[Federal Register Volume 71, Number 106 (Friday, June 2, 2006)]
[Notices]
[Pages 32145-32153]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 06-5044]
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NUCLEAR REGULATORY COMMISSION
Notice of Opportunity to Comment on Model Safety Evaluation on
Technical Specification Improvement to Modify Requirements Regarding
the Addition of LCO 3.0.9 on the Unavailability of Barriers Using the
Consolidated Line Item Improvement Process
AGENCY: Nuclear Regulatory Commission.
ACTION: Request for comment.
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SUMMARY: Notice is hereby given that the staff of the Nuclear
Regulatory Commission (NRC) has prepared a model safety evaluation (SE)
and model
[[Page 32146]]
application relating to the modification of requirements regarding the
impact of unavailable hazard barriers, not explicitly addressed in
technical specifications, but required for operability of supported
systems in technical specifications (TS). The NRC staff has also
prepared a model no-significant-hazards-consideration (NSHC)
determination relating to this matter. The purpose of these models is
to permit the NRC to efficiently process amendments that propose to add
an LCO 3.0.9 that provides a delay time for entering a supported system
TS when the inoperability is due solely to an unavailable hazard
barrier, if risk is assessed and managed. Licensees of nuclear power
reactors to which the models apply could then request amendments,
confirming the applicability of the SE and NSHC determination to their
reactors. The NRC staff is requesting comment on the model SE and model
NSHC determination prior to announcing their availability for
referencing in license amendment applications.
DATES: The comment period expires July 3, 2006. Comments received after
this date will be considered if it is practical to do so, but the
Commission is able to ensure consideration only for comments received
on or before this date.
ADDRESSES: Comments may be submitted either electronically or via U.S.
mail. Submit written comments to Chief, Rules and Directives Branch,
Division of Administrative Services, Office of Administration, Mail
Stop: T-6 D59, U.S. Nuclear Regulatory Commission, Washington, DC
20555-0001. Hand deliver comments to: 11545 Rockville Pike, Rockville,
Maryland, between 7:45 a.m. and 4:15 p.m. on Federal workdays. Copies
of comments received may be examined at the NRC's Public Document Room,
11555 Rockville Pike (Room O-1F21), Rockville, Maryland. Comments may
be submitted by electronic mail to [email protected].
FOR FURTHER INFORMATION CONTACT: T.R. Tjader, Mail Stop: O-12H4,
Division of Inspection and Regulation Support, Office of Nuclear
Reactor Regulation, U.S. Nuclear Regulatory Commission, Washington, DC
20555-0001, telephone 301-415-1187.
SUPPLEMENTARY INFORMATION:
Background
Regulatory Issue Summary 2000-06, ``Consolidated Line Item
Improvement Process for Adopting Standard Technical Specification
Changes for Power Reactors,'' was issued on March 20, 2000. The
consolidated line item improvement process (CLIIP) is intended to
improve the efficiency of NRC licensing processes by processing
proposed changes to the standard technical specifications (STS) in a
manner that supports subsequent license amendment applications. The
CLIIP includes an opportunity for the public to comment on a proposed
change to the STS after a preliminary assessment by the NRC staff and a
finding that the change will likely be offered for adoption by
licensees. This notice solicits comments on a proposed change that
allows a delay time for entering a supported system TS when the
inoperability is due solely to an unavailable hazard barrier, if risk
is assessed and managed. The CLIIP directs the NRC staff to evaluate
any comments received for a proposed change to the STS and to either
reconsider the change or announce the availability of the change for
adoption by licensees. Licensees opting to apply for this TS change are
responsible for reviewing the staff's evaluation, referencing the
applicable technical justifications, and providing any necessary plant-
specific information. Each amendment application made in response to
the notice of availability will be processed and noticed in accordance
with applicable rules and NRC procedures.
This notice involves the addition of LCO 3.0.9 to the TS which
provides a delay time for entering a supported system TS when the
inoperability is due solely to an unavailable hazard barrier, if risk
is assessed and managed. This change was proposed for incorporation
into the standard technical specifications by the owners groups
participants in the Technical Specification Task Force (TSTF) and is
designated TSTF-427, Revision 1 (Rev 1). TSTF-427, Rev 1, can be viewed
on the NRC's Web page at http://www.nrc.gov/reactors/operating/licensing/techspecs.html.
Applicability
This proposal to modify technical specification requirements by the
addition of LCO 3.0.9, as proposed in TSTF-427, Rev 1, is applicable to
all licensees.
To efficiently process the incoming license amendment applications,
the staff requests that each licensee applying for the changes proposed
in TSTF-427, Rev 1, to use the CLIIP. The CLIIP does not prevent
licensees from requesting an alternative approach or proposing the
changes without the requested Bases and Bases control program.
Variations from the approach recommended in this notice may require
additional review by the NRC staff, and may increase the time and
resources needed for the review. Significant variations from the
approach, or inclusion of additional changes to the license, will
result in staff rejection of the submittal. Instead, licensees desiring
significant variations and/or additional changes should submit a LAR
that does not claim to adopt TSTF-427, Rev 1.
Public Notices
This notice requests comments from interested members of the public
within 30 days of the date of publication in the Federal Register.
After evaluating the comments received as a result of this notice, the
staff will either reconsider the proposed change or announce the
availability of the change in a subsequent notice (perhaps with some
changes to the safety evaluation or the proposed no significant hazards
consideration determination as a result of public comments). If the
staff announces the availability of the change, licensees wishing to
adopt the change must submit an application in accordance with
applicable rules and other regulatory requirements. For each
application the staff will publish a notice of consideration of
issuance of amendment to facility operating licenses, a proposed no
significant hazards consideration determination, and a notice of
opportunity for a hearing. The staff will also publish a notice of
issuance of an amendment to an operating license to announce the
modification of requirements related to systems in TS, due to
unavailable non-technical specification barriers, for each plant that
receives the requested change.
