ML20081E263

Requests Exemption from Requirements of 10CFR50,App J,Section III.D.1.(a) Re Type a Periodic Retests,To Extend Second Type a Test from 54 Months to 72 Months

ML20081E263
Person / Time
Site:	Nine Mile Point
Issue date:	03/09/1995
From:	Terry C NIAGARA MOHAWK POWER CORP.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
NMP2L-1531, NUDOCS 9503210223
Download: ML20081E263 (10)

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M V NIAGARA.

R.U MOHAWK NIAGARA 800 HAWK POWER CORPORATION /NINE MtLE POINT NUCLEAR STATION, P.o. BOX 63, LYCOMING N.Y.1293 /TEL (315) 349 7263 L

_ FAX (315)3494753 cAnL at March 9,1995 Nucesor EnWnemino NMP2L 1531 s U. S. Nuclear Regulatory Commission

' Attn: Document Control Desk Washington, DC 20555 RE: Nine Mile Point Unit 2 Docket No. 50-410 NFP-69 Gentlemen:

Subject:

Exemption frern the Requirements of Appendix J to 10CFR Part 50 Regarding Type A Periodic Retest Schedule 10CFR50 Appendix J, Section III.D.1.(a), requires that a set of three type A tests shall be performed at approximately equal intervals during each ten-year service period. In accordance with Amendment No. 43, a Type A test is required to be completed by the end of RF-04 currently scheduled to start in April 1995. Niagara Mohawk Power Corporation hereby requests, pursuant to 10CFR50.12(a), an exemption for Nine Mile Point Unit 2 from the requirements set forth in 10CFR50 Appendix J, Section III.D.1.(a), relating to type A periodic retests. Specifically. Niagara Mohawk requests to extend the second type A test from 54 months to 72 months. This represents a delay from RF-04 to RF-05.

This letter is accompanied by a proposed amendment, dated March 9,1995 (NMP2L 1530),

which requests an increase from 54 months to 72 months to perform the second Containment Integrated Leak Rate Test, Technical C,wification Surveillance Requirement 4.6.1.2a.

The attachment to this letter demonstrates that the requested exemption presents no undue risk to the health and safety of the public, that special circumstances are present to justify granting the request, the exemption is authorized by law and is consistent with the common defense and security.

Niagara Mohawk is requesting this exemption to Appendix J of 10CFR50 be issued by April 30,1995. in conjunction with the accompanying submittal, identified above, to support the fourth refueling outage which is scheduled to begin April 8,1995.

Very truly yours, 210040 C. D. Terry Vice President - Nuclear Engineering I

CDT/MGM/kab p Attachment 9503210223 950309 kWjI l PDR ADOCK 05000410 p PDR

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Page 2 xc: Regional Administrator, Region I Mr. B. S. Norris, Senior Resident Inspector -

Mr. L. B. Marsh, Director, Project Directorate I-1, NRR

' Mr. G. E. Edison, Project Manager, NRR Records Management i

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U. S. NUCLEAR REGULATORY COMMISSION In the Matter of )

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Niagara Mohawk Power Corporation ) Docket No. 50-410

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Nine Mile Point Nuclear Station No.'2 )

AFFIDAVIT C. D. Terry, being duly sworn, states that he is Vice President - Nuclear Engineering of Niagara Mohawk Power Corporation; that he is authorized on the part of said Corporation to sign and file with the Nuclear Regulatory Commission the documents attached hereto; and that all such documents are true and correct to the best of his knowledge, information, and belief.

