[Federal Register Volume 61, Number 29 (Monday, February 12, 1996)]
[Proposed Rules]
[Pages 5318-5326]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 96-2698]
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NUCLEAR REGULATORY COMMISSION
10 CFR Part 50
RIN 3150-AF33
Reporting Reliability and Availability Information for Risk-
significant Systems and Equipment
AGENCY: Nuclear Regulatory Commission.
ACTION: Proposed rule.
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SUMMARY: The Nuclear Regulatory Commission (NRC) is proposing to amend
its regulations to require that licensees for commercial nuclear power
reactors report plant-specific summary reliability and availability
data for risk-significant systems and equipment 1 to
[[Page 5319]]
the NRC. The proposed rule would also require licensees to maintain on
site, and to make available for NRC inspection, records and
documentation that provide the basis for the summary data reported to
the NRC. The systems and equipment for which data would be provided are
a subset of the systems and equipment within the scope of the
maintenance rule.
\1\ In relation to this proposed rule, the term equipment is
intended to apply to an ensemble of components treated as a single
entity for certain probabilistic risk assessments (PRAs) where a
system or train treatment would not be appropriate.
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The Commission has determined that reporting of reliability and
availability information is necessary to substantially improve the
NRC's ability to make risk-effective regulatory decisions consistent
with the Commission's policy statement on the use of probabilistic risk
assessments (PRAs) (August 16, 1995; 60 FR 42622). This would assist
the NRC in improving its oversight capabilities with respect to public
health and safety and becoming more efficient by focusing its
regulatory program on those issues of greatest risk significance and
reducing unnecessary regulatory burdens on licensees. The Commission
would use the data that would be required by the proposed rule in
generic issue resolution, developing quantitative indicators that can
assist in assessing plant safety performance, performing risk-based
inspections, and pursuing modifications to specific plants and basic
regulations and guidelines. Furthermore, this information would improve
the NRC's oversight of licensees' implementation of the maintenance
rule. It would also enhance licensees' capabilities to implement the
evaluation and goal-setting activities required by the maintenance rule
by providing licensees with access to current industry-wide reliability
and availability information for some of the systems and equipment
within the scope of the maintenance rule.
DATES: Comments regarding any aspect of the proposed rule are due to
the Commission by June 11, 1996. Comments received after that date will
be considered if it is practical to do so, but the Commission can give
no assurance of consideration for late comments. The Commission intends
that this expiration date will be at least 30 days after publication of
an associated draft regulatory guide for public comment.
In addition, comments regarding the collection of information,
including the burden estimate and suggestions for reducing the burden,
should be submitted to the Office of Management and Budget (OMB), and
to the NRC, by March 13, 1996. For further information see the
discussion below under the heading Paperwork Reduction Act Statement.
ADDRESSES: Mail written comments to: U.S. Nuclear Regulatory
Commission, Washington, DC 20555-0001, ATTN.: Docketing and Service
Branch. Deliver written comments to the NRC at One White Flint North,
11555 Rockville Pike, Rockville, MD, between 7:30 am and 4:15 pm on
Federal workdays.
Send comments regarding the collection of information, including
the burden estimate and suggestions for reducing the burden, to: (1)
Desk Officer, Office of Information and Regulatory Affairs, NEOB-10202
(3150-0011), Office of Management and Budget, Washington, DC 20503, and
(2) Information and Records Management Branch (T-6F33), U.S. Nuclear
Regulatory Commission, Washington, DC 20555-0001. For further
information see the discussion below under the heading Paperwork
Reduction Act Statement.
Copies of the draft regulatory analysis, the supporting statement
submitted to the OMB, and comments received may be examined, and/or
copied for a fee, at: The NRC Public Document Room, 2120 L Street NW.
(Lower Level), Washington, DC.
FOR FURTHER INFORMATION CONTACT: Dennis Allison, Office for Analysis
and Evaluation of Operational Data, U.S. Nuclear Regulatory Commission,
Washington, DC 20555-0001, Telephone (301) 415-6835.
SUPPLEMENTARY INFORMATION:
Background
Current Requirements
There are no existing requirements to systematically report
reliability and availability information; nor is there an industry-wide
database to provide such information.
Current reporting requirements in 10 CFR 50.72, ``Immediate
notification'' and 10 CFR 50.73, ``Licensee event report system,''
require the submittal of extensive descriptive information on selected
plant and system level events. The Nuclear Plant Reliability Data
System, a data base that industry supports and the Institute for
Nuclear Power Operations (INPO) maintains, provides data on component
engineering characteristics and failures. Neither of these sources
includes all the data elements (i.e., number of demands on a system,
number of hours of operation, and information on maintenance
unavailability) that are needed to determine the reliability and
availability of systems and equipment. Maintenance effectiveness
monitoring requirements in 10 CFR 50.65, ``Requirements for Monitoring
the Effectiveness of Maintenance at Nuclear Power Plants'', also do not
contain reporting requirements.
In recent years, plants have performed Individual Plant Evaluations
(IPEs), as requested in Generic Letter 88-20 and its supplements, and
submitted the results to the NRC. These submittals provide measures of
risk such as core damage frequency, dominant accident sequences, and
containment release category information. While system and component
reliability data have been collected as part of some utility IPEs, this
information is typically not included in the IPE submittals to the NRC.
Prior Efforts
In late 1991 and through 1992, the NRC staff participated on an
INPO-established NRC/industry review group to make recommendations for
changes to the Nuclear Plant Reliability Data System (NPRDS). The
group's final recommendations to INPO to collect PRA-related
reliability and availability data would have provided most of NRC's
data needs. However, INPO took no action on these recommendations.
