It would be difficult for terrorists to attack a U.S. city using a nuclear weapon, but such anattack is plausible and would have catastrophic consequences. A report of June 2004 by the NationalCommission on Terrorist Attacks upon the United States found that even though an attempt by alQaeda in 1994 to purchase uranium failed, "al Qaeda continues to pursue its strategic objective ofobtaining a nuclear weapon." (1) A book by the Center for Nonproliferation Studies emphasizes theurgency of taking steps to reduce the risk that terrorists could obtain nuclear weapons ormaterials. (2) A May 2004report by Harvard University's Project on Managing the Atom finds that a nuclear attack "would beamong the most difficult types of attacks for terrorists to accomplish," but that with the necessaryfissile materials, "a capable and well-organized terrorist group plausibly could make, deliver, anddetonate at least a crude nuclear bomb capable of incinerating the heart of any major city in theworld." (3) An earlier reportby the same group estimated the consequences of a ten-kiloton weapon (two-thirds the yield of theHiroshima bomb) detonated at Grand Central Station in Manhattan as over a half-million peoplekilled immediately, hundreds of thousands injured, the possibility (depending on wind direction) ofhaving to evacuate all of Manhattan, much of lower Manhattan permanently destroyed, direct costsof well over $1 trillion, indirect costs several times that, and the prospect for nationwide panic andeconomic chaos if terrorists subsequently claimed to have another bomb. (4) The latter two reports, and acompanion website, (5) provide detailed data on U.S. threat reduction programs and argue that there is an urgent need toaccelerate these programs. This report divides the threat into two aspects, the acquisition of a bomb and its delivery toa target. The former could involve obtaining a nuclear weapon, or obtaining fissile material andmaking it into a bomb. Delivery involves more common and less sophisticated skills to move theweapon covertly to its target. Experts have raised concerns that terrorists might try to acquire two types of nuclearweapons. In the simplest, a "gun-type" weapon, a mass of uranium highly enriched in the fissileisotope 235 (highly enriched uranium, or HEU) is shot down a tube (resembling an artillery tube)into another HEU mass, creating a supercritical mass and a nuclear explosion. The Hiroshima bombused this approach; its designers had such high confidence in it that they did not test this type ofweapon prior to using it. The second type, an implosion weapon, typically uses weapons-gradeplutonium (WGPU, composed mainly of the isotope 239). A shell of WGPU is surrounded bychemical explosives arrayed to produce a symmetrical inward-moving (implosion) shock wave thatcompresses the plutonium enough to be supercritical. The Nagasaki bomb was of this type. It ismuch more complex in design and manufacture than a gun-assembly weapon. An implosion devicewas tested in New Mexico prior to use on Nagasaki. A National Academy of Sciences report asserts,"Crude HEU weapons could be fabricated without state assistance." (6) Some experts believe thatterrorists could create an implosion weapon; (7) others disagree. (8) Terrorists or rogue states might acquire nuclear weapons or fissile materials in various ways. The source of greatest concern is Russia. (9) It has much fissile material. A National Nuclear SecurityAdministration (NNSA) document shows that considerable work remains for the disposition of thismaterial, (10) and aNational Academy of Sciences report states that the risk of diversion of special nuclear material(SNM, or fissile material) from Russia is "high" because "large inventories of SNM are stored atmany sites that apparently lack inventory controls, and indigenous threats have increased." (11) A related concern is that Pakistan might be the source of nuclear weapons or materials forterrorists under several scenarios: (1) Islamists in the armed services might provide such assistancecovertly under the current government; (2) if that government were overthrown by fundamentalists,the new government might make weapons available to terrorists; or (3) such weapons might becomeavailable if chaos, rather than a government, followed the overthrow. Other nations are seeking nuclear weapons. President Bush, in his 2005 State of the UnionAddress, said, "Today, Iran remains the world's primary state sponsor of terror, pursuing nuclearweapons ... it must give up its uranium enrichment program and any plutonium reprocessing ..." (12) According to a pressreport, Mohamed ElBaradei, Director General of the International Atomic Energy Agency, "says heis now certain that the