95-13514. Proposed Generic Letter; Relocation of the Pressure Temperature Limit Curves and Low Temperature Overpressure Protection System Limits  

  • [Federal Register Volume 60, Number 106 (Friday, June 2, 1995)]
    [Notices]
    [Pages 28805-28808]
    From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
    [FR Doc No: 95-13514]
    
    
    
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    NUCLEAR REGULATORY COMMISSION
    
    
    Proposed Generic Letter; Relocation of the Pressure Temperature 
    Limit Curves and Low Temperature Overpressure Protection System Limits
    
    AGENCY: Nuclear Regulatory Commission.
    
    ACTION: Notice of opportunity for public comment.
    
    -----------------------------------------------------------------------
    
    SUMMARY: The Nuclear Regulatory Commission (NRC) is proposing to issue 
    a generic letter. This draft generic letter would allow licensees to 
    voluntarily relocate the pressure temperature limit curves and low 
    temperature overpressure protection system limits from the technical 
    specifications to a licensee-controlled document. The NRC is seeking 
    comment from interested parties regarding both the technical and 
    regulatory aspects of the proposed generic letter presented under the 
    Supplementary Information heading. This proposed generic letter and 
    supporting documentation were sent to the Committee to Review Generic 
    Requirements (CRGR). CRGR will review the proposed generic letter after 
    resolution and incorporation of public comments. Relevant information, 
    including model technical specifications and a model safety evaluation, 
    that was sent to the CRGR is available in the Public Document Rooms 
    under accession number 9505220128. The NRC will consider comments 
    received from interested parties in the final evaluation of the 
    proposed generic letter. The NRC's final evaluation will include a 
    review of the technical position and, when appropriate, an analysis of 
    the value/impact on licensees. Should this generic letter be issued by 
    the NRC, it will become available for public inspection in the Public 
    Document Rooms.
    
    DATES: Comment period expires July 3, 1995. Comments submitted after 
    this date will be considered if it is practical to do so, but assurance 
    of consideration cannot be given except for comments received on or 
    before this date.
    
    ADDRESSES: Submit written comments to Chief, Rules Review and 
    Directives Branch, U.S. Nuclear Regulatory Commission, Washington, DC 
    20555. Written comments may also be delivered to 11545 Rockville Pike, 
    Rockville, Maryland, from 7:30 am to 4:15 pm, Federal workdays. Copies 
    of written comments received may be examined at the NRC Public Document 
    Room, 2120 L Street NW. (Lower Level), Washington, DC.
    
    FOR FURTHER INFORMATION CONTACT: Maggalean W. Weston, Technical 
    Specifications Branch, Division of Project Support, Office of Nuclear 
    Reactor Regulation, U.S. Nuclear Regulatory Commission, Washington, DC 
    20555-001, Telephone (301) 415-3151.
    
    SUPPLEMENTARY INFORMATION:
    
    NRC Generic Letter 95-XX: Relocation of the Pressure Temperature Limit 
    Curves and Low Temperature Overpressure Protection System Limits
    
    Addressees
    
        All holders of operating licenses or construction permits for 
    nuclear power reactors.
    
    Purpose
    
        The U.S. Nuclear Regulatory Commission (NRC) is issuing this 
    generic letter to advise licensees that they may request a license 
    amendment to relocate the pressure temperature (P/T) limit curves and 
    low temperature overpressure protection (LTOP) system limits from the 
    technical specifications (TS) to a pressure temperature limits report 
    (PTLR) or a similar document.
    
    Description of Circumstances
    
        During the development of the improved standard technical 
    specifications (STS), a change was proposed to relocate the P/T curves 
    and LTOP setpoint curves and values currently contained in the TS to a 
    licensee-controlled document. As part of the improvements to the STS, 
    the NRC staff agreed with the industry that the curves and setpoints 
    may be relocated outside the TS where these limits could be maintained 
    more efficiently and at a lower cost to the licensee, provided the 
    parameters for constructing the curves and setpoints are derived using 
    a methodology approved by the NRC.
    
