ML23151A490

PR-050 - 59FR47817 - Steam Generator Tube Integrity for Operating Nuclear Power Plants (Advance Notice of Proposed Rulemaking)

ML23151A490
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Issue date:	09/19/1994
From:	Taylor J NRC/EDO
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PR-050, 59FR47817
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ADAMS Template: SECY-067 09/19/1994 PR-050 - 59FR47817 - STEAM GENERATOR TUBE INTEGRITY FOR OPERATING NUCLEAR POWER PLANTS (ADVANCE NOTICE OF PROPOSED RULEMAKING)

PR-050 59FR47817 RULEMAKING COMMENTS Document Sensitivity: Non-sensitive - SUNSI Review Complete

STATUS OF RULEMAKING PROPOSED RULE:

PR-050 OPEN ITEM {Y/N) N RULE NAME:

STEAM GENERATOR TUBE INTEGRITY FOR OPERATING NUCLEAR POWER PLANTS {ADVANCE NOTICE OF PROPOSED RULEMAKING)

PROPOSED RULE FED REG CITE:

59FR47817 PROPOSED RULE PUBLICATION DATE:

09/19/94 ORIGINAL DATE FOR COMMENTS: 12/05/94 NUMBER OF COMMENTS:

EXTENSION DATE:

I I

FINAL RULE FED. REG. CITE:

FINAL RULE PUBLICATION DATE:

2 I

I NOTES ON: ANPR CONSIDERS REGULATORY APPROACHES THAT WOULD MAINTAIN ADEQUATE STATUS ASSURANCE OF SG TUBE INTEGRITY WHILE ALLOWING SG SURVEILLANCE &

OF RULE: MAINTENANCE ACTIVITIES AT NPPS. ANPR WITHDRAWN--63FR66496, 12/2/98 HISTORY OF THE RULE PART AFFECTED: PR-050 RULE TITLE:

STEAM GENERATOR TUBE INTEGRirY FOR OPERATING NUCLEAR POWER PLANTS {ADVANCE NOTICE OF PROPOSED RULEMAKING)

PROPOSED RULE DATE PROPOSED RULE PROPOSED RULE SECY PAPER: 94-202 SRM DATE:

08/23/94 SIGNED BY SECRETARY:

09/08/94 FINAL RULE SECY PAPER: 95-205 CONTACT!: T. A. REED CONTACT2:

FINAL RULE SRM DATE:

DATE FINAL RULE 10/12/95 SIGNED BY SECRETARY:

STAFF CONTACTS ON THE RULE I

I MAIL STOP: O-14B20 PHONE: 504-1462 MAIL STOP:

PHONE:

DOCKET NO. PR-050 (59FR47817)

DATE DOCKETED 09/14/94 12/06/94 12/19/94 11/27 /98 01/11/99 In the Matter of STEAM GENERATOR TUBE INTEGRITY FOR OPERATING NUCLEAR POWER PLANTS (ADVANCE NOTICE OF PROPOSED RULEMAKING)

DATE OF DOCUMENT 09/08/94 12/05/94 12/14/94 11/24/98 12/10/98 TITLE OR DESCRIPTION OF DOCUMENT FEDERAL REGISTER NOTICE - PROPOSED RULE COMMENT OF NUCLEAR ENERGY INSTITUTE (THOMAS E. TIPTON) (

1)

COMMENT OF VIRGINIA POWER (M.L. BOWLING) (

FEDERAL REGISTER NOTICE - PROPOSED RULE:

WITHDRAWAL FEDERAL REGISTER NOTICE - PROPOSED RULE:

WITHDRAWAL; CORRECTION

2)

DOCKET NUMBER PR PROPOSED RULE 5 O DOCKETED Uc. p0

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( 5'1FR'l7811) r Nuclear Regulatory Commission Oh RL'L 10 CFR Part 50 ADJLX;

• RIN 3150-AF04 Steam Generator Tube Integrity for Operating Nuclear Power Plants; Correction AGENCY:

Nuclear Regulatory Commission.

ACTION:

Proposed rule: Withdrawal; Correction.

SUMMARY

This document corrects a notice appearing in the Federal Register on December 2, 1998 (63 FR 66496), that withdraws a notice of proposed rulemaking that requested public comments pertaining to steam generator tube integrity. This action is necessary to correct an erroneous telephone number.

