ML20079H354

Forwards Responses to Questions Re Standby Shutdown Sys Per NRC 821203 Request

ML20079H354
Person / Time
Site:	McGuire, Mcguire
Issue date:	12/14/1982
From:	Tucker H DUKE POWER CO.
To:	Adensam E, Harold Denton Office of Nuclear Reactor Regulation
References
NUDOCS 8212160249
Download: ML20079H354 (16)

Text

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DUKE POWER GOMPAhT P.O. Isox 33189 GilAltLoTTE, N.O. 28242 II AL II. TUCKEH TELE PHONE (704) 373-4631 vu.e remnionwr

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December 14, 1982 Mr. Harold R. Denton, Director Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission Washingten. D. C.

20555 Attention:

Ms. E. G. Adensam, Chief e

Licensing Branch No. 4 Re: McGuire Nuclear Station Docket Nos. 50-369, 50-370

Dear Mr. Denton:

Attached are responses to questions concerning the McGuire Standby Shutdown System which were transmitted by telecopy on December 3, 1982.

Very truly yours, cW Y O&

Ital B. Tucker REll:j fw h*

Enclosure (s)

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Mr. James P. O'Reilly, Regional Administrator t,Fa.S"3od U. S. Nuclear Regulatory Commission E. sy *ygg, Region Il 101 Marietta Street, Suite 3100 y, w g6[

Atlanta, Georgia 30303 Senior Residenc Inspector McGuire Nuclear Station 8212160249 821214 PDR ADOCK 05000369 P

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ftCGUIRE ' APP. R ADDITICilAL DOCUt5.flTATI0'l - ITEMS VERIFIED BY 11/23/82 TELEC0fl State that access to "B" disconnect cubic le is from "A" switchgear B.

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Response

Access to the "B" disconnect cubicle is from "A" switchgea'r room.

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E.

Verify cold shutdown capability in accordance with our original request for information in the draft SER - i.e. provide all information as requested to verify they can reach cold shutdown within 72 hrs.

Respo'nse:

The capability to safely shutdown the, unit in the event of fire has been greatly enhanced by the addition of the standby shutdown system.

This system provides all the functions, including dedicated power supplies, necessary to secure and maintain the unit in the hot standby condition (i.e. natural circulation mode) for 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> without offsite power. While in the standby shutdown mode of operation, damage control measures can be taken, as necessary, to restore capability to achieve cold shutdown.

The fire recovery scenarios that can be postulated are innumerable, however, based on an engineering assessment, it has been determined that the unit has the capability to reach cold shutdown within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> without offsite power and with no re. placement of major equipment such as pump motors.

Separation of major normal shutdown equipment has been addressed in previous fire hazard analysis submittals and 10CFR50 Appendix R responses. We have reviewed fire protection features for equipment required for cold shutdown and have established that a fire would not result in loss of the minimum complement of essential major components needed for cold shutdown. A summary is as follows:

1) Diesel Generator Sets (Elev. 736), Redundant normal shutdown diesel generator sets are located in separate fire areas.

Each set is protected by fixed detection and automatic Halon 1301 suppression systems.

2) Switchgear (Elev. 733 and 750) Redundant normal shutdown switchgear is located in separate fire areas with fire detection systems in each area.

3) Component Cooling Pumps (Elev. 733 and 750) Redundant components are located in separate fire areas.

Fire detection and automatic sprinklers are provided in each fire area.

4) fluclear Service Water Pumps (Elev. 716) Redundant components are separated by a three hour fire rated barrier.

Fire detection and automatic sprinklers are provided.

5) Residual Heat Removal Pumps (Elev. 696) Pumps are separated by three hour fire rated walls in a labyrinth arrangement. The adjoining corridor does not have sufficient in situ combustibles for fire propagation.

Fire detection and automatic sprinklers are provided in each pump room and the adjoining corridor to mitigate potential for fire spread.

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Responze: (Cont.)

6) Centrifugal Charging Pumps (Elev.116) Redundant components are located in separate rooms isolated from each other by three hour fire rated barriers in a labryinth arrangement.

Fire detection and automatic sprinliiers are provided to reduce potential for fire damage to components.

7) Safety Injection Pumps (Elev. 716) Redundant components are located in separate rooms isolated from each other by three hour fire rated barriers.

Fire detection is provided for prompt notification of a fire in either room.

Auxiliary Feedwater Pumps (motor-driven) (Elev. 716) The turbine driven 8) auxiliary feedwater pump which is redupdant to motor driven pumps is located '

in a separate fire area. Aut'omatic sprinklers and fire detection are provided in each fire area.

Damage control measures during the 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> required to achieve cold shutdown

,may involve replacing damaged cables. Cables will be available to replace any which may be damaged by fire and needed for cold shutdown.

The actual method for achieving cold shutdown will be determined based on assessment of available options which will be dictated by location and extent of damage resulting from the fire. Assuming a control room or cable room fire, for example, safe cold shutdown can be achieved using equipment from either one of two normal shutdown trains, as follows;

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1) Pumps required to achieve cold shutdown can be controlled manually 1

at the switchgear.

