1

 Copies may be obtained from the American Society of Mechanical Engineering, Three Park Avenue, New

York, NY 10016-5990. Phone (212)591-8500; fax (212)591-8501.

This regulatory guide is being issued in draft form to involve the public in the early stages of the development of a regulatory position in this area. It has

not received complete staff review or approval and does not represent an official NRC staff position.

Public comments are being solicited on this draft guide (including any implementation schedule) and its associated regulatory analysis or value/impact

statement. Comments should be accompanied by appropriate supporting data. Written comments may be submitted to the Rules and Directives

Branch, Office of Administration, U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001. Comments may be submitted electronically or

downloaded through the NRCís interactive web site at <WWW.NRC.GOV> through Rulemaking. Copies of comments received may be examined at the

NRC Public Document Room, 11555 Rockville Pike, Rockville, MD. Comments will be most helpful if received by March 25, 2002.

Requests for single copies of draft or active regulatory guides (which may be reproduced) or for placement on an automatic distribution list for

single copies of future draft guides in specific divisions should be made to the U.S. Nuclear Regulatory Commission, Washington, DC 20555,

Attention: Distribution Services Section, or by fax to (301)415-2289; or by email to DISTRIBUTION@NRC.GOV. Electronic copies of this draft

guide are available through NRCís interactive web site (see above), on the NRCís web site <WWW.NRC.GOV> in the Reference Library under

Regulatory Guides, and in NRCís Electronic Reading Room at the same web site, under Accession Number ML013120071.

 U.S. NUCLEAR REGULATORY COMMISSION December 2001

 OFFICE OF NUCLEAR REGULATORY RESEARCH Division 1

 DRAFT REGULATORY GUIDE

Contact: W.E. Norris (301)415-6796

DRAFT REGULATORY GUIDE DG-1112

ASME CODE CASES NOT APPROVED FOR USE

A. INTRODUCTION

In 10 CFR 50.55a, ìCodes and Standards,î of 10 CFR Part 50, ìDomestic Licensing of

Production and Utilization Facilities,î paragraph (c), ìReactor Coolant Pressure Boundary,î

requires, in part, that components of the reactor coolant pressure boundary be designed,

fabricated, erected, and tested in accordance with the requirements for Class 1 components of

Section III, ìRules for Construction of Nuclear Power Plant Components,î1

 of the American

Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (BPV Code) or

equivalent quality standards. In 10 CFR 50.55a, paragraph (f), ìInservice Testing

Requirements,î requires, in part, that Class 1, 2, and 3 components and their supports meet the

requirements of the ìCode for Operation and Maintenance of Nuclear Power Plantsî (OM Code),

of the ASME OM Code or equivalent quality standards. Finally, in 10 CFR 50.55a, paragraph

(g), ìInservice Inspection Requirements,î requires, in part, that Classes 1, 2, 3, MC, and CC

Components and their supports meet the requirements of Section XI, ìRules for Inservice

Inspection of Nuclear Power Plant Components,î of the ASME BPV Code or equivalent quality

standards. The ASME publishes a new edition of the BPV and OM Codes every three years

and new addenda every year. The latest editions and addenda of Section III, Section XI, and

the OM Code that have been approved for use by the NRC are referenced in 10 CFR 50.55a(b). 

The ASME also publishes Code Cases for Section III and Section XI quarterly and Code Cases

for the OM Code yearly. Code Cases provide alternatives developed and approved by ASME or

explain the intent of existing Code Requirements. Draft Regulatory Guide DG-1090 (the

proposed Revision 32 of Regulatory Guides 1.84 and 1.85 combined), ìDesign, Fabrication, and
2

 The NRC is proposing to combine Regulatory Guides 1.84 and 1.85; therefore Proposed Revision 32 of

Regulatory Guides 1.84 and 1.85 combined, issued as DG-1090, reflects the title change.

2

Materials Code Case Acceptability, ASME Section III,î2

 Draft Regulatory Guide DG-1089,

ìOperation and Maintenance Code Case Acceptability, ASME OM Code,î and Draft

Regulatory Guide DG-1091, (Proposed Revision 13 to Regulatory Guide 1.147),

ìInservice Inspection Code Case Acceptability, ASME Section XI, Division 1,î identify the

Code Cases that have been determined by the NRC to be acceptable alternatives to

applicable parts of Section III, the OM Code, and Section XI.

