ML17194B299
| ML17194B299 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 09/02/1982 |
| From: | Oconnor P Office of Nuclear Reactor Regulation |
| To: | Delgeorge L COMMONWEALTH EDISON CO. |
| Shared Package | |
| ML17194B300 | List: |
| References | |
| TASK-09-05, TASK-9-5, TASK-RR LSO5-82-09-017, LSO5-82-9-17, NUDOCS 8209160451 | |
| Download: ML17194B299 (19) | |
Text
........
Docket No. 50-237 LSOS-82-09-017 Mr. L.. DelGeorge Director *of Nuclear Licensing",.
Commonwealth Edison Company Post Office Box 767 Chi ca go, IJ)l l i noi s 60690
Dear Mr. Del George:
September 02, 1982
SUBJECT:
FORWARDING EVALUATION REPORT OF SEP TOPIC IX-5, VENTILATION SYSTEMS FOR THE DRESDEN NUCLEAR POWER PLANT UNIT 2
- Enclosed is a copy of a Safety Evaluation Report of Systematic Evaluation
...... \\, Program Topic IX-5, Ventilation Systems. This evaluation is based on our
\\'*contractor's, The Frankl in Research Center, Technical Evaluation Report
- ._ {TER-C5257-410} and reflects the commerrts provided in your July 12, 1982 letter.
f]hi s /assessment compares your 'cf ad H.ty, as described in Docket No. 50-237, wit.fl' the criteria curc~ntly used by the regulatory staff itor licensing
"+-,1 I
neW facilities.
This evaluation w111 be a basic input to the integrated safety assessment for your facility. A d~termination of the need to actually implement modifications will be made during the ilitegrated assessment. This topic.
assessment rriay be. revised in the future 1.f your facility design is changed or if NRC criteria relating to this topic are modified before: the f ntegrated.
ass~s_s_ment.1 s completed.
Enclosure:
As stated.
cc w/enclosure:
See next page
/
Sincerely, Paul W. O'Connor, Project M~nager Operating Reacto\\5-s Branch No. 5 Division of Licensing NRC FORM 316 (10-60) NRCM 0240 OFFICIAL RECORD COPY USGP0:1981-335-S60.,.
.* tJ~
Mr. L. DelGeorge cc Robert G. Fitzgibbons Jr.
Isham; Lincoln & Beale Counselors at Law.
Three First National Plaza Suite 5200 Chicago, Illinois 60602 Mr.
B~ B. Stephenson Plant Superintendent Dresden Nuclear Power Station Rural Route #1 Morris, Illinois 60450
- The Honorable Tom Corcoran United States House of Representatives Washington, D. c.
20515
- U *. S. Nuclear Regulatory Commission Resident Inspectors Office Dresden Station RR #1 Morris, 1llinois 60450 Mary Jo Murray Assistant Attorney General Environmental Control Division 188 W. Randolph Street Suite 2315 Chicago, Illinois 60601 Chairman Board of Supervisors of
.,Grundy County Grundy *county Courthouse Morris, Illinois 60450 John F. Wolf, Esquire 3409 Shepherd Street Chevy Chase, Maryland 20015 Dr. Linda W. Little 500 Henni tage Ori ve Raleigh, North Carolina 27612 Judge Forrest J. Remick The Carriage House - Apartment 205 2201 L Street, N. W.
Washington, D. c.
20037 Illinois Department of Nuclear Safety 1035 Outer Pa~k Drive, 5th Floor Springfield, Illinois 62704 U. S. Environmental Protection Agency Federal Activities Branch
. Region V Offi¢e
- ATTN:
Regi on~l Ra di a ti on Representative 230 South Deafborn Street
- Chicago, Illi~ois 60604
-~
James G. Kepp1er, ~egional Administrator Nuc1ear Regulatory Commission, Region Ill 799 RooseveltiStreet Glen Ellyn, Illinois 60137
-~
TOPIC IX-5 SEP REVIEW VENTILATION SYSTEMS FOR THE DRESDEN NUCLEAR POWER STATION UNIT 2
L
- e.
