[Federal Register Volume 60, Number 105 (Thursday, June 1, 1995)]
[Notices]
[Pages 28633-28634]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 95-13357]
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NUCLEAR REGULATORY COMMISSION
[Docket No. 50-443 (License No. NPF-86)]
Exemption
In the Matter of North Atlantic Energy Service Corporation
(Seabrook Station, Unit No. 1).
I
North Atlantic Energy Service Corporation (North Atlantic or the
licensee) is the holder of Facility Operating License No. NPF-86, which
authorizes operation of Seabrook Station, Unit No. 1 (the facility or
Seabrook), at a steady-state reactor power level not in excess of 3411
megawatts thermal. The facility is a pressurized water reactor located
at the licensee's site in Rockingham County, New Hampshire. The license
provides among other things, that it is subject to all rules,
regulations, and Orders of the U.S. Nuclear Regulatory Commission (the
Commission or NRC) now or hereafter in effect.
II
Section III.D.I.(a) of Appendix J to 10 CFR Part 50 requires the
performance of three Type A containment integrated leakage rate tests
(ILTRs) at approximately equal intervals during each 10-year service
period of the primary containment. The third test of each set shall be
conducted when the plant is shutdown for the 10-year inservice
inspection.
III
By letter dated February 17, 1995, North Atlantic requested
temporary relief from the requirement to perform a set of three Type A
tests at approximately equal intervals during each 10-year service
period of the primary containment. The requested exemption would permit
delaying performance of the of the second Type A test by approximately
22 months (from the 1995 refueling outage currently scheduled to being
November 4, 1995, to the 1997 refueling outage projected to start
September 1997). The last Type A test was completed October 30, 1992.
Thus, if the next Type A test is delayed until the 1997 refueling
outrage, the interval between tests will be 59 months.
North Atlantic's request cites the special circumstances provision
of 10 CFR 50.12, paragraph (a)(2)(ii), as the basis for the exemption.
North Atlantic notes that the existing Type B and C testing programs
are not being modified by its request and that these testing programs
will continue to detect effectively containment leakage caused by the
degradation of active containment isolation components as well as
containment penetrations. It has been the consistent and uniform
experience at Seabrook during the three Type A tests conducted from
1986 to date, that any significant containment leakage paths are
detected by the Type B and C testing. The Type A test results have been
only confirmatory of the results of the Type B and C tests results.
Therefore, application of the regulation in this particular
circumstances would not serve, nor is it necessary to achieve the
underlying purpose of the rule.
Additionally, North Atlantic stated that the exemption request
meets the requirements of 10 CFR 50.12, paragraphs (a)(1) and
(a)(2)(ii), for the following reasons:
Based on the excellent performance of the Appendix J Type
B and C test program and companion programs, the exemption would not
result in undue risk to the health and safety of the public.
The Type A test results demonstrate that Seabrook has a
low-leakage containment. Three Type A tests have been performed at
Seabrook without a single test failure, and the highest [as-found]
leakage rate of 0.07092 percent per day is well below the acceptance
limit of 0.1125 percent per day and the design limit of 0.15 percent
per day.
An assessment of the risk-impact of the exemption
concludes that there would be no undue risk to the public health and
safety as a result of the proposed schedular extension of the Type A
test.
Resources now being expended on meeting the requirements
of Appendix J for the fourth refueling outage Type A test could be
better utilized to prepare for and execute other functions with a
higher impact on safety during the remainder of Cycle 4 and during the
refueling outage.
The proposed exemption only extends the ILRT from the
fourth refueling outage to the fifth refueling outage. North Atlantic
is requesting a one time exemption from Section III.D.1(a) of Appendix
J that refers to performing ILRTs ``* * * at approximately equal
intervals'' during each 10-year service period.
IV
Section III.D.1.(a) of Appendix J to 10 CFR part 50 states that a
set of three Type A leakage rate tests shall be performed at
approximately equal intervals during each 10-year period.
North Atlantic has proposed an exemption to this section which
would provide a one-time interval extension for the second Type A test
in the current 10-year service period by approximately 22 months.
The Commission has determined that pursuant to 10 CFR 50.12(a)(1)
this exemption is authorized by law, will not present an undue risk to
the public health and safety, and is consistent with the common defense
and security. The Commission further determines that special
circumstances, as provided in 10 CFR 50.12(a)(2)(ii), are present
justifying the exemption; namely, that application of the regulation in
the particular circumstances is not necessary to achieve the underlying
purpose of the rule.
