TMI Timeline

8/16/2019 TMI Timeline

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Chronology of Key Milestones and NRC Actions Taken During theThree Mile Island Unit 2 Recovery and Decontamination

03/28/1979 Turbi ne Trip, Reactor Trip, H.P. Injection . At 4:00 a.m., the crew in the Three

Mile Island Unit 2 (TMI-2) control room made the following entry in the controlroom log book:

―0400 Turbine trip, Reactor trip, H.P. injection ES‖

(―H.P. injection ES‖ refers to high-pressure injection engineered safeguards.)

03/28/1979 NRC Site Team Began Arriv in g. A team began to form with the arrival ofNRC’s Office of Inspection and Enforcement (IE) and Region I inspectors shortlyafter the accident, and continued to expand with the arrival of the first contingentfrom the Office of Nuclear Reactor Regulation (NRR) on March 29 and additionalinspectors from all five regional offices. On March 30, the Director of NRR and

additional NRR staff arrived at the site to assist in the recovery operation. APublic Affairs Office was also established in Middletown, PA, and staffed on a 24-hour basis to manage the flow of information to the public and the media.

Initially, the NRC site team supported emergency response functions for the NRCand the U.S. Government. Within days of the accident, the site team performedon-site recovery activities, which can be broken down into four major areas:

NRC managers at Three Mile Island. From left to right: Roger Mattson (back to camera),Harold Denton, Denwood Ross, Richard Vollmer, and Victor Stello (back to camera).


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Review system modifications and system additions.

Review all procedures, both emergency and normal operation andmaintenance, which were necessary to post-accident activities.

Provide close and continuous monitoring for the operations.

Provide consultation, review, and analysis of the ongoing radwaste, cleanup,and health physics activities.

04/01/1979 President Carter TouredTMI. President and Mrs.Carter, accompanied byPennsylvania GovernorRichard Thornburgh andNRC Office of NuclearReactor RegulationDirector Harold Denton,

toured Three Mile Islandfor thirty minutes on April1, 1979 (photo at right).

04/01/1979 NRC Bullet ins Issued. On April 1, 1979, theNRC’s Office of Inspectionand Enforcement issued aseries of bulletinsinstructing all holders ofoperating licenses to takea number of immediate

actions to avoid repeatingseveral events thatcontributed significantly tothe accident’s severity (BL79-05, 05A, 05B, 05C, 06,06A, 06B, 06C, and 08). The bulletins and other related evaluations alsoprovided substantial input on other staff activities, such as those associated withthe generic study efforts and the Lessons Learned Task Force.

04/11/1979 President ’ s Comm ission Created. On April 11, 1979, President Carter issuedExecutive Order #12130, creating the President’s Commission on the Accident atThree Mile Island and charging its members to ―conduct a comprehensive study

and investigation of the recent accident involving the nuclear power facility onThree Mile Island in Pennsylvania.‖ A full-time staff was engaged, eventuallynumbering over 60 persons; more than 30 separate staff reports were prepared,and many of them were published alongside the report by the Commission,which was issued on October 30, 1979. In the course of its investigation, theCommission conducted 12 days of public hearings, and its staff compiled morethan 150 separate depositions.


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04/25/1979 B&W Plants Shut Down. After a series of discussions between NRC staff andlicensees of operating Babcock & Wilcox (B&W) plants, the licensees agreed toshut down these plants until the actions identified to the NRC could becompleted. This agreement was confirmed by a Commission Order to eachlicensee. Authorizations to resume operations were issued between late Mayand early July, as individual plants satisfactorily completed the short-term actions

and NRC staff completed on-site verifications of the plants’ readiness to resumeoperations.

04/27/1979 Natural Circulat ion Cooling Achieved. The reactor coolant system wasintentionally placed in natural circulation cooling mode, with decay heat to thecondenser. On the afternoon of April 27, 1979, the reactor coolant pump thathad been providing the flow through the core of the TMI-2 reactor and takingaway the decay heat for removal through a steam generator was intentionallyshut down, and natural circulation cooling was achieved. The reactor was thusbrought to a stable condition, which could be sustained without dependence onelectrically activated equipment.

On May 1, 1979, the NRC’s Office of Nuclear Reactor Regulation (NRR)Technical Review Group issued a 55-page report, ―TMI-2 Plant Modifications forCold Shutdown,‖ that evaluated the licensee-proposed modifications to becarried out over the following few weeks. The modifications included thoseassociated with transitioning to natural circulation, permitting solid plantoperations, diverse reactor coolant system pressure control capability, correctingleaks in the decay heat removal (DHR) system, and installing a skid-mountedDHR system. To facilitate the early completion of the design and installation ofthese system modifications, system functional capability following a seismicevent was not a design requirement. However, the Seismic Category I DHR andreactor coolant makeup system could be used to remove decay heat and controlprimary pressure.

The NRR Technical Review Group report, issued on May 1, 1979, includedNUREG-0557, ―Evaluation of Long-Term Post-Accident Core Cooling of ThreeMile Island Unit 2.‖ Based on their understanding of the accident scenario andthe available data, the staff evaluated the condition of the core and the core flowresistance according to its effect on the ability to cool the core by naturalcirculation. TMI-2’s natural circulation cooling capability for the estimated coreflow resistance and a variety of other conditions were evaluated, and acomparison of the base case and off-nominal plant configurations was presented.The potential for and effects of natural convection core cooling were addressed,and the staff ’s recommendations for reactor performance acceptance criteriaupon initiation of natural convection were presented.

The inadvertent shutdown of the reactor coolant pump provided the proof ofconcept for natural circulation cooling mode, given the unknown integrity of thereactor core.

05/1979 Bullet ins and Orders Task Force Formed. In May 1979, NRC’s Office ofNuclear Reactor Regulation formed a task force responsible for reviewing anddirecting the TMI-2-related staff activities regarding loss-of-feedwater transientsand small-break loss-of-coolant accidents for all operating reactors. Its findings


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were documented in the report NUREG-0645, ―Final Report of Bulletins andOrders Task Force of the Office of Nuclear Reactor Regulation,‖ issued inJanuary 1980.

05/1979 TMI-2 Lessons L earned Task Forc e Form ed. In May 1979, an interdisciplinaryteam of engineers from the NRC’s Offices of Nuclear Reactor Regulation,

Nuclear Regulatory Research, Inspection and Enforcement, and StandardsDevelopment began to identify and evaluate those safety concerns originatingfrom the TMI-2 accident that required licensing actions.

The scope of the task force assignment covered the following general technicalareas:

Reactor operations, including operator training and licensing.Licensee technical qualifications.Reactor transient and accident analysis.Licensing requirements for safety and process equipment,instrumentation, and controls.

On-site emergency preparations and procedures.NRR accident response role, capability, and management.Feedback, evaluation, and utilization of reactor operating experience.

The task force proceeded in two phases:

Short-Term Recommendations. The first phase culminated in the issuance ofNUREG-0578, ―TMI-2 Lessons Learned Task Force: Status Report and Short-Term Recommendations‖ (July 1979). The Director of NRR ordered theimplementation of 23 short-term licensing requirements in September 1979,based on a favorable review by NRC’s independent Advisory Committee onReactor Safeguards (ACRS) received in August.

Final Recommendations. In the second phase of its work, the task forceconsidered more fundamental questions in the design and operation of nuclearpower plants, and in the licensing process. The issues were grouped into fourgeneral categories: (1) general safety criteria, (2) system design requirements,(3) nuclear power plant operations, and (4) nuclear power plant licensing.NUREG-0585, ―TMI-2 Lessons Learned Task Force: Final Recommendations,‖ was issued in October 1979 to complete this phase.

05/10/1979 Ad Hoc Dose Assessm ent Group Report Issued. On May 10, 1979, NUREG-0558, ―Population Dose and Health Impact of the Accident at the Three MileIsland Nuclear Station: Preliminary Estimates for the Period March 28, 1979

through April 7, 1979,‖ was issued by the Ad Hoc Dose Assessment Group,which comprised various federal agencies. The report contained a preliminaryassessment of the radiation dose and potential health impact of the accident.This assessment was prepared by a task group composed of technical staff fromthe Environmental Protection Agency, the Department of Health, Education, andWelfare, and the Nuclear Regulatory Commission. The report concluded that theestimated dose that might have been received by an individual was less than 100mrem. The collective dose received by the 2,164,000 people estimated to live


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within a 50-mile radius of the reactor site was calculated to be 3,300 person-rem(with a range of 1600 - 5300 person-rem). This corresponds to an average doseof approximately 1.5 mrem.

