ML20072P621

Proposed TS 3/4.6.1.3, Primary Containment Air Locks, Allowing Continued Plant Operation If Interlock Becomes Inoperable as Long as Operable Door Locked Shut & Periodically Checked as Being Locked Shut

ML20072P621
Person / Time
Site:	Nine Mile Point
Issue date:	08/26/1994
From:	NIAGARA MOHAWK POWER CORP.
To:
Shared Package
ML20072P610	List: ML20072P607 ML20072P615 ML20072P621
References
NUDOCS 9409080108
Download: ML20072P621 (5)

Text

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. l CONTAINMENT SYSTEMS  !

. PRIMARY CONTAINMENT PRIMARY CONTAINMENT AIR LOCKS LIMITING CONDITIONS FOR OPERATION 3.6.1.3 Each primary containment air lock shall be OPERABLE with:

a. Both doors closed except when the air lock is being used for normal transit entry and exit through the containment, then at least one air lock door shall be closed, and

b. An overall air lock leakage rate of less than or equal to 0.05 La et Pa,39.75 psig.

APPLICABILITY: OPERATIONAL CONDITIONS 1,2*, and 3.

ACTION:

a. With one primary containment air lock door inoperable:

1. Maintain at least the OPERABLE air lock door closed and either restore the inoperable air lock door to OPERABLE status within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> or lock the OPERABLE air lock door closed.

2. Operation may then continue until performance of the next required overall air lock leakage test provided that the OPERABLE air lock door is verified to be locked closed at least once per 31 days.

3. Otherwise, be in at least HOT SHUTDOWN within the next 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> and in COLD SHUTDOWN within the following 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.

4. The provisions of Specification 3.0.4 are not applicable.

b. With the primary containment air lock interlock mechanism inoperable, verify an OPERABLE door is closed within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />, lock an OPERABLE door closed within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> and verify that an OPERABLE door is locked closed once per 31 days; otherwise be in at least HOT SHUTDOWN within the next 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> and in COLD SHUTDOWN within the following 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.

c. With the primary containment air lock n'.,perable, except as a result of an inoperable air lock door or inoperable interlock mechanism, mAtwn at least one air lock door closed; restore the inoperable air lock to OPERABLE status within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> or be in at least HOT SHUTDOWN within the next 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> and in COLD SHUTDOWN within the following 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.

• See Special Test Exception 3.10.1.

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NINE MILE POINT - UNIT 2 3/4 6-8 j 9409080109 940826 PDR ADOCK 05000410 i e PDR j

1 ATTACHMEN ) 3 NIAGARA MOHAWK POWER CORPORATION LICENSE NO. NPF-69 DOCKET NO. 50-410 Suonortina Information and No Sianificant Hazards Consideration Analysis introduction Primsry containment integrity ensures that the release of radioactive materials from the containment will be restricted to those leakage paths and associated leak rates assumed in the accident analyses. This restriction, in conjunction with the leakage rate limitation, will limit the Control Room and site boundary radiation doses to within the limits of General Design Criterion 19 and 10 CFR 100 during accident conditions.

The primary containment contains an emergency air lock that serves as an attemate personnel escape route to the main air lock should the need arise and provides additional service accessibility. The air lock consists of two doors, each sealed with a double-gasket compression seal with a test tap for leak testing between the seals. The doors can be leak rate tested from outside containment. Both doors swing inward (toward containment) so as to seat under positive accident pressure. To ensure containment integrity, the doors are mechanically interlocked so that if one door is open, the other cannot be opened. The doors are equipped with valves for equalizing air pressure prior to opening. Limit switches are provided on the doors to enable their operation to be monitored from outside each door. Other primary containment air locks are similar in design.

On May 12,1994, while performing the 39.75 psig (pounds per square inch gauge) primary containment air lock leak test, technicians were unable to establish the required test pressure. The leakage was determined to be into the drywell based on containment oxygen alarms received during performance of the test. Two leak paths exist for air to enter the drywell, past the door seals and/or through the associated equalizing valve. The inner doors are tensioned to perforrn the 39.75 psig test. To determine the leakage path, I the inner door strong backs were detensioned and the 10 psig seal test performed on the  !

inner door seals. The test verified the integrity of the door seals indicating that the leakage was through the equalizing valve. I The air lock door handwheel is used to open the inner (handwheel turned to the left) or i outer door (handwheel tumed to the right), and the associated equalizing valve. The I handwheel indicator is normally located at the 12:00 position. To re-perform the 39.75 )

psig air lock leak test the strong backs were retensioned. The air lock leak test was l performed but was unsuccessful. To close the inner equalizing valve, the handwheel was j turned to the 1:00 position. The air lock leak test was again performed with acceptable '

leak rates. To assure that the handwheel was not moved from the 1:00 position (i.e., the l satisf actorily tested condition), a sign was posted on the air lock warning that any l manipulation of the handwheel may violate containment integrity. Also, operations placed I a Holdout tag on the door handle stating that the plant must be in COLD SHUTDOWN prior l to operating the handle.

