Text

Forwards Evaluation of SEP Topic III-4.C, Internally Generated Missiles
	ML20052F137
Person / Time
Site:	Big Rock Point File:Consumers Energy icon.png
Issue date:	05/04/1982
From:	Vincent R; CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.)
To:	Crutchfield D; Office of Nuclear Reactor Regulation
References
	TASK-03-04.C, TASK-3-4.C, TASK-RR NUDOCS 8205120152
	Download: ML20052F137 (27)
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Operating Reactors Branch No 5 e

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US Nuclear Regulatory Commission N.h>

Washington, DC 20555 DOCKET 50-155 - LICENSE DPR BIG ROCK POINT PLANT - SEP TOPIC III-4.C, INTERNALLY GENERATED MISSILES Attached is the Consumers Power Company evaluation of SEP Topic III-4.C, Interrally Generated Missiles for the Big Rock Point Plant.

It should be noted that the Instrument and Service Air System has been included in this evaluation. This system was previously considered vital because it was needed to provide makeup water to the shell side of the emergency condenser. Recent modifications, however, have removed this dependency; this system is no longer required for safe shutdown. It needs only to be addressed as a potential missile source, therefore, and not a missile target.

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' 'hT U2~3 Robert A Vincent e,

Staf f Licensing Er.gineer

'CC Administrator, Region III, USNRC NRC Resident Inspector-Big Rock Point 3 pages (C>3

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I SYSTEMATIC EVALUATION PROGRAM SAFETY TOPIC III-4.C INTERNALLY GENERATED MISSILES BIG ROCK POINT NUCLEAR PLANT l

l l

Prepared By Bechtel Power Corporation May 1, 1982

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SEP Topic III-4.C Subjob 12447-073 May 1, 1982 SYSTEMATIC EVALUATION PROGRAM SAFETY TOPIC III-4.C INTERNALLY GENERATED MISSILES BIG ROCK POINT NUCLEAR PLANT CONTENTS Page I.

INTRODUCTION 1

II.

REVIEW CRITERIA 1

III.

RELATED SAFETY TOPICS AND INTERFACES A.

SEP Topic III-4.A, " Tornado Missiles" B.

SEP Topic III-4.B, " Turbine Missiles" C.

SEP Topic III-4.C, " Safety-Related Water Supply" D.

SEP Topic III-1, " Classification of Structures, Systems, and Components" E.

SEP Topic VII-3, " Systems Required for Safe Shutdown" F.

SEP Topic IX-3, " Station Service and Cooling Water System" IV.

REVIEW GUIDELINES Identification of systems and components needed to perform safety functions were based on the " System Quality Group Classification" identified in SRP Section 3.3.2.m A.

Systems needed to perform safety function (safe plant shutdown or accident mitigations):

1.

Nuclear steam supply system (NSSS) 2.

Control rod drive system (CRDS) 3.

Main steam system (portion of) 4.

Feedwater and condensate system (portion of) 5.

Cooling water system 6.

Emergency core cooling system 7.

Post-incident cooling system (enclosure spray) 8.

Instrument and service air system 9.

Ventilation system

10. Reactor protection system B.

Systems and structures whose failure may result in release of unacceptable amounts of radioactivity:

1.

Containment building 2.

Spent fuel pool cooling system 3.

Airborne waste processing system 4.

Liquid waste processing system 2

SEP Topic ITI-4.C Subjob 12447-073 May 1, 1982 5.

Sampling system C.

Electrical systems necessary to support those fluid systems needed to perform safety functions:

1.

Direct current power system 2.

2,400 V and 480 V switchgear 3.

Cable spreading trays 4.

Electrical penetration room 5.

Control room V.

REVIEW AND EVALUATION A.

SYSTEMS NEEDED TO PERFORM SAFETY FUNCTIONS 1.

Nuclear Steam Supply System The nuclear steam supply system is composed of the equipment in the main recirculation loop, plus those auxiliary systems required to provide a safe and operable system.

a)

Main Recirculation Loop The main recirculation loop is composed of the reactor vessels and internals, steam drum, reactor recirculating pumps, interconnecting piping and valves, and safety valves.

The reactor vessel is designed, fabricated, and tested in accordance with the requirements of the American Society of Mechanical Engineers ( ASME)

Boiler and Pressure Vessel (B&PV) Code and applicable code case rulings.

The closure head is bolted in place with forty-two 4-3/4-inch diameter studs.

The studs are stressed by using hydraulic stud tensioners and are not subjected i

to reactor pressure.

There is, therefore, no accelerating force sufficient to cause them to become missiles.

l The steam drum, with its piping, is mounted at elevation 644'-6" inside a 3 to 5-foot thick i

concrete enclosure.

Approximately 500 cubic feet l

of water is stored in the drum, 65 feet above the recirculating water pump suction centerline.

The i

steam drum is 40 feet long with an inside diameter of 78 inches and a 4-3/8-inch wall I

thickness.

The drum is supported from the concrete overhead structure by eight constant l

3 t

SEP Topic III-4.C Subjob 12447-073 May 1, 1982 support hangers.

The suspension and support system for the steam drum is capable of withstanding the forces developed by a riser or downcomer line break.

Major structural concrete barriers, 3 to 6 feet thick, provide protection for the recirculating loop from postulated IGMs inside containment.

The two recirculating pumps are vertical, single-stage, double suction pumps, which recirculate 17,000 gpm of saturated water from the steam drum to the reactor.