SYSTEMATIC EVALUATION PROGRAM TOPIC IX-5 DRESDEN 2 Topic:
IX-5, Ventilation Systems
- I.
INTRODUCTION 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 systems.
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 pennit personnel access, and to control airborne radioactivity in the area during normal operation, anticipated opera-tional tranisents, and following postulated fuel hpndling accidents.
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.
I I.
- REV! EW CRITERIA The current c~iteria 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. l, "Control Room Area Ventilation Sys-
- tem, 11 9.4.2, "Spent Fuel Pool *Area Ventilation Sy$tem," 9.4.3, "Auxilh ary And Radwaste Area Ventilation System," 9.4.4, 11Turbine Area Ventila-tion System" and 9.4.5, "Engineered Safety Feature Ventilation System."
In determining if plant design conforms to a safety o_bjective, use is made, where pcssible, of applicable portions of previous staff reviews.
- .. III.
RELATED SAFETY TOPICS AND INTERFACES The scope of review for this }Opie 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 III-1 II 1-6 VI-4 VI-7.C. l VI-8 Vl-10.B VI I-3 IX-6 XV-20 Severe Weather Phenomean Classification of Structures, Components and Systems (Seismic and Quality)
Seismic Design Considerations Containment Isolation System Independence of Onsite Power Control Room Habitability Shared Engineered Safety Features, On-si,te Emergency Power and Service Systems for Multiple Unit Facilities 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 l E SAFETY RELATED EQUIPMENT IV.
REVIEW GUIDELINES In determining which systems to evaluate under this topic, the staff used the definition of "systems important to safety" provided in Regula-tory Gui.de 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 mai*n-tai.n it in a safe condition, or (.3) the capability to prevent, or mitigate the consequences of accidents that could result in potential offsite exposures comparable to the guidelines of 10 CFR Part 100, "Reactor Site Criteria.
11 This definition was used to determine which systems or.
- portions of systems were "essential." Systems or portions of systems which perform functions important to safety were considered to be essential.
V.
EVALUATION The systems reviewed under the topic are the control room area ventilation system, reactor building ventilation system, fuel storage pool area venti-lation system, turbine building ventilation systems, radwaste area venti-lation systems and engineered 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 trans.i-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 compliance with Criterion 19, "Control Room" of Appendix A, "General Design Criteria for Nuclear Power Pl ants, 11 to l 0 CFR Part 50.
Therefore, the CRAVS was not reviewed under this topic.
B.
Reactor Building Ventilation System The reactor building ventilation s~stem 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 ~ 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 provistorr is made to filter the exhaust air.
Instead, w.tien 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 2/3B 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 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 th~ 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 iii the review
- criteria identified in Section II, with two exceptions:
- 1)
The capability of the standby gas treatment system to direct ventilation air from areas of low radioactivity to areas of higher radioactivity levels due to its relatively low syst_em design flow rate (4000 cfm).
However,- the licensee has stated that access into this area is unnecessary after an accident.
Therefore, the issue of meandering radioactivity is not a concern,'
the staff agrees.
- 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 result in loss of power to the standby gas treatment system.
This issue will be evaluated under SEP Topic VI-10.B (see Section III).
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 operatini 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 building 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 was 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-essenti a 1 and non-redundant el e.ctri c p~wer). 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 0-4 on Drawing M-936 (Rev. E) that 40Qn cfm of air from this system is directed to the battery room (details on
.... Drawing M-973, Revision 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 shutdown, and air will not be supplied to the battery room where charging of the batteries may continue to generate hydrogen.
This is discussed in greater depth in Section V-F.6, "Battery Rooms Ventilation System."
Drawing M-936, Revision 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 equipment room, with air flow controlled by a temperature controller.
This system will not supply ventilation air if offsite power is lost.
Further discussion 1s 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-§aS Filter Building,
- 4)
Radwaste Solidification Building; and
- 5)
Maximum Recycle Radwaste Building.
Based on the Frankl in 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.1.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.
Since they are located with the LPCI pumps and heat exchanger, they are discussed together with LPCI sub-system ventilation in the 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 af 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 cont~ins 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.
