ML17194A603
| ML17194A603 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 04/12/1982 |
| From: | Oconnor P Office of Nuclear Reactor Regulation |
| To: | Delgeorge L COMMONWEALTH EDISON CO. |
| References | |
| TASK-09-05, TASK-9-5, TASK-RR LSO5-82-04-027, LSO5-82-4-27, NUDOCS 8204150448 | |
| Download: ML17194A603 (48) | |
Text
TOPIC IX-5 SEP REVInJ VENTILATION SYSTEMS Received wth ltr dtd 04/12/82
. NOTIC-E
. THE ATTACHED FILES ARE OFFICIAL RECORDS OF THE DIVISION OF DOC.UMENT CONTROL. THEY HAVE BEEN CHARGED TO YOU FOR A LIMITED TIME PERIOD AND MUST BE RETURNED TO ~THE RECORDS FACILITY BRANCH 016.
PLEASE DO NOT SEND DOCUMENTS CHARGED OUT THROUGH THE MAIL REMOVAL OF ANY
. PAGE(S) FROM DOCUMENT FOR REPRODUCTION MUST BE'REFERRED TO FILE PERSONNEL.
DtH;~rri #
~o-a..37 Coritrttl # e.z. o 4-15 o -+~ &
DEADLIN.E RETURN DATE Date oe/--0?..- e;,a nf OnrHIJml RtGUl.ATORY DOCi\\IT nu RECORDS FACILITY BRANCH
TOPIC IX-5 SEP REVIEW VENTILATION SYSTEMS FOR THE DRESDEN NUCLEAR POWER STATION UNIT 2
. REGUlATO.RY DOCKET FILE COPY
SYSTEMATIC EVALUATION PROGRAM TOPIC IX-5 DRESDEN 2 Topic:
IX-5, Ventilation Systems I.
INTRO DU CTI ON To assure that the ventilation systems have the capability to provide a safe environment for plant personnel and for engineered safety fea-tures, it is necessary to review the design and operation of these sys terns.
For example.; the function of the spent fuel pool area vent-ilation system is to provide ventilation in the spent fuel pool equipment areas, to permit personnel access, and to control airborne radioactivity in the area during normal operation, anticipated opera-tional tranisents, and following postulated fuel handling accfdents.
The function of the engineered safety feature ventilation system is to provide a suitable and controlled environment for engineered safety feature components following certain anticipated transients and design basis accidents.
II.
REVIEW CRITERIA The current criteria and guidelines used to determine if the plant,sys-tems meet the topic safety objective are those provided in Standard Review Plan (SRP) Sections 9.4.1, "Control Room Area Ventilation Sys-tem," 9.4.2, "Spent Fuel Pool Area Ventilation System," 9.4.3, "Auxili-ary And Radwaste Area VentHation System," 9.4.4, "Turbine Area Ventila-tion System" and 9.4.5, "Engineered Safety Feature Ventilation System."
In determining if plant design conforms to a safety objective, use is made, where possible, of applicable portions of previous staff reviews.
III.
RELATED SAFETY TOPICS AND INTERFACES The scope of review for this topic was limited to avoid duplication of effort since some aspects of the review were performed under related topics.
The related topics and the subject matter are identified below.
Each of the related topic*reports contains the acceptance criteria and review guidance for its subject matter.
II-2.A I II-1 III-6 VI-4 VI-7.C.l VI-8 VII-3 I X-6 XV-20 Severe Weather Phenomena Classification of Structures, Components and Systems (Seismic and Quality)
Seismic Design Considerations Containment Isolation System Independence of Onsite Power Control.Room *Habitability Systems Required for Safe Shutdown Station Service and Cooling Water Systems Radiological Consequences of Fuel Damaging Accidents (Inside and Outside Containment)
TMI III.D.3.4 Control Room Habitability USI-A24, QUALIFICATION OF CLASS lE SAFETY RELATED EQUIPMENT IV.
REVIEW GUIDELINES In determining which systems to evaluate under this topic, the staff used the definition of 11 systems important to safety 11 provided in Regula-tory Guide 1.105.
The definition states that systems important to safety are those necessary to ensure (1) the integrity of the reactor coolant pressure boundary, (2) the capability to shutdown the reactor and main-tain it in a safe condition, or (3) the capability to prevent, or mitigate the consequences of accidents that could result in potential offsite ex-posures comparable to the guidelines of 10 CFR Part 100, 11 Reactor Site Criteria.
11 This definition was used to determine which systems or portions of systems were 11 essential.
11 Systems or portions of systems which perform functions important to safety were considered to be essential.
-3:-
V.
EVALUATION The systems reviewed under. the topic are the control roo~ area ventilation system, reactor building ventilation system, fuel storage pool* area venti-lation system, turbine building ventilation systems, radwaste area venti-lation systems and ~ngineered safety features ventilation systems.
A.
Control Room Area Ventilation System The function of the Control* Room Area Ventilation System {CRAVS) 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 operating, anticipated operational transi-ent 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_ co_mpliance with Criterion 19_, "Control Room" of Appendix A,
- ~General Design Criteria for* Nuclear Power Plants," to 10 CFR Part 50.. Therefore, the CRAVS was not reviewed under this topic.
B.
Reactor Building Ventilation System The reactor building ventilation system is designed to supply 100,000 cubic feet per minute {CFM) of filtered, tempered outside air, distri-bute it through all working areas and equipment rooms in the reactor building while maintaining a negative pressure of 0.25 inch of water in the building, and exhaust the air (in normal operation) directly to the reactor building vent stack.
No provision is made to filter the exhaust air.
Instead, when radioactive exhaust is detected in the vent stack, the reactor building ventilation system is isolated by redundant pairs of butterfly valves from both the supply and exhaust fan systems, whereupon all exhaust is directed to the standby gas treatment system.
The standby gas treatment system is essential for maintaining a negative pressure in the reactor building, assuring that there will be infiltration of outside air into, instead of leakage of radio-active effluent out of, the building.
Induced draft fans 2/3A and 2/38 operate in parallel from a common fan inlet plenum to provide flow through two separate parallel efflu-ent processing lines, one for Unit 2 and one for Unit 3.
Since the standby gas treatment system processes from both Unit 2 and Unit* 3, the parallel fans are powered, respectively, by MCC 28-2 (diesel generator 2/3) and MCC 29-2 (diesel generator 3).
Each parallel treatment system is rated for 4000 cfm, as is each fan.
A negative pressure of 0.25 inch of water is maintained in the reactor building with the use of pneumatic-operated inlet dampers in the standby gas treatment system.
The treated effluent from the fans is ducted to the main plant chimney.
Both the normal reactor building ventilation system and the standby gas treatment system meets the requirements provided in the review criteria identified in Section II, with two exceptions:
l) The capability of the standby gas treatment system to dir'ect ventilation air from areas of low radioactivity to areas of higher radioactivity levels due to its relatively low system design flow rate (4000 cfm).
- 2)
A single active failure could result in the loss of systems functional performance capability. That is, a failure of Diesel 3 to start coupled with loss of off-site power will re-sult in loss of power to the standby gas treatment system.
C.
Fuel Storage Pool Area Ventilation System The fuel storage pool area ventilation system is an integral part of the reactor building ventilation system.
Filtered, tempered air is supplied first to the north and south operating floors, from which it flows to the fuel storage pool and the dryer and separator pool.
Exhaust air flow from the pool areas and the operating floor areas is regulated by a series of manually operated dampers.
The acceptance criterion requiring flow of the ventilation air to be from areas of lower radiation potential to areas of higher potential is satified in that conditioned air is first directed to the operating floor, then across the pool areas, and finally is collected into exhaust ducts that carry the effluent directly to the reactor building vent stack or, in the case of radiation detection, to the standby gas treatment system.
Other criteria, including the redundancy of emergency electrical power and the ability of this system to remain functional following a single active failure, are also satisfied.
D.
Turbine Building Ventilation System The turbine buHding ventilation system is comprised of the following subsystems, the main turbine room ventilation system, the reactor feed-water pump ventilation system, the motor-generator (M-G) room ventila-tion system, and the east turbine room ventilation system.
Only one of
' \\\\'*
these subsystems were found to potentially interact with essential safety systems, the east turbine room ventilation system.
D.
East Turbine Room Ventilation System The east turbine room ventilation system supplies filtered, tempered outside air to the north and south HVAC equipment rooms, the switch-gear room, the battery room, the auxiliary electrical equipment room, and other areas in this part of the turbine building.
Supply air and exhaust air are each handled by a set of three 50-percent-capacity fans, all of which are powered by motor control cen-ter MCC 26-4 (non-essential and non-redundant electric power).
