ML052140501
| ML052140501 | |
| Person / Time | |
|---|---|
| Issue date: | 08/17/2005 |
| From: | Norris W Materials Engineering Branch |
| To: | |
| Norris W E 415-6796 | |
| References | |
| RG-1.193, Rev. 1 | |
| Download: ML052140501 (13) | |
Text
1 Copies may be obtained from the American Society of Mechanical Engineers, Three Park Avenue, New York, NY 10016-5990; phone (212) 591-8500; fax (212) 591-8501; www.asme.org.
This regulatory guide lists the Code Cases that the NRC has determined not to be acceptable for use on a generic basis. Licensees may submit a 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 ASME Code requirements referenced in 10 CFR 50.55a provided that the proposed alternatives result in an acceptable level of quality and safety.
This guide was issued after consideration of comments received from the public. The NRC staff encourages and welcomes comments and suggestions in connection with improvements to published regulatory guides, as well as items for inclusion in regulatory guides that are currently being developed. The NRC staff will revise existing guides, as appropriate, to accommodate comments and to reflect new information or experience. Written comments may be submitted to the Rules and Directives Branch, Office of Administration, U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001.
Regulatory guides are issued in 10 broad divisions: 1, Power Reactors; 2, Research and Test Reactors; 3, Fuels and Materials Facilities; 4, Environmental and Siting; 5, Materials and Plant Protection; 6, Products; 7, Transportation; 8, Occupational Health; 9, Antitrust and Financial Review; and 10, General.
Requests for single copies of draft or active regulatory guides (which may be reproduced) should be made to the U.S. Nuclear Regulatory Commission, Washington, DC 20555, Attention: Reproduction and Distribution Services Section, or by fax to (301) 415-2289; or by email to Distribution@nrc.gov. Electronic copies of this guide and other recently issued guides are available through the NRCs public Web site under the Regulatory Guides document collection of the NRCs Electronic Reading Room at http://www.nrc.gov/reading-rm/doc-collections/
and through the NRCs Agencywide Documents Access and Management System (ADAMS) at http://www.nrc.gov/reading-rm/adams.html, under Accession No. ML052140501. Note, however, that the NRC has temporarily suspended public access to ADAMS so that the agency can complete security reviews of publicly available documents and remove potentially sensitive information. Please check the NRCs Web site for updates concerning the resumption of public access to ADAMS.
U.S. NUCLEAR REGULATORY COMMISSION Revision 1 August 2005 REGULATORY GUIDE OFFICE OF NUCLEAR REGULATORY RESEARCH REGULATORY GUIDE 1.193 (Draft was issued as DG-1126, dated August 2004)
ASME CODE CASES NOT APPROVED FOR USE A. INTRODUCTION In Title 10, Part 50, of the Code of Federal Regulations (10 CFR Part 50), Domestic Licensing of Production and Utilization Facilities, Section 50.55a(c), Reactor Coolant Pressure Boundary, 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, Rules for Construction of Nuclear Power Plant Components,1 of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (B&PV Code) or equivalent quality standards. Section 50.55a(f), Inservice Testing Requirements, requires, in part, that Class 1, 2, and 3 components and their supports meet the requirements of the Code for Operation and Maintenance of Nuclear Power Plants (OM Code) of the ASME OM Code or equivalent quality standards.
Finally, 10 CFR 50.55a(g), Inservice Inspection Requirements, requires, in part, that Classes 1, 2, 3, MC (metal containment), and CC (concrete containment) components and their supports meet the requirements of Section XI, Rules for Inservice Inspection of Nuclear Power Plant Components, of the ASME B&PV Code or equivalent quality standards.
The ASME publishes a new edition of the B&PV and OM Codes every 3 years and new addenda every year.
The latest editions and addenda of Section III,Section XI, and the OM Code that the U.S. Nuclear Regulatory Commission (NRC) has approved for use are referenced in 10 CFR 50.55a(b). The ASME also publishes
2 Revision 32 to Regulatory Guide 1.84 combined Regulatory Guides 1.84 and 1.85 to list all the Section III Code Cases in one guide. The title of Regulatory Guide 1.84 has been modified to reflect this.