05/30/1979 Feedwater Transients Studied and Report Issued. The NRC issued NUREG-0560, ―Staff Report on the Generic Assessment of Feedwater Transients in

Pressurized Water Reactors Designed by the Babcock & Wilcox Company,‖ which considers the particular design features and operational history of Babcock& Wilcox operating plants in light of the TMI-2 accident and related currentlicensing requirements. As a result of this study, a number of findings andrecommendations were pursued. Similar studies were published for theoperating reactors designed by Westinghouse and Combustion Engineering.

07/12/1979 IE Special Review Gro up Formed. A Special Review Group from the NRC’sOffice of Inspection and Enforcement (IE) was commissioned on July 12, 1979 todevelop and recommend changes in IE programs based on TMI experience.Both preventive and responsive aspects of IE programs and operations werestudied. A total of 219 separate recommendations for change were generated in

this review. Preventive changes pervade all parts of the routine IE InspectionProgram, ranging from plant design to operation. Responsive changes focus onthe emergency preparedness of licensees and the NRC. When combined, thesechanges enhance the program and organizational effectiveness of the office.The relative priority of the recommended changes and the estimation of theresources needed to implement them were left to IE line management.

The findings were later documented in NUREG-0616, ―Report of Special ReviewGroup, Office of Inspection and Enforcement on Lessons Learned from ThreeMile Island,‖ in December 1979.

08/03/1979 IE Task Force on L essons L earned Issued Report. On August 3, 1979, the

NRC’s Office of Inspection and Enforcement (IE) task force on lessons learnedissued a report of the investigation of the TMI accident, NUREG-0600,―Investigation into the March 28, 1979 Three Mile Island Accident by Office ofInspection and Enforcement.‖ The scope of the investigation was limited to (1)the licensee’s operational activities before the initiating event, from about 4:00a.m. on March 28 up to about 8:00 p.m. that evening, when primary coolant flowwas reestablished by the starting of the reactor coolant pump; and (2) stepstaken by the licensee to control the release of radioactive material to off-siteenvirons and to implement its emergency plan, from the initiating event untilmidnight on March 30.

Violat ions Identi f ied. As a result of the findings in NUREG-0600, the IE

Director notified the licensee later in 1979 that their investigation had revealed―numerous items of noncompliance‖ with NRC regulations on the part of thelicensee. Six ―violations,‖ were alleged by IE, including serious weaknesses inthe licensee’s health physics program, control of maintenance activities,development and review of procedures, adherence to prescribed procedures,and audit activities. The licensee was cited for failure to operate the facility inaccordance with the Technical Specifications approved and adopted for thatparticular plant, and for authorizing a surveillance procedure that placed certainvalves in a status that rendered emergency feedwater unavailable on three


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separate occasions, including on March 28, when it was needed. Personneltraining were also found to be insufficient, as well as record maintenance and in-house inspections.

ACRS Review . In a letter to Chairman Hendrie, the NRC’s independent Advisory Committee on Reactor Safeguards (ACRS) registered its view of the IE

investigation later in 1979, and its conclusions based on that investigation.Taking note of the study’s limited scope, the ACRS felt that the emphasis put byIE on the licensee’s departure from technical specifications prior to the accidentand from approved procedures during it resulted in too little consideration ofother relevant factors. The ACRS concluded that the limited scope of the IEreport tended to lead to a catalogue of violations, and expressed its concern thatthe IE report might give the impression that failure to follow accident proceduresautomatically counts as a violation. The ACRS noted that the procedures wereprepared by the licensee and were not approved by the NRC (although thelicensee was required by the NRC to follow them), and affirmed that suchprocedures cannot be so detailed as to allow for every accident scenario. On thecontrary, the ACRS declared, a deviation from the conditions assumed in the

writing of the procedures may make it necessary to depart from thoseprocedures. There was a question as to whether an operator who, using his best

judgment, consciously takes an action that deviates from the procedures (whichin themselves may contain confusing or incorrect guidance), is guilty of aviolation. The ACRS stated that this was ―the wrong approach to protecting thepublic health and safety‖ in an emergency, and that an operator, guided bywritten procedures, should be allowed to use his best judgment to deal with aproblem. That judgment would be subject to post-factum appraisal byresponsible parties, but it should not necessarily be deemed an error or aviolation of regulations. The ACRS found the IE report ―less than satisfactory‖ forthese reasons and recommended issuance of a consolidated report on thefindings of the NRC task forces investigating the TMI accident.

08/29/1979 Personnel Overexposure Event. On August 29, 1979, six workers incurredradiation overexposure in the TMI-2 fuel-handling building while inspecting andtightening leaking valves in preparation for the decontamination of the area.Reactor coolant water, highly contaminated by the March 28 accident, wasleaking from the valves. The radiation survey instrument used by the workersshowed a gamma dose rate in the room of 10 – 15 rems per hour in general,and, in one small zone, of 25 rems per hour. It was decided that the time limit foreach worker to stay in the radiation area was four minutes. What the surveyinstrument failed to disclose, however, was the beta radiation rates in the room,which were running as high as 2500 rems per hour. It was later ascertained thatthe workers had received doses in excess of regulatory limits from the beta

radiation. The doses were as high as 166 rems to the whole body in oneinstance, and 161 rems in another. No medically significant effects wereidentified by medical examination.

09/13/1979 Recommendations from the Lessons Learned Task Force Sent toLicensees. Letters (e.g., Generic Letter 79-43, ―Follow-up Actions Resultingfrom the NRC Staff Reviews Regarding the TMI-2 Accident‖) were sent to alloperating nuclear power plants, advising them that they should implement therecommendations of the Lessons Learned Task Force and the additional items


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resulting from comments by NRC’s independent Advisory Committee on ReactorSafeguards and review by the Director of NRC’s Office of Nuclear ReactorRegulation. A series of briefings was held to apprise reactor owners of theserequirements. Letters were also sent to applicants for construction permits andoperating licenses, instructing them to implement the short-term lessons learned.The approach adopted by NRC staff in seeking swift implementation of the short-

term requirements allowed licensees to fulfill those requirements prior to NRCstaff review.

10/1979 Socioeconom ic Impact Study Report Issued. The NRC implemented aresearch program on the socioeconomic impact of the accident on the area. Thefirst element of this program was done as a telephone survey covering 1,500households within 55 miles of TMI, seeking information on the activities ofhousehold members during and after the accident, their attitudes toward TMI andnuclear power in general, their demographic characteristics, and both the short-term and continuing socioeconomic effects of the accident. This survey was thebroadest and most detailed of the studies undertaken in the wake of the TMIaccident, as of the end of fiscal year 1980. The survey results were published in

October 1979 in the preliminary report NUREG/CR-1093, ―Three Mile IslandTelephone Survey.‖

A second report, NUREG/CR-1215, ―The Social and Economic Effects of the Accident at Three Mile Island: Findings to Date,‖ expands upon the telephonesurvey, and was prepared with the cooperation of the Governor ofPennsylvania’s Office of Policy and Planning and published in January 1980.The report deals with the impact of the accident on the regional economy, thebusiness community, local government agencies, churches, schools, hospitals,prisons, and homes for the elderly. It also appraises the accident’s effect onagriculture and tourism, both of which were adversely affected in the short run.Finally, the report estimates the long-term effects of the accident on persons,

business firms, the value of real estate, and political institutions.

10/16/1979 Epicor-II System A pprov ed. On August 14, 1979, the NRC issued for publiccomment an environmental assessment for the use of Epicor-II in thedecontamination of the intermediate level of contaminated water (less than 100microcuries per milliliter) in the auxiliary building. On October 3, 1979, the NRCissued NUREG-0951, ―Environmental Assessment Use of Epicor-II at Three MileIsland Unit 2.‖ On October 16, 1979, the Commission issued a Memorandumand Order directing the use of Epicor-II.


