ML18072A147

(External_Sender) Industry Feedback for March 14th RIS Public Meeting - Public Comments Related to Digital I&C RIS 2002-22, Supplement 1

ML18072A147
Person / Time
Site:	Nuclear Energy Institute
Issue date:	03/12/2018
From:	Hanson J Nuclear Energy Institute
To:	Eric Benner, Tekia Govan Division of Engineering, Division of Licensing Projects
References
Download: ML18072A147 (36)

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1 NRR-DMPSPEm Resource From: HANSON, Jerud <jeh@nei.org>

Sent: Monday, March 12, 2018 1:54 PM To:Benner, Eric; Govan, Tekia Cc: REMER, Jason; HANSON, Jerud

Subject:

[External_Sender] Industry Feedback for March 14th RIS Public Meeting Attachments:

NEI Members Comment Worksheet -

March 2018 RIS Version 3-12-2018.xlsx; ML18051A084 - RIS 2017-XX - With Line Number s.pdf; RIS Operating Experience Section Suggested Rewrite.pdf; Table 2 Suggested Revision.pdf Eric/Tekia, Attached you will find documents detailing comments provided by NEI members on the latest version of the RIS. There are a total of 34 comments for our discussion on Wednesday with the following breakdown:

• Priority 1 (Showstoppers) - 18

• Priority 2 (Important and should be incorporated) - 11

• Priority 3 (Editorial) - 5

For each of the comments, we have provided a suggested rewr ite that incorporates our recommendation. In some cases, the proposed rewrite is included in a separate document and attached to this email. Each comment is identified with a line number corresponding to the attached version of the RIS with line numbers added. I recommend we start with the Priority 1 comments, and work our way down the list. The spreadsheet is arranged such th at the Priority 1 comments are first, followed by the Priority 2, and then Priority 3. As we work our way through the comments, we will refer to the supplemental attachments provided, which include a suggested rewrite of the operating experience section, as well as Table 2. I think it would also be very helpful if you could provide hard copies during the public meeting.

Please contact me with any questions.

Thank you,

Jerud Jerud E. Hanson l Sr. Project Manager, Life Extension & New Technology 1201 F Street, NW, Suite 1100 l Washington, DC 20004 P: 202.739.8053 M: 202.497.2051 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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[External_Sender] Industry Feedback for March 14th RIS Public Meeting Sent Date: 3/12/2018 1:53:37 PM Received Date: 3/12/2018 1:54:12 PM From: HANSON, Jerud Created By: jeh@nei.org Recipients: "REMER, Jason" <sjr@nei.org>

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Post Office: MBX023-E2-VA-2.EXCH023.DOMAIN.LOCAL Files Size Date & Time MESSAGE 2614 3/12/2018 1:54:12 PM NEI Members Comment Worksheet - March 2018 RIS Version 3-12-2018.xlsx 28896 ML18051A084 - RIS 2017-XX - With Line Numbers.pdf 321831 RIS Operating Experience Section Suggested Rewrite.pdf 29849 Table 2 Suggested Revision.pdf 64825

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LINE NO.PAGE NO.PRIORITYINDUSTRY COMMENTRECOMMENDED CHANGEADDITIONAL COMMENTSACTION TAKEN612 of 51 Stating that DI&C upgrades associated with the RPS/ESFAS is out-of-scope for the RIS Supplement has the potential to communicate that

SSCs supporting or actuated by the RPS/ESFAS logic would also be off

the table. This significantly limits the SSCs available to be upgraded

under this RIS Supplement.

Suggest replacing 2 sentences starting on line 61: "This RIS Supplement is not directed toward large-scale analog-to-digital upgrades of the reactor trip and engineered safety features actuation logic, since application of the

guidance in this RIS Supplement to such changes would likely involve additional

considerations. This RIS Supplement does not provide new design process guidance;

however it does highlight vulnerabilities that could be introduced by a digital modification

that should be considered in the design process."4454 of 171 Section 3: Suggesting revising (or deleting) the wording in Section 3 (Lines 446 to 491).

The existing wording will be interpreted by licensees such that of a non-safety related DCS would require a LAR to implement. Additionally, item

1.c would prevent a licensee from a simple one-for-one replacement of

antiquated analog/pneumatic sequencer timing relays with modern

timing relays containing an embedded digital device. Item 3

reintroduces 100% testing which is not possible to achieve with

software and then introduces an input/output state analysis. Licensees

will assume this requirement applies to non-safety related equipment

as well as safety related equipment.

Suggested wording:

The following examples of proposed changes are considered within the scope of this RIS.

The list is by no means inclusive and is simply provided to illustrate the nature and relative

complexity of proposed changes targeted by the RIS.

• A one-for-one replacement of analog timing relays with digital timing relays on redundant load sequencer trains

• Replacement of emergency diesel generator (EDG) analog voltage regulators with digital

voltage regulators

• Replacement of EDG auxiliary support system analog controls with digital controls

• Replacement of turbine driven auxiliary feedwater system controls with digital controls

• Installation of safety related breakers and relays (including timing relays) containing

embedded digital devices

• Replacement of safety related analog and electromechanical protective relays with

digital multifunction relays

• All digital upgrades to non-safety related systems are within the scope of this RIS Proposed changes that employ digital equipment with complex application software in redundant safety related trains is considered beyond the scope of this RIS (e.g., a

complete analog-to-digital RPS upgrade). Additionally, proposed changes that add new

cross-channel communications between redundant safety related trains/equipment would

also be considered beyond the scope of this RIS.4825 of 171 Section 3, Item 1c) should be deleted from the RIS, as it already excludes RPS and ESFAS. With respect to emergency load sequencers, this is new requirement that was not previously contained in any of the

I&C guidance documents. The emergency load sequencers are clearly

not part of the RPS or ESFAS. They are within the scope of the onsite

AC power system, with guidance contained in SRP Section 8.3.

Remove this section from the RIS. Including the emergency load sequencers would appear to be a backfit issue.4855 of 171 Section 3, Item 2: "reduces, redundancy, diversity, separation or independence" - if these attributes are design features, rather than

design, or regulatory requirements for that design function, it may not

be necessary to maintain that level of UFSAR described redundancy, diversity, separation, or independence to be an acceptable design. In

other words, if these are not "credited" then maintaining those design

features may not be required. This particularly true for non-safety

related systems, where these attributes are not typical required.

Suggest eliminating this section. If it is kept, then suggest clarifying that the impact of reducing these needs to be assessed for the impact on the plant safety analysis.4895 of 171 The industry has previously commented on the use of the term "100%" testing, and the terms "simple" or "simplicity". These should be noted

as examples of, but not the only examples of, design attributes that can

be used in conjunction with other things, such as quality and Operating

Ex p erience.Suggest removing this from this section, and correcting it in the later table in the RIS attachment. Industry and NRC had previously settled on the term "highly testable". For

example, a circuit breaker or timing relay with an EDD would be examples of digital

devices that are "highly testable". They each have one input and one output and can be

easil y tested to verif y full functionalit y and re p eatabilit y.INDUSTRY COMMENTS TO MARCH 2018 DRAFT RIS 17-XX SUPPLEMENT-1 TO RIS 2002-22 Page 1 of 7 LINE NO.PAGE NO.PRIORITYINDUSTRY COMMENTRECOMMENDED CHANGEADDITIONAL COMMENTSACTION TAKEN INDUSTRY COMMENTS TO MARCH 2018 DRAFT RIS 17-XX SUPPLEMENT-1 TO RIS 2002-225737 of 171 Section 3.1.2 - Quality of the Design Process: This comment applies to Lines 573 through 590. The two paragraphs discussing industry

standards. Licensees will interpret this guidance in a way that concludes

non-safety related equipment must comply with industry standards.

Consider replacing the last 3 paragraphs of this section with the following: "Quality of the design process is a key element in determining the dependability of SSCs affected by proposed modifications. Licensees employing design processes consistent with

their NRC-approved quality assurance programs will result in a quality design process.""The use of applicable industry consensus standards contributes to a quality design process and provides a previously established acceptable approach. In some cases, other

nuclear or non-nuclear standards also provide technically justifiable approaches that can

be used if confirmed applicable for the specific application.""For non-safety related SSCs, adherence to generally accepted quality standards is sufficient. The qualitative assessment should list the generally accepted industry standards

utilized by the equipment manufacturer. If an equipment manufacturer used NRC-

endorsed industry standards during the design and/or manufacturing process for non-

safety related equipment, these standards should be documented in the qualitative

assessment to provide additional evidence of quality.""Specific NRC-endorsed industry standards may be required for qualification of safety related equipment depending on the licensees Appendix B quality assurance program and

specific commitments made within their licensing bases. The qualitative assessment

should provide evidence that the required industry standards were used in the design as

applicable. Any additional industry standards used should also be documented as this can

help bolster the quality argument."5927 of 171 Section 3.1.3 - Operating Experience - Several issues noted.

The language seems focused on applicability with specific sited references or evidence:

Examples:

• Page 8 - 1st para - "-with comparable performance standards and

operating environments."

• Page 8 - 2nd para - "In all cases, the architecture of the referenced

equipment-."

• Page 8 - 3rd para - "-what operating conditions were experienced by

the reference design."

At the site inspection level, this type of language would be problematic as it appears to focus on traceability of documented evidence rather

than evaluating and using operating history to inform the design.

Vendors will not usually provide names of customers associated with a

given problem report, so traceability or specific references to

environmental conditions and other design attributes are not generally

possible to obtain.

Suggestions:

Be less prescriptive on specific evidence required and focus more on what the value of operating history can provide and define what industry should be looking for such as:

• Operating history should be viewed as the largest test bed you could ask for. What you want is a large population used across various industries and in a vast range of operating

conditions, many different applications, etc. The vendor should have published

requirements (e.g., temperature, humidity, voltage limits) for the product. Licensees have

an engineering design process that verifies plant environments against these published

vendor design specs. This should be left to engineering judgment - the RIS should not

require specific environmental evidence as part of the operating history evaluation.

• Another area to look at is whether the vendor has a corrective action or problem reporting structure, what is their threshold for problem reporting, and is the data used to

fix and improved the product. This was touched on in last sentence of page 8, para 1.

See industry provided write-up for the Operating Experience section.