The supply and exhaust systems are balanced to provide a differential negative pressure of O.T25 inch of water relative to the atmosphere.
Used air is exhausted to the atmosphere.
It is noted at location D-4 on Drawing M-936 (Rev. E) that 4000 cfm of air from this system is directed to the battery room (details on Drawing M-973, Rev. A) for ventilation and cooling and returned to the north HVAC equipment room.
With a loss of offsite power, the east turbine room ventilation system will shut down, and air will not be supplied to the battery room where charging and discharging of the bat-teries may continue to generate hydrogen.
This is discussed in greater depth in Section V-F.6, "Battery Rooms Ventilation System."
Drawing M-936, Rev. E, shows a flow of 10,000 to 15,000 cfm of air from the east turbine room ventilation system directed to the auxiliary elec-tric equipment room, with air flow controlled by a temperature controller.
This system will not supply ventilation air if offsite power is lost.
Further discussion is continued in Section V.F.5, "Auxiliary Electric Equipment Room Ventilation."
E.
Radwaste Area Ventilation System The radwaste area ventilation system is comprised of subsystems which service the following areas:
- 1)
Radwaste Building,
- 2)
Off-gas Recombiner Rooms,
- 3)
Off-gas Filter Building,
- 4)
Radwaste Solidification Building; and
- 5)
Maximum Recycle Radwaste Building.
Based on the Franklin Research Center Report, we have determined that the above mentioned radwaste area ventilation subsystems are non-essential as defined in Section IV.
F.
Engineered Safety Features Ventilation Systems F.l Engineered Safeguards Systems Ventilation and Cooling The engineered safeguards system is comprised of the following subsystems; the emergency core spray, low pressure coolant in-jection (LPCI), and high pressure coolant injection (HPCI).
F.l.a Emergency Core Spray Subsystem Ventilation The emergency core spray pumps are the only components of the emergency core spray subsystem serviced by ventilation systems.
Si'nce they are _located with the LPCI pumps and
- heat exchanger, they are discussed together with LPCI sub-system ventilation in fhe following section.
F.1.b Low Pressure Coolant Injection Subsystem Ventilation The LPCI and emergency core spray pumps are located in cor-ner rooms on the basement level of the reactor building ventilated by the reactor building ventilation system.
Since the reactor building ventilation system can be supplied with emergency diesel power, ventilation is assured following the loss of offsite power.
In addition, each LPCI pump room contains its own room cooler.
These individual units cool by means of the diesel generator cooling water system, and their fan motors are supplied by electrical motor control centers MCC 28-1 and 29-4, designated as diesel-powered essential service: however, operator action is required.*
Drawing 12E-2302B list only two cubical coolers, 2A on MCC 28-1 and 2B on MCC 29-4.
These coolers appear to be in two different rooms (their locations are not explicit-ly indicated). If so, then despite provision of essential electrical service, the fans of the LPCI cubical coolers do not have the redundancy to assure cooling in the event of a failure within the unit.
These coolers are important because they would be the only source of cooling for the LPCI pump motors should the detection of radiation shut do~n the teactor
- Where operator action is required, a justification should be provided that the "ventilation function 11 will be initiated when required.
building ventilation system and cause its effluent to be di-rected to the standby gas treatment system where the air flow rate is comparatively very small.
F.l.c High Pressure Coolant Injection (HPCI) Subsystem Ventilation The HPCI pumps are driven by a steam turbine.
The HPCI room is serviced by the reactor building ventilation system sup-plemented by a room cooler which uses cooling water from the di es el generator coo 1 ing*iwater system.
Drawing l 2E-2302B show essential service electrical power being provided by MCC 29-4,
{again, operator action is required)* but there is no 1 indica-tion of redundancy of fans or electrical service.
As discussed above for the LPCI subsystem, the equipment in the HPCI room is cooled solely by the room cooler if the reactor building ventilation system is shut down due to detection of radiation in the vent stack.
Therefore, the HPCI ventilation and cooling system does not have sufficient redundancy and is vulnerable to a single failure.
F.2 Reactor Shutdown Cooling System Ventilation The shutdown cooling system is ventilated by the reactor building vent-ilation system.
However, since the shutdown cooling system is not considered to be one of the minimum number required for safe shutdown, its adequacy was not reviewed.
- Where operator action is required a justification should be provided that the "ventilation function" will be initiated when required.
F.3 Reactor Building Closed Cooling Water System Ventilation The reactor building closed cooling water (RBCCW) system serves as an intermediate between the reactor shutdown cooling system (and other reactor building equipment) and the service water system.
While it may be used for shutdown heat removal, it is not the pri-mary system required to perform post-accident safe shutdown heat removal.
The RBCCW system is ventilated by the reactor building ventilation system since the RBCCW system is not considered to be essential for safe shutdown, it was not reviewed.
F.4 Service Water System Ventilation Reference 21, SEP Topic IX-3, "Station Service Water System Review, 11 identifies two service water systems that are essential for safe shutdown:
the diesel generator cooling water (DGCW) and containment cooling service water (CCSW) systems.
F.4.a Diesel Generator Cooling Water System Ventilation In addition to providing cooling water to diesel generators 2, 3, and 2/3, the DGCW system provides the service water cooling medium to the room coolers of the LPCI (two coolers) and HPCI (one cooler) equipment rooms of Dresden Unit 2.
The pumps for the DGCW system are located in the crib house since the original pumps have been replaced with submersible types, ventilation of the pumps and/or pump motors is not requi'red.
F.4.b Containment Cooling Service Water System Ventilation The CCSW system, also known as the emergency service water system, supplies cooling water to the LPCI system.
Using four pumps located in the condensate pit of the turbine build-ing, the CCSW system draws water from the crib house and sup-plies it to the LPCI heat exchanger in the reactor building.
Ventilation is provided by the main turbine room ventilation system which supplies 34,000 cfm of filtered heated air to the CCSW system.
In the review of the turbine building ventilation system, it was established that this was a non-essential system that would not be operating during emergency shutdowns in which offsite power is lost.
Under these conditions, cooling of the CCSW pumping equipment is provided by a set of room coolers using the service water from the CCSW system as the cooling medium.
Drawing M-274 shows the arrangement of the room coolers for the CCSW system.
Four cubical coolers, each containing two fans, cool the equipment located in the service water flood-protected cubical.
Drawing M-5 shows pumps 2B and 2C in the flood-protec-ted cubical and pumps 2A and 2D in other separate cubicals.
Thus, only two of the four containment cooling water.pumps are cooling by four cubical coolers.
Operator action is required*
to initiate area cooling.
- Where operator action is required, a justification should be provided that the. nventilation function" will be initiated when required.
ll tf i F.5 Auxiliary Electrical Equipment Room Ventilation System The auxiliary electrical equipment room houses equipment and systems essential for safe shutdown, including the reactor protection system motor-generators and'iDstrumentation, the ESS generators, and essen-tial relays and switch gear.
The normal means of ventilation and cooling for this room is a separate dedicated HVAC system.
In addition to this HVAC system the east turbine room ventilation system functions as a backup ventilation system.
Electrical power to the HVAC compressors and fan is from motor control center MCC 25-2, which is not an essential power center supplied by the emergency diesel generators.
However, MCC 25-2 can be connected by operator action* through buses 25 and 23 to bus 23-1 which is powered by diesel 2/3.
Although the auxiliary electrical equipment room is shared with Unit 3, there appears to be no counterpart HVAC system powered by Unit 3.
Redundancy depends instead on the east turbine ventilation system's deriving its electrical power from motor control center MCC 26-4.
Electrical bus 26 is not essential electrical service but may be connected through buses 24 and 24-1 to power from diesel 2.
The adequacy of the electrical power redundancy depends upon the adequacy of the complex power interconnections between Units 2 and 3,and among the three diesel generators.
- Where operator action is required, a justification should be provided that the "ventilation function" will be initiated when required.
I.
t F.6 Battery Room Ventilation System The battery room contains the batteries that provide emergency DC power essential for post-accident shutdown of the reactor.
Ventilation designed for the.purpose is considered essential to assure that the hydrogen given off from the batteries during heavy discharging is removed.
Ventilation is provided by the east turbine room ventilation system from which 4000 cfm of filtered, heated air (outside air, but with recirculation capability) is ducted to the battery room and discharged through the north HVAC equipment room.
Redundancy of air handling is provided by three 50-percent-capacity supply and discharge fans.
However, all six fans are supplied from one motor control center, MCC 26-4, powered from bus 26.
