[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.

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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