[Federal Register Volume 59, Number 180 (Monday, September 19, 1994)]
[Unknown Section]
[Page 0]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 94-23136]


[[Page Unknown]]

[Federal Register: September 19, 1994]


                                                   VOL. 59, NO. 180

                                         Monday, September 19, 1994

NUCLEAR REGULATORY COMMISSION

10 CFR Part 50

RIN 3150-AF04

 

Steam Generator Tube Integrity for Operating Nuclear Power Plants

AGENCY: Nuclear Regulatory Commission.

ACTION: Advance notice of proposed rulemaking.

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SUMMARY: The Nuclear Regulatory Commission is considering amending its 
regulations regarding steam generator tube surveillance and maintenance 
at operating nuclear power plants. The advanced notice of proposed 
rulemaking (ANPRM) considers regulatory approaches that would maintain 
adequate assurance of steam generator tube integrity while allowing a 
more appropriate approach to steam generator surveillance and 
maintenance activities at nuclear power plants. The NRC is issuing this 
ANPRM to invite comments, advice, and recommendations from interested 
parties on the proposed steam generator rule.

DATES: The comment period expires December 5, 1994. Comments received 
after this date will be considered if it is practical to do so, but the 
Commission is able to assure consideration only for comments received 
on or before this date.

ADDRESSES: Mail comments to: The Secretary of the Commission, U.S. 
Nuclear Regulatory Commission, Washington, DC 20555, Attention: 
Docketing and Services Branch. Deliver comments to: 11555 Rockville 
Pike, Rockville, Maryland, between 7:45 am and 4:15 pm on Federal 
workdays. Examine copies of comments received at: The NRC Public 
Document Room, 2120 L Street NW. (Lower Level), Washington, DC.

FOR FURTHER INFORMATION CONTACT: T.A. Reed, Office of Nuclear Reactor 
Regulation, U.S. Nuclear Regulatory Commission, Washington, DC 20555, 
telephone (301) 504-2795.

SUPPLEMENTARY INFORMATION:

Background

    Steam generator tube degradation at nuclear power plants continues 
to be a problem for the nuclear industry. Industry actions have been 
effective in controlling many of the forms of degradation experienced 
in late 1970s and early 1980s; however, new degradation mechanisms 
continue to occur. State-of-the-art nondestructive inspection and tube 
repair methods have improved significantly in recent years. Changes in 
types of degradation being experienced and improvements in inspection 
and tube repair technology have made the NRC's existing regulatory 
requirements and guidance out-of-date and in some cases overly 
conservative or impractical. In addition, the NRC staff has determined 
that factors other than the material tube degradation should be 
considered when assessing tube integrity.
    The objective of the proposed rule would be to maintain steam 
generator tube integrity such that there is an extremely low 
probability of steam generator tube leakage that could result in core 
damage or otherwise exceed allowable off-site doses while allowing a 
reasonable approach to steam generator surveillance and maintenance 
activities (i.e., degradation-specific management). A performance-based 
rule with quantitative criteria would achieve the desired goals without 
being prescriptive in nature. A flexible rule would accommodate changes 
in operating experience and technology while giving incentives for the 
industry to continue to improve the state-of-the art tube inspection 
and repair methods. Incorporation of an integrated approach considers 
the overall factors of safety and risk, including systems and 
radiological assessments.
    The NRC staff's rulemaking effort would establish a flexible 
framework that allows steam generator tube integrity to be addressed 
using a degradation-specific management approach. This approach 
involves establishing and implementing preventive measures such as 
inspection, evaluation, and repair criteria that are applicable to 
distinct steam generator degradation mechanisms, and default criteria 
for the remaining forms of steam generator tube degradation where 
experience does not enable a degradation-specific approach. The NRC 
staff's rulemaking effort would also address issues relevant to 
containment bypass probability and severe accidents associated with 
bypass of containment. The NRC staff would consider application of more 
realistic analytical assumptions, as well as defense-in-depth measures 
that could be implemented to further ensure safety. The proposed rule 
would acknowledge new degradation mechanisms and technological advances 
in inspection techniques to improve characterization of these 
mechanisms.
    Recognizing that the steam generator rule would contain broad 
criteria while an associated regulatory guide would contain more 
detailed guidance, a proposed outline of the NRC staff's perception of 
the necessary elements of a steam generator rule follows:

(a) Applicability
(b) Definitions
(c) Requirements
(1) Licensee Surveillance and Maintenance Program
    (i) Preservice and Inservice Inspection Program
    (ii) Water Chemistry Program
    (iii) Tube Integrity
    (iv) Repair Criteria
    (v) Repair Methods
    (vi) Nondestructive Examination Considerations
    (vii) Normal Operating Primary-to-Secondary Leakage Monitoring/
Limits
(2) Accident Mitigation
    (i) Accident Condition Primary-to-Secondary Leakage Monitoring
    (ii) Procedures
    (iii) Operator Training
(3) Radiological Consequences
(d) Severe Accident Considerations
(e) Implementation

