ML22298A215

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TSTF Meeting Handout Natural Phenomena and Operability Workshop
ML22298A215
Person / Time
Site: Technical Specifications Task Force
Issue date: 10/20/2022
From:
PWR Owners Group, Technical Specifications Task Force
To:
NRC
Honcharik, Michelle
References
Download: ML22298A215 (39)
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Technical Specifications Task Force TSTF A Joint Owners Group Activity Natural Phenomena and Operability TSTF/NRC Workshop Drew Richards, South Texas Project TSTF Member, PWROG LC Chair October 20, 2022 1

Technical Specifications Task Force TSTF A Joint Owners Group Activity Introduction

  • Protection from natural phenomena is a required design function described in a licensees UFSAR.
  • There is no definitive guidance on whether protection from natural phenomena is also an aspect of TS operability.

- Protection from natural phenomena is not called out in the Standard TS (STS) or Bases as a specified safety function or required support function.

- Most regulatory guidance on protection from natural phenomena does not discuss TS.

- For most licensees, UFSAR Chapter 15 accident analyses do not discuss natural phenomena.

  • However, industry and NRC have sometimes considered TS systems inoperable due to lack of protection from natural phenomena.

2

Technical Specifications Task Force TSTF A Joint Owners Group Activity

Background

  • The lack of definitive guidance has led to questions, such as:

- Does opening a watertight door that protects equipment from a hurricane make the protected equipment inoperable if there is no severe weather?

- Does a clogged floor drain installed for external flooding protection render the equipment in the room inoperable if there is currently no risk of external flooding?

- Does an ECCS ventilation duct that cannot withstand the low pressures associated with a tornado make the equipment in the room inoperable if there is currently no threat of a tornado?

3

Technical Specifications Task Force TSTF A Joint Owners Group Activity

Background

  • The issue is complicated because the NRC and industry have typically considered "required support functions" to be situational.

- Room coolers are a required support function in summer but may not be in the winter.

- Heat tracing on pipes is a required support function in winter but not in the summer.

  • Is there a distinction between a weather-related support function (e.g.,

winter/summer) versus a natural phenomena-related support function?

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Technical Specifications Task Force TSTF A Joint Owners Group Activity Problem Statement

  • The issuance of several new guidance documents led the industry to reexamine the issue of TS operability and natural phenomena protection with the goal of working with the NRC to bring clarity and consistency to the application of the Technical Specifications.
  • Today we will present the results of our research.
  • We look forward to hearing the staffs feedback on the industry research, and to working with the NRC to establish consistent positions that may be used by licensees and the NRC.

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Technical Specifications Task Force TSTF A Joint Owners Group Activity OVERVIEW Brian Mann, Excel Services Corporation TSTF Program Manager 6

Technical Specifications Task Force TSTF A Joint Owners Group Activity GDC 2

- "Structures, systems, and components important to safety shall be designed to withstand the effects of natural phenomena such as earthquakes, tornados, hurricanes, floods, tsunami, and seiches without loss of capability to perform their safety functions. The design bases for these structures, systems, and components shall reflect: (1) Appropriate consideration of the most severe of the natural phenomena that have been historically reported for the site and surrounding area, with sufficient margin for the limited accuracy, quantity, and period of time in which the historical data have been accumulated, (2) appropriate combinations of the effects of normal and accident conditions with the effects of the natural phenomena and (3) the importance of the safety functions to be performed."

  • A licensees implementation of GDC 2 (or equivalent design criteria) is described in their UFSAR, typically in Chapter 3.

- The GDCs are not requirements. However, the plant-specific implementation of GDC 2 as described in the UFSAR is part of the design and licensing basis.

- If there are any "appropriate combinations of the effects of normal and accident conditions with the effects of the natural phenomena," in a plants licensing basis, they would be described in Chapter 3 of the UFSAR and evaluated in Chapter 15 of the UFSAR.

