ADVANCED TECHNOLOGY OF LUMINOPHOR SCREENS FOR SOLID RADIOLUMINESCENT LIGHT SOURCES

The article observes different methods of coating the phosphor screens on the tritiated titanium matrices for creating the solid-state radioluminescent light sources (SRLS). Technology of SRLS is alternative to the existing technology of the gas-filled radioluminescent light sources. The main idea of SRLS is in bonding the working isotope (tritium) in the solid matrix and combining it with the phosphor. The key problem of SRLS is to provide the closest contact between the tritiated carrier matrix and phosphor screen. The basic requirements for the phosphor screens for SRLS would be the strength of fixation on the plate, uniformity and radiological and thermal stability. There have been made a comparison of various techniques of coating and fixing the phosphor screens by their effect on spectral and brightness characteristics of SRLS. The improved sol-gel technique of suspended sedimentation of phosphor screen from the potassium water glass binder solution was developed. The composition of the solution was established experimentally and we get the strong and uniform experimental prototypes of the glass coated phosphor screens of various thickness. The developed technology allows to deposit the strong and uniform phosphor coatings without using any additional dispersing agents. Screen thickness regulates by the amount of phosphor in the suspension. Also the optimal thickness of the phosphor screen, giving the maximum luminescence intensity was determined. The two laboratory prototypes of solid-state radioluminescent light sources were manufactured by coating the phosphor directly on the tritium β-source.

Application of Computed Radiography in Pressure Vessel Welds: ASME Sec V Requirements and Recommendations of ASTM E2007

Computed radiography or CR has been used in the Radiography NDT industry for quite a long time. Use of CR in the pressure vessel welds has not been so popular or common industry practice, particularly in this region, may be because of cost and to some extent acceptance by the client. However ASME BPV Code has already approved use of CR and DR techniques in pressure vessel welds in place of film Radiography. The latest edition of ASME BPV Code Sec V has added some new requirements for qualification and certification of NDT personnel in Computed Radiography (ASME Sec V: 2015 Article I; Mandatory Appendix II). Typically, as we all know, CR or computed radiography uses a storage phosphor imaging plates, known as SPIP, which emits photo-stimulable luminescence in place of Silver Bromide coated films, that luminescence or light radiation is amplified by photomultiplier tubes and passes through A/D converter and several filters which produce an image on the suitable computer monitor. Most of the requirements of ASME Sec V for CR are similar to that of film radiography except in some cases as resolution, brightness and contrast in place of density and contrast used for film radiography. Although it requires expertise for processing the images, but the technique is very useful in replacing film radiography particularly in terms of chemical hazards and environmental issues of film processing, exposed film archiving and computer assisted image enhancement. But more than in traditional radiography, the use of digital images is a trade-off between the speed and the required quality. Better image quality is obtained by longer exposure times, slower phosphor screens and higher scan resolutions. Therefore, different kinds of storage phosphor screens are needed in order to cover every application. ASTM E2007 & E2033 provide excellent information and guidance of the process and application of computed radiography. Here in this presentation, we have described our understanding and experience of using computed radiography in lieu of film radiography for a pressure vessel meeting all the requirements of ASME Code.