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The "Epicor-II" system that was used to decontaminate some 380,000 gallons of intermediate-level radioactivewater held in the auxiliary building tank at the TMI-2 site is shown above. It consists of three process vessels(steel liners) shielded by four-inch lead enclosures located in the chemical cleaning building. Each vesselcontains ion-exchange resin. The vessel at the top of the photo at the left is the system prefilter/demineralizer,the center vessel is a cation ion-exchanger, and the third vessel is a mixed-bed polishing ion-exchanger. Each isfitted with three quick-disconnect hoses: a liquid waste influent line, a processed waste effluent line, and a ventline with attached overflow hose. Vented air from each vessel passes through a special filter and charcoalabsorber. "Spent" ion-exchange resin liners containing radioactive material removed from the water aretransferred by crane to cells (shown at top right) which are housed in modular concrete storage structures(shown at bottom right). The cells are concrete-shielded, galvanized corrugated steel cylinders seven feet indiameter and 13 feet high. The storage module shown under construction has 4-foot thick walls and is 57 feetwide and 91 feet long. Each module holds about 60 storage cells. The modular design allowed additionalstorage modules that could be built on an as-needed basis. (Source: NRC Annual Report, 1979)

10/30/1979 President’s Commission on the Accident at Three Mile Island Submits itsFinal Report (also know n as the K emeny Report). The President’sCommission on the Accident at Three Mile Island presented its final report to thePresident on October 30, 1979. President Carter assigned a nine-personinteragency panel to review the report by the Kemeny Commission. Dr. FrankPress, Director of the Office of Science and Technology Policy, Executive Office

of the President was the Chairman. Also on the interagency panel were: EnergyUndersecretary John Deutch; Chairman of the Council on Environmental Quality,Gus Speth; Director of the Office of Management and Budget, James McIntyre;White House Counsel, Lloyd Cutler; White House Energy Policy Coordinator,Elliot Cutler; Domestic Policy Advisor, Stuart Eizenstat; National Security

Advisor, Zbigniew Brzezinski and Director of the Federal EmergencyManagement Agency, John Macy.


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the Commission. The Atomic Energy Act of 1954, as amended, defines the term―extraordinary nuclear occurrence‖ as:

―...any event causing a discharge or dispersal of source, special nuclear,or byproduct material from its intended place of confinement in amountsoff-site, or causing radiation levels off-site, which the Commission

determines to be substantial, and which the Commission determines hasresulted or will probably result in substantial damages to persons off-siteor property off-site. The Act further states that the Commission shallestablish criteria in writing setting forth the basis upon which thedetermination shall be made.‖

The Commission concluded that proceeding with the determination was in thepublic interest for two reasons. First, the Commission noted that the events atThree Mile Island constituted the most serious nuclear accident to date at alicensed U.S. facility, and thus should be rigorously scrutinized from thestandpoint of its effect on the public. Second, the Commission noted thependency of various lawsuits concerning the accident, in which the determination

of whether or not an ENO had taken place was pertinent, and acknowledged theinformal request of the federal district court in Harrisburg to make thisdetermination as expeditiously as possible.

The findings were documented in NUREG-0637, ―Report to the NuclearRegulatory Commission from the Staff Panel on the Commission’s Determinationof an Extraordinary Nuclear Occurrence (ENO),‖ in January 1980. This staffreport finds and recommends that the TMI-2 accident did not constitute an ENO.

02/11/1980 Recovery Technical Specif icat ions Implemented. Back on June 25, 1979, theNRC provided draft Recovery Technical Specifications to the licensee for review.On February 11, 1980, the NRC issued NUREG-0647, ―Safety Evaluation and

Environmental Assessment, Metropolitan Edison Company, Jersey CentralPower and Light Company, Pennsylvania Electric Company, Docket No. 50-320,Three Mile Island Nuclear Station, Unit No. 2.‖ This report contained an NRCOrder for the Three Mile Island Nuclear Station, Unit 2, that (1) required that,effective immediately, the facility be maintained in accordance with therequirements of the attached proposed Technical Specifications; and (2)proposed to formally amend the Facility Operating License to include theproposed Technical Specifications, taking into account the present condition ofplant systems, so as to ensure that the unit would remain in a safe posture duringthe Recovery Mode.

Early 1980 Undergroun d Monitoring Wells Instal led. In early 1980, NRC staff requested

that the TMI licensee install a series of monitoring wells around the auxiliary andreactor buildings to monitor for leakage of radioactive water into the ground.

05/1980 NRC Act ion Plan (NUREG-0660) Issu ed. In May 1980, the NRC issuedNUREG-0660, ―NRC Action Plan Developed as a Result of the TMI-2 Accident,‖ which provided a comprehensive and integrated plan for the actions now judgednecessary by the NRC to correct or improve the regulation and operation ofnuclear facilities, based on the experience from the accident at TMI-2 and the


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official studies and investigations of the accident. NRC activities and programsnot related to the accident at TMI-2 were not described in this Action Plan.

06/28/1980 Purging of the Reactor Build ing Atm osph ere Began.

Environmental Assessment prior to purging. Back in March 1980, NRC staff

issued for public comment a draft environmental assessment of a number ofalternative options for the decontamination of the reactor building atmosphere.

Approximately 800 responses were received from various federal, state, andlocal agencies and officials, as well as from non-governmental organizations andprivate individuals. Following appropriate revisions responding to the commentsreceived, and additional reviews and analyses by NRC staff, NUREG-0662,―Final Environmental Assessment for Decontamination of the Three Mile IslandUnit 2 Reactor Building Atmosphere,‖ was issued in May 1980. The statement discussed several alternative options and the potential environmental impactsassociated with each.

NRC Issued Order to Purge. Having reviewed the staff assessment and

recommendations, together with the comments from the public, the Governor ofPennsylvania, and many others, the NRC’s Commission issued a Memorandumand Order authorizing the licensee to clean the reactor building atmosphere bymeans of a controlled purge, or release of contaminated air through filtersystems. On the same day, the Commission issued a modification of the TMIoperating license setting off-site dose limits for the purge.

Purging Operations Began. The purging operation, which began on June 28,1980, was carried out under detailed procedures approved by NRC staff. Theoperation was completed 14 days later (see below).

07/1980 NRC Action Plan for Cleanup Operations Issued. The NRC’s TMI Program

Office issued NUREG-0689, ―NRC Plan for Cleanup Operations at Three MileIsland Unit 2,‖ which defined the functional role of the NRC in cleanup operationsat TMI-2 to ensure that agency regulatory responsibilities and objectives wouldbe fulfilled. The plan outlined NRC functions in TMI-2 cleanup operations in thefollowing areas: (1) the functional relationship between the NRC and othergovernment agencies, the public, and the licensee in coordinating activities; (2)the functional roles of these organizations in cleanup operations; (3) the NRC’sreview and decision making procedure for the licensee’s proposed cleanupoperation; (4) the NRC’s/licensee’s estimated schedule for major actions; and(5) the NRC’s functional role in overseeing the implementation of approvedlicensee activities.

Two revisions were later issued in February, 1982, and March, 1984.

07/1980 Special Senate Investigation o f the TMI Ac cident Issued its Report. Thereport by the Special Senate Investigation of the TMI accident—undertaken atthe behest of the Subcommittee on Nuclear Regulation of the Senate Committeeon Environment and Public Works—was published in July 1980. Theinvestigation focused on three discrete aspects of the TMI accident: events of thefirst day, cleanup activities at the TMI site, and events prior to the initiation of theTMI accident.


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07/11/1980 Purging of the Reactor Build ing A tmos phere Completed. The purgingoperation, which began on June 28, 1980, was completed on July 11, 1980.Measurements showed that about 43,000 curies of krypton-85 was releasedduring this period. Samples from the release flow were analyzed to ascertain thepresence of radionuclides other than krypton, and the amounts were determined

to be insignificant.

During the entire operation, members of the NRC staff were on-site to monitorthe licensee’s activities. In addition, off -site radiation monitoring programs wereconducted by the licensee, the NRC, the Environmental Protection Agency, theDepartment of Environmental Resources of the Commonwealth of Pennsylvania,and also by private individuals through the Community Radiation MonitoringProgram set up by the U.S. Department of Energy and the Commonwealth ofPennsylvania. The maximum cumulative radiation dose and the maximum doserate measured at off-site locations were a fraction of the limits allowed underNRC regulations.

