ML20091Q957

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Proposed TS 3.6.1.7,increasing Time 12-inch & 14-inch Containment Purge Sys Supply & Exhaust Valves May Be Open in Operational Condition 1,2 & 3 from 90 H Per 365 Days to 135 H Per 365 Days & Deleting Expired Footnotes for Clarity
ML20091Q957
Person / Time
Site: Nine Mile Point Constellation icon.png
Issue date: 08/28/1995
From:
NIAGARA MOHAWK POWER CORP.
To:
Shared Package
ML20091Q937 List:
References
NUDOCS 9509060161
Download: ML20091Q957 (14)
v • d • e


Text

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ATTACHMENT A

. Niagara Mohawk Power Corporation l-License No. NPF-69 E

Docket No. 50-410 Proposed Chances to Technical Specifications i

Replace existing Technical Specification pages 3/4 6-13,3/4 6-14 and BASES page B3/4 6-2 with the attached revised pages 3/4 6-13,3/4 6-14 and B3/4 6 2. These pages have been retyped in their entirety with marginal markings to indicate changes to the text.

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L 9509060161 950828 PDR ADDCK 05000410

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-,__ _ _ _ _ PDR __

CONTAINMENT SYSTEMS PRIMARY CONTAINMENT PRIMARY CONTAINMENT PURGE SYSTEM LIMITING CONDITIONS FOR OPERATION 3.6.1.7 The drywell and suppression chamber 12-inch and 14-inch purge supply and exhaust isolation valves shall be OPERABLE and:

l a.

The 12-inch (2 CPS *AOV105, 2 CPS *AOV107,2 CPS *AOV109,2 CPS *AOV111) and 14-inch (2 CPS *AOV104, 2 CPS *AOV106, 2 CPS *AOV108, 2 CPS *AOV110) valves in the purge system supply and exhaust lines may be open for up to 135 hours0.00156 days <br />0.0375 hours <br />2.232143e-4 weeks <br />5.13675e-5 months <br /> per 365 days for l VENTING or PURGING.*

b.

Purge system valves 2 CPS *AOV105 (12-inch), 2 CPS *AOV107 (12-inch), 2 CPS *AOV109 (12-inch), and 2 CPS *AOV110 (14-inch) shall be blocked to limit the opening to 70.

Purge system valve 2 CPS *AOV111 (12-inch) shall be blocked to limit the opening to 60.

APPLICABILITY: OPERATIONAL CONDITIONS 1,2, and 3.

ACTION:

a.

With the drywell and suppression chamber purge supply and/or exhaust isolation valve (s) inoperable, or open for more than 135 hours0.00156 days <br />0.0375 hours <br />2.232143e-4 weeks <br />5.13675e-5 months <br /> per 365 days for other than pressure l

control *, close the open valve (s); otherwise isolate the penetration (s) within 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-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 />.

b.

With a drywell and suppression chamber purge supply and/or exhaust isolation valve (s) with resilient material seals having a measured leakage rate exceeding the limit of Surveillance Requirement 4.6.1.7.2, restore the inoperable valve (s) 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 />.

l The 135 hour0.00156 days <br />0.0375 hours <br />2.232143e-4 weeks <br />5.13675e-5 months <br /> limit shall not apply to the use of valves 2 CPS *AOV108 (14-inch) and l

2 CPS *AOV110 (14-inch), or 2 CPS *AOV109 (12-inch) and 2 CPS *AOV111 (12-inch), for primary containment pressure control, provided 2GTS*AOV101 is closed, and its 2-inch bypass line is the only flow path to the standby gas treatment system.

I NINE MILE POINT - UNIT 2 3/4 6-13 Amendment No. N i

CONTAINMENT SYSTEMS' PRIMARY CONTAINMENT PRIMARY CONTAINMENT PURGE SYSTEM SURVEILLANCE REQUIREMENTS t

4.6.1.7.1 At least once per refueling outage each drywell and suppression chamber purge supply and exhaust isolation valve of Specification 3.6.1.7.b shall be verified to be blocked to limit the opening to 70* or 60', as applicable.

4.6.1.7.2 At least once per 92 days each 12-and 14-inch drywell and suppression chamber purge supply and exhaust isolation valve with resilient material seals shall be demonstrated OPERABLE by verifying that the measured leakage rate is less than or equal to 4.38 scf per hour per 14-inch valve and 3.75 scf per hour per 12-inc.h valve when pressurized to Pa,39.75 psig.