Bus 26 is not considered essential electrical service and must be connected by operator action* to bus 24-1 which is powered by diesel generator 2 through bus 24.
F.7 Diesel Rooms Ventilation Systems Diesels 2 and 2/3 are housed in separate rooms served by separate ventilation systems.
Cooling is provided by the diesel service water systems, and the ventilation systems both vent the rooms and cool associated switchgear equipment.
- Where operator action is required, a justification should be provided that the 11velltilation function" will be initiated when required.
Diesel 2 is ventilated by a single 30-hp fan which is automatically, loaded to motor control center (MCC) 29-2 (essential service, diesel 2). Outside air and/or turbine building air 3s supplied to the fan *through a set of temperature controlled dampers.
Air is discharged from the diesel room through a set of louvered doors into the turbine building.
Diesel 2/3 is housed in a separate room off the reactor building.
It, too, is ventilated by a single 30-hp fan similar to that used for di es el 2.
Should the single ventilation fan fail, the large double doors be-tween the turbine building and diesel 2 could be opened to promote natural convection from the turbine building.
However, natural convection through the doors cannot equal the air supplied by a 30-hp fan.
If the fan.'s airflow is deemed necessary by design for ventilation in the event of a prolonged post-accident shutdown, then redundancy is not provided.
The system does not satisfy fail-ure criterion.
V.
CONCLUSION The ventilation systems for the Dresden 2 Plant were found to be in conform-ance with current criteria for this topic except for the following:
- 1) Operator action is required to bring the following systems on line.
a)
Low Pressure Coolant Injection Subsystem Ventilation, b)
High Pressure Coolant Injection Subsystem Ventilation,
. e c)
Containment Cooling Service Water System Veiltflat1on, d)
Auxiliary Electrical Equipment Room Ventilation System; and e)
Battery Room Ventilation System.
The licensee should evaluate if sequencing of these ventilation systems by the operator is sufficient to preclude adverse interaction with the systems serviced.
- 2)
Systems which are subject to disabling single failures a)
LPCI/Core Spray Ventilation Systems b)
HPCI Room Ventilation Systems c)
Diesel Rooms Ventilation Systems d)
Standby Gas Treatment Systems The licensee should evaluate the consequences of losing any of the above systems.
If it is determined that ventilation 1.s required for system performance the need for upgrading to the associated ventilation system will be determined as part of the integrated assessment.
- 3)
Non-Capability of Directing Ventilated Air From Low to Higher Areas of Radioactivity Standby Gas Treatment System - The licensee *should address the conse-quences of this event by either demonstrating that there will be no need for entering the reactor building or that personnel access would not be inhibited.
- 4)
Non-Ventilation of Safety Equipment Containment Cooling Service Water System - The licensee should evaluate the effect of not providing post accident ve~tilation for two of the four containment cooling service water system pumps (pumps 2A and 2D).
l
<DRAFT)
TECHNICAL EVALUATION REPORT REVIEW OF THE DESIGN AND OPERATION OF VENTILATION SYSTEMS FOR SEP PLANTS COMMONWEALTH EDISON COMPANY DRESDEN NUCLEAR POWER PLANT UNIT 2 NRC DOCKET NO. 50-237 NRC TAC NO. 4 7071 NRC CONTRACT NO. NRC-03-79-118 Prepared by Franklin Research Center The Parkway at Twentieth Street Philadelphia, PA 19103 Prepared for Nuclear Regulatory Commission Washington, D.C. 20555 FRC PROJECT C5257 FRC ASSIGNMENT 15 FRCTASK 410 Author:
R. c. Herrick FRC Group Leader: R. C. Herrick Lead NRC Engineer: S. Brown January 20, 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, ex-pressed or implied, or assumes any legal liability or responsibility for any third party's use, or the results of such use, of.any information, apparatus, product or process disclosed in this report, or represents that its use by such third party would not infringe privately owned rights.
~nklin Research Center A Division of The Franklin Institute The Benjamin Franklin Partcway, Phila.* Pa. 19103 (215) 448* 1000
.e TER-C5257-410 CONTENTS Section Title 1
INTRODUCTION.
2 REVIEW CRITERIA
- 3 RELATED SAFETY 'IDPICS 4
TECHNICAL EVALUATION.
4.1 Control Room Area Ventilation 4.2 Reactor Feedwater Pump Ventilation System 4.3 Fuel Storage Pool Area Ventilation System
- 4. 4 Turbine Building VentilatiOn Sy stem.
4.4.1 Main Turbine Room Ventilation System.
4.4.2 Reactor Feedwater Pump Ventilation System 4.4.3 Motor-Generator Room Ventilation System
- 4.4.4 East Turbine Room Ventilation System.
4.5 Radwaste Area Ventilation System 4-. 5.1 Radwaste Building Ventilation.
4.5.2 Standby Gas Treatment Facility 4.5.3 Off-Gas Recombiner Rooms.
4.5.4 Off-Gas Filter Building
- 4.'s. 5 Radwaste Solidification Building.
4.5.6 Maximum Recycle Radwaste Building 4.6 Engineered Safety Features Ventilation Systems
- 4.6.1 Engineered Safeguards Systems Ventilation and Cooiing **
4.6.2 Reactor Shutdown Cooling Systems Ventilation.
4.6.3 Reactor!Building Closed Cooling Water System Ventilation
~nklin Research Center A OMsion ol The Pranldln lnll!b.lte iii Page 1
2 4
5 5
s*
8 8
8 9
10 10 11 11 11 13 14 14 15 16 16 17 18
TER-C5257-410 CONTENTS (Cont.)
Section Title 4.6.4 Service Water System Ventilation.
4.6.5 Auxiliary Electrical Equipment Room Ventilation System 4.6.6 Battery Room Ventilation System
- 4.6.7 Diesel Rooms Ventilation Systems.
5 CONCLUSIONS
- 6 5.1 Onsite Diesel-Generated Power 5.2 Control Room Area Ventilation 5.3 Reactor Building Ventilation System 5.4 Fuel Storage Pool Area Ventilation
- 5.5 Turbine Rooms Ventilation Systems 5.6 Radwaste Areas Ventilation Systems
- 5.7 Engineered Safety Features Ventilation Systems
- 5.7.1 Engineered Safeguards Ventilation Systems 5.7.2 Reactor Shutdown Cooling System Ventilati~n and Reactor Building Closed Cooling Water System Ventilation
- 5.7.3 Service Water System Ventilation.
5.7.4 Auxiliary Electrical Equipment Room Ventilation System 5.7.5 Battery Room Ventilation System.
REFERENCES iv
~nklin Research Center A Division ol The Fl'llllklln lnllltute Page 18 19 20 21 22 22 22 22 22 23 23 24 24 24 24 25 25 26
TER-C5257-410 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 I
technical evaluation was conducted in accordance with criteria established by the NRC.
~nklin Rese~rch Center A Otvtsion of The Franklln Institute v
TER-C5257-410
- 1.
INTRODUCTION This review of the design and operation of ventilation systems at the Dresden Nuclear Power Plant Unit 2 is part of Topic IX-5 of the Systematic Evaluation Program (SEP) and consists of the review and assessment of safety margins in light of changes in design conditions and criteria.
The purpose of this review is to assure that ventil.ation systems at the Dresden plant Unit 2 can provide a safe environment for plant personnel under all modes of operation and to determine whether all safety-related equipment can function properly to assure safe shutdown of the reactor under normal and emergency conditions.
The SEP was established to evaluate the safety of 11 of the older nuclear plants.
An important part of the SEP is the evaluation of each plant according to current licensing criteria with regard to 137 selected topics.
A wide range of information sources is used, including final safety analysis reports, more recent drawings and sys.tem descriptions~ licensee submittals, and onsite review and inspection.
Information for this review includea the above sources, elements of related SEP topics already reviewed for Dresden pla'nt Unit 2, and a plant visit on August 11-12, 1981.
~nkli~ Research Center A OMsion ol The Franlclln lnlUtute TER-C5257-410 i
- 2.
REVIEW CRITERIA In determining the ventilation systems to be evaluated, Franklin Research Center (FRC) was guided by the purposes of the SEP with its emphasis on the review and assessment of safety margins.
In accordance with Assignment 15, 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 condi tiori' o
the capability to prevent or mitigate the consequences of accidents that could result in potential offsite exposures comparable to the guidelines of 10CFRlOO, "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, applicable portions of related safety topic reviews were used where possible.
In accordanc~ with Task 1, Paragraph E, of Assignment 15, the following criteria will alsp be used to evaluate those heating, ventilation, and air conditioning (HVAC) systems or portions thereof that are relied upon to assure the operation of safety-related equipment:
- 1.
