ML14079A134

Review of Design & Operation of Ventilation Sys for SEP Plants, Technical Evaluation Rept

ML14079A134
Person / Time
Site:	San Onofre
Issue date:	08/24/1982
From:	Herrick R FRANKLIN INSTITUTE
To:	Brown S NRC
Shared Package
ML14079A135	List: ML14079A134 ML14138A087
References
CON-NRC-03-79-118, CON-NRC-3-79-118, TASK-09-05, TASK-9-5, TASK-RR TER-C5257-413, NUDOCS 8208270383
Download: ML14079A134 (26)

Text

TECH iCAL. EVALUATION R RT OF VENT LATQN SYSTEMS FOR SEP PLANTS SOUTHERN CAL IFORNIA EDISON COMPANY (SEP IX-5 SAN ONOFRE NUCLEAR GENERATING STATION UNIT 1 NRCDOCKTNO. 50-206 FRC PROJECT C5257 NRC TAC NO. 47074 FRCASSIGNMENT 15 NRC CONTRACT NO. NRC-03-79-118 FRCTASK 413 Prepared by Author: R. C. Herrick Franklin Research Center 20th and Race Street FRC Group Leader R. C Herrick Philadelphia, PA 19103 Prepared for.

Nuclear Regulatory Commission Lead NRC Engineer:

S Brown Washington, D.C. 20555 August 24, 1982.

This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, or any of their employees, makes any warranty, expressed or implied, or assumes any legal liability or responsibility for any third party's use, or the results of such use, of any information, appa ratus, product or process disclosed in this report, or represents that its use by such third partywou d not infnnge pnvately owned rights....

.U'Franklin Research Center 7

'A Division of The Franklin Institute The Beniarrun Frankhin Parkway. Phda.. Pa. 19103 (213) 448-1000

TECHNICAL EVALUATION REPORT REVIEW OF THE DESIGN AND OPERATION OF VENTILATION SYSTEMS FOR SEP PLANTS SOUTHERN CALIFORNIA EDISON COMPANY (SEP, IX-5)

SAN ONOFRE NUCLEAR GENERATING STATION UNIT 1 NRCDOCKETNO. 50-206 FRC PROJECT C5257 NRCTACNO. 47074 FRCASSIGNMENT 15 NRC CONTRACT NO. NRC-03-79-118 FRC TASK 413 Prepared by Author: R. C. Herrick Franklin Research Center 20th and Race Street FRC Group Leader: R. C. Herrick Philadelphia, PA 19103 Prepared for Nuclear Regulatory Commission Lead NRC Engineer:

S. Brown Washington, D.C. 20555 August 24, 1982 This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, or any of their employees, makes any warranty, expressed or implied, or assumes any legal liability or responsibility for any third party's use, or the results of such use, of any information, appa ratus, product or process disclosed in this report, or represents that its use by such third party would not infringe privately owned rights.

Prepared by:

Approved by:

Principal Author:

Proj ct Manager Department Diiectol4 Date:

z4 /q 792 Date:

, -,2 -f2 Date: 62 nFrankin Research Center A Division of The Franklin Institute The Benjamin Franklin Parkway, Phila.. Pa. 19103 (215) 448-1000

TER-C5257-413 CONTENTS Section Title Page 1

INTRODUCTION 1

2 REVIEW CRITERIA 2

3 RELATED SAFETY TOPICS 4

4 TECHNICAL EVALUATION 5

4.1 Control Room Area Ventilation System 5

4.2 Containment Sphere Purging and Exhaust System 5

4.3 Fuel Storage BuildingVentilation System 7

4.4 Reactor Auxiliary Building Ventilation System 8

4.5 Radwaste Areas Ventilation Systems.

10 4.6 Turbine Building Ventilation System 12 4.7 Engineering Safety Features Ventilation Systems 13 5

CONCLUSIONS 18 5.1 Control Room Area Ventilation System 18

.5.2 Containment Sphere Purging and Exhaust System.

18 5.3 Fuel Storage Building Ventilation System 18 5.4 Reactor Auxiliary Building Ventilation System.

19 5.5 Radwaste Area Ventilation Systems 19 5.6 Turbine Building Ventilation system 19 5.7 Engineered Safety Features Ventilation Systems 19 6

REFERENCES 22 157Fnkin Institute Research Laboratory, Inc..

A Subsidiary of The Franklin Institute

TER-C5257-413 FOREWORD This Technical Evaluation Report was prepared by Franklin Research Center under a contract with the U.S. Nuclear Regulatory Commission (Office of Nuclear Reactor Regulation, Division of Operating Reactors) for technical assistance in support of NRC operating reactor licensing actions. The technical evaluation was conducted in accordance with criteria established by the NRC.

v IMranklin Research Center A DMsion of The Franklin institute 0

TER-C5257-413

1. INTRODUCTION This review of the design and operation of ventilation systems at San Onofre Nuclear Generating Station Unit 1 is under Topic IX-5 of the Systematic Evaluation Program (SEP) and consists of the technical review and assessment of safety systems in light of changes in design conditions and criteria. The purpose of this review is to ascertain whether ventilation systems at San Onofre Unit 1 have the capability to provide a safe environment for plant personnel under all modes of operation and whether all safety-related equipment can function properly to ensure safe shutdown of the reactor under normal and emergency conditions.

