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Despite Israel’s impressive achievements in nuclear weaponry, it still need imports to maintain and develop its existing arsenal. According to a 1992 Pentagon study, “The Militarily Critical Technologies List,” Israel’s strongest capabilities lie in processing nuclear materials and in developing high explosives for nuclear weapon detonation. Israel is less capable in enriching fissile material, building power reactors and mastering thermonuclear fusion.

One of Israel’s most important recent imports has been people. Following the breakup of the Soviet Union, Israel began recruiting Soviet nuclear scientists. In 1991 alone, nearly 20 top Soviet scientists reportedly emigrated to Israel, some of whom were involved in operating nuclear power plants and planning for the next generation of Russian reactors. In September 1992, German intelligence was quoted in the press as estimating that 40 Soviet nuclear scientists had emigrated to Israel since 1989.

The biggest challenge for Israel’s nuclear weapon program has been its inability to openly conduct explosive tests. To compensate for this limitation, Israel must rely on imported high-speed computers. Supercomputers can simulate what goes on inside both fission and fusion weapons. Israel will also have a continuing need for other diagnostic and development tools such as vibrational test equipment, flash X-ray machines and multistage light gas guns.

To continue enriching uranium with gas centrifuges, Israel will need to replace worn-out centrifuges and their parts. This, in turn, will require continued access to high-speed balancing equipment, high-strength rotor materials such as fibrous and filamentary materials, to filament winding machines, and to frequency changers and inverters. Israel also needs a steady supply of tritium to boost the yield of its existing nuclear bombs. Tritium decays at the rate of approximately 5 percent per year, so existing supplies must be constantly replenished. This means that Israel must continue to run the Dimona reactor to irradiate lithium, Israel’s only means of producing tritium. In addition, Israel will continue to need tritium storage containers, oil and rubber-free mechanical vacuum pumps, and palladium and palladium alloy diffusers for separating tritium from helium-3 and other gases. Cryogenic distillation equipment will also be needed to handle tritium.

Today, Israel is the world’s sixth most powerful nuclear state, with a stockpile of more than 100 nuclear weapons and with the components and ability to build atomic, neutron and hydrogen bombs. Israel’s nuclear program began and still operates under tight secrecy, but in the 1980s a series of revelations showed the crucial role played by foreign suppliers.

France launched Israel on the nuclear path in the late 1950s by building the Dimona reactor, which is still the source of Israel’s plutonium–its main nuclear weapon fuel. The reactor’s heavy water, essential to achieve a chain reaction, was supplied by Norway in 1959. In 1963, when the reactor started operation, the United States supplied four more tons of heavy water.

Israel got other nuclear help from the United States, which also supplied a small 5-megawatt (thermal) research reactor at Nahal Soreq. The reactor started in 1960, but cannot produce significant quantities of plutonium. Instead, the reactor offered an early training ground for Israeli nuclear technicians. Later in the 1960s, Israel was widely thought to have smuggled more than 100 kilograms of highly enriched uranium out of a nuclear materials plant in Pennsylvania.

France’s contribution

Franco-Israeli nuclear cooperation is described in detail in the book “Les Deux Bombes” (1982) by French journalist Pierre Pean, who gained access to the official French files on Dimona. The book revealed that the Dimona’s cooling circuits were built two to three times larger than necessary for the 26-megawatt reactor Dimona was supposed to be–proof that it had always been intended to make bomb quantities of plutonium. The book also revealed that French technicians had built a plutonium extraction plant at the same site. According to Pean, French nuclear assistance enabled Israel to produce enough plutonium for one bomb even before the 1967 Six Day War. France also gave Israel nuclear weapon design information.

In 1986, Francis Perrin, high commissioner of the French atomic energy agency from 1951 to 1970, was quoted in the press as saying that France and Israel had worked closely together for two years in the late 1950s to design an atom bomb. Perrin said that the United States had agreed that the French scientists who worked on the Manhattan Project could apply their knowledge at home provided they kept it secret. But then, Perrin said, “We considered we could give the secrets to Israel provided they kept it a secret themselves.” He added: “We thought the Israeli bomb was aimed against the Americans, not to launch it against America but to say ‘if you don’t want to help us in a critical situation we will require you to help us, otherwise we will use our nuclear bombs.'”