    Discussion
    
        Technical specifications include limiting conditions for operation 
    (LCOs) that establish P/T and LTOP system limits for the reactor 
    coolant system. The limits are defined by figures and values that 
    provide an acceptable range of operating temperatures and pressures for 
    heatup, cooldown, low temperature overpressure, criticality, and 
    inservice leak and hydrostatic testing conditions. These parameters are 
    generally valid for a specified number of effective full-power years.
        License amendments are generally required at the end of the 
    effective period for P/T limit curves or when surveillance specimens 
    are withdrawn [[Page 28806]] and tested. Also, each time the curves are 
    revised, the LTOP system must be reevaluated to ensure that its 
    functional requirements can still be met using relief valves or other 
    methods. Processing amendment requests for changes to TS that are 
    developed using an accepted methodology is an unnecessary burden on 
    licensee and NRC resources. An alternative approach for the control of 
    these limits was proposed during the development of the improved STS. 
    This approach, like that used for the core operating limits, would 
    relocate the P/T curves and the LTOP setpoint curves or values to a 
    PTLR or a similar document and reference that document in the affected 
    LCOs and bases.
        The methodology for determining P/T and LTOP system limit 
    parameters must comply with the specific requirements of Appendices G 
    and H to Part 50 of Title 10 of the Code of Federal Regulations (10 
    CFR), be documented in an NRC-approved topical report or in a plant-
    specific submittal, and be incorporated by reference into the TS. As 
    such, subsequent changes in the methodology must be approved by a 
    license amendment.
    
    Requested Information
    
        Licensees and applicants who voluntarily choose to adopt this line 
    item improvement are encouraged to propose changes that are consistent 
    with the attached guidance. The guidance requires that the licensee be 
    able to reference a methodology for developing the curves and setpoints 
    that has been approved by the NRC, develop a PTLR or a similar document 
    that contains the figures, values, parameters, and explanations derived 
    from the methodology, and make appropriate changes to the applicable 
    sections of the TS. The NRC project manager for the facility will 
    review the amendment requests that conform to the guidance in this 
    generic letter and coordinate the appropriate staff review of the 
    methodology proposed for calculating the P/T limit curves and the LTOP 
    system limits. Amendment requests that do not conform to the guidance 
    in this generic letter will require additional review time.
    
    Required Response
    
        Licensees and applicants who voluntarily choose to adopt this line 
    item improvement should submit a response to the requested information 
    described above.
    
    Backfit Discussion
    
        Any action by licensees to propose TS changes in accordance with 
    the guidance of this generic letter is voluntary and, therefore, not a 
    backfit analysis.
    
    Guidance for a Proposed License Amendment To Relocate the Pressure 
    Temperature Limit Curves and Low Temperature Overpressure Protection 
    System Limits
    