As background for this review, the SEP has been established to evaluate the safety of 11 of the older nuclear plants. Comparison of each plant against current licensing criteria is an important part of the SEP, with 137 selected topics being studied.

Information for these studies is derived from a wide range of sources, including final safety analysis reports (FSARs), more recent drawings and system descriptions, and licensee submittals. _

Information for. this review included the above sources and elements of related SEP topics already reviewed for San Onofre Unit 1. Specifically, this report comprises a review of the Licensee's assessment [1] with emphasis upon ventilation of safety-related systems neccessary for safe shutdown (2, 3].

((WFranklin Research Center A Division of The Franklin Institute

TER-C5257-413

2.

REVIEW CRITERIA In accordance with Nuclear Regulatory Commission (NRC) guidance for this evaluation, a ventilation system or portion thereof is considered essential to safety if it services systems or parts of systems that are necessary to ensure:

o the integrity of the reactor coolant pressure boundary o the capability to shut down the reactor and maintain it in a safe condition o the capability to prevent or mitigate the consequences of accidents that could result in potential offsite exposures comparable to the guidelines of 10CFRl00, "Reactor Site Criteria."

The criteria and guidelines used to determine if the ventilation systems meet the topic safety objectives are those provided in the following sections of the Standard Review Plan:

Section Subject 9.4.1 Control Room Area Ventilation System 9.4.2 Spent Fuel Pool Area Ventilation System 9.4.3 Auxiliary and Radwaste Area Ventilation System 9.4.4 Turbine Area Ventilation System 9.4.5 Engineered Safety Feature Ventilation System.

In addition, applicabie. portions of related safety topic reviews were used where possible.

In accordance with NRC guidance, the following criteria (expressed in the form of questions to be determined) also were used to evaluate those heating, ventilation, and air conditioning (HVAC) systems or portions thereof that are relied upon to ensure the operation of safety-related equipment:

1. Whether a single active failure cannot result in loss of the system functional performance capability.

2. Whether the failure of a non-safety-related portion of a system will affect the performance of the essential portion of the system or will

-2 Frankin Research Center A Division of The Franklin Institute

TER-C5257-413 result in an unacceptable release, as was defined during licensing review, of radioactive contaminants.

3. Whether the capability exists to detect the need for isolation and to isolate safety-related portions of the system in the event of failures or malfunctions, and the capability of the isolated system to function under such conditions.

4. Whether the ventilation systems (except for the control room) have the capability to direct ventilation air from areas of low radioactivity to areas of progressively higher radioactivity.

5. Whether both control room and engineered safety feature area HVAC systems have the capability to maintain temperature within the design parameters range for safety-related equipment.

6. Whether the engineered safety feature area ventilation system has the capability to circulate air to prevent accumulation of flammable or explosive fuel vapor mixtures from stored fuel.

Franklin Research Center A Division of The Frankin Institute

TER-7

/-7-413

3. RELATED SAFETY TOPICS The scope of review for this topic was limited to avoid duplication of effort, since some aspects of the review are covered under related topics.

These related topics are identified below. Each related topic report contains acceptance criteria and review guidance for its subject matter.

SEP Topic Subject II-2.A Severe Weather Phenomena II-3.B Flooding Potential and Protection Requirements 11-4 Geology and Seismology III-1 Classification of Structures, Components and Systems (Seismic and Quality) 111-2 Wind and Tornado Loadings 111-3 Hydrodynamic Loads 111-4 Missile Generation and Penetration 1III-5.A Pipe.Break Inside Containment III-5.B Pipe Break Outside Containment.

111-6 Seismic Design Considerations VI-4 Containment IsolationSystem VI-7.C Independence of Onsite Power VII-3 Systems Required for Safe Shutdown VIII-2 Onsite Emergency Power Systems IX-3 Station Service and Cooling Water IX-6 Fire.Protection XV-20 Radiological Consequence of Fuel Damaging Accidents (Inside and Outside Containment)

TMI III.D.3.4 Control Room Habitability.

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%Franklin Research Center A Division of The Franikin Institute

TER-C5257-413

4.

TECHNICAL EVALUATION 4.1 CONTROL ROOM AREA VENTILATION SYSTEM While the control room ventilation system is being reviewed under Topic TMI III.D.3.4, Control Room Habitability, the Licensee provided the following with respect to this system [11 "The function of the Control Area Heating, Ventilating, and Air Conditioning System is to provide a controlled environment for the comfort and safety of control room personnel and to assure the operability of control room components during normal operation, anticipated operational transients and design basis accident conditions.