FOR FURTHER INFORMATION CONTACT: David L. Meyer, Chief, Rules and Directives Branch, Division of Administrative Services, Office of Administration, telephone (301) 415-7162.

SUPPLEMENTARY INFORMATION:

On page 66496, in the third column, under the ADDRESSES section, the telephone number, "(202) 512-2249" is corrected to read "(202) 634-3273."

Dated at Rockville, Maryland, this day of December 1998.

For the Nuclear Regulatory Commission.

David L. Meyer, Chief Rules and Directives Branch Division of Administrative Services Office of Administration

NUCLEAR REGULATORY COMMISSION 10 CFR Part 50 RIN 3150-AF04 Steam Generator Tube Integrity for Operating Nuclear Power Plants AGENCY: Nuclear Regulatory Commission.

ACTION: Proposed rule: Withdrawal.

DOCKETED

[7590-ti *p,; C "98 NOV 27 P 2 :44

SUMMARY

The Nuclear Regulatory Commission (NRC) is withdrawing an advance notice of proposed rulemaking (ANPRM) that was published to request public comment on the Commission's regulations pertaining to steam generator (SG) tube integrity. The proposed rule would have implemented a more flexible regulatory framework for steam generator surveillance and maintenance activities that would maintain adequate assurance of tube integrity while allowing a degradation-specific management approach. Because the NRC has concluded that the regulatory objectives set forth for this effort can be achieved by equally effective regulatory alternatives, the ANPR is being withdrawn.

ADDRESSES: The Commission paper, the staff requirement memoranda (SAM), and associated documents are available for public inspection, and copying for a fee, at the NRC Public Document Room located at 2120 L Street NW. (Lower Level), Washington, DC 20012-7082, telephone: (202) 512-2249.

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FOR FURTHER INFORMATION CONTACT: Tim Reed, Office of Nuclear Reactor Regulation, U. S. Nuclear Regulatory Commission, Washington, DC 20555-0001, telephone (301) 415-1462, e-mail tar@nrc.gov.

SUPPLEMENTARY INFORMATION:

On September 19, 1994 (59 FR 47817), the Commission published an ANPRM that requested comments, advice, and recommendations from interested parties on the proposed steam generator rule. In response to the ANPRM, two public comments were received. The primary comment was a coordinated industry response submitted by the Nuclear Energy Institute (NEI). The remaining comment, submitted by Virginia Power, endorsed the NEI comment. Subsequently, the NRC staff developed a draft rule and draft regulatory guide intended to implement a performance-based regulatory structure that provides for the development and implementation of appropriate measures to ensure the consistency and quality of inspection methods, repair criteria, and tube condition assessment, while giving appropriate consideration to risk. As part of the rulemaking process, the NRC staff estimated the risk associated with SG tube degradation and used the results to provide the insights required for performing a regulatory analysis of the proposed rulemaking approach.

In COMSECY-97-013, dated May 23, 1997, the NRC staff provided a risk assessment summary and major conclusions from a regulatory analysis. Based on these results, the NRC staff reassessed whether a rulemaking is the appropriate regulatory vehicle for addressing the problems associated with SG tube integrity. It should be recognized that the NRC staff found that the current regulations governing SG tube integrity provide an adequate basis to ensure public health and safety due to SG operation. However, the NRC staff concluded that further 2

guidance is needed for the industry to continue to effectively meet these regulations. Issues involving a plant's technical specifications (TS) are amenable to a generic letter approach.

Given these considerations, the NRC staff informed the Commission that it planned to pursue the following approach in lieu of a new steam generator rulemaking: (1) complete development of a SG tube integrity regulatory guide which describes an acceptable performance-based program for ensuring adequate tube inspection, monitoring, and assessment; (2) request licensees, through a generic letter, to propose performance-based technical specification changes to address the issues regarding inspection, monitoring, and assessment of SG tube condition to ensure that SG tube integrity is maintained consistent with the plant licensing basis; (3) provide licensees with an option to change current SG tube repair criteria and implement a degradation-specific management approach, if it can be demonstrated that risk will be maintained at an acceptable level. An application-specific regulatory guide would provide guidance on acceptable approaches for proposing changes to SG tube integrity criteria and assessing changes in risk associated with relaxation of tube integrity criteria. Licensees would not be able to implement alternate repair criteria until an appropriate risk assessment is submitted and found acceptable by the NRC staff; and (4) as part of the IPE follow-up program, the NRC staff will evaluate pressurized water reactors (PWRs) that appear to have a high potential for core damage sequences that can challenge SG tubes. Any additional requirements would be imposed consistent with the backfit requirements of § 50.109.

