[Federal Register Volume 60, Number 49 (Tuesday, March 14, 1995)]
[Notices]
[Pages 13738-13739]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 95-6205]



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NUCLEAR REGULATORY COMMISSION
[Docket No. 50-413]


Duke Power Company, et al. (Catawba Nuclear Station, Unit No. 1); 
Exemption

I

    The Duke Power Company, et al. (DPC or the licensee) is the holder 
of Facility Operating License No. NPF-35, which authorizes operation of 
the Catawba Nuclear Station, Unit No. 1 (the facility), 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 York County, South Carolina. The license provides, among other 
things, that the Catawba Nuclear 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 service 
period of the primary containment. The third test of each set shall be 
conducted when the plant is shut down for a 10-year inservice 
inspection of the primary containment.

III

    By letters dated October 18, 1994, and February 7, 1995, the 
licensee 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 a one-time interval extension of the third Type 
A test by approximately 16 months (from the 1995 refueling outage, 
which began on February 11, 1995, to the end-of-cycle 9 (EOC-9) 
refueling outage, currently scheduled for June 1996) and would permit 
the third Type A test of the second 10-year inservice inspection period 
to not correspond with the end of the current inservice inspection 
interval.
    The licensee's request concluded that the proposed change, a one-
time extension of the interval between the second and third ILRTs at 
Catawba Unit 1, is justified for the following reasons:
    The previous testing history at Catawba Unit 1 provides substantial 
justification for the proposed test interval extension. In each of the 
two previous periodic ILRTs at Catawba Unit 1, the as-found leakage was 
less than or equal to 22.5% of the allowable leakage, thereby 
demonstrating that Catawba Unit 1 is a low-leakage containment. There 
are no mechanisms which would adversely affect the structural integrity 
of the containment, or that would be a factor in extending the test 
interval by 20 months. However, as a preventative maintenance measure, 
a containment civil inspection, currently required by Appendix J prior 
to a Type A test, will be performed during EOC-8 to verify that no 
structural degradation exists. Any additional risk created by the 
longer interval between ILRTs is considered to be negligible, primarily 
because Type B and C testing will continue unchanged.
    Additionally, the licensee stated that its exemption request meets 
the requirements of 10 CFR 50.12, paragraphs (a)(1) and (a)(2)(ii), for 
the following reasons:

    In order to justify the granting of an exemption to the 
requirements of 10 CFR Part 50, paragraph 50.12(a)(1) requires that 
the licensee show that the proposed exemption will not pose an undue 
risk to the public. That this proposed change will not pose an undue 
risk is demonstrated by the analysis presented in draft NUREG-1493, 
which concludes that an increase in the test interval to once every 
20 years would ``lead to an imperceptible increase in risk.'' The 
analyses in draft NUREG-1493 are considered to be specifically 
applicable to Catawba because: (1) The requested exemption would 
result in a one-time increase in the test interval to 5 years, not 
20; (2) the population density around Catawba is less than that used 
in the study (329 people per square mile, vs. 340 used in the study; 
(3) no ILRT at Catawba has jailed; (4) the core inventory used in 
the study was represented by a 3412 Mwt PWR [pressurized water 
reactor]. Catawba is a 3411 Mwt PWR. Other factors which lead to the 
conclusion that the proposed change will not pose an undue risk 
include the fact that local leak rate testing, which identifies 97% 
of leakage in excess of prescribed limits, will remain in place at 
its current test frequency; the detailed, proceduralize containment 
civil inspection which is normally performed in conjunction with an 
ILRT will be performed in place of the scheduled ILRT, to identify 
potential structural deteriorations; and the historical leak-
tightness of the containment structure, as evidenced by two 
successive ILRTs in which the as-found leakage did not exceed 22.5% 
of the allowable leakage rate.
    A comparison was made between the risk analysis presented in 
draft NUREG-1493 and a probabilistic risk assessment performed for 
Catawba Nuclear Station. While the quantitative results of the NUREG 
are not directly applicable to plants not used in the study, similar 
conclusions can be made concerning Catawba. NUREG-1493 indicates 
that reactor accident risks are dominated by accident sequences that 
result in failure or bypass of the containment. This conclusion is 
also valid for Catawba. Considering only the Catawba accident 
sequences that do not result in containment failure, containment 
leakage contributes approximately 0.08 to 0.09 percent to off-site 
risk (whole-body person-rem, thyroid nodules, and latent 
fatalities). NUREG-1493 indicated that containment leakage 
contributed from 0.02 to 0.10 percent to latent cancer risk. The 
comparison between the analysis of NUREG-1493 and the Catawba PRA 
concludes that increases in containment leakage at Catawba are 
expected to produce increases in accident risk similar to the 
results in NUREG-1493.
    Special circumstances, as defined in 10 CFR [50].12(a)(2)(ii), 
are present in that the requirement to perform the third ILRT during 
the ISI outage is not necessary to achieve the underlying purpose of 
the rule. The purposes of the rule, as stated in Section I of 
Appendix J, are to ensure that: (a) Leakage through the primary 
reactor containment and systems and components penetrating 
containment shall not exceed allowable values, and (b) periodic 
surveillance of reactor containment penetrations and isolation 
valves is performed so that proper maintenance and repairs are made. 
One of the significant factors in assuring that the proposed 
exemption will not pose an undue risk to the public, as noted above, 
is the local leak rate testing (LLRT) which is performed. That the 
LLRT program at Catawba provides an effective mechanism for 
maintaining containment integrity is perhaps best demonstrated by 
the fact that the most recent ILRT at Catawba Unit 1 was performed 
at the front end of the refueling outage; before any repairs or 
adjustments were made to valves or penetrations. Nevertheless, the 
as-found leakage did not exceed 22.5% of the allowable leakage rate. 
The fact that no leakage paths were identified by an ILRT, and that 
the ILRT met the acceptance criteria with significant margin 
confirms the results of the Type B and C testing.
    The frequency and scope of the Type B and C LLRT program are not 
being changed by this exemption request. The LLRT program 
[[Page 13739]] will continue to effectively detect containment 
leakage resulting from the degradation of active containment 
isolation components, as well as containment penetrations. 
Administrative limits have been established for each Type B or C 
component at a fraction of the allowable leak rate, such that any 
leakage detected in excess of the administrative limit will indicate 
a potential valve or penetration degradation. In instances in which 
a component's leakage exceeds its administrative limit, 
proceduralized controls in the test program require that a work 
order be written to repair the component.

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 Type A test by 
approximately 16 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 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. The NRC staff has 
noted that the licensee has a good record of ensuring a leak tight 
containment. 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 licenses has stated that it will continue to perform the 
general containment civil inspection although it is only required by 
Appendix J (Section V.A.) to be performed 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.
    The NRC staff has also made use of 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 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% of all failures This study agrees with previous NRC staff studies 
which show that Type B and C testing can detect a very large percentage 
of containment leaks. the Catawba Unit 1 experience has also been 
consistent with this.
    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 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).
    Based on generic and plant-specific data, the NRC staff finds the 
licensee's proposed one-time exemption to permit a schedular extension 
of one cycle for the performance of the Appendix Type A test 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 CFR 11125).
    This exemption is effective upon issuance and shall expire at the 
completion of the 1996 refueling outage.

    Dated at Rockville, Maryland, this 7th day of March 1995.

    For the Nuclear Regulatory Commission.
John A. Zwolinski,
Acting Director, Division of Reactor Projects -- I/II, Office of 
Nuclear Reactor Regulation.
[FR Doc. 95-6205 Filed 3-13-95; 8:45 am]
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