As a result of TMI this system is being reviewed generically (TMI Item III.D.3.4, Control Room Habitability) to assure compliance with Criterion 19, "Control Room" of Appendix A to 10 CFR Part 50.

Therefore this system was not reviewed under this topic."

In some designs, the control room ventilation system is called upon to provide ventilation for safety-related equipment in adjacent rooms. For San Onofre Unit 1, the safe shutdown report [2] indicates that essential instrumentation, including RES pressure and temperature, pressurizer level, and steam generator level instrumentation, are located in the control room.

However, these items are normally located in the control room and do not constitute additional safety-related equipment ventilated by the control room ventilation system. Therefore, a review of the ventilation system was not carried further.

4.2 CONTAINMENT SPHERE PURGING AND EXHAUST SYSTEM This system provides a common exhaust facility for a number of ventilation systems. It was described by the Licensee as follows:

"The function of the Containment Sphere Purging and Exhaust System (CSPES) is to exhaust air to the vent stack from the RABVS [reactor auxiliary building ventilation system].

The FSBVS [fuel storage building ventilation system] and the containment equalizing line after filtration or other treatment and also to supply outside air to the containment sphere when personnel access is required. During normal operation the CSPES is used to exhaust air from the RABVS, the FSBVS and the contain ment equalizing line, Purging and exhaust from the containment is used

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TER-C5257-413 only during shutdown and is isolated during normal operation by POV 9 and POV 10.

Purging and exhaust will be discussed in SEP Topic VI-4, Containment Isolation System.

The CSPES consists of three air handling units, A-21, A-22, and A-24.

Suction dampers (PO-19 and PO-29) and discharge dampers (PO-17 and PO-18) are provided on air handling units A-22 and A-24. HEPA filters are provided on units A-22 and A-24. A prefilter is provided on unit A-21.

Units A-21 and A-22 are powered from safety bus 2. Unit A-24 is powered from safety bus 1. Units A-22 and A-24 are connected by a common upstream plenum.

During normal operation, one air handling unit (A-22.or A-24) discharges exhaust air from the fuel storage building and the reactor auxiliary building to the vent stack. Fan A-21 is normally operating to provide vent stack dilution. The operating fan, A-22 or A-24, takes suction through dampers PO-19 or PO-20 which are controlled by dPS-14 and dPS-15, respectively. The differential pressure switches (dPS-14 or 15) maintain a constant negative pressure (approx. 5 in. w.g.) in the exhaust ducts from the fuel storage and reactor auxiliary buildings by automatically positioning the fan suction dampers (PO-19 or 20).

The second unit (A-22 or A-24) is in the OFF position. Fan A-21 is operated manually from the heating and ventilating control board and takes suction from outside air through louvers. Dampers PO-17 and PO-18 at the discharge of fans A-22 and 24, respectively, are interlocked to open when the fans--are started and close when the fans are stopped.

The CSPES is not required under design basis accident conditions since the containment is isolated. Failure of this system will result in loss of negative pressure in the RABVS and FSBVS. This will result in the release of airborne radioactivity from these buildings instead of from the vent stack. Hoever, this will not affect the maximum calculated doses at the site boundary."

It should be noted, that the statement, "The CSPES is not required under design basis accident conditions since the containment is isolated," refers only to the use of this system for ventilation of the containment sphere.

Other essential systems in the reactor auxiliary building depend upon this exhaust system for ventilation and cooling, in addition to maintaining negative pressures in the buildings served. The system is essential following design basis accidents as well as for safe shutdown.

This common exhaust system is fully redundant. Fans A-22 and A-24 are each full capacity units wherein one unit operates while the other acts as a standby. Each draws exhaust air from a common inlet plenum and is equipped

-6 lrankJin Research Center A Division of The Franklin Institute

TER-C5257-413 with inlet and outlet flow dampers as well as with a HEPA filter. Fan A-22 receives electrical power from motor control center MCC-2, supplied by onsite diesel generator No. 2 when offsite power is not available. Fan A-24 receives power from motor control center MCC-1, supplied by diesel generator No. 1.

The combinations of two independent mechanical units and independent emergency electrical power sources constitutes full redundancy of the exhaust system for safe shutdown and post-accident conditions during a loss of offsite power.

This common exhaust system satisfies all acceptance criteria.

4.3 FUEL STORAGE BUILDING VENTILATION SYSTEM The Licensee provided the following statement of the purpose of this ventilation system [1]:

"The function of the Fuel Storage Building Ventilation System (FSBVS) is to maintain ventilation in the spent fuel pool equipment areas, to permit personnel access, and Eo control airborne radioactivity in the area during normal operation, anticipated operational transients, and following postulated fuel handling accidents."

The fuel storage building is made up of three areas:

the new fuel storage area, the decontamination area, and the spent fuel storage area.