Regulatory guides are issued to describe to the public methods acceptable to the

NRC staff for implementing specific parts of the NRC's regulations, to explain techniques 

used by the staff in evaluating specific problems or postulated accidents, and to provide

guidance to applicants. Regulatory guides are not substitutes for regulations, and

compliance with regulatory guides is not required. Regulatory guides are issued in draft

form for public comment to involve the public in developing the regulatory positions. Draft

regulatory guides have not received complete staff review; they therefore do not represent

official NRC staff positions. 

This regulatory guide does not approve the use of the Code Cases listed herein. 

Thus, it does not contain new or amended information collection requirement subject to

the Paperwork Reduction Act of 1995 (44 U.S.C. 3501 et seq.). If a means used to

impose an information collection does not display a currently valid OMB control number,

the NRC may not conduct or sponsor, and a person is not required to respond to, the

information collection.

B. DISCUSSION

This regulatory guide lists the Code Cases that the NRC has determined are not

acceptable for use on a generic basis. A brief description of the basis for the

determination is provided with each Code Case. Licensees may submit a request to

implement one or more of the Code Cases listed below through 10 CFR 50.55a(a)(3),

which permits the use of alternatives to the Code requirements referenced in 10 CFR

50.55a provided that the proposed alternatives result in an acceptable level of quality and

safety, by addressing the NRCís concern and submitting a plant-specific request.

C. REGULATORY POSITION

For this guide, the NRC staff reviewed the Section III and Section XI Code Cases

listed in Supplement 4 to the 1992 Edition through Supplement 11 to the 1998 Edition,

and OM Code Cases OMN-1 through OMN-13. Licensees may not implement Code

Cases listed in this guide without prior NRC approval. Licensees may request to

implement one or more of the Code Cases listed in this regulatory guide through 10 CFR

50.55a(a)(3), which permits the use of alternatives to the Code requirements referenced

in 10 CFR 50.55a provided that the proposed alternatives result in an acceptable level of

quality and safety, by addressing the NRCís concern and submitting a plant-specific

request. Periodic updates to this regulatory guide are planned to accommodate new

Code Cases and any revisions of existing Code Cases.

1. UNACCEPTABLE SECTION III CODE CASES
3

The following Section III Code Cases were determined to be unacceptable for use

by licensees in their Section III design and construction programs. The ASME issues

Section III Code Cases quarterly in supplements to a specific edition, i.e., a new edition of

Section III is published every three years and supplements are published quarterly. 

Hence, there are 12 supplements to each edition. To assist users of Section III, Column 3

of Table 1 lists the supplement and edition in which each Code Case was published (e.g.,

7/95E means Code Case Supplement 7 to the 1995 Edition).

TABLE 1 - UNACCEPTABLE SECTION III CODE CASES

CODE

CASE

NUMBER

TABLE 1, UNACCEPTABLE SECTION III CODE CASES SUPPLEMEN

T/EDITION

SUMMARY

N-284-1 Metal Containment Shell Buckling Design Methods, Section

III, Division 1, Class MC

10/98E

(1) The Code Case contains many errors and must be

revised to correct these errors before it can be accepted.

(2) As the Code Case is presently structured, if the

errors were corrected and no further changes were

made, prior to implementation of the Code Case, the

applicant would have to demonstrate to the satisfaction of

the NRC staff (via Safety Analysis Report) that any

axisymmetric techniques that are proposed will be

applicable to a vessel having large asymmetric openings

and that the overall margin used to prevent shell buckling

is acceptable.

N-483-2

N-483-3

Alternative Rules to the Provisions of NCA-3800,

Requirements for Purchase of Material

5/98E

Use of the Code Case would violate Appendix B to 10

CFR Part 50. The Code Case would permit purchase of

materials from sources without approved QA programs.
CODE

CASE

NUMBER

TABLE 1, UNACCEPTABLE SECTION III CODE CASES SUPPLEMEN

T/EDITION

SUMMARY

4

N-510

N-510-1

Borated Stainless Steel for Class CS Core Support Structures

and Class 1 Component Supports, Section III, Division 1

10/95E

No technical basis was provided for expanding the Code

Case to include borated stainless steel Types 304B,

304B1, 304B2, and 304B3. A considerable amount of

information was required to support the types presently

contained in the Code Case. The revised Code Case

would permit borated stainless steel to be used for

component supports within the reactor vessel. The

technical basis to support the Code Case only addresses

the use of these materials as component supports in

spent fuel racks and transportation casks.

