NRC

REACTOR OVERSIGHT PROCESS

CONTENTS

	 1	 INTRODUCTION

	 1	 REACTOR OVERSIGHT PROCESS

	 2	 CORNERSTONES OF SAFE OPERATION

	 3	 CROSS-CUTTING AREAS

	 4	 MEASURING AND INSPECTING NUCLEAR PLANT PERFORMANCE

	 6	 ASSESSMENT OF PLANT PERFORMANCE

	 7	 NRC RESPONSE TO PLANT PERFORMANCE

	 8	 VIOLATIONS OF NRC REQUIREMENTS

	 9	 PERFORMANCE INFORMATION AVAILABLE TO THE PUBLIC

10	 GLOSSARY

NRC REACTOR OVERSIGHT PROCESS / DECEMBER 2006

INTRODUCTION

The Nuclear Regulatory Commission’s mission is to ensure adequate protection of public health and safety in the peaceful uses of 

nuclear materials, including nuclear power 

plants. The agency does not operate the 

plants. Rather it regulates the safe operation 

of commercial nuclear power plants by mandating requirements for the design, construction and operation of such plants.

The safety of these plants has always been 

important as an accident could result in the 

release of radioactive material and potentially harm public health and the environment. 

NRC’s oversight has become even more important as the U.S. considers the potential resurgence of nuclear power in helping to meet 

the nation’s growing energy needs.

The NRC conducts a rigorous process for 

licensing plants to allow them to operate, as 

well as licensing individual plant operators. 

The agency provides continuous oversight of 

plant operations to verify they are being conducted in accordance with regulations.

The NRC also establishes plant-specific technical specifications which plant operators 

(i.e., licensees) must follow to ensure that the 

proper combination of safety-related equipment is available to safely shut down the plant 

in the event of an accident. The NRC has full 

authority to take whatever action is necessary to protect public health and safety and 

may demand immediate licensee actions, up 

to and including a plant shutdown.

The commercial nuclear power industry in the 

United States is a mature industry with 104 

operating reactors under NRC oversight. 

More than two-thirds of the plants have been 

operating for more than 20 years, and all have 

operated for 10 years or more. All the evidence 

suggests that the safety and reliability of the 

nuclear industry has improved markedly since 

the late 1980’s and early 1990’s. The number of automatic shutdowns, the number of 

significant safety problems, and the number 

of unplanned outages caused by equipment 

problems have all decreased since 1990. (See 

Glossary for definitions of terms).

Additional information about the NRC is available on its website: http://www.nrc.gov

REACTOR OVERSIGHT PROCESS

The NRC’s Reactor Oversight Process is the agency’s 

program to inspect, measure, and assess the safety 

performance of commercial nuclear power plants 

and to respond to any decline in performance. 

It reflects the Commission’s strategic goals for safety, 

security, openness, and effectiveness. 

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NRC

REACTOR OVERSIGHT PROCESS

The process spells out clearly what a nuclear plant 

operator and the public — can expect from the NRC 

with good plant performance and what can be expected from the NRC if performance declines. 

The oversight process calls for:

Focusing inspections on activities where the 

potential risks are greater.

Applying greater regulatory attention to nuclear 

power plants with performance problems, while 

maintaining a normal level of regulatory attention on facilities that perform well. 

Using objective measurements of the performance of nuclear power plants.

Giving both the public and the nuclear industry 

timely and understandable assessments of plant 

performance.

Responding to violations of regulations in a predictable and consistent manner that reflects the 

potential safety impact of the violations.

CORNERSTONES

OF SAFE OPERATION

The Reactor Oversight Process is, of course, 

anchored in the NRC’s mission to ensure public 

health and safety in the operation of commercial 

nuclear power plants. The objective is to monitor 

performance in three key areas —

Reactor Safety—avoiding accidents and reducing the consequences of accidents if they occur;

Radiation Safety—for both plant workers and 

the public from unnecessary radiation exposure 

during routine operations; and 

Safeguards—protection of the plant against 

sabotage or other security threats.

