September 3, 2004

The question has been asked of us: was a "Geiger Counter" (radiation detector) used at the crash site of the CH-53D helicopter in Okinawa?

• The answer is yes. One of the standard tools used in examining some aircraft or helicopter wreckage is a radiation detector. In response to the crash of the CH-53D helicopter on August 13 in Okinawa, safety and rescue personnel of the U.S. Marine Corps followed a careful series of procedures to ensure the safety of bystanders and the crew, and the integrity of the wreckage. The wreckage must be carefully examined to prevent damage to the environment and, ultimately, to learn the cause of the crash.

• What were we looking for with a radiation detector? The CH-53D, is equipped with a rotor safety device and an ice detector that contain a low level radioactive isotope, Strontium-90. A radiation detector was used to find and account for this equipment in the wreckage. The rotor safety device that contains this material is called an In-flight Blade Inspection System (IBIS), a sensor attached to the helicopter rotor blades that alerts the pilot to any cracks or weaknesses in the blades.

• The IBIS safety device includes six sources in separate casings. The casings are located on the root of the blades attached to the rotor. Each casing contains approximately 500 microcuries of Strontium 90, encased in a tiny stainless steel protective cylinder about the size of the press button on a ballpoint pen. Five of the six cases were recovered from the crash site; evidence strongly indicates one was vaporized in the burnt and melted wreckage and is no longer identifiable. The amount of Strontium 90 consumed in the fire poses no risk to humans. This amount equates to an exposure much less than a normal chest x-ray or a flight across the Pacific. The ice detector contains approximately 50 microcuries of Strontium 90, which was recovered at the site.

• The Marines, in coordination with a private Japanese company, will conduct an environmental impact study and release the results as soon as possible. They will check for any kind of materials still at the site, including strontium-90, fuel, other composite materials and any other potential contaminants. Preliminary findings suggest, however, that there are no traces of radioactive contamination at the crash site.