ML18064A658

Requests Exemption Re Extension of 10CFR50,App J Integrated Leak Rate Test Interval

ML18064A658
Person / Time
Site:	Palisades
Issue date:	03/17/1995
From:	Haas K CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.)
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
NUDOCS 9503240015
Download: ML18064A658 (13)

Text

consumers Power KurtM. Haas Plant Safety and Licensing Director POWERlll&

MICHl&AN"S PIUl&IUSS Palisades Nuclear Plant: 27780 Blue Star Memorial Highway, Covert, Ml 49043 March 17, 1995 Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555 DOCKET 50-255 - LICENSE DPR PALISADES PLANT REQUEST FOR EXEMPTION - EXTENSION OF 10 CFR PART 50, APPENDIX J,. INTEGRATED LEAK RATE TEST INTERVAL Pursuant to the regulatory requirements of 10 CFR 50.12, "Specific exemptions", an exemption from certain requirements of 10 CFR 50, Appendix J, "Primary Reactor Containment Leakag.e Testing for Water Cooled Power Reactors,"

is hereby requested for the Palisades Plant. This exemption would provide a one time extension of the interval between Type A tests, containment Integrated Leak Rate Tests (ILRTs). The scheduled interval between successive ILRTs would. be extended from the currently planned 54 month interval to a 71 month interval. This extension would result in a delay of the ILRT from the 1995 refueling oµtage to the 1997 refueling outage. The exemption request is provided as Attachment 1 and was prepared in accordance with recent NRC guidance.

The NRC Staff is conducting an expedited rulemaking effort to revise Appendix J as part of the initiative to eliminate requirements that are marginal to safety. This effort is discussed in; SECY-94-036, "Staff Plans for Revising 10 CFR 50, Appendix J, 'Containment Leakage Testi~g,' and for Handling Exemption Requests," dated 2/17/94, SECY 94-090, "Institutionalization of Continuing Program for Regulatory Improvement," dated 3/31/94, and NRC Internal letter from CY Shiraki to all NRR Project Directors, "Guidance for Requesting .Exemptions to the Requirements for Type A Testing in 10 CFR 50, Appendix J", dated 2/10/95. The NRC Staff plans to have Appendix J revised by August 1995. As discussed in SECY-94-036, the NRC Staff is considering changing the Type A test frequency requirements from the current three tests per ten-year interval to a performance based interval that could potentially require only one test per ten-year period. The Appendix J revision will .

effectively reduce the significant hardship and costs associated with ILRTs without a corresponding decrease in plant safety performance.

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The proposed schedular exempti.on for Palisades is limited to aspects within the scope of the contemplated Appendix J changes. By obtaining an. exemption from the current Appendix J testing frequency requirements, the scheduled date for the next Type A test wi 11 occur after approval of the proposed revision to Appendix J. The Appendix J revision will allow Palis~des to implement the anticipated performance based criteria for ILRT testing frequencies. The estimated savings from not performing the ILRT in August, 1995, exceeds

$1,000,000. .

SUMMARY

OF COMMITMENTS This letter contains no new commitments.

Kurt MHaas Plant Safety and ~icensing Director CC Administrator, Region Ill, USNRC

~RC Resident Inspector - Palisades Attachment

ATTACHMENT 1 Consumers Power Company Palisades Plant Docket 50-255 SAFETY ASSESSMENT 7 Pages

DESCRIPTION OF PROPOSED CHANGES Appendix J, section 11.F defines Type A tests as " tests intended to measure the primary reactor containment overall integrated leak rate (1) after the containment has been completed and is ready for operation, and (2) at periodic intervals thereafte~." Exemption is requested for the following portion of Appendix J, Section 111.0.1.(a) for Type A test intervals:

"Type A tests shall be performed at approximately equal intervals during each 10-year service period. The third test of each set shall be conducted when the plant is shutdown for the 10-year plant inservice inspections."