Those purge supply and exhaust isolation valves listed on Table 3.6.1.2-1 shall be pressurized to 40.0 psig.

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NINE MILE POINT - UNIT 2 3/4 6-14 Amendment No. d/

CONTAINMENT SYSTEMS BASES l

PRIMARY CONTAINMENT 3/4.6.1.4 PRIMARY CONTAINMENT STRUCTURAL INTEGRITY This limitation ensures that the structural integrity of the containment will be maintained comparable to the original design standards for the life of the unit. Structural integrity is required to ensure that the containment will withstand the design pressure of 45 psig in the event of a loss-of-coolant accident (LOCA). A visual inspection in conjunction with Type A leakage tests is sufficient to demonstrate this capability.

3/4.6.1.5 DRYWELL AND SUPPRESSION CHAMBER INTERNAL PRESSURE The limitations on drywell and suppression chamber internal pressure ensure that the containment peak pressure of less than 39.75 psig does not exceed the design pressure of 45.0 psig during LOCA conditions or that the external pressure differential does not exceed the design maximum extemal pressure differential of 4.7 psi. The limit of 14.2 to 15.45 psia for initial positive containment pressure will limit the total pressure to 39.75 psig, which is less than the design pressure and is consistent with the safety analysis.

3/4.6.1.6 DRYWELL AVERAGE AIR TEMPERATURE The limitation on drywell average air temperature ensures that the containment peak air temperature does not exceed the design temperature of 340 F during steam line break conditions and is consistent with the saf' ty analysis.

in addition, the maximum drywell average air temperature is also the limiting initial condition u';ed to determine the maximum negative differential pressure acting on the drywell and suppression chamber following inadvertent actuation of the containment sprays.

3/4.6.1.7 PRIMARY CONTAINMENT PURGE SYSTEM The 14-inch drywell and 12-inch suppression chamber supply and exhaust valves are limited to 135 hours0.00156 days <br />0.0375 hours <br />2.232143e-4 weeks <br />5.13675e-5 months <br /> of use per 365 days during purge or vent operations in OPERATIONAL CONDITIONS 1, j 2, and 3 to meet the requirements of Branch Technical Position CSB 6-4 and Generic Letter 83-02 for valves greater than 8 inches in diameter. The requirement to limit the opening of 2 CPS *AOV105,2 CPS

  • AOV107,2 CPS *AOV109, and 2 CPS *AOV110 to 70 degrees, and 2 CPS *AOV111 to 60 degrees ensures these valves will close during a LOCA or steam line break accident, and therefore, the site boundary dose guidelines of 10 CFR 100 would not be exceeded in the event of an accident during purging or venting operations.

NINE MILE POINT - UNIT 2 B3/4 6-2 Amendment No. dd

ATTACHMENTB Niagara Mohawk Power Corporation License No. NPF-69 Docket No. 50-410 Supportina Information and No Sianificant Hazards Consideration Analy111 Introduction Niagara Mohawk Power Corporation (NMPC) proposes revisions to the Nine Mile Point Unit 2 (NMP2) Technical Specification 3.6.1.7, Primary Containment Purae System. The proposed change would increase the maximum allowable time the 12-inch and 14-inch containment purge systern supply and exhaust lines may be used for VENTING and PURGING, from 90 hours0.00104 days <br />0.025 hours <br />1.488095e-4 weeks <br />3.4245e-5 months <br /> pcr 365 days to 135 hours0.00156 days <br />0.0375 hours <br />2.232143e-4 weeks <br />5.13675e-5 months <br /> per 365 days, in OPERATIONAL CONDITION 1,2 and 3 (Power Operation, Startup and Hot Shutdown). As described in Attachment C, NMP2 has logged approximately 84.4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> of purge system operation over the past 365 days.

