THE UNIVERSITY OF THE WEST INDIES MONA CAMPUS EPNG 3010 Nuclear Power Systems and Reactor Operations Module 3: Decommissioning, Nuclear Waste and the Environmental Impact of Nuclear Power EPNG 3010 Nuclear Power Systems and Reactor Operation What is Decommissioning? • According to the Jamaican Nuclear Safety and Radiation Protection Act (2015), “decommissioning” means; • All steps leading to the release of a facility, other than a disposal facility, from regulatory control, other than confirming the decommissioned status of a facility and the processes of decontamination and dismantling. • In regards to disposal facilities, the term ‘closure’ instead of ‘decommissioning’ is used. • The two main objectives of decommissioning are to render the site permanently safe and to recover it, as far as practicable, for reuse. Nuclear Waste, Decommissioning and the Environmental Impact of Nuclear Power EPNG 3010 Nuclear Power Systems and Reactor Operation Stages of decommissioning Nuclear Waste, Decommissioning and the Environmental Impact of Nuclear Power EPNG 3010 Nuclear Power Systems and Reactor Operation Approach to Decommissioning • Operational phase • Shut-down (defueling, period of controlled operation) • Preparation for safe enclosure • Safe enclosure period • Final dismantling • “decommission .. as soon as reasonably practicable.. taking account of all relevant factors” • Minimise total discounted costs, including infrastructure costs • Decouple site strategy from uncertainty about waste repository • Passively safe waste forms Nuclear Waste, Decommissioning and the Environmental Impact of Nuclear Power EPNG 3010 Nuclear Power Systems and Reactor Operation Relevant Factors for Decommissioning • Relevant factors which need to be taken into account in the timing of decommissioning. • the potential hazards to public, workers and the environment • the availability of waste management options • corporate memory - experienced personnel • the time required to plan the work and develop decommissioning techniques and equipment, • radioactive decay • benefit from decay of Co60 in reactors • ingrowth of 241Am in plutonium contaminated material Nuclear Waste, Decommissioning and the Environmental Impact of Nuclear Power EPNG 3010 Nuclear Power Systems and Reactor Operation Relevant Factors for Decommissioning • Relevant factors which need to be taken into account in the timing of decommissioning. • structural integrity • changes in regulatory requirements • changes in the real value over time of costs and benefits • time value of money (discounting effect) • the impact on support and infrastructure costs Nuclear Waste, Decommissioning and the Environmental Impact of Nuclear Power EPNG 3010 Nuclear Power Systems and Reactor Operation Decommissioning Planning • Define the site end point and site strategy • Determine the work required to achieve the strategy & end point • Work is then planned in detail: – Scope – Timescales – Cost Nuclear Waste, Decommissioning and the Environmental Impact of Nuclear Power EPNG 3010 Nuclear Power Systems and Reactor Operation Decommissioning Planning Stakeholder consultation Strategic Overview • End-point definition • Initial waste volume assessment & inventory • Decommissioning options and outline methodology • Safety Case strategy • Waste management principles • Contract strategy Best practicable environmental option (BPEO) Environmental impact assessment & statement Waste management plan Waste discharge authorisations Preliminary safety report Technical specification • Planning cost Pre-qualification & contractor shortlist Implementation Project Detailed scheme Additional sampling Best practicable means Contractor assessment and selection Precommencement safety report, etc. Nuclear Waste, Decommissioning and the Environmental Impact of Nuclear Power EPNG 3010 Nuclear Power Systems and Reactor Operation Reactor Decommissioning • Normally defueled immediately after final shut-down • defueling typically removes 99% of the hazard • most of the rest is Co-60 (half-life 5 years) • delaying the later stages of