[Federal Register Volume 60, Number 67 (Friday, April 7, 1995)]
[Notices]
[Pages 17829-17831]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 95-8585]



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NUCLEAR REGULATORY COMMISSION

[Docket No. STN 50-528]


Arizona Public Service Company, et al.; (Palo Verde Nuclear 
Generating Station, Unit No. 1), Exemption

I

    The Arizona Public Service Company, et al. (APS or the licensee) is 
the holder of Facility Operating License No. NPF-41, which authorizes 
operation of the Palo Verde Nuclear Generating Station, Unit No. 1 
(PVNGS-1). The license provides, among other things, that PVNGS-1 is 
subject to all rules, regulations, and orders of the U.S. Nuclear 
Regulatory Commission (the Commission or NRC) now or hereafter in 
effect. The PVNGS-1 facility is a pressurized water reactor located at 
the licensee's site in Maricopa County, Arizona.

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 the 10-year inservice 
inspection.

III

    By letter dated December 28, 1994, 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 20 months 
(from the 1995 refueling outage, which begins in May 1995, to the sixth 
refueling outage (1R6), currently scheduled for September 1996) and 
would permit the third Type A test of the 10-year inservice inspection 
period not to correspond with the end of the inservice inspection 
interval.
    The licensee's request concluded that the proposed changes for 
PVNGS-1, a one-time extension of the interval between the second and 
third ILRTs and a decoupling of the third test from the outage 
corresponding to the end of the 10-year inservice inspection period, is 
justified for the following reasons:
    The previous testing history at PVNGS-1 provides substantial 
justification for the proposed test interval extension. Type A testing 
is performed to determine that the total leakage from primary 
containment does not exceed the maximum allowable leakage rate 
(La) as specified in the PVNGS-1 technical specifications (TS). 
The primary containment maximum allowable leakage rate provides an 
input assumption to the calculation required to ensure that the maximum 
potential offsite dose during a design basis accident does not result 
in a dose in excess of that specified in 10 CFR 100. The allowable 
La for PVNGS-1 is 0.10 percent by weight of the containment air 
per 24 hours at Pa, where Pa is defined as the calculated 
peak internal containment pressure related to the design basis 
accident, specified in the PVNGS-1 TS as 49.5 psig. The acceptance 
criteria for the Type A test is 75 percent of La or 0.075 percent 
by weight of the containment air per 24 hours at Pa.
    In each of the two previous periodic ILRTs at PVNGS-1 (the results 
were 0.066 percent and 0.067 percent by weight of the containment air 
per 24 hours at Pa, respectively), the results obtained were below 
the test acceptance criteria of 75 percent of La or 0.075 percent 
by weight of the containment air per 24 hours at Pa, thereby, 
demonstrating that PVNGS-1 is a low-leakage containment.
    The licensee performed a plant-specific study concluding that the 
extension of the Type A test has a negligible impact on overall risk. 
This study relied heavily on the existing Type B and C testing program 
which is not affected by this exemption, and will continue to 
effectively detect containment leakage.
    Additionally, the licensee stated that its exemption request meets 
the requirements of 10 CFR 50.12, paragraphs (a)(2)(ii) (the underlying 
purpose of the regulation is achieved), and (a)(2)(iii) (compliance 
would result in undue hardship or other costs that are significantly in 
excess of those contemplated when the regulation was adopted), for the 
following reasons:
    The licensee categorized mechanisms that could cause degradation of 
the containment into two types: (1) Degradation due to work which is 
performed as part of a modification or maintenance activity on a 
component or system (activity based); or (2) degradation resulting from 
a time based failure mechanism (i.e., deterioration of the containment 
structure due to pressure, temperature, radiation, chemical or other 
such effects). To address the potential degradation due to an activity 
based mechanism, the licensee reviewed containment system related 
modifications performed since the last Type A test. The licensee 
concluded that the modifications performed did not impact containment 
integrity, or the modifications have, or will be, tested adequately to 
ensure that there is no degradation from an activity based mechanism. 
In addition, the licensee maintains administrative controls which 