NMPC has scheduled a shutdown of NMP2 on September 1,1995, to perform corrective maintenance on recirculation flow control valve position monitoring instrumentation and to repair the normal position monitoring instrumentation for a suppression chamber to drywell vacuum breaker. The outage is scheduled for approximately five days. Containment purge system operation is necessary to de-inert the containment to allow personnel entry, and to inert the conteinment to allow unit restart. Without approval of the requested time limit extension, insufficient purge system operating time would be available to allow containment inerting following entry into the primary containment under hot, pressurized conditions during restart from the planned outage. If personnel access to the primary containment is limited to Cold Shutdown conditions due to the present limitations on purge system operation, the performance of inspections inside primary containment with the reactor coolant pressure boundary at hot, pressurized conditions is precluded. Inability to perform these inspections would impair NMPC's ability to detect and correct minor leakage from hot, pressurized systems inside primary containment, and to evaluate the effectiveness of the corrective maintenance on the recirculation flow control valve position monitoring instrumentation prior to resumption of normal power operation, thereby increasing the potential for thermal cycling of the reactor vessel and a forced unit shutdown. Approval of this Application for Amendment is therefore requested by September 1,1995.

The proposed amendment also includes an editorial change to delete footnotes to Specification 3/4.6.1.7. This change is editorial because the footnotes have expired.

Description of Proposed Technical Snecification Chanae The proposed change would revise the Limiting Conditions For Operation (LCO) 3.6.1.7a, Action "a" of LCO 3.6.1.7, and its corresponding "*" footnote, to reflect an increase in the allowable containment purge system operating time from 90 hours0.00104 days <br />0.025 hours <br />1.488095e-4 weeks <br />3.4245e-5 months <br /> per 365 days to 135 hours0.00156 days <br />0.0375 hours <br />2.232143e-4 weeks <br />5.13675e-5 months <br /> per 365 days.

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The proposed' change would also revise LCO 3.6.1.7, action b, Surveillance Requirement 1

4.6.1.7.2 and their corresponding footnotes, to delete an expired provision relaxing the operability requirements of purge valve 2 CPS *AOV106.

Current Version of LCO 3.6.1.7a i

3.6.1.7 The drywell and suppression chamber 12-inch and 14-inch purge supply and exhaust isolation valves shall be OPERABLE *

  • and:

a.

The 12-inch (2 CPS *AOV105, 2 CPS *AOV107,2 CPS *AOV109,2 CPS'AOV111) and 14-inch (2 CPS

  • AOV110) valves in the purge system supply and exhaust lines may be open for up to 90 hours0.00104 days <br />0.025 hours <br />1.488095e-4 weeks <br />3.4245e-5 months <br /> per 365 days for VENTING or PURGING.*

Proposed Chance to LCO 3.6.1.7a 3.6.1.7 The drywell and suppression chamber 12-inch and 14 inch purge supply and exhaust isolation valves shall be OPERABLE and:

a.

The 12-inch (2 CPS

  • AOV111) and 14-inch (2 CPS
  • AOV108, 2 CPS' AOV110) valves in the purge system supply and exhaust lines may be open for up to 135 hours0.00156 days <br />0.0375 hours <br />2.232143e-4 weeks <br />5.13675e-5 months <br /> per 365 days for VENTING or PURGING.*

Current Version of LCO 3.6.1.7 Action "a" a.

With the drywell and suppression chamber purge supply and/or exhaust isolation valve (s) inoperable, or open for more than 90 hours0.00104 days <br />0.025 hours <br />1.488095e-4 weeks <br />3.4245e-5 months <br /> per 365 days for other than pressure control *,

close the open valve (s); otherwise isolate the penetration (s) within 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-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 Chanae to LCO 3.6.1.7. Action a.

a.

With the drywell and suppression chamber purge supply and/or exhaust isolation valve (s) inoperable, or open for more than 135 hours0.00156 days <br />0.0375 hours <br />2.232143e-4 weeks <br />5.13675e-5 months <br /> per 365 days for other than pressure control *, close the open valve (s); otherwise isolate the penetration (s) within 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-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 />.

Current Version of LCO 3.6.1.7 Action "b" b.

With a drywell and suppression chamber purge supply and/or exhaust isolation valve (s) with resilient material seals having a measured leakage rate exceeding the limit of Surveillance Requirement 4.6.1.7.2, restore the inoperable valve (s) 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 />."*

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1

t 4

Eronosed Cha' nae _10 LCO 3.6.1.7, Action b.

b.

With a drywell and suppression chamber purge supply and/or exhaust isolation valve (s) with resilient material seals having a measured leakage rate exceeding the limit of Surveillance Requirement 4.6.1.7.2, restore the inoperable valve (s) 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 />.

