VIENNA – The UN’s nuclear agency will help protect this summer’s Athens Olympics against any nuclear threat, such as a «dirty bomb» attack. A document to governors of the International Atomic Energy Agency this week said the IAEA would «provide advice and equipment to prevent and detect any unauthorized use of nuclear and other radioactive materials» during the Olympics. The document obtained by Reuters said the United States was helping to upgrade security at nuclear research installations in Greece, and France was involved in reviewing «incident response arrangements.» An IAEA spokesman declined to comment on the document titled «Nuclear Security – Measures to Protect Against Nuclear Terrorism.» Western intelligence sources say they do not believe groups like Al Qaeda have access to nuclear weapons, but that militants probably do have the capacity to build a crude «dirty bomb.» Using radioactive material packed around conventional explosives, such a device would contaminate the area of the blast and trigger mass panic, even if it did not kill large numbers of people. Attacks using chemical, biological or radiological weapons are among the ultimate threats faced by security planners for the Athens Olympics in August, the first Summer Games since the September 11 attacks on the United States in 2001. Such scenarios are expected to figure in a two-week Olympic security exercise, code-named Hercules’ Shield, which began in Greece on Wednesday and involves several hundred US troops. Details of the operation are secret. Separately, the IAEA paper said the agency is working with member states to guard against the possibility of sabotage at nuclear installations. Much attention has focused since September 11 on the risk of external attacks on nuclear plants, including the possibility of strikes from the air. But the document cites the need for «protection against an ‘insider’ threat,» and refers several times to the possibility of sabotage. Without going into details, it stresses the need for «protection of technical systems that are important for the safety of the installation,» and for adequate response plans.