The new fuel storage area is ventilated by outside air drawn through prefilters by supply fan A-27. Exhaust is to the outside atmosphere through a pressure relief damper that maintains a positive pressure in the low radiation potential new fuel storage area. With a low pressure maintained in the adjacent spent fuel storage area, the differential pressure between the two areas will induce all leakage flow to be from the low radiation potential of the new fuel area to the higher radiation potential of the spent fuel area.

Power to fan A-27 is from a 120-240 VAC single-phase distribution panel supplied from 480V MCC-1.

Available information only shows an exhaust fan, EF-11, for the decontamination area. The assumption is that the effluent from this area would be.exhausted to the spent fuel pool storage area to maintain the flow of air from areas of lower radiation potential to areas of higher potential to minimize hazards to personnel.

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TER-C5257-413 The spent fuel storage area is ventilated by an air supply unit, A-23, powered from motor control center MCC-2. This unit supplies outside air via a prefilter and a damper.

Exhaust air is directed to the plant vent stack by a common exhaust system serving the containment sphere, the reactor auxiliary building, and the CVI waste gas treatment system, as well as the spent fuel area. This exhaust system is discussed in more detail in Section 4.2.

In summary, the Licensee stated f1]:

"During normal operation, the dose rate in the fuel storage building is low due to the shielding of the water as discussed in Section 4.2.6 of the FSAR. Based on review of the fuel handling accident analysis in References 4 and 5, it is concluded that the system is nonessential as defined in Section IV, because the potential radiation releases are below those defined in 10 CFR Part 100."

The fuel storage building ventilation system is not essential to safe shutdown and was reviewed only with respect to personnel hazards. In this respect, the ventilation system satisfies the acceptence-criteria.

4.4 REACTOR AUXILIARY BUILDING VENTILATION SYSTEM The Licensee provided the following description of this system (11:

"The function of the Reactor Auxiliary Building Ventilation System (RABVS) is to provide ventilation during normal operation for areas within the reactor auxiliary building, including the liquid radwaste hold up tank rooms, the demineralizer area, the spent resin cubicle, the liquid radwaste processing area, the gaseous radwaste processing and--

decay area, the charging pump room, and the boric acid control area.

These areas house equipment (charging pumps) which operates post-accident or for safe shutdown of the plant.

The RABVS consists of an air handling unit, A-25, with a prefilter and a gravity operated discharge damper. Air handling unit A-25 is powered from train 2 of the safety bus.

Filtered fresh air is supplied to the reactor auxiliary building by air handling unit A-25. This unit is manually started at the heating and ventilating control board. The ventilating air to the various compartments in the building is provided in such a manner as to ensure a

-8 F~ranklin Research Center A Division of The Frankin Institute

TER-C5257-413 supply of fresh air to occupied areas and maintain air flow in a direction toward possible contaminated areas. The containment sphere purging and exhaust system air handling units maintain the reactor auxiliary building under a negative pressure of 1.0 inch w.g. through pressure switches dPs-14 and 15.

If the air pressure rises to -0.5 inch w.g., the supply air unit A-25 is stopped by pressure switch dPS-12. This will keep any radioactive particles and gases under control."

As stated by the Licensee, the reactor auxiliary building ventilation system provides ventilation to the areas within that building. Additional safety-related systems include the component cooling water pumps, the test pump that acts as a backup to the charging pumps, the safety injection pumps, and the refueling water pumps. All this additional equipment is mounted on the roof of the auxiliary building and ventilated directly by the atmosphere.

As stated, filtered outside air is provided by air handling unit A-25 which receives electrical power from motor control center MCC-2A via 480V switchgear No. 2. In the event of an offsite power outage, 480V switchgear No. 2 is powered from onsite diesel generator No. 2. Thus, air handling unit A-25 can be connected to emergency diesel generated power, at least as load management permits.

It is noted that air flow is from areas of low radioactivity potential to areas of higher potential, in satisfaction of one acceptance criterion. The building is maintained at a negative pressure to prevent any outward flow of radioactive effluent.

The exhaust system acts in common with the containment exhaust, the fuel storage buildirng exhaust, and the CVI waste gas treatment building exhaust.

The common system evaluated in Section 4.2 is powered by exhaust fans A-22 and A-24, both full-capacity units wherein one unit operates and the other acts as standby. The exhaust system is fully redundant.

With respect to the single air supply unit, the Licensee stated the following (1]:

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TER-C5257-413 "If pressure switch dPS-12 fails to operate to stop air handling unit A-25, airborne radioactivity could escape from the building due to loss of negative pressure. However, such releases are expected to be minimal.

Active equipment in the RABVS is air handling unit A-25 and differential pressure switch dPS-12. On failure of either of these items, ventilation of the charging pump room could be lost. SCE will perform an analysis to determine the effect of losing A-25 on charging pump operation and/or investigate modification to ensure a reliable source of ventilation to the charging pump room. The results of this analysis are scheduled to be available by February 15, 1981."

