U.S. Unfreezes $8 Billion in Iranian Assets — Iran Continues to Enrich Uranium Approaching Weapons Grade — Will Not Give Up Right to Enrich Uranium — Videos
Uranium enrichment ‘a red line’ for Iran
In an address to Parliament in Tehran on Sunday, the Iranian President said the country made progress with world powers during talks over Tehran’s nuclear programme, but insisted the nation cannot be pushed to give up uranium enrichment.
“The Islamic Republic of Iran have not bowed to threats by any power and it will not do so,” he said.
Mr Rouhani repeated past declarations the country has a right to produce nuclear fuel, seeking to assure hard-line critics at home that Iran will not make sweeping concessions in the negotiations.
Talks ended without agreement in Geneva early on Sunday morning, but all sides said progress had been made and negotiations are scheduled to resume next week.
The West and its allies fear Iran’s uranium enrichment labs could one day produce weapons-grade material.
Iran insists it does not seek nuclear weapons and says its reactors are only for electricity and medical applications.
Mr Rouhani said asking Iran to end all uranium enrichment would be crossing a red line.
“National interests are our red line. Among those rights are nuclear rights within the framework of international law, including the right to enrich uranium on Iranian soil,” he said.
The US and others are considering easing economic sanctions in return for a possible suspension of 20 percent enrichment.
Rouhani said this proved sanctions had failed.
“They have come to the negotiating table to talk to us because they have realised that sanctions are not the answer,” he told Parliament.
The six powers party to the talks, especially France, expressed concern about a new reactor under construction that will make a plutonium by-product that could be used to build nuclear weapons, although Iran does not currently possess the technology required.
Making a nuclear weapon
How to enrich Uranium – Periodic Table of Videos
President Obama’s Statement on Iran Nuclear Program Deal: The World Will Be Safer
BREAKING: Deal Reached With Iran Halts Its Nuclear Program –
11/25/13 Former Amb. Bolton on the Obama’s Iran deal lies
Iran’s Arak heavy water nuclear reactor
Breaking: Explosion at Iran’s Nuclear Facility! Was it Israel?
UN Nuclear Watchdog says Iran can Double Uranium Enrichment
Iran’s ability to enrich Uranium in Qom to 20% doesn’t say anything about any nuclear bomb
Nuclear Power – Virtual Tour of Highly Enriched Uranium Materials Facility
Cold War Nuclear Factories [FULL VIDEO]
Reports: U.S. Unfreezes $8 Billion in Iranian Assets
The United States released $8 billion in frozen assets to Iran on Sunday in a move meant to ensure Tehran’s compliance with a nuclear pact signed over the weekend, according to top Iranian officials.
Iranian government spokesman Mohammad Baqer Nobakht confirmedon Monday morning that the U.S. government had unfrozen $8 billion in assets that had been previously blocked by the Obama administration.
Iran will be provided with about $7 billion in sanctions relief, gold, and oil sales under anuclear deal inked late Saturday in Geneva with Western nations.
Iranian officials lauded the deal as a path to opening up greater trade relations between Iran and the world.
“The agreement will open a new path towards Iran,” Alinaqi Khamoushi, the former head of Iran’s Chamber of Commerce said on Sunday as he announced the release by the United States of some $8 billion in assets, according to the Islamic Republic News Agency (IRNA).
Nobakht confirmed the figure early Monday during a briefing with reporters in Tehran.
“The agreement will ease the anti-Iran sanctions, which will have significant impacts on the Iranian economy,” the state-run Fars News Agency quoted him as saying.
One senior GOP aide on Capitol Hill was not pleased with the reports.
“It’s pretty clear the White House and State Department have been lying to the American people since the beginning of this process so it wouldn’t shock me to learn they are lying about how much sanctions relief they’re giving Iran now,” said the aide.
Sen. Chuck Schumer (D., N.Y.) criticized the deal on Sunday, when he said to a Jewish audience that both Democrats and Republicans in the Senate were united in opposition.
“Democrats and Republicans are going to work to see that we don’t let up on these sanctions … until Iran gives up not only all of their weapons but all nuclear weapon capabilities,” Schumer said. “I want to leave you with that assurance.”
A State Department spokesman did not immediately respond to a Washington Free Beacon request for comment on the reported assets relief.