Whether a single active failure cannot result in loss of the system functional performance capability.
~nklin Res~arch Center A OMsion ol The Franldln lnslllute
- 2.
- 3.
- 4.
- s.
- 6.
TER-C5257-410 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 result in an unacceptable rele~se, as was defined during licensing review, of radioactive contaminants.
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.
Whether the ventilation systems (except for the control room) have the capability to direct ventilation air from areas of low radio-activity to areas of progressively higher radioactivity.
Whether both control room and engineered safety feature area ventilation systems, have the capability to maintain temperature within the design parameters range for safety-related equipment.
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.
~nklin Research Center A OMslon of The F ranlclln lnslllute TER-C5257-410
- 3.
RELATED SAFETY 'IDPICS 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 II-2.A II-3.3 II-4 III-1 III-2 III-3 III-4 III-5.A III-5.B III-6 III-12 VI-4 VI-7.C.l VII-3 IX-3 IX-6 xv-20
'!MI I II. D. 3. 4 Subject Severe Weather Phenomena Flooding Potential Geology and Seismology Classification of Structures, Components and Systems (Se~smic and Quality)
Win~ and Tornado Loadings Hydrodynamic Loads Missile Generation and Penetration Pipe Breaks Inside Containment Pipe Breaks Outside Containment Seismic Design Considerations Environmental Qualification of Safety-Related Equipment Containment Isolation System Independence of Onsite Power Systems Required for Safe Shutdown Station Service and Cooling Water Fire Protection Radiological Consequence of Fuel Damaging Accidents (Inside and Outside Containment)
~nklin Res~arch Center A DMIJon of The Fianklln lnsdtute I 1
TER-C5257-410
- 4.
TECHNICAL EVALUATION 4.1 CONTROL ROOM'AREA VENTILATION The function of the control room area ventilation system is to provide a controlled environment for the safety and comfort of control room personnel and to assure the operability of control room components during normal operating, anticipated operational transient, and design basis accident conditions.
However, the control room system is being reviewed generically under TMI Item III.D.3.4, "Control Room Habitability," to assure compliance with 10CFRSO, Appendix A, "General Design Criteria for Nuclear Power Plants,"
Criterion 19, "Control Room."
For this reason, the control room area ventilation system was not evaluated as a part of this review.
4.2 REACTOR BUILDING VENTILATION SYSTEM In the following evaluation, those portions of the reactor building ventilation system which specifically service the fuel storage pool and engineered safeguards areas are discussed under separate headings.
As an overview, the reactor building ventilation system is designed to supply 100,000 cubic feet per minute (cfm) of filtered, tempered outside air, distribute it through all working areas and equipment rooms in the reactor building while maintaining a negative pressure of 0.25 inch of water in the building, and exhaust the air (in normal operation) directly to the reactor building vent stack.
No provision is made to filter the exhaust air.
Instead, when radioactive exhaust is detected in the vent stack, the reactor building ventilation system is isolated by redundant pa_irs of butterfly valves from both the supply and exhaust fan systems, whereupqn all exhaust is i
directed to the standby gas treatment system.
The air supply system tempers filtered outside air by means of a non-freezing type steam heating coil or by evaporative cooling, after which the air is directed by three SO-percent-capacity fans through a redundant pair of pneumatically actuated isolation butterfly valves to the building's duct system.
Each of the three SO-percent-capacity supply fans is equipped with
~nklin Res~arch Center A OMsion ol The Franklin INlilule
-s-
TER-C5257-410 inlet and outlet pnuematic-actuated dampers to isolate each fan as necessary.
Pow~r to the fans is supplied by electrical buses 28 and 29, which may be connected to the emergency diesel power in the event of an offsite power failure.
It is noted that two fans are on bus 28 (diesel 2/3) and one is on bus 29 (diesel 2).
The conditioned supply air is then. directed to all working areas and equipment rooms of the reactor building as shown on drawing M-269.
Flow to and within these areas is indicated and controlled by means of temperature indicators and pneumatically operated dampers.
Air* flow through the plant
- does a~pear to satisfy the acceptance criterion for flow from areas of low potential radioactivity to a:reas of higher. potential radioactivity.
Exhaust air is collected by a network of ducts throughout the reactor building that is designed to direct the air through flow control, isolation, pneumaticaily operated dampers to the building's exhaust system.
This system consists of a set of three SO-percent-capacity fans designed to exhaust 100,000 cfm, plus the building's infiltration, *to the reactor building vent stack.;
The drywell purg~ system.is ducted to these exhaust fans sq that drywell effluent is also exhausted by this system when the drywell is. opened for access.
The three exhaust fans are powered by eniergency'diesel-powered electric buses 28 and 29.
Two fans are on bus 29 (diesel 2) arid one is on bus 28.(diesel 2/3).
Thus, fan redundancy is provided in that any two of the three fans will provide full capacity.
This is also true of the supply fans.
It was noted that the exhaust air is not filtered but is ducted directly to the stack.
Radiation monitors in the stack detect the presence of radioactive effluent; when required, the reactor building ventilation system will be automatically isolated by the redundant butterfiy valves located just after ~he supply fans and just before the exhaust fans.
With the isolation valves 'closed, no air enters or.leaves the reactor building by the usual ventilation ports and all radioactivity is contained.
1n*p1ace of the exhaust stack, the exhaust effluent is directed to the standby gas treatment system for effluent decontamination, after which the clean gas is exhausted through the radwaste ventilation chimney.
~nklin Research Center
! A Oivblon ol The Franklin lnsdlule TER-C5257-410 It was noted that the drywell purge system does include prefilters and absolute filters which serve to remove radioactive particulates in the drywell exhaust before this effluent reaches the reactor building ventilation exhaust system.
Should radioactive particles pass through the drywell purge filter system, the effluent will be directed to the standby gas treatment system.
With, the detection of radioactivity and isolation of the reactor building ventilation system, the standby gas treatment system processes the reactor building effluent and exhausts the cleaned air (and other gases) to the plant chimney.
This is accomplished by passing the effluent, in order, through an eiectric heater, ~ rough prefilter, a high efficiency prefilter, an activated-carbon iodine absrlrber, and a high efficiency afterfilter.
The flow rate of 4000 cfm provided by the standby gas treatment system appears to be low for the proper removal of radioactive substances from the reactor building.
For a building using 100,000 cfm for normal ventilation, it appears that the local flow rates at critical regions within the reactor build-ing in conjunction with the 4000 cfm rate provided by the standby gas treatment system would be insufficient to assure the proper upsweep of the qontaminated air into the ducts and could allow the contamination to drift into uncontami-nated areas.
Local temperature differences could set up convective currents to further such a spread.
In summary, the reactor builaing ventilation system appears to meet the acceptance criteria of Section 2.
Equipment redundancy is provided so that a single failure, other than a diesel power failure, will not prevent the system from providing adequate service.
With a failure of either diesel generator, the main ventilation system will provide somewhat less than the design flow volume; since two of each set of three fans (supply and exhaust) are on one or the other diesel. ! Concerns over the standby gas treatment system are expressed above.
'l'he sharing of a diesel generator between Units 2 and 3 is a further concern.
The Conclusions section of this report contains* further discussion of the shared-diesel topic.
e.nkli.n Rese~rch Center A OMsion of The Fnlnicun lllllllute TER-C5257-410 4.3 FUEL STORAGE POOL AREA VENTILATION.SYSTEM The fuel storage pool area ventilation system is an integral part of the reactor buildi.ng ventilation system.
Filtered, tempered air is supplied first to the north and south operating floors, from which it flows to the fuel
'storage pool and the dryer and separator pool.
Exhaust air flow from the pool areas and the operating floor areas is regulated by a series of manually operated dampers.
The acceptance criterion requiring flow of the ventilation air to be from areas of lower radiation potential to areas of higher potential' appears to be satisfied in that conditioned air is first directed to the operating floor, then across the pool areas, and finally is collected into exhaust due.ts that carry the effluent directly to the reactor.building vent stack or, in the case of radiation detection, to the standby gas treatment system.
Other criteria, including the redundancy of emergency electrical*
power and the ability of this system to remain functional following a single active failure, also appear to be satisfied.
- 4. 4 TURBINE BTJILDING VENTILATION SYSTEM The turbine building ventilation system* is ~de up of the main turbine room ventilation system, the reactor feedwater. pump ventilation system, the motor-generator (M-G) room ventilation system, and the east turbine room*
ventilation system. -These are separate systems with separate intake and exhaust points..
Only the main turbine room system is exhaus'ted to the main plant chimney.