Dated at Rockville, Maryland, this 26th day of May 2006.
For the Nuclear Regulatory Commission.
Timothy J. Kobetz,
Chief, Technical Specifications Branch, Division of Inspection and
Regional Support, Office of Nuclear Reactor Regulation.
Office of Nuclear Reactor Regulation
Technical Specification Task Force (TSTF) Change TSTF-427
1.0 Introduction
On February 6, 2006, the Nuclear Energy Institute (NEI) Risk
Informed Technical Specifications Task Force (RITSTF) submitted a
proposed change, TSTF-427, Revision 1, to the standard technical
specifications (STS) (NUREGs 1430-1434) on behalf of the industry
(TSTF-427, Revision 0 was a prior draft iteration). TSTF-427, Revision
1, is a proposal to add an STS Limiting Condition for Operation (LCO)
3.0.9, allowing a delay time for entering a
[[Page 32147]]
supported system technical specification (TS), when the inoperability
is due solely to an unavailable hazard barrier, if risk is assessed and
managed. The postulated initiating events which may require a
functional barrier are limited to those with low frequencies of
occurence, and the overall TS system safety function would still be
available for the majority of anticipated challenges.
This proposal is one of the industry's initiatives being developed
under the risk-informed TS program. These initiatives are intended to
maintain or improve safety through the incorporation of risk assessment
and management techniques in TS, while reducing unnecessary burden and
making TS requirements consistent with the Commission's other risk-
informed regulatory requirements.
The proposed change adds a new limiting condition of operation, LCO
3.0.9, to the TS. LCO 3.0.9 allows licensees to delay declaring an LCO
not met for equipment supported by barriers unable to perform their
associated support function, when risk is assessed and managed. This
new LCO 3.0.9 states:
``When one or more required barriers are unable to perform their
related support function(s), any affected supported system LCO(s)
are not required to be declared not met solely for this reason for
up to 30 days provided that at least one train or subsystem of the
supported system is OPERABLE and supported by barriers capable of
providing their related support function(s), and risk is assessed
and managed. This specification may be concurrently applied to more
than one train or subsystem of a multiple train or subsystem
supported system provided at least one train or subsystem of the
supported system is OPERABLE and the barriers supporting each of
these trains or subsystems provide their related support function(s)
for different categories of initiating events. [BWR only: For the
purposes of this specification, the [High Pressure Coolant
Injection/High Pressure Core Spray] system, the [Reactor Core
Isolation Cooling] system, and the [Automatic Depressurization
System] are considered independent subsystems of a single system.]
If the required OPERABLE train or subsystem becomes inoperable
while this specification is in use, it must be restored to OPERABLE
status within 24 hours or the provisions of this specification
cannot be applied to the trains or subsystems supported by the
barriers that cannot perform their related support function(s). At
the end of the specified period, the required barriers must be able
to perform their related support function(s), or the affected
supported system LCO(s) shall be declared not met.''
2.0 Regulatory Evaluation
In 10 CFR 50.36, the Commission established its regulatory
requirements related to the content of TX. Pursuant to 10 CFR 50.36, TS
are required to include items in the following five specific categories
related to station operation: (1) Safety limits, limiting safety system
settings, and limiting control settings; (2) limiting conditions for
operation (LCOs); (3) surveillance requirements (SRs); (4) design
features; and (5) administrative controls. The rule does not specify
the particular requirements to be included in a plant's TS. As stated
in 10 CFR 50.36(c)(2)(I), the ``Limiting conditions for operation are
the lowest functional capability or performance levels of equipment
required for safe operation of the facility. When a limiting condition
for operation of a nuclear reactor is not met, the licensee shall shut
down the reactor or follow any remedial action permitted by the
technical specification * * *.'' TS Section 3.0, on ``LCO and SR
Applicability,'' provides details or ground rules for complying with
the LCOs.
Barriers are doors, walls, floor plugs, curbs, hatches, mechanical
devices, or other devices, not explicitly described in TS, that support
the performance of the functions of systems described in the TS. For
purposes of this TS, the term ``barrier'' refers to one or more devices
which protect one train of a safety system from a given initiating
event. A ``degraded barrier'' refers to a barrier that has been found
to be degraded and must be repaired, or to a barrier that is
purposefully removed or reconfigured to facilitate maintenance
activities. As stated on NEI 04-08, LCO 3.0.9 specifically does not
apply to fire barriers, snubbers, barriers which support ventilation
systems or non-TS systems, or barriers which support TS systems where
the unavailability of the barrier does not render the supported system
inoperable.
Some TS required systems may require one or more functional
barriers in order to perform their intended function(s) for certain
initiating events for which the barriers provide some protective
support function. For example, there are barriers to protect systems
from the effects of internal flooding, such as floor plugs and
retaining walls, and barriers are used to protect equipment from steam
impingement in case of high energy line breaks. Barriers are also used
to protect systems against missiles, either internally generated, or
generated by external events.
Barriers are not explicitly described in the TS, but are required
to be capable of performing their required support function by the
definition of OPERABILITY for the supported system which is described
in the TS. Therefore, under the current STS, the supported system must
be declared inoperable when the related barrier(s) are unavailable.
However, the magnitude of plant risk associated with the barrier which
cannot perform its related support function is much less than the risk
associated with direct unavailability of the supported system, since
barriers are only required for specific, low frequency initiating
events.