Additionally, Iran announced on Sunday that its nuclear work will continue despite the deal, which aimed to curb Tehran’s nuclear ambitions and enrichment of uranium, the key component in a nuclear weapon.
Iranian foreign minister Javad Zarif, who helped ink the deal, praised it for recognizing Iran’s right to enrich uranium, a key sticking point that had delayed the deal until Saturday evening.
“The [nuclear] program has been recognized and the Iranian people’s right to use the peaceful nuclear technology based on the NPT [Non-Proliferation Treaty] and as an inalienable right has been recognized and countries are necessitated not to create any obstacle on its way,” Zarif told reporters over the weekend.
“The program will continue, and all the sanctions and violations against the Iranian nation under the pretext of the nuclear program will be removed gradually,” he added.
Iran’s most well-known nuclear sites will remain operational under the deal, according to Zarif, who presented a very different version of the agreement than that described by the White House on Saturday.
Over the next six months, Iran will see “the full removal of all [United Nations] Security Council, unilateral and multilateral sanctions, while the country’s enrichment program will be maintained,” Zarif said.
The Fordo and Natanz nuclear sites will also continue to run, he said.
“None of the enrichment centers will be closed and Fordo and Natanz will continue their work and the Arak heavy water [nuclear reactor] program will continue in its present form and no material [enriched uranium stockpiles] will be taken out of the country and all the enriched materials will remain inside the country,” Zarif said. “The current sanctions will move towards decrease, no sanctions will be imposed and Iran’s financial resources will return.”
America recognized Iran’s right to enrich uranium up to 5 percent under the deal, according to both the Iranians and a White House brief on the deal.
The United States agreed to suspend “certain sanctions on gold and precious metals, Iran’s auto sector, and Iran’s petrochemical exports, potentially providing Iran approximately $1.5 billion in revenue,” according to a fact sheet provided by the White House.
Iran could earn another $4.2 billion in oil revenue under the deal.
Another “$400 million in governmental tuition assistance” could also be “transferred from restricted Iranian funds directly to recognized educational institutions in third countries to defray the tuition costs of Iranian students,” according to the White House.
The State Department denied that sanctions have been altered since an interim deal with Iran was announced.
“This report is false. Sanctions today are same as they were last week,” a senior State Department official said in response to the Fars report. “We will be forthcoming with guidance on how the technical terms of the relief package are worked out once all that is determined.”
Iran nuclear deal: Saudi Arabia warns it will strike out on its own
Saudi Arabia claims they were kept in the dark by Western allies over Iran nuclear deal and says it will strike out on its own
A senior advisor to the Saudi royal family has accused its Western allies of deceiving the oil rich kingdom in striking the nuclear accord withIran and said Riyadh would follow an independent foreign policy.
Nawaf Obaid told a think tank meeting in London that Saudi Arabia was determined to pursue its own foreign and policy goals. Having in the past been reactive to events, the leading Sunni Muslim nation was determined to be pro-active in future.
Mr Obaid said that while Saudi Arabia knew that the US was talking directly to Iran through a channel in the Gulf state of Oman, Washington had not directly briefed its ally.
“We were lied to, things were hidden from us,” he said. “The problem is not with the deal struck in Geneva but how it was done.”
In a statement the Saudi government gave a cautious welcome to the Geneva nuclear deal. It said “good intentions” could lead to a comprehensive agreement on Tehran’s atomic programme. “This agreement could be a first step towards a comprehensive solution for Iran’s nuclear programme, if there are good intentions,” the Saudi government said
But it warned that a comprehensive solution should lead to the “removal of all weapons of mass destruction, especially nuclear, from the Middle East and the Gulf”.
A fellow of Harvard University’s Belfer Centre and adviser to Prince Mohammad, the Saudi ambassador to London, Mr Obaid said Saudi Arabia would continue to resist Iranian involvement in the Syrian civil war. In particular he pointed to Iranian Revolutionary Guards involvement in battles in Syria on behalf of the regime.
European Union foreign policy chief Catherine Ashton (L) hugs French Foreign Affairs Minister Laurent Fabius
“[Saudi Arabia] will be there to stop them wherever they are in Arab countries,” he said. “We cannot accept Revolutionary Guards running round Homs.”
