Determination of scale deposition in a flare line by neutron back-diffusion.

Flares are used in the oil industry and other industries to dispose of waste gasses by burning. Damaged or blocked flares can lead to incomplete combustion and the release of contaminating gasses into the atmosphere. In this study, the neutron back-diffusion technique was used to measure the scale inside a flare stack. The neutron source employed was 241Am-Be with an activity of 1.11 × 1011 Bq (3 Ci), and a BF3 slow neutron detector. Scanning was conducted for scale in the stack at a refinery. Back-diffused neutron counts were doubled when moving from no scale to a scale thickness of about 17 cm. The scale thickness measured up to 20 cm and a change in the thickness of about 0.25 cm could be detected in a counting time of 1 min. The counting system weighed about 3 kg and it allowed scanning at a high stack elevation. The source employed yielded a total dose of 0.12 mSv h-1 at 1 m, which is significantly smaller than the doses from sources used in industrial radiography.

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.

Determination of air/water ratio in pipes by fast neutrons: experiment and Monte Carlo simulation.

Fast neutron dose attenuation from a (252)Cf neutron source is used for the determination of air to water ratio in pipes. Such measurement of the two-phase flow volume fraction is important for many industrial plants such as desalination plants and oil refineries. Fast neutrons penetrate liquid more than slow neutrons or gamma rays. Using diameters from 11.5 cm to 20.76 cm and with wall thicknesses from 0.45 to 1.02 cm, attenuation was independent of pipe wall thicknesses and diameters. Experimental data was in good agreement with values calculated using MCNP codes. The measured neutron flux values decreased with increasing water levels in pipes up to about 14 cm, indicating that our system can be used successfully in desalination plants in pipes of different sizes. The experimental sensitivity was found to be about 0.015 mSv/hcm and the system can be used to measure water level changes down to few millimeters. Use of such a system in fixed positions in the plant can provide information on plant's overall performance and can detect loss of flow immediately before any consequences. A portable system could be designed to measure the air to water ratio in different locations in the plant in a relatively short time.