[Federal Register Volume 60, Number 137 (Tuesday, July 18, 1995)]
[Notices]
[Pages 36834-36836]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 95-17564]
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NUCLEAR REGULATORY COMMISSION
[Docket No. 50-295]
Commonwealth Edison Co. (Zion Nuclear Power Station, Unit 1);
Exemption
I
Commonwealth Edison Company (ComEd or the licensee) is the holder
of Facility Operating License No. DPR-39, which authorizes operation of
the Zion Nuclear Power Station, Unit 1, at a steady-state reactor power
level not in excess of 3250 megawatts thermal. The facility is a
pressurized water reactor located at the licensee's site in Lake
County, Illinois. The license provides, among other things, that the
Zion Nuclear Power Station 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 inservice
inspection period. Furthermore, the third test of each set is to be
conducted during the shutdown for the 10-year plant inservice
inspections.
III
In a letter dated May 12, 1995, the licensee requested relief from
the requirement to perform a set of three Type A tests at approximately
equal intervals during each 10-year inservice
[[Page 36835]]
inspection period. The requested exemption would permit a one-time
interval extension of the third Type A test of the second 10-year
inservice inspection period by approximately 18 months and would result
in the interval between successive Type A leakage rate tests being
approximately 60 months. If the revised 10 CFR part 50 requirements are
approved and implemented, the next Type A test could be deferred up to
an additional 60 months.
The licensee's request justified the proposed change, on the
following basis.
In the Type A test conducted in the RFO in March 1988, the leakage
rate was below the maximum allowable. In the Type A test conducted
during the RFO in March 1992, after adding all required penalties
associated with local leakage rate tests (LLRTs), the as-found Type A
test result was a failure. However, the majority of the leakage in the
LLRTs was due to a valve in one penetration. Prior to repairing the
valve, a leakage rate that was double the allowed limit was measured.
The licensee's corrective maintenance on the valve and its post-repair
leakage rate testing resulted in a Type A test leakage rate that was
about 20 percent of the allowable limit.
The licensee stated that there are no mechanisms which would
adversely affect the structural integrity of the containment or that
would be a factor in evaluating the extension of the test interval by
18 months. However, as a preventive maintenance measure, the visual
containment inspection currently required by 10 CFR part 50, appendix
J, prior to a Type A test, will be conducted during the September 1995
RFO to verify that there are no apparent signs of containment
degradation and to provide added confidence that the containment
structural integrity was not affected during the period since the last
visual inspection. Any additional risk created by the longer interval
between Type A testing is considered by the licensee to be negligible,
primarily because all Type B and Type C leakage rate testing will
continue to be performed in accordance with the requirements of 10 CFR
part 50, appendix J, Sections III.B and III.C.
To justify granting an exemption to the requirements of 10 CFR Part
50, a licensee must show that the requirements of 10 CFR 50.12(a)(1)
are met. The licensee stated that its exemption request meets the
requirements of 10 CFR 50.12(a)(1), for the following reasons:
(1) The requested one time exemption and the associated
activities are authorized by law.
There are no prohibitions of law which preclude the activities
which would be authorized by the requested exemption. Similar
exemptions have been granted for ComEd's Zion Station and other
utilities. Therefore, the NRC is authorized by law to approve the
proposed exemption.
(2) The requested exemption will not present undue risk to the
public.
An exemption from the requirements of 10 CFR 50 Appendix J to
perform reactor containment leakage testing will not present undue
risk to the health and safety of the public. Past testing has
demonstrated the leak tight nature of the primary reactor
containment structure and systems and components penetrating the
primary containment and the ability to maintain total leakages,
including conservatisms, within required limits. A more detailed
discussion of the past reactor containment integrated leakage rate
test results is included below.
(3) The requested exemption will not endanger the common defense
and security.
The common defense and security are in no way compromised by
this proposed exemption since approval of the exemption would in no
way alter the plant in any physical manner.
In addition, the licensee must show that at least one of the
special circumstances, as defined in 10 CFR 50.12(a)(2), is present.
One of the special circumstances that a licensee may show to exist is
that the application of the regulation in the particular circumstances
is not necessary to achieve the underlying purposes of the rule. The
purposes of the rule, as stated in section I of 10 CFR part 50,
appendix J, are to ensure that: 1) leakage through the primary reactor
containment and systems and components penetrating containment shall
not exceed allowable values, and 2) periodic surveillance of reactor
containment penetrations and isolation valves is performed so that
proper maintenance and repairs are made. The licensee presented the
following discussion to show that the requirement to perform the third
Type A leakage rate test during the September 1995 RFO is not necessary
to achieve the underlying purpose of the rule.
