[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
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Provisions for
methodology from Minimum requirements to Minimum requirements
administrative controls be included in to be included in PTLR
section in sts methodology
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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.
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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