    Introduction
    
        This generic letter provides guidance for preparing a license 
    amendment request to modify the technical specifications (TS) to 
    relocate the pressure temperature (P/T) limit curves and low 
    temperature overpressure protection (LTOP) system limits currently 
    contained in the TS to a pressure temperature limits report (PTLR) or a 
    similar document. This alternative was based on a change included in 
    the improved standard technical specifications (STS) to remove the P/T 
    limit curves and LTOP system limits from the TS and relocate them to a 
    PTLR or a similar document to reduce the number of amendment requests 
    associated with changes to the P/T limit curves and LTOP system limits. 
    Since an amendment request must be submitted whenever a change is made 
    to the TS, the relocation of the P/T curves and LTOP system limits will 
    result in a resource savings for the licensees and the NRC by 
    eliminating unnecessary license amendment requests for changes to the 
    P/T limit curves and LTOP system limits in TS when surveillance 
    specimens are withdrawn and tested and additional vessel toughness data 
    become available. To relocate the P/T curves and LTOP system limits 
    from the TS, the licensee must be able to reference a methodology 
    approved by the NRC for deriving the parameters used for constructing 
    the curves and setpoints, develop a PTLR or a similar document, and 
    make appropriate changes to the applicable sections of the TS.
        In evaluating the relocation, the NRC staff concluded that, while 
    it is essential to safety to operate the plant within the bounds of P/T 
    limits and to satisfy the regulations that ensure the integrity of the 
    reactor coolant pressure boundary (RCPB), the periodic adjustment of 
    those limits to account for time-dependent parametric changes could be 
    calculated in accordance with a methodology approved by the NRC. 
    Criterion 2 of the Commission's final policy on TS improvements, which 
    was published in the Federal Register (58 FR 39132) on July 22, 1993, 
    requires that the TS include operating restrictions (pressure/
    temperature limits) needed to preclude unanalyzed accidents and 
    transients. However, once the methodology is approved, the licensee may 
    modify the figures, values, and parameters without the need for a 
    license amendment and without affecting nuclear safety, provided these 
    changes are determined using the approved methodology and are 
    consistent with all applicable limits of the plant design assumptions 
    as stated in the FSAR. Additionally, the licensee must submit to the 
    NRC a formal PTLR or a similar document containing the figures, values, 
    and parameters derived from the application of the methodology approved 
    by the NRC. This reporting requirement augments a reporting requirement 
    that is already in effect. Section III of Appendix H currently requires 
    a summary technical report of data relating to capsule withdrawal and 
    specimen test results. Application of these results will also be 
    included in the PTLR. This report will allow the NRC staff to continue 
    monitoring the status of the structural integrity of the reactor vessel 
    even though prior NRC approval of the changes to these limits would not 
    be required if they do not involve an unreviewed safety question.
        A new provision was also added to the administrative controls 
    section of the TS indicating that the figures, values, and parameters 
    for inclusion in the PTLR will be verified after each reactor vessel 
    fluence period or when surveillance specimens are withdrawn and tested 
    and a report submitted to the NRC. Hence, the staff can confirm proper 
    application of the methodology approved by the NRC. Further, the PTLR 
    will be referenced in the TS so that the same degree of control on 
    plant operation will be maintained. As a result, this alternative 
    provides the same assurance of compliance with design specifications as 
    before, yet removes the unnecessary burden on both plant and NRC staff 
    of processing amendment requests.
    