Type A tests are intended to measure the primary reactor
containment overall integrated leakage rate after the containment
has been completed and is ready for operation, and at periodic
intervals. The performance of a periodic ILRT (Type A) and local
penetration tests (Type B and C) during containment life provides a
current assessment of potential leakage from the containment during
accident conditions. The periodic tests are performed at a pressure
sufficiently high to provide an accurate measurement of the leakage
rate. This pressure is at least 50 percent of design accident
pressure for the Type A tests and at least design accident pressure
for the Type B and C tests.
Application of the regulation is not necessary to achieve the
underlying purpose of the rule because:
(1) Prior testing has verified the ability of the reactor
containment to maintain leakage below the limits set forth in the
Technical Specifications and the regulation:
(2) Type B & C testing, which detects the majority of
containment leakage, will continue to be performed as required;
(3) The availability of the seal water and penetration
pressurization systems provides added confidence that leakage would
be maintained below the limits in the unlikely event of a LOCA; and
(4) There is no significant impact on risk to the public
associated with extending the period of time between successive Type
A tests on Unit 1 by approximately 18 months.
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 inservice inspection
period.
The licensee proposes an exemption to this section which would
provide a one-time interval extension for the Type A test of
approximately 18 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 determined, for the reasons
discussed below, 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 leakage rate tests at intervals during the 10-year
inservice inspection period, is to ensure that any potential leakage
pathways through the containment boundary are identified within a time
span that prevents significant degradation from commencing or
continuing without the knowledge of the licensee. The stafff has
reviewed the basis and supporting information provided by the licensee
in the exemption request and considers that the licensee has a good
record of ensuring a leak-tight containment. The one Type A test that
did not pass was shown to be due to a leaking valve. The licensee took
aggressive and appropriate corrective action that resulted in a final
as-left leakage rate that was significantly below the maximum allowable
value. Therefore, the containment was shown to be leak tight, the
licensee demonstrated that it has an effective
[[Page 36836]]
corrective action program and the results of the Type A test were
confirmatory of the Type B and Type C tests rather than providing
information that would otherwise not have been available. The licensee
has stated that the visual containment inspection will be performed
during the September 1995 RFO although it is only required by 10 CFR
part 50, appendix J, to be performed in conjunction with Type A tests.
The staff considers that these inspections, though limited in scope,
provide an important added level of confidence in the continued
structural integrity of the containment boundary.
The staff has also made use of the information in a draft stafff
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 ILRT, 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 LLRT (Type B and Type 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 five ILRT failures were found which local
leakage rate testing could not detect. This is 3 percent of all
failures. This study agrees with previous staff studies which show that
Type B and Type C testing detect a very large percentage of containment
leaks. The Zion Station, Unit 1, experience has also been consistent
with these results.
The Nuclear Management and Resources Council (NUMARC), now the
Nuclear Energy Institute (NEI), collected and provided the staff with
summaries of data to assist in the 10 CFR part 50, appendix J,
rulemaking effort. The NEI collected results of 144 ILRTs from 33 units
of which 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 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 qualified. These data show that, for those ILRTs
for which the leakage was quantified, the leakage values are small when
compared 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 18 months for the
performance of the appendix J, type A tests at Zion would result in
significant degradation of the overall containment integrity. Thus, 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 staff finds the
licensee's proposed one-time exemption to permit a schedular extension
of one cycle for the performance of the 10 CFR part 50, appendix J,
type A test, provided that the visual containment inspection is
performed, to be acceptable.
Pursuant to 10 CFR 51.32, the Commission has determined that
granting this exemption will not have a significant impact on the human
environment (60 FR 34305).
This exemption is effective upon issuance and shall expire at the
completion of the Type A test scheduled to be performed during the
March 1997 refueling outage.
Dated at Rockville, Maryland this 12th day of July 1995.
For the Nuclear Regulatory Commission.
Jack W. Roe,
Director, Division of Reactor Projects--III/IV, Office of Nuclear
Reactor Regulation.
[FR Doc. 95-17564 Filed 7-17-95; 8:45 am]
BILLING CODE 7590-01-M