The single air supply unit is vulnerable to a single active failure in the unit and to the differential pressure switch, as stated by the Licensee.

While the failure of this single air supply unit equipped with a gravity damper could reduce the air flow in the reactor building sufficiently to impair the cooling of the safety equipment therein, a number of methods are available to prevent the building's negative pressure from being lost. First, the exhaust fans (A-22 or A-24) are 40 hp units while supply fan, A-25, is only 3 hp.

It appears, then, that should the differential pressure switch fail and thus prevent the automatic shutdown of supply fan in order to maintain the negative pressure, the exhaust fans would be capable of maintaining a partial negative pressure to prevent leakage of radioactive effluent from the building.

In summary, while the exhaust system offers full redundancy, including that of available onsite generated emergency power, the supply air handler, A-25, is a single unit and subject to single active failure. The Licensee is encouraged to complete its study of the effects of loss of the supply air handler, A-25, upon the safety-related equipment (charging pumps, CCW pumps) in the reactor auxiliary building. The Licensee's study was not available for this review.

4.5 RADWASTE AREAS VENTILATION SYSTEMS Two radwaste areas are noted:

one area in the reactor auxiliary building, and the other area in the CVI waste gas treatment building.

Neither area is essential for safe shutdown; they are reviewed here only with respect to personnel hazards.

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TER-C5257-413 The radwaste area in the reactor auxiliary building is serviced by that building's ventilation system (discussed in Section 4.4).

As shown there, the supply air handler, A-25, is a single unit subject to single active failure, as is a differential pressure switch which can shut down A-25 should the building pressure rise. A study of the effect of losing A-25 upon ventilation of the safety-related equipment necessary for safe shutdown is in progress.

While the radwaste area is not essential to safe shutdown, perhaps the study could reveal whether modifications are needed to ensure the proper flow of air from areas of low radioactivity potential to areas of higher potential. In addition, such a study could indicate what steps should be taken to prevent radioactive effluent leakage from the building; should the pressure in the building rise due to failure of the differential pressure switch.

The CVI waste gas treatment building is ventilated by a single fan that supplies outside air through a prefilter. Exhaust air is removed by the common vent stack exhaust system that services the reactor auxiliary building, the spent fuel storage area, and the containment sphere. This system is discussed in Section 4.2.

The CVI gas treatment building supply fan is controlled by a differential pressure switch to maintain a negative building pressure (see Section 4.4) for the reactor auxiliary building supply air handler unit. Neither flow dampers nor isolation dampers are shown for the supply fan, indicating that the differential pressure switch is relied upon to control building negative pressure. The only damper in the system is located at the entrance to the vent stack exhaust fan plenum of the exhaust duct common to the reactor auxiliary building and the CVI gas treatment building. Closing this damper would isolate both the reactor auxiliary building and the CVI gas treatment building from the common vent stack, but there would be an open duct between the reactor auxiliary.building and the CVI gas treatment building. With no air supply damper indicated in the CVI gas treatment building, this open duct would vent both buildings to the atmosphere should closing of the damper at the common exhaust fan be necessary. The integrity of both the.CVI gas treatment building and the reactor auxiliary building to prevent leakage of

-11 F1r[anklin Research Center A Division of The Franilin Institute

TER-C5257-413 radioactive effluent depends upon sustaining the exhaust system. The exhaust fan, as discussed in Section 4.2, are mechanically and electrically redundant.

In summary, two concerns are evident:

the capability of the differential pressure switch on the supply fan in the gas treatment building to operate without failure, and the apparent lack of'isolation capability, should that be needed.

4.6 TURBINE BUILDING VENTILATION SYSTEM A major portion of the turbine building is open to the outside atmosphere for direct ventilation; however, no mention was made by the Licensee (1]

as to supplementary ventilation and cooling systems in the turbine building. A survey of the general arrangement drawings indicates that the plant air compressors and emergency air compressor are located in the turbine building.

The safe shutdown report [2] indicates that the instrument air system is essential to safe shutdown. If the compressors in the turbine building shown on the general arrangement drawings supply the instrument air system, the.

Licensee should evaluate the ventilation and cooling requi-rements of these components.

The turbine building houses additional safety-related equipment related to the emergency.core cooling system (ECCS). This includes the two feedwater pumps that, in response to a safety injection signal, operate in conjunction with the safety injection pumps to supply emergency water to the core.

Included also in the turbine building are the invertor, the invertor battery, and the battery charger for the ECCS valve, MOV850C.

Motor control center MCC No. 3, which supplies power to essential.

equipment, is also located in the turbine building.

No additional ventilation system in the turbine was noted for this equipment other than that provided by the side of the turbine.building that is open to the atmosphere for natural direct passive cooling by the free flow of outside air.

It is suggested that the Licensee address the adequacy of this ventilation as it affects the safety-related equipment described above.