The SRM on COMSECY-97-013, dated June 30, 1997, approved the revised approach.

The SRM also directed the NRC staff to seek industry input, as appropriate, in developing the technical basis for the proposed TS changes to ensure that the proposed changes are consistent with current steam generator tube degradation modes. In support of this commitment, the NRC staff developed a proposed generic letter that: (1) informs PWR 3

licensees that plant TSs for maintaining SG tube integrity do not alone provide the needed assurance that SG tube integrity is being adequately monitored and maintained in accordance with NRC regulations and plant licensing bases; (2) advises licensees that they may request license amendments to their plant TSs to implement the model TSs attached to the generic letter for maintaining SG tube integrity, or justify alternate approaches for ensuring that SG tube integrity; and (3) requires that licensees submit to the NRC written responses that describe their ongoing or planned activities to monitor and maintain SG tube integrity. By letter dated December 16, 1997, the NRC staff was informed that Lile industry, through the NEI Nuclear Strategic Issues Advisory Committee, had voted to adopt NEI 97-06. The chief objective of the industry initiative is for PWR licensees to evaluate their existing SG programs and, where necessary, to revise or strengthen program attributes to meet the intent of the NEI 97-06 guidelines. The NEI 97-06 guidelines are intended to improve both the quality and the consistency of SG programs throughout the industry. Consistent with Direction Setting Issue (DSI) 13, the NRC staff's preferred approach is to endorse an industry initiative that addresses all NRC staff and stakeholder concerns, rather than issue a generic letter. As a result, the NRC staff has temporarily deferred issuing the proposed generic letter for public comment while it works with industry to resolve issues associated with NEI 97-06, with the objective of endorsing NEI 97-06 in a regulatory guide.

Whether the NRC staff ultimately endorses the NEI 97-06 guidance or continues with its efforts to issue a generic letter addressing SG tube integrity, the NRC has concluded that 4

equally effective regulatory alternatives to rulemaking are available to address the issue of SG tube integrity. Therefore, the proposed rule is not required and is being withdrawn.

rl Dated at Rockville, Maryland, this ~ Y -

day of November, 1998.

For the Nuclear Regulatory Commission.

5

5000 Dominion Boulevard Glen Allen, Virginia 23060 DOCKETED

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• 94 DEC 19 P 2 : 11 (59FR'-\\:~1'1)@

December 14, 1994 Secretary of the Commission U.S. Nuclear Regulatory Commission Attention: Docketing and Service Branch Washington, DC 20555

Dear Sir:

VIRGINIA POWEil Serial No. GL 94-050 NL&P/JBL R1 REGARDING ADVANCED NOTICE OF PROPOSED RULEMAKING ON STEAM GENERATOR TUBE INTEGRITY FOR OPERATING NUCLEAR OPERATING PLANTS 10 CFR PART 50 In the September 19, 1994 Federal Register, the NRC announced that it is considering amending the regulations regarding steam generator tube surveillance and maintenance at operating nuclear power plants. In so doing, the NRC invited comments, advice, and recommendations on the proposed steam generator rule.

Virginia Power encourages the NRC's efforts to solicit industry advice and recommendations in developing its approach to this proposed rulemaking.

Specifically, Virginia Power endorses the Nuclear Energy lnstitute's (NEI) comments in response to this advance notice of proposed rulemaking provided to the NRC by letter dated December 5, 1994.

If you have any questions, please contact us.

Very truly yours, M. L. Bowling, Manager Nuclear Licensing and Programs MAR -1 19951

U.S. NUCLEAR REGULATORY COMMISSIO~,

DOCKETING & SERVICE SECTION OFFICE Of THE SECRETARY OF THE COMMISSION Dorument Statistics Postmark Date \\o.\\ 1':\\:\\3 1+/-:. ______ _

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Mr. William Rasin Nuclear Energy Institute 1776 I Street Suite 300 Washington, D. C. 20006-3706 Mr. Thomas E. Tipton Nuclear Energy Institute 1776 I Street Suite 400 Washington, D. C. 20006-3706

