ML20078R622

Proposed Tech Specs Substituting for Pages Contained in Proposed TS Amends Submitted Prior to 950130 Authorization

ML20078R622
Person / Time
Site:	Pilgrim
Issue date:	02/15/1995
From:	BOSTON EDISON CO.
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ML20078R621	List: ML20078R617 ML20078R622
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NUDOCS 9502230054
Download: ML20078R622 (17)

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, - - - g PNPS TABLE 3.2.A 114 ES INSTRUMENTATION THAT INITIATES PRINARY CONTAINMENT IS01ATION .

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$ Operable Instrument Channels Per Trip System (1)

Minimum Available Instrument Trio Level Settinz Action (2)

M N 2(7) 2 Reactor Low Water Level 211.7" indicated level (3) A and D

'iEgg 4 W 1 1 Reactor High Pressure 576 psig D l 2 2 Reactor Low-Low Water Level at or above - 46.3 in. A indicated level (4) 2 2 Reactor High Water Level $45.3" indicated level (5) B 2(7) 2 High Drywell Pressure $2.22 psig A 2 2 Low Pressure Main Steam Line 2810 psig (8) B 2(6) 2 High Flow Main Steam Line $136% of rated steam flow B 2 2 Main Steam Line Tunnel Exhaust Duct High Temperature 5170 F B 2 2 Turbine Basement Exhaust Duct High Temperature $150 F B 1 1 Reactor Cleanup System' High Flow $300% of rated flow C 2 2 Reactor Cleanup System High Temperature 5150 F C Amendment No. 34;-42;-86;-147;-159;-151;-154 3/4.2-7

M PNPS '

TABLE 3.2.B (Cont)

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INSTRUMENTATION THAT INITIATES OR CONTROLS THE CORE AND CONTAINMENT COOLING SYSTEMS .

Minimum # of Operable Instrument -

Channels Per Trip System (1) Trip Function Trio Level Setting Remarks 2 High Drywell Pressure $2.22 psig 1. Initiates Core Spray; LPCI; HPCI.

2. In conjunction with Low-Low Reactor Water Level, 94.4-115.6 second time delay and LPCI or Core Spray pump running, initiates Auto Blowdown (ADS)

3. Initiates starting of Diesel Generators

4. In conjunction with Reactor Low Pressure initiates closure of HPCI vacuum breaker containment isolation valves.

1 Reactor Low Pressure 400 psig i 5 Permissive for opening Core Spray and LPCI Admission valves.

1 Reaci.cr' Low Pressure $76 psig In conjunction with PCIS signal permits l closure of RHR (LPCI) injection valves.

1 Reactor Low Pressure 400 psig i 5 In conjunction with Low-Low Reactor Water Level initiates Core Spray and LPCI.

2 Reactor Low Pressure 900 psig i 5 Prevents actuation of LPCI break detection circuit.

2 Reactor Low Pressure 80 psig 15 Isolates HPCI and in conjunction with High Drywell Pressure initiates closure of HPCI vs.cuum breaker containment isolation valves.

Amendment No. 42;-113 1 -148;-151 3/4.2-11

EASES:

3.2 PRO'fECTIVE INSTRUMENTATION In addition to reactor protection instrumentation which initiates a reactor scram,. protective instrumentation has been provided which initiates action to mitigate the consequences of accidents which are beyond the operator's ability to control, or terminates operator errors before they result in serious consequer.ces. This set of specifications provides the limiting conditions of operation for the primary system isolation function, initiation of the core cooling systems, control rod block and standby gas treatment systems. The objectives of the Specifications are (i) to assure the effectiveness of the protective instrumentation when required by preserving its capability to tolerate a single failure of any component of such systems even during periods when portions of such systems are out of service for maintenance, and (ii) to prescribe the trip settings required to assure adequate performance. When necessary, one channel may be made inoperable for brief intervals to conduct required functional tests and calibrations.