Some potential undesirable consequences of the current TS
requirements include:
1. When maintenance activities on the supported TS system require
removal and restoration of barriers, the time available to complete
maintenance and perform system restoration and testing is reduced by
the time spent maneuvering the barriers within the time constraints of
the supported system LCO;
2. Restoration of barriers following maintenance may be given a
high priority due to time restraints of the existing supported system
LCO, when other activities may have a greater risk impact and should
therefore be given priority; and
3. Unnecessary plant shutdowns may occur due to discovery of
degraded barriers which require more time than provided by the existing
supported system LCO to complete repairs and restoration of the
barrier.
To improve the treatment of unavailable barriers and enhance
safety, the TSTF proposed a risk-informed TS change that introduces a
delay time before entering the actions for the supported equipment,
when one or more barriers are found to be degraded, or are removed or
reconfigured to support maintenance activities, if risk is assessed and
managed. Such a delay time will provide needed flexibility in the
performance of maintenance and at the same time will enhance overall
plant safety by:
1. Performing system maintenance and restoration activities,
including post-maintenance testing, within the existing TS LCO time,
and allowing barrier removal and restoration to be performed outside of
the TS LCO, providing more time for the safe conduct of maintenance and
testing activities on the supported TS system;
2. Requiring barrier removal and restoration activities to be
assessed and prioritized based on actual plant risk impacts; and
3. Avoiding unnecessary unscheduled plant shutdowns and thus
minimizing plant transition and realignment risks.
[[Page 32148]]
3.0 Technical Evaluation
The industry submitted TSTF-427, Revision 1 (Reference 1),
``Allowance for Non Technical Specification Barrier Degradation on
Supported System OPERABILITY'' in support of the proposed TS change.
This submittal documents a risk-informed analysis of the proposed TS
change. Probabilistic risk assessment (PRA) methods are used, in
combination with deterministic and defense-in-depth arguments, to
identify and justify delay times for entering the actions for the
supported equipment associated with unavailable barriers at nuclear
power plants. The industry also submitted implementation guidance NEI
04-08, November 2005 (Reference 2). This submittal provides detailed
guidance on assessing and managing risk associated with unavailable
barriers. This is in accordance with guidance provided in Regulatory
Guides (RGs) 1.174 (Reference 3) and 1.177 (Reference 4).
The risk impact associated with the proposed delay times for
entering the TS actions for the supported equipment can be assessed
during the same approach as for allowed completion time (CT)
extensions. Therefore, the risk assessment was performed following the
three-tiered approach recommended in RG 1.177 for evaluating proposed
extensions in currently allowed CTs:
1. The first tier involves the assessment of the change in plant
risk due to the proposed TS change. Such risk change is expressed (1)
by the change in the average yearly core damage frequency ([utri]CDF)
and the average yearly large early release frequency ([utri]LERF) and
(2) by the incremental conditional core damage probability (ICCDP) and
the incremental conditional large early release probability (ICLERP).
The assessed [utri]CDF and [utri]LERF values are compared to acceptance
guidelines, consistent with the Commission's Safety Goal Policy
Statement as documented in RG 1.174, so that the plant's average
baseline risk is maintained within a minimal range. The assessed ICCDP
and ICLERP values are compared to acceptance guidelines provided in RG
1.177, which aim at ensuring that the plant risk does not increase
unacceptably during the period the equipment is taken out of service.
2. The second tier involves the identification of potentially high-
risk configurations that could exist if equipment in addition to that
associated with the change were to be taken out of service
simultaneously, or other risk-significant operational factors such as
concurrent equipment testing were also involved. The objective to
ensure that appropriate restrictions are in place to avoid any
potential high-risk configurations.
3. The third tier involves the establishment of an overall
configuration risk management program (CRMP) to ensure that potentially
risk-significant configurations resulting from maintenance and other
operational activities are identified. The objective of the CRMP is to
manage configuration-specific risk by appropriate scheduling of plant
activities and/or appropriate compensatory measures.
A simplified risk assessment was performed to justify the proposed
addition of LCO 3.0.9 to the TS. This approach was necessitated by (1)
the general nature of the proposed TS change (i.e., it applies to all
plants and is associated with an undetermined number of barriers that
are n not able to perform their function), and (2) the lack of detailed
modeling in most plant-specific PRAs which do not include passive
structures as barriers.
The simplified risk assessment considers three different
parameters:
1. The length of time the affected barrier is unavailable,
2. The initiating event frequency for which the affected barrier is
designed to mitigate, and
3. The importance to CDF (or LERF) of the TS equipment (train,
subsystem, or component) for which the affected barrier is designed to
protect, measured by the risk achievement worth of the equipment.
[GRAPHIC] [TIFF OMITTED] TN02JN06.011
Where:
--Tc is the time the barrier is unavailable (hours)
--Tc/8766 is therefore the fraction of the year during which
the barrier is unavailable,
--IEi/IET is the ratio of the initiating event
frequency for which the affected barrier is designed to mitigate,
IEi, and the total initiating event frequency,
IET,
--RAWj is the risk achievement worth of the component(s) for
which the barrier provides protection, and
--CDFbase is the baseline core damage frequency (per year).
ICLERP also may be similarly determined, using baseline LERF and
RAW values with respect to LERF. It is assumed that the magnitude of
the LERF risk resulting from the barrier unable to perform its related
support function would be generally at least one order of magnitude
less than the corresponding CDF risk. Containment bypass scenarios,
which are typically the significant contributors to LERF, would not be
uniquely affected by application of LCO 3.0.9, and initiating events
which would be significant LERF contributors, such as steam generator
tube rupture and interfacing systems LOCA, are not typically associated
with barriers within the scope of LCO 3.0.9. Therefore, the assumption
regarding LERF risk is reasonable and acceptable for the generic risk
evaluation, provided that LERF risk impacts are considered on a plant-
specific basis for unavailable barriers, as described in section 3.3.
