postulated accidents and other anticipated transients. However, there is no study that analyzes the effect of PTS induced by one of the most frequent anticipated operational occurrences—inadvertent operation of the safety injection system. In this paper, a sequential Abaqus-FRANC3D simulation method is proposed to study the integrity status of an ageing pressurized water reactor subjected to PTS induced by inadvertent actuation of the safety injection system. A sequential thermal-mechanical coupling analysis is first performed using a three-dimensional reactor pressure vessel finite element model (3D-FEM). A linear elastic fracture mechanics submodel with a postulated semielliptical surface crack is then created from the 3D-FEM. Subsequently, the submodel is used to evaluate the stress intensity factors based on the M-integral approach coupled within the proposed simulation method. Finally, the stress intensity factors (SIFs) obtained using the proposed method are compared with the conventional extended finite element method approach, and the result shows a good agreement. The maximal thermomechanical stress concentration was observed at the inlet nozzle-inner wall intersection. In addition, The ASME fracture toughness of the reactor vessel’s steel compared with SIFs show that the PTS event and crack configuration analysed may not pose a risk to the integrity of the RPV. This work serves as a critical reference for the ageing management and fatigue life prediction of reactor pressure vessels.

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 ageing of civil structures receive more attention internationally. In order to increase the knowledge in the field of civil structures, this paper focusses on investigation of ageing of civil structures and determining an ageing management strategy. Knowledge of the ageing mechanisms of civil structures and especially concrete, will lead to improvement of ageing management and assessment methods of concrete. As a first step international information was gathered on civil structures ageing issues and management thereof (see PVP2019-93029). In addition a highlevel 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 another PWR with a steel containment. With this experience the assessment methodology is tested, compared and improved (see PVP2020-21838). The results indicated 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 of IGALL AMPs to a practical AMPs that will deal with the right 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 project 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. The results of this ongoing work are presented in this report. For the research reactor all SSCs in scope of the Continued Safe Operation could be linked to the relevant AMP(s) and a resulting set of plant specific AMPs for civil ageing management was obtained. Including the international developments, literature and guidelines, a more general applicable list was created (Table 5 through Table 13). The conclusion is that Figure 2 represents a practical method for obtaining a set of plant specific civil AMPs ready for implementation. For representation in this paper the final outcome is given in as a generic list of actions for a generic reactor (Table 5 through Table 13). In these tables the relevant SSCs, ageing mechanisms and actions are listed. The tables represent an generic list of actions for civil ageing management that might others help develop their ageing management program. Future steps are shifting the focus from the general but practical assessment 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 are planned.

High Flux Reactor Continued Safe Operation: Time Limited Ageing Analyses

The High Flux Reactor (HFR) is a multipurpose nuclear reactor located in Petten, the Netherlands. With its 45 MWth it is one of the most powerful and versatile research reactors in the world. Its main roles are material irradiation and medical isotopes production. The output of the reactor in terms of medical isotopes is important at a global level (60% of European demand). Every day in the Netherlands alone 30.000 patients are treated using isotopes produced in the HFR. The importance of the HFR dates back in time. The HFR has been in service since 1961. Due to the long life (58 years to date) of the reactor an efficient integrated ageing management program (AMP) is envisaged as it is foreseen that the HFR will continue to operate for a prolonged period of time. The development of the AMP has begun in 2018 (CSO project) and will be completed in view of the IAEA CSO mission. The HFR is the second reactor in the world to undergo this type of IAEA review and one of the objectives of this project is to set a state of the art when it comes to research reactors long term operation. The CSO project foresees four major sections: scoping and screening, development and improvement of plant programs, (re) validation of time limited ageing analyses (TLAAs) and realization of the ageing management program. In this paper the focus will lie on the TLAAs. The applicable TLAAs were scoped starting from the IGALLs TLAAs list. The TLAAs relevant for the HFR are: TLAA fatigue, TLAA reactor vessel, TLAA leak before break, TLAA manufacturing flaws TLAA beryllium and TLAA equipment qualification. The latter was developed in the framework of the equipment qualification plant program and does not figure as an independent TLAA in the CSO project. For each TLAA the principal problematics will be highlighted and the possible solutions illustrated.

