Since the al-Qaida attacks on New York and Washington in 2001, there has been scientific debate about whether terrorists could obtain used nuclear fuel from storage facilities at nuclear power plants and make a radiation bomb from it.
Most of the spent fuel rods are stored in big, deep pools of water, which cool them and shield radiation. Many are below ground, although some are in more vulnerable pools above ground. Some used fuel is stored in dry steel and concrete casks after it is cooled for about five years.
A panel of experts has recommended that U.S. government nuclear power plant regulators take measures to better secure spent nuclear fuel from terrorists.
The U.S. Congress asked the National Academy of Sciences to determine how vulnerable the system is. A panel of private experts appointed by the academy says its investigation shows spent fuel stores are relatively safe from theft.
"Our committee has concluded that given existing security measures in place at commercial nuclear power plants in the United States, the likelihood that terrorists could steal enough spent fuel for use in a dirty bomb is small. That is very good news," said Louis Lanzerotti of the New Jersey Institute of Technology, who is chairman of the group.
Nevertheless, the panel says the spent nuclear fuel stored at some plants, mainly in above-ground facilities, is vulnerable to attack.
"We found that a terrorist attack that partially or completely drains a plant's spent fuel pool might be capable of setting off a high temperature fire that could release large quantities of radioactive material into the environment. Our committee identified several terrorist attack scenarios that potentially could have serious consequences at some plants," said Mr. Lanzerotti.
To reduce the risk, the experts recommend rearranging the rods in the pools to more evenly distribute the heat loads and radioactive decay. They also urge the installation of water spray systems to cool the fuel rods and call for power plant operators to consider moving the spent rods from pools to dry casks earlier than five years in some situations.
The Bush administration defends the safety of the pools. Government regulators and the nuclear power industry they oversee warn that moving large amounts of fuel to dry storage would be unnecessary and expensive.
The National Academy of Sciences expert team was unable to obtain information about plant security arrangements from U.S. government nuclear regulators, so it urged the government to review these arrangements at each facility and upgrade them where necessary.The panel says prompt adoption of its recommendations would improve the U.S. national defense against terrorism.