To monitor and measure plant performance, the 

oversight process focuses on seven “cornerstones” 

which support the safety of plant operations in the 

three key areas. These are described below. 

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Reactor Safety Area

#1 Initiating Events—Any potential occurrence 

that could disrupt plant operations and challenge 

safety functions is an initiating event. This cornerstone focuses on limiting the occurrence of these 

type of events. These events could include equipment failures leading to a plant shutdown, shutdowns with unexpected complications, or large 

changes in the plant’s power output.

#2 Mitigating Systems—These are safety systems designed into each plant which alleviate the 

effects of initiating events. Mitigating systems can 

prevent an accident or reduce the consequences of a 

possible accident. This cornerstone monitors the 

function of these safety systems through periodic 

testing and actual performance.

#3 Barrier Integrity—There are three important barriers between the highly radioactive fuel 

inside the reactor and the public and the environment outside the plant. These barriers are: (1) the 

sealed rods containing the fuel pellets, (2) the heavy 

steel reactor vessel and associated piping, and (3) 

the reinforced concrete containment structure 

surrounding the reactor. The integrity of the fuel 

rods, the vessel, and the piping is continuously 

checked for leakage, while the ability of the containment structure to prevent leakage is measured on a 

regular basis.

#4	 Emergency Preparedness—Each nuclear 

plant is required to have comprehensive emergency 

plans to effectively respond to a possible accident. 

This cornerstone measures the effectiveness of the 

plant staff in carrying out emergency plans. Such 

emergency plans are tested every two years involving 

plant staff as well as local, state, and, in some cases, federal agencies. The plant staff itself conducts 

emergency exercises even more frequently.

Radiation Safety Area

#5 Occupational Radiation Safety—NRC 

regulations set a limit on radiation doses received by 

plant workers. Exposures could be from poorly con2
NRC REACTOR OVERSIGHT PROCESS / DECEMBER 2006

trolled or uncontrolled radiation areas or radioactive materials located at the plant. This cornerstone 

monitors the effectiveness of the plants’ program to 

control and minimize those doses.

#6 Public Radiation Safety—NRC regulations 

are designed to protect public health and safety 

from exposure to radioactive materials that may be 

released into the public domain. This cornerstone 

measures the procedures and systems designed to 

minimize radioactive releases from a nuclear plant 

during normal operations and to keep those releases 

within federal limits.

Safeguards Area

#7 Physical Protection—Nuclear plants are 

required to have well-trained security personnel 

and a variety of protective systems to guard vital 

plant equipment, as well as programs to assure that 

employees are constantly fit for duty through drug

and alcohol testing. This cornerstone measures 

the effectiveness of the security and fitness-forduty programs.

Although the NRC actively oversees the security and 

safeguards activities and facilities at nuclear plants, 

the inspection and assessment information is not 

publicly available to ensure that potentially useful 

information is not provided to a possible adversary 

(only the cover letter is publicly available).

CROSS-CUTTING AREAS

In addition to the cornerstones, the Reactor Oversight Process features three “cross-cutting” areas, so 

named because they can affect each of the cornerstones across all the key areas. 

These are:

Human performance

Workers’ ability to raise safety issues (Also 

known as “safety-conscious work environment”) 

Finding and fixing problems (plant owners 

corrective action program)

The review and assessment of these cross-cutting 

areas have an important role in the Reactor Oversight Process. They are considered during all NRC 

inspections and are covered during periodic plant 

assessments.

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 REACTOR OVERSIGHT FRAMEWORK 

Protect Public Health And Safety in the Use of Nuclear Power

Reactor Safety Safeguards

Initiating 

Events

Public 

Radiation

Emergency 

Preparedness

Barrier 

Integrity

Mitigating 

Systems

Occupational 

Radiation 

Physical 

Protection

Radiation Safety

Human Performance Safety Conscious Work Environment Problem Identification and Resolution CROSS-CUTTING 

AREAS:

MISSION:

KEY AREAS: 

CORNERSTONES:

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NRC

REACTOR OVERSIGHT PROCESS

MEASURING AND INSPECTING

NUCLEAR PLANT PERFORMANCE

Nuclear plant performance is measured and 

assessed by a combination of objective performance 

indicators reported by the licensee and by NRC 

inspection findings. They are both closely focused 

on those plant activities having the greatest impact 

on safety and overall risk. While performance indicators can provide insights into plant performance 

for selected areas, the NRC’s inspection program 

provides greater depth and breadth of information 

for consideration by the NRC in assessing plant 

performance.