Current Version of "*" Footnote for LCO 3.6.1.7 The 90 hour0.00104 days <br />0.025 hours <br />1.488095e-4 weeks <br />3.4245e-5 months <br /> limit shall not apply to the use of valves 2 CPS *AOV108 (14-inch) and 2 CPS'AOV110 (14-inch), or 2 CPS

Proposed Chanae to "** Footnote for LCO 3.6.1.7 The 135 hour0.00156 days <br />0.0375 hours <br />2.232143e-4 weeks <br />5.13675e-5 months <br /> limit shall not apply to the use of valves 2 CPS *AOV108 (14-inch) and 2 CPS

  • AOV110 (14-inch), or 2 CPS *AOV109 (12-inch) and 2 CPS

Current Version of ** *" Footnote for LCO 3.6.1.7 Operability requirements of LCO 3.6.1.7 and Action statement "b" do not apply to 2 CPS

  • AOV106 from April 24,1991 until the next plant cold shutdown but not later than September 30,1991 provided that 2 CPS *AOV104 and 2 CPS *AOV106 are closed and deactivated and 2 CPS-V6 is 1(>cked closed.

Prooosed Chance to "* *" Footnote for LCO 3.6.1.7 DELETED Current Version of Surveillance Reouirement 4.6.1.7.2 4.6.1.7.2 At least once per 92 days each 12-and 14-inch drywell and suppression chamber purge supply and exhaust isolation valve with resilient material seals shall be demonstrated OPERABLE by verifying that the measured leakage rate is less than or equal to 4.38 scf per hour per 14-inch valve and 3.75 scf per hour per 12-inch valve when pressurized to Pa,39.75 psig.

Those purge supply and exhaust isolation valves listed on Table 3.6.1.2-1 shall be pressurized to 40.0 psig '

Proposed Chance to Surveillance Reouirement 4.6.1.7.2 4.6.1.7.2 At least once per 92 days each 12-and 14-inch dr/well and suppression chamber purge supply and exhaust isolation valve with resilient material seals shall be demonstrated OPERABLE by verifying that the measured leakage rate is less than or equal to 4.38 scf per hour per 14-inch valve and 3.75 scf per hour per 12-inch valve when pressurized to Pa,39.75 psig.

Those purge supply and exhaust isolation valves listed on Table 3.6.1.2-1 shall be pressurized to 40.0 psig.

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b

_C_urrent Version of "*" Footnote for SR 4.6.1.7.2 Surveillance requirement 4.6.1.7.2 does not apply to 2 CPS *AOV106 from April 24,1991 until the next plant cold shutdown but not later than September 30,1991 provided that 2 CPS *AOV104 and 2 CPS *AOV106 are closed and deactivated and 2 CPS-V6 is locked closed.

Proposed Chance to "*" Footnote for SR 4.6.1.7.2 DELETED Current Version of BASES Section 3/4.6.1.7 3/4.6.1.7 PRIMARY CONTAINMENT PURGE SYSTEM The 14-inch drywell and 12-inch suppression chamber supply and exhaust valves are limited to 90 hours0.00104 days <br />0.025 hours <br />1.488095e-4 weeks <br />3.4245e-5 months <br /> of use per 365 days during purge or vent operations in OPERATIONAL CONDITIONS 1, 2, and 3 to meet the requirements of Branch Technical Position CSB 6-4 for valves greater than 8 inches in diameter. The requirement to limit the opening of 2 CPS *AOV105,2 CPS *AOV107, 2 CPS *AOV109, and 2 CPS *AOV110 to 70 degrees, and 2 CPS *AOV111 to 60 degrees ensures these valves will close during a LOCA or steam line break accident, and therefore, the site boundary dose guidelines of 10 CFR 100 would not be exceeded in the event of an accident during purging or venting operations.

Proposed Chance to BASES Section 3/4.6.1.7 3/4.6.1.7 PRIMARY CONTAINMENT PURGE SYSTEM The 14-inch drywell and 12-inch suppression chamber supply and exhaust valves are limited to 135 hours0.00156 days <br />0.0375 hours <br />2.232143e-4 weeks <br />5.13675e-5 months <br /> of use por 365 days during purge or vent operations in OPERATIONAL CONDITIONS 1, 2, and 3, to meet the requirements of Branch Technical Position CSB 6-4 and Generic Letter 83-02 for valves greater than 8 inches in diameter. The requirement so limit the opening of 2 CPS'AOV105,2 CPS *AOV107,2 CPS *AOV109, and 2 CPS *AOV110 to 70 degrees, and 2 CPS *AOV111 to 60 degrees ensures these valves will close during a LOCA or steam line break accident, and therefore, the site boundary dose guidelines of 10 CFR 100 would not be exceeded in the event of an accident during purging or venting operations.

