Inspection Manual by Cornerstone

On this page:

• ROP Regulatory Framework
• Initiating Events
• Mitigating Systems
• Barrier Integrity
• Emergency Preparedness
• Public Radiation
• Occupational Radiation
• Security

ROP Regulatory Framework

The regulatory framework for reactor oversight is shown in the diagram below. It is a risk-informed, tiered approach to ensuring plant safety. There are three key strategic performance areas: reactor safety, radiation safety, and safeguards. Within each strategic performance area are cornerstones that reflect the essential safety aspects of facility operation. Satisfactory licensee performance in the cornerstones provides reasonable assurance of safe facility operation and assurance that the U.S. Nuclear Regulatory Commission's (NRC's) safety mission is being accomplished.

Within this framework, the NRC's operating Reactor Oversight Process (ROP) provides a means to collect information about licensee performance, assess the information for its safety significance, and provide for appropriate licensee and NRC response. The NRC evaluates plant performance by analyzing two distinct inputs: inspection findings resulting from the NRC's inspection program and performance indicators (PIs) reported by the licensees.

Additional background information can be found in NUREG-1649, a plain language description of the ROP published by the Office of Public Affairs.

Initiating Events

The objective of this cornerstone is to limit the frequency of those events that upset plant stability and challenge critical safety functions, during shutdown as well as power operations. If not properly mitigated, and if multiple barriers are breached, a reactor accident could result, which might compromise public health and safety. Licensees can reduce the likelihood of a reactor accident by maintaining a low frequency of these initiating events. Such events include reactor trips (scrams) due to turbine trips, loss of feedwater, loss of offsite power, and other reactor transients.

Inspection Procedures (link to procedures)

There are 10 attachments to the inspection procedure for the reactor safety strategic performance area, which includes the initiating events cornerstone, mitigating systems cornerstone, and the barrier integrity cornerstone:

Performance Indicators

There are three PIs in the initiating events cornerstone:

• Unplanned Scrams (IE01) – The number of unplanned scrams during the previous four quarters, both manual and automatic, while critical per 7,000 hours. The scram rate is calculated per 7,000 critical hours because that value is representative of the critical hours of operation in a year for a typical plant.
• Unplanned Power Changes (IE03) – The number of unplanned changes in reactor power of greater than 20-percent full-power, per 7,000 hours of critical operation, excluding manual and automatic scrams.
• Unplanned Scrams with Complications (IE04) – The number of unplanned scrams while critical, both manual and automatic, during the previous four quarters require additional operator actions as defined by the flowchart in NEI 99-02 Rev 7 , "Regulatory Assessment Performance Indicator Guideline."

Mitigating Systems

The objective of this cornerstone is to monitor the availability, reliability, and capability of systems that mitigate the effects of initiating events to prevent core damage. Licensees reduce the likelihood of reactor accidents by maintaining the availability and reliability of mitigating systems. Mitigating systems include those systems associated with safety injection, decay heat removal, and their support systems, such as emergency alternating current (AC) power. This cornerstone includes mitigating systems that respond to both operating and shutdown events.

Inspection Procedures

As listed above, there are twenty-three attachments to the inspection procedure for the reactor safety strategic performance area, which includes the initiating events cornerstone, mitigating systems cornerstone, and the barrier integrity cornerstone.

Performance Indicators

There are currently six PIs in the mitigating systems cornerstone:

• Safety System Functional Failures (MS05)—The number of events or conditions that alone prevented, or could have prevented, the fulfillment of the safety function of structures or systems in the previous four quarters.
• Emergency AC Power Systems (MS06)—The sum of the unavailability of the emergency AC power plus the unreliability for the emergency AC power system during the previous 12 quarters.
• High Pressure Injection Systems (MS07)—The sum of the unavailability of the high pressure injection system plus the unreliability for the high pressure injection system during the previous 12 quarters.
• Heat Removal Systems (MS08)—The sum of the unavailability of the heat removal system plus the unreliability for the heat removal system during the previous 12 quarters.
• Residual Heat Removal Systems (MS09)—The sum of the unavailability of the residual heat removal system plus the unreliability for the residual heat removal system during the previous 12 quarters.
• Cooling Water Systems (MS10) —The sum of the unavailability of cooling water systems plus the unreliability for the cooling water systems during the previous 12 quarters.

Note 1: Thresholds that are specific to a site or unit will be provided in Appendix D, of NEI 99-02 Rev 7 , when identified.

Note 2: PLE System Component Performance Limit Exceeded (see Appendix F, Section F4, page F-44)

Barrier Integrity

The objective of this cornerstone is to provide reasonable assurance that the physical design barriers protect the public from radionuclide releases caused by accidents. Licensees can reduce the effects of reactor accidents if they do occur by maintaining the integrity of the barriers. The barriers are the fuel cladding, reactor coolant system (RCS) boundary, and the containment.

Inspection Procedures

As listed above under the initiating events cornerstone, there are 23 attachments to the inspection procedure for the reactor safety strategic performance area, which includes the initiating events cornerstone, mitigating systems cornerstone, and the barrier integrity cornerstone.