N-519 Use of 6061-T6 and 6061-T651 Aluminum for Class 1 Nuclear

Components

10/92E

Code Case is applicable to only one DOE aluminum

vessel.

N-530 Provisions for Establishing Allowable Axial Compressive

Membrane Stresses in the Cylindrical Walls of 0-15 Psi

Storage Tanks, Classes 2 and 3

11/92E

There are numerous errors in the equations. The errors

must be corrected before the Code Case can be

approved for use.

N-565 Alternative Methods of Nozzle Attachment for Class 1 Vessels 7/98E

The Code Case essentially requires a design using a seal

to protect the threads from the contained fluid, and seals

are not a Code item. The seal, which plays a very

important part in the integrity of the joint, imposes too

great a vulnerability in the design. The supporting

information for the Code Case does not demonstrate the

resulting threaded nozzle configuration is equivalent in

integrity to that of a welded connection.
CODE

CASE

NUMBER

TABLE 1, UNACCEPTABLE SECTION III CODE CASES SUPPLEMEN

T/EDITION

SUMMARY

5

N-595

N-595-1

N-595-2

Requirements for Spent Fuel Storage Canisters, Section III,

Division 1

6/98E

Revision 2 of the Code Case contains typographical errors

and technical changes are being made to its provisions that

will result in Revision 3 to this Code Case. In addition,

regulatory approval for the use of multi- purpose casks is

presently addressed by the NRC Spent Fuel Project Office

Interim Staff Guidance No. 4, Rev. 1 (ISG-4, Rev. 1). The

interim staff guidance provides a framework to ensure that the

cask system, as designed, and when fabricated and used in

accordance with the conditions specified in its Certificate of

Compliance, meets the requirements of 10 CFR Part 72.

2. UNACCEPTABLE SECTION XI CODE CASES

The following Section XI Code Cases were determined to be unacceptable for use by

licensees in their Section XI inservice inspection programs. The ASME issues Section XI

Code Cases quarterly in supplements to a specific edition, i.e., a new edition of Section XI is

published every three years and supplements are published quarterly. Hence, there are 12

supplements to each edition. To assist users of Section XI, Column 3 of Table 2 lists the

supplement and edition in which each Code Case was published (e.g., 7/95E means Code

Case Supplement 7 to the 1995 Edition).

TABLE 2 - UNACCEPTABLE SECTION XI CODE CASES

CODE

CASE

NUMBER

TABLE 2, UNACCEPTABLE SECTION XI CODE CASES SUPPLEMEN

T/EDITION

SUMMARY

N-322 Examination Requirements for Integrally Welded or Forged

Attachments to Class 1 Piping at Containment Penetrations,

Section XI, Division 1

10/98E

Code Case would permit excluding from examination highenergy piping welds at containment penetrations in Boiling

Water Reactors (BWRs) that are subject to intergranular

stress corrosion cracking and in BWRs and pressurized

water reactors (PWRs) that may be part of the break

exclusion zone. Sufficient clearance is present to permit

UT examination of these critical welds. [Note: condition

contained in 10 CFR 50.55a(b)(2)(xi).]

N-323-1 Alternative Examination for Welded Attachments to Pressure

Vessels, Section XI, Division 1

4/98E
CODE

CASE

NUMBER

TABLE 2, UNACCEPTABLE SECTION XI CODE CASES SUPPLEMEN

T/EDITION

SUMMARY

6

This Code Case was reinstated but modified from the

original Code Case. The revised Code Case would permit

surface examinations from the accessible side, which are

of limited value. Volumetric examination of the Class 1

integrally welded attachment from the accessible side is

practical and must be performed to adequately determine

the condition of the weld.

N-465

N-465-1

Alternative Rules for Pump Testing, Section XI, Division 1 10/92E

The draft standard referenced in the Code Case is

outdated. The requirements contained in the OM Code,

ìCode for Operation and Maintenance of Nuclear Power

Plants,î should be used.