In one shutdown train for example, all of the major pump motors receive power from a single switchgear lineup; Component Cooling Water Pumps, a.

b.

Nuclear Service Water Pump,,

c.

Residual Heat Removal Pump, d.

Centrifugal Charging Pump, Safety Injection Pump, and e.

f.

Auxiliary Feedwater Pump (motor-driven).

2) Valves necessary to align the systems for. cold shutdown or modulate flow can be manually controlled either at the motor control center or by handwheels Additionally, portable starters with prefabricated cables at the valves.

and plugs have been specifically provided for the reactor coolant / residual heat removal boundary valves.

3) Instrumentation to monitor the following parameters is provided at the standby shutdown facility; Steam Generator wide range level, a.

b.

Pressurizer level, Reactor coolant system pressure, and c.

d.

Incore temperatures Other required parameters can be monitored locally at the respective gauges, transmitters, or test points.

Parameters to be monitored would include; Charging and letdown flows (if necessary),

a.

b.

Refueling water storate tank level, Volume control tank level, and c.

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d.

Pressurizer relief tank level, o

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E. Response:

(Cont)

During the first phase of cooldown, the motor-driven or turbine-drive auxiliary feedwater pumps and the main steam power-operated relief valves would be used to reduce reactor coolant system temperature to 3500 F.

Auxiliary feedwater flow to the steam generators would be controlled by throttling valves in the auxiliary feedwater lines or, in the case of the turbine driven auxiliary feedwater pump, throttling steam flow.

The. standby makeup pump would be used _.to maintain reactor coolant system inventory and boration during the cooldown operation. Additionally, either one centrifugal charging pump (or one safety injection pump would be a SI & CC) the refueling water storage tank would For. these pumps as support.

serve as a m&seup water and boration source with flow directed to each of the four reactor coolant system cold legs. Letdown flow would be directed to the volume control tank, if necessary.

The UHI accumulators would be isolated to prever.t nitrogen release and the pressurizer will be vented, as necessary, to reduce reactor coolant system pressure.

At approximately 385 psig an'd 3500 F., the reactor coolant system / residual heat removal system boundary isolation valves would be opened to begin the second phase of cooldown. Cooldown rate would be controlled by regulating reactor coolant system flow through the residual heat removal heat exchanger and by regulating nuclear service water flow through the component cooling water heat' exchanger, as necessary.

Component cooling and nuclear service water systems would be required to Nuclear service support the residual heat removal process, as noted above.

water would also be required to cool the motors of the major pumps.

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2 Question Describe how standby makeup pump suction piping (non-seismic) can be F.

manually) isolated from the spent fuel pool (seismic I manual iso or gates

Response

In the seismic event where valve NV842AC cannot be used to isolate the F.

standby makeup pump suction piping from the spent fuel pool transfer tube, j

isolation can be achieved by manually closing the transfer tube Category 1 isolation valve KF122, located in the fuel building. An alternate isolation method would be to install the transfer canal weir gate.

In the worst case the spent fuel pool cannot be drained below the top of spent fuel storage rack (i.e., spent fuel assemblies will not be uncovered), due

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to physical fuel pool / transfer canal design.

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Change response to be less ambiguous by using words stated in telecon:

all primary & secondary system pressure boundary valves that required isolation are includeo in previous discussed 1-4 (H, I, J, K).

Response

We have verified that all reactor coolant system boundary isolations required to maintain acceptable pressurizer level with only the standby makeup pump can be controlled / assured closed. Additionally, secondary system boundary valves required to assure a source of steam to the turbine driven auxiliary feedwater pump are guaranteed closed when in the standby shutdown system mode of operation.

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Question tb State that flow from the RMWST or'RWST is by gravity to the spent fuel pool M.

and can be initiated by manual operation of valves.

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Response

The RWST and RMWST are located at ground elevation 760'..The minimum M.

RWST level, during plant operation per Tech Spec., is approximately The full RMWST level is approximately elevation 783'.

. elevation 780'.

771' 4 3/4".

Due to Spent fuel pool minimum water level is elevation relative locations between required spent fuel pool level and RWST or RMWST water levels, makeup flow is by gravity and can be initiated 'by manual valve operation outside the fuel building.

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State that portable radios will be available for connunication between SSF and AW local control stations.

Response

Portable radios will be available for communication between SSF and AFW local control stations.

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'S, U, V Statement

" State that there are no intervening combustibles in the. distances separa ting the SSF instrumentation and normal ins trument cables."

t Response: There are n.) intervening combustibles between SSF instrumentation and normal instrumentation in the Reactor Building except in the annulus where detection and automatic sprinklers are provided in accordance with Appendix R Sec t ion G.2.a, as sta ted in October 12, 1982 correspondence to H R Denton from H B Tucker.

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4 I.

H,1,J. For a fire in any; fire area (outside containment) that could result in spurious operation of these valves, verify that the capability would be i

maintained to manually start a normal charging pump or high pressure injection pump and manually align a flow path from makeup water source to reactor for that pump.