C. D. Terry / '

Vice President - Nuclear Engineering SubscribedAnd sworn to before me, a Not ublic in and for S of New York and County of UA J1c2 , this day of (2A ' ,1995. ,

o r dt' r7AA Notary Public in an'd Tor t#/B County, New York Mb/ 80 (q$8,27,Z My Commission Expires:

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ATTACHMENT 9

EXEhWrlON REQUEST NINE MILE POINT UNIT 2 DOCKET NO. 50-410 NPF-69 .1 1

A. Introduction j I

The purpose of Appendix J leak test requirements, as stated in the introducti'on to 10CFR50 '

. Appendix J is to'" assure that (a) leakage through the primary reactor containment and systems and components penetrating primary containment shall not exceed allowable 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 service life of the containment and systems and components penetrating primary containment." " Type A Tests" are defined in Appendix J Section II.F as " tests intended to measure the primary reactor containment overall integrated leakage rate (1) after the containment has been completed and ready for

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operation, and (2) at periodic intervals thereafter."

The proposed change would allow for an extension of the interval between the first and' second Type A test during the first ten-year service period. The extension would allow the Type A integrated leak rate test (ILRT) to be performed at the fifth refueling outage (RF-05) instead of the fourth refueling outage (RF-04) as currently scheduled.

B. Background i The purpose of containment leak testing is to detect any containment leakage resulting from degradation isolation boundaries. The major containment leakage paths include:

Penetration Seal Leakaser Air lock door seals, doors with resilient seals or gaskets' except for seal welded doors, and penetrations whose design incorporates resilient seals, gaskets, or sealant compounds, piping penetrations fitted with expansion bellows, and electrical penetrations fitted with flexible metal seal assemblies may all exhibit leakage. Type B tests would identify this type ofleakage. Type B test schedules will not be affected by the proposed change in the ILRT test schedule.

t Containment Isolation Valvest These valves r ovide either a potential or direct

- connection between the inside and outside atmospheres of the primary reactor containment under normal operation. They are required to close automatically upon receipt of a containment isolation signal in response to controls intended to effect containment isolation and are required to operate intermittently under post-accident conditions. Leakage through these valves can be caused by leaking valve seals, isolation valve closure failure. This type of leakage is detectable by Type C local leak rate testing. Following any maintenance on a containment isolation valve, an 1 of 7

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LLRT is performed followed by an independent valve alignment verification to ensure

. that leakage remains within acceptable levels. Type C tests will not be affected by.

the proposed change in the ILRT test schedule.

Gross Containment Failure Degradation of the primary containment structure is a ,

low probability event and is detected by Type A tests. +

' C. Evaluation

.10CFR50 Appendix J Section II.K defines the acceptable leakage limit la as "the maximum -

allowable leakage rate at pressure Pa (calculated design basis accident peak containment .

pressure) as specified for preoperational tests in the Technical Specifications or associated ,

bases and as specified for periodic tests in the operating license."

The preoperational (initial) Type A test was performed in accordance with'10CFR50 Appendix J, ANS N45.4/ ANSI 56.8-1981. This method employs:  :

4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> (minimum) stabilization period i

24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> (minimum) ILRT test period (utilizing total time analysis of BN-TOP-1 and -

mass point analysis technique of ANSI 56.8) 1 to 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> (minimum) verification period This 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> Type A test provided a baseline for post-operational tests. This program is equivalent to the inservice testing program that will be used for subsequent Type A refueling outage tests. These Type A tests will be performed using total time analysis which provides the bases for a Type A test duration of 8 hr. (minimum) with 20 data sets (minimum) 3

- (BN-TOP-1).

The test procedure, test equipment and facilities, period of testing, and verification ofleak f test accuracy follow the recommendations of BN-TOP-1, Rev.1,1972.  !

The allowable as-found leakage rate for NMP2.is 1.1%/ day at test pressure 39.75 psig. The i pre-operational Type A test performed on April 14,1986 resulted in an as-found integrated

, leakage rate of 0.2903%/ day, For NMP2, the Type A test identifies leakage that is ,

attributable to CRD insert and withdrawal lines, drywell and suppression chamber-instrumentation, and the containment liner. Similarly, the Type A test performed on January [

