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BALTIMORE GAS AND ELECTRIC COMPANYP. O. B OX 147 5

BALTIMORE, M ARYLAN D 21203

April 7, 1980Antuun E.LuNovan,JR.

v cc Pats.ormeSu pp6v

Office of Nuclear Reactor RegulationU. S. Nuclear Regulatory CommissionWashington, D. C. 20555

Attn: Mr. Robert W. Reid, Chief.Operating Reactors Branch #hDivision of Operating Reactors

Subject: Calvert Cliffs Nuclear Power PlantUnits Nos. 1 & 2, Dockets Nos. 50-317 & 50-318Containment Purre and Isolation

Refeience: NRC letter dated 2/25/80 fron R. W. Reid toA. E. Lundvall, Jr., same subject.

Gentlemen:.

The referenced letter requested that we provide additionalinformation rerarding the design of the Calvert Cliffs containment uurgesystem esnecially with rerard to electrical reset, override and bypass.You also requested that we describe our design with respect to specificNRC design criteria. The attachnent to this letter provides our responsesto the six cuestions posed in your letter.

Very truly yours,

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for Vice President, Supply

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cc: J. A. Biddison, EsquireG. P. Trowbridge, Esquire

Mr. E. L. Conner. Jr.

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Ihe only containment isolation valves that have a containmentisolation signal override which overrides more than one initiating para-meter are the reactor coolant system sanple, and the containment air samplevalves . These valves are automaticalJv closed via high containmentpressure and/or low pressurizer pressure, i.e. , the SIAS signal. The .Calvert Cliffs engineered safety features actuation system (ESFAS) designis such that the initiating parameters for SIAS are combined in a two-of-four logic on an individual parameter basis, and then combined again in an"and/or" logic for ultimately initiating SIAS. It is this SIAS signal tothe individual sample isolation valves which is provided with an override.Because the individual initiating parameters' isolation signals are not eachsent to the valve, this above criteria for these sample valves can not bemet.

This override is being incorporated in resconse to NUREG-0578,section 2.1.8a., requirements for post-accident samnling. In this NUREG veare directed by the NRC to obtain reactor coolant system and conte.inmentatmosphere samnles under accident conditions.

To implement this NUREG requirement and the above NRC designcriteria at Calvert Cliffs vould require eight (8) override handsvitches perisolation valve; one for each initiating parameter's process transmitter.It would also nean that a means vould be created to override all SIASinitiation functions.

The above consequences are unacceptable to BG&E, and even thoughwe concur with the intent of the above design criteria, we are not applyingit to these sample valves nor their return lines.

We can appreciate the intent of this F.iteria when applied to acontainment penetration such as containment p".rge, wherein one may wish tooverride one isolation signal (e.g. , high containment pressure for thenurpose of releiving this condition), whi'.e still maintaining an automaticclosure on high radiation. We do not feel this criteria is applicable tothese samnle valves, because NUREG-0578 requires that this sample be obtain-able under accident conditions regardless of what the ESFAS is electricallydirecting the valves to do. Providing overrides for the individual initiatingparameters would be superfluous, very expensive, and with no other changesto the ESPAS to eliminate the possibility of a total SIAS override, it woulddegrade the reliability of SIAS.

Criterion 2: Sufficient physical features (e.g. , key lock switches) shouldbe provided to facilitate adequate administrative controls.

Key lock switches are provided for those valves with a containmentisolation signal override.

Criterion 3: The system-level annunciation of the overriden status shouldbe provided for every safety system impacted when an overrideis active.

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This criteria does not apply to Calvert Cliffs since no safety

nystems (RPS or ESF ) are imnacted by containment isolation override.We are providing annunication of the overriding of the individual valves.

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Criterion h: At least two diverse signals should be provided to initiate ;isolation of the containment ventilation system. Specifically , !containment high radiation, safety injection actuation, and/or ,containment high pressure should automatically initiate contain- i

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ment isolation.

The Calvert Cliffs containment purge valves are isolated by theSIA3 signal and/or the containment high radiation signal.

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Criterion 5: The instrumentation and control systems provided to initiate

icontainment isolation should be designed and qualified assafety-grade equipment.

The containment isolation equipment is part of the ESFAS, and itsdesign criteria is deceribed in the Calvert Cliffs FSAR, Chanter 7,reproduced below-

7.3 1 Design Basis

7.31.1 Conformance to Standards

The design of the engineered safety features actuation systems ardcomponent parts was based on the apulicable requirements of IEEE 279Criteria for Itotection Systems for Nuclear Power Generating Stations.Maximum consideration has been given to the following criteria cenaistentwith the objectives of this document:

a. Fingle Failure

Any single failure within the protection system vill not preventprover protection srstem action when required.i

b. Quality of Components and Modules

Components and modules used in the manufacture of the actuationsystems exhibit a quality consistent with the nuclear power plantLO year design life objective and with minimum maintenancerequirements and lov failure rates,

c Channel Independence

The actuation systems include four redundant sensor subsystemsand two redundant actuation subsystems. Indenendence has beenprovided between redundant subsystems or channels to accomnlish

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decounling of the effects of unsafe environmental factors, elec-tric transients, and physical accident consequences, and toreduce the likelihood of interactions between channels duringmaintenance operations or in the event of channel malfunction.Indenendence has been obtained by:

1. Electrical Isolation

Electrical isolation has been provided between redundantchannels, between sensor and actuation subsynte=s and betweenthe engineered safety features actuation system and ancillaryequipment. Where electrical isolation is provided, an applica-tion of short circuit, open wire, ground, or notential does not

inhibit a nrotective action as a result of the failure of theredundant system.

