Testing Environmentally Assisted Cracking (EAC) of Reactor Materials Using Pneumatic Servo Controlled Fracture Mechanics Device (PSCFM)

Initiation and growth of cracks caused by the combined attack of tensile stresses and aggressive environments is considered to be one of the most dangerous failure mechanisms in structural alloys. The degradation mechanism, known as Stress Corrosion Cracking (SCC) or Environmentally Assisted Cracking (EAC) has long been recognized as a major cause for the failure of components and structures but the basic mechanisms of this process are not still fully understood and the development of standardized and practicable methods of testing is definitely a key element in a strategy to understand the kinetics of failure and possibly to provide for mitigation measures. At the JRC-IE, Institute for Energy, a new laboratory for EAC testing of nuclear power engineering materials, in particular core internals materials, has been recently commissioned. The laboratory allows to carry-out EAC tests in any BWR and PWR conditions. The main part of the facility consists of a PSCFM (Pneumatic Servo Controlled Fracture Mechanics) loading system for 3-Point-Bending tests of fatigue pre-cracked SEN(B) specimens of different sizes, in a high temperature and pressure autoclave. A first test campaign have been carried out and focused on the comparison of the results obtained on 10 x 10 x 55 mm3 and 3 x 4 x 27 mm3 SEN(B) 316L stainless steel specimens loaded by constant displacement rate increase tests in typical BWR conditions. The crack growth was monitored on-line by DCPD as well as the water chemistry parameters; measured in the inlet and outlet part of the loop. The first testing campaign succeeded in the determination of the influence of the loading rate on crack initiation, the comparison of the results measured on different size of specimens, and the verification of the usability of LEFM and EPFM parameters for the evaluation of the results. Such evaluation is presented in details in this paper together with the results of microstructural investigations of the fracture surfaces done by optical microscopy and SEM.

NOVOTNY Radek;  SEVINI Filippo;  DEBARBERIS Luigi;  SAJDL Petr;  MILOS Kytka; 

2007-02-12

ELSEVIER SCI LTD

JRC34035

https://publications.jrc.ec.europa.eu/repository/handle/JRC34035,   

10.1016/j.ijpvp.2006.08.001,