Performance Indicators

There are two PIs in the barrier integrity cornerstone:

• Reactor Coolant System (RCS) Specific Activity (BI01) – The maximum monthly RCS activity in microcuries per gram dose equivalent Iodine-131 per the technical specifications, expressed as a percentage of the technical specification limit.
• Reactor Coolant System (RCS) Leakage (BI02) – The maximum RCS identified Leakage in gallons per minute each month as defined in technical specifications, expressed as a percentage of the technical specification limit.

Emergency Preparedness

The objective of this cornerstone is to ensure that licensees are capable of implementing adequate measures to protect public health and safety during a radiological emergency. Licensees provide reasonable assurance that their emergency preparedness program is effective through drills and exercises, participation in actual events, and testing of the Alert and Notification System (ANS). This cornerstone does not include the offsite actions, which are covered by the Federal Emergency Management Agency.

Inspection Procedures (link to procedures)

There are eight attachments to the inspection procedure for the emergency preparedness cornerstone:

Performance Indicators

There are three PIs in the emergency preparedness cornerstone:

• Drill/Exercise Performance (EP01)—The percentage of all drill, exercise, and actual opportunities that were performed timely and accurately during the previous eight quarters.
• Emergency Response Organization (ERO) Drill Participation (EP02)—The percentage of key ERO members that have participated in a drill, exercise, or actual event during the previous eight quarters, as measured on the last calendar day of the quarter.
• Alert and Notification System Reliability (EP03) [RETIRED]—The percentage of ANS sirens that are capable of performing their function, as measured by periodic siren testing during the previous 12 months. Periodic tests are the regularly scheduled tests that are conducted to actually test the ability of the sirens to perform their function (e.g., silent, growl, siren sound test).  This PI was retired on January 1, 2025.
• Emergency Response Facility and Equipment Readiness (EP04)—The number of occurrences that the technical support center or emergency operations facility is nonfunctional, or equipment necessary to implement the emergency plan is not available or functional, such that a risk significant planning standard function or response action could not be performed for greater than 168 hours from the time of discovery and no compensatory measure(s) was implemented. This PI became effective on January 1, 2025.

Public Radiation Safety

The objective of this cornerstone is to ensure adequate protection of public health and safety from exposure to radioactive material released into the public domain as a result of routine civilian nuclear reactor operations. These releases include routine gaseous and liquid radioactive effluent discharges, the inadvertent release of solid contaminated materials, and the offsite transport of radioactive materials and wastes. Licensees can maintain public protection by meeting the applicable regulatory limits and as low as is reasonably achievable (ALARA) guidelines.

Inspection Procedures (link to procedures)

There are three attachments to the inspection procedure for the public radiation safety cornerstone:

Performance Indicators

There is one PI in the public radiation safety cornerstone:

• Radiological Effluent Technical Specifications/Offsite Dose Calculation Manual (RETSs/ODCM) (PR01)—Radiological effluent release occurrences per reactor unit that exceed the values listed below:
  • Liquid Effluents
    • Whole Body—1.5 millirems per quarter (mrem/qtr)
    • Organ—5 mrem/qtr
  • Gaseous Effluents
    • Gamma Dose—5 millirads per quarter (mrad/qtr)
    • Beta Dose—10 mrad/qtr
    • Organ Doses from I-131, iodine-133, tritium, & particulates—7.5 mrem/qtr

Occupational Radiation Safety

The objective of this cornerstone is to ensure adequate protection of worker health and safety from exposure to radiation from radioactive material during routine civilian nuclear reactor operation. This exposure could come from poorly controlled or uncontrolled radiation areas or radioactive material that unnecessarily exposes workers. Licensees can maintain occupational worker protection by meeting applicable regulatory limits and ALARA guidelines.

Inspection Procedures (link to procedures)

There are four attachments to the inspection procedure for the occupational radiation safety cornerstone:

Performance Indicators

There is one PI in the occupational radiation safety cornerstone:

• Occupational Exposure Control Effectiveness (OR01)—The PI for this cornerstone is the sum of the following:
  • Technical specification high radiation area occurrences
  • Very high radiation area occurrences
  • Unintended exposure occurrences

Security

The objective of this cornerstone is to provide assurance that the licensees' security system and material control and accounting programs use a defense-in-depth approach and can protect against (1) the design basis threat if radiological sabotage from external and internal threats, and (2) the loss of radiological materials.

The security cornerstone is an important component of the ROP, which includes various security inspection activities the NRC uses to verify licensee compliance with Commission regulations and thus ensure public health and safety. The Commission determined in the staff requirements memorandum (SRM) for SECY-04-0191, "Withholding Sensitive Unclassified Information Concerning Nuclear Power Reactors from Public Disclosure," dated November 9, 2004, that specific information related to findings and performance indicators associated with the security cornerstone will not be publicly available to ensure that security-related information is not provided to a possible adversary. Security inspection report cover letters will be available on the NRC Web site; however, security-related information on the details of inspection finding(s) will not be displayed.