ensure that an appropriate retest, including local leak rate testing, 
if applicable, is specified for maintenance activities which affect 
primary containment integrity.
    Regarding time based failure mechanisms, the licensee concluded 
that risk of a non-detectable increase in the primary containment 
leakage is considered negligible due to the 10 CFR Part 50, Appendix J, 
Type B and C testing program. The licensee stated that without actual 
accident conditions, structural deterioration is a gradual phenomenon 
which requires periods of time well in excess of the proposed 81-month 
test interval which would result by performing the third periodic Type 
A test during the sixth refueling outage in Unit 1. Other than accident 
conditions, the only external mechanism inducing stress of the 
containment structure is the test itself. The licensee maintains that 
the longer test interval would, therefore, lessen the frequency of 
stressing the containment.
    Additionally, the licensee has performed the general inspections of 
the accessible interior and exterior surfaces of the containment 
structures and components prior to the previous Type A tests, as 
required by 10 CFR Part 50, Appendix J, Section V.A. These inspections 
are intended to uncover any evidence of structural deterioration which 
may affect either the containment structural integrity or leak 
tightness. At PVNGS-1, there has been no evidence of structural 
deterioration that would impact structural integrity or leak tightness. 
In a phone conversation with the licensee on March 23, 1995, the staff 
noted that these inspections, though limited in scope, provide an 
important added level of confidence. The licensee committed to perform 
the general containment civil inspection during the upcoming refueling 
outage (1R5).
    The 10 CFR Part 50, Appendix J, Type B tests are intended to detect 
local leaks and to measure leakage across pressure containing or 
leakage limiting-boundaries other than valves, such as containment 
penetrations incorporating [[Page 17830]] resilient seals, gaskets, 
doors, hatches, etc. The 10 CFR Part 50, Appendix J, Type C tests are 
intended to measure reactor system primary containment isolation valve 
leakage rates. The frequency and scope of Type B and C testing is not 
being altered by this proposed exemption request. The acceptance 
criterion for Type B and C testing is 0.6 La. This acceptance 
criterion is for the sum of all valves and penetrations subject to Type 
B and C testing and represents a considerable portion of the Type A 
test allowable leakage. The results of the as-left combined Type B and 
C leakage measured since the last Unit 1 Type A test are 0.054 La, 
0.06 La, and 0.13 La (for the February 1991, May 1992, and 
November 1993 outages, respectively). The licensee maintains that these 
test results are substantially below the acceptance criterion of 0.60 
La and demonstrate a good historic performance of containment 
integrity.
    The proposed schedular exemption would allow the third Type A 
leakage rate test in Unit 1 to be performed during the Fall 1996 (IR6) 
refueling outage, which meets the 10 CFR Part 50, Appendix J, 
requirement of performing three tests in a 10-year time period. The 
performance of a fourth Type A test during the Unit 1 seventh refueling 
outage, in order to coincide with the outage at the completion of the 
extended 10-year ISI interval, is not deemed to be appropriate, as it 
would result in additional radiation exposure to personnel, increased 
length of the refueling outage and significant additional cost. 
Omitting the test will result in dose savings by eliminating 
contamination and by reducing radiation exposure from the venting and 
draining of piping penetrations necessary to establish the appropriate 
test conditions. There would also be dose savings from eliminating the 
need to install and remove the temporary instrumentation necessary to 
perform the Type A test. Performing a fourth Type A test would also 
increase the duration of the affected outage by approximately 3 days 
and result in additional costs associated with this increase.
    A PVNGS-1 plant-specific analysis was performed to evaluate the 
potential for extending the Type A test frequency. The PVNGS-1 plant-
specific analysis considered the extension of the interval to as much 
as 240 months. The conclusion of the analysis was that the extension of 
the Type A test interval has a negligible impact on overall risk. The 
licensee's exemption request does not alter the frequency for 
performance of Type A testing (i.e., it still maintains a frequency of 
3 tests per 10 years). However, the licensee maintains that the data 