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TER-C5257-413 4.7 ENGINEERING SAFETY FEATURES VENTILATION SYSTEMS 4.7.1 Diesel Generator Building Ventilation System The Licensee described the ventilation system as follows [1]:

"The function of the Diesel Generator Building Heating and Ventilating System (DGBHVS) is to provide ventilation to the diesel generator building. The diesel generator building contains the diesel generators and their auxiliaries, station batteries and hydrogen recombiner control panels. Since the diesel generators and the batteries supply power to essential services after a loss of offsite power, the DGBHVS is essential. Each diesel generator is located in a separate room. The station batteries are also located in a separate room.

The active components of the DGBHVS are four cooling fans for each generator room; EF-1A, EF-lB, EF-lC and EF-lD; EF-2A, EF-2B, EF-2C and EF-2D; respectively. A common intake plenum is shared by the four fans in each room.

In each of the diesel generator rooms, outside air is drawn in through the removable wall louvers at one end of the building and exhausted by one to four ventilating exhaust fans located at the other end (west) of the room. Normally, only the normal/emergency fan,_EF-1D, (for DG 1) and EF-2D (for DG 2) is started and running at slow speed. On a rise in the room temperature to 95*?, the first emergency fan, EF-lA (EF-2A) will start and EF-LD (EF-2D) will shut-off automatically. A continuing rise in room termperature will automatically trigger the other emergency fans to run. Fan EF-lB (EF-2B) will start at 100*F and EF-lC (EF-2C) will start at 105 0F. Further temperature rise to 113*F will automaticaloly re-start the normal/emergency fan, EF-lD (EF-2D) on high speed.

Temperature switches for the fans are set accordingly for the step control operation.

A single failure of any one fan or the associated controls will not result in excessive temperatures because the system is designed to operate satisfactorily with one fan not in service. Failure of an electrical train will not result in unacceptable consequences because the fans for each generator are powered by the train supplied by the generator they are ventilating. The other train and fans would therefore be available."

This review corroborates the Licensee's evaluation. The four fans for each diesel generator with one serving as a standby in the event of a single failure of one fan, provide a reasonable level of redundancy so long as the fan sizes are adequate to keep the room temperature low enough so that the fourth fan remains on standby. This capability should be verified by the Licensee.

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TER-C5257-413 From the Licensee's description, it is seen that the adequacy and independence of the four fans depends to a large extent on the adequacy of the common intake plenum. The Licensee should verify the design adequacy of the intake plenum.

In addition to the diesel generators, the diesel generator building ventilation system services the station battery room located in the building.

The Licensee provides the following description [1]:

"The battery room is normally ventilated by the diesel generator room fans(s) through an 18" x 18" opening on the ceiling. Heating is furnished by an electric baseboard heater located on the west wall, beside the outside air intake opening. The heater is non-safety related, designed for AT = 250F and is controlled by a wall-mounted thermostat set at 61*F. A wall-mounted temperature switch will sound an alarm in the control room when the temperature falls below 610F. No active equipment is used for essential battery room ventilation. The heater is not normally energized during an accident situation.

A ceiling-mounted ventilating fan, EF-3 is provided to operate in the abnormal event that the diesel room exhaust fans are inoperable or the diesel generator is down for overhaul. The fan is classified as non-safety related, however, seismic category A structural supports are provided for it. A local switch will turn on the fan to effect 4 air changes per hour."

The ventilation of battery rooms is for the purpose of dispersing hydrogen as it is generated by the batteries to prevent its accumulation.

Batteries generate hydrogen when being charged and at times during heavy discharge. Unless the room is large as compared to the batteries, has good connective currents and ample paths for leakage to the outdoors, a ventilating fan should be provided. The Licensee should clarify whether-diesel generator.

fans EF-1D and EF-2D are normally in constant operation and whether these fans will properly disperse the hydrogen from the battery room. If fans EF-lD and EF-2D cannot provide adequate ventilation to the battery room, then the ceiling-mounted fan, EF-3, should be used to accomplish it.

4.7.2 Switchgear and Cable Spreading Room Ventilation This room, located in the administration building, contains the 4160 V switchgear, 480V switchgear No. 1, and a cable spreading, all of which are

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TER-C5257-413 essential following an accident and for safe shutdown [2, 3].

The Licensee's assessment (1) describes the ventilation of this room:

"The 4160 V switchgear room is located in the control administration building. The room houses switchgear and power cabling for the reactor protection and control system, instrumentation for shutdown and cool down, emergency power (AC and DC), and control power for safe shutdown systems all of which are considered important to safety.

The 4160 V switchgear room ventilation consists of one ventilation fan.

If this fan were to fail, ventilation to this room would be lost. A study is currently in progress to evaluate the need for cooling and ventilating equipment for this room. Results of this study are scheduled to be available by May, 1982."

