Three Mile Island

Accident of 1979

Knowledge

Management Digest

Overview

NUREG/KM-0001, Revision 1

Office of Nuclear Regulatory Research
ii

Three Mile Island on April 10, 1979, 13 days after the accident
iii

Contents

Digital Versatile Disc (DVD) Contents ............................................. v

1 Introduction ............................................................................... 1

2 The Accident............................................................................. 3

3 Investigations and Lessons Learned ......................................... 9

4 Regulatory Actions.................................................................. 13

5 Research ................................................................................ 17

6 Plant Recovery and Cleanup................................................... 21

7 Retrospectives ........................................................................ 29

8 DVD Navigation and Interpretation.......................................... 33

9 Contributions to the Main Report............................................. 37

President Jimmy Carter observes the radiation monitors in the Three Mile 

Island, Unit 2 control room on April 1, 1979, accompanied by 

Pennsylvania Governor Richard Thornburgh and the NRC’s Harold 

Denton.
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Location of dosimetry sites within a 2 mile radius of the Three Mile Island 

station. NRC deployed thermoluminescent dosimeters at 37 offsite locations on 

March 31, 1979, and an additional 10 locations the following day. NRC placed 

portable air samplers around the plant area and observation center and 

analyzed the results. NRC also placed liquid effluent monitors at the station 

discharges. 
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Digital Versatile Disc (DVD) Contents

Main Report Disc (NUREG/KM-0001, DVD-1) Folder

Photos & Videos

Photo Gallery 0a-Photos

DOE “The TMI Story: A Documentary” (1988) 0b-Video-DOE

NRC 30th Anniversary Seminar (2009) 0c-Video-30th

NRC 35th Anniversary Seminar (2014) 0d-Video-35th

Response to the Accident

Commission/Operations Center Response 1a-Transcript

Response Preliminary Notices 1b-PN-Response

Press Releases/Conferences 1c-Press

International Cables 1d-International

Other Response 1e-Other

Investigations and Lessons Learned

President's Commission 2a-Kemeny

Rogovin Investigation 2b-Rogovin

NRC Investigations 2c-L2-NUREG

Other Investigations 2d-Other

Industrywide Regulatory Actions

Generic Communications 3a-Generic

Policy Statements 3b-Policy

NUREG Reports 3c-REG-NUREG
vi

An aerial view of Three Mile Island looking south. TMI-2 and both of its 

cooling towers are in the background. Although the island, which is located 

on the Susquehanna River, is almost three miles long, the island was named 

from its location three miles downriver from Middletown, PA. (Middletown 

was founded in 1755 and named from its location halfway between Lancaster 

and Carlisle, PA.)
1

1 Introduction

Although it caused no deaths or injuries, the accident at the Three Mile 

Island, Unit 2 (TMI-2) nuclear power plant was the most serious incident in 

U.S. commercial nuclear power history. The accident began in the early 

morning hours of March 28, 1979, at the newly-licensed power plant near 

Middletown, Pennsylvania, and its effects on nuclear safety and regulation 

continue to this day. Three Mile Island spurred the U.S. Nuclear Regulatory 

Commission (NRC) to tighten and heighten its regulatory oversight of the 

nuclear power industry to ensure the safety of the public and the 

environment. Investigations and the implementation of lessons learned 

brought about sweeping changes in the U.S. nuclear industry. These 

included improvements in emergency response planning, reactor operator 

training, human factors engineering, radiation protection, and many other 

areas of nuclear power plant operations and design. The NRC and the 

U.S. Department of Energy (DOE) have intensively studied and 

documented the TMI-2 accident.

This multimedia digest was the first in the NRC’s NUREG knowledge 

management (NUREG/KM) series. One of the missions for NUREG/KMs is 

to preserve knowledge for future generations of the important historical 

events and research that have shaped the NRC’s regulatory programs. This 

knowledge management digest and supporting DVD contain the most 

important documents that the NRC, the licensee, and other government 

organizations issued following investigations and cleanup of the accident. 

Although a few key documents have become available electronically, this 

NUREG/KM marks the first time that the NRC has digitized these 

historically important documents. On the DVD, the table of contents on the 

welcome page provides access to these reports.

About Revision 1. This revision of NUREG/KM-0001 has evolved into two 

volumes. This volume presents overviews of the accident: emergency 

response, investigations, regulatory implications, and accident recovery. 

This volume includes topics and documents provided on the original DVD 

with new ones added. Supplement 1 expounds upon the technical details of 

recovery and cleanup activities: management and oversight, plant 

stabilization, worker protection, data acquisition and analysis, waste 

management, decontamination, defueling, and after defueling. The 

document collections in this supplement are derived from correspondence 

between the utility and NRC, and from the results of research activities. The 

accompanying DVDs for both volumes contain about 4,000 documents.
2

In addition to the large collection of documents, this volume provides three

NRC multimedia presentations, “The Accident at Three Mile Island, A 

Look Back: Preserving the Institutional Memory after 30 Years,” “The 

35th Anniversary of the Three Mile Island Nuclear Power Plant Accident 

of 1979: Working at TMI During and Following the Accident,” and 

“Moments in NRC History, Three Mile Island, March 28, 1979.”

This NUREG/KM does not fully convey the complete NRC experience in 

the aftermath of the accident. Other interesting topics for future studies of

the TMI-2 accident include: legal lawsuits and actions; court proceedings, 

including those at the U.S. Supreme Court; Atomic Safety and Licensing 

Board proceedings; enforcement actions; the utility’s financial crisis;

interactions with Congress; interactions with Federal, State, and local 

government agencies; public outreach; the TMI Unit 1 restart; and oversight 

by the NRC’s Advisory Committee for Reactor Safeguards (ACRS).

How to Use this Digest. A few suggestions for navigating through this 

NUREG/KM, and the many documents on the DVD, are provided at the end 

of this NUREG/KM (see the section on DVD Navigation and 

Interpretation). The historical documents provided on the DVD are for 

reference only, and are not official NRC records.

Shortly after the accident, NRC staff gathers in the NRC office trailer at 

Three Mile Island. Shown (front-left to right): Thomas Essig, George Smith, 

Richard Volmer, Frank Congel, Robert Bores (wearing hardhat), and 

J. Philip Stohr (wearing vest).
3

2 The Accident

The sequence of certain events—equipment malfunctions, design-related 

problems, and operator errors—led to a partial meltdown of the TMI-2 

reactor core, resulting in a very small offsite release of radioactivity. In an 

atmosphere of growing uncertainty about the condition of the plant, on the 

morning of March 30, 1979, Pennsylvania Governor Richard Thornburgh 

advised people within a 5-mile radius of the plant to stay indoors. He also 

advised pregnant women and preschool-age children to evacuate the area 

within a 5-mile radius of TMI. By the close of the weekend of March 30

through April 1, 1979, TMI-2 was determined to be in a stable shutdown 

condition. On Sunday, April 1, 1979, the President of the United States 

James Earl “Jimmy” Carter, Jr., First Lady Rosalynn Carter, Governor 

Thornburgh, and the NRC’s Harold Denton visited the damaged unit. 