from this study support the requested exemption from the requirement of 
10 CFR Part 50, Appendix J, regarding ``approximately equal 
intervals.'' The interval between the second and third Type A tests 
would be 81 months with this exemption. The PVNGS-1 plant-specific 
analysis supports the use of a 240-month interval with a negligible 
impact on overall risk.
    The licensee referenced 10 CFR 50.12(a)(2)(ii) as a basis for this 
exemption. This section defines such a circumstance where ``application 
of the regulation in the particular circumstances would not serve the 
underlying purpose of the rule or is not necessary to achieve the 
underlying purpose of the rule * * *.'' The underlying purpose of 10 
CFR Part 50, Appendix J, Section III.D.1.(a), is to establish and 
maintain a level of confidence that any primary containment leakage, 
during a hypothetical design basis accident, will remain less than or 
equal to the maximum allowable value, La, by performing periodic 
Type A testing. Compliance with the ``approximately equal intervals'' 
clause of Appendix J is not necessary to achieve the underlying purpose 
of the rule, as explained in the above technical justification.
    The licensee also referenced 10 CFR 50.12(a)(2)(iii) in its 
submittal, which states the NRC may grant exemptions from requirements 
of 10 CFR Part 50 when ``compliance would result in undue hardship or 
other costs that are significantly in excess of those contemplated when 
the regulation was adopted, or that are significantly in excess of 
those incurred by others similarly situated * * *.'' The current PVNGS-
1 Type A test schedule would require that four Type A tests be 
performed in an extended ISI interval. This current schedule would 
result in unnecessary additional radiation exposure in order to perform 
the test and unnecessary costs associated with the performance of the 
test and the costs associated with the increase in the length of the 
refueling outage. Regarding the impact of this exemption on overall 
risk, it is the staff's experience that risk is insensitive to the Type 
A test frequency at values of leakage close to La. Therefore, 
while the staff agrees with the licensee's conclusion that the risk 
increase resulting from granting this exemption is small, the time 
interval has no particular significance. Additionally, the staff has 
previously discussed with the licensee that its scheduling of 
containment ILRTs early in the ISI interval is largely responsible for 
the necessity of performing an additional test, and would not 
constitute a hardship that was not anticipated at the time the rule was 
written. Therefore, the staff has reviewed this exemption request 
against the criteria of 10 CFR 50.12(a)(2)(ii).
    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 20 months. Additionally, for schedular reasons, the final 
Type A test of the 10-year inservice inspection period is proposed to 
be decoupled from the requirement to perform it during the same outage 
(the final Type A test would be performed the outage prior (1R6) to the 
end of the inservice inspection period).
    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 adequate margin. The licensee has also 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). Additionally, the 
licensee has committed to perform the general containment civil 
inspection during the upcoming refueling outage (1R5), thereby 
providing an added level of confidence in the continued integrity of 
the containment boundary. [[Page 17831]] 
    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 
three percent 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 PVNGS-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 
1.0 La. 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 2 La; in one case the leakage 
was found to be approximately 2 La; in one case the as-found 
leakage was less then 3 La; one case approached 10 La; and in 
one case the leakage was found to be approximately 21 La. 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 the La (approximately 200 La, 
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, and the 
decoupling of the third test to be performed coincident with the 
completion of the inservice inspection period, 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 16180).
    This exemption is effective upon issuance and shall expire at the 
completion of the 1R7 refueling outage.

    For the Nuclear Regulatory Commission.
    Dated at Rockville, Maryland, this 31st day of March 1995.
Elinor G. Adensam,
Acting Director, Division of Reactor Projects--III/IV, Office of 
Nuclear Reactor Regulation.
[FR Doc. 95-8585 Filed 4-6-95; 8:45 am]
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