decommissioning allows radiation levels to decay • reactor structures are normally robust and can be safely maintained for many years Nuclear Waste, Decommissioning and the Environmental Impact of Nuclear Power EPNG 3010 Nuclear Power Systems and Reactor Operation Plutonium Facilities • No benefit from radioactive decay • dose-rates increase with time due to in-growth of Americium-241 • deterioration of equipment due to alpha radiation damage increases risk of failure • early decommissioning of alpha-active facilities is normally recommended Nuclear Waste, Decommissioning and the Environmental Impact of Nuclear Power EPNG 3010 Nuclear Power Systems and Reactor Operation Decommissioning End-point • “Endpoint” (or “endstate”) is the physical condition reached when cleanup actions are complete • Expressed in terms of residual dose from use of the cleaned up area, taking account of an appropriate range of potential use • Must be derived from the goals and objectives of the restoration project • Must be acceptable to Stakeholders Nuclear Waste, Decommissioning and the Environmental Impact of Nuclear Power EPNG 3010 Nuclear Power Systems and Reactor Operation Delicensing • The Jamaican Nuclear Safety and Radiation Protection Act (2015) requires demonstration that “….the end state in the decommissioning plan has been reached and that any other regulatory requirements have been met: Nuclear Waste, Decommissioning and the Environmental Impact of Nuclear Power EPNG 3010 Nuclear Power Systems and Reactor Operation Decontamination and Dismantling • Objectives of decontamination: • Reduce the inventory of radioactive material in a facility or item of equipment • Reduce radiation levels and minimise the potential for release of radioactivity • Reduce the quantity of radioactive waste produced • Complete the final stages of decommissioning - i.e. building demolition and site restoration Nuclear Waste, Decommissioning and the Environmental Impact of Nuclear Power EPNG 3010 Nuclear Power Systems and Reactor Operation Constraints in Decontamination • Availability of suitable disposal options for secondary wastes • Possible interference with effluent processing • Exposure of operators to radiation dose • Potential spread of contamination • Damage to structural integrity of building • Difficulty in demonstrating that end-point has been achieved Nuclear Waste, Decommissioning and the Environmental Impact of Nuclear Power EPNG 3010 Nuclear Power Systems and Reactor Operation Decontamination Techniques • Non-attritive methods • swabbing, sweeping, vacuuming • substrate surface undamaged • Chemical / electrochemical • removes a layer of the substrate along with R/A • Physical attrition • scabbling concrete • routing / milling (e.g. lead bricks) Nuclear Waste, Decommissioning and the Environmental Impact of Nuclear Power EPNG 3010 Nuclear Power Systems and Reactor Operation Foam Cleaning Equipment Nuclear Waste, Decommissioning and the Environmental Impact of Nuclear Power EPNG 3010 Nuclear Power Systems and Reactor Operation Scabbling Nuclear Waste, Decommissioning and the Environmental Impact of Nuclear Power EPNG 3010 Nuclear Power Systems and Reactor Operation Removal of hotspot from a wall Nuclear Waste, Decommissioning and the Environmental Impact of Nuclear Power EPNG 3010 Nuclear Power Systems and Reactor Operation Chemical Decontamination • Used to decontaminate metallic items such as pipes, tanks and heat exchangers from reactor dismantling (BR3 PWR) • Uses cerium IV as oxidising agent • Claim free release of treated material and 95% reduction in volume of radioactive waste • Spent solution precipitated, filtered and encapsulated in asphalt Nuclear Waste, Decommissioning and the Environmental Impact of Nuclear Power EPNG 3010 Nuclear Power Systems and Reactor Operation CO2 Abrasion Nuclear Waste, Decommissioning and the Environmental Impact of Nuclear Power EPNG 3010 Nuclear Power Systems and Reactor Operation Plutonium Handling Facility Before After Nuclear Waste, Decommissioning and the Environmental Impact of Nuclear Power EPNG 3010 Nuclear Power