Protecting People and the EnvironmentUNITED STATES NUCLEAR REGULATORY COMMISSION
UNITED STATES
NUCLEAR REGULATORY COMMISSION
WASHINGTON, D. C. 20555
January 20, 1988
TO ALL POWER REACTOR LICENSEES
Gentlemen:
SUBJECT: Integrated Safety Assessment Program II (ISAP II)
(Generic Letter 88-02)
The Integrated Safety Assessment Program (ISAP) was a pilot program
initiated in May 1985 for Millstone Unit 1 and Haddam Neck. The program was
designed to provide a comprehensive review for operating reactors to address
all safety Issues and to provide an integrated cost-effective implementation
plan using deterministic and probabilistic techniques. ISAP also provided
the technical bases to resolve all outstanding licensing actions,
established overall plant improvement schedules, and served as a benchmark
from which future regulatory actions could be judged or a plant-specific
basis. ISAP is described in a policy statement published in the Federal
Register on November 15, 1984 (49 FR 45112) and in Generic Letter 85-07.
On November 4, 1987, the staff briefed the Commission on the status and
results of ISAP and made recommendations for future activities relating to
that program. At that meeting the staff recommended that the benefits of the
ISAP approach be made available to all licensees. Identified benefits of the
ISAP program include (1) finding common elements in separate review areas
and proposing a single integrated action to resolve the concerns, (2)
addressing pending requirements on a plant-specific basis, and (3) dropping
issues from further consideration because of low safety significance. The
Commission deferred action on extending the ISAP concept beyond the pilot
program and, among other things, asked the staff to determine the industry's
interest in such a program. Accordingly, the staff is issuing this generic
letter to describe ISAP II, a derivative of ISAP, and to ascertain utility
interest in participating in this proposed program.
ISAP II is a disciplined program to address regulatory issues within an
integrated schedule based on two analytical tools: probabilistic risk
assessment (PRA) and operating experience review. The operating experience
review will determine systematic weaknesses and trends as well as provide
actual historical plant operating information against which to judge the
reasonableness of PRA findings. An integrated assessment based on the two
analytical tools will determine the ranking of issues from which the
integrated schedule will be developed. The integrated schedule will allow
regulatory issues and utility-initiated items to be prioritize and scheduled
within the framework of all scheduled items.
ISAP II is designed to accomplish the same objectives as ISAP with certain
programmatic differences. Unlike ISAP, ISAP II would not again review issues
against current Standard Review Plan sections. Therefore, incorporating
lessons learned from the Systematic Evaluation Precram (SEP) would not be a
requirement for participants in ISAP as it was in ISAP. ISAP II would only
include current and future items for a plant. In addition, ISAP II
participants would not be expected to address unresolved genetic issues
ahead of the staff's generic resolution. Through the ISAP II process, it may
be determined that certain issues
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can be combined and resolved concurrently or that certain issues have a low
safety significance, which would make them candidates for a lower priority
or for being dropped. Enclosure 1 provides additional details regarding ISAP
II.
An important advantage of ISAP II is that its minimum-required Level 1 PRA
combined with a containment vulnerability assessment (or a Level 2 or Level
3 PRA) constitutes an acceptable method for a utility to perform its
Individual Plant Examination (IPE). This examination is the means of
satisfying certain requirements of the Commission's Severe Accident Policy
Statement, which was published in the Federal Register on August 9, 1985 (50
FR 32138). Therefore, by performing a PRT for ISAP II, the licensee would
have made substantial progress toward completing its IPE.
Benefits to those licensees participating in ISAP II include:
o The integrated schedules for the ISAP II implementation of issues will
provide a predictable safety basis for the staff and licensee to manage
current workloads and to estimate the resources, necessary to meet
future requirements. Required resources are expected to be reduced in
the long run by combining issues and eliminating low safety significant
issues.
o Licensing and generic issues are treated on a plant-specific basis and
are weighed against all other pending actions. Through the ISAP II
process, the licensee will have an opportunity to demonstrate, by using
its PRA, that various generic issues are not justified at its facility
on the basis of the safety significance of the issue.
o Safety will be enhanced and the safety value for each dollar spent-will
be increased because issues of highest safety significance will
generally be worked on first.
o ISAP II is a process that may form part of the basis to consider plant
life extension requests and plant aging issues.
o Bases for optimization of maintenance/surveillance intervals may be
derived from ISAP II. For example, a PRA analysis provided a basis for
increased surveillance intervals and out-of-service times for
Westinghouse reactor trip system maintenance and surveillance
frequencies.
o The process will help improve outage planning by providing, a longer
term outlook of modifications for the upcoming outages. This could
reduce outage delays.
o Participation in ISAP II will involve the licensee in a detailed PFA
leading to an enhanced understanding of plant capabilities for both it
and the NRC. The ISAP II process will improve the interface between
licensee engineering and plant operations by fostering communications
in areas of mutual responsibility addressed in the performance of a
plant-specific PRA.
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The staff wants to identify participants for ISAP II starting in 1988.
Potential interest will be assessed on the basis of utility response to the
survey of Enclosure 2. We request your response, indicating positive or
negative interest in participating, within 30 days of the date of this
letter so that the staff may meet its commitment to the Commission to
evaluate industry interest by March 1988. An expression of interest will not
be construed as a licensee commitment to participate. Since the staff is not
seeking a particular cross-section of plants or utilities, it will determine
the participants through further communication with those utilities
expressing interest.
If you have questions regarding the information discussed in this generic
letter, contact Melanie Miller at (301) 492-1281.
This request is covered by Office of Management and Budget Clearance Number
3150-0011 which expires December 31, 1989. Comments on burden and
duplication may be directed to the Office of Management and Budget, Room
3208, New Executive Office Building, Washington, D. C. 20503.
