ML22224A053

DG-1400 (RG 1.156 Rev 2) Public Comments Resolution Table

ML22224A053
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Issue date:	02/06/2023
From:	Sheila Ray NRC/NRR/DEX
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Steckel J
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ML22224A037	List: ML22224A053 ML22255A125 ML22271A828
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DG-1400 RG-1.156, Rev 2
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Response to Public Comments on Proposed Revision 2 to Regulatory Guide (RG) 1.156 - Draft Regulatory Guide (DG)-1400 Qualification of Class 1E Connection Assemblies for Production and Utilization Facilities, April 2022 (ML21288A562)

On April 11, 2022 the U.S. Nuclear Regulatory Commission (NRC) published a notice in the Federal Register (87 FR 21221) that Draft Regulatory Guide DG-1400, a proposed regulatory guide revision, was available for public comment. The Public Comment Period ended on May 11, 2022; the NRC received comments from the following:

Carrie Fosaaen for NuScale Power, LLC 1100 NE Circle Blvd., Suite 200 Corvalis, Oregon 97330 ADAMS Accession No. ML22138A017 Nuclear Utility Group On Equipment Qualification Winston & Strawn LLP 1901 L Street, N.W.

Washington, D.C. 20036-0081 ADAMS Accession No. ML22138A018 Comments are in ADAMS at their accession numbers, or at Docket Number PROJ0689, and their proposed resolutions are in the following Public Comment Resolution table:

Table of Public Comments and their NRC Resolutions to Proposed Revision 2 of Regulatory Giude 1.156: Draft Regulatory Guide DG-1400 Commenter DG-1400 Section Specific Comments NRC Resolution NuScale C

NuScale_1 DG-1400 Section C does not clarify that the scope of qualification extends to all cable and connection assemblies subject to 10 CFR 50.49 (which can include more than Class 1E).

The title of DG-1400 changed from the current title of RG 1.156 R1 to reflect that it is specific to Class 1E connection assemblies. Section B states, The NRC has updated this revision of the guide (Revision 2) to endorse IEEE Std. 572-2019 to provide the latest technical information on approaches to satisfy the qualification requirements for Class 1E connection assemblies.

Effectively, wording from Section B of RG 1.156 R1 as it relates to paragraphs b(1), b(2), and b(3) of 10 CFR 50.49 has been removed from DG-1400. The result is that it is unclear if qualification of connection assemblies using IEEE 572-2019 is intended to be specifically limited to qualification of The staff partially agrees with the comment. The title is revised to remove Class 1E to demonstrate that the RG can be utilized for qualification assemblies within the scope of 10 CFR 50.49.

In Section A, Applicable Regulations, 10 CFR 50.49 is listed and thus, indicates that the RG can be used to comply with requirements listed in 10 CFR 50.49. Therefore, the staff finds that no additional clarification is needed to indicate that methods in IEEE 572-2019 are acceptable to meet 10 CFR 50.49.

2 Class 1E connectors, or whether it is intended to apply to qualification of all important to safety connection assemblies.

Recommendation: Clarify DG-1400 to reflect that methods in IEEE 572-2019 are acceptable to meet 10 CFR 50.49 requirements.

NuScale C

NuScale_2 Section C of DG-1400 does not clarify the definition of mild environment.

IEEE 572-2019 and IEEE 572-2006 define mild environment differently from 10 CFR 50.49(c) and definition 3.18 of IEC/IEEE-60780-323-2016 (aka dual logo standard).

IEEE 572-2019 defines a mild environment as: An environment that at no time would be significantly more severe than the environment that would occur during normal plant operations, including normal operational occurrences. The term normal operational occurrences should be clarified as being the same as anticipated operational occurrences.

Recommendation: Include a statement in DG-1400 Section C that the definition of mild environment from either 50.49(c) or the dual logo standard applies, so that it is clear that RG 1.156 does not endorse the definition of mild environment in IEEE 572-2019.

The staff agrees with the comment.