NUCLEAR ENERG Y INSTITUTE DOCKETED USHPC DOCKET NUMBER PROPOSED RULE PR 5

• 94 0EC - 6 A10 :27 Thomas E. Tipton VICE PRE SIDENT,

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0 FF ICE CF s ~CR E Tlt'ff'rN S & EN G INEERIN G DOCK!:. T!tJG 1 c,ER'J!CE December 5, 1994 Mr. John C. Hoyle Office of the Secretary of the Commission U. S. Nuclear Regulatory Commission Washington, DC 20555 BR.4NCH

SUBJECT:

Advance Notice of Proposed Rulemaking "Steam Generator Tube Integrity for Operating Nuclear Power Plants," Federal Register 4 7817, September 19, 1994

Dear. Mr. Hoyle:

The Nuclear Energy Institute (NEI) 1 is submitting comments, on behalf of the nuclear industry, on the Advance Notice of Proposed Rulemaking (ANPR). These comments were developed by the NEI Steam Generator Issues Working Group with significant technical input from industry personnel involved in the EPRI Steam Generator Management Program (SGMP). We appreciate the opportunity to provide the enclosed comments because of the significance of steam generator integrity in terms of plant safety, performance and economics.

To briefly summarize the enclosure, we believe that rulemaking is the preferred regulatory mechanism for addressing steam generator tube integrity. We support the concept as proposed in the ANPR that the final rule be performance-based, resulting in a blend of risk-based and performance-based objectives. Further, the associated regulatory guidance, existing and new, can be revised or developed, to endorse generic industry guidance (e.g.,

the degradation specific management methodology developed by EPRI) as a generic framework for implementation. Detailed activities relating to specific forms of steam generator tube degradation and repair would not necessarily require NRC endorsement within such a performance-based approach. Nevertheless, the results of such activities evaluated to the stated objectives of a _performance-based rule would be the threshold for further NRC involvement with individual utility licensees. Additionally, we believe the 1 NET is the organization responsible for establishing unified nuclear industry policy on matters affecting the nuclear energy industry, including the regulatory aspects of generic operational and technical issues. NEl's members include all utilities licensed to operate commercial nuclear power plants in the United States, nuclear plant designers, major architect/engineering firms, fuel fabrication facilities, materials licensees, and other organizations and individuals involved in the nuclear energy industry. NEI is the successor organization to the Nucl

_ 1 1995..1 Management and Resources Council (NUMARC).

Acknowledged by card............,......... ~--

I 776 I STREET, NW SUITE 400 WASHINGTON, 0C 20006-3708 PHONE 202 739.8107 FAX 202. 785. 1898

. NUCLEAR R::GLtLo.TGfW COMMtSSION DOCKETi~,G & StfWiCE SECTION OFFICE OF lHE SECRETARY OF THE COMMISSION Document Statistics ostmark Date /...Ja.it\\,,t k l, v~

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Mr. John C. Hoyle December 5, 1994 Page 2 proposed rule and associated guidance should recognize the design features and performance history of new and replacement steam generators.

The industry, through the efforts of EPRI, has aggressively pursued the development of enhanced steam generator maintenance, inspection and repair techniques to improve overall performance. The result of these efforts, to date and in the future, is the development and implementation of a methodology for the identification of distinct defect mechanisms causing tube degradation, development of techniques to identify and characterize the extent of degradation, and application of effective repair criteria. This methodology is referred to as steam generator degradation specific management (SGDSM).

A lead plant group of utilities was formed in 1993 to achieve NRC acceptance of the SGDSM methodology with specific emphasis on repairing steam generator tubes based upon the specific mode of degradation and maintaining steam generator tube structural integrity during normal and accident conditions. A number of the documents were previously transmitted to the NRC in draft form for review as part of this lead plant effort.

We believe timely review by NRC of these documents is necessary so that they can be finalized and distributed to utilities. This review is important to the overall industry effort. Further, we believe that the successful development and implementation of the SGDSM methodology will ensure continued plant safety, maxirnire utility flexibility for repair and operation, and assure the adequacy and reliability of steam generator tube inspections.

If you or any members of the NRC staff have any questions about these comments, please do not hesitate to contact, Alex Marion, Clive Callaway or me.

TET/AM/clb Enclosure c:

Mr. William T. Russell, NRR

Enclosure Question 1:

What are the 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, fl.aw acceptance criteria, and steam generator tube repair methods?