RG 1.193, Rev. 1, Page 2 Code Cases for Section III and Section XI quarterly and Code Cases for the OM Code yearly.
Code Cases provide alternatives to the ASME Code.
Revision 33 of Regulatory Guide 1.84, Design, Fabrication, and Materials Code Case Acceptability, ASME Section III,2 and Revision 14 of Regulatory Guide 1.147, Inservice Inspection Code Case Acceptability, ASME Section XI, Division 1, which the NRC published concurrently with this guide, identify the Code Cases that the NRC has determined to be acceptable alternatives to applicable parts of Sections III and XI of the ASME B& PV Code. This regulatory guide does not approve the use of the Code Cases listed herein.Section III and Section XI Code Cases listed in Supplement 12 to the 1998 Edition of the ASME B&PV Code through Supplement 6 to the 2001 Edition were reviewed by the NRC during the revision of these regulatory guides.
Because this regulatory guide does not approve the use of the Code Cases listed herein, it does not contain new or amended information collection requirements subject to the Paperwork Reduction Act of 1995 (44 U.S.C. 3501 et seq.). The NRC may neither conduct nor sponsor, and a person is not required to respond to, an information collection request or requirement unless the requesting document displays a currently valid OMB control number.
B. DISCUSSION This regulatory guide lists the Code Cases that the NRC has determined not to be 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. A licensee must submit a plant-specific request that addresses the NRCs concern about the Code Case at issue.
RG 1.193, Rev. 1, Page 3 C. REGULATORY POSITION For this guide, the NRC staff reviewed the Section III and Section XI Code Cases listed in Supplement 12 to the 1998 Edition of the ASME B&PV Code through Supplement 12 to the 2001 Edition. Licensees must not implement Code Cases listed in this guide without prior NRC approval.
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 The NRC determined that the following Section III Code Cases are unacceptable for use by licensees in their Section III design and construction programs. The ASME issues a new edition of Section III every 3 years, and publishes quarterly supplements to the edition containing Section III Code Cases. Hence, there are 12 supplements to each edition. To assist users, the third column of Table 1 lists the date of approval by the ASME, or for new Code Cases, the supplement and edition in which each Code Case was published (e.g., 3/01E means Code Case Supplement 3 to the 2001 Edition).
RG 1.193, Rev. 1, Page 4 Table 1. Unacceptable Section III Code Cases Code Case Number Table 1, Unacceptable Section III Code Cases Date or Supplement/Edition Summary N-284-1 Metal Containment Shell Buckling Design Methods,Section III, Division 1, Class MC 10/2/00 (1)
The following errata, misprints, recommendations, and errors have been identified:
Fig. -1511.1, The curve for L should not exceed 0.8 for any value of (R/t).
- 1512, The statement See Fig.-1512-1 then see
-1713.1.2 for method of calculating M should be rephrased as: See -1713.1.2 for method of calculating M, then see Fig. -1512-1.
- 1513, Recommend Use the value of il given for spherical shells in accordance with -1512.
- 1521, (i) In (a) Axial Compression, G = L should be changed to G = L. (ii) The source of the equations shown under (a) Axial Compression provided separate instability equations for stringer-stiffened and ring-stiffened cylindrical shells.
The Code Case adopted the instability equations pertaining to ring-stiffened shells, which are less conservative than those for stringer instability, for both ring and/or stringer stiffened cylindrical shells. Is this the intent? (Ref. Summary of Buckling Tests on Fabricated Steel Cylindrical Shells in USA, by C. D. Miller, in Buckling of Shells in Offshore Structures, 1982.)
- 1712.1.1, The equation Ch = 0.92/(M - 0.636) should be changed to Ch = 0.92/(M - 0.636).
Fig. -1712.1.1-1, The leftmost curve should be labeled Ch
- 1712.2.2, (a) Axial Compression, (i) In the formula for ej, the denominator should be (m/Lj)2 C t.
(ii) The expressions for C and C should be separated.
- 1712.2.3, (i) The factor 1.944 in an older edition has been changed to 2.00. No basis is apparent. (ii) The misprint t 1 1/4 should be corrected to t1 1/4.