Some of the settings on the instrumentation that initiate or control core and containment cooling have tolerances explicitly stated where the high and itw values are both critical and may have a substantial effect on safety. The aet points of other instrumentation, where only the high or low end of the setting has a direct bearing on safety, are chosen at a level away from the normal operating range to prevent inadvertent actuation of the safety system involved and exposure to abnormal situations.

Actuation of primary containment valves is initiated by protective instrumentation shown in Table 3.2.A which senses the conditions for which isolation is required. Such instrumentation must be available whenever primary containment integrity is required.

The instrumentation which initiates primary system isolation is connected in a dual bus arrangement. 1 The low wate level instrumentation closes all isolation valves except those in Groups 1, 4 and 5. This trip setting is adequate to prevent core uncovery in the case of a break in the largest line assuming a 60 second valve closing time. Required closing times are less than this.

Reactor pressure instrumentation is used for closure of Group isolation valves and is set to trip at $76 psig. This prevents overpressurization of the RHR shutdown cooling piping. The isolation setpoint is chosen: (1) at a pressure below where the RHR piping could be overpressurized, (2) so that the isolation valves can close in the required time, and (3) at the point where the maximum differential pressure associated with the isolation valves is not exceeded.

The low low reactor water level instrumentation closes the Main Steam Line Isolation Valves, Main Steam Drain Valves, Recire Sample Valves (Group 1) activates the CSCS subsystems, starts the emergency diesel generators and trips the recirculation pumps. This trip setting level was chosen to be high enough to prevent spurious actuation but low enough to initiate CSCS operation and primary system isolation so that no fuel damage will occur and so that post accident cooling can be accomplished and the guidelines of 10CFR100 will not be violated. For large breaks Amendment No. 1951 -1131 -151 B3/4.2-1 l

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I ATTACHMENT B TO BECo Letter #95- 022  :

Keep-Fill Switches t (BECo Ltr. #2.94.098 dated 94/94) i i

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l 112 3/4.5-9 121 B3/4.5-6 -

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LIMITING CONDITION FOR OPERATION SURVEILLANCE REQUIREMENT 3.5 COR$ANDCONTAINMENTCOOLING 4.5 CORE AND CONTAINMENT COOLING

• SYSTEMS (Cont) SYSTEMS (Cont)

H. Maintenance of Filled Discharne Zine (Cont)

2. Following any period where the LPCI system or core spray systems have not been required to be operable, the discharge piping of the inoperable system shall be vented from the high point prior to the return of the system to service.

3. Whenever the HPCI or RCIC system is lined up to take i

suction from the torus, the discharge piping of the HPCI and RCIC shall be vented from the high point of the system and water flow observed on a monthly basis.

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l Amendment No. 397 -135 3/4.5-9

. 1 e BASES: l l

3.5 CORE AND CONTAINMENT COOLINC SYSTEMS (Cont) j

' occur. A potential draining of the reactor vessel (via control rod blade leakage) would allow this water to enter into the torus and after approximately 140,000 gallons have accumulated (needed to meet minimum NPSH requirements for the LPCI and/or core spray pumps), tha torus would be able to l serve as a common suction header. This would allow a closed loop operation of  !

the LPCI system and the core spray system (once re-aligned) to the torus. In j addition, the other core spray system is lined up to the condensate storage j tanks which can supplement the refuel cavity and dryer / separator pool water to '

provide core flooding, if required.

i Specification 3.9 must also be consulted to determine other requirements for the diesel generators.

C. Deleted H. Maintenance of Filled Discharve Pine If the discharge piping of the core spray, LPCI system, HPCI, and RCIC are not filled, a water hammer can develop in this piping when the pump and/or pumps are started. An analysis has been done which shows that if a water hammer were to occur at the time at which the system were required, the system would I

still perform its design function. However, to minimize damage to the discharge piping and to ensure added margin in the operation of these systems, this Technical Specification requires the discharge lines to be filled whenever the system is in an operable condition.

