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Safe, low-rad sphere tests detectors

Homeland security includes radiation monitors at transportation portals. Y-12 constructed a new, safe device for testing and calibrating portal monitors.

Guarding against nuclear smuggling is a constantly evolving challenge. Every day the U.S. Department of Homeland Security (DHS) processes about 64,000 containers arriving via ship, truck and railcar, as well as 365,000 vehicles and more than 1.1 million people, according to a 2006 Government Accounting Office report. Radiation detection monitors screen this flood of commerce, and the monitors must be tested and calibrated to work properly.

To test them, though, nobody wants to send out large quantities of special nuclear materials (SNM), because they're very expensive to safely and securely transport and they provide an opportunity for theft. A far better approach is to create a testing object that simulates a high quantity of SNM but actually contains a much smaller amount.

Y‑12 has constructed a grapefruit-size device that does just that. As a combination of SNM and aluminum, the testing device offers two important advantages. First, the SNM reading is intensified so it appears to be a much higher quantity of SNM. Second, the alloyed SNM is less attractive to thieves because it is no longer pure weapons-grade material.

“With the Highly Enriched Uranium Equivalent Test Sphere Project, Y‑12 demonstrated a tool that can revolutionize the way special nuclear material detectors are tested,” said Program Manager Lloyd Jollay.

Working with Oak Ridge National Laboratory, Y‑12 used its precision manufacturing expertise to create the first of several spheres. The sphere contains only 46 g of highly enriched uranium (HEU) but has a gamma ray spectrum more than 50 times bigger—equivalent to a solid 2.5-kg HEU sphere.

“The amount of HEU is small enough to have minimal packaging and transportation requirements,” said Todd Hawk, project manager for Nuclear Technology and Nonproliferation. The spherical shape eliminates any orientation effects, allowing the source to be measured and to emit a consistent reading from any direction.

The equivalent spheres will be used to check and calibrate portal monitors and similar devices. The current sphere is already being used to test a passenger baggage screening system and a mobile detection system at the Nevada Test Site. Another application will be in NNSA's Second Line of Defense Program, which collaborates with foreign partners to supply border crossings, airports and seaports with radiation detection equipment. The spheres will also be part of NNSA's Megaports Initiative, which works with partner countries to make sure ports have state-of-the-art portal monitors to reveal SNM or other radioactive material in cargo containers.

Likely users of the spheres include DOE laboratories, DHS agencies and the Defense Threat Reduction Agency. The successful demonstration of an HEU sphere is leading to a significant market for additional sources of this type as well as more complex designs.

Y‑12's manufacturing capabilities are the obvious choice to meet the challenge to provide monitoring equipment to detect and deter the threat of terrorism.

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