nuclear material his agency once monitored there [in North Korea] has beenconverted into fuel for four to six nuclear bombs." (13) And in a statement of February 2005, North Korea declared thatit had nuclear weapons. (14) There is also evidence of transfers of nuclear weapon materials, designs, productionequipment, and expertise to other nations. A.Q. Khan, the father of Pakistan's atomic bomb, ran acovert operation for many years that reportedly provided Libya, North Korea, and Iran withequipment for making HEU and plans for making an atomic bomb. (15) Reports of February 2005pointed to evidence that strongly indicated that North Korea had provided Libya with uraniumhexafluoride, a chemical used as the feedstock to produce HEU, though another report said that the"evidence ... could just as easily point to Pakistan." (16) Transfers to rogue states, or directly or indirectly to terroristgroups, are a source of concern. Nuclear research reactors offer still another route to obtaining a weapon. Securing the Bomb states, "More than 130 research reactors still use HEU as their fuel, in more than 40 countries. Mostof these facilities have very modest security -- in many cases, no more than a night watchman anda chain-link fence." (17) A more recent Government Accountability Office report stated that as of July 30, 2004, "39 of the105 research reactors targeted by DOE [for conversion from HEU to low-enriched uranium, or LEU]have converted to LEU fuel." (18) Six of these reactors are reportedly on U.S. universitycampuses. (19) A gun-assembly weapon need not be particularly large. The Hiroshima bomb, according toone source, weighed 8,900 pounds and was 10 feet long and 28 inches in diameter. (20) Much of that size andweight, however, was taken up by an armored steel shell and stabilizing fins, as well as by arming,fuzing, and firing devices. (21) The gun barrel -- the actual nuclear explosive device -- measured6 feet in length by over 6 inches in diameter and weighed about a half-ton. (22) Simple improvementsmight shrink size and weight. A terrorist-made implosion weapon or a weapon stolen from a nation'sarsenal could be smaller. In short, a weapon could fit in a car, boat, or small airplane, and wouldoccupy a small corner of a shipping container. The United States has many thousands of miles of land and water borders, as well as severalhundred sea, land, and air ports of entry -- 317 by one count -- giving terrorists many pathways tosmuggle a nuclear bomb into this nation. (23) There are many types of borders, as the following table shows-- oceans (tropical to temperate to Arctic), land and river borders with Mexico and Canada, and theGreat Lakes. Each poses its own set of opportunities for smugglers. Legal and illegal crossings into the United States also present terrorists with different risksand opportunities. Legal crossings are points, such as seaports, airports, and border stations on roadsentering the United States. Illegal crossings are lines -- the thousands of miles of unguardedstretches of coasts and land borders. Securing points poses different requirements from securinglines. Points have an immense volume of traffic, almost all of it legal, and a correspondingconcentration of people and resources of U.S. Customs and Border Protection (CBP). The task ofCBP is to find the needle in the haystack while expediting legal traffic. Attempts to smuggle anuclear weapon through a legal crossing would run the risk that the weapon might be detected bycomputerized screening of cargo manifests, imaging devices (similar to x-rays), neutron activationdevices, or physical inspection, as discussed below. That risk is reduced by the need for CBP agentsto process huge numbers of vehicles, vessels, and passengers, leaving little time or attention for thosenot raising suspicions, and by the low radioactivity of fissile uranium-235 -- approximately onehundred-millionth that of radioactive material that might be used in a "dirty bomb." (24) ABC News attempted to highlight the difficulty of detecting smuggled material. OnSeptember 11 of 2002 and 2003, that organization smuggled a 15-pound cylinder of depleteduranium (DU -- natural uranium minus most of its uranium-235) into the United States in cargocontainers; CBP did not detect it. ABC News said that DU is a good surrogate for HEU; CBP saidthat was not the case, and that there was no reason for CBP to have detected the DU because it islegal to import up to 15 pounds of DU as long as it is declared. The DHS Inspector General found"Improvements are needed in the inspection process to ensure that weapons of mass destruction ...do not gain access to the U.S. through oceangoing cargo containers. Detection equipment and searchprotocols and procedures are the two areas where improvements would enhance the effectivenessof the inspection process." (25) Source: The World Almanac and Book of Facts, 1998. Mahwah, NJ, World Almanac Books, 1997. World Book page and source for each border segment are as follows: U.S. coasts, p. 541, U.S.Department of Commerce, National Oceanic and Atmospheric Administration; Great Lakes, p. 598,U.S. Department of Commerce, National Ocean Service; border with Canada excluding Alaska andGreat Lakes, p.543, Department of the Interior, U.S. Geological Survey, and p. 598, U.S. Departmentof Commerce, National Ocean Service; Alaska-Canada border, p. 543, no source given; andU.S.