Feasibility of using neutron radiography to inspect the Space Shuttle solid rocket booster aft skirt, forward skirt and frustum. Part 1: Summary report

The space shuttle's solid rocket boosters (SRB) include components made primarily of aluminum that are parachuted back for retrieval from the ocean and refurbished for repeated usage. Nondestructive inspection methods used on these aging parts to reduce the risk of unforeseen problems include x-ray, ultrasonics, and eddy current. Neutron radiography tests on segments of an SRB component show that entrapped moisture and naturally occurring aluminum corrosion can be revealed by neutron radiography even if present in only small amounts. Voids in sealant can also be evaluated. Three alternatives are suggested to follow-up this study: (1) take an SRB component to an existing neutron radiography system; (2) take an existing mobile neutron radiography system to the NASA site; or (3) plan a dedicated system custom designed for NASA applications

Statistical Uncertainty in Quantitative Neutron Radiography

We demonstrate a novel procedure to calibrate neutron detection systems commonly used in standard neutron radiography. This calibration allows determining the uncertainties due to Poisson-like neutron counting statistics for each individual pixel of a radiographic image. The obtained statistical errors are necessary in order to perform a correct quantitative analysis. This fast and convenient method is applied to data measured at the cold neutron radiography facility ICON at the Paul Scherrer Institute. Moreover, from the results the effective neutron flux at the beam line is determined

Neutron Radiography

The field of neutron radiography with special reference to isotopic neutron radiography has been reviewed. Different components viz., sources, collimators, imaging systems are described. Various designs of neutron radiography facilities, their relative merits and demerits , the appropriateness of each design depending on the object to be radiographed, and economics of each technique are also dealt. The applications of neutron radiography are also briefly presented

Neutron radiography based visualization and profiling of water uptake in (un)cracked and autonomously healed cementitious materials

Given their low tensile strength, cement-based materials are very susceptible to cracking. These cracks serve as preferential pathways for corrosion inducing substances. For large concrete infrastructure works, currently available time-consuming manual repair techniques are not always an option. Often, one simply cannot reach the damaged areas and when making those areas accessible anyway (e.g., by redirecting traffic), the economic impacts involved would be enormous. Under those circumstances, it might be useful to have concrete with an embedded autonomous healing mechanism. In this paper, the effectiveness of incorporating encapsulated high and low viscosity polyurethane-based healing agents to ensure (multiple) crack healing has been investigated by means of capillary absorption tests on mortar while monitoring the time-dependent water ingress with neutron radiography. Overall visual interpretation and water front/sample cross-section area ratios as well as water profiles representing the area around the crack and their integrals do not show a preference for the high or low viscosity healing agent. Another observation is that in presence of two cracks, only one is properly healed, especially when using the latter healing agent. Exposure to water immediately after release of the healing agent stimulates the foaming reaction of the polyurethane and ensures a better crack closure

Internal curing of cement pastes by superabsorbent polymers studied by means of neutron radiography

Autogenous shrinkage is a problem in cementitious materials with a low water-to-binder ratio. When the internal relative humidity decreases due to the ongoing hydration reaction and selfdesiccation, autogenous shrinkage takes place if no external or internal water source is present. This may lead to cracking and eventually cause durability problems in constructions. Ideally, the internal relative humidity should be maintained during hydration of the cement paste. Superabsorbent polymers (SAPs) may be used to mitigate autogenous shrinkage. When self-desiccation occurs, these polymers will release their absorbed additional mixing water due to increasing capillary forces to stimulate internal curing. This release of water towards the cementitious matrix and the effect on the cementitious matrix itself can be studied by means of neutron radiography. In this study, thin samples of cement paste were casted between glass plates and the evolution of the internal water amount was studied as a function of time. In specimens without SAPs and a water-to-binder ratio of 0.30, shrinkage was seen. Furthermore, autogenous shrinkage was reduced in cement pastes when using SAPs and an additional entrained water-to-binder ratio of 0.054. The release of water from smaller SAPs (100 μm dry size) seemed to be more promising compared to bigger SAPs (500 μm) with the same absorption properties. The technique of neutron radiography supports the findings of shrinkage tests where SAPs were already proven to be useful. This opens additional insights towards the application of SAPs in the construction area

International Neutron Radiography Newsletter

At the First World Conference on Neutron Radiography i t was decided to continue the "Neutron Radiography Newsletter", published previously by J.P. Barton, as the "International Neutron Radiography Newsletter" (INRNL), with J.C. Doraanus as editor. The British Journal of Non-Destructive Testing (BJNDT) has agreed to publish the INRNL in i t s column "NDT Bookcase". The Revue Practique de Control Industriel has also agreed to publish the French version of the INRNL. Up t i l l now 12 issues of the INRNL were published in the BJNDT. They are reviewed below