During 1992 and 1993, the NRC staff continued through
correspondence and meetings to outline the particular data needed and
to seek INPO's assistance in obtaining the data. In a December 1993
meeting with NUMARC (now the Nuclear Energy Institute (NEI)), INPO
representatives suggested their Safety System Performance Indicator
(SSPI) as a surrogate for reliability data. They proposed expanding the
indicator to additional systems and indicated that data elements could
be modified to compute actual reliability and availability data.
Although general agreements were reached with INPO on which systems and
components and what types of data elements are appropriate for risk-
related applications and maintenance effectiveness monitoring, no
voluntary system of providing data resulted from these discussions. In
the fall of 1994, the NRC staff began work on this rulemaking action.
In June 1995, NEI proposed to discuss a voluntary approach of providing
reliability and availability data to the NRC based on SSPI data. The
NRC staff will continue to work with industry on voluntary submittal of
reliability data, under a program that will meet the needs of all
parties, while at the same time proceeding to obtain public comment on
this proposed rule.
Industry representatives have expressed concern that reliability
data, if publicly available, would be subject to
[[Page 5320]]
misuse. In certain circumstances it is permissible for the NRC to
withhold information from public disclosure. For example, pursuant to
10 CFR 2.790(b)(1), a licensee may propose that a document be withheld
from public disclosure on the grounds that it contains trade secrets or
privileged or confidential commercial or financial information.
However, the data that would be reported under this proposed rule would
not appear to qualify for withholding. Reliability data used as input
to risk-based regulatory decisions should be scrutable and accessible
to the public. The Commission's PRA policy statement indicates that
appropriate supporting data for PRA analyses that support regulatory
decisions should be publicly available. Similarly, the Commission's
draft report on public responsiveness (March 31, 1995; 60 FR 16685)
indicates that the policy of the NRC is to make information available
to the public relating to its health and safety mission, consistent
with its legal obligations to protect information and its deliberative
and investigative processes. Commenters who believe that there is
information subject to a proper 10 CFR 2.790(b)(1) withholding
determination requested by the proposed rule should provide a specific
justification for such belief.
Move to Risk-Based Regulation
For several years the Commission has been working towards increased
use of PRAs in power reactor regulation. In its policy statement on the
use of PRAs, the Commission has indicated that the use of PRA
technology should be increased in all regulatory matters to the extent
supported by the state-of-the-art in terms of methods and data, and
this implies that the collection of equipment and human reliability
data should be enhanced. Implementation of these policies would improve
the regulatory process through (1) improved risk-effective safety
decision making, (2) more efficient use of agency resources, and (3)
reduction in unnecessary burdens on licensees. These improvements would
enhance both efficiency and safety.
The data reported under this proposed rule would improve the NRC's
oversight capability with respect to public health and safety by
focusing the NRC's regulatory programs in a risk-effective manner.
Generally, the NRC's ability to identify plants and systems at
increased risk for significant events and, thus, to take appropriate
action would be substantially improved. For example, a generic
indication of low reliability or availability for a system might
indicate a technical problem, with its attendant risk, that may warrant
generic action. Similarly, a plant-specific indication of low
reliability or availability for several systems might indicate a
programmatic problem, with its attendant risk, and may warrant plant-
specific action.
It has been noted that prior to some significant events (such as
the scram failure at Salem and the accident at Three Mile Island) there
was previously existing information (such as challenge data and
reliability data for scram breakers and power operated relief valves)
which, if collected, recognized, and acted upon might have led to
preventive actions. Accordingly, it is expected that reliability and
availability information for selected risk-significant systems would
improve the NRC's oversight capability with respect to public health
and safety--i.e., the ability to maintain or enhance safety by
identifying and reviewing indications of increased risk and, if
appropriate, taking generic or plant-specific action.
Such problems could be subtle in nature. For instance, licensee(s)
might schedule train outages for maintenance at certain times, such
that risks are substantially increased over what would be expected
based on random outages. This situation would not be indicated by
current reporting requirements, or even by simply reporting train
unavailability, but it could be indicated by the concurrent
unavailability of two or more trains, as would be reported under the
proposed rule. Additional examples discussed below describe further
specific uses of the data that would help to enhance safety.
In order to move towards risk-based regulation and the increased
use of PRA information, the NRC needs scrutable, plant-specific and
generic reliability and availability information. The framework for an
overall move towards risk-based regulation involves the development of
a regulatory process. This process includes operational procedures and
decision criteria that require credible PRA methods, models, and data.
This framework would provide for predictable, consistent, and objective
risk-based regulatory decision making. The data that would be reported
under this rule represent one of the needed elements. In addition,
these data are needed to improve the efficiency and effectiveness of
NRC regulatory applications that employ a risk-based perspective in
advance of defining the entire framework.
Generally, plant-specific information is needed because there can
be wide plant-to-plant variations in the design, importance,
reliability and availability of particular systems and equipment. It is
necessary to identify similar equipment in various plants so that the
data can be properly grouped and analyzed to estimate overall industry
performance and plant-specific performance and to identify outliers
(good or bad).\2\
\2\ For many of the systems involved, plant specific demand and
failure data will be sparse, at least initially. Until data have
been collected for some time, it will be necessary to use data from
similar equipment, applications, and environments at several plants
in order to obtain practical estimates of reliability and
uncertainty. Even when sufficient plant-specific data exist to
estimate plant performance, comparison to industry or group averages
is often desirable.
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Some examples of how reliability and availability information would
be used to improve current NRC regulatory applications that consider
risk in the decision process are discussed below. One of the examples
involves the need for information to support generic regulatory
actions--i.e., generic issue resolution and its associated rulemaking
or regulatory guide revision. Another example involves the need for
information to determine whether further NRC action is needed at
specific plants--i.e., indicators of plant performance. Some involve a
mixture of plant specific and generic elements. For example, analyzing
an event at a given plant could lead to a plant-specific action such as
a special inspection and/or to a generic action such as a bulletin or
generic letter.