Frank J. Miraglia, Associate Director
for Projects
Office of Nuclear Reactor Regulation
Enclosure:
As stated
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Enclosure 1
Additional Details on Integrated Safety
Assessment Program II (ISAP)
A probabilistic risk assessment (PRA), operating experience review, and
integrated assessment are the bases of the ISAP II process for determining
ranking, and resolving issues. Licensees may need to perform deterministic
evaluations of those plant issues that cannot be evaluated within the
context of a PRA. The minimum acceptable PRA would be a Level 1 PRA.* The
utility would be expected to periodically update its PRA so that plant
configuration and procedural changes are reflected in a timely manner.
Periodic updates within 2 months of significant changes would be typical.
The process of maintaining a PRA with appropriate management attention would
favorably demonstrate management involvement. For multi-unit sites, the
utility would need to have PRAs that consider the different features of each
unit.
The operating experience review would evaluate total plant operating
experience to determine any particular systematic weaknesses and trends. The
experience review then would be used as a tool against which to compare the
PRA findings and validate their reasonableness. The staff has not yet
determined whether it or licensees will evaluate the operating experience
review to identify trends. However, as part of the PRA, the staff would
anticipate that utilities would make use of plant-specific equipment failure
rates and performance data. The review of this type of information would be
the first step in an operating experience review.
The Level 1 PRA, along with completion of a containment vulnerability
analysis, (or the Level 2 or 3 PRA) would allow a utility to complete its
IPE for that particular facility because, as the Severe Accident Policy
Statement requires, vulnerabilities would be identified and addressed on a
plant-specific basis. For ISAP II participants, these vulnerabilities would
be evaluated and ranked for overall safety significance in order to assume
their appropriate priority as compared to other issues. ISAP II participants
could address these vulnerabilities in the time frame of the IPE response
and would not be penalized for participation in ISAP II by the staff
requiring participants to address the vulnerabilities ahead of the IPE
schedule. Details of how a containment vulnerability analysis should be
performed will be provided in the IPE generic letter.
Issues required by regulation, order, or license condition and items
committed to by the licensee would be included in ISAP II as a minimum. The
utility, at its discretion, also may opt to include its own initiatives in
ISAP II. The benefit of expanding the ISAP II list of issues is that
licensee-initiated items may have a higher safety significance than some
NRC-specified items (and may allow certain items to be deleted from the
licensee's schedule) because of their greater contribution to overall plant
risk reduction. For instance, a
* The PRA levels are defined as follows: Level 1 is the determination of
core melt frequencies based on system and human-factor evaluations; Level 2
is the determination of the physical and chemical phenomena that affect the
performance of the containment and other mitigating features and the
behavior of the fission products within the plant; and Level 3 is the
determination of the offsite transport, deposition, and health effects of
fission product releases.
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licensee could initiate a trip reduction modification that, although riot an
NRC requirement, could significantly reduce plant risk and hence could rank
higher in priority than some NRC items.
ISAP II also would include future issues that would be incorporated into the
process as they arise. Future issues would include new utility and staff
issues and newly resolved generic issues. The staff would not require ISAP
II participants to address generic issues ahead of the rest of the industry.
Instead, as resolution is achieved, these generic issues will be evaluated
for the specific facility within the overall context of ISAP II.
A tentative schedule for initiation of ISAP II with a given utility is
provided in Table 1. This schedule is subject to charge as the program
evolves. Once the scope of issues to be included in ISAP II has been
determined by the NRC and the licensee, the licensee would evaluate the
issues on an integrated basis, propose resolution of the issue, and place
each issue into one of three categories based on such criteria as safety
significance and contribution to risk reduction, personnel exposure, and
ease of implementation. As a general rule, issues that are ranked highest
should be resolved in approximately one refueling outage, or two at most;
issues ranked in the middle should be resolved in two to four refueling
outages; issues ranked lowest may be deferred to four refueling outages and
may be considered for dropping from the utility's schedule. The specific
ranking criteria would be developed by each utility.
The licensee then submits its evaluation, solution, and ranking of each
issue to the NRC for review. Following resolution of staff comments, the
staff will issue an Integrated Safety Assessment Report (ISAR) documenting
the agreed-upon resolution of each issue. in the pilot ISAP, this document
was a draft ISAR that was circulated for peer review ana ACRS comments. In
ISAP II, the staff will issue only a final ISAR. The draft ISARs for
Millstone Unit 1 and Haddam Neck are NUREG-1184 dated April 1987 and
NUREG-1185 dated July 1987, respectively. Following issuance of the ISAR,
the staff and licensee will negotiate an integrated schedule detailing
milestones and completion dates for each issue or decide whether an issue
should be dropped.
To instill a certain amount of rigor to the process, the staff would require
that the operating license be amended to include ISAP II by, at a minimum,
outlining the process for modifying accepted schedules. The staff also may
opt to include the schedule for significant items in the license condition.
The staff will work closely with the licensee prior to license amendment
submittal to develop an acceptable application. The need to revise the
integrated schedule would likely be evaluated following each outage as an
integral part of the preparation for the subsequent outage. Justification
for schedule changes would include newly identified issues by the staff or
licensee, chances in NRC regulations, modifications in the scope of
scheduled work, and delivery or procurement problems. The staff envisions a
certain category of items for which staff approval is not required to change
schedules as long as the schedules of significant issues are not negatively
impacted. However, if the staff or licensee determines that prompt action is
required on an ISAP issue to protect public health and safety, the action
must be taken on an accelerated schedule consistent with the items newly
identified safety significance.