N-473

N-473-1

Alternative Rules for Valve Testing, Section XI, Division 1 10/95E

The draft standard referenced in the Code Case is

outdated. The requirements contained in the OM Code,

ìCode for Operation and Maintenance of Nuclear Power

Plants,î should be used.

N-480 Examination Requirements for Pipe Wall Thinning Due to Single

Phase Erosion and Corrosion, Section XI, Division 1

9/98E

Code Case has been superseded by Code Case N-597,

ìRequirements for Analytical Evaluation of Pipe Wall

Thinning.î

N-498-2

N-498-3

N-498-4

Alternative Rules for 10-Year System Hydrostatic Testing for

Class 1, 2, and 3 Systems, Section XI, Division 1

12/95E

1/98E

3/98E

These revisions to the Code Case eliminate hold times

during the tests. The capability of detecting a small leak is

directly proportionally to the hold time while the system is

pressurized, especially if it is insulated. Hydrostatic tests

or system leakage and pressure tests performed without

hold times may be insensitive to smaller leaks, thereby

defeating the purpose of performing these tests. The NRC

staff will review reduced hold times on a case-by-case

basis. [Note: conditions consistent with established

regulatory position.]
CODE

CASE

NUMBER

TABLE 2, UNACCEPTABLE SECTION XI CODE CASES SUPPLEMEN

T/EDITION

SUMMARY

7

N-542 Alternative Requirements for Nozzle Inside Radius Section

Length Sizing Performance Demonstration, Section XI, Division

1

12/95E

This Code Case has been superseded by Code Case

N-552, ìAlternative MethodsñQualification for Nozzle Inside

Radius Section from the Outside Surfaceî

N-547 Alternative Examination Requirements for Pressure Retaining

Bolting of Control Rod Drive (CRD) Housings, Section XI,

Division 1

1/98E

Code Case Nñ547 deletes the examination of CRD bolting

whenever the CRD housing is disassembled. Examination

of CRD bolting is required to verify that service-related

degradation has not occurred, or that damage such as

bending and galling of threads has not occurred when

performing maintenance activities that require the removal

and reinstallation of bolting.

N-560

N-560-1

N-560-2

Alternative Examination Requirements for Class 1, Category BJ Piping Welds10/98E

(1) The Code Case does not address inspection strategy

for existing augmented and other inspection programs such

as intergranular stress corrosion cracking (IGSCC), flowassisted corrosion (FAC), microbiological corrosion (MIC),

and pitting.

(2) The Code Case does not provide system-level

guidelines for change in risk evaluation to ensure that the

risk from individual system failures will be kept small and

dominant risk contributors will not be created.

N-561

N-561-1

Alternative Requirements for Wall Thickness Restoration of

Class 2 and High Energy Class 3 Carbon Steel Piping, Section

XI, Division 1

2/98E

Neither the ASME Code nor the Code Case have criteria

for determining the rate or extent of degradation of the

repair or the surrounding base metal. Reinspection

requirements are not provided to verify structural integrity

since the root cause may not be mitigated.
CODE

CASE

NUMBER

TABLE 2, UNACCEPTABLE SECTION XI CODE CASES SUPPLEMEN

T/EDITION

SUMMARY

8

N-562

N-562-1

Alternative Requirements for Wall Thickness Restoration of

Class 3 Moderate Energy Carbon Steel Piping, Section XI,

Division 1

2/98E

Neither the ASME Code nor the Code Case have criteria

for determining the rate or extent of degradation of the

repair or the surrounding basemetal. Reinspection

requirements are not provided to verify structural integrity

since the root cause may not be mitigated.

N-568 Alternative Examination Requirements for Welded Attachments,

Section XI, Division 1

8/98E

The Code Case does not require (1) examination of similar

attachments that may be unobstructed in lieu of the

obstructed attachment, (2) an evaluation of the

acceptability of examinations with limited coverage, and (3)

consideration of alternative examinations in cases (1) and

(2).

N-574 NDE Personnel Recertification Frequency, Section XI,

Division 1

10/95E

Based on data obtained by the NRC staff during its review

of Appendix VIII, ìPerformance Demonstration for

Ultrasonic Examination Systems,î to Section XI, the NRC

staff noted that proficiency decreases over time. The data

does not support re-certification examinations at a

frequency of every 5 years.