07/23/1980 First Reactor Build in g Entry. Thefirst entry into the reactor buildingcontainment was conducted by twoutility staff on July 23, 1980 (photo atleft). During the entry intocontainment, 29 pictures and six100-cm swipes were taken, and ageneral area beta and gammasurvey was conducted to acquiredata at the entry level. The firstentry team spent approximately 20minutes inside the reactor building.

08/14/1980 Programm atic Environm entalImpact Statement Issued for

Publ ic Comment. Responding to adirective issued by the Commissionon November 21, 1979, NRC staffprepared the draft ProgrammaticEnvironmental Impact Statementdealing with the decontaminationand disposal of radioactive wasteresulting from the TMI accident. The statement (NUREG-0683, ―ProgrammaticEnvironmental Impact Statement Related to Decontamination and Disposal of

Radioactive Wastes Resulting from March 28, 1979 Accident, Three Mile IslandNuclear Station, Unit 2, Docket No. 50-320‖) was released for public comment on

August 14, 1980. It discussed four fundamental activities necessary to thecleanup: (1) treatment of radioactive liquids, (2) decontamination of the buildingand equipment, (3) removal of fuel and decontamination of the coolant system,and (4) packaging, handling, storing, and transporting nuclear waste. Thestatement addressed the principal environmental impacts that can be expected tooccur as a consequence of cleanup activities, including occupational and off-site


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radiation doses and resultant health effects, socioeconomic effects, and theeffects of psychological stress.

09/1980 NRC Issued Report on the Consequences of Bankru ptcy. In a report to theCommission by the Director of NRC’s Office of Nuclear Reactor Regulation inSeptember 1980, the possibility and potential consequences of bankruptcy on

the part of the TMI licensee were explored at length. Findings were documentedin NUREG-0689, ―Potential Impact of Licensee Default on Cleanup of TMI-2.‖

09/09/1980 First GAO Report Issued. The General Accounting Office (GAO) issued itsreport on the TMI-2 accident to Congress on September 9, 1980, in a documententitled ―Three Mile Island: The Most Studied Nuclear Accident in History.‖ TheGAO endorsed the directive of the Senate Committee on Environment and PublicWorks (in the draft authorizing legislation for the NRC for fiscal year 1981), whichcalled for the development of a safety goal for nuclear reactor regulation.

11/1980 Clari f icat ion o f the TMI Action Plan Issued. In November 1980, the NRCissued NUREG-0737, ―Clarification of TMI Action Plan Requirements,‖ which was

a letter from the NRC to licensees of operating power reactors and applicants foroperating licenses forwarding post-TMI requirements that had been approved forimplementation. Following the accident at TMI-2, NRC staff developed the

Action Plan, NUREG-0660, to provide a comprehensive and integrated plan toimprove safety at power reactors. Specific items from NUREG-0660 have beenapproved by the Commission for implementation at reactors. In this report, thesespecific items comprise a single document, which includes additional informationon schedules, applicability, methods of implementation review, submittal dates,and clarification of technical positions. It should be noted that the total set ofTMI-related actions have been collected in NUREG-0660, but only those itemsthat the Commission had approved for implementation prior to publication wereincluded in NUREG-0737.

11/12/1980 Public Ad visory Panel Form ed by NRC. The Advisory Panel for theDecontamination of TMI-2 met for the first time on November 12, 1980 inHarrisburg, Pennsylvania. The 12-member Panel included local citizens, localand state governmental officials, and scientists, and held 78 meetings over 13years, meeting regularly with both the public and NRC Commissioners. Inaddition to soliciting views from members of the public, the Panel interacted withCongress and other federal agencies to ensure the safe and expeditious cleanupof TMI-2.

NUREG/CR-6252, ―Lessons Learned from the Three Mile Island-Unit 2 AdvisoryPanel,‖ was issued in August 1994, and documented the analysis of the lessons

learned and preliminary conclusions on the effectiveness of the Panel.

12/1980 Public Whole Body Coun ting Program Report Issued. Back in April 1979, theNRC instituted a program to determine whether any radioactivity released as aresult of the TMI-2 accident was accumulating in members of the general publicliving near Unit 2. In December 1980, NUREG-0636, ―The Public Whole BodyCounting Program Following the Three Mile Island Accident: Technical Report,

April-September 1979,‖ was issued. The program used a device called a wholebody counter, which measures very small quantities of radioactivity in people. A


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total of 753 men, women, and children were successfully counted; nine of thesewere counted a second time, leading to a total of 762 whole body counts. Therewas no radioactivity identified in any member of the public that could haveoriginated from the radioactive materials released following the accident. Severalpeople with higher-than-average levels of naturally occurring radioactivity wereidentified. The counting systems used were briefly described. Technical

problems, results, and conclusions were discussed.

1981

01/05/1981 Plant Entered Loss-to-Amb ient Cooling Mode. Following tests starting inNovember 1980, the reactor coolant system was placed in the loss-to-ambientcooling mode on January 5, 1981 by heat losses to the reactor building ambient(maintained by the reactor building fan coolers). This permitted severalpreviously required cooling systems to be de-energized and decommissioned.

01/1981 Investigation into Inform ation Flow During th e Accident Report Issued . InJanuary 1981, NUREG-0760, ―Investigation into Information Flow During the

Accident at Three Mile Island,‖ was issued in response to a request from NRCChairman Ahearne, which directed the Office of Inspection and Enforcement toresume its investigation of information flow during the accident at TMI-2. Thetransfer of information between individuals, agencies, and personnel fromMetropolitan Edison was analyzed to ascertain what knowledge was held byvarious individuals regarding the specific events, parameters, and systemsduring the accident at TMI. Maximum use was made of existing records, andadditional interviews were conducted to clarify areas that had not been pursuedduring earlier investigations. Although the passage of time between the accidentand post-accident interviews hampered precise recollections of events andcircumstances, the investigation revealed that information was not intentionallywithheld during the accident, and that the system for the effective transfer of

information was inadequate during the accident.

02/27/1981 Final Programmatic Enviro nmental Impact Statement Issued. On February27, 1981, the NRC issued NUREG-0683, ―Programmatic Environmental ImpactStatement Related to Decontamination and Disposal of Radioactive WastesResulting from March 28, 1979 Accident, Three Mile Island Nuclear Station, Unit2, Docket No. 50-320.‖ NRC staff held 31 meetings with the public, media, andlocal officials. The final Programmatic Environmental Impact Statement (PEIS)included the staff ’s responses to nearly 1,000 comments received on the draftstatement (following a 90-day comment period). The final PEIS reaffirmed thedraft statement’s conclusion that the decontamination of the TMI-2 facility,including the removal of the nuclear fuel and radioactive waste from the TMI site,

was necessary for the long-term protection of public health and safety, and thatmethods exist or can be suitably adapted to perform the cleanup operations withminimal release of radioactivity to the environment. The final PEIS alsoconcluded that the only environmental impact that might be of significance wouldbe the cumulative radiation doses to the cleanup workers.

03/25/1981 NRC Approved Disp osal of Epicor-I I Resin Liners; Some Ac cepted by DOE. The licensee requested that the requirement for the solidification of spent Epicor-II resins be waived, and that those spent resin liners that were similar to normal


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reactor resin wastes be disposed of by shallow land burial at a commercialdisposal site. NRC approval to dispose of these 22 liners in this manner wasissued on March 25, 1981. The last of these liners was shipped on June 27,1981 from the TMI site to the U.S. Ecology burial site at Richland, Washington, inwhich all 22 liners were successfully disposed.

The requirement to solidify the remaining 50 Epicor-II pre-filter spent resin linerswas also waived, and a Department of Energy (DOE) program of research anddevelopment on waste characterization examined and characterized thecondition of one of these liners and its contents at a DOE contractor facility.Research in resin radiation degradation was reported in several NRC and DOEreports.

