Questions. 1. What is the difference between a terrorist and a guerilla fighter? 2. What is a dirty bomb?

Transcription

1 Questions 1. What is the difference between a terrorist and a guerilla fighter? 2. What is a dirty bomb? 3. What is the radiological danger of the dirty bomb?

2 The Nuclear Weapons Fuel Cycle The fuel cycle requires a number of mechanical milling, chemical conversion, and nuclear enrichment processes that require an industrial complex described as nuclear fuel cycle. The fuel cycle produces substantial amounts of nuclear radioactive waste which needs to be reprocessed or stored for a long time.

3 Mining Uranium Ore Uranium is a naturally occurring element that is more abundant in granites (~3.5 ppm) than in basalts (~1 ppm). The large size of the uranium atom prevents it from easily entering the structures of common rock forming minerals, so it is an element that tends to remain in magmas until a late stage of crystallization, when it forms minerals, or oxidizes to uranium oxide, uraninite (UO 2 ). Uranium minerals dissolve in hot water and is dispersed by hydrothermal processes, causing uranium deposition. There are about 200 known uranium minerals, but only a few are being mined commercially.

4 World Wide Uranium Mining

5 Closed and Operating Uranium Mines in 2004

6 Mining Practice The depth of uranium mineralization and deposition by hydrothermal cycles decides between open pit mining and deep underground mining. Open pit mining has the advantage of higher productivity, higher recovery, safer working conditions, and lower costs. The disadvantage is the ecological impact and the costs associated with the mine closure. Production from open pit mining (27%), underground mining (40%), in situ leaching (21%), and byproducts (12%). Both open pit mining produce wastes, which are comprised of overburden (soil and rock covering the ore deposit, containing trace amounts of the ore and radioactive decay products).

7 Mine rehabilitation Ecarpiere Uranium Mine in France, operated between 1957 and 1995 The U.S. Environmental Protection Agency EPA is currently embroiled in a massive effort to assess 520 open abandoned uranium mines all over the Navajo reservation. It is claimed that there are about 1300 abandoned uranium mines on Navajo land alone.

8 Underground Uranium Mining For uranium deposits at a depth of more than 200 m underground mining becomes the financially more advantageous method. It involves the use of heavy mining equipment.

9 Milling the Ore The ore material is crushed mechanically and grounded to suitable site. Toasting of the ore is necessary to destroy organic carbon material which could interfere with the purification process. The ground ore is leached with sulphuric acid or sodium carbonate to generate a more solvable uranium component (leaching). Liquid solid separation by diffusion, centrifuge techniques, or drainage techniques is followed by chemical purification process to produce uranium tri oxide (yellow cake) as final product of the milling process.

10 Leaching of Mill tailings Considerable amounts of heavy metals and long term radioactivity may be released and distributed through aqueous or acidic solution processes from mine waste material (mill tailing). In situ leaching by H 2 SO 4 or Na 2 CO 3 chemistry is an often applied technique to resolve uranium in the mining process. Tailings pond of a uranium processing plant

11 Natural Uranium Isotope Distribution Uranium comes in two long lived isotope components 235 U and 238 U, with the abundance ratios depending on the physical and chemical fractionation processes associated with the uranium deposition and mineralization process. The example shows that uranium in sea water contains more 235 U than uranium containing minerals. (except for marine carbonate samples which are correlated with the sea water abundance ratio through chemical exchange processes.

12 Uranium Enrichment Requirements The use of uranium in fission reactors or in fission weapon devices requires an enrichment of 235 U from the natural ~0.72% to higher values suitable for the respective application. Modern light water reactors require an 235 U enrichment of 3%. Reactors for ship propulsion require 10% enrichment to reduce the reactor dimensions. Nuclear submarine fuel requires 90% (weapon grade) enrichment because of reactor size limitations Fission weapons require 90% enrichment to maximize neutron flux and explosive power. Boundary between low enrichment and high enrichment is set at 20% Light water reactor NS Savannah 1962 USS Nautilus 1954 Modern warhead