We agree that the rule should allow for a performance-based methodology for determining steam generator operability requirements. Such a methodology should consider and quantify overall safety factors of risk, radiological assessments, and conditional probability of tube rupture. This would allow a quantification of the cumulative effects of all pertinent safety features on plant safety. The result would permit flexibility in plant operation through managed inspection, planned maintenance options, operational monitoring, and prepared mitigation plans. The rule should establish performance objectives relative to accident frequencies challenging core integrity, radiological consequences and conditional tube failure probability for the degradation distribution. Specific performance-based criteria used to measure performance to these objectives should not be included within the rule itself.

Generic industry documents endorsed in the Regulatory Guide are the appropriate mechanisms to establish the performance criteria and identify acceptable industry methods for meeting the performance goals. The industry guidance identifying the performance criteria and methods, acceptable to the NRC, can build upon the EPRI Steam Generator Degradation Specific Management (SGDSM) documentation.

Two possible performance measures for steam generator operation and maintenance are:

1.

Forced outage frequency due to primary-to-secondary leakage, and

2.

Maintaining acceptable tube integrity at end-of-cycle (EOC).

Appropriate performance based objectives for the inspection scope and frequency, nondestructive examination (NDE) equipment capabilities, NDE data analyst capabilities, performance demonstration and qualification of NDE systems are contained in the Electric Power Research Institute (EPRI) SGDSM documentation. This includes:

Sampling inspection plan based on statistically limiting the number of potentially undetected indications, and 1

Enclosure Sampling inspection plan that identifies an acceptable degradation distribution for tubes allowed to remain in service.

The sampling plan will also credit the performance history and new steam generator design features.

Elements of the sampling plan that can achieve these criteria may include the following:

NDE analyst assessment of tubing indications; Demonstration of degraded tube performance using industry-wide pulled tube results; Tube structural integrity and leakage correlations using the appropriate NDE measurement parameter; and

• Uncertainties in the predicted leak rate that account for crack growth and NDE measurement uncertainty or error.

A possible performance measure for NDE effectiveness could be monitoring PWR forced outage frequency attributed to steam generator primary-to-secondary tube leakage limits.

Appropriate performance-based criteria for flaw acceptance could be the projected EOC conditional probability of tube rupture and accident leak rate. Specific performance-based criteria for tube integrity could include the ISI results to demonstrate that leak rate and burst probability obtained at EOC do not exceed allowable limits.

Steam generator water chemistry requirements should not be considered within the rule or Regulatory Guide. Due to the variability of the effect of water chemistry on steam generator tubing and plant specific nature of water sources and secondary system materials, chemistry guidance should be addressed outside the rule on a plant specific basis.

Steam generator tube repair methods should not be identified within the rule or Regulatory Guide. Repair methods are evolving as new technologies are developed. The overall effects of tube repair on steam generator performance will be captured within the overall performance criteria of the rule.

In summary, the above provides a performance-based approach with identification of clear, attainable objectives in the rule. Performance criteria within the associated guidance 2

Enclosure documents provide the flexibility within the methodology to measure performance to demonstrate utilities meet the stated objectives.

Question 2:

What are the appropriate performance based criteria that should be incorporated into the proposed rule to define adequate tube integrity (vis-a-vis) 10CFR50 Appendix A GDC 14?

GDC 14 - Reactor Coolant Pressure Boundary - is acceptable as presently written.

Suggested performance-based criteria that can be used to establish steam generator tube integrity are as follows:

1.

Degradation distributions in steam generator tubes can remain in service, with appropriate consideration of inservice degradation growth rate, during the time interval in which the following criteria are satisfied for the degraded distributions:

(a)

The radiation dose will not exceed 10 CFR 100 limits during postulated faulted loads.

(b)

The frequency of a large radiation release resulting from core melt must be acceptably low when operating under SGDSM. This is generally described as a "safety goal." This frequency is based on analysis of risk. Acceptable risk has been defined by the NRC and should not be specified in the rule. The overall methodology for risk assessment should be contained in the industry's guidelines, (e.g., the higher level SGDSM documentation) rather than the rule. The risk associated with a consequence measure (e.g.,

probability of exceeding allowable dose) can generally be expressed as the product of the following terms: the frequency of accident sequence x the conditional probability of a containment release mode given an accident x the mean magnitude of the consequence given a fission product source term for the release mode and sequence, where the fission product source term is unique to the accident sequence and containment release mode.

