Neutron Radiographic Technique Research Articles

Feasibility of volumetric expansion of molten chlorides by conventional pushrod dilatometry

This study is a short communication on progress made in the adaptation of conventional push-rod dilatometry for the measurement of volumetric expansion of liquid salts up to 1300 K. A new crucible design is offered as a practical solution for measurement of liquid salts by this method. Proof-of-concept measurements of the volumetric expansion of sodium chloride (NaCl) are compared to the available data in literature. Measurement of the coefficient of thermal expansion (CTE) of solid NaCl compared favorably to the available data in literature, confirming both magnitude and trend. The average CTE of NaCl (solid) was overline{alpha }_{{{text{NaCl}};{text{Solid}}}} = 5.63 cdot 10^{ - 5} {raise0.7exhbox{1} !mathord{left/ {vphantom {1 K}}right.kern-nulldelimiterspace} !lower0.7exhbox{K}}. The volumetric expansion of liquid NaCl was measured as beta_{{{text{NaCl}};{text{Liquid}}}} approx 3.96 cdot 10^{ - 5} 1/K and is essentially constant from the melt point to 1300 K. The volumetric expansion produced by this method is in reasonable agreement with the available published data and previous measurements made by the authors by neutron radiographic technique.

Visualization of Two-Phase Flow in Metallic Pipes Using Neutron Radiographic Technique

The study of two-phase flow is a matter of great interest both for the engineering and oil industries. The production of oil and natural gas involves the transportation of fluids in their liquid and gaseous states, respectively, to the processing plant for refinement. The forecasting of two-phase flow in oil pipes is of the utmost important yet an extremely difficult task. With the development of the Electronic Imaging System, installed in J-9 irradiation channel of the IEN/CNEN Argonauta Reactor, it is possible to visualize the different types of two phase air-water flows in small-diameter metallic pipes. After developing the captured image the liquid-gas drift flux correlation as well as the void fraction in relation to the injected air outflow for a fixed water outflow can be obtained.

Advances in neutron radiographic techniques and applications: a method for nondestructive testing

A brief history of neutron radiography is presented to set the stage for a discussion of significant neutron radiographic developments and an assessment of future directions for neutron radiography. Specific advances are seen in the use of modern, high dynamic range imaging methods (image plates and flat panels) and for high contrast techniques such as phase contrast, and phase-sensitive imaging. Competition for neutron radiographic inspection may develop as these techniques offer application prospects for X-ray methods.

Vapor fraction measurements in a steam–water tube at up to 15 bar using neutron radiography techniques

Real-time neutron radiography has been used to study the dynamic behavior of two-phase flow and measure the time averaged vapor fraction in a heated metal tube containing boiling steam–water operating at up to 15 bar pressure. The neutron radiographic technique is non-intrusive and requires no special transparent window region. This is the first time this technique has been used in an electrically heated pressurized flow loop. This unique experimental method offers the opportunity to observe and record on videotape, flow patterns and transient behavior of two-phase flow inside opaque containers without disturbing the environment. In this study the test sections consisted of stainless steel tubes with a 1.27 cm outer diameter and wall thicknesses of 0.084 and 0.124 cm. The experiments were carried out at the Pennsylvania State University 1 MW TRIGA reactor facility utilizing a Precise Optics neutron radiography camera. The inlet water temperature to the test section was varied between 120°C and 170°C and the flow rate set to 2.3 l/min. T sat is 200°C at these conditions. The tube was resistively heated by passing high currents (∼1000 A) through the stainless steel wall. Scattering due to water in the ∼1 cm tube is significant and Monte Carlo calculations simulating the experiment were made to correct for this effect on the vapor fraction measurement. Details of the experimental technique, methods for analyzing the data and the results of the experiments are discussed.

Application of capillary optics to neutron radiography

We propose two neutron radiographic techniques that make use of the converging beam from a tapered monolithic lens. The first is a focusing technique that enables one to obtain an image of a given cross section within an object. The second technique is neutron radiography that uses a beam emanating from a near point source. Both methods provide an improvement in spatial resolution for neutron radiography.

Visualization and analysis of forced diffusion of hydrogen in palladium by electrotransport

This study analyzes electrotransported hydrogen in palladium hydride by the neutron radiographic technique. Electrotransport was utilized to densify hydrogen in palladium metal. The effectiveness of electrotransport on hydrogen densification was verified by neutron radiographic visualization. The concentration was enhanced up to 0.75 ± 0.05 of the (H/Pd) ratio at 395 K, which was equivalent to hydrogen equilibrium pressure of 100 MPa. From the hydrogen profile in electrotransported PdH x , the effective number of the electric charge of hydrogen in PdH 0.75( Z H *) was determined to be 0.38 ± 0.08.