Within 2 weeks, the Governor’s precautionary advisory to pregnant women 

and preschool-aged children was lifted.

While the utility and NRC were primarily charged with mitigating the 

consequences of the accident through plant actions, reducing the effects of 

offsite radiological releases is the responsibility of State and Federal

agencies. The TMI accident initiated an institutional and public response 

that was unprecedented in the history of nuclear power in the United States. 

Many organizations participated substantially in the response to this 

accident, including approximately 24 Federal and 12 State agencies; the 

military; 27 counties of the Commonwealth of Pennsylvania; innumerable 

local jurisdictions; public and private organizations; 4 bordering states; and 

several quasi-Federal organizations. Operational code name “Ivory 

Purpose” was chosen for the purpose of citing accident support by military 

and other agencies. These institutions provided many kinds of support 

services to the utility in evaluating the status of the plant, and in bringing 

the plant to a safe-shutdown condition. Support was also provided to the 

state in evaluating the extent of public hazards, preparing for possible 

evacuation, and considering or preparing for the implementation of other 

protective actions.

The NRC played an active role as the regulator by responding to the 

accident. A team began to form at the site with the arrival of the NRC’s 

Region I inspectors during the morning of the first day of the accident, and 

continued to expand throughout the weekend with the arrival of engineers, 

scientists, and public affairs specialists from headquarters and other regional 

offices. The incident response centers, located in the Region I office in King

of Prussia, Pennsylvania, and at headquarters in Bethesda, Maryland, were 
4

staffed by NRC incident response teams during the morning of March 28. 

Other NRC offices, such as State Programs, International Programs, Public 

Affairs, and Administration, supported the NRC incident response effort. 

The five commissioners, who provided the general policy that determined

the overall course of action that the NRC staff would take in response to 

incidents, were located at their downtown office on H Street in northwest

Washington, DC.

The NRC sponsored a Special Inquiry Group that was tasked with 

investigating the accident and reporting their findings in NUREG 

Contractor Report 1250 (NUREG/CR-1250). Volume 1 of that report 

contains an informative and nontechnical discussion of the accident, 

including onsite actions and offsite responses. Another good resource on the 

accident is the main report by the President’s Commission on the Accident 

at Three Mile Island. Additional volumes of both these reports provide 

technical details of the accident and discussions of emergency actions by the 

NRC, other Federal agencies, and State and local government offices. The 

NRC’s training manual on reactor safety (NUREG/CR-6042, Section 2.2) 

provides a technical summary of the accident, as well as an overview of the 

regulatory implications of the accident (Section 2.3).

The chronology of events can be found in all of the aforementioned

documents. Both “Backgrounder”, written by the NRC’s Office of Public 

Affairs, and the NRC’s 1979 annual report (NUREG-0690), specifically 

Chapter 2, contain additional nontechnical summaries of the accident;

Three Mile Island “trailer city” at the visitor center during the accident 

response (helicopter pad upper left).
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these, and other reports on the accident are provided on the accompanying 

DVD.

One of many functions of the NRC incident response organization during 

the accident was to notify appropriate internal offices and external agencies,

and keep them and the public informed. Document collections related to the 

first few weeks of the NRC response effort include the following:

• Preliminary notification (PN) reports, which were used by the NRC 

Operations Center to communicate daily status of the accident (see 

DVD folder, Response Preliminary Notices)

• Press releases issued by the NRC public affairs staff (see DVD folder,

Press Releases/Conferences)

• Transcripts of press conferences held by NRC emergency managers,

and many times, jointly with State executives (see DVD folder, Press 

Releases/Conferences)

• International cables issued by the NRC international programs staff and 

used by State Department officials to keep foreign governments

informed of the accident (see DVD folder, International Cables)

NRC’s Harold Denton briefs the news media at the NRC press 

center located at the basketball court in the Middletown 

Borough Hall.
6

During the course of the accident, the NRC commissioners (known 

collectively as the “Commission”), met frequently to discuss the accident 

and related matters. Because of their emergency nature, these meetings were 

not open to the public. At the time of the accident, the five commissioners

were John Ahearne, Peter Bradford, Victor Gilinsky, Joseph Hendrie

(chairman), and Richard Kennedy. Meetings were recorded and transcripts

were prepared in accordance with the Government in the Sunshine Act. 

These transcripts were later released to the public and used in internal and 

external investigations of the accident. Notably, the Commission meetings

were sometimes held in locations other than where they normally would be, 

making the creation of complete and high-quality recordings difficult. As 

such, these transcripts do not represent formal or official Commission 

statements (see DVD folder, Commission/Operations Center Response).

Lessons from investigations of the accident led to vast improvements in 

how the NRC, nuclear power plant utilities, and Federal and State agencies 

respond to accidents. Revised NRC rules and guidance mandated utilities to 

The NRC Executive Management Team at the NRC Operations Center 

located in the East-West Towers Building, Bethesda, Maryland, during 

the accident response. Shown (left-right): Lee Gossick (team director

and Executive Director for Operations), Edson Case (Deputy Director, 

Office of Nuclear Reactor Regulation), Norman Moseley (Director, 

Division of Reactor Operations Inspection), John Davis (Acting 

Director, Office of Inspection and Enforcement), and James Sniezek

(Director, Division of Fuel Facilities and Materials Safety Inspection).
7

upgrade their overall state of emergency preparedness for a wide range of 

accidents, including the integration of onsite and offsite emergency 

preparedness. The newly established Federal Emergency Management

Agency (FEMA) consolidated offsite Federal emergency planning and 

response to radiological accidents. (Although Congress approved the 

President’s Reorganization Plan No. 3 of 1978 that created FEMA on 

September 16, 1978, the transfer of Federal functions had not been 

completed at the time of the TMI accident. In the reorganization, each State

retained responsibility for protection of its citizens and the NRC retained

Federal jurisdiction over plant activities.)