-Mexico border, p. 543, listed as "approximately," referenced to 1963 boundary agreement. Note that measurements of the U.S. coasts vary sharply, depending on such things as the length ofthe "yardstick" used and how far up inlets and rivers the seacoast is measured. See also CRS Report RS21729 , U.S. International Borders: Brief Facts, by Marilyn Nelson and [author name scrubbed]. CBP resources are spread much more thinly along lines. Attempts to smuggle a nuclearweapon across an unguarded section of border would avoid the risk that the weapon might bedetected, but CBP agents would only need to detect the smugglers, not the weapon: anyone oranything entering the United States across lines is illegal. On the other hand, risk to smugglers isreduced because CBP faces an immense task in patrolling the vast stretches of borders. (26) Terrorists could avoid the risks attendant to smuggling across both points and lines if theycould place a weapon on board an airplane or ship bound for the United States and detonate it beforeit could be inspected, such as in the air above a city or as it entered a seaport. Scenarios for smuggling a nuclear weapon across unguarded coasts or borders are similarto those for smuggling bales of marijuana, many of which are reportedly flown in, brought by smallboats, or carried across land borders; the difficulty of patrolling the borders makes such scenariosfeasible. A key difference between smuggling marijuana and a nuclear weapon is that in the formercase, smugglers expect losses due to interception by CBP and view them as a cost of doing business. Terrorists attempting to smuggle a nuclear weapon into the United States, in contrast, wouldpresumably have only one or a few weapons and would have to go to great lengths to succeed. Conversely, because of the great value of a nuclear weapon to terrorists, methods that create asubstantial probability of detecting an attempt to smuggle a weapon into the United States mightdeter such an attempt. Another scenario commonly discussed is smuggling a nuclear weapon in a shippingcontainer. (27) Thesemetal boxes, typically 8 by 8 by 20 feet or 8 by 8 by 40 feet, are used to transport vast quantities ofgoods ranging from clothes to computers to automobile engines. Nearly 9 million containers enterthe United States by ship each year; (28) container ships may carry several thousand containers. Fromseaports, they are transported by truck or rail throughout the country. The concern is that if terroristscould place a bomb in a container overseas, they could ship it into the United States and transportit anywhere in the country. Under the Container Security Initiative (CSI), discussed below, CBPagents and their foreign counterparts screen containers being loaded onto container ships at certainforeign ports, and the foreign agents inspect containers that the screening identifies as suspicious,based on ports of call, manifest data, shipping company, etc. Terrorists, however, might try tocircumvent CSI by acquiring a trusted shipping company to avoid suspicion, falsifying manifest data,infiltrating CSI ports, shipping from non-CSI ports. A nuclear explosion in a U.S. port from a bombin a shipping container would have not only direct effects, but could also have far-reaching effectson the world economy because of its dependence on container traffic, an effect magnified byindustry's use of "just-in-time" deliveries. According to Robert Bonner, Commissioner of Customsand Border Protection, Simply put, the shipping of sea containers would stop.The American people, for one, would not likely permit one more sea container to enter the UnitedStates until there was a significantly greater assurance -- such as 100% inspections -- that noadditional terrorist weapons would be smuggled into the country. Governments in other majorindustrial countries would no doubt adopt a similar policy, thus bringing the global economy to itsknees. (29) Stephen Flynn, an authority on U.S. vulnerabilities to terrorist attack, cites John Meredith,a director of Hutchison Port