Evaluation The containment purge system is designed to purge the primary containment of nitrogen prior to personnel entry, and to inert the primary containment with nitrogen during restart, using 14-inch and 12-inch lines for the drywell and suppression chamber, respectively. Purge exhaux is drawn from the drywell and suppression chamber through the standby gas treatment system for filtration and monitored release through the plant stack. A 2-inch bypass line is used in this pressure control mode of purge system operation. The 2-inch bypass line serves to elimir' ate the need to use the larger purge exhaust lines for primary containment pmssure control during normal power operation.

NMP2's current Technical Specification LCO 3.6.1.7 includes a restriction on the number of hours per year that the 12-inch and 14-inch containment purge system valves may be opened in 4 of 7

j OPERATIONAL CONDITION 1,2, and 3. This time limit ensures that the probability of a design basis accident resulting in a potential radiological release, concurrent with purge system operation, is maintained sufficiently low so that such an event is not deemed credible. The restriction is intended to conservatively balance the operational needs of the plant (i.e.,

containment de-inerting and inerting) with the requirement to preclude a radiological release through the containment purge system and avoid a potentially damaging pressure transient in the l

Standby Gas Treatment System (GTS) downstream of the purge system isolation valves.

NRC Standard Review Plan (SRP) Section 6.2.4 and Branch Technical Position CSB 6-4 contain criteria for containment purge system design and operation. These criteria include a provision to waive an eight inch limit in line size and justification of a larger line size via acceptable dose consequence analysis, provided a 90 hour0.00104 days <br />0.025 hours <br />1.488095e-4 weeks <br />3.4245e-5 months <br /> per year operating limit is imposed during power operation, startup and hot shutdown. Recognizing that the operating limit should be dependent on plant specific parameters, and that the need for purging during normal operations was not always anticipated in early plant designs, the NRC later clarified the general criteria for purge system operation and design in Generic Letter (GL) 83-02. The GL criteria and NMP2's compliance are discussed below:

Containment purge or vent valves are locked closed if not qualified for LOCA. The NMP2 12-inch and 14-inch purge system isolation valves listed in Technical Specification 3.6.1.7 are qualified for closure post-LOCA, as documented in Appendix J to Supplement 3 of the NMP2 NRC Safety Evaluation Report (NUREG-1047, Supplement 3).

Containment purge or vent valves are used only as needed for safety related reasons.

Operation of the 12-inch and 14-inch purge lines is limited to necessary activities associated with containment purging and venting consistent with plant and personnel safety.

Purge or vent valves with resilient seating materials are subject to periodic testing and replacement. Purge system valves with resilient seal material are subject to augmented testing per Technical Specification 4.6.1.7, and are replaced as warranted by testing and operating history.

The allowable time per year of vent / purge system operation will be considered on a case-by-case basis. The proposed increase in allowable use of the purge system is based on a plant specific assessment demonstrating that the risk of challenges to the standby gas treatment system and a radiological release associated with purge system operation, b maintained acceptably low. Therefore, the proposed amendment would continue to ensure consistency with the NRC criteria set forth iri SRP 6.2.4, Branch Technical Position CSB 6-4 and Generic Letter 83-02.

Recent operating experience at NMP2 has resulted in purge system operation approaching the current operating limit of 90 hours0.00104 days <br />0.025 hours <br />1.488095e-4 weeks <br />3.4245e-5 months <br /> per year. As stated in Attachment C, NMPC considers the use l

of the purge system over the past 365 day period to have been necessary and prudent. As previously discussed, NMPC is planning to take NMP2 off line during the early part of September.