The relevant initiating events (i.e., events for which barriers
subject to LCO 3.0.9 provide protection) are:
--Internal and external floods
--High energy line breaks
--Feedwater line breaks
--Loss of coolant accident (small, medium, and large)
--Tornados and high winds
--Turbine missiles.
Generic frequencies for most of these initiating events were
obtained from NUREG/CR-5750 (Reference 5). For external floods, turbine
missiles, and tornados, other industry source documents were
referenced. The most limiting (highest frequency) initiating event was
obtained for a high energy line break from NUREG/CR-5750, with a
frequency of 9.1E-3 per year. The risk assessment is therefore based on
this limiting frequency, and the proposed methodology to apply LCO
3.0.9 is similarly restricted to barriers protecting against initiating
events whose total frequency is no more than 9.1E-3 per year.
3.1 Risk Assessment Results and Insights
The results and insights from the implementation of the three-
tiered approach of RG 1.177 to support the
[[Page 32149]]
proposed addition of LCO 3.0.9 to the TS are summarized and evaluated
in the following Sections 3.1.1 to 3.1.3.
3.1.1 Risk Impact
The bounding risk assessment approach, described in Section 3.0,
was developed for a range of plant baseline CDF values and for a range
of protected component RAW values. The maximum allowable 30-day outage
time was used. The results are summarized in Table 1.
Table 1.--Risk Assessment Results for a Postulated 30-Day Barrier Outage
------------------------------------------------------------------------
RAW ICCDP ICLERP
------------------------------------------------------------------------
Baseline CDF = 1E-6 Per Year
------------------------------------------------------------------------
2................................................. 7.5E-10 7.5E-11
10................................................ 6.7E-09 6.7E-10
50................................................ 3.7E-08 3.7E-09
100............................................... 7.4E-08 7.4E-09
------------------------------------------------------------------------
Baseline CDF = 1E-5 Per Year
------------------------------------------------------------------------
2................................................. 7.5E-09 7.5E-10
10................................................ 6.7E-08 6.7E-09
50................................................ 3.7E-07 3.7E-08
100............................................... 7.4E-07 7.4E-08
------------------------------------------------------------------------
Baseline CDF = 1E-4 Per Year
------------------------------------------------------------------------
2................................................. 7.5E-08 7.5E-09
10................................................ 6.7E-07 6.7E-08
50................................................ 3.7E-06 3.7E-07
100............................................... 7.4E-06 7.4E-07
------------------------------------------------------------------------
The above results represent a sensitivity analysis covering the
expected range of plant baseline CDF values and component RAW values.
The most limiting configurations involving very high risk components
(RAW > 10) would not be anticipated to occur for most planned
maintenance activities.
The calculations conservatively assume the most limiting (highest
frequency) initiating event and the longest allowable outage time (30
days). Occurrence of the initiating event during unavailability of the
barrier is conservatively assumed to directly fail the protected
equipment; no credit is taken for event-specific circumstances which
may result in the equipment remaining functional even with the barrier
unavailable. (For example, a barrier required to protect equipment from
steam impingement for high energy line breaks may only be required for
breaks occurring in specific locations and orientations relative to the
protected equipment, and only for large size breaks.) No credit is
taken for avoided risk identified in Section 2.
The risk assessment results of Table 1 were compared to guidance
provided in the revised Section 11 of NUMARC 93-01, Revision 2
(Reference 6), endorsed by RG 1.182 (Reference 7), for implementing the
requirements of paragraph (a)(4) of the Maintenance Rule, 10 CFR 50.65.
Such guidance is summarized in Table 2. Guidance regarding the
acceptability of conditional risk increase in terms of CDF for a
planned configuration is provided. This guidance states that a specific
configuration that is associated with a CDF higher than 1E-3 per year
should not be entered voluntarily. The staff notes that the higher risk
configurations documented in Table 1 would exceed this guidance, and
would therefore not be permitted to be entered voluntarily. For
example, with a baseline CDF of 1E-4 per year, a component with a RAW
greater than 10 would exceed the 1E-3 per year criteria. Therefore, the
sensitivity analyses presented in Table 1 are understood to include
higher risk configurations which would not be permitted under the
guidance of Reference 6.
Table 2.--Guidance for Implementing 10 CFR 50.65(a)(4)
------------------------------------------------------------------------
------------------------------------------------------------------------
[Delta]RCDF............................ Guidance.
Greater than 1E-3/year................. Configuration should not
normally be entered
voluntarily.
------------------------------------------------------------------------
ICCDP Guidance ICLERP
------------------------------------------------------------------------
Greater than 1E-5............. Configuration should Greater than 1E-
not normally be 6.
entered voluntarily.
1E-6 to 1E-5.................. Assess non- 1E-7 to 1E-6.
quantifiable factors.
Establish risk
management actions.
Less than 1E-6................ Normal work controls.. Less than 1E-7.
------------------------------------------------------------------------
Guidance regarding the acceptability of ICCDP and ICLERP values for
a specific planned configuration and the establishment of risk
management actions is also provided in NUMARC 93-01. This guidance, as
shown in Table 2, states that a specific plant configuration that is
associated with ICCDP and ICLERP values below 1E-6 and 1E-7,
respectively, is considered to require ``normal work controls.'' Table
1 shows that for the majority of barrier outage configurations the
conservatively assessed ICCDP and ICLERP values are within the limits
for what is recommended as the threshold for the ``normal work
controls'' region.
As stated in the implementation guidance for LCO 3.0.9 (Reference
2), plants are required to commit to the guidance of NUMARC 93-01
Section 11, and therefore the above limits would be applicable. Plant
configurations including out of service barriers may therefore be
entered voluntarily if supported by the results of the risk assessment
required by 10 CFR 50.65(a)(4), and by LCO 3.0.9.