The RG is revised to state that operational occurrence and normal operational occurrence is same as anticipated operational occurrence, as defined in 10 CFR 50 App A (Anticipated operational occurrences. - Anticipated operational occurrences mean those conditions of normal operation which are expected to occur one or more times during the life of the nuclear power unit and include but are not limited to loss of power to all recirculation pumps, tripping of the turbine generator set, isolation of the main condenser, and loss of all offsite power.)

Further, the staff revised the RG to state that mild environment is defined per 10 CFR 50.49(c).

3 NuScale C

NuScale_3 DG-1400 Section C does not clarify methods acceptable to satisfy 10 CFR 50.34, 10 CFR 50.44, and 10 CFR 50.115 to establish equipment survivability.

DG-1400 Section C does not provide clarification that differentiates environmental qualification to DBA conditions from equipment survivability for design extension conditions to establish equipment survivability to design extension/severe accident conditions. This differentiation between qualification and equipment survivability is consistent with SECY-90-016, SECY-93-087 and RG 1.7.

Section 6.2.8 of IEEE 572-2019 provided guidance on qualification testing for design extension conditions to be performed after DBE tests. This section also points to Figure 1 of IEEE 572-2019 that reflects that testing to design extension conditions is a continuation of the qualification test sequence for design basis conditions Methods to address equipment survivability can include qualitative assessments, analysis, or separate effects testing in addition to a qualification type test as described in Chapter 19 of NuScales DCA NuScales DSRS is specific to DBA conditions. The dual logo standard introduces design extension conditions. The conditions will be treated consistent with NRC guidance on equipment survivability as these are outside the scope of environmental qualification.

Recommendation: Clarify that equipment survivability for severe accidents under 10 CFR 50.34 and 10 CFR 50.115 is not limited to type tests that are a continuation of the DBA type tests. Clarify that design extension conditions do not require qualification per 10 CFR 50.49 requirements.

The staff partially disagrees - equipment survivability and beyond design basis is outside the scope of 50.49. The staff revised the RG in Section C that the qualification test program is not required to include design extension conditions but may be included.

4 NuScale C

NuScale_4 DG-1400 Section C does not address limitations of submergence requirements beyond cables and connection assemblies.

Additionally, Section C does not include basis for when accelerated submergence could be applied.

Section 6.2.7.3 of IEEE 572-2019 contains guidance on post-DBE submergence that is not considered to be limited to connection assemblies based on Section C.3.a of RG 1.89 R1.

NuScale has equipment that is subjected to periodic submergence during normal operation, infrequent events, and design basis accident conditions, and some continuously submerged applications. For these applications, the position in IEEE 572-2019 should be clarified as not applicable to equipment whose performance under submerged conditions is not dependent on age-sensitive or age-degradable seals (e.g., equipment design relies on seal welded enclosures, glass seals, ceramic seals, or metallic seals/gaskets).

Recommendation: Consider coordinating response to DG-1400 with DG-1361 resolutions to provide clarification that submergence is not limited to cables and connection assemblies only and that inability to accelerate submergence during a qualification type test is specific to equipment with accident performance under submerged conditions that is dependent upon agesensitive seals.

The staff partially agrees with the comment. The staff has ensured consistency with DG-1400 and the revision of RG 1.89.

Staff understands that submergence is not limited to connectors and consideration for submergence should be applied per 10 CFR 50.49. However, staff did not revise the RG to include information on submergence since it is addressed in 10 CFR 50.49.

NuScale C

NuScale_5 DG-1400 Section C does not provide clarification that differentiates environmental qualification to DBA conditions from equipment survivability for design extension conditions to establish equipment survivability to design extension/severe accident conditions. This differentiation between qualification and equipment survivability is consistent with SECY-90-016, SECY-93-087 and RG 1.7.

NuScales DSRS is specific to DBA conditions. The dual logo standard introduces design extension conditions. The conditions will be treated consistent with NRC guidance on equipment survivability as these are outside the scope of qualification.

Also see comment 3 above.