Generic Issue Resolution
The NRC currently uses risk estimates in: (1) prioritizing safety
issues, (2) deciding whether new requirements or staff positions to
address these issues are warranted, and (3) deciding whether proposed
new requirements or staff positions should be implemented. Knowing the
current, updated reliability and availability of key systems would, in
some cases, lead to a better understanding of the risk in these areas
and, thus, to more risk-effective decisions. This should both enhance
public protection and reduce unnecessary regulatory burdens. Generic
data would usually suffice for this purpose; however, in some cases the
data would need to be divided to account for specific classes or groups
of plants.
Indicators of Plant Performance
PRA models with plant-specific reliability and availability data
would be used to develop indicators of plant performance and trends in
plant performance which are more closely related to risk than those
currently in use. These new indicators would replace some of those
currently in use
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and thereby enhance NRC's ability to make risk-effective decisions with
regard to identifying plants for increased or decreased regulatory
attention. For example, it is important to detect situations where an
individual plant may be having reliability or availability problems
with multiple systems.
Accident Sequence Precursor (ASP) and Event Analysis
Plant-specific, train-level reliability and unavailability data
would be used to improve the plant-specific ASP models which the NRC
uses to compute conditional core damage probability for determining the
risk-significance of operational events. In addition, dates and causes
of equipment failures would be used to identify common cause failures
and to compute common cause failure rates for input to these models.
Improving these methods would enhance the staff's ability to make risk-
effective decisions about which events warrant further inspections or
investigations and/or generic actions such as bulletins and generic
letters. Plant-specific data are needed to better understand an event
and calculate the associated conditional core damage probability. It is
also useful to identify systems that have the most influence on the
results. Then the risk associated with the potential for similar events
at other plants, which may be known to have low reliability for the key
systems, can be considered in determining whether further actions are
warranted.
Risk-Based Inspections
Current and updated system reliability, availability and failure
data in a generic and plant-specific risk-based context would be used
to enhance the staff's ability to plan inspections focused on the most
risk-significant plant systems, components, and operations. While
generic data would be used in developing risk-based inspection guides
and a framework for inspections, plant-specific data would be used to
focus and optimize inspection activities at specific plants. For
example, an individual plant may have an atypical reliability problem
with a specific risk-significant system and thereby warrant additional
attention. In addition, special studies can be conducted to determine
the root cause of reliability problems by comparing the characteristics
of plants that have these problems with those that do not.
Aging
Equipment reliability data would help identify equipment that is
being degraded by aging and define the extent and the risk-significance
of aging problems.
Another class of examples involves the need for information to
evaluate anticipated cost beneficial licensing actions, where the
rationale is that risk permits reductions in previous margins of safety
or less prescriptive requirements without adverse impact on overall
safety. The NRC is actively pursuing a variety of modifications to the
basic regulations and guidelines that govern the operation of
commercial nuclear power reactors. These modifications are
characterized by allowing individual licensees to utilize insights from
plant-specific risk evaluations to reduce or remove current
requirements that are found to have low risk-significance. Current
regulatory requirements under consideration for risk-based modification
include those prescribing quality assurance, in-service inspection, in-
service testing, and surveillance testing. It is anticipated that a
significant number of additional requests will be received that rely
upon risk-based arguments. These changes could adversely affect the
level of safety achieved by the plants if the risk evaluations are
flawed or the changes are improperly executed or the changes involve
synergistic effects that are not covered by the risk models or captured
by historical data. Current, plant-specific reliability and
availability data would help the NRC monitor the licensees' programs to
maintain safety while reducing regulatory burdens. Relaxation of undue
regulatory burdens then can proceed with confidence that there will be
appropriate feedback to assure that the level of safety is not being
degraded. Some examples are discussed below.
Risk-Based Technical Specification
Technical Specification requirements specify surveillance intervals
and allowed outage times for safety equipment for the various modes of
plant operation. It is anticipated that licensees will request a number
of relaxations in surveillance intervals and allowed outage times.
Current, plant-specific reliability and availability data would help
the NRC monitor performance for the systems and equipment subject to
the proposed rule. Thus, proposed relaxations of surveillance intervals
and allowed outage times for such systems could be evaluated more
effectively based on past performance and on confidence that there
would be appropriate feedback to ensure that performance is not being
degraded. In addition, failure rates from actual demands will be used
to verify that failure rates estimated from testing are approximately
the same.
Inservice Testing
Inservice testing requirements, which are based on the provisions
of the American Society of Mechanical Engineers Boiler and Pressure
Vessel Code (ASME Code), measure the functional characteristics of
equipment performance, such as pump flow, in order to detect
degradation. The ASME and licensee owners' groups are working toward
establishing risk-based frequencies for inservice testing, based on
plant-specific risk ranking methodologies. Changes in testing frequency
can affect reliability in many ways. For example, less frequent valve
testing might lead to an increase in the demand failure rate because
the valve actuating mechanism tends to bind or freeze after extended
periods of idleness. However, using plant-specific demand failure and
unavailability data, proposed changes can be more effectively evaluated
based on the risk-significance and performance of plant systems and
based on confidence that there will be appropriate feedback to assure
that the level of safety is not being degraded.
NRC Maintenance Rule
The maintenance rule, 10 CFR 50.65, was issued on July 10, 1991 (56
FR 31306). The reliability and availability information that would be
required by the proposed reporting rule would improve the NRC's
oversight of licensees' implementation of the maintenance rule. It
would also enhance licensee's capabilities to implement the evaluation
and goal-setting activities required by the maintenance rule by
providing licensees with access to current industry-wide reliability
and availability information for some of the systems and equipment
within the scope of the maintenance rule.