The proposed exemption to 10 CFR 50 Appendix J, Section 111.D.1.{a), ."Type A Periodic Retest Schedule," would allow for a orie-time extension of the i.nterval between the second and third Type A tests.during the second ten year service-period. The extension would allow the Type A integrated leak rate test (ILRT) to be performed during the 1997 Refueling Outage instead of the 1995 Refueling Outage. The 10 yea*r plant inservice inspection is currently scheduled for the 1995 Refueling Outage and thus an approved ILRT extension would place the third ILRT into a different plant outage than the ten year plant inservice inspection outage.

The purpose of Appendix J leak test requirements, as stated in the Introduction to 10 CFR 50 Appendix J, is to "assure that {a) leakage through the primary reactor containment and systems and components penetrating primary containment shall not exceed leakage rate values as specified in the technical specifications or associated bases and (b) periodic surveillance of reactor containment penetrations and isolation valves is performed so that proper maintenance and repairs are made during the s~rvice life of the containment, and systems and components penetrating primary containment." The exemption request concerns only part (a) of the stated purpose of Appendix J .. Part (b) of the stated purpose of Appendix J applies to penetrations, airlocks, and isolation valves, which are tested by Type B and C Local Leak Rate Tests (LLRTs) ..

Palisades Technical Specifications 4.5.1 specify that the containment overall integrated leakage rate shall meet the 10 CFR 50, Appendix J, Type A test requirements or approved exemptions. Thus, a Technical Specification amendment will not be necessary in conjunction with this exemption request.

REGULATORY BASIS FOR SPECIFIC EXEMPTION UNDER 10 CFR 50.12 Pursuant to 10CFR 50.12(a)(l) and (2), the NRC will not consider granting an exempti-0n to a requirement unless special criteria are met. This exemption request meets the requirements of paragraph 50.12(a)(l) and discusses the special circumstances as defined in paragraph 50.12(a)(2)(ii). The requested schedular extension of one cycle for the performance of our Appendix J Type A test will be authorized by law, does not present an undue risk to the public health and safety, and does not impact common defense and security. The 1

underlying purpose of the Appendix J requirements is more appropriately implemented through the LLRT program pertaining to the detection and repair of active containment isolation devices such as valves and airlocks.

BACKGROUND INFORMATION The NRC is currently examining regulations which may be revised to reduce regulatory burden on licensees without a significant impact on safety. As part of this effort, the NRC is currently processing a proposed revision to 10 CFR 50 Appendix J. The current proposal for a revised Appendix J will allow for relaxing the schedule for Type A, ILRTs, and allow for a change in the schedule for Type B and C, LLRTs, to a performance based schedule. According to SECY 94-036, this proposed rule change will not be approved until approximately August 1995. Therefore, licensees who have refueling outages scheduled prior to August 1995 will not be able to implement the revised rule during these refueling outages.

The Cycle 11 Refueling Outage for Palisades is currently scheduled to begin in late May, 1995. Palisades is therefore requesting a one-time exemption to the Type A ILRT schedule for the Cycle 11 Refueling Outage. Although changes to the acceptance criteria for leak rate tests and schedules for Type B and C tests are part of the proposed rule change, an exemption is not being sought for these requirements.

DESCRIPTION OF CONTAINMENT The Palisades containment structure consists of a post-tensioned, reinforced concrete cylinder and dome connected to and supported by a reinforced concrete foundation slab. The entire interior surface of the containment structure is lined with 1/4-inch-thick welded ASTM A-442 steel plate to ensur~ a high degree of leak tightness. Numerous mechanical and electrical systems penetrate the containment wall through steel penetrations which are welded to the containment liner plate. A more detailed description is contained in Palisades FSAR Section 5.8. The principal dimensions are as follows:

Inside Diameter 116 Feet Inside Height (Including Dome) 189 Feet Vertical Wall Thickness. 3 1/2 Feet Dome Thickness 3 Feet Foundation Slab Thickness 8 1/2 to 13 Feet Liner Plate Thickness 1/4 Inch lnternal Free Volume 1,640,000 Cubic Feet HISTORICAL TYPE A TESTING RESULTS 10 CFR 50, Appendix J, Section 11.K defines the acceptable leakage limit L8 as, "the maximum allowable leakage rate at pressure P (calculated design