The pump driver is a 400 horsepower, 900 rpm induction motor.

The pump casing is designed and fibricated in accordance with ASME B&PV Code Section VIII.

These pumps are the principal sources of rotational energy located inside the recirculating pump room and steam drum enclosure (cavity).

The potential for missile generation has been analyzed for overspeed assuming a postulated break in the pump discharge.

In general, the impeller will be retained within the casing and the likelihood of ejecting an impeller missile from the broken pipe appears low because of the configuration and low speed of the pump.

The primary loop piping connecting all the major components of the NSSS is of heavy wall thickness and is isolated from other high-energy fluid systems and from rotating components postulated as damaging missile sources.

Based on design features and plant layout, the primary loop piping is considered acceptable with respect to postulated IGMs.

The primary loop piping was separately evaluated.5'"3 All valves in the recirculating loop meet or exceed ASA code requirements for power piping wall thickness.

Six top-mounted safety relief l

valves on the steam drum are equipped with l

rupture disks; their position ensures that any part blown off the relief valves would strike the thick concrete ceiling or side walls and is not likely to damage other NSSS components or piping.

Blind flanges and valve bonnets are firmly secured by multiple bolts; it is unlikely that all of these bolts would simultaneously fail to generate missiles.

Nuts, bolts, and their combinations used to support piping, pump motors, etc, have only a small amount of stored energy and have adequate margins of design strength.

Based on design features, equipment layout, and a 4

SEP Topic III-4.C Subjob 12447-073 May 1, 1982 physical walkdown of the plant, failures in the NSSS recirculating loop due to missiles generated by valve bonnets, nuts, and bolts are not considered likely.

b)

Auxiliary Systems The NSSS auxiliary systems consist of the shutdown cooling system, emergency cooling system, reactor cleanup demineralizer system, and liquid poison system.

The shutdown cooling system consists of two redundant trains of vertical 500 gpm centrifugal pumps and heat exchangers.

The system is isolated during normal operation by double block valves at both ends.

This system is located inside a 2-foot thick concrete enclosure and protected against externally generated missiles.

Additionally, it is not considered to be a significant source of damaging missiles because it is a low-pressure system, which operates during plant shutdown.

The emergency condenser located at elevation 667'-3" is a natural circulation cooling device, which takes steam from the steam drum through two 6-inch steam lines and returns the cooled condensate to the reactor through two 4-inch lines.

The redundant cooling coils are normally pressurized and can be sectionalized to remove heat from the core when the main condenser is unavailable.

Because the system contains a minimum of moving parts, there is little likelihood of it becoming a missile generator.

Nearby components (RDS valves and liquid poison system valves) are potential missile sources; however, they are not likely to cause significant damage to the emergency condenser because of their size and energy constraints.

In any event, alternative shutdown systems are available to enable safe plant shutdown.

The reactor cleanup system controls and maintains reactor coolant system purity.

Water from the reactor flows through a 3-inch line to four regenerative heat exchangers and one nonregenerative heat exchanger.

After cooling to l

approximately 110F, the water is pumped through the cleanup demineralizer.

Water leaving the demineralizer passes through the shell side of the regenerative heat exchangers to the recirculating pump and back up into the reactor.

The regenerative heat exchangers and 5

SEP Topic III-4.C Subjob 12447-073 May 1, 1982 nonregenerative heat exchanger, cleanup pump, and cleanup demineralizer are located inside the steel spherical shell in separate enclosures and protected against externally generated missiles.

The cleanup pump is the only significant postulated missile generator.

Even if a missile is generated causing failure in the cleanup system, it could be isolated, and the plant could be safely shut down'.

The liquid poison system is a backup to the CRDS for bringing the reactor to subcritical condition.

The neutron absorber, a solution of sodium pentaborate (Na B 2 9 Og 10H O), is contained 2

in a spherical poison tank located at elevation 640'-0".

It is maintained in a standby operational status whenever the reactor is critical.

The discharge line from the tank is routed to alternate injection points at the bottom of the reactor vessel and the suction of the recirculating pumps.

The tank is isolated from the nuclear steam supply system by explosion-activated valves in both the discharge and equalizing lines.

Pressurization is provided by a bank of 2,000 psig nitrogen bottles.

The line is normally valved off so that the tank is maintained in an unpressurized condition.

The valves associated with the injection of poison are designed for high reliability and leaktightness.

Each valve consists of a sealed inlet fitting (in which flow is normally blocked by a precision machined shear plug) and a trigger assembly (in which a ram is forced out by an explosive charge to shear the plug).

The pressurized nitrogen bottles are securely anchored outside the reactor building east wall at elevation 600'-6" and are not likely to become gravitational missiles.

The relief valves (regulator valves) on the pressurized bottles are pointed toward the concrete ceiling.

There is no safety-related equipment in the vicinity; therefore, missile generation caused by relief valve failure will not compromise safe plant shutdown.

Based on design features, separation from other systems, and location, it is concluded that no failure due to postulated IGMs is expected for the liquid poison system.

From our evaluation and walkdown of the system, relative to the NSSS main recirculation loop and auxiliary systems, it is considered that the 6

SEP Topic III-4.C Subjob 12447-073 May 1, 1982 likelihood of missile generation, and resultant damage, is minimized by equipment design features, component arrangement, and compartmentalization.

2.

