Samir Abdul-Majid

Radioactivity concentration in soil in Jeddah area, Saudi Arabia

Abstract The level of radioactivity in soil was measured in Jeddah area. 137Cs concentration was determined as an indication of the degree of contamination from Chernobyl accident. Natural uranium and thorium radioactive series, as well as 40K concentration levels have been determined. These radioisotopes contribute to the background exposure both indoor and outdoor. The concentration of 214Bi a member of 238U Series and that of 228Ac from 232Th series were measured. For the gamma spectroscopy method 10% efficiency high purity vertifical Ge detector of 2 KeV resolution at 1.332 Mcv was utilized. Standard soil sources were made using 152Eu and 137Cs of known activities. The concentration of 137Cs, 214Bi, 228Ac and 40K in Bq/Kg were 0.32, 9,25, 7.4 and 369 respectively. The energy dependent Ge detector efficiency for measuring radioactivity in soil was further determined.

Single Side Imaging of Corrosion Under Insulation Using Single Photon Gamma Backscattering

In this work, a gamma ray Compton backscatter technique is used for imaging defects and thickness variations in insulated pipes and metal plates containing depressions of various diameters and at various depths from one side of the object. The scattered radiation was measured by a scintillation detector that scans the object using a two-dimensional mechanical scanning system. The gamma spectrum was displayed with a multichannel analyzer (MCA), and the energy window width was selected so that only Compton single scatter counts were measured. Images were constructed using the LabVIEW computer program. Successful images of defects on the outer surface of the object under the insulation were obtained, and the system was found to be able to detect wall thickness changes in large pipes with walls more than 15 mm thick. Low activity sources of 108 Bq (a few mCi) were used, and the dose rate near the surface is four orders of magnitude lower than conventional industrial radiography sources, permitting it to be much safer.

Neutron-capture gamma-ray technique for scale identification inside pipes

Abstract Identification of scale from out-side the pipe without having to stop the station may have some economical advantage. There is a possibility that scale can be removed while the plant is in operation by some chemical method. In this technique neutrons from a neutron source such as 241 Am - 9Be are allowed to interact with the pipe material. Some of these neutrons are absorbed by the scale materials or by pipe material. Immediately after absorption they will emit gamma-ray photons which are characteristics of the materials. Their intensity will be proportional to the amount of scale while their energy will indicate the type of elements of the scale. Pure Ge gamma detector with multichannel analyzer can be used for measuring the energy and intensity of these photons. By using this technique it was possible to identify CaSO4, and other deposits.

Use of a solar panel as a directionally sensitive large-area radiation monitor for direct and scattered x-rays and gamma-rays

The characteristics of a 25.4 X 91 cm solar cell panel used as an x-ray and gamma-ray radiation monitor are presented. Applications for monitoring the primary x-ray beam are described at different values of operating currents and voltages as well as for directional dependence of scattered radiation. Other applications in gamma-ray radiography are also given. The detector showed linear response to both x-ray and gamma-ray exposures. The equipment is rigid, easy to use, relatively inexpensive and requires no power supply or any complex electronic equipment.

Determination of scale thickness and general and localized metal removal in desalination plants by the gamma-ray interaction method

Abstract The gamma-ray back-scattering technique was utilized for measuring corrosion and scale deposit likely to be found at desalination plants. The method can be applied on hot and unprepared surfaces where the commonly used ultrasonic technique fails to produce successful results. CaSO4 deposits inside CuNi or ion pipes and scale accumulated on the wall of superheaters underneath the aluminum cladding was successfully measured. Change in pipe wall thickness that may take place due to erosion of the carbon steel pipes was also measured accurately. In these applications an NaI(Tl) scintillation detector — with a 1024 channel multichannel analyzer and the nuclear electronics including a preamplifier, amplifier and power supply — were utilized. These are relatively inexpensive, uncomplicated equipment that can be portable. Therefore, scanning of pipes from the outside can be performed. Localized metal removal from inside the pipes that may take place due to pitting was also successfully measured by using a pure Ge detector and more powerful multichannel analyzed or 8192 channels. Cracks, voids or other defects may also be measured by this technique. Studies were made at different gamma-ray energies for the appropriate selection of a source. Radioactivity level was of an order of 104 Bq, giving a negligible radiation dose. It is 108 times less than those used in gamma radiography.