Inspection Findings + Performance Indicators = Plant Assessment

In addition, the NRC conducts both periodic and 

annual reviews of the effectiveness of each utility’s 

programs to identify and correct problems. These 

programs, and their inputs and products, are 

described in more detail in the following sections. 

Performance Indicators

Each performance indicator has criteria for measuring acceptable performance. As in all industrial 

activities, nuclear power plants are not error-free or 

risk-free. Equipment problems and human errors

will occur. Each performance indicator determines

acceptable levels of operation within substantial 

safety margins. The criteria are designed to be 

objective and reflect risk according to established 

safety margins. Performance indicators for each 

cornerstone are shown in the following table. 

Safety Cornerstone Performance Indicators

#1 Initiating Events • Unplanned reactor shutdowns (automatic and manual)

• Loss of normal reactor cooling system following unplanned shutdown

• Unplanned events that result in significant changes in reactor power

#2 Mitigating Systems • Safety system availability and reliability 

• Safety system failures

#3 Barrier Integrity • Fuel cladding (measured by radioactivity in reactor cooling system)

• Reactor cooling system leak rate

#4 Emergency Preparedness • Emergency response organization drill performance

• Readiness of emergency response organization

• Availability of notification system for area residents

#5 Occupational Radiation Safety • Compliance with regulations for controlling access to radiation areas

 in plant

• Uncontrolled radiation exposures to workers greater than 10 percent

 of regulatory limit

#6 Public Radiation Safety • Effluent releases requiring reporting under NRC regulations and 

 license conditions

#7 Physical Protection • Security system equipment availability

• Personnel screening program performance

• Employee fitness-for-duty program effectiveness

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NRC REACTOR OVERSIGHT PROCESS / DECEMBER 2006

Use of Performance Indicators

Each indicator is measured against the criteria 

using a color-coded system for safety performance.

Green indicates performance within an expected performance level where the associated cornerstone objectives are met.

White represents performance outside an expected 

range of nominal utility performance but related 

cornerstone objectives are still being met.

Yellow indicates related cornerstone objectives 

are being met, but with a minimal reduction in the

safety margin.

Red signals a significant reduction in safety margin 

in the area measured by the performance indicator. 

The performance indicator data is evaluated and 

integrated with findings of the NRC inspection program to provide a broad assessment of the plant’s 

safety performance. 

The indicators are compiled by the licensee and 

reported to the NRC on a quarterly basis. Following compilation and review by the NRC staff, the 

quarterly performance indicators are posted on the 

NRC’s web site: http://www.nrc.gov.

The Reactor Oversight Process includes inspections 

by NRC staff with a variety of backgrounds and 

skills – among them are plant operations, engineering, radiation protection, emergency preparedness, 

and security.

The inspection program is founded on “baseline” 

inspections common to all nuclear plants. The baseline inspection program, based on the cornerstones, 

focuses on activities and systems that are "risk 

significant," that is, those activities and systems 

that have a potential to trigger an accident, can 

mitigate the effects of an accident, or increase the 

consequences of a possible accident. Additionally, 

inspections beyond the baseline program are set 

for plants with performance below established thresholds, as 

assessed through information gained 

from performance indicators and NRC inspections.

The inspection program uses a “risk-informed” 

approach to select areas to inspect within each cornerstone. The inspection areas were chosen because 

of their importance to potential risk, past operational experience, and regulatory requirements. 

The baseline inspection program has three parts:

Inspection of areas not covered by performance 

indicators or where a performance indicator 

does not fully cover the inspection area; 

Inspections to verify the accuracy of a licensee’s 

reports on performance indicators; and 

A thorough review of the licensee’s effectiveness 

in finding and resolving problems on its own.

