The 5th meeting of the international decommissioning network
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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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The 5th meeting of the international decommissioning network

Three Mile Island Unit 2 Overview and Management Issues


1 through 3 November, 2011

Chuck Negin, Project Enhancement Corp.

Subjects framework
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
The TMI-2 Location & System

Unit 2


Important locations for the tmi 2 cleanup
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
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
Various Areas for Defueling Cleanup

  • 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
Fuel Removal Tools and Equipment Cleanup

Powered Equipment

  • Core Boring Machine

  • Plasma Arc

    • Power Assisted shears

  • Bulk Removal

  • WaterVacuum and Air Lift

Some Manual Tools

Work platform
Work Platform Cleanup

Remote technology in the 1980s
Remote Technology in the 1980s Cleanup

  • 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


Core boring machine 1
Core Boring Machine (1) Cleanup

  • 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
Core Boring Machine (2) Cleanup

1.5 minute Core Bore & Cavity after Core Bore

Packaging transport storage of fuel and debris at idaho
Packaging, Transport, & Storage of Fuel and Debris at Idaho Cleanup

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
Defueling Progress and CleanupKey Impacts


Defueling Options Evaluations


First Video of Core


First Sample


Sonar Mapping &

Improved Video


Defueling Method Decision

Dry Canal & Mostly Manual




Vessel Head Lift

Core Former


Lower Grid





Lost Water Clarity





Final clean out verification
Final Clean-Out Verification Cleanup

* 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
Measurement & Documentation (Accountability) Cleanup

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
Water Management Cleanup

“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
Some TMI-2 Conclusions Cleanup

  • 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
Other than Technical Cleanup

  • 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
View Post Accident Decommissioning as Three Phases Cleanup


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 - Stabilization Cleanup

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 - Post-Accident Cleanup 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
Phase 3 - Final Decommissioning Cleanup

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.


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 challenges putting together the project
Management Challenges CleanupPutting 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 challenges a few accident specific decisions
Management Challenges CleanupA 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
IAEA Guidance Exists Cleanup

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
Special Nuclear Material Accountability Cleanup

  • 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
Fuel Debris Cleanup

  • 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
Keeping a Record of the Fukushima CleanupDaichi 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 challenges on site long term decisions
Management Challenges CleanupOn-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
Mobilization of Cleanup Resources Cleanup

  • 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 challenges highly radioactive materials
Management Challenges CleanupHighly 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?