An acceptable method of ensuring that the lines are full is to vent at the high points. The monthly frequency is based on the gradual nature of void buildup in the ECCS piping, the procedural controls, and operating experience.

4.5 CORE AND CONTAINMENT COOLING SYSTEMS SURVEILLANCE FREOUENCIES The testing interval for the core and containment cooling systems is based on industry practice, quantitative reliability analysis, judgment and practicality. The core cooling systems have not been designed to be fully testable during operation. For example, in ti.e case of the HPCI, automatic initiation during power operation would result in pumping cold water into the reactor vessel which is not desirable. Complete ADS testing during power operation causes an undesirable loss-of-coolant inventory. To increase the availability of the core and containment cooling systems, the components which make up the system; i.e., instrumentation, p' imps, valves, etc., are tested frequently. The pumps and motor operated valves are tested in accordance with ASME B&PV Code,Section XI (IWP and IWV, except where specific relief is granted) to assure their operability. The frequency and methods of testing are described in the PNPS IST program. The PNPS IST Program is used to assess the operational readiness of pumps and valves that are safety-related or ,

important to safety. When components are tested and found inoperable the '

impact on system operability is determined, and corrective action or Limiting conditions of Operation are initiated. A simulated automatic actuation test once each cycle combined with code inservice testing of the pumps and valves is deemed to be adequate testing of these systems. I The surveillance requirements provide adequate assurrace that the core and containment cooling systems will be operatle when required.

Amendment No. 395 -135 3-149 B3/4.5-6 l

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i 4 ATTACHMENT C TO BECo Letter #95- 022 l

. Standby Gas and Control Room High i Efficiency Air Filtration Systems  !

(BECo Ltr. #2.94.099 dated 9/6/94) -l i

e,d eso. # m .o. , j 158 3/4.7-11 l 158A 3/4.7-12 158B 3/4.7-13 158C 3/4.7-14 158D 3/4.7-15 3/4.7-16 3/4.7-17

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c. 1 LIMITING CONDITIONS FOR OFFJLATION SURVEILLANCE REQUIREMENTS  !

3,7- CONTAINMENT SYSTEMS (Conti) 4.7 CONTAINMENT SYSTEMS (Cont)

A'. Primary Containment (Cont)

With no H2 analyzer operable, reactor operation  !

-is allowed for up to 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br />. If one of the '

inoperable analyzers is not  :

made fully operable within  ;

48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br />, the reactor shall be in a least Hot Shutdown j within the next 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />. .

B. Standby Gas Treatment System and B. Standby Gas Treatment System and-Control Room High Efficiency Air Control Room High Efficiency Air Filtration System l Fmrah Sem .;

1. Standby Cas Treatment System 1. Standby Gas Treatment System

a. Except as specified in y

,, y, g , f l 3.7.B.1.c or 3.7.B.1.f operating cycle, it shall below, both trains of the be demonstrated that standby gas treatment system pressura drop across the and the diesel generators combined high efficiency

, required for operation of i filters and charcoal such trains shall be adsorber banks is less operable at all times when than 8 inches of water at '

secondary containment 4000 cfm. -

integrity is required or the reactor shall be shutdown in

2. At least once per 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />. operating cycle, demonstrate that the

b. 1. The results of the in-ne ea ers on each place cold DOP tests on train are operable and j HEPA filters shall show 8re c8Pable of an output E99% DOP removal. The at least M W.

results of halogenated hydrocarbon tests on '

3. The tests and analysis of charcoal adsorber banks Specification 3.7.B.1.b.

shall show 299% shall bp performed at halogenated hydrocarbon least once per operating

1. • " ""1' cycle or following painting, fire or chemical release in any ,

ventilation zone communicating with the j system while the system is operating that could contaminate the HEPA filters or charcoal ,

adsorbers. '