See resolution to NuScale_3

5 Recommendation: Clarify that design extension conditions do not require qualification per 10 CFR 50.49 requirements.

NUGEQ Commenter DG-1400 Section Specific Comments NRC Resolution NUGEQ NUGEQ General Comment_1 The following clarifications or exceptions to IEEE 572-2019 have been identified based on our review of DG-1400. These clarifications or exceptions are presented below based on the topic or focus of the comment. The first four comment topics cover clarifications related to environmental qualification of connection assemblies. The remaining comments are related to differences between the guidance in IEEE 572-2019 on design extension conditions and methods to address equipment survivability under severe accident (beyond design basis) conditions See resolution to NuScale_3 NUGEQ NUGEQ Comment_1 Inconsistent Definition of Mild Environment There should be a clarification regarding the definition of a mild environment in Section 3 of IEEE 572-2019 so that it is consistent with both IEC/IEEE 60780-323-2016 and 10 CFR 50.49(c). Specifically, the wording of...,

including normal operational occurrences. should be clarified as meaning..., including anticipated operational occurrences.

Basis for Comment: Need for Consistency with 10 CFR 50.49(c) and the definition of a mild environment in Section 3.18 of IEC/IEEE 60780-323-2016.

See NuScale_2 Commenter DG-1400 Section Specific Comments NRC Resolution

6 NUGEQ NUGEQ Comment_2 Asserted Need to Establish Qualified Life and Qualified Condition DG-1400 should include a clarification or exception regarding the wording in Section 4 of IEEE 572-2019 (page 11) that indicates that it is necessary to establish a qualified life and qualified condition for connection assemblies required to function during and following a DBE, extreme natural event, and/or SAC. Specifically, NUGEQs concerns with the wording in IEEE 572-2019 are related to the need for clarification in DG-1400 are noted below:

Item a: For consistency with the staff position in DG-1361 (Section C.1.c) that modifies the definition of qualified life in the dual logo standard, DG-1400 should similarly indicate that qualified life is specific to equipment with significant aging mechanisms and subject to environmental qualification for harsh design basis accident conditions. As currently worded, IEEE 572-2019 indicates the need to establish a qualified life for extreme external events or severe accident conditions which are beyond the scope of 10CFR50.49.

Item b: DG-1400 should clarify that there is no regulatory requirement to establish a qualified condition. Section 4 of IEEE 572-2019 indicates that it is necessary (e.g., a requirement) to establish a qualified condition for connection assemblies required to function during and/or following a DBE, extreme natural event, and/or severe accident condition, which goes beyond the scope of 10 CFR 50.49 as well as the guidance in IEC/IEEE-60780-323-2016. It also expands the definition for a qualified condition which is specific to the condition of equipment prior to the start of a design basis event2 to cover design extension conditions. The position in IEEE 572-2019 regarding the need to establish a qualified condition is also inconsistent with the wording in Section 5.2 of IEC-IEEE-60780- 323-2016, which states that it is necessary to establish a qualified life for equipment with significant aging mechanisms that is being qualified for DBE conditions. It goes on to clarify that the qualified condition is inherent in the establishment of a qualified life.

Since the establishment of a qualified condition is inherent to the Item a: the staff partially agrees with the comment. The definition of qualified life and qualified condition in IEEE 572-2019 state for the specified service conditions,and Section 6.2.8, Design extension conditions, states that qualification test program shall include, as appropriate, tests for environmental conditions that are beyond the design basis Thus, the inclusion of beyond design basis conditions would depend on the licensing basis and is not required per 50.49.

The staff revised the RG with following definition of qualified life instead of the definition in Section 3 of IEEE 572-2019: period for which an equipment has been demonstrated, through testing, analysis and/or experience, to be capable of remaining functional during and following design basis events to ensure that the criteria specified in 10 CFR 50.49(b) are satisfied.

Item b: The staff agrees and added a position that Section 4, Background should be clarified such that qualified life is required in order to meet the requirements of 10 CFR 50.49. The staff revised the RG to add a regulatory position that qualified life is required per 10 CFR 50.49.

Staff agrees that qualified condition is not required by 10 CFR 50.49.