2. Physical Senaration

Physcial senaration has been maintained between redundantsensor subsystems, Vetween sensor and actuation subsystems,and between redundant actuation subsystems by providingseparate and isolated cabinets for each of the four sensor isubsystems and each of the two actuation subsystems. Each ofthe twelve containment pressure transmitters has an individualsensing point. A minimum clearance of 3 feet is provided foreach sensing point and its associated transmitter.

3 System Repair

The system has been designed such that routine servicing andpreventative maintenance can be performed without interferenceto normal plant oneration or without loss of system functionavailability. Performance of these operations does not resultin a simultaneous unavailability of both actuation subsystems.

See Section 7.3.1.2. The system is mechanically and electrical-ly divided into subunits or modules based on the followingconsiderations:

a) Standardization of subunits

b) Minimization of interconnections and interviring

c) Interchangeability of subunits

The subunits include associated equipment such as indicatinglights, pushbuttons, potentiometers, and selector switches.

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7.3.1.2 Mocale Withdrawal

Withdrawal of any module results in an annunciation of the affectedchannel. In the case of the sensor subsystem, the withdrawal also results ina trip signal to the two-out-of-four logie matrix. An electrical interlockis provided which prevents the opening of the doors to both actuation channelcabinets at the same tine.

7.3.1.3 Seismic Requirements

The engineered safety features actuation systems are classifiedas seismic Class I and are designed to withstand all simultaneous horizontaland vertical accelerations resulting from the design basis earthquakewithout loss of function.

7.3.1.h Environmental Requirements

All components which must operate in a LOCI environment were type:tested at the expected temocrature, pressure and humidity,

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Criterion 6: The overriding or resetting of the isolation actuation signalshould not cause tha automatic reopening of any isolation />purge valve.

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The purpose of overriding an isolation signal to a particularj valve vould be to allow the opening of this valve, so this criteria is

contrary to the purpose of overriding.

Please note that the containment isolation valves are overriddenon an individual valve basis, rather than on an entire isolation system

basis.

The containment isolation reset scheme, as described above in 1.,is designed so that there vill be no automatic opening of any containmentisolation valves when this signal is reset.

Question h: Describe any differences between the control of containmentventilation isolation valves and dampers and the valves anddampers of all other engineered safety features (EST).

Resnonse

' The design criteria for the control of all the ESF valves, includingthe containnent ventilation isolation valves, is described in the CalvertCliffs FDAR section 7.3, and reproduced in our resnonse to criteria 5 above.

The only difference in the control schemes for the containmentventilation valves and the other automatic containment isolation valves isthat the ventilation valves response (close) on either a SIAS or a high

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radiation signal, and the other containment isolation valves respond to aSIAC nignal or a CIS signal . (Note? SIAS is initiated on high containmentpressure and/or low pressurizer nressure). Additionally, the sample valvesdescribed above are provided with a SIAS override and the containmentventilation valves are not.

Question 5: If the system design of any ESF system contains an override,vill the overriding of one type of safety actuation signal causethe blocking of any other type of safety actuation signal?

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Rennonse,

This question vill be answered on two levels: The ESF systemlevel and the individual component level.

At the ESF system level, neither of the two manual overrides(pressurizer pressure block and steam generator isolation system block)vill block any safety actuation sicnal other than the signal intended tobe blocked. These are described in Calvert Cliffs FSAR section 7.3.2.2.

At the individual component level the following equipment havemanual overrides that override more than one ESF signal to the component:

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1. The reactor coolant system sample containment isolation valves;

2. The containment air sample containment isolation valves;

3. The salt water valves to the component cooling and service watercooling heat exchangers; and

k. The low pressure safety injection (LPSI) pumps.

Items 1 and 2 above are discussed in our response to Criterion 1.

The operation of the valves in item 3 above are discussed in theCalvert Cliffs FSAR Chapter 9, section 9.5.2 3. The handsvitches areprovided to allow isolation and realignment of the system in the event of arutture in the salt water cooling to and from these heat exchangers.

The LPSI pumps have an override handsvitch which overrides SIASand the recirculation actuation signal (RAS) to the pumns. This overrideis on an individual pump basis.

Question 6: Describe the features that are provided for bypassed andinoperable status indication.

Resnonce'

The containment purge system (fans, filters, dampers, and ducts)can not be bypassed, so no such bypassed status indication features areprovided.

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