4. At least once per operating cycle, automatic initiation of i I

Amendment No. 15,+42 1 50 1 -51 7 -52 1 -112;-144 2 -151 3/4.7-11

LIMITING CONDITIONS FOR OPERATION SURVEILLANCE REQUIREMENTS 3.7 ,

CONTAINMENT SYSTEMS (Cont) 4.7 CONTAINMENT SYSTEMS (Cont)

B. Standby Gas Treatment System and B. Standby Gas Treatment System and control Room Hirh Efficiency Air Control Room Hirh Efficiency Air Filtration System (Cont) Filtration System (Cont)

2. The results of the each branch of the laboratory carbon sample standby gas treatment analysis shall show t95% system shall be methyl iodide removal at demonstrated, with a velocity within 10% of Specification 3.7.B.1.d system design, 0.5 to 1.5 satisfied.

mg/m' inlet methyl iodide concentration, 270% R.H. 5. Each train of the standby anda190'F. The analysis gas treatment system results are to be shall be operated for at verified as acceptable least 15 minutes per within 31 days after month, sample removal, or declare that train 6. The tests and analysis of inoperable and take the Specification 3.7.B.1.b.2 actions specified shall be performed after 3.7.B.1.c. every 720 hours0.00833 days <br />0.2 hours <br />0.00119 weeks <br />2.7396e-4 months <br /> of system operation.

c From and after the date that one train of the Standby Gas b. 1. In-place cold DOP testing Treatment System is made or shall be performed on the found to be inoperable for HEPA filters after each any reason, except as completed or partial specified in 3.7.B.1.f replacement of the HEPA below, continued reactor filter bank and after any operation, irradiated fuel structural maintenance on handling, or new fuel the HEPA filter system handling over spent fuel housing which cculd pool or core is permissible affect the HEPA filter only during the succeeding bank bypass leakage.

seven days providing that within 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> all active 2. Halogenated hydrocarbon v, ; onents of the other testing shall be

.dby gas treatment train performed on the charcoal shall be demonstrated to be adsorber bank after each operable. partial or complete replacement of the charcoal adsorber bank or after any structural maintenance on the charcoal adsorber housing which could affect the charcoal adsorber bank bypass leakage.

l Amer.dment No. 421 -50r-511-112r-144 3/4.7-12 j l

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LIMITING CONDITIONS FOR OPERATION SURVEILIANCE REQUIREMENTS

. 3 . '/ CON AINMENT SYSTEMS (Cont) 4 .' 7 CONTAINMENT SYSTEMS'(Cont)-

B. Standby Cas Treatment System and B. Standby Gas Treatment System and

. Control Room High Efficiency Air Control Room High Efficiency Air Filtration System.(Cont) Filtration System (Cont)

d. Fans shall operate within i 10% of 4000 cfm.

e Except as specified in )

3.7.B.l.c or 3.7.B.l.f, both  ;

l trains of the Standby Gas  :

- Treatment System shall be  ;

operable during irradiated .

fuel handling, or new fuel j' handling over the spent fuel pool or core. If the system is not operable, fuel ,

movement shall not be i started. Any fuel assembly  ;

movement in progress may be l completed. ,

f. During refueling, one train of the Standby Gas  :

Treatment System can be t without its safety-related i bus and/or emergency diesel ,

generator without entering the LCO action statement i provided the following conditions'are met:  ;

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Fuel movement will not '

occur until five days  !

following reactor shutdown. ,

Frior to and during fuel movement, the SB0 D /G or the Shutdown Transforaer is required to be operable ,

and capable of supply power 't to the emergency bus.  ;

Fuel movement will not i occur until the reactor ,

vessel is flooded up to [

elevation 114'.