Commenter DG-1400 Section Specific Comments NRC Resolution

7 establishment of a qualified life, there is no need for a specific requirement or expectation to establish a qualified condition.

Basis for Comment: (1) Need for clarity/consistency with Section 5.2 of IEC/IEEE-60780-323-2016, including the change in the definition of qualified life in Section C.1.c of DG-13613 and; (2) the wording in Section 4 of IEEE 572-2019 (page 11) should be consistent with and not expand upon the wording in Section 5.2 of the dual logo standard and; (3) the need to establish a qualified condition is not a regulatory requirement under 10 CFR 50.49.

NUGEQ NUGEQ Comment_3 Acceleration of Submergence Effects Section 6.2.7.3 of IEEE 572-2019 contains guidance on post-DBE submergence. Specifically, it states that: Note that the connector function is typically proven during the entire submergence time, as submergence cannot be accelerated via Arrhenius analysis. The endorsement of this limitation on thermal acceleration of submergence effects is not currently reflected in Section C.3.a of RG 1.89 Rev. 1 (or DG-1361) and is not specifically limited to connection assemblies. DG-1400 should also clarify that the limitation on using the Arrhenius methodology to extrapolate the duration of submergence during a test is specific to equipment whose performance under submerged conditions depends on age-sensitive environmental seals. This limitation should not apply to equipment whose environmental sealing is not susceptible to age-related degradation (e.g., seal welded, oil filled housings, glass, ceramic, metallic gaskets or O-rings, etc.).

Basis for Comment: The limitation on acceleration of submergence duration using the Arrhenius methodology in Section 6.2.7.3 of IEEE 572-2019 is not specific or unique to connection assemblies and should be generally applicable to all electric equipment subject to submergence under DBA conditions. As such, this comment is also relevant to DG-1361 that is endorsing IEC/IEEE-60780-323-2016.

The staff partially agrees with the comment. The staff agrees that the limitation on acceleration of submergence duration using the Arrhenius methodology in Section 6.2.7.3 of IEEE 572-2019 is not specific or unique to connection assemblies.

The staff agrees that Arrhenuis cant be used for submergence per IEEE Std. 572-2019.

For equipment not susceptible to age-related degradation or submergence, analysis can be used to show testing under certain environmental conditions is not needed (i.e. temperature aging for metals).

Commenter DG-1400 Section Specific Comments NRC Resolution

8 NUGEQ NUGEQ Comment_4 Application of Normative References Whose Edition is not Currently Endorsed IEEE 572-2019 cites IEEE 317-2013 as a normative reference, which is not currently endorsed by the NRC. Currently, RG 1.63 (Revision 3) endorses IEEE 317-1983, which is a previous edition. DG-1400 should provide some clarification or guidance regarding the application of normative references that are not currently endorsed.

Also see Comment No. 2 in Attachment 2 regarding the need to coordinate the timing of endorsement of normative reference IEC/IEEE-60780-323-2016 by the proposed revision to RG 1.89 (DG-1361) with the endorsement of IEEE 572-2019 by DG-1400.

Basis for Comment: Per Section 2 of IEEE 572-2019, normative references are indispensable for the application of this document (i.e., they must be understood and used, so each referenced document is cited in text and its relationship to this document is explained).

The staff partially agrees with the comment. The staff has ensured consistency with DG-1400 and the revision of RG 1.89.

Normatives references can provide valuable info; they may not always be included in the RG.

NUGEQ NUGEQ Comment_5 Equipment Survivability vs Environmental Qualification DG-1400 should clarify that the confidence the equipment will survive severe-accident conditions is referred to as equipment survivability and not environmental qualification. RG 1.7 clearly reflects that the evaluation for equipment survivability under beyond design basis accident environments need not be qualified in accordance with 10 CFR 50.49. The harmonized IEC/IEEE standards related to environmental qualification (e.g., IEC/IEEE-60780-323-2016 and the associated daughter standards like IEEE 572-2019) have evolved from being methods to establish qualification for electrical equipment subject to design basis conditions to providing guidance on addressing design extension conditions from beyond design basis events (including severe accidents) under the umbrella of qualification. This blending of severe accident conditions with design basis conditions under the context of EQ is not consistent with the NRC staffs position on Equipment The staff disagrees with the comment. RG 1.7 is combustible gas control and discusses equipment survivability but is not related to electrical equipment.