Page 2 of 7 LINE NO.PAGE NO.PRIORITYINDUSTRY COMMENTRECOMMENDED CHANGEADDITIONAL COMMENTSACTION TAKEN INDUSTRY COMMENTS TO MARCH 2018 DRAFT RIS 17-XX SUPPLEMENT-1 TO RIS 2002-225927 of 171 Section 3.1.3 - Operating Experience (Continued):

• It is not clear what are we looking for operating experience to do for us? o Provide a failure rate number or o Provide us insight into the vendors product and processes

o The insights can be a lot better than the calculated failure rates Failure rate numbers are normally military spec numbers based upon sub-component failure rates and are normally inflated (i.e., module has

a failure rate of 1000 yrs.). We should be looking at real failure rate

numbers based upon operating history.

Applicability in the past has meant documenting a specific software/hardware version. Also, looking at operating history across

revision changes is very valuable. It can provide supporting evidence

along with identifying weaknesses in the vendor's programs (e.g., SQA, change management and testing).

Additional Suggestions:

The OE evaluation should not be specifically focused on a failure rate number. Evaluations should look at the number of failures but it should look at the data (the failure report

description) for weaknesses.

o Review the problem reports (filtering on specific areas of interest such a redundancy

helps to manage large amounts of data)

o Repetitive failures would point to a weakness in processes

o Look for software failure vs hardware failures (hardware may be more of a concern)

o Do not limit operating experience to specific revisions (provides insight into the vendor

change process)

o Problem reporting process (data representative and are reporting thresholds) and what

is done with the data (did they fix the issue)

• Table 1 - 3rd bullet - User configurable software applications should not be an issue if

you have large population set. Operating experience of user configurable devices will get a

large number of different and representative configurations to provide valuable insights.6289 of 171 Table 1 - Design Attributes:

Second bullet - with respect to watchdog timers, suggest the changing to the following to clarify: "Watchdog timers that interface with but

operate independently of the software" Fourth Bullet: Suggest changing simple (i.e., enabling 100 percent testing or comprehensive testing in combination with analysis of

likelihood of occurrence of input/output states not tested)" to "(i.e.,

highly testable)" as stated on Line 334 of the RIS.

Fifth Bullet: Suggest changing this item to the following: "Assurance that failures in the new equipment either (1) places the affected SSC in

a safe state, (2) are equivalent to or bounded by the failure state of the

equipment being replaced, or (3) result in a failure state that is

inconsequential at the plant level." The last version of the RIS had the following Design Attribute: "Unlikely series of events - evaluation of a given digital I&C modification requires

postulating multiple independent detected and/or undetected random

failures in order to arrive at a state in which a CCF is actually a concern."

Industry would like NRC to consider maintaining this Design Attribute.

Page 3 of 7 LINE NO.PAGE NO.PRIORITYINDUSTRY COMMENTRECOMMENDED CHANGEADDITIONAL COMMENTSACTION TAKEN INDUSTRY COMMENTS TO MARCH 2018 DRAFT RIS 17-XX SUPPLEMENT-1 TO RIS 2002-226289 of 171 Table 1 - Quality of the Design Process: Industry would like NRC to consider changing this part of Table 1 to the following:

Safety related equipment

• Compliance with industry software standards as applicable and

required by the plant's licensing basis and preferably those consensus

standards currently endorsed by the NRC.

• For non-NRC endorsed codes and standards, the licensee should

provide a documented explanation for why use of the particular non-

endorsed software or system standard is acceptable.

• Use of Appendix B vendors or use of the commercial grade dedication

process based on the guidance provided in EPRI TR-106439.

• Demonstrated qualification testing to withstand environmental

conditions within which the SSC is credited to perform its design

function (e.g., temperature, humidity, seismic, and EMI/RFI

susceptibility) as well as not creating unacceptable EMI/RFI emissions.

Non-safety related equipment

• Adherence to generally accepted quality standards.

• Documentation that equipment manufacturer specifications meet or

exceed the temperature, humidity, and EMI/RFI emissions and

susceptibility requirements levels equal or better than the equipment

being replaced.6289 of 171 Table 1 - Operating Experience: Consider updating the portion of Table 1 based on previous comments on Operating Experience.73012 of 171 The statement: "Sources of CCF, could include the introduction of identical software into redundant channels, the use of shared

resources; or the use of common hardware and software among

systems performing different design functions." implies that a licensee

must evaluate every occurrence within the facility where a digital

device is being used. This is a new concept for licensees. A licensee does

not currently perform an evaluation of the entire plant to determine if a

new piece of equipment to be installed as part of a plant modification

happens to be used in some other plant system.

Consider deleting Section 4.3, Failure Analysis. Licensees already have procedural design guidance on the development of various types of failure analyses, including Failure Modes

and Effects Analyses, Single Failure Analyses, and Software Hazard Analyses, to name a

few.As an alternate suggestion - consider removing "or the use of common hardware and software among systems performing different design functions".

Section 4.3 - Failure Analyses - is particularly troubling in that it requires a licensee to evaluate every SSC in

the plant for each design change to identify if a given

digital component was previously installed. Then the

licensee is required to perform an evaluation to

determine the potential for CCF across SSCs that use a

similar digital device. This in and of itself would turn

out to be a very difficult research project. For

example, assume a licensee desires to install a digital

timing relay in a given SSC. Per the guidance, the

licensee would have to identify any other place in the

plant where that relay was used and then determine if

there is a potential for CCF. Or perhaps a licensee

desires to replace an analog Rosemount transmitter

with a digital Rosemount transmitter in a given

system. Per this guidance, the licensee would have to

evaluate the thousands of Rosemount digital

transmitter installed across the plant to identify if

there is a potential for CCF. This is simply not

reasonable. In some cases, the research to comply

with this portion of the guidance would take longer

than the time needed to complete development of

the engineering change package needed to implement

the change.

Page 4 of 7 LINE NO.PAGE NO.PRIORITYINDUSTRY COMMENTRECOMMENDED CHANGEADDITIONAL COMMENTSACTION TAKEN INDUSTRY COMMENTS TO MARCH 2018 DRAFT RIS 17-XX SUPPLEMENT-1 TO RIS 2002-2280714 of 171 Consider deleting Figure 1. This figure leads a licensee to believe that only a Dependability Evaluation is needed. Licensees would prefer to

have the RIS provide guidance strictly on Qualitative Assessments for

determining equipment/SSC reliability, and then using the Qualitative

Assessment to support arguments made in the 50.59 Evaluation.81015 of 171 Table 2 - See industry version of Table 2.NANA1 This document provides a lot of guidance on I&C design, in particular, for non-safety related systems. In some cases, the requirements go

beyond what is required by the operational quality assurance program

used by licensees, and design and licensing bases requirements for non-

safety related systems. The RIS should focus on the licensing aspects, not the design aspects of digital upgrades.

Remove design requirements from the RIS. Inclusion of design attributes is useful, and should remain.

Licensees know how to design - they have very detailed and proceduralized guidance along with a

quality assurance program. NRC and licensees have

not been aligned on adequate documentation of

design considerations. The new RIS is supposed to

provide licensees with acceptable methods for

documenting qualitative assessments for relaying

their design thought process in a way that an

inspector can understand pertinent design considerations.2641 of 171 Introduction of the term "Dependability Evaluation" is not beneficial.

Industry would like to limit the RIS scope to development of a

Qualitative Assessment. Suggest deleting this entire paragraph.

Suggest eliminating the use of Dependability Evaluation throughout the document, including Section 4.5, and provide guidance only on development of Qualitative

Assessment guidance as NEI 01-01 appears to use these two terms interchangeably.

To simplify the RIS, consider only providing guidance on development of a qualitative assessment. With the

addition of dependability assessments, a licensee will 2801 of 171 Last paragraph of page, second sentence states: "Section 4 of this attachment provides acceptable approaches for engineering

evaluations that may be used in performing and documenting a

qualitative assessment." Industry would ask the NRC to consider

removing the engineering evaluation sections of the RIS as licensees

have existing guidance on development of engineering evaluations for

di g ital chan g es.4705 of 171"implicitly" - The use of "implicitly modeled, or "implicitly described" in this section and (b) below are much too vague, and cannot be

accuratel y assessed.

Remove "implicitly" described, or provide a regulatory basis for including it.662 of 52 The statement: "Additional guidance for addressing potential common cause failure of digital I&C equipment is contained in other NRC

guidance documents and NRC-endorsed industry guidance documents."

should be deleted. This RIS Supplement is essentially providing

guidance on how to address DI&C CCF through qualitative assessments.

As such, this sentence is somewhat contradictory.

Suggest deleting the sentence or provide a reference to the additional NRC guidance documents that address DI&C CCF.1323 of 52 This sends an unbalanced message to the public and other stakeholders, implying that digital modifications are adverse to safety.

Replace the first two sentences starting on line 132 with the following: "In general, utilization of proven digital technology has the potential for significant improvements in the performance and reliability of equipment used in nuclear plants.

Care is appropriate in the implementation of digital technology to avoid unintended

consequences that could include potential software failure, including common cause

failure, or changes introduced in the transition from analog to digital technology including

the scope and effect of a potential failure due to consolidation or reconfiguration of

equipment. The potential for these unintended consequences can be appropriately

managed in the design process as documented in engineering evaluations and addressed

in the assessment of the change required by 10 CFR 50.59 to determine whether NRC

approval is required prior to implementation."3543 of 172 The following statement is problematic: "For digital modifications, particularly those that introduce software, there may be the potential

increase in likelihood of failure, including a single failure. For redundant

SSCs, this potential increase in the likelihood of failure creates a similar

increase in the likelihood of a common cause failure." Suggest deleting this statement as it is irrelevant to the discussion and is not an accurate statement. Please provide the basis for declaring that the potential for SCCF is directly

proportional to the potential increase in likelihood of failure, as not all failures are

common cause.

As an alternative

, use the wordin g su gg ested for Line 132 above.

In practice, the introduction of digital equipment has proven to decrease the likelihood of failure due to

such things as elimination of single points of

vulnerability and self diagnostics.

Page 5 of 7 LINE NO.PAGE NO.PRIORITYINDUSTRY COMMENTRECOMMENDED CHANGEADDITIONAL COMMENTSACTION TAKEN INDUSTRY COMMENTS TO MARCH 2018 DRAFT RIS 17-XX SUPPLEMENT-1 TO RIS 2002-223753 of 172"directly related" - Not all equipment in a system that performs a design function has an equal contribution to the likelihood of

malfunction of that design function. It may be directly related, but may

not directly increase the likelihood. In other words, the contribution of

the I&C potential common cause failure to the overall failure probability

of the design function, is not a "one to one" relationship.

This should be clarified here, and in other sections of the document that use this discussion.4555 of 172"vulnerability" - There is not an issue if a CCF vulnerability is created, that is either bounded by existing analyses, or has no safety impact.