The train of SGTS ,

without its safety related bus or without is emergency  ;

diesel generator will have power supplied from a normal offsite source via a non safety-related bus. The >

normal offsite source 4 consists of either the Startup Transformer or Unit Auxiliary Transformer (Backfeed Mode). t Amendment No. 42 1 -50;-51,-52;-191 1 -112;-144 1 -151 3/4.7-13 i

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LIMITING CONDITIONS FOR OPERATION SURVEILIANCE REQUIREMENTS  ;

L3 .7 CONTAINMENT SYSTEMS (Cont) 4.7 CONTAINMENT SYSTEMS (Cont) t B. ' Standby Cas Treatment System and B. Standby Cas Treatment System and Control Hoom High Efficiency Air Control Room High Efficiency Air Filtration System (Cont) Filtration System (Cont)

2. Control R J,pm Hieh Efficiency 2. Control Room High Efficienev Air Filtration System Air Filtration System a Except as specified in a. At least once-per operating Specification 3.7.B.2.c or cycle the pressure drop I 3.7.B.2.e below, both trains across each combined filter of the Control Room High train'shall be demonstrated Efficiency Air Filtration to be less than 6 inches of System used for the water at 1000 cfm or the processing of inlet air to calculated equivalent.

the control room under accident conditions and the .b. 1. The tests and analysis of diesel generator (s) required Specification 3.7.B.2.b for operation of each train shall be performed once +

of the system shall be per operating cycle or operable whenever secondary following painting, fire ,

containment integrity is or chemical release in required and during fuel any ventilation zone handling operations. communicating with the system while the system

b. 1. The results of the in- is operating.

place cold DOP tests on HEPA filters shall show 2. In-place cold DOP testing ,

299% DOP removal. The shall be performed after results of the 'each complete or partial halogenated hydrocarbon replacement of the HEPA tests on charcoal filter bank or after any ,

adsorber banks shall show structural maintenance on l 199% halogenated the system housing which '

hydrocarbon removal when could affect the HEPA test results are filter bank bypass extrapolated to the leakage.

initiation of the test.

3. Halogenated hydrocarbon

2. The results of the testing shall be laboratory carbon sample performed after each analysis shall showh95% complete or partial methyl iodide removal at replacement of the a velocity within 10% of charcoal adsorber bank or system design, 0.05 to after any structural ,

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0.15 mg/m 5 inlet methyl maintenance on the system i iodide concentration, housing which could '

E70% R.H. , and 2125 ' F. affect the charcoal The analysis results are adsorber bank bypass to be verified as leakage, acceptable within 31 days after sample removal, or 4. Each train shall be declare that train operated with the heaters inoperable and take the in automatic for at least 15 minutes every month.

' Amendment No. 42r-50 1 -52r-ll2r-144r-151 3/4.7-14 j i

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-s LIMITING CONDITIONS.FOR OPERATION SURVEILIANCE REQUIREMENTS

3.7 ,

CONTAINMENT SYSTfJiS,(Cont) 4.7 CONTAINMENT SYSTEMS (Cont).

Shutdown Transformer is i requirer to be operable and

-capable of supply power to

'the emergency bus.

- Fuel movement will not occur until the reactor vessel-is flood up to elevation.114'. r

- The train of CRHEAF ,

without is safety relared ,

bus or without its emergency i diesel generator will have

_ power supplied from a normal '

offsite source via a non safety-related bus. The normal offsite source consists of either the Startup Transformer or Unit  :

Auxiliary Transformer (Backfeed Mode).

C. Secondary Containment Secondary Containment C.

1. Secondary containment integrity 1. Secondary containment shall be maintained during all surveillance shall be performed  !

modes of plant operation except as indicated below: I when all of the following conditions are met. a. A preoperational secondary I containment capability test

a. The reactor is suberitical shall be conducted after and Specification 3.3.A is isolating the reactor met, building and placing either standby gas treatment system

b. - The 7:eactor water filter train in operation.

temperature is below 212

• F Such tests shall demonstrate and the reactor coolant the capability to maintain system is vented. 1/4 inch of water vacuum under calm wind (<5 mph)

c. No activity is being conditions with a filter performed which can reduce t rain flow rate of not more the shutdown margin below than 4000 cfm.