U.S. intelligence reports

After the United States discovered the Dimona reactor in 1960, U.S. nuclear specialists inspected Dimona every year from 1965 through 1969, looking for signs of nuclear weapon production. It is not clear what they found, but in 1968 the Central Intelligence Agency (CIA) reported to President Lyndon Johnson its conclusion that Israel had already made an atomic bomb. In 1969, Israel limited inspection visits by U.S. scientists to such an extent that the Americans complained in writing. Without explanation, the Nixon administration ended the visits the following year.

The CIA continued to report on Israel’s nuclear weapon progress during the 1970s. In a September 1974 memorandum, “Prospects for Further Proliferation of Nuclear Weapons,” the CIA cited “Israeli acquisition of large quantities of uranium, partly by clandestine means” as further evidence that “Israel already has produced nuclear weapons.” The CIA also cited Israeli missile development as evidence that Israel had made nuclear weapons–the CIA said the Jericho made little sense as a conventional missile and was “designed to accommodate nuclear warheads.” In a February 1976 report to the Nuclear Regulatory Commission, CIA Deputy Director for Science and Technology Carl Duckett reported that Israel was already making bombs with plutonium produced in its Dimona reactor.

Israeli deployment and possible test

According to a detailed account contained in Time magazine, Israel assembled about a dozen bombs and readied them for use during the October 1973 Arab-Israeli war. The bombs could have been delivered by aircraft or missiles. In 1974, Israeli President Ephraim Katzir said that “it has always been our intention to develop a nuclear potential … We now have that potential.” This remark was followed five years later by a spectacular and still controversial event.

On September 22, 1979, an American “Vela” satellite detected a distinctive double flash off the southern coast of Africa. The satellite data, together with other information from U.S. intelligence sources, offered strong evidence that the flash had been caused by a low-yield nuclear explosion. Defense Department and State Department officials pointed out that this was only the 42nd time that a satellite of this type had registered such a signal; and in the first 41 cases, according to these officials, the Vela had correctly detected atmospheric nuclear tests. A State Department official later told the Washington Post: “Look, the Vela satellite picked up a signature like this 41 times before. In every one of those 41 instances, there was never any question about the fact that a nuclear test had taken place. Each of those 41 was undeniably a nuclear explosion. This was, too.”

A 1979 CIA memorandum stated that “of all the countries which might have been responsible for the 22 September event, Israel would probably have been the only one for which a clandestine approach would have been virtually its only option.” The CIA also observed that Israelis had participated in South African nuclear research during the preceding several years.

In June 1980, the CIA reported to the National Security Council that a 2-3 kiloton nuclear test had taken place at the time and place of the Vela reading, and that it had probably involved Israel and South Africa. However, a panel of scientific experts assembled by the Carter White House analyzed the technical data and concluded that the information was too ambiguous to prove that the event was a nuclear test.

In 1981, after Israeli planes destroyed Iraq’s Osirak reactor (also built by France), former Defense and Foreign Minister Moshe Dayan told the New York Times: “We do have the capacity to produce nuclear weapons, and if the Arabs are willing to introduce nuclear weapons into the Middle East, then Israel should not be too late in having nuclear weapons, too.”

Israel’s continuing need for imports was revealed in 1985, when Los Angeles businessman Richard Smyth was indicted for smuggling to Israel 810 krytrons, high-speed electronic switches used as nuclear weapon detonators. The krytrons were shipped between 1979 and 1983 to an Israeli firm under contract to the government for defense work. The Israeli Ministry of Defense returned only 469 of the krytrons, and Smyth vanished a week before he was to appear for trial. Records obtained by NBC News from Smyth’s firm, Milco International, also showed that two related firms, Heli Trading and Milchan Brothers, both owned by Hollywood producer Arnon Milchan, ordered large quantities of missile-related equipment and materials between 1977 and 1982. Among the nuclear items listed were the 810 krytrons, plus neutron generators, high-speed oscilloscopes and high-voltage condensers.

Vanunu’s disclosures

In September 1986, Mordecai Vanunu, an Israeli arms technician who had worked at the secret Dimona site for eight years, provided the world with the first detailed account of Israel’s nuclear weapon progress. He provided almost 60 color photographs to the London Sunday Times of what he said was Israel’s underground bomb factory. He also described Israel’s nuclear weapon production techniques in an account accepted by weapons experts on both sides of the Atlantic. According to Vanunu’s data, the solid plutonium spheres for Israel’s nuclear weapons weighed 4.4 kilograms. He also said that Israel had produced 100 to 200 advanced fission bombs by 1986, had mastered a thermonuclear design, and appeared to have a number of thermonuclear bombs ready for use.

