United States Nuclear Regulatory Commission - Protecting People and the Environment

Operability Guidance

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Outline of Operability Guidance

What RIS replaced GL 91-18?

The NRC issued Regulatory Issue Summary (RIS) 2005-20 to inform licensees that it has revised the guidance contained in two sections of NRC Inspection Manual Part 9900, Technical Guidance, “Operable/Operability:  Ensuring the Functional Capability of a System or Component” and “Resolution of Degraded and Nonconforming Conditions,” and has combined these two documents into a single document. The revised inspection guidance reflects relevant changes that have been made to NRC regulations, policies, and practices, and clarifies selected issues based on operating experience.  This guidance supercedes the guidance previously provided in GL 91-18 and Revision 1 to GL 91-18.

What is the Purpose of the Revised ODP?

The RIS informs all holders of operating licenses for nuclear power reactors that the guidance is provided to NRC inspectors to assist their review of licensee determinations of operability and resolution of degraded or nonconforming conditions.  In addition, many licensees have found this guidance useful in developing their plant-specific operability determination process. Users of the guidance should be aware that, although it generally reflects existing practice, it may not be directly applicable in every case at every plant. Therefore, inspectors should discuss significant differences among licensee practices with NRC management to ensure that the guidance is applied in a reasonable and consistent manner.

NRC inspectors are cautioned that if, during an inspection, an NRC inspector obtains information reasonably indicating a degraded or nonconforming condition affecting any of the structures, systems, and components (SSCs) described in Section 2.0 (Scope and Applicability), the inspector should promptly inform the appropriate level of licensee management so that the licensee can evaluate the operability or functionality of the SSCs.

NRC regulations and the plant-specific operating license, including technical specifications (TSs), establish requirements for SSCs to ensure that plant operation does not pose an undue risk to public health and safety. Although these requirements limit the risk of plant operation, it is not possible to address all conceivable events or plant conditions.

What is the Scope and Applicability of the ODP?

Licensees assess operability and functionality when degraded or nonconforming conditions affecting SSCs are identified. The operability determination process is used to assess operability of SSCs described in TSs. Functionality assessments should be performed for SSCs not described in TSs, but which warrant programmatic controls to ensure that SSC availability and reliability are maintained.

The licensee's immediate and primary concern should be safe operation of the plant. When a degraded or nonconforming condition is identified that may pose a threat to public health and safety, whether or not explicitly discussed in regulatory or licensee documents, the plant should be placed in a safe condition. The TSs require that an SSC be operable given the plant condition (operational mode); thus there should be a reasonable expectation that the SSC in question is operable while an operability determination is being made, or an appropriate TS action requirement should be entered.

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Development of the ODP

  • Time line for Development of Operability Guidance
  • Operability Workshops Meeting - August 2004 & August 2003
  • NEI ODP Workshop on the Operability Determination Process July 14, 2005, Sofitel Chicago O'Hare

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Issuance of Inspector Guidance on the Operability Determination Process (ODP)

Presentations at Training Workshops

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Operability Workshops

On November 7, 1991, NRC issued GL 91-18 to give licensees these two inspection manual sections. On October 8, 1997, NRC issued Revision 1 to this generic letter to describe the role of the 10 CFR 50.59 evaluation process in the resolution of degraded and nonconforming conditions.

Rather than totally revising GL 91-18, NRC is attempting to clarify and update the GL by possibly:

  • consolidating the two inspection manual sections into a single document;
  • incorporating other existing inspection manual technical guidance, if appropriate; and
  • adding discussion of the revised 10 CFR 50.59, the maintenance rule, approved risk-informed technical specifications, and other appropriate regulatory changes.
Date Description
08/25/2004 NRC's Technical Specifications Section staff will sponsor a workshop on a draft RIS: NRC Regulatory Issue Summary 2004-XX: Revision to Guidance Formerly Contained in NRC Generic Letter 91-18, "Information to Licensees Regarding Two NRC Inspection Manual Sections on Resolution of Degraded and Nonconforming Conditions and on Operability".

NRC's Technical Specification Section staff sponsored a workshop on a proposed Revision to Generic Letter (GL) 91-18 regarding two inspection manual sections on resolution of degraded and nonconforming conditions and on operability. NRC held the workshop to gather information from inspectors, licensees, the public, and other stakeholders on areas in the existing generic letter that can be clarified.

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Page Last Reviewed/Updated Wednesday, June 25, 2014