A new state-of-the-art NRC Operations Center, located in the Fairmont 

Building (also known as the Maryland National Bank Building) in Bethesda, 

Maryland, was completed in early 1985 and remained in operation until the 

NRC consolidated at the current White Flint complex in Rockville, Maryland, 

during the summer of 1994. This first dedicated use operations center was 

designed using lessons learned from the TMI-2 accident and human factors 

principles to ensure seamless flow of information inside and outside the 

center. Shown is the Executive Team during the Saint Lucie Plant exercise on 

March 20, 1991. Clockwise: Commissioner Kenneth Rogers (back to camera), 

Brian Sheron (standing while briefing the team on reactor safety team 

assessments), Edward Jordon (Director, Office of Analysis and Evaluation of 

Operational Data), Themis Speis (Deputy Director, Office of Nuclear 

Regulatory Research), Robert Bernaro (Director, Office of Nuclear Material 

Safety and Safeguards), Thomas Murley (Director, Office of Nuclear Reactor 

Regulation), and James Talyor (Executive Director for Operations).
8

In 1980, the NRC and FEMA signed memoranda of understanding to further 

delineate responsibilities regarding emergency planning and activities at 

NRC-licensed facilities. In the President’s Reorganization Plan No. 1 

of 1980, the Commission’s emergency response functions were transferred 

to the NRC Chairman for defined emergencies. The Commission approved 

the revised NRC Incident Response Plan in 1983, which, among numerous

improvements, established a site team that takes the agency’s lead for larger 

responses. The Chairman could delegate specific authorities to the site team 

leader during a defined emergency. The completion of TMI 

recommendations relating to emergency preparedness and response are 

summarized in NUREGs 0933 and 1355. Other documents specific to the 

TMI-2 response, and generic to emergency preparedness for all 

NRC-licensed activities, are provided on the DVD (see the DVD folders,

Other Response and NUREG Reports).

The pilot-operated relief valve on top of the pressurizer (see 

arrow) failed to close at the start of the accident. Steam leaked 

out through the stuck-open valve into the basement of the 

reactor building at a rate equivalent of some 220 gallons of 

water per minute, which continued for more than 2 hours and 

20 minutes before operators realized that the valve had failed 

to shut. This was a failure for which the TMI operators had 

never been trained, and which was not described in their 

written emergency procedures. This lack of preparation led to 

a misreading of the symptoms and mistaken responses that 

would uncover the reactor core.
9

3 Investigations and Lessons Learned

Two weeks after the accident, the President of the United States, Jimmy 

Carter, appointed a 12-member Presidential Commission to investigate the 

accident at Three Mile Island. This group, known as the “Kemeny 

Commission,” conducted a comprehensive investigation of the accident and 

made recommendations based upon their findings. Their final report was 

issued to the President on October 30, 1979. Another 10 volumes 

documented details of their investigation. The NRC published its initial 

response to the Presidential Commission’s recommendations in 

November 1979 as NUREG-0632 entitled, “NRC Views and Analysis of the 

Recommendations of the President’s Commission on the Accident at Three 

Mile Island.”

The President responded to those reports in his statement on 

December 7, 1979. By Executive Order 12202 of March 18, 1980, President 

Carter established the Nuclear Oversight Committee for a short period of 

time to report to him on the progress of implementing the approved 

recommendations of the Kemeny Commission. A later report, 

NUREG-1355, “Status of Recommendations of the President’s Commission 

on the Accident at Three Mile Island—a 10-Year Review,” updated the 

NRC’s initial response to include the status of the 44 recommendations 

made by the Kemeny Commission over a 10-year period.

To help gain comprehensive insight into the accident, the NRC sponsored 

both internal and external investigations. In mid-June 1979, the NRC asked 

the independent Special Inquiry Group to perform an investigation under the 

directorship of the law firm of Rogovin, Stern, and Huge. Most of the 

people who assisted in the inquiry were drawn from the NRC staff, and 

One highly publicized operating error was 

the initial failure of emergency feedwater 

(EFW) flow to the steam generators by two 

improperly closed EFW block valves. One 

of these tags obscured one of the block 

valve indicator lights. The Special Inquiry 

Group was not able to determine how the 

block valves were closed; however, they 

concluded that the 8-minute delay in 

restoring EFW flow did not directly affect 

the outcome of the accident. With the 

pressurizer relief valve stuck open and the 

high-pressure injection flow throttled, core 

damage would have occurred anyway.
10

carefully screened to avoid any conflicts of interest; a number of technical 

consultants were also engaged to assist in the inquiry. The Special Inquiry 

Group provided a thorough analysis and assessment of the causes and 

implications of the accident. As already noted, the NRC published this work 

in the four volumes of NUREG/CR-1250, “Three Mile Island, a Report to 

the Commissioners and to the Public.”

Working internally, the NRC created a Lessons Learned Task Force in 

May 1979. The NRC task force identified and evaluated safety concerns 

originating from the TMI-2 accident that required licensing actions at other 

nuclear power plants. The NRC published the task force’s conclusions in 

NUREG-0578, “TMI-2 Lessons Learned Task Force Status Report and 

Short-Term Recommendations,” and NUREG-0585, “TMI-2 Lessons 

Learned Task Force Final Report.”

Many other groups, both internal and external to the NRC, also performed 

separate investigations. These included the U.S. Congress and its General 

Accounting Office; the Ad Hoc Dose Assessment Group, which comprised 

various Federal agencies (see NUREG-0558); the NRC’s Advisory 

Committee on Reactor Safeguards; the Bulletins and Orders Task Force of 

the NRC’s Office of Nuclear Reactor Regulation (see NUREG-0645); the 

NRC’s former Office of Inspection and Enforcement’s Special Review 

Group (see NUREG-0616), Task Force on Lessons Learned (see 

The NRC Commissioners testifying before the U.S. Senate Subcommittee on 

Nuclear Regulation for the Committee on Environment and Public Works.
11

NUREG-0600), and Division of Program Development and Appraisal (who 

investigated information flow during the accident—see NUREG-0760); the 

NRC’s Siting Task Force, which identified site location requirements for 

nuclear power plants; the NRC’s Emergency Preparedness Task Force; the 

Staff Panel on the Commission’s Determination of an Extraordinary 

Nuclear Occurrence (see NUREG-0637); the NRC’s Office of Nuclear 

Regulatory Research; and the NRC’s former Office of Standards 

Development.

The DVD provides many of the key investigation reports on TMI (see DVD

folders, President's Commission, Rogovin Investigation, NRC 

Investigations, and Other Investigations). Many of the aforementioned

investigation reports are summarized in NRC annual reports, primarily 

NUREG-0690 (1979) and NUREG-0774 (1980). 
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TMI-2 Core End-State Configuration. In 1988, the NRC reported the final 

state of the damaged TMI-2 reactor core, shown above. The accident was 

terminated by reflooding of the core. This action did not immediately stop 

further core melting, but it did prevent the core from melting through the 

reactor vessel.
13

4 Regulatory Actions

The NRC implemented a number of regulatory actions resulting from 

investigations and lessons learned reviews, and completed many more 

“spinoff” actions in the decades following the accident. The first wave of 

actions that the NRC approved included orders to individual NRC licensees,

and generic communications, such as bulletins and letters; these regulatory 

tools were implemented in the days and months following the accident.