Vanunu’s photographs also showed the processing of what appeared to be large hollow hemispheres of lithium deuteride–parts for a thermonuclear bomb with a destructive power of about 200 kilotons. According to Vanunu, other Dimona products included copper hemispheres, into which the plutonium was sealed, and beryllium neutron reflectors, which reduced the amount of plutonium required to achieve a nuclear explosion. Dimona was also making the thermonuclear bomb ingredients tritium and deuterium. Vanunu reported that the plutonium spheres and bomb components from Dimona were taken at regular intervals by convoy with armed escorts to an airfield near Haifa for assembly.

Experts’ conclusions

Theodore Taylor, a highly respected former U.S. weapon designer, reviewed Vanunu’s claims in detail. Taylor concluded that Israel’s thermonuclear weapon designs appeared to be “less complex than those of other nations,” and “not capable of producing yields in the megaton or higher range.” Nevertheless, “they may produce at least several times the yield of fission weapons with the same quantity of plutonium or highly enriched uranium.” In other words, Israel could “boost” the yield of its nuclear fission weapons. According to Taylor, the uncertainties involved in the process of boosting required more than theoretical analysis for full confidence in the weapons’ performance. Taylor therefore concluded that Israel had “unequivocally” tested a miniaturized nuclear device.

In 1987, the Institute for Defense Analyses (IDA), which does Pentagon-funded research, released a Pentagon-sponsored report confirming that Israel was still conducting extensive research in the technology required for the design and fabrication of nuclear weapons. According to the report, Israel’s facilities at Soreq and Dimona have the same mission as the Los Alamos, Lawrence Livermore and Oak Ridge National Laboratories in the United States. IDA reported that Israel was developing the computer “codes which will enable them to make hydrogen bombs…. However, it is doubtful they have the codes to completely design such devices.” The report concluded that as of 1987, “the Israelis are roughly where the U.S. was in the fission weapon field in about 1955 to 1960.”

Since 1988, Israel has been trying to buy supercomputers that would allow it to speed up its nuclear weapon calculations by a factor of one hundred. Supercomputers can simulate the implosive shock waves that detonate nuclear warheads, calculate the multiplication of neutrons in an explosive chain reaction, and solve the equations of state that describe the behavior of nuclear explosives (plutonium and high-enriched uranium) under high temperature and pressure–all essential problems for nuclear weapon design. Although it is possible to develop unsophisticated nuclear weapons with less powerful computers, supercomputers are particularly valuable to countries such as Israel that seek to avoid conducting nuclear tests. They also can be used for missile design by modeling the forces acting on a flying body, such as the heat and shock waves encountered by a long-range missile reentering the atmosphere.

In January 1992, Israel’s Technion University procured two “parallel” computers capable of reaching supercomputer speeds from the U.K. company Meiko Scientific Ltd.. The sale effectively circumvented U.S.- and Japanese-imposed restrictions for countries that had not signed the Nuclear Nonproliferation Treaty (NPT). But in November 1994, the United States approved the sale of nine supercomputers to Israel: two from Cray Research, five from IBM and two from Silicon Graphics. (The speeds of the nine computers ranged from 1,071 to 6,796 MTOPS.) The end-users–Technion University, Hebrew University and the Weizmann Institute–all have links to Israel’s nuclear and missile programs. U.S. officials opposed to the sales were concerned that Israel would get a boost in computing power to work on a major engineering problem: shrinking thermonuclear warheads to fit on long-range missiles.

Israel has relied on plutonium, rather than high-enriched uranium, as the primary fuel for its nuclear weapons. Nonetheless, Israel has developed the ability to process and enrich uranium at the Dimona nuclear complex. Israeli nuclear technician Mordechai Vanunu told the Sunday Times of London in 1986 that Israel had been operating a secret uranium enrichment facility “on a production scale” since 1979-80. Vanunu also told former U.S. nuclear weapon designer Theodore Taylor that uranium was enriched by gas centrifuges. Based on Vanunu’s information, Taylor concluded that Israel was enriching uranium to weapon grade. Vanunu also confirmed earlier reports that Israel was conducting research on laser enrichment at Dimona.