NRC Monitoring
As discussed above, current plant-specific data can provide
feedback on the effectiveness of licensee programs, including
maintenance programs. Accordingly, these data would improve the NRC's
monitoring ability by providing risk-based measures of the
effectiveness of individual licensee maintenance programs and the
overall effectiveness of the maintenance rule.
In addition, the NRC has expressed concern about the extent to
which some reactor licensees are taking systems and equipment out of
service for maintenance during plant operation. Although this practice
may offer economic benefits by reducing plant
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downtime, it must be properly managed to assure that safety is not
compromised. It should be noted that licensees are required by 10 CFR
50.65(a)(3) to periodically conduct assessments and make adjustments to
ensure that the objective of preventing failures through maintenance is
appropriately balanced against the objective of minimizing
unavailability due to monitoring and preventive maintenance. The NRC
would use the hours when any two or more trains from the same or
different systems are concurrently unavailable to monitor how well
licensees are managing the risk associated with such maintenance. As
discussed below, under ``Licensee Implementation,'' the data would also
enhance licensees' capabilities to make prudent on-line maintenance
decisions.
The maintenance rule is also important to license renewal (10 CFR
Part 54). Hence, improving the NRC's oversight of the maintenance rule
could strengthen one of the bases for the scope of the license renewal
rule.
Licensee Implementation
In connection with the NRC's PRA policy, the NRC staff has defined
the data elements that would improve the evaluation of maintenance and
has established that they are the same as those needed to support a
transition toward a risk- and performance-based regulatory process. The
NRC believes that the reliability and availability data that would be
required by this rule would enhance licensee's capabilities to
implement the evaluation and goal-setting activities required by the
maintenance rule by providing licensees with access to current
industry-wide reliability and availability information for some of the
systems and equipment within the scope of the maintenance rule.3
\3\ The systems and equipment covered by this proposed rule are
a subset of the systems and equipment within the scope of the
maintenance rule. The data elements are more extensive than what
would be required for compliance with the maintenance rule; however,
for the systems covered, these data elements would serve to improve
implementation of the maintenance rule. To cite one example, under
10 CFR 50.65(a)(2), risk-significant systems may be considered to be
subject to an effective preventive maintenance program and, thus,
not subject to condition or performance monitoring unless
``maintenance preventable'' failures occur. However, gathering the
reliability and availability information specified in this proposed
rule, including data elements such as concurrent outages and the
causes of failures, would provide a better picture of a system's
performance and the effectiveness of the preventive maintenance
program than simply awaiting the occurrence of ``maintenance
preventable'' failures.
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In some circumstances, the maintenance rule requires licensees to
establish performance or condition goals, taking into account industry-
wide operating experience where practical. It also requires periodic
program evaluations, including consideration of unavailability due to
monitoring or preventive maintenance, taking industry-wide operating
experience into account, where practical. Licensees will need to
monitor reliability and availability of risk-significant systems,
particularly for the periodic program evaluations.4
\4\ NUMARC 93-01, which the NRC has endorsed as describing one
acceptable way of meeting the requirements of the NRC's maintenance
rule, indicates in Section 12.2.4 that the adjustment for balancing
of objectives needs to be done for risk-significant structures,
systems, and components (SSCs). However, for other SSCs it is
acceptable to measure operating SSC performance against overall
plant performance criteria and standby system performance against
specific performance criteria. This is reasonable in that, for
systems that are less risk-significant, the expense of a rigorous
balancing is not warranted.
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For many of the systems involved, plant-specific demand and failure
data will be sparse, at least initially. However statistical analysis
techniques exist that allow a licensee to analyze and evaluate data
from similar equipment, applications and environments from other
plants, besides the data from their plant. These analyses yield
meaningful reliability estimates for the subject plant that can be
compared with performance goals. Industry-wide data would also provide
a practical source for comparing plant-specific performance with
industry operating experience. Although plant-specific information is
generally available on site, and utilities review licensee event
reports and other generic event information, NRC site visits,
associated with early efforts to prepare for maintenance rule
implementation in 1996, indicate that utilities do not use industry
operating experience in a systematic and consistent way for goal
setting purposes under the maintenance rule. Based on these
considerations, the availability of current, industry-wide reliability
and availability data would enhance licensee's capabilities to
implement the evaluation and goal-setting activities required by the
maintenance rule.
As discussed previously, the NRC has recently found cause for
concern about how some reactor licensees handle on-line maintenance.
Prudent on-line maintenance decisions depend on a full appreciation of
the risk-significance of taking equipment out of service (individually
or collectively) and use of plant-specific and generic reliability and
availability data would play a significant role in improving such
decision making.
Description of Proposed Rule
The proposed rule would require holders of operating licenses for
nuclear power reactors to report reliability and availability data for
certain risk-significant systems and equipment. The proposed reporting
requirements would apply to the event-mitigating systems and equipment
which have or could have a significant effect on risk in terms of
avoiding core damage accidents or preserving containment integrity.
Summary information reported to the NRC would be:
1. The number of demands, the number of failures to start
associated with such demands, and the dates of any such failures,
characterized according to the identification of the train affected,
the type of demand (test, inadvertent/spurious, or actual need), and
the plant mode at the time of the demand (operating or shutdown);
2. The number of hours of operation following each successful
start, characterized according to the identification of the train
affected and whether or not the operation was terminated because of
equipment failure, with the dates of any such failures;
3. The number of hours equipment is unavailable, characterized
according to the identification of the train affected, the plant mode
at the time equipment is unavailable (operating or shutdown),
characterization of the unavailable period (planned, unplanned, or
support system unavailable), and, if due to a support system being
unavailable, identification of the support system;
4. For each period equipment is unavailable due to component
failure(s), a failure record identifying the component(s) and providing
the failure date, duration, mode, cause, and effect; and
5. The number of hours when two or more trains from the same or
different systems were concurrently unavailable, characterized
according to the identification of the trains that were unavailable.