Saudi Arabia’s fury at the diplomatic detente with Iran is commonly held with Israel. While both countries are in the same posion Saudi Arabia disavows any suggestion of an open alliance. Until the Palestinians have a state, Saudi Arabia will not work with Israel.
Saudi Arabia is increasingly at odds with Washington over Syria. It rejected a seat on the UN Security Council in protest at the body’s failure to “save” Syria.
Qatar is the latest Gulf Arab state to welcome the nuclear deal between Iran and world powers, calling it a step toward greater stability in the region.
Saudi Arabia, has previously expressed unease about US overtures to Iran. The dialogue helped pushed along efforts by Washington and others to strike a deal with Iran seeking to ease Western concerns that Tehran could move toward nuclear weapons.
Qatar’s Foreign Ministry said the deal is an “important step toward safeguarding peace and stability in the region”.
Bahrain, Kuwait and the United Arab Emirates have issued similar statements.
Iran nuclear deal ‘loophole’ may allow off-site reactor work
Nuclear agreement bans “further advances” at Arak reactor but off-site component work not explicitly banned.
Sunday’s agreement to curb Iran’s nuclear program contains an apparent gap that could allow Tehran to build components off-site to install later in a nuclear reactor where it has promised to halt work, experts said.
They said any impact of the omission is likely to be small if Iran follows other undertakings in the interim accord, which is designed to restrain Tehran’s nuclear program for six months in return for limited sanctions relief.
But the gap, which one diplomat described as a potential “loophole”, could provide a test of Iran’s intentions, and demonstrates how difficult it will be to reach a final deal to resolve Iran’s nuclear standoff with the West once and for all.
Iran’s uncompleted heavy-water research reactor near the town of Arak emerged as one of the most important issues in marathon negotiations in Geneva last week that ended early on Sunday with a breakthrough deal.
Tehran has earlier said it could open the reactor as soon as next year. It says its purpose is only to make medical isotopes, but Western countries say it could also produce plutonium, one of two materials, along with enriched uranium, that can be used to make the fissile core of a nuclear bomb.
Much of the final day of negotiations was taken up with the major powers pressing hard for language that would stop Iran from completing the reactor.
In the deal, Iran agreed that it will “not make any further advances of its activities” at Arak, language that also covers its two big uranium enrichment plants, Fordow and Natanz.
Footnotes hammered out in the final hours of the talks set out a range of activities that would be forbidden at the reactor. For the half year covered by the agreement, Iran is barred from starting the reactor up, bringing fuel or heavy water to it, testing or producing more fuel for it, or installing any remaining components.
But no language explicitly prevents it from making components elsewhere, which could then be installed later.
Former chief UN nuclear inspector Olli Heinonen, now at Harvard university, said the measures were good, but could have been better: “I would have also included the manufacturing of key components,” he told Reuters in an e-mail.
One Western diplomat, who deals with nuclear issues but is not from one of the six world powers that negotiated the deal with Iran, said he did not see the gap as big.
While it was one of several possible “loopholes” in a very complicated agreement, the accord would still achieve its main aims, provided that Iran abides by it.
“If Iran is committed then none of these loopholes are fatal,” said the diplomat, who is based in Vienna, headquarters of the International Atomic Energy Agency which will play an expanded role monitoring Iran’s nuclear program.
Among other steps, Iran has agreed to the suspension of its most sensitive enrichment of uranium, to constraints on other atomic activities and to improved monitoring by the IAEA.
International inspectors say they are confident they can keep tabs on Iran’s declared nuclear activities at known sites, although without wider access they cannot rule out undeclared activity at secret locations.
The diplomat said the most important work to complete Arak is the work to be done at the plant which is barred by the accord, meaning that any manufacturing of components at another location may not be that significant for the timeline.
“The estimate of one to two years to actually get the thing going assumes everything required offsite is already procured and/or manufactured,” the diplomat said.
Mark Fitzpatrick, director of the non-proliferation program at the International Institute for Strategic Studies (IISS) think-tank, also noted the lack of prohibition on the manufacture of components but said most parts had probably already been built.
“I expect that most of the work on those components has already been completed, but no doubt some such work will continue,” he said. “Iran adheres to the principle that what is not prohibited is allowed.”
“DEVIL IN THE DETAIL”
Iran appears to have largely built the facility’s external structure in a valley among barren desert highlands, gradually installing key components over the years.