N-575 Alternative Examination Requirements for Full Penetration

Nozzle-to-Vessel Welds in Reactor Vessels with Set-On Type

Nozzles, Section XI, Division 1

10/95E

The supporting basis for the Code Case applies to the

specific configuration of one plant and is not applicable on

a generic basis. In addition, there are insufficient controls

on stress and operating conditions to permit a generic

reduction in examination volume. Finally, the boundaries

of the volume of the weld, cladding, and heat affected zone

from Figure 2 are ambiguous. 
CODE

CASE

NUMBER

TABLE 2, UNACCEPTABLE SECTION XI CODE CASES SUPPLEMEN

T/EDITION

SUMMARY

9

N-577

N-577-1

Risk-Informed Requirements for Class 1, 2, and 3 Piping,

Method A, Section XI, Division 1

9/98E

(1) The Code Case does not address inspection strategy

for existing augmented and other inspection programs such

as intergranular stress corrosion cracking (IGSCC), flowassisted corrosion (FAC), microbiological corrosion (MIC),

and pitting.

(2) The Code Case does not provide system-level

guidelines for change in risk evaluation to ensure that the

risk from individual system failures will be kept small and

dominant risk contributors will not be created.

N-578

N-578-1

Risk-Informed Requirements for Class 1, 2, and 3 Piping,

Method B, Section XI, Division 1

9/98E

(1) The Code Case does not address inspection strategy

for existing augmented and other inspection programs such

as intergranular stress corrosion cracking, flow-assisted

corrosion, microbiological corrosion, and pitting.

(2) The Code Case does not provide system-level

guidelines for change in risk evaluation to ensure that the

risk from individual system failures will be kept small and

dominant risk contributors will not be created.

N-583 Annual Training Alternative, Section XI, Division 1 10/95E

Training using manual techniques is not provided for, and

the alternative is less complete than that provided by

Appendix VII, VII-4220, of the 1998 Edition or earlier. Also,

the provisions do not meet the Appendix VIII qualification

requirements as required by 10 CFR 50.55a(b)(2)(xiv).

N-586 Alternative Additional Examination Requirements for Class 1, 2,

and 3 Piping, Components, and Supports, Section XI, Division 1

5/98E

Code Case would permit areas that have been determined

by engineering evaluation to be subject to the same root

cause and degradation mechanism as those areas that

originally exceeded the Section XI acceptance criteria to go

unexamined if their numbers exceed the number of

additional examinations required by Section XI.
CODE

CASE

NUMBER

TABLE 2, UNACCEPTABLE SECTION XI CODE CASES SUPPLEMEN

T/EDITION

SUMMARY

10

N-587 Alternative NDE Requirements for Repair/Replacement

Activities, Section XI, Division 1

11/98E

The NRC believes this Code Case is in conflict with the

review process for approval of alternatives under 10 CFR

50.55a(a)(3). The Code Case would permit a licensee and

the Authorized Nuclear Inspector to choose unspecified

alternatives to regulatory requirements.

N-589 Class 3 Nonmetallic Cured-in-Place Piping, Section XI, Division

1

6/98E

1) Insufficient controls are provided for the installation

process.

2) There are no qualification requirements for installers and

installation procedures such as those for welders and

welding procedures.

3) Fracture toughness properties of the fiberglass are such

that the cured-in-place piping (CIPP) could crack during a

seismic event.

4) Equations 4 and 5 in the Code Case contain an îiî term

[a stress intensification factor] that is derived from fatigue

considerations. Stress intensification factors, however,

have not been developed for fiberglass materials.

N-590 Alternative to the Requirements of Subsection IWE,

Requirements for Class MC and Metallic Liners of Class CC

Components of Light-Water Cooled Plants, Section XI, Division

1

5/98E

The NRC staff is developing a rule that will endorse the

ASME Code through the 2000 Addenda. Several licensees

have submitted relief requests to use Subsection IWE,

1998 Edition. This Code Case is a duplicate of the

provisions contained in Subsection IWE, 1998 Edition. The

licensee submittals and NRC approval, as supplemented

by the licenseeís commitments in the responses to the

staffís Request for Additional Information, were plantspecific. A draft generic approval of Subsection IWE has

been developed for the proposed rule but, at this time, is

considered predecisional. Thus, a generic position is not

yet available for this Code Case.
CODE

CASE

NUMBER

TABLE 2, UNACCEPTABLE SECTION XI CODE CASES SUPPLEMEN

T/EDITION

SUMMARY

11

N-591 Alternative to the Requirements of Subsection IWL,

Requirements for Class CC Concrete Components of LightWater Cooled Plants, Section XI, Division 1