Holdings, which Flynn describes as "the world's largest terminaloperator," as "worried about the cascading consequences ... should the U.S. government close itsports for two to three weeks [after a terrorist attack], Meredith warned, the entire system would gointo gridlock." (30) Another possible scenario is the use of an oil tanker to transport a nuclear weapon. (31) The Middle East is thedominant source of anti-American terrorism, the United States imports an average of more than 2million barrels of crude oil a day from Persian Gulf nations, (32) this crude oil is transportedby ship, and it would be very difficult to detect a bomb inside a supertanker. Part of the difficulty of detecting a bomb inside a floating vat of crude oil would arise fromthe sheer size of supertankers, which carry 100,000 deadweight tons or more of crude oil. (33) For example, twosupertankers built in 2003 for COSCO (China Ocean Shipping) Group were 330 meters (almost aquarter-mile) long and 60 meters in beam, and had a capacity of about 300,000 deadweighttons. (34) There are evenlarger tankers that carry 500,000 deadweight tons of crude oil, and have a length of 396 meters anda beam of 71 meters. (35) On land, some detection devices use gamma rays (high-energy x-rays) to peer inside a shippingcontainer and create an x-ray-type image, but the size of a supertanker and the thickness of the steel(especially with the use of double hulls) make this technique unworkable. Another possible meansof detecting a nuclear weapon is neutron activation, in which a burst of neutrons is sent into the itemto be examined, such as a shipping container; neutrons that strike uranium-235 (or other radioactivematerial) will cause some atoms to fission, releasing neutrons and gamma rays. Any neutron comingback as a result of neutron bombardment would be suspicious. The gamma rays produced by thedisintegration of each isotope have a unique set of energies, creating a "fingerprint" that permitsidentification of the isotope. However, neutrons sent into the oil and any produced by fissioning ofuranium would be absorbed (forming deuterium or tritium) or scattered by the hydrogen atoms incrude oil, and the large volume of oil would attenuate any gamma rays produced, defeating this formof detection. At the same time, designing a means to detonate a bomb inside a tanker could provea technical challenge for terrorists. A bomb in a tanker could devastate an oil port by the blast and by secondary fires in nearbyrefineries and oil storage tanks. A tanker bomb might be used against other maritime targets, suchas the Panama Canal. And if a bomb in a shipping container could lead to the shutdown of containertraffic, seriously damaging the world economy, a tanker bomb might by the same token lead to thesuspension of crude oil shipments, with similar results. By now, over three years after the attacks of September 11, the components of the U.S. andglobal response have become clearer. The response is often termed "layered defense," reflecting theidea that terrorists would have to proceed through many steps to acquire a nuclear weapon andsmuggle it into the United States, and that attempting to thwart them at each step has a higherlikelihood of success than trying to block one step only. (36) Whether layered defense is an overarching strategy, as is the casein ballistic missile defense, or simply a name given to what would have happened anyway as manyagencies with different capabilities contribute in the ways each is able to, or some of both, is anothermatter. In any event, many programs have been established to deal with nuclear terrorism since 9/11,and others created well before then have acquired new urgency. The following six categories ofprograms are presented in the order in which they bear on a terrorist or rogue state effort to acquireand deliver a nuclear weapon. Threat Reduction Programs in the Former SovietUnion. The Soviet Nuclear Threat Reduction Act of 1991 ( P.L. 102-226 , Title II),also known as the Nunn-Lugar Amendment, authorized a Department of Defense (DOD) programto assist in the destruction of Soviet nuclear and other weapons. The United States now funds threatreduction and nonproliferation programs through three agencies: DOD runs the Cooperative ThreatReduction program to secure and dismantle former Soviet nuclear and other weapons; theDepartment of Energy (DOE) runs several programs within its Defense Nuclear Nonproliferationaccount, such as International Nuclear Materials Protection and Cooperation and Elimination ofWeapons-Grade Plutonium Production, to secure nuclear weapons materials and knowledge; and theDepartment of State runs such programs as Science and Technology Centers in Russia and Ukraineto