Once the various investigative groups had documented their findings, the 

Commission considered the recommendations. The NRC staff consolidated 

all the recommendations that the Commission approved into NUREG-0737, 

“TMI Action Plan,” published in 1980. The plan included approximately 

371 individual requirements. The NRC found that, of these, 13,863 action 

plan items were applicable when reviewed against each specific licensed 

nuclear power plant. Some requirements involved changes to the internal 

NRC organization, processes, and practices. 

A few requirements caused the Commission to issue policy statements and 

specific changes to the NRC’s regulations through the rulemaking process. 

Both of these long-term regulatory tools required extensive internal and 

external stakeholder involvement, and were completed during the 1980s. 

NRC issued a requirement for nuclear power plants to have a simulation 

facility appropriate to conduct operator licensing tests. All plants now have a 

certified plant-referenced simulator that demonstrates anticipated plant 

responses to normal, transient, and accident conditions. Shown is one control 

room simulator at the NRC Technical Training Center in Chattanooga, 

Tennessee, used to train NRC inspectors and technical staff.
14

The NRC’s training manual on reactor safety, (NUREG/CR-6042, 

Section 2.3), provided an overview of the regulatory implications of the 

accident. NUREG-0933, “Resolution of Generic Safety Issues,” 

documented the prioritization and closeout of the TMI Action Plan 

requirements.

Generic Communications. Within 3 days of the accident, the NRC’s Office 

of Inspection and Enforcement started to issue a series of bulletins 

instructing all operating power plant licensees to take a number of 

immediate actions to avoid repeating several of the events that occurred 

during the accident and contributed significantly to its severity 

(Bulletins 79-05, -05A, -05B, -05C, -06, -06A, -06B, -06C, and -08). The 

bulletins and resulting evaluations also substantially informed other staff 

activities, such as those associated with the generic study efforts of the 

Bulletins and Orders Task Force (NUREG-0645) and the Lessons Learned 

Task Force (NUREG-0585). The NRC issued other types of generic 

communications, including generic letters (that transmitted information and 

usually required action or a response) and information notices (related to 

issues for which the licensees considered action appropriate). The DVD 

provides most of the generic communications relevant to TMI-2 (see DVD

folder, Generic Communications).

TMI Action Plan. Each of the investigating groups organized their 

recommendations in a different way. These recommendations were 

collected and transformed into discrete, scheduled tasks in NUREG-0660, 

“NRC Action Plan Developed as a Result of the TMI-2 Accident.” The 

report NUREG-0737, “Clarification of TMI Action Plan Requirements,” 

documented the specific items from NUREG-0660 that the Commission 

approved for implementation at nuclear power plants. In October 1980, the 

NRC issued NUREG-0737 for implementation in Generic Letter 80-090. 

This report comprised specific items and included additional information 

about schedules, applicability, methods of implementation, submittal dates, 

and clarification of technical positions. The Generic Safety Issues Program 

prioritized and tracked the TMI Action Plan items detailed in NUREG-0660 

and NUREG-0737. NUREG-0933, “Resolution of Generic Safety Issues,” 

documented the closeout of action items.

The DVD provides the above NUREGs and other select NUREGs that were 

associated with the implementation and closeout of TMI Action Items (see 

DVD folder, NUREG Reports).
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Rulemaking and Regulatory Guides. In most cases, the NRC implemented 

the TMI Action Plan items through the review of new licensee applications,

and the imposition of confirmatory orders and specific license conditions,

rather than through specific changes to the NRC’s regulations. In several 

instances, implementation of the TMI Action Plan resulted in new or 

modified regulations. These regulations, and a few others that could be 

considered relevant to the TMI accident, included the following: improved 

emergency planning requirements in 1980; requirements related to hydrogen

control in Mark I and Mark II containments for boiling-water reactors

(BWRs) in 1981; improved requirements for operations personnel and 

staffing at nuclear power plants in 1983; requirements for event reporting

in 1983; requirements related to hydrogen control in Mark III containments 

for BWRs and ice condenser containments for pressurized-water reactors

in 1985; improved backfitting process for power reactors in 1985; improved

personnel dosimetry processing in 1987; improved requirements for 

operator licensing in 1987; and mandated participation in the Emergency 

Response Data System Program in 1991.

In support of the NRC Special Inquiry Group investigation, a mockup of the 

TMI-2 control room (above) was constructed by a contractor to study the 

extent to which factors incorporated within the discipline of human factors 

engineering (e.g., man-machine interface design, procedures, manning, and 

training) were influential in causing or contributing to the course of the 

accident. NRC required all licensees and applicants of new plants to conduct 

similar detailed reviews to determine if their control rooms provided 

satisfactory information to allow operators to prevent and cope with accidents.
16

In general, a regulatory guide (RG) describes one acceptable method for 

implementing agency regulations. Regulatory guides are not substitutes for 

regulations and the NRC does not require that licensees comply with them. 

Notable regulatory guides that the NRC revised or created during the 

implementation of the TMI Action Plan include RG 1.8, “Qualification and 

Training of Personnel for Nuclear Power Plants”; RG 1.97, “Criteria for 

Accident Monitoring Instrumentation for Nuclear Power Plants”; RG 1.101, 

“Emergency Planning and Preparedness for Nuclear Power Reactors”; and 

RG 1.149, “Nuclear Power Plant Simulation Facilities for Use in Operator 

Training and License Examinations.” NRC annual reports summarized

rulemakings and regulatory guides (see DVD folder, NRC Annual Reports, 

in Supplement 1 to this NUREG/KM).

NRC Commission Policy Statements. Several policy statements that the 

Commission issued were directly or indirectly related to the TMI Accident. 

A policy statement is not a regulation and does not impose specific 

regulatory requirements, but rather, provides the Commission’s rationale 

and motivation for future regulatory positions. Two notable policy 

statements that continue to have far-reaching regulatory applications include 

“Severe Reactor Accidents Regarding Future Designs and Existing Plants,” 

issued in 1985 and “Safety Goals for the Operations of Nuclear Power 

Plants,” issued in 1986. The former provided the basis for redirecting NRC 

research programs and other regulatory programs; the latter provided the 

basis for backfitting and regulatory analyses, and for the use of probabilistic 

risk assessment in risk-informed decisions on plant-specific changes to the 

plant’s licensing basis. The DVD contains NRC Commission policy 

statements relevant to TMI-2 (see DVD folder, Policy Statements).