Control Rod Drive System There are 32 bottom-entry, hydraulically operated control rod drives (CRDs) mounted vertically in the thimbles welded into the reactor bottom head penetrations.

Normally, reactor water is supplied through the 40-horsepower CRD pumps via valving and piping connections to the thimble flange to hydraulically actuate the CRDs.

The hydraulic system is composed of a central system for inserting and withdrawing CRDs and a scram system for rapid insertion of all rods.

Each CRD is equipped with a nitrogen-charged gas / water accumulator as a backup source of hydraulic pressure.

The CRD system also provides makeup water to the reactor, at 50 gpm, from the 25,000-gallon condensate storage tank and the main condenser hotwell.

Pressurized nitrogen bottles for the accumulators are located in the storage room at elevation 599'-6",

beneath the instrument room, inside the steel spherical shell.

These bottles are securely anchored to the wall and are isolated from other safety-related equipment.

The CRDs, accumulators, pumps, and associated accessories are located in missile-protected compartments and are separated from other safety-related equipment.

Also, CRD support structure is located below the CRDs and is provided to hold the CRDs in place in case the thimble weld fails and a CRD is ejected from the core.

Consequently, the support would prevent the CRDs from becoming missiles and damaging adjacent CRDs or other safety-related equipment.

From our evaluation and walkdown of the system, it is concluded that the CRD system is neither a likely i

source nor a probable target for any postulated IGMs.

3.

Main Steam System (portion of)

The main steam system consists of a steam drum (discussed earlier with the NSSS recirculation loop),

a 12-inch main steam supply line to the turbine, and another 12-inch main steam line connected to the reactor depressurization system (discussed with emergency core cooling systems).

The main steam line 7

SEP Topic III-4.C Subjob 12447-073 May 1, 1982 is directed downward from the steam drum and enters the steam pipe tunnel at elevation 607'-9" inside containment.

It is of heavy-walled (1 inch thick) material and is well supported and protected from postulated IGMs from other sources by its physical location behind structural walls and floors.

The main steam line is equipped with a main steam isolation valve (MSIV) located in the steam pipe tunnel inside containment, a turbine bypass valve, and a stop valve located in the steam pipe tunnel outside containment.

Considering the design features, restraints, and orientation of these valves as observed during a walkdown, they are not likely to generate postulated IGMs that could damage other systems.

In view of the valve sizes and their relative isolation in the steam tunnel, they are not credible targets for missiles generated by other systems or components.

In any event, if missile damage were to occur upstream of the MSIV, the consequences of the resulting accident are enveloped by the design basis accident analysis.D' Should damage to the main steam line downstream of the valve occur, valve closure would terminate the accident.

The main steam line was evaluated for high-energy line breaks in CPCo's report, " Big Rock Point Pipe Break Evaluation."53 The balance of the main steam system is in the turbine building, where postulated IGMs would not be expected to affect plant safety.

From our evaluation and walkdown of the system, it is concluded that the main steam system (because of its features and its protection from postulated IGMs provided by plant layout) is neither a credible source nor a target for any postulated IGMs that could l

prevent safe plant shutdown.

l 4.

Feedwater and Condensate System (portion of) l Condensate is taken from the condenser hotwell (located in the steam pipe tunnel outside containment) through condensate pumps to the air ejectors, gland seal condenser, and low and intermediate pressure heaters to the suction of two 1,500-horsepower, i

l 1,600 gpm, horizontal, multistage centrifugal reactor feedwater pumps.

The feedwater is then directed through the feedwater regulating valve (CV-4000) in the turbine building and the high-pressure heater located in the steam pipe tunnel (outside containment) to the steam drum inside containment.

There is no safety-related equipment located near the system; i

therefore, postulated missiles and their damaging effects are not considered credible.

Considering its design features, orientation, and location, the 8

SEP Topic III-4.C Subjob 12447-073 May 1, 1982 feedwater regulating valve is not believed to be a likely missile source or target.

In any event, the plant can be brought to safe shutdown condition.51 A

discussion and evaluation of safe shutdown water requirements have been given in Appendix A of Topic VII-3.ml From our evaluation and walkdown of the system, it is concluded that the feedwater and condensate system is adequately protected from postulated IGMs, as described above.

5.

Cooling Water Systems The cooling water systems include the service water, reactor cooling water, demineralized water, and the fire suppression water systems.

The service water system (SWS) consists of two 60-horsepower, 2,100 gpm, centrifugal pumps located in the screenhouse/ diesel generator room.

It takes supply from Lake Michigan and provides cooling water services to several heat loads located in the turbine, service, and reactor buildings.

One pump can supply the normal needs of the SWS.

The fire suppression water system provides backup in the event of SWS failure.

[See also SEP Topic IX-3, " Station Service and Cooling Water System." S3 ] The service water discharge exiting containment is continuously monitored for unacceptable radioactive release to the water canal.

The service water pumps are not likely missile sources, because of their casing strength, submergence, low operating speed, and low system pressure (1,750 rpm and below 100 psig).

Consequently, they would not damage the diesel-driven and motor-driven fire pumps located in the screenhouse.

Based on the above discussion, it is concluded that the SWS is not a potential source of damaging missiles, nor would its loss of function due to postulated missile damage prevent achieving safe shutdown using alternative systems.

(Refer to Section A.4.)

The reactor cooling water system (RCWS) provides cooling water to the reactor shield cooling panels and other potentially radioactive cooling systems.