In May, UN nuclear inspectors observed that the reactor vessel had been delivered to the site.
But the IAEA’s latest quarterly report on Iran said other major parts – such as control room equipment, the refuelling machine and reactor cooling pumps – had yet to be put in place.
IAEA Director General Yukiya Amano told Reuters on Nov. 13 that Iran still had “quite a lot to do” to complete the plant, which the U.S. Institute for Science and International Security (ISIS) said has been under construction since mid-2004.
While attention has long focused on Iran’s established uranium enrichment work, its progress at Arak also rang alarm bells, raising concern that Tehran could pursue both possible bomb core alternatives – uranium and plutonium – simultaneously.
To make a plutonium bomb, Iran would also need to build a reprocessing plant to extract the material, and it has no declared plans to do so.
Nuclear analyst Mark Hibbs of the Carnegie Endowment think-tank said Iran might be able to do some Arak-related work off-site under Sunday’s interim accord.
“But the agreement puts a firewall around the reactor, meaning that no equipment will be installed … and no fuel will be loaded,” Hibbs said.
Middle East expert Shashank Joshi of the Royal United Services Institute (RUSI) said it could be argued that the deal also covers building components at another location.
“Of course, the fact that we are having this argument is itself acknowledgment of a possible loophole. Remember the US-DPRK ‘leap day’ deal? Devil in the detail,” Joshi said, referring to an ultimately failed agreement between North Korea and the United States early last year.
Source: Netanyahu Scolded Obama in Phone Call on Iran Deal
“The prime minister made it clear to the most powerful man on earth that if he intends to stay the most powerful man on earth, it’s important to make a change in American policy because the practical result of his current policy is liable to lead him to the same failure that the Americans absorbed in North Korea and Pakistan, and Iran could be next in line.”
That was the message conveyed by Israeli Prime Minister Benjamin Netanyahu to President Barack Obama in a private telephone call Sunday to discuss the interim deal on Iran’s nuclear program, according to a senior Israeli lawmaker in Netanyahu’s ruling coalition, as reported by the Jerusalem Post.
The White House’s own official statement on the telephone call made no mention of any disagreement being aired, merely referring to “their shared goal of preventing Iran from obtaining a nuclear weapon.”
Meanwhile, Netanyahu said that he would send a high-level diplomatic team to the U.S. to lobby for a tough final agreement with Iran that sees that country’s entire nuclear enrichment program dismantled.
In a development that may be related, British Foreign Secretary William Hague warned Israel not to interfere with the emerging deal, perhaps voicing a sentiment shared by Obama and other diplomatic partners.
Enriched uranium is a type of uranium in which the percent composition of uranium-235 has been increased through the process ofisotope separation. Natural uranium is 99.284% U238 isotope, with U235 only constituting about 0.711% of its weight. U235 is the onlynuclide existing in nature (in any appreciable amount) that is fissile with thermal neutrons.
Enriched uranium is a critical component for both civil nuclear power generation and military nuclear weapons. The International Atomic Energy Agency attempts to monitor and control enriched uranium supplies and processes in its efforts to ensure nuclear power generation safety and curb nuclear weapons proliferation.
During the Manhattan Project enriched uranium was given the codename oralloy, a shortened version of Oak Ridge alloy, after the location of the plants where the uranium was enriched. The term oralloy is still occasionally used to refer to enriched uranium. There are about 2,000 tonnes (t, Mg) of highly enriched uranium in the world, produced mostly for nuclear weapons, naval propulsion, and smaller quantities for research reactors.
The U238 remaining after enrichment is known as depleted uranium (DU), and is considerably less radioactive than even natural uranium, though still very dense and extremely hazardous in granulated form – such granules are a natural by-product of the shearing action that makes it useful for armor-penetrating weapons and radiation shielding. At present, 95% of the world’s stocks of depleted uranium remain in secure storage.
Slightly enriched uranium (SEU)
A drum of yellowcake (a mixture of uranium precipitates)
Slightly enriched uranium (SEU) has a 235U concentration of 0.9% to 2%. This new grade can be used to replace natural uranium (NU) fuel in some heavy water reactors like the CANDU. Fuel designed with SEU could provide additional benefits such as safety improvements or operational flexibility, normally the benefits were considered in safety area while retaining the same operational envelope. Safety improvements could lower positive reactivity feedback such as reactivity void coefficient. Operational improvements would consist in increasing the fuel burnup allowing fuel costs reduction because less uranium and fewer bundles are needed to fuel the reactor. This in turn reduces the quantity of used fuel and its subsequent management costs.
