The attacks of September 11, 2001, heightened interest in port and maritime security. Much of this interest has focused on cargo container ships because of concern that terrorists could use containers to transport weapons into the United States, yet only a small fraction of the millions of cargo containers entering the country each year is inspected. Some fear that a container-borne atomic bomb detonated in a U.S. port could wreak economic as well as physical havoc. Robert Bonner, former head of Customs and Border Protection (CBP) in the Department of Homeland Security (DHS), has argued that such an attack would lead to a halt to container traffic worldwide for some time, bringing the world economy to its knees. Stephen Flynn, a retired Coast Guard commander and an expert on maritime security at the Council on Foreign Relations, holds a similar view. While container ships accounted for 30.4% of vessel calls to U.S. ports in 2005, other ships carried crude oil (12.9%), dry bulk cargo (18.7%), and vehicles (6.0%), among other things. These ships merit attention as well because terrorists will look for the weak link. The 9/11 Commission stressed the importance of a balanced approach to maritime security. To this end, this report focuses on the threat of a terrorist nuclear attack using oil tanker ships. This threat is of particular interest because the Middle East is the chief source of anti-U.S. terrorism. Crude oil and other petroleum products account for almost all export earnings of many Middle Eastern nations. In turn, 28.8% of net U.S. crude oil imports in September 2006 came from the Middle East. Crude oil from the Middle East went to 30 U.S. ports in 2003. Those handling the most oil were Blaine, WA; El Segundo, Long Beach, Los Angeles, and Richmond, CA; Corpus Christi, Freeport, Galveston, Houston, Port Arthur, and Texas City, TX; Baton Rouge, Gramercy, Lake Charles, Morgan City, and New Orleans, LA; Pascagoula, MS; Mobile, AL; Wilmington, DE; and Paulsboro, NJ. Crude oil from the Middle East is typically shipped to the United States in supertankersâVery Large Crude Carriers (VLCCs) and Ultra Large Crude Carriers (ULCCs). Their size is measured in deadweight tons (DWT), the weight of the stores, fuel, and cargo they can carry. One DWT is 2,240 lb. While definitions vary slightly, VLCCs can carry about 200,000 to 300,000 DWT and ULCCs can carry more than 300,000 DWT. Crude oil accounts for almost all of the deadweight tonnage of such ships. A representative ULCC was 60 meters wide and 350 meters long, and had a draft (depth below the waterline) of 22 meters. They are the largest ships ever built. The interior of a tanker is divided into multiple storage tanks. Both the Coast Guard and the Navy stated that they do not have responsibility for, or authority over, security of foreign-flagged vessels at foreign ports. Nor do other American forces. Security of foreign ports rests with foreign governments. The simplest type of atomic bomb, and by far the easiest to fabricate, is a gun-assembly bomb, in which one mass of uranium highly enriched in the fissile isotope 235 (highly enriched uranium, or HEU) is shot down a tube into another mass of HEU, forming a critical mass and causing a nuclear explosion. The Hiroshima bomb was of this type; its designers had such confidence in the design that it was not tested before use. This bomb had an explosive yield of 15 kilotons (equivalent to 15,000 tons of TNT). Excluding the bomb's outer casing, fins, and fuses, this device was 6 feet long and about 6 inches in diameter, and weighed about 1,000 pounds. Some items loaded onto large cargo ships are of similar or greater size and weight. It might be possible to make a lighter gun-assembly bomb. To stage a nuclear attack using a tanker, terrorists would need to acquire a nuclear device and smuggle it (or key components) onto a ship. Their ability to accomplish this latter task would likely depend on their ability to circumvent local security; on the reliability of security personnel in oil-exporting countries such as Saudi Arabia, Kuwait, and Algeria; and on the reliability of the ship's officers and crew. Terrorists might seek to place a nuclear device inside one of a tanker's oil tanks, which would require sealing and cushioning the bomb and possibly attaching it to the tank wall; or in a dry space on the ship; or in a blister attached to the ship underwater. Remotely detonating a bomb inside an oil tank or underwater might be difficult: it might not be possible to attach wires leading out to dry spaces, or to send an electromagnetic signal (e.g., a cell phone call) through water or oil to the bomb. Detonating the bomb with a timer would run the risk of the ship not being at the