- 1713.1.1, (i) The equation a=Cel/FS should be changed to a=LCel/FS. (ii) The title of (c) should be changed to Axial Compression Plus In-Plane Shear.
Fig. -1713.1-1, In (b), the lower value Ks=ra on the vertical axis should be changed to Ks=ha
- 1713.2.1, (i) The headings for (b) and (c) should include the words In-Plane. (ii) In (b) Axial Compression Plus Shear, should be changed to.
(2)
Applicants intending to use Code Case N-284-1 shall submit a request to the NRC staff for its review and approval on a plant-specific basis.
Code Case Number Table 1, Unacceptable Section III Code Cases Date or Supplement/Edition Summary RG 1.193, Rev. 1, Page 5 N-483-2 N-483-3 Alternative Rules to the Provisions of NCA-3800, Requirements for Purchase of Material,Section III, Divisions 1 and 3 5/7/99 2/25/02 The Code Case lacks sufficient detail to ensure that the supplied material is as represented by the Certified Material Test Report.
N-510 N-510-1 Borated Stainless Steel for Class CS Core Support Structures and Class 1 Component Supports,Section III, Division 1 12/9/93 8/14/01 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 2/23/00 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 5/5/00 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 12/3/99 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 Date or Supplement/Edition Summary RG 1.193, Rev. 1, Page 6 N-595 N-595-1 N-595-2 N-595-3 Requirements for Spent Fuel Storage Canisters,Section III, Division 1 2/26/99 9/24/99 12/8/00 6/01E 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. The ASME is presently developing Code Case N-717 to replace Code Case N-595-3.
Thus, Code Case N-595-3 will be retained in Regulatory Guide 1.193, and the NRC staff will review Code Case N-717 when it is published.
N-645 N-645-1 Use of Rupture Disk Devices on Nuclear Fuel Storage Canisters, Class 1,Section III, Division 1 6/14/00 4/01E The NRC does not permit the use of rupture disk devices in spent nuclear fuel storage canister designs.
RG 1.193, Rev. 1, Page 7 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 a new edition of Section III every 3 years, and publishes quarterly supplements to the edition containing Section III Code Cases. Hence, there are 12 supplements to each edition. To assist users, the third column of Table 1 lists the date of approval by the ASME, or for new Code Cases, the supplement and edition in which each Code Case was published (e.g., 3/01E means Code Case Supplement 3 to the 2001 Edition).
Table 2. Unacceptable Section XI Code Cases Code Case Number Table 2. Unacceptable Section XI Code Cases Date or Supplement/Edition Summary N-465 N-465-1 Alternative Rules for Pump Testing,Section XI, Division 1 11/30/88 8/14/97 The draft standard referenced in the Code Case is outdated. The requirements contained in the OM Code, Code for Operation and Maintenance of Nuclear Power Plants, should be used. Note that Revision 12 of RG 1.147 approved N-465 for use. The disapproval of N-465 for use applies only to new users.
N-473 N-473-1 Alternative Rules for Valve Testing,Section XI, Division 1 3/8/89 8/14/97 The draft standard referenced in the Code Case is outdated. The requirements contained in the OM Code, Code for Operation and Maintenance of Nuclear Power Plants, should be used. Note that Revision 12 of RG 1.147 approved N-473 for use. The disapproval of N-473 for use applies only to new users.
N-480 Examination Requirements for Pipe Wall Thinning Due to Single Phase Erosion and Corrosion,Section XI, Division 1 Annulled on 9/18/01 Code Case has been superseded by Code Case N-597, Requirements for Analytical Evaluation of Pipe Wall Thinning, implemented in conjunction with NSAC-202L, Recommendations for an Effective Flow Accelerated Corrosion Program.
N-498-2 N-498-3 Alternative Requirements for 10-Year System Hydrostatic Testing for Class 1, 2, and 3 Systems,Section XI, Division 1 6/9/95 5/20/98 Code Case N-498-4 is conditionally approved in Revision 13 to Regulatory Guide 1.147. Those licensees choosing to implement this Code Case are to implement Revision 4.