Reprocessed uranium (RepU)
Reprocessed uranium (RepU) is a product of nuclear fuel cycles involving nuclear reprocessing of spent fuel. RepU recovered from light water reactor (LWR) spent fuel typically contains slightly more U-235 than natural uranium, and therefore could be used to fuel reactors that customarily use natural uranium as fuel, such as CANDU reactors. It also contains the undesirable isotope uranium-236 which undergoes neutron capture, wasting neutrons (and requiring higher U-235 enrichment) and creating neptunium-237 which would be one of the more mobile and troublesome radionuclides in deep geological repository disposal of nuclear waste.
Low-enriched uranium (LEU)
Low-enriched uranium (LEU) has a lower than 20% concentration of 235U. For use in commercial light water reactors (LWR), the most prevalent power reactors in the world, uranium is enriched to 3 to 5% 235U. Fresh LEU used in research reactors is usually enriched 12% to 19.75% U-235, the latter concentration being used to replace HEU fuels when converting to LEU.
Highly enriched uranium (HEU)
A billet of highly enriched uranium metal
Highly enriched uranium (HEU) has a greater than 20% concentration of 235U or 233U. The fissile uranium in nuclear weapons usually contains 85% or more of 235U known as weapon(s)-grade, though for a crude, inefficient weapon 20% is sufficient (called weapon(s)-usable); in theory even lower enrichment is sufficient, but then the critical mass for unmoderated fast neutrons rapidly increases, approaching infinity at 6% 235U. For criticality experiments, enrichment of uranium to over 97% has been accomplished.
The very first uranium bomb, Little Boy dropped by the United States on Hiroshima in 1945, used 64 kilograms of 80% enriched uranium. Wrapping the weapon’s fissile core in a neutron reflector (which is standard on all nuclear explosives) can dramatically reduce the critical mass. Because the core was surrounded by a good neutron reflector, at explosion it comprised almost 2.5 critical masses. Neutron reflectors, compressing the fissile core via implosion, fusion boosting, and “tamping”, which slows the expansion of the fissioning core with inertia, allow nuclear weapon designs that use less than what would be one bare-sphere critical mass at normal density. The presence of too much of the 238U isotope inhibits the runaway nuclear chain reaction that is responsible for the weapon’s power. The critical mass for 85% highly enriched uranium is about 50 kilograms (110 lb), which at normal density would be a sphere about 17 centimetres (6.7 in) in diameter.
Later US nuclear weapons usually use plutonium-239 in the primary stage, but the secondary stage which is compressed by the primary nuclear explosion often uses HEU with enrichment between 40% and 80% along with the fusion fuel lithium deuteride. For the secondary of a large nuclear weapon, the higher critical mass of less-enriched uranium can be an advantage as it allows the core at explosion time to contain a larger amount of fuel. The 238U is not fissile but still fissionable by fusion neutrons.
HEU is also used in fast neutron reactors, whose cores require about 20% or more of fissile material, as well as in naval reactors, where it often contains at least 50% 235U, but typically does not exceed 90%. The Fermi-1 commercial fast reactor prototype used HEU with 26.5% 235U. Significant quantities of HEU are used in the production of medical isotopes, for example molybdenum-99 for technetium-99m generators.
Isotope separation is difficult because two isotopes of the same elements have very nearly identical chemical properties, and can only be separated gradually using small mass differences. (235U is only 1.26% lighter than 238U.) This problem is compounded by the fact that uranium is rarely separated in its atomic form, but instead as a compound (235UF6 is only 0.852% lighter than 238UF6.) A cascade of identical stages produces successively higher concentrations of 235U. Each stage passes a slightly more concentrated product to the next stage and returns a slightly less concentrated residue to the previous stage.
There are currently two generic commercial methods employed internationally for enrichment: gaseous diffusion (referred to as first generation) and gas centrifuge (second generation) which consumes only 2% to 2.5% as much energy as gaseous diffusion. Later generation methods will become established because they will be more efficient in terms of the energy input for the same degree of enrichment and the next method of enrichment to be commercialized will be referred to as third generation. Some work is being done that would use nuclear resonance; however there is no reliable evidence that any nuclear resonance processes have been scaled up to production.
