Panoramic irradiators are commonly used to disinfect and sterilize products such as medical supplies, cosmetic raw materials, food, food containers, and medical supplies. The irradiators typically use Cobalt 60 as a source of radiation — a material that could potentially be used to build a “dirty bomb.” As a result, the Nuclear Regulatory Commission requires installation of a security system for each irradiator; however, current electronic security systems have a short lifespan due to the fact that the radiation source must be stored in a pool of water.

The tamper detector includes a network of sealed tubing that spans at least a portion of the access porthole. A gas source connector is provided to establish gas pressure in the tubing. A pressure drop sensor detects a drop in the gas pressure below a preset value.

To use the radiological source, it is raised out of the pool of water through an access porthole into a shielded irradiation room that contains the materials to be sterilized. Typically, the pool of water is in a storage room below the shielded irradiation room, and the access porthole provides a passageway through the ceiling of the storage room and through the floor of the shielded irradiation room. When such radiological sources are raised out of the pool of water into the shielded irradiation room, they emit such intense radiation that a person near the source would die within a few seconds. Consequently, even a suicide terrorist would not likely be able to steal or tamper with an unshielded radiological source of this type. A plausible threat for such theft or tampering might be that a vandal or terrorist could lower a shielding cask over the source while it is in the pool of water, and then raise the source (covered by the shielding cask) out of the water.

The Irradiator Security Gate is a tamper sensor for safeguarding a radiological source that has an associated shipping cask, where the radiological source is accessible through an access porthole. The tamper sensor typically includes a network of sealed tubing that spans at least a portion of the access porthole. There is an opening in the network of sealed tubing that is large enough for passage of the radiological source, but is small enough to prevent passage of the shipping cask.

The sensor includes a coupling for establishing a gas pressure in the tubing network, as well as a pressure drop sensor for detecting a drop in the gas pressure below a preset value. The electronic pressure sensor is adaptable to fit almost any environment where security and durability are a concern, especially in extreme conditions such as high-radiation areas. Electronic components are located remotely from the security system, providing a greater reliability and a longer lifecycle.

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Sensor Technology Magazine

This article first appeared in the March, 2018 issue of Sensor Technology Magazine.

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