Chalk River Laboratories

About: Chalk River Laboratories is a based out in . It is known for research contribution in the topics: Neutron diffraction & Neutron scattering. The organization has 2297 authors who have published 2700 publications receiving 73287 citations.

Effect of solution heat treatment on residual stress in Al alloy engine blocks using neutron diffraction

Abstract: Tensile residual stress in the cylinder bore region is a significant problem associated with Al engine blocks containing cast-in gray iron cylinder liners as it can result in cylinder distortion or engine block fracture. These issues can lead to significant environmental (emissions) and economic (recalls) problems for automotive OEMs. In this study, in-situ and ex-situ neutron diffraction was used to measure the change in residual strain in the cylinder bridge as a function of time during solution heat treatment and map to the stress profiles following heat treatment. A heating system, consisting of coiled tubular heaters in the cylinder bores and strip heaters along the front and side faces of the engine block, was designed and built to heat the blocks to the solution temperatures The results indicated that solutionizing at 470 °C caused a gradual relief of tensile residual strain up to approximately 5 h, where strain was completely relieved. At 500 °C, the strain relieved more rapidly, which resulted in complete relief in under 0.5 h. Cooling to ambient temperature caused the partial re-development of tensile residual stress throughout the cylinder depth due to thermo-mechanical mismatch, however the magnitude was lower than for the as-cast condition.

Pulsed Eddy Current Inspection of Support Structures in Steam Generators

Abstract: Degradation and fouling of support structures in nuclear steam generators (SGs) can lead to SG tube damage and loss of SG efficiency. Inspection and monitoring of support structures combined with preventative maintenance programs can alleviate these effects and extend SG life. Conventional eddy current inspection technologies are extensively used for detecting and sizing indications from wall loss, frets at supports, cracks and other degradation modes in the tubes, as well as assessing the condition of support structures. However, these methods have limited capabilities when more than one degradation mode is present simultaneously, or when combined with fouling. Pulsed eddy current combined with principal components analysis (PCA) was examined for inspection of 15.9 mm (5/ $8^{{\prime }{\prime }}$ ) Alloy-800 tubes and surrounding stainless steel (SS410) support structures. Clear separation of PCA scores associated with tubes from those associated with ferromagnetic SS410 supports permitted measurement of tube-to-support gaps, in either the presence of tube fretting or variation of relative position of the tube within SS410 supports. For concentric tubes, frets could be sized independently of SS410 hole diameter variations, which in other materials could represent support corrosion. Capability to clearly separate scores was attributed to large differences in relaxation times for diffusion of transient fields through the tube compared with diffusion into the ferromagnetic support structure.

Miniature tissue-equivalent proportional counters for BNCT and BNCEFNT dosimetry

Abstract: A dual miniature tissue-equivalent proportional counter (TEPC) system has been developed to facilitate microdosimetry for BoronNeutron Capture Therapy (BNCT). This system has been designed specifically to allow the analysis of the single event charged particle spectrum in phantom in high intensity BNCT beams and to provide this microdosimetric information with excellent spatial resolution. Paired A-150 and 10 B -loaded A-150 TEPCs with 12.3 mm3 collecting volumes have been constructed. These TEPCs allow more accurate neutrondosimetry than current techniques, offer a direct measure of the boronneutron capture dose, and provide a framework for predicting the biological effectiveness of the absorbed dose. Design aspects and characterization of these detectors are reviewed, along with an exposition of the advantages of microdosimetry using these detectors over conventional dosimetry methods. In addition, the utility of this technique for boronneutron capture enhancement of fast neutron therapy (BNCEFNT) is discussed.