RG 1.177 (Ref. 4) provides guidance of 5E-7 ICDP and 5E-8 ILERP as
the limit for a TS allowed outage time. As shown in Table 1, the
guidance is met for the typically anticipated configurations, unless
either the baseline CDF for the plant approaches 1E-4 per year or the
RAW of the protected components is well above 10. Such configurations
may exceed the criteria described in Ref. 6 (Table 2) and would not be
voluntarily entered. Such configurations are not expected to be
frequently encountered, and may be addressed on a case-by-case plant-
specific basis by limiting the allowed outage time and by implementing
plant-specific risk management actions, as per the implementing
guidance (Reference 2).
RG 1.174 (Ref. 3) provides guidance of 1E-5 per year [Delta]CDF and
1E-6 per year [Delta]LERF. The ICCDP calculations demonstrated that
each individual 30-day barrier outage is anticiapted to be low risk.
Although there is no explicit limit on the number of times per year
that LCO 3.0.9 may be applied, even assuming barrier outages occurred
continuously over the entire year, the risk incurred would still be
anticipated to be below the limits of the guidance.
The staff finds that the risk assessment results support the
proposed addition of LCO 3.0.9 to the TS. The risk increases associated
with this TS change will be insignificant based on guidance
[[Page 32150]]
provided in RGs 1.174 and 1.177 and within the range of risks
associated with normal maintenance activities.
3.1.2 Identification of High-Risk Configurations
The second tier of the three-tiered approach recommended in RG
1.177 involves the identification of potentially high-risk
configurations that could exist if equipment, in addition to that
associated with the TS change, were to be taken out of service
simultaneously. Insights from the risk assessments, in conjunction with
important assumptions made in the analysis and defense-in-depth
considerations, were used to identify such configurations. To avoid
these potentially high-risk configurations, specific restrictions to
the implementation of the proposed TS changes were identified.
When LCO 3.0.9 is applied, at least one train or subsystem is
required to be operable with required barriers in place, such that this
train or subsystem would be available to provide mitigation of the
initiating event. LCO 3.0.9 may be applied to multiple trains of the
same system only for barriers which provide protection for different
initiating events, such that at least one train or subsystem is
available to provide mitigation of the initiating event. The use of LCO
3.0.9 for barriers which protect all trains or subsystems from a
particular initiating event is not permitted. Therefore, potentially
high-risk configurations involving a loss of function required for
mitigation of a particular initiating event are avoided by the
restrictions imposed on applicability of LCO 3.0.9.
LCO 3.0.9 also addresses potential emergent conditions where
unplanned failures or discovered conditions may result in the
unavailability of at least one train or subsystem for a particular
initiating event. Such conditions may result during application of LCO
3.0.9 from equipment failure on the operable train, or discovery of
degraded barriers. In such cases, a 24-hour allowed time is provided to
restore the conditions to permit continued operation with unavailable
barriers, after which the applicability of LCO 3.0.9 ends, and the
supported system LCO becomes effective. This allowed time is provided
so that emergent conditions with low risk consequences may be
effectively managed, rather than requiring immediate exit of LCO 3.0.9
and the potential for an unplanned plant shutdown.
A limit of 30 days is applied to the LCO 3.0.9 allowed outage time
for each barrier, after which the barrier must be restored to an
available status, or the supported system TS must be applied. This 30-
day backstop applies regardless of the risk level calculated, and
provides assurance that installed plant barriers will be maintained
available over long periods of time, and that the application of LCO
3.0.9 will not result in long term degradation of plant barriers.
The staff finds that the restrictions on the applicability of LCO
3.0.9 assuring that one safety train remains available to mitigate the
initiating event, along with the 30-day limit applicable to each
barrier, assure that potentially high-risk configurations are avoided
in accordance with the guidance provided in RGs 1.174 and 1.177.
3.1.3 Configuration Risk Management
The third tier of the three-tiered approach recommended in RG 1.177
involves the establishment of an overall configuration risk management
program (CRMP) to ensure that potentially risk-significant
configurations resulting from maintenance and other operational
activities are identified. The objective of the CRMP is to manage
configuration-specific risk by appropriate scheduling of plant
activities and/or appropriate compensatory measures. This objective is
met by licensee programs to comply with the requirements of paragraph
(a)(4) of the Maintenance Rule (10 CFR 50.65) to assess and manage risk
resulting from maintenance activities, and by LCO 3.0.9 requiring risk
assessments and management using (a)(4) processes if no maintenance is
in progress. These programs can support licensee decision making
regarding the appropriate actions to manage risk whenever a risk-
informed TS is entered.
The implementation guidance for LCO 3.0.9 (Reference 2) requires
that the risk determination for an unavailable barrier be performed per
the ICCDP calculation as described in Section 3.1 using the plant-
specific configuration as the basis for determining the protected
component RAW value. Further, the calculations are to be updated
whenever emergent conditions occur. These requirements assure that the
configuration-specific risk associated with unavailable barriers is
assessed and managed prior to entry into LCO 3.0.9 and during its
applicability as conditions change.
These evaluations for the unavailable barrier are performed as part
of the assessment of plant risk required by 10 CFR 50.65(a)(4). The
numerical guidance identified in Table 2 are applicable to
implementation of LCO 3.0.9, using the results of the configuration-
specific risk assessment which addresses the risk impact of the
unavailable barrier along with all other out of service components and
plant alignments.
Risk management actions are required to be considered when the
calculated risk exceeds specific thresholds per NUMARC 93-01 Section
11, as identified in Table 2. Additional guidance on risk management
actions are provided in the implementation guidance for LCO 3.0.9.