An Assessment Methodology for Civil Ageing Management and Concrete 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 ageing of civil structures receive more attention internationally (for example concrete degradation in bunker building Doel and buried piping attention in topical peer review EU). In order to increase the knowledge in the field of civil structures, this work focusses on investigation of ageing of civil structures and determining an ageing management strategy. Knowledge of the ageing mechanisms of civil structures and especially concrete, will lead to improvement of ageing management and assessment methods of concrete. As a first step international information was gathered on civil structures ageing issues and management thereof (see PVP2019-93029). In addition a very high level assessment methodology was proposed. The goal of the project 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. The results of this ongoing work are presented in this report. The initial proposed assessment methodology has been tested by application to the HFR research reactor. The resulting list of relevant AMPs has been verified with the outcome for another PWR with a steel containment. With this experience the assessment methodology is improved. In addition each civil SSC in the scope of the Continued Safe Operation program is linked to the relevant AMP(s). The improved, but not finalized assessment method of ageing management for civil structures can be seen in figure 2. The proposed assessment method for ageing of civil structures has been tested, compared and improved. The results indicated that the method can be used to obtain a list of plant specific AMPs. The comparison of the list of relevant AMPs for a steel containment PWR, showed similar results. What is added to the assessment method is the link to the TLAAs for civil structures. The detailing to a level of practical work instructions for the maintenance of the plant has to be made in the near future. In the near future the step will be made from a high level of IGALL AMP to a practical AMP that will deal with the relevant mechanisms at the various locations. Therefore further steps are in studying of relevant degradation mechanisms, relevant AMPs (like AMP305 [9],AMP306 [10]) and applicable literature (e.g.[21]) in combination with the practical knowledge from operation of a reactor. The international developments on ageing management of concrete will be included. It is foreseen that the future report will contain information on concrete degradation mechanisms relevant for nuclear reactors. If findings requires calculations the assessment method will be verified with the finite element modelling techniques.

Active Aging Management in Iran: Designing a model

Objective: Active ageing constitutes one of the guiding perspectives on policies, but the factors influencing ageing have not received considerable attention. The present study aimed to identify the factors affecting active ageing management in Iran. Design: Drawing on quantitative data gathered through a questionnaire filled out by 287 participants and an interview with 20 experts. Main outcome measures: The instrument was a questionnaire based on the five-point Likert scale. Questions with CVR>0.49 and with CVI>0.7 were accepted. To assess the reliability of the questionnaire, Cronbach's alpha coefficient was (0.92) used. The adequacy of the sample size was estimated at 0.952, based on the Kaiser-Meyer-Olkin (KMO) index. The collected data were analyzed by SPSS Ver 22. An exploratory factor analysis was used to explore and evaluate the dimensions of the model through a mathematical approach. Also, confirmatory factor analysis was utilized to verify the model, using AMOS 24 software. Results: Eight factors were identified as effective factors in active ageing management in Iran, which include: Organizational structure (0/83), services (0/80), control (0/74), financing (0/72), government grants (0/71), policy making (0/68), selected area to focus (0/65), members (0/63). Organizational structure and member components had the most and least significant effects. Conclusions: Establishing a High Council with the presence of the President's representative, allocating a specific budget for the elderly, determining the responsibilities of the government and the related organizations, determining the responsibility and providing suitable services can lead to the effective management of active ageing.

NPP Unit Life Management based on Digital Twin Application

IAEA activities on ageing management started in 1990 are a part of NPP Units life management or License Renewal as specified in national regulatory documents of member countries. Development of digital technologies makes it possible to manage lifetime NPP Unit issues in effective manner by application of Digital Twin.