The first annual report would identify the systems, trains, and
ensembles of components covered by the reporting requirements of the
rule; subsequent annual reports would either state that no changes were
made subsequent to the previous annual report or describe the changes
made.
The summary information would be reported annually and compiled on
the basis of calendar quarters, or on a more frequent basis at the
option of each individual licensee. Records and documentation of each
occurrence of a demand, failure, or unavailable period
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that provide the basis for the summary data reported to the NRC would
be required to be maintained on site and made available for NRC
inspection.
In developing these data elements the NRC has, over the past three
years, reached a consensus on the minimum data needed to support risk-
based applications and enhance implementation of the maintenance rule.
During this period NRC staff has also interacted extensively with INPO
and NEI in an effort to define the minimum reliability and availability
data needed to satisfy the needs of both NRC risk-based regulatory
applications and industry (licensee) uses of PRA.
The number of demands and the number of successful starts are
needed to estimate demand reliability, i.e., the fraction of demands
that result in successful starts. (The complement of this fraction
provides an estimate of the probability of failure on demand). The
actual number of demands and successes, as opposed to the ratio, is
needed for purposes such as: (1) providing a measure of confidence in
the results and (2) permitting proper combination of data from
different plants.
The type of demand is needed to determine whether or not the demand
reliability estimated by testing is approximately the same as the
demand reliability for actual demands. Sometimes it is not, indicating
a need for additional data analysis in making reliability estimates.
The plant mode at the time of a demand is needed to estimate the
demand frequency, demand reliability, and unavailability according to
plant mode. These factors, as well as the risk associated with
unreliability and unavailability, can be quite different depending on
whether the plant is in operation or shut down.
The hours of operation following successful starts are needed to
estimate the probability the equipment will function for a specified
period of time. This information is needed for systems that must
operate for an extended period following an accident to fulfill a risk-
significant safety function.
The number of hours that equipment is not available (unavailable
hours) is needed to estimate the fraction of time that a train is not
available to perform its risk-significant safety function. For some
systems this can be an important or dominant contributor to the overall
probability of failure to perform the system's safety function. It can
be significantly affected by elective maintenance.
The type of unavailable hours (planned or unplanned) is needed to
effectively utilize these estimates. For example, a high unplanned
unavailability may indicate a need for more preventive maintenance; a
high planned unavailability may indicate the opposite.
The unavailable hours due to support systems failure or
unavailability are needed to properly capture concurrent outages and to
eliminate double counting. For example, an Emergency Service Water
(ESW) train being unavailable may result in other trains being
unavailable as well; however, for purposes of estimating risk in a PRA
study, that unavailability should not be counted more than once.
The date of each failure is needed to allow screening for potential
common cause failures. Failures that occur closely together in time
warrant review to see whether a common cause failure may be involved.
Common cause failures may indicate a need for revised maintenance
procedures or staggered testing. Common cause failure rates are also
needed for PRA models because of their importance in system reliability
and availability estimates.
Failure cause and failure mode information are needed to support
common cause failure analysis as discussed above and to associate the
failure with the correct failure mode for input into PRA models.
Quarterly data are needed to conduct first order trending studies
to identify areas of emerging concern with regard to overall plant and
system performance. More frequent compilation is acceptable at the
discretion of each licensee.
An identification of the systems, trains, and ensembles of
components subject to the rule is needed because identification of the
components within the systems, trains, and ensembles is necessary for
proper use and evaluation of the data by the staff and for industry
wide generic applications to account for physical differences between
plants. For example, simplified system diagrams could be marked to show
the systems, trains, and ensembles against which the data would be
reported.
Retention of records and documentation that provide the bases for
the summary data report to the NRC for a period of several years is
consistent with maintenance rule applications. For example, monitoring
reliability for a few years may be used to determine trends in order to
achieve the balance described in 10 CFR 50.65(a)(3)--i.e., the balance
between preventing failures through maintenance and minimizing
unavailability due to monitoring and preventive maintenance. In
addition, on-site data are needed to provide a scrutable basis for
regulatory decisions. For example, it is expected to be necessary to
review the actual unavailable hours in order to estimate the mean
repair times for key components for the purpose of updating the staff's
PRA models.
Regulatory Guide
A new regulatory guide will be prepared and issued to provide
supplementary guidance. The guide will present an acceptable way to
define the systems and equipment subject to the rule and it will
provide risk-based definitions of failure as well as train and system
boundaries consistent with PRA applications. The format in which data
would be provided to the NRC and a suggested format for maintaining on-
site documentation and record keeping would be included. In order to
reduce costs, use of electronic data submittal will be considered a
priority objective in developing and implementing the guide. A draft
guide will be published for comment before it is finalized. A public
workshop is planned after publication of the draft guide. The comment
period for this proposed rule will not expire until at least 30 days
after publication of the draft regulatory guide.
Definitions
The basic definitions used in reporting under Sec. 50.76 are
discussed below; further details will be addressed in the regulatory
guide. For example, the basic definition of failure is provided here;
further details, such as how to handle a case where the operators
prematurely terminate system operation following a real demand, will be
discussed in the regulatory guide. In particular, the regulatory guide
will define risk-significant safety function(s) and failures for
systems and equipment covered by this proposed rule.