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Technical Specifications Task Force TSTF A Joint Owners Group Activity Operability

  • The STS definition of Operability states:

- "A system, subsystem, division, component, or device shall be OPERABLE or have OPERABILITY when it is capable of performing its specified safety function(s) and when all necessary attendant instrumentation, controls, normal or emergency electrical power, cooling and seal water, lubrication, and other auxiliary equipment that are required for the system, subsystem, division, component, or device to perform its specified safety function(s) are also capable of performing their related support function(s)."

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Technical Specifications Task Force TSTF A Joint Owners Group Activity Purpose of Technical Specifications

  • The NRC's "Final Policy Statement on Technical Specifications Improvements for Nuclear Power Reactors," (Final Policy Statement) states the Commission's policy as

- "The purpose of Technical Specifications is to impose those conditions or limitations upon reactor operation necessary to obviate the possibility of an abnormal situation or event giving rise to an immediate threat to the public health and safety by identifying those features that are of controlling importance to safety and establishing on them certain conditions of operation which cannot be changed without prior Commission approval."

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Technical Specifications Task Force TSTF A Joint Owners Group Activity What Changed?

- The 2019 version of IMC-0326 stated:

  • "SSCs may also have design functions that do not perform a necessary and related support function for TS SSCs. These design functions are not within the scope of an OD."
  • "Not all SSC functions described in the CLB are specified safety functions required for operability..."

- Previous versions of IMC-0326 implied that all functions described in the UFSAR were specified safety functions.

  • "In order to be considered operable, an SSC must be capable of performing the specified safety functions of its design, within the required range of physical conditions, initiation times, and mission times in the CLB." 10

Technical Specifications Task Force TSTF A Joint Owners Group Activity What Else Changed?

  • February 28, 2019, memorandum from Ho K. Nieh, Director, NRC Office of Nuclear Reactor Regulation, to the NRC Regional Administrators, titled, "Closeout of Low Safety Significant/Low Risk Concerns - Tornado-Generated Missile Protection," states,

- "The General Design Criteria (GDC) of Appendix A to Part 50 of Title 10 of the Code of Federal Regulations (10 CFR), as well as the pre-GDC, were intended to provide a basis for judging the adequacy of the preliminary design of the facility at the construction permit stage and the detailed design and construction at the operating license stage.

The GDC were not intended to be living requirements for the control and operation of nuclear power plants."

  • This position supersedes the 1995 memo from Tom Murley to the Regional Administrators, "Relationship between the General Design Criteria (GDC) and Technical Specifications,"

which described GDC 2 as "applicable natural phenomena are inherently considered in the operability of safety-related SSCs that satisfy the criteria for inclusion in TS."

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Technical Specifications Task Force TSTF A Joint Owners Group Activity Industry Program

  • The changes to these documents highlighted questions that have been raised by licensees regarding natural phenomena protection and operability.
  • The industry formed a team that reviewed the regulations, regulatory guidance, and history.

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Technical Specifications Task Force TSTF A Joint Owners Group Activity SRP Review

  • The SRP discusses seismic design, wind loading, tornado missiles, and flooding in Chapter 3, "Design of Structures, Components, Equipment, and Systems."

- A search of the SRP for discussion of TS requirements related to natural phenomena found few references, which well discuss.

  • There is no discussion of natural phenomena in SRP Chapter 16.0, "Technical Specifications."
  • It appears that the NRCs SRP guidance on implementing GDC 2 is based on design, and not on operational restrictions in the TS.

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Technical Specifications Task Force TSTF A Joint Owners Group Activity Technical Specifications Review

- "Limiting conditions for operation are the lowest functional capability or performance levels of equipment required for safe operation of the facility."

  • The four criteria in 10 CFR 50.36(c)(2)(ii) further define the equipment and functions that satisfy the LCO definition.
  • None of the criteria (or the developmental documents on which they are based) discuss protection from natural phenomena.
  • Few TS Bases discuss natural phenomena. Those will be discussed.
  • It appears that, in most cases, the TS were not designed or intended to govern design features that protect from natural phenomena.