The RCWS, which is contained in a closed loop independent of the SWS, is located inside containment and is composed of a 53,000-gallon concrete tank, two 1,500 gpm pumps, two heat exchangers, piping, valves, 9

SEP Topic III-4.C Subjob 12447-073 May 1, 1982 controls, and instrumentation.

The RCWS supplies cooling water to two reactor recirculating pump coolers, two shutdown cooling pump gland coolers, a nonregenerative heat exhanger, two fuel pool heat exchangers, two shutdown heat exchangers, and two reactor shield cooling panels.

The demineralized water system (DMNS) provides makeup water to the RCWS via the reactor cooling water tank.

The RCWS is a low-energy (pressure / temperature) system, which uses low-speed (1,750 rpm) pumps for cooling water recirculation.

The system is protected from postulated IGMs by virtue of its separation from other systems and the location of its components and concrete cooling water tank inside containment.

Thus, it is concluded that the RCWS is not of concern with respect to postulated IGMs.

The DMWS is a source of makeup water to the reactor cooling water supply tank and the emergency condenser, which may be used for plant cooldown.

The DMW feedpump is driven by a 7.5-horsepower motor and takes suction from a 5,000-gallon DMW storage tank.

It is a low-energy system, and its components are separated from other systems and components by virtue of plant arrangement and location.

Based on design features, system arrangement, and availability of backup systems, it is concluded that the DMWS is not of concern with respect to postulated IGMs.

The fire suppression water system provides backup cooling water to the emergency condenser, the RCW heat exchangers, and the main condenser hotwell.

This system also supplies necessary water for the primary core spray, redundant core spray, enclosure sprays for the steel spherical shell, and fire protection.

The main components of the fire suppression water system are the 670-gallon accumulator; 3-horsepower jockey pump; and 1,000 gpm capacity, 100-horsepower diesel and electric fire pumps located in the screenhouse.

These pumps take suction from the condenser circulating water intake structure and offshore intake line and discharge into the fire suppression water system.

The fire suppression water piping exits the screenhouse and connects to an octagonal underground loop circling the containment, turbine, and service buildings.

It enters containment through the turbine building steam pipe tunnel and, as a backup, through the core spray pump and heat exchanger room.

The fire suppression water system is a low-pressure system (about 100 psig) and uses low-speed pumps (1,750 rpm).

The diesel and electric fire pumps in the screenhouse are 15 to 30 feet away from the service water pumps 10

SEP Topic III-4.C Subjob 12447-073 May 1, 1982 i

(refer to the discussion of potential SWS missiles) and circulating water pumps, which might be considered as potential sources of IGMs.

The two 200-horsepower circulating water pumps operate below 100 psig at 1,750 rpm and are submerged in the circulating water compartment of the intake structure.

Based on the system's low pressure, heavy pump casing, and 4

redundancy, it is concluded that the circulating water i

pumps are not of concern relative to IGMs.

Based on walkdown and review of the system's design and layout, the fire suppression water system does not appear to be a significant source or target for postulated IGMs.

In summary, it is concluded that the cooling water systems are capable of performing their intended function considering postulated IGMs.

6.

Emergency Core Cooling Systems The Big Rock Point emergency core cooling system (ECCS) provides water for core protection when primary coolant is lost.

It consists of the core spray system l

and the reactor depressurization system (RDS).

The core spray system is designed to supply sufficient water to remove core decay heat and minimize release i

of fission products into the containment atmosphere.

A 6-inch header for the core spray ring and'a 4-inch header for the core spray nozzle supply low-pressure water from the underground fire suppression water loop for injection into the core.

Two redundant, 50-horsepower, 400 gpm vertical core spray pumps take suction from the containment sump beneath the reactor vessel and deliver water to the core spray lines for I

l long-term cooling in the recirculation mode.

These pumps can only operate when the water level in the containment vessel rises above the suction strainers.

In this situation, supply fro.t the fire suppression water system is shut off by the manual valves in the machine shop.

The core spray pumps, core spray heat exchanger, and associated accessories are located in a separate' concrete room outside containment.

Piping runs are primarily underground and isolated from potential missile sources except for the recirculation line.

This line leads from the core spray pumps and passes through the recirculating pump room to the core spray headers and is missile protected.

The 6-and 4-inch core spray headers, supplying core spray water from the fire suppression water system, pass through the steam pipe tunnel and the recirculating pump room.

The redundant core spray line from the recirculating pump room is anchored below the blowout panel located l

11 l

l

SEP Topic III-4.C Subjob 12447-073 May 1, 1982 above the reactor deck level and would not be subject to direct impingement from the blowout panel.00 Systems and components in those areas have been evaluated, in Section A.1, relative to potential IGMs.

The system is not a reascnable source of IGMs because it is not a high-energy system, does not normally operate, and is well isolated.

The use of redundant subsystems further ensures that no missile is likely to cause loss of the core spray function.

The reactor depressurization system (RDS) automatically depressurizes the reactor to allow core cooling via the low-pressure core spray system.

The RDS consists of four parallel blowdown paths through 10-inch, pilot-operated isolation valves connected to the main steam header.

The isolation valves require air to keep them closed.

Loss of air contributes to the potential for a loss-of-coolant accident (LOCA).OO These valves are designed in accordance with Section III of the ASME B&PV code and are orientated upward toward the steel spherical shell.