04/27/1981 NRC Policy Statement that Endorsed the Programm atic EnvironmentalImpact Statement Issued. The Commission issued a policy statementendorsing the final Programmatic Environmental Impact Statement (PEIS), andconcluded that the PEIS (NUREG-0683) satisfied the Commission’s obligationsunder the National Environmental Policy Act, with the exception of the disposal of

processed accident-generated water. The Commission later issued asupplement stating that the PEIS allows staff to act on each major cleanupactivity if the activity and associated impacts fall within the scope of thoseassessed in the PEIS. On June 26, 1981, NRC staff amended the EnvironmentalTechnical Specifications of the TMI-2 license to define the criteria in Appendix Rof the final PEIS as limiting conditions of the cleanup operations.

The Commission’s policy statement declared that the cleanup should beexpedited and activities carried out in accordance with the criteria in Appendix Rof the PEIS, which limited the doses to off-site individuals from radioactiveeffluents resulting from cleanup activities. These effluent limits were numericallyidentical to the design objectives of radioactive effluents for operating power

reactors contained in Appendix I of 10 CFR Part 50. The criteria in Appendix Rof the PEIS for TMI-2 cleanup activities were more restrictive than those for theoperating power reactors, since the Appendix R values were limits that could notbe exceeded, whereas, for operating power reactors, they were design objectivesto be met on the ―as low as reasonably achievable‖ principle.

Epicor-II liners at TMI-2 aretransferred from site storageareas in the cask shown attop, and lowered intoshipping casks beneath tomaintain shielding ofradioactive material. During1982, several shipments ofthe casks were made tovarious laboratories forstudy and tests. (Source:NRC Annual Report, 1981)


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06/18/1981 NRC Approv ed the Use of the Subm erged Demin eral izer System. TheNRC’s review of the submerged demineralizer system (SDS) formally startedwhen the licensee submitted the report ―Technical Evaluation Report,Submerged Demineralizer System‖ in April 1980. However, due to a number ofdesign changes and technical questions from the staff, formal NRC approval wasnot given until June 1981.

On April 10, 1980, the licensee formally submitted its Technical EvaluationReport (TER) and requested permission to operate an underwaterdemineralization system. The SDS described in the licensee’s TER wasdesigned to provide controlled handling and treatment of the highly contaminatedwastewater generated during the accident. The SDS operated underwater, inone of the spent fuel pools of TMI Unit 2. It consisted of a liquid waste treatmentsubsystem, a gaseous waste treatment subsystem, and a solid waste handlingsubsystem. The liquid waste treatment subsystem was designed todecontaminate the high-activity wastewater by filtration and ion exchange. Theprimary components of the liquid waste treatment subsystem included two filters,and two parallel trains of four identical inorganic zeolite-filled ion exchanger

vessels. In the event that additional cleanup of the effluent from SDS wasrequired, it could be recycled through SDS or ―polished‖ (refined) with the Epicor-II system.

On June 18, 1981, the licensee was directed to promptly commence andcomplete processing of the remaining intermediate-level contaminated water(less than 100 microcuries per milliliter) in the auxiliary building tanks and thehighly contaminated water in the reactor building sump and the reactor coolantsystem.

On August 9, 1981, the remaining 100,000 gallons of intermediate-level waterwere completely processed. The licensee started processing the high-activity

water in September 1981. The approval to operate SDS did not include waterdisposal. All processed water was stored in existing on-site tanks. Decisionsrelated to the disposal of processed water were made by the Commission at alater date (see NUREG-0683, Supplement 2, issued in June 1987).

07/15/1981 NRC and DOE Signed Memo randum o f Understanding. On July 15, 1981,the NRC and Department of Energy (DOE) signed a Memorandum ofUnderstanding (MOU), which formalized the working relationship between thetwo agencies with respect to the removal and disposal of solid nuclear wastegenerated during the cleanup of TMI-2. This was a significant step towardensuring that the TMI site would not become a long-term waste disposal facility.The MOU covered only solid nuclear waste, and did not cover liquid waste

resulting from the cleanup activities. The MOU addressed three basic categoriesof TMI-2 waste: (1) waste determined by DOE to be of generic value in terms ofbeneficial information to be obtained from further research and developmentactivities (the MOU calls for DOE to perform such activities at appropriate DOEfacilities); (2) waste determined to be unsuitable for commercial land disposalbecause of high levels of contamination, but which DOE may also undertake toremove, store, and dispose of on a reimbursable basis from the licensee; and (3)waste considered suitable for shallow land burial, to be disposed of by thelicensee in licensed, commercial low-level waste burial facilities.


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The MOU is provided in Appendix A to NUREG-0698, Revision 1, ―NRC Plan forCleanup Operations at Three Mile Island Unit 2.‖

08/1981 GAO Issued Report. The General Accounting Office (GAO) issued a reportentitled ―Greater Commitment Needed to Solve Continuing Problems at Three

Mile Island.‖ GAO made two recommendations to the NRC:

GAO recommended that the NRC closely follow the current efforts of theinsurance and utility industries to increase insurance coverage to what itdetermines to be an acceptable level.

To mitigate future regulatory constraints on nuclear accident cleanupactivities, GAO recommended that the NRC establish a set of guidelines thatwould facilitate the development of recovery procedures by utility companiesin the event of other nuclear reactor accidents.

1982

03/15/1982 NRC and DOE Revised Memo randum of Understanding to Acc ept Fuel andResins. The NRC and Department of Energy (DOE) agreed to a revision of theMemorandum of Understanding (MOU). Instead of taking only samples of thedamaged fuel from TMI-2, DOE agreed to accept the entire core for research anddevelopment, and for storage at a DOE facility. The terms of ultimate disposal ofthe core will be negotiated between DOE and the utility operating the TMI facility.DOE also agreed to take possession of highly radioactive resins from thepurification system, again on the basis of future reimbursement by the utility, andplanned to take possession of zeolite waste from the submerged demineralizersystem and retain it for research and testing with regard to waste immobilization.

The revised MOU is provided in Appendix A to NUREG-0698, Revision 2, ―NRCPlan for Cleanup Operations at Three Mile Island Unit 2.‖

05/21/1982 First SDS Liner Shipped to DOE . On May 21, 1982, the first waste vesselfrom the submerged demineralizer system (SDS) was shipped from TMI to DOEfacilities in Hanford, Washington for disposal. This vessel was used to processwastewater from the reactor-coolant bleed tanks, and contained approximately12,000 curies of radioactive material on zeolite ion-exchange media.Subsequent shipments included liners containing more than 50,000 curies ofradioactive material removed from reactor building sump water. DOE conductedresearch on glass vitrification (solidification) of this type of solid waste at Hanford.

On July 27, 1982, one of the 49 high specific activity Epicor-II liners stored on-site was sampled for gas composition at TMI, and was shipped on August 17 tothe Battelle Columbus Laboratories in West Jefferson, Ohio for radiation andchemical characterization tests. The liner contained approximately 1,800 curiesof radioactive material, and was shipped in a special cask designed to withstandsevere transportation accidents. On August 25, a second liner was shipped fromTMI to the Idaho National Engineering Laboratory for characterization tests.


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07/21/1982 “ Quick Look ” Fuel Inspection. The first closed-circuit television inspections ofthe reactor core were performed on July 21, 1982. During this ―Quick Look‖ inspection, a camera lowered into the core region revealed a rubble bedapproximately five feet below the normal location of the top of the fuelassemblies. Results are reported in GEND-030-VOL-1, ―Quick Look InspectionReport on the Insertion of a Camera into the TMI-2 Reactor Vessel.‖

First closed-circuit television inspections of the reactor core were performed on July 21, 1982.

1983

08/30/1983 Last SDS Liners Shipped to DOE. The last two of the 50 Epicor-II prefilters ofhigh specific activity were shipped from TMI-2 on July 12, 1983, and the last ofthe 13 highly contaminated submerged demineralizer system (SDS) liners left theTMI site on August 30, 1983.