Inspections beyond the baseline program are performed in response to specific events at a plant or 

changes in the plant’s performance. For example, if a 

performance indicator or inspection finding shows 

increased safety significance, the NRC may conduct 

a special or supplemental inspection to review the 

situation and assess the effectiveness of the plant operator’s response. For more complicated situations, 

the agency may dispatch an “augmented” inspection 

team, bringing in added experts from other NRC 

regions or headquarters staff. For more serious 

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Example of Performance Indicators on the Web
NRC

REACTOR OVERSIGHT PROCESS

Green indicates a finding of very low safety

 significance; 

White represents a finding of low to moderate

 safety significance; 

Yellow indicates a finding of substantial safety 

 significance; and

Red is a finding of high safety significance.

Remaining inspection findings — which may have 

an effect on plant risk — are subjected to a more 

thorough risk assessment, using the next phase of 

the Significance Determination Process. This more 

detailed assessment may involve NRC risk experts 

from the appropriate regional office and further 

review by the utility’s plant staff. The final outcome 

of the review — evaluating whether the finding is 

green, white, yellow, or red — is used to determine 

further NRC actions that may be needed.

Quarterly Plant Assessments

Each calendar quarter, the resident inspectors and 

regional inspection staff review the performance of 

all nuclear power plants in that region, as measured 

by the performance indicators and by inspection 

findings. Every six months this review involves a 

more detailed assessment of plant performance that 

includes staff from NRC headquarters, the regions, 

and resident inspectors as well as preparation of a 

performance report. Also every six months, based 

on plant performance reviews, NRC inspection 

plans for each reactor are determined for the following 18-month period.

Annual Performance Reports and

Public Meetings

Annual performance reports are available on 

the agency’s web site at: http://www.nrc.gov/NRR/

OVERSIGHT/ASSESS/index.html#plantassess. In addition, each year the NRC staff holds a public meeting 

with the licensee at each plant to discuss the previous 

year’s performance. This provides individuals living 

near the plant an opportunity to find out the status 

of a plant’s safety performance and talk with NRC 

staff.

events, a high-level “Incident Investigation Team” 

may be formed. 

The inspection program also includes review of 

cross-cutting areas of human performance, the 

“safety-conscious work environment,” and how the 

plant operator finds and fixes problems. The Reactor Oversight Process was revised in July 2006 to 

enhance the ability of the NRC to detect a declining safety culture. Adjustments were also made to 

selected baseline, event response and supplemental 

inspection procedures. 

The inspections are performed by NRC resident 

inspectors stationed full time at each nuclear power 

plant and by inspectors based in one of the four NRC 

regional offices or in NRC headquarters in Rockville, 

Maryland. The regional offices are located in King 

of Prussia, Pennsylvania; Atlanta, Georgia; Lisle, Illinois; and Arlington, Texas.

Inspection reports are issued for all inspections. 

Baseline inspection reports, compiled by the resident 

inspectors and inspection specialists are issued at the 

close of each calendar quarter. Special and supplemental inspection reports are issued several weeks 

after completion of those inspections. The inspection 

reports are available on the NRC web site’s “Library” 

link, in the NRC’s online document collection called 

“ADAMS,” and from the Public Document Room 

at NRC headquarters. 

ASSESSMENT OF PLANT

PERFORMANCE

Significance Determination Process

The inspection staff uses a process, called the “Significance Determination Process,” to help inspectors 

determine the safety significance of inspection findings. This process provides an initial screening to 

identify those inspection findings that do not result 

in a significant increase in plant risk and thus need 

not be analyzed further (a “green” finding). 

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NRC REACTOR OVERSIGHT PROCESS / DECEMBER 2006

if there are signs of declining performance. This 

approach to enforcement is intended to be more 

predictable than previous practices by linking 

regulatory actions to performance criteria. The 

process uses five levels of regulatory response

with NRC regulatory review increasing as plant 

performance declines. The first three levels involve response by the appropriate regional office. 

The next two levels call for an agency response,

 involving senior management attention from both 

headquarters and regional offices. 