• basis accident peak containment pressure) as specifie~ for preoperational tests in the technical specifications or associated bases, and as specified for periodic tests in the operating license." The Palisades containment 2

design pressure is 55 psig with a calculated loss of coolant accident peak pre~sute of 52.64 psig. The maximum allowed or acceptable leakage limit, La, used in accident analysts is a leak rate.of 0.1 wt% per day. The current Appendix J and Palisades Technical Specification leakage limit for ILRTs is

.75 L~ or 0.075 wt% per day; The measured leakage rates for the Palisades containment structure during preoperational tests were 0.00482 wt % per day at 55 psig and 0.0223 wt % per day at 28 psig. The reduced leakage rate at full accident pressure is believed to be due to the greater pressure differential which provides more sealing force for some penetrations. The recent Palisades Type A test history provides substantial justification for the requested test schedule change as shown in the fo 11 owing paragraphs.

FIRST PERIODIC TYPE A TEST RESULTS The first periodic Type A test was successfully completed in April, i974. The test was performed at a reduced pressure of 28 psig with the following results: 1) The measured leak rate was 0.0342 wt %/day using the total time method, 2) The measured leak rate adjusted to Pa at a 95 % upper confidence limit was 0.0611 wt %/day. This as-found calculated value met the Appendix J criteria.

SECOND PERIODIC TYPE A TEST RESULTS The second periodic Type A test was completed in March, 1978. The test was performed at a reduced pressure of 28 psjg with the following results: 1) The measured leak rate was -0.0071 wt %/day using the mass:.point analysis method, (The negative measured leak rate was evaluated and did not invalidate the test results, however improvements in the test method were instituted for future tests}, 2) The measured leak rate adjusted to Pa at a 95 % upper confiderice limit was 0.0027 wt %/day, 3) The as-found calculated containment leak rate was determined to be 0.1422 wt %/day based on accounting for the pre-test repair of a contatnment penetration leak. Thi~ as-found calcul~ted value exceeded the Appendii J criteria. During the external survey of containment penetrations at the initial ILRT hold pressure of 14 psig, a containment leak

• .was found on a grease fitting for a containment i~olatio~ valve. The leak was located on the piping section between containment and the inner isolation valve, and thus this leak path could not be identified during the associated LLRT for the penetration configuration that existed at that time. The leak was repaired and the ILRT test completed as indicated. Plant modifications were subsequently initiated to improve the penetration design to eliminate de~ign and testing ~eficiencies.

THIRD PERIODIC TYPE A TEST RESULTS The third periodic Type A test was completed in November, 1981. The test was performed at a reduced pressure of 28 psig with the following results: 1) The me~sured leak rate was 0.0328 wt %/day using the mass-point analysis method,

2) The measured leak rate adjusted to Pij at a 95 % upper ~onfidence limit was 0.0507 wt %/day, 3) The as-found calcu1ated containment leak rate was determined to be*0.1175 wt %/day based on accounting for pre-test repairs of containment penetrations. This as-found calculated valu~ exceeded the 3

Appendix J criteria. The as-found results of three containment penetrations LLRTs accounted for the majority of the before maintenance adjustment to the as~found ILRT result. The three penetrations were; the containment service air supply line valves, safety injection tank drain line valves, and the containment sump drain line valves. Attachment 2 contains a brief description of the corrective actions taken to minimize future leakage from these three penetrations.

FOURTH PERIODIC TYPE A TEST RESULTS The fourth periodic Type A test was completed in January, 1986. The test was performed at a reduced pressure of 28 psig with the following results: 1) The measured leak rate was 0.0157 wt %/day using the mass-point analysis method, 2} The measured leak rate adjusted to Pa at a 95 % upper confidence limit was 0.0290 wt %/day, 3) The as-found calculated containment leak rate was determined to be 0.1061 wt %/day based on accounting for pre-test repairs of containment penetrations. This as-found calculated value exceeded the Appendix J criteria. The as-found results of four containment p.enetrations LLRTs accounted for the majority of the before maintenance adjustment to the as-found ILRT result. The four penetrations were; the primary coolant sample line valves, the clean waste receiver tanks pumps suction line valves, the south electrical penetration, and the B steam generator south manway. contairis a brief description of the corrective actions taken to minimize future leakage from these four penetrations.

