ML20209G837
| ML20209G837 | |
| Person / Time | |
|---|---|
| Site: | Duane Arnold  |
| Issue date: | 01/30/1987 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20209G830 | List: |
| References | |
| NUDOCS 8702050473 | |
| Download: ML20209G837 (6) | |
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UNITED STATES y
g NUCLEAR REGULATORY COMMISSION g
E WASmNGTON, D. C. 20555
\\.....J SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SUPPORTING AMENDMENT NO. 140 TO FACILITY OPERATING LICENSE NO. DPR-49 IOWA ELECTRIC LIGHT AND POWER COMPANY CENTPAL IOWA POWER COOPERATIVE CORN BELT POWER COOPERATIVE DUANE ARNOLD ENERGY CENTER DOCKET NO. 50-331
1.0 INTRODUCTION
By letter dated November 14, 1986 as clarified by a letter dated Ja'nuary 2,1987, the Iowa Electric Light and Power Company (IELP/ licensee) requested a revision to the Technical Specifications (TS) for the Duane Arnold Energy Center (DAEC). The proposed change will permit DAEC to extend by approximately 10 weeks the surveillance test intervals for the functional testing of snubbers, the local leak rate testing of primary containment isolation valves and penetrations, and for the replacement of the T-ring seals in the primary containment purge and vent valves.
The extensions are reauested on a one-time only basis to prevent a premature reactor shutdown until the cycle 8/9 Refuel Outage, and the potential need for a similar extension to reach the scheduled September 1988 Cycle 9/10 Refueling Outage.
2.0 EVALUATION A.
SNUBBER SURVEILLANCE TEST INTERVAL The DAEC was scheduled to shutdown for the Cycle 8/9 Refuel Outage on February 1, 1987.
IELP chose this date to compl Specifications surveillance requirements for (1)y with the Technical the functional testing of snubbers, (2) the 10 CFR 50, Appendix J Type B and C local leak rate testing of primary containment penetrations and isolation valves, and (3) the replacement of the T-ring seals in the primary containment purge and vent valves. However, the shutdown had to be rescheduled because of the unanticipated extension of the Cycle 7/8 Refueling Outage and other unscheduled shutdowns during the Cycle 8 operation making the target end-of-cycle core exposure unachievable by February 1, 1987. The requested extension is approximately 75 days.
The purpose of functional testing of snubbers is to assure that safety related snubbers will perform their function as designed during dynamic leadings such as those caused by seismic events. The surveillance testing requirement is to test 10% of the safety related snubbers every IS months, and for every inoperable snubber discovered, an additional sample of 5% of the snubbers will be tested. The period of 18 months was selected to match approximately the fuel cycle length and the refueling outage.
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eg, During the < Cycle 6/7 Outage in spring 1983, 100% of the safety-related snubbers in DAEC were replaced or refurbished. Since then, only one inoperable snubber was detected by all functional tests and visual inspections. The inoperability was found in a mechanical snubber located on the reactor head spray line and was caused by dried lubricant due to high ambient temperature. This deficiency was corrected by removing the lubricant, which is not required for proper operation of the snubber. Also, lubricant was removed from another snubber in the same area, precluding a similar failure. However, since analysis indicates that these two snubbers can be replaced by rigid struts, the replacements will be done in the coming refueling outage.
Rased on the good performance record in the past 3 years, it is.iudged that an extension of approximately 75 days will not increase the probability of snubber failures.
In addition, the lubricant in mechanical snubbers in high temperature areas, which was the cause for the only known failure, was removed. The reauest to extend the functional testing period should be granted.
1 B.
LOCAL LEAK RATE TESTING INTERVALS The extension of the leak rate testing interval by the licensee involves tests which must be performed at least every 24 months as indicated in 10 CFR Part 50, Appendix J.
The TS change would extend the 24 month surveillance interval for leakage testing of selected containment penetrations and isolation valves by approximately 10 weeks beyond the time allowed by the TS. This would pennit the licensee to delay performing this testing until a refueling outage which will begin on or about mid-March 1987.
l The unit was originally scheduled to shutdown for its end-of-cycle-8 refuel outage on February 1, 1987. This would have allowed the Appendix J Type B and C testing to be completed during the required two-year interval. A mid-March outage would result in extending the two-year test interval requirement of 10 CFR 50, Appendix J about 45 days. However, to provide a margin for contingencies, the licensee has asked that the TS extension be granted until April 17, 1987 (about 75 days).
Appendix J requires that leakage rate tests for all containment isolation valves and penetrations be performed at a frequency not exceeding 24 months. This is to ensure that primary containment integrity will be maintained during any accident within the design bases.
In their November letter, the licensee requested that the amendment
- cover 144 penetrations and isolation valves, approximately 70% of the total components. After discussions with the staff, the licensee agreed to test all isolation valves that have a leakage history and are capable of being tested at power (letter dated January 2, 1987).
As a result, 18 valves were removed from the licensee's request and will be tested (see Table 11.
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Our review of the leak rate data on the remaining 126 components during 1983 and 1985 outages indicated that their performance has been excellent.
Based on this performance it is believed that the leakage will remain under the TS allowable limit even when their service life is extended 10 weeks beyond the 2 year test interval. The staff, therefore, concludes that the TS change requested by the licensee on those components is acceptable.
The following discussion provides a detailed basis for our conclusion.
Out of 126 components for which the TS amencment applies, 64 involve penetrations. Data supplied by the licensee in a January 2, 1987 letter demonstrated that leakage rates from the penetrations are extremely small. The as-left leakage rate from the tests performed during the 1985 outage totalled approximately 4900 Standard Cubic Centimeters per Minute (sccm).
This value is less than 3% of the TS allowable of 185,221 sccm. Leakage rates from the 1983 outage tests were equally insignificant.