Specific Considerations

    Comments, advice and recommendations on a proposed rule reflecting 
the aforementioned features and any other pertinent points are invited 
from all interested persons. Particularly, comments and supporting 
reasons are requested on the following questions:
    1. What are appropriate performance based criteria that should be 
included in the steam generator proposed rule to address steam 
generator inspection scope and frequency, nondestructive examination 
(NDE) equipment capabilities, NDE data analyst capabilities, 
performance demonstration and qualification of NDE systems, steam 
generator water chemistry requirements, flaw acceptance criteria, and 
steam generator tube repair methods?
    2. What are the appropriate performance based criteria that should 
be incorporated into the proposed rule to define adequate tube 
integrity (vis-a-vis 10 CFR 50 Appendix A GDC 14)?
    3. What information should be part of the steam generator proposed 
rule, and what information should be addressed in a Regulatory Guide?
    4. How should the proposed rule be structured to assure that 
licensees make use of available operational experience and data 
applicable to steam generator integrity, and that licensees can 
establish and readily update steam generator programs?
    5. How should the proposed rule address new or replacement steam 
generators versus degraded steam generators?
    6. Should the Regulatory Guide be prescriptive in terms of the 
methods to be used to ensure that the proposed rule's performance 
criteria are achieved?
    7. Should the proposed rule require licensees to submit their 
programs to NRC for review and approval before implementation?
    8. What requirements should be instituted to provide improved or 
additional monitoring of primary-to-secondary leakage as a means to 
enhance defense-in-depth relative to steam generator tube degradation?
    9. What changes should be made in the NUREG-0800 radiological 
calculation guidance used to address the safety significance of steam 
generator tube leakage and rupture?
    10. What beyond design basis considerations related to steam 
generator tube integrity should be addressed during the rulemaking 
process (e.g., the potential for containment bypass)?
    11. How should tube failure prevention and mitigation measures be 
balanced in the proposed rule?
    12. What interim measures are appropriate to allow continued 
operation of a unit in which new degradation modes are discovered?
    13. Is the proposed rulemaking action considered a necessary or 
preferred course of action for addressing steam generator maintenance 
and surveillance issues, or are there other alternative regulatory 
mechanisms that are equally effective for addressing these issues? If 
alternatives to rulemaking are preferred, describe the preferred 
alternatives, including the pros and cons of pursuing the alternative 
course of action.
    14. How should the steam generator rule or associated Regulatory 
Guide address the following technical issues: (1) Calculation of tube 
leakage following postulated events such as the main steam line break 
and the potential for this leakage to exceed the make-up capacity of 
the refueling water storage tank (supply source for the emergency core 
cooling system), (2) application of eddy current parameters such as 
voltage that are indirect measures of tube structural or leakage 
integrity (as compared to more direct measures such as crack depth or 
crack length), and (3) calculation of radiologically significant 
isotope concentrations in released materials (I-131 equivalent) 
following postulated events such as the main steam line break with 
steam generator tube leakage where there is a paucity of data on 
fission product iodine release rates.
    The preliminary views expressed in this notice may change in light 
of comments received. In any case, there will be an opportunity later 
for additional public comment in connection with any proposed rule that 
may be developed by the NRC.

List of Subjects in 10 CFR Part 50

    Antitrust, Classified information, Criminal penalties, Fire 
protection, Intergovernmental relations, Nuclear power plants and 
reactors, Radiation protection, Reactor siting criteria, Reporting and 
record keeping requirements.

    Authority: Secs. 102, 103, 104, 105, 161, 182, 183, 186, 189, 68 
Stat. 936, 937, 938, 948, 953, 954, 955, 956, as amended, sec. 234, 
83 Stat. 1244, as amended (42 U.S.C. 2132, 2133, 2134, 2135, 2201, 
2232, 2233, 2236, 2239, 2282); secs. 201, as amended, 202, 206, 88 
Stat. 1242, as amended 1244, 1246 (42 U.S.C. 5841, 5842, 5846).
    Section 50.7 also issued under Public Law 95-601, sec. 10, 92 
Stat. 2951 (42 U.S.C. 5851). Section 50.10 also issued under secs. 
101, 185, 68 Stat. 936, 955, as amended (42 U.S.C. 2131, 2235); sec. 
102, Public Law 91-190, 83 Stat. 853 (42 U.S.C. 4332). Sections 
50.13, 50.54(dd), and 50.103 also issued under sec. 108, 68 Stat. 
939, as amended (42 U.S.C. 2138). Sections 50.23, 50.35, 50.55, and 
50.56 also issued under sec. 185, 68 Stat. 955 (42 U.S.C. 2235). 
Sections 50.33a, 50.55a and Appendix Q also issued under sec. 102, 
Public Law 91-190, 83 Stat. 853 (42 U.S.C. 4332). Sections 50.34 and 
50.54 also issued under sec. 204, 88 Stat. 1245 (42 U.S.C. 5844). 
Sections 50.58, 50.91, and 50.92 also issued under Public Law 97-
415, 96 Stat. 2073 (42 U.S.C. 2239). Section 50.78 also issued under 
sec. 122, 68 Stat. 939 (42 U.S.C. 2152). Sections 50.80-50.81 also 
issued under sec. 184, 68 Stat. 954, as amended (42 U.S.C. 2234). 
Appendix F also issued under sec. 187, 68 Stat. 955 (42 U.S.C. 
2237).

    Dated at Rockville, Maryland, this 8th day of September 1994.

    For the Nuclear Regulatory Commission.
James M. Taylor,
Executive Director for Operations.
[FR Doc. 94-23136 Filed 9-16-94; 8:45 am]
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