Israel has obtained natural uranium supplies on the world market from a number of sources. Starting in the mid-1970s, Israel clandestinely imported 600 metric tons of yellowcake from South Africa. Israel has also devised a method of extracting uranium from the phosphate deposits in the Negev desert, where there is an estimated thirty to sixty thousand tons of uranium contained in low-level phosphate ores. Active mining of phosphate deposits takes place in the Negev near Beersheba. The Nuclear Engineering International industry handbook lists the Negev Phosphates Chemicals Company, at Mishor Rotem, as Israel’s only fuel cycle facility.

The French companies that built the Dimona reactor also supplied a uranium fuel fabrication plant. At the plant, uranium metal is encased in aluminum cladding to make reactor fuel rods. The plant’s capacity is unknown but is apparently sufficient to fuel the Dimona reactor.

Israel makes plutonium for atomic bombs at Dimona, a secret nuclear complex in the Negev Desert. The French-supplied reactor there has produced plutonium free from international controls since 1963. The quality of the plutonium created by the Dimona reactor is ideal for making atomic bombs.

The size of the reactor at Dimona is listed by the International Atomic Energy Agency [IAEA] as 26 megawatts (thermal). However, experts believe it is much more powerful than that. Mordechai Vanunu, an Israeli technician who worked at Dimona for eight years, reported that the reactor had been scaled up twice before he arrived at the site in 1977. The first scale-up was from 26MWt to 70MWt; the second was to some higher level.

The first scale-up was planned when Dimona was built. Israel convinced France to make the reactor’s critical components–including its cooling circuit–three times larger than needed for a facility of its nominal size, and three times larger than originally agreed upon. This modification permitted a scale-up to 70MWt without the addition of extra cooling circuits, which would have attracted outside attention. Further evidence of a scale-up came in late 1968, when Israel diverted 200 metric tons of Belgian uranium on the high seas–a quantity considerably greater than a 26-megawatt reactor would have required. Israel probably needed the additional uranium for the first scale-up, which appears to have occurred in 1970.

Vanunu also said that Dimona had been producing 40 kilograms of plutonium per year for some time before he arrived in 1977. If the reactor at Dimona was unusually efficient (i.e., producing more than 1 gram of plutonium per megawatt day) and ran for as many as 300 days per year, the 40 kilograms could have been produced with a peak power of sightly more than 100MWt. If the reactor were less efficient, and operated for fewer days per year, the peak power would have to approach 150MWt.

Plutonium extraction

To be used in weapons, plutonium must be extracted chemically from irradiated nuclear reactor fuel. A French firm, St. Gobain Techniques, supplied Israel with a chemical extraction plant at Dimona. The plant’s first trial runs were in late 1965. By 1968, Israel had extracted enough plutonium for an atomic bomb.

The Dimona reactor, if operated continuously, could have created as much as 870 kilograms of plutonium through 1994. This figure assumes that the reactor started operating at 26MWt in 1963, was scaled up to 70MWt in 1970, and was scaled up again in 1977 to a level at which it could produce about 40kg of plutonium per year. Vanunu reported that the extraction plant where he worked produced 1.17 kilograms of plutonium per week for 34 weeks per year, a total of 40 kilograms annually. At this rate, 320 kilograms of plutonium would have been produced during the eight years Vanunu worked at Dimona. If the reactor experienced shutdowns, or was operated at a lower power, this figure could be significantly smaller.

Future plutonium production at Dimona is uncertain, primarily because of the reactor’s age. The United States has urged Israel to cap its nuclear program and cease plutonium production at Dimona, but Israel has not agreed to do so.

Size of Israel’s arsenal

The above figures for plutonium production indicate that Israel could have up to 175 bombs’ worth of plutonium in its nuclear arsenal today. This figure assumes roughly 5 kilograms of plutonium are needed per bomb, including processing losses. (Vanunu reported in 1986 that Israel was using about 4.4kg of plutonium per bomb, an amount slightly greater than the reflected fast critical mass of plutonium-239.)

It is impossible to estimate the exact size of Israel’s arsenal without knowing Dimona’s true operating history and the characteristics of Israeli nuclear weapon designs. For example, Israel has produced enriched uranium, which could be used to make additional weapons. Israel has also made a number of “boosted” weapons using tritium, also produced at Dimona. Tritium can be produced by irradiating lithium-6 targets in the Dimona reactor.

Dimona reactor:

Reactor: IRR-II
Type: Heavy water
Power: 26-megawatt (thermal) scaled up to 70MWt or more
Start-up: 1963
Safeguards: None
Plutonium created through 1994: Up to 870 kilograms