Systems and Reactor Operation Dismantling • Mechanical Cutting • • • • • • Saws (reciprocating, circular, band, wire) Cropping shears Nibblers Drill bits Routers Jack hammers Nuclear Waste, Decommissioning and the Environmental Impact of Nuclear Power EPNG 3010 Nuclear Power Systems and Reactor Operation Mechanical tools Nuclear Waste, Decommissioning and the Environmental Impact of Nuclear Power EPNG 3010 Nuclear Power Systems and Reactor Operation Stitch Drilling Setting up core drilling rig Removing penetration block from shield wall Nuclear Waste, Decommissioning and the Environmental Impact of Nuclear Power EPNG 3010 Nuclear Power Systems and Reactor Operation Thermal Cutting • Flame cutting • Plasma arc • Laser Nuclear Waste, Decommissioning and the Environmental Impact of Nuclear Power EPNG 3010 Nuclear Power Systems and Reactor Operation Dismantling • Chemical and other methods • • • • • Reactive chemicals (expansive grout) to initiate crack formation Accelerated chemical corrosion High pressure water jets Microwave spalling Explosive cutting (shaped charges) Nuclear Waste, Decommissioning and the Environmental Impact of Nuclear Power EPNG 3010 Nuclear Power Systems and Reactor Operation Chemical Splitting PLUTO External storage block Crack induced by Butomite Nuclear Waste, Decommissioning and the Environmental Impact of Nuclear Power EPNG 3010 Nuclear Power Systems and Reactor Operation Waste Size Reduction Nuclear Waste, Decommissioning and the Environmental Impact of Nuclear Power EPNG 3010 Nuclear Power Systems and Reactor Operation Waste Packaging Nuclear Waste, Decommissioning and the Environmental Impact of Nuclear Power EPNG 3010 Nuclear Power Systems and Reactor Operation Remote handling systems • Tongs • Master-Slave Manipulators (MSM) • Power Manipulators • NEATER Robot • Remotely Operated Vehicle (ROV) Nuclear Waste, Decommissioning and the Environmental Impact of Nuclear Power EPNG 3010 Nuclear Power Systems and Reactor Operation TeleRobot NEATER Nuclear Engineered Advanced Nuclear Waste, Decommissioning and the Environmental Impact of Nuclear Power EPNG 3010 Nuclear Power Systems and Reactor Operation Personal Protective Equipment • Respirators • Air hoods • Full pressurised suits Nuclear Waste, Decommissioning and the Environmental Impact of Nuclear Power EPNG 3010 Nuclear Power Systems and Reactor Operation Decommissioned Alpha Materials Lab Nuclear Waste, Decommissioning and the Environmental Impact of Nuclear Power EPNG 3010 Nuclear Power Systems and Reactor Operation Nuclear Waste Management • Integrated Waste Management Strategy • avoid the unnecessary creation of wastes • reduce waste arising by the appropriate design of processes and equipment • reuse and recycle materials under appropriate regulatory control • use the BPEO (best practicable environmental option) to manage residual wastes • deliver value for money. Nuclear Waste, Decommissioning and the Environmental Impact of Nuclear Power EPNG 3010 Nuclear Power Systems and Reactor Operation Nuclear Waste • Nuclear waste is segregated into several classifications. • Low level waste is not dangerous but sometimes requires shielding during handling. • Intermediate level waste typically is chemical sludge and other products from reactors. • High level waste consists of fissionable elements from reactor cores and transuranic wastes. • Transuranic waste is any waste with transuranic alpha emitting radionuclides that have half-lives longer than 20 years. Nuclear Waste, Decommissioning and the Environmental Impact of Nuclear Power EPNG 3010 Nuclear Power Systems and Reactor Operation Nuclear Waste Low Level Waste (LLW) • Low level waste is any waste that could be from a high activity area. • Solid material • 90% volume of waste • < 12 GBq/t beta/gamma • < 4 GBq/t alpha (note Pu restriction) Nuclear Waste, Decommissioning and the Environmental Impact of Nuclear Power EPNG 3010 Nuclear Power Systems and Reactor Operation Nuclear Waste Intermediate Level Waste (ILW) • Intermediate level waste typically requires shielding when being handled or handled remotely. • 