I During this outage, NMPC plans to perform corrective maintenance on recirculation flow control valve position monitoring instrumentation and repair the normal position rnonitoring instrumentation for a suppression chamber to drywell vacuum breaker. In support of system inspections inside the drywell during plant restart under hot, pressurized conditions, the purge 5 of 7 i

system cumulative operating time will exceed 90 hours0.00104 days <br />0.025 hours <br />1.488095e-4 weeks <br />3.4245e-5 months <br />, necessitating this request to extend the operational limit to 135 hours0.00156 days <br />0.0375 hours <br />2.232143e-4 weeks <br />5.13675e-5 months <br /> per year. The proposed increase is based on a conservative assessment of the risk associated with purge system operation, which is summarized below.

A plant specific Probabilistic Risk Assessment (PRA) was performed to determine the safety significance of a 45 hour5.208333e-4 days <br />0.0125 hours <br />7.440476e-5 weeks <br />1.71225e-5 months <br /> per year increase in the use of the containment purge system. The probability of a LOCA large enough to cause a rapid depressurization of the reactor pressure vessel (i.e., large LOCA) with core damage, occurring during the additional 45 hour5.208333e-4 days <br />0.0125 hours <br />7.440476e-5 weeks <br />1.71225e-5 months <br /> period is 1.5E-9. Assuming a radiological release would occur for any large LOCA with core damage, the increased frequency of a radiological accident in containment during purge system operation is 1.5E-9 per year. Assuming purge system operation up to the proposed limit of 135 hours0.00156 days <br />0.0375 hours <br />2.232143e-4 weeks <br />5.13675e-5 months <br /> per year, the total frequency is 4.5E-9 per year. Conservatively assuming the purge system is operated at the proposed limit each year over a 40 year period, the probability of a radiological accident concurrent with purge system operation would be 1.8E-7. This assumption is judged to be conservative in that the current limit of 90 hours0.00104 days <br />0.025 hours <br />1.488095e-4 weeks <br />3.4245e-5 months <br /> per year has not been exceeded since the plant commenced operation (full power license was granted in July,1987).

The low safety significance of purge system operation during plant operation is reflected in the NMP2 individual Plant Examination (IPE) which was reviewed by the NRC via letter to NMPC dated August 22,1994. The IPE assumed that each of the purge system containment penetrations are open 10% of the time, or 876 hours0.0101 days <br />0.243 hours <br />0.00145 weeks <br />3.33318e-4 months <br /> per year, which is significantly greater than the proposed time limit of 135 hours0.00156 days <br />0.0375 hours <br />2.232143e-4 weeks <br />5.13675e-5 months <br /> per year. The IPE calculated an Early Large Release (greater than 10% of core source term released within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> of an accident) frequency of 8.0E-7 per year using this assumption.

Conclusion The proposed amendment to increase the time limit of containment purge system operation would continue to maintain a low risk of a design basis accident occurring concurrent with operation cf the purge system. Therefore, operation of NMP2 in accordance with the proposed amendment to NMP2 Technical Specification 3.6.1.7 would continue to ensure the public health and safety.

i 10CFR50.91 requires that at the time a licensee requests an amendment, it must provide to the Commission its analysis using the standards in 10CFR50.92 concerning the issue of no significant hazards consideration. Therefore,in accordance with 10CFR50.91, the following analysis has been performed:

The operation of Nine Mile Point Unit 2. In accordance with the orocosed amendment. will not involve a sianificant increase in the orobability or conseagences of an accident oreviousiv evaluated.

The proposed amendment would revise NMP2 Technical Specification 3.6.1.7, to increase the allowable time of containment purge system operation in operational conditions 1,2 and 3 (power operation, startup and hot shutdown), from 90 hours0.00104 days <br />0.025 hours <br />1.488095e-4 weeks <br />3.4245e-5 months <br /> per year to 135 hours0.00156 days <br />0.0375 hours <br />2.232143e-4 weeks <br />5.13675e-5 months <br /> per year. The request would also delete expired footnotes for editorial clarity. This proposed change does not affect the consequences of any previously evaluated accident, as it does not affect the progression of any accident sequence in ti:e NMP2 licensing basis, it is, however, necessary to evaluate the proposed change for its impact on the probability of a design basis accident concurrent with purge system operation. ProbObilistic Risk Assessment (PRA) was used to j

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determine the incrementalincrease in probability associated with the proposed change. This increase was found to be extremely small, and would maintain an extremely low total probability of a radiological accident concurrent with purge system operation.

Therefore, the proposed change will not involve a significant increase in the probability or consequences of an accident previously evaluated.