14, 1991 resulted in an as-found integrated leakage rate of 0.623%/ day of which 0.312%/ day  ;

was due to leaking through the high side bleed and vent valve on 2RCS-IFI'84A, These test .i results show that little or no degradation has occurred during the 57 months between the pre-operational test and the first inservice test. Hence, the 72-month interval between the first and second Type A tests would not jeopardize the ability of the containment to maintain the  !

leakage rate at or below the required Type A limits. :j q

There have been no temporary or permanent modifications to the containment structure, j liner, or penetrations since the last Type A test that could adversely affect the Type A test 2 of 7

results. Ariy unplanned modifications to the containment prior to the next scheduled Type A test would be subject to the special testing requirements of Section IV.A of Appendix J. In addition, there have been no pressure or temperature excursions in the containment which could have adversely affected containment integrity.

Actual testing at Nine Mile Point Unit 2 has shown that the majority of the total leakage from the primary containment is from penetrations that receive Type B and C Local Leak Rate Tests. These Type B and C tests will continue to be performed at the frequency required by Nine Mile Point Unit 2's Technical Specifications with repairs being performed as necessary. Demonstrated operability of these penetrations and components will provide added assurance that overall containment leakage remains satisfactory.

D. Risk Assessment A risk evaluation of the NMP2 primary containment shows that there is an extremely low safety impact resulting from deferral of the Type A ILRT. The ILRT is designed to assure a high degree of primary containment " leak-tightness." However, the safety benefit of this test is negligible from three perspectives: 1) limited risk significance of containment leakage, 2) alternate indicators of containment leakage are available, 3) unique design features and inspection practices make it unlikely that abnormal leakage will develop.

As concluded in the NMP2 Individual Plant Examination (IPE),74% of reactor accident risk is dominated by low-probability, high consequence scenarios in which the containment is failed or bypassed. In these types of accidents, there is little benefit derived from a high degree of containment leak-tightness. Also, these types of accidents are beyond Design Basis, and therefore, not the purpose of ILRT.

In the other 26% of the scenarios where the primary containment remains intact, there are two factors that significantly reduce the consequences of any leakage out of containment: 1) suppression pool scrubbing which reduces potential source terms prior to entering the reactor building, and 2) a large portion of these fission products would be entrained in secondary containment and removed by the standby gas treatment system prior to release.

Furthermore, even without a Type A ILRT, there are design and operational features that assure a leak-tight containment. They provide adequate assurance that the assumed leakage or probability of undetected leakage will not increase above what has already been assumed in the NMP2 IPE. These features are as follows:

1. Nitrogen inerting - Technical specifications require containment pressure be maintained between 14.2 and 15.45 psia during normal operation. Primary containment pressure is monitored at least once per 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> in accordance with technical specification surveillance requirements. Normally this pressure is maintained between .3 to .7 psi above atmospheric pressure. This provides the capability to detect abnormal containment leakage during normal operation, by monitoring containment pressure decay. Normally, primary containment pressure decays at a rate approximately 0.1 psi per day. However, a leak equivalent to a 5/8 inch diameter hole will result in a pressure decay rate of approximately 0.1 psi per 3 of 7

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-.i hout. This hole size is equivalent to approximately 14% per day containment leakage

, rate, which during a severe accident would result in an EAB thyroid dose still within the 10CFR100 guidelines of 300 Rem. These factors assure that no significant .

containment mechanical or structural leakage would go undetected before the next '  :

~ Type A ILRT test.  ;

2. Type' B and C leak rate' tests - These tests check the integrity of containment'-

penetrations, resilient seals, and drywell head 0-ring seals. The ILRT with the : y exception of checking for mechanical and structural failures of the containment shell j' is confirmatory to the Type B and C tests.

3. -Visual inspection - A thorough and comprehensive internal and external inspection j of the mechanical and structural integrity of the containment shell is completed during -

every refuel outage. >

4. Containment drywell head design - NMP2 containment drywell head is pinned in l place and uses double O-ring seals. This design is superior to the bolted flange type _'

used in other containments, which often cause warping of the head during flange bolt; torquing.  ;

5. Continuously pressurized penetrations - Type B electrical penetrations are- .

continuously pressurized and monitored routinely. Annunciation is provided in the control rcom on low penetration pressure.