The ke y is to assess the vulnerabilit y.Suggest eliminating this section. If it is kept, then suggest clarifying that the vulnerability needs to be assessed for the impact on the plant safety analysis.7012 Combining design functions - This section uses several similar, but very different terms, such as "design functions", "component functions" and "design functions of SSCs". This is confusing. In particular for non-

safety related systems, there is no requirement to keep SSCs separate, nor a restriction on combinin g them. This section should be simplified to state that if design functions are combined as a result of a digital upgrade, that the vulnerabilities to common cause software failure need to be

identified, understood, and analyzed for impact on the plant safety analysis. The rationale

should be explained in the engineering documentation or qualitative assessment.77512 of 172"risk significant" - The use of the term "risk significant" needs to be clarified here, and in other places in the document. The context

appears to be implying "safety significant". If that is the case, then the

document should tie together this concept by equating risk significant

to "important to safety" in technical space. This would better align with

the use of "design functions" in 50.59 space.

Define the use of risk significant, or remove it.79413 of 172 Section 4.6, Engineering Documentation. Consider deleting this section as licensees already have procedural guidance for development of

retainment of the various engineering products required to support a

engineering design change in accordance with their Appendix B quality p ro g rams.81015 of 172 Table 2 - Step 1, last bullet - the use of "mode" needs to be defined.

This could be interpreted that an evaluation of design functions in

different plant modes (Mode 1, Mode 2, etc.) is required.

Clarify the use of mode, or delete it.1373 of 52 Concern: The RIS expands the use of "qualitative assessment" beyond its use in NEI 01-01. In NEI 01-01, the term is primarily used to address

software. Hardware can be assessed deterministically (i.e. not

qualitatively, or with engineering judgment). In the RIS, the qualitative

assessment is expanded to include deterministic hardware

considerations.

Minor changes throughout the document can resolve the consistency issue.

Page 6 of 7 LINE NO.PAGE NO.PRIORITYINDUSTRY COMMENTRECOMMENDED CHANGEADDITIONAL COMMENTSACTION TAKEN INDUSTRY COMMENTS TO MARCH 2018 DRAFT RIS 17-XX SUPPLEMENT-1 TO RIS 2002-221373 of 52 Concern: The sentence starting with "A qualitative assessment-" on line 137 is an abrupt change that introduces new terminology and

concepts without appropriate transition.

Propose that the balance of that paragraph and the following paragraph, lines 137 through 153, be replaced with the following: "Conforming changes will follow in the body of the RIS Appropriate considerations in the engineering evaluations can avoid potential unintended consequences of a digital upgrade

and provide reasonable assurance that the change results in dependable equipment

supporting design functions, including that the software will support the intended design

functions. Hardware implemented in the change can be designed to ensure functions are

not combined in a manner that expands the impact of a potential failure beyond that

evaluated in the plant Final Safety Analysis Report, as updated. Utilization of appropriate

software development processes, design attributes, and operating experience can provide

assurance that the software will be reliable, with a sufficiently low likelihood of failure."Prior to implementing a digital upgrade, licensees assess the change using the criteria in 10 CFR 50.59 to determine whether the change can be implemented without prior NRC

approval. Assessment of the hardware and design configuration considerations can be

addressed deterministically. Assessment of the software can be addressed qualitatively to

conclude that the likelihood of a consequential software failure is sufficiently low, such

that the effects of a software failure, including potential common cause failure, need not

be further evaluated. Both hardware and software considerations need to be assessed to

support a conclusion that prior NRC approval is not required. The attachment to this RIS

supplement provides a framework for preparing and documenting engineering evaluation

and qualitative assessments of software."1373 of 53 Concern: The sentence starting with "A qualitative assessment-" on line 137 is the start of a new topic and should start a new paragraph.

Start a new paragraph.

EDITORIAL3112 of 173"Adverse" has a distinct meaning in the 50.59 screening process. The use of adverse in the RIS does line up with the meaning of adverse in

50.59.Replace "adverse" with "negative' in both places it appears in the document.

EDITORIAL3452 of 173 Suggest deleting the following statement: "This "sufficiently low" threshold is not interchangeable with that for distinguishing between

events that are "credible" or "not credible." The threshold for

determining whether an event is credible or not is whether it is "as

likely as" (i.e., not "much lower than") malfunctions already assumed in

the UFSAR." Suggest deleting this statement as it is irrelevant to the discussion and may cause confusion. In addition, the term is not used anywhere else in the document.

EDITORIAL3713 This example uses a steam generator tube rupture event. This does not support use by I&C engineers.

Suggest using an I&C example.

EDITORIAL5276 of 173 Consider striking "need to" in the following statement: "However, design features external to the proposed modification (e.g., mechanical

sto p s on valves

) ma y also need to be considered." EDITORIAL Page 7 of 7 UNITED STATES 1 NUCLEAR REGULATORY COMMISSION 2 OFFICE OF NUCLEAR REACTOR 3 REGULATION OFFICE OF NEW REACTORS 4 WASHINGTON, D.C. 20555-0001 5 6 Month XX, 2018 7 8 DRAFT NRC REGULATORY ISSUE

SUMMARY

2002-22, SUPPLEMENT 1 9 CLARIFICATION ON ENDORSEMENT OF NUCLEAR ENERGY INSTITUTE GUIDANCE 10 IN DESIGNING DIGITAL UPGRADES IN INSTRUMENTATION AND CONTROL SYSTEMS 11 12 13 ADDRESSEES 14 15 All holders and applicants for power reactor operating licenses or construction permits under 16 Title 10 of the Code of Federal Regulations (10 CFR) Part 50, ~Domestic Licensing of 17 Production and Utilization Facilities.~

18 19 All holders of and applicants for a combined license, standard design approval, or 20 manufacturing license under 10 CFR Part 52, ~Licenses, Certifications, and Approvals for 21 Nuclear Power Plants.~ All applicants for a standard design certification, including such 22 applicants after initial issuance of a design certification rule.

23 24 All holders of, and applicants for, a construction permit or an operating license for non-power 25 production or utilization facilities under 10 CFR Part 50, including all existing non-power reactors 26 and proposed facilities for the production of medical radioisotopes, such as molybdenum-99, 27 except those that have permanently ceased operations and have returned all of their fuel to the 28 U.S. Department of Energy.

29 30 INTENT 31 32 The U.S. Nuclear Regulatory Commission (NRC) is issuing a supplement to Regulatory Issue 33 Summary (RIS) 2002-22, dated November 25, 2002 (Agencywide Documents Access and 34 Management System (ADAMS) Accession No. ML023160044). In RIS 2002-22, the NRC staff 35 endorsed ~Guideline on Licensing Digital Upgrades: EPRI TR-102348, Revision 1, NEI 01-01: A 36 Revision of EPRI TR-102348 to Reflect Changes to the 10 CFR 50.59 Rule,~ (Nuclear Energy 37 Institute (NEI) hereinafter ~NEI 01-01~) (ADAMS Accession No. ML020860169). NEI 01-01 38 provides guidance for designing, licensing, and implementing digital upgrades and 39 replacements to instrumentation and control (I&C) systems (hereinafter ~digital I&C~) in a 40 consistent and comprehensive manner.

41 42 The purpose of this RIS Supplement is to clarify RIS 2002-22, which remains in effect. The 43 NRC continues to endorse NEI 01-01 as stated in RIS 2002-22, as clarified by this RIS 44 Supplement. Specifically, the guidance in this RIS Supplement clarifies the NRC staff~s 45 endorsement of the guidance pertaining to Sections 4, 5, and Appendices A and B of NEI 01-01.

46 This RIS Supplement clarifies the guidance for preparing and documenting ~qualitative 47 assessments,~ that can be used to evaluate the likelihood of failure of a proposed digital 48 modification, including the likelihood of failure due to a common cause, i.e., common cause 49 failure (CCF). Licensees can use these qualitative assessments to support a conclusion that a 50 51 52 53 ML18051A084 54 Draft RIS 2002-22 Supplement 1 Page 2 of 5 55 proposed digital I&C modification has a sufficiently low 1 likelihood of failure. This conclusion, 56 and the reasons for it, should be documented, per 10 CFR 50.59(d)(1), as part of the 57 evaluations of proposed digital I&C modifications against some of the criteria in 10 CFR 50.59, 58 ~Changes, tests and experiments.~

59 60 This RIS Supplement is not directed toward digital I&C upgrades and replacements of reactor 61 protection systems and engineered safety features actuation systems, since application of the 62 guidance in this RIS Supplement to such changes would likely involve additional considerations.

63 This RIS Supplement does not provide new design process guidance for addressing common 64 cause failure of the reactor protection systems and engineered safety features actuation 65 systems. Additional guidance for addressing potential common cause failure of digital I&C 66 equipment is contained in other NRC guidance documents and NRC-endorsed industry 67 guidance documents.

68 69 This RIS Supplement requires no action or written response on the part of an addressee.

70 71 BACKGROUND INFORMATION 72 73 By letter dated March 15, 2002, NEI submitted EPRI TR-102348, Revision 1 (NEI 01-01) for 74 NRC staff review. NEI 01-01 replaced the original version of EPRI TR-102348, dated 75 December 1993, which the NRC endorsed in Generic Letter 1995-02, ~Use of NUMARC/EPRI 76 Report TR-102348, ~Guideline on Licensing Digital Upgrades,~ in Determining the Acceptability 77 of Performing Analog-to-Digital Replacements Under 10 CFR 50.59,~ dated April 26, 1995 78 (ADAMS Accession No. ML031070081). In 2002, the NRC staff issued RIS 2002-22 to notify 79 addressees that the NRC staff had reviewed NEI 01-01 and was endorsing the report for use as 80 guidance in designing and implementing digital upgrades to nuclear power plant instrumentation 81 and control systems.

82 83 Following the NRC staff~s 2002 endorsement of NEI 01-01, holders of construction permits and 84 operating licenses have used that guidance in support of digital design modifications in 85 conjunction with Regulatory Guide 1.187, ~Guidance for Implementation of 10 CFR 50.59, 86 Changes, Tests, and Experiments,~ dated November 2000 (ADAMS Accession 87 No. ML003759710), which endorsed NEI 96-07, ~Guidelines for 10 CFR 50.59 Implementation,~

88 Revision 1, dated November 2000 (ADAMS Accession No. ML003771157).

89 90 NRC inspections of documentation for digital I&C plant modifications prepared by some 91 licensees using the guidance in NEI 01-01 identified inconsistencies in the performance and 92 documentation of licensee engineering evaluations. NRC inspections also identified 93 documentation issues with the written evaluations of the 10 CFR 50.59(c)(2) criteria. The term 94 ~engineering evaluation~ refers to evaluations performed in designing digital I&C modifications 95 other than the 10 CFR 50.59 evaluation, for example, evaluations performed under the 96 licensee~s NRC approved quality assurance program. This RIS Supplement clarifies the 97 guidance for licensees performing and documenting engineering evaluations and the 98 development of qualitative assessments.