The number of isolation valves requiring the time extension totals 62.
Review of the licensee data indicated that 17 of these valves.had a tested zero leakage rate for the 1985 outage. Tests during the 1983 outage also showed no significant leakage. The combined leakage rate of the 17 valves was 294 sccm and represents less than 0.2% of the TS allowable. They are mostly 3/4" valves on the oxygen analyzer.
Out of the remaining 45 valves, 4 valves are inaccessible for testing during power operation (inside drywell or steam tunnel), 8 valves cannot be isolated because they are essential for power generation,15 valves require entering a TS Limiting Condition for Operation, and 18 valves cannot be tested due to lack of accessibility of the vent valve and test connection. As indicated in the licensee's letter dated January 2,1987, the last measured combined leakage rate from these 45 valves was quite low. Therefore, significant increases would not be expected to result in exceeding the TS limit. The as-left leakage rate of these valves for the 1985 outage totalled 23,000 secm, about 13% of the TS allowable. Thus, leakage through these valves would have to increase many times before a significant portion of the total allowable leakage rate is reached. Combined as-left leakage rate of the entire list of components, some 200 penetrations and valves, at the 1985 outage was only 75,835 sccm (providing close to a 60% margin before reaching the 185,221 sccm TS limit).
Data supplied by the licensee on the 45 valves demonstrated that no such large degradation of valve performance has been seen from previous tests.
Comparison ( f as-found and as-left 1983 outage leakage rates with that of the 1985 outage indicated that the rate of degradation of valve performance (i.e., leakage increase) is stable and predictable. These data provide reasonable assurance that there is adequate margin to accommodate an additional 10 week operation without fear of exceeding the allowable leakage limit. Therefore, containment l
integrity would not be compromised.
. Additionally, after the Local Leak Rate Test (LLRT) was conducted on the last of the affected components during the 1985 outage, the plant remained in a cold shutdown condition for another 12 weeks. Therefore, the actual period of operation will be less than the 2-year maximum allowable interval. This is expected to provide additional assurance that the leakage limit will not be exceeded.
On the bases discussed above, the staff has concluded that the licensee has provided sufficient justification for the one-time extension of the 24 month surveillance interval requirement of Appendix J and the TS change is acceptable.
The one-time extension of the Technical Specification-required surveillance interval for the performance of Type B and C LLRTs applies to 126 components as discussed above and in the licensee's November 14, 1986 and January 2,1987 letters.
There are 64 penetrations,17 small diameter valves and 45 inaccessible or untestable isolation valves. The remaining 18 components listed in Table 1 of this evaluation are to be tested in accordance with 10 CFR 50, Appendix J, requirements.
C.
PURGE AND VENT T-RING SEAL REPLACEMENT The primary containment purge and vent valves have an inflatable T-ring seal which ensures leak tightness of the valve by inflating and thereby pressing the valve disk against the valve seat when the valve is closed. The T-ring seals are made of an ethylene-propylene elastomer, which has an in-service life of 4 years. This 4 year in-service life is based on a consideration of the aging of the material with continued exposure to high temperatures and a radiation environment. The environmental conditions for the aging model consists of 4 continuous years at expected drywell conditions, plus 30 days at post-accident conditions. As these T-ring seals are l
actually located outside the drywell, their operating environment is less stringent than that used to determine the 4 year in-service life. The 4 year in-service life is based upon continuous exposure to the operating environment. Therefore, when the plant is in the cold shutdown condition, or the purge / vent valves are closed, the seals are exposed to a reduced radiation and temperature environment and the T-ring seal material is not expected to be affected. The plant has been in the cold shutdown condition, or had the purge / vent valves closed, over a significant fraction of the lifetime of the present T-ring seals. The extension now requested (10 weeks) is substantially less than the seal lifetime, and the seals were not exposed to operating conditions over much of the time they have been in place.
Furthermore, the quarterly results for T-ring seal integrity demonstrate that there has been no degradation in leak tightness.
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- Based on the actual in-service time of the T-ring seals being less than the maximum allowable interval, even with the 10 week extension, and the fact that the purge / vent valves have continued to demonstrate leak tightness, the staff concludes that there should not be degradation in leakage over the 10-week period beyond the allowable TS value and that the requested one-time-only TS change is acceptable.
3.0 ENVIRONMENTAL CONSIDERATION
S This amendment changes a requirement with respect to installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20 and changes to the surveillance requirements.
The staff has determined that the amendment involves no significant increase in the amounts, and no significant change in the types, of any effluents that may be released offsite, and that there is no l
significant increase in individual or cumulative occupational radiation exposure. The Commission has previously issued a proposed finding that the amendment involves no significant hazards consideration and there has been no public comment on such finding. Accordingly, the amendment meets the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9). Pursuant to 10 CFR 51.??.fb), no environmental impact statement or environmental assessment need be prepared in connection with the issuance of the amendment.
4.0 CONCLUSION
We have concluded, based on the considerations discussed above, that:
(1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, and
(?) such activities will be conducted in compliance with the Commission's regulations, and the issuance of the amendment will not be inimical to the common defense and security or to the health and safety of the public.
Principal Contributor:
P. Hearn, S. Kim, and H. Shaw Dated:
January 30, 1987
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Table 1 List of Isolation Valves to be Tested on Power Penetration No.
Description of Values 231 e
231 CV-4304
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V-43-169 268220 CV-4312 220 CV-4313 2118 SV-4334A 211B SV-43348 39A SV-4332A 39A SV-43328 229C SV-8109A 229C SV-8110A 56D SV-81038 560 SV-8104B 268220 CV-4306 268220 CV-4307 26&220 CV-4308 211A SV-4333B 39B SV-4331B 211A SV-4333A e
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