[Federal Register Volume 60, Number 68 (Monday, April 10, 1995)]
[Notices]
[Pages 18152-18153]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 95-8707]
-----------------------------------------------------------------------
NUCLEAR REGULATORY COMMISSION
[Docket No. 50-318]
Exemption
In the matter of Baltimore Gas and Electric Comp. (Calvert
Cliffs Nuclear Power Plant Unit No. 2).
I
Baltimore Gas and Electric Company (BG&E or the licensee) is the
holder of Facility Operating License No. DPR-69, which authorizes
operation of Calvert Cliffs Nuclear Power Plant Unit No. 2 (the
facility/CC-2), at a steady-state reactor power level not in excess of
2700 megawatts thermal. The facility is a pressurized water reactor
located at the licensee's site in Calvert County, Maryland. 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.1.(a) of appendix J to 10 CFR part 50 requires the
performance of three Type A containment integrated leakage rate tests
(ILRTs), 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 of the primary containment.
III
By letter dated February 24, 1995, BG&E requested temporary relief
for
CC-2 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 a one-time
interval extension of the second Type A test by approximately 24 months
(from the 1995 refueling outage, currently scheduled to begin in March
1995, to the spring 1997 refueling outage) and would permit the third
Type A test to be performed during the spring 1999 refueling outage,
coincident with the end of the current American Society of Mechanical
Engineers Boiler and Pressure Vessel Code (ASME Code) inservice
inspection interval. This would extend the CC-2 second 10-year service
period to 12 years.
The licensee's request cites the special circumstance of 10 CFR
50.12, paragraph (a)(2)(ii), as the basis for the exemption. The
existing Type B and C testing programs are not being modified by this
request and will continue to effectively detect containment leakage
caused by the degradation of active containment isolation components as
well as containment penetrations. The licensee has analyzed the results
of the previous Type A tests performed at CC-2. Four Type A tests have
been conducted from 1979 to date. The initial Type A test failed;
however, prompt corrective actions were taken and the subsequent tests
were successful as detailed in Section IV of this Exemption. It is also
noted that the licensee, as a condition of the proposed exemption, will
perform the visual containment inspection although it is only required
by Appendix J to be conducted in conjunction with 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. Therefore, application of the
regulation in this particular circumstance is not necessary to achieve
the underlying purpose of the rule.
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 service period.
The licensee proposes an exemption to this section which would
provide a one-time interval extension for the second Type A test by
approximately 24 months. This would permit the test to be performed
during the spring 1997 refueling outage, as noted above, and would
extend the second 10-year service period to 12 years. The Commission
has determined, for the reasons discussed below, 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
[[Page 18153]] 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 the licensee
in the exemption request.
As previously noted, the initial Type A test failed. This failure
was due to three sources: (1) The containment recirculation sump
isolation valve, MOV-4145; (2) the temporary level indicators on the
steam generators; and (3) the packing gland of a main steam line
inboard vent valve. The first leakage source was identified as a
problem with the limit switch setting on MOV-4145 that prevented full
closure. Resetting the switches and closing the valve electrically
corrected the source of leakage. This valve is now tested periodically
to ensure the limit switch settings allow full closure, and the value
has not demonstrated excessive leakage in any subsequent Type A test.
The temporary level indicators, are components which are only in place
while the plant is shutdown. Upon identification of the leakage path,
the temporary configuration was isolated and has not resulted in any
further leakage. The third component condition which led to an
excessive leakage rate during this test was attributed to a packing
failure in the main steam inboard vent valves. This condition was
corrected by backseating the vent valves to eliminate leakage. In a
subsequent refueling outage, the vent valves were removed and the
connection was sealed with blind flanges. Following the licensee's
prompt identification and corrective actions, three additional Type A
tests have been successful and have demonstrated a good containment
performance. Thus, the Type A test results only confirm the results of
the Type B and C test results. The NRC staff has noted that the
licensee has a good record of ensuring a leak-tight containment. Since
the first failure, all Type A tests have passed with significant margin
and the licensee 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.
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 test (Type B and C). According to results given
in NUREG-1493, out of 180 ILRT 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. This is 3
percent of all failures. 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 CC-2 experience has also been
consistent with these results as previously noted.
The Nuclear Management and Resources Council (NUMARC), now the
Nuclear Energy Institute (NEI), collected and 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
1.0La. 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 allowage 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 CC-2 would result in significant degradation of the
overall containment integrity. As a result, the application of the
regulation of 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 the licensee's proposed exemption to allow a one-time
exemption to permit a schedular extension for CC-2 of one cycle (24
months) for the performance of the appendix J, Type A test, and to
permit the third Type A test to be performed during the spring 1999
refueling which extends the second 10-year service period to 12 years
to be acceptable. As a condition for granting this exemption, the
licensee will perform visual containment inspections.
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 14979).
This Exemption is effective upon issuance and shall expire at the
completion of the 1997 refueling outage.
Dated at Rockville, Maryland, this 3rd day of April 1995.
For the Nuclear Regulatory Commission.
Steven A. Varga,
Director, Division of Reactor Projects--I/II, Office of Nuclear Reactor
Regulation.
[FR Doc. 95-8707 Filed 4-7-95; 8:45 am]
BILLING CODE 7590-01-M