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Technical Specifications Task Force TSTF A Joint Owners Group Activity What About Risk-Informed TS?

  • The TS LCOs are based on the safety analyses in the UFSAR and include deterministic assumptions such as the single failure criteria.
  • PRA has been used to extend Completion Times (e.g., Risk Informed Completion Times) or to manage SR Frequencies (Surveillance Frequency Control Program), while the associated LCOs continue to be based on the deterministic assumptions of the accident analysis.

- PRA considers events that are not addressed in the accident analysis, such as fires and natural phenomena, and considers multiple failures.

  • However, using risk to establish Completion Times for inoperable equipment or testing frequencies doesnt change the specified safety functions or required support functions required for operability and the LCO.

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Technical Specifications Task Force TSTF A Joint Owners Group Activity What About Sequential Events?

  • If a natural phenomenon occurred and rendered a system inoperable due to a deficiency, the condition would be treated like an inoperability due to any other cause.

- If a tornado missile damaged a diesel generator, the diesel generator would be inoperable.

- If an accident subsequently occurred, it would be no different than if the diesel generator were inoperable for other reasons, such as maintenance.

  • If an accident occurred and subsequently a natural phenomenon occurred for which the plant was not protected, it would be addressed like any other post-accident equipment failure.

- The emergency operating procedures address post-accident equipment failures.

  • Deficiencies related to protection from natural phenomena require no special treatment such as TS inoperability to address sequential events.

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Technical Specifications Task Force TSTF A Joint Owners Group Activity How Would Deficiencies in Natural Phenomena be Handled?

  • If it is determined that the plant is not consistent with the design, the issue is entered into the Corrective Action Program (CAP).
  • TS Operability and the CAP serve different purposes:

- The purpose of an operability determination is to provide a basis for making a timely decision on LCO compliance.

- The purpose of the CAP is to ensure actions are taken to correct the deficient condition.

  • The licensees CAP programs are inspected by the Problem Identification & Resolution inspection module.
  • Resident inspectors review CAP reports.

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Technical Specifications Task Force TSTF A Joint Owners Group Activity The TS Are Not a Backstop to the CAP Process

  • The TS are not a substitute for other regulatory requirements.
  • The Final Policy Statement states, "

- "[T]here has been a trend towards including in Technical Specifications not only those requirements derived from the analyses and evaluation included in the safety analysis report but also essentially all other Commission requirements governing the operation of nuclear power reactors. ... It has diverted both staff and licensee attention from the more important requirements in these documents to the extent that it has resulted in an adverse but unquantifiable impact on safety."

- "The purpose of Technical Specifications is to impose those conditions or limitations upon reactor operation necessary to obviate the possibility of an abnormal situation or event giving rise to an immediate threat to the public health and safety by identifying those features that are of controlling importance to safety...

  • The TS are the Commissions highest level of control over a licensees actions and should be applied judiciously.

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Technical Specifications Task Force TSTF A Joint Owners Group Activity What About Safety?

  • Licensees have extensively studied the effect of natural phenomena, for example:

- Generic Letter 88-20, "Individual Plant Examination of External Events for Severe Accident Vulnerabilities," and

- Response to the Fukushima Dai-ichi accident lessons-learned that added capabilities to maintain key plant safety functions following a large-scale natural disaster and reevaluating the potential impact from seismic and flooding events.

  • These studies and others have demonstrated that the plant risk associated with natural phenomena is low compared to other plant risks.
  • The Commissions policy is that TS are intended to address an immediate threat to the public health and safety and apply to features of controlling importance to safety .

- The risks from natural phenomena do not meet this threshold.

  • The protections from natural phenomena, while important, do not warrant being treated as TS requirements.