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1) verify that at least 1 such pump has its power cable routed outside of the areas through which the valve cables.are routed,.

2) verify that all valves in the flow path can be manually aligned.

3) verify that the pump can be started locally.

Response

1) The power cables for the redundant charging pumps are separated by three hour fire barriers; therefore, any fire which can reposition any of these valves can not disable both pumps.

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2) All valves in the charging flow path can be manually aligned.

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3) The charging pumps can be started locally at the switchgear.

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l We understand that the conductors for the control cables for the "A" K.~

RHR suction line isolation valve will be separated and routed in any This is an acceptable method to separate, armored, grounded _ cable.-

prevent spurious operation of the valve due to fire induced internal or Describe external hot shorts for all fires except control room fires.

the method used to prevent spurious RHR valve operation for a postulated control room fire.

Response

Once aligned for standby shutdown system operation, the controls and power for one RHR suction valve are fully isolated from the control l

room to preclude spurious operation. Spurious operation of both valves prior'to SSS alignment is considered an incredible event byThe virtue of the location and number of control circuit interlocks.

open circuit for each RHR suc2 ion valve contains in series a control

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, switch contact, a pressure' interlock contact, and valve position inter-The pressure interlock and valve position interlocks lock contacts.

The control both inhibit opening of the valve under normal operation.

switch location, pressure interlock cabinets, and valve limit switches are spa tially sepa ra ted. The valve position interlocks originate from

.outside the control room and cannot be bypassed by a short in the control room.

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In the draft. response, it was indicated that 2 AFW isolation valves will be powered and controlled from the SSF.

In the Nov. 23 1982 teleco'n, the licensee said something to the effect that a fire would not preclude flow to at least 1 steam generator.

It is my understanding;that flow is required to 2 steam generators for shutdown.

Verify that the SSS includes provisions to assure that a flow path to at least 2 steam. generators can be aligned from the SSF.

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Response

On transfer to the standby shutdown system, valves necessary to assure a flow path of auxiliary feedwater to two steam / generators are automatically opened.

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Verify that the. capability to deenergize the solenoids in the pneumatic control line to each MSIV and steam generator atmespherie-dump power operated relief valve can be maintained for a fire in any plant area.

Response

J The itSIV and PORV associated with one steam generator are guaranteed closed on transfer to the standby shutdown system to assure a source

,l of steam for the turbine driven auxiliary feedwater pump.

Furthermore, it is considered incredible for any one MSIV o'r PORV associated with one of the other three steam generators to spuriously open by virtue of i-the depth of design.

Each valve is pneumatically controlled and requires air pressure to keep the valve open.

In the pneumatic control line of each MSIV there are two solenoids, any one of which will cause' the respective MSIV to close when deenergized.

In the pneumatic control line of each PORV there are three solenoids, any one of which will cause the respective PORV to close when deenergized. Shorts in any of these circuits are much more likely to be a short to ground resulting in fuse or breaker-isolation (thus closing the valve) than the precise hot short.needed to open a single solenoid. The occurance of the precise hot shorts necessary to energize redundant solenoids is considered extremely unlikely.

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In the riovember 23,-1982 telecon, the licensee stated that AFW flow indication and pump discharge pressure indication are available

.i in the turbine driven pump room.

Verify that at least one of these indications are available for any fire requiring operation of the SSF (causing loss of offsite power).

Res po'nse:

With offsite power, instrumentation is provided local to the turbine driven AFW pump for flow to each steam generator and for pump discharge pressure. The flow indication loop is an electronic, battery-backed circuit and the discharge pressure indication loop is pneumatic..Since auxiliary feedwater -flow rate only affects steam generator level, the

. key parameter to monitor is steam generator level.

Dedicated instrumen-

, tation for steam generator level is provided in the standby' shutdown

's facility. This instrumentation,is powered from the dedicated SSS pawer supplies and the Appendix R circuit separation from normal plant indication has been verifi'ed.

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Question Provide temperature and source range neutron flux indication at the SSF as originally stated in our draft SER.

(The need for this instrumentation is reinforced by the possibility, as discussed in I & J that a fire inside containment could result in spurious opening of RCS letdown lines that would result in small-break LOCA condi-tions.]

Response

1.

For a fire inside containment, transfer of control from the main control room to the SSF will not be necessary. Thus, normal charging pumps will be available and r. heir flow capability exceeds any potential loss of flow caused by opening RCS letdown lines.

2.

The incore thermocouple temperature indication provided in the Standby Shutdown Facility (SSF) provides adequate indication of core cooling.

Therefore, RCS cold leg or average temperature indication is not necessary.

3.

Source range neutron flux is only required where there is a potential for positive reactivity addition. The following reasons constitute why Duke does not consider this instrumentation to be necessary:

a)

Plant is to be held at hot standby while controlled from the SSF.

Cold shutdown will be achieved using normal plant controls.

b)

Control rods are inserted c)

RCS makeup and boration (2000 ppm) is with fuel pool water.

d)

In meeting Appendix R requirements, no credit is taken for any operator action that would require having this instrumentation availabic in the SSF.

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