Code Case Number Table 2. Unacceptable Section XI Code Cases Date or Supplement/Edition Summary RG 1.193, Rev. 1, Page 8 N-532-2 Alternative Requirements to Repair and Replacement Documentation Requirements and Inservice Summary Report Preparation and Submission as Requested by IWA-4000 and IWA-6000 5/01E The following concerns were identified during review of the Code Case:
(1)
Clarification is needed relative to the intent of Footnote 1 and Table 4 regarding the applicable edition and addenda; and (2)
Submission of Form OAR-1 is at the end of each inspection period rather than 90 days following the outage.
N-542 Alternative Requirements for Nozzle Inside Radius Section Length Sizing Performance Demonstration,Section XI, Division 1 Annulled on 3/28/01 Code Case N-542 was subsumed by Code Case N-552, Alternative Methods-Qualification for Nozzle Inside Radius Section from the Outside Surface, which is being implemented by licensees. Thus, there is no need to approve N-542.
N-547 Alternative Examination Requirements for Pressure Retaining Bolting of Control Rod Drive (CRD) Housings,Section XI, Division 1 Annulled on 5/20/01 Code Case N-547 states that the examination of CRD housing bolts, studs, and nuts is not required. However, 10 CFR 50.55a(b)(2)(xxi)(B) requires the examination of CRD bolting material whenever the CRD housing is disassembled and the bolting material is to be reused. Examination of CRD bolting material 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 B-J Piping Welds,Section XI, Division 1 8/9/96 2/26/99 3/28/00 (1)
The Code Case does not address inspection strategy for existing augmented and other inspection programs such as intergranular stress corrosion cracking (IGSCC), flow-assisted 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.
Code Case Number Table 2. Unacceptable Section XI Code Cases Date or Supplement/Edition Summary RG 1.193, Rev. 1, Page 9 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 12/31/96 3/28/01 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.
N-562 N-562-1 Alternative Requirements for Wall Thickness Restoration of Class 3 Moderate Energy Carbon Steel Piping,Section XI, Division 1 12/31/96 3/28/01 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-574 NDE Personnel Recertification Frequency,Section XI, Division 1 8/14/97 Based on data obtained by the NRC staff during its review of Appendix VIII, Performance Demonstration for Ultrasonic Examination Systems, 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 8/14/97 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.
N-577 N-577-1 Risk-Informed Requirements for Class 1, 2, and 3 Piping, Method A,Section XI, Division 1 9/2/97 3/28/00 (1)
The Code Case does not address inspection strategy for existing augmented and other inspection programs such as intergranular stress corrosion cracking (IGSCC), flow-assisted 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.
Code Case Number Table 2. Unacceptable Section XI Code Cases Date or Supplement/Edition Summary RG 1.193, Rev. 1, Page 10 N-578 N-578-1 Risk-Informed Requirements for Class 1, 2, and 3 Piping, Method B,Section XI, Division 1 9/2/97 3/28/00 (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-587 Alternative NDE Requirements for Repair/Replacement Activities,Section XI, Division 1 12/12/97 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 N-589-1 Class 3 Nonmetallic Cured-in-Place Piping,Section XI, Division 1 4/19/02 5/01E (1)
The installation process provides insufficient controls on wall thickness measurement.
(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 i 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 Annulled on 4/8/02 The provisions of the Code Case were incorporated into the 1998 Edition which has been approved by the NRC. Thus, the Code Case is no longer needed and was annulled by the ASME.
Code Case Number Table 2. Unacceptable Section XI Code Cases Date or Supplement/Edition Summary RG 1.193, Rev. 1, Page 11 N-591 Alternative to the Requirements of Subsection IWL, Requirements for Class CC Concrete Components of Light-Water Cooled Plants,Section XI, Division 1 Annulled on 4/8/02 The provisions of the Code Case were incorporated into the 1998 Edition which has been approved by the NRC. Thus, the Code Case is no longer needed and was annulled by the ASME.