As a study of the ventilation requirements of this room is in progress, the conclusions regarding this ventilation system must await completion of the study.

4.7.3 480V Switchgear Room Ventilation The Licensee stated (1]:

"The 480 V switchgear room is located in the fuel storage building. The room houses switchgear and power cabling for the reactor protection and control system, instrumentation for shutdown and cooldown, emergency power (AC and DC), and control power for safe shutdown systems, all of which are considered important to safety.

The 480 V switchgear room ventilation consists of one ventilation fan.

If this fan were to fail, ventilation to this room would be lost. A study is currently in progress to evaluate the need for cooling and ventilating-equipment for-this-room.- Results of this study are scheduled to be available by May, 1982."

Further evaluation must await conclusion of this study.

4.7.4 Battery Room and DC Switchgear Room Ventilation These are separate rooms within the administration building ventilated by the administration building ventilating system. The Licensee states (1]:

"The function of the Administration Building Heating, Ventilating, and Air Conditioning System (ABHVACS) is to provide a controlled environment in the administrative building for the comfort of the personnel. This

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TER-C5257-413 building also contains the battery room, the radiochemical laboratory, the sample station, and the chemical control room. Only the battery and inverter rooms are considered essential.

If the portion of the system ventilating the battery and inverter room fails, ventilation to these rooms would be lost.

SCE will perform an analysis to determine the effect of losing ventilation in these rooms and/or investigate modifications to ensure a reliable source of ventila tion. The results of this analysis are scheduled to be available by February 15, 1981."

Again, the importance of ventilation to a battery room is the removal of hydrogen, as it is generated by battery charging (and discharging, in some circumstances).

The Licensee should consider all available methods for this accomplishment in the event that the main ventilation system should fail.

4.7.5 Residual Heat Removal (RHR) Pumps Ventilation The RHR pumps are listed among the minimum systems necessary for safe shutdown [2].

In the San Onofre Unit.1 plant, these pumps are located in the containment sphere. The containment sphere is not within the scope of this review and will be addressed under another SEP topic.

4.7.6 Component Cooling Water Pumps Ventilation The component cooling water pumps are located on the roof of the reactor auxiliary building and are ventilated directly by the atmosphere ventilation system. The component cooling water pumps are listed among the minimum systems and components essential to safe shutdown (2].

While the Licensee did not comment on these pumps, it would appear that their history of operation indicates that they are adequately ventilated and that all applicable acceptance criteria for this review are satisfied.

4.7.7 Saltwater Cooling System Pumps Ventilation The review of safe shutdown systems (2] indicated saltwater cooling systems pumps to be essential to safe shutdown. These pumps are installed in the outdoors intake area and ventilated directly by the atmosphere. The

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TER-C5257-413 history of operation to date indicates that this is adequate and the ventila tion of the salt water pumps is evaluated to meet all acceptance criteria.

4.7.8 Instrument Air System The safe shutdown report [3] indicates the instrument air system to be essential for safe shutdown. Ventilation air system to be essential for safe shutdown. Ventilation of this system was not addressed by the Licensee [1].

A search of the plant arrangement drawings.determined the main plant air compressors and the emergency air compressor to be located in lower levels of the turbine building. Another search of available drawings did not reveal a ventilation system or other cooling means for this part of the turbine building, allowing the inference to be drawn that this part of the turbine building is also ventilated by exposure to the atmosphere, as is the main turbine level of the building.

In summary, the Licensee should address the ventilation requirement of the instrument air system.

4.7.9 Emergency Core Cooling System Components Ventilation The safety injection pumps and the refueling water pumps are located on the roof of the auxiliary building and are open to the atmosphere for ventilation and cooling.

The feedwater pumps, which act in conjunction-with the safety injection pumps upon a safety injection signal to supply emergency water to the core, are located in the turbine building. These are ventilated-by the atmosphere through the open walls of the turbine building.

The batteries, battery charger, and the inverter that supplies power to ECCS motor-operated valve MOV 850C are located in the turbine building and pressurized to be ventilated and cooled by outside air permitted to circulate through the open walls of the turbine building.

Ventilation of these components were not addressed by the Licensee, and so it is suggested that the Licensee comment on the adequacy of these ventilation arrangements.'

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5. CONCLUSIONS Section 4 of this report covering the technical evaluation includes some of the conclusions drawn and implies others. This section provides a short concluding statement.

5.1 CONTROL ROOM AREA VENTILATION SYSTEM Since the control room ventilation system does not service essential equipment and systems other than those normally located in the control room, and since control room habitability is being reviewed under a separate topic, TMI Item III.D.3.4, the control room ventilation system was not reviewed further in this evaluation.

5.2 CONTAINMENT SPHERE PURGING AND EXHAUST SYSTEM This system of stack vent exhaust, filtering, and dilution equipment serves-as the exhaust system for the reactor building ventilation system,-which is essential for safe shutdown. This review indicated the containment sphere purging and exhaust system to be fully redundant and to satisfy all acceptance criteria.