The allowed outage time for a barrier is calculated based on an
ICCDP limit of 1E-6. This is the NUMARC 93-01 Section 11 guidance for
applicability of normal work controls, and is conservatively lower than
the guidance of 1E-5 for voluntary maintenance activities. The use of
1E-6 will result in conservatively short allowed outage times for
barriers compared to allowed times for other maintenance activities.
If the scope of the PRA model used to support the plant-specific
CRMP does not include the initiating event for which a barrier provides
protection, then LCO 3.0.9 applicability is limited to one barrier on a
single train. Multiple barriers for such initiating events may not be
unavailable under LCO 3.0.9, and in such situations the LCO(s)
associated with the protected components would be applicable.
Applicability of LCO 3.0.9 to the single barrier for an initiating
event that is not modeled in the plant PRA is acceptable based on the
generic risk analysis provided by TSTF-427, as described in Section
3.1.
Assessment of the LERF risk impact on an unavailable barrier is
required to be performed in accordance with NUMARC 93-01 Section 11. If
an unavailable barrier provides protection to equipment which is
relevant to the containment function, or which protects equipment from
the effects of an initiating event which is a contributor to LERF, then
the methodology requires a calculation for ICLERP similar to the
calculations performed for ICCDP, described in Section 3.1, or the
applicability of LCO 3.0.9 must be limited to that one barrier.
The staff finds that the risk evaluations required to support the
applicability of LCO 3.0.9 appropriately consider the risk from
unavailable barriers in an integrated manner based on the overall plant
configuration. Therefore potentially high-risk configurations can be
identified and managed in accordance with the guidance provided in RGs
1.174 and 1.177.
3.2 Summary and Conclusions
The unavailability of barriers which protect TS required components
from the effects of specific initiating events is typically a low risk
configuration which
[[Page 32151]]
should not require that the protected components be immediately
declared inoperable. The current TS require that when such barriers are
unavailable, the protected component LCO is immediately entered. Some
potential undesirable consequences of the current TS requirements
include:
1. When maintenance activities on the supported TS system requires
removal and restoration of barriers, the time available to complete
maintenance and perform system restoration and testing is reduced by
the time spent maneuvering the barriers within the time constraints of
the supported system LCO;
2. Restoration of barriers following maintenance must be given a
high priority due to time restraints of the existing supported system
LCO, when other more risk important activities may have a greater risk
impact and should therefore be given priority; and
3. Unnecessary plant shutdowns due to discovery of degraded
barriers which may require more than the existing supported system LCO
time to complete repairs and restoration.
To remove the overly restrictive requirements in the treatment of
barriers, licensees are proposing a risk-informed TS change which
introduces a delay time before entering the actions for the supported
equipment when one or more barriers are found degraded or removed to
facilitate planned maintenance activities. Such a delay time will
provide needed flexibility in the performance of maintenance during
power operation and at the same time will enhance overall plant safety
by (1) performing system maintenance and restoration activities,
including post-maintenance testing, within the existing TS LCO time,
and allowing barrier removal and restoration to be performed outside of
the TS LCO, providing more time for the safe conduct of maintenance and
testing activities on the supported system; (2) requiring barrier
removal and restoration activities to be assessed and prioritized based
on actual plant risk impacts; and (3) avoiding unnecessary unscheduled
plant shutdowns, thus minimizing plant transition and realignment
risks.
The risk impact of the proposed TS changes was assessed following
the three-tiered approach recommended in RG 1.177. A simplified
bounding risk assessment was performed to justify the proposed TS
changes. This bounding assessment was selected due to the lack of
detailed plant-specific risk models for most plants which do not
include failure modes of passive structures such as barriers. The
impact from the addition of the proposed LCO 3.0.9 to the TS on
defense-in-depth was also evaluated in conjunction with the risk
assessment results.
Based on this integrated evaluation, the staff concludes that the
proposed addition of LCO 3.0.9 to the TS would lead to insignificant
risk increases. Indeed, this conclusion is true without taking any
credit for the removal of potential undesirable consequences associated
with the current conservative treatment of barriers.
Consistent with the staff's approval and inherent in the
implementation of TSTF-427, licensees interested in implementing LCO
3.0.9 must, as applicable, operate in accordance with the following
stipulations:
1. The licensee must commit to the guidance of NUMARC 93-01,
Section 11 (Reference 6) and to NEI 04-08 (Reference 2).
2. Licensee procedures must be revised to ensure that the risk
assessment and management process described in NEI 04-08 is used
whenever a barrier is considered unavailable and the requirements of
LCO 3.0.9 are to be applied. This must be done in accordance with an
overall CRMP to ensure that potentially risk-significant configurations
resulting from maintenance and other operational activities are
identified and avoided.
4.0 State Consultation
In accordance with the Commission's regulations, the [] State
official was notified of the proposed issuance of the amendment. The
State official had [(1) no comments or (2) the following comments--with
subsequent disposition by the staff].
5.0 Environmental Consideration
The amendments change a requirement with respect to the
installation or use of a facility component located within the
restricted area as defined in 10 CFR Part 20 and change surveillance
requirements. The NRC staff has determined that the amendments involve
no significant increase in the amounts and no significant change in the
types of any effluents that may be released offsite, and that there is
no significant increase in individual or cumulative occupational
radiation exposure. The Commission has previously issued a proposed
finding that the amendments involve no-significant-hazards
considerations, and there has been no public comment on the finding [FR
]. Accordingly, the amendments meet the eligibility criteria for
categorical exclusion set forth in 10 CFR 51.22(c)(9) [and (c)(10)].
Pursuant to 10 CFR 51.22(b), no environmental impact statement or
environmental assessment need be prepared in connection with the
issuance of the amendments.