13 Uranium Conversion Process The three primary enrichment processes are electromagnetic separation, gaseous diffusion, and centrifugation. All of these methods rely on volatile uranium compounds, primarily uranium hexafluoride UF 6 which must be produced chemically from yellow cake. Milled uranium ore U 3 O 8 or "yellowcake" is dissolved in nitric acid HNO 3, yielding a solution of uranyl nitrate UO 2 (NO 3 ) 2.Pureuranylnitrate is obtained by solvent extraction, then treated with ammonia to produce ammonium diuranate (NH 4 ) 2 U 2 O 7. Reduction with hydrogen gives UO 2, which is converted with hydrofluoric acid (HF) to uranium tetrafluoride, UF 4. Oxidation with fluorine yields UF 6. During nuclear reprocessing, uranium is reacted with chlorine trifluoride to give UF 6 : U+2ClF 3 UF 6 +Cl 2

14 Chemical Conversion and Storage

15 Conversion Facilities Country Owner/Controller Plant Name/Location Capacity [MTU/year] Brazil IPEN São Paulo 90 Canada Cameco Port Hope, Ontario 10,500 China CNNC Lanzhou 3000 COMURHEX France (100% Areva NC ) Pierrelatte 14,000 Areva NC Pierrelatte TU5 350 Iran AEOI Isfahan 193 Ekaterinburg 4,000 Russia Rosatom Angarsk 20,000 Springfields Fuels Ltd. Springfields, United Kingdom 6,000 (Westinghouse) Lancashire United States Converdyn (50% Honeywell International, Metropolis, Illinois 17,600 50% General Atomics) Total 75,733

16 Electromagnetic separation Calutron, originally designed by Ernest Lawrence and operated on ORNL Y 12 plant Calutrons use substantial amounts of electrical power. It is estimated that calutrons built in Iraq by the Baath regime of Sadam Hussein after the Israeli bombing of the Osirak reactor required about 140MW of power for operating 90 calutrons.

17 Gaseous diffusion UF 6 is sufficiently volatile to be used in the gaseous diffusion process. UF 6,asolid at room temperature, sublimes at 56.5 C (133 F) at 1 atmosphere.the triple point is at C and 1.5 bar. Applying Graham's Law to uranium hexafluoride: where: Rate 1 is the rate of effusion of 235 UF 6. Rate 2 is the rate of effusion of 238 UF 6. M 1 is the molar mass of 235 UF 6 M 1 = = g mol 1 M 2 is the molar mass of 238 UF 6 M 2 = = g mol 1

18 Diffusion Cascade K 25 diffusion plant A cascade is a sequence of diffusion stages with the enriched 235 U from one stage being fed into the next stage, gradually improving enrichment level.

19 Gaseous Diffusion Plants Country Owner/Controller Plant Name/Location Capacity [1000 SWU/year] Argentina CNEA Pilcaniyeu 20 China CNNC Lanzhou 900? France EURODIF Tricastin 10,800 United States U.S. Enrichment Corp. Paducah, Kentucky 11,300 Portsmouth, Ohio (closed since May (7,400) 2001) Subtotal 23,020 SWU stands for Separative Work Units or 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. SWU is expressed in units which are calculated to be proportional to the total input (energy / machine operation time) and to the mass processed.

20 Gas Centrifuge Separation of uranium isotopes requires a centrifuge that can spin at 1,500 revolutions per second.

21 Zippe Centrifuge The centrifuge was developed in the Soviet Union by a team of 60 Austrian and German scientists captured after World War II, working in detention. The centrifuge is named after the team's experimental leader Gernot Zippe ( ). After the scientists were released from Soviet captivity in 1956, Gernot Zippe was able to reproduce his design at the in the United States. Dr. Zippe left the United States when he was effectively barred from continuing his research unless he would become citizen. He refused, returned to Europe where he and his colleagues improved the centrifuge by changing the material of the rotor from aluminum to a stronger alloy, which allowed higher speed. This improved centrifuge design is used by the commercial company Urenco to produce enriched uranium fuel. In 2004 Abdul Qadeer Khan, a Pakistani engineer at Urenco smuggled plans and critical parts of the centrifuge from the Netherlands to Pakistan, providing the basis for the Pakistani enrichment and nuclear weapon program.

