ML20210K777

Responds to 860317 Request for Addl Info Re Proposed Dedication Sys for Ensuring Safe Shutdown Capability Independent of 4,160-volt Switchgear Room

ML20210K777
Person / Time
Site:	Point Beach
Issue date:	04/23/1986
From:	Fay C WISCONSIN ELECTRIC POWER CO.
To:	Harold Denton, Lear G Office of Nuclear Reactor Regulation
References
CON-NRC-86-35 860023, VPNPD-86-188, NUDOCS 8604290052
Download: ML20210K777 (6)

Text

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l l%sconsin Electnc roara couranr 231 W. MICHIGAN,P.O. BOX 2046, MILWAUKEE.WI 53201 (414)277-2345 VPNPD-86-188 NRC-86-35 April 23, 1986 Mr. H. R. Denton, Director Office of Nuclear Reactor Regulation U. S. NUCLEAR REGULATORY COMMISSION Washington, D. C. 20555 Attention: Mr. G. Lear, Project Director PWR Project Directorate No. 1 Gentlemen:

DOCKET NOS. 50-26 6 AND 50--301 FIRE PROTECTION REQUIREMENTS 4160-VOLT SWI'ICHGEAR ROOM POINT BEACH NUCLEAR PLANT, UNITS 1 AND 2 This is in response to your March 17, 1986 request for additional information with regard to our proposed dedicated system for ensuring safe shutdown capability independent of the 4160-volt switchgear room. The proposed system was described conceptually in our letter of February 7, 1986.

The enclosure to your March 17 letter requests details of instru-mentation design, associated circuits ar;alysis, cable routing, and physical location of the various components of the proposed system. As noted in our February 7 letter and discussed with your staff, we have completed only preliminary evaluations of the proposed system. Detailed design of the system has not been done pending NRC approval of the conceptual system as an acceptable means of providing alternate shutdown capability for the 4160-volt switchgear room. Therefore, our responses to your requests, provided below, describe measures which will be incorporated into system design and other details to the extent they can be idantified at the present time.

NRC QUESTION 1 Describe instrumentation associated with the proposed dedicated shutdown system, including its function, physical location, and independence from the 4360-volt switchgear room. Include instru-mentation necessary for the functioning, monitoring, and processing of. variables with respect to the new system.

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Mr.' H. R. Denton April 23, 198r Page 2

RESPONSE

Instrumentation associated with the proposed system consists primarily of existing controls for the gas turbine which can be operated remotely in the~ plant centrol room or locally in the gas turbine building. ' Local control is obtained by operation of a transfer switch in the gas turbine building.

Controls and instrumentation for operation of the gas turbine from the control rcom include the following:

1. Start, stop, and loading controls.

2. Synchronizing scope.

3. Voltage, vars, and megawatt indication.

4. Breaker position indication.

5. A common annunciator for the gas turbine system.

The controls and instrumentation in the control room are duplicated in the gas turbine building on local control panels.

In addition, controls and instrumentation are provided in the gas turbine building for gas turbine auxiliary systems.

The gas turbine building is a separate building not connected tx) the main plant buildings and is located on site approximately 110 feet west of the Unit 1 containment facade.

DC power for instrumentation and breaker operation is provided presently by the plant DC distribution buses and local batteries provided for the gas turbine auxiliaries. Alternate sources of DC power will be provided independent of the 4160-volt switchgear room.

NRC QUESTION 2 Provide details of your associated circuits analysis with respect co the new system.

RESPONSE

Associated Circuits of Concern The Staff's " Clarifications to Generic Letter 81-12" defines associated circuits of concern as those which have a physical separation less than that required by Section III.G.2 of Appendix R and which have one of the following:

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Mr. H. R. Denton April 23, 1986 Page 3

1. A common power source with the shutdown equipment and the power source is not electrically protected from the circuit of concern by coordinated breakers, fuses, or similar devices.

2. A connection to circuits of equipment whose spurious operation would adversely affect the shutdown capability.

3. A common enclosure with the shutdown cable, and which:

a. Are not electrically protected by circuit breakers, fuses, or aimilar devices (Type 1).

b. Will allow propagation of the fire into the common enclosure (Type 2) .