See NuScale_3 Commenter DG-1400 Section Specific Comments NRC Resolution

9 Survivability in SECY-93-087 and SECY-90-016, which makes a clear differentiation between environmental qualification to design basis conditions and equipment survivability for severe accidents. Therefore, DG-1400 should distinguish environmental qualification under 10 CFR 50.49 as being separate and distinct from equipment survivability for severe accidents.

Basis for Comment: In effect, the approach in the harmonized IEEE standards (e.g., IEC/IEEE 60780-323-2016 and the associated daughter standards) is effectively commingling methods to satisfy §§ 50.49, 50.34, 50.44 and 50.155. DG-1400 should be consistent with the position in RG 1.7 regarding equipment survivability being independent from environmental qualification in accordance with 10 CFR 50.49.

NUGEQ NUGEQ Comment_6 Methods to Establish Equipment Survivability DG-1400 should provide specific clarification that the methods to demonstrate survivability of equipment required to function under severe accident conditions is not limited to a qualification type test. Based on a review of approaches used in Design Control Document (DCD) Chapter 19 for several Part 52 plants, the methods used to evaluate equipment survivability are not limited to extensions of qualification type tests to DBA conditions. Licensees may employ a variety of approaches such as qualitative or quantitative assessments, extrapolation of existing qualification test results to severe accident conditions, additional analysis, separate effects testing or a combination of these methods to demonstrate equipment survivability to severe accident conditions.

As currently written, the guidance in IEEE 572-2019, Section 6.2.8, Design extension conditions specifically focuses on the qualification test program for demonstrating equipment survivability for severe accident conditions.

Specifically, Section 6.2.8 begins by stating that: The qualification test program shall include, as appropriate, tests for environmental conditions that are beyond the design basis of the plant. This section refers to the flowchart in Figure 1, which indicates that testing for design extension conditions is part of the overall qualification test sequence. This section also states that:

See NuScale_3 The staff partially agrees with the comment and revised the RG to state that the qualification test program is not required to include design extension conditions, but may be included.

Commenter DG-1400 Section Specific Comments NRC Resolution

10 The user shall determine the appropriate qualification approach to address any design extension conditions without any additional guidance on methods other than qualification type testing.

Basis for Comment: The need to keep the concept of equipment survivability for severe accidents separate and distinct from environmental qualification for design basis accidents. DG-1400 should be consistent with the position in RG 1.7 regarding equipment survivability.

NUGEQ NUGEQ Comment_7 Applicability of Qualification Margin to Design Extension Conditions There should be some clarification in DG-1400 that the suggested qualification margins for connection assemblies presented in Annex A of IEEE 572-2019 are not applicable to design extension conditions for severe accidents. Imposing qualification margin on design extension conditions is inconsistent with the guidance regarding service condition margin in Section 7.4.1.7 of IEC/IEEE-60780-323-2016, which clearly indicates that margin is specific to DBE service conditions.

Basis for Comment: Section 5.1 of IEEE 572-2019 contains the following statement: b) The test conditions are at least as severe as the service conditions, plus margin, including DBEs, extreme natural events and severe accidents given in the qualification specification (see 6.1).

The staff agrees with the comment.

The staff revised the RG to state that margin is applied to design basis event profiles and not for severe accident conditions.

Further, test conditions are at least as severe as service conditions.