7% volume of waste • Dependent on the amount of activity it can be buried in shallow repositories. • Not recognized in the United States. • Not significantly heat generating Nuclear Waste, Decommissioning and the Environmental Impact of Nuclear Power EPNG 3010 Nuclear Power Systems and Reactor Operation Nuclear Waste High Level Waste (HLW) • Originate from the reprocessing of nuclear fuels. • It is significantly heat generating • 3% volume of waste • 95% of radioactivity • Current levels of HLW are increasing about 12,000 metric tons per year. • Most HLW consists of Pu-238, 239, 240, 241, 242, Np-237, U-236 Nuclear Waste, Decommissioning and the Environmental Impact of Nuclear Power EPNG 3010 Nuclear Power Systems and Reactor Operation Nuclear Waste Transuranic Waste (TRUW) • Transuranic waste consists of all waste that has radionuclides above uranium. • TRUWs typically have longer half-lives than other forms of waste. • Typically a byproduct of weapons manufacturing. • Only recognized in the United States. • The two options for managing nuclear waste are direct disposal and reprocessing Nuclear Waste, Decommissioning and the Environmental Impact of Nuclear Power EPNG 3010 Nuclear Power Systems and Reactor Operation Nuclear Waste Before any of those options spent fuel is usually stored on site for several years Wet storage • The great majority of spent nuclear fuel is initiallys tored as spent fuel assemblies in water-filled pools on power plant sites. • The pools provide radiation shielding and cooling Dry Storage • Spent Fuel is usually placed in dry cask storage after 5 years in wet storage. (NRC regulation requires at least 1 year in wet storage.) • Dry cask storage uses concrete or steel containers as a radiation shield and is cooled by inert gas or air. • The casks are built to withstand the elements and accidents and do not require electricity, water, maintenance, or constant supervision Nuclear Waste, Decommissioning and the Environmental Impact of Nuclear Power EPNG 3010 Nuclear Power Systems and Reactor Operation Nuclear Waste Spent Fuel Pool/Pond Nuclear Waste, Decommissioning and the Environmental Impact of Nuclear Power EPNG 3010 Nuclear Power Systems and Reactor Operation Nuclear Waste Nuclear Waste, Decommissioning and the Environmental Impact of Nuclear Power EPNG 3010 Nuclear Power Systems and Reactor Operation Reprocessing • Reprocessing reduces the volume of waste Nuclear Waste, Decommissioning and the Environmental Impact of Nuclear Power EPNG 3010 Nuclear Power Systems and Reactor Operation Reprocessing • Reprocessing is the chemical separation and removal of fission products from the SNF • U, Pu may be separated and reused or stored • Fission products vitrified as HLW glass (ideally) • Many processes (we, dry, transmutation) • Spent Fuel 238U • 95% 235U • 1% • 1% Pu • 3% fission products • Reprocessing separates it into 3 groups •U • Pu • Waste (Actinides – Am, Np, Cm & Fission products – Cs, Sr, I, Tc) Nuclear Waste, Decommissioning and the Environmental Impact of Nuclear Power EPNG 3010 Nuclear Power Systems and Reactor Operation Reprocessing • Wet Process • Many different wet processes exist but the standard method for reprocessing is the PUREX method. • PUREX: Plutonium and Uranium Recovery by Extraction • The process extracts uranium and plutonium from the spent nuclear fuel for reuse and leaves the remaining fission products. • Dry Process • Sometimes called pyro-reprocessing, pyro-metallurgical processing • Uses melting, electrolysis, volatilization to separate U/Pu from fission products • Proposed in transmutation schemes • Difficult to adapt to commercial fuels Nuclear Waste, Decommissioning and the Environmental Impact of Nuclear Power EPNG 3010 Nuclear Power Systems and Reactor Operation Reprocessing • Transmutation • Transformation of radionuclides into other radionuclides that are either non-radioactive or significantly less radioactive/shorter half lives • Some Fission Products and Transuranics radioactive/hazardous for 10,000+ years and environmentally mobile • Main focus on Actinides (Np, Pu, Am, Cm) • Secondary focus on Tc, I, Ni, Zr • Tertiary focus on Cs, Sr Nuclear Waste, Decommissioning and the Environmental Impact of Nuclear Power EPNG 3010 Nuclear Power Systems and Reactor Operation Reprocessing • PUREX: Plutonium and Uranium Extraction • Most widely used method • Results in a pure stream of plutonium • UREX: Uranium Reduction Extraction • Replacement for PUREX • Results in pure uranium stream • The plutonium remains mixed with the fission products and minor actinides • UREX+ • Refinement of the UREX process Nuclear Waste, Decommissioning and the Environmental Impact of Nuclear Power EPNG 3010 Nuclear Power Systems and Reactor Operation Reprocessing • About 30% of the world’s LWR spent fuel is reprocessed using PUREX • Among the nuclear-armed states, France, India, Russia, and the United Kingdom engage in reprocessing • Japan is the only non-nuclear-armed state that has a civilian reprocessing program Nuclear Waste, Decommissioning and the Environmental Impact of Nuclear Power EPNG 3010 Nuclear Power Systems and Reactor Operation Disposal of Nuclear Waste • Nuclear waste is “disposed” of based on its classification • LLW and ILWSL (short-lived) -. • Low and intermediate level short-lived radioactive liquids are either: • Incinerated • Solidified • Low and intermediate level short-lived radioactive solids are either: • “Supercompacted” at ~30,000 psi to reduce the volume and buried in relatively shallow concrete-lined pits • Encased in concrete and buried Nuclear Waste, Decommissioning and the Environmental Impact of Nuclear Power EPNG 3010 Nuclear Power Systems and Reactor Operation Disposal of Nuclear Waste • Nuclear waste is “disposed” of based on its classification • LLW and ILWSL (short-lived) -. • Low and intermediate level short-lived radioactive liquids are either: • Incinerated • Solidified • Low and intermediate level short-lived radioactive solids are either: • “Supercompacted” at ~30,000 psi to reduce the volume and buried in relatively shallow concrete-lined pits • Encased in concrete and buried Nuclear Waste, Decommissioning and the Environmental Impact of Nuclear Power EPNG 3010 Nuclear Power Systems and Reactor Operation Disposal of Nuclear Waste Nuclear waste is “disposed” of based on its classification ILW-LL and HLW – no finalized disposal route ILW is compacted or cemented to make packages that are stored HLW is vitrified. This involves incorporating highly radioactive waste into molten glass. • The waste, which is in a liquid form, is mixed with molten glass and poured into stainless steel containers, then hermetically sealed by a welded lid. • Once the glass has cooled down, the radioactivity is trapped inside the matrix • These are then stored long-term • • • • Nuclear Waste, Decommissioning and the Environmental Impact of Nuclear Power EPNG 3010 Nuclear Power Systems and Reactor Operation Disposal of Nuclear Waste • Deep Geological Disposal concept Nuclear Waste, Decommissioning and the Environmental Impact of Nuclear Power EPNG 3010 Nuclear Power Systems and Reactor Operation Disposal of Nuclear Waste • Deep Geological Disposal concept Nuclear Waste, Decommissioning and the Environmental Impact of Nuclear Power EPNG 3010 Nuclear Power Systems and Reactor Operation Environmental Impact of Nuclear Power • Nuclear fuel cycle includes: • Mining and processing of uranium to controlled fission • Reprocessing of spent fuel • Decommissioning of power plants • Disposal of radioactive waste • Throughout the cycle radiation can enter and affect the environment. Nuclear Waste, Decommissioning and the Environmental Impact of Nuclear Power EPNG 3010 Nuclear Power Systems and Reactor Operation Nuclear Power Plant Accidents • There have been three major nuclear power plant accidents • Three Mile Island – 1979 • Chernobyl – 1986 • Fukushima Daiichi - 2011 Nuclear Waste, Decommissioning and the Environmental Impact of Nuclear Power EPNG 3010 Nuclear Power Systems and Reactor Operation Nuclear Power Plant Accidents • Three Mile Island – USA, 1979 • Main cause was a faulty valve on pressurizer • Resulted