RDS valve stems or bonnets, if ejected, could rebound l

from the spherical shell and strike the emergency condenser, poison tank, or HVAC expansion tank.

Other areas of potential impact include the safety-related NSSS panels on the floor at elevation 616'-0" and redundant instrumentation on the wall, as well as the spent fuel pool inside containment.

The postulated missile impact on these components other than the NSSS panels is not critical because of their design features, location, arrangement, redundancy, and the backup systems available for safe shutdown of the plant.

An adverse effect on the safety-related NSSS panels could be postulated to occur from a missile ejected from the high-pressure RDS valves.

However, this is improbable because the panels are not in close proximity to the RDS valves.

An analysis of RDS valve stem failure indicated that the postulated missile would not penetrate the steel spherical shell.

Based on system layout and design features, the RDS itself is not considered a target of postulated IGMs generated by other systems.

7.

Post-Incident Cooling System (Enclosure Spray)

The branch lines from the fire suppression system lead to two post-incident sprays sets (nozzles) in the upper part of the steel spherical shell.

The primary spray set, rated at 146 gpm, is initiated automatically; the secondary spray set, rated at 233 gpm, may be initiated remote-manually upon failure of the primary spray set.*

12

SEP Topic III-4.C Subjob 12447-073 May 1, 1982 Operation of only one spray set is sufficient to provide the spray flow for temperature and pressure suppression following a LOCA.

Also, the spray lines are extended from the spray headers to the steam drum enclosure (cavity) such that the spray set (s) will simultaneously spray inside and outside the cavity.

The post-incident system water is initially supplied automatically from the fire suppression system motor-driven fire pump or from the backup diesel-driven fire pump.

Later, the water is supplied by the core spray recirculation system.

The post-incident cooling spray sets are not under pressure during normal plant operation, and they are isolated from other high-energy postulated missile generating sources.

However, the 6-inch core spray recirculating line, which also supplies water to the post-incident spray sets, is considered to be vulnerable to high-energy IGM impact because it passes through the recirculating pump room (discussed in Section A.6).

Based on the system review and plant walkdown, it is concluded that the system will not generate postulated missiles and is not a potential target of postulated IGMs generated by other systems or components.

In summary, post-incident cooling system, with its redundant features and separation, is capable of performing its design function in the event of postulated IGMs.

8.

Instrument and Service Air System This system consists of three air compressors, three aftercoolers, three air receivers, air dryers, prefilters, and filters located in the station power room.

The three 70 cfm, motor-driven, nonlubricated I

air compressors, which are rated at 105 psig, supply both instrument and service air to the plant.

Each compressor has its own receiver and is sized to l

provide approximately 10 minutes of the normal air requirement after loss of auxiliary power.

Normally, one compressor will supply all plant air, with a second on automatic standby.

Air from the receiver passes into a common header, which supplies service and instrument air to the plant.

The air compressor system is cooled by the service water system.

The equipment controlled by the instrument and service air system is either not required for safe shutdown or accident mitigation, or is designed for fail-safe operation upon loss of air, with the exception of the vacuum relief system (discussed in Section A.9) and 13 l

r

SEP Topic IIf-4.C Subjob 12447-073 May 1, 1982 the reactor depressurization system (discussed in Section A.6).

As determined during a review of system design and configuration, the service air system is a low-pressure system operated below 125 psig.

The only sources of credible postulated missiles are the air compressors and air receivers.

Based on design features such as low compressor speeds, ASME code compliance for the air receivers, and safety valves located on the air receivers near the ceilings, it is concluded that the system is not likely to generate damaging missiles.

However, the system is vulnerable to postulated missile impact caused by flywheel failure in the nearby motor generators (see evaluation of electrical systems).

If one of the air receivers is ruptured due to such a missile, the other two receivers would adequately supply instrument and service air.

Release of the compressed air, due to severance of the air supply header, could be averted by separating the danaged section by locally closing the valve in the station power room.

From our evaluation and walkdown of the system, it is concluded that failure of the instrument and service air system will not jeopardize safe shutdown.

9.

Ventilation System The reactor containment vessel and the portion of the turbine building are provided with both forced and induced draft ventilation.

Cooling for the pipeway, steam drum area, and reactor cavity is provided by passing makeup air through local cooling coils j

supplied from the service water system.

Two 24-inch inlet and outlet containment vents are equipped with a set of pneumatically operated vacuum relief valves, which fail close for containment isolation but open to relieve excessive pressure differential between the inside and outside of the steel spherical shell.

In the event of failure of the instrument and service air system, a bank of pressurized nitrogen bottles (located in the airshed area) would provide backup to the system, and the vacuum relief valves could be activated from the main control room.

The nitrogen bottles are securely anchored to the supporting structure and are not considered to be sources of gravitational missiles.

The small valves and gages on the nitrogen bottles are unlikely to become missiles because they are restrained by interconnecting tubing.

In any event, a single isolation valve failure due to a missile would not cause an uncontrolled release of radioactivity.

14

\\

SEP Topic III-4.C Subjob 12447-073 1

'May 1, 1982 Interior cooling of the steel spherical shell is provided by two cooling units located at elevation 616'-0".

The units are isolated from other safety-related equipment, and they are not of concern relative to postulated IGMs.

The equipment in the station power room is protected against high ambient temperature by a recirculating fan coil unit using the service water system for cooling.

The control room is air conditioned by a separate ventilation unit.

