![]() Mitigating systems include those systems associated with safety injection, decay heat removal, and their support systems, such as emergency alternating current (AC) power. Licensees reduce the likelihood of reactor accidents by maintaining the availability and reliability of 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. 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." 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. ![]() ![]() 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 Scrams (IE01) – The number of unplanned scrams during the previous four quarters, both manual and automatic, while critical per 7,000 hours. There are three PIs in the initiating events cornerstone: ![]() Maintenance Risk Assessments and Emergent Work ControlĮvaluations of Changes, Tests, or Experiments and Permanent Plant Modifications Licensed Operator Requalification Program Reactor Safety-Initiating Events, Mitigating Systems, Barrier Integrity 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: IP Such events include reactor trips (scrams) due to turbine trips, loss of feedwater, loss of offsite power, and other reactor transients. Licensees can reduce the likelihood of a reactor accident by maintaining a low frequency of these initiating events. If not properly mitigated, and if multiple barriers are breached, a reactor accident could result, which might compromise public health and safety. 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. 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.Īdditional background information can be found in NUREG-1649, a plain language description of the ROP published by the Office of Public Affairs. 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. 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 each strategic performance area are cornerstones that reflect the essential safety aspects of facility operation. There are three key strategic performance areas: reactor safety, radiation safety, and safeguards. It is a risk-informed, tiered approach to ensuring plant safety. ![]() The regulatory framework for reactor oversight is shown in the diagram below. ![]()
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