99 100 In response to staff requirements memorandum (SRM)-SECY-16-0070 ~Integrated Strategy to 101 Modernize the Nuclear Regulatory Commission~s Digital Instrumentation and Control Regulatory 102 103 1 NEI 01-01, Page 4-20, defines ~sufficiently low~ to mean much lower than the likelihood of failures that are 104 considered in the UFSAR (e.g., single failures) and comparable to other common cause failures that are 105 not considered in the UFSAR (e.g., design flaws, maintenance errors, calibration errors).

106 Draft RIS 2002-22 Supplement 1 Page 3 of 5 107 Infrastructure~ (ADAMS Accession No. ML16299A157), NRC staff has engaged the public, 108 including NEI and industry representatives, to improve the guidance for applying 10 CFR 50.59 109 to digital I&C-related design modifications as part of a broader effort to modernize I&C 110 regulatory infrastructure. Making available the guidance in this RIS Supplement is described as 111 a near-term action in the integrated action plan to provide specific guidance for documenting 112 qualitative assessments concluding that a proposed digital I&C modification will exhibit a 113 sufficiently low likelihood of failure.

114 115 Applicability to Non-Power Reactor Licensees 116 117 The examples and specific discussion in this RIS Supplement and other guidance referenced 118 by this RIS Supplement (i.e., NEI 01-01 and original RIS 2002-22) primarily focus on power 119 reactors. Nonetheless, licensees of non-power production or utilization facilities (NPUFs) may 120 also use the guidance in RIS 2002-22 and apply the guidance in this RIS Supplement to 121 develop written evaluations addressing the criteria in 10 CFR 50.59(c)(2). In particular, NPUF 122 licensees may use the guidance to prepare qualitative assessments that consider design 123 attributes, quality measures, and applicable operating experience to evaluate proposed digital 124 I&C changes to their facilities as described in Sections 4, 5, and Appendix A of NEI 01-01.

125 However, certain aspects of the guidance that discuss the relationship of other regulatory 126 requirements to 10 CFR 50.59 may not be fully applicable to NPUFs (e.g., 10 CFR Part 50, 127 Appendix A and B are not applicable to NPUFs).

128 129

SUMMARY

OF ISSUE 130 131 In general, digital I&C modifications may include a potential for an increase in the likelihood of 132 equipment failures occurring within modified SSCs, including common cause failures. In 133 particular, digital I&C modifications that introduce or modify identical software within 134 independent trains, divisions, or channels within a system, and those that introduce new shared 135 resources, hardware, or software among multiple control functions, may include such a 136 potential. A qualitative assessment can be used to support a conclusion that there is not more 137 than a minimal increase in the frequency of occurrence of accidents or in the likelihood of 138 occurrence of malfunctions (10 CFR 50.59(c)(2)(i) and (ii)). A qualitative assessment can also 139 be used to support a conclusion that the proposed modification does not create the possibility of 140 an accident of a different type or malfunction with a different result than previously evaluated in 141 the UFSAR (10 CFR 50.59(c)(2)(v) and (vi)).

142 143 For digital I&C modifications, an adequate basis for a determination that a change involves a 144 sufficiently low likelihood of failure may be derived from a qualitative assessment of factors 145 involving system design features, the quality of the design processes employed, and an 146 evaluation of relevant operating experience of the software and hardware used (i.e., product 147 maturity and in-service experience). A licensee may use a qualitative assessment to document 148 the factors and rationale for concluding that there is an adequate basis for determining that a 149 digital I&C modification will exhibit a sufficiently low likelihood of failure. In doing so, a licensee 150 may consider the aggregate of these factors. The attachment to this RIS Supplement provides 151 a framework for preparing and documenting qualitative assessments and engineering 152 evaluations.

153 154 In addition, this RIS Supplement clarifies the applicability of some aspects of the NRC policy 155 described in Item II.Q of SRM/SECY 93-087, ~Policy, Technical, and Licensing Issues 156 Pertaining to Evolutionary and Advanced Light Water Reactor (ALWR) Designs,~ (ADAMS 157 Draft RIS 2002-22 Supplement 1 Page 4 of 5 158 No. ML003708056), in regard to the application of 10 CFR 50.59(c)(2) criteria for digital I&C 159 modifications.

160 161 BACKFITTING AND ISSUE FINALITY DISCUSSION 162 163 This RIS Supplement clarifies but does not supersede RIS 2002-22, and includes additional 164 guidance regarding how to perform and document qualitative assessments for digital I&C 165 changes under 10 CFR 50.59.

166 167 The NRC does not intend or approve any imposition of the guidance in this RIS Supplement, 168 and this RIS Supplement does not contain new or changed requirements or staff positions that 169 constitute either backfitting under the definition of backfitting in 10 CFR 50.109(a)(1) or a 170 violation of issue finality under any of the issue finality provisions in 10 CFR Part 52. Therefore, 171 this RIS Supplement does not represent backfitting as defined in 10 CFR 50.109(a)(1), nor is it 172 otherwise inconsistent with any issue finality provision in 10 CFR Part 52. Consequently, the 173 NRC staff did not perform a backfit analysis for this RIS Supplement or further address the issue 174 finality criteria in 10 CFR Part 52.

175 176 FEDERAL REGISTER NOTIFICATION 177 178 The NRC will publish a notice of opportunity for public comment on this draft RIS in the Federal 179 Register. 180 181 CONGRESSIONAL REVIEW ACT 182 183 This RIS is a rule as defined in the Congressional Review Act (5 U.S.C. §§ 801-808). However, 184 the Office of Management and Budget has not found it to be a major rule as defined in the 185 Congressional Review Act.

186 187 PAPERWORK REDUCTION ACT STATEMENT 188 189 This RIS provides guidance for implementing mandatory information collections covered by 190 10 CFR Part 50 that are subject to the Paperwork Reduction Act of 1995 (44 U.S.C. 3501 et.

191 seq.). This information collection was approved by the Office of Management and Budget 192 (OMB) under control number 3150-0011. Send comments regarding this information collection 193 to the Information Services Branch, U.S. Nuclear Regulatory Commission, Washington, DC 194 20555-0001, or by e-mail to Infocollects.Resource@nrc.gov , and to the Desk Officer, Office of 195 Information and Regulatory Affairs, NEOB-10202, (3150-0011) Office of Management and 196 Budget, Washington, DC 20503.

197 198 Public Protection Notification 199 200 The NRC may not conduct or sponsor, and a person is not required to respond to, a request 201 for information or an information collection requirement unless the requesting document 202 displays a currently valid OMB control number.

203 Draft RIS 2002-22 Supplement 1 Page 5 of 5 204 CONTACT 205 206 Please direct any questions about this matter to the technical contact(s) or the Lead Project 207 Manager listed below.

208 209 210 211 Timothy J. McGinty, Director Christopher G. Miller, Director 212 Division of Construction Inspection Division of Inspection and Regional Support 213 and Operation Programs Office of Nuclear Reactor Regulation 214 Office of New Reactors 215 216 217 Technical Contacts: David Rahn, NRR Wendell Morton, NRR 218 301-415-1315 301-415-1658 219 e-mail: David.Rahn@nrc.gov e-mail: Wendell.Morton@nrc.gov 220 221 Norbert Carte, NRR David Beaulieu, NRR 222 301-415-5890 301-415-3243 223 e-mail: Norbert.Carte@nrc.gov e-mail: David.Beaulieu@nrc.gov 224 225 Duane Hardesty, 226 NRR 301-415-3724 227 email: Duane.Hardesty@nrc.gov (Specifically for non-power reactors) 228 229 230 Project Manager Contact: Tekia Govan, NRR 231 301-415-6197 232 e-mail: Tekia.Govan@nrc.gov 233 234 235 Note: NRC generic communications may be found on the NRC public Web site, 236 http://www.nrc.gov, under NRC Library/Document Collections.

237 238 239

Attachment:

Qualitative Assessment and Engineering Evaluation Framework 240 Qualitative Assessment and Engineering Evaluation Framework 241 242 243 1. Purpose 244 245 Regulatory Issue Summary (RIS) 2002-22 provided the U.S. Nuclear Regulatory Commission 246 (NRC) staff~s endorsement of Nuclear Energy Institute (NEI) Guidance document NEI 01-01, 247 ~Guideline on Licensing Digital Upgrades: EPRI TR-102348, Revision 1, NEI 01-01: A Revision 248 of EPRI TR-102348 To Reflect Changes to the 10 CFR 50.59 Rule.~ NEI 01-01 provides 249 guidance for implementing and licensing digital upgrades, in a consistent, comprehensive, and 250 predictable manner, as well as guidance in performing qualitative assessments of the 251 dependability of digital instrumentation and control (I&C) systems.

252 253 The purpose of this attachment is to provide supplemental clarifying guidance to licensees to 254 ensure that, if qualitative assessments are used, they are described and documented 255 consistently, through an evaluation of applicable qualitative evidence. Following the guidance in 256 RIS 2002-22 and NEI 01-01, as clarified by the guidance in this RIS Supplement, will help 257 licensees document qualitative assessments ~in sufficient detail ~ that an independent third 258 party can verify the judgements,~ as stated in NEI 01-01. While this qualitative assessment is 259 used to support the Title 10 of the Code of Federal Regulations (10 CFR) 50.59, ~Changes tests 260 and experiments,~ evaluation, it does not provide guidance for screening and it does not 261 presume that all digital modifications ~screen in.~

262 263 NEI 01-01 uses the terms ~qualitative assessment~ and ~dependability evaluations~

264 interchangeably. Within this document only the terms ~qualitative assessment~ and ~sufficiently 265 low 2~ are used in conjunction with performance of 10 CFR 50.59 evaluations. The term 266 ~dependability evaluation~ is used in the context of engineering evaluations, which are not 267 performed or documented as part of a 10 CFR 50.59 evaluation, but engineering evaluations 268 are performed in accordance with the licensee~s NRC quality assurance program in developing 269 digital I&C modification.