6.0 Conclusion
The Commission has concluded, on the basis of the considerations
discussed above, that (1) there is reasonable assurance that the health
and safety of the public will not be endangered by operation in the
proposed manner, (2) such activities will be conducted in compliance
with the Commission's regulations, and (3) the issuance of the
amendments will not be inimical to the common defense and security or
to the health and safety of the public.
7.0 References
1. TSTF-427, Revision 1, ``Allowance for Non Technical
Specification Barrier Degradation on Supported System OPERABILITY,''
February 3, 2006.
2. NEI 04-08, ``Allowance for Non Technical Specification
Barrier Degradation on Supported System OPERABILITY (TSTF-427)
Industry Implementation Guidance'', March 2006.
3. Regulatory Guide 1.174, ``An Approach for Using Probabilistic
Risk Assessment in Risk-Informed Decisions on Plant-Specific Changes
to the Licensing Basis,'' USNRC, August 1998.
4. Regulatory Guide 1.177, ``An Approach for Plant-Specific,
Risk-Informed Decisionmaking: Technical Specifications,'' USNRC,
August 1998.
5. ``Rates of Initiating Events at U.S. Nuclear Power Plants,''
NUREG/CR-5750, Idaho National Engineering and Environmental
Laboratory, February 1999.
6. Nuclear Energy Institute, ``Industry Guideline for Monitoring
the Effectiveness of Maintenance at Nuclear Power Plants'', NUMARC
93-01, Revision 2, Section 11.
7. ``Assessing and Managing Risk Before Maintenance Activities
at Nuclear Power Plants'', Regulatory Guide 1.182.
Proposed No-Significant-Hazards-Consideration Determination
Description of Amendment Request: A change is proposed to the
standard technical specifications (STS)(NUREGs 1430 through 1434) and
plant specific technical specifications (TS), to allow a delay time for
entering a supported system technical specification (TS) when the
inoperability is due solely to an unavailable hazard barrier, if risk
is assessed and managed consistent with the program in place for
complying with the requirements of 10 CFR 50.65(a)(4). LCO 3.0.9 will
be added to individual TS providing this allowance.
Basis for proposed no significant hazards consideration
determination: As required by 10 CFR 50.91(a), an analysis of the issue
of no significant hazards consideration is presented below:
[[Page 32152]]
Criterion 1--The Proposed Change Does Not Involve a Significant
Increase in the Probability of Consequences of an Accident Previously
Evaluated
The proposed change allows a delay time for entering a supported
system technical specification (TS) when the inoperability is due
solely to an unavailable hazard barrier if risk is assessed and
managed. The postulated initiating events which may require a
functional barrier are limited to those with low frequencies of
occurrence, and the overall TS system safety function would still be
available for the majority of anticipated challenges. Therefore, the
probability of an accident previously evaluated is not significantly
increased, if at all. The consequences of an accident while relying on
the allowance provided by proposed LCO 3.0.9 are no different than the
consequences of an accident while relying on the TS required actions in
effect without the allowance provided by proposed LCO 3.0.9. Therefore,
the consequences of an accident previously evaluated are not
significantly affected by this change. The addition of a requirement to
assess and manage the risk introduced by this change will further
minimize possible concerns. Therefore, this change does not involve a
significant increase in the probability or consequences of an accident
previously evaluated.
Criterion 2--The Proposed Change Does Not Create the Possibility of a
New or Different Kind of Accident From Any Previously Evaluated
The proposed change does not involve a physical alteration of the
plant (no new or different type of equipment will be installed).
Allowing delay times for entering supported system TS when
inoperability is due solely to an unavailable hazard barrier, if risk
is assessed and managed, will not introduce new failure modes or
effects and will not, in the absence of other unrelated failures, lead
to an accident whose consequences exceed the consequences of accidents
previously evaluated. The addition of a requirement to assess and
manage the risk introduced by this change will further minimize
possible concerns. Thus, this change does not create the possibility of
a new or different kind of accident from an accident previously
evaluated.
Criterion 3--The Proposed Change Does Not Involve a Significant
Reduction in the Margin of Safety
The proposed change allows a delay time for entering a supported
system TS when the inoperability is due solely to an unavailable hazard
barrier, if risk is assessed and managed. The postulated initiating
events which may require a functional barrier are limited to those with
low frequencies of occurrence, and the overall TS system safety
function would still be available for the majority of anticipated
challenges. The risk impact of the proposed TS changes was assessed
following the three-tiered approach recommended in RG 1.177. A bounding
risk assessment was performed to justify the proposed TS changes. This
application of LCO 3.0.9 is predicated upon the licensee's performance
of a risk assessment and the management of plant risk. The net change
to the margin of safety is insignificant. Therefore, this change does
not involve a significant reduction in a margin of safety.
Based upon the reasoning presented above and the previous
discussion of the amendment request, the requested change does not
involve a no-significant-hazards consideration. Dated at Rockville,
Maryland, this 26 day of May 2006.
For the Nuclear Regulatory Commission.
Timothy J. Kobetz,
Branch Chief, Technical Specifications Branch, Division of Inspection
and Regional Support, Office of Nuclear Reactor Regulation.
For Inclusion on the Technical Specifications Web Page
The following example of an application was prepared by the NRC
staff to facilitate use of the consolidated line item improvement
process (CLIIP). The model provides the expected level of detail and
content for an application to revise technical specifications regarding
the addition of LCO 3.0.9 on the unavailability of barriers using
CLIIP. Licensees remain responsible for ensuring that their actual
application fulfills their administrative requirements as well as
nuclear regulatory commission regulations.