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Technical Specifications Task Force TSTF A Joint Owners Group Activity Discussion of Specific Phenomena Phil Lashley, Energy Harbor 20

Technical Specifications Task Force TSTF A Joint Owners Group Activity Natural Phenomena

  • The industry review grouped natural phenomena into four categories:

- External flooding (floods, hurricane, tsunami, local intense precipitation, seiches),

- High winds (tornados, hurricanes, straight winds, derechos),

- Tornado missiles, and

- Earthquakes 21

Technical Specifications Task Force TSTF A Joint Owners Group Activity External Flooding 22

Technical Specifications Task Force TSTF A Joint Owners Group Activity External Flooding

  • Regulatory guidance on flooding:

- RG 1.59, "Design Basis Floods for Nuclear Power Plants"

- RG 1.102, "Flood Protection for Nuclear Power Plants"

  • Both documents are focused on the design aspects.
  • Neither document discusses the combination of a design-basis flood in conjunction with other accidents.
  • RG 1.102 discusses the potential for a flooding technical specification if circumstances dictate, and a few plants have TS on flooding protection.
  • Both RGs refer to using alternate "hardened protection" in lieu of the designed protection.

- Therefore, absent a plant-specific LCO on flooding, the design flooding protection is not a "condition of operation which cannot be changed without prior Commission approval" like the TS, and is not required for the SSC to perform its specified safety function.

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Technical Specifications Task Force TSTF A Joint Owners Group Activity External Flooding

  • We concluded that flooding protection is situational, like other required support functions. It is required to prevent actual flooding, not postulated flooding.

- Plants with flooding-related TS may have different requirements.

  • Deficiencies in the flooding protection would only result in TS inoperability if a flood renders TS equipment incapable of performing its specified safety function.

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Technical Specifications Task Force TSTF A Joint Owners Group Activity High Winds Jordan Vaughan, Duke Energy TSTF Member 25

Technical Specifications Task Force TSTF A Joint Owners Group Activity High Winds

  • Regulatory Guidance

- SRP 3.3.1, "Wind Loading"

- RG 1.117, "Protection Against Extreme Wind Events and Missiles for Nuclear Power Plants"

  • Neither the SRP Section 3.3.1 nor RG 1.117 discuss the need for TS requirements or operability.

- RG 1.117 uses the term "functional" instead of "operable."

  • There are no TS or TS Bases requirements related to high winds.

- High winds can result in the BWR secondary containment differential pressure requirements not being met.

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Technical Specifications Task Force TSTF A Joint Owners Group Activity High Winds

  • Hurricanes

- Hurricanes are a subset of high winds.

- 10 CFR 50.63, "Loss of all alternating current power," required the submittal of information related to station blackout events.

- NUMARC 87-00 requires plants which are potentially affected by hurricane conditions to have procedurally established actions to begin site preparations 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> prior to anticipated hurricane arrival and a shutdown 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> prior to anticipated arrival.

- There are no TS SSCs declared inoperable due to the impending hurricane, but rather prudent actions are taken because of the increased potential of a loss of offsite power.

- There are no TS requirements to shut down in anticipation of a hurricane.

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Technical Specifications Task Force TSTF A Joint Owners Group Activity High Winds

  • We concluded that the lack of protection from high winds for a TS system does not render that system inoperable unless high winds actually render a TS SSC LCO or SR not met (such as secondary containment differential pressure) or causes the TS system to otherwise be unable to perform its specified safety function.

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Technical Specifications Task Force TSTF A Joint Owners Group Activity Tornado Missiles 29

Technical Specifications Task Force TSTF A Joint Owners Group Activity Tornado Missiles

  • The STS do not impose operational restrictions based on the ability to withstand a contemporaneous tornado and an accident.

- An unprotected condensate storage tank may be struck by a tornado missile and lose volume below the TS required capacity. However, the tanks inoperability would be based on an actual tornado missile, not based on a hypothesized scenario related to lack of protection.

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Technical Specifications Task Force TSTF A Joint Owners Group Activity Tornado Missiles

  • The previously referenced memo from the Director of NRR (Nieh) to the Regional Administrators stated,

- "NRR's position is that this issue, based on both these insights and the experience to date, when plant-specific considerations such as tornado missile probabilities are considered, is typically of very low safety significance and well below a level where adequate protection would be in question."

