The risk of terrorist attacks involving radiological dispersal devices (RDDs) or even crude nuclear devices is still high on the list of non-conventional threats. Preventing radioactive materials or devices from being smuggled through ports is the primary focus of countermeasures programmes.
Practice scenarios have revealed vulnerabilities at points of entry. For example, in 2002 and 2003, ABC News successfully shipped radioactive material undetected into the US from overseas in two scenario tests. In March 2005, a cargo container holding a radioactive source passed undetected through US Department of Energy equipment installed at a foreign seaport due to the presence of large amounts of scrap metal in the container. It is also possible that a terrorist group with limited resources could fly a bomb directly into the country using a private or commercial aircraft, rather than trying to slip it through in a commercial shipping container. Effective detection techniques and equipment are therefore vital for authorities to successfully and speedily intercept illicit materials. Trained first-responders, including the police, fire and ambulance services, must also be available to identify the use of such materials in the event of an attack.
Even before the 11 September 2001 attacks on the New York and Washington, the US and several other countries had begun deploying detection equipment to intercept radioactive materials and devices smuggled across borders and into ports of entry. Detection equipment was also given to first-responder crews and installed at selected sites and buildings classed as prime targets. Beginning in 2002, thousands of radiation detectors were installed outside buildings in New York, Washington and other major US cities.
By May 2005, the Department of Homeland Security had installed more than 470 radiation portal monitors at international mail and package handling facilities, land border crossings and sea ports throughout the US. According to a June 2005 General Accounting Office (GAO) report, Combating nuclear smuggling: efforts to deploy radiation detection equipment in the US and in other countries, the US government has spent about USD300 million on these measures since 1994.
However, according to the GAO report, much of the radiation detection equipment currently in use has limitations. Some of the detectors are unable to identify specific isotopes immediately, cannot detect shielded materials and have frequent false alarms. The equipment's ability to detect nuclear material depends on the amount of material present, the size and capacity of the detection device, the distance between the detection device and the nuclear material and whether the material is shielded from detection with lead casing. Hand-held sensors are more effective when used in conjunction with portal monitors.
The difficulty of spotting a weapon is compounded by the weakness of the signal given off by highly enriched uranium and plutonium, which are relatively feeble emitters of gamma particles. The key to detecting them is to look for neutrons, which are difficult to detect. While newer detectors can scan for gamma particles as well as neutrons, they may fail to detect weapons-grade radioactive material stored in a well-shielded container. A 2003 study by Stanford University found that there is less than a 10 per cent chance of border and customs inspectors detecting a shielded nuclear weapon transported by an unknown carrier.
Improvements are needed to enable detectors to distinguish between radiation-based weapons and harmless sources of radiation, such as cat litter, foodstuffs such as bananas, fertilisers, cement, granite tiles and ceramics, and patients undergoing radiation therapy, all of which set off false alarms. Current detectors tend to set off alarms when the devices pick up low levels of radiation. Sensors posted around the US sound around 150 alarms each day; none of these have proven to come from weapons material. As many as 20,000 hand-held radiation detectors carried by police, fire and emergency personnel throughout New York are said to go off regularly. Vehicles transporting medical isotopes often trigger stationary devices. Low error rates are also essential for radiation detectors at border crossings, as a significant number of false alarms would seriously interfere with trade and tourism.
To improve detection capabilities, the newly established US Domestic Nuclear Detection Office (DNDO) is planning a major push to spur the development of new active and passive radiation detection technology, as well as systems that combine the two.
The detectors currently used by the Department of Homeland Security are mainly passive, meaning they sense radiation constantly emitted by sources and that the detector does not emit any kind of energy. This type of detector is generally viewed as inadequate for detecting nuclear devices. Active detection, which involves stimulating radiation externally, would allow shielded materials to be spotted, but current power and cooling requirements pose an obstacle to widespread use. The DNDO is turning its focus to spectroscopic techniques, which could be used in portal monitors using passive sodium iodide detectors. These are able to distinguish between radioactive sources and innocuous sources such as fertiliser and cat litter. Sodium iodide detectors can be used with handheld instruments or large stationary radiation monitors such as those installed at ports.
In January 2006, US scientists began testing 30 commercially available devices at the Nevada test site. The devices range in size from handheld sensors to portal detectors and include the next generation of spectroscopic detectors. The tests are part of the Radiological/Nuclear Countermeasures Test and Evaluation Complex, which the DNDO set up in 2005 at the Nevada test site to produce a buying guide on the sensors for use by state and local emergency agencies and to discover equipment that can detect real threats, even with a weak signal. The new detectors are intended for use by people with little technological training.
The Nevada testing involves between 70 and 80 different material and shielding scenarios and uses actual special nuclear materials - weapons-grade uranium and plutonium - which are housed at the site. Handheld sensors currently in development are expected to be able to identify sources of radiation in closed shipping containers. The devices could ultimately be used across the US.
Improved radiation detectors are due to be installed at US ports of entry by early 2006, when detection systems will be deployed to the US borders with Mexico and Canada. Field-testing at select ports will begin by June 2006, with a production decision expected in 2007, when sensors will be installed at 2,500 US ports of entry. The DNDO portal programme is part of a worldwide effort to track illegally transported nuclear materials and keep them away from US soil. A future counternuclear plan involves fusing detection data and intelligence assessments in near real-time. Achieving this will require co-ordination with allied countries and other US agencies.
The Bush administration's Homeland Security Department budget request of USD42.7 billion for fiscal year 2007 indicates a big increase for nuclear-detection programmes, including USD536 million for the DNDO. The funding will be for work on detecting shielded plutonium and weapons-grade uranium, deploying radiation monitors at US points of entry and making the transition to next-generation portal monitors.
The Department of Homeland Security is working to create a network of domestic detectors as part of a system of global radiation sensors. It plans to use mobile detection systems and fixed systems to enable random screening around the US, in transit zones, aircraft in flight and container ships. It also plans to use detectors to screen entry points into cities that are at high risk of being attacked and alert law enforcement authorities on discovering suspicious objects. Data from sensors around the world would be compiled in databases to create a global information network.
The General Accounting Office's June 2005 report on deploying radiation detection equipment pointed out that most known seizures of weapons-usable nuclear materials have resulted from police investigations rather than from detection by radiation sensors installed at border crossings. However, there have been recent reports of incidents in which radioactive materials were discovered and seized as a result of alarms raised by detection equipment.
Nevertheless, critics insist that US efforts should focus on securing sensitive nuclear materials in the most vulnerable areas - primarily Russia and the former Soviet Union - and that securing thousands of radioactive sources in these countries should take priority over domestic countermeasures. The first major initiatives to combat nuclear smuggling have concentrated on installing detection equipment at borders in former Soviet countries and in central and Eastern Europe. By the end of 2004, the Department of Energy's Second Line of Defense programme had installed equipment at 66 sites, mostly in Russia. The success of this and other programmes, however, depends on the presence of properly trained border security personnel and effective intelligence-gathering on potential nuclear smuggling operations.
There are also calls for more sensors to be installed at foreign ports with cargo destined for the US. The Megaports Initiative, which was set up by the US in 2003 to deter, detect and interdict illicit nuclear materials trafficking throughout the global maritime network, depends on co-operation from countries with 'chokepoint' destinations. Negotiations are under way with 18 nations, and the US plans to install equipment at 20 ports by 2010. Progress has been slowed by fears on the part of some governments that large-scale use of the detectors on cargoes could slow down work at the ports. Other ports are reluctant to hire additional personnel to operate the equipment.
Andy Oppenheimer is a consultant in nuclear, biological and chemical weapons for Jane's Information Group.