To facilitate timely NRC responses, 

more stringent notification 

requirements were placed on 

licensees in February 1980 with the 

publication of 10 CFR 50.72 as an 

immediately effective rule. The rule 

required notification from licensees to 

the NRC Operations Center within 

one hour of emergencies and certain 

significant events, via a dedicated 

direct telephone “Hot Line.” Shown 

is a 1985 photo of operations officers, 

Chauncey Gould and Raymond Smith 

(back), at the new Operations Center 

that opened in February 1985.
17

Closed-circuit video inspections of the reactor core revealed a rubble bed 

approximately 5 feet below the normal location of the top of the fuel 

assemblies.

5 Research

The NRC’s approach to safety changed dramatically after the TMI-2 

accident. The agency’s emphasis shifted from providing safety by relying 

on the traditional design-basis approach, to relying on a multi-faceted 

approach, which emphasized improved operations; human factors 

considerations in control room and emergency procedures; realistic 

performance of systems and containments under severe accident conditions;

and probabilistic risk assessments to identify generic and plant-specific 

vulnerabilities. NRC research and development programs also reflected this 

change.

After the accident, the scope and diversity of the NRC’s efforts in severe 

accidents increased substantially. Some examples included allocating 

additional resources to research and development activities, such as the 

construction of new experimental facilities; the development of analytical 

tools; and, in general, the development of the information needed to gain 

greater insight into severe accident behavior. Since the accident, the NRC, 

DOE, the U.S. nuclear power industry, and international organizations have 

developed a large body of information on severe accidents, including their

probability; core-melt phenomenology; associated accident sequences; and 

the effects of severe accidents on plant systems, components, and structures, 
18

especially those that provide barriers to fission product release to the 

atmosphere, such as the reactor containment structure.

Shortly after the accident, the DOE also supported an extensive research 

program, known as the “TMI-2 Accident Evaluation Program,” to develop a 

consistent understanding of the accident. The primary objective of the 

program was to develop an understanding of core-damage progression in the 

upper core region; the heatup and the formation and growth of the molten 

central region of the core; the relocation of approximately 19 metric tons of 

debris to the lower head; and the release of fission products to the reactor 

vessel and containment.

Collaboration between the U.S. Government and nuclear industry 

organizations also yielded important post-accident research. In 1980, four 

organizations—the General Public Utilities (GPU), Electric Power Research 

Institute (EPRI), NRC, and DOE—formed a group known as “GEND,” 

signing a coordination agreement to implement the TMI-2 Information and 

Examination Program. This program executed research and development 

At left is a page recorded at 

the NRC Operations Center 

on the second day of the 

accident showing temperature 

readings that were measured 

by plant technicians with a 

handheld voltage meter on 

the wires from reactor core 

exit thermocouples. These 

thermocouples were 

temporary installed to 

measure coolant temperatures 

above the reactor fuel in 

support of startup testing of 

the new reactor. We now 

know that many of these 

temperature readings were 

measured at newly formed 

false junctions located in the 

“liquefied fuel” regions of the 

core. Today, all pressurized 

water reactors are required to 

have redundant, qualified, 

Class 1E instrumentation for 

core exit thermocouples, subcooling margin monitors, and 

reactor coolant inventory 

monitors.
19

activities relating to the cleanup of TMI-2, and the study of the accident for 

the enhancement of nuclear power safety and reliability. The group 

documented the results of this program in a series of approximately

200 GEND and GEND-INF (informal) reports, as well as many other 

technical reports issued by the NRC, the DOE and its laboratories, EPRI, 

and GPU.

A cooperation agreement was signed in April 1984 by the DOE and 17 

Japan nuclear power organizations for a program of participation in the 

DOE research and development programs relating to the

TMI-2 cleanup. This Japan-U.S. agreement provided information 

exchanges, Japanese research staff at TMI-2 and DOE national laboratories, 

and Japanese funding for research and development activities. A total of 43 

engineers from 10 electric power companies, 3 reactor vendors, 2 

engineering companies, the Nuclear Power Engineering Test Center 

(currently the Japan Atomic Energy Agency), and the Japan Atomic Energy 

Research Institute (currently the Nuclear Regulation Authority) worked in 

almost every area of the TMI-2 cleanup project during the 5-year period.

In August and September of 1983, the core topography system, designed and 

built by DOE, was used to develop an ultrasonic profile of the void area in the 

upper reactor core region. The data and information obtained included the 

radial and axial extent of the reactor core cavity, the location of supported and 

unsupported fuel assembly end-fittings, and the location of the core cavity 

boundary with respect to structurally intact fuel assemblies. The analysis of 

this data supported upper plenum lift and defueling operations. Shown is the 

topographic model of the cavity in the upper core region based on this 

ultrasonic profile. This model is currently located at NRC Headquarters.
20

Supplement 1 of the NUREG/KM provides most of the NRC and DOE 

reports and presentation papers, which documented research and 

development activities relating to the TMI-2 accident and its unique 

recovery and cleanup. GEND reports are provided in Supplement 1. NRC 

annual reports provided summaries of NRC research activities (see DVD-2

folder NRC Annual Reports).

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 load debris into fuel

canisters positioned underwater in the reactor vessel. Later, a core boring 

machine (lower right) was used to break apart once liquefied materials.
21

6 Plant Recovery and Cleanup

By the close of the weekend of March 30 through April 1, 1979, TMI-2 was 

determined to be in a stable shutdown condition. Within 2 weeks, the 

Governor’s precautionary advisory to pregnant women and preschool-aged 

children to evacuate the area within a 5-mile radius of TMI was lifted. 

Within 1 month, the reactor was placed in natural circulation, with decay 

heat flowing to the condenser and out of the cooling towers. The purging of 

radioactive krypton gas from the reactor-building atmosphere, followed by 

the first entry into the reactor building by two utility engineers, was 

accomplished after the first anniversary of the accident. Shortly before the 

second anniversary, the reactor was placed in loss-to-ambient cooling mode, 

in which heat losses are transferred from component and piping surfaces 

into the reactor building’s ambient environment and out through the reactor 

building’s fan coolers. 

The reactor vessel head was removed in 1985, while the removal of loose 

fuel debris from the reactor vessel began later that year, and was completed 

in 5 years. Workers used numerous manual and hydraulically-powered,

long-handled tools to perform a variety of functions, such as pulling, 

grappling, cutting, scooping, and breaking up the core debris. In 1986, 

7 years after the accident, a special core-sampling drilling rig was used to

The first entry into the reactor building occurred on July 23, 1980 (shown). 

