Cargo Container X-ray Inspection Systems

1 Hitachi Review Vol. 53 (2004), No. 2 97 Cargo Container X-ray Inspection SystemsOVERVIEW: Container Inspection is categorized into three stages. In theinitial stage, large-size X-ray DR (digital radiography) is used to inspectfull containers sitting on their trailers. If that Inspection identifies suspiciouscargo, the trailer and Container are relocated to a nearby Inspection positionfor opening the Container and inspecting all Cargo inside. In the secondstage, small-size X-ray DR equipment is used to inspect each Cargo . If asuspicious Cargo is detected here, it is then opened, the contents are extractedand checked by manual procedure.

2 For cargoes that cannot be opened, suchas religious statues or works of art such as sculptures, third-stage inspectionsare conducted using an X-ray (computed tomographic) scanner. Hitachi,Ltd. is the only manufacturer in the world that can provide the equipmentneeded in all three Cargo - Container Inspection single Container ship carries an average of 3,000 8,000 containers. To open each Container and removeand inspect its Cargo would be both time-consumingand unrealistic. In order to conduct inspectionseffectively and efficiently, large-size X-ray DR (digitalradiography) equipment is used to inspect containersloaded aboard their trailers (see Fig.)

3 1). For X-rayscapable of scanning Cargo inside a Container actually, a steel-walled box a linear accelerator(linac) that generates 9 MeV (9 mega electron-volts)is the first Inspection stage identifies suspiciouscargo in a Container , the trailer is driven to a nearbystation in the Inspection center where the Container isopened and each piece of Cargo inside is inspectedusing X-ray DR equipment. Suspicious cargoesdetected in that Inspection are then opened, thecontents are extracted and checked manually. Theequipment used in this second-stage inspectionincludes an X-ray tube that generates several hundredkeV (kilo electron-volts).

4 For Cargo that cannot be opened, such as religiousstatues or works of art, including sculptures, an X-rayCT (computed tomographic) scanner is used to createtomographic images for viewing. Since Cargo in thisthird-stage Inspection process is often made of metalor marble, a linac with energy of about 1 MeV is scanning equipment is convenient to usebecause turning off the power source halts itsoperation. It is used in a wide range of following paper introduces various types ofinspection OF X-ray INSPECTIONEQUIPMENTX-ray Equipment for Inspecting Containers(1) Outline of equipmentThe X-ray equipment available for inspectingFig. 1 Overall View of Container Inspection Container Inspection center is often located near a seaportcontainer terminal.

5 The center consists of two types ofinspection facilities. One is for inspecting Cargo containersusing large-size X-ray equipment while loaded on trailers. Theother unit is for individual Inspection of all Cargo inside acontainer when the trailer X-ray Inspection identifies asuspicious piece of Container X-ray Inspection Systems 98No. 2 shielding doorNo. 1 shielding doorExit zoneInspection zoneContainer trailerEntrance zoneAfter the first shielding door opens, the trailer is pulledto the center of the Inspection zone and halted. TheNo. 1 trailer conveyor is then removed from under thetrailer s front wheels and returns to its original positionin the entrance zone.

6 At that point, the No. 2 trailerconveyor takes over by once again raising the trailer stwo front wheels. After the No. 1 shielding door isclosed the entire Container is exposed to X-rays emittedfrom two directions relative to the direction thecontainer is heading, horizontal and vertical. After theX-ray process ends, the No. 2 shielding door opensand the trailer is pulled into the exit zone. The waitingdriver then boards the trailer and drives it from theinspection the X-rays pass through the Container andare attenuated, a detector detects and measures on how strong the X-rays are the detectorconverts them into analog electric signals and transmitsthem to an image-processing computer.

7 If the resultantimages show suspicious objects in the Container ,additional processing raises the level of contrastsensitivity and enlarges the objects inside to determinewhat they are. The Inspection images are transmittedto an electronic image data server, and the computerreceiving the Inspection data transmits the informationto a data server. From there, the horizontal images,vertical images, and declared information are alltransmitted to an inspector s computer are inspected at the rate of 20/h.(3) Conveying deviceThe trailer conveyor is fixed to a trailer s two frontwheels and pulls the trailer forward. As the trailer ispulled forward at a set speed, the perpendicular X-raybeams from the vertical and horizontal X-ray sourcespass through the Container .

8 The structure of the trailerconveyor is designed so as not to interfere with the X-ray inspections. An interlock control prevents the trailerconveyor from colliding with each other or with theshielding doors.(4) Safety equipmentSafety equipment is installed to determine whetheranyone is in the Inspection zone, and an interlockprevents the X-ray equipment from operating whensomeone is detected. The following safety equipmentis fitted to the facility:(1) Buzzer for confirming that the driver has alightedfrom the trailer(2) Safety confirmation device (device for confirmingmoving objects)(3) Surveillance camera(4) Emergency stop switchcontainers includes fixed type for use inside a buildingand mobile type used outside in the open.

9 The powersource for X-ray equipment used inside is 9 MeV andfor that used outside because there is no shield andin order to reduce the space for managing radiation is somewhat low energy of 6 2 shows a typical facility for housing fixed-type Inspection equipment. It has an entrance zone,an Inspection zone, and an exit zone. The inspectionzone is built of concrete, with shielding doors at itsentrance and exit. The concrete structure preventsradiation leaks to the outside. In fact, the concrete isthicker in the areas nearest the X-ray source and X-ray detection equipment. The equipment and structuresmost closely related to the X-rays are the first shieldingdoor at the entrance, the second shielding door at theexit, the X-ray source for horizontal inspections, theX-ray detector used for horizontal inspections, the X-ray source for vertical inspections, and the X-raydetector used for vertical inspections.

10 The equipmentused for conveying the trailer inside the structureincludes the No. 1 and No. 2 trailer conveyors.(2) Flow of Inspection proceduresThe Container trailer driver drives the trailer to adesignated position in the entrance zone, turns off theignition, and alights from the vehicle. During theinspection he/she waits in a special waiting area in theexit zone. The No. 1 trailer conveyor located in theinspection structure s underground area raises thetrailer s two front wheels in order to pull it 2 Schematic of Facility and Equipment for X-RayInspection of the central Inspection zone is X-ray Inspection equipment forboth horizontal and vertical Review Vol.