N-613 Ultrasonic Examination of Full Penetration Nozzles in Vessels, Examination Category B-D, Item Nos. B3.10 and B3.90, Reactor Vessel-To-Nozzle Welds, Fig. IWB-2500-7(a), (b), and (c),
Section XI, Division 1 7/30/98 The Code Case conflicts with and unacceptably reduces the requirements of 10 CFR 50.55a(b)(2)(xv)(K)(2)(i). A revision to the Code Case has been developed to address the concerns.
N-615 Ultrasonic Examination as a Surface Examination Method for Category B-F and B-J Piping Welds,Section XI, Division 1 12/98E The Code Case requires that the ultrasonic technique used be demonstrated capable of detecting certain size flaws on the outside diameter of the weld, but it does not specify any demonstration requirements. To be acceptable,Section XI, Appendix VIII, type rules for performance demonstration need to be developed and applied.
N-622 Ultrasonic Examination of RPV and Piping, Bolts, and Studs,Section XI, Division 1 R4/19/02 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-653 Qualification Requirements for Full Structural Overlaid Wrought Austenitic Piping Welds,Section XI, Division 1 3/01E (1)
Section XI, Appendix VIII, Supplement 11, requires a personnel performance qualification as part of the procedure qualification. The detection acceptance criteria in the Code Case do not require personnel performance qualification as part of the procedure qualification.
Personnel qualification is necessary to validate the effectiveness of the procedure qualification.
(2)
The minimum grading unit is 1.0 inch in the circumferential direction. The acceptance tolerance, however, is 0.75 inch root mean square error. Thus, the length sizing acceptance criteria do not adequately prevent the use of testmanship rather than skill to pass length sizing tests.
Code Case Number Table 2. Unacceptable Section XI Code Cases Date or Supplement/Edition Summary RG 1.193, Rev. 1, Page 12 N-654 Acceptance Criteria for Flaws in Ferritic Steel Components 4 in. and Greater in Thickness,Section XI, Division 1 4/01E Licensees intending to apply the rules of this Code Case must obtain NRC approval of the specific application in accordance with 10 CFR 50.55a(3).
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 a new edition or addenda. No new OM Code Cases were added in this revision. 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).
Table 3. Unacceptable OM Code Cases Code Case Number Table 3. Unacceptable OM Code Cases Date or 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.
RG 1.193, Rev. 1, Page 13 D. IMPLEMENTATION The purpose of this section is to provide information to applicants and licensees regarding the NRC staffs plans for using this guide. No backfitting is intended or approved in connection with the issuance of this guide.
Except when an applicant or licensee proposes or has previously established an acceptable alternative method for complying with specified portions of the NRCs regulations, the methods described in this guide will be used in evaluating (1) submittals in connection with applications for construction permits, design certifications, operating licenses, and combined licenses, and (2) submittals from operating reactor licensees who voluntarily propose to initiate system modifications that have a clear nexus with this guidance.
E. REGULATORY ANALYSIS This regulatory guide lists only the Code Cases that the NRC staff has determined to be unacceptable for use in the design and construction, inservice inspection, and inservice testing of nuclear power plant systems and components. Therefore, the NRC staff did not prepare a regulatory analysis for this guide.
Previous reviews of ASME Code Cases discussed only the Code Cases that the NRC staff determined to be acceptable. The agency developed this guide at industry request 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, including a summary of the basis for disapproval.
Providing the basis for disapproval of a Code Case affords 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 requirements, provided that the proposed alternatives result in an acceptable level of quality and safety and their use is authorized by the Director of the NRCs Office of Nuclear Reactor Regulation.
Providing the basis for disapproval of a Code Case in this guide also helps to conserve industry resources. The cognizant ASME committees will be able to focus their attention on specific issues.
In addition, licensees who choose to request alternatives under 10 CFR 50.55a(a)(3) will understand the NRC staff concerns to be addressed. NRC resources will be saved because the 10 CFR 50.55a(a)(3) process will be more efficient. When the ASME modifies a Code Case to address NRC staff concerns, additional NRC resources will be saved because the agency will be able to generically approve the Code Cases, thereby obviating the need for case-by-case approval. 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 further reduce allocated resources.