4.4.l Main Turbine Room Ventilation System
- The main turbine room is supplied by two parallel air.handling systems, the south turbine room system and the nortW turbine room system, both of which provid~ tempered, filtered outside air.
'l'tfis air is ducted throughout the main turbine area, including the operating floor, the ground floor, and mezzanine areas, and is collected to a conunon exhaust system, powered by three SO-percent-capacity fans, and then to the main plant chimney.
Pneumatically operated dampers on the inlet ~nd exhaust of each fan are used to achieve isolation.
Control systems, using pilot tubes and differential pressure
~nklin Research Center A Division ol The F ranklln lnslltute TER-C5257-410 i
i sensors, operate preumatically actuated flow control dampers on each of the two air supply systems to maintain the main turbine area at a pressure of 0.125 inch of water, negative relative to the atmosph~re. Additional dampers maintain the turbine cavity, moisture separating areas, and various other more critical rooms at a negative differential pressure of 0.25 inch of water.
This promotes inflow to these areas so that contaminants are properly collected and delivered to the plant chimney.
Redundancy of air handling capacity is provided by either two full-capacity or three SO-percent-capacity fans in each set, with electric power for each fan in a set supplied from a different electrical bus.
The three fans of the north turbine room inlet air supply are powered by buses 25, 26, and 27, as are the main turbine room exhaust fans.
The two south turbine room inlet supply fans are supplied from buses 28 and 29.
Although 34,000 cfm are supplied from the north turbine room supply fans to the containment cooling service water pumps located in the condenser pit, this main turbine room system is not powered by an essential diesel-powered bus.
No ventilation is provided upon loss of offsite power.
The adequacy of this provision with respect to the essential containment cooling service water pumps is discussed in a following section devoted to the low pressure coolant injection (LPCI) system.
4.4.2 Reactor Feedwater Pump Ventilation System A separate ventilation system for the reactor feedwater pump rooms is housed in the turbine building.
This system, powered by two full-capacity fans supplied by 480-V buses 25 and 26, supplies filtered outside air to the reactor feedwater pumps for ventilation and cooling.
Provisions are included for recirculated flow.
Used air is exhausted directly to the atmosphere separately from the main turbine room system.
This system is not considered essential for safe shutdown [16] and upon loss of offsite power the ventilation system will shut down.
However, should it be necessary, buses 25 and 26 can be connected to the emergency diesel generator power by operator action.
~nklln Research Center A Division ol The Franldln lnstilute TER-C5257-410 4.4.3 Motor-Gener~ator Room Ventilation System The M-G room ventilation system is a separate ventilation system within the turbine building that provides filtered outside air, with recirculation capability, to ventilate the M-G sets and control cabinets.
Used air is exhausted to the atmosphere.
The system is powered by two full-capacity, redundant fans powered by 480-V electrical buses 28 and 29.
This system ~s not essential to safe shutdown.
4.4.4 East Turbine Room Ventilation System The east turbine room ventilation system supplies filtered, tempered outside air to the north and south HVAC equipment rooms, the switchgear room, the battery room, the auxiliary electrical equipment room, and other areas in this part of the turbine building.
Supply air and exhaust air are each handled by a set of three 50-percent-capacity fans, all of which are powered by motor control center MCC 26-4
- (non-essential and non-redundant el~ctric power).
The supply and exhaust systems are balanced to provide a differential negative pressure of 0.125 inch of water relative to the atmosphere.
Used air is exhausted to the atmosphere.
It is noted at location D-4 on Drawing M-936 (Rev. E) that 4000 cfm of air from this system is directed to the battery room (details on Drawing M-973, Rev. A) for ventilation and cooling and returned to the north HVAC equipment room.
With a loss of offsite power, the east turbine room ventilation system will shut down, and air will not be supplied to the battery room where charging and discharging of the batteries may continue to generate hydrogen.
This is discussed in greater depth under the topic "Battery Rooms" in a later sectidh of this report.
Drawing M-936, Rev. E, shows a flow of 10,000 to 15,000 cfm of air from the east turbine room ventilation system directed to the auxiliary electric i
equipment room, wi!th air flow controlled by a temperature controller.; This i
system will not su;pply ventilation air if offsite power is lost.
Further discussion is continued in this report under the topic aAuxiliary Electric Equipment Room Ven:tilation. a i
~nklin Rese~rch Center A. OMsion ol The Franklin lnslllute TER-CS2S7-410 4.S RADWASTE AREA VENTILATION SYSTEltffi With the exception of the standby gas treatment facility, the following radwaste area ventilation systems were reviewed only with regard to the radiation exposure-related items of the acceptance criteria.
The radwaste facilities are not essential to safe shutdown and, therefore, are not evaluated against safe shutdown criteria.
4.5.1 Radwaste Building Ventilation The main radwaste building, a facility shared with Dresden Unit 3, is supplied with filtered, heated fresh air by three SO-percent-capacity fans.
In satisfaction of an acceptance criterion, it appears that the air is ducted throughout the building so that the air flow progresses from areas of low radiation potential to areas of higher potential.
Dampers are provided to maintain a negative pressure of 0.125 inch of water in the general areas of the building, with certain areas of higher radiation potential maintained at 0.2S inch of water negative pressure.
Infiltration of air will be inward toward these areas.
Ventilation exhaust is provided by three SO-percent-capacity fans that draw the exhaust air through two parallel filter sets, each composed of a prefilter followed by an absolute fii'ter, and discharge the air to the main plant chimney.
Each fan is equipped with isolating dampers on both inlet and discharge!
The supply fans are similarly equipped with dampers.
Electric power is supplied from motor control centers MCC 27-2, 27-4, and 27-S, which may, in turn, be supplied by either Unit 2 power or Unit 3 power.
Two supply fans are on MCC 27-S, one on MCC 27-2.
Two exhaust fans are supplied by MCC 27-4 and one by MCC 27-2.
Thus, at least SO% power redundancy is achieved.
4.S.2 Standby Gas Treatment Facility The standby gas treatment system, shown on Dwg. M-49, is a facility shared by Units 2 and 3 and powered by 480-V essential service buses of both Units 2 and 3.
~nklin Research Center A OMslon cl The Franlclln lnsdtute i
j le I
TER-C5257-410 Effluent sources include the reactor building ventilation system, the drywell purge (either directly or via the reactor building ventilation system), and the gland seal condenser.
This review focuses principally upon the gas treatment facility's role as the reactor bu~lding's only source of ventilation following the detection of radioactive effluent in the reactor building stack and the subsequent shutting down and isolation of the reactor building ventilation system.
The standby gas treatment system is essential for maintaining a negative pressure in the reactor building, assuring that there will be infiltration of outside air into, instead of leakage of radioactive effluent out of, the building.
Induced draft fans 2/3A and 2/3B operate in parallel from a common fan inlet plenum to provide flow through two Separate parallel effluent processing lines, one for Unit 2 and one for Unit 3.
Since the standby gas treatment system processes effluent from both Unit 2 and Unit 3, the parallel fans are powered, respectively, by MCC 28-2 (diesel generator 2/3) and MCC 39-2 (diesel generator 3).
Each parallel treatment system is rated for 4000 cfm, as is each fan.
A negative pressure of 0.25 inch of water is maintained in the reactor building with the use of pneumatic-operated inlet dampers in the standby gas treatment system.
The treated effluent from the fans is ducted to the main plant chimney.
- Isolation of the system is assured by normally-closed single isolation dampJrs on the input and output ends of each treatment path, in addition to a set Qlf normally-open dampers that may be actuated to close.
This system I
appea!rs to satisfy the acceptance criteria identified in Section 2, except for a possible failure scenario associated with the use of diesel 2/3 to provide power to either Unit 2 or Unit 3.
This failure.scenario lies in the use of diesel 2/3 to provide power on demand to either Unit 2 or Unit 3.
Consider a failure of diesel 3 following a loss of offsite power.
This would cause diesel 2/3 to switch to Unit 3.
It appears then that both buses (bus 39 of Unit 3 and bus 28 of Unit 2) powering the standby gas treatment system could be down until the operator acts to restructure the loadings of the diesel generators and restore power to the standby gas treatment system.
~nklin Research Center A OMslon ol The FrenJclln lllldlule l I I
I i
~
l
. i I
I 1
TER-C5257-410 While this scenario does not give rise to a release of radioactive substances, it does appear that the period of no flow is conducive to the spreading of radioactive substances to areas of lesser radioactive potential.
4.5.3 Off-Gas Recombiner Rooms With respect to gaseous discharge from Dresden Unit 2, the previously discussed reactor building ventilation system discharges a large gas volume to a stack, and, upon detection of radioactive substances, shuts down to vent through the standby gas treatment center.