Air is recirculated and fresh air is added to create a slight positive pressure in the control room.

Both fresh and recirculated air is filtered prior to admittance to the control room.

The ventilation systems are low-pressure systems; therefore, they are not expected to produce postulated missiles.

Although ductwork can be penetrated by missiles, the total cooling capability is not lost, and time is available to restore adequate ventilation for the damaged area.

It is thus considered that the ventilation systems, as discussed above, will be capable of performing their functions following postulated missile strikes.

10. Reactor Protection System The reactor protection system (RPS) initiates rapid control rod insertion (scram) for reactor shutdown in the event that certain undesirable conditions develop in the NSSS or certain auxiliary systems.

Depending on the initiating cause for shutdown, other secondary protective functions (such as containment isolation, actuation of the scram dump tank valves, and turbine trip) are initiated by the reactor protection system.

Each of the two RPS safety channels features its own power supply, chain of sensor trip contacts, and logic circuitry to effect reactor protection and certain other protective functions.

The channc -: are designed l

on the fail-safe principle such that deenergizing the channels will initiate the protective functions.

In l

addition, failure of a single major component or power supply does not prevent a "real" scram or cause a spurious scrala.

Each reactor protection channel is powered by a separate motor-generator set with l

three-phase, 480 V motor inputs from two separate buses (1A and 2A).

Loss of the power supplied by one of the motor-generator sets would cause only one RPS channel to operate.

By manual actuation of the alternative power controller in the main control room, an alternative 120 V supply from panel lY can be 15

SEP Topic III-4.C Subjob 12447-073 May 1, 1982 switched to either of the two protection buses through the 30 kVA instrument and control transformer 1A.

If this system is unavailable, an automatic throwover operates to supply power from the 30 kVA instrument and control transformer 2B, on emergency bus 2. B,.03,27)

From our evaluation of the system, it is concluded that the RPS is not of concern relative to IGMs.

B.

SYSTEMS WHOSE FAILURE MAY RESULT IN RELEASE OF UNACCEPTABLE AMOUNTS OF RADIOACTIVITY 1.

Containment Building The containment building is a steel spherical shell, 130 feet in diameter and approximately 0.875 inch thick.

Besides the reactor, it houses the steam drum, recirculation piping and pumps, reactor cleanup system, liquid poison system, emergency cooling system, and storage and handling facilities for new and spent fuels.

The design of containment has taken into consideration the " hot standby" condition in which the internal energy of the coolant is maximum and the peak enclosure pressure is 27 psig.

Design and construction of the vessel is in accordance with the ASME B&PV Code, Sections II, VIII, and IX.

The shell is constructed to SA-201 Grade B specifications.m The containment is a passive structure and is not considered to generate postulated missiles.

Also, rupture of the reactor system is considered unlikely, and because of the ductile nature of such a rupture it is not conducive to the development of penetrating missiles.

A blowout panel, consisting of high-density sand and gravel confined in place by light gage metal siding, has been provided in the north wall of the

(

steam drum enclosure and recirculating pump room.

This panel relieves sudden pressure buildup in those areas due to steam line rupture accident.

The blowout l

panel is held in place securely enough that it would not be dislodged by blowing off steam drum safety valves.

Also, the severed panel and gravel would not have sufficient energy to damage the steel spherical shell.

The structural integrity of the Big Rock Point containment was evaluated and found to be in compliance with the current requirements of 10 CFR 50.0 2)

Based on its design features, the containment building is not of concern relative to postulated IGMs.

Therefore, as discussed above, no unacceptable amount l

of radioactivity will be released to the environment.

16 t

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SEP Topic III-4.C Subjob 12447-073 May 1, 1982 2.

Spent Fuel Pool Cooling System The spent fuel pool cooling system is a closed loop system consisting of two 10-horsepower, 250 gpm pumps; two heat exchangers; a bypass filter; a surge tank; piping; valves; and instrumentation.

All are located inside containment.

Heat from the spent fuel pool is transferred by the heat exchangers to the reactor cooling water system.

The spent fuel pool cooling system is a low-energy system, unlikely to generate missiles or be impacted by a missile because of the compartmentalization and layout of its components.

If the equipment becomes inoperable due to postulated missile damage, there is sufficient time to effect repair or take other appropriate remedial action.

From our evaluation and walkdown of the system, it is concluded that the spent fuel pool cooling system is acceptable with respect to postulated IGMs, as discussed above.

3.

Airborne Waste Processing System The airborne waste processing system consists of holdup piping, a 240-foot stack, and associated controls and instrumentation.

This system provides controlled release and dispersion of the noble gases, primarily xenon and krypton.

Off-gases collected from the main condenser air ejector and the turbine gland seal system carry the same radioactive constituents and proceed to the stack after spending a specified time in the holdup piping.

All process gases, before release, are dilv ed with approximately 30,000 cfm of ventilation air by two full-capacity stack exhaust fans in the base stack.

The potential hazard resulting from a stoichiometric mixture of hydrogen and oxygen in the airborne waste was analyzed.

It was concluded that static spark or detonation are not credible because of the presence of saturated water vapor in the system.m However, the system is designed to withstand the pressure encountered in such reactions.

Also, the radioactive gas release rate is continuously monitored; in the event of excessive release, the system is isolated and the plant can be safely shut down.

The airborne waste processing system is a low-pressure system and is isolated from other systems.