Drywell to Suppression Chamber bypass leakage test - This test checks for leakage I 6.

from the drywell to the suppression pool by pressurizing the drywell to 3 psig for at '

least 30 minutes. The results of this test would indicate any degradation of the drywell volume containment shell. This test is performed every refuel outage and results have been well within the acceptance criteria.

Based on the above, deferral of the Type A ILRT will not increase the probability of any ~,

accident. Therefore, this deferral will not impose additional risk to public health and safety. t This conclusion is consistent with the findings of draft NUREG-1493, Performance-Based  !

Containment Leak Test Program, a i

E. Conclusion i l

Technical Specification Surveillance Requirement 4.6.1.2.a schedule requires that the second j Type A test be performed during RF-04. The proposed change to perform the second Type A test at RF-05 extends the interval to 72 months. The pre-operational Type A test resulted in an as-found and as-left leakage rate of 0.2903%/ day. The first inservice Type A test resulted in an as-found integrated leakage rate of 0.623%/ day of which 0.312%/ day was attributable to 2RCS-PT84A. These results are significantly less than the as-found limit of.

1.1%/ day and as-left of 0.825%/ day. Type B and C tests will continue to be performed at the frequency required by Nine Mile Point Unit 2's Technical Specifications, with repairs being performed as necessary. The absence of degradation of the primary containment and performance of Type B and C testing provides reasonable assurance that an extension of the 4 of 7

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e test interval to 72 months between the first and second Type A periodic test will not jeopardize the ability of the containment to maintain the leakage rate at or below the required Type A limits.

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Based on the information provided above, Niagara Mohawk concludes that ths exemption from the requirements of 10CFR50 Appendix J is justified pursuant to 10CFR50.12 Section (a)(1)in that this exemption will not present an undue risk to the public health and safety.

In addition, in accordance with 10CFR50.12(a)(2)(ii) and (v), special circumstances are present which warrant issuance of the exemption.

(ii) " Application of the regulation in the particular circumstances...is not necessary to achieve the underlying purpose of the rule."

The underlying purpose of 10CFR50 Appendix J is still achieved. Appendix J states that the leakage test requirements set forth in this appendix provide for periodic verification by tests of the leak tight integrity of the primary reactor containment.

The appendix further states that the purpose of the tests is to assure that leakage through the primary reactor containment shall not exceed the allowable leakage rate values as specified in the technical specifications or associated bases.

10CFR50. Appendix J,Section III.D.I.(a) states that a set of three periodic tests shall be perforn.ed at approximately equal intervals during each ten-year period and that the third test shall be conducted when the plant is shutdown for the ten-year plant inservice inspections. This exemption would extend the time between the first and second tests from 54 to 72 months. The methodology, acceptance criteria, and technical specification leakage limits for the performance of the Type A test will not change.

Two Type A tests have been conducted from 1986 to date with no failures. The first Type A test conducted in 1986 was the preoperational test that resulted in an as-found integrated leak rate of 0.2903%/ day. This test was conducted over a period of 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> and was as stringent in all aspects to the inservice Type A tests which are now being performed. The second Type A test performed in January 1991 resulted in an as-found leakage of 0.623%/ day. The increased leakage associated with this test was found to be leakage through the high side bleed and vent valve on 2RCS-Irr84A equivalent to 0.312%/ day. These results show a significant margin between the acceptance criteria of 1.1 %/ day. The Type B and C testing programs at NMP2 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 j as containment penetrations. It has been the experience that any significant l containment leakage paths are detected by Type B and C testing. The Type A tests results have only been confirmatory of the results of the Type B and C tests, i.e. no significant leakage has been detected during Type A testing.

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The local leak rate testing program at NMP2 has resulted in both Type B and C

. failures, however, the majority of failures are isolation valves (Type C). Repairs consist mainly of disassembly and reworking the valves or in some instances, even

> replacement.