(c)

The conditional prob9:bilitr of ~team _generato~ tube 1;up~e (SGTR) must be acceptably low. This value should be specified in the industry's guidelines (e.g., the SGDSM documents) rather than the rule.

2.

A degradation-specific repair criteria can be established for each degradation mechanism. A generalized degradation repair criteria (e.g., present technical 3

Enclosure specification), may be used for plants that do not have a history of significant inservice degradation or that choose to use the current depth based repair criteria or for mechanisms where degradation-specific repair criteria have not yet been developed.

Question 3: What information should be part of the steam generator proposed rule, and what information should be addressed in a Regulatory Guide?

Generic industry guidance (e.g., the SGDSM documents) endorsed in a Regulatory Guide is the appropriate mechanism to establish the performance criteria and identify acceptable industry methods for meeting that criteria. The generic industry guidance identifying the performance criteria and methods, acceptable to the NRC, can build upon the EPRI Steam Generator Degradation Specific Management (SGDSM) documentation. This documentation includes the upper tier SGDSM requirements document, inspection guidelines, a methodology document for relating leakage to acceptable radiological consequences, leakage monitoring guidelines and degradation specific management guidance.

EPRI developed documents can provide the methodology for using risk information related to the following items:

An allowable median conditional probability of tube rupture; Generic median values and specification of methods acceptable to the NRC for computing site specific values of event initiation frequencies; Generic median values and specification of methods acceptable to the NRC for computing site specific values of conditional probability of failure to mitigate the event relative to core melt; Inspection methods that can reliably detect the specified degradation mechanism; NDE measurement parameter(s) that can be used to assess the structural and leakage integrity of degraded tubes; Determination of the NDE measurement parameter error; An experimental database to relate the rupture strength of degraded tubes with the NDE measurement parameter(s);

Criteria that will ensure adequate margins against tube rupture; Conditional probability of tube rupture; 4

Enclosure An experimental database to relate the leak rate from degraded tubes with the NDE measurement parameter; Criteria that ensure leakage during postulated faulted loads will result in off-site doses that are less than 10CFRlOO limits; A degradation growth rate database; An on-going, industry-wide, degradation specific management database and related support for developing, implementing, and maintaining degradation specific management; and Degradation specific repair criteria guidance.

Question 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?

The rule should not address this subject since utility evaluation of operating experience and data applicable to steam generator integrity is addressed by 10CFR50.65, "Requirements for Monitoring the Effectiveness of Maintenance at Nuclear Power Plants."

Steam generators are a risk significant component and the effect of steam generator maintenance, specifically inspection and repair, will be evaluated based upon plant specific and industry-wide operating experience.

Question 5:

How should the proposed rule address new or replacement steam generators versus degraded steam generators?

The Rule should apply equally to new, replacement or degraded steam generators. AB described in the response to question 3, the generic industry guidance can include considerations of items such as inspection sampling using statistically based limits on undetected indications, steam generator specific design features, materials and historical performance. The industry inspection guidelines can describe an acceptable methodology that can be effectively,applied to all steam generators. _.

5

Enclosure Question 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?

The Regulatory Guide should not be prescriptive. Rather, the Regulatory Guide should endorse industry guidance that identifies specific performance criteria and a generic, qualitative methodology acceptable to the NRC to meet these criteria. The Regulatory Guide can be treated as a higher order document that does not incorporate prescriptive methods. The Regulatory Guide is the appropriate mechanism to endorse industry guidance (e.g., the EPRI Steam Generator Degradation Specific Management (SGDSM) documentation) as an acceptable method to meet the rule. This documentation includes the upper tier SGDSM requirements document, inspection guidelines, a methodology document for relating leakage to acceptable radiological consequences, leakage monitoring guidelines and degradation specific reports Question 7:

Should the proposed rule require licensees to submit their programs to NRC for review and approval before implementation?

The proposed rule should not require licensees to submit their programs to the NRC for review and approval before implementation.

A performance-based rule as suggested in the ANPR should identify performance objectives relative to core integrity, conditional probability of tube rupture and radiological consequences. By endorsing the generic industry guidance (e.g., EPRI SGDSM documents), the Regulatory Guide will identify acceptable performance criteria by which the effectiveness of utility licensee programs will be evaluated according to the objectives as described by the rule.