Corrosion and scale measurements in iron pipes by prompt gamma-ray analysis

Abstract Neutron prompt gamma-ray analysis has been used to measure the changes in wall thickness of iron pipes due to corrosion, as well as to determine the type and amount of scale that may accumulate inside pipes at desalination plants. The intensities of the 7.632 and 7.646 MeV gamma rays of iron were linear within the iron wall thickness of interest. Elements of interest in scale were Ca, S and Si and were found in different compounds. The intensities of emitted photons from CaSO4, for example, were found to increase with scale thickness. The technique can provide information on the corrosion of pipes and the amount and type of scale simultaneously while the plant is in operation.

Applications of neutron back-diffusion technique for wall thickness and scale measurements at desalination or chemical plants

Abstract A neutron back-diffusion method was used for measurements likely to be found at desalination plants, refineries or chemical plants. Thickness change due to erosion can successfully be measured. The range of thickness measured was more than 5 cm in iron and more than 10 cm in concrete, aluminum and glass. Scale deposit that accumulated on thick walls or inside pipes was also determined by this technique. These measurements can be made without the wall penetration needed for insertion of measuring instruments and without any system disturbance. Neutrons from a 241 Am-Be source are allowed to be incident on the pipe or container. They are moderated by the water or liquid inside, diffuse backward following reduction in energy where some will get absorbed by the pipes wall or the deposit before being measured by a BF 3 slow neutron detector where counts will decrease with thickness.

Measurement of localized metal removal in pipes by gamma-ray back-scattering method

Abstract Localized metal removal in pipes, especially those carrying liquid at high pressure, can creat a real problem where it may make a whole causing a jet stream of the liquid to out-side. Measuring the the localized metal removal region before it develope to a hole will prevent reaching this situation. In this method, which can be used to scan the pipe from out-side, a point gamma-ray source is attached to the center a high resolution portable Ge detector which is connected to a multi-channel analyzer. When the detector and the source are attached to the pipe wall from out-side, gamma photons will interact with the pipe material and some will back-scatter to the detector with lower energy than those of the primary photons. Therefore they will fall in a lower channel number and will not overlap with the primary ones. The amount of the back-scattered photons is proportional to the thickness of the pipe at the source position. Thicker material will scatter more photons and vice-versa. The intensity will depend also on the photon energy and pipe material. In localized metal removal region less photons will back-scatter to the detector and therefore the region can immediately be found out. Localized metal removal region down to a mm range was measured.

Corrosion Imaging and Thickness Determination Using Micro-Curie Radiation Sources Based on Gamma-Ray Backscattering: Experiments and MCNP Simulation

Gamma radiography is used to monitor the corrosion of pipelines in remote locations; usually high radioactivity (1011–1012 Bq) is used. The technique is also not useful for imaging pipes with thick walls or large vessel walls. In this work, Compton backscattered radiation was used for the wall-thickness determination and corrosion imaging of pipe and flat materials using extremely-low-activity sources with radioactivities on the order of 104–105 Bq. A two-dimensional scanning system was designed to scan object surfaces, and the signals from a NaI(Tl) scintillation detector were fed into a computer for image construction using the LabView program. Thicknesses greater than 1 cm and 1.5 cm could be measured for Fe and Al and for polyvinyl chloride (PVC) and poly methyl methacrylate (PMMA), respectively. It was also possible to detect changes of less than 1 mm in depression depth for depressions measuring 3 mm in diameter. One- and two-dimensional images artificial defects on a pipe surface were successfully constructed.

Determination of wax deposition and corrosion in pipelines by neutron back diffusion collimation and neutron capture gamma rays

Wax deposition in pipelines can be very costly for plant operation in oil industry. New techniques are needed for allocation and thickness determination of wax deposits. The timely removal of wax can make large saving in operational cost. Neutron back diffusion and neutron capture gamma rays were used in this study to measure paraffin, asphalt and polyethylene deposition thicknesses inside pipes and to enable simultaneous determination of scale and pipe corrosion. It was possible to determine a thickness change of less than one mm in 2 min. It was also possible to detect localized scale from a small region of the pipe of approximately 2 cm in diameter. Although experiments were performed in lab, the system can be made portable for field applications.