The turbine building also vents a large volume of air through the main plant chimney but with relatively little radioactivity.
The main source.of radioactive gaseous discharge is deaeration of steam in the. steam condensers.
The main purposes of the off-gas system are to recomb;ine hydrogen, to promote the decay of radioactive substances in shielded piping,.and to filter out radioactive substances for waste disposal.
Ventilation of the off-gas recombiner rooms is provided by two parallel sets of inlet air handling units and exhaust fans.
Although this provides redundancy of the mechanical' systems, the air handling units and the exhaust fans are all powered from the same motor control center, MCC 26-7.
This electric power is not essential service, and the*fans will shut down with the loss of offsite power.
Filtered, heated outside air is supplied by the air handling units *. The parallel exhaust fans draw from a common point and exhaust without further filtering to the main plant chimney.
The system is isolated by two dampers in series on each parallel inlet and exhaust duct; with one set of dampers indicated to be normally closed.
Assuming that these pneumatically actuated dampers fail closed upon loss of ~neumatic power, the system appears to have*
satisfactory isolation. 'The only question regarding complia11ce with the acceptance criteria identified in Section 2 concerns how long the off-gas recombine~ system could operate without ventilation if electric power to motor control cen~er MCC 26-7 is lost.
~nklin Research Center i /\\ OMsion of The Frenldln INdtuu!
I I i 1
i I
- TER-C5257-410 4.5.4 Off-Gas Filter Building The off-gas filter building ventilation system is supplied by two parallel full-capacity HVAC units equipped with refrigeration cooling.
Each of these units supplies filtered, heated, and/or cooled air from separate outside sources.
Duct heaters are used to control local temperatures.
Numerous dampers control the flow throughout the building.
Two full-capacity exhaust fans in parallel draw the exhaust air from a common point through separate sets of roughing and.HEPA filters and direct the exhaust to the main plant chimney.
Single isolation valves on each exhaust fan discharge isolate the system from the plant chimney.
Single isolation dampers on each inlet air system, located downstream of the HVAC units, isolate the system from the outside air supply.
Electric power is supplied from both Units 2 and 3.
One air supply HVAC system and one exhaust fan are on MCC 20-1, while the other parallel set is powered by MCC 30-1.
Further assurance of power is provided by a cross tie between MCC 20-1 and MCC 30-1.
4.5.5 Radwaste ~Solidification Building The radwast 1e solidification building control room is supplied with I
filtered, temper:
1ed air by its own HVAC system.
The control room HVAC system draws 800 cfm ofi outside air in addition to 2600 cfm of recirculated air.
Control room excbss air is lost by leakage to the surrounding systems and to the truck bay.
~ower for the control room HVAC system is drawn from both Units 2 and 3.
As indicated in Reference 20, the air.handler appears to be supplied by MCC 20-6, while its compressor and an elec~ric duct heater are supplied by MCC 30-5.
This does not provide redundan9y in that there appears to be only one fan and one electric supply. It is noted that the control room HVAC equipment is ventilated by its own HVAC system powered from Unit 3.
The radwaste solidification building is ventilated by a system that supplies heated, filtered outside air, circulates it throughout the building, and exhausts the used air to the main plant chimney through a heat recovery heat exchanger.
~nklin ResJarch Center A OMslon of The Fiankun lnslllute l
i r I
't i
.. t i
I J..
I TER-C5257-410 Full redundancy of equipment and power sources is indicated, except that Drawing M-851, which illustrates the supply and exhaust systems, does not indicate whether each fan is rated for full capacity.
Since this is a facility shared oy Units 2 and 3, the redundant air supply and exhaust systems are powered by both Units 2 and 3.
Electric power is supplied by non-essential motor control centers MCC 20-6 and 30-5.
Each flow path of the redundant pairs of flow paths of the air supply and exhaust systems is equipped with two "fail closed" dampers, one on each end of each flow path.
In addition, two pairs of redundant isolation dampers are employed to isolate the radwaste solidification building from the air supply and exhaust systems.
The effluent from the radwaste solidification building is filtered by prefilters and HEPA filters before being directed to the main plant chimney.
The radwaste solidification building ventilation systems appear to satisfy the acceptance criteria in Section 2.
4.5.6 Maximum Recycle Radwaste Building The ventilation system supplies this building with filtered outside air that is heated electrically or cooled by HVAC system refrigerant.
The air is ducted through the building in a manner which apppears to satisfy the acceptance criterion that flow from area to area be in the direction of increasing radioactivity potential.
Air is discharged from the building through two redundant flow paths, each including a flow damper, ~refilter, HEPA filter, exhaust fan, and butterfly isolation damper.
This exhaust fan system discharges the air to the main plant chimney through a heat recovery (to the air supply) heat exchanger.
Isolation in this system is primarily isolation of the ventilation from the main plant radwaste chimney by the butterfly isolation dampers and an opposed-blade damper on each of the redundant exhaust.fan paths *.
This.facility is shared with Unit 3.
Because non-essential electric power is supplied from both Units 2 and 3, redundancy is achieved.
The air supply HVAC system is powered by motor control center MCC 20-5.
Each of the e;nkl~ Research Center A OMslon of The Franldln lnllllute l
I I I f
J J
L
. ' :e I
TER-C5257-410 two exhaust fans is supplied, respectively, by motor control centers 20-5 and 30-4.
Further redundancy of electric power is provided by the tie line between motor control centers MCC 20-5 (Unit 2) and MCC 30-5 (Unit 3).
The maximum recycle radwaste building ventilation system appears to satisfy the acceptance criteria identified in Section 2.
4.6 ENGINEERED SAFETY FEATURES VENTILATION SYSTEMS 4.6.l Engineered Safeguar<;is Systems Ventilation and Cooling The emergency core cooling system (ECCS) is the one engineered safeguard system essential for safe shutdown that is ventilated and cooled by ventilation systems within the scope of this review.
The review includes the emergency core spray, low pressure coolant injection (LPCI), and high pressure coolant injection (HPCI) subsystems of the ECCS.
4.6.1.1 Emergency Core Spray Subsystem Ventilation The emergency core spray pumps are the only components of the emergency core spray subsystem serviced by ventilation systems within the scope of this review.
Since they are located with the LPCI pumps and heat exchanger, they are discussed together with LPCI subsystem ventilation in the following section.
4.6.1.2 Low Pressure Coolant Injection Subsystem Ventilation The LPCI and emergency core spray pumps are located in corner rooms on the basement level of the reactor building ventilated by the reactor building ventilation system.
Since the reactor building ventilation system can be supplied with emergency diesel power, ventilation is assured following the loss of offsite power.
In addition, each LPCI pump room contains its own room cooler.
These individual units cool by means of the diesel generator cooling water system, and their fan motors are supplied by electrical motor control centers MCC 28-1 and 29-4, designated as diesel-powered essential service.
~nklfn Research Center A DIYtsion ol The Franklln lnsdlllle t
- ~ '
J TER-C5257-410 Reference 20 and Drawing 12E-2302B list only two cubical coolers, 2A on MCC 28-1 and 2B on MCC 29-4.
These coolers appear to be in two different rooms (their locations are not explicitly indicated).
If so, then despite provision of essential electrical service, the fans of the LPCI cubical coolers do not have the redundancy to assure cooling in the event of a failure within the unit.
These coolers are important because they would be the only source of cooling for the LPCI pump motors should the detection of radiation shut down the reactor building ventilation system and cause its effluent to be directed to the standby gas treatment system where the air. flow rate is comparatively very small.
4.6.1.3 High Pressure Coolant Injection (HPCI) Subsystem Ventilation The HPCI pumps are driven by a steam turbine.
The HPCI room is serviced by the reactor building ventilation system supplemented by a room cooler which uses cooling water from the diesel generator cooling water system.
Reference 20 and Drawing 12E-2302B show essential service electrical power being provided by MCC 29-4, but there is no indication of redundancy of fans or electrical service.
As discussed above for the LPCI subsystem, the equipment in the HPCI room is cooled solely by the room cooler if the reactor building ventilation system is shut down due to detection of radiation in the vent stack.
It appears that the HPCI ventilation and cooling system does not have sufficient redundancy and is vulnerable to a single failure.
4.6.2 Reactor Shutdown Cooling System Ventilation The reactor shutdown cooling system is the Dresden Unit 2 equivalent of a residual heat removal (RHR) system.
The shutdown cooling system is ventilated by the reactor building ventilation system, but, since the shutdown cooling system is not considered by References 16 and 21 to be one of the minimum.
number required for safe shutdown, its ventilation is not discussed further in this review.