Gaseous diffusion is a technology used to produce enriched uranium by forcing gaseous uranium hexafluoride (hex) through semi-permeable membranes. This produces a slight separation between the molecules containing 235U and 238U. Throughout the Cold War, gaseous diffusion played a major role as a uranium enrichment technique, and as of 2008 accounted for about 33% of enriched uranium production, but is now an obsolete technology that is steadily being replaced by the later generations of technology as the diffusion plants reach their ends-of-life.
Thermal diffusion utilizes the transfer of heat across a thin liquid or gas to accomplish isotope separation. The process exploits the fact that the lighter 235U gas molecules will diffuse toward a hot surface, and the heavier 238U gas molecules will diffuse toward a cold surface. The S-50 plant at Oak Ridge, Tennessee was used during World War II to prepare feed material for the EMIS process. It was abandoned in favor of gaseous diffusion.
A cascade of gas centrifuges at a U.S. enrichment plant
The gas centrifuge process uses a large number of rotating cylinders in series and parallel formations. Each cylinder’s rotation creates a strong centrifugal force so that the heavier gas molecules containing 238U move toward the outside of the cylinder and the lighter gas molecules rich in 235U collect closer to the center. It requires much less energy to achieve the same separation than the older gaseous diffusion process, which it has largely replaced and so is the current method of choice and is termed second generation. It has a separation factor per stage of 1.3 relative to gaseous diffusion of 1.005, which translates to about one-fiftieth of the energy requirements. Gas centrifuge techniques produce about 54% of the world’s enriched uranium.
Diagram of the principles of a Zippe-type gas centrifuge with U-238 represented in dark blue and U-235 represented in light blue
The Zippe centrifuge is an improvement on the standard gas centrifuge, the primary difference being the use of heat. The bottom of the rotating cylinder is heated, producing convection currents that move the 235U up the cylinder, where it can be collected by scoops. This improved centrifuge design is used commercially by Urenco to produce nuclear fuel and was used by Pakistan in their nuclear weapons program.
Laser processes promise lower energy inputs, lower capital costs and lower tails assays, hence significant economic advantages. Several laser processes have been investigated or are under development. Separation of Isotopes by Laser Excitation (SILEX) is well advanced and licensed for commercial operation in 2012.
Atomic vapor laser isotope separation (AVLIS)
Atomic vapor laser isotope separation employs specially tuned lasers to separate isotopes of uranium using selective ionization of hyperfine transitions. The technique uses lasers which are tuned to frequencies that ionize 235U atoms and no others. The positively charged 235U ions are then attracted to a negatively charged plate and collected.
Molecular laser isotope separation (MLIS)
Molecular laser isotope separation uses an infrared laser directed at UF6, exciting molecules that contain a 235U atom. A second laser frees a fluorine atom, leaving uranium pentafluoride which then precipitates out of the gas.
Separation of Isotopes by Laser Excitation (SILEX)
Separation of isotopes by laser excitation is an Australian development that also uses UF6. After a protracted development process involving U.S. enrichment company USEC acquiring and then relinquishing commercialization rights to the technology, GE Hitachi Nuclear Energy (GEH) signed a commercialization agreement with Silex Systems in 2006.[dead link] GEH has since built a demonstration test loop and announced plans to build an initial commercial facility. Details of the process are classified and restricted by intergovernmental agreements between United States, Australia, and the commercial entities. SILEX has been projected to be an order of magnitude more efficient than existing production techniques but again, the exact figure is classified. In August, 2011 Global Laser Enrichment, a subsidiary of GEH, applied to the U.S. Nuclear Regulatory Commission (NRC) for a permit to build a commercial plant. In September 2012, the NRC issued a license for GEH to build and operate a commercial SILEX enrichment plant, although the company had not yet decided whether the project would be profitable enough to begin construction, and despite concerns that the technology could contribute to nuclear proliferation.
Schematic diagram of an aerodynamic nozzle. Many thousands of these small foils would be combined in an enrichment unit.