Specific plant SGDSM activities could be implemented without prior NRC approval but would be available for NRC review during future inspections that may be initiated when plant performance to the objectives. of the rule are not satisfied 6

Enclosure Question 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?

A significant element to the concept of defense-in-depth is the effective monitoring of steam generator primary-to-secondary tube leakage. Leak rate monitoring programs are important to minimizing the frequency of steam generator tube ruptures. Requirements for acceptable monitoring methods and tighter margins for allowed leak rates provide defense-in-depth to ensure the design basis dose rates and accident management criteria are maintained, and that tube rupture frequency remains at an acceptably low level.

Key attributes of an effective leakage monitoring program are:

1.

Multiple on-line radiation monitors;

2.

Real time trending of radiation monitoring instruments in the control room. This trending should provide both absolute and rate of change trends;

3.

Primary-to-secondary leak rate monitoring procedures which enable the operators to commence immediate unit shutdown based on confirmation that leakage limits may have been exceeded. The procedures and additional monitors, if necessary, should be sufficient to respond to rapidly propagating steam generator tube defects; and

4.

Action levels should include both absolute level of leak rate and rate of change of leak rate.

The industry through EPRI is developing primary to secondary side leakage guidelines.

These guidelines can be endorsed by the Regulatory Guide associated with the rule.

Question 9:

What changes should be made in NUREG-0800 radiological calculation guidance used to address the safety significance of steam generator tube leakage and rupture?

The radiological calculation guidance in NUREG-0800 should be revised by the NRC to permit use of a probabilistic radiological dose analysis methodology. An appropriate methodology has been developed by EPRI and is offered as a basis for this revision.

NUREG-0800 presents an overly conservative methodology for assessing the dose consequences associated with design basis accidents. The dose assessment method described in the EPRI methodology incorporates the radiological consequence assessment 7

Enclosure by recasting the dose limits into an allowed steam generator primary to secondary leak rate. Uncertainties in the data and information are used to quantify the radiological consequences and establish an associated confidence limit on the allowable limit. The methodology considers limiting criteria associated with both the plant's boundary and control room dose. By comparing the allowed leak rate with the predicted rate, acceptable safety margins for design basis accident events can be quantified. Additionally, the data and information used in the noted methodology were taken from NRC documentation sources and their references.

The above methodology was developed for generic application. It is recommended that guidelines for application in specific plant operations be developed by industry. These guidelines would establish screening criteria for assessing additional safety margin that may be established by a more detailed evaluation of plant specific features that limit boundary and/or control room dose. Credit for these plant features should be allowed under this new methodology of dose assessment for design basis accidents.

Question 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)?

The rule should establish the performance objectives relative to core integrity, conditional probability of tube rupture and radiological consequences. The associated performance criteria to meet these performance objectives would be identified in the generic industry guidance that addresses plant specific operating regions relating to tube rupture probability and allowable leak rates. For example, when the frequency of a beyond design basis event is acceptably low, no additional analysis incorporating beyond design basis considerations are required for SGDSM implementation. Guidance relative to beyond design basis events considering steam generator tube integrity issues should be addressed in the industry's guidance and not in the rule.

Question 11: How should tube failure prevention and mitigation measures be balanced in the proposed rule?

Tube failure prevention and mitigation measures should not be addressed in the proposed rule. A performance-based rule should allow consideration of overall safety, risk, and 8

Enclosure radiological consequence factors when determining various mitigation and prevention activities. The rule should identify the overall performance objectives. Acceptable methodologies and other considerations for implementing various mitigation and prevention measures can be in the plant-specific implementation program. This will allow the licensee to select the most prudent course of action based on plant specific situations and steam generator conditions. Operator training requirements should also not be addressed within the rule.

Question 12: What interim. measures are appropriate to allow continued operation of a unit in which new degradation modes are discovered?

Current procedures are sufficient as an interim measure in considering the continued operation of steam generators where new modes of degradation of tubing are discovered.

Such measures include:

Use of NDE to bound affected regions;

• Use of NDE to characterize beginning of cycle degradation; Consideration of degradation growth rates;

• Maintaining of tube integrity requirements at end of cycle, (EOC);

Consideration of operational experience;

• A balance of deterministic and probabilistic analyses; Defense-in-depth; Consideration of remedial measures; and Report results of new degradation findings.

Industry will continue to evaluate new degradation modes experienced at operating nuclear power plants and review recommended repair techniques with the NRC.