Heavy-duty outerwear provided protection from high-energy, low-penetration 

beta radiation. 
22

reveal the extent of the hard crust layer of the damaged core. Between 

1986 and 1990, the DOE shipped the fuel debris by rail to the DOE site at 

the Idaho National Engineering Laboratory (currently called Idaho National 

Laboratory), and placed the debris in wet pool storage for study and 

safekeeping. The evaporation of 2.3 million gallons of slightlycontaminated, accident-generated water at TMI was conducted over a 2- to 

3-year period, and completed in 1993.

In late 1993, TMI-2 was placed in NRC-approved, post-defueling,

monitored storage, a passive monitored state in which the plant will remain 

until both units are decommissioned simultaneously. From 2000 to 2001, 

the fuel debris was moved into NRC-approved aboveground dry storage at a 

DOE facility to await final disposal.

NRC Actions at TMI. The NRC played an active role as the regulator, first 

by responding to the accident, and then by approving and overseeing 

recovery activities by the licensee and its contractors. With the arrival of the 

NRC’s Region I inspectors during the first day of the accident, a team began 

to form and continued to expand throughout the weekend with the arrival of 

engineers, scientists, and public affairs specialists from headquarters and 

other regional offices. Early in 1980, the NRC established the TMI Program 

Water level in the reactor building basement reached the first stairwell 

landing, indicating about 8 feet of water. The submerged demineralizer system 

or “SDS” was designed and installed to cleanup the 700,000 gallons of highly 

contaminated basement water. The SDS started operations in September 1981 

after NRC approval and completed processing basement water in May 1982.
23

Office (TMIPO) within the NRC’s Office of Nuclear Reactor Regulation to 

provide overall direction for the TMI-2 cleanup operations and inspections 

(see NUREG-0698). About 30 NRC employees staffed the onsite TMIPO 

office during the first few years. NRC’s regulatory responsibilities in 

recovery operations included reviewing and approving the licensee’s 

proposals for recovery actions, overseeing the licensee’s implementation of 

approved activities, coordinating with other Federal and State government 

agencies on their activities in the recovery, and informing local officials and 

the public about the status of the recovery operation.

Important NRC actions during TMI-2 recovery are summarized below and 

discussed in detail in Supplement 1 to this NUREG/KM.

• issuance of the environmental assessment (NUREG-0591) and 

Commission order to use the EPICOR II system to decontaminate

intermediate-level radioactive accident water in the auxiliary building in 

October 1979

• creation of the NRC Special Panel on TMI-2 Radiation Protection 

Program in September 1979 to provide an independent review of the

Workers perform defueling operations from a shielded defueling work 

platform, which was located 9 feet above the reactor vessel flange. The 

platform had a rotating surface with 6-inch steel plates and a diagonal slit for 

access into the reactor vessel for removing debris.
24

licensee’s existing and planned radiation protection program during 

recovery and cleanup (NUREG-0640)

• issuance of the Commission order to implement the TMI-2 recovery 

technical specifications in February 1980 (NUREG-0647) 

• issuance of a research coordination agreement with the DOE, EPRI, and 

the licensee in March 1980 to jointly sponsor and participate in the TMI 

Information and Examination Program, and to obtain valuable 

information from the accident

• approval by the Commission in April 1980 to allow small radioactive 

releases for the purpose of data gathering and maintenance operations 

(SECY-80-175)

• issuance of the environmental assessment (NUREG-0662) and 

Commission order to purge radioactive krypton gas from the reactor 

building atmosphere in June 1980

The first piece of core debris was placed into the defueling 

canister in November 1985 (shown). The long-handled vice-grip 

tool was clamped onto an upper end fitting of a partial fuel 

element. A long-handled tamping tool (upper left) was used to 

tap the piece into the canister.
25

• issuance of the NRC action plan for cleanup operations in July 1980 

(NUREG-0698)

• issuance of the draft Programmatic Environmental Impact Statement 

(NUREG-0683) for public comment in August 1980 and 

implementation in February 1981

• creation of the public Advisory Panel for the Decontamination of Three 

Mile Island in November 1980 (see NUREG/CR-6252)

• issuance of the Commission Policy Statement endorsing the 

Programmatic Environmental Impact Statement in May 1981

• issuance of the safety evaluation report and order to use the submerged 

demineralizer system to process the highly-contaminated,

accident-generated water in the reactor building sump and reactor 

coolant system in June 1981 (NUREG-0796)

The NRC issued certificates of compliance to the DOE in April 1986 for

casks used to ship fuel debris by rail to the Idaho National Engineering 

Laboratory (INEL) for research and temporary storage. Each cask 

contained up to seven defueling canisters. Each rail shipment included up to 

three cask rail cars. A total of 342 defueling canisters were shipped to INEL 

in 22 trips between 1986 and 1990.
26

• issuance of a March 1982 amendment to the memorandum of 

understanding with the DOE to accept the entire reactor core and 

highly-radioactive solid waste for research and long-term storage (see 

Appendix A to Revision 2 of NUREG-0698)

• approval, in November 1983, of the licensee’s safety evaluation for the 

refurbishment and use of the reactor building polar crane for defueling 

operations 

• issuance of Supplement 1 to the Final Programmatic Environmental 

Statement (NUREG-0683) on dealing with occupational radiation dose 

in October 1984

• issuance of certificates of compliance in April 1986 for three shipping 

casks to be used for shipment of fuel debris to DOE by rail

• issuance of Supplements 2 and 3 to the Final Programmatic 

Environmental Statement (NUREG-0683) on the final disposal of 

2.3 million gallons of slightly-contaminated, accident-generated water 

in June 1987, and dealing with post-defueling monitored storage and 

subsequent cleanup in August 1989

• approval in September 1989 to use the evaporator for the final disposal 

of 2 million gallons of accident-generated water

TMI-2 Independent Spent Fuel Storage Installation located at DOE’s Idaho 

National Laboratory for interim storage of the TMI-2 core debris.
27

• issuance of two amendments to the facility operating license in 

September and December 1993 to issue a possession-only license and 

issue technical specifications for post-defueling monitored storage

The NRC Headquarters wrapped up onsite involvement at TMI-2 by the 

time that the agency terminated the TMI-2 Project Directorate in 

February 1988. The NRC’s TMI resident inspector office took over the 

inspection program for TMI-2 and a headquarters project directorate 

assumed responsibility for the technical review and project management 

functions. In September 1993, the NRC approved “post-defueling monitored 

storage” at TMI-2 and associated license conditions and technical 

specifications. The last meeting (78th overall) of the 10-member public 

Advisory Panel for the Decontamination of Three Mile Island Unit 2 was 

held in September 1993 (see NUREG/CR-6252 for lessons learned). See 

Supplement 1 to this NUREG/KM for more documents covering recovery 

and cleanup activities.

