BASIC PROFESSIONAL TRAINING COURSE Module XVII Fuel cycle
BASIC PROFESSIONAL TRAINING COURSE Module XVII Fuel cycle, spent fuel management and transport of radioactive materials Case Studies Version 1. 1, September 2015 This material was prepared by the IAEA and co-funded by the European Union.
2 Introduction • For an international course, students should be divided into groups according to the country they represent. • For a national course, students should be divided into groups; so that each includes regulators and operators if possible, to maximize exchange of information from different perspectives. • Each group will address all the topics and prepare a short presentation for the plenary session. Basic Professional Training Course; Module XVII Fuel cycle, spent fuel management and transport of radioactive materials
3 Nuclear fuel cycle • Through uranium production to spent fuel reprocessing and recycling, there a range of stages in the nuclear fuel cycle. • Once you have selected one of the stages in the NFC, you will then progress to consider key steps. • In cases where is more than one bullet point, all of the points should be considered and divided among different groups of participants. Basic Professional Training Course; Module XVII Fuel cycle, spent fuel management and transport of radioactive materials
4 Case 1 • Select one of the milling methods and describe the production of “yellowcake”. • For the selected milling method explain what are the advantages and what are the disadvantages in comparison with the other milling methods. Basic Professional Training Course; Module XVII Fuel cycle, spent fuel management and transport of radioactive materials
5 Case 2 The next step, following yellowcake production, is conversion. Describe: • What is meant by conversion? • What is the product of conversion used for? • What two principal methods can be used for conversion? Basic Professional Training Course; Module XVII Fuel cycle, spent fuel management and transport of radioactive materials
6 Case 3 After conversion, the UF 6 is ready for enrichment. • Describe what enrichment is and what is meant by “levels of enrichment”. • Select one enrichment method. Describe and compare the selected enrichment method to the other methods. Basic Professional Training Course; Module XVII Fuel cycle, spent fuel management and transport of radioactive materials
7 Case 4 • Label the indicated fuel rod components. • Outline the process of fuel fabrication. Basic Professional Training Course; Module XVII Fuel cycle, spent fuel management and transport of radioactive materials
8 Case 5 After the removal of fuel from the reactor, it becomes radioactive waste. • Describe how can spent fuel be stored and reprocessed. • One week after discharging a ton of spent fuel, it generates about 100 kilo. Watts. Consider discharging a full core comprising 72 tons of spent fuel into a spent fuel pool with dimensions of 21 m 9 m. If there is no cooling of the spent fuel pool, how much time it would take for the water above the fuel to boil off? In the beginning, there is about 6 m of water, above the fuel. Basic Professional Training Course; Module XVII Fuel cycle, spent fuel management and transport of radioactive materials
9 Transport of nuclear material The table on the next slide presents a compilation of important activity levels for some common radionuclides. The Exemption Level originates from International Basic Safety Standard and A 1/A 2 are the quantities that of “special form” and other than “special form” to limit annual worker doses to 50 m. Sv, and the D-value is that quantity of radioactive material which, if uncontrolled, could result in the death of an exposed individual or a permanent injury that decreases that person’s quality of life. This value is used for determining the need for emergency arrangements. Basic Professional Training Course; Module XVII Fuel cycle, spent fuel management and transport of radioactive materials
10 Transport of nuclear material Co-60 Ni-63 Sr-90 (Y-90) Mo-99 Tc-99 m I-131 Cs-137 Ir-192 Ra-226 Am-241 Cf-252 Only beta or gamma emitting nuclides are known to be present Alpha emitting nuclides but no neutron emitters are known to be present Neutron emitting nuclides are known to be present or no relevant data are available Exemption level (Bq) 1× 10+5 1× 10+8 1× 10+4 1× 10+6 1× 10+7 1× 10+6 1× 10+4 1× 10+4 A 1 (Bq) A 2 (Bq) D (Bq) 4× 10+11 4× 10+13 3× 10+11 1× 10+12 1× 10+13 3× 10+12 2× 10+12 1× 10+12 2× 10+11 1× 10+13 1× 10+11 4× 10+11 3× 10+13 3× 10+11 6× 10+11 4× 10+12 7× 10+11 6× 10+11 3× 10+9 1× 10+9 3× 10+10 6× 10+13 1× 10+12 3× 10+11 7× 10+11 2× 10+11 1× 10+11 8× 10+10 4× 10+10 6× 10+10 2× 10+10 1× 10+11 2× 10+10 2× 10+11 9× 10+7 1× 10+9 9× 10+7 Basic Professional Training Course; Module XVII Fuel cycle, spent fuel management and transport of radioactive materials
11 Case 1 Identify the packages required for: • 1 TBq of Cs-137 in special form. • 1 TBq of Cs-137 in other than special form. • An unknown mixture of radionuclides in special form with a total activity of 0. 0005 TBq. • An unknown mixture of radionuclides in other than special form with a total activity of 0. 05 TBq. Basic Professional Training Course; Module XVII Fuel cycle, spent fuel management and transport of radioactive materials
12 Case 2 • You have 60 Co solid, metal source with 0. 27 GBq activity that should be shipped to your customer. You also have certified Type A packaging. Determine the following packaging survey data: − Surface dose rate, − Dose rate at distance 1 m from package surface, − Removable contamination. • Answer the following questions: − Is Type A packaging appropriate for this shipment based upon activity alone? − What transport index should be assigned to this package? − Which label should be used for the package and what should be written on the label? − What additional marking, if any, should be on the package? Basic Professional Training Course; Module XVII Fuel cycle, spent fuel management and transport of radioactive materials