5.3 FUEL STORAGE BUILDING VENTILATION SYSTEM This system does not service any equipment essential for safe shutdown, and was reviewed only with respect to personnel hazards and leaking of radioactive effluent from the plant. All acceptable criteria are satisfied with respect to fuel storage.

There is, however, a separate room in the building that contains 480V switchgear and power cabling for the reactor protection and control system, and instrumentation that is considered essential for safe shutdown. This separate room is ventilated by a single supply fan subject to single active failure. A study of the ventilation requirements of this room is in progress. Final evaluations should be made upon completion of this study.

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TER-C5257-413 5.4 REACTOR AUXILIARY BUILDING VENTILATION SYSTEM Exhaust from this system is handled by the containment purge and exhaust system which collects exhaust effluent from a number of sources and expells it through the plant stack vent. The exhaust system is redundant mechanically and electrically.

The air supply is provided by a single air handling unit and controlled by a differential pressure switch, both of which are subject to single failures. The reactor auxiliary building ventilation system does service equipment essential to safe shutdown. Accordingly, the Licensee has a study in progress to determine the ventilation requirements. It is recommended that an evaluation of the system be made following completion of the Licensee's study.

5.5 RADWASTE AREA VENTILATION SYSTEMS While the radwaste areas are not essential to safe shutdown, two radwaste areas were reviewed with respect to personnel hazards and capacity for isolation. One area is in the reactor auxiliary building, and the other is in a separate building. Both share a common exhaust line. It was concluded that the capacity for isolation does not satisfy the acceptance criteria.

5.6 TURBINE BUILDING VENTILATION SYSTEM At least part of the turbine building is exposed to the atmosphere. The Licensee made no mention of any turbine building ventilation system or that safety-related equipment was in the building. The Licensee should address their ventilation requirements and the provisions for such ventilation.

5.7 ENGINEERED SAFETY FEATURES VENTILATION SYSTEMS 5.7.1 Diesel Generator Building Ventilation The ventilation system satisfies the acceptance criteria with the exception that the Licensee should (1) verify the adequacy of the three fans to cool each diesel so that the fourth actually remains as a standby and (2)

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TER-C5257-413 verify the adequacy of the common intake ducting so that the four fans can be considered independent of a commonmode failure.

With respect to the battery room in the diesel building, the Licensee should verify that there is continuity of ventilation for the removal of hydrogen during charging and heavy discharging operations.

5.7.2 Switchgear and Cable Spreading Room Ventilation The single ventilation fan is subject to single failure. A study of the ventilation requirements of this room is in progress. A final evaluation should be made upon receipt of this study.

5.7.3 480V Switchgear Room Ventilation Conclusions regarding this ventilation system were included in Section 5.3, Fuel Storage Building, in which the room is located.

5.7.4 Battery Room and D.C. Switchgear Room Ventilation These rooms are in the administration building and are serviced by the administration building ventilation system. Without provision for backup, the system is subject to single failure. A study is in progress to determine the ventilation requirements of these rooms.

It is recommended that this evaluation be completed upon the submittal of the Licensee's study.

5.7.5 RHR Pumps Ventilation The RHR pumps are located in the containment sphere and were not reviewed as a part of this study.

5.7.6 Component Cooling Water Ventilation Pumps These pumps are located on the roof of the auxiliary building and are ventilated directly by the atmosphere. While the Licensee did not comment on these pumps, their history of operation would indicate that they are adequately

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TER-C5257-413 ventilated and that all applicable acceptance criteria for this review are satisfied.

5.7.7 Saltwater Cooling System Pumps Ventilation These are located outdoors and, with a history of satisfactory operation, the ventilation is viewed to meet the acceptance criteria.

5.7.8 Instrument Air System Ventilation Conclusions regarding this system are included with the conclusions for the turbine building ventilation system in Section 5.6.

5.7.9 Emergency Core Cooling System Components Ventilation The safety injection pumps and refueling water pumps are located on the roof of the auxiliary building. The feedwater pumps located in the turbine building adjacent to the open walls of that building. All three sets of pumps are ventilated directly by the atmosphere.

However, since the batteries, battery charger, and inverter supplying power to ECCS valve MOV-850C are located within the turbine building where the ventilation path is not obvious, the Licensee should comment on the adequacy of their ventilation.

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6. REFERENCES

1. Review of Ventilation Systems, SEP Topic IX-5 San Onofre Nuclear Plant Unit 1 Southern California Edison Company December 16, 1981

2. SEP Review of Safe Shutdown Systems San Onofre Nuclear Power Plant Nuclear Regulatory Commission, Division of Licensing June 20, 1981

3. SEP Topic VII-3, Electrical, Instrumentation and Control Features of Systems Required for Safe Shutdown San Onofre Nuclear Power Plant Unit 1 EG&G Idaho, Inc.

October 1981

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