The system components are behind shield walls and protected from IGMs from outside sources, and the potential for IGMs from the system itself is considered very small.

The stack exhaust fans are considered to be potential IGM sources; however, because of their location in the base stack and isolation from other safety-related 17

SEP Topic III-4.C Subjob 12447-073 May 1, 1982 equipment, they are not of concern relative to postulated IGMs.

Frcm our evaluation and walkdown of the system, it is concluded that the airborne waste processing system is protected from postulated IGMs from outside sources, and the potential for postulated IGMs from the system itself is small.

Further, postulated missile damage to the system will not affect safe shutdown of the plant nor will there be an unacceptable amount of radioactivity released to the environment.

4.

Liquid Waste Processing System The liquid waste processing system is capable of handling approximately 70,000 gallons of liquid waste per day.

The system is composed of collection sumps, receiver tanks, tank mixing eductors, strainers, filters, demineralizer holdup tanks, concentrators, pumps, interconnecting piping, and instrumentation.

The liquid waste processing system includes clean waste, dirty waste, and laundry waste.

Liquid wastes (likely to contain radionuclides of plant origin) are sampled, analyzed, and released on a batch basis.

All untreated radioactive waste liquids are stored in steel tanks placed in concrete waterproof underground vaults and protected against postulated IGMs.

The largest pumps are on the order of 3-horsepower, 75 gpm, 3,500 rpm; therefore, they are not likely to generate postulated missiles.

Further, if postulated missiles damage this system and/or the contents are drained, the resulting liquid release would be retained in the building long enough to allow cleanup; therefore, no unacceptable amount of radioactivity will be released to the environment.

5.

Sampling System An isokinetic probe, permanently fixed in the stack, collects stack gas samples that are withdrawn with a gas pump through flow metering and regulating equipment.

The sample is passed through a replaceable filter, which is periodically removed and checked for particulate contamination.

After filtering, the continuous flow gas sample is presented to the continuous monitoring gamma-spectrcmeter.

Grab samples are collected from the water leaving the cleanup demineralizer (reactor cleanup system) and analyzed in the chemistry lab.

The likelihood of missiles causing damage to the sampling system is considered very remote.

Further, a 18

.w m.

m

SEP Topic III-4.C Subjob 12447-073 May 1, 1982 missile strike to this system would not result in unacceptable consequences.

C.

ELECTRICAL SYSTEMS NECESSARY TO SUPPORT THOSE FLUID SYSTEMS NEEDED TO PERFORM SAFETY FUNCTIONS 1.

Direct Current Power System The Big Rock Point nuclear plant has seven separate dc power systems that supply safety-related plant loads.

These systems are:

a)

One 125 V de station power supply b)

Four uninterruptible power supplies c)

A diesel generator battery and charger d)

A diesel fire pump battery and charger The station dc power system is equipped with a 125-volt, 60-cell battery; two battery chargers; associated control panels; and a de control center located in the station power room.

It provides power for normal switchgear control, turbine control, annunciators, and various emergency functions.

Based on walkdown and system review, it is concluded that the system is not a source of postulated missiles.

However, because of its location in the station power room, the de power system is considered vulnerable to postulated missile impact resulting from high-energy, rotating motor-generator set flywheel failure.

Four uninterruptible power supplies (each composed of a battery and a charger) are located in individual rooms.

The units provide uninterrupted power supply to the reactor depressurization system.

Based on system review and walkdown, these systems are not considered to be sources of postulated missiles, nor l

are they likely targets because of their isolation and compartmentalization.

An emergency diesel generator is located in a separate compartment in the screenhouse.

A redundant mobile diesel generator is also installed near the well water pump house, and it can be made fully operational within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.

Based on system review and walkdown, the emergency diesel generators and their auxiliaries are not considered to be likely sources or targets of postulated missiles.

A battery and charger are both located near the diesel fire pump in the screenhouse.

They are designated exclusively to serve the diesel fire pump load.

Based 19

SEP Topic III-4.C Subjob 12447-073 May 1, 1982 on system review and walkdown, it is concluded that the system will not produce postulated IGMs.

In the event of damage from postulated IGMs from other systems, the safe shutdown of the plant will not be affected because the motor-operated fire pump is considered to be available.

2.

2,400 V and 480 V Switchgear Auxiliary power is obtained (either from the main generator or from the transmission system for normal plant operating or shutdown conditions, respectively) through a 750 kVA station service transformer connected to a 2,400-volt switchgear bus located in the station power room.

There is another transformer, of similar capacity, connected to the 2,400-volt bus that supplies power to two 480-volt systems.

The reactor instrumentation and protection circuits are fed from three 120-volt ac buses.

The two buses are supplied from different 480-volt systems through separate motor-generator sets.

Each motor-generator set is equipped with a flywheel to sustain operation during normal power system disturbances.

The third bus is supplied from the It5-volt de system through a static inverter.

The station power room also houses switchgear for the reactor recirculating and reactor feed pumps, motor control centers, and control panels.

Based on review and walkdown of the system, it is concluded that the motor-generator set flywheel, rotating at 1,800 rpm, develops a substantial amount of kinetic energy.

Overspeed failure of the flywheel may generate missiles that could damage safety-related electrical equipment in the vicinity.

Otherwise, the system is acceptable with respect to postulated IGMs.

3.

Cable Spreading Trays l

The overhead cable spreading trays are also located in the station power room.

Cables are routed through these trays to the control room.