11/18/1983 NRC Approved Use of Reactor Build in g Crane. The TMI-2 polar cranesuffered severe damage as a result of the accident. Besides being highlycontaminated, the crane’s electrical components were damaged by hydrogenburns and exposure to the excessive moisture in the containment buildingatmosphere. Restoration of the crane was required to accomplish defueling(removal of the reactor vessel head and internal structure, and other cleanupactivities). The staff approved the licensee’s safety evaluation for therefurbishment and use of the Reactor Building Polar Crane. The initial climb tothe polar crane was made on May 14, 1981. Mechanical and electricalinspections were made in August 1982. The crane was successfully load-tested


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on February 29, 1984, when a test assembly weighing 214 tons was lifted andmoved along predetermined test paths. Details are documented in NUREG/CR-3884, ―Evaluation of Nuclear Facility Decommissioning Projects: SummaryReport - Three Mile Island Unit 2 Polar Crane Recovery.‖

Survey in progress of the polar crane inside the reactor building. (Source: NRC Annual Report,1981)

1984

07/1984 Reactor Pressur e Vessel Head Removed. In July 1984, the reactor pressurevessel head was removed using the reactor building polar crane and placed inshielded storage inside the reactor building. Details of the planning, training, andoperations are documented in GEND-044, ―TMI-2 Reactor Vessel HeadRemoval.‖

10/1984 NRC Issued Supp lement 1 to the Final Programm atic Environmental Imp actStatement Dealing w ith Occ upational Radiat ion Dose. In October 1984, the NRC’s TMI Program Office issued NUREG-0683,

Supplement 1, ―Programmatic Environmental Impact Statement Related toDecontamination and Disposal of Radioactive Wastes Resulting from March 28,1979 Accident, Three Mile Island Nuclear Station, Unit 2, Docket No. 50-320 -Supplement Dealing with Occupational Radiation Dose.‖ In accordance with theNational Environmental Policy Act, the Programmatic Environmental ImpactStatement (PEIS) was supplemented to revise the staff’s earlier estimates ofoccupational radiation exposure resulting from the cleanup. The supplement wasrequired because information indicated that the cleanup may entail substantiallymore occupational radiation dose to the cleanup work force than originally


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anticipated. Cleanup was originally estimated to result in from 2000 to 8000person-rem of occupational radiation dose. New estimates indicated thatbetween 13,000 and 46,000 person-rem were expected to be required.

Alternative cleanup methods considered in the supplement either did not result inappreciable dose savings or were not known to be technically feasible. The draftsupplement to the PEIS was issued back in March 1984 for public comment.

1985

01/1985 Cleanup Fund ing from Indu stry Pledged. The Edison Electric Institute,representing the utility industry, voluntarily pledged funds totaling $25 million peryear for six years, beginning in January 1985. A group of Japanese utilitycompanies pledged $18 million ($3 million for six years) to the cleanup, makingthe total level of funding for cleanup activities in 1984 approximately $95 million.

02/1985 First Video Inspection of L ower Head Region. In February 1985, the firstvideo inspection of the reactor vessel lower head region revealed theaccumulation of a substantial quantity—an estimated 10 to 20 tons—of accident-

generated debris. The debris bed had the appearance of a gravel pile,composed of pieces normally three to four inches long and half as wide. Similarmaterial was observed by sighting up through the lower diffuser plate of the coresupport assembly.

Although the composition of the debris could not be determined from the videoinspections, it was evident that some molten material was generated during theaccident, and that it resolidified and collected in the lower head area. Additionalinspections conducted in July 1985, focusing on other quadrants in the lowerhead, disclosed that the debris bed was shallower and the individual piecessmaller in those areas, in contrast to the earlier determinations.

In a separate effort, Edgerton, Germeshausen, and Grier, Inc. (EG&G), undercontract to the Department of Energy, ascertained that some areas of the corehad reached temperatures of at least 5,100° F (the melting point of uraniumdioxide fuel) during the 1979 accident. This information, along with the lowerhead inspection data, was used to revise certain theories of the TMI-2 accidentsequence.

05/15/1985 Reactor Vessel Plenum Assembly Remov ed. On May 15, 1985, the reactorvessel plenum assembly was lifted from its jacked position in the reactor vesselby the polar crane, using three specially designed pendant assemblies. It wasthen transferred by air to the flooded deep end of the refueling canal and loweredinto its storage stand, where it remained throughout the defueling effort. The

operation was completed in just under three hours by a lift team located in ashielded area within the reactor building. Details of the planning, training, andoperations are documented in GEND-054, ―TMI-2 Reactor Vessel Plenum FinalLift.‖

08/1985 Licensee ’ s Waste Burial Priv i leges Suspended. The licensee’s burialprivileges at the U.S. Ecology burial site in Richland were temporarily suspendedin August 1985 when three barrels, out of a shipment of 104, were erroneouslyclassified, labeled, and certified by the licensee as Class A radioactive waste.


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The privileges were restored after Washington State officials approved correctivemeasures taken by the licensee to prevent future shipping and classificationviolations.

10/1985 Operators Started Removin g Fuel Debris from Reactor. In October 1985,operators began to remove damaged fuel and structural debris from the reactor

vessel by ―pick and place‖ defueling of the loose TMI-2 core debris. Workersperformed defueling operations from a shielded defueling work platform (DWP),which was located nine feet above the reactor vessel flange. The platform had arotating 17-foot diameter surface with six-inch steel shield plates, and wasdesigned to provide access for defueling tools and equipment into the reactorvessel. The DWP supported defueling operators, specially designed long-handled tools, remote viewing equipment, and two jib cranes used to manipulatethe tools. Numerous manual and hydraulically powered long-handled tools wereused to perform a variety of functions, such as pulling, grappling, cutting,scooping, and breaking up the core debris. These tools were used to load debrisinto defueling canisters positioned underwater in the reactor vessel. Thecanisters were then sealed and transported using shielded canister transfer

equipment to submerged storage racks in spent fuel pool ― A‖ of the auxiliary andfuel handling building (AFHB). The canisters were designed and stored toprevent an inadvertent criticality event. Following dewatering to control thebuildup of combustible gases, the canisters were loaded into a speciallydesigned shipping cask and transported to a Department of Energy facility inIdaho for interim storage and research.

In December 1985, several defueling canisters were filled with debris consistingof fuel assembly end fittings, control rod spiders, and small pieces of fuelassemblies. In January 1986, the first group of defueling canisters was sealed,dewatered, and transferred to storage racks in spent fuel pool ― A‖ in the AFHB.

Dose rates to personnel during the initial phase of defueling were low andremained low throughout the year, averaging less than 10 mrem/hr on the DWPand less than 40 mrem/hr near the shielded canisters during transfer. Thelicensee discontinued the use of respirators during defueling activities, based onair sample data collected during the first month.


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Workers performed defueling operations from a shielded defueling work platform (DWP), which was located nine feetabove the reactor vessel flange. The platform had a rotating 17-foot diameter surface with six-inch steel shield

plates, and was designed to provide access for defueling tools and equipment into the reactor vessel.

Numerous manual and hydraulically powered long-handled tools were used to perform a variety of functions,such as pulling, grappling, cutting, scooping, and breaking up the core debris. These tools were used to loaddebris into defueling canisters positioned underwater in the reactor vessel.


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1986

04/1986 Microorg anisms Inside the Reactor Vessel. In April 1986, a large populationof microorganisms rapidly developed in the reactor coolant system (RCS),clogging the defueling water cleanup system filters and hindering the operators’

ability to remotely view the defueling activities in the vessel. These growths,consisting of algae, fungi, and bacteria, as well as both aerobic and anaerobicorganisms, proved difficult to kill in several tests. In April and May, the licenseeconducted a multi-phase program to restore reactor vessel water clarity. Theprogram consisted of high-pressure hydrolancing to remove growths adhering toreactor vessel surfaces, the addition of hydrogen peroxide as a biocide, and theuse of a high-pressure positive displacement pump to kill the microorganisms. Adiatomaceous earth (swimming pool-type) filter was then operated in conjunctionwith the letdown and makeup of batches of reactor coolant, to remove theorganic material and improve the clarity of the RCS water. These techniquesproved successful in restoring visibility in the vessel, and were repeated asnecessary to maintain water clarity throughout defueling activities for fiscal year

1986. Pick and place defueling was resumed in May, following the completion ofthe water treatment program. However, it took more than a year to completelyrestore clarity and visibility.