Technical Specification Surveillance requirement 4.6.1.3 requires the air lock interlock test be performed every six months. Accordingly, the next required test is scheduled to be performed no later than November 13,1994 or with the 25 percent extension, Page 1 of 4

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D:cember 29,1994. To perform the interlock test, the outer door must be openzd (by turning the handwheel) and then the inability of the inner door to be opened is verified.

. However, in moving the handwheel from the 1:00 position, the leak tightness of the inner I equalizing valve would be indeterminate. In addition, the strongbacks on the inner door j would need to be removed to perform the interlock test. The strong backs were not '

detensioned as normal following the last air lock test because air lock entry, and the required handwheel movement, would have made the leak tightness of the inner equalizing valve indeterminate. Because the strongbacks have been tensioned for an extended length of time, once detensioned, the operability of the door seals cannot be guaranteed.

In summary, repositioning the handwheel from the 1:00 position, which is required to perform the air lock interlock test, would cause loss of primary containment integrity.

This Amendment will allow Niagara Mohawk to declare the air lock interlock inoperable, based on the failure to perform the surveillance, but take compensatory measures to allow continued plant operation. Niagara Mohawk requests approval of this Application for Amendment by December 1,1994,in order to provide sufficient time to implement the approved Amendment by December 29,1994, which is the latest date for the next air lock interlock test, and avoid a plant shutdown.

Proposed Chances to Technical Specifications Add the following ACTION statement to Technical Specification 3/4.6.1.3.

b. With the primary containment air lock interlock mechanism inoperable, verify in OPERABLE door is closed within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />, lock an OPERABLE door closed within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> and verify that an OPERABLE door is locked closed once per 31 days; otherwise be in at least HOT SHUTDOWN within the next 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> and in COLD SHUTDOWN within the following 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.

Current Technical Specification ACTION Statement 3/4.6.1.3.b

b. With the primary containment air lock inoperable, except as a result of an inoperable air lock door, maintain at least one air lock door closed; restore the inoperable air lock to OPERABLE status within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> or be in at least HOT SHUTDOWN within the next 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> and in COLD SHUTDOWN within the following 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.

Proposed Technical Specification ACTION Statement 3/4.6.1.3.c (Previously 3/4.6.1.3.b)

c. With the primary containment air lock inoperable, except as a result of an inoperable air lock door or inoperable interlock mechanism, maintain at least one air lock door closed; restore the inoperable air lock to OPERABLE status within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> or be in at least HOT SHUTDOWN within the next 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> and in COLD SHUTDOWN within the following 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.

Ey_aluation Technical Specification Surveillance Requirement 4.6.1.3 requires that primary containment air lock door seats be leak rate tested at 10 psig and the air lock doors be leak tested at 39.75 psig. Technical Specification 4.6.1.3 also requires verification every six months that only one air lock door can be openad at a time (i.e., the air lock interlocks are operab:a).

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, i Niagara Mohawk proposes to revise Spacification 3/4.6.1.3 to add an ACTION statement to specifically address the circumstances when an air lock interlock becomes inoperable.

. Currently, an inoperable interlock ruch3nism would require entry into Specification 3/4.6.1.3, ACTION b. ACTION b requires that with a primary containment air lock inoperable, maintain at least one air lock door closed; restore the inoperable air lock to OPERABLE status within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> or be in at least HOT SHUTDOWN within the next 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> and in COLD SHUTDOWN within the following 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> in comparison, the proposed ACTION statement requires, following determination that an interlock is inoperable, that an OPERABLE door be verified closed within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />, an OPERABLE door be locked closed within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> and that an OPERABLE door be verified locked closed every 31 days.