The operation of Nine Mile Point Unit 2. In accordance with the orocosed amendment, will not treate the possibility of a new or different kind of accident from any oreviousiv evaluated.

The proposed change would increase the allowable time the containment purge system may be used during plant operation. It does not involve any new physical plant changes or new operational configurations. No new failure modes are introduced.

Therefore, this proposed change does not create the possibility of a new or different kind of accident from any previously evaluated.

The coeration of Nine MHe Point Unit 2. In accordance with the orooosed amendment, will not involve a sianificant reduction in a maroin of safety.

The proposed change would not affect the ability o maintain primary containment integrity.

Based on a conservative, plant specific evaluation, the proposed change is shown to maintain an acceptably low risk associated with containment purge system operation, consistent with NRC criteria contained in Standard Review Plan Section 6.2.4, Branch Technical Position CSB 6-4, and Generic Letter 83-02. Therefore, this proposed change does not involve a significant reduction in a margin of safety.

Niagara Mohawk's evaluation of this proposed amendment pursuant to 10CFR50.91 has determined that it involves no significant hazards consideration.

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ATTACHMENT C Niagara Mohawk Power Corporation License No. NPF-69 Docket No. 50 410 Exolanation of Why Emer.gency Occurred and Why the Situation Could Not Have Been Avoided LCO 't.C. i.7.8, " Primary Containment Purge System," establishes a maximum allowable time duration of 90 hours0.00104 days <br />0.025 hours <br />1.488095e-4 weeks <br />3.4245e-5 months <br /> per 365 days for OPERATIONAL CONDITION 1,2 and 3 during which the 12-inch and 14-inch purge supply and exhaust primary containment isolation valves in the purge system supply and exhaust lines may be open for VENTING and PURGING primary containment.

The purge supply and exhaust primary containment isolation valves are: 12-inch valves 2 CPS *AOV105,2 CPS

A cumu!ative time of approximately 84.4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> has been reached for OPERATIONAL CONDITION 1,2 and 3 during which the above purge supply and exhaust primary containment isolation valves have been opened during the past 365 days. The accumulation of these hours is attributed to the five plant shutdowns during the last 365 days, four of which required personnel entry into the primary containment including the fourth refueling outage. For nne of these shutdowns, entry into primary containment was initially planned but subsequently determined to be unnecessary.

Since it is Niagara Mohawk's practice not to allow personnel entry into an inerted containment, PURGING (i.e., de-inerting) was necessary to permit drywell entry. The cumulative time also includes operation of these primary containment isolation valves to permit re-inerting of the primary containment after personnel have exited and secured primary containment.

It is industry practice, including at NMP2, during a plant shutdown to perform PURGING (i.e., de-inerting) of the primary containment in OPERATIONAL CONDITION 1,2 and 3, as permitted by LCO 3.6.6.2, Drvwell and Suooression Chamber Oxvaen ConcentratioD, to minimize the time before the primary containment can be entered by plant personnel and to allow containment entry while systems are in a hot, pressurized condition to detect system leakage. Likewise, for plant restart, LCO 3.6.6.2 permits delaying of PURGING (i.e., re-inerting) of primary containment until OPERATIONAL CONDITION 1.

For plant restarts, this above practice is necessary to allow inspections within primary containment to detect rninor leakage from hot, pressurized systems. These inspections enhance the timely detection and possible repair of minor leakage prior to resumption of normal power operation. Performance of these inspections in OPERATIONAL CONDITION 4 would result in far i

less meaningful results. In addition, certain types of minor leakage can be corrected without depressurization of the reactor pressure vessel which minimizes thermal cycles on the reactor pressure vessel. NMPC believes that continuation of these practices for the planned outage are in the best interests of maintaining the safe operation of the plant. Therefore, Niagara Mohawk has concluded that it has prudently managed the operation of the purge supply and exhaust isolation valves to minimize the accumulation of hours towards the 90 hour0.00104 days <br />0.025 hours <br />1.488095e-4 weeks <br />3.4245e-5 months <br /> time limit.

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NMPC has de'cided to shutdown NMP2 and de-inert the primary containment to allow personnel entry into primary containment to perform corrective maintenance on recirculation flow control valve position monitoring instrumentation. Primary containment entry is highly desirable during restart of the unit under hot pressurized conditions to evaluate the effectiveness of the corrective maintenance on the monitoring instrumentation. Recent attempts to correct the problem with this instrumentation without drywell entry have been unsuccessful. Currently, the maximum power of NMP2 is limited to approximately 95% of rated power due to problems with this instrumentation.