    Discussion
    
        Technical specifications include limiting conditions for operation 
    (LCOs) that establish P/T limits for the RCS. This system is designed 
    to withstand the effects of cyclic loads resulting from system 
    temperature and pressure changes. These cyclic loads are introduced by 
    normal load transients, reactor trips, startup and shutdown operations, 
    and hydrostatic and leak rate tests. During startup and shutdown, the 
    rates of temperature and pressure changes are limited so that the 
    maximum specified heatup and cooldown rates are consistent with the 
    design assumptions and satisfy operating limits that provide a wide 
    [[Page 28807]] margin of safety to brittle failure of the reactor 
    vessel. The P/T limits are periodically modified as the reactor vessel 
    material toughness decreases as a result of material embrittlement 
    caused by neutron irradiation. The periodic modifications are necessary 
    when the applicable effective full-power years (EFPYs) for the P/T 
    limits contained in the TS are about to expire or the reactor vessel 
    material surveillance data indicate an increase in the nil-ductility 
    transition reference temperature (RTNDT).
        As required by Appendix G to Part 50 of Title 10 of the Code of 
    Federal Regulations (10 CFR), operating P/T limits are calculated and 
    adhered to by plant operations personnel to ensure that fracture 
    toughness requirements for Part 50, specimens of reactor vessel 
    material are installed near the inside reactor vessel wall and are 
    withdrawn on a schedule to provide data on the effects of radiation 
    fluence and the thermal environment on the vessel material. These data 
    are used to adjust the P/T limits, as necessary, to compensate for the 
    shift in material transition temperature as indicated by tests on the 
    withdrawn specimens. The withdrawal and analysis of the specimens and 
    resulting revision of the P/T limit curves make up the requirements 
    necessary to compensate for the shift in material transition 
    temperature. This ensures that the reactor vessel is operated at high 
    enough temperatures to preclude brittle fracture of the vessel 
    material.
        The LTOP system controls RCS pressure at low temperatures so that 
    the integrity of the RCPB is not compromised by violating the P/T 
    limits of Appendix G to 10 CFR part 50. The LTOP system provides 
    overpressure protection by limiting coolant input capability and having 
    adequate pressure relief capacity. Each time the P/T limit curves are 
    revised, the LTOP system must be reevaluated to ensure that its 
    functional requirements can still be met. The LTOP system for pressure 
    relief typically consists of two power-operated relief valves (PORVs), 
    two residual heat removal (RHR) suction relief valves, or a combination 
    of both. Some plants have only one PORV. The LTOP system limits consist 
    of PORV and RHR setpoints. The RHR suction relief valves do not have 
    variable pressure and temperature lift setpoints like the PORVs and, 
    therefore, are still addressed in the TS. As designed for the LTOP 
    system, each PORV is signaled to open if the RCS pressure approaches a 
    limit determined by the LTOP system actuation logic. This logic 
    monitors both RCS temperature and RCS pressure to determine when a 
    condition not acceptable in the PTLR is approached. The PORV setpoints 
    should be included in the PTLR and updated when the revised P/T limits 
    conflict with the LTOP system limits. LTOP requirements do not apply to 
    boiling water reactors.
    
    Requirements for Relocating the Curves and Setpoints
    
        Relocation of the curves and setpoints to a licensee-controlled 
    document requires three separate licensee actions. The licensee must 
    (1) have a methodology approved by the NRC to reference in its TS; (2) 
    develop a report such as a PTLR or a similar document to contain the 
    figures, values, parameters, and any explanation necessary; and (3) 
    modify the applicable sections of the TS accordingly.
    
    bulletMethodology and PTLR
    
        The first two of the three requirements for relocating the P/T 
    curves and LTOP system limits are an NRC-approved methodology and the 
    associated reporting requirements in the PTLR. The methodology will 
    consist of only those methods used for calculation, not the 
    calculations themselves. The PTLR will consist of the explanations, 
    figures, values, and parameters derived from the calculations. Since 
    the PTLR will be provided to the NRC upon issuance after each fluence 
    period and after approval of the methodology, a preliminary or draft 
    PTLR should be provided when the methodology is submitted so that 
    questions regarding the content and format can be addressed prior to 
    its formal completion.
        The following table shows the relationship between the provisions 
    specified in the STS for the approved methodology and the requirements 
    to be included in the methodology and the PTLR. The provisions for the 
    methodology are those shown in the administrative controls section of 
    the STS.
    