13 Case 3 Yellow cake (U 3 O 8) is classified as LSA-1 radioactive material and usually transported in 200 L steel drums that meet IP-1 requirements. There is about 10 GBq of 238 U in the drum and the transport index for the drum is 0. 4. Drums are usually handled with a forklift truck, where the distance between the forklift operator and drum is about 2 m. Estimate the annual effective dose for a forklift operator considering that he effectively handles the drums with yellowcake 200 hours per year. Basic Professional Training Course; Module XVII Fuel cycle, spent fuel management and transport of radioactive materials
14 Safety aspects of the nuclear fuel cycle Students should be divided into groups of 4 to 5 students. Each group should address the following questions with reference to the Tokaimura criticality accident: • How was criticality safety breached? • What was the root cause of the breach of criticality safety from the technical point of view? • What was the root cause of the breach of criticality safety from the safety culture point of view? • Could the breach of criticality safety have been averted? • What were the consequences of this criticality accident? Basic Professional Training Course; Module XVII Fuel cycle, spent fuel management and transport of radioactive materials
15 Tokaimura Criticality Accident – Case Study A criticality accident occurred at the uranium processing facility in Tokaimura, Japan, in 1999. Three operators were preparing a small batch of fuel for an experimental fast breeder reactor in a facility that uses a wet process. This included combining uranium oxide with nitric acid to produce a uranium-containing solution. The material involved was 18. 8% enriched uranium. It was JCO's first batch of fuel for that reactor in three years. The operators worked according to a procedure which differed from the original procedure approved by the regulatory body. Basic Professional Training Course; Module XVII Fuel cycle, spent fuel management and transport of radioactive materials
16 Tokaimura Criticality Accident – Case Study The approved procedure was based on prevention of criticality by mass, volume and geometry limitations of the tanks used that were designed to control the amount of fissile material in the process. Without permission from the regulatory authorities the procedure was modified by the management to speed up the process and even further modified by the operators who had no proper qualification and training for that role. They were used to working with the modified procedure, but only with less than 5% enriched uranium. The operators had no understanding of the criticality hazards involving 18. 8% enrichment. Basic Professional Training Course; Module XVII Fuel cycle, spent fuel management and transport of radioactive materials
17 Tokaimura Criticality Accident – Case Study When the operators filled the tank with about 40 litres of an aqueous uranyl nitrate solution containing some 16 kilograms of uranium, criticality was reached and the nuclear chain reaction became self -sustaining. The water in the solution served as a neutron moderator. Intense gamma and neutron radiation was emitted immediately; a blue flash due to Cherenkov radiation was observed by the operators who fled the location. Gamma radiation alarms sounded. There was no explosion, but fission products were released inside the building. The criticality lasted for about 20 hours, its intensity being governed by boiling of the solution and voids forming. Basic Professional Training Course; Module XVII Fuel cycle, spent fuel management and transport of radioactive materials
18 Tokaimura Criticality Accident – Case Study The reaction was stopped by draining the cooling water from the jacket surrounding the precipitation tank. The surrounding cooling water provided a neutron reflector for the “reactor” inside the tank. Finally the boric acid solution (neutron absorber) was added to the tank to ensure the sub-criticality of the whole assembly. Basic Professional Training Course; Module XVII Fuel cycle, spent fuel management and transport of radioactive materials
19 Tokaimura Criticality Accident – Case Study The two operators closest to the tank experienced symptoms of severe irradiation (nausea, pain, breathing difficulties) immediately after they fled. By measuring the concentration of sodium-24 due to neutron activation of sodium-23 nuclei, the doses received by the operators were deduced to be 17 Sv, 10 Sv and 3 Sv. The two more irradiated workers subsequently died. 36 other workers on the site may have received abnormal doses, as well as 3 firemen and 7 nearby members of the public. The accident was an irradiation accident involving beams of radiation, not widespread contamination or dispersal to the environment. Basic Professional Training Course; Module XVII Fuel cycle, spent fuel management and transport of radioactive materials
20 Tokaimura Criticality Accident – Case Study The Japanese government has rated this accident as INES level 4 (International Nuclear Event Scale), implying limited risk of radiological contamination off the site. IAEA investigation determined that the cause of the accident was "human error and serious breaches of safety principles". Basic Professional Training Course; Module XVII Fuel cycle, spent fuel management and transport of radioactive materials The views expressed in this document do not necessarily reflect the views of the European Commission.
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