The Reactor Oversight Process uses various tools for 

dealing with declining plant performance and violations. These tools are used in a predictable manner 

that is commensurate with the decreased safety 

performance. NRC actions may include meetings 

with the plant operator, additional inspections, and 

required stronger action by the agency, including a 

civil order or even the suspension of the operating 

license. (See NRC Response Plan)

Additionally, NRC 

senior management 

reviews the adequacy 

of agency actions for 

plants with significant 

performance problems. The managers 

also take a wider view 

both of the overall industry performance and of the 

performance of the agency’s regulatory programs. 

The performance of plants requiring heightened 

agency scrutiny is then discussed during a public 

meeting with the NRC Commissioners at the agency’s Rockville, Maryland, headquarters.

NRC RESPONSE TO PLANT

PERFORMANCE

The quarterly reviews of plant performance, using 

both the plant operator’s reported performance indicators and NRC inspection findings, determines 

what additional action, if any, the NRC will take 

NRC Response Plan or “Action Matrix”

Assessment of Plant Performance

 (in order of increasing safety significance)

NRC Response

I. All performance indicators and cornerstone inspection 

findings GREEN

• Cornerstone objectives fully met

Normal Regional Oversight

• Routine inspector and staff Interaction

• Baseline inspection program 

• Annual assessment public meeting

II. No more than two WHITE inputs in different cornerstones

• Cornerstone objectives fully met

Response at Regional Level

• Public meeting with NRC and plant management

• Plant operator corrective actions to address WHITE inputs 

• NRC inspection follow up on WHITE inputs and corrective action

III. One degraded cornerstone (two WHITE inputs or one 

YELLOW input or three WHITE inputs in any strategic area)

• Cornerstone objectives met with minimal reduction in safety 

margin

Response at Regional Level

• Public meeting with NRC and senior regional management and plant management

• Plant operator self-assessment with NRC oversight

• Additional NRC inspections focused on cause of degraded performance

IV. Repetitive degraded cornerstone, multiple degraded corner

stones, or multiple YELLOW inputs, or one RED input

• Cornerstone objectives met with longstanding issues or 

significant reduction in safety margin

Response at Agency Level

• Public meeting with NRC Executive Director for Operations and senior plant 

management

• Plant operator improvement plan with NRC oversight

• NRC team inspection focused on cause of degraded performance

• Demand for Information, Confirmatory Action Letter, or Order

V. Unacceptable Performance Response at Agency Level

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NRC

REACTOR OVERSIGHT PROCESS

failure to report required information, failure 

to obtain NRC approval for plant changes, failure to maintain accurate records, or failure to 

provide the NRC with complete and accurate 

information.

Incidents with actual safety consequences, 

including radiation exposures above NRC limits, releases of radioactive material above NRC 

limits, or failure to notify government agencies 

when emergency response is required.

PERFORMANCE INFORMATION

AVAILABLE TO THE PUBLIC

Information on plant performance is updated each 

quarter on the NRC’s web site where performance 

histories and inspection findings are also available. Full inspection reports are available on the 

web site, in the NRC’s online document collection called “ADAMS,” and from the NRC’s Public 

Document Room.

The performance indicators and the assessment of 

inspection findings are placed on the NRC web site

using the color notation of their significance 

green, white, yellow, or red. The statistics and NRC 

inspection findings which underlie the color 

notation are also posted on the web site. 

The Reactor Oversight Process is instrumental 

to the NRC’s highest priority and commitment to 

the day-to-day business of overseeing operating 

reactors to make sure they continue to operate safely.

Additional information on the Reactor Oversight 

Process is available at NRC’s web site at: http://www.

nrc.gov/NRR/OVERSIGHT/ASSESS/index.html.

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VIOLATIONS OF NRC

REQUIREMENTS

Each violation of NRC requirements found during 

NRC inspections is evaluated to determine its effect 

on plant safety and risk. If the violation is of very 

low safety significance, it is discussed in NRC’s inspection report with no formal enforcement action. 

Through its corrective action program, the plant 

operator is expected to deal with the violation correcting the violation and taking steps to prevent a 

recurrence. The issue may also be reviewed during 

future NRC inspections.