~nklin Research Center A Division of The Franklin 1...iltute I
"I:
l l
TER-C5257-410 4.6.3 Reactor Building Closed C_ooling Water System Ventilation The reactor building closed cooling water (RBCCW) system serves as an intermediate between the reactor shutdown cooling system (and other reactor building equipment) and the service water syst~m. While it may be used for shutdown heat removal, as stated by References 16 and 21, it is not the primary system required to perform post-accident safe.shutdown heat removal.
The RBCCW system is ventilated by the reactor building ventilation system but, since the RBCCW system is not considered by Reference 21 to be essential for safe shutdown, its ventilation will not be diseussed further.
4.6.4 Service Water System Ventilation Reference 21, SEP Topic IX-3, "Station _Service Water System Review,"
identifies two service water systems that are essential for safe shutdown:
the diesel generator cooling water (DGCW) and containment cqoling service water (CCSW) systems.
4.6.4.1 Diesel Generator Cooling Water System Ventilation In addition to providing cooling water to diesel generators 2, 3, and 2/3, the DGCW system provides. the service water cooling medium to the room coolers of the LPCI (two coolers) and HPCI (one cooler) equipment rooms of Dresden Unit 2.
The pumps for the DGCW system are located in the crib house.
Reference 21 indicates that the original pumps have been replaced with submersible types so that ventila.tion and air cooling of the pumps or pump motors are not required *.
4.6.4.2 Containment Cooling.Service Water System Ventilation 1rhe CCSW system, also known as the emergency service water system, supplies cooling water to the LPCI system.
Using four pumps located in he condensate pit of the turbine building, the CCSW system draws water from the crib house and supplies it to the LPCI heat exchanger in the reactor building.
~nklin Research Center A Olvislon ol The FranldJn lnldtute TER-C5257-410 Ventilation is provided by the main turbine room ventilation system which supplies 34,000 cfm of filtered heated air to the CCSW system.
In the review of the turbine building ventilation system, it was established that this was a non-essential system that would not be operating during emergency shutdowns in which offsite power is lost.
Under these conditions, cooling of the CCSW pumping equipment is provided by a set of room coolers using the service water from the CCSW system as the cooling medium.
Drawing M-274 shown the arrangement of the room coolers for the CCSW system.
Four cubical coolers, each containing two fans, cool the equipment located in the service water flood-protected cubical.
Drawing M-5 shows pumps 2B and 2C in the center cubical and pumps 2A and 2D in other separate cubicals.
Thus, Drawing M-5, and also Drawing M-274, indicate that only pumps 2B and 2C are within the cooled and protected cubical.
Within this cubical, two of the four containment cooling water pumps are cooled by four cubical coolers, two of which are powered by MCC 28-2 and two by MCC 29-2, both diesel-powered essential service.
One CCSW pump is powered by bus 23 and the other by bus 24, buses that may be connected to the emergency diesel power by the operator.
CCSW pumps 2A and 2D, outside the protected cubical, are also powered by buses 23 and 24.
Cooling, other than by ventilation air, is not shown in the plant drawings.
4.6.5 Auxiliary Electrical Equipment Room Ventilation System The auxiliary electrical equipment room houses equipment and systems essential for safe shutdown, including the reactor protection system motor-generators and instrumentation, the ESS generators, and essential relays and switch gear.
Although the auxiliary electrical equipment room is ventilated by the east turbine room ventilation system, the usual means of ventilation and cooling is a separate HVAC system dedicated to this room.
- Electrical power to the HVAC compressors and fan is from motor control center MCC 25-2, which is not an essential power center supplied by the emergency diesel generators.
However, MCC 25-2 can be connected by operator action through buses 25 and 23 to bus 23-1 which is powered by diesel 2/3.
~nkli.n Research Center A OMsion ol The Franklln lnslltute I )
TER-C5257-410 Although the auxiliary electrical equipment room is shared with Unit 3, there appears to be no counterpart HVAC system powered by Unit 3.
Redundancy depends instead on the east turbine ventilation system's deriving its electrical power from motor control center MCC 26-4.
Electrical bus 26 is not essential electrical service but may be connected through buses 24 and 24-1 to power from diesel 2.
The adequacy of the_ electrical i.:>ower redundancy depends upon the adequacy of the complex power interconnections between Units 2 and 3 and among the three diesel generators.
This is the subject of SEP Technical Evaluation Topic VI.7.C.l, "Redundant Onsite Power Systems, Dresden 2,"
December 1979, currently undergoing revision.
The east turbine building ventilation system is designed (Drawing M-963) to supply filtered, heated outside air (with recirculation capability) to the auxiliary electrical equipment room.
This ventilation. system employs an exhaust fan to provide a local recirculation capability around the auxiliary electrical equipment room.
No cooling is provided in this mode of operation other than that inherent in outside air.
Temperatures may range up to l04°F in this mode.
Except for the adequacy of electrical power, which is to be addressed by revisions of SEP Technical Topic VI.7.C.l, the ventilation system for the auxiliary electrical equipment room complies with the acceptance criteria of Section 2.
4.6.6 Battery Room Ventilation System The battery room contains the batteries that provide emergency DC power essential for post-accident shutdown of the reactor.
Ventilation.designed for the purpose is considered essential to assure that the*hydrogen given off from the batteries during heavy discharging and recharging is removed.
Ventilation is provided by the east turbine',room ventilation system from which 4000 cfm of filtered, heated air (outside air, but with recirculation capability) is ducted to the battery room and discharged through the north HVAC equipment room.
~nkli~ Research Center A DMslon ol The Franlclln Institute
- I j
te l
i TER-C5257-410 Redundancy of air handling is provided by three SO-percent-capacity supply and discharge fans.
However, all six fans are supplied from one motor control center, MCC 26-4, powered from bus 26.
Bus 26 is not cons~dered essential electrical service and must be connected by operator action to bus 24-1 which is powered by diesel generator 2 through bus 24.
This is satisfactory, provided the proper procedures are in place to enable these connections to be made to prevent any buildup of hydrogen gas in the battery rooms.
However, a critique of redundant onsite power sources is not within the scope of this review., That is the subject of Reference 22, now being revised.
4.6.7 Diesel Rooms Ventilation Systems Diesels 2 and 2/3 are housed in separate rooms served by separate ventilation systems.
Cooling is provided by the diesel service water systems, and the ventilation systems both vent the rooms and cool associated switchgear equipment.
Diesel 2 is ventilated by a single 30-hp fan powered by motor control center MCC 29-2 (essential service, diesel 2).
Outside air and/or turbine building air is supplied to the fan through a set of temperature controlled dampers.
Air is discharged from the diesel room through a set of louvered doors into the turbine building.
Diesel 2/3 is housed in a separate room off the reactor building.
It, too, is ventilated by a single 30-hp fan similar to that used for diesel 2.
Should the single ventilation fan fail, the large double doors between the turbine building and diesel 2 could be opened to promote natural convection from the turbine building.
However, natur_al convection through the doors cannot equal the air supplied by a 30-hp fan.
If the fan's airflow is deemed necessary by design for ventilation in the event of a prolonged post-accident shutdown, then redundancy is not provided.
The system does not satisfy the single failure criterion.
~nkli~ Research Center A DMsion of The FrankJin lnsrltute..
TER-C5257-410
- 5.
CONCLUSIONS 5.1 ONSITE DIESEL GENERATED POWER Although a review of the redundancy ofonsite diesel-generated power is not within the scope of this evaluation, the nature and extent of such redundancy and a plan for diesel power management affect the availability and effectiveness of ventilation systems.
Reference 22, SEP Topic VII.7.C.l, "Redundant Onsite Power Systems,* which deals with this subject; is currently under revision.
Conclusions reached in the course of the revision will have relevance to.this review of ventilation systems.
5.2 CONTROL ROOM AREA VENTILATION Ventilation of the control room was not reviewed here because it is a part of the generic study, "Control Room Habitability," being conducted under
'IMI Item III.D.3.4.
That study is designed to assure compliance with 10CFR50, Appendix A, General Design Criterion 19, "Control Room".
5.3 REACTOR BUILDING VENTILATION SYSTEM The reactor building ventilation system has redundancy in isolation dampers ana in intake and exhaust fans supplied by onsite emergency power from both diesels. It therefore satisfies the single failure criterion.
- However, effluent from the reactor building is vented to the reactor building vent stack without filtration.
if radiation is detected, the reactor building is isolated and connected to the standby gas treatment system which cleans the effluent but draws only 4000 cfm of air as compared with 100,000 cfm for the reactor building ventilation system.