provide weapons scientists with grant funding or employment on nonweapons projects. (37) Efforts To Secure HEU Worldwide. HEU is usedin many research reactors around the world. The United States and the Soviet Union provided thismaterial to many nations years ago. As noted above, much is said to be poorly guarded. It is aconcern because acquiring a suitable quantity of HEU would be the most difficult step for terroristsintent on making a nuclear bomb. Efforts to secure some of this material have been ad hoc ratherthan part of a comprehensive plan. For example, in 1994 Project Sapphire reportedly removed froma "poorly guarded warehouse" in Kazakhstan enough HEU to make 20-50 nuclear weapons andbrought it to the United States. (38) In August 2002, Project Vinca reportedly removed enough HEUfor two nuclear weapons from a research reactor in Serbia and flew it to Russia, where it hadoriginated. (39) Securingthe Bomb asserts that the pace of securing fissile material has slowed since September 11, 2001, andsuggests a "global cleanout" of HEU. (40) On May 26, 2004, responding to such concerns, Secretary ofEnergy Spencer Abraham announced a new Global Threat Reduction Initiative to secureRussian-origin fresh HEU by the end of 2005; to secure spent fuel of Russian/Soviet origin by 2010,and of U.S. origin within a decade; to convert the cores of civilian research reactors using HEU tobe able to use uranium with a concentration of uranium-235 too low to be used in a nuclear weapon,and to try to identify and secure other nuclear and radiological materials that may pose a threat. (41) For this effort, SecretaryAbraham said, the United States plans to dedicate more than $450 million. Other DOE personnelindicated that sum is the approximate cost to complete the program, that the funds would probablybe spent over more than 10 years, and that most of the funds would be for already-existingprograms. (42) There are also concerns about the security of any Iranian and North Korean HEU, asdiscussed above, and Pakistani HEU. A discussion of diplomatic efforts to secure such material goesbeyond the scope of this report. (43) Control of Former Soviet and Other Borders. While some programs discussed earlier seek to secure former Soviet nuclear weapons and fissilematerials, DOE's Second Line of Defense (SLD) and the State Department's Export Control andRelated Border Security Assistance (EXBS) Program provide assistance to Russia and othercountries to prevent nuclear materials from being smuggled out through their borders. DOE statesthat SLD "deploys radiation detection monitors at strategic transit and border crossings and at air andsea transshipment hubs." (44) Container Security Initiative. CSI was started inJanuary 2002 by the former U.S. Customs Service, now a part of CBP in the Department ofHomeland Security (DHS). (45) Shipping containers account for 90 percent of all world cargo;nearly 9 million are offloaded in U.S. seaports annually. Terrorists might attempt to ship a nuclearweapon to a U.S. port in a container and detonate it before the container was inspected. Accordingly,CSI screens containers in overseas ports before they are loaded onto U.S.-bound ships. CSI wasoperational in 34 ports, with another 13 possible, both as of February 2005. (46) Participating ports haveU.S. CBP agents who work with host country officers to decide which containers to target forinspection; host country officers inspect suspicious containers using non-intrusive inspection devicessuch as gamma-ray imaging machines or using physical inspection. A portion of DOE's SLDprogram, Mega-Ports, supports CSI by equipping some foreign seaports that are part of CSI withradiation detection equipment, and providing the necessary training, to "screen cargo for nuclear andradioactive materials that could be used in a weapon of mass destruction or a RDD (dirty bomb)..." (47) Proliferation Security Initiative. PSI began inMay 2003; by August 2004, 16 nations had joined, (48) and in his February 2005 State of the Union Address, PresidentBush said, "We are cooperating with 60 governments" in PSI. (49) The participants seek tointerdict sea or air shipments of WMD or WMD-related materials to or by states "of proliferationconcern" trying to acquire or transfer such items. Shipments could be interdicted at ports, interritorial waters, on the high seas, or in national airspace. According to press reports, the firstinterdiction under PSI was of the German ship BBC China in October 2003; the seizure of itsLibya-bound cargo, thousands of parts for special centrifuges of value for enriching uranium, mayhave been influential in convincing Libya to abandon its WMD programs. (50) U.S. Border Security. The final line of