Further, the normal position indication (control room display) for one suppression chamber to drywell vacuum breaker is not available, necessitating the use of alternate means of periodically verifying vacuum breaker position. The planned outage will also allow repair of the normal position monitoring instrumentation located within primary containment.

The problems with the recirculation flow control valve monitoring instrumentation and the vacuum breaker position monitoring instrumentation occurred after the restart of the unit from the fourth refueling outage. Absent these problems, NMP2 was expected to operate normally through this fuel cycle and would have recovered significant hours against the 90 hour0.00104 days <br />0.025 hours <br />1.488095e-4 weeks <br />3.4245e-5 months <br /> limit by the end of 1995. Therefore, Niagara Mohawk has concluded that it could not have anticipated or avoided the situation leading up to this request.

Niagara Mohawk requests that this application for amendment be considered an emergency situation so as to prevent the loss of the ability to perform visual inspections ci systems within primary containment during hot, pressurized conditions. Based on the current cumulative time, there is insufficient time remaining below the 90 hour0.00104 days <br />0.025 hours <br />1.488095e-4 weeks <br />3.4245e-5 months <br /> limit to permit entry during restart.

Without this proposed change, inspections would have to be performed in cold shutdown and thereby be far less likely to identify minor leakage from systems within the primary containment.

Furthermore, the loss of visual inspection capability during hot, pressurized conditions increases the likelihood of thermal cycles on the reactor pressure vessel since certain types of leakage could be corrected in OPERATIONAL CONDIT!ON 1,2, or 3 without depressurization of the reactor pressure vessel. Therefore, the proposed change enhances nuclear safety by increasing the likelihood of the identification of leakage from systems inside primary containment and by reducing the potential for thermal cycles on the reactor pressure vessel.

Delaying the unit shutdown until sufficient time below the 90 hour0.00104 days <br />0.025 hours <br />1.488095e-4 weeks <br />3.4245e-5 months <br /> limit becomes available to permit such inspections in the primary containment would prevent NMP2 from increasing power output to its licensed power level for an additional 3% months, thus forcing continued derated operation.

Accordingly, Niagara Mohawk requests this application be considered an emergency situation per 10CFR50.91(a)(5), so as to maintain the capability to detect undesirable leakage from systems inside the containment, to allow inspection of the repaired flow control valve position monitoring instrumentation under hot condition, and to minimize thermal cycles on the reactor pressure vessel. Based on the planned outage schedule, approval of this application for amendment is requested by September 1,1995 in order to support unit startup.

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ATTACHMENT D Niagara Mohawk Power Corporation License No. NPF-69 Docket No. 50-410 Environmental Considerations The proposed amendment involves an increase to the number of hours the containment purge system may be operated in operational conditions 1,2 and 3, from 90 hours0.00104 days <br />0.025 hours <br />1.488095e-4 weeks <br />3.4245e-5 months <br /> per year to 135 hours0.00156 days <br />0.0375 hours <br />2.232143e-4 weeks <br />5.13675e-5 months <br /> per year. It also includes an editorial change to delete expired footnotes. The proposed change:

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Does not involve a significant hazards consideration.

The basis for no significant hazards consideration is contained in Attachment B.

2)

Does not involve a significant change in the types or significant increase in the amounts of any effluents that may be released offsite.

The proposed increase in purge system operating time does not involve any new plant evolutions that could possibly affect the types of offsite effluent releases. The amount of effluents released offsite during normal plant operation will continue to be subject to the limits of Technical Specification 3/4.11 and 10 CFR 20, Radioactive Effluents, and is not affected by this change.

Based on the significant hazards analysis in Attachment B, there is no significant increase in the radiological consequences of an accident.

3)

Does not involve a significant increase in individual or cumulative occupational radiation exposure.

The proposed change has no impact on NMPC's ability to maintain occupational radiation exposure as low as reasonably achieveble.

Based on the above, the proposed amendment does not involve any irreversible adverse environmental consequences, and meets the categorical exclusion criteria set forth in 10 CFR 51.22(c)(9). Pursuant to 10 CFR 51.22(b), no environmental impact statement nor environmental assessment need be prepared in connection with the issuance of this proposed amendment.

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