If the NRC risk evaluation finds that the violation 

has higher safety significance, a Notice of Violation 

will be issued. A Notice of Violation may also be 

issued if the licensee fails to correct a violation of 

low safety significance in a reasonable period of time 

or if a violation is found to be willful. 

The Notice of Violation requires the plant operator to respond formally to the NRC identifying its 

actions to correct the violation and what steps it will 

take to prevent the violation from occurring again. 

The agency then reviews the operator’s actions in a 

later inspection.

Normally, these violations are not the subject of a 

fine. However, some violations may warrant a fine 

because of their unusual significance. These violations are likely to be uncommon. Possible examples 

include exceeding a safety limit specified in a reactor 

license or the inadvertent startup of a reactor.

In addition, some violations call for the traditional 

enforcement approach, including the possible issuance of fines. 

Examples include:

Discrimination against workers for raising safety 

issues or other willful violations.

Actions that may adversely affect the NRC’s 

ability to monitor utility activities, including 

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NRC REACTOR OVERSIGHT PROCESS / DECEMBER 2006

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PERFORMANCE INFORMATION ON NRC WEBPAGES

Step 1

Click here on plant name

http://www.nrc.gov/NRR/OVERSIGHT/ASSESS/index.html

Step 2

Step 3

Click here for details

Click here for details
NRC

REACTOR OVERSIGHT PROCESS

Reactor Oversight Process—The NRC’s program to 

inspect, evaluate, and assess the safety performance 

of commercial nuclear power plants.

Regulatory Conference—A meeting between the 

NRC staff and a utility to discuss potential safety 

issues or to discuss a change in performance as 

indicated by a declining performance indicator or inspection finding. These meetings are open to public 

observation unless they cover security issues, NRC 

investigation findings, or similar sensitive topics.

Resident Inspector—An NRC inspector assigned to 

a nuclear plant on a full-time basis. Each site has at 

least two resident inspectors.

Risk-informed—Incorporating an assessment 

of safety significance or relative risk in NRC 

regulatory actions.

Safety Conscious Work Environment—An 

environment in which employees feel free to raise 

safety concerns, both to their management and to 

the NRC, without fear of retaliation and where such 

concerns are promptly reviewed, given the proper 

priority based on their potential safety significance, 

and appropriately resolved with timely feedback to 

employees.

Safety Culture—the assembly of characteristics 

and attitudes in organizations and individuals 

which establishes that, as an overriding priority, nuclear plant safety issues receive the attention 

warranted by their significance.

Significance Determination Process—The 

process used by the NRC staff to evaluate inspection 

findings to determine their safety significance. This 

involves assessing how much the inspection findings 

increase the risk of nuclear operations.

GLOSSARY

ADAMS—Agencywide Document Access and 

Management System.

Baseline Inspection Program—The normal 

inspection program performed at all nuclear 

power plants. The program will focus on plant 

activities that are not adequately measured by 

performance indicators, on the corrective action 

program, and on verifying the accuracy of the 

performance indicators.

Cornerstone of Safety—Nuclear plant activities 

that are essential for the safe operation of the facility. 

These cornerstones are grouped under the categories 

of reactor safety, radiation safety, and safeguards.

Corrective Action Program—The system by 

which a utility finds and fixes problems at the nuclear plant. It includes a process for evaluating the 

safety significance of the problems, setting priorities 

in correcting the problems, and tracking them until 

they have been corrected.

Cross-cutting Area—Nuclear plant activity that 

affects most or all safety cornerstones. These include 

the plant’s cornerstone action program, human 

performance, and “safety-conscious work environment.”

Inspection Reports—Reports are issued periodically to document inspection findings. These 

may cover a specific time period for the baseline 

inspection or a particular event or problem 

examined in a reactive inspection. All inspection 

reports are public documents and, when issued, are 

posted to the NRC’s internet web site.

Performance Indicator—Objective data which 

records performance in a specific cornerstone of 

safety at a nuclear power plant.

Reactive Inspection—An inspection to examine the 

circumstances surrounding an operational problem 

or event occurring at a nuclear plant.

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