Demand is an occurrence where a system or train is called upon to
perform its risk-significant safety function. A demand may be manual or
automatic. It may occur in response to a real need, a test, an error,
an equipment malfunction or other spurious causes. For the purposes of
reporting under this rule, the demands of interest are those which are
actual demands or closely simulate actual demands for the train or
specific equipment involved.
Failure, for the purpose of reporting under this rule, is an
occurrence where a system or train fails to perform its risk-
significant safety function. A failure may occur as a result of a
hardware malfunction, a software malfunction, or a human error.
Failures to start in response to a demand are reported under paragraph
50.76(b)(1)(i). Failures
[[Page 5324]]
to run after a successful start are reported under paragraph
50.76(b)(1)(ii).
Unavailability is the probability that a required system or train
is not in a condition to perform or is not capable of performing its
risk-significant safety function. This may result from failure to
start, from failure to run, or from intentional or unintentional
removal of equipment from service (e.g., for maintenance or testing).
Risk-significant safety function is a safety function that has or
could have a significant effect on risk (in terms of avoiding core
damage accidents or preserving containment integrity for the purposes
of reporting under this proposed rule).
Reportable systems and equipment are the event-mitigating systems
and equipment which have or could have a significant effect on risk in
terms of avoiding core damage accidents or preserving containment
integrity. The reportable systems and equipment will be determined by
each licensee. The regulatory guide will describe acceptable methods
for making that determination.
It is expected that the rule will produce a set of basic systems
for which reliability data will be reported for all plants that have
them. However, these basic systems are not sufficient by themselves.
Additional systems and equipment to be addressed will depend on plant-
specific features. Listed below is the set of basic systems that the
Commission is currently considering for identification in the draft
regulatory guide.
------------------------------------------------------------------------
Basic PWR systems Basic BWR systems
------------------------------------------------------------------------
Auxiliary feedwater....................... Reactor core isolation
cooling or isolation
condenser.
High pressure safety injection............ Feedwater coolant injection,
high pressure coolant
injection or high pressure
core spray, as appropriate.
Reactor protection........................ Reactor protection.
Low pressure safety injection............. Low pressure coolant
injection and low pressure
core spray.
Emergency ac power........................ Emergency ac power.
------------------------------------------------------------------------
As discussed above, the systems and equipment to be included in the
scope of the rule would be those event-mitigating systems and equipment
that have or could have a significant effect on risk in terms of
avoiding core damage accidents or preserving containment integrity. To
ensure that this approach is consistent with operating experience, the
NRC has considered the systems and equipment that have been
substantially involved in significant events in U. S. reactors. These
systems were found to fall into the following categories:
1. Basic systems. As indicated above, the NRC expects that these
systems would be included in the scope of the rule for all plants. The
basic systems on the proposed list have been confirmed to have been
substantially involved in significant events.
2. Plant-specific systems. Systems such as service water and
component cooling water are risk-significant, but the significance
varies widely, depending upon plant-specific designs. It is expected
that these systems will be included, as appropriate, based on plant-
specific PRA studies. Other systems, such as containment purge, appear
infrequently in connection with significant events and are not expected
to be risk-significant for any plants.
3. Initiating systems. Systems such as main feedwater and offsite
power are primarily considered to be initiators of significant events,
rather than mitigation systems. Existing reporting requirements in 10
CFR 50.72 and 10 CFR 50.73 provide enough information to characterize
the important initiating systems for the purpose of PRA studies.
4. Non-measurable items. Items such as reactor coolant system
corrosion are not amenable to meaningful measurement by the methods of
this proposed rule.
Based on this review, the systems and equipment to be included in
the scope of the rule are considered reasonably consistent with
operating experience in terms of involvement in significant events.
Accordingly, it is expected that reliability and availability
information for those systems and equipment will be well suited for
identifying plants and systems at increased risk for significant
events.
Minimizing Costs. The NRC intends that the data required to be
collected and reported under this proposed rule be essentially the same
as would be required for monitoring reliability and/or availability for
other purposes, such as monitoring system reliability where that is the
option chosen for compliance with the maintenance rule. Thus, it should
be practical to gather and report the data without significant
additional cost. This will be a priority goal in developing the
guidance to be included in the new regulatory guide.
Sunset Provision. As experience is gained with implementing the
proposed rule and utilizing the information required to be collected
and reported, a reassessment may be necessary or desirable. One way of
assuring such a reassessment would be to include a ``sunset provision''
in the rule, whereby the rule would automatically expire after a
specified period of time unless: (i) a condition specified in the rule
is fulfilled, or (ii) the Commission engages in a rulemaking which
extends the effectiveness of the rule. The Commission requests public
comments on whether the proposed rule should contain such a sunset
provision, and if so, the period of time after which the rule should
automatically expire.
Grandfather Provision. There may be some plants for which, at the
time that the proposed rule may be adopted by the Commission as a final
rule, licensees have already announced plans to discontinue operation
in the near future. Furthermore, licensees may determine in the future
to discontinue operation at some plants. In either case, there may be
less reason to require collection and reporting of the information
contemplated by the proposed rule at such plants and it may be
advisable to exempt such plants from the information collection and
reporting requirements of the proposed rule (i.e., ``grandfathering'').
The Commission requests public comments on whether the proposed rule
should exempt plants that have announced (or will announce) plans to
discontinue operation within a short time (e.g., two years).
Conclusion
As discussed under the subject ``Move to Risk-Based Regulation,''
the information to be collected under the proposed rule is necessary
for the development and implementation of risk-based regulatory
processes. Risk-based regulatory approaches provide a means for the
Commission to maintain, and in some cases improve, safety while
reducing impacts on licensees as well as NRC resource expenditures, by
focusing regulatory requirements and activities on the most risk-
significant areas. In addition, this information would improve the
NRC's oversight of licensees' implementation of the maintenance rule.