defensetries to keep terrorists from smuggling a nuclear weapon across U.S. borders. It involves borderpatrols, barriers, remote sensors, radiation monitors, Customs inspections, seaport security, and thelike, generally within the purview of CBP. Yet as noted in "Weapon Delivery," above, there aregreat difficulties in securing the many "points" through which people and goods may enter legally,and the thousands of miles of "lines," thinly-guarded stretches of coasts and land borders acrosswhich entry is illegal. These difficulties illustrate the importance of the other defensive layers notedearlier in this section and show why it would be unwise to rely solely on border security. Supporting Capabilities. Technology,intelligence, and forensics cut across and support the foregoing steps to keep terrorists or rogue statesfrom acquiring and delivering a nuclear weapon. Technology Development. The Homeland SecurityAct of 2002 ( P.L. 107-296 , Sec. 302) makes the DHS Under Secretary for Science and Technologyresponsible for "coordinating the Federal Government's civilian efforts to identify and developcountermeasures to" terrorist WMD threats. DHS is charged with coordinating efforts by manyagencies, including DOE's National Nuclear Security Administration and the Department ofCommerce's National Institute of Standards and Technology, to develop technology for homelandsecurity. DHS has proposed various technology programs and organizations forFY2005-FY2006. (51) U.S. national laboratories (including the three nuclear weapons labs, Los Alamos, Livermore, andSandia), U.S. and foreign corporations, universities, and others have been conducting R&D for newtechnologies to detect smuggling of nuclear materials and weapons. Detection of HEU and WGPUis difficult because, as noted, they are not highly radioactive. (52) Various technologies arein use, (53) such asradiation portal monitors, which passively detect radiation emitted by a source, (54) and active imagingsystems, like the Vehicle and Cargo Inspection System (VACIS), which operate like x-raymachines. (55) Moreadvanced systems are being developed. For example, Livermore is developing aneutron-interrogation system to screen containers. It bombards a container with neutrons, producingnuclear fissions in such material as HEU and WGPU. (56) The fissions produce gamma rays with specific energy levelsunique to each substance, permitting identification. Detecting illegal movement across U.S. borders,in contrast, does not require detecting fissile material; relevant technologies include surveillancesensors and data analysis software. (57) The FY2006 DHS budget includes the establishment of a new Domestic Nuclear DetectionOffice (DNDO) within DHS: The DNDO will develop, acquire and support thedeployment and improvement of a domestic system to detect and report attempts to import,assemble, or transport a nuclear explosive device, fissile material or radiological material intendedfor illicit use. (58) Intelligence. The possibility that terrorists couldevade any of the layers described above necessitates an enhanced intelligence capability tocomplement other means of detecting movement of nuclear materials and warheads. Such acapability could also focus the efforts of particular defenses, whether alerting a Russian facility thata smuggling plan was in the works or indicating that a particular cargo container might hold anuclear weapon. Improving and organizing intelligence for homeland security have been sharplydebated. (59) Nuclear Forensics. The ability to glean informationfrom nuclear weapon debris and other radioactive material lies at the intersection of technology andintelligence. During the Cold War, the United States obtained much information by analyzing falloutfrom Soviet nuclear weapon tests. For example, analysis confirmed that the Soviet Union hadconducted its first atomic bomb test, and analysis of fallout from the first Soviet hydrogen bomb testrevealed many details about that weapon's design. (60) Even minute samples are of value. (61) With the currentmoratorium on nuclear testing, forensic studies are applied to verifying the safety of U.S. nuclearwarheads, detecting signs of nuclear proliferation, and thwarting illicit trafficking of nuclearmaterials. (62) In theevent of a terrorist nuclear attack, forensics might be able to identify the nation that originated thefissile material or weapon, and determine whether terrorists had fabricated the weapon on their ownor obtained it from a nation's stockpile. This information would aid efforts to prevent furtherleakage. The ability to attribute a weapon or material to a nation might also deter a nation fromproviding such items to terrorists by holding the prospect of a