                      Requirements for Methodology and PTLR                 
    ------------------------------------------------------------------------
         Provisions for                                                     
        methodology from     Minimum requirements to   Minimum requirements 
    administrative controls       be included in      to be included in PTLR
         section in sts            methodology                              
    ------------------------------------------------------------------------
    1. The methodology       Describe transport       Provide the values of 
     shall describe how the   calculation methods      neutron fluences that
     neutron fluence is       including computer       are used in the      
     calculated (reference    codes and formulas       adjusted reference   
     new Regulatory Guide     used to calculate        temperature (ART)    
     when issued).            neutron fluence.         calculation.         
                              Provide references.                           
    2. The Reactor Vessel    Briefly describe the     Provide the           
     Material Surveillance    surveillance program.    surveillance capsule 
     Program shall comply     Licensee transmittal     withdrawal schedule, 
     with Appendix H to 10    letter should identify   or reference by title
     CFR Part 50. The         by title and number      and number the       
     reactor vessel           report containing the    documents where the  
     material irradiation     Reactor Vessel           schedule is located. 
     surveillance specimen    Surveillance Program    Reference the         
     removal schedule shall   and surveillance         surveillance capsule 
     be provided, along       capsule reports.         reports by title and 
     with how the specimen    Topical/generic report   number if ARTs are   
     examinations shall be    contains placeholder     calculated using     
     used to update the       only. Reference          surveillance data.   
     PTLR curves.             Appendix H to 10 CFR                          
                              Part 50.                                      
    3. Low temperature       Describe how the LTOP    Provide setpoint      
     overpressure             system limits are        curves or setpoint   
     protection (LTOP)        calculated applying      values.              
     system lift setting      system/thermal                                
     limits developed using   hydraulics and                                
     NRC-approved             fracture mechanics.                           
     methodologies may be     Reference SRP Section                         
     included in the PTLR.    5.2.2; Code Case N-                           
                              514; ASME Code,                               
                              Appendix G, Section XI                        
                              as applied in                                 
                              accordance with 10 CFR                        
                              50.55.                                        
    4. The adjusted          Describe the method for  Identify both the     
     reference temperature    calculating the ART      limiting ART values  
     (ART) for each reactor   using Regulatory Guide   and limiting         
     beltline material        1.99, Revision 2.        materials at the 1/4T
     shall be calculated,                              and 3/4T locations   
     accounting for                                    (T=vessel beltline   
     irradiation                                       thickness).          
     embrittlement, in                                PWRs--identify RTPTS  
     accordance with                                   value in accordance  
     Regulatory Guide 1.99,                            with 10 CFR 50.61.   
     Revision 2.                                                            
    [[Page 28808]]
                                                                            
    5. The limiting ART      Describe the             Provide the P/T curves
     shall be incorporated    application of           for heatup, cooldown,
     into the calculation     fracture mechanics in    criticality, and     
     of the pressure and      constructing P/T         hydrostatic and leak 
     temperature limit        curves based on ASME     tests.               
     curves in accordance     Code, Appendix G,                             
     with NUREG-0800, SRP     Section XI, and SRP                           
     Section 5.3.2,           Section 5.3.2.                                
     Pressure-Temperature                                                   
     Limits.                                                                
    6. The minimum           Describe how the         Identify minimum      
     temperature              minimum temperature      temperatures on the P/
     requirements of          requirements in          T curves such as     
     Appendix G to 10 CFR     Appendix G to 10 CFR     minimum boltup       
     Part 50 shall be         Part 50 are applied to   temperature and      
     incorporated into the    P/T curves.              hydrotest            
     pressure and                                      temperature.         
     temperature limit                                                      
     curves.                                                                
    7. Licensees who have    Describe how the data    Provide supplemental  
     removed two or more      from multiple            data and calculations
     capsules should          surveillance capsules    of the chemistry     
     compare for each         are used in the ART      factor in the PTLR if
     surveillance material    calculation.             the surveillance data
     the measured increase   Describe procedure if     are used in the ART  
     in reference             measured value exceeds   calculation.         
     temperature (RTNDT) to   predicted value.        Evaluate the          
     the predicted increase  WHEN OTHER PLANT DATA     surveillance data to 
     in RTNDT; where the      ARE USED.                determine if they    
     predicted increase in   1. Identify the           meet the credibility 
     RTNDT is based on the    source(s) of data when   criteria in          
     mean shift in RTNDT      other plant data are     Regulatory Guide     
     plus the two standard    used.                    1.99, Revision 2.    
     deviation value         2.a Identify by title     Provide the results. 
     (2)    and number the safety                         
     specified in             evaluation report that                        
     Regulatory Guide 1.99,   approved the use of                           
     Revision 2. If the       data for the plant.                           
     measured value exceeds   Justify applicability.                        
     the predicted value     OR                                             
     (increase in RTNDT +    2.b Compare licensee                           
     2),    data with other plant                         
     the licensee should      data for both the                             
     provide a supplement     radiation environments                        
     to the PTLR to           (e.g., neutron                                
     demonstrate how the      spectrum, irradiation                         
     results affect the       temperature) and the                          
     approved methodology.    surveillance test                             
                              results.                                      
    ------------------------------------------------------------------------
    