Timeline. The timeline feature on the DVD provides a summarized 

chronology of key recovery milestones and NRC actions. Users may read a 

short description of many of the actions by clicking on the text of the 

timeline in the interactive window of the DVD.

Status Reports. Several document collections in Supplement 1 to this 

NUREG/KM provide informative daily, weekly, and annual summaries of 

TMI-2 recovery and cleanup experiences. These status documents, which 

are related to topics discussed in all volumes and sections of this 

NUREG/KM, are provided in the following document collections in 

Supplement 1:

• NRC TMI Program Office (TMIPO) weekly status reports (see DVD

folder TMI Program Office Weekly Status Reports)

• preliminary notification reports—an early notice of an event of possible

safety or public interest significance issued by TMIPO or other NRC 

offices (see DVD folder NRC Preliminary Notifications)

• NRC annual reports to the President of the United States (see DVD

folder NRC Annual Reports)

• DOE reports, such as annual and lessons-learned reports, and periodical 

publications (see DVD folder DOE/National Laboratory Status Reports)
28

• licensee event reports—a written report of a reportable event submitted

by the licensee to the NRC (see DVD folder Licensee Event Reports)

• licensee summary reports required by regulatory requirements (see 

DVD folder GPU Status Reports)

NRC’s Harold Denton, Governor Richard Thornburgh, President Jimmy 

Carter, and Rosalynn Carter tour the TMI-2 control room on April 1, 1979.
29

7 Retrospectives

30th Anniversary. For the 30th anniversary of the TMI-2 accident, the 

NRC’s Office of Nuclear Regulatory Research (RES) hosted a special 

all-day event entitled, “The Accident at Three Mile Island, 

30th Anniversary, A Look Back: Preserving the Institutional Memory.” The 

event featured several presentations, including an overview of the accident 

by Brian Sheron, Director of the NRC’s Office of Nuclear Regulatory 

Research; perspectives from TMI-2 Reactor Operator Edward Frederick; 

lessons learned from TMI-2 by Gary Holahan, Deputy Director of the 

NRC’s Office of New Reactors, and former member of the TMI-2 Lessons 

Learned Task Force; and an historical perspective by NRC Historian 

Samuel Walker.

Following the individual presentations, the NRC hosted a panel discussion 

titled “Remembering the Accident.” The panel included a distinguished 

group, all of whom made key decisions during the accident: Richard 

Thornburgh, former Governor of the State of Pennsylvania; Harold Denton, 

former Director of the NRC’s Office of Nuclear Reactor Regulation and the 

lead Federal onsite manager; and Jessica Mathews, former assistant to 

President Jimmy Carter.

A press conference during the early days of the accident with 

Pennsylvania Governor Richard Thornburgh (right) and the 

NRC’s Harold Denton.
30

In April 1984, a comprehensive video mapping of the upper reactor core 

region between the plenum and rubble bed was completed. Video snapshots 

were assembled into a mosaic panoramic view of the rubble bed and core 

periphery. Videos of the rubble bed showed broken fuel rods scattered around, 

fuel rod internal springs, intact fuel pellets, control-rod assembly end 

couplings, and partially intact fuel assemblies around the periphery of the 

reactor core region. The video also showed unsupported partial fuel 

assemblies hanging from the underside of the upper plenum grid section 

which had to be removed before plenum lifting. This map supported planning 

of defueling operations and eventually the removal of fuel debris.
31

35th Anniversary. For the 35th anniversary of the TMI-2 accident, RES

hosted a special NRC research seminar event entitled, “The 

35th Anniversary of the Three Mile Island Nuclear Power Plant Accident 

of 1979: Working at TMI During and Following the Accident.” The seminar 

featured a presentation by Mr. Gordon Skillman, a current member of 

NRC’s Advisory Committee on Reactor Safeguards, who was an immediate

responder to the TMI-2 accident. As an employee of Babcock and Wilcox

during and after the accident, he served for 7 years of the stabilization and 

cleanup of TMI-2 as recovery support engineering manager and later as the 

defueling manager.

The presentation covered Mr. Skillman’s firsthand experiences while 

working on technical issues involving plant and reactor core stabilization, 

accident water cleanup, and early defueling the damaged core. Mr. Skillman 

shared his personal experiences while living in a nearby community and

working closely with people from the utility, many contractors, the NRC, 

the DOE, national laboratories, and Pennsylvania’s and Maryland’s 

environmental agencies.

Moments in NRC History. As part of the video series on NRC history, the 

Office of the Secretary and the Office of Public Affairs prepared a video 

entitled, “Moments in NRC History, Three Mile Island, March 28, 1979.” 

The video features a short documentary by the NRC’s historian, Dr. Thomas 

Wellock. Dr. Wellock studies nuclear power’s history for its relevance to 

the NRC today and to capture important insights for future generations. This 

video recounts the plant response during the accident, the emergency 

response to the accident, improvements to plant safety, and current status of 

the plant.

The DVD provides a multimedia presentation of these events (see DVD

folders, 30th Anniversary Seminar, 35th Anniversary Seminar, and 

Moments in NRC History).
32
33

8 DVD Navigation and Interpretation

This knowledge management guide is an HTML-based collection of 

information, documents, videos, and photos related to the 1979 accident at 

the Three Mile Island nuclear power plant. This interactive feature is 

provided on the DVD to help you navigate through the historical records.

Refer to the “Readme” file located on any DVD for viewing instructions.

Navigation

• Main welcome page. From the welcome page, you can navigate the 

different sections of the guide using the blue tabs from the menu on the 

left side of the page. Each tab is linked to a page that contains one or 

more subtabs that appear to the right of the tab. Each tab corresponds to 

a document collection and each subtab links to a folder of documents. 

This interactive feature will prompt you to load the appropriate DVD to 

retrieve the document, if necessary. Additionally, there is a photo 

gallery, interactive timeline, and a document index (green tab). You 

may also click on the text box on the timeline for a short description.

• Document retrieval. Documents can be accessed from the document 

page (see figure below) linked to the subtab. Next to each document is a 

hyperlink which will display the associated document, photo, or video. 

Because the document collection spans several DVDs, you may be 

prompted to insert a different DVD as you navigate the guide. A sorting 

feature is provide on select columns on the document page.

