7.2.3 Cargo and Vehicle Inspection Systems
There are many types of automated inspection equipment for large vehicle or cargo
inspection. Some of the types available, which provide an image of the contents of a vehicle
or container, include X-ray and Gamma Ray inspection systems. There are other systems
available such as neutron or vapor/particle analysis which aim to detect the common chemical
elements associated with explosives or other contraband. Currently the most commonly used
equipment is imaging systems. Generally, this equipment can be divided into mobile and fixed
installations. Many installations are considering procuring mobile systems that afford the
possibility of varying the location of the equipment amongst various entry control facilities.
Installations that plan centralized truck inspection facilities, will consider a fixed installation,
which potentially has an increased throughput and a reduced space requirement. Due to the
wide-ranging requirements for the different manufactured systems, it is not possible to
provide detailed guidance that will support all types of this equipment. However, this section
will attempt to identify the important infrastructure considerations associated with both mobile
and fixed x-ray/gamma-ray inspection systems. Several manufacturers were consulted to
obtain the data used to develop the following guidelines. However, the user is encouraged to
consult with manufacturers of these systems during the design of an entry control facility to
ensure data concerning operational considerations is current and the best available.
These systems offer the ability to inspect vehicles or containers without removing the cargo.
The equipment typically consists of a transmitter (x-ray or gamma ray) and a detector on the
opposite side of the target vehicle. Gamma ray systems utilize a low-level, gamma-ray
radiation source to generate a beam of gamma rays to penetrate the object. The detectors
on the opposite side then measure the amount of gamma ray absorption. This data is then
translated into an image of the contents of the vehicle or container. X-ray systems typically
utilize electro-mechanical equipment to generate X-rays to penetrate the object. Detectors on
the opposite side then record the x-ray transmission, which is then translated into an image.
The MobileSearch and Shaped Energy ISO Search systems (discussed below) also include a
detector on the transmission side of the unit that detects the x-ray reflections, which occur from
organic materials, producing a second type of image of the contents.
Due to the use of gamma or x-ray radiation, there are safety and regulatory considerations
in the use of these systems. The requirements vary depending on the system. Normally an
exclusion zone is established within and around the inspection equipment. The region outside
of the exclusion zone is considered safe during scanning operations. The size of the exclusion
zone varies greatly depending on the type of equipment. Nuclear Regulatory Commission
regulations state that radiation dose limits in Public-Uncontrolled areas are 2 mR in any hour
or 100 mR in any year. Therefore depending on the characteristics of the source, the
frequency of scans, and the expected occupancies the exclusion zone can vary. Additionally,
a shielding wall can be constructed to reduce the dose substantially. Some x-ray systems
have qualified as a "cabinet x-ray system" in accordance with FDA regulations or similar
standards, meaning minimal shielding is required and the exclusion zone does not extend
outside of the footprint of the inspection area. In order to qualify for this designation, FDA
regulations require an emission limit of 0.5 mR per hour at 5 cm from the surface of the
cabinet. Another regulatory consideration is that systems utilizing radioactive sources may
require operation under a radiation materials license held and administered by the owner of
the equipment (the installation).