ML17332A843
| ML17332A843 | |
| Person / Time | |
|---|---|
| Site: | Cook  |
| Issue date: | 07/06/1995 |
| From: | Capra R NRC (Affiliation Not Assigned) |
| To: | INDIANA MICHIGAN POWER CO. (FORMERLY INDIANA & MICHIG |
| Shared Package | |
| ML17332A844 | List: |
| References | |
| NUDOCS 9507140144 | |
| Download: ML17332A843 (7) | |
Text
~ Q UNITED STATES OF AMERICA NUCLEAR REGULATORY COMMISSION In the Matter of
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)
Indiana Michigan Power Company
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)
(D.C.
Cook Nuclear Plant, Unit 1)
)
Docket No. 50-315 EXEMPTION Indiana Michigan Power Company (IMPCo, the licensee) is the holder of Facility Operating License No.
DPR-58 which authorizes operation of the Donald C.
Cook Unit 1 Nuclear Plant at steady-state reactor power levels not in excess of 3250 megawatts thermal.
The Cook 1 facility is a pressurized water reactor located at the licensee's site in Berrien County, Michigan.
The license provides, among other things, that the facility is subject to all rules, regulations, and orders of the Nuclear Regulatory Commission (the Commission) now or hereafter in effect.
Pursuant to 10 CFR 50. 12(a),
the NRC may grant exemptions from the requirements of the regulations (1) which are authorized by law, will not present an undue risk to the public health and safety, and are consistent with the common defense and security; and (2) where special circumstances are present.
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 9507i40i44 950706 PDR ADGCK 050003i5 P
PDR plant is shut down for the 10-year inservice inspection required by 10 CFR 50.55a.
By letter dated Harch 17,
- 1995, IHPCo 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, currently scheduled to begin in September 1995, to the 1997 refueling outage) 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 American Society of Hechanical Engineers Boiler and Pressure Vessel Code (ASHE Code) inservice inspection interval.
The licensee's request cites the special circumstances of 10 CFR 50. 12, paragraph (a)(2)(ii), as the basis for the exemption.
In addition, the licensee states that the exemption would eliminate a cost of $ 130,000 for the Type A test which is not necessary to achieve the underlying purpose of the rule.
10 CFR Part 50 Appendix J, states that the purpose of the Type A, B, and C tests is to assure that leakage through the primary containment shall not exceed the allowable leakage rate values as specified in the technical specifications or associated bases.
IHPCo points out that 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.
It has been the experience at the D.
C.
Cook Plant that during the six Type A tests conducted from 1974 to date, any significant containment leakage paths are detected by the Type 8 and C testing.
The Type A test results have only been confirmatory of the results of the Type 8 and C test results.
The testing history, structural capability of the containment, and the risk assessment establish that there is significant assurance that the extended interval between Type A tests will not adversely impact the leak-tight integrity of the containment and that performance of the Type A test is not necessary to meet the underlying purpose of Appendix J.
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 20 months.
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 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.
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.
The licensee notes 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 licensee has stated that it will perform the general containment inspection although it is required by Appendix J (Section V.A.) to be performed only 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 Cook containment structure consists of a reinforced concrete cylindrical structure with a hemispherical dome.
The interior of the containment has a welded steel liner, with a minimum thickness of 3/8 inch at the dome and wall and 1/4 inch at the bottom, which is attached to the inside face of the concrete shell to ensure a high degree of leak tightness.
The NRC staff has also made use of the information in a draft staff
- report, NUREG-1493, "Performance-Based Containment Leak-Test Program," 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 Local Leak 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 3X 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 Cook Plant experience has also been consistent with these results.
The Nuclear Hanagement and Resources Council (NUHARC), now the Nuclear Energy institute (NEI), collected and provided the NRC staff with summaries of data to assist in the Appendix J rulemaking effort.
NUHARC collected results of 144 ILRTs from 33 units; 23 ILRTs exceeded 1L,.
Of these, only nine were not 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 2L,; in one case the leakage was found to be approximately 2L,; in one case the as-found leakage was less than 3L,; one case approached 10L,;
and in one case the leakage was found to be approximately 21L,.
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 L, (approximately 200L as discussed in NUREG-'I493).
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 the D. C.
Cook Plant 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.
Therefore, special circumstances exist pursuant to 10 CFR 50.12(a)(2)(ii).
Accordingly, the Commission has determined that, pursuant to 10 CFR 50. 12, this exemption
.as described in Section III above 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
'I 1
special circumstances as provided in 10 CFR 50. 12(a)(2)(ii) are present J
justifying the exemption.
Based on the generic and plant-specific data, the NRC staff finds the basis for the licensee's proposed one'-time'schedular exemption to allow an extension of one cycle for the performance of-th'e Appendix J, Type A test, provided that the general containment inspection is performed, to be acceptable, pursuant to 10 CFR 50. 12(a)(l) and (2).
Pursuant to 10 CFR 51.32, the Commission has determined that granting. this exemption will not have a significant effect on the quality of the human environment (60 FR 32354).
This exemption is effective upon issuance.
Dated at Rockville, Maryland, this 6th day of Ju] y 1995.
FOR THE NUCLEAR REGULATORY COMMISSION Original signed by Robert A. Capra, Acting Dir'ector Division of Reactor Projects III/IV Office of Nuclear Reactor Regulation DOCUMENT NAME G:ItWPDOCS(WPDOCS(DCCOOK'ItC091853.EXH
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