ISO 11537 pdf download

ISO 11537 pdf download.Non-destructive testing — Thermal neutron radiographic testing — General principles and basic rules 1 Scope This International Standard specifies the basic practices and conditions that are to be observed for thermal neutron radiography of materials and components for flaw detection. It is concerned with techniques using photosensitive film as a recording medium. However, it recognizes that alternative methods of imaging may be used more widely in the future. The scope includes neutron production and collimation methods, converter screen selection, radiographic film, neutron radiographic inspection techniques and the type of material to be inspected. This practice is generally applicable to specific material combinations, processes and techniques. 2 Background material A glossary of terms relating to neutron radiography is presented in annex A. Attenuation of neutrons in matter is presented in annex B. 3 Neutron radiography method Neutron radiography and X-radiography share some similarities but produce different results when applied to the same object. Neutrons replace X-rays as the penetrating beam of radiation whose intensity is modulated by an object, resulting in a film image of the features of the object. Since the absorption characteristics of materials for X-rays and neutrons are very different, the two techniques generally tend to complement one another. Neutron and X-ray attenuation coefficients, presented in figure 1 as a function of atomic number, are a measure of this difference. 5 Neutron sources Neutron sources suitable for thermal neutron radiography can be classified into three general categories: — radioactive isotopes; — sealed tubes and accelerators of particles; and — nuclear reactors. Each of these sources produces high-energy neutrons that require moderation (slowing down) to thermal energies. This can be accomplished by surrounding the neutron source with beryllium, graphite, water, oil, plastic or some other moderator material.5.1 Isotopic sources Isotopic sources have the advantage of being small and portable but because of their relatively low neutron yield require long exposure times to achieve a given radiographic quality. Many isotopic sources have been used for neutron radiography and the most common of these are shown in table 1. Californium ( 252 Cf) is one of the most popular isotopic sources used for thermal neutron radiography because of its low neutron energy and small physical size which permit efficient moderation and high total neutron yield.5.2 Accelerator sources Sealed tubes and low-voltage accelerators utilizing the 3 H(d,n) 4 He reaction, high-energy X-ray machines utilizing the (x, n) reaction, and...