Studies revealed that small amounts of hydraulic fluid from the defueling toolsleaked into the reactor coolant and provided the organic food source for themicroorganisms. This was aided by the correct water temperature and light fromthe underwater TV camera lights.

04/1986 NRC Approved Shipping Casks for Fuel Debris. In April 1986, the NRCissued certificates of compliance for the two NuPac 125-B Rail Casks to be usedin shipping the fuel debris by rail. Each cask was designed to hold seven

defueling canisters. The results of the tests required by Title 10 of the Code ofFederal Regulations, Part 71, ―Packaging and Transporting of RadioactiveMaterial,‖ are summarized in GEND-055, ―U.S. Department of Energy Three MileIsland Research and Development Program 1985 Annual Report.‖

NRC issued certificatesof compliance for the twoNuPac 125-B Rail Caskto be used for shipmentof the fuel debris by rail.Each cask was designedto hold seven defuelingcanisters. (DOE Photo)


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07/1986 Licensee Submitted Proposal to Dispo se Slightly ContaminatedRadioacti ve Water. The licensee submitted for NRC approval a proposal fordisposing of approximately 2.1 million gallons of slightly radioactive water,contaminated during the accident and used in subsequent cleanup operations.Out of the proposed alternatives, the licensee requested approval for a methodinvolving the forced evaporation of the water at the TMI site over a 2.5-year

period. The residue from this operation, containing small amounts of theradioactive isotopes cesium-137 and strontium-90, and large volumes of boricacid and sodium hydroxide, would require solidification and disposal as low-levelwaste.

07/1986 First Fuel Debris Shipped to DOE. The first off-site shipment of the fuel anddebris removed from the damaged TMI-2 core took place in July 1986. Under aprevious agreement with the NRC, Department of Energy took possession of thehigh-level waste at the TMI site boundary, and was responsible for the transportof the material and interim storage at the Idaho National Engineering Laboratory.

07/1986 Extent o f Core Melt Realized . The licensee conducted a core stratification

sample acquisition program. Most of the loose core debris had been removedfrom the reactor vessel, and more data were needed to plan the defueling of thematerial under the hard crust layer of the damaged core. A special drilling rigwas assembled on top of the Defueling Work Platform, and 10 full-lengthsampling penetrations were made from the surface of the debris bed to inchesabove the lower head of the reactor vessel. The samples of the reactor core(approximately 2.5 inches in diameter and eight feet long) were analyzed atIdaho National Engineering Laboratory, along with earlier samples of the debriscollected from the lower vessel head, in order to provide data on the materialproperties of the core debris.

09/1986 Dri l l ing Operations Comm enced. The heavy-duty tools were only marginally

successful, so the drilling rig that was used earlier for boring core samples wasreinstalled as the primary tool for breaking up the hard mass of core debris.

12/1986 Licensee Submitted Plans fo r Post-Defuel ing Mon itored Storage. InDecember 1986, the licensee proposed to place TMI-2 in an interim monitoredstorage condition for an unspecified period of time, after the completion of thecurrent defueling effort. The licensee’s term for this condition was ―post-defueling monitored storage.‖ The facility would remain in the storage conditionuntil TMI-1 was ready to be decommissioned. Both facilities would then bedecommissioned together. NRC staff began the environmental review of thelicensee’s proposal.

1987

06/1987 NRC Issued Supp lement 2 to the Programmatic Environmental Imp actStatement for Wastewater Dispo sal. In June 1987, the NRC issued FinalSupplement No.2 to NUREG-0683, ―Programmatic Environmental ImpactStatement,‖ (PEIS) which dealt with the final disposal of 2.1 million gallons ofslightly contaminated accident-generated water. The staff concluded that thelicensee’s proposal to dispose of the water by forced evaporation to theatmosphere, followed by the on-site solidification of the remaining solids and their


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disposal at a low-level waste facility, was an acceptable plan. The staff alsoconcluded that no alternative method of disposing of the contaminated water wasclearly preferable to the licensee’s proposal. An opportunity for a prior hearing toconsider removing the prohibition on the disposal of the contaminated water wasoffered, and the matter was pending before the Atomic Safety and LicensingBoard at the end of fiscal year 1987.

The NRC evaluated the licensee’s proposal together with eight alternativeapproaches, giving consideration to the risk of radiation exposure to workers andto the general public; the probability and consequences of potential accidents;the necessary commitment of resources, including costs; and regulatoryconstraints.

09/1987 Sludge Removal Comp leted . Sludge removal from the auxiliary building sumpand the reactor building was completed, and flushing of the reactor buildingbegan in September 1987.

1988

1988 SDS Operations Comp leted. In 1988, the submerged demineralizer system(SDS), which was originally used to decontaminate the water in the reactorbuilding basement, was removed from service. During its service life, itprocessed 4,566,000 gallons of water. The defueling water cleanup system wasused to process water from the reactor coolant system and the ― A‖ spent fuelpool. The Epicor-II system processed the remainder of the contaminated waterat TMI-2.

02/1988 TMI-2 Project Directo rate Dissolved . The TMI-2 Project Directorate wasdissolved in February 1988. The inspection program for TMI-2 was assumed bythe TMI resident inspection staff. Technical review and project management

functions were assumed by a NRC Headquarters project directorate.

1989

04/1989 NRC Appro ved Evaporation o f Ac cident-Generated Water. Public hearingson the licensee’s proposal to evaporate 2.3 million gallons of accident-generatedwater were held by the Atomic Safety and Licensing Board (ASLB). Thehearings concluded on November 15, 1988. On February 3, 1989, the Boardissued a decision in favor of the licensee on all relevant issues. On April 13,1989, the Commission affirmed the ASLB’s decision without prejudice to anyappeals. The licensee began to construct the evaporator in August 1989.

07/1989 NRC Co-Sponsor ed Research of Cracks in th e Lower Reactor Vessel Head. A 1989 video inspection of the reactor vessel’s lower head disclosed severalcracks that appeared to be associated with in-core instrument penetrationnozzles. Higher quality color videos and a mechanical probe were used in

August 1989 to obtain better information on the cracks. The cracks appeared tobe up to approximately six inches long, 0.25 inches wide, and more than 0.19inches deep, but not ―through-wall‖ (see photo below).


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The TMI Vessel Investigation Project (VIP) was an international programsponsored jointly by the NRC and the Organization for Economic Co-operationand Development/Nuclear Energy Agency (OECD/NEA). Participants in thisprogram included the U.S., Japan, Belgium, Germany, Finland, France, Italy,Spain, Sweden, Switzerland, and the United Kingdom. As described in theformal project agreement, the objectives of the VIP were to jointly carry out a

study to evaluate the potential failure modes and the TMI-2 reactor vessel’smargin for failure during the TMI-2 accident. The conditions and properties of thematerials extracted from the lower head of the TMI-2 pressure vessel wereinvestigated to determine the extent of the damage to the lower head bychemical and thermal attack, the thermal input to the vessel, and the margin ofstructural integrity that remained during the accident. The examinationsperformed under the VIP went beyond the work that had been performed duringthe previous TMI-2 examinations; specifically, the VIP obtained and examinedsamples of the lower head steel, instrument penetrations, and previously moltendebris that was attached to the lower head, and used this information to estimatethe vessel’s margin for failure. The VIP included the development of the cuttingtools to remove lower head samples, the metallurgical laboratory work, and the

study and analyses of results. It took nearly five years to carry out the project,during which time nearly all of the objectives were accomplished.

A 1989 video inspection of the reactor vessel’s lower head disclosed several cracks that appeared tobe associated with in-core instrument penetration nozzles.


