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Radiation Sensors (LRAD) for Uranium Cylinders

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Tech ID: 1560
Project Overview
This device is a small, hand-held device that uses the principle of the Long-Range Alpha Detection (LRAD) technology (TechID #681). LRAD detectors can be used as survey tools to locate leaking cylinders and contaminated areas. They have several advantages over conventional alpha-particle detectors: LRAD detectors are easier to use, monitor large areas more quickly, and monitor areas that cannot be reached with conventional detectors.

Technology Description
The LRAD technology was developed at Los Alamos National Laboratories (LANL) and has been demonstrated to be a highly sensitive method of measuring alpha activity. Alpha particles are highly ionizing particles that lose their energy by creating electron/ion pairs in air. In most gases an energy of approximately 35 electron volts is required to produce an electron/ion pair and thus a typical 5,000,000 eV alpha particle will produce around 150,000 ion pairs. These ions can be collected and measured directly as a current of several femtoamperes (10-15 amperes) per becquerel (Bq). The ions can be transported over a range of several meters in the air current created by using a fan to pass air over the potentially contaminated item to be measured. The ion pairs are transported by moving air to a collection grid. The collected ions create a current flow which is proportional to the alpha activity producing the ions. A detector unit measures the current and converts this electric signal into a number representing the amount of alpha contamination causing the ions. This method relies on the fact that it takes several seconds for half of the ions in the air to recombine. Alpha particles must be able to escape from where they are emitted into the air, i.e., not covered by paint, grease or liquid. Alpha particles must also be able to deposit a large fraction of their energy into the air, i.e. cannot be located in very small grooves etc.

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