NUGEQ: Attachment 2 - Additional NUGEQ Comments on DG-1400 - Proposed Revision 2 to Regulatory Guide 1.156

11 Commenter DG-1400 Section Specific Comments NRC Resolution NUGEQ Various NUGEQ Attachment 2, Question 1 - General Comment Based on the change in title and wording changes in Section B, it appears that the focus of RG 1.156 has changed from a method acceptable to the staff for environmentally qualifying connectors, terminations and environmental seals that satisfies the requirements of 10 CFR 50.49 to what appears to be an overly narrow focus on Class 1E connection assemblies. As used in the Proposed Revision, different safety-classes of connectors, terminations, and environmental seals (other than Class 1E) that are to be qualified under 10 CFR 50.49 would be dealt with separately without any regulatory basis or guidance related to the NRC harsh environment qualification regulatory structure.

Basis for Comment: DG-1400 should not be worded in a manner that implies a limitation to just Class 1E connection assemblies since non-Class 1E connector assemblies can fall under the jurisdiction of 10CFR50.49 (b)(2) and certain (b)(3) variables. This comment is based on:

a) Revising the title of RG 1.156 by adding Class 1E to the title of the document, and b) The revised wording in Section B that the NRC has updated this revision of the guide (Revision 2) to endorse IEEE Std 572-2019 to provide the latest technical information on approaches to satisfy qualification requirements for Class 1E connection assemblies, and c) The removal of third paragraph in Section B of RG 1.156 R1 that clearly reflected that the focus was on compliance with 10CFR50.49.

The staff agrees with the comment (see NuScale_1)

The title is revised to remove Class 1E to demonstrate that the RG can be utilized for qualification assemblies within the scope of 10 CFR 50.49.

Commenter DG-1400 Section Specific Comments NRC Resolution

12 NUGEQ Section A

Section B

NUGEQ Attachment 2, Question 2 Current Wording: Section B includes a statement that: This includes guidance used in conjunction with that in RG 1.89 as an acceptable method of demonstrating compliance with the NRC regulations pertaining to the environmental qualification of connectors, terminations and environmental seals.

Comment Since DG-1400 is endorsing IEEE 572-2019, which identifies IEC/IEEE 60780-323-2016 as a normative reference, Revision 2 to RG 1.156 should be issued concurrent with or subsequent to the issuance of RG 1.89, Rev. 2. We note that such inconsistencies can/do apply in other NRC regulatory contexts. (Examples noted herein.) We believe those intertwined, inter-wrapped, NRC, IEEE guidances should be recognized in each instance and addressed from a regulatory sequence perspective to assure clarity of NRC recognition and applicant/licensee consideration.

Basis for Comment To ensure that Rev. 2 to RG 1.156 is used with IEC/IEEE-60780-323-2016 as modified by RG 1.89, Rev 2 (DG-1361).

The staff partially agrees with the comment. The staff has ensured consistency with DG-1400 and the revision of RG 1.89.

NUGEQ Section B,

Consid eration of Internati onal Standar ds NUGEQ Attachment 2, Question 3 Current Wording: The following IAEA Safety Requirements and Guides were considered in the development update of the Regulatory Guide:

• IAEA Safety Report Series 3, Equipment Qualification in Operational Nuclear Power Plants: Upgrading, Preserving and Reviewing, issued April 1998 (Ref. 12)

Comment The development of Revision 2 to RG 1.156 should also consider IAEA Specific Safety Guide SSG-69, Environmental Qualification for Nuclear Installation that was issued in 2021 since it specifically references both IEEE 572-2019 and IEC/IEEE 60780-323-2016.

The staff agrees with the comment and revised the RG to include IAEA SSG-69.

Commenter DG-1400 Specific Comments NRC Resolution

13 Section Basis for Comment To be consistent with that stated purpose of the revision to provide the latest technical information on approaches to satisfy qualification requirements for connection assemblies.

NUGEQ Referenc es NUGEQ Attachment 2, Question 4 - General Comment DG-1400 should include a reference citation for all of the normative references in IEEE 572-2019 that have been endorsed. References 4, 5, 6, and 7 only cover four of the five normative references. RG 1.73, Rev. 1, which endorses IEEE 382-2006, should be included.

Basis for Comment None The staff agrees with the comment and revised the RG to include RG 1.73, Revision 1, Qualification Tests for Safety-Related Actuators in Nuclear Power Plants, in the Related Guidance section.