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Three Mile Island Unit 2 Overview and Management Issues. THE 5TH MEETING OF THE INTERNATIONAL DECOMMISSIONING NETWORK. 1 through 3 November, 2011 Chuck Negin, Project Enhancement Corp. Subjects & Framework. Subjects TMI-2 Cleanup Description
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Three Mile Island Unit 2 Overview and Management Issues THE 5TH MEETING OF THE INTERNATIONAL DECOMMISSIONING NETWORK 1 through 3 November, 2011 Chuck Negin, Project Enhancement Corp.
Subjects & Framework • Subjects • TMI-2 Cleanup Description • Accident vs. Non-Accident Decommissioning Comparisons • Questions for IAEA Consideration • Framework – This does not address the stabilization time frame that immediately follows emergency response
The TMI-2 Location & System Unit 2 Containment
Important Locations for the TMI-2 Cleanup 2600 miles 4200 km 2100 miles 3400 km Fuel & Debris Storage Idaho National Laboratory • Zeolite Vessels • Hanford, Washington Three Mile Island Middletown, Pennsylvania 600 miles 1000 km Commercial Low Level Waste Disposal Barnwell, South Carolina
A Few Good Luck /Bad Luck Observations Affecting the TMI-2 Cleanup • Good • Reactor had only operated 3 months • Accident was terminated before there was serious damage to the reactor pressure vessel or primary coolant system • Spent fuel pool was empty • Existing Department of Energy personnel and facilities had experience with highly radioactive materials • Not so good • There were no significant precedents for the TMI-2 accident • Robotics and vision technology were not well advanced • Did not anticipate biological growth in the defueling water • Could not discharge processed “Accident Water”
Various Areas for Defueling • Core Cavity • Lower Support Grid • Flow Distributor • Behind and within the Core Baffle Plates • Lower Head • Elsewhere in the Reactor Systems (not shown) Reactor Pressure Vessel Cutaway View
Fuel Removal Tools and Equipment Powered Equipment • Core Boring Machine • Plasma Arc • Power Assisted shears • Bulk Removal • WaterVacuum and Air Lift Some Manual Tools
Remote Technology in the 1980s • Much of what was done was innovation based on the immediate need • The wagon is one example. A toy remote controlled vehicle was used to survey a very radioactive equipment cubicle. • Several robotic devices were created specifically for TMI-2; ROVER is one example. A miniature submarine in the pressurizer is another. Mini Submarine Low Tech but Effective ROVER
Core Boring Machine (1) • Adapted from commercial mining drilling equipment • One of the most important machines for the project • First use with hollow core bits: 10 samples 1.8 m long x 6.4 cm diameter (figure below) • Second use with solid face bits to chew through the hard once-molten mass in the core region • Third use was assisting lower grid and instrument tubes by grinding metal (next viewgraph) Tungsten Carbide Teeth with Synthetic Diamond
Core Boring Machine (2) 1.5 minute Core Bore & Cavity after Core Bore
Packaging, Transport, & Storage of Fuel and Debris at Idaho 1986 to 1990 341 canisters of fuel & debris in 46 shipments by rail cask to the Idaho National Laboratory 1990 to 2000 Wet Storage in Spent Fuel Storage Pool 2000 – 2001 Removed from pool, dewatered, dried, and placed in dry storage
Defueling Progress and Key Impacts 1982-1983 Defueling Options Evaluations 1982 First Video of Core 1983 First Sample 1983 Sonar Mapping & Improved Video 1984 Defueling Method Decision Dry Canal & Mostly Manual Feb-1990 May-1989 Mid-1984 Vessel Head Lift Core Former Disassembly Lower Grid Cutting Dec-1988 Dec-1987 Sept-1987 Lost Water Clarity April-1987 Dec-1986 Feb-86 Oct-1985
Final Clean-Out Verification * GPU Nuclear Defueling Completion Report, pages ES-9 and ES-10 ** EPRI NP-7156 Section 3.2.3 Residual Fuel* • RPV: < 900 kg • In the Reactor Coolant System: < 133 kg; greatest single location amount is ≈36 kg on the B Steam Generator upper tube sheet • Criticality ruled out by analysis Assessment Required a Combination of**: • Video inspection for locations • Gamma dose rate and spectroscopy • Passive neutron solid state track recorders, activation, BF3 detectors • Active neutron interrogation • Alpha Detectors • Sample Analysis