270 271 If a ~qualitative assessment~ determines that a potential failure (e.g., software common cause 272 failure (CCF) has a sufficiently low likelihood, then the effects of the failure do not need to be 273 considered in the 10 CFR 50.59 evaluation. Thus, the ~qualitative assessment~ provides a 274 means of addressing software CCF. In some cases, the effects of a software CCF may not 275 create a different result than any previously evaluated in the updated final safety analysis report 276 (UFSAR). 277 278 Sections 2 and 3 of this attachment provide acceptable approaches for describing the scope, 279 form, and content of the type of a qualitative assessment described above. Section 4 of this 280 attachment provides acceptable approaches for engineering evaluations that may be used in 281 performing and documenting a qualitative assessment.

282 283 284 285 286 287 288 289 2 NEI 01-01, Page 4-20, defines ~sufficiently low~ to mean much lower than the likelihood of failures that are 290 considered in the UFSAR (e.g., single failures) and comparable to other common cause failures that are 291 not considered in the UFSAR (e.g., design flaws, maintenance errors, calibration errors).

292 293 294 Attachment 295 Draft RIS 2002-22 Supplement 1, Attachment Page 2 of 17 296 2. Regulatory Clarification~Application of Qualitative Assessments to Title 10 of the 297 Code of Federal Regulations, Section 50.59 298 299 When a licensee decides to undertake an activity that changes its facility as described in the 300 updated final safety evaluation report, the licensee first performs the engineering and technical 301 evaluations in accordance with plant procedures. If the licensee determines that an activity is 302 acceptable through appropriate engineering and technical evaluations, the licensee enters the 303 10 CFR 50.59 process. The regulations in 10 CFR 50.59 provide a threshold for regulatory 304 review, not a determination of safety, for the proposed activities. In addition, 10 CFR 50.59 305 establishes the conditions under which licensees may make changes to the facility or 306 procedures and conduct tests or experiments without prior NRC approval.

307 308 Evaluations must address all elements of proposed changes. Some elements of a change may 309 have positive effects on SSC failure likelihood while other elements of a change may have 310 adverse effects. As derived from the guidance in NEI 96-07, positive and negative elements 311 can be considered together if they are interdependent. This means that if elements are not 312 interdependent, they must be evaluated separately.

313 314 2.1 Likelihood 315 316 Properly documented qualitative assessments may be used to support a conclusion that a 317 proposed digital I&C modification has a sufficiently low likelihood of failure, consistent with the 318 UFSAR analysis assumptions. This conclusion is used in the 10 CFR 50.59 written evaluation 319 to determine whether prior NRC approval is required.

320 321 Qualitative Assessment 322 323 The determination that a digital I&C modification will exhibit a sufficiently low likelihood of failure 324 can be derived from a qualitative assessment of factors involving system design attributes, the 325 quality of the design processes employed, the operating experience with the software and 326 hardware used (i.e., product maturity and in-service experience). Documenting the qualitative 327 assessment includes describing the factors, rationale, and reasoning (including engineering 328 judgement) for determining that the digital I&C modification exhibits a sufficiently low likelihood 329 of failure.

330 331 The determination of likelihood of failure may consider the aggregate of all the factors described 332 above. Some of these factors may compensate for weaknesses in other areas. For example, 333 for a digital device that is simple and highly testable, thorough testing may provide additional 334 assurance of a sufficiently low likelihood of failure that helps compensate for a lack of operating 335 experience.

336 337 Qualitative Assessment Outcome 338 339 There are two possible outcomes of the qualitative assessment: (1) failure likelihood is 340 ~sufficiently low,~ and (2) failure likelihood is not ~sufficiently low.~ Guidance in NEI 01-01, 341 Section 4.3.6, states, ~sufficiently low~ means much lower than the likelihood of failures that are 342 considered in the UFSAR (e.g., single failures) and comparable to other common cause failures 343 that are not considered in the UFSAR (e.g., design flaws, maintenance error, calibration errors).

344 This ~sufficiently low~ threshold is not interchangeable with that for distinguishing between 345 events that are ~credible~ or ~not credible.~ The threshold for determining whether an event is 346 Draft RIS 2002-22 Supplement 1, Attachment Page 3 of 17 347 credible or not is whether it is ~as likely as~ (i.e., not ~much lower than~) malfunctions already 348 assumed in the UFSAR.

349 350 Likelihood Thresholds for 10 CFR 50.59(c)(2)(i), (ii), (v), and (vi) 351 352 A key element of 10 CFR 50.59 evaluations is demonstrating whether the modification 353 considered will exhibit a sufficiently low likelihood of failure. For digital modifications, 354 particularly those that introduce software, there may be a potential increase in likelihood of 355 failure. For redundant SSCs, this potential increase in the likelihood of failure creates a similar 356 increase in the likelihood of a common cause failure.

357 358 The ~sufficiently low~ threshold discussions have been developed using criteria from NEI 96-07, 359 Revision 1, and NEI 01-01. They are intended to clarify the existing 10 CFR 50.59 guidance 360 and should not be interpreted as a new or modified NRC position.

361 362 Criteria 363 364 Although it may be required by other criteria, prior NRC approval is not required by 10 CFR 365 50.59(c)(2)(i), (ii), (v), and (vi) if there is a qualitative assessment outcome of sufficiently low, as 366 described below:

367 368 10 CFR 50.59(c)(2)(i) 369 370 Does the activity result in more than a minimal increase in the frequency of occurrence of an 371 accident previously evaluated in the UFSAR?

372 373 ~Sufficiently low~ threshold ~ The frequency of occurrence of an accident is directly 374 related to the likelihood of failure of equipment that initiates the accident (e.g., an 375 increase in the likelihood of a steam generator tube failure has a corresponding increase 376 in the frequency of a steam generator tube rupture accident). Thus, an increase in 377 likelihood of failure of the modified equipment results in an increase in the frequency of 378 the accident. Therefore, if the qualitative assessment outcome is ~sufficiently low,~ then 379 there is a no more than a minimal increase in the frequency of occurrence of an accident 380 previously evaluated in the UFSAR.

381 382 10 CFR 50.59(c)(2)(ii) 383 384 Does the activity result in more than a minimal increase in the likelihood of occurrence of a 385 malfunction of a structure, system, or component (SSC) important to safety 3 previously 386 evaluated in the UFSAR?

387 388 ~Sufficiently low~ threshold ~ The likelihood of occurrence of a malfunction of an SSC 389 important to safety is directly related to the likelihood of failure of equipment that causes 390 a failure of SSCs to perform their intended design functions 4 (e.g., an increase in the 391 392 3 NEI 96-07, Revision 1, Section 3.9, states, ~Malfunction of SSCs important to safety means the failure of SSCs to 393 perform their intended design functions described in the UFSAR (whether or not classified as safety-related in 394 accordance with 10 CFR [Part] 50, Appendix B).~

395 4 The term ~design functions,~ as used in this RIS Supplement, conforms to the definition of ~design functions~ in NEI 396 96-07, Revision 1.

397 Draft RIS 2002-22 Supplement 1, Attachment Page 4 of 17 398 likelihood of failure of an auxiliary feedwater (AFW) pump has a corresponding increase 399 in the likelihood of occurrence of a malfunction of SSCs~the AFW pump and AFW 400 system). Thus, the likelihood of failure of modified equipment that causes the failure of 401 SSCs to perform their intended design functions is directly related to the likelihood of 402 occurrence of a malfunction of an SSC important to safety. Therefore, if the qualitative 403 assessment outcome is ~sufficiently low,~ then the activity does not result in more than a 404 minimal increase in the likelihood of occurrence of a malfunction of an SSC important to 405 safety previously evaluated in the UFSAR.

406 407 10 CFR 50.59(c)(2)(v) 408 409 Does the activity create a possibility for an accident of a different type than any previously 410 evaluated in the UFSAR?

411 412 ~Sufficiently low~ threshold~NEI 96-07, Revision 1, Section 4.3.5, states, ~Accidents of a 413 different type are limited to those that are as likely to happen as those previously 414 evaluated in the UFSAR.~ Accidents of a different type are caused by failures of 415 equipment that initiate an accident of a different type. If the outcome of the qualitative 416 assessment of the proposed change is that the likelihood of failure associated with the 417 proposed activity is ~sufficiently low,~ then there are no failures introduced by the activity 418 that are as likely to happen as those in the UFSAR that can initiate an accident of a 419 different type. Therefore, the activity does not create a possibility for an accident of a 420 different type than any previously evaluated in the UFSAR. If the qualitative assessment 421 determines that a potential failure (e.g., software CCF) does not have a sufficiently low 422 likelihood, then the effects of this failure need to be considered in the 10 CFR 50.59 423 evaluation.

424 425 10 CFR 50.59(c)(2)(vi) 426 427 Does the activity create a possibility for a malfunction of an SSC important to safety with a 428 different result than any previously evaluated in the UFSAR?

429 430 ~Sufficiently low~ threshold ~ NEI 96-07, Section 4.3.6, states, ~~malfunctions with a 431 different result are limited to those that are as likely to happen as those in the UFSAR.~

432 A malfunction of an SSC important to safety is an equipment failure that causes the 433 failure of SSCs to perform their intended design functions. If the outcome of the 434 qualitative assessment of the proposed change is that the likelihood of failure associated 435 with the proposed activity is ~sufficiently low,~ then there are no failures introduced by the 436 activity that are as likely to happen as those in the UFSAR. Therefore, the activity does 437 not create a possibility for a malfunction of an SSC important to safety with a different 438 result than any previously evaluated in the UFSAR. If the qualitative assessment 439 determines that a potential failure (e.g., software CCF) does not have a sufficiently low 440 likelihood, then the effects of this failure need to be considered in the 10 CFR 50.59 441 evaluation using methods consistent with the plant~s UFSAR.

442 443 3. Qualitative Assessments 444 445 The NRC staff has determined that proposed digital I&C modifications having the characteristics 446 listed below are likely to result in qualitative assessment outcomes that support a sufficiently low 447 likelihood determination:

448 Draft RIS 2002-22 Supplement 1, Attachment Page 5 of 17 449 450 451 452 1. Digital I&C modifications that:

453 454 a) Do not create a CCF vulnerability due to the integration of subsystems or 455 components from different systems that combine design functions that were 456 not previously combined within the same system, subsystem, or component 457 being replaced.

458 459 Note: ~Integration,~ as used in this RIS supplement refers to the process of 460 combining software components, hardware components, or both into an overall 461 system, or the merger of the design function of two or more systems or 462 components into a functioning, unified system or component. Integration also 463 refers to the coupling of design functions (software/ hardware) via bi-directional 464 digital communications. Modifications can result in design functions of different 465 systems being integrated or combined either directly in the same digital device or 466 indirectly via shared resources, such as bi-directional digital communications or 467 networks, common controllers, power supplies, or visual display units. Such 468 integration could be problematic because the safety analysis may have explicitly 469 or implicitly modeled the equipment performing the design functions that would 470 be integrated on the basis that it is not subject to any potential source of common 471 cause failure.