5/98E

The NRC staff is developing a rule that will endorse the

ASME Code through the 2000 Addenda. Several licensees

have submitted relief requests to use Subsection IWL,

1998 Edition. This Code Case is a duplicate of the

provisions contained in Subsection IWL, 1998 Edition. The

licensee submittals and NRC approval, as supplemented

by the licenseeís commitments in the responses to the

staffís Request for Additional Information, were plantspecific. A draft generic approval of Subsection IWL has

been developed for the proposed rule but, at this time, is

considered predecisional. Thus, a generic position is not

yet available for this Code Case.

N-619 Alternative Requirements for Nozzle Inner Radius Inspections

for Class 1 Pressurizer and Steam Generator Nozzles, Section

XI, Division 1

3/98E

The Code Case is not acceptable to the NRC staff because

the study upon which it is based was not sufficiently broad

to address all applicable plants and conditions. In addition,

the UT data provided in the basis is inconclusive.

N-622 Ultrasonic Examination of RPV and Piping, Bolts, and Studs,

Section XI, Division 1

4/98E

The Code Case was published in May 1999. Industry

Performance Demonstration Initiative efforts since that time

have made this Code Case obsolete. Issues associated

with supplements to Appendix VIII are being addressed

individually in separate Code Cases.

N-648 Alternative Requirements for Inner Radius Examination of Class

1 Reactor Vessel Nozzles, Section XI Division 1

11/98E

The Code Case references a Table (IWB-3513-3) for

surface flaw acceptance criteria which does not exist.
12

3. UNACCEPTABLE OM CODE CASES

The following OM Code Cases were determined to be unacceptable for use by

licensees in their inservice testing programs. The ASME issues OM Code Cases annually

with publication of new edition or addenda. To assist users of the OM Code, Column 3 of

Table 3 lists the edition or addenda to which each Code Case was attached (E: edition;

A: addenda), and whether the Code Case is new or reaffirmed.

TABLE 3 - UNACCEPTABLE OM CODE CASES

CODE CASE

NUMBER

TABLE 3, UNACCEPTABLE OM CODE CASES EDITION/

ADDENDA

SUMMARY OF BASIS FOR EXCLUSION

OMN-10, Rev. 0 Requirements for Safety Significance Categorization of

Snubbers Using Risk Insights and Testing Strategies for

Inservice Testing of LWR Power Plants

July 1, 2000A

The method used for categorizing snubbers could result

in certain snubbers being inappropriately categorized

as having low safety significance. These snubbers

would not be adequately tested or inspected to provide

assurance of their operational readiness. In addition,

unexpected extensive degradation in feedwater piping

has occurred which would necessitate a more rigorous

approach to snubber categorization than presently

contained in this Code Case. [Note: Condition is

consistent with established regulatory position.]
13

DRAFT IMPACT STATEMENT

This guide should be developed to list the Code Cases that the NRC staff has

determined to be unacceptable for use in licensee design and construction, inservice

inspection, and inservice testing programs. The guide should be developed in response to

industry requests for the NRC to provide such a list, including a summary of the basis for

disapproval.

Previous reviews of ASME Code Cases discussed only the Code Cases that the NRC

staff had found acceptable. Providing the basis for any disapprovals will afford licensees the

opportunity to address NRC staff concerns through 10 CFR 50.55a(a)(3), which permits the

use of alternatives to the mandated ASME Code requirement provided the proposed

alternatives result in an acceptable level of quality and safety and their use is authorized by

the Director of the Office of Nuclear Reactor Regulation.

It is expected that this guide will save industry resources as licensees will know

exactly how to address NRC staff concerns. This in turn will save NRC resources by

reducing the length of the review process. In addition, since many Code Cases generally

simplify implementation of ASME Code provisions, reduce radiological exposure, or

incorporate operating experience and technological improvements, it is anticipated that,

when NRC staff concerns have been addressed, licensees will still be able to reduce

resources relative to present ASME Code requirements.