9

Enclosure Question 13: Is the proposed rufomaking 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 cause of action.

A performance based rule is the preferred regulatory mechanism for addressing steam generator maintenance and surveillance issues. In order to adequately address the emerging issues surrounding both new and degraded steam generators, we agree that the rule should be performance-based, using a degradation-specific management approach, where applicable.

The associated Regulatory Guide should endorse the relevant industry guidance as a means acceptable to the NRC for implementation of the rule. These documents would be revised, where necessary, to incorporate appropriate performance-based criteria and risk insights.

Question 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 (1-131 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.

1.

The regulatory guia.e should ititlicate; through the 'use 'of industry documents, that key safety assumptions and plant para.meters remain within anticipated limits on a generic or site specific basis when degradation specific repair criteria are applied. An example would be to verify that the predicted leakage from degraded tubes is less than make-up capacity.

10

Enclosure

2.

The regulatory guide should indicate, through the use of industry documents, that an appropriate NDE measurement parameter be defined and used for each degradation specific repair criteria. The effectiveness of these parameters for each application will be made available to the NRC as part of the review of each document provided for individual degradation specific repair criteria.

3.

As part of the SGDSM program, industry has submitted documentation for NRC review to support values of the accident initiated 1181 source term based on the available data sources from plant operating experience. This document should be referenced by the Regulatory Guide or by other NRC documents addressing this subject.

11

Copy !o StCY-o~;g:r,::I sent to the DOCKET NUMBER Pl o ooy:E;io PROPOSED RULE.=.

• .::_5 ___

111!

Office of the Federal Register for publicallon ------

(sq FR '1 13'17)

• 94 SEP 14 P 2 : 7. 8 AGENCY:

ACTION:

NUCLEAR REGULATORY COMMISSION 10 CFR Part 50 RIN 3150-AF04 Steam Generator Tube Integrity for Operating Nuclear Power Plants Nuclear Regulatory Commission.

Advance notice of proposed rulemaking.

[7590-01-P]

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.

DATE:

The comment period expires (75 dt::--lr!i.t of publication),.

Comments received after this date will be considered if it is practical to do so, but the Commission is able to assure consideration received on or before this date.

only for comments

('Jr* q 1,1 \\tt'"I

2 ADDRESSES:

Mail conunents to: The Secretary of the Convnission, U.S. Nuclear Regulatory Comnission, Washington, DC 20555, Attention: Docketing and Services Branch. Deliver corrments to:

11555 Rockville Pike, Rockville, Maryland, between 7:45 am and 4:15 pm on Federal workdays.

Examine copies of conunents 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-9ate 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.

3 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 acconunodate 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 applicati~n 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

4 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)

(ii)

(iii)

(iv}

(v)

(vi)

(vii}

Preservice and Inservice Inspection Program Water Chemistry Program Tube Integrity Repair Criteria Repair Methods Nondestructive Examination Considerations Nonnal Operating Primary-to-Secondary Leakage Monitoring/Limits (2) Accident Mitigation (i}

Accident Condition Primary-to-Secondary Leakage Mpnitoring (ii) Procedures (iii) Operator Training

5 (3) Radiological Consequences (d) Severe Accident Cons1derat1ons (e) Implementation Specific Considerations Comments, advice and reconmendations on a proposed rule reflecting the aforementioned features and any other pertinent points are invited from all interested persons.

Particularly, conwnents.and supporting reasons are requested on the following questions:

1.

What are appropriate perfonnance based criteria that should be included in the steam generator proposed rule to address steam generator inspection scope and frequency, nondestructive examination (NOE) equipment capabilities, NOE data analyst capabilities, performance demonstration and qualification of NOE 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

6 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 ste~

generator tube leakage and rupture?

10.

What beyond design basis considerations related to steam generator

7 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 mo~e direct measures such as crack depth or crack length), and 3) calculation of radiologically significant isotope concentratio~s in released materials (1-131 equivalent) following postulated events such as the main steam line break with

8 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 co1T111ent 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.

The authority citation for this document is: 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 Pub. L.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, Pub. L.91-190, 83

9 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, Pub. L.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 Pub. L.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 Falso issued under sec. 187, 68 Stat. 955 (42 u.s.c. 2237).

~

/-I-Dated at Rockville, Maryland, this____,,_~--

day of,>d-v/.

1994.

For the Nuclear Regulatory Connnission.

ctor for Operations,