that specified in Specification 3.3.A. b. Additional tests shall be performed during the first

d. The fuel cask or irradiated operating cycle under an fuel is not being moved in adequate number of different the reactor building. environmental wind conditions to enable valid ,

2. If Specification 3.7.C.1 cannot extrapolation of the test l be met, procedures shall be results.  !

initiated to establish conditions listed in Speci- c. Secondary containment fication 3.7.C.1.a through d. capability to maintain 1/4 inch of water vacuum under Amendment No. 0 3/4.7-16

ff ff LIMITING CONDITIONS FOR OPERATION SURVEILIANCE REQUIREMENTS l

3.7 CONTAINMENT SYSTEMS (Cont) 4.7 CONTAINMENT SYSTEMS (Cont)

C .- Secondary Containment (Cont) C. Secondary Containment (Cont) calm wind (5 mph) conditions with a filter train flow rate of not more than 4000 cfm, shall be demonstrated at each refueling outage prior to refueling.

Amendment No. 0 3/4.7-17

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ATTACHMENT D TO BECo Letter #95-022 Primary Containment (BECo Ltr. #2.94.100 dated 9/6/94) l Old Pace # New Paae #  !

157 3/4.7-8 170 B3/4.7-7 ,

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LIMITING CONDITION FOR OPERATION SURVEILMNCE REQUIREMENTS 3.7 CONTAINMENT SYSTEMS (Cont) 4.7 CONTAINMENT SYSTEMS (Cont) i l

A. ' Primary Containment (Cont) A. Primary Containment (Cont)

.1. The valve is demonstrated b. During each refueling ,

to,open with the applied interval-force of the installed j test actuator as 1. Each vacuum breaker shall indicated by the position be tested to determine switches and remote that the disc opens ,

position indicating freely to the touch and j lights . returns to the closed position by gravity with

2. The valve shall return by no indication of binding. 4 gravity when released I after being opened by 2. Vacuum breaker position- '

remote or manual means, switches and installed to within 3/32" of the alarm systems shall be j fully closed position. calibrated and j functionally tested.  ;

3. Neither of the two .

position alarm systems, 3. At least 25% of the which annunciate in the vacuum breakers shall be Control Room when any visually inspected such i vacuum breaker opening that all vacuum breakers ,

exceeds 3/32", are in shall have been inspected l alarm. following every fourth  :

refueling interval. If l

b. Any drywell-suppression deficiencies are found, .

chamber vacuum breaker may all vacuum breakers shall l be non-fully closed as be visually inspected and i determined by the position deficiencies corrected.  ;

switches provided that the l drywell to suppression 4. A drywell to suppression I chamber differential decay chamber leak rate test rate is demonstrated to be shall demonstrate that ,

not greater than 25% of the the differential pressure differential pressure decay decay rate does not .

rate for the maximum exceed the rate which  ;

allowable bypass area of would occur through a 1 }

0.2f t 2. inch orifice without the l addition of air or

c. Reactor operation may nitrogen.

continue provided that no ,

more than 2 of the drywell-  ;

pressure suppression chamber  !

vacuum breakers are determined to be inoperable  !

provided that they are secured or known to be in the closed position.

i Amendment No. 681 -871-149 3/4.7-8 i

LIMITING CONDITIONS FOR OPERATION SURVEILIANCE REQUIREMENTS l 3.7_ CONTAINMENT SYSTEMS (Cont) 4.7 CONTAINMENT SYSTEMS (Cont)

B. Standby'Cas Treatment System and B. Standby Gas Treatment System and  :

Control Room High Efficiency Air Control Room High Efficiency Air l Filtration System (Cont) Filtration System (Cont) actions specified in 5. The test and analysis of .  ;

3.7.B.2.c. Specification 3.7.B.2.b.2 ,

shall be performed after i every 720 hours0.00833 days <br />0.2 hours <br />0.00119 weeks <br />2.7396e-4 months <br /> of system-operation. j c From and after the date that  !