It would also enhance licensee's capabilities to implement the
evaluation and goal-setting activities required by the maintenance rule
by providing licensees with access to current industry-wide reliability
and availability information for some of the risk-significant systems
and equipment within the scope of the maintenance rule. The Commission
has also prepared a regulatory analysis (see ``Regulatory Analysis'')
which identified alternatives for collecting the information for use by
both licensees and the NRC, and evaluated the costs of each viable
alternative. Based upon these factors, the Commission believes that the
costs
[[Page 5325]]
of the proposed rule's information collection and reporting
requirements are justified in view of the potential safety significance
and projected benefits of the information in NRC regulatory activities.
Submission of Comments in Electronic Format
Commenters are encouraged to submit, in addition to the original
paper copy, a copy of their comments in an electronic format on IBM PC
DOS- compatible 3.5- or 5.25-inch, double-sided, diskettes. Data files
should be provided in WordPerfect 5.0 or 5.1. ASCII code is also
acceptable, or if formatted text is required, data files should be
submitted in IBM Revisable Format Text Document Content Architecture
(RFT/DCA) format.
Environmental Impact: Categorical Exclusion
The proposed rule sets forth requirements for the collection,
maintenance, and reporting of reliability and availability data for
certain risk-significant systems and equipment. The NRC has determined
that this proposed rule is the type of action described in categorical
exclusion, 10 CFR 51.22(c)(3)(ii). Therefore, neither an environmental
impact statement nor an environmental assessment has been prepared for
this proposed regulation.
Paperwork Reduction Act Statement
This proposed rule amends information collection requirements that
are subject to the Paperwork Reduction Act of 1995 (44 U.S.C. 3501 et
seq.). This rule has been submitted to OMB for review and approval of
the Paperwork Reduction Act requirements.
The public reporting burden for this collection of information is
estimated to average 1375 hours per response (i.e., per commercial
nuclear power reactor per year), including the time for reviewing
instructions, searching existing data sources, gathering and
maintaining the data needed, and completing and reviewing the
collection of information. The Commission is seeking public comment on
the potential impact of the collection of information contained in the
proposed rule and on the following issues:
1. Is the proposed collection of information necessary for the
proper performance of the functions of the NRC, and does the
information have practical utility?
2. Is the estimate of burden accurate?
3. Is there a way to enhance the quality, utility, and clarity of
the information to be collected?
4. How can the burden of the collection of information be minimized
including by using automated collection techniques?
Send comments on any aspect of this proposed collection of
information, including suggestions for reducing the burden, to the
Information and Records Management Branch (T-6-F33), U.S. Nuclear
Regulatory Commission, Washington, DC 20555-0001, and to the Desk
Officer, Office of Information and Regulatory Affairs, NEOB-10202,
(3150-0011), Office of Management and Budget, Washington, DC 20503.
Comments to OMB on the collections of information or on the above
issues should be submitted by March 13, 1996. Comments received after
this date will be considered if it is practical to do so, but assurance
of consideration cannot be given to comments received after this date.
Public Protection Notification
The NRC may not conduct or sponsor, and a person is not required to
respond to, a collection of information unless it displays a currently
valid OMB control number.
Regulatory Analysis
The Commission has prepared a draft regulatory analysis on this
proposed regulation. The analysis examines the costs and benefits of
the alternatives considered by the Commission. The draft analysis is
available for inspection in the NRC Public Document Room, 2120 L Street
NW. (Lower Level), Washington, DC. Single copies of the draft analysis
may be obtained from: Dennis Allison, Office for Analysis and
Evaluation of Operational Data, U.S. Nuclear Regulatory Commission,
Washington, DC 20555-0001, Telephone (301) 415-6835.
Regulatory Flexibility Certification
In accordance with the Regulatory Flexibility Act of 1980 (5 U.S.C.
605 (B)), the Commission certifies that this rule will not, if
promulgated, have a significant economic impact on a substantial number
of small entities. The proposed rule affects only the licensing and
operation of nuclear power plants. The companies that own these plants
do not fall within the scope of the definition of ``small entities''
set forth in the Regulatory Flexibility Act or the size standards
adopted by the NRC on April 11, 1995 (60 FR 18344--10 CFR 2.810.
Backfit Analysis
The proposed rule sets forth requirements for reporting and record
keeping. The NRC has determined that the backfit rule, 10 CFR 50.109,
does not apply to this proposed rule, and therefore, a backfit analysis
is not required for this proposed rule because these amendments do not
involve any provisions which would impose backfits as defined in 10 CFR
50.109(a)(1).
However, as discussed above in ``Regulatory Analysis,'' the
Commission has prepared a regulatory analysis which summarizes the
purpose and intended use of the information proposed to be collected,
identifies alternatives for collection and reporting of the proposed
information, and identifies the impacts and benefits of the
alternatives.
This regulatory analysis constitutes a disciplined process for
evaluating the potential benefits and projected impacts (burdens) of
information collection and reporting requirements such as the proposed
rule. The Commission therefore concludes that the objective underlying
the Commission's adoption of the Backfit Rule--that regulatory impacts
are assessed under established criteria in a disciplined process--is
being met for this proposed rule.
List of Subjects in 10 CFR Part 50
Antitrust, Classified information, Criminal penalties, Fire
protection, Intergovernmental relations, Nuclear power plants and
reactors, Radiation protection, Reactor siting criteria, Reporting and
record keeping requirements.
For the reasons set out in the preamble and under the authority of
the Atomic Energy Act of 1954, as amended, the Energy Reorganization
Act of 1974, as amended, and 5 U.S.C. 553, the NRC is proposing to
adopt the following amendments to 10 CFR Part 50.