On June 30, 1986, a Corrective Action Plan was submitted under the guidelines of NRC Information Notice 85-71 and in response to NRC Inspection Report 86-005. The information notice indicated that an improved maintenance and testing program for containment penetration boundaries and isolation valves could be an acceptable alternative to increasing the frequency of Type A tests, due to consecutive Type A test failures. Upon NRC review of the Corrective Action Plan, an exemption to Appendix J was granted to Palisades.

The exemption stated that if the conditions of the Plan were met, and the next scheduled Type A test was successfully completed, then normal resumption of the Type A test frequency would* be allowed.

FIFTH PERIODIC TYPE A TEST RESULTS The fifth periodic Type A test was successfully completed in November, 1988.

The test was performed at a reduced pressure of 28 psig with the following results: 1) The measured leak rate was 0.01651 wt %/day using the mass-point analysis method, 2) The measured leak rate adjusted to Pa at a 95 % upper confidence limit was 0.02617 wt %/day, 3) The as-found calculated containment leak rate was determined to be 0.0408'wt %/day based on accounting for pre-test repairs of containment penetrations. This as-found calculated value met the Appendix J and Palisades Technical Specification criteria of 0.075 wt

%/day. As shown by these test results, the LLRT Corrective Action Plan tmplemented after the. 1986 ILRT was successful in eliminating original plant design, maintenance, and testing deficiencies.

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SIXTH PERIODIC TYPE A TEST RESULTS The sixth periodic Type A test was successfully completed in February, 1991 following containment structural' restoration from the steam generator replacement project. A short duration test was performed at a pressure of 55 psig with the following results: 1) The measured leak rate was 0.02473 wt

%/day using the total time method, 2) The measured leak rate adjusted to a 95 % upper confidence limit was 0.07008 wt %/day, 3) The as-found calculated containment leak rate was determined to be 0.073017 wt %/day based on accounting for pre-test repairs of containment penetrations. This as-found calculated value met the Appendix J and Palisades Technical Specification criteria of 0.075 wt %/day. The test results were described in a special report dated May 17, 1991. The report described the selected test method which; minimized the test duration, reduced the total accumulated test data, and provided a preselected minimal margin for the final results. The reduced amount of test data lead to significant analytical penalties which became a large percentage of the reported as-found containment leak rate. The measured leak rate of 0.02473 wt%/day, prior to the application of data uncertainties, is comparable to the measured leak rates from previous ILRTs. The lack of margin in this 1991 ILRT was not due to increased containment leakage.

Based on the results of Type A testing at Palisades, especially the recent results, it is apparent that the Type A testing results have been largely a confirmation of the results already determined through the Type B and C testing program. With the exception of the 1978 ILRT test, the Type A tests have not identified any significant containment leakage paths that wer~ not p.reviously identified py the Type B and C tests. The penetration associated with the 1978 test fatlure was significantly modified in the mid-1980s to improve the LLRT test configuration to properly monitor the entire penetratiori boundary~ The implementation of our LLRT Program every two years and periodic ILRTs will ensure that containment leakage is maintained within the criteria of Appendix J. Our current LLRT total identified leakage is les~ than 13~000 cc/min which equates to approxi.mately 0.012 wt%/day. Previously, the total LLRT leakage upon plant start-ups from the last three refueling outages have b~en 16,273 cc/min, 16,171 ~c/min, and 11,927 cc/min for the 1990, 1992, and 1993 refueling outages respectively .. An aggressive LLRT Program ensures that identified penetrations whose 1eakage rates increase moderate 1y wil 1 be restored to minimal historical leak rates.

Draft NUREG 1493, "Performance Based Containment Leak Test Program," indicated that 97% of the failures associated with Type A tests were caused by leakage through Type B and C tested penetrations. The only known Type A test failures attributed to containment structural leakage were appropriately identified prior to plant operatipns during initi.al fabrication testing or post-modi fication testing of containment structures, (testing required by current Appendix J and its proposed revision,)

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BASIS FOR EXEMPTION The proposed interval extension meets the criteria described in 10 CFR 50.12(a)(l) and (a)(2)(ii).