military response. Further, if aterrorist nuclear weapon were found, forensic analysis could contribute to an understanding of theweapon's design, which could help determine whether it could be moved and how best to disable it. Other issues that bear on nuclear terrorism include missile defense, export controls, andnuclear nonproliferation efforts more generally. Many organizations and other groups are involved,such as the U.N., the International Atomic Energy Agency, and the Group of Eight. (63) In combating nuclear terrorism, the standard for success for the United States is daunting --zero nuclear detonations, which may require stopping every terrorist or rogue state attempt to acquireand deliver a nuclear weapon -- while a single nuclear detonation in the United States wouldconstitute a terrorist success. Measured against that binary standard, it is impossible to determinethe extent to which, or even if, the initiatives discussed above have increased U.S. security. Nonetheless, studies have shown many potential weaknesses in U.S. ability to thwart nuclearterrorism. The main response of policymakers has been to strengthen, consolidate, coordinate, orinitiate a wide array of programs. A Government Accountability Office report, for example, notesa number of recommendations that it and congressionally chartered commissions have made fordefending against catastrophic threats. (64) Categories of recommendations include "Enhanced or clarified federal or state authority to manage a terrorist incidentinvolving Weapons of Mass Destruction" "Improvements to incident planning, management, and response capabilitiesfor dealing with a WMD terrorist incident" "Better management and more resources for research and development oftechnologies to prevent or respond to terrorist WMD incidents" and "Laws, cooperative agreements, and regulatory regimes to better control theprecursors to WMD." A report by the House Policy Committee makes a number of recommendations for addressingnuclear proliferation, including: "Strengthen international regimes and controls to limit the legal spread ofproliferation-enabling technology." "Expand flexible, responsive multilateral activities to find, disrupt, andeliminate networks and trafficking." "Engage multi- and bi-lateral initiatives to quickly secure materials and keepexpertise off the market." "Assure the credibility of consequences, as well as advantages of positivebehavior." "Advance technical and analytic tools and improve human assets to detectproliferation activities, networks and materials." (65) Specific policy options available to counter nuclear terrorism include (1) accelerate thesafeguarding of Russian fissile materials; (2) broaden that effort to a global cleanout of HEU, suchas at research reactors; (3) expand CSI to more ports; (4) strengthen the Coast Guard, such asthrough its Integrated Deepwater Systems program, which would, among other things, improve itsability to conduct interdictions for PSI; (66) and (5) strengthen capabilities to detect and disable terroristnuclear devices, such as Nuclear Incident Response Teams of DOE and the EnvironmentalProtection Agency. Two books released in the summer of 2004 discuss policy options in detail. (67) Congress funds programs to counter nuclear terrorism through several authorization andappropriations bills. The annual National Defense Authorization Act and Department of DefenseAppropriations Act fund DOD Cooperative Threat Reduction programs; the annual National DefenseAuthorization Act and Energy and Water Development Appropriations Act fund DOE DefenseNuclear Nonproliferation and nuclear weapons programs. Regarding funding for DHS, bill referralpatterns for authorizations may shift based on the changed jurisdictions of the new HomelandSecurity Committees and other related committees, and the subcommittee structures to handle DHSappropriations are in flux, both as of early February 2005. Other agencies, funded by other bills, alsoconduct R&D. The FY2006 requests for Cooperative Threat Reduction, Defense NuclearNonproliferation, and DHS Directorate of Science and Technology (S&T) are $415.5 million,$1,637.2 million, and $1,368.4 million, respectively. (Much of DHS S&T is for programs in threatareas other than nuclear.) Congress also holds oversight hearings, establishes specific legislativerequirements and restrictions on programs, and calls public attention to these issues. Other bills introduced in the 109th Congress that bear on nuclear terrorism include thefollowing. All entries show the latest major action as of February 10, 2005. H.R. 173 (Millender-McDonald). Anti-Terrorism and Port Security Act of2005. To prevent and respond to terrorism and crime at or through ports. Introduced January 4,2005, and referred to the Committees on the Judiciary, Transportation and Infrastructure, Ways andMeans, and Homeland Security. H.R. 282 (Ros-Lehtinen). Iran Freedom Support Act. To hold the currentregime in Iran accountable for its threatening behavior and to support a transition to democracy inIran. Would codify sanctions related to WMD. Introduced January 6, 2005, and referred to theHouse Committee on International Relations. H.R. 422 (Tauscher). 