Aerodynamic enrichment processes include the Becker jet nozzle techniques developed by E. W. Becker and associates using the LIGA process and the vortex tube separation process. These aerodynamic separation processes depend upon diffusion driven by pressure gradients, as does the gas centrifuge. They in general have the disadvantage of requiring complex systems of cascading of individual separating elements to minimize energy consumption. In effect, aerodynamic processes can be considered as non-rotating centrifuges. Enhancement of the centrifugal forces is achieved by dilution of UF6 with hydrogen or helium as a carrier gas achieving a much higher flow velocity for the gas than could be obtained using pure uranium hexafluoride. The Uranium Enrichment Corporation of South Africa (UCOR) developed and deployed the continuous Helikon vortex separation cascade for high production rate low enrichment and the substantially different semi-batch Pelsakon low production rate high enrichment cascade both using a particular vortex tube separator design, and both embodied in industrial plant. A demonstration plant was built in Brazil by NUCLEI, a consortium led by Industrias Nucleares do Brasil that used the separation nozzle process. However all methods have high energy consumption and substantial requirements for removal of waste heat; none is currently still in use.
Electromagnetic isotope separation
Schematic diagram of uranium isotope separation in a calutron shows how a strong magnetic field is used to redirect a stream of uranium ions to a target, resulting in a higher concentration of uranium-235 (represented here in dark blue) in the inner fringes of the stream.
In the electromagnetic isotope separation process (EMIS), metallic uranium is first vaporized, and then ionized to positively charged ions. The cations are then accelerated and subsequently deflected by magnetic fields onto their respective collection targets. A production-scale mass spectrometer named the Calutron was developed during World War II that provided some of the 235U used for the Little Boy nuclear bomb, which was dropped over Hiroshima in 1945. Properly the term ‘Calutron’ applies to a multistage device arranged in a large oval around a powerful electromagnet. Electromagnetic isotope separation has been largely abandoned in favour of more effective methods.
One chemical process has been demonstrated to pilot plant stage but not used. The French CHEMEX process exploited a very slight difference in the two isotopes’ propensity to change valency in oxidation/reduction, utilising immiscible aqueous and organic phases. An ion-exchange process was developed by the Asahi Chemical Company in Japan which applies similar chemistry but effects separation on a proprietary resin ion-exchange column.
Plasma separation process (PSP) describes a technique that makes use of superconducting magnets and plasma physics. In this process, the principle of ion cyclotron resonance is used to selectively energize the 235U isotope in a plasma containing a mix of ions. The French developed their own version of PSP, which they called RCI. Funding for RCI was drastically reduced in 1986, and the program was suspended around 1990, although RCI is still used for stable isotope separation.
Separative work unit
“Separative work” – the amount of separation done by an enrichment process – is a function of the concentrations of the feedstock, the enriched output, and the depleted tailings; and is expressed in units which are so calculated as to be proportional to the total input (energy / machine operation time) and to the mass processed. Separative work is not energy. The same amount of separative work will require different amounts of energy depending on the efficiency of the separation technology. Separative work is measured in Separative work units SWU, kg SW, or kg UTA (from the German Urantrennarbeit – literally uranium separation work)
- 1 SWU = 1 kg SW = 1 kg UTA
- 1 kSWU = 1 tSW = 1 t UTA
- 1 MSWU = 1 ktSW = 1 kt UTA
The work necessary to separate a mass of feed of assay into a mass of product assay , and tails of mass and assay is given by the expression
where is the value function, defined as
The feed to product ratio is given by the expression
whereas the tails to product ratio is given by the expression
For example, beginning with 102 kilograms (225 lb) of NU, it takes about 90 SWU to produce 10 kilograms (22 lb) of LEU in 235U content to 4.5%, at a tails assay of 0.3%.
The number of separative work units provided by an enrichment facility is directly related to the amount of energy that the facility consumes. Modern gaseous diffusion plants typically require 2,400 to 2,500 kilowatt-hours (kW·h), or 8.6–9 gigajoules, (GJ) of electricity per SWU while gas centrifuge plants require just 50 to 60 kW·h (180–220 MJ) of electricity per SWU.
A large nuclear power station with a net electrical capacity of 1300 MW requires about 25 tonnes per year (25 t/a) of LEU with a 235U concentration of 3.75%. This quantity is produced from about 210 t of NU using about 120 kSWU. An enrichment plant with a capacity of 1000 kSWU/a is, therefore, able to enrich the uranium needed to fuel about eight large nuclear power stations.