Measurement & Documentation (Accountability) 300,000 lbs = 13,600 kg From EPRI TR-100640, Page 10-4 • Standard accountability (at the gram level) was impossible • NRC granted an exemption to the requirement • Required a detailed survey conducted after defueling for what remained • Computer code analyses conducted for fissionable nuclides: 1) existing prior to the accident, 2) remaining after the accident, and 3) radioactive decay • Therefore the net balance is what was sent to Idaho
Water Management “Accident” Water (in Containment and Reactor Systems) • Zeolite (Submerged Demineralizer System) • Resin Demineralizers Defueling Water Cleanup System • Primarily filtration to control suspended solids • Included zeolite and sand-charcoal media Final Water Disposal • Not allowed to discharge to the river because of tritium fears • Used open cycle low temperature evaporator
Some TMI-2 Conclusions • In addition to the Information Presented • Efficiency improved when all the on-site companies were integrated into a single organizational for responsibility and reporting • On-site tool development resources and radio-chemistry labs helped considerably • A 6 to 8 member independent senior technical advisory group that met every month or two was important • Participation by DOE facilities and resources was essential • From the Presentation • Much planning, methods, equipment development could only be done as real conditions became known • Manual, less complex methods that meant a long schedule allowed quicker adjustment for unexpected surprises and to try new approaches • Often several options had to be carried forward until one evolved as preferable
Other than Technical • Early • Governor's Concern about Evacuation Recommendation • Surrounding Area Citizens • Citizens Advisory Panel; Local area representatives to review plans (this was very important!) and periodically hold public meetings • Citizens monitoring program • Annual protests outside the gate • City of Lancaster (down river) • Concern about tritium in drinking water intake
View Post Accident Decommissioning as Three Phases Stabilization No similarity to normal decommissioning TMI-2 Example; 1 to 2 years Post-Accident Cleanup Many activities similar to normal decommissioning but with conditions an order of magnitude more severe TMI-2 Example; 8 to 9 years Final Decommissioning Activities are similar to long term care and maintenance followed by removal and/or entombment TMI-2 example; 40 years or more
Phase 1 - Stabilization Phase 1 end state is one for which conditions are that parameters such as pressure, temperature, water movements, gas release, and radioactive material migration are under human operational control. As a project this phase is in no way similar to normal decommissioning Establishing control requires specific activities that require decommissioning skills and methods; such as localized decontamination and system flushing
Phase 2 - Post-Accident Cleanup Phase 2 end state is one for which conditions have been established to place the facility in a monitored storage and maintenance configuration while waiting final decommissioning. Elements of this phase will likely begin while the accident stabilization activities are being conducted. Major Goals Capturing and storing the damaged fuel and fuel debris, removal from the site if a destination is available. Processing of highly radioactive water and gas. Storing and disposing of the concentrated process media. On-site decontamination is primarily as needed for worker protection and area accessibility.
Phase 3 - Final Decommissioning Final decommissioning begins with the establishment of the storage and maintenance configuration The end state is either: complete demolition and removal of all facilities, or partial demolition of facilities with entombment of what remains. Goals Removal of materials fuel and fuel debris and processing media in storage Removal of all radioactive materials. A partial exception to this would be when the end state includes entombment. Demolition to the degree decided and removal of the demolition debris for disposal or recycle. Decontamination to meet established criteria.