This reduced airflow is low enough to allow radioactivity to spread within the reactor building.
Although this will not result in a release of radioactivity outside the plant, it may create a hazard for plant personnel.
5.4 FUEL STORAGE POOL AREA VENTILATION The fuel storage "pool area ventilation system is not essential for safe shutdown and was reviewed only with respect to personnel hazards and the
~nklin Researc~ Center A Division of The F ranklln Institute TER-C5257-410 release of radioactivity outside the plant. It was concluded that the criteria listed in Section 2 are satisfied
- 5.5 TURBINE ROOMS VENTILATION SYSTEMS The main turbine room ventilation system supplies ventilation to only one essential system, the containment cooling service water pumps.
Since a separate cooling system is provided for these pumps and motors, the main turbine room ventilation system was judged not essential for safe shutdown.
Other criteria regarding the release of radioactive substances outside the plant are satisfied.
The east turbine room ventilation system supplies ventilation and cooling to the battery room as well as backup ventilation to the auxiliary electrical equipment room.
The equipment in both these rooms is essential for safe shutdown.
Although three SO-percent-capacity fans are provided on both inlet and exhaust for redundancy, the six fans are all powered by the same.
non-essential electrical motor control center. It is concluded, therefore, that assurance is required for continued ventilation of the battery room and the auxiliary electrical equipment room during post-accident shutdown when offsite power is not available.
It is recommended that the Licensee provide a plan for emergency electrical load management to assure ventilation of these essential areas.
5.6 RADWASTE AREAS VENTILATION SYSTEMS
.The review of radwaste areas venti.lation systems included:
o Radwaste Building Ventilation System o
Standby Gas Treatment Facility Ventilation Sy.stem o
Off-Gas Recombiner Rooms Ventilation System o
Off-Gas Filter Building HVAC System o
Radwaste Solidification Building Ventilation System o
Maximum Recycle Radwaste Building Ventilation System It was concluded that all these systems comply with the acceptance criteria of Section 2, except as follows:
~nklin Research Center A Olvlsion of The F ronklin Institute TER-C5257-410 o
The standby gas treatment facility ventilation system is vulnerable to a single failure because of the use of the swing diesel 2/3 as discussed in Section 4.5.2. Clarification of the use of diesel 2/3 is needed under SEP Topic V.I.7.C.l.
o With respect to the off-gas recombiner rooms ventilation system, it was concluded that the Licensee should justify the dependence upon only one source of power (MCC 26-7) for all inlet and exhaust fans.
5.7 ENGINEERED SAFETY FEA~'URES VENTILATION SYSTEMS 5.7.1 Engineered Safeguards Ventilation Systems o
LPCI/Core Spray Ventilation:
Although the separate cooiing units on separate essential electrical power sources will continue to provide cooling if the reactor building ventilation system shuts down, it was concluded, based on the discussion in Section 4.6.1.2, that full redundancy is not provided because the cooling units are in different rooms.
o HPCI Room Ventilation:
It was concluded from the discussion in Section 4. 6.1. 3 that, during a shutdown in which onsite diesel power is used and the reactor building ventilation system is switched to the standby gas treatment facility, cooling is provided by only one room cooler.
It was further concluded that this cooler is vulnerable to a single failure becau5e it has only one fan and one source of essential power.
5.7.2 Reactor Shutdown Cooling System Ventilation and Reactor Building Closed Cooling Water System Ventilation Neither of these. systems is relied upon as essential.for safe shutdown.
Therefore, they were not assessed for compliance with the acceptance criteria.
5.7.3 Service Water System Ventilation The following conclusions were drawn regarding the essential service water systems:
o Diesel Generator Cooling Water System Ventilation:
Section 4.6.4.l discusses the replacement of the original pumps with submersible type pumps.
No ventilation is necessary.
~nklin Research Center A OIYislon ol The F ranklln Institute I
~
I I
i,_
l
)
0 TER-C5257-410 Containment Cooling Service Water System Ventilation:
Without the quidelines of Reference 22 which is now under revision, and without a plan for adding loads throughout the electrical bus system to the onsite diesel power sources, it was concluded that, during a shutdown following a loss of offsite power, the east turbine rooms ventilation system would not operate to ventilate and cool the containment cooling service water pump motors.
In accordance with the discussion in Section 4.6.4.2, it was concluded further that area cooling is directed only to pumps 2B and 2C.
Therefore, it is recommended that the Licensee address this issue to clarify the plan for onsite diesel power generation and its management relative to the containment cooling service water pumps.
5.7.4 Auxiliary Electrical Equipment Room Ventilation System Since this room contains key equipment for the reactor protection system, its ventilation system is judged essential for safe shutdown.
Although a aedicated HVAC system is backed up by ventilation supplied by the east turbine room ventilation system, it was concluded, as discussed in Section 4.6.5, that the availability of either ventilation system depends upon the more complex issue of onsite diesel-generated power, interconnections between Unit 2 and
- Unit 3, and a load management plan for adding to the diesels loads that are not on essential buses.
The Licensee is urged to clarify this issue.
5.7.5 Battery Room Ventilation System Since batteries may continue to discharge and recharge during a post-accident shutdown, it was concluded that the ventilation of the battery room is essential for safe shutdown.
With ventilation of the battery room also provided by the east turbine room ventilation system, the considerations that apply are the same as those discussed in the two preceding sections. It is recommended that the Licensee clarify the management of power to the east turbine room ventilation system in the event of a los's of offsite po'.A'er and/or a failure of motor control center MCC 26-4 on bus 26.
~nklfn Research Center I\\ Division of The F ranklln Institute l
I J 1*
' 'J.
TER-CS2S7-410
- 6.
REFERENCES
- 1.
10 CFR Part SO, Appendix A, General Design Criterion 2, "Design Basis for Protection Against Natural Phenomena"
- 2.
10 CFR Part SO, Appendix A, General Design Criterion 4, "Environmental and Missile Design Bases"
- 3.
10 CFR Part SO, Appendix A, General Design Criterion S, "Sharing of Structures, Systems and Components"
- 4.
Standard Review Plan, Section 9.4.l, "Control Room Area Ventilation System" S.
Standard Review Plan, Section 9.4.2, "Spent Fuel Pool Area Ventilation System"
- 6.
Standard Review Plan, Section 9.4.3, "Auxiliary andRadwaste Area Ventilation System"
- 7.
Standard Review Plan, Section 9.4.4, "Turbine Area Ventilation System"
- 8.
Standard Review Plan, 9.4.S, "Engineered Safety Feature Ventilation Sy stern"
- 9.
Standard Review Plan, Section 9.S.l, "Fire Protection Systems"
- 10.
Regulatory Guide 1.13, "Spent Fuel Storage Facility Design Basis"
- 11.
Regulatory Guide 1.26, "Quality Group Classifications and Standards for Water, Stearn and Radioactive-Waste-Containing Components of Nuclear* Power Plants"
- 12.
Regulatory Guide 1.29, "Seismic Design Classification"
- 13.
Regulatory Guide l.lOS, "Instrument Setpoints 0
- 14.
Regulatory Guide 1.117, "Tornado Design Classification" lS.
Branch Technical Position ASB 9.S-1, "Guidelines for Fire Protection for Nuclear Power Plants"
- 16.
SEP Topic VII**3, "SEP Review of Safe Shutdown Sy stems for the Dresden Unit 2 Nuclear Power Plant, Revision 2," April 1981 *
- 17.
SEP Topic VII-3, "Electrical, Instrumentation and Control Features of Systems Required for Safe Shutdown," Final Draft, Dresden Nuclear Power*
Station Unit 2, Commonwealth Edison Company, June 1981
~nklin Research Center A OMsion ol The Franklin lnalitute
.~.\\
/
TER-C525 7-410
- 18.
Technical Evaluation Report on Environmental Qualification, Dresden Nuclear Power Station Unit 2, Docket No. 50-237, NRC TAC No. 42519, Franklin Research Center, May 4, 1981
- 19.
Letter, Sam Power, Jr., Commonwealth Edison Company, to Paul s. Manzon, Target Technology, Ltd., August 4, 1981
- 20.
Dresden Station Electrical Distribution (Red Handbook), Commonwealth Edi son Company
- 21.
Sep Topic IX-3, "Review of Sta*tion Service and. Cooling Water Systems for the Dresden Nuclear Power Plant Unit 2," June 30, 1981
- 22.
SEP Topic VI.7.C.l, "Redundant Onsite Power Systems, Dresden Unit 2,"
December 1979
~nklin Research.Center A DMslon ol The Franlclln INll!ute
-27..;.