The only postulated l

missile source in the vicinity is the motor-generator set flywheel (Refer to section C.2).

Otherwise, the system and structure are acceptable considering postulated IGMs.

4.

Electrical Penetration Room The electrical penetration room is located adjacent to l

the station power room.

It does not contain any rotating equipment or pressurized sources other than an isolated nitrogen bottle.

Failure of the nitrogen

(

bottle relief valve / regulator is not likely to create 20 l

L

SEP Topic III-4.C Subjob 12447-073 May 1, 1982 a damaging missile because of the bottle's location and separation from other safety-related equipment.

Based on a walkdown, it is concluded that the electrical penetration room is acceptable considering postulated IGMs.

5.

Control Room The control room is located in the northwest corner on the third floor of the service building.

There are no credible missile sources within the control room or in its immediate vicinity.

Based on a walkdown of the area, it is concluded that there are no missile sources that could affect the proper functioning of the control room.

VI.

CONCLUSION Internally generated missiles associated with rotating component failure, high-energy fluid system failure, and the gravitational effects on structures, syst' ems, or the components at the Big Rock Point nuclear plant have been reviewed.

The following conclusions have been reached with respect to:

A.

SYSTEMS NEEDED TO PERFORM SAFETY FUNCTIONS The motor-generator set flywheel cover and its supporting bolts may fail to withstand postulated IGMs due to overspeed failure of the flywheel.

Thus, the safety-related electrical equipment in the station power room is vulnerable to postulated missile damage.

In other i

areas, postulated IGMs due to component overspeed are not credible.

4 The high-energy fluid system component failure of the pilot-operated RDS valve bonnet / stem may generate postulated missiles that could damage the NSSS electrical panels inside containment.

(Reference Section A.6. )

I

(

B.

SYSTEMS AND STRUCTURES WHOSE FAILURE MAY RESULT IN RELEASE i

OF UNACCEPTABLE AMOUNTS OF RADIOACTIVITY Radiological control during normal plant operation, design features for preventing accidents, and features for l

mitigating the effects of accidents are considered to be i

adequate to prevent radiological effects on the general public due to postulated IGMs.04u,u) 4 6

21

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SEP Topic III-4.C Subjob 12447-073 May 1, 1982 C.

ELECTRICAL SYSTEMS NECESSARY TO SUPPORT THOSE FLUID SYSTEMS NEEDED TO PERFORM SAFETY FUNCTIONS Positive anchorage of safety-related and nonsafety-related electrical equipment that could damage or interfere with the operation of safety-related equipment during seismic events have been identified in the Blume Report.m Considering gravitational IGMs due to seismic events, Big Rock Point structures, systems, and components are considered to be acceptable.

Thus, the systems and components needed to perform safety functions at Big Rock Point nuclear plant meet the intent of the criteria listed in Section II and are believed to be acceptable, subject to the above noted considerations, which should become part of the integrated assessment.

22

SEP Topic III-4.C Subjob 12447-073 May 1, 1982 VII.

REFERENCES

Standard Review Plan,. Sections 3.5.1.1 and 3.5.1.2,

" Internally Generated Missiles (Inside Containment and Outside Containment)," Rev 2, July 1981.

Standard Review Plan, Section 3.2.2,

" System Quality Group Classification," Rev 2, July 1981.

Big Rock Point Final Safety Report, Volumes 1 and 2 (4) 10 CFR Part 50, Appendix A, General Design Criterion 4,

" Environment and Missile Design Bases"

Technical Specification Change Request - Containment Spray System

Nutech Report, " Big Rock Point Pipe Break Evaluation" URS/ John A. Blume Report, " Consultation for Safety-Related Electrical Equipment at Big Rock Point Nuclear Power Plant" (Draft) 181 SEP Topic VII-3, " Systems Required for Safe Shutdown at Big Rock Point Nuclear Plant" (9) SEP Topic IX-3, " Station Service and Cooling Water System at Big Rock Point Nuclear Plant" II) Big Rock Point Nuclear Plant "Probabilistic Risk Assessment"

" Letter from R.A. Vincent (CPCo) to D.M.

Crutchfield (U.S. NRC), dated July 22, 1981 (Big Rock Point Plant SEP Topic III-6, " Seismic Design Consideration")

("' Big Rock Point Nuclear Plant SEP Topic III-7.D,

" Containment Structural Integrity Test" (u) Big Rock Point Nuclear Plant SEP Topic VI-10. A,

" Electrical Instrumentation of Control Portions of the Testing of RPS and ESF" (16) U. S. NRC Regulatory Guide 1.115, " Protection Against Low-Trajectory Turbine Missile" I" Big Rock Point Nuclear Plant SEP Topic XV-19, " Loss-of-Coolant Accidents Resulting from Spectrum of Postulated Piping Break within the Reactor Coolant Boundary (System Portion)"

(16 )

Big Rock Point Nuclear Plant SEP Topic XV-15, " Inadvertent Opening of a PWR Pressurizer Safety / Relief Valve or a BWR Safety / Relief Valve" 23

c.

SEP Topic III-4.C Subjob 12447-073 May 1, 1982

("I SEP Topic VII-2, " Engineered Safety Features System Control Logic and Design, Safety Evaluation Report for Big Rock Point" Os) Science Application, Inc. Report, " Common Mode Failures of Safety Equipment," prepared for the Big Rock Point plant t.

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ML20052F137

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