ML19309D300

Forwards Response to NRC 800225 Request for Addl Info Re Facility Containment Purge Sys Design.Includes Info Re Electrical Reset,Override & Bypass

ML19309D300
Person / Time
Site:	Calvert Cliffs
Issue date:	04/07/1980
From:	Lundvall A BALTIMORE GAS & ELECTRIC CO.
To:	Reid R Office of Nuclear Reactor Regulation
References
NUDOCS 8004100227
Download: ML19309D300 (14)

Text

y BALTIMORE GAS AND ELECTRIC COMPANY P. O. B OX 147 5 BALTIMORE, M ARYLAN D 21203 April 7, 1980 Antuun E.LuNovan,JR.

v cc Pats.orme Su pp6v Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission Washington, D. C.

20555 Attn:

Mr. Robert W. Reid, Chief Operating Reactors Branch #h Division of Operating Reactors

Subject:

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

NRC letter dated 2/25/80 fron R. W. Reid to A. E. Lundvall, Jr., same subject.

Gentlemen:

The referenced letter requested that we provide additional information rerarding the design of the Calvert Cliffs containment uurge system esnecially with rerard to electrical reset, override and bypass.

You also requested that we describe our design with respect to specific NRC design criteria. The attachnent to this letter provides our responses to the six cuestions posed in your letter.

Very truly yours, for Vice President, Supply cc:

J. A. Biddison, Esquire G. P. Trowbridge, Esquire Mr. E. L. Conner. Jr.

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ATACE"E'"f Pesnonnes to NRC Duestions (6)

Question 1:

Provide the details, including schematic drawings, of the modifications made to meet the Lessons Learned requirement 2.1.h.

Resnonse The details of these modifications were described in our letters to Mr. D. G. Eisenhut of October 10, 1979 and November 20, 1979. Schematic diagrams of the reset modification, annotated with the containment penetration identification referenced to our FSAR documents, were submitted to your Mr.

E. L. Conner..Tr. on February lb,1980, and February 19, 1980. To facilitate your review, we have enclosed another set of these diagrams, Enclosure 1.

These previous submittals can be summarized as follows:

To =cet the requirements of 2.1.h., we modified all non-essential automatic containment isolation valves so that they onerate on diverse parameters, and the ESFAS reset circuit was modified so that all containment isolation valves must be in their isolation position prior to a CIS/SIAS reset.

Question 2: Describe how the modified containment isolation system prevents any valves from changing position automatically when the CIAS signal is reset.

Resnonse Before the CIAS sicnal reset can be effected, the associated containment isolation valves must have their control switches in the closed position. This is being accomplished by viring the valves' control switches so as to form a reset permissive.

Placing the valves' control switch in the closed position de-energizes the valves' control circuit. Therefore, when the reset clears the CIAS signal, power is not available to open the isolation valve until the control switch is placed in its open position.

Question 3: Discuss how your present safety system design conforms with each of the Enclosure 1 criteria.

Resnonse ELECTRICAL OVERRIDE / BYPASS DESIGN CRITERIA j

Containment Isolation l

l Criterion la The overriding of one type of safety actuation signal (e.g.,

l radiation) should not cause the blocking of any other type of safety actuation signal (e.g., pressure) to the isolation valves.

l

v Pare 2 Ihe only containment isolation valves that have a containment isolation signal override which overrides more than one initiating para-meter are the reactor coolant system sanple, and the containment air sample valves. These valves are automaticalJv closed via high containment pressure and/or low pressurizer pressure, i.e., the SIAS signal. The Calvert Cliffs engineered safety features actuation system (ESFAS) design is 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 to the individual sample isolation valves which is provided with an override.

Because the individual initiating parameters' isolation signals are not each sent to the valve, this above criteria for these sample valves can not be met.

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

To implement this NUREG requirement and the above NRC design criteria at Calvert Cliffs vould require eight (8) override handsvitches per isolation valve; one for each initiating parameter's process transmitter.

It would also nean that a means vould be created to override all SIAS initiation functions.

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

We can appreciate the intent of this F.iteria when applied to a containment penetration such as containment p".rge, wherein one may wish to override one isolation signal (e.g., high containment pressure for the nurpose of releiving this condition), whi'.e still maintaining an automatic closure on high radiation. We do not feel this criteria is applicable to these samnle valves, because NUREG-0578 requires that this sample be obtain-able under accident conditions regardless of what the ESFAS is electrically directing the valves to do.