10 CFR 50.12(a)(l)- No Significant Risk to Public Health and Safety The requested schedular extension of one cycle for the performance of our Appendix J Type A test will be authorized by law, does not present an undue risk to the public health and safety, and does not impact common defense and security. From a risk standpoint, the purpose of Appendix J leak testing is to periodically detect any containment leakage, resulting from failures in the containment isolation boundary, before a postulated accident occurs. Such leakage could be the result of leakage through containment penetrations, through airlocks, or through containment structural faults. The only potential effect of the proposed one-time change to the Palisades ILRT test frequency is the probability that containment structural leakage would increase beyond the established leak criteria between tests. The Appendix J Type B and C tests, which are unaffected by this proposed change, will continue to detect leakage through containment valves, penetrations, and airlocks.

The containment structure is passive. Under normal operating conditions, there is no significant environmental or operational stress present that could contribute to its degradation. There are two potential mechanisms that could adversely affect the passive structural capability of containm~nt. The first mechanism is deterioration of the structure due to pressure, temperature, radiati-0n, chemical, or other such effects. Secondly, modifications can be made to the structure which, if not carefully controlled could leave the structure with reduced capacitj. Absent actual accident conditions, the structural deterioration is a gradual phenomenon requiring periods of time well in excess of the proposed interval extension. Other than accident conditions, the only pressure challenge to containment is the ILRT test itself.

10 CFR 50, Appendix J, Section V.A. requires a general ins~ection of accessible interior and exterior surfaces of the containment structures and components to be performed prior to any Type A test. This inspection is intended to uncover any evidence of structural deterioratiQn which could affect containment leak tightness. Based on the results of the six completed inspections for the Palisades plant, there has been no evidence of structural deterioration that would impact structural i~tegrity or leak tightness.

Modifications that would alter the passive containment structure are infrequent and would receive extensi~e review to ensure containment capabilities are properly reviewed and verified. The present requirement in Appendix J,Section IV.A, requires Type A, B, or C testing to be performed as

~pplicable following any major modification to the containment pressure boundary. This requirement wi 11 be mai nta i.ned.

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Draft NUREG-1493 includes the results of a sensitivity study performed to explore the risk impact of several alternate leak rate testing schedules.

"Alternative 4" from this study examines relaxing the ILRT frequency from 3 tests in 10 years to 1 test in 10 years. Using best estimate data, the draft NUREG concludes that the increase in population exposure risk to those in the vicinity of the five representative plants ranged from 0.02 to 0.14%. This very low impact on risk is attributable to; 1) the effectiveness of Type B and C tests in identifying potential leak paths, 2) a low likelihood of ILRT identified leakage rates in excess of 2 times allowable, and 3) the insensitivity of risk to containment leak rate, (e.g. no- discernable increase in population dose risk with containment leak rates 100 times greater than

• currently allowed). This led the authors of draft NUREG-1493 to conclude that even intreasin~ the ILRT frequency to once per 20 years would "lead to an imperceptible inctease in risk." Palisades believes that there is sufficient information in the draft NUREG-1493 to conclude that the risk increase from the requested exemption is low and that the value, in terms of enhanced public safety, of performing the ILRT in 1995 is e~tremely low.

50.12{a)(2}(ii) Application of the Regulati-0n is not necessary to Achieve the Underlying Purpose of the Rule

• The underlying purpose of Appendix J is still achieved. Appendix J states that the leakage test requirements provide for periodic verificati~n testing of ttie leak tightness integrity of the primary reactor containment. The

. appendix further ~tates that the purpose of the tests is to assure that leakage through the .primary containment sha 11 not exceed the a11 owab le 1eakage rate values as* specified in the te.chnical sp.ecifications or associated bases.

As stated previously, for Palisades and a large percentage of other plants,~

the Appendix J Type .B and C testing programs provide the most significant and.

meaningful assessment of containment leak tightness. The testing history, .

structural capability of the containment, and the risk assessment discussed.*

previously 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.