472 473 b) Do not create a CCF vulnerability due to new shared resources (such as 474 power supplies, controllers, and human-machine interfaces) with other design 475 functions that are (i) explicitly or implicitly described in the UFSAR as 476 functioning independently from other plant design functions, or (ii) modeled in 477 the current design basis to be functioning independently from other plant 478 design functions.

479 480 c) Do not affect reactor trip or engineered safety feature initiation/control logic or 481 emergency power bus load sequencers.

482 483 2. Digital I&C modifications that maintain the level of diversity, separation, and 484 independence of design functions described in the UFSAR. A change that reduces 485 redundancy, diversity, separation or independence of USFAR-described design 486 functions is considered a more than minimal increase in the likelihood of malfunction.

487 488 3. Digital I&C modifications that are sufficiently simple (as demonstrated through 100 489 percent testing or a combination of testing and input/output state analysis); or 490 demonstrate adequate internal diversity.

491 492 3.1 Qualitative Assessment Categories 493 494 Consistent with the guidance provided in NEI 01-01, this attachment specifies three general 495 categories of characteristics: design attributes, quality of the design process, and operating 496 experience. Qualitatively assessing and then documenting these characteristics separately, by 497 category, and in the aggregate provides a common framework that will better enable licensees 498 Draft RIS 2002-22 Supplement 1, Attachment Page 6 of 17 499 to document qualitative assessments ~in sufficient detail ~ that an independent third party can 500 verify the judgements.

501 502 Table 1 provides acceptable examples of design attributes, quality of the design processes, and 503 documentation of operating experience. This listing is not all inclusive nor does the qualitative 504 assessment need to address each specific item.

505 506 3.1.1 Design attributes 507 508 NEI 01-01 Section 5.3.1 states:

509 510 To determine whether a digital system is sufficiently dependable, and therefore 511 that the likelihood of failure is sufficiently low, there are some important 512 characteristics that should be evaluated. These characteristics, discussed in 513 more detail in the following sections include: Hardware and software design 514 features that contribute to high dependability (See Section 5.3.4). Such 515 [hardware and software design] features include built-in fault detection and failure 516 management schemes, internal redundancy and diagnostics, and use of software 517 and hardware architectures designed to minimize failure consequences and 518 facilitate problem diagnosis.

519 520 Consistent with the above-quoted text, design attributes of a proposed modification can prevent 521 or limit failures from occurring. A qualitative assessment describes and documents hardware 522 and software design features that contribute to high dependability. Design attributes focus 523 primarily on built-in features such as fault detection and failure management schemes, internal 524 redundancy and diagnostics, and use of software and hardware architectures and facilitate 525 problem diagnosis. However, design features external to the proposed modification (e.g., 526 mechanical stops on valves) may also need to be considered.

527 528 Many system design attributes, procedures, and practices can contribute to significantly 529 reducing the likelihood of failure (e.g., CCF). A licensee can account for this by deterministically 530 assessing the specific vulnerabilities through postulated failure modes (e.g., software CCF) 531 within a proposed modification and applying specific design attributes to address those 532 vulnerabilities (see Table 1). An adequate qualitative assessment regarding the likelihood of 533 failure of a proposed modification would consist of a description of: (a) the potential failures 534 introduced by the proposed modification, (b) the design attributes used to resolve identified 535 potential failures, and (c) how the chosen design attributes and features resolve identified 536 potential failures.

537 538 Diversity is one example of a design attribute that can be used to demonstrate an SSC modified 539 with digital technology is protected from a loss of design function due to a potential common 540 cause failure. In some cases, a plant~s design basis may specify diversity as part of the design.

541 In all other cases, the licensees need not consider the use of diversity (e.g., as described in the 542 staff requirements memorandum on SECY 93-087) in evaluating a proposed modification.

543 However, diversity within the proposed design, and any affected SSCs is a powerful means for 544 significantly reducing the occurrence of failures affecting the accomplishment of design 545 functions.

546 Draft RIS 2002-22 Supplement 1, Attachment Page 7 of 17 547 3.1.2 Quality of the Design Process 548 549 Section 5.3.3 of NEI 01-01 states:

550 551 ~For digital equipment incorporating software, it is well recognized that 552 prerequisites for quality and dependability are experienced software engineering 553 professionals combined with well-defined processes for project management, 554 software design, development, implementation, verification, validation, software 555 safety analysis, change control, and configuration control.

556 557 Consistent with the guidance provided in NEI 01-01, ~Quality Design Processes~ means those 558 processes employed in the development of the proposed modification. Such processes include 559 software development, hardware and software integration processes, hardware design, and 560 validation and testing processes that have been incorporated into the development process.

561 For safety-related equipment this development process would be documented and available for 562 referencing in the qualitative assessment for proposed modifications. However, for 563 commercial-grade-dedicated or non-safety related equipment documentation of the 564 development process may not be readily available. In such cases, the qualitative assessment 565 may place greater emphasis on the design attributes included and the extent of successful 566 operating experience for the equipment proposed.

567 568 Quality of the design process is a key element in determining the dependability of proposed 569 modifications. Licensees employing design processes consistent with their NRC-approved 570 quality assurance programs will result in a quality design process.

571 572 When possible, the use of applicable industry consensus standards contributes to a quality 573 design process and provides a previously established acceptable approach (e.g., Institute of 574 Electrical and Electronics Engineers (IEEE) Standard 1074-2006, ~IEEE Standard for 575 Developing a Software Project Life Cycle Process,~ endorsed in Regulatory Guide 1.173, 576 ~Developing Software Life Cycle Processes for Digital Computer Software Used in Safety 577 Systems of Nuclear Power Plant~). In some cases, other nuclear or non-nuclear standards also 578 provide technically justifiable approaches that can be used if confirmed applicable for the 579 specific application.

580 581 Quality standards should not be confused with quality assurance programs or procedures.

582 Quality standards are those standards which describe the benchmarks that are specified to be 583 achieved in a design. Quality standards should be documents that are established by 584 consensus and approved by an accredited standards development organization. For example, 585 IEEE publishes consensus-based quality standards relevant to digital I&C modifications and is a 586 recognized standards development organization. Quality standards used to ensure the 587 proposed change has been developed using a quality design process do not need to be solely 588 those endorsed by the NRC staff. The qualitative assessment document should demonstrate 589 that the standard being applied is valid for the circumstances for which it is being used.

590 591 3.1.3 Operating Experience 592 593 Section 5.3.1 of NEI 01-01 states, ~Substantial applicable operating history reduces uncertainty 594 in demonstrating adequate dependability.~

595 Draft RIS 2002-22 Supplement 1, Attachment Page 8 of 17 596 Consistent with the above-quoted text, relevant operating experience can be used to help 597 demonstrate that software and hardware employed in a proposed modification have adequate 598 dependability. The licensee may document information showing that the proposed system or 599 component modification employs equipment with significant operating experience in nuclear 600 power plant applications, or in non-nuclear applications with comparable performance standards 601 and operating environment. The licensee may also consider whether the suppliers of such 602 equipment incorporate quality processes such as continual process improvement, incorporation 603 of lessons learned, etc., and document how that information demonstrates adequate equipment 604 dependability.

605 606 Operating experience relevant to a proposed digital I&C change may be credited as part of an 607 adequate basis for a determination that the proposed change does not result in more than a 608 minimal increase in the frequency of occurrence of initiating events that can lead to accidents or 609 in more than a minimal increase in the likelihood of occurrence of a malfunction of an SSC 610 important to safety previously evaluated in the UFSAR. Differences may exist in the specific 611 digital I&C application between the proposed digital I&C modification and that of the equipment 612 and software whose operating experience is being credited. In all cases, however, the 613 architecture of the referenced equipment and software should be substantially similar to that of 614 the system being proposed.

615 616 Further, the design conditions and modes of operation of the equipment whose operating 617 experience is being referenced also needs to be substantially similar to that being proposed as 618 a digital I&C modification. For example, one needs to understand what operating conditions 619 (e.g., ambient environment, continuous duty, etc.) were experienced by the referenced design.

620 In addition, it is important to recognize that when crediting operating experience from other 621 facilities, one needs to understand what design features were present in the design whose 622 operating experience is being credited. Design features that serve to prevent or limit possible 623 common cause failures in a design referenced as relevant operating experience should be 624 noted and considered for inclusion in the proposed design. Doing so would provide additional 625 support for a determination that the dependability of the proposed design will be similar to the 626 referenced application.

627 Draft RIS 2002-22 Supplement 1, Attachment Page 9 of 17 628 Table 1~Qualitative Assessment Category Examples Cate gories Exam ples for Each Cate g or y Design Attributes

• Design criteria~Diversity (if applicable), Independence, and Redundancy.

• Inherent design features for software, hardware or architectural/network~

Watchdog timers that operate independent of software, isolation devices, segmentation of distributed networks, self-testing, and self-diagnostic features.

• Basis for identifying that possible triggers are non-concurrent.

• Sufficiently simple (i.e., enabling 100 percent testing or comprehensive testing in combination with analysis of likelihood of occurrence of input/output states not tested).

• Failure state always known to be safe, or at least the same state as allowed by the previously installed equipment safety analysis. Quality of the Design Process

• Justification for use of industry consensus standards~for codes and standards not endorsed by the NRC.

• Justification for use of other standards.

• Use of Appendix B vendors. If not an Appendix B vendor, the analysis can state which generally accepted industrial quality program was applied.

• Use of Commercial Grade Dedication processes per guidance of EPRI TR-106439, Annex D of IEEE 7-4.3.2, and examples within EPRI TR-107330.

• Demonstrated capability (e.g., through qualification testing) to withstand environmental conditions within which the SSC is credited to perform its design function (e.g., EMI/RFI, Seismic).

• Development process rigor (adherence to generally-accepted commercial or nuclear standards.)

• Demonstrated dependability of custom software code for application software through extensive evaluation or testing. Operating Experience

• Wide range of operating experience in similar applications, operating environments, duty cycles, loading, comparable configurations, etc., to that of the proposed modification.

• History of lessons learned from field experience addressed in the design.

• Relevant operating experience: Architecture of the referenced equipment and software (operating system and application) along with the design conditions and modes of operation of the equipment should be substantially similar to those of the system being proposed as a digital I&C modification. High volume production usage in different applications~Note that for software, the concern is centered on lower volume, custom, or user-configurable software applications. High volume, high quality commercial products with relevant operating experience used in other applications have the potential to avoid design errors.