U.S. Nuclear Regulatory Commission, Document Control Desk,
Washington, DC 20555
SUBJECT: PLANT NAME
DOCKET NO. 50--APPLICATION FOR TECHNICAL SPECIFICATION CHANGE TO
ADD LCO 3.0.9 ON THE UNAVAILABILITY OF BARRIERS USING THE
CONSOLIDATED LINE ITEM IMPROVEMENT PROCESS
Gentlemen:
In accordance with the provisions of Title 10 of the Code of
Federal Regulations (CFR) 50.90, [LICENSEE] is submitting a request
for an amendment to the technical specifications (TS) for [PLANT
NAME, UNIT NOS.].
The proposed amendment would modify TS requirements for
unavailable barriers by adding LCO 3.0.9.
Enclosure 1 provides a description of the proposed change, the
requested confirmation of applicability, and plant-specific
verifications. Enclosure 2 provides the existing TS pages marked up
to show the proposed change. Enclosure 3 provides revised (clean) TS
pages. Enclosure 4 provides a summary of the regulatory commitments
made in this submittal.
[LICENSEE] requests approval of the proposed License Amendment
by [DATE], with the amendment being implemented [BY DATE OR WITHIN X
DAYS].
In accordance with 10 CFR 50.91, a copy of this application,
with attachments, is being provided to the designated [STATE]
Official.
I declare under penalty of perjury under the laws of the United
States of America that I am authorized by [LICENSEE] to make this
request and that the foregoing is true and correct. (Note that
request may be notarized in lieu of using this oath or affirmation
statement).
If you should have any questions regarding this submittal,
please contact [NAME, TELEPHONE NUMBER]
Sincerely,
[Name, Title]
Enclosures:
1. Description and Assessment
2. Proposed Technical Specification Changes
3. Revised Technical Specification Pages
4. Regulatory Commitments
5. Proposed Technical Specification Bases Changes.
cc: NRC Project Manager
NRC Regional Office
NRC Resident Inspector
State Contact
Enclosure 1--Description and Assessment
1.0 Description
The proposed amendment would modify technical specifications (TS)
requirements for unavailable barriers by adding LCO 3.0.9.
The changes are consistent with Nuclear Regulatory Commission (NRC)
approved Industry/Technical Specification Task Force (TSTF) STS change
TSTF-427 Revision 1. The availability of this TS improvement was
published in the Federal Register on [DATE] as part of the consolidated
line item improvement process (CLIIP).
2.0 Assessment
2.1 Applicability of Published Safety Evaluation
[LICENSEE] has reviewed the safety evaluation dated [DATE] as part
of the CLIIP. This review included a review of the NRC staff's
evaluation, as well as the supporting information provided to support
TSTF-427. [LICENSEE] has concluded that the justifications presented in
the TSTF proposal and the safety evaluation prepared by the NRC staff
are applicable to [PLANT, UNIT NOS.] and justify this amendment for
[[Page 32153]]
the incorporation of the changes to the [PLANT] TS.
2.2 Optional Changes and Variations
[LICENSEE] is not proposing any variations or deviations from the
TS changes described in the TSTF-427 Revision 1 or the NRC staff's
model safety evaluation dated [DATE].
3.0 Regulatory Analysis
3.1 No Significant Hazards Consideration Determination
[LICENSEE] has reviewed the proposed no significant hazards
consideration determination (NSHCD) published in the Federal Register
as part of the CLIIP. [LICENSEE] has concluded that the proposed NSHCD
presented in the Federal Register notice is applicable to [PLANT] and
is hereby incorporated by reference to satisfy the requirements of 10
CFR 50.91(a).
3.2 Verification and Commitments
As discussed in the notice of availability published in the Federal
Register on [DATE] for this TS improvement, plant-specific
verifications were performed as follows:
1. [LICENSEE] commits to the guidance of NUMARC 93-01 Section 11,
which provides guidance and details on the assessment and management of
risk during maintenance.
2. [LICENSEE] will revise procedures to ensure that the risk
assessment and management process described in NEI 04-08 is used
whenever a barrier is considered unavailable and the requirement of LCO
3.0.9 are to be applied, in accordance with an overall CRMP to ensure
that potentially risk-significant configurations resulting from
maintenance and other operational activities are identified and
avoided.
4.0 Environmental Evaluation
[LICENSEE] has reviewed the environmental evaluation included in
the model safety evaluation dated [DATE] as part of the CLIIP.
[LICENSEE] has concluded that the staff's findings presented in that
evaluation are applicable to [PLANT] and the evaluation is hereby
incorporated by reference for this application.
Enclosure 2--Proposed Technical Specification Changes (Mark-Up)
Enclosure 3--Proposed Technical Specification Pages
Enclosure 4--List of Regulatory Commitments
The following table identifies those actions committed to by
[LICENSEE] in this document. Any other statements in this submittal are
provided for information purposes and are not considered to be
regulatory commitments. Please direct questions regarding these
commitments to [CONTACT NAME].
------------------------------------------------------------------------
Regulatory commitments Due date/event
------------------------------------------------------------------------
[LICENSEE] commits to the guidance of [Ongoing or implement with
NUMARC 93-01, Revision 2, Section 11, amendment].
which provides guidance and details on
the assessment and management of risk
during maintenance.
[LICENSEE] commits to the guidance of NEI [Implement with amendment,
04-08, ``Allowance for Non Technical when barrier(s) are
Specification Barrier Degradation on unavailable].
Supported System OPERABILITY (TSTF-427)
Industry Implementation Guidance,'' March
2006.
------------------------------------------------------------------------
Enclosure 5--Proposed Changes to Technical Specification Bases Pages
[FR Doc. 06-5044 Filed 6-1-06; 8:45 am]
BILLING CODE 7590-01-M