22 Centrifuge Plants Country Owner/Controller Plant Name/Location Capacity a) [1000 SWU/year] Brazil INB Resende? China CNNC Hanzhong 500 Lanzhou 500 France Eurodif Georges Besse II, Tricastin (under constr.) Germany Urenco Deutschland GmbH Gronau 4,200 India DAE Nuclear Fuel Comple Ratnahalli, Karnataka 4.5 Iran AEOI Natanz? Qom? Japan JNC Ningyo Toge 200 Japan Nuclear Fuel Ltd (JNFL) Rokkasho mura 1,050 Korea, DPR Yongbyon 8 Tongchang? Netherlands Urenco Nederland BV Almelo 5,000 Pakistan Pakistan Atomic Energy Commission (PAEC) Kahuta 5 Russia Rosatom Urals Electrochemical Integrated Enterprise 7,000 Siberian Chemical Combine (SKhK), Seversk 4,000 Electrochemical Plant (ECP), Zelenogorsk 3,000 Angarsk Electrolytic Chemical Combine 2,600 United Kingdom Urenco UK Ltd. Capenhurst 5,050 USA Urenco USA National Enrichment Facility, Lea County, NM (under constr.) Subtotal 33,117.5

23 Enrichment Plants 1980 Separation Work Units 1980: 49,700 kswu/y Today: 56,195 kswu/y Separation capability increased since 1980.

24 Nuclear Waste Disposal Decades of production of plutonium and enriched uranium for nuclear weapons left immense legacies of contamination and toxic wastes in the United States. This created significant cleanup challenges at more than 100 locations, some covering hundreds of square miles. This legacy includes 75 million cubic meters of contaminated soil and 1.8 billion cubic meters of contaminated groundwater. Toxic materials and wastes deposited in the environment by nuclear materials production include radioisotopes, large amounts of organic compounds like carbon tetrachloride and metals such as lead, cadmium, chromium, beryllium and mercury. The Department of Energy, which inherited the nuclear weapons production complex, must store, treat and dispose of more than 160,000 cubic meters of solid radioactive and hazardous waste and more than 100 million gallons of liquid, high level radioactive waste. Add to these more than 2,300 metric tons of spent nuclear fuel and at least 38 tons of separated plutonium 239 declared a surplus to the weapons stockpile. In 2000, the Energy Department estimated that cleaning up the nuclear weapons production complex would cost $212 billion and take 70 years. Even so, long term monitoring and maintenance of contaminants left in place would be needed at 109 sites across the country.

25 Waste Isolation Pilot Plant WIPP

26 WIPP underground storage Long term storage in salt mine environment with permanent enclosure within 70 years!

27 Future uncertain, Yucca Mountain? Long term storage site for industrial waste and high level military nuclear waste 1. Canisters of waste, sealed in special casks, are shipped to the site by truck or train. 2. Shipping casks are removed, and the inner tube with the waste is placed in a steel, multilayered storage container. 3. An automated system sends storage containers underground to the tunnels. 4. Containers are stored along the tunnels, on their side.

28 Storage and Distribution System For 30 years pursued by DOE and developed by LLNL engineering

29 America without a site? DOE officials filed a motion on March 2010 with the Nuclear Regulatory Commission to withdraw the agency's license application for the Yucca Mountain site. The DOE request to withdraw the license application was turned down by the Atomic Safety and Licensing Board (ASLB) on June 29, Special Commission looks for solution! How big is the US high level radioactive waste problem? More than 75,000 metric tons of spent nuclear fuel are stacked up at 122 temporary sites in 39 states. America s 104 commercial nuclear reactors produce about 2,000 metric tons of spent nuclear fuel each year. If all reactors were to be relicensed for 60 years, they would produce about 130,000 metric tons of spent nuclear fuel over that time, the DOE reported in Alternatives are: 1. Reprocessing spent uranium reactor fuel. 2. Fast neutron reactors. 3. Accelerator Driven Systems ADS. 4. Deep geological disposal.