• Experience working with software development tools used to create configuration files.

Draft RIS 2002-22 Supplement 1, Attachment Page 10 of 17 629 3.2 Qualitative Assessment Documentation 630 631 The U.S. Nuclear Regulatory Commission endorsed guidance for documenting 10 CFR 50.59 632 evaluations to meet the requirements of 10 CFR 50.59 (d) is provided in both NEI 96-07, 633 Revision 1 in Section 5.0, ~Documentation and Reporting~ and NEI 01-01, Appendix B. Both of 634 these documents reiterate the principles that documentation should include an ~~ explanation 635 providing adequate basis for the conclusion~ so that a ~knowledgeable reviewer could draw the 636 same conclusion.~

637 638 Considerations and conclusions reached while performing qualitative assessments supporting 639 the evaluation criteria of 10 CFR 50.59, are subject to the aforementioned principles. In order 640 for a knowledgeable reviewer to draw the same conclusion regarding qualitative assessments, 641 details of the considerations made, and their separate and aggregate effect on any qualitative 642 assessments need to be included or clearly referenced in the 10 CFR 50.59 evaluation 643 documentation. References to other documents should include the document name and location 644 of the information within any referenced document.

645 646 If qualitative assessment categories are used, each category would be discussed in the 647 documentation including positive and negative aspects considered, consistent with the 648 examples provided in Table 1. In addition, a discussion of the degree to which each of the 649 categories was relied on to reach the qualitative assessment conclusion would be documented.

650 651 4. Engineering Evaluations 652 653 4.1 Overview 654 655 This section describes approaches that could be used for conducting and documenting 656 engineering evaluations. completed in accordance with the licensee~s NRC approved quality 657 assurance program. The term ~engineering evaluation~ refers to evaluations performed in 658 designing digital I&C modifications. These evaluations are performed under the licensee~s NRC 659 approved quality assurance program. These engineering evaluations may include, but are not 660 limited to discussion of compliance with regulatory requirements and conformity to the UFSAR, 661 regulatory guidance, and design standards.

662 663 In addition, these engineering evaluations may include discussions of: a) the performance of 664 deterministic failure analyses, including analysis of the effects of digital I&C failures at the 665 component-level, system-level, and plant-level; b) the evaluation of defense-in-depth; and c) the 666 evaluation of the proposed modification for its overall ~dependability.~ The qualitative 667 assessment framework discussed in the previous sections of this attachment may rely, in part, 668 on the technical bases and conclusions documented within these engineering evaluations.

669 Thus, improved performance and documentation of engineering evaluations can enable better 670 qualitative assessments.

671 672 One result of performing these evaluations is to provide insights as to whether a proposed 673 digital I&C design modification may need to be enhanced with the inclusion of different or 674 additional design attributes. Such different or additional design attributes would serve to 675 prevent the occurrence of a possible CCF or reduce the potential for a software CCF to cause a 676 loss of design function.

677 Draft RIS 2002-22 Supplement 1, Attachment Page 11 of 17 678 These approaches are provided for consideration only. They do not represent NRC 679 requirements and may be used at the discretion of licensees.

680 681 4.2 Selected Design Considerations 682 683 During the design process, it is important to consider both the positive effects of installing the 684 digital equipment (e.g., elimination of single-point vulnerabilities (SPVs), ability to perform signal 685 validation, diagnostic capabilities) with the potential negative effects (e.g., software CCF).

686 687 Digital I&C modifications can reduce SSC independence. Reduction in independence of design 688 functions from that described in the USFAR would require prior NRC approval.

689 690 4.2.1 Digital Communications 691 692 Careful consideration of digital communications is needed to preclude adverse effects on SSC 693 independence. DI&C-ISG-04, Revision 1, ~Highly-Integrated Control Rooms - Communications 694 Issues~ (Agencywide Documents Access and Management System Accession Number 695 ML083310185) provides guidance for NRC staff reviewing digital communications. This ISG 696 describes considerations for the design of communications between redundant SSCs, echelons 697 of defense-in-depth 5 or SSCs with different safety classifications. The principles of this ISG or 698 other technically justifiable considerations, may be used to assess non-safety related SSCs.

699 700 4.2.2 Combining Design Functions 701 702 Combining design functions of different safety-related or non-safety related SSCs in a manner 703 not previously evaluated or described in the UFSAR could introduce new interdependencies and 704 interactions that make it more difficult to account for new potential failure modes. Failure of 705 combined design functions that: 1) can effect malfunctions of SSCs or accidents evaluated in 706 the UFSAR; or 2) involve different defense-in-depth echelons; are of significant concern.

707 708 Combining previously separate component functions can result in more dependable system 709 performance due to the tightly coupled nature of the components and a reduction in complexity.

710 If a licensee proposes to combine previously separate design functions in a safety-related 711 and/or non-safety related digital I&C modification, possible new failures need to be carefully 712 weighed with respect to the benefits of combining the previous separately controlled functions.

713 Failure analyses and control system segmentation analyses can help identify potential issues.

714 Segmentation analyses are particularly helpful for the evaluation of the design of non-safety 715 related distributed networks.

716 717 4.3 Failure Analyses 718 719 Failure analysis can be used to identify possible CCFs in order to assess the need to further 720 modify the design. In some cases, potential failures maybe excluded from consideration if the 721 failure has been determined to be implausible as a result of factors such as design 722 features/attributes, and procedures. Modifications that employ design attributes and features, 723 724 5 As stated in NEI 01-01, Section 5.2, ~A fundamental concept in the regulatory requirements and expectations for 725 instrumentation and control systems in nuclear power plants is the use of four echelons of defense-in-depth: 1) 726 Control Systems; 2) Reactor Trip System (RTS) and Anticipated Transient without SCRAM (ATWS); 3) Engineered 727 Safety Features Actuation System (ESFAS); and 4) Monitoring and indications.~

728 Draft RIS 2002-22 Supplement 1, Attachment Page 12 of 17 729 such as internal diversity, help to minimize the potential for CCFs. Sources of CCF, could 730 include the introduction of identical software into redundant channels, the use of shared 731 resources; or the use of common hardware and software among systems performing different 732 design functions. Therefore, it is essential that such sources of CCF be identified, to the extent 733 practicable, and addressed during the design stage as one acceptable method to support the 734 technical basis for the proposed modification.

735 736 Digital designs having sources of CCF that could affect more than one SSC need to be closely 737 reviewed to ensure that an accident of a different type from those previously evaluated in the 738 UFSAR has not been created. This is particularly the case when such common sources of CCF 739 also are subject to common triggers. For example, the interface of the modified SSCs with 740 other SSCs using identical hardware and software, power supplies, human-machine interfaces, 741 needs to be closely reviewed to ensure that possible common triggers have been addressed.

742 743 A software CCF may be assessed using best-estimate methods and realistic assumptions.

744 Unless already incorporated into the licensee~s UFSAR, ~best-estimate~ methods cannot be 745 used for evaluating different results than those previously evaluated in the UFSAR.

746 747 4.4 Defense-in-Depth Analyses 748 749 NEI 01-01 describes the need for defense-in-depth analysis as limited to substantial digital 750 replacements of reactor protection system and ESFAS. A defense-in-depth analysis for 751 complex digital modifications of systems other than protection systems may also reveal the 752 impact of any new potential CCFs due to the introduction of shared resources, common 753 hardware and software, or the combination of design functions of systems that were previously 754 considered to be independent of one another. Additionally, defense-in-depth analysis may 755 reveal direct or indirect impacts on interfaces with existing plant SSCs. This type of analysis 756 may show that existing SSCs and/or procedures could serve to mitigate effects of possible 757 CCFs introduced through the proposed modification.

758 759 4.5 Dependability Evaluation 760 761 Section 5.3.1 of NEI 01-01 states that a digital system that is sufficiently dependable will have a 762 likelihood of failure that is sufficiently low. This section describes considerations that can be 763 used to determine whether a digital system is ~sufficiently dependable.~

764 765 The dependability evaluation relies on some degree of engineering judgment to support a 766 conclusion that the digital modification is considered to be ~sufficiently dependable.~ When 767 performing a dependability evaluation, one acceptable method is to consider: (1) inclusion of 768 any deterministically-applied defensive design features and attributes; (2) conformance with 769 applicable standards regarding quality of the design process for software and hardware; and (3) 770 relevant operating experience. Although not stated in NEI 01-01, judgments regarding the 771 quality of the design process and operating experience may supplement, but not replace the 772 inclusion of design features and attributes.

773 774 For proposed designs that are more complex or more risk significant, the inclusion of design 775 features and attributes that: serve to prevent CCF, significantly reduce the possible occurrence 776 of software CCF, or significantly limit the consequences of such software CCF, should be key 777 considerations for supporting a ~sufficiently dependable~ determination. Design features 778 Draft RIS 2002-22 Supplement 1, Attachment Page 13 of 17 779 maximizing reliable system performance, to the extent practicable, can also be critical in 780 establishing a basis for the dependability of complex or risk significant designs.

781 782 Section 5.1.3 of NEI 01-01 states that ~Judgments regarding dependability, likelihood of failures, 783 and significance of identified potential failures should be documented~.~ Depending on the 784 SSCs being modified and the complexity of the proposed modification, it may be challenging to 785 demonstrate ~sufficient dependability~ based solely upon the quality of the design process 786 and/or operating history. Engineering judgments regarding the quality of the design process 787 and operating experience may supplement, but not replace the inclusion of design features and 788 attributes when considering complex modifications.

789 790 Figure 1 of this attachment provides a simplified illustration of the engineering evaluations 791 process described in Section 4 of this attachment.

792 793 4.6 Engineering Documentation 794 795 Documentation for a proposed digital I&C modification is developed and retained in accordance 796 with the licensee~s design engineering procedures, and the NRC-approved QA program. The 797 documentation of an engineering evaluation identifies the possible failures introduced in the 798 design and the effects of these failures. It also identifies the design features and/or procedures 799 that document resolutions to identified failures, as described in NEI 01-01, Section 5.1.4. The 800 level of detail used may be commensurate with the safety significance and complexity of the 801 modification in accordance with licensee~s procedures.

802 803 Although not required, licensees may use Table 2 of this attachment to develop and document 804 engineering evaluations. Documentation should include an explanation providing adequate 805 bases for conclusions so that a knowledgeable reviewer could draw the same conclusion.