• Document searches. A simple keyword search feature is provided on 

the welcome page and each document page. A search is applied to a list 

of all documents on all DVDs in this NUREG/KM. This feature 

searches words in the file name.

• Document lists. Several convenient lists of documents on the DVD can 

be viewed from the “Document Folder Index” tab. These lists are also 

provided in spreadsheet format in the “Common” folder on the DVD

(located in the “Documents” folder). A list of more than 25,000 TMI-2 

records in the Public Legacy Library is included in the spreadsheet.

• Alternative. Documents are titled and arranged in topical folders on the 

DVD (located in the "Documents" folder) to provide a usable alternative 

to the interactive guide. The document can be accessed directly on the 

DVD using a file explorer.
34

Things to Keep in Mind

• Legacy documents. Many of the documents on the DVD are historical 

in nature and might contain information that is obsolete or superseded 

by current regulations and research results. The historical documents 

provided on the DVD are for historical reference only and are not 

official NRC records. Please refer to the NRC’s public website

(http://www.nrc.gov) for current information on regulations, policy 

statements, regulatory guidelines, regulatory processes, and research 

results.

• Units of measure. The unit of measure (in English units or the 

International System of Units) that was used in the original source 

document was used in this digest. A conversion chart is provided on the 

back cover.

• Abbreviations. A small set of abbreviations was used throughout this 

report in order to improve readability: ALARA (as low as reasonably 

achievable), CFR (U.S. Code of Federal Regulations), DOE, DVD, 

EPRI, GEND, GPU, INEL, NRC, NUREG, NUREG/CR, NUREG/KM, 

PDMS, and TMI-2. Abbreviations that were less frequently repeated in 

the report were spelled out at the beginning of each subsection or 

paragraph that contained them.

• Recovery vs. cleanup. The term “recovery” is used in this NUREG/KM 

to mean actions taken to keep the plant in a stable condition and to 

prevent the inadvertent release of radioactivity. The term “cleanup” is 

used to mean actions taken to decontaminate and defuel the plant and 

dispose of radioactive waste. These two terms are often used 

interchangeably for certain actions.

• EPRI and GPU documents. Documents generated by EPRI and GPU 

are generally not provided on the DVD unless the documents were 

submitted to the NRC or funded by DOE.

• “GPU” and “licensee.” Unless otherwise noted, the GPU Corporation 

and its subsidiaries (including GPU Service Corporation, GPU Nuclear 

Corporation, and Metropolitan Edison Company) are referred to 

collectively in a historical context as “GPU” or the “licensee” in the text 

of this NUREG/KM and document filenames.
35

• Document accession number. Each document and each enclosure of a 

document that was cataloged in the Agencywide Documents Access and 

Management System (ADAMS) Public Legacy Library was assigned a 

unique accession number. This number can be found on the first page of 

each document. Each enclosure to a transmittal letter was typically 

assigned its own accession number.

• Document filename. The filenames used on the DVD typically contain 

the date of the document (generally the date of the transmittal letter); 

originating organization (e.g., NRC or GPU); document type 

(e.g., safety evaluation or system description); short title; document 

revision, if any; and reference date of previous correspondence, if any. 

Technical reports by the NRC (e.g., NUREGs), DOE, and national 

laboratories start with the report’s identification number, short title, and 

year and month issued. See examples below.

(1990-01-18) GPU, Defueling Completion Report, Rev. 3 (re 08-18, 10-09-1989)

NUREG-0698, Rev. 2, NRC Plan for Cleanup Operations at TMI-2 (1984-03)

• Documents, photographs, and diagrams in this NUREG/KM and DVD 

were copied from the best available (surviving) sources. Photographs 

were generally taken by GPU and DOE contractors.

A typical document page listing the contents of a document folder. Columns 

can be sorted. Keywords in document file names can be searched. The 

hyperlink directs you to the document, photo, or video. 
36

The certificate of appreation given to NRC staff who contributed to the 

NRC’s response to the accident. By the end of the second week, over 200 

NRC staff were badged for site access, or about 10 percent of all external 

responders at TMI. Names of NRC staff who responded to the accident at 

the TMI site and offsite response centers are discsussed in the Rogovin 

report (see NUREG/CR-1250, Volume 2, Part III, Appendix III.2).
37

9 Contributions to the Main Report

 (NUREG/KM-0001, Overview)

Knowledge

Harold Denton

Edward Frederick

Gary Holahan

Don Marksberry

Jessica Mathews

Brian Sheron

Gordon Skillman

Governor Richard Thornburgh

J. Samuel Walker

Thomas Wellock

Management

Don Marksberry

Felix Gonzalez

Kenneth Hamburger

Theodore Smith

Anita Aikins-Afful

Robert Norman

David Aird

Ian Gifford

Brian McGrattan

Amy Bonaccorso

Tom Kardaras

Mark Henry Salley

and

The NRC Print Shop and Publications Staff

Document Collections

NRC’s Agencywide Documents Access and Management System 

Publications Branch of the NRC’s Office of Administration

NRC’s Office of the Secretary

U.S. Department of Energy

Idaho National Laboratory

Dickinson College Community Studies Center

Pennsylvania State University Engineering Library

National Archives and Records Administration
38



CONVERSIONS

Radiation Dose

1 mrem (1 millirem, 10-3) = *10 microsieverts (10 μSv, 10-5)

100 mrem = *1 millisievert (1 MSv)

1 rem = *10 mSv

100 rem = *1 Sv

Radioactive Concentration

27 picocuries (27 pCi, 2.7 × 10-11) = *1 becquerel (1 Bq)

1 millicurie (1 mCi, 0.001) = *37 megabecquerels (37 MBq, 3.7 × 107)

1 curie (1 Ci) = *37 gigabecquerels (37 GBq, 3.7 × 1010)

Radiation Absorbed Energy

1 roentgen = *0.877 rad = *0.00877 Gy

100 rad = *1 gray (Gy)

Length

1 inch (in) = *2.54 centimeters (cm)

1 foot (ft) = 0.3048 meter (m)

Volume and Weight

1 gallon (gal) = 3.7854 liters (l)

1 pound (lb) = 0.4536 kilograms (kg)

1 ton (U.S.) = *2000 lb = 907.1847 kg

Pressure

1 pound per square inch (psi) = 6.8948 kilopascals (kPa)

1 atmosphere (atm) = *101.325 kPa

Temperature

Degrees Celsius (°C) = 5/9 × (°F - 32) 

Degrees Fahrenheit (°F) = (9/5 × °C) + 32

* Exact conversion factors

NUREG/KM-0001, Revision 1

June 2016