ML19087A026

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NEI High Level Comments on BTP 7-19
ML19087A026
Person / Time
Site: Nuclear Energy Institute
Issue date: 03/28/2019
From: Vaughn S
Nuclear Energy Institute
To: Wendell Morton
Office of Nuclear Reactor Regulation
Govan T, 415-6197, NRR/DIRS
References
Download: ML19087A026 (12)
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Text

From: VAUGHN, Stephen To: Morton, Wendell Cc: Govan, Tekia; Paige, Jason

Subject:

[External_Sender] NEI High-level comments on BTP 7-19 Date: Thursday, March 21, 2019 4:36:08 PM Attachments: BTP 7-19 NEI High Level Comments - Rev 4.pdf

Wendell, As promisedattached are some high-level comments that the NEI Digital I&C working group put together. Over the next two weeks (in preparation for the 4/4 public meeting) the industry team will be adding to these slides and adding more detail, etc.
Regards, Steve STEPHEN J. VAUGHN l SENIOR PROJECT MANAGER, ENGINEERING AND RISK 1201 F Street, NW, Suite 1100 l Washington, DC 20004 P: 202.739.8163 M: 202.256.5393 sjv@nei.org This electronic message transmission contains information from the Nuclear Energy Institute, Inc. The information is intended solely for the use of the addressee and its use by any other person is not authorized. If you are not the intended recipient, you have received this communication in error, and any review, use, disclosure, copying or distribution of the contents of this communication is strictly prohibited. If you have received this electronic transmission in error, please notify the sender immediately by telephone or by electronic mail and permanently delete the original message. IRS Circular 230 disclosure: To ensure compliance with requirements imposed by the IRS and other taxing authorities, we inform you that any tax advice contained in this communication (including any attachments) is not intended or written to be used, and cannot be used, for the purpose of (i) avoiding penalties that may be imposed on any taxpayer or (ii) promoting, marketing or recommending to another party any transaction or matter addressed herein.

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MP1D - BTP 7-19 Revision NEI Proposed Changes March 21, 2019

©2018 Nuclear Energy Institute

The Goal of MP 1D MP 1D

Purpose:

Revise BTP 7-19 to provide clear guidance to the staff on the appropriate scope and boundaries when evaluating CCF and associated defense-in-depth and diversity analyses.

BTP 7-19 should be limited to the Reactor Protection System (RPS) logic and the regulatory guidance should be:

  • Risk-informed
  • Use a graded approach

©2019 Nuclear Energy Institute 2

=

Background===

Branch Technical Position (BTP) 7-19 provides the staff review guidance to implement Digital I&C guidance in SRM-SECY-93-087.

There have been three revisions of BTP 7-19 from 1997 to 2012.

  • Revision 4 (1997) is 8 pages, Revision 5 (2007) is 9 pages, and Revision 6 (2012) is 28 pages Over that time period, the scope of BTP 7-19 was expanded to include auxiliary supporting features After Revision 4, validated operator actions were eliminated:
  • Credit of primary/secondary leak detection and pre-defined operating procedures, that together, can enable operators to take corrective actions before a large break (LBLOCA/MSLB)

©2019 Nuclear Energy Institute 3

NEI Proposed High Level Changes

Title:

  • Move Diversity after Defense-in-Depth to de-emphasize diversity and emphasize Defense-in-Depth
  • Emphasizing Defense-in-Depth focuses on whether the digital protection system change affected other layers of defense (i.e., control system and monitoring/manual control)
  • Emphasizing Diversity detracts on the primary focus
  • Consider changing the title completely (e.g., Evaluation of Digital Reliability)

Background:

©2019 Nuclear Energy Institute 4

NEI Proposed High Level Changes BTP 7-19, Section 1.4, Four-Point Position

  • Include text to credit defensive measures and non-concurrent triggers
  • Existing coping analyses (e.g., Station Blackout) should be leveraged as appropriate to assess consequences
  • Move away from the premise that a CCF could disable a safety function and embrace risk-informed concepts of likelihood and consequence
  • Text should be revised to reflect risk-informed coping mechanisms for LBLOCA and MSLB

©2019 Nuclear Energy Institute 5

NEI Proposed High Level Changes Section 1.6, D3 Assessment

  • More flexibility should be added to use other beyond design basis strategies and methods (e.g., FLEX, B.5.b, etc.)

©2019 Nuclear Energy Institute 6

NEI Proposed High Level Changes Section 1.7, The Diverse Means

  • Control of equipment outside the main control room (MCR) should be acceptable for mitigation of CCF, which is a beyond design basis event Section 1.8, Potential Effects of CCF: Failure to Actuate and Spurious Actuation
  • Introduction of spurious actuation CCF modes has the real potential to lead to a seemingly endless what if analysis
  • Should be limited only to failures to actuate.

©2019 Nuclear Energy Institute 7

NEI Proposed High Level Changes Section 1.9, Design Attributes to Eliminate Consideration of CCF

  • Defensive measures must be considered:
  • Independent watchdog timers
  • Non-concurrent triggers
  • The use of very structured module software can be used to support likelihood of CCF decisions or be credited as a sufficient defensive measure (e.g., IEC-style function blocks are extensively tested with a large amount of OE)

©2019 Nuclear Energy Institute 8

NEI Proposed High Level Changes Section 3.1, Specific Acceptance Criteria

  • Point 9 demonstrates the added complexity which can force an I&C architecture to add a diverse actuation system (DAS)
  • Adding a DAS can increase the overall plant risk due to added complexity Section 3.7, Effects of Spurious Actuation Caused by CCF
  • See earlier discussion for Section 1.8 Section 3.9, System Testability
  • See earlier discussion for Section 1.9

©2019 Nuclear Energy Institute 9

NEI Proposed High Level Perspective Changes Section 4.7, Justification for Not Correcting Specific Vulnerabilities

  • Later versions removed guidance that allowed a risk-informed, graded approach in performing a CCF coping analysis:

Earlier versions suggested that a CCF unlikely conclusion was possible based on reasonable application of prevention and limitation measures

©2019 Nuclear Energy Institute 10

Conclusions BTP 7-19 guidance should:

  • Be risk-informed and use a graded approach
  • Be more general to restore flexibility and simplify the assessment of certain CCF modes
  • Include other industry-recognized defensive measures to preclude a CCF (e.g., independent watchdog timer, logic corruption detection, and other extensive diagnostics)

©2019 Nuclear Energy Institute 11

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