  • The Commissions policy is that the purpose of TS it to prevent an event giving rise to an immediate threat to the public health and safety by imposing requirements on features that are of controlling importance to safety.
  • The 2019 memorandum leads to the conclusion that tornado missile protection is not a specified safety function required for operability of TS systems because tornado missiles are not an immediate threat to public health and safety and are not features of controlling importance to safety.

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Technical Specifications Task Force TSTF A Joint Owners Group Activity Earthquakes Phil Lashley, Energy Harbor 32

Technical Specifications Task Force TSTF A Joint Owners Group Activity Earthquakes

- "The possibility that an earthquake would disrupt a response to a radiological emergency is so extremely low as to be, for any practical purpose, nonexistent."

- The court considered "contemporaneously" to mean, for example, "within the space of a single week during the life of the plant."

  • Therefore, it is not necessary to postulate a seismic event concurrent with a design basis accident or transient.

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Technical Specifications Task Force TSTF A Joint Owners Group Activity Earthquakes

  • The courts ruling is consistent with earlier NRC guidance.
  • July 8, 1985 memo from Dennis Crutchfield, Assistant Director for Safety Assessment, to the Regional Administrators, titled, "Technical Specification Operability Requirements," states:

- "the fact that safety related structures, systems, and components are designed to remain functional during a Safe Shutdown Earthquake (SSE) and assure the integrity of the reactor coolant pressure boundary, the capability to shut down the reactor and maintain it in a safe condition or the capability to mitigate the consequences of accidents, as a design basis event the SSE is not assumed to occur simultaneous with accidents."

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Technical Specifications Task Force TSTF A Joint Owners Group Activity Earthquakes

- "... that earthquake which produces the maximum vibratory ground motion for which certain structures, systems, and components are designed to remain functional. "

  • The phrase "are designed to remain functional" makes clear that the ability to withstand an SSE is a design criterion.
  • There is no reference to maintaining operability of systems.
  • RG 1.29 describes as seismic Category I those SSCs that must be designed to remain functional if the SSE occurs.

- The RG does not discuss TS or require Category I SSCs to be subject to TS operability.

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Technical Specifications Task Force TSTF A Joint Owners Group Activity Earthquakes

  • There were two significant initiatives where the NRC weighed in on the seismic requirements of SSCs that required site-specific responses:

- In response to the Individual Plant Examination of External Events (IPEEE),

licensees developed a Safe Shutdown Equipment List (SSEL) documenting the SSCs credited with remaining functional during and after an SSE.

  • The NRC did not require the SSEL SSCs be included in the TS, or that their seismic capacity be a facet of operability if the SSCs were in the TS.

- Following Fukushima, the NRC directed a seismic hazard re-evaluation for all sites and issued a series of orders related to the ability to withstand a seismic event.

  • The NRC did not require any changes to the TS related to mitigating a seismic hazard and there was no change to the application of TS operability related to seismic capability.

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Technical Specifications Task Force TSTF A Joint Owners Group Activity Earthquakes

  • TS LCOs primarily 1) protect an initial condition of a design basis accident or transient analysis, or 2) protect a structure, system, or component that actuates to mitigate a design basis accident or transient.
  • Protection from an earthquake that does not occur concurrently with a design basis accident or transient is not a specified safety function or related support function.
  • We concluded that the lack of seismic protection for a TS system does not render that system inoperable unless a seismic event occurs and renders the TS system unable to perform its specified safety function.

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Technical Specifications Task Force TSTF A Joint Owners Group Activity Next Steps Drew Richards, South Texas Project TSTF Member, PWROG LC Chair 38

Technical Specifications Task Force TSTF A Joint Owners Group Activity Next Steps

  • The industry would like to obtain the staff's feedback on the industry research, benefit from the staff's insights, and identify opportunities to establish durable guidance on this issue.

- If there are areas in which the industry and the NRC agree, what would be the best way to document it?

- If there are areas in which we currently arent in agreement, we would like to schedule future meetings to discuss those differences and try to reach a consensus position.

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