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Results from the VIP are documented in the following reports:

NUREG/CR-6185, ―TMI-2 Instrument Nozzle Examinations at ArgonneNational Laboratory‖ NUREG/CR-6187, ―Results of Mechanical Tests and SupplementaryMicrostructural Examinations of the TMI-2 Lower Head Samples‖

NUREG/CR-6194, ―Metallographic and Hardness Examinations of TMI-2Lower Pressure Vessel Head Samples‖ NUREG/CR-6195, ―Examination of Relocated Fuel Debris Adjacent to theLower Head of the TMI-2 Reactor Vessel‖ NUREG/CR-6196, ―Calculations to Estimate the Margin to Failure in the TMI-2 Vessel‖ NUREG/CR-6198, ―TMI-2 Nozzle Examinations Performed at the IdahoNational Engineering Laboratory‖

08/1989 NRC issued Supplement 3 to the Programm atic Environmental Imp actStatement for Post-Defuel ing Mon itored Storage. In August 1989, the NRCissued NUREG-0683 Supplement 3, ―Programmatic Environmental ImpactStatement Related to Decontamination and Disposal of Radioactive WastesResulting from March 28, 1979 Accident Three Mile Island Nuclear Station, Unit2, Final Supplement Dealing with Post Defueling Monitored Storage andSubsequent Cleanup.‖ This supplement evaluated the licensee’s proposal tocomplete the current cleanup effort and place the facility into monitored storagefor an unspecified period of time. The licensee had indicated that the facilitywould likely be decommissioned following the storage period, at the time thatUnit 1 was decommissioned. Specifically, the supplement provided anenvironmental evaluation of the licensee’s proposal and a number of alternativecourses of action from the end of the current defueling effort to the beginning ofdecommissioning. However, it did not provide an evaluation of the environmentalimpacts associated with decommissioning. NRC staff had concluded that thelicensee’s proposal to place the facility in monitored storage would notsignificantly affect the quality of the human environment. Furthermore, anyimpacts associated with this action were outweighed by its benefits. The benefitof this action was the ultimate elimination of the small but continuing riskassociated with the conditions of the facility, resulting from the March 28, 1979,accident. The draft supplement was issued for public comment in April 1988.

1990

03/1990 Defuel ing Com pleted. The licensee’s defueling crews completed bulk defuelingin December 1989. In March 1990, they completed the final re-flushing and re-vacuuming for loose, dust-like debris. A total of 308,000 pounds of core debris

and commingled structural materials was removed from the reactor vessel andcoolant system during the five-year effort.


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04/15/1990 Final Fuel Debris Sh ipped . The final fuel shipment of fuel debris to the IdahoNational Engineering Laboratory was made on April 15, 1990.

Last shipment of fuel debris leaving TMI to DOE in 1990. (DOE Photo)

04/26/1990 Plant Operations Transit ioned. The licensee submitted documentation to justify

transition from Mode 1 (defueling) to Modes 2 through 3. In Mode 2, defuelingwas completed and, thus, boration of the reactor coolant system and staffing ofthe control room by licensed operators was no longer required. In Mode 3, off-site shipment of the fuel was completed and boration of the spent-fuel storagepools was no longer required. The three criteria for changing from Mode 1 toMode 2 were as follows:

(1) The reactor vessel and reactor coolant system were defueled to theextent reasonably achievable.

(2) The possibility of a criticality in the reactor building was precluded.(3) There were no canisters containing core material in the reactor building.

The additional requirement for transition to Mode 3 was that no canisterscontaining core material remained on the TMI site. The NRC staff andconsultants from Battelle Memorial Institute, Pacific Northwest Laboratory,performed a detailed technical review and inspection to verify that the criteriawere met. The facility made the transition from Mode 1 to Mode 2 on April 26,1990, and to Mode 3 the following day.


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1991

01/24/1991 Evaporator Operations Began. The evaporator system began to vaporize theslightly contaminated accident-generated water on January 24, 1991, after aprolonged period of system testing, modification, and repair. At the end ofSeptember 1991, a total of 738,800 gallons had been decontaminated and

vaporized.

07/1991 Reactor Vessel Drained. The reactor vessel was drained to take finalmeasurements of the residual fuel remaining in the vessel. The reactor vesselfuel measurement program was the final step in the special nuclear materialsaccountability program at TMI-2. The measurement technique made use of anarray of helium-filled detectors to measure fast neutrons produced by the residualfuel. Calibrations were made using americium-beryllium and californium sources.

1992

02/1992 NRC Issu ed a Safety Evaluatio n for Post-Defueling Mo nito red Storage.

Back in August 1988, the licensee submitted a Safety Analysis Report todocument and support their proposal to amend the TMI-2 license to a―possession-only‖ license, and to allow the facility to enter post-defuelingmonitored storage (PDMS). In February 1992, the NRC issued a SafetyEvaluation for ―post-defueling monitored storage,‖ which addressed the licenseconditions and technical specifications necessary to implement PDMS followingevaluations by NRC staff and contractor consultants from Battelle MemorialInstitute’s Pacific Northwest Laboratory. As part of the evaluation, the staffpublished a technical evaluation report, which appraised PDMS as an integratedprocess and assessed licensee commitments that were not within the technicalspecifications. These two documents and Final Supplement 3 to the―Programmatic Environmental Impact Statement‖ (NUREG-0683), which was

issued in August 1989, formed the basis for the NRC’s position on the PDMS.

Later, the NRC issued a possession-only license on September 14, 1993.

1993

07/1993 Residual Fuel Remaining in TMI Systems Determin ed. In July 1993, NRCstaff issued an analysis confirming earlier analyses by the licensee, whichindicated that the fuel remaining in the TMI-2 reactor vessel would remainsubcritical, with an adequate margin for safety, during post-defueling monitoredstorage. NRC staff and consultants from Battelle Pacific Northwest Laboratoriesperformed independent evaluations and made independent measurements of

these earlier fuel measurements in the auxiliary and reactor buildings. Thelicensee’s current best estimate of the residual fuel in the reactor vessel was2,040 pounds (925 kilograms), based on data from recently completed fast-neutron measurements. For the balance of the facility external to the reactorvessel, earlier licensee estimates, based on measurements, sample analyses,and visual observations, indicated that no more than 385 pounds (174.6kilograms) of residual fuel remained.


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08/1993 Evaporation of Accid ent Water Completed. The decontamination andevaporation of 2.23 million gallons of accident-generated water were completedin August 1993.

09/14/1993 NRC Issued Pos session-Only License. On September 14, 1993, the NRCapproved the post-defueling monitored storage and issued a possession-only

license.

09/23/1993 Last Meeting of th e Public Adviso ry Panel Held. The last meeting (78th overall) of the 10-member Advisory Panel for the Decontamination of Three MileIsland Unit 2 was held on September 23, 1993. The Panel, composed ofcitizens, scientists, and state and local officials, was formed by the NRC in 1980to provide input to the Commission on major cleanup issues. The principal topicsdiscussed at these meetings included the NRC staff ’s safety evaluation andtechnical evaluation report addressing post-defueling monitored storage, thestatus and progress of cleanup at the TMI-2 facility, and the decommissioningfunding status and plans.

Lessons learned from the Public Advisory Panel were published in NUREG/CR-6252, ―Lessons learned from the Three Mile Island Unit 2 Advisory Panel.‖

The Advisory Panel for the Decontamination of Three Mile Island Unit 2 held its last meeting in 1993. Panel membersattending the final meeting are pictured (names are provided in the NRC 1994 Annual Report, NUREG- 1145, Vol.10, Page 50).


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1994

1994 TMI-2 Placed in Post-Defueling Mo nito red Storage. In 1994, TMI-2 wasplaced in post-defueling monitored storage (PDMS), a passive, monitored state.The licensee will maintain Unit 2 in PDMS until TMI Unit 1 permanently ceaseoperation. At that time, the licensee would decommission both units

simultaneously. NRC staff continues to monitor TMI-2, and requires the licenseeto submit regular PDMS reports summarizing ongoing Unit 2 activities.

References

Primary sources used in these timeline narratives include the NRC annual reports listed belowand abstracts from NRC technical (NUREG) reports mentioned in this timeline.

1. USNRC, ―1979 NRC Annual Report,‖ NUREG-0690, March 1980.2. USNRC, ―1980 NRC Annual Report,‖ NUREG-0774, March 1981.3. USNRC, ―1981 NRC Annual Report,‖ NUREG-0920, June 1982.

4. USNRC, ―1982 NRC Annual Report,‖ NUREG-0998, June 1983.5. USNRC, ―1983 NRC Annual Report,‖ NUREG-1090, June 1984.6. USNRC, ―NRC Annual Report,‖ NUREG-1145, Vols. 1-12 (1984-1995), various dates.

9/6/2012

TMI Timeline

Documents

Transcript of TMI Timeline