- There are two cubical coolers for the LPCI corner rooms 2A (east cooler# 2-5746A) on MCC 28-1, powered from bus 28, and 2B (west cooler # 2-5746B) on MCC 29-4, powered from bus 29.
Bus 28 is nonrially powered from Unit 2 auxiliary transformer 21 and upon loss of otfsite power is powered automatically from standby diesel 2/3.
Bus 29 is normally powered from reserve auxiliary transformer 22, but upon loss of offsite power is powered automatically from standby diesel 2.
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 shutdown 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.
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 supplemented by a room cooler which uses cooling water from the diesel generator cooling water system.
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 the LPCI
~-
~*
- subsystem, the equipment in the. HPCI room is cooled solely by the room cooler if the reactor building ventilation system is shutdown due to detection of radiation in the vent stack. Therefore, the HPCI ventilation and cooling systems does not have sufficient redundancy and is vulnerable to a single failure.
However, because this plant's design includes fully redundant and independent system to the HPCI (auto-depressurization system) the staff does not see the need for an additional HPCI ventilation.
F.2 Reactor Shutdown Cooling System Ventilation The shutdown cooling system is ventilated by the reactor building ventilation 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.
F.3 Reactor Building Closed Cooling Water System Ventilation The reactor building closed ~ooling water (RBCCW) syste~ serves as an intermediate between the reactor shutdown cooling_system (Jnd other reactor building equipment) and the service water system.
While it may be used for shutdown heat removal, 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 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, 11Station 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 required.
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 building, the CCSW sysiem draws water from the crib house
- and supplies it to the LPCI heat exchanger in the reactor building.
Ventilation is provided b~, the main turbine room ventila-tion system which supplies 34,000 cfm of filtered heated air to the CCSW syst~m.
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.
Presently, there are four cubical coolers, each containing two fans, cool the equipment located in the flood-protected cubicle for pumps 2B and 2C with 2A and 20 located outside the flood-protected cubicle.
CCSW pump 28 with coolers 30C and 300, each have two fans powered from MCC 29-2
(~ssential electric service) through bus 29.
Bus 29 is normally powered from auxiliary transfonner 22 and upon loss of off-site power is automatically powered from standby diesel 2.
CCSW pump 2C with cooleri 30A and 30B, each h~ve two fans is powered from MCC 28-2 (essential electri~ sefvite),
powered from bus 28. *Bus 28 is nonnally powered from auxiliary transformer 21 and standby diesel 2/3.
Based on a site visit the staff has determined that specific ventilation of pumps 2A and 20 is not required, due to the heat load to area volume ratio.
- 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 instrumentation, 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 ~epends upon the adequacy of the complex power interconnections between Units 2 and 3 and ~mong the three diesel generators.
- ~
F.6 Battery Room Ventilation System The battery room contains the batteries that provide emergency de power essential for post-accident shutdown of the reactor.
Ventilation designed forthis purpose is considered essential to assure that the hydrogen given off from the batteries as a result of a possible continued charging, after loss of off-site power, 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) js 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 separat.e rooms served by *separate ventilation systems.
Cooling is provided by the diesel *service water systems, and the ventilation systems both ~ent the rooms and cool associated switcngear equipment.
- Where operator action is required, a justification should be provided that the 11ventilation 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 is supplied to the fan through a set of tempera-ture 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, natural convection through the doors cannot equal the air supplied by a 30-hp fan. lf 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 failure criterion.
VI.
CONCLUSION The ventilation systems for the Dresden 2 Plant were found to be in conformance with current criteria for this topic except for the fol lowing:
I
~
- 1) Following a loss of off-site power event, operator action is required to reinitiate the battery room ventilation system.
During that inoperative period hydrogen is generated due to continued battery charging.
The licensee should define the maximum period the system could be inoperative, and demonstrate that the amount of hydrogen generated during that period will not exceed the minimum combustion limits.
2}_
Both the LPCI/core spray and diesel rooms ventilation systems are subject to disabling single failures.
The Jicensee should evaluate the consequences of lostng either systems.
If it is determined that ventilation is required for system performance the need for upgrading to the associated ventilation system will be determined as part of the integrated assessment.