Session: CS-19-01 Small Scale Mechanical Testing

Paper Number: 122615

122615 - Fracture Toughness Tests on Western Rpv Steels Using Small Scale Specimen Technique – Evaluation of Results 

In order to ensure continued safe operation of European nuclear reactors, it is necessary to solve specific issues that arise from irradiation induced reactor pressure vessel (RPV) embrittlement under long term operation. This requires an extension of the RPV surveillance programs to cover longer operation times than originally planned. The limited availability of surveillance materials poses a challenge for the feasibility of such programs. Among others, the use of the small specimen technology is a promising option to overcome the lack of materials. For example, a number of not less than 16 sub-sized 0.16T-C(T) specimens (4 mm thickness) can be manufactured from two tested Charpy sized (10 mm x 10 mm x 55 mm) specimens, allowing a reliable determination of the reference temperature T₀. Such Charpy sized fracture mechanics specimens are currently widely used in the RPV surveillance programs.

To support the acceptability for fracture mechanics testing of irradiated and unirradiated RPV steels using sub-sized specimens, a joined R&D project was launched partly financed by the German Federal Ministry for Economic Affairs and Energy. The partners are the technical University of Dresden / Helmholtz-Zentrum Dresden-Rossendorf (research institutes) and the Framatome GmbH (commercial nuclear company / supplier).

The objectives of the presented project are to identify a set of relevant RPV materials in unirradiated as well as irradiated conditions, to manufacture 0.16T-C(T) specimens and to test these specimens in accordance with the standard ASTM E 1921. The results shall be compared with results measured on standard sized fracture toughness specimens to demonstrate the transferability of the data. Moreover, the applicability of small scale testing under hot cell conditions will be demonstrated in view of manufacturing, pre-cracking procedure, measurements of crack-opening displacement and load line displacement.

The primary purpose is to demonstrate that the results measured on sub-sized specimens can safely be used in the safety assessment of RPVs. In addition, the results will establish a basis to assess results from international projects regarding sub-sized fracture mechanics specimens.

This paper presents the selected materials, the fracture toughness test results from small scale specimen testing, a comparison with results from standard sized specimen and fractography examinations. Results of a local approach analysis to support the interpretation of the test results are presented as well.

Presenting Author: Florian Obermeier Framatome GmbH

Presenting Author Biography: Engineer in fracture mechanics since 2009. Responsible for fracture mechanics assessments and R&D projects on nuclear reactor pressure vessel and piping. Accomplished a wide range of engineering work on nuclear power plants including leak-before-break analysis for pressurized water reactors, reactor pressure vessel safety analyses as well as finite element weld residual stress and distortion calculations. Acted as a non-testifying expert in an international arbitration. Involved in different international and national R&D projects like FRACTESUS, STYLE, NESC, ATLAS and MULTIMETAL.

Authors:

Florian Obermeier Framatome GmbH
Eberhard Altstadt Helmholtz-Zentrum Dresden-Rossendorf
Hieronymus Hein Framatome GmbH
Aniruddh Das Technische Universität Dresden
Johannes May Framatome GmbH