target at the specified time. Overcoming these challenges might be within the ability of a terrorist group resourceful enough to acquire an atomic bomb. Terrorists might also smuggle a bomb onto a ship at sea, as discussed later. Terrorists could be expected to select as their target a port that handled a large volume of oil and other goods and that had a densely-populated area that tankers passed on their way through a harbor to an unloading terminal. Various cities worldwide meet these criteria. If terrorists sought major economic damage while minimizing loss of life, they might target the Louisiana Offshore Oil Port, or LOOP, the only U.S. deepwater oil port that can handle fully loaded supertankers. LOOP, 18 miles off the Louisiana coast, handles about 10% of U.S. crude oil imports. The Panama Canal might be another potential economic target. Some means of detecting atomic bombs in a tanker would fail, especially for a bomb inside an oil tank. Gamma rays, essentially high-energy x-rays, are used to create x-ray-type pictures of the contents of cargo containers, but a tanker's huge mass of oil and steel would prevent gamma rays from traveling the width of a tanker. Neutrons may be used to detect fissile material; neutrons of the appropriate energy level cause such material to fission, producing neutrons and gamma rays that can be detected. The hydrogen atoms of crude oil, however, would block neutrons from penetrating. Other candidate techniques include chemical sampling of oil for traces of extraneous material, and preparing an acoustic profile of a ship when known to be "clean" to compare with a profile taken as the ship nears port. The vast amount of oil in a supertanker works against the former technique; the complex configuration of tanks on a tanker works against the latter. A more remote possibility, muon detection, might work if daunting technical challenges could be overcome. The difficulty of detecting a bomb aboard a tanker underscores the importance of keeping bombs off tankers. Securing tankers at loading terminals would likely involve a security perimeter (including underwater), and measures to ensure personnel reliability. Items brought on a ship would have to be screened. A National Nuclear Security Administration program, "Second Line of Defense," screens people and baggage for fissile material; similar technology might help secure tankers. Securing tankers in port might not be sufficient if terrorists could smuggle a bomb onto a ship at sea. It may be possible to improve security by using surveillance aircraft or satellites. Security may be a greater issue as tankers slow to navigate straits or approach port. Several issues arise: (1) Would shippers let crew spend time to upgrade security beyond current levels? VLCCs have small crews, perhaps 25 to 40 people, who may have no time for added tasks. (2) If intelligence data indicated a plot to board a tanker at sea to place a bomb, could a warning be passed without compromising U.S. intelligence capabilities? (3) This scenario would require the connivance of the entire crew, or silencing those who opposed the plot. Screening for personnel reliability may be the only defense against this prospect. Possible oversight questions include the following: How does the Administration view the potential for terrorists to use a tanker for a nuclear attack? To what extent has the Administration considered this threat in planning for port and maritime security? If considered a serious threat, what measures is the Administration implementing to respond to it? When will they be in place? How much funding is programmed for them over the next few years? Which areas of detection technology may merit development? Which executive branch office has overall responsibility for examining or addressing this potential threat? What other executive offices have responsibilities in this area? Is there adequate coordination among them? Congress might consider options such as the following to further explore the threat discussed in this report. Clarify federal responsibility for tanker security by requiring a lead federal agency for tanker security and making more explicit the responsibilities of various federal agencies involved in tanker security. Create a Tanker Security Initiative (TSI) analogous to the Container Security Initiative for improving containerized cargo security. TSI might set security standards for tankers that transport oil to U.S. ports, and for the ports where they load. Tankers not meeting the standards, or that come from ports not meeting the standards, could be denied entry to U.S. ports. Establishing such a regime would undoubtedly require negotiations with other countries. (See " Legislative Activities ," below.)