Management ChallengesPutting Together the Project Functionally similar to a Normal Decommissioning Project in that Management Challenges Include Financing and cash flow. Assembling the personnel with some degree of skill in the many technical and operational areas, recognizing that many activities do not have a large base from which to draw. Organization; creating an efficient on-site organization that interfaces well with the parallel operational organization. Need to ensure the many contractors work as one organization. Working pro-actively with regulators. Regulations are generally not created with post-accident cleanup considerations; which is not surprising because regulations are standards and these situations are one-of-a-kind. Working pro-actively with the responsible local community leaders to keep the public informed of the status of hazards and risks.
Management ChallengesA Few Accident Specific Decisions The need for on-site facilities for management and support staff, labs for radiochemical analysis, machine shop for quickly fabricating tools and repairing equipment, etc. Water management and accident water processing, selection of systems and how to store the processing media. Large volumes of processed water; its storage, use for cleanup, and eventual release A critical goal is to obtain characterization data and information regarding the true physical conditions of fuel, contamination, equipment function, and structural integrity. Without such information when needed, decision making is tentative. Adapting robotic and video technology to the physical constraints How to capture fuel and debris including methods, equipment, safety issues. Should a highly automated system be developed or can mostly-manually controlled operations be used? For both the highly radioactive processing concentrates and damaged fuel, selecting on-site staging and storage locations and designing their features.
IAEA Guidance Exists Based on Windscale, TMI-2, A2 Two reports that provide detail are: IAEA Technical Reports Series No. 321, “management of Severely Damaged Nuclear Fuel and Related Waste” IAEA-TECDOC-935, “Issues and decisions for nuclear power plant management after fuel damage events.” TECDOC-935 also addresses fuel damage events less serious than the Fukushima/TMI-2 accidents.
Special Nuclear Material Accountability • It is impossible to accurately account for the special nuclear material in a core that has been melted. ( • Fukushima cleanup will need relief from normal standards just as was the case for TMI-2. • The TMI-2 experience provides an example from which to formulate this relief. • Should the IAEA address this (e.g., for Fukushima Daiichi)?
Fuel Debris • Damaged fuel and fuel debris is unlike any standard waste forms • The form of debris can vary considerably • Should the IAEA develop criteria for packaging and storage of such materials?
Keeping a Record of the Fukushima Daichi Accident Cleanup • The experience of the TMI-2 cleanup was well recorded during and at the end of the cleanup. • Focus was on decisions, options, what went wrong and what was successful, why certain choices were made, etc. • IAEA guidance on post-accidentcleanup has used this information. • Many of these reports and supporting information have been provided to Japan; provides insights although solutions may be much different • Recording the Fukushima recovery and cleanup • Conditions are considerably different than either TMI-2 or Chernobyl • Much of the cleanup will provide new lessons • An English language record will be useful if ever needed • Is there a role for the IAEA in this?
Management ChallengesOn-Site Long Term Decisions How does post-accident cleanup ramp down? At what point does the accident cleanup phase end with: The facility is in a monitored storage mode; or The project proceeds to dismantling the facility and achieving final cleanup criteria. What are the criteria for completing final decommissioning? What is to be the ultimate end state and conditions for the site and facility, including residual radioactivity? Should part of the facility be permanently entombed or must all be removed and transported elsewhere? Who will own it?
Mobilization of Cleanup Resources • Japan, Russia , the UK, and the USA where severe accidents have occurred have the resources to deal with the cleanup. • Resources needed for major cleanup include personnel, equipment, and examination facilities that have past use and experience with high radiation materials and damaged fuel. • Is there a need to address this for countries that do have such capabilities?
Management ChallengesHighly Radioactive Materials In an accident situation, there will be several decisions for which many factors are not within the authority and control of the power plant owner and operator. Examples that relate to ultimate destination of highly radioactive materials; which are: Ion exchange and filtration media resulting from processing accident contaminated water, particularly with high levels of Cs-137. The concentrations may be too high for acceptance within low or intermediate level disposal facilities. Damaged fuel and fuel debris. What to do will likely involve government leaders and regulators. How to store, package, and transport this material can all be affected by where it will be sent; or whether it will be on-site indefinitely. Does it make sense to address these questions now? Is there a role for the IAEA in this?