PART 50--DOMESTIC LICENSING OF PRODUCTION AND UTILIZATION
FACILITIES
1. The authority citation for Part 50 continues to read as follows:
Authority: Sections 102, 103, 104, 105, 161, 182, 183, 186, 189,
68 Stat. 936, 937, 938, 948, 953, 954, 955, 956, as amended, sec.
234, 83 Stat. 1244, as amended (42 U.S.C. 2132, 2133, 2134, 2135,
2201, 2232, 2233, 2236, 2239, 2282); secs. 201, as amended, 202,
206, 88 Stat. 1242, as amended, 1244, 1246 (42 U.S. C. 5841, 5842,
5846).
Section 50.7 also issued under Pub. L. 95-601, sec. 10, 92 Stat.
2951 as amended by Pub. L. 102-486, sec. 2902, 106 Stat 3123, (42
U.S.C. 5851). Section 50.10 also issued under secs. 101, 185, 68
Stat. 936, 955, as amended (42 U.S.C. 2131, 2235); sec. 102, Pub. L.
91-190, 83 Stat. 853 (42 U.S.C. 4332). Sections 50.13, and
50.54(dd), and 50.103 also issued under sec. 108, 68 Stat. 939, as
amended (42 U.S.C. 2138). Sections 50.23, 50.35, 50.55,
[[Page 5326]]
and 50.56 also issued under sec. 185, 68 Stat. 955 (42 U.S.C. 2235).
Sections 50.33a, 50.55a and Appendix Q also issued under sec. 102,
Pub. L. 91-190, 83 Stat. 853 (42 U.S.C. 4332). Sections 50.34 and
50.54 also issued under sec. 204, 88 Stat. 1245 (42 U.S.C. 5844).
Sections 50.58, 50.91, and 50.92 also issued under Pub. L. 97-415,
96 Stat. 2073 (42 U.S.C. 2239). Section 50.78 also issued under sec.
122, 68 Stat. 939 (42 U.S.C. 2152). Sections 50.80--50.81 also
issued under sec. 184, 68 Stat. 954, as amended (42 U.S.C. 2234).
Appendix F also issued under sec. 187, 68 Stat. 955 (42 U.S.C.
2237).
2. Section 50.8(b) is revised to read as follows:
Sec. 50.8 Information collection requirements: OMB approval.
* * * * *
(b) The approved information collection requirements contained in
this part appear in Secs. 50.30, 50.33, 50.33a, 50.34, 50.34a, 50.35,
50.36, 50.36a, 50.48, 50.49, 50.54, 50.55, 50.55a, 50.59, 50.60, 50.61,
50.63, 50.64, 50.65, 50.71, 50.72, 50.75, 50.76, 50.80, 50.82, 50.90,
50.91, 50.120, and Appendices A, B, E, G, H, I, J, K, M, N, O, Q, and
R.
* * * * *
3. Section 50.76 is added to read as follows:
Sec. 50.76 Reporting reliability and availability information for
risk-significant systems and equipment.
(a) Applicability. This section applies to all holders of operating
licenses for commercial nuclear power plants under 10 CFR 50.21b or
50.22 and all holders of combined operating licenses for commercial
nuclear power plants under 10 CFR 52.97.
(b) Requirements. (1) Each licensee shall submit an annual report
to the NRC that contains the following information, compiled on the
basis of calendar quarters, or on a more frequent basis at the option
of each licensee, for systems, trains, and ensembles of components in
paragraph (b)(3) of this section:
(i) The number of demands, the number of failures to start
associated with such demands, and the dates of such failures,
characterized according to the identification of the train affected,
the type of demand (test, inadvertent/spurious, or actual need), and
the plant mode at the time of the demand (operating or shutdown);
(ii) The number of hours of operation following each successful
start, characterized according to the identification of the train
affected and whether or not the operation was terminated because of
equipment failure, with the dates of any such failures;
(iii) The number of hours equipment is unavailable, characterized
according to the identification of the train affected, the plant mode
at the time equipment is unavailable (operating or shutdown),
characterization of the unavailable period (planned, unplanned, or
support system unavailable), and, if due to a support system being
unavailable, identification of the support system;
(iv) For each period equipment is unavailable due to component
failure(s), a failure record identifying the component(s) and providing
the failure date, duration, mode, cause, and effect; and
(v) The number of hours when two or more trains from the same or
different systems were concurrently unavailable, characterized
according to the identification of the trains that were unavailable.
(2) The initial annual report described in (b)(1) above shall
identify the systems, trains, and ensembles of components covered by
paragraph (b)(3) below; subsequent annual reports shall either state
that no changes were made subsequent to the previous annual report or
describe any changes made.
(3) The requirements of paragraphs (b)(1) and (b)(2) of this
section apply to those event-mitigation systems, and ensembles of
components treated as single entities in certain probabilistic risk
assessments where a system or train treatment would not be appropriate,
which have or could have a significant effect on risk in terms of
avoiding core damage accidents or preserving containment integrity.
(4) Each licensee shall maintain records and documentation of each
occurrence of a demand, failure, or unavailable period that provide the
basis for the data reported in paragraph (b)(1) of this section on site
and available for NRC inspection for a period of 5 years after the date
of the report specified in paragraph (b)(1) of this section.
(c) Implementation. Licensees shall begin collecting the
information required by paragraph (b) of this section on January 1,
1997, and shall submit the first report required by paragraph (b)(1) of
this section by January 31, 1998. Thereafter, each annual report
required by paragraph (b)(1) of this section shall be submitted by
January 31 of the following year.
Dated at Rockville, MD, this 2nd day of February, 1996.
For the Nuclear Regulatory Commission.
John C. Hoyle,
Secretary of the Commission.
[FR Doc. 96-2698 Filed 2-9-96; 8:45 am]
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