    Technical Specifications
        The following changes must be made to the plant TS to complete the 
    three requirements for relocating the curves and setpoints to an 
    alternative document.
        Three separate actions are necessary to modify the plant TS: (1) 
    ``Definitions''--the addition of the definition of a named formal 
    report (PTLR or a similar document) that would contain the 
    explanations, figures, values, and parameters derived in accordance 
    with an NRC-approved methodology and consistent with all of the design 
    assumptions and stress limits for cyclic operation; (2) LCOs--the 
    addition of references to the PTLR noting that the P/T limits shall be 
    maintained within the limits specified in the PTLR; and (3) 
    ``Administrative Controls''--the addition of a reporting requirement to 
    submit to the NRC the PTLR, when it is issued, for each reactor vessel 
    fluence period.
    1. Definitions
        Section 1.0, ``Definitions,'' should contain the following 
    language:
    
    Pressure Temperature Limits Report (PTLR)
    
        The PTLR is the unit-specific document that provides the reactor 
    vessel P/T limits and setpoints, including heatup and cooldown rates, 
    for the current reactor vessel fluence period. These P/T limits shall 
    be determined for each fluence period in accordance with Specification 
    5.X.X.X. Plant operation within these operating limits is addressed in 
    LCO 3.X.X, ``RCS Pressure and Temperature (P/T) Limits,'' and LCO 
    3.X.X, ``Low Temperature Overpressure Protection (LTOP) System.''
    2. Limiting Conditions for Operation (LCOs) and Bases
        LCO 3.X.X, ``RCS Pressure and Temperature (P/T) Limits,'' and LCO 
    3.X.X, ``Low Temperature Overpressure Protection (LTOP) System,'' must 
    reference the PTLR as the document where the limits and curves can be 
    found as demonstrated in the attached model TS. The bases for these 
    LCOs should be modified accordingly.
    3. Administrative Controls
        Section 5.X, ``Administrative Controls,'' Subsection 5.X.X, 
    ``Reporting Requirements,'' must contain the following information:
    Section 5.X.X.X  Reactor Coolant System (RCS) PRESSURE AND TEMPERATURE 
    LIMITS REPORT (PTLR)
        a. RCS pressure and temperature limits for heatup, cooldown, LTOP, 
    criticality, and hydrostatic testing as well as heatup and cooldown 
    rates shall be established and documented in the PTLR for the 
    following: [The individual specifications that address RCS pressure and 
    temperature limits must be referenced here.]
        b. The analytical methods used to determine the RCS pressure and 
    temperature limits shall be those previously reviewed and approved by 
    the NRC, specifically those described in the following document(s): 
    [Identify the NRC staff approval document(s) by date.]
        c. The PTLR shall be provided to the NRC upon issuance for each 
    reactor vessel fluence period and for any revision or supplement 
    thereto.
    * * * * *
        Dated at Rockville, Maryland, this 25th day of May 1995.
    
        For the Nuclear Regulatory Commission.
    Brian K. Grimes,
    Director, Division of Project Support, Office of Nuclear Reactor 
    Regulation.
    [FR Doc. 95-13514 Filed 6-1-95; 8:45 am]
    BILLING CODE 7590-01-P
    
    

Document Information

Published:
06/02/1995
Department:
Nuclear Regulatory Commission
Entry Type:
Notice
Action:
Notice of opportunity for public comment.
Document Number:
95-13514
Dates:
Comment period expires July 3, 1995. Comments submitted after this date will be considered if it is practical to do so, but assurance of consideration cannot be given except for comments received on or before this date.
Pages:
28805-28808 (4 pages)
PDF File:
95-13514.pdf