Circuits Associated by Common Power Supply and Common Enclosure Cable and components for the new system will be installed to the greatest extent practicable with separation from other safe shutdown cables and components in accordance with the requirements of Appendix R. The new system will include the existing gas turbine as a source of power. While the gas turbine is not part of the emergency power systems, it is connected to the plant 13.8 KV system. Ground fault protection is provided by circuit breakers whose DC control power is presently furnished from the existing 125 VDC distribution buses and the emergency batteries. An alternate source of DC control power will be provided to eliminate these associated circuits.

As noted in the response to Question 1, the gas turbino can be operated locally or remotely in the control room. The transfer switch at the gas turbine does not isolate the control room control circuits. Therefore, these circuits will be fused as necessary to ensure control room decoupling capability for local operation.

The remainder of the system consists of new equipment which will be:

1. Installed in accordance with Appendix R separation requirements.

y Mr. H. R. Denton April 23, 1986 Page-4

2. Connected to safe shutdown equipment through manually operated selector switches and'normally open circuit breakers _as shown on Figure 2 of our February 7 submittal.

t . 3. Provided with fire seals in locations _where a fire could propagate and damage redundant safe shutdown cables or equipment.

The provision of circuit breaker protection and the gas turbine circuit modifications described above provide assurance:that no associated circuits of concern by common power supply-or common enclosure will exist in the system.

Circuits Causing Spurious Operation The effects of spurious operations may be conceptually divided into two classes as follows:

1. Maloperation of safe shutdown equipment due to control circuit electrical interlocks between safe shutdown circuits and other circuits.

2. Maloperation of equipment which is not defined as.part of the safe. shutdown systems, but which could prevent the accomplishment of a shutdown safety function; for example, inadvertent depressurization of the reactor coolant system by spurious cpening of boundary valves.

The naw system will not provide any alternate means for process control. It will be a dedicated power supply system to provide power to safe shutdown components independent As such, the system will of the 4160-volt switchgear room.

not provide for or interface with the control of process variables. Control features are associated only with gas turbine operation for which complete decoupling of in-plant circuits will be provided. Other features of the system are manual operation of deenergized breakers and breaker position indication in the control room. These circuits will be considered as shutdown circuits rather than associated circuits, and the separation requirements for these circuits will be the same as for those circuits required for system function. In order to achieve the required separation, new system cables will be installed in dedicated raceways where necessary. On this basis, the new system will not contain circuits which cause-spurious operation.

-Mr. H. R. Denton April 23, 1986 Page 5 NRC QUESTION 3 Provide details of the physical location of major components of the new system (both existing equipment and new equipment) ,

including cable routing, location of power supplies, location of major switchgear, electrical isolations, etc.

RESPONSE j As stated above, detailed design of the system has not been done and physical locations of various components cannot be specified exactly. In addition to. Appendix R requirements and independence from the 4160-volt switchgear room, final physical location of the various components will be based upon available space which provides an acceptable environment and ease of access for manual operation and monitoring of system operation. Our preliminary evaluations of the proposed system have identified the following alternatives for major component location:

1. 13.8 KV Power Supply Breaker This component would be located in or near the existing gas turbine building which is remote from the main plant buildings.

2. 13.8 KV/480-Volt Transformer and Switchgear This equipment would be located inside main plant structures in either elevation 8' of the auxiliary building near the ,

Unit 1 charging pump area or near the non-vital switchgear aren at elevation 26' in the turbine building. Either location is remote from and independent of the 4160-volt switchgear room.

3. '480-Volt Power Supply Switches and Class lE Breaker Panels These components will be located as close as practicable to the individual safe shutdown components for which alternate power is being provided by the proposed system.

4. Cable Routing Detailed cable routing is dependent upon final system design and configuration and cannot be defined at the present time. However, as stated in the response to Question 2 above, alternate power and control cables will be routed independent of the 4160-volt switchgear room to ensure alternate shutdown capability for this room.

Mr. H. R. Denton April 23, 1986 Page 6 We trust that the above responses to your requests for additional information are sufficient to allow a determination by your staff that the proposed system provides acceptable means for safe shutdown independent of the 4160-volt switchgear room. We request your approval of the system in concept such that detailed design of the system and associated modifications can proceed.

Should you have further questions, please contact us.

Very truly yours, t $ v' Ej'y C. W./ Fay Vice President Nuclear Power Copy to NRC Resident Inspector