Neutron irradiation embrittlement could limit the service life of some of the reactor-pressure vessels in existing commercial nuclear-power plants. Improved understanding the of the underlying causes of embrittlement has provided regulators and power-plant operators better estimates of vessel-operating margins. This article presents an overview of embrittlement, emphasizing the status of mechanistic understanding and models, and their role in increasing the reliability of vessel-integrity assessments. Finally, a number of outstanding issues and significant opportunities, including a new fracture-toughness master-curve method, are briefly described.

Embrittlement of nuclear reactor pressure vessels

https://digital.library.unt.edu/ark:/67531/metadc897034/m2/1/high_res_d/941022.pdf

A Physically Based Correlation of Irradiation-Induced Transition Temperature Shifts for RPV Steels

A field indentation microprobe (FIM) apparatus was developed (and patented) to evaluate, nondestructively in situ, the integrity of metallic structures. This study investigated the applicability of using a new automated ball indentation (ABI) test, which is a major part of the FIM, to measure the flow properties of metallic materials including those exhibiting Lueders or inhomogeneous strains (carbon steels, titanium alloys, aluminum alloys, etc.) and to estimate their fracture toughness. The ABI test is based on multiple indentations (at the same penetration location) of a polished metallic surface by a spherical indenter. Automation of the test, where a computer and test controller were used in innovative ways to control the test as well as to analyze test data, made it simple, rapid, accurate, economical, and reproducible. Results of ABI tests on different metals, welds, and irradiated materials are presented and discussed in this paper. Excellent agreement was obtained between ABI-derived data and those from standard ASTM uniaxial tensile and fracture toughness tests. 17 refs., 20 figs., 2 tabs.

Peter Lombrozo

Papers

Relationship Between Irradiation Hardening and Embrittlement of Pressure Vessel Steels