806 Draft RIS 2002-22 Supplement 1, Attachment Page 14 of 17 807 808 Draft RIS 2002-22 Supplement 1, Attachment Page 15 of 17 809 810 Table 2~Example - Engineering Evaluation Documentation Outline to support a Qualitative Assessment To pical Area Descri ption Step 1- Identification Describe the full extent of the SSCs to be modified~boundaries of the design change, interconnections with other SSCs, and potential commonality to vulnerabilities with existing equipment.

• What are all of the UFSAR-described design functions of the upgraded/modified components within the context of the plant system, subsystem, etc.?

• What design function(s) provided by the previously installed equipment are affected and how will those design functions be accomplished by the modified design? Also describe any new design functions that were not part of the original design.

• What assumptions and conditions are expected for each associated design function? For example, the evaluation should consider both active and inactive states, as well as transitions from one mode of operation to another. Step 2~Identify potential failure modes and undesirable behavior Consider the possibility that the proposed modification may have introduced potential failures.

• Are there potential failure modes or undesirable behaviors as a result of the modification? A key consideration is that undesirable behaviors may not necessarily constitute an SSC failure, but a misoperation. (e.g., spurious actuation)

• Are failures including, but not limited to, hardware, software, combining of functions, shared resources, or common hardware/software considered?

• Are there interconnections or interdependencies among the modified SSC and other SSCs?

• Are there sources of CCF being introduced that are also subject to common triggering mechanisms with those of other SSCs not being modified?

• Are potential failure modes introduced by software tools or programmable logic devices? Step 3~Assess the effects of identified failures

• Could the possible failure mode or undesired behavior lead to a plant trip or transient?

• Can the possible failure mode or undesired behavior affect the ability of other SSCs to perform their design function?

• Could the possible failure mode of the SSC, concurrent with a similar failure of another SSC not being modified but sharing a common failure and triggering mechanism affect the ability of the SSC or other SSCs to perform their design functions?

• What are the results of the postulated new failure(s) of the modified SSC(s) compared to previous evaluation results described in the UFSAR? Step 4~Identify appropriate What actions are being taken (or were taken) to address significant identified failures?

• Are further actions warranted?

Draft RIS 2002-22 Supplement 1, Attachment Page 16 of 17 811 Table 2~Example - Engineering Evaluation Documentation Outline to support a Qualitative Assessment To pical Area Descri ption resolutions for each identified failures

• Is re-desi gn warranted to add additional desi gn features or attributes?

• Is the occurrence of failure self-revealing or are there means to annunciate the failure or misbehavior to the operator? Step 5~ Documentation

• Describe the resolutions identified in Step 4 of this table that address the identified failures.

• Describe the conformance to regulatory requirements, plant~s UFSAR, regulatory guidance, and industry consensus standards (e.g., seismic, EMI/RFI, ambient temperature, heat contribution).

• Describe the quality of the design processes used within the software life cycle development (e.g., verification and validation process, traceability matrix, quality assurance documentation, unit test and system test results).

• Describe relevant operating history (e.g., platform used in numerous applications worldwide with minimal failure history).

• Describe the design features/attributes that support the dependability conclusion (e.g., internal design features within the digital I&C architectures such as self-diagnostic and self-testing features or physical restrictions external to the digital I&C portions of the modified SSC), defense-in-depth (e.g., internal diversity, redundancy, segmentation of distributed networks, or alternate means to accomplish the design function).

• Summarize the results of the engineering evaluation including the dependability determination.

Draft RIS 2002-22 Supplement 1, Attachment Page 17 of 17 812 DRAFT NRC REGULATORY ISSUE

SUMMARY

2002-22, SUPPLEMENT 1, CLARIFICATION 813 ON ENDORSEMENT OF NUCLEAR ENERGY INSTITUTE GUIDANCE IN DESIGNING 814 DIGITAL UPGRADES IN INSTRUMENTATION AND CONTROL SYSTEMS DATE: Month 815 XX, 2018 816 817 818 819 OFFICE NRR/DIRS/IRGB/PM NRR/PMDA OE/EB OCIO NAME TGovan LHill JPeralta DCullison DATE 02/16/2018 01/18/2018 01/22/2018 01/17/2018 OFFICE NRR/DE/EICB/BC NRR/DIRS/IRGB/LA NRR/DIRS/IRGB/PM NRR/DIRS/IRGB/BC NAME MWaters ELee TGovan HChernoff DATE 03/01/2018 02/22/2018 03/01/2018 03/01/2018 820 Industry Suggested Revision to RIS 2017-XX Section 3.1.3 - Operating Experience 3.1.3 Operating Experience Relevant operating experience can be used to help evaluate and demonstrate that software and hardware employed in a proposed modification have adequate dependability. The licensee may document information showing that the proposed system or component modification employs equipment with significant operating experience in nuclear power plant applications, or in non-nuclear applications with comparable performance standards and operating environment. With a large population of in-service components/systems, operating experience provides a large installed test bed with many different environments and applications. Operating experience is normally used in two basic ways 1) calculation of an actual failure rate number or 2) a qualitative method that mines the failure data for both positives and negatives. Failure rate numbers based upon real performance data is the best quality indicator and calculated failure rate numbers can provide a comparison to the plant's existing components/systems. Qualitative methods involve review of the actually reported failure descriptions. These reviews can provide supporting evidence and trends of strengths or weaknesses in the manufacture's quality processes, such as design control processes, product testing effectiveness, and hardware robustness. The licensee may also consider whether the manufacturer of such equipment incorporate quality processes such as continual process improvement, incorporation of lessons learned, etc., and document how that information demonstrates adequate equipment dependability.Some key areas in evaluating operating experience are: Strength of the manufacture's problem reporting system Identification of the manufacture's threshold for problem reporting and how this information is utilized (i.e., how problems are tracked, are critical problems fixed in a timely manner, is data used for continuous improvement) Evaluating for repetitive failure trends which could be indicative of a process weakness that requires further evaluation. Evaluate different revisions and versions of hardware/software for issues that occur during design or manufacturing changes. How "no problem found" is addressed and how large is this population. Operating experience relevant to a proposed digital I&C change may be credited as part of an adequate basis for a determination that the proposed change does not result in more than a minimal increase in the frequency of occurrence of initiating events that can lead to accidents or in more than a minimal increase in the likelihood of occurrence of a malfunction of an SSC important to safety previously evaluated in the UFSAR. Differences may exist in the specific digital I&C application between the proposed digital I&C modification and that of the equipment and software whose Deleted: Section 5.3.1 of NEI 01-01 states, "Substantial applicable operating history reduces uncertainty in demonstrating adequate dependability."¶

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operating experience is being credited.

The architecture of the referenced equipment and software should be similar to that of the system being proposed.

Note that an evaluation of multiple versions can provide evidence of good and stable design and manufacturing processes.Further, the design conditions and modes of operation of the equipment whose operating experience is being referenced also needs to be similar to that being proposed as a digital I&C modification.

It is important to recognize that when crediting operating experience, one needs to understand what design features are being credited. Highly-configurable components/systems may require a larger population of in-service data to address the potential different applications. Customized or rarely used functions should be avoided in operating experience evaluations. Design features that serve to prevent or limit possible common cause failures as relevant operating experience should be noted and considered for inclusion in the proposed design. Doing so would provide additional support for a determination that the dependability of the proposed design will be similar to the referenced application. Deleted: In all cases, however, tDeleted: substantially Deleted: substantially Deleted: For example, one needs to understand what operating conditions (e.g., ambient environment, continuous duty, etc.) were experienced by the referenced design.

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control.Step 2-Failure Mode Comparison Provide a comparison between the failure modes of the new digital equipment and the failure modes of the equipment being replaced. If the failure modes are different, describe the resulting effect of equipment failure on the affected UFSAR-described design function(s).

Step 3-Determination of Equipment Reliability and CCF Likelihood Using the qualitative assessment categories provided in Table 1, address the following questions: Is the new digital equipment as reliable as the equipment being replaced? Is the new digital equipment CCF susceptibility much lower than the likelihood of failures considered in the UFSAR (e.g., single failures) and comparable to CCFs that are not considered in the UFSAR (e.g., design flaws, maintenance errors, calibration errors)?

Step 4-Assessment of Equipment Reliability and CCF Likelihood Results IF the results of Step 3 indicate the new digital equipment is as reliable as the equipment being replaced AND CCF likelihood is determined to be sufficiently low, perform the following: Document that no new plant-level vulnerabilities were identified (i.e., the proposed activity will not increase accident frequency/malfunction likelihood or create an accident of a different type/malfunction with a different result) Continue to Step 5 IF the results of Step 3 indicate the new digital equipment is not as reliable as the equipment being replaced, perform the following: Using the guidance provided in NEI 96-07, Rev. 1, Section 4.3.1 and Section 4.3.2, determine if the decrease in reliability will result in more than a minimal increase in accident frequency or malfunction likelihood and document the justification.

IF the results of Step 3 indicate the CCF likelihood is not sufficiently low, perform the following: Using the guidance provided in NEI 96-07, Rev. 1, Section 4.3.5 and Section 4.3.6, determine if a postulated CCF will result in a different type of accident or a malfunction with a different result and document

the justification.

Table 2-Example Engineering Evaluation Documentation Outline to Support a Qualitative Assessment Topical Area Description Step 5-Conclusion Provide a summarization of the qualitative assessment results and overall conclusions reached. Include a discussion of the pros and cons associated with implementation of the proposed activity (e.g., elimination of single points of vulnerability, self-diagnostics and testing). Discuss the effect of the proposed activity, if any, on applicable UFSAR-described design functions. Provide discussion on any differences in equipment failure modes and the associated impact of different failure modes on applicable UFSAR-described design functions. Step 6-Supporting Documentation Provide a list of references used to support arguments made and conclusions reached in the qualitative assessment. References should be retrievable for future review and inspection activities. If not retrievable, consider attaching references to the qualitative assessment. The level of supporting documentation should be commensurate to the safety significance of the SSCs being modified. Examples of references include: Applicable codes and standards applied in the design Equipment environmental qualifications (e.g., ambient temperature, EMI/RFI, seismic) Quality design processes employed (e.g., NQA-1, Part II, Subpart 2.7; Commercial Grade Dedication documentation per EPRI TR-106439) Failure Modes and Effects Analysis (if applicable) Software Hazard Analysis (if applicable) Critical Digital Reviews (if applicable) Documentation of equipment operating experience Step 7-Application of Qualitative Assessment Results Apply the qualitative assessment results when responding to the 10 CFR 50.59 Evaluation questions. List the qualitative assessment as a reference (or include as an attachment) to the 10 CFR 50.59 Evaluation.