Quantitative limits of thermal and fluid phenomena measurements using the neutron attenuation characteristics of materials

Temporal and spatial resolution of the neutron radiographic technique were investigated in order to apply this technique to the visualization and measurement of thermal and fluid phenomena. The temporal resolution of three imaging methods of temporally resolved neutron radiography-static neutron radiography with a pulsed neutron beam and high frame rate neutron radiography with either a pulsed or steady neutron beam-was studied. It was determined that the temporal resolution was determined by the sensitivity and light decay time of the image detector and statistical variation of neutrons, and the resolution limits of static and dynamic imaging methods were estimated to be a few microseconds and a few hundred microseconds, respectively. An image processing method was proposed to measure flow characteristics such as void fraction. By performing an error analysis to calculate the limit value of liquid film thickness that can be measured by neutron radiography, it was determined that the limit value of a rectangular channel gap or round tube diameter should be smaller than 3.25 or 4.00 mm, respectively, for measuring the void fraction of air-water flow within an error of 10%. The void fraction measuring method was experimentally confirmed by comparing the void fraction values in a rectangular duct with a 2.4-mm gap obtained by neutron radiography with those obtained by optical and conductance probe methods. It was shown quantitatively that the measurement error decreased when consecutive frames were temporally integrated.

Development of a neutron-radiographic technique for investigating physical models of fluidized beds : Catchen, G.L.; Hughes, D.E.; Kulkarni, A.K.; Ross, K.M.; Ammerman, W.R. Chemical Engineering communications, Vol. 54, no. 1–6, pp. 73–84 (1987)

Development of a neutron-radiographic technique for investigating physical models of fluidized beds : Catchen, G.L.; Hughes, D.E.; Kulkarni, A.K.; Ross, K.M.; Ammerman, W.R. Chemical Engineering communications, Vol. 54, no. 1–6, pp. 73–84 (1987)

Transient gas density measurement using neutron radiography

Neutron radiography is discussed as a line-of-sight gasdynamic diagnostic technique for studying internal flows in opaque, complicated geometry flow systems which are not optically accessible. Because neutron attenuation is very sensitive to nuclear structure, many material combinations that are difficult or impossible to image with optical techniques or x rays can be imaged by means of neutron radiography. The problem presented to demonstrate the neutron radiographic technique is the determination of the time-resolved gas-gas interface location inside a gas transfer system composed of three pressure vessels connected by opaque, thick-walled tubing.

Neutron Radiography Experiments at JRR-4, (II)

Experiments have been performed at JRR-4 (Japan Research Reactor) to investigate the capability of neutron radiographic techniques in applying to the nondestructive inspection of UO2-PuO2 mixed-oxide fuels. The object of the inspection was to detect “Pu particles” in the mixed-oxide fuels. In place of the actual fuel, two stages of TiO2-EU2O3 mixed-oxide fuel dummy samples (the 1st stage for preliminary experiments and the 2nd stage for simulating the ATR fuel) were fabricated and radiographed with the direct exposure method using a Gd converter screen and high resolution films. Neutron radiographs of the 1st stage dummy samples showed the excellent capability of the detection technique. Those of the 2nd stage dummy samples, however, revealed the detection limit of the technique, which showed that the present technique had not enough capability to satisfy the requirements in the inspection and that improvements of the detection technique especially on the contrast should be accomplished.

Neutron Radiography Experiments at JRR-4, (I)

Experiments have been performed at JRR-4 (Japan Research Reactor) to investigate the capability of neutron radiographic techniques in applying to the nondestructive inspection of UO2-PuO2 mixed-oxide fuels. The object of the inspection was to detect “Pu particles” in the mixed-oxide fuels. In place of the actual fuel, two stages of TiO2-EU2O3 mixed-oxide fuel dummy samples (the 1st stage for preliminary experiments and the 2nd stage for simulating the ATR fuel) were fabricated and radiographed with the direct exposure method using a Gd converter screen and high resolution films. Neutron radiographs of the 1st stage dummy samples showed the excellent capability of the detection technique. Those of the 2nd stage dummy samples, however, revealed the detection limit of the technique, which showed that the present technique had not enough capability to satisfy the requirements in the inspection and that improvements of the detection technique especially on the contrast should be accomplished.

Neutron radiography of osseous tumours.

THE use of a beam of neutrons to create an image of an object is a procedure with wide application1–4. Neutron radiography provides a non-destructive diagnostic technique giving information not obtainable by density-dependent X-ray techniques. We believe we have developed the first effective neutron radiographic technique of detecting pathological tissue within unsectioned biopsied bone specimens.

Neutron radiographic study of limiting planar heat pipe performance

A condition limiting the maximum heat transfer rate attainable by heat pipes has been investigated experimentally. Using neutron radiographic techniques, a detailed investigation of the vaporization processes which occur interior to the wick structure of a planar heat pipe employing water as a working fluid was conducted for a number of wicks having different mean pore sizes and for several angles of inclination of the wick. The neutron radiographic system employed permitted measurements of the liquid layer thickness, in the wick, to be made with an accuracy of 0·006 in. for thicknesses up to 0·125 in. of water, and with a lateral resolution of 0·0135 in. Two models of the heat transfer process occurring in planar heat pipes were postulated and analytically formulated. The first model assumed that evaporation occurred only from the upper surface of the wick whereas the second assumed that vapor was generated at the wick's base and released solely from the sides of the wick. With a secondary assumption of variable pore size, the second model proved to be more realistic for correlating the test date than the first. The apparent variation of pore size, indicated by the data to be a function of heat transfer rate, has been interpreted as a manifestation of the “Leverett effect”.

Neutron Radiographic Inspection of Radioactive Irradiated Reactor Fuel Specimens

A method for nondestructive inspection of highly radioactive, irradiated reactor fuel specimens is described. The method is a neutron radiographic technique which employs image detectors of metal s...