ML13329A602
| ML13329A602 | |
| Person / Time | |
|---|---|
| Issue date: | 11/20/2013 |
| From: | Armijo J Advisory Committee on Reactor Safeguards |
| To: | Satorius M NRC/EDO |
| References | |
| G20130827, RG-1.168 | |
| Download: ML13329A602 (4) | |
Text
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CE m isio Prol'c'inv htooht" ad lbe Environnient Ticket No: G20130827 50423 Assigned Office: RES OEDO Due Date: 12/20/2013 Other Assignees:
SECY Due Date:
Date Response Requested by Originator:
Other Parties:
Subject:
Draft Final Revisions of Regulatory Guides 1.68 through 1.73, Software Processes for Digital Computers in Safety Systems of Nuclear Power Plants
==
Description:==
CC Routing: NRO, NRR ADAMS Accession Numbers - Incoming:
Response I Package:
~ ~
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4 0A0~-
.S Cross Reference No: R.G. 1.168, R.G. 1.169, R.G. 1.170, R.G. 1.171, R.G. 1.172, R.G. 1.173 SRM\\Other: No 0-4 0M Action Type: Letter OEDO Concurrence: No
.Signature Level: EDO OCM Concurrence: No Special Instructions:
OCA Concurrence: No Please prepare response to ACRS for the signature of the EDO. Add the Commission and SECY as cc's.
Also, include: RidsAcrsAcnwMaiICTR to your distribution on the concurrence page. USE SUBJECT LINE IN RESPONSE.
- 45, 4
-4 Originator Name: J. Sam Armijo Originator Org: ACRS Date of Incoming: 11/20/2013 Document Received by OEDO Date: 11/21/2013 Addressee: Mark A. Satorius, EDO Incoming Task: Letter Ttrc-p~d ti- £C-no1 OEDO POC: Ian Jung
UNITED STATES NUCLEAR REGULATORY COMMISSION ADVISORY COMMITTEE ON REACTOR SAFEGUARDS WASHINGTON, DC 20555 - 0001 November 20, 2013 Mr. Mark A. Satorius Executive Director for Operations U.S. Nuclear Regulatory Commission Washington, DC 20555-0001
SUBJECT:
DRAFT FINAL REVISIONS OF REGULATORY GUIDES 1.168 THROUGH 1.173, SOFTWARE PROCESSES FOR DIGITAL COMPUTERS IN SAFETY SYSTEMS OF NUCLEAR POWER PLANTS
Dear Mr. Satorius:
During the 6 0 9 th meeting of the Advisory Committee on Reactor Safeguards, November 7-8, 2013, we reviewed your August 29, 2013, response to the recommendations in our June 18, 2013, letter report on Draft Regulatory Guides (RGs) 1.68 through 1.73, Software Processes for Digital Computers in Safety Systems of Nuclear Power Plants.
Our letter noted that a footnote in each of these draft RGs stated:
The term "safety systems" is synonymous with "safety-related systems." The scope of the GDC includes structures, systems, and components "important to safety." However, the scope of this regulatory guide is limited to "safety systems," which are a subset of "systems important to safety."
We noted that the current regulatory framework for reactors licensed under 10 CFR Part 50 and for new designs licensed under 10 CFR Part 52 contains provisions for enhanced design, quality, reliability, and regulatory oversight for non-safety-related structures, systems, and components (SSCs) that are "important to safety." These enhanced programs generally apply criteria that are less stringent than the requirements for safety-related SSCs, but are more restrictive than the criteria for other non-safety-related SSCs. We recommended that the staff expedite the development of consistent regulatory guidance for enhanced design, development, operation, and maintenance of digital hardware and software which controls non-safety-related equipment that is "important to safety."
The staff agreed that the footnote was overly restrictive and revised it by adding the following clarification:
EDO -- G20130827 Although not specifically scoped to include non-safety-related but "important to safety systems" this regulatory guide provides methods that the staff finds appropriate for the design, development and implementation of all important to safety systems. The NRC may apply this guidance in licensing reviews of non-safety but important to safety digital software and may tailor it to account for the safety significance of the system software.
The staff stated that the revised footnote aligns well with existing guidance in Chapter 7 of NUREG-0800, "Standard Review Plan for the Review of Safety Analysis Reports for Nuclear Power Plants," and with the criteria for regulatory treatment of non-safety systems in RG 1.206, "Combined License Applications for Nuclear Power Plants."
The revised footnote appropriately clarifies the scope and context of the subject RGs. It also informs licensees and applicants that the staff intends to use similar guidance in their reviews of non-safety digital systems, which support functions that are important to plant safety. This is an excellent start. However, it is evident that additional guidance is needed for those reviews, tailored to the safety significance of those systems and their functions.
The IEEE standards that are referenced in these RGs define four levels of integrity for software.
Level 4 is the most stringent, and the subject RGs recommend its use for safety-related systems. Complementary regulatory guidance is needed to clarify the intent and the degree to which the most appropriate software integrity levels should be applied for reviews of non-safety-related systems that are "important to safety." This is a challenging effort, but vital for common understanding of staff expectations. We encourage the staff to begin the development of formal regulatory guidance to support those reviews.
We look forward to future interactions with the staff on this important matter.
Sincerely, IRA!
J. Sam Armijo Chairman REFERENCES
- 1. EDO Letter,
Subject:
"Draft Final Revisions of Regulatory Guides 1.168 Through 1.173, Software Processes for Digital Computers in Safety Systems of Nuclear Power Plants,"
August 29, 2013 (ML13219A062)
- 2. ACRS Letter,
Subject:
"Draft Final Revisions of Regulatory Guides 1.168 Through 1.173, Software Processes for Digital Computers in Safety Systems of Nuclear Power Plants," June 18, 2013 (ML13161A243)
- 3. NUREG-0800 Standard Review Plan (SRP) - Chapter 7, Instrumentation and Controls,"
Standard Review Plan for the Review of Safety Analysis Reports for Nuclear Power Plants: LWR Edition," (ML110550791)
- 4. Regulatory Guide 1.206,"Combined License Applications for Nuclear Power Plants,"
June 2007 (ML 07072184)