The underlying purpose of the requirement to perform Type A
containment leak rate tests at intervals during the 10-year service
period is to ensure that any potential leakage pathways through the
containment boundary are identified within a time span that prevents
significant degradation from continuing or becoming unknown. The NRC
staff has reviewed the basis and supporting information provided by
North Atlantic in the exemption request. The NRC staff has noted that
North Atlantic has a good record of ensuring a leak-tight containment.
All Type A tests have passed with significant margin and North Atlantic
has noted that the results of the Type A testing have been confirmatory
of the Type B and C tests which will continue to be performed. North
Atlantic also has committed to perform, notwithstanding the granting of
the proposed exemption, a general inspection of the containment and
containment enclosure during the fourth refueling outage even though
such an inspection is required by Appendix J, Section V.A. and the
Seabrook Appendix A Technical Specifications to be performed only prior
to Type A tests. The NRC staff considers that these inspections, though
limited in scope, provide an important added level of confidence in the
continued integrity of the containment boundary.
The licensee performed a risk analysis which demonstrates that the
extension in the Type A test interval would result in a negligible
increase in risk. These results are consistent with calculations
performed for EPRI (as reported in EPRI [[Page 28634]] TR-104285,
``Risk Impact Assessment of Revised Leak Rate Testing Intervals, August
1994) and the staff study reported in NUREG-1493, ``Performance-Based
Containment Leak Test Program.''
the NRC staff has also made use of the information in a draft staff
report, NUREG-1493, which provides the technical justification for the
present Appendix J rulemaking effort which also includes a 10-year test
interval for Type A tests. The integrated leakage rate test, or Type A
test, measures overall containment leakage. However, operating
experience with all types of containments used in this country
demonstrates that essentially all containment leakage can be detected
by local leakage rate tests (Type B and C). According to results given
in NUREG-1493, out of 180 ILRT failure reports covering 110 individual
reactors and approximately 770 years of operating history, only 5 ILRT
failures were found which local leakage rate testing could not detect.
Thus, Type A testing detected failures not discovered by Type B and C
testing in about 3% of the tests, and in these tests the actual leakage
rates were only marginally in excess of leak-tightness requirements.
This study agrees well with previous NRC staff studies which show that
Type B and C testing can detect a very large percentage of containment
leaks.
The Nuclear Management and Resources Council (NUMARC), now known as
the Nuclear Energy Institute (NEI), provided the NRC staff with
summaries of data to assist in the Appendix J rulemaking effort. NUMARC
collected results of 144 ILRTs from 33 units; 23 ILRTs exceeded
1.OLa. Of these, only nine were not due to Type B or C leakage
penalties. The NEI data also added another perspective. The NEI data
show that in about one-third of the cases exceeding allowable leakage,
the as-found leakage was less than 2La; in one case the leakage
was found to be approximately 2La; in one case the as-found
leakage was less than 3La; one case approached 10La; and in
one case the leakage was found to be approximately 21La. For about
half of the failed ILRTs the as-found leakage was not quantified. These
data show that, for those ILRTs for which the leakage was quantified,
the leakage values are small in comparison to the leakage value at
which the risk to the public starts to increase over the value of risk
corresponding to La (approximately 200La, as discussed in
NUREG-1493). Therefore, based on these considerations, it is unlikely
that an extension of one cycle for the performance of the Appendix J,
Type A test at Seabrook would result in significant degradation of the
overall containment integrity. As a result, the application of the
regulation in these particular circumstances is not necessary to
achieve the underlying purpose of the rule.
Based on generic and plant specific data, the NRC staff finds the
basis for North Atlantic's proposed exemption to allow a one-time
exemption to permit a schedular extension of one cycle for the
performance of the Appendix J Type A test to be acceptable provided
that the general containment inspection is performed.
Pursuant to 10 CFR 51.32, the Commission has determined that
granting this Exemption will not have a significant impact on the
environment (60 FR 27569).
This Exemption is effective upon issuance and shall expire at the
completion of the fifth refueling outage, presently expected to start
in September 1997.
Dated at Rockville, Maryland, this 25th day of May 1995.
For the Nuclear Regulatory Commission.
John A. Zwolinski,
Acting Director, Division of Reactor Projects--I/II, Office of Nuclear
Reactor Regulation.
[FR Doc. 95-13357 Filed 5-31-95; 8:45 am]
BILLING CODE 7590-01-M