The purpose of the air lock interlock mechanism is to allow only one door in each penetration to be opened at a time. This mechanism ensures that a gross breach of primary containment does not exist when primary contsinment is required to be operable. [

Closure of a sincl e door in each air lock is sufficient to provide a 'eak tight barrier following postuleted events. The proposed ACTION statement requires that an operable door be locked shut if the associated air lock interlock is inoperable. Locking an operable air lock door shut assures that at least one air lock door is closed and provides the function of the interlock mechanism. The 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> completion time to verify an operable door is clnsed is consistent with Specification 3/4.6.1, " Primary Containment integrity," which allows 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> to re-establish containment integrity. The 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> completion time to lock an operable door closed is considered reasonable considering that the operable door is being maintained closed and is consistent with ACTION a.1 which permits 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> to lock an operable door if a door is inoperable. Verifying that an operable door is locked shut at a 31 day frequency is based on engineering judgement and is considered adequate in view of the low likelihood of a locked door being mispositioned. Also, the 31 day frequency is consistent with Surveillance Requirement 4.6.1.1.b, which requires that containment penetratior,s be verified isolated every 31 days. The proposed ACTION Statement is consistent with Specification 3.6.1.2, " Primary Conta: ament Air Lock," of the improved Technical Specifications. Based on the cbove discussion, Niagara Mohawk has concluded the proposed changes will have no impact on the performance or reliability of the primary containment or the primary containment air locks.

1 Conclusions  !

The purpose of a primary containment air lock interlock mechanism is to allow only one door to be opened at a time. This mechanism ensures that a gross breach of primary containment does not exist when primary containment is required to be operable. Closure ,

of a single door in each air lock is sufficient to provide a leak tight barrier following l postulated events, if an air lock interlock is inoperable, the proposed ACTION statement requires that an operable door be locked shut and periodically verified locked shut. This assures that at least one rperable air lock door is locked closed which provides the function of the interlock. Therefore, these changes will not be inimical to the common defense and security or the health and safety of the public.

No Sianificant Hazards Consideration Analysis 10 CFR 50.91 requires that at the time a licensee requests an amendment, it must provide to the Commission its analysis, using the standards in Section 50.92 about the issue of no significant hazards consideration. Therefore,in accordance with 10 CFR 50.91 and 10 CFR 50.92, the following analysis has been performed:

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The operation of Nine Mile Point Unit 2. In accordance with the orocosed amendment, will

. not involve a sianificant increase in the orobability or cong_auences of an accident

.previously evaluated.

The primary containment and containment air locks are not initiators or precursors to an ,

accident. Primary containment integrity ensures that the release of radioactive materials from the containment will be restricted to those leakage paths and associated leak rates i assumed in the accident analyses. Therefore, the proposed changes to the air lock ACTION statements cannot affect the probability of a previously evaluated accident.

The purpose of a primary containment air lock interlock is to allow only one door to be opened at a time in each penetration. This provision ensures that a gross breach of primary containment does not exist when primary containment is required to be operable.

Closure of a single door in each air lock is sufficient to provide a leak tight barrier following postulated events. If an air lock interlock is inoperable, the proposed ACTION requires that an operable door be locked shut and periodically verified locked and shut. This assures that at least one air lock door is closed, which provides the function of the interlock, thereby assuring containment integrity is maintained. Therefore, the proposed change will not significantly increase the consequences of an accident previously evaluated.

The operation of Nine Mile Point Unit 2. In accordance with the proposed amendment, will not create the nossibility of a new or dilfgrent kind of accident from any accident previousiv evaluated.

The proposed changes to the primary containment air lock specification will allow continued plant operation with an inoperable interlock as long as an operable door is locked closed and periodically verified to be locked closed. The changes do not introduce any new accident precursors and do not involve any alterations to plant configurations which could initiate a new or different kind of accident. The change provides an alternate means of ensuring that only one primary containment air lock door is opened at a time in each penetration. Therefore, the proposed changes will not create the possibility of a new or different kind of accident from any previously evaluated.

The operation of Nine Mile Point Unit 2 in accordance with the orocosed amendment, wj!!I.

not involve a sianificant reduction in a marain of safety.

The proposed changes to the primary containment air lock ACTION statements will not affect the ability of the containment to respond to an accident and limit releases to wi:hin 10 CFR Part 100 and GDC 19 guidelines. The changes do not affect the design or performance characteristics of the containment or containment air locks but simply provide an alternative means of ensuring that only one air lock door is opened at a time.

Therefore, the proposed changes do not involve a significant reduction in a margin of safety.

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