one. train of the Control c. At least once per operating Room High Efficiency Air cycle demonstrate that the Filtration System is made or ' inlet heaters on each train found to be incapable of are operable and capable of supplying filtered air to an output of at least 14 kw.

the control room for any reason, reactor operation or ,

refuelin6 operations-are .

permissible only during the j succeeding 7 days providing that within 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> all active components of the other CRHEAF train shall be demonstrated operable. If ,

the system is not made fully operable within 7 days, reactor shutdown shall be initiated and the reactor ,

shall be in cold shutdown ,

within the next 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br /> and i irradiated fuel handling operations shall be terminated within 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />.

Fuel handling operations in progress may be completed.

d. Perform an instrument

d. Fans shall operate within functional test on the j 10% of 1000 cfm. humidistats controlling the heaters once per operating

e. During refueling, one train cycle, of the CRHEAF can be without i its safety-related bus and/or emergency diesel generator without entering the LCO action statement ,

provided the following conditions are met:

- Fuel movement will not occur until five days following reactor shutdown. i Prior to and during fuel movement, the SBO D/G or the Amendment No. 42 1 -50s-51 2 -571 -1121-1441 -151 3/4.7-15 l

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~' 1 B&EEE' 3/4.7 CONTAINMENT SYSTEMS'(Cent) .

A. -

• Primary Containment (Cont); .

a Each drywell suppression chamber vacuum breaker is equipped with three i switches. One switch provides full open indication only. Another switch {

provides closed indication and an alarm should any vacuum breaker come off l l its closed seat by greater than 3/32". The third switch provides a separate ,

and redundant alarm should any vacuum breaker come off its closed seat by l greater than 3/32". The two alarms above are those referred to in Section 3.7.A.4.a.3 and 3.-7.A.4.d. .

The water in the suppression chamber is used only for cooling in the event of l an accident; i.e., it is not used for normal operation; therefore, a daily check of the temperature and volume is adequate to assure that adequate heat removal capability is present.

Inerting The relatively small containment volume inherent in the GE-BWR pressure ,

suppression containment and the large amount of zirconium in the core are such  ;

that the occurrence of a very limited (a percent or so) reaction of the zirconium and steam during a loss-of-coolant accident could lead to the  ;

liberation of hydrogen combined with an air atmosphere to result in a  !

flammable concentration in the containment. If a sufficient amount of  ;

hydrogen is generated and oxygen is available in stoichiometric quantities, the subsequent ignition of the hydrogen in rapid recombination rate could lead to failure of the containment to maintain a low leakage integrity. The 4% ,

oxygen concentration minimizes the possibility of hydrogen combustion following a loss-of-coolant. l The occurrence of primary system leakage following a major refueling outage or-other scheduled shutdown is much more probable than the occurrence of the i loss-of-coolant accident upon which the specified oxygen concentration limit l is based. Permitting access to the drywell for leak inspections during a ,

startup is judged prudent in terms of the added plant safety offered without  !

significantly reducing the margin of safety. Thus, to preclude the _

possibility of starting the reactor and operating for extended periods of time 1 with significant leaks in the primary system, leak inspections are scheduled ,

during startup periods, when the primary system is at or near rated operating temperature and pressure. The 24-hour period to provide inerting is judged to be sufficient to perform the leak inspection and establish the required oxygen  ;

concentration.  :

The primary containment is normally slightly pressurized during periods of )

reactor operation. Nitrogen used for inerting could leak out.of the containment but air could not leak in to increase oxygen concentration. Once ,

the containment is filled with nitrogen to the required concentration, no monitoring of oxygen concentration is necessary. However, at least twice a J week the oxygen concentration will be determined as added assurance. Mark I Containment Long Term Program testing showed that maintaining a drywell to i

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Amendment No. 31 7 -53 t -55 1 -113 B3/4.7-7 l

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