In addition to the separative work units provided by an enrichment facility, the other important parameter to be considered is the mass of natural uranium (NU) that is needed to yield a desired mass of enriched uranium. As with the number of SWUs, the amount of feed material required will also depend on the level of enrichment desired and upon the amount of 235U that ends up in the depleted uranium. However, unlike the number of SWUs required during enrichment which increases with decreasing levels of 235U in the depleted stream, the amount of NU needed will decrease with decreasing levels of 235U that end up in the DU.
For example, in the enrichment of LEU for use in a light water reactor it is typical for the enriched stream to contain 3.6% 235U (as compared to 0.7% in NU) while the depleted stream contains 0.2% to 0.3% 235U. In order to produce one kilogram of this LEU it would require approximately 8 kilograms of NU and 4.5 SWU if the DU stream was allowed to have 0.3% 235U. On the other hand, if the depleted stream had only 0.2% 235U, then it would require just 6.7 kilograms of NU, but nearly 5.7 SWU of enrichment. Because the amount of NU required and the number of SWUs required during enrichment change in opposite directions, if NU is cheap and enrichment services are more expensive, then the operators will typically choose to allow more 235U to be left in the DU stream whereas if NU is more expensive and enrichment is less so, then they would choose the opposite.
- Uranium enrichment calculator designed by the WISE Uranium Project
The opposite of enriching is downblending; surplus HEU can be downblended to LEU to make it suitable for use in commercial nuclear fuel.
The HEU feedstock can contain unwanted uranium isotopes: 234U is a minor isotope contained in natural uranium; during the enrichment process, its concentration increases but remains well below 1%. High concentrations of 236U are a byproduct from irradiation in a reactor and may be contained in the HEU, depending on its manufacturing history. HEU reprocessed from nuclear weapons material production reactors (with an 235U assay of approx. 50%) may contain 236U concentrations as high as 25%, resulting in concentrations of approximately 1.5% in the blended LEU product. 236U is a neutron poison; therefore the actual 235U concentration in the LEU product must be raised accordingly to compensate for the presence of 236U.
The blendstock can be NU, or DU, however depending on feedstock quality, SEU at typically 1.5 wt% 235U may used as a blendstock to dilute the unwanted byproducts that may be contained in the HEU feed. Concentrations of these isotopes in the LEU product in some cases could exceed ASTM specifications for nuclear fuel, if NU, or DU were used. So, the HEU downblending generally cannot contribute to the waste management problem posed by the existing large stockpiles of depleted uranium.
A major downblending undertaking called the Megatons to Megawatts Program converts ex-Soviet weapons-grade HEU to fuel for U.S. commercial power reactors. From 1995 through mid-2005, 250 tonnes of high-enriched uranium (enough for 10,000 warheads) was recycled into low-enriched-uranium. The goal is to recycle 500 tonnes by 2013. The decommissioning programme of Russian nuclear warheads accounted for about 13% of total world requirement for enriched uranium leading up to 2008.
The United States Enrichment Corporation has been involved in the disposition of a portion of the 174.3 tonnes of highly enriched uranium (HEU) that the U.S. government declared as surplus military material in 1996. Through the U.S. HEU Downblending Program, this HEU material, taken primarily from dismantled U.S. nuclear warheads, was recycled into low-enriched uranium (LEU) fuel, used by nuclear power plants to generate electricity.
- A uranium downblending calculator designed by the WISE Uranium Project
Global enrichment facilities
The following countries are known to operate enrichment facilities: Argentina, Brazil, China, France, Germany, India, Iran, Japan, the Netherlands, North Korea, Pakistan, Russia, the United Kingdom, and the United States. Belgium, Iran, Italy, and Spain hold an investment interest in the French Eurodif enrichment plant, with Iran’s holding entitling it to 10% of the enriched uranium output. Countries that had enrichment programs in the past include Libya and South Africa, although Libya’s facility was never operational. Australia has developed a laser enrichment process known as SILEX, which it intends to pursue through financial investment in a U.S. commercial venture by General Electric. It has also been claimed that Israel has a uranium enrichment program housed at the Negev Nuclear Research Center site near Dimona.