Providing overrides for the individual initiating parameters would be superfluous, very expensive, and with no other changes to the ESPAS to eliminate the possibility of a total SIAS override, it would degrade the reliability of SIAS.

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

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

Criterion 3: The system-level annunciation of the overriden status should be provided for every safety system impacted when an override is active.

L

Pare 3 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.

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 ment isolation.

The Calvert Cliffs containment purge valves are isolated by the SIA3 signal and/or the containment high radiation signal.

Criterion 5: The instrumentation and control systems provided to initiate i

containment isolation should be designed and qualified as safety-grade equipment.

The containment isolation equipment is part of the ESFAS, and its design 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 ard component parts was based on the apulicable requirements of IEEE 279 Criteria for Itotection Systems for Nuclear Power Generating Stations.

Maximum consideration has been given to the following criteria cenaistent with the objectives of this document:

a.

Fingle Failure Any single failure within the protection system vill not prevent prover protection srstem action when required.

i b.

Quality of Components and Modules Components and modules used in the manufacture of the actuation systems exhibit a quality consistent with the nuclear power plant LO year design life objective and with minimum maintenance requirements and lov failure rates, c

Channel Independence The actuation systems include four redundant sensor subsystems and two redundant actuation subsystems. Indenendence has been provided between redundant subsystems or channels to accomnlish i

i l

Page h decounling of the effects of unsafe environmental factors, elec-tric transients, and physical accident consequences, and to reduce the likelihood of interactions between channels during maintenance operations or in the event of channel malfunction.

Indenendence has been obtained by:

1.

Electrical Isolation Electrical isolation has been provided between redundant channels, between sensor and actuation subsynte=s and between the engineered safety features actuation system and ancillary equipment. 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 the redundant system.

2.

Physical Senaration Physcial senaration has been maintained between redundant sensor subsystems, Vetween sensor and actuation subsystems, and between redundant actuation subsystems by providing separate and isolated cabinets for each of the four sensor i

subsystems and each of the two actuation subsystems. Each of the twelve containment pressure transmitters has an individual sensing point. A minimum clearance of 3 feet is provided for each sensing point and its associated transmitter.

3 System Repair The system has been designed such that routine servicing and preventative maintenance can be performed without interference to normal plant oneration or without loss of system function availability. Performance of these operations does not result in 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 following considerations:

a) Standardization of subunits b) Minimization of interconnections and interviring c) Interchangeability of subunits The subunits include associated equipment such as indicating lights, pushbuttons, potentiometers, and selector switches.

Pace 5 7.3.1.2 Mocale Withdrawal Withdrawal of any module results in an annunciation of the affected channel. In the case of the sensor subsystem, the withdrawal also results in a trip signal to the two-out-of-four logie matrix. An electrical interlock is provided which prevents the opening of the doors to both actuation channel cabinets at the same tine.

7.3.1.3 Seismic Requirements The engineered safety features actuation systems are classified as seismic Class I and are designed to withstand all simultaneous horizontal and vertical accelerations resulting from the design basis earthquake without 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, t

Criterion 6: The overriding or resetting of the isolation actuation signal should not cause tha automatic reopening of any isolation /

purge valve.

The purpose of overriding an isolation signal to a particular j

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 overridden on 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 containment isolation valves when this signal is reset.

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

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

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

Page 6 radiation signal, and the other containment isolation valves respond to a SIAC nignal or a CIS signal.

(Note? SIAS is initiated on high containment pressure and/or low pressurizer nressure). Additionally, the sample valves described above are provided with a SIAS override and the containment ventilation 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 cause the blocking of any other type of safety actuation signal?

l Rennonse This question vill be answered on two levels: The ESF system level 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 to be blocked. These are described in Calvert Cliffs FSAR section 7.3.2.2.

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

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 water cooling 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 the Calvert Cliffs FSAR Chapter 9, section 9.5.2 3.

The handsvitches are provided to allow isolation and realignment of the system in the event of a rutture in the salt water cooling to and from these heat exchangers.

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

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

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

- _ _ _ ~ _ _ _. _

t i

Page 7 4

4 The containment purge system inoperable status indication features are:

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• Tag out" system; I

2.

Control power available lights on the main control board; and, j

I 3

Alarms in the main control room to indicate high differential

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pressure across the exhaust filters.

i The containment purge syetem containment isolation valves are equinned "ith position switches that indicate, via lights in the nain f

control room, the pocition of these valves.

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