The review is concerned with the use of miniature specimens to identify the mechanical/creep properties of metals and alloys. It is not intended to consider the nanoscales, which have been reviewed elsewhere, but focus on the size ranges and forms that are of use to areas such as alloy development, surveillance monitoring, effects of irradiation, properties of weld structures and remaining life. For many of these cases, there are technical advantages in the use of small specimens. Where possible, available reviews in this area are used and identified. The needs for small specimen sizes are considered, and the wide range of sizes of both conventional and more unusual specimen designs is reviewed. The potential effects of specimen size are considered: the microstructural features of the material, the effect of constraint and the actual region of the specimen that is undergoing deformation, and finally statistical approaches. The results of published studies are considered under the general groupings of yield/deformation behaviour, creep properties, toughness and fatigue, with an examination of the current state of interpretation of data from mini-specimens because interpretation is one of the key areas of interest. Finally, the current status of each area is considered, as certain designs of specimen will be better suited to answering specific technical questions. The need for standards for specific designs is also examined.

Requirements for and use of miniature test specimens to provide mechanical and creep properties of materials : a review

Evolution of manganese–nickel–silicon-dominated phases in highly irradiated reactor pressure vessel steels

Nuclear plant life extension to 80 years will require accurate predictions of neutron irradiation-induced increases in the ductile-brittle transition temperature (ΔT) of reactor pressure vessel steels at high fluence conditions that are far outside the existing database. Remarkable progress in mechanistic understanding of irradiation embrittlement has led to physically motivated ΔT correlation models that provide excellent statistical fits to the existing surveillance database. However, an important challenge is developing advanced embrittlement models for low flux-high fluence conditions pertinent to extended life. These new models must also provide better treatment of key variables and variable combinations and account for possible delayed formation of “late blooming phases” in low copper steels. Other issues include uncertainties in the compositions of actual vessel steels, methods to predict ΔT attenuation away from the reactor core, verification of the master curve method to directly measure the fracture toughness with small specimens and predicting ΔT for vessel annealing remediation and re-irradiation cycles.

Predictive reactor pressure vessel steel irradiation embrittlement models: Issues and opportunities

Atom probe tomography characterizations of high nickel, low copper surveillance RPV welds irradiated to high fluences

Nonlinear ultrasound was used to monitor radiation damage in two reactor pressure vessel (RPV) steels. The microstructural changes associated with radiation damage include changes in dislocation density and the formation of precipitates, and nonlinear ultrasonic waves are known to be sensitive to such changes. Six samples each of two different RPV steels were previously irradiated in the Rheinsberg power reactor to two fluence levels, up to 1020 n/cm2 (E > 1 MeV). Longitudinal waves were used to measure the acoustic nonlinearity in these samples, and the results show a clear increase in the measured acoustic nonlinearity from the unirradiated state to the medium dose, and then a decrease from medium dose to high dose.

Evaluation of radiation damage using nonlinear ultrasound

Evolution of the nanostructure of VVER-1000 RPV materials under neutron irradiation and post irradiation annealing

Thermal ageing mechanisms of VVER-1000 reactor pressure vessel steels

Consolidation of Scientific and Technological Expertise to Assess the Reliability of Reactor Pressure Vessel Embrittlement Prediction in Particular for the Arctic Area Plant (COBRA)

This paper presents the results of a study on degradation due to irradiation occurring in WWER-440 reactor pressure vessel (RPV) steel, using subsize Charpy specimens (5×5×27.5 mm 3 ). An application of subsize specimens for estimation of irradiation embrittlement of RPV steel has been substantiated. Comparison between ductile-to-brittle transition temperatures (DBTT) for full-size and subsize Charpy specimens has been carried out. The relation between these two values has been clarified. The results of testing trepans and templates cut out from WWER-440 reactor pressure vessels are considered. The main results of the program TACIS-91/1.1. are discussed.

The Actual Properties of WWER-440 Reactor Pressure Vessel Materials Obtained by Impact Tests of Subsize Specimens Fabricated out of Samples Taken from the RPV

YI Shtrombakh

Papers

Evolution of the nanostructure of VVER-1000 RPV materials under neutron irradiation and post irradiation annealing

Thermal ageing mechanisms of VVER-1000 reactor pressure vessel steels

Consolidation of Scientific and Technological Expertise to Assess the Reliability of Reactor Pressure Vessel Embrittlement Prediction in Particular for the Arctic Area Plant (COBRA)

The Actual Properties of WWER-440 Reactor Pressure Vessel Materials Obtained by Impact Tests of Subsize Specimens Fabricated out of Samples Taken from the RPV

Irradiation Embrittlement of Reactor Pressure Vessel Steels due to Mechanisms Other than Radiation Hardening