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ATTACHMENT 2 Consumers Power Company Palisades Plant Docket 50-255 CORRECTIVE ACTIONS TAKEN TO REDUCE LLRT TOTAL LEAKAGE FROM 1981 AND 1986 REFUELING OUTAGES 2 Pages

-CORRECTIVE ACTIONS TO REDUCE LLRT LEAKAGE FROM PENETRATIONS WITH EXCESSIVE LEAKAGE NOTED DURING THE 1981 REFUELING OUTAGE Penetration # 10 - Service Air Supply Line to Containment During the 1981 Refueling Outage, new replacement valves were installed.

Also, at this time a modification was initiat~d ~nd completed during the following Refueling Outage, in 1983~ to reconfigure the penetration piping and val v~s to improv.e .reliability. The most recent LLRT leak rate for this penetration during the 1993 Refout was 367.2 cc/min.

Penetration# 33 ~Safety.Injection Tank Drain Line During the 1981 Refueling Outage, the existing valves internals were repaired and future modifi~ations were initiated to install new valves of different design. In the 1983 Refueling Outage, one of the penetration valves was replaced with a different style valve. In the 1983 Refueling Outage the penetration valve configuration was significantly modified to reduce the number of penetration i~olation valves to enhance future maintenance and testing. The most recent LLRT leak rate for this penetration during the 1993 Refout was 97.8 cc/min.

Penetration. # 52 - Containment Sump Drain Line During the 1981 Refueling Outage, the existing valves internals were repai.red.

After several sub~equent outages, the existing valves design was found to be unreliable in maintaining the desired low leakage criteria for individual penetrations at Palisades. A screen was installed on the drain line in 1988,

• and the penetration valves were replaced in the 1990 Refueling Outage with a valve type better .suited for this application. The most recent LLRT leak rate for this penetration. du~ing the 1993 Refout was 38.1 cc/min.

CORRECTIVE ACTIONS TO REDUCE LLRT LEAKAGE FROM PENETRATIONS WITH EXCESSIVE LEAKAGE NOTED DURING THE 1986 REFUELING OUTAGE Penetration# 40 -.Primary Coolant System Sample Line During the 1986 Refueling Outage, the existing valves were replaced and the valve position indication mechanis~ was redesigned to eliminate interference with full closure of the valves. High flow rates exist through the valves during daily primary .coolant system sampling and also duri.ng primary coolant system degassing operations required as part of plant shutdown activities.

The procedural steps for restoration from the daily sampling valve line-up .

wer~ revised to include a general daily check for gross leakage through these-penetration valves. The recorded leak rates are monitored for adverse trends~

The implementation of chemical deg.assing for the primary coolant system in the 1995 Refueling Outage will reduc~ the wear rates for these. penetration valves.

The most recent LLRT leak rate for this penetration during the 1993 Refout was 95.6 cc/min.

1

~

~

~Penitration #

69 - Clean Waste Receiver Tank Pump Suction Line During the 1986 Refueling Outage, misplaced demineralizer resin fines were removed from the piping and the existing valve internals were repaired. The most recent LLRT leak rate for this penetration during the 1993 Refout was 513.6 cc/min.

South Electrical Penetration The south electrical penetration contains approximately 20 canisters. During the 1986 Refueling Outage, the as-found leakage of 15,674 cc/min in the electrical penetration was determined to be primarily due to a leak in one of these canisters. Thi leaking canister, desi~nated as EZ-104r was removed and the penetration capped off. The as-left leakage after this modification was measured to be 800 cc/mtn. The most recent LLRT leak rate for this penetration during the 1993 Refout was 1449~0 cc/mfn. This present leak rate is consistent with the historical leak rates measured for both the North and South electrical penetrations for the Palisades containment building.

Steam Generator E-508 South Manwav Cover During the 1986 Refueling Outage, the penetratiDn o~ter flange cover gasket was replaced and the inner door hold down bolts were tightened. This .

. configuration was changed to a standard flange configuration in the 1990 Refuel.ing Outage with the replacement of the steam generators. Based on this modification to th~ manways, the new confi~uration eliminates the need for LLRT testing.

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