9-11 Commission Combating ProliferationImplemen-tation Act. Would, among other provisions, establish an office for combating theproliferation of WMD, request that Russia form a similar office, authorize $100 million a year foraccelerating the removal or securing of fissile and radiological material (pursuant to P.L. 108-375 ,Ronald W. Reagan National Defense Authorization Act for FY2005, Section 3132), and authorizefunds for Cooperative Threat Reduction programs. Introduced January 26, 2005, and referred to theHouse Committee on International Relations. S. 3 (Gregg) Protecting America in the War on Terror Act of 2005. Amongother provisions, criminalizes the transport by vessel of radioactive or nuclear material. IntroducedJanuary 24, 2005, and referred to the Senate Committee on Finance. S. 21 (Collins) Homeland Security Grant Enhancement Act of 2005. Amongother provisions, would bar any commercial motor vehicle carrying municipal solid waste fromentering the United States until Customs and Border Protection can screen such waste forradiological and nuclear weapons. Introduced January 25, 2005, and referred to the SenateCommittee on Homeland Security and Governmental Affairs. 

Summary: It would be difficult for terrorists to mount a nuclear attack on a U.S. city, but such an attackis plausible and would have catastrophic consequences, in one scenario killing over a half-millionpeople and causing damage of over $1 trillion. Terrorists or rogue states might acquire a nuclear weapon in several ways. The nations ofgreatest concern as potential sources of weapons or fissile materials are widely thought to be Russiaand Pakistan. Russia has many tactical nuclear weapons, which tend to be lower in yield but moredispersed and apparently less secure than strategic weapons. It also has much highly enricheduranium (HEU) and weapons-grade plutonium, some said to have inadequate security. Many expertsbelieve that technically sophisticated terrorists could, without state support, fabricate a nuclear bombfrom HEU; opinion is divided on whether terrorists could make a bomb using plutonium. The fearregarding Pakistan is that some members of the armed forces might covertly give a weapon toterrorists or that, if President Musharraf were overthrown, an Islamic fundamentalist government ora state of chaos in Pakistan might enable terrorists to obtain a weapon. Terrorists might also obtainHEU from the more than 130 research reactors worldwide that use HEU as fuel. If terrorists acquired a nuclear weapon, they could try many means to bring it into the UnitedStates. This nation has thousands of miles of land and sea borders, as well as several hundred portsof entry. Terrorists might smuggle a weapon across lightly-guarded stretches of borders, ship it inusing a cargo container, place it in a crude oil tanker, or bring it in using a truck, a boat, or a smallairplane. The architecture of the U.S. response is termed "layered defense." The goal is to try to blockterrorists at various stages in their attempts to obtain a nuclear weapon and smuggle it into the UnitedStates. The underlying concept is that the probability of success is higher if many layers are usedrather than just one or two. Layers include threat reduction programs in the former Soviet Union,efforts to secure HEU worldwide, control of former Soviet and other borders, the Container SecurityInitiative and Proliferation Security Initiative, and U.S. border security. Several approaches underliemultiple layers, such as technology, intelligence, and forensics. Many policy options have been proposed to deal with nuclear terrorism, such as developingnew detection technologies, strengthening U.S. intelligence capability, and improving planning torespond to an attack. Congress funds programs to counter nuclear terrorism and holds hearings andless-formal briefings on the topic. Several bills have been introduced in the 109th Congress relatedto nuclear terrorism. This report is intended for background, not for tracking current developments. It will beupdated occasionally. It does not cover radiological terrorism; see CRS Report RS21766 , Radiological Dispersal Devices: Select Issues in Consequence Management, and CRS Report RS21528 , Terrorist 'Dirty Bombs': A Brief Primer.