in coolant loss from the core • Emergency cooling systems came in to add additional coolant but was later turned of by operators (they didn’t know exactly what was happening) • Partial core meltdown • Minimal radioactive release to environment • Fatalities – Estimated release was 33 man-Sv to total population, and at 20 man-Sv/death = <2 deaths predicted Nuclear Waste, Decommissioning and the Environmental Impact of Nuclear Power EPNG 3010 Nuclear Power Systems and Reactor Operation Nuclear Power Plant Accidents • Chernobyl – USSR, 1986 • Standard test to determine how long turbine would produce electricity if steam supply was shut off • Was to be run at 25% power (reactor very unstable at lower powers) • Decreased power from 100% and at 50% they got a call that the city needed the electricity so they continued operating at 50% for some hours • Later got the go-ahead to continue with the test • While reducing to 25%, power fell to 0% then was stabilized at 7% • Due to the instability, the power increased to 100x full power in about 1 second which caused the explosion • Massive release of radioactivity over europe • Health effects • 28 plant operators died from radiation exposure • “Liquidators” sent to clean up reactor site, of the 211,000 in the first year 1600 died • Estimated total deaths is 4,000 – 50,000 • The Exclusion Zone covers an area of approximately 2,600 km2 Nuclear Waste, Decommissioning and the Environmental Impact of Nuclear Power EPNG 3010 Nuclear Power Systems and Reactor Operation Nuclear Power Plant Accidents • Fukushima – Japan, 2011 • 9.0 Earthquake caused reactors to shut down as designed to do • Electrical power supply from grid was cut off • Back up diesel generators came online to provide core cooling • Tsunami flooded basement with generators • Back up batteries the powered coolant pumps but ran out after ~8 hours • Back up generators were safe on a hill nearby but switch-gear was in flooded basement • Fatalities • Earthquake and tsunami - 16,000 deaths, 6,000 injuries, >3,000 still missing • Radiation exposure100-1000 predicted, none to date • ~1/10th of radiation release at Chernobyl over ~1/10th land area Nuclear Waste, Decommissioning and the Environmental Impact of Nuclear Power EPNG 3010 Nuclear Power Systems and Reactor Operation Environmental Impact of Nuclear Power • Virtually no greenhouse gas emission • “virtually” because emissions are associated with uranium mining, plant construction, transportation of materials, fuel fabrication and enrichment, etc. • According to the NCRP (National Council on Radiation Protection and Measurements) coal-fired plants release 100 times more radioactive particles than nuclear plants (of the same output) into the atmosphere. • It is better to live close to a nuclear plant than a coal-fired plant (of course except in the case of an accident) • Per TWh of electricity produced, nuclear along with wind power has killed the least amount of people. Nuclear Waste, Decommissioning and the Environmental Impact of Nuclear Power EPNG 3010 Nuclear Power Systems and Reactor Operation Environmental Impact of Nuclear Power Nuclear (Chernobyl included) Oil Coal 0.04 36 161 Nuclear Waste, Decommissioning and the Environmental Impact of Nuclear Power EPNG 3010 Nuclear Power Systems and Reactor Operation Nuclear Power Plant Footprint Nuclear Waste, Decommissioning and the Environmental Impact of Nuclear Power EPNG 3010 Nuclear Power Systems and Reactor Operation Nuclear Power and Climate Change Nuclear Waste, Decommissioning and the Environmental Impact of Nuclear Power EPNG 3010 Nuclear Power Systems and Reactor Operation Nuclear Power Pros and Cons Advantages Disadvantages Low generation cost High initial investment required Virtually no Greenhouse gas emissions Accidents have widespread consequences Able to provide base load electricity Radioactive waste Availability 80-95% Relatively small quantities of waste Low operation and maintenance costs Small physical footprint Plant life up to 80 years Nuclear Waste, Decommissioning and the Environmental Impact of Nuclear Power