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There are no mechanisms which would adversely affect the structural capability of the containment.~ Structural deterioration of the containment would be due to .

temperature, pressure, radiation, chemical which is a gradual phenomena which -

- requires time periods well in excess of the proposed interval extension. Other than associated conditions, the only pressure challenge to the containment is the ILRT (Type A test).  ;

Based on the results of both the pre-operational and first inservice ILRT,' structural

. integrity of containment is ensured and there is negligible risk impact associated with' changing the Type A test schedule on a one-time basis.

This exemption request does not affect the periodic schedule for Type B and C tests which will continue to be performed in accordance with Appendix J and approved 1 exemptions. Demonstrated operability of the associated components and penetrations through Type B and C tests adds assurance that the overall Type _ A leakage rates remain satisfactory. No significant leakage trends have been identified which threaten the overall containment leakage specifications. There is no significant change in the  ;

types or increase in the amounts of any effluents that may be released offsite due to the delay in the performance of the second Type A test during the first ten-year interval. This change does not impact the design basis of the plant and would not ,

affect the response of containment during a design basis accident.

Thus, there is significant assurance that the extended interval between Type A tests

will continue to provide periodic verification of the leak tight integrity.of the  !

containment.

l (v) "The exemption would provide only temporary relief from the applicable regulation i and the licensee or applicant has made good faith efforts to comply with the regulation."

, This request for exemption only applies to the first ten-year Appendix J service period. The methodology, acceptance criteria, and Technical Specification leakage ,

i limits for performance of the Type A test will not change. Therefore, this exemption

, provides only temporary relief and compliance with all other aspects of Appendix J l remains the same.

Type B and C tests will continue to be performed in accordance with 10CFR50 Appendix J.

With regard to the " common defense and security" standard, the grant of the requested exemption is consistent with the common defense and security of the United States. The ,

Commission's Statements of Consideration, in support of the amendment of Section 50.12(a)

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which became effective in 1986, notes with approval the explanation of the " common defense and security" standard set forth in Long Island Lighting Company (Shoreham Nuclear Power Station, Unit 1), LBP-84-45,20 NRC 1343,1400 (1984). See 50 Fed. Reg. 50764,50766 (1985). As stated in Shoreham, the term " common defense and security" refers principally to the safeguarding of special nuclear material, the absence of foreign control over the applicant, the prot:ction of Restricted Data and the availability of special nuclear material for defense.needs. The granting of the requested exemption will not affect any of these matters and, thus such a grant is consistent with the common defense and security.

Therefore, an exemption from the requirements of 10CFR50 Appendix J, Section III.D.1.(a) is justified pursuant to the requirements of 10CFR50.12.

F. Environmental Assessment

1. EnvironmentalImpacts of the Proposed Action The proposed exemption would not significantly increase the probability of consequences of any previously analyzed accidents. Although the requirements of 10CFR50, Appendix J, Section III.D.1.(a) state that three Type A tests be performed in each ten-year service period and at approximately equal intervals during that period, we have concluded that performing the second Type A test approximately 72 months after the first Type A test would meet the underlying purpose of the rule and that any primary containment leakage during a design basis accident will remain less than the maximum allowable leakage rate, La.

2. Alternatives to the Proposed Actions Niagara Mohawk has concluded that there is no measurable environmental impact associated with the proposed exemption, any alternatives with equal or greater environmental impact need not be evaluated.

3. Alternate Use of Resources The proposed exemption does not involve the use of resources not previously 4

considered in the " Final Environmental Statement Related to the Operation of Nine Mile Point Nuclear Station Unit No. 2," dated May 1985.

4. Finding of No Significant Impact Niagara Mohawk has concluded, based on the preceeding environmental assessment